I. Field
The present invention relates generally to data communication, and more specifically to orthogonal frequency division multiplexing (OFDM) communication systems and techniques for providing OFDM symbol sizes to increase wireless efficiency.
II. Background
Wireless communication systems are widely deployed to provide various types of communication services such as voice, packet data, and so on. These systems may utilize OFDM, which is a modulation technique capable of providing high performance for some wireless environments. OFDM effectively partitions the overall system bandwidth into a number of (NS) orthogonal subbands, which are also commonly referred to as tones, bins, and frequency subchannels. With OFDM, each subband is associated with a respective carrier that may be modulated with data.
In OFDM, a stream of information bits is converted to a series of frequency-domain modulation symbols. One modulation symbol may be transmitted on each of the NS subbands in each OFDM symbol period (defined below). The modulation symbols to be transmitted on the NS subbands in each OFDM symbol period are transformed to the time-domain using an inverse fast Fourier transform (IFFT) to obtain a “transformed” symbol that contains NS samples. The input to an NS-point IFFT is NS frequency-domain values and the output from the IFFT is NS time-domain samples. The number of subbands is determined by the size of the IFFT. Increasing the size of the IFFT increases the number of subbands and also increases the number of samples for each transformed symbol, which correspondingly increases the time required to transmit the symbol.
To combat frequency selective fading in the wireless channel used for data transmission (described below), a portion of each transformed symbol is typically repeated prior to transmission. The repeated portion is often referred to as a cyclic prefix, and has a length of NCP, samples. The length of the cyclic prefix is typically selected based on the delay spread of the system, as described below, and is independent of the length of the transformed symbol. An OFDM symbol is composed of a transformed symbol and its cyclic prefix. Each OFDM symbol contains NS+Ncp samples and has a duration of NS+Ncp sample periods, which is one OFDM symbol period.
The size of the cyclic prefix relative to that of the OFDM symbol may have a large impact on the efficiency of an OFDM system. The cyclic prefix must be transmitted with each OFDM symbol to simplify the receiver processing in a multipath environment but carries no additional information. The cyclic prefix may be viewed as bandwidth that must be wasted as a price of operating in the multipath environment. The proportion of bandwidth wasted in this way can be computed using the formula
For example, if Ncp is 16 samples and NS is 64 samples, then 20% of the bandwidth is lost to cyclic prefix overhead. This percentage may be decreased by using a relatively large value of NS. Unfortunately, using a large value of NS can also lead to inefficiency, especially where the size of the information unit or packet to be transmitted is much smaller than the capacity of the OFDM symbol. For example, if each OFDM symbol can carry 480 information bits, but the most common packet contains 96 bits, then packing efficiency will be poor and much of the capacity of the OFDM symbol will be wasted when this common packet is sent.
Orthogonal frequency division multiple-access (OFDMA) can ameliorate the inefficiency due to excess capacity resulting from the use of a large OFDM symbol. For OFDMA, multiple users share the large OFDM symbol using frequency domain multiplexing. This is achieved by reserving a set of subbands for signaling and allocating different disjoint sets of subbands to different users. However, data transmission using OFDMA may be complicated by various factors such as, for example, different power requirements, propagation delays, Doppler frequency shifts, and/or timing for different users sharing the large OFDM symbol.
Existing OFDM systems typically select a single OFDM symbol size that is a compromise of various objectives, which may include minimizing cyclic prefix overhead and maximizing packing efficiency. The use of this single OFDM symbol size results in inefficiency due to excess capacity when transmitting packets of varying sizes. There is therefore a need in the art for an OFDM system that operates efficiently when transmitting packets of varying sizes.
Techniques are provided herein to use OFDM symbols of different sizes to achieve greater efficiency for OFDM systems. These techniques can address both objectives of minimizing cyclic prefix overhead and maximizing packing efficiency. The OFDM symbol sizes may be selected based on the expected sizes of the different types of payload to be transmitted in an OFDM system. The system traffic may be arranged into different categories. For each category, one or more OFDM symbols of the proper sizes may be selected for use based on the expected payload size for the traffic in that category.
For example, the system traffic may be arranged into control data, user data, and pilot data. Control data may be transmitted using an OFDM symbol of a first size, user data may be transmitted using an OFDM symbol of a second size and the OFDM symbol of the first size, and pilot data may be transmitted using an OFDM symbol of a third size (or the first size). The user data may further be arranged into sub-categories such as, for example, voice data, packet data, messaging data, and so on. A particular OFDM symbol size may then be selected for each sub-category of user data. Alternatively or additionally, the data for each user may be transmitted using an OFDM symbol of a particular size selected for that user. For improved packing efficiency, OFDM symbols of different sizes may be used for a given user data packet to better match the capacity of the OFDM symbols to the packet payload.
In general, any number of OFDM symbol sizes may be used for an OFDM system, and any particular OFDM symbol size may be selected for use. In one illustrative design, a combination of two OFDM symbol sizes are used so as to maximize packing efficiency. In the illustrative design, a small or short OFDM symbol size (e.g., with 64 subbands) is used for pilot and control data. User data may be sent within zero or more OFDM symbols having a large or long OFDM symbol size (e.g., with 256 subbands) and zero or more OFDM symbols having the small OFDM symbol size, depending on the payload size.
The processing at a transmitter and receiver (e.g., encoding, interleaving, symbol mapping, and spatial processing) may be performed in a manner to account for the use of OFDM symbols of different sizes, as described below. Various aspects and embodiments of the invention are also described in further detail below.
The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.
For each OFDM symbol period, one modulation symbol may be transmitted on each subband used for data transmission, and a signal value of zero is provided for each unused subband. An inverse fast Fourier transform (IFFT) unit 110 transforms the NS modulation symbols and zeros for all NS subbands in each OFDM symbol period to the time domain using an inverse fast Fourier transform (IFFT), to obtain a transformed symbol that comprises NS samples.
A cyclic prefix generator 120 then repeats a portion of each transformed symbol to obtain a corresponding OFDM symbol that comprises NS+Ncp samples. The cyclic prefix is used to combat frequency selective fading (i.e., a frequency response that varies across the overall system bandwidth), which is caused by delay spread in the system. The delay spread for a transmitter is the difference between the earliest and latest arriving signal instances at a receiver for a signal transmitted by that transmitter. The delay spread of the system is the expected worst-case delay spread for all transmitters and receivers in the system. The frequency selective fading causes inter-symbol interference (ISI), which is a phenomenon whereby each symbol in a received signal acts as distortion to subsequent symbols in the received signal. The ISI distortion degrades performance by impacting the ability to correctly detect the received symbols. To effectively combat ISI, the length of the cyclic prefix is typically selected based on the delay spread of the system such that the cyclic prefix contains a significant portion of all multipath energies. The cyclic prefix represents a fixed overhead of Ncp samples for each OFDM symbol.
As illustrated in
The use of the largest possible OFDM symbol may be inefficient from other standpoints. In particular, if the data-carrying capacity of the OFDM symbol is much greater than the size of the payload to be sent, then the remaining excess capacity of the OFDM symbol will go unused. This excess capacity of the OFDM symbol represents inefficiency. If the OFDM symbol is too large, then the inefficiency due to excess-capacity may be greater than the inefficiency due to the cyclic prefix.
In an illustrative OFDM system, both types of inefficiency are minimized by using OFDM symbols of different sizes. The OFDM symbol sizes used to transmit a unit of data may be selected from a set of available OFDM symbol sizes, which may in turn be selected based on the expected sizes of the different types of payload to be transmitted in the OFDM system. The system traffic may be arranged into different categories. For each category, one or more OFDM symbols of the proper sizes may be selected for use based on the expected payload size for the traffic in that category and possibly other considerations (e.g., implementation complexity). An OFDM symbol may be viewed as a boxcar that is used to send data. One or more boxcars of the proper sizes may be selected for each category of data depending on the amount of data expected to be sent for that category. A unit of data may be sent using multiple boxcars having identical sizes or having varying sizes. For example, if a unit of data consumes 2.1 times the capacity of a “large” boxcar, then the unit of data may be sent using two “large” boxcars and one “small” boxcar.
As an example, the system traffic may be divided into three basic categories—control data, user data, and pilot data. Control data typically constitutes a small fraction (e.g., less than 10%) of the total system traffic and is usually sent in smaller blocks. User data constitutes the bulk of the system traffic. To minimize cyclic prefix overhead and maximize packing efficiency, a short OFDM symbol may be used to send control data and pilot, and a combination of long OFDM symbols and short OFDM symbols may be used to send user data.
As shown in
In general, any number of OFDM symbol sizes may be used for the OFDM system, and any particular OFDM symbol size may be selected for use. Typically, the minimum OFDM symbol size is dictated by the cyclic prefix overhead and the maximum OFDM symbol size is dictated by the coherence time of the wireless channel. For practical considerations, OFDM symbol sizes that are powers of two (e.g., 32, 64, 128, 256, 512, and so on) are normally selected for use because of the ease in transforming between the time and frequency domains with the IFFT and fast Fourier Transform (FFT) operations.
For a TDM frame structure, such as the one shown in
The outputs from last butterfly stage 420s are provided to a selector unit 430, which provides the time-domain samples for each OFDM symbol. To perform an Nmax -point IFFT, all butterfly stages are enabled and Nmax samples are provided by selector unit 430. To perform an Nmax/2-point IFFT, all but the last butterfly stage 420s are enabled and Nmax/2 samples are provided by selector unit 430. To perform an Nmax/4-point IFFT, all but the last two butterfly stages 420r and 420s are enabled and Nmax/4 samples are provided by selector unit 430. A control unit 440 receives an indication of the particular OFDM symbol size to use for the current OFDM symbol period and provides the control signals for units 410 and 430 and butterfly stages 420.
IFFT unit 400 may implement a decimation-in-time or a decimation-in-frequency IFFT algorithm. Moreover, IFFT unit 400 may implement radix-4 or radix-2 IFFT, although radix-4 IFFT may be more efficient. IFFT unit 400 may be designed to include one or multiple butterfly computation units. At the extremes, one butterfly computation unit may be used for a time-shared IFFT implementation, and Nmax/radix butterfly computation units may be used for a fully parallel IFFT implementation. Typically, the number of butterfly computation units required is determined by the clock speed for these units, the OFDM symbol rate, and the maximum IFFT size. Proper control of these butterfly computation units in conjunction with memory management allow IFFT of different sizes to be performed using a single IFFT unit.
As described above in
OFDM symbols of different sizes may be advantageously used in various types of OFDM systems. For example, multiple OFDM symbol sizes may be used for (1) single-input single-output OFDM systems that use a single antenna for transmission and reception, (2) multiple-input single-output OFDM systems that use multiple antennas for transmission and a single antenna for reception, (3) single-input multiple-output OFDM systems that use a single antenna for transmission and multiple antennas for reception, and (4) multiple-input multiple-output OFDM systems (i.e., MIMO-OFDM systems) that use multiple antennas for transmission and reception. Multiple OFDM symbol sizes may also be used for (1) frequency division duplexed (FDD) OFDM systems that use different frequency bands for the downlink and uplink, and (2) time division duplexed (TDD) OFDM systems that use one frequency band for both the downlink and uplink in a time-shared manner.
The use of OFDM symbols of different sizes in an exemplary TDD MIMO-OFDM system is described below.
I. TDD MIMO-OFDM System
In
On the downlink, a BCH segment 610 is used to transmit one BCH protocol data unit (PDU) 612, which includes a portion 614 for a beacon pilot, a portion 616 for a MIMO pilot, and a portion 618 for a BCH message. The BCH message carries system parameters for the user terminals in the system. An FCCH segment 620 is used to transmit one FCCH PDU, which carries assignments for downlink and uplink resources and other signaling for the user terminals. An FCH segment 630 is used to transmit one or more FCH PDUs 632 on the downlink. Different types of FCH PDU may be defined. For example, an FCH PDU 632a includes a portion 634a for a pilot (e.g., a steered reference) and a portion 636a for a data packet. The pilot portion is also referred to as a “preamble”. An FCH PDU 632b includes a single portion 636b for a data packet. The different types of pilots (beacon pilot, MIMO pilot, and steered reference) are described in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309.
