WO2008156264A1

WO2008156264A1 - Method and apparatus for supporting collaborative mimo in wireless communication system

Info

Publication number: WO2008156264A1
Application number: PCT/KR2008/003322
Authority: WO
Inventors: Dong-Jun Lee; Zheng Zi Li
Original assignee: Posdata Co., Ltd.
Priority date: 2007-06-19
Filing date: 2008-06-13
Publication date: 2008-12-24
Also published as: KR20080111681A; KR100945098B1

Abstract

A method for supporting and processing Collaborative Multiple Input Multiple Output (C-MIMO) in wireless communication system is provided. The C-MIMO supporting method includes sorting a plurality of C-MIMO-capable terminals using at least one of position information and channel quality information; grouping a highest-priority terminal among the sorted terminals with each of a plurality of terminals selected except for the highest-priority terminal; and transmitting a message including burst allocation information for the grouped terminals.

Description

Description Method and apparatus for supporting collaborative MIMO in wireless communication system Technical Field

[1] The present invention relates generally to a method and apparatus for supporting and processing Collaborative Multiple Input Multiple Output (C-MIMO) in wireless communication system, and in particular, to a scheduling method and apparatus in C- MIMO wireless communication system, and a method and apparatus for processing C- MIMO. Background Art

[2] Recently, to meet the increasing need for transmitting a large volume of data over wireless channels at high speed, intensive research is being conducted on high-speed wireless data transmission systems for supporting Portable Internet Service in the mobile environment, and a Multiple Input Multiple Output (MIMO) system attracts attention as a technology for supporting high-speed Portable Internet Service in the mobile environment.

[3] FIG. 1 is diagram illustrating the outlines of a Single Input Single Output (SISO) system and a MIMO system, respectively.

[4] As illustrated in FIG. 1, a SISO system 100, a technology in which a transmitter and a receiver each use their one antenna RxAnt and TxAnt, respectively, transmits and receives signals through one channel H formed between, for example, a base station with one antenna RxAnt and a terminal with one antenna TxAnt. In this SISO system, a multipath phenomenon may occur due to the obstacles on propagation paths, such as hills, valleys, pylons, etc., causing fading problems. The fading causes a decrease in data rate and an increase in error rate in digital communication such as the mobile Internet.

[5] A MIMO system is a technology of increasing the number of antennas of the base station and the terminal to transmit data through several paths. In this technology, a receiver can reduce interference by detecting signals received through each of the paths, and a transmitter can increase its transmission efficiency through Space-Time Transmit Diversity (STTD) and Spatial Multiplexing (SM). For example, FIG. 1 illustrates a 2 2 MIMO system 450 that uses a base station with two antennas RxAntO and RxAnt 1 and a terminal with two antennas TxAntO and TxAnt 1. As illustrated in FIG. IB, four channels of a first channel HOO, a second channel HOl, a third channel HlO and a fourth channel HI l are formed between first and second antennas RxAntO and RxAnt 1 of the base station and first and second antennas TxAntO and TxAnt 1 of the terminal. Since the MIMO system 450 has a higher data rate as it includes a plurality of transmit/receive antennas, the capacity of its radio link can be improved during transmission/reception period compared with that of the SISO system 100. That is, in the multipath-rich environment, as multiple orthogonal channels can be created between a transmitter and a receiver, the data for every single user can be simultaneously transmitted over the air in parallel through the orthogonal channels using the same bandwidth, thereby achieving higher spectral efficiency compared with the SISO system 100.

[6] As described above, however, in the uplink of the 2 2 MIMO system 450, each terminal should have two antennas, causing an increase in its power loss and hardware complexity. Therefore, a study is being conducted on C-MIMO for increasing a data rate to that of the conventional MIMO using terminals each having simpler hardware structure and one antenna. Thus, there is a demand for schemes efficient in processing

C-MIMO.

