This invention generally relates to wireless cellular communication, and in particular to encoding a reference signal in orthogonal frequency division multiple access (OFDMA), DFT-spread OFDMA, and single carrier frequency division multiple access (SC-FDMA) systems.
Wireless cellular communication networks incorporate a number of mobile UEs and a number of NodeBs. A NodeB is generally a fixed station, and may also be called a base transceiver system (BTS), an access point (AP), a base station (BS), or some other equivalent terminology. As improvements of networks are made, the NodeB functionality evolves, so a NodeB is sometimes also referred to as an evolved NodeB (eNB). In general, NodeB hardware, when deployed, is fixed and stationary, while the UE hardware is portable.
In contrast to NodeB, the mobile UE can comprise portable hardware. User equipment (UE), also commonly referred to as a terminal or a mobile station, may be fixed or mobile device and may be a wireless device, a cellular phone, a personal digital assistant (PDA), a wireless modem card, and so on. Uplink communication (UL) refers to a communication from the mobile UE to the NodeB, whereas downlink (DL) refers to communication from the NodeB to the mobile UE. Each NodeB contains radio frequency transmitter(s) and the receiver(s) used to communicate directly with the mobiles, which move freely around it. Similarly, each mobile UE contains radio frequency transmitter(s) and the receiver(s) used to communicate directly with the NodeB. In cellular networks, the mobiles cannot communicate directly with each other but have to communicate with the NodeB.
Control information bits are transmitted, for example, in the uplink (UL), for several purposes. For instance, Downlink Hybrid Automatic Repeat ReQuest (HARQ) requires at least one bit of ACK/NACK transmitted in the uplink, indicating successful or failed circular redundancy check(s) (CRC). Moreover, a one bit scheduling request indicator (SRI) is transmitted in uplink, when UE has new data arrival for transmission in uplink. Furthermore, an indicator of downlink channel quality (CQI) needs to be transmitted in the uplink to support mobile UE scheduling in the downlink. While CQI may be transmitted based on a periodic or triggered mechanism, the ACK/NACK needs to be transmitted in a timely manner to support the HARQ operation. Note that ACK/NACK is sometimes denoted as ACKNAK or just simply ACK, or any other equivalent term. As seen from this example, some elements of the control information should be provided additional protection, when compared with other information. For instance, the ACK/NACK information is typically required to be highly reliable in order to support an appropriate and accurate HARQ operation. This uplink control information is typically transmitted using the physical uplink control channel (PUCCH), as defined by the 3GPP working groups (WG), for evolved universal terrestrial radio access (EUTRA). The EUTRA is sometimes also referred to as 3GPP long-term evolution (3GPP LTE). The structure of the PUCCH is designed to provide sufficiently high transmission reliability.
In addition to PUCCH, the EUTRA standard also defines a physical uplink shared channel (PUSCH), intended for transmission of uplink user data. The Physical Uplink Shared Channel (PUSCH) can be dynamically scheduled. This means that time-frequency resources of PUSCH are re-allocated every sub-frame. This (re)allocation is communicated to the mobile UE using the Physical Downlink Control Channel (PDCCH). Alternatively, resources of the PUSCH can be allocated semi-statically, via the mechanism of persistent scheduling. Thus, any given time-frequency PUSCH resource can possibly be used by any mobile UE, depending on the scheduler allocation. Physical Uplink Control Channel (PUCCH) is different than the PUSCH, and the PUCCH is used for transmission of uplink control information (UCI). Frequency resources which are allocated for PUCCH are found at the two extreme edges of the uplink frequency spectrum. In contrast, frequency resources which are used for PUSCH are in between. Since PUSCH is designed for transmission of user data, re-transmissions are possible, and PUSCH is expected to be generally scheduled with less stand-alone sub-frame reliability than PUCCH. The general operations of the physical channels are described in the EUTRA specifications, for example: “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8).”