On the uplink, an RCH segment 640 is used to transmit one or more RCH PDUs 642 on the uplink. Different types of RCH PDU may also be defined. For example, an RCH PDU 642a includes a single portion 646a for a data packet. An RCH PDU 642b includes a portion 644b for a pilot (e.g., a steered reference) and a portion 646b for a data packet. An RACH segment 650 is used by the user terminals to gain access to the system and to send short messages on the uplink. An RACH PDU 652 may be sent in RACH segment 650 and includes a portion 654 for a pilot (e.g., a steered reference) and a portion 656 for a message.
The durations of the portions and segments are not drawn to scale in
Since different transport channels may be associated with different types of data, a suitable OFDM symbol size may be selected for use for each transport channel. If a large amount of data is expected to be transmitted on a given transport channel, then a large OFDM symbol may be used for that transport channel. The cyclic prefix would then represent a smaller percentage of the large OFDM symbol, and greater efficiency may be achieved. Conversely, if a small amount of data is expected to be transmitted on a given transport channel, than a small OFDM symbol may be used for that transport channel. Even though the cyclic prefix represents a larger percentage of the small OFDM symbol, greater efficiency may still be achieved by reducing the amount of excess capacity.
Thus, to attain higher efficiency, the OFDM symbol size for each transport channel may be selected to match the expected payload size for the type of data to be transmitted on that transport channel. Different OFDM symbol sizes may be used for different transport channels. Moreover, multiple OFDM symbol sizes may be used for a given transport channel. For example, each PDU type for the FCH and RCH may be associated with a suitable OFDM symbol size for that PDU type. A large OFDM symbol may be used for a large-size FCH/RCH PDU type, and a small OFDM symbol may be used for a small-size FCH/RCH PDU type.
For simplicity, an exemplary design is described below using a small OFDM symbol size NS1=64 and a large OFDM symbol size NS2=256. In this exemplary design, the BCH, FCCH, and RACH utilize the small OFDM symbol, and the FCH and RCH utilize both the small and large OFDM symbols as appropriate. Other OFDM symbol sizes may also be used for the transport channels, and this is within the scope of the invention. For example, a large OFDM symbol of size NS3=128 may alternatively or additionally be used for the FCH and RCH.
For this exemplary design, the 64 subbands for the small OFDM symbol are assigned indices of −32 to +31. Of these 64 subbands, 48 subbands (e.g., with indices of ±{1, . . . , 6, 8, . . . , 20, 22, . . . , 26}) are used for data and are referred to as data subbands, 4 subbands (e.g., with indices of ±{7, 21}) are used for pilot and possibly signaling, the DC subband (with index of 0) is not used, and the remaining subbands are also not used and serve as guard subbands. This OFDM subband structure is described in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309.
The 256 subbands for the large OFDM symbol are assigned indices of −128 to +127. The subbands for the small OFDM symbol may be mapped to the subbands for the large OFDM symbol based on the following:
l=4k+i, Eq (1)
where k is an index for the subbands in the short OFDM symbol (k=−32, . . . +31);
i is an index offset with a range of i=0, 1, 2, 3; and
l is an index for the subbands in the long OFDM symbol (l=−128, . . . +127).
For this exemplary design, the system bandwidth is W=20 MHz, the cyclic prefix is Ncp1=16 samples for the BCH, FCCH, and RACH, and the cyclic prefix is configurable as Ncp2=8 or 16 for the FCH and RCH. The small OFDM symbol used for the BCH, FCCH, and RACH would then have a size of Nos1=80 samples or 4.0 μsec. If Ncp2=16 is selected for use, then the large OFDM symbol used for the FCH and RCH would then have a size of Nos2=272 samples or 13.6 μsec.
For this exemplary design, the BCH segment has a fixed duration of 80 μsec, and each of the remaining segments has a variable duration. For each TDD frame, the start of each PDU sent on the FCH and RCH relative to the start of the FCH and RCH segments and the start of the RACH segment relative to the start of the TDD frame are provided in the FCCH message sent in the FCCH segment. Different OFDM symbol sizes are associated with different symbol durations. Since different OFDM symbol sizes are used for different transport channels (and different OFDM symbol sizes may also be used for the same transport channel), the offsets for the FCH and RCH PDUs are specified with the proper time resolution. For the exemplary design described above, the time resolution may be the cyclic prefix length of 800 nsec. For a TDD frame of 2 msec, a 12-bit value may be used to indicate the start of each FCH/RCH PDU.
The same PHY frame structure may be used for a message sent on the BCH or FCCH. In particular, a BCH/FCCH message may be sent using an integer number of PHY frames, each of which may be processed to obtain one OFDM symbol. Multiple OFDM symbols may be transmitted for the BCH/FCCH message.
For the embodiment shown in
For the exemplary design described above, the small PHY frame and small OFDM symbol are used for the BCH and FCCH. Both small and large PHY frames and small and large OFDM symbols may be used for the FCH and RCH. In general, a data packet may be sent using any number of large OFDM symbols and a small number of small OFDM symbols. If the large OFDM symbol is four times the size of the small OFDM symbol, then a data packet may be sent using NL large OFDM symbols and NSM small OFDM symbols (where NL≧0 and 3≧NSM≧0). The NSM small OFDM symbols at the end of the NL large OFDM symbols reduce the amount of unused capacity. OFDM symbols of different sizes may thus be used to better match the capacity of the OFDM symbols to the packet payload to maximize packing efficiency.
The OFDM symbol sizes used for data transmission may be provided to a receiver in various manners. In one embodiment, the FCCH provides the start of each data packet transmitted on the FCH and RCH and the rate of the packet. Some other equivalent information may also be signaled to the receiver. The receiver is then able to determine the size of each data packet being sent, the number of long and short OFDM symbols used for that data packet, and the start of each OFDM symbol. This information is then used by the receiver to determine the size of the FFT to be performed for each received OFDM symbol and to properly align the timing of the FFT. In another embodiment, the start of each data packet and its rate are not signaled to the receiver. In this case, “blind” detection may be used, and the receiver can perform an FFT for every 16 samples (i.e., the cyclic prefix length) and determine whether or not a PHY frame was sent by checking the CRC value included in the PHY frame.
For a given pairing of access point and user terminal in MIMO-OFDM system 500, a MIMO channel is formed by the Nap antennas at the access point and the Nut antennas at the user terminal. The MIMO channel may be decomposed into NC independent channels, with NC≦min {Nap, Nut}. Each of the NC independent channels is also referred to as an eigenmode of the MIMO channel, where “eigenmode” normally refers to a theoretical construct. Up to NC independent data streams may be sent concurrently on the NC eigenmodes of the MIMO channel. The MIMO channel may also be viewed as including NC spatial channels that may be used for data transmission. Each spatial channel may or may not correspond to an eigenmode, depending on whether or not the spatial processing at the transmitter was successful in orthogonalizing the data streams.
The MIMO-OFDM system may be designed to support a number of transmission modes. Table 2 lists the transmission modes that may be used for the downlink and uplink for a user terminal equipped with multiple antennas.
For the beam-steering mode, one PHY frame of a selected rate may be generated for each OFDM symbol period for transmission on the best spatial channel. This PHY frame is initially processed to obtain a set of modulation symbols, which is then spatially processed to obtain NT sets of transmit symbols for NT transmit antennas. The set of transmit symbols for each antenna is further processed to obtain an OFDM symbol for that antenna.
For the spatial multiplexing mode, up to NC PHY frames of the same or different rates may be generated for each OFDM symbol period for transmission on the NC spatial channels. The up to NC PHY frames are initially processed to obtain up to NC sets of modulation symbols, which are then spatially processed to obtain NT sets of transmit symbols for NT transmit antennas. The set of transmit symbols for each antenna is further processed to obtain an OFDM symbol for that antenna.
The processing at the transmitter and receiver for the beam-steering and spatial multiplexing modes are described in detail in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309. The spatial processing for the beam-steering and spatial multiplexing modes is essentially the same for both the short and long OFDM symbols, albeit with more subbands for the long OFDM symbol. The diversity mode is described below.
In an embodiment, the diversity mode utilizes space-time transmit diversity (STTD) for dual transmit diversity on a per-subband basis. STTD supports simultaneous transmission of independent symbol streams on two transmit antennas while maintaining orthogonality at the receiver.
The STTD scheme operates as follows. Suppose that two modulation symbols, denoted as s1 and s2, are to be transmitted on a given subband. The transmitter generates two vectors or STTD symbols, x1=[s1 s2*]T and x2=[s2−s1*]T, where each STTD symbol includes two elements, “*” denotes the complex conjugate, and “T” denotes the transpose. Alternatively, the transmitter may generate two STTD symbols, x1=[s1 s2]T and x2=[−s2* s1*]T. In any case, the two elements in each STTD symbol are typically transmitted sequentially in two OFDM symbol periods from a respective transmit antenna (i.e., STTD symbol x1 is transmitted from antenna 1 in two OFDM symbol periods, and STTD symbol x2 is transmitted from antenna 2 in the same two OFDM symbol periods). The duration of each STTD symbol is thus two OFDM symbol periods.
It is desirable to minimize the processing delay and buffering associated with STTD processing for the large OFDM symbol. In an embodiment, the two STTD symbols x1 and x2 are transmitted concurrently on a pair of subbands from two antennas. For the two STTD symbols x1=[s1 s2]T and x2=[−s2* s1*]T, the two elements s1 and s2 for the STTD symbol x1 may be transmitted on subband k from two antennas, and the two elements −s2*, and s1* for the STTD symbol x2 may be transmitted on subband k+1 from the same two antennas.
If the transmitter includes multiple antennas, then different pairs of antennas may be selected for use for each data subband in the diversity mode. Table 3 lists an exemplary subband-antenna assignment scheme for the STTD scheme using four transmit antennas.
For the embodiment shown in Table 3, transmit antennas 1 and 2 are used for short OFDM subband with index −26, transmit antennas 3 and 4 are used for short OFDM subband with index −25, and so on. The subband-antenna assignment is such that (1) each of the six possible antenna pairings with four transmit antennas is used for 8 data subbands, which are uniformly distributed across the 48 data subbands, and (2) the antenna pairing to subband assignment is such that different antennas are used for adjacent subbands, which may provide greater frequency and spatial diversity. The subband-antenna assignment scheme shown in Table 3 may also be used for the long OFDM symbol based on the mapping shown in equation (1) between the short and long OFDM symbol subband indices. For example, transmit antennas 1 and 2 may be used for long OFDM subbands with indices {−104, −103, −102, −101}, which are associated with short OFDM subband with index −26.
The processing at the transmitter and receiver for the diversity mode is described in detail in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309.
1. Physical Layer Processing
On the downlink, at access point 510x, a transmit (TX) data processor 810 receives user data (i.e., information bits) from a data source 808 and control data and other data from a controller 830 and possibly a scheduler 834. The functions of the controller 830 and the scheduler 834 may be performed by a single processor or multiple processors. These various types of data may be sent on different transport channels. TX data processor 810 processes the different types of data based on one or more coding and modulation schemes and provides a stream of modulation symbols for each spatial channel to be used for data transmission. A TX spatial processor 820 receives one or more modulation symbol streams from TX data processor 810 and performs spatial processing on the modulation symbols to provide one stream of “transmit” symbols for each transmit antenna. The processing by processors 810 and 820 is described below.
Each modulator (MOD) 822 receives and processes a respective transmit symbol stream to provide a corresponding stream of OFDM symbols, which is further processed to provide a corresponding downlink signal. The downlink signals from Nap modulators 822a through 822ap are then transmitted from Nap antennas 824a through 824ap, respectively.
At each user terminal 520, one or multiple antennas 852 receive the transmitted downlink signals, and each antenna provides a receiver input signal to a respective demodulator (DEMOD) 854. Each demodulator 854 performs processing complementary to that performed at modulator 822 and provides “received” symbols. A receive (RX) spatial processor 860 then performs spatial processing on the received symbols from all demodulators 854 to provide “recovered” symbols, which are estimates of the modulation symbols sent by the access point.
An RX data processor 870 receives and demultiplexes the recovered symbols into their respective transport channels. The recovered symbols for each transport channel may be processed to provide decoded data for that transport channel. The decoded data for each transport channel may include recovered user data, control data, and so on, which may be provided to a data sink 872 for storage and/or a controller 880 for further processing.