Disclosure of Invention

Technical Problem

[7] An aspect of the present invention is to address at least the problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a method and apparatus for supporting and processing C-MIMO in wireless communication system.

[8] Another aspect of the present invention is to provide a scheduling method and apparatus for supporting C-MIMO in wireless communication system.

[9] Further another aspect of the present invention is to provide a scheduling method and apparatus for optimally grouping C-MIMO-capable terminals to support C-MIMO in wireless communication system.

[10] Yet another aspect of the present invention is to provide a scheduling method and apparatus for optimally grouping C-MIMO-capable terminals and efficiently allocating resources to the grouped terminals in C-MIMO wireless communication system. Technical Solution

[11] According to one aspect of the present invention, there is provided a method for supporting Collaborative Multiple Input Multiple Output (C-MIMO) in wireless communication system. The C-MIMO supporting method includes sorting a plurality of C- MIMO-capable terminals using at least one of position information and channel quality information; grouping a highest-priority terminal among the sorted terminals with each of a plurality of terminals selected except for the highest-priority terminal; and transmitting a message including burst allocation information for the grouped terminals. [12] According to another aspect of the present invention, there is provided a method for scheduling in Collaborative Multiple Input Multiple Output (C-MIMO) wireless communication system. The scheduling method includes sorting, in a current frame, a plurality of C-MIMO-capable terminals, grouping a first-priority terminal with each of a first plurality of terminals selected except for the first-priority terminal, and transmitting first burst allocation information for the grouped terminals; and selecting, in a next frame of the current frame, a first terminal group having a greatest amount of allocated bursts among the grouped terminals, re-grouping a second-priority terminal except for the first terminal group with each of a second plurality of terminals selected except for the second-priority terminal, and transmitting second burst allocation information for the first terminal group and the re-grouped terminals.

[13] According to further another aspect of the present invention, there is provided a method for supporting Collaborative Multiple Input Multiple Output (C-MIMO). The C-MIMO supporting method includes receiving a registration message including terminal information from each of a plurality of terminals; and transmitting an Up-Link MAP (UL-MAP) message to be allocated the same at least one subburst region in a burst region allocated to a first terminal supporting C-MIMO, selected based on the terminal information by the first terminal and another terminal.

[14] According to yet another aspect of the present invention, there is provided a method for supporting Collaborative Multiple Input Multiple Output (C-MIMO). The C- MIMO supporting method includes rreceiving, by a first terminal supporting C-MIMO, a message to allocat the same Up-Link (UL) subburst region as that of a second terminal supporting C-MIMO, from a base station; and transmitting, by the first terminal, data and pilots with a pilot pattern different from that of the second terminal using the subburst region according to the message.

[15] According to still another aspect of the present invention, there is provided a method for processing Collaborative Multiple Input Multiple Output (C-MIMO) by a terminal in wireless communication system. The C-MIMO processing method includes pairing the terminal and a first terminal, and transmitting data and pilots of the terminal to a base station using a first Up-Link (UL) burst region in a UL frame; and pairing the terminal and a second terminal, and transmitting data and pilots of the terminal to the base station using a second UL burst region in the UL frame; wherein a pilot pattern for the terminal is equal in the first UL burst region and the second UL burst region.

[16] According to still another aspect of the present invention, there is provided an apparatus for scheduling in Collaborative Multiple Input Multiple Output (C-MIMO) wireless communication system. The scheduling apparatus includes a grouper for grouping a first terminal selected based on information on C-MIM0-capable terminals with each of a first plurality of C-MIM0-capable terminals selected except for the first terminal; and an allocator for allocating a burst region for the grouped terminals.

[17] According to still another aspect of the present invention, there is provided a base station in Collaborative Multiple Input Multiple Output (C-MIMO) wireless communication system. The base station includes a receiver for receiving a registration message including terminal information from each of a plurality of terminals; and a transmitter for transmitting a burst allocation message to be allocated the same at least one subburst region in a burst region allocated to a first terminal supporting C-MIMO, selected based on the terminal information by the first terminal and another terminal.

