Patent Application
20110019573
The invention relates to wireless communication system and methods and, more particularly, but not exclusively to a systems and methods for space division multiple access.
Space division multiple access (SDMA) is a wireless communication method known in the art. SDMA enables a transmitter to transmit several and different data streams to several receivers, concurrently, using the same frequency and time resources. This is done by pointing each data stream to its target receiver in a way that other receivers do not receive data streams that are not intended for them. To achieve this goal the communication area is spatially divided between the receivers and the transmitter communicates concurrently with those receivers that are appropriately positioned in respective space divisions.
Practically, in the downlink (DL), SDMA is an advanced multiple input—multiple output (MIMO) transmission method in which a base-station transmits multiple beamformed streams of independent information to multiple user terminals simultaneously, using the same frequency and time resources. A typical MIMO system contains an antenna array, which contains several antenna elements. The transmitter uses the antenna array to create a plurality of beams, where each beam is directed to an appropriate receiver and carries a respective data stream. The beams are typically designed for minimal multi-user interference, which means that the beam conveying the information to the i-th receiver approximately nulls out at the direction of all other active receivers (null steering). The following U.S. patents and patent applications are believed to represent the most relevant prior art: 20070223423, 20070109630, 20060040672, 20030064754,U.S. Pat. Nos. 7,299,073, 7,206,293, 6,973,314, 6,650,881, 6,441,784.
Typically, the number of receivers with which an SDMA system can communicate concurrently in a given time is smaller than the number of receivers in the reception area. Thus, the base-station should determine which of the receivers should participate in a group of concurrent transmissions. The base-station therefore divides the receivers into several groups where members of each group can receive concurrent data streams.
In a mobile communication system, the location of the receivers changes rapidly. Thus, the base station must compute the groups' membership frequently. Given the large number of combinations of group memberships, the computational load is very high, adversely affecting the practical usability of the SDMA technology. There is thus a widely recognized need for, and it would be highly advantageous to have, an SDMA system devoid of the above limitations.
According to one aspect of the invention there is provided a method for selecting a group of terminal devices from a plurality of terminal devices; wherein the plurality of terminal devices is operative in a wireless communication network containing at least one transmitter operative to communicating with a multiplicity of terminal devices from the plurality of terminal devices; and wherein the transmitter is operative to transmit a beamformed plurality of concurrent data transmissions oriented at the selected group of terminal devices. The method containing the steps of:
measuring radiated power received by the terminal devices when a beamformed data transmission is sent by the transmitter to at least one another terminal device, wherein the measuring of radiated power forms channel correlation measurement;
reporting the channel correlation measurement to the transmitter; and
selecting, at the transmitter, the group of terminal devices from the multiplicity of terminal devices, wherein the group consists of terminal devices reporting low channel correlation with all other terminal devices in the group.
According to another aspect of the invention there is provided a method for selecting a group of terminal devices from a plurality of terminal devices wherein the beamformed plurality of concurrent data transmissions forms a group of beams, each directed towards at least one terminal device of a the selected group of terminal devices.
According to yet another aspect of the invention there is provided a method for selecting a group of terminal devices from a plurality of terminal devices wherein the transmitter is a base-station.
According to still another aspect of the invention there is provided a method for selecting a group of terminal devices from a plurality of terminal devices wherein the channel correlation measurement contains at least one of:
Further according to another aspect of the invention there is provided a first terminal device operative in a wireless network, the wireless network containing a base-station and a plurality of terminal devices, the first terminal device containing:
wherein the reception characteristics feedback contains at least one of a group containing:
Yet further according to another aspect of the invention there is provided a base-station operative in a wireless network, the wireless network containing a plurality of terminal devices, the base-station containing:
wherein the reception characteristics feedback contains at least one of a group containing:
Still further according to another aspect of the invention there is provided an integrated circuit device for use in a first terminal device, the first terminal device operative in a wireless network, the wireless network containing a base-station and a plurality of terminal devices, the integrated circuit device containing:
wherein the reception characteristics feedback contains at least one of a group containing:
Even further according to another aspect of the invention there is provided an integrated circuit device for use in a base-station, the base-station operative in a wireless network, the wireless network containing a plurality of terminal devices, the integrated circuit device containing:
Additionally according to another aspect of the invention there is provided a computer program product, stored on one or more computer-readable media, containing instructions operative to cause a programmable processor of a first terminal device, the first terminal device operative in a wireless network, the wireless network containing a base-station and a plurality of terminal devices, the computer program product containing:
wherein the reception characteristics feedback contains at least one of:
Also according to another aspect of the invention there is provided a computer program product, stored on one or more computer-readable media, containing instructions operative to cause a programmable processor of a base-station operative in a wireless network, the wireless network containing a plurality of terminal devices, the computer program product containing:
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples provided herein are illustrative only and not intended to be limiting. Except to the extend necessary or inherent in the processes themselves, no particular order to steps or stages of methods and processes described in this disclosure, including the figures, is intended or implied. In many cases the order of process steps may varied without changing the purpose or effect of the methods described.