The processing by access point 510 and terminal 520 for the downlink is described in further detail below and in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309. The processing for the uplink may be the same or different from the processing for the downlink.
For the downlink, at each active user terminal 520, RX spatial processor 860 further estimates the downlink channel and provides channel state information (CSI). The CSI may include channel response estimates, received SNRs, and so on. RX data processor 870 may also provide the status of each packet/frame received on the downlink. A controller 880 receives the channel state information and the packet/frame status and determines the feedback information to be sent back to the access point. Controller 880 may further process the downlink channel estimates to obtain steering vectors, which are used to transmit a steered reference to the access point and for spatial processing of downlink data reception and uplink data transmission. The feedback information and uplink data are processed by a TX data processor 890, multiplexed with pilot data and spatially processed by a TX spatial processor 892 (if present), conditioned by one or more modulators 854, and transmitted via one or more antennas 852 back to the access point.
At access point 510, the transmitted uplink signal(s) are received by antennas 824, demodulated by demodulators 822, and processed by an RX spatial processor 840 and an RX data processor 842 in a complementary manner to that performed at the user terminal. The recovered feedback information is then provided to controller 830 and a scheduler 834. Scheduler 834 may use the feedback information to perform a number of functions such as (1) selecting a set of user terminals for data transmission on the downlink and uplink, (2) selecting the rates for the selected user terminals, and (3) assigning the available FCH/RCH resources to the selected terminals. Controller 830 may further use information (e.g., steering vectors) obtained from the uplink transmission for the processing of the downlink transmission, as described below.
Controllers 830 and 880 control the operation of various processing units at the access point and the user terminal, respectively. For example, controller 830 may determine the payload size of each data packet sent on the downlink and select OFDM symbols of the proper sizes for each downlink data packet. Correspondingly, controller 880 may determine the payload size of each data packet sent on the uplink and select OFDM symbols of the proper sizes for each uplink data packet.
The OFDM symbol size selection may be performed for the downlink and uplink in various manners. In one embodiment, controller 830 and/or scheduler 834 determines the specific OFDM symbol sizes to use for both the downlink and uplink. In another embodiment, the controller at the transmitter determines the specific OFDM symbol sizes to use for transmission. The OFDM symbol size selection may then be provided to the receiver (e.g., via signaling on an overhead channel or signaling within the transmission itself). In yet another embodiment, the controller at the receiver determines the specific OFDM symbol sizes to use for transmission, and the OFDM symbol size selection is provided to the transmitter. The OFDM symbol size selection may be provided in various forms. For example, the specific OFDM symbol sizes to use for a given transmission may be derived from scheduling information for that transmission, which may include, for example, the transmission mode, spatial channels, rate, and time interval to use for the transmission. The scheduling information may be generated by controller 830 and/or scheduler 834, the controller at the transmitter, or the controller at the receiver.
For both the downlink and uplink, the specific combination of large and small OFDM symbols to use for each data packet is dependent on the packet payload size and the OFDM symbol capacity for each of the available OFDM symbol sizes. For each data packet, the controller may select as many large OFDM symbols as needed, and where appropriate select one or more additional small OFDM symbols for the data packet. This selection may be performed as follows. Assume that two OFDM symbol sizes are used (e.g., with 64 subbands and 256 subbands), the data carrying capacity of the small OFDM symbol is TSM=48 modulation symbols, and the capacity of the large OFDM symbol is TL=192 modulation symbols. The modulation and coding scheme allows M information bits to be sent per modulation symbol. The capacity of the small OFDM symbol is then CSM=48·M information bits, and the capacity of the large OFDM symbol is CL=192·M information bits. Let the data packet be NP bits in length. The controller computes two intermediate values, l and m, as follows:
l=int[NP/CL], and Eq (2)
m=ceiling[(Np−l·CL)/CSM], Eq (3)
where the “int” operation on a provides the integer value of a, and the “ceiling” operation on b provides the next higher integer value for b. If m<4, then the number of large OFDM symbols to use for the data packet is NL=l and the number of small OFDM symbols to use is NSM=m. Otherwise, if m=4, then the number of large OFDM symbols to use for the data packet is NL=l+1 and the number of small OFDM symbols to use is NSM=0.
Controllers 830 and 880 provide the OFDM symbol size control signals to modulators/demodulators 822 and 854, respectively. At the access point, the OFDM symbol size control signal is used by the modulators to determine the size of the IFFT operations for downlink transmission, and is also used by the demodulators to determine the size of the FFT operations for uplink transmission. At the user terminal, the OFDM symbol size control signal is used by the demodulator(s) to determine the size of the FFT operations for downlink transmission, and is also used by the modulator(s) to determine the size of the IFFT operations for uplink transmission. Memory units 832 and 882 store data and program codes used by controllers 830 and 880, respectively.
An encoder 914 then codes the scrambled data in accordance with a selected coding scheme to provide code bits. The encoding increases the reliability of the data transmission. A repeat/puncture unit 916 then either repeats or punctures (i.e., deletes) some of the code bits to obtain the desired code rate for each PHY frame. In an exemplary embodiment, encoder 914 is a rate ½, constraint length 7, binary convolutional encoder. A code rate of ¼ may be obtained by repeating each code bit once. Code rates greater than ½ may be obtained by deleting some of the code bits from encoder 914.
An interleaver 918 then interleaves (i.e., reorders) the code bits from unit 916 based on a particular interleaving scheme. The interleaving provides time, frequency, and/or spatial diversity for the code bits. In an embodiment, each group of 48 consecutive code bits to be transmitted on a given spatial channel is interleaved across the 48 data subbands for the short OFDM symbol to provide frequency diversity. For the interleaving, the 48 code bits in each group may be assigned indices of 0 through 47. Each code bit index is associated with a respective short OFDM subband. Table 3 shows an exemplary code bit-subband assignment that may be used for the interleaving. All code bits with a particular index are transmitted on the associated subband. For example, the first code bit (with index 0) in each group is transmitted on short OFDM subband −26, the second code bit (with index 1) is transmitted on subband 1, and so on.
For the long OFDM symbol, each group of 192 consecutive code bits to be transmitted on a given spatial channel is interleaved across the 192 data subbands for the long OFDM symbol. In particular, the first subgroup of 48 code bits with indices of 0 through 47 may be transmitted on the 48 data subbands with indices l=4k, where k=±{1 . . . 6, 8 . . . 20, 22 . . . 26}, the second subgroup of 48 code bits with indices of 48 through 95 may be transmitted on the subbands with indices l=4k+1, the third subgroup of 48 code bits with indices of 96 through 143 may be transmitted on the subbands with indices l=4k+2, and the last subgroup of 48 code bits with indices of 144 through 191 may be transmitted on the subbands with indices l=4k+3. The same interleaving scheme is thus essentially used for both the short and long OFDM symbols.
A symbol mapping unit 920 then maps the interleaved data in accordance with one or more modulation schemes to provide modulation symbols. As shown in Table 1, the specific modulation scheme to use is dependent on the selected rate. The same modulation scheme is used for all data subbands in the diversity mode. A different modulation scheme may be used for each spatial channel in the spatial multiplexing mode. The symbol mapping may be achieved by (1) grouping sets of B bits to form B-bit binary values, where B≧1, and (2) mapping each B-bit binary value to a point in a signal constellation corresponding to the selected modulation scheme. Symbol mapping unit 920 provides a stream of modulation symbols to TX spatial processor 920.
An exemplary design for framing unit 910, scrambler 912, encoder 914, repeat/puncture unit 916, interleaver 918, and symbol mapping unit 920 is described in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309. The scrambling, coding, and modulation may be performed based on control signals provided by controller 830.
TX spatial processor 820 receives the modulation symbols from TX data processor 810 and performs spatial processing for the spatial multiplexing, beam-steering, or diversity mode. The spatial processing is described in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309. TX spatial processor 820 provides one stream of transmit symbols to each of Nap modulators 822a through 822ap.
2. Pilot
Various types of pilots may be transmitted to support various functions, such as timing and frequency acquisition, channel estimation, calibration, and so on. Table 4 lists four types of pilot and their short description.
A MIMO pilot may be sent by a transmitter (e.g., an access point) with the short OFDM symbol and used by a receiver (e.g., a user terminal) to estimate the channel response matrices H(k), for subband indices kεK, where K=±{1 . . . 26}. The receiver may then perform singular value decomposition of the channel response matrix H(k) for each subband, as follows:
H(k)=U(k)Σ(k)VH(k), for kεK, Eq (4)
where U(k) is an (NT×NR) unitary matrix of left eigenvectors of H(k);
A “wideband” eigenmode may be defined as the set of same-order eigenmodes of all subbands after the ordering. Thus, wideband eigenmode m includes eigenmode m of all subbands. Each wideband eigenmode is associated with a respective set of eigenvectors for all of the subbands. The “principal” wideband eigenmode is the one associated with the largest singular value in each matrix Σ(k) after the ordering.
If the same frequency band is used for both the downlink and uplink, then the channel response matrix for one link is the transpose of the channel response matrix for the other link. Calibration may be performed to account for differences in the frequency responses of the transmit/receive chains at the access point and user terminal. A steered reference may be sent by a transmitter and used by a receiver to estimate the eigenvectors that may be used for spatial processing for data reception and transmission.
A steered reference may be transmitted for wideband eigenmode m by a transmitter (e.g., a user terminal), as follows:
xm(k)=vm(k)·p(k), for kεK, Eq (5)
where xm(k) is an (NT×1) transmit vector for subband k of wideband eigenmode m;
The received steered reference at a receiver (e.g., an access point) may be expressed as:
where rm(k) is a received vector for subband k of wideband eigenmode m;
As shown in equation (6), at the receiver, the received steered reference (in the absence of noise) is approximately um(k)σm(k)p(k). The receiver can thus obtain estimates of um(k) and σm(k) for subband k based on the steered reference received on that subband, as described in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309.
The steered reference is sent for one wideband eigenmode in each OFDM symbol period (without subband multiplexing), and may in turn be used to obtain an estimate of one eigenvector um(k) for each subband of that wideband eigenmode. Since estimates of multiple eigenvectors for the unitary matrix U(k) are obtained over different OFDM symbol periods, and due to noise and other sources of degradation in the wireless channel, the estimated eigenvectors for the unitary matrix (which are individually derived) are not likely to be orthogonal to one another. To improve performance, the NC estimated eigenvectors um(k) of each unitary matrix U(k) may be forced to be orthogonal to each other using QR factorization or some other orthogonalization technique, as described in the aforementioned provisional U.S. Patent Application Ser. No. 60/438,601.
The steered reference may be sent using the short OFDM symbol. The receiver is able to process the received steered reference to obtain a steering vector for each short OFDM subband that was used for steered reference transmission. For the above exemplary design, each short OFDM subband is associated with four long OFDM subbands. If the steered reference is sent using the short OFDM symbol, then the steering vectors for the long OFDM subbands may be obtained in various manners.
In one embodiment, the steering vector obtained for short OFDM subband k is used for long OFDM subbands l=4k through l=4k+3. This embodiment provides good performance for low to moderate SNRs. For high SNRs, some degradation is observed when the coherence bandwidth of the channel is small. The coherence bandwidth is the bandwidth over which the channel is essentially constant or flat.
In another embodiment, the steering vectors um(k) obtained for the short OFDM subbands are interpolated to obtain the steering vectors um(l) for the long OFDM subbands. The interpolation may be performed in a manner such that the steering vectors um(l) do not exhibit substantially more variability from subband to subband than the underlying channel response matrix H(k). One source of variability is phase ambiguity in the left and right eigenvectors of H(k), which results from the fact that the left and right eigenvectors of H(k) are unique up to a unit length complex constant. In particular, for any pair of unit length vectors vm(k) and um(k) that satisfy the following equation:
H(k)vm(k)=um(k)σm(k), Eq (7)
any other pair of unit length vectors ejφvm(k) and ejφum(k) also satisfy the equation.