[18] According to still another aspect of the present invention, there is provided a terminal in Collaborative Multiple Input Multiple Output (C-MIMO) wireless communication system. The terminal includes a receiver for receiving, from a base station, a message to allocat the same Up-Link (UL) subburst region as that of a separate C- MIMO-capable terminal; and a transmitter for transmitting data and pilots with a pilot pattern different from that of the separate C-MIMO-capable terminal using the UL subburst region according to the message.

Advantageous Effects

[19] Accordingly, the present invention can enable efficient utilization of resources in processing C-MIMO.

[20] Further, the present invention can efficiently allocate resources for the grouped terminals in C-MIMO wireless communication system, thereby obtaining improved system performance and making the best use of the limited resources.

[21] Moreover, the present invention can group one of C-MIMO-capable terminals together with multiple terminals in a C-MIMO wireless communication system, making it possible to fast search for the terminal group most suitable for C-MIMO, to group even an odd number of terminals, and to reduce a MAP size. Brief Description of the Drawings

[22] The above and other aspects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[23] FIG. lis diagram illustrating the outlines of a SISO system and a MIMO system, respectively;

[24] FIG. 2 is a diagram illustrating an uplink C-MIMO system processed between two terminals and one base station according to the present invention;

[25] FIG. 3 is a diagram illustrating a frame structure used in a Portable Internet system supporting IEEE 802.16;

[26] FIG. 4 is a block diagram illustrating a structure of a base station for supporting C-

MIMO according to the present invention; [27] FIG. 5 is diagram illustrating a structure of the scheduler shown in FIG. 4;

[28] FIG. 6 is a diagram illustrating a method for grouping C-MIMO terminals in a base station according to the present invention;

[29] FIG. 7 is a diagram illustrating a method for grouping C-MIMO terminals in a base station according to the present invention;

[30] FIG. 8 is a diagram illustrating a burst allocation method according to the present invention;

[31] FIG. 9 is diagram illustrating pilot patterns being applied to a UL PUSC mode in a

2x2 C-MIMO system according to the present invention;

[32] FIG. 10 is a diagram illustrating a burst allocation method according to the present invention;

[33] FIG. 11 is a signaling diagram illustrating a method for supporting C-MIMO according to the present invention; and

[34] FIG. 12 is a flowchart illustrating a scheduling method for supporting C-MIMO according to the present invention. Mode for the Invention

[35] Preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for clarity and conciseness.

[36] FIG. 2 illustrates an uplink Collaborative Multiple Input Multiple Output (MIMO)

(C-MIMO) system. Shown in FIG. 2 is an example of an uplink C-MIMO system processed between two terminals (e.g. Mobile Station or Portable Subscriber Station) and one base station (e.g. Radio Access Station).

[37] In brief, a first terminal and a second terminal perform their transmission via a first transmit antenna TxAntO and a second transmit antenna TxAntl, respectively, using different pilot patterns. Then, signals on a first channel HOO and a third channel HlO transmitted from the first terminal and signals on a second channel HOl and a fourth channel HI l transmitted from the second terminal undergo Spatial Multiplexing (SM) through the same subcarriers using different pilot patterns before transmission, and a base station with first and second receive antennas RxAntO and RxAntl receives the signals transmitted from the first terminal and the second terminal.

[38] FIG. 3 illustrates a frame structure used in a Portable Internet system supporting

IEEE 802.16.

[39] A Portable Internet system based on Time Division Duplex (TDD) time-divides one frame into a frame for transmission and a frame for reception. Referring to FIG. 3, one frame is divided into a Down-Link (DL) frame over which a base station transmits data to a terminal, and an Up-Link (UL) frame over which a terminal transmits data to a base station, and a Transmit/receive Transition Gap (TTG) and a Receive/transmit Transition Gap (RTG) are inserted there between. In the illustrated example, the DL frame includes at least one of a Preamble interval, a Partial Usage of Sub-Channels (PUSC) Subchannel interval, a Full Usage of Sub-Channels (FUSC) Subchannel interval, and an Adaptive Modulation & Coding (AMC) Subchannel interval, and the UL frame includes at least one of a UL Control Symbol interval, a PUSC Subchannel interval and an AMC Subchannel interval.