Implementation of the method and system of the invention involves performing or completing certain selected tasks or steps manually, automatically, or any combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and system of the invention, several selected steps could be implemented by hardware or by software on any operating system of any firmware or any combination thereof. For example, as hardware, selected steps of the invention could be implemented as a chip or a circuit. As software, selected steps of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In any case, selected steps of the method and system of the invention could be described as being performed by a data processor, such as a computing platform for executing a plurality of instructions.
The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the embodiments of the invention only, and are presented in order to provide what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
In the drawings:
The invention, in embodiments thereof, comprises a system and method for cooperation between network devices in a wireless communication network. The wireless communication network uses space diversity multiple access technology (SDMA) and the cooperation enables the creation of at least one group of network devices. The grouping enables an SDMA transceiver to communicate with the members of the group concurrently, using the same frequency and time resources. The present embodiments comprise a low complexity user selection for SDMA groups in the wireless communication network. The principles and operation of a system and method for low complexity user selection for SDMA groups according to the invention may be better understood with reference to the drawings and accompanying description.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
In this document, an element of a drawing that is not described within the scope of the drawing and is labeled with a numeral that has been described in a previous drawing has the same use and description as in the previous drawings. Similarly, an element that is identified in the text by a numeral that does not appear in the drawing described by the text, has the same use and description as in the previous drawings where it was described.
Reference is now made to
As seen in
As seen in
It is appreciated that though the SDMA network 10 of
As seen in
The feedback-information 20 preferably contains channel correlation information. The channel correlation information indicates to the base-station 11 the reception level at the reporting user terminal 12 for a signal transmitted to a destination terminal. In the example of
As seen in
As seen in
The mathematical model for the received signals in an SDMA system such as the SDMA network 10 is provided below. It is assumed that M is the number of transmission antennas, for example at the base-station 11. It is also assumed that N is the number of reception antennas. In the examples herein, the N reception antennas belong to a group of user terminals 12 where each user terminal 12 contains one reception antenna. The number of transmission antennas M is equal or larger than the number of reception antennas N. The received signal at a reception antenna is then given by Eq. (1):
y=HWs+ρn where:
y is the value of signal received at a reception antenna;
s is the value of signal transmitted by a transmission antenna;
H is channel matrix;
W is precoding matrix, also known as beamforming matrix;
ρp is noise factor; and
n is white noise vector.
Therefore, si is the information signal transmitted by the base-station 11 to the i-th user terminal 12, and the signal yi is the corresponding signal received at the antenna of the i-th user terminal 12.
In the SDMA network 10, each user terminal 12 uses its single antenna to reconstruct the single information stream addressed to it. Thus, the precoding matrix W has to be devised such that HW is diagonal or nearly diagonal. Otherwise, multi-user interference (MUI) is introduced.
Assuming that the SNR is high and MUI is the main concern, the beamforming matrix W satisfies Eq. (2):
HW=αD
where:
D is a diagonal matrix, and
α is a scaling factor.
The precoding matrix W also meets the unity power constraint as described by Eq. (3):
E∥Ws∥=1 and thus Eq. (4):
||W||
2
F=1.
The physical interpretation of SDMA implies that for the i-th receiver, an SDMA transmitter uses wi, which creates a beam that amplifies si at the direction of that receiver, and attenuates si at the directions of all other N−1 receivers (spatial nulls). Eq. (5) for the SDMA beamforming matrix W also implies that an array of M transmission antennas can create up to M−1 nulls.
Typically, a base-station containing M antennas communicates with Nu user terminals. Typically, Nu>>M and therefore the base-station cannot use SDMA technology to transmit simultaneously to all the user terminals 12. Thus, when SDMA transmission is employed, the base-station has to divide the user-terminals into groups of NG users where NG≦M . The base station can then use SDMA technology to transmit simultaneously to all the NG user terminals in a group G.