This phase ambiguity may be avoided by taking some precautions in the computation of the singular value decomposition of H(k). This may be achieved by constraining the solution to the singular value decomposition so that the first element in each column of V(k) is non-negative. This constraint eliminates arbitrary phase rotations from subband to subband when the variations in the eigenvectors are otherwise smooth and the magnitude of the leading element of the eigenvector is not close to zero. This constraint may be enforced by post-multiplying a diagonal matrix R(k) with each of the unitary matrices U(k) and V(k), which may be obtained in the normal manner and may contain arbitrary phase rotations. The diagonal elements ρi(k) of the matrix R(k) may be expressed as:
ρi(k)=e−arg(v
where v1,i(k) is the first element of the i-th column of V(k), and
The constrained eigenvectors in R(k)V(k) may then be used for the steered reference, as shown in equation (5). At the receiver, the received vector rm(k) may be processed to obtain estimates of um(k) and σm(k), which may be interpolated to obtain estimates of um(l) and σm(l), respectively.
The use of the short OFDM symbol for the MIMO pilot and steered reference reduces the processing load associated with singular value decomposition of the channel response matrices H(k). Moreover, it can be shown that interpolation, with the constraint described above to avoid arbitrary phase rotation from subband to subband, can reduce the amount of degradation in performance due to interpolation of the steering vectors based on steered reference transmission on fewer than all subbands used for data transmission.
The carrier pilot may be transmitted by the access point and used by the user terminals for phase tracking of a carrier signal. For a short OFDM symbol, the carrier pilot may be transmitted on four short OFDM subbands with indices±{7, 21}, as shown in Table 3. For a long OFDM symbol, the carrier pilot may be transmitted on the 16 corresponding long OFDM subbands with indices±{28+i, 84+i}, for i=0, 1, 2, 3. Alternatively, the carrier pilot may be transmitted on four long OFDM subbands with indices±{28, 84}, in which case the other 12 long OFDM subbands may be used for data transmission or some other purpose.
The various types of pilots and their processing at the transmitter and receiver are described in detail in the aforementioned provisional U.S. Patent Application Ser. No. 60/421,309.
For simplicity, the techniques for using of OFDM symbols of different sizes have been described for the downlink. These techniques may also be used for the uplink. A fixed OFDM symbol size may be used for some uplink transmissions (e.g., messages sent on the RACH) and OFDM symbols of different sizes may be used for other uplink transmissions (e.g., data packets sent on the RCH). The specific combination of large and small OFDM symbols to use for each uplink data packet may be depending on the packet payload size and may be determined by controller 880 (e.g., based on scheduling information generated by controller 880 or provided by controller 830 and/or scheduler 834, as described above).
The techniques described herein for using OFDM symbols of different sizes in OFDM systems may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the elements used to implement any one or a combination of the techniques may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.
For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit (e.g., memory units 832 and 882 in
Headings are included herein for reference and to aid in locating certain sections. These headings are not intended to limit the scope of the concepts described therein under, and these concepts may have applicability in other sections throughout the entire specification.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
This application is a continuation of U.S. application Ser. No. 10/375,162, entitled “OFDM Communication System with Multiple OFDM Symbol Sizes,” filed Feb. 24, 2004, now abandoned, which claims the benefit of provisional U.S. Application Ser. No. 60/421,309, entitled “MIMO WLAN System,” filed on Oct. 25, 2002, and provisional U.S. Application Ser. No. 60/438,601, entitled “Pilot Transmission Schemes for Wireless Multi-Carrier Communication Systems,” filed on Jan. 7, 2003, all of which are assigned to the assignee of the present application and incorporated herein by reference in their entirety for all purposes.
Number | Name | Date | Kind |
---|---|---|---|
4736371 | Tejima et al. | Apr 1988 | A |
4750198 | Harper | Jun 1988 | A |
4797879 | Habbab et al. | Jan 1989 | A |
5239677 | Jasinski | Aug 1993 | A |
5241544 | Jasper et al. | Aug 1993 | A |
5295159 | Kerpez | Mar 1994 | A |
5404355 | Raith | Apr 1995 | A |
5422733 | Merchant et al. | Jun 1995 | A |
5471647 | Gerlach et al. | Nov 1995 | A |
5479447 | Chow et al. | Dec 1995 | A |
5491837 | Haartsen | Feb 1996 | A |
5493712 | Ramesh et al. | Feb 1996 | A |
5506861 | Bottomley | Apr 1996 | A |
5509003 | Snijders et al. | Apr 1996 | A |
5528581 | De Bot | Jun 1996 | A |
5606729 | DAmico et al. | Feb 1997 | A |
5638369 | Ayerst et al. | Jun 1997 | A |
5677909 | Heide | Oct 1997 | A |
5710768 | Ziv et al. | Jan 1998 | A |
5729542 | Dupont | Mar 1998 | A |
5790550 | Peeters et al. | Aug 1998 | A |
5799005 | Soliman | Aug 1998 | A |
5818813 | Saito et al. | Oct 1998 | A |
5822374 | Levin | Oct 1998 | A |
5832387 | Bae et al. | Nov 1998 | A |
5859875 | Kato et al. | Jan 1999 | A |
5867478 | Baum et al. | Feb 1999 | A |
5867539 | Koslov | Feb 1999 | A |
5883887 | Take et al. | Mar 1999 | A |
5886988 | Yun et al. | Mar 1999 | A |
5929810 | Koutsoudis et al. | Jul 1999 | A |
5959965 | Ohkubo et al. | Sep 1999 | A |
5963589 | Nagano et al. | Oct 1999 | A |
5973638 | Robbins et al. | Oct 1999 | A |
5982327 | Vook et al. | Nov 1999 | A |
6005876 | Cimini, Jr. et al. | Dec 1999 | A |
6011963 | Ogoro | Jan 2000 | A |
6049548 | Bruno et al. | Apr 2000 | A |
6067290 | Paulraj et al. | May 2000 | A |
6072779 | Tzannes et al. | Jun 2000 | A |
6084915 | Williams | Jul 2000 | A |
6097771 | Foschini | Aug 2000 | A |
6115354 | Weck | Sep 2000 | A |
6122247 | Levin et al. | Sep 2000 | A |
6131016 | Greenstein et al. | Oct 2000 | A |
6141388 | Servais et al. | Oct 2000 | A |
6141542 | Kotzin et al. | Oct 2000 | A |
6141555 | Sato | Oct 2000 | A |
6141567 | Youssefmir et al. | Oct 2000 | A |
6144711 | Raleigh et al. | Nov 2000 | A |
6154661 | Goldburg | Nov 2000 | A |
6163296 | Lier et al. | Dec 2000 | A |
6167031 | Olofsson et al. | Dec 2000 | A |
6175588 | Visotsky et al. | Jan 2001 | B1 |
6178196 | Naguib et al. | Jan 2001 | B1 |
6192256 | Whinnett | Feb 2001 | B1 |
6205410 | Cai | Mar 2001 | B1 |
6222888 | Kao et al. | Apr 2001 | B1 |
6232918 | Wax et al. | May 2001 | B1 |
6266528 | Farzaneh | Jul 2001 | B1 |
6272354 | Saario | Aug 2001 | B1 |
6275543 | Petrus et al. | Aug 2001 | B1 |
6278726 | Mesecher et al. | Aug 2001 | B1 |
6292917 | Sinha et al. | Sep 2001 | B1 |
6298035 | Heiskala | Oct 2001 | B1 |
6298092 | Heath, Jr. et al. | Oct 2001 | B1 |
6308080 | Burt et al. | Oct 2001 | B1 |
6310704 | Dogan et al. | Oct 2001 | B1 |
6314113 | Guemas | Nov 2001 | B1 |
6314289 | Eberlein et al. | Nov 2001 | B1 |
6317467 | Cox et al. | Nov 2001 | B1 |
6317612 | Farsakh | Nov 2001 | B1 |
6330277 | Gelblum et al. | Dec 2001 | B1 |
6330293 | Klank et al. | Dec 2001 | B1 |
6330462 | Chen | Dec 2001 | B1 |
6333953 | Bottomley et al. | Dec 2001 | B1 |
6339399 | Andersson et al. | Jan 2002 | B1 |
6345036 | Sudo et al. | Feb 2002 | B1 |
6346910 | Ito | Feb 2002 | B1 |
6347217 | Bengtsson et al. | Feb 2002 | B1 |
6347234 | Scherzer | Feb 2002 | B1 |
6348036 | Looney et al. | Feb 2002 | B1 |
6351499 | Paulraj et al. | Feb 2002 | B1 |
6363267 | Lindskog et al. | Mar 2002 | B1 |
6369758 | Zhang | Apr 2002 | B1 |
6377812 | Rashid-Farrokhi et al. | Apr 2002 | B1 |
6385264 | Terasawa et al. | May 2002 | B1 |
6389056 | Kanterakis et al. | May 2002 | B1 |
6426971 | Wu et al. | Jul 2002 | B1 |
6452981 | Raleigh et al. | Sep 2002 | B1 |
6463290 | Stilp et al. | Oct 2002 | B1 |
6473467 | Wallace et al. | Oct 2002 | B1 |
6478422 | Hansen | Nov 2002 | B1 |
6492942 | Kezys | Dec 2002 | B1 |
6510184 | Okamura | Jan 2003 | B1 |
6512737 | Agee | Jan 2003 | B1 |
6515617 | Demers et al. | Feb 2003 | B1 |
6532225 | Chang et al. | Mar 2003 | B1 |
6532255 | Gunzelmann et al. | Mar 2003 | B1 |
6532562 | Chou et al. | Mar 2003 | B1 |
6545997 | Bohnke et al. | Apr 2003 | B1 |
6574211 | Padovani et al. | Jun 2003 | B2 |
6574267 | Kanterakis et al. | Jun 2003 | B1 |
6574271 | Mesecher et al. | Jun 2003 | B2 |
6590883 | Kitade et al. | Jul 2003 | B1 |
6594473 | Dabak et al. | Jul 2003 | B1 |
6594798 | Chou et al. | Jul 2003 | B1 |
6597682 | Kari | Jul 2003 | B1 |
6608874 | Beidas et al. | Aug 2003 | B1 |
6611231 | Crilly et al. | Aug 2003 | B2 |
6615024 | Boros et al. | Sep 2003 | B1 |
6628702 | Rowitch et al. | Sep 2003 | B1 |
6631121 | Yoon | Oct 2003 | B1 |
6636496 | Cho et al. | Oct 2003 | B1 |
6636568 | Kadous | Oct 2003 | B2 |
6654590 | Boros et al. | Nov 2003 | B2 |
6654613 | Maeng et al. | Nov 2003 | B1 |
6668161 | Boros et al. | Dec 2003 | B2 |
6683916 | Sartori et al. | Jan 2004 | B1 |
6690660 | Kim et al. | Feb 2004 | B2 |