A reference signal (RS) is a pre-defined signal, pre-known to both transmitter and receiver. The RS can generally be thought of as deterministic from the perspective of both transmitter and receiver. The RS is typically transmitted in order for the receiver to estimate the signal propagation medium. This process is also known as “channel estimation.” Thus, an RS can be transmitted to facilitate channel estimation. Upon deriving channel estimates, these estimates are used for demodulation of transmitted information. This type of RS is sometimes referred to as De-Modulation RS or DM RS. Note that RS can also be transmitted for other purposes, such as channel sounding (SRS), synchronization, or any other purpose. Also note that Reference Signal (RS) can be sometimes called the pilot signal, or the training signal, or any other equivalent term.
Particular embodiments in accordance with the invention will now be described, by way of example only, and with reference to the accompanying drawings:
A UE in a cell may be stationary such as within a home or office, or may be moving while a user is walking or riding in a vehicle. UE 109 moves within cell 108 with a velocity 112 relative to base station 102.
Channel quality indicator (CQI) needs to be fed back in uplink (UL) to support dynamic scheduling and multiple-input-multiple-output (MIMO) transmission on downlink (DL). In 3GPP EUTRA, if a UE (user equipment) has no uplink data transmission, its CQI is transmitted on a dedicated UL control channel (i.e. PUCCH). Given that the ACK/NACK needs to be transmitted in a timely manner to support the HARQ operation, in one embodiment of the invention ACKNK may be embedded in one or more of the RS symbols of a CQI transmission.
The ACKNAK response 706 is firstly mapped 708 to a constellation point, e.g. according to a quadrature amplitude modulation mapping scheme. The constellation point mapped from the ACKNAK response is transmitted in the second RS symbol 703b by modulating/multiplying the reference signal with the constellation point. A pre-defined reference signal 710 is transmitted in the first RS symbol 703a. It is not precluded that a transmission signal can comprise more than two RS symbols, where the ACKNAK response is transmitted in a subset of the RS symbols and pre-defined reference signals are transmitted in the rest RS symbols. The pre-defined reference signal transmitted in each RS symbol can be the same. Alternatively, the pre-defined reference signals can be different in different RS symbols, provided these pre-defined reference signals are known to both the transmitter and the receiver.
In some embodiments of the invention, said ACKNAK information element is produced by receiving a data packet, followed by performing error detection or error checking on the received data packet. In some embodiments of the invention, the error checking is achieved using a circular redundancy check (CRC), where the CRC can “pass” or “fail.” If a CRC “fails” an error detection is declared, whereas if the CRC “passes” a transmission success is declared. If an error is detected, a NAK is transmitted as a specific realization of ACKNAK information element, whereas if no error is detected, an ACK is transmitted as another specific realization of the ACKNAK information element.
The ACK/NAK response is firstly mapped 808 to a constellation point, e.g. according to a quadrature amplitude modulation mapping scheme. The constellation point mapped from the ACKNAK response is used to form an OFDM signal 832, which is transmitted in the second RS symbol 803b. A pre-defined signal 810 is used to form a pre-defined OFDM reference signal 831, which is transmitted in the first RS symbol 803a. It is not precluded that a transmission signal can comprise more than two OFDM RS symbols, where the ACKNAK response is transmitted in a subset of the RS symbols and pre-defined OFDM reference signals are transmitted in the rest RS symbols. The pre-defined OFDM reference signal transmitted in each RS symbol can be the same. Alternatively, the pre-defined OFDM reference signals can be different in different RS symbols, provided these pre-defined OFDM reference signals are known to both the transmitter and the receiver.
The ACK/NAK response 906 is mapped 908 to a QAM constellation point d2(0). A second sequence is generated and used to form an OFDM signal. The transmission signal in the second RS symbol 903b is the product of the OFDM modulated second sequence 934b and the constellation point mapped from the ACKNAK response, i.e. d2(0). The multiplication 942 of the OFDM modulated second sequence and the ACKNAK constellation d2(0) is performed such that the entire OFDM modulated second sequence is multiplied with d2(0). A second sequence 934a is generated and used to form a pre-defined OFDM signal, which is transmitted in the first RS symbol 903a. Note that the second sequence in different RS symbols can be different, provided these second sequences are known to both the transmitter and the receiver.