In the example described in accordance with
One way to divide user-terminals into groups would select user-terminals with orthogonal channel vectors into the same group. In this case, maximal ratio transmission (MRT) may be applied to each user-terminal independently, and no MUI is introduced (due to the orthogonal channels). In this case, MRT would also be the optimal solution. It is appreciated that in real scenarios perfect orthogonality cannot be found, and therefore groups of user-terminal with minimal correlation are desirable. This user-terminal selection algorithm implies exhaustive search and is thus difficult to realize. The purpose of the invention is to avoid this exhaustive search.
It is appreciated that not all user terminals 12 must transmit feedback-information 20 in response to each feedback request from the base-station 11. It is also appreciated that not all user terminals 12 must transmit feedback-information 20 in response to any number of feedback requests from the base-station 11. It is further appreciated that not all user terminals 12 must be grouped to enable base-station 11 to operate in an SDMA network 10. It is therefore appreciated that an SDMA network 10 can include only some of the user terminals 12 in groups, and other user terminals 12 as individual receivers. It is also appreciated that groups may include different numbers of user terminals 12. It is further appreciated that a user terminal 12 can be member in more than one group, for example to increase throughput to the user terminal 12.
Reference is now made to
As seen in
As seen in
As described in accordance with
For example, the i-th user-terminal, such as user-terminal 18 of
Hence, when the base-station 11 transmits an SDMA beamformed transmission to the j-th user-terminal (e.g. user-terminal 18 of
This signal power is then used as an estimation of the channel correlation. The signal power, or a derivative of the signal power, is sent to the base-station 11 as a part of the feedback-information 20.
The beamformed signal to the i-th user-terminal is described by Eq(6):
Therefore, the received signal at the j-th user-terminal, which is, for example, one of the user-terminals 19 of
Hence, the channel correlation is obtained at the N−1 user terminals, which are for example, all user-terminals 19 of
Therefore, channel correlation is obtained for all user-terminals 19. Thus each user-terminal 19 can select the other user-terminals in its SDMA group according to the strength of the beamformed signal addressing the user-terminal 18 measured at its reception antenna. Once a suitable user-terminal is found (one received with low strength implying low correlation), the j-th user-terminal send to the base-station 11 feedback-information 20 containing a pointer to the allocation.
It is appreciated that the feedback-information 20 can indicate the channel correlation in a number of alternative ways. For example, the feedback-information 20 can contain the received signal power as measured, or an indication of the level of the received signal power, for example, with respect to a threshold level of signal power, or a predetermined set of signal levels. Alternatively or additionally, the feedback-information 20 can contain an identification of the terminal for which the received signal power was measured. Alternatively or additionally, the feedback-information 20 can contain an identification of the time slot at which the received signal power was measured.
Hence, as the base-station 11 scans the plurality of user-terminals 12, as shown in the sequence of
This approach may be extended to SDMA transmissions, where each transmission is composed of multiple beams towards multiple user-terminals in an SDMA group. Assuming that the channel correlation within the group is low, the transmitted SDMA signal Tx may be approximated by the sum of MRT beamformers depicted by Eq(8):
where K is the number of beams or user terminals 12 with to the base station 11 transmits concurrently over the MIMO system, such as user terminals 23 of
Therefore, the received signal Rx at the reception antenna of the j-th user-terminal is presented by Eq(9):
In this case, the strength of the measured signal at the Rx antenna of the j-th user-terminal reflects its channel correlation with all the SDMA group members (the average correlation). If this strength is low, the user-terminal may join the SDMA group.
It is appreciated that for SDMA systems where a user-terminal contains a plurality of Rx antennas the user-terminal measures the strength of the beamformed signal at each of its Rx antennas.
Thus, the wireless communication network includes a plurality of network devices, of which at least one network device is an SDMA transceiver that contains a plurality of antennas forming an antenna array. The network devices of this communication network cooperate to enable the SDMA transceiver to create at least one group of other network devices. The SDMA transceiver can then create a set of beamformed data streams wherein each data stream is directed to one member of the group, such as beamformed data streams 24 of
It is appreciated that a beamformed data stream can address two or more user-terminals 12 as shown in
As seen in
Reference is now made to
As seen in
Preferably, the received signal-measuring unit 32 measures, via the receiver unit 30 and the antenna circuitry 29, the signal Rx received at the antenna 28. The received signal measuring unit 32 then calculates the cross-terminal-feedback 20 and transmits the cross-terminal-feedback 20 to the base-station 11 via the via the transmitter unit 31, the antenna circuitry 29 and the antenna 28.