6693992 | Jones et al. | Feb 2004 | B2 |
6694155 | Chin et al. | Feb 2004 | B1 |
6697346 | Halton et al. | Feb 2004 | B1 |
6711121 | Gerakoulis et al. | Mar 2004 | B1 |
6721267 | Hiben et al. | Apr 2004 | B2 |
6728233 | Park et al. | Apr 2004 | B1 |
6731668 | Ketchum | May 2004 | B2 |
6735188 | Becker et al. | May 2004 | B1 |
6738020 | Lindskog et al. | May 2004 | B1 |
6744811 | Kantschuk | Jun 2004 | B1 |
6747963 | Park et al. | Jun 2004 | B1 |
6751187 | Walton et al. | Jun 2004 | B2 |
6751199 | Sindhushayana et al. | Jun 2004 | B1 |
6751444 | Meiyappan | Jun 2004 | B1 |
6751480 | Kogiantis et al. | Jun 2004 | B2 |
6757263 | Olds | Jun 2004 | B1 |
6760313 | Sindhushayana et al. | Jul 2004 | B1 |
6760388 | Ketchum et al. | Jul 2004 | B2 |
6760882 | Gesbert et al. | Jul 2004 | B1 |
6763244 | Chen et al. | Jul 2004 | B2 |
6768727 | Sourour et al. | Jul 2004 | B1 |
6771706 | Ling et al. | Aug 2004 | B2 |
6785341 | Walton et al. | Aug 2004 | B2 |
6785513 | Sivaprakasam | Aug 2004 | B1 |
6788948 | Lindskog et al. | Sep 2004 | B2 |
6792041 | Kim et al. | Sep 2004 | B1 |
6795424 | Kapoor et al. | Sep 2004 | B1 |
6798738 | Do et al. | Sep 2004 | B1 |
6801790 | Rudrapatna | Oct 2004 | B2 |
6802035 | Catreux et al. | Oct 2004 | B2 |
6804191 | Richardson | Oct 2004 | B2 |
6821535 | Nurmi et al. | Nov 2004 | B2 |
6842460 | Olkkonen et al. | Jan 2005 | B1 |
6847828 | Miyoshi et al. | Jan 2005 | B2 |
6850252 | Hoffberg | Feb 2005 | B1 |
6850498 | Heath et al. | Feb 2005 | B2 |
6859503 | Pautler et al. | Feb 2005 | B2 |
6862271 | Medvedev et al. | Mar 2005 | B2 |
6862440 | Sampath | Mar 2005 | B2 |
6868079 | Hunt | Mar 2005 | B1 |
6873651 | Tesfai et al. | Mar 2005 | B2 |
6879578 | Pan et al. | Apr 2005 | B2 |
6879579 | Myles et al. | Apr 2005 | B1 |
6882868 | Shattil | Apr 2005 | B1 |
6885708 | Thomas et al. | Apr 2005 | B2 |
6888809 | Foschini et al. | May 2005 | B1 |
6888899 | Raleigh et al. | May 2005 | B2 |
6891858 | Mahesh et al. | May 2005 | B1 |
6907270 | Blanz | Jun 2005 | B1 |
6920192 | Laroia et al. | Jul 2005 | B1 |
6920194 | Stopler et al. | Jul 2005 | B2 |
6927728 | Vook et al. | Aug 2005 | B2 |
6937592 | Heath, Jr. et al. | Aug 2005 | B1 |
6940917 | Menon et al. | Sep 2005 | B2 |
6950632 | Yun et al. | Sep 2005 | B1 |
6952426 | Wu et al. | Oct 2005 | B2 |
6952454 | Jalali et al. | Oct 2005 | B1 |
6956813 | Fukuda | Oct 2005 | B2 |
6956897 | Honig | Oct 2005 | B1 |
6956906 | Tager et al. | Oct 2005 | B2 |
6959171 | Tsien et al. | Oct 2005 | B2 |
6961388 | Ling et al. | Nov 2005 | B2 |
6963741 | Johansson et al. | Nov 2005 | B2 |
6963742 | Boros et al. | Nov 2005 | B2 |
6965762 | Sugar et al. | Nov 2005 | B2 |
6970722 | Lewis | Nov 2005 | B1 |
6975868 | Joshi et al. | Dec 2005 | B2 |
6980601 | Jones | Dec 2005 | B2 |
6980800 | Noerpel et al. | Dec 2005 | B2 |
6985434 | Wu et al. | Jan 2006 | B2 |
6985534 | Meister | Jan 2006 | B1 |
6987819 | Thomas et al. | Jan 2006 | B2 |
6990059 | Anikhindi et al. | Jan 2006 | B1 |
6992972 | Van Nee | Jan 2006 | B2 |
6996380 | Dent | Feb 2006 | B2 |
7002900 | Walton et al. | Feb 2006 | B2 |
7003044 | Subramanian et al. | Feb 2006 | B2 |
7006464 | Gopalakrishnan et al. | Feb 2006 | B1 |
7006483 | Nelson, Jr. et al. | Feb 2006 | B2 |
7006848 | Ling et al. | Feb 2006 | B2 |
7009931 | Ma et al. | Mar 2006 | B2 |
7012978 | Talwar | Mar 2006 | B2 |
7020110 | Walton et al. | Mar 2006 | B2 |
7020482 | Medvedev et al. | Mar 2006 | B2 |
7020490 | Khatri | Mar 2006 | B2 |
7023826 | Sjoberg et al. | Apr 2006 | B2 |
7024163 | Barratt et al. | Apr 2006 | B1 |
7031671 | Mottier | Apr 2006 | B2 |
7035359 | Molnar | Apr 2006 | B2 |
7039125 | Friedman | May 2006 | B2 |
7039363 | Kasapi et al. | May 2006 | B1 |
7042858 | Ma et al. | May 2006 | B1 |
7043259 | Trott | May 2006 | B1 |
7054378 | Walton et al. | May 2006 | B2 |
7058367 | Luo et al. | Jun 2006 | B1 |
7062294 | Rogard et al. | Jun 2006 | B1 |
7068628 | Li et al. | Jun 2006 | B2 |
7072381 | Atarashi et al. | Jul 2006 | B2 |
7072410 | Monsen | Jul 2006 | B1 |
7072413 | Walton et al. | Jul 2006 | B2 |
7076263 | Medvedev et al. | Jul 2006 | B2 |
7088671 | Monsen | Aug 2006 | B1 |
7095709 | Walton et al. | Aug 2006 | B2 |
7095722 | Walke et al. | Aug 2006 | B1 |
7099377 | Berens et al. | Aug 2006 | B2 |
7103325 | Jia et al. | Sep 2006 | B1 |
7110378 | Onggosanusi et al. | Sep 2006 | B2 |
7110463 | Wallace et al. | Sep 2006 | B2 |
7113499 | Nafie et al. | Sep 2006 | B2 |
7116652 | Lozano | Oct 2006 | B2 |
7120134 | Tiedemann, Jr. et al. | Oct 2006 | B2 |
7120199 | Thielecke et al. | Oct 2006 | B2 |
7120657 | Ricks et al. | Oct 2006 | B2 |
7127009 | Berthet et al. | Oct 2006 | B2 |
7130362 | Girardeau et al. | Oct 2006 | B2 |
7133459 | Onggosanusi et al. | Nov 2006 | B2 |
7137047 | Mitlin et al. | Nov 2006 | B2 |
7149190 | Li et al. | Dec 2006 | B1 |
7149239 | Hudson | Dec 2006 | B2 |
7149254 | Sampath | Dec 2006 | B2 |
7151809 | Ketchum et al. | Dec 2006 | B2 |
7155171 | Ebert et al. | Dec 2006 | B2 |
7158563 | Ginis et al. | Jan 2007 | B2 |
7164649 | Walton et al. | Jan 2007 | B2 |
7164669 | Li et al. | Jan 2007 | B2 |
7184713 | Kadous et al. | Feb 2007 | B2 |
7187646 | Schramm | Mar 2007 | B2 |
7190749 | Levin et al. | Mar 2007 | B2 |
7191381 | Gesbert et al. | Mar 2007 | B2 |
7194237 | Sugar et al. | Mar 2007 | B2 |
7197084 | Ketchum et al. | Mar 2007 | B2 |
7200404 | Panasik et al. | Apr 2007 | B2 |
7206354 | Wallace et al. | Apr 2007 | B2 |
7218684 | Bolourchi et al. | May 2007 | B2 |
7221956 | Medvedev et al. | May 2007 | B2 |
7224704 | Lu et al. | May 2007 | B2 |
7231184 | Eilts et al. | Jun 2007 | B2 |
7233625 | Ma et al. | Jun 2007 | B2 |
7238508 | Lin et al. | Jul 2007 | B2 |
7242727 | Liu et al. | Jul 2007 | B2 |
7248638 | Banister | Jul 2007 | B1 |
7248841 | Agee et al. | Jul 2007 | B2 |
7254171 | Hudson | Aug 2007 | B2 |
7260153 | Nissani | Aug 2007 | B2 |
7260366 | Lee et al. | Aug 2007 | B2 |
7263119 | Hsu et al. | Aug 2007 | B1 |
7269127 | Mody et al. | Sep 2007 | B2 |
7272162 | Sano et al. | Sep 2007 | B2 |
7274734 | Tsatsanis | Sep 2007 | B2 |
7277679 | Barratt et al. | Oct 2007 | B1 |
7280467 | Smee et al. | Oct 2007 | B2 |
7280625 | Ketchum et al. | Oct 2007 | B2 |
7283508 | Choi et al. | Oct 2007 | B2 |
7283581 | Itoh | Oct 2007 | B2 |
7289570 | Schmidl et al. | Oct 2007 | B2 |
7292854 | Das et al. | Nov 2007 | B2 |
7298778 | Visoz et al. | Nov 2007 | B2 |
7298805 | Walton et al. | Nov 2007 | B2 |
7308035 | Rouquette et al. | Dec 2007 | B2 |
7310304 | Mody et al. | Dec 2007 | B2 |
7317750 | Shattil | Jan 2008 | B2 |
7324429 | Walton et al. | Jan 2008 | B2 |
7327800 | Oprea et al. | Feb 2008 | B2 |
7333556 | Maltsev et al. | Feb 2008 | B2 |
7342912 | Kerr et al. | Mar 2008 | B1 |
7356004 | Yano et al. | Apr 2008 | B2 |
7356089 | Jia et al. | Apr 2008 | B2 |
7379492 | Hwang | May 2008 | B2 |
7386076 | Onggosanusi et al. | Jun 2008 | B2 |
7392014 | Baker et al. | Jun 2008 | B2 |
7403748 | Keskitalo et al. | Jul 2008 | B1 |
7421039 | Malaender et al. | Sep 2008 | B2 |
7453844 | Lee et al. | Nov 2008 | B1 |
7466749 | Medvedev et al. | Dec 2008 | B2 |
7480278 | Pedersen et al. | Jan 2009 | B2 |
7486740 | Inanoglu | Feb 2009 | B2 |
7492737 | Fong et al. | Feb 2009 | B1 |
7508748 | Kadous | Mar 2009 | B2 |
7548506 | Ma et al. | Jun 2009 | B2 |
7551546 | Ma et al. | Jun 2009 | B2 |
7551580 | Du Crest et al. | Jun 2009 | B2 |
7573805 | Zhuang et al. | Aug 2009 | B2 |
7599443 | Ionescu et al. | Oct 2009 | B2 |
7603141 | Dravida | Oct 2009 | B2 |
7606296 | Hsu et al. | Oct 2009 | B1 |
7606319 | Zhang et al. | Oct 2009 | B2 |
7616698 | Sun et al. | Nov 2009 | B2 |
7623871 | Sheynblat | Nov 2009 | B2 |
7636573 | Walton et al. | Dec 2009 | B2 |
7646747 | Atarashi et al. | Jan 2010 | B2 |
7653142 | Ketchum et al. | Jan 2010 | B2 |
7653415 | Van Rooyen | Jan 2010 | B2 |
7656967 | Tiirola et al. | Feb 2010 | B2 |
7778337 | Tong et al. | Aug 2010 | B2 |
7787514 | Shattil | Aug 2010 | B2 |
7822140 | Catreux et al. | Oct 2010 | B2 |
7843972 | Nakahara et al. | Nov 2010 | B2 |
7885228 | Walton et al. | Feb 2011 | B2 |
7986742 | Ketchum et al. | Jul 2011 | B2 |
8134976 | Wallace et al. | Mar 2012 | B2 |
8145179 | Walton et al. | Mar 2012 | B2 |
8169944 | Walton et al. | May 2012 | B2 |
8170513 | Walton et al. | May 2012 | B2 |
8194770 | Medvedev et al. | Jun 2012 | B2 |
8203978 | Walton et al. | Jun 2012 | B2 |
8208364 | Walton et al. | Jun 2012 | B2 |
8213292 | Ma et al. | Jul 2012 | B2 |
8218609 | Walton et al. | Jul 2012 | B2 |
8254246 | Ma et al. | Aug 2012 | B2 |
8260210 | Esteve et al. | Sep 2012 | B2 |
8320301 | Walton et al. | Nov 2012 | B2 |
8325836 | Tong et al. | Dec 2012 | B2 |
8355313 | Walton et al. | Jan 2013 | B2 |
8358714 | Walton et al. | Jan 2013 | B2 |
8406118 | Ma et al. | Mar 2013 | B2 |
8462643 | Walton et al. | Jun 2013 | B2 |
8483188 | Walton et al. | Jul 2013 | B2 |
8570988 | Wallace et al. | Oct 2013 | B2 |
8855226 | Medvedev et al. | Oct 2014 | B2 |
9013974 | Walton et al. | Apr 2015 | B2 |
20010017881 | Bhatoolaul et al. | Aug 2001 | A1 |
20010031621 | Schmutz | Oct 2001 | A1 |
20010033623 | Hosur | Oct 2001 | A1 |
20010046205 | Easton et al. | Nov 2001 | A1 |
20020003774 | Wang et al. | Jan 2002 | A1 |
20020004920 | Cho et al. | Jan 2002 | A1 |
20020018310 | Hung | Feb 2002 | A1 |