In one embodiment of the invention, the first type of information is a channel quality indicator and the second type of information is a 1-bit ACK/NAK response. The CQI is mapped to a multiple of QAM constellation points, each of which is transmitted in one data OFDM symbol. The 1-bit ACKNAK response is mapped according to a binary phase shift keyed (BPSK) constellation mapping scheme. The generated ACKNAK BPSK constellation is transmitted in one of the RS symbols, as described in more detail with respect to
In another embodiment of the invention, the first type of information is a CQI and the second type of information is a 2-bit ACK/NAK response. The CQI is mapped to a multiple of QAM constellation points, each of which is transmitted in one data OFDM symbol. The 2-bit ACKNAK response is mapped according to a quadrature phase shift keyed (QPSK) constellation mapping scheme. The generated ACKNAK QPSK constellation is transmitted in one of the RS symbols, as described in more detail with respect to
One embodiment of the user signal [ck(0) . . . ck(L-1)] 1050, 1150 in
u,v(n)=ejφ(n)π/4, 0≦n≦MscRS−1
where MscRS=12 and φ(n) is defined in Table 1.
In this disclosure, the cyclically shifted or phase ramped CAZAC-like sequence is sometimes denoted as cyclic shifted base sequence, cyclic shifted root sequence, phase ramped base sequence, phase ramped root sequence, or any other equivalent term.
The first sequence in different data symbols in
The second sequence in different RS symbols in
In 3GPP EUTRA UL, single carrier OFDMA (SC-OFDMA) is adopted as the transmission scheme due to its low peak-to-average ratio (PAR) or cubic metric (CM) property. In the context of CQI transmission on PUCCH, SC-OFDMA essentially means a UE can only transmit on one cyclic shift at each OFDM symbol to keep the PAR/CM low. For example, in
The CQI data symbols convey the (coded) CQI information bits by modulating the cyclic shifted (UE specific) CAZAC sequence with QAM constellation points mapped from the (coded) CQI information bits. Therefore, ten (coded) CQI bits can be transmitted with QPSK in one slot per UE, using the four point constellation as shown in
ACK/NAK in UL is a 1-bit control response to each DL packet to support hybrid ARQ (HARQ) retransmission. Depending on the number of packets transmitted within one DL subframe, multiple ACK/NAK bits may need to be transmitted by a UE. For example, with multiple-input-multiple-output (MIMO) technology, a UE can be scheduled with simultaneous transmission of two packets within one subframe. Thus, an ACKNAK response of two ACK/NAK bits is needed. In one embodiment of the invention, it is assumed the number of ACK/NAK bits per UE per subframe is either one or two. However, in other embodiments larger numbers of ACK/NAK bits may be accommodated by increasing the QAM modulation order.
The ACKNAK response is mapped to a QAM constellation point, which is transmitted in the second RS symbol in each slot, as shown in
Depending on the ACK/NAK information bits and the number of ACKNAK bits, a certain QAM symbol (BPSK for one ACK/NAK bit and QPSK for two ACKNAK bits) can be obtained to modulate/multiply the cyclic shifted CAZAC sequence in the second CQI RS of a slot.
If a UE has not received a DL packet that requires an ACKNAK response and therefore only CQI to transmit, then in the second CQI RS, it may modulate/multiply the second CQI RS with the “NAK, NAK” or “NAK” QAM symbol. It is beneficial to map the 2-bit “NAK, NAK” response and 1-bit “NAK” response onto the same QAM symbol, in case a DL grant is missed by the UE. For example, the 1-bit “NAK” constellation point in
The Node-B can have prior knowledge on whether ACKNAK bits are expected in the second CQI RS or not. If the Node-B knows there are no ACK/NAK bits in the second CQI RS, then it demodulates the second CQI RS by the “NAK, NAK” or “NAK” QAM symbol to provide channel estimation for coherent demodulation of the CQI data symbols. If the Node-B expects ACKNAK bits in the second CQI RS, then it decodes the QAM symbol carried in the second CQI RS with the channel estimation obtained from the first CQI RS. Further, after ACKNAK demodulation and decoding on the second CQI RS, the second RS can also serve as a channel estimate for CQI data symbols. In another embodiment, a joint ACKNAK and CQI decoding can be performed.