The received signal measuring unit 32 preferably contains a microprocessor, and the memory unit 33 preferably contains storage area and cross-terminal-feedback software program 34 containing instructions for the processor of the received signal measuring unit 32.
Alternatively, the received signal measuring unit 32 can be implemented in hardware, such as by using a programmed gate array, for example by using a field programmable gate array (FPGA).
Reference is now made to
As seen in
Preferably, the group-correlating unit 41 receives cross-terminal-feedback 20 from the receiver unit 39. The group-correlating unit 41 then analyzes the cross-terminal-feedback 20 to create groups of user-terminal 12. The group correlating unit 41 then instructs the transmit beamforming unit 40 to create beamformed transmissions to the user-terminal 12 forming each group.
The transmit beamforming unit 40 preferably contains a microprocessor, and the memory unit 42 preferably contains storage area and grouping software program 43 containing instructions for the processor of the transmit beamforming unit 41.
Alternatively, the transmit beamforming unit 40 can be implemented in hardware, such as by using a programmed gate array, for example by using a field programmable gate array (FPGA).
Reference is now made to
The cross-terminal-feedback software program 43 preferably starts in step 44 when the user-terminal 12 receives a request for cross-terminal-feedback from the base-station 11.
The cross-terminal-feedback software program 43 preferably proceeds to step 45 to measure the signal received at the reception antenna of the user-terminal 12 when the base-station 11 transmits to another user-terminal 12, herein designated as terminal J, such as user-terminal 18 of
Alternatively, the cross-terminal-feedback software program 43 starts automatically in step 45.
The cross-terminal-feedback software program 43 preferably proceeds to step 46 to analyze the measured signal. Preferably, the cross-terminal-feedback software program 43 compares the signal level to a predefined threshold. Preferably, if the measured signal is above the predefined threshold the cross-terminal-feedback software program 43 proceeds to step 47 to send negative feedback information, and preferably, if the measured signal is below the predefined threshold the cross-terminal-feedback software program 43 proceeds to step 48 to send positive feedback information.
Alternatively, the cross-terminal-feedback software program 43 sends cross-terminal-feedback containing the value of the measured signal. It is appreciated that sending an accurate value of the measured signal is advantageous with respect to the ability of the base-station to optimally group the user-terminals, while sending a positive or negative feedback-information demands lower bandwidth.
Reference is now made to
As seen in
The grouping software program 43 then preferably proceeds to step 50 to send a transmission to one of the user-terminals 12, such as user-terminal 18 of
The grouping software program 43 then preferably proceeds to step 53 to repeat steps 50, 51 and 52 until the scanning of the user-terminals 12 is complete.
Then, the grouping software program 43 preferably proceeds to step 54 to create groups of user terminals 12 according to the collected cross-terminal-feedback 20. Preferably, each of the groups that the software program 43 creates contains a number of user terminals 12 that is equal or less than the maximum number of concurrent data streams that the base-station 11 can handle. Typically, the number of user terminals 12 in a group is equal or less than the number of antenna elements 16. Preferably, each group contains only user terminals 12 that sent cross-terminal-feedback 20 containing low channel correlation for all other members of that group.
The grouping software program 43 then preferably proceeds to step 55 to group data transmissions according to the terminal groups created in step 54. Then, the grouping software program 43 preferably proceeds to step 56 to create a beamformed data transmission for each group created in step 54. Preferably, The grouping software program 43 preferably proceeds to step 57 to send a request for cross-terminal-feedback 20, preferably to all user terminals 12. As the beamformed data transmissions are transmitted in step 58, the grouping software program 43 then preferably receives the cross-terminal-feedback 20, preferably from all user terminals 12 (steps 59 and 60). The grouping software program 43 then preferably proceeds to step 61 to evaluate and optionally recreate the groups of user terminals 12. According to the newly received cross-terminal-feedback 20. The steps 55 to 61 preferably repeat as necessary.
It is expected that during the life of this patent many relevant wireless devices and systems will be developed and the scope of the terms herein, particularly of the terms “SDMA” and “MIMO”, is intended to include all such new technologies a priori.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention.
The present application claims priority from U.S. provisional patent application 61/033,033, filed Mar. 3, 2008, the contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB09/50855 | 3/3/2009 | WO | 00 | 9/2/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 61033033 | Mar 2008 | US |