20020018453 | Yu et al. | Feb 2002 | A1 |
20020027951 | Gormley et al. | Mar 2002 | A1 |
20020041632 | Sato et al. | Apr 2002 | A1 |
20020044591 | Lee et al. | Apr 2002 | A1 |
20020044610 | Jones | Apr 2002 | A1 |
20020057659 | Ozluturk et al. | May 2002 | A1 |
20020062472 | Medlock et al. | May 2002 | A1 |
20020064214 | Hattori et al. | May 2002 | A1 |
20020075830 | Hartman, Jr. | Jun 2002 | A1 |
20020085620 | Mesecher | Jul 2002 | A1 |
20020085641 | Baum | Jul 2002 | A1 |
20020098872 | Judson | Jul 2002 | A1 |
20020105928 | Kapoor et al. | Aug 2002 | A1 |
20020115467 | Hamabe | Aug 2002 | A1 |
20020115473 | Hwang et al. | Aug 2002 | A1 |
20020122381 | Wu et al. | Sep 2002 | A1 |
20020122393 | Caldwell et al. | Sep 2002 | A1 |
20020136271 | Hiramatsu et al. | Sep 2002 | A1 |
20020147032 | Yoon et al. | Oct 2002 | A1 |
20020150182 | Dogan et al. | Oct 2002 | A1 |
20020154705 | Walton et al. | Oct 2002 | A1 |
20020177447 | Walton et al. | Nov 2002 | A1 |
20020183010 | Catreux et al. | Dec 2002 | A1 |
20020184453 | Hughes et al. | Dec 2002 | A1 |
20020191535 | Sugiyama et al. | Dec 2002 | A1 |
20020193146 | Wallace et al. | Dec 2002 | A1 |
20020196842 | Onggosanusi et al. | Dec 2002 | A1 |
20030002450 | Jalali et al. | Jan 2003 | A1 |
20030007463 | Li et al. | Jan 2003 | A1 |
20030012308 | Sampath et al. | Jan 2003 | A1 |
20030039217 | Seo et al. | Feb 2003 | A1 |
20030039317 | Taylor et al. | Feb 2003 | A1 |
20030045288 | Luschi et al. | Mar 2003 | A1 |
20030045318 | Subrahmanya | Mar 2003 | A1 |
20030048856 | Ketchum et al. | Mar 2003 | A1 |
20030050069 | Kogiantis et al. | Mar 2003 | A1 |
20030072395 | Jia et al. | Apr 2003 | A1 |
20030073409 | Nobukiyo et al. | Apr 2003 | A1 |
20030076812 | Benedittis | Apr 2003 | A1 |
20030078024 | Magee et al. | Apr 2003 | A1 |
20030095197 | Wheeler et al. | May 2003 | A1 |
20030099306 | Nilsson et al. | May 2003 | A1 |
20030103584 | Bjerke et al. | Jun 2003 | A1 |
20030112745 | Zhuang et al. | Jun 2003 | A1 |
20030117989 | Kim | Jun 2003 | A1 |
20030119452 | Kim et al. | Jun 2003 | A1 |
20030123389 | Russell et al. | Jul 2003 | A1 |
20030125040 | Walton et al. | Jul 2003 | A1 |
20030128656 | Scarpa | Jul 2003 | A1 |
20030139194 | Onggosanusi et al. | Jul 2003 | A1 |
20030142732 | Moshavi et al. | Jul 2003 | A1 |
20030153345 | Cramer et al. | Aug 2003 | A1 |
20030153360 | Burke et al. | Aug 2003 | A1 |
20030162519 | Smith et al. | Aug 2003 | A1 |
20030174676 | Willenegger et al. | Sep 2003 | A1 |
20030174686 | Willenegger et al. | Sep 2003 | A1 |
20030185311 | Kim | Oct 2003 | A1 |
20030186650 | Liu | Oct 2003 | A1 |
20030190897 | Lei et al. | Oct 2003 | A1 |
20030202492 | Akella et al. | Oct 2003 | A1 |
20030202612 | Halder et al. | Oct 2003 | A1 |
20030206558 | Parkkinen et al. | Nov 2003 | A1 |
20030210668 | Malladi et al. | Nov 2003 | A1 |
20030235149 | Chan et al. | Dec 2003 | A1 |
20030235255 | Ketchum et al. | Dec 2003 | A1 |
20040005887 | Bahrenburg et al. | Jan 2004 | A1 |
20040013103 | Zhang et al. | Jan 2004 | A1 |
20040017785 | Zelst | Jan 2004 | A1 |
20040037257 | Ngo | Feb 2004 | A1 |
20040047284 | Eidson | Mar 2004 | A1 |
20040052228 | Tellado et al. | Mar 2004 | A1 |
20040062192 | Liu et al. | Apr 2004 | A1 |
20040071104 | Boesel et al. | Apr 2004 | A1 |
20040071107 | Kats et al. | Apr 2004 | A1 |
20040076224 | Onggosanusi et al. | Apr 2004 | A1 |
20040081131 | Walton et al. | Apr 2004 | A1 |
20040121730 | Kadous et al. | Jun 2004 | A1 |
20040151108 | Blasco Claret et al. | Aug 2004 | A1 |
20040151122 | Lau et al. | Aug 2004 | A1 |
20040160921 | Kaipainen et al. | Aug 2004 | A1 |
20040160987 | Sudo et al. | Aug 2004 | A1 |
20040176097 | Wilson et al. | Sep 2004 | A1 |
20040198276 | Tellado et al. | Oct 2004 | A1 |
20040252632 | Bourdoux et al. | Dec 2004 | A1 |
20050002326 | Ling et al. | Jan 2005 | A1 |
20050047384 | Wax et al. | Mar 2005 | A1 |
20050047515 | Walton et al. | Mar 2005 | A1 |
20050099974 | Kats et al. | May 2005 | A1 |
20050120097 | Walton et al. | Jun 2005 | A1 |
20050128953 | Wallace et al. | Jun 2005 | A1 |
20050135284 | Nanda et al. | Jun 2005 | A1 |
20050135295 | Walton et al. | Jun 2005 | A1 |
20050135308 | Vijayan et al. | Jun 2005 | A1 |
20050135318 | Walton et al. | Jun 2005 | A1 |
20050147177 | Seo et al. | Jul 2005 | A1 |
20050174981 | Heath et al. | Aug 2005 | A1 |
20050185575 | Hansen et al. | Aug 2005 | A1 |
20050195915 | Raleigh et al. | Sep 2005 | A1 |
20050208959 | Chen et al. | Sep 2005 | A1 |
20050220211 | Shim et al. | Oct 2005 | A1 |
20050245264 | Laroia et al. | Nov 2005 | A1 |
20050276343 | Jones | Dec 2005 | A1 |
20060018247 | Driesen et al. | Jan 2006 | A1 |
20060018395 | Tzannes | Jan 2006 | A1 |
20060039275 | Walton et al. | Feb 2006 | A1 |
20060067417 | Park et al. | Mar 2006 | A1 |
20060072649 | Chang et al. | Apr 2006 | A1 |
20060077935 | Hamalainen et al. | Apr 2006 | A1 |
20060104196 | Wu et al. | May 2006 | A1 |
20060104340 | Walton et al. | May 2006 | A1 |
20060114858 | Walton et al. | Jun 2006 | A1 |
20060153237 | Hwang et al. | Jul 2006 | A1 |
20060159120 | Kim | Jul 2006 | A1 |
20060176968 | Keaney et al. | Aug 2006 | A1 |
20060183497 | Paranchych et al. | Aug 2006 | A1 |
20060209894 | Tzannes et al. | Sep 2006 | A1 |
20060209937 | Tanaka et al. | Sep 2006 | A1 |
20070177681 | Choi et al. | Aug 2007 | A1 |
20070274278 | Choi et al. | Nov 2007 | A1 |
20080267138 | Walton et al. | Oct 2008 | A1 |
20080285488 | Walton et al. | Nov 2008 | A1 |
20080285669 | Walton et al. | Nov 2008 | A1 |
20090129454 | Medvedev et al. | May 2009 | A1 |
20090161613 | Kent et al. | Jun 2009 | A1 |
20090291642 | Cozzo et al. | Nov 2009 | A1 |
20100067401 | Medvedev et al. | Mar 2010 | A1 |
20100119001 | Walton et al. | May 2010 | A1 |
20100142636 | Heath, Jr. et al. | Jun 2010 | A1 |
20100183088 | Inanoglu | Jul 2010 | A1 |
20100208841 | Walton et al. | Aug 2010 | A1 |
20100220825 | Dubuc et al. | Sep 2010 | A1 |
20100260060 | Abraham et al. | Oct 2010 | A1 |
20100271930 | Tong et al. | Oct 2010 | A1 |
20110096751 | Ma et al. | Apr 2011 | A1 |
20110235744 | Ketchum et al. | Sep 2011 | A1 |
20120134435 | Kapoor et al. | May 2012 | A1 |
20120140664 | Walton et al. | Jun 2012 | A1 |
20120176928 | Wallace et al. | Jul 2012 | A1 |
20120219093 | Jia et al. | Aug 2012 | A1 |
20130040682 | Chang et al. | Feb 2013 | A1 |
20130235825 | Walton et al. | Sep 2013 | A1 |
20140036823 | Ma et al. | Feb 2014 | A1 |
Number | Date | Country |
---|---|---|
2002259221 | Nov 2002 | AU |
2690245 | Oct 2001 | CA |
2690247 | Oct 2001 | CA |
1086061 | Apr 1994 | CN |
1234661 | Nov 1999 | CN |
1298266 | Jun 2001 | CN |
1308794 | Aug 2001 | CN |
1314037 | Sep 2001 | CN |
1325198 | Dec 2001 | CN |
1325243 | Dec 2001 | CN |
1339885 | Mar 2002 | CN |
1347609 | May 2002 | CN |
1469662 | Jan 2004 | CN |
1489836 | Apr 2004 | CN |
1537371 | Oct 2004 | CN |
19951525 | Jun 2001 | DE |
0755090 | Jan 1997 | EP |
0762701 | Mar 1997 | EP |
0772329 | May 1997 | EP |
0805568 | Nov 1997 | EP |
0869647 | Oct 1998 | EP |
0895387 | Feb 1999 | EP |
0929172 | Jul 1999 | EP |
0951091 | Oct 1999 | EP |
0991221 | Apr 2000 | EP |
0993211 | Apr 2000 | EP |
1061446 | Dec 2000 | EP |
1075093 | Feb 2001 | EP |
1087545 | Mar 2001 | EP |
1117197 | Jul 2001 | EP |
1126673 | Aug 2001 | EP |
1133070 | Sep 2001 | EP |
1137217 | Sep 2001 | EP |
1143754 | Oct 2001 | EP |
1170879 | Jan 2002 | EP |
1175022 | Jan 2002 | EP |
1182799 | Feb 2002 | EP |
1185001 | Mar 2002 | EP |
1185015 | Mar 2002 | EP |
1185048 | Mar 2002 | EP |
1207635 | May 2002 | EP |
1207645 | May 2002 | EP |
1223702 | Jul 2002 | EP |
1241824 | Sep 2002 | EP |
1265411 | Dec 2002 | EP |
1315311 | May 2003 | EP |
1379020 | Jan 2004 | EP |
1387545 | Feb 2004 | EP |
1416688 | May 2004 | EP |
1447934 | Aug 2004 | EP |
1556984 | Jul 2005 | EP |
2300337 | Oct 1996 | GB |
2373973 | Oct 2002 | GB |
1132027 | May 1989 | JP |
03104430 | May 1991 | JP |
06003956 | Jan 1994 | JP |
6501139 | Jan 1994 | JP |
8274756 | Oct 1996 | JP |
9135230 | May 1997 | JP |
9266466 | Oct 1997 | JP |
9307526 | Nov 1997 | JP |
09327073 | Dec 1997 | JP |
9512156 | Dec 1997 | JP |
10028077 | Jan 1998 | JP |
10051402 | Feb 1998 | JP |
10084324 | Mar 1998 | JP |
10209956 | Aug 1998 | JP |
10303794 | Nov 1998 | JP |
10327126 | Dec 1998 | JP |
1141159 | Feb 1999 | JP |
11074863 | Mar 1999 | JP |
11163823 | Jun 1999 | JP |
11205273 | Jul 1999 | JP |
11252037 | Sep 1999 | JP |
11317723 | Nov 1999 | JP |
2991167 | Dec 1999 | JP |
2000068975 | Mar 2000 | JP |
2000078105 | Mar 2000 | JP |
2000092009 | Mar 2000 | JP |
2001044930 | Feb 2001 | JP |
200186045 | Mar 2001 | JP |
2001103034 | Apr 2001 | JP |
2001186051 | Jul 2001 | JP |
2001510668 | Jul 2001 | JP |
2001217896 | Aug 2001 | JP |
2001231074 | Aug 2001 | JP |
2001237751 | Aug 2001 | JP |
200264879 | Feb 2002 | JP |
2002504283 | Feb 2002 | JP |
200277098 | Mar 2002 | JP |
200277104 | Mar 2002 | JP |
2002111627 | Apr 2002 | JP |
2002118534 | Apr 2002 | JP |
2002510932 | Apr 2002 | JP |
2002514033 | May 2002 | JP |
2002164814 | Jun 2002 | JP |
2002176379 | Jun 2002 | JP |
2002204217 | Jul 2002 | JP |
2002232943 | Aug 2002 | JP |
2003504941 | Feb 2003 | JP |
2003198442 | Jul 2003 | JP |
2003530010 | Oct 2003 | JP |
2004266586 | Sep 2004 | JP |
2004297172 | Oct 2004 | JP |
2004535694 | Nov 2004 | JP |