Further, in case there are more than two ACKNAK bits or some additional UL control signaling bits (e.g. UL scheduling request) to be transmitted together with CQI, a higher order QAM modulation can be used in the second CQI RS symbol to convey the multiple UL control signaling bits.
ACK/NAK DTX (discontinuous transmission) refers to the scenario where the UE misses the DL grant and thus does not receive any packet and transmits no ACK/NAK bit in UL. However, the NodeB expects ACK/NAK from the UE. Moreover, the NodeB needs to detect ACK/NAK DTX for proper HARQ operations. Referring again to
For two ACK/NAK bits, there are five hypotheses to detect in the receiver side (NodeB), i.e. [DTX], [ACK, ACK], [ACK, NAK], [NAK, ACK], and [NAK, NAK]. For one ACK/NAK bit, there are three hypotheses to detect, i.e. [DTX], [ACK], and [NAK].
Table 1 shows an example of the proposed modulation scheme for two ACK/NAK bits with DTX detection. The symbols in Table 1 represent the QPSK symbols, which modulate/multiply the cyclic shifted CAZAC-like sequence in either slot 0 or slot 1. The design principles are:
For DTX, the same QPSK symbol is transmitted in both slots of a subframe;
For the four possibilities of two ACK/NAK bits, i.e. [NAK, NAK], [NAK, ACK], [ACK, ACK], and [ACK, NAK], the QPSK symbol transmitted in the second slot is the negative of the QPSK symbol transmitted in the first slot.
Tables 2-4 list other possible modulation schemes for two ACK/NAK bits with DTX detection. Note any common phase rotation can be applied to the proposed modulation (or all QPSK symbols) in Tables 1-4. Alternatively, Tables 5-8 list modulation schemes for two ACK/NAK bits with DTX detection.
Moreover, it is possible to design a 5-PSK modulation scheme for two ACK/NAK bits with DTX detection. The 5 PSK symbols are shown in
For one ACK/NAK bit, Tables 12-16 show possible modulation schemes with the same design principle as discussed above.
It is important to keep the same DTX symbols for one and two ACK/NAK bits. In various embodiments, any common phase rotation can be applied to the example modulation (or all QPSK symbols) in Tables 12-16.
Alternatively, for one ACK/NAK bit with DTX detection, the mapping scheme in Tables 17-20 are also applicable, where the symbols W1, W2, and W3 are shown in
For ACK/NAK signaling in CQI RS, it is possible to treat DTX as (NAK) or (NAK, NAK). Thus, in another embodiment, BPSK and QPSK modulation can be utilized for one and two ACK/NAK bits, respectively. Again, it is important that the DTX symbol is the same for one and two ACK/NAK bits. Thus, the mapping illustrated in Tables 21 and 22, or Tables 23 and 24, may be used where DTX is treated the same as (NAK) or (NAK, NAK).
Any rotations to the symbols (or subset of the symbols) in Tables 21-24 are applicable, as long as the DTX symbol remains the same for the one and two ACK/NAK bits.
As shown, the mobile UE device 1901 comprises a processor 1903 coupled to a memory 1907 and a Transceiver 1904. The memory 1907 stores (software) applications 1905 for execution by the processor 1903. The applications 1905 could comprise any known or future application useful for individuals or organizations. As an example, such applications 1905 could be categorized as operating systems (OS), device drivers, databases, multimedia tools, presentation tools, Internet browsers, e-mailers, Voice-Over-Internet Protocol (VOIP) tools, file browsers, firewalls, instant messaging, finance tools, games, word processors or other categories. Regardless of the exact nature of the applications 1905, at least some of the applications 1905 may direct the mobile UE device 1901 to transmit UL signals to the eNB (base-station) 1902 periodically or continuously via the transceiver 1904. In at least some embodiments, the mobile UE device 1901 identifies a Quality of Service (QoS) requirement when requesting an uplink resource from the eNB 1902. In some cases, the QoS requirement may be implicitly derived by the eNB 1902 from the type of traffic supported by the mobile UE device 1901. As an example, VOIP and gaming applications often involve low-latency uplink (UL) transmissions while High Throughput (HTP)/Hypertext Transmission Protocol (HTTP) traffic can involve high-latency uplink transmissions.
Transceiver 1904 includes uplink logic which may be implemented by execution of instructions that control the operation of the transceiver. Some of these instructions may be stored in memory 1907 and executed when needed. As would be understood by one of skill in the art, the components of the Uplink Logic may involve the physical (PHY) layer and/or the Media Access Control (MAC) layer of the transceiver 1904. Transceiver 1904 includes one or more receivers 1920 and one or more transmitters 1922. The transmitter(s) may be embodied as described with respect to
The ACKNAK response is firstly mapped to a constellation point, e.g. according to a quadrature amplitude modulation mapping scheme. The constellation point mapped from the ACKNAK response is transmitted in the second RS symbol by modulating/multiplying the reference signal with the constellation point. A pre-defined reference signal is transmitted in the first RS symbol. It is not precluded that a transmission signal can comprise more than two RS symbols, where the ACKNAK response is transmitted in a subset of the RS symbols and pre-defined reference signals are transmitted in the rest RS symbols. The pre-defined reference signal transmitted in each RS symbol can be the same. Alternatively, the pre-defined reference signals can be different in different RS symbols, provided these pre-defined reference signals are known to both the transmitter and the receiver.
As shown in
Transceiver 1910 comprises an uplink Resource Manager 1912, which enables the eNB 1902 to selectively allocate uplink PUSCH resources to the user device 1901. As would be understood by one of skill in the art, the components of the uplink resource manager 1912 may involve the physical (PHY) layer and/or the Media Access Control (MAC) layer of the transceiver 1910. Transceiver 1910 includes a Receiver 1911 for receiving transmissions from various UE within range of the eNB and transmitters for transmitting data and control information to the various UE within range of the eNB.
Uplink resource manager 1912 executes instructions that control the operation of transceiver 1910. Some of these instructions may be located in memory 1913 and executed when needed. Resource manager 1912 controls the transmission resources allocated to each UE that is being served by eNB 1902 and broadcasts control information via the physical downlink control channel PDCCH. In particular, for the transmission of ACK/NAK, eNB 1902 arranges the cyclic shifted base sequences in the time-frequency resource, as described above. The Node-B can have prior knowledge on whether ACKNAK bits are expected in the second CQI RS or not. If the Node-B knows there are no ACK/NAK bits in the second CQI RS, then it demodulates the second CQI RS by the “NAK, NAK” or “NAK” QAM symbol to provide channel estimation for coherent demodulation of the CQI data symbols. If the Node-B expects ACKNAK bits in the second CQI RS, then it decodes the QAM symbol carried in the second CQI RS with the channel estimation obtained from the first CQI RS. Further, after ACKNAK demodulation and decoding on the second CQI RS, the second RS can also serve as a channel estimate for CQI data symbols, as described in more detail above.
RF transceiver 1006 includes a receiver for receiving a stream of coded data frames and commands from a cellular base station via antenna 1007 and a transmitter for transmitting a stream of coded data frames to the cellular base station via antenna 1007. Transmission of the PUSCH data is performed by the transceiver using the PUSCH resources designated by the serving eNB. In some embodiments, frequency hopping may be implied by using two or more bands as commanded by the serving eNB. In this embodiment, a single transceiver can support multi-standard operation (such as EUTRA and other standards) but other embodiments may use multiple transceivers for different transmission standards. Other embodiments may have transceivers for a later developed transmission standard with appropriate configuration. RF transceiver 1006 is connected to DBB 1002 which provides processing of the frames of encoded data being received and transmitted by the mobile UE unite 1000.