[40] In particular, the present invention relates to a method for allocating bursts in the UL frame of FIG. 3, and the burst allocation information is transmitted to terminals on UL- MAP of the DL frame during DL transmission.

[41] A description will now be made of an apparatus for supporting C-MIMO according to an embodiment of the present invention. For convenience sake, it will be assumed herein that this embodiment considers a 2x2 MIMO system based on Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA), and each terminal is capable of C-MIMO.

[42] FIG. 4 is a block diagram illustrating a structure of a base station (i.e., transmission apparatus) for supporting C-MIMO according to the present invention.

[43] As illustrated in FIG. 4, the base station includes an interface 410, a baseband signal processor 420, a transmitter 430, a receiver 460, a scheduler 450, and antennas 440. The base station can be divided into a reception path and a transmission path for supporting TDD.

[44] In the reception path, the receiver 460 receives one or more radio signals transmitted by terminals, via the antennas 440, and converts the received radio signals into baseband signals. For example, the receiver 460 removes noises from the received signals and amplifies the noise-removed signals for data reception of the base station. Further, the receiver 460 down-converts the amplified signals into baseband signals and digitalizes the down-converted baseband signals. The baseband signal processor 420 extracts information or data bits from the digitalized signals, and performs demodulation, decoding and error correction thereon. The received information is delivered to adjacent wire/wireless networks via the interface 410, or transmitted to other terminals being serviced by the base station.

[45] In the transmission path, the interface 410 receives voice, data and/or control information from a base station controller or a radio network, and the baseband signal processor 420 encodes the voice, data and/or control information provided from the interface 410, and outputs the results to the transmitter 430. The transmitter 430 modulates the coded voice, data and/or control information with a carrier signal having a desired transmission frequency or frequencies, amplifies the modulated carrier signal to a level suitable for transmission, and transmits the amplified signal over the air through the antennas 440.

[46] The scheduler 450 controls operations of the reception path and transmission path, and operations of the constituent elements, and a configuration of the C-MIMO system according to the present invention is as shown in FIG. 5.

[47] FIG. 5 is diagram illustrating a structure of the scheduler shown in FIG. 4. As illustrated in FIG. 5, the scheduler 450 includes a C-MIMO searcher 510, a parameter acquirer 550, a C-MIMO sorter 520, a C-MIMO grouper 530, and a resource allocator 540.

[48] The C-MIMO searcher 510 searches for terminals capable of C-MIMO (hereinafter referred to as 'C-MIMO-capable terminals' or 'C-MIMO terminals') in the SISO/ MIMO-mixed system environment, depending on the basic capacity such as physical parameter information, bandwidth allocation information, etc., provided from terminals.

[49] The parameter acquirer 550 acquires information on the C-MIMO terminals searched by the C-MIMO searcher 510. The information on the terminals can be divided into position information of the terminals and channel quality information of the terminals, and the channel quality information of the terminals can include ranging channel information of terminals, UL sounding channel information of terminals, Carrier to Interference and Noise Ratio (CINR) information based on Channel Quality Indicator (CQI) channels of terminals, power allocation information of terminals, Modulation & Coding Scheme (MCS) level information of terminals, etc.

[50] The C-MIMO sorter 520 sorts the terminals using the parameters or a combination of the parameters according to the information on the terminals acquired by the parameter acquirer 550. For example, the C-MIMO sorter 520 sorts the terminals in order of a terminal located closest to the base station when it performs the sorting using the position information of terminals; sorts the terminals in order of a terminal, low interference and good signal state of which is detected through a CQI channel of the terminal, i.e., in order of a terminal having a high CINR, when it performs the sorting using the CINR information of terminals; and sorts the terminals in order of a terminal having higher allocated power when it performs the sorting using the power allocation information of terminals. In this case, it is also possible to sort the terminals taking at least two parameters into account.

[51] The C-MIMO grouper 530 performs grouping using the terminals sorted by means of the C-MIMO sorter 520. For convenience sake, the grouping is assumed herein as pairing in a 2x2 C-MIMO system. The C-MIMO grouper 530, as shown in FIG. 5, can further include terminal selector 532 for selecting terminals having the greatest amount of bursts among the grouped terminals using the fed-back burst allocation information for each terminal, and a C-MIMO re-grouper 534 for re-grouping another one terminal except for the grouped terminals with each of multiple terminals except for the another one terminal.

[52] With reference to FIGs. 6 and 7, a detailed description will now be made of the grouping method.

[53] FIG. 6 is a diagram illustrating a method for grouping C-MIMO terminals in a base station according to the present invention. Herein, the method groups the remaining lower-priority terminals on the basis of the highest-priority terminal among the terminals sorted by the C-MIMO sorter 520. That is, the method groups the one highest-priority terminal with the remaining multiple terminals.

[54] Referring to FIG. 6, if the C-MIMO sorter 520 sorts the terminals in order of terminals a, b, c, and d based on the parameters or a combination of the parameters, the C-MIMO grouper 530 groups the terminal a with the terminal b, the terminal a with the terminal c, and the terminal a with the terminal d. This grouping is available even for 5 terminals. That is, it can be noted that for C-MIMO, grouping is available even for an odd number of terminals, thereby contributing to a reduction in size of the UL-MAP.

[55] After selecting terminals having the greatest amount of allocated bursts based on the burst allocation information fed back from the resource allocator 540, the C-MIMO grouper 530 groups the terminals in the next frame, and performs re-grouping using the remaining terminals. For example, if the terminal a and the terminal c are allocated the greatest amount of bursts in the current frame, the C-MIMO grouper 530 groups the terminal a and the terminal c in the next frame, and re-groups the terminal b or the terminal d except for the terminal a and the terminal c with the remaining terminals e, f, ..., z.

[56] Although it has been described herein that for convenience' sake, the C-MIMO grouper 530 selects and groups the terminals having the greatest amount of allocated bursts in the next succeeding frame, it should be noted that the C-MIMO grouper 530 can select and group the terminals having the greatest amount of allocated bursts (i.e., having the highest performance) by constantly monitoring several frames instead of only the just next frame.

[57] FIG. 7 is a diagram illustrating a method for grouping C-MIMO terminals in a base station according to the present invention. Shown in FIG. 7 is a method for grouping the optimal terminals for C-MIMO.

[58] Referring to FIG. 7, if the C-MIMO sorter 520 sorts the terminals in order of terminals a, b, c, and d based on the parameters or a combination of the parameters, the C-MIMO grouper 530 groups the terminal a with the terminal b, the terminal a with the terminal c, and the terminal a with the terminal d in the current frame. The resource allocator 540 allocates different amounts of bursts for the grouped terminals, and feeds back the burst allocation information to the C-MIMO grouper 530 so that reference can be made thereto for terminal re-grouping in the next frame. Accordingly, in the next frame, the C-MIMO grouper 530 selects the terminals having the greatest amount of allocated bursts based on the fed-back burst allocation information, and then performs re-grouping on the remaining terminals except for the selected terminals.

[59] In the illustrated example, if the resource allocator 540 allocates the greatest amount of bursts to the terminal a and the terminal c in the current frame, the C-MIMO grouper 530, after grouping the terminal a and the terminal c, re-groups in the next frame the remaining terminals on the basis of the terminal b in the manner of FIG. 6 to group other terminals, and also re-groups the remaining terminals on the basis of the terminal d in the manner of FIG. 6, thereby making the optimal group.