2005519520 | Jun 2005 | JP |
2006504336 | Feb 2006 | JP |
2006504372 | Feb 2006 | JP |
4860925 | Nov 2011 | JP |
200011799 | Feb 2000 | KR |
20010098861 | Nov 2001 | KR |
1020020003370 | Jan 2002 | KR |
20030085040 | Nov 2003 | KR |
20060095576 | Aug 2006 | KR |
2015281 | Jun 1994 | RU |
2111619 | May 1998 | RU |
2134489 | Aug 1999 | RU |
2139633 | Oct 1999 | RU |
2141168 | Nov 1999 | RU |
2146418 | Mar 2000 | RU |
2149509 | May 2000 | RU |
2152132 | Jun 2000 | RU |
2157592 | Oct 2000 | RU |
2158479 | Oct 2000 | RU |
2168277 | May 2001 | RU |
2168278 | May 2001 | RU |
2197781 | Jan 2003 | RU |
2201034 | Mar 2003 | RU |
2335852 | Oct 2008 | RU |
419912 | Jan 2001 | TW |
496620 | Jul 2002 | TW |
503347 | Sep 2002 | TW |
200300636 | Jun 2003 | TW |
545006 | Aug 2003 | TW |
567689 | Dec 2003 | TW |
567701 | Dec 2003 | TW |
583842 | Apr 2004 | TW |
1230525 | Apr 2005 | TW |
I263449 | Oct 2006 | TW |
I267251 | Nov 2006 | TW |
8607223 | Dec 1986 | WO |
9210890 | Jun 1992 | WO |
9307684 | Apr 1993 | WO |
9507578 | Mar 1995 | WO |
WO-9516319 | Jun 1995 | WO |
9521501 | Aug 1995 | WO |
9530316 | Nov 1995 | WO |
9532567 | Nov 1995 | WO |
9622662 | Jul 1996 | WO |
9635268 | Nov 1996 | WO |
9702667 | Jan 1997 | WO |
9719525 | May 1997 | WO |
9736377 | Oct 1997 | WO |
9809381 | Mar 1998 | WO |
9809395 | Mar 1998 | WO |
9824192 | Jun 1998 | WO |
9826523 | Jun 1998 | WO |
9830047 | Jul 1998 | WO |
9857472 | Dec 1998 | WO |
9903224 | Jan 1999 | WO |
9914878 | Mar 1999 | WO |
9916214 | Apr 1999 | WO |
9929049 | Jun 1999 | WO |
9944379 | Sep 1999 | WO |
9952224 | Oct 1999 | WO |
9957820 | Nov 1999 | WO |
0011823 | Mar 2000 | WO |
0036764 | Jun 2000 | WO |
0062456 | Oct 2000 | WO |
0105067 | Jan 2001 | WO |
0126269 | Apr 2001 | WO |
0163775 | Aug 2001 | WO |
0169801 | Sep 2001 | WO |
0171928 | Sep 2001 | WO |
0176110 | Oct 2001 | WO |
0180510 | Oct 2001 | WO |
0182521 | Nov 2001 | WO |
0195531 | Dec 2001 | WO |
0197400 | Dec 2001 | WO |
0201732 | Jan 2002 | WO |
0203557 | Jan 2002 | WO |
WO-0205506 | Jan 2002 | WO |
0215433 | Feb 2002 | WO |
0225853 | Mar 2002 | WO |
02060138 | Aug 2002 | WO |
02062002 | Aug 2002 | WO |
02065664 | Aug 2002 | WO |
02069523 | Sep 2002 | WO |
02069590 | Sep 2002 | WO |
02073869 | Sep 2002 | WO |
02075955 | Sep 2002 | WO |
02078211 | Oct 2002 | WO |
02082689 | Oct 2002 | WO |
02088656 | Nov 2002 | WO |
02093784 | Nov 2002 | WO |
02099992 | Dec 2002 | WO |
03010984 | Feb 2003 | WO |
03010994 | Feb 2003 | WO |
03019984 | Mar 2003 | WO |
03028153 | Apr 2003 | WO |
03034646 | Apr 2003 | WO |
03047140 | Jun 2003 | WO |
03075479 | Sep 2003 | WO |
04002011 | Dec 2003 | WO |
04002047 | Dec 2003 | WO |
2004038985 | May 2004 | WO |
2004038986 | May 2004 | WO |
2004039011 | May 2004 | WO |
2004039022 | May 2004 | WO |
2005041515 | May 2005 | WO |
2005043855 | May 2005 | WO |
2005046113 | May 2005 | WO |
Entry |
---|
3 rd Generation Partnership Project (3GPP); Technical Specification Group (TSG); Radio Access Network (RAN); RF requirements f o r 1.28Mcps UTRA TDD option, 3GPP Standard; 3G TR 25.945, 3rd Generation Partnership Project (3GPP), Mobile Competence Centre ; 650, Route Des Lucioles ; F-06921 Sophia-Antipolis Cedex; France, No. V2.0.0, Dec. 20, 2000, pp. 1-144, XP050400193, [retreived on Dec. 20, 2000], p. 126. |
3GPP2 TIA/EIA/IS-2000.2-A, “Physical Layer Standard for cdma2000: Standards for Spread Spectrum Systems,” (Mar. 2000), Telecommunications Industry Association, pp. 1-446. |
3rd Generation Parthership Project ; Technical Specification Group Radio Access Network; Radio Resource Control (RRC); Protocol Specifiation (Release 5 ), 3GPP Standard; 3GPP TS 25.331, 3rd Generation Partnership Project (3GPP), Mobile Competence Centre ; 650, Route Des Lucioles ; F-06921 Sophia-Antipolis Cedex; France, No. V5.2.0, Sep. 1, 2002, pp. 1-938, XP050367950, pp. 124, 358-p. 370. |
“3rd Generation Partnership Project ; Technical Specification Group Radio Access 6-18, Network; Physical channels and mapping of 21-24 transport channels onto physical channels (TDD) (Release 5 )” , 3GPP Standard; 3GPP TS 25.221, 3rd Generation Partnership Project (3GPP), Mobile Competence Centre ; 650, Route Des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France, No. V5.2.0, Sep. 1, 2002, pp. 1-97, XP050366967. |
Alamouti, S.M., “A Simple Transmit Diversity Technique for Wireless Communications,” IEEE Journal on Select Areas in Communications, vol. 16, No. 8, Oct. 1998, pp. 1451-1458. |
Bingham J.A.C., “Multicarrier modulation for data transmission: An idea whose time has come,” Communications Magazine, , IEEE, vol. 28, Issue 5, pp. 5-14 (May 1990). |
Catreux S., et al., “Simulation results for an interference-limited multiple input multiple output cellular system”., Global Telecommmunications letters . IEEE: U.S.A. Nov. 2000. vol. 4(11), pp. 334-336. |
Chen, K.C. et al., “Novel Space-Time Processing of DS/CDMA Multipath Signal,” IEEE 49th, Vehicular Technology Conference, Houston, Texas, May 16-20, 1999, pp. 1809-1813. |
Choi, R. et al., “MIMO Transmit Optimization for Wireless Communication Systems,” Proceedings of the First IEEE International workshops on Electronic Design, pp. 1-6, Piscataway, New Jersey, Jan. 29-31, 2002. |
Chung, J. et al: “Multiple antenna systems for 802.16 systems.” IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/I6>, IEEE 802.16abc-01/31, Sep. 7, 2001, pp. 1-5. |
Coleri, S. et al: “Channel Estimation Techniques Based on Pilot Arrangement in OFDM Systems,” IEEE Transactions on Broadcasting, Sep. 1, 2002, pp. 223-229, vol. 48, No. 3, IEEE Service Center, XP011070267, ISSN: 0018-9316. |
Co-pending U.S. Appl. No. 07/624,118, filed Dec. 7, 1990. |
Co-pending U.S. Appl. No. 08/118,473, filed Sep. 8, 1993. |
Co-pending U.S. Appl. No. 60/421,309, filed Oct. 25, 2002. |
Co-pending U.S. Appl. No. 60/421,428, filed Oct. 25, 2002. |
Deneire, Luc, et al.: “A Low Complexity ML Channel Estimator for OFDM,” Proc IEEE ICC (Jun. 2001), pp. 1461-1465. |
Diggavi, S. et al., “Intercarrier interference in MIMO OFDM,” IEEE International Conference on Communications, (Aug. 2002), vol. 1, pp. 485-489, doi: 10.1109/ICC.2002.996901. |
Editor: 3GPP Draft; 3rd Generation Partnership Project (3GPP), Technical Specification Group (TSG) Radio Access Network (RAN); Working Group 4(WG4); base Station conformance and testing, TS 25.141 V0.1.1 (May 1999), R4-99349, Mobile Competence Centre; 650, Route Des Lucioles; F-06921 Sophia-Antipolis Cedex; France, vol. RAN WG4, no.Miami; Oct. 24, 2001, XP050166323. |
EPO Communication pursuant to Article 94(3) EPC issued by the European Patent Orifice for Application No. 10174926.5 dated Aug. 1, 2013 (for counterpart docket No. 020554EPD3D1). |
EPO Communication pursuant to Article 94(3) EPC issued by the European Patent Orifice for Application No. 10174932.3 dated Jul. 30, 2013 (for counterpart docket No. 020554EPD3D2). |
ETSI TS 101 761-1 v1.3.1, “Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part 1: Basic Data Transport Functions,” ETSI Standards, European Telecommunications Standards Institute BR (V131), pp. 1-88 (Dec. 2001). |
European Search Report—EP11173875—Search Authority—Hague—Oct. 25, 2011. |
Fujii, M.: “Pseudo-Orthogonal Multibeam-Time Transmit Diversity for OFDM-CDMA” pp. 222-226 (2002). |
G. Bauch, J. Hagenauer, “Smart Versus Dumb Antennas—Capacities and FEC Performance,” IEEE Communications Letters, vol. 6, No. 2, pp. 55-57, Feb. 2002. |
Gao, J. et al. “On implementation of Bit-Loading Algorithms for OFDM Systems with Multiple-Input Multiple Output,” VTC 2002-Fall. 2002 IEEE 56th. Vehicular Technology Conference Proceedings. Vancouver, Canada, (Sep. 24-28, 2002), IEEE Vehicular Technology Conference, pp. 199-203. |
Gore, D. A., et al.: “Selecting an optimal set of transmit antennas for a low rank matrix channel,” 2000 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings. (ICASSP). Istanbul, Turkey, Jun. 5-9, 2000, New York, NY; IEEE, US, vol. 5 of 6, (Jun. 5, 2000), pp. 2785-2788, XP001035763, abstract. |
Grunheid, R. et al., “Adaptive Modulation and Multiple Access for the OFDM Transmission Technique,” Wireless Personal Communications 13: May 13, 2000, 2000 Kluwer Academic Publishers, pp. 4-13, XP000894156. |
Harada H., et al., “An OFDM-Based Wireless ATM Transmission System Assisted by a Cyclically ExtendedPN Sequence for Future Broad-BandMobile Multimedia Communications”, IEEE Transactions on Vehicular Technology, IEEE Service Center, Piscataway, NJ, US, vol. 50, No. 6, Nov. 1, 2001, XP011064321, ISSN: 0018-9545. |
Hassibi, B. et al., “High Rate Codes That Are Linear in Space and Time,” Lucent Technologies, 2002, pp. 1-55. |
Haustein, T. et al.: “Performance of MIMO Systems with Channel Inversion,” IEEE 55th Vehicular Technology Conference, Birmingham, Alabama, May 6-9, 2002, pp. 35-39. |
Hayashi, K. et al.: “A New Spatio-Temporal Equalization Method Based on Estimated Channel Response,” Sep. 2001, IEEE Transactions on Vehicular Technology, vol. 50, No. 5, pp. 1250-1259. |
Heath et al., “Multiuser diversity for MIMO wireless systems with linear receivers”, Conference Record of the 35th Asilomar Conference on Signals, Systems, & Computers, Nov. 4, 2001, pp. 1194-1199, vol. 2, IEEE, XP010582229, DOI: 10.1109/ACSSC.2001.987680, ISBN: 978-0-7803-7147-7. |