The EUTRA defines SC-FDMA (via DFT-spread OFDMA) as the uplink modulation. The basic SC-FDMA DSP radio can include discrete Fourier transform (DFT), resource (i.e. tone) mapping, and IFFT (fast implementation of IDFT) to form a data stream for transmission. To receive the data stream from the received signal, the SC-FDMA radio can include DFT, resource de-mapping and IFFT. The operations of DFT, IFFT and resource mapping/de-mapping may be performed by instructions stored in memory 1012 and executed by DBB 1002 in response to signals received by transceiver 1006.
For ACK/NAK transmission, a transmitter(s) within transceiver 1006 may be embodied as described with respect to
The ACKNAK response is firstly mapped to a constellation point, e.g. according to a quadrature amplitude modulation mapping scheme. The constellation point mapped from the ACKNAK response is transmitted in the second RS symbol by modulating/multiplying the reference signal with the constellation point. A pre-defined reference signal is transmitted in the first RS symbol. It is not precluded that a transmission signal can comprise more than two RS symbols, where the ACKNAK response is transmitted in a subset of the RS symbols and pre-defined reference signals are transmitted in the rest RS symbols. The pre-defined reference signal transmitted in each RS symbol can be the same. Alternatively, the pre-defined reference signals can be different in different RS symbols, provided these pre-defined reference signals are known to both the transmitter and the receiver.
DBB unit 1002 may send or receive data to various devices connected to universal serial bus (USB) port 1026. DBB 1002 can be connected to subscriber identity module (SIM) card 1010 and stores and retrieves information used for making calls via the cellular system. DBB 1002 can also connected to memory 1012 that augments the onboard memory and is used for various processing needs. DBB 1002 can be connected to Bluetooth baseband unit 1030 for wireless connection to a microphone 1032a and headset 1032b for sending and receiving voice data. DBB 1002 can also be connected to display 1020 and can send information to it for interaction with a user of the mobile UE 1000 during a call process. Display 1020 may also display pictures received from the network, from a local camera 1026, or from other sources such as USB 1026. DBB 1002 may also send a video stream to display 1020 that is received from various sources such as the cellular network via RF transceiver 1006 or camera 1026. DBB 1002 may also send a video stream to an external video display unit via encoder 1022 over composite output terminal 1024. Encoder unit 1022 can provide encoding according to PAL/SECAM/NTSC video standards.
As used herein, the terms “applied,” “coupled,” “connected,” and “connection” mean electrically connected, including where additional elements may be in the electrical connection path. “Associated” means a controlling relationship, such as a memory resource that is controlled by an associated port. While the invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various other embodiments of the invention will be apparent to persons skilled in the art upon reference to this description. For example, a larger or smaller number of symbols then described herein may be used in a slot.
It is therefore contemplated that the appended claims will cover any such modifications of the embodiments as fall within the true scope and spirit of the invention.
This application for Patent claims priority to U.S. application Ser. No. 12/183,242 entitled “Transmission of ACK/NACK Bits and their Embedding in the CQI Reference Signal” filed Jul. 31, 2008, incorporated by reference herein. This application for Patent claims priority to U.S. Provisional Application No. 60/954,355 entitled “Embedding ACK/NAK Bits in CQI Reference Signals” filed Aug. 7, 2007, incorporated by reference herein. This application for Patent claims priority to U.S. Provisional Application No. 60/976,720 entitled “Embedding ACK/NAK in CQI Reference Signal with DTX Detection” filed Oct. 1, 2007, incorporated by reference herein. This application for Patent claims priority to U.S. Provisional Application No. 60/978,644 entitled “Embedding ACK/NAK in CQI Reference Signal with DTX Detection” filed Oct. 7, 2007, incorporated by reference herein. This application for Patent also claims priority to U.S. Provisional Application No. 61/022,878 entitled “Embedding ACK/NAK in CQI Reference Signal with DTX Detection” filed Jan. 23, 2008, incorporated by reference herein.
Number | Date | Country | |
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60954355 | Aug 2007 | US | |
60976720 | Oct 2007 | US | |
60978644 | Oct 2007 | US | |
61022878 | Jan 2008 | US |
Number | Date | Country | |
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Parent | 12183242 | Jul 2008 | US |
Child | 13438584 | US |