[60] Meanwhile, the resource allocator 540 allocates resources for the terminals grouped by the C-MIMO grouper 530, i.e., designates a region where it will allocate bursts for the grouped terminals, allocates a pilot pattern to each of the terminals, and then generates a UL-MAP message based thereon. The resource allocator 540 includes a feedback unit 548 for feeding back the burst allocation information to the C-MIMO grouper 530 so that reference can be made thereto when the C-MIMO grouper 530 regroups the C-MIMO terminals during transmission of the next frame.

[61] In this case, the burst allocation can be performed based on positions of the terminals in a cell, or can be performed based on channel qualities of the terminals.

[62] For example, when the bursts are allocated based on the positions, the same amount of bursts are allocated for the terminals having the same distance from the base station. On the contrary, when the distances between the base station and the terminals are different, a greater amount of bursts are allocated to the terminals having a shorter distance from the base station, while a less amount of bursts are allocated to the terminals having a longer distance from the base station, thereby increasing resource utilization.

[63] On the other hand, when the bursts are allocated based on the channel qualities, a greater amount of bursts are allocated to the terminals having a good channel quality, while a less amount of bursts are allocated to the terminals having a poor channel quality. For this, the resource allocator 540, as shown in FIG. 5, includes a burst allocator 542 for allocating bursts for the terminals, a pilot pattern allocator 544 for allocating different pilot patterns for the terminals, and a MAP Information Element (IE) recorder 546 used for recording the burst allocation information and pilot pattern allocation information in UL-MAP.

[64] Alternatively, the resource allocator 540 includes a first burst allocator (not shown) for allocating bursts for a first plurality of terminals, i.e., a first terminal group, a burst segmentation unit (not shown) for segmenting a burst region for a second terminal into a plurality of subburst regions, a second burst allocator (not shown) for allocating bursts for a second plurality of terminals to at least one of the subburst regions, the pilot pattern allocator 544 for allocating different pilot patterns for terminals belonging to the first terminal group, and allocating different pilot patterns for the second terminal and the second plurality of terminals, and the MAP IE recorder 546 for recording, in UL-MAP, the burst allocation information for terminals of the first terminal group, the second terminal and the second plurality of terminals, and the pilot pattern allocation information.

[65] With reference to FIGs. 8 to 10, a detailed description will now be made of the resource allocator 540.

[66] FIG. 8 is a diagram illustrating a burst allocation method according to the present invention. This method generates a UL-MAP message so that a base station designate a burst region in an OFDM/OFDMA UL frame, segments a part of the designated burst region into subburst regions UL_subburst_ab, UL_subburst_ac and UL_subburst_ad, and then allocates bursts for terminals to the segmented subburst regions.

[67] Referring to FIG. 8, a DL interval (or DL frame) includes Preamble, Frame Control

Header (FCH), DL-MAP, UL-MAP, and DL Bursts, and a UL interval (or UL frame) includes Ranging, ACK & CQI, and UL Bursts. Herein, Preamble is used for providing time/frequency synchronization and cell information to users, FCH contains information used for decoding DL-MAP, and DL-MAP includes information indicating to data of which terminal the DL Bursts transmitted from the base station are mapped, and indicating in which region the DL Bursts are situated in the frame. Further, UL- MAP includes information on UL Bursts transmitted by terminals. Accordingly, the base station transmits resource allocation information for terminal pairs to terminals on UL-MAP of the OFDM/OFDMA frame during a DL transmission interval, and the terminals each allocate data to their allocated bursts, and transmit the data bursts to the base station during a UL transmission interval.

[68] In the illustrated example, the base station generates a UL-MAP message including information for making an order to allocate bursts for terminals a and b in a subburst region ab UL_subburst_ab, information for making an order to allocate bursts for terminals a and c in a subburst region ac UL_subburst