Hong, D. K. et al.: “Robust Frequency Offset Estimation for Pilot Symbol Assisted Packet CDMA with MIMO Antenna Systems,” IEEE Communications Letters, vol. 6, No. 6, pp. 262-264, XP-001133262 (Jun. 2002). |
IEEE Std 802.11a-1999 (Supplement to IEEE Std 801.11-1999) “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-Speed physical Layer in the 5GHZ Band”, pp. 1-90, Sep. 1999. |
International Search Report PCT Application No. PCT-US03-033907, International Search Authority, European Patent Office, filed on Aug. 23, 2004. |
Iserte, P., et al., “Joint beamforming strategies in OFDM-MIMO systems,” Acoustics, Speech, and Signal Processing, 1993. ICASSP-93., 1993 IEEE International Conference on , vol. 3, sections 2-3, Apr. 27-30, 1993, doi: 10.1109/ICASSP.2002.1005279. |
Joham, M. et al.: “Symbol Rate Processing for the Downlink of DS-CDMA Systems”, IEEE Journal on Selected Areas in Communications, vol. 19, No. 1, paragraphs 1, 2; IEEE Service Center, Piscataway, US, (Jan. 1, 2001), XP011055296, ISSN: 0733-8716. |
Jongren, G. et al.: “Utilizing Quantized Feedback Information in Orthogonal Space-Time Block Coding,” 2000 IEEE Global Telecommunications Conference, 2(4): 995-999, Nov. 27, 2000. |
Kiessling, M. et al., “Short-term and long-term diagonalization of correlated MIMO channels with adaptive modulation” IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, vol. 2, Sep. 15, 2002, pp. 593-597. |
Kousa M, et al., “Multichannel adaptive forward error-correction system”, IEEE Proceedings I. Solid-State & Electron Devices, Institution of Electrical Engineers. Stevenage, GB, vol. 140, No. 5, Part 1, Oct. 1, 1993, pp. 357-364, XP000403498, ISSN: 0956-3776. |
Lal D et al: “A novel MAC layer protocol for space division multiple access in wireless ad hoc networks”, Computer Communications and Networks, 2002 Proceedings, Eleventh International Conference on Oct. 14, 2002, pp. 614-619. |
Le Goff, S. et al: “Turbo-codes and high spectral efficiency modulation,” IEEE International Conference on Communications, 1994. ICC ″94, SUPERCOMM/ICC ″94, Conference Record, ‘Serving Humanity Through Communications.’ pp. 645-649, vol. 2, May 1-5, 1994, XP010126658, doi: 10.1109/ICC.1994.368804. |
Lebrun G., et al., “MIMO transmission over a time varying TDD channel using SVD,” Electronics Letters, 2001, vol. 37, pp. 1363-1364. |
Li, Lihua, et al., “A practical space-frequency block coded OFDM scheme for fast fading broadband channels,” 2002. The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio communications, vol. 1, Sep. 15-18, 2002.pp. 212-216 vol. 1. |
Li, Ye et. al., “Simplified Channel Estimation for OFDM Systems with Multiple Transmit Antennas,” IEEE Transactions on Wireless Communications, Jan. 2002, vol. 1, No. 1, pp. 67-75. |
Louvigne J.C., et al., “Experimental study of a real-time calibration procedure of a CDMA/TDD multiple antenna terminal,” IEEE Antennas and Propagation Society International Symposium, 2002 Digest.APS.San Antonio, TX, Jun. 16-21, 2002,vol. 2, Jun. 16, 2002, pp. 644-647, XP010591780, DOI: 10.1109/APS.2002.1016729, ISBN: 978-0-7803-7330-3. |
Miyashita, K. et al: “High data-rate transmission with eigenbeam-space division multiplexing (E-SDM) in a MIMO channel,” VTC 2002-Fall. 2002 IEEE 56th. Vehicular Technology Conference Proceedings. Vancouver, Canada, Sep. 24-28, 2002, IEEE Vehicular Technology Conference, New York, NY: IEEE, US, vol. vol. 1 of 4. Conf. 56, (Sep. 24, 2002), pp. 1302-1306, XP010608639. |
Nogueroles R., et al., “Performance of a random OFDMA system for mobile communications”, Broadband Communications, 1998. Accessing, Transmission, Networking. Proceedings. 1998 International Zurich Seminar on Zurich, Switzerland Feb. 17-19, 1998, New York , NY, USA , IEEE, US, Feb. 17, 1998, pp. 37-43, XP010277032 , DOI : 10.1109/IZSBC.1998.670242 ISBN: 978-0-7803-3893-7, p. 1-p. 2. |
Partial European Search Report —EP11173875—Search Authority—Hague—Aug. 18, 2011. |
Pautler, J. et al.: “On Application of Multiple-Input Multiple-Output Antennas to CDMA Cellular Systems,” IEEE 54th Vehicular Technology Conference Proceedings, Atlantic City, New Jersey, Oct. 7-11, 2001, pp. 1508-1512. |
Sakaguchi et al, “Comprehensive Calibration for MIMO System”, International Symposium on Wireless Personal Multimedia Communications, IEEE, vol. 2, Oct. 27, 2002, pp. 440-443. |
Sampath et al., “A Fourth-Generation MIMO-OFDM Broadband Wireless System: Design, Performance and Field Trial Results”, IEEE Communications Magazine, Sep. 1, 2002, pp. 143-149, vol. 40, No. 9, IEEE Service Center, XP011092922, ISSN: 0163-6804, DOI: 10.1109/MCOM.2002.1031841. |
Sampath, H., et al., “Joint transmit and receive optimization for high data rate wireless communication using multiple antennas,” Signals, Systems, and Computers, 1999. Conference Record of the Thirty-Third Asilomar Conference, Oct. 24, 1999, XP010373976, pp. 215-219, IEEE, Piscataway, NJ, US. |
Song, Bong-Gee et al., “Prefilter design using the singular value decomposition for MIMO equalization,” 1996 Conference Record of the Thirtieth Asilomar Conference on Signals, Systems and Computers, vol. 1, pp. 34-38, Nov. 3-6, 1996, XP010231388, DOI : 10.1109/ACSSC.1996.600812, p. 35, col. 2, paragraph 4 through p. 36, col. 1. |
Taiwanese Search Report for Application No. 092129820 TIPO filed on Apr. 16, 2014. |
Tarighat, a. et al. “Performance Analysis of Different Algorithms for cdma2000 Antenna Array System and a New Multi User Beamforming (MUB) Algorithm”, Wireless Communications and Networking Conference, vol. 1, pp. 409-414, Sep. 23, 2000. |
Technical Search Report issued by the Taiwan Patent Office for TW Application No. 098143050, dated Aug. 2, 2013. |
The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, IEEE Press: New York (Dec. 2000), p. 902. |
Theon, S. et al.: “Improved Adaptive Downlink for OFDM/SDMA-Based Wireless Networks,” IEEE VTS 53rd Vehicular Technology Conference, pp. 707-711, Rhodes, Greece, May 6-9, 2001. |
Tujkovic, D.: “High bandwidth efficiency space-time turbo coded modulation”, Institute of Electrical and Electronics Engineers, ICC 2001. 2001 IEEE International Conference on Communications, Conference Record, pp. 1104-1109, Helsinki, Finland, Jun. 11-14, 2001. |
Van Zelst, A. et al.: “Space Division Multiplexing (SDM) for OFDM Systems,” IEEE 51st Vehicular Technology Conference Proceedings, pp. 1070-1074, Tokyo, Japan, May 15-18, 2000. |
Varanasi M.K, et al., “Optimum decision feedback multiuser equalization with successive decoding achieves the total capacity of the Gaussian multiple-access channel”, Signals, Systems & Computers, 1997. Conference Record of the Thirty-First Asilomar Conference on Pacific Grove, CA, USA Nov. 2-5, 1997, Los Alamitos, CA, USA,IEEE Comput. Soc, US, vol. 2, Nov. 2, 1997, pp. 1405-1409 , XP010280667, DOI: 10.1109/ACSSC.1997 . 679134 ISBN : 978-0-8186-8316-9 * pp. 1,3,5; figures 1,3 *. |
Vook, F. W. et al., “Adaptive antennas for OFDM”, Vehicular Technology Conference, vol. 1, May 18-21, 1998, pp. 606-610, XP010287858, New York, NY, USA, IEEE, US DOI: 10.1109/VETEC.1998.686646 ISBN: 978-0-7803-4320-7. |
Wales, S.W. “A mimo technique within the UTRA TDD standard,” MIMO: Communications Systems from Concept to Implementations (Ref. No. 2001/175), IEE Seminar on, (Dec. 12, 2001), pp. 1-8., London, UK. |
Warner, W. et al.: “OFDM/FM Frame Synchronization for Mobile Radio Data Communication”, IEEE Transactions on Vehicular Technology, Aug. 1993, vol. 42, No. 3, pp. 302-313. |
Wolniansky P.W., et al., “V-BLAST: An architecture for realizing very high data rates over the rich-scattering wireless channel,” Signals, Systems, and Electronics, 1998. ISSE 98. 1998 URSI International Symposium, pp. 295-300, (Sep. 29-Oct. 2, 1998), doi: 10.1109/ISSSE.1998.738086. |
Wong, et al., “Multiuser OFDM With Adaptive Subcarrier, Bit, and Power Allocation,” Oct. 1999, IEEE Journal on Selected Areas in Communications, vol. 17, No. 10, pp. 1747-1758. |
Wong K. K., et al., “Optimizing time and space MIMO antenna system for frequency selective fading channels,” IEEE Journal on Selected Areas in Communications, vol. 19, No. 7, Jul. 2001, Sections II and III and V, 1396, pp. 1395-1407. |
Wyglinski, Alexander. “Physical Layer Loading Algorithms for Indoor Wireless Multicarrier Systems,” Thesis Paper, McGill University, Montreal, Canada, Nov. 2004, p. 109. |
Yamamura, T et al., “High Mobility OFDM transmission system by a new channel estimation and ISI cancellation scheme using characteristics of pilot symbol inserted OFDM signal”., Vehicular Technology Conference, vol. 1, Sep. 19, 1999-Sep. 22, 1999, pp. 319323, XP010352958 IEEE, Piscataway, NJ, USA, ISBN: 0-7803-5435-4. |
Yoshiki, T., et al., “A Study on Subcarrier Adaptive Demodulation System using Multilevel Transmission Power Control for OFDM/FDD System,” The Institute of Electronics, Information and Communications Engineers general meeting, lecture collection, Japan, Mar. 7, 2000, Communication 1, p. 400. |
Number | Date | Country | |
---|---|---|---|
20130279614 A1 | Oct 2013 | US |
Number | Date | Country | |
---|---|---|---|
60421309 | Oct 2002 | US | |
60438601 | Jan 2003 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 10375162 | Feb 2003 | US |
Child | 13920971 | US |