Patent Application
20070189289
The exemplary and non-limiting embodiments of this invention relate generally to wireless communications systems and, more specifically, relate to the transmission of unicast and multicast information streams to a receiver.
The following abbreviations are herewith defined:
The so-called evolved UTRAN (E-UTRAN) is currently a study item within the 3GPP. For the E-UTRAN system OFDM has been selected as the multiple access scheme for the downlink (i.e., in the direction from the BS to the UE).
Two types of data transmission can be considered: unicast (to single users or very small groups of users), and multicast (broadcast type of messages to a larger group of users subscribing to a certain service). The current assumption is that unicast will be implemented such that seven OFDM symbols are transmitted within a sub-frame having a duration of 0.5 milliseconds (ms), while multicast messages will be transmitted using only six OFDM symbols within a 0.5 ms sub-frame.
The multicast approach based OFDM will typically require that the BSs (or Node Bs) be time synchronized such that the data messages received from neighboring BSs will be decodable with a simple FFT operation. One implementation, when considering the multiplexing of unicast and multicast technologies, would use time multiplexing (i.e., TDM), such that certain sub-frames are reserved for multicast traffic, while other sub-frames are reserved for unicast traffic. However, it can be shown that time multiplexing of the two services within a single sub-frame would not bring any gain to the system, but rather would place limitations and requirements on the coordination of the network to facilitate the multiplexing operation.
One of the disadvantages of the use of TDM arises from the expectation that the multicast and unicast services may not demand the same requirements for transmission power. Another problem is that some UEs may have reduced RF bandwidth capability. For example, a particular UE may be only capable of receiving a signal with a 10 MHz BW, while the cellular system bandwidth may be, for example, 20 MHz. As a result, if the multicast and unicast services are time multiplexed then spectrum will be wasted since the multicast transmission must be limited to 10 MHz.
Thus far a default proposal has been to multiplex unicast and multicast services in the time domain on a single carrier on a per sub-frame basis (see Qualcomm: “Channel structure for E-UTRA MBMS evaluation”, R1-050901, London, August 2005).
An alternative approach would use dedicated carriers for unicast and multicast, respectively. However, this approach would require placing two receivers in the UE, which is disadvantageous at least with regard to increased space, cost and power consumption requirements.
In an exemplary aspect of the invention a method is provided for sending a multicast transmission over a first plurality of sub-carriers of a carrier, sending a unicast transmission over a second plurality of sub-carriers of the carrier, and interposing a guardband between the first plurality of sub-carriers and the second plurality of sub-carriers of the carrier.
In accordance with another exemplary embodiment of the invention, there is provided a program of machine-readable instructions, tangibly embodied on an information bearing medium and executable by a digital data processor, to perform actions including placing a multicast signal over a first plurality of sub-carriers of a carrier, placing a unicast signal over a second plurality of sub-carriers of the carrier, interposing a guardband between the unicast sub-carriers and the multicast sub-carriers, and transmitting the carrier signal.
In accordance with another exemplary embodiment of the invention, a network element includes a processor configured to allocate a multicast signal to a first plurality of sub-carriers of a carrier, to allocate a unicast signal to a second plurality of sub-carriers of the carrier, and to allocate a guardband signal to a third plurality of sub-carriers interposed between the first plurality of sub-carriers and the second plurality of sub-carriers; and a transmitter coupled to the processor to transmit the carrier signal.
In accordance with another exemplary embodiment of the invention, a user equipment includes a receiver configured to receive a plurality of sub-carriers on a carrier, and a processor coupled to the receiver to process a first plurality of sub-carriers allocated to a multicast signal, to process a second plurality of sub-carriers allocated to a unicast signal and to process a third plurality of sub-carriers that form a guardband signal interposed between the first plurality of sub-carriers and the second plurality of sub-carriers on the carrier.
In another exemplary embodiment of the invention there is provided an integrated circuit comprising a first circuit operable to accept a carrier signal comprising a first plurality of sub-carriers, a second plurality of sub-carriers, and a third plurality of sub-carriers comprising a guardband interposed between the first plurality of sub-carriers and the second plurality of sub-carriers, where the guardband comprises x sub-carriers, where x can be fixed or variable from sub-frame to sub-frame; a second circuit operable to sample the sub-carriers on the carrier signal, comprising isolating the guardband signal; a third circuit operable to digitize the sampled sub-carriers; a fourth circuit operable to process the digitized samples; and a fifth circuit comprising at least one signal type receiver circuit operable to receive the processed signals.
In yet another exemplary embodiment of the invention there is provided an electronic device comprising first circuit means for allocating a first plurality of sub-carriers comprising a multicast signal on the carrier signal, second circuit means for allocating a second plurality of sub-carriers comprising a unicast signal on the carrier signal, third circuit means for allocating a third plurality of sub-carriers comprising a guardband signal interposed between the first plurality of sub-carriers and the second plurality of sub-carriers on the carrier signal, where the guardband comprises x sub-carriers, where x is fixed or variable from sub-frame to sub-frame, and fourth circuit means operable to transmit the first, second and third plurality of sub-carriers on the carrier signal.
The foregoing and other aspects of embodiments of this invention are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figures:
a shows a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention
b illustrates in greater detail the receiver of
a illustrates the principle underlying service multiplexing in the time domain and, in accordance with exemplary embodiments of this invention,
a, 4b and 4c depict methods to reduce loss due to the presence of a guard band.
Reference is made first to
In general, the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
The embodiments of this invention may be implemented by computer software executable by the DP 10A of the UE 10 and other DPs such as the DP 12A, or by hardware, or by a combination of software and hardware.
The MEMs 10B, 12B and 14B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs 10A, 12A and 14A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.
In accordance with exemplary embodiments of this invention, and referring to
In accordance with exemplary embodiments of this invention both unicast and multicast services are simultaneously operable within the system bandwidth (single carrier). However, since these services operate using different values for the cyclic prefix, there is a potential loss of orthogonality between sub-carriers of the OFDM symbols. This potential loss of orthogonality is beneficially avoided by reserving as the guardband one or more sub-carriers between selected unicast and multicast bands. The guardband need not be larger than a few (e.g., four) sub-carriers, given the currently proposed E-UTRAN parameters.
Referring also to
Consider as an example that the unicast service uses bandwidth U, the multicast service uses bandwidth M, and the guardband is G. Then U+M+G=B, where B is one of the EUTRA operating bandwidths. The operating bandwidth is distinguished from the system bandwidth (for example 20 MHZ), wherein the operational bandwidth is the actual used bandwidth, and may correspond to 90% of the system bandwidth (or in this case 18 MHZ).
As non-limiting examples, the full bandwidths in EUTRA correspond to 75, 150, 300, 600, 900 or 1200 active sub-carriers (not counting the DC subcarrier) of 15 kHz, on 1.25, 2.5, 5, 10, 15 and 20 MHz system bandwidths, respectively, as shown in the table of
Referring to the receiver in
Note that while shown as two separate receivers, the unicast and multicast receivers 26, 28 may share one or more functional units and/or program code segments between them.
A user who is interested in both the unicast data and the multicast data processes the received samples with both the unicast receiver 26 and the multicast receiver 28. Note, however, that the allowed unicast and multicast subbands in B may be according to a EUTRAN parameterization for a smaller bandwidth so that, e.g., U=B′, where B′=<B. Thus for example, with B=10 MHz (600 subcarriers), U=B′ may take the value 600, and one or many of 300, 150, 75. With such an embodiment, a unicast user not interested in the multicast data may filter out the multicast signal at RF, and operate as if receiving only B′.
Referring to the method illustrated in
Still referring to
In addition, in
In
As was noted above, depending on what is the critical ICI, different solutions can be applied. In
In
Based on the foregoing description it can be appreciated that the use of the exemplary embodiments of this invention provides a number of advantages. For example, support is provided for constant data rate multicast services. Further by example, the multicast portion is constant for a full (segment of a) network, thus having a reserved resource for this service, resulting in a need for less network planning and coordination. Further by example, the Node B 12 output power can be optimized to provide optimum power balancing between the unicast and multicast services, since these services may not have the same power requirements. Further by example, other interference control mechanisms such as, but not limited to, power sequencing in the frequency domain can be applied for the unicast sub-band. As another example of the advantages realized by the sue of the exemplary embodiments of this invention, support is provided for those UEs with reduced RF BW capability, without a corresponding loss of spectrum usage
Note that while some potential system capacity is consumed by the introduction of the guardband, the reduction is less than about 1% of the system bandwidth, at least for system bandwidths of 10 MHz or above.
In accordance with another exemplary embodiment of the invention, an electronic device includes a first circuit operable to allocate a first plurality of sub-carriers comprising a multicast signal to a carrier signal, a second circuit operable to allocate a second plurality of sub-carriers comprising a unicast signal to the carrier signal, a third circuit operable to allocate a third plurality of sub-carriers comprising a guardband signal to a carrier signal, where the circuits of the integrated circuit operates to interpose the third plurality of sub-carriers between the first plurality of sub-carriers and the second plurality of sub-carriers, and a fourth circuit operable to transmit the first, second and third plurality of sub-carriers on the carrier signal over a system which can include, but is not limited to, a UTRAN or E-UTRAN system.
Referring to illustration in
Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide a method, apparatus and computer program product(s) to simultaneously transmit and receive a unicast and a multicast transmission using a substantially OFDM technique, and to also suppress at least ICI by the use of one of a fixed or variable BA guard band interposed between the unicast sub-carriers and the multicast sub-carriers.
In a further non-limiting aspect of the invention, the exemplary embodiments may be applied in the setting of a multi-antenna transmission. So called multiple-input multiple-output (MIMO) methods increase the data rate by adding the possibility to transmit multiple signal streams simultaneously to a user.
In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.
Programs, such as those provided by Synopsys, Inc. of Mountain View, Calif. and Cadence Design, of San Jose, Calif. automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or “fab” for fabrication.
Various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. For example, while the exemplary embodiments of the invention have been described above in the context of the UTRAN and E-UTRAN systems, it should be appreciated that the exemplary embodiments of this invention can be applied as well to other types of wireless communications systems, methods and schemes. Further, the exemplary embodiments are not restricted for use with any specific set of bandwidths, or any specific TTI durations. Thus, any and all modifications of the teachings of this invention will still fall within the scope of the non-limiting embodiments of this invention.
Furthermore, some of the features of the various non-limiting embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.
This patent application claims priority under 35 U.S.C. §119(e) from Provisional Patent Application No. 60/754,437, filed Dec. 27, 2005, the disclosure of which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60754437 | Dec 2005 | US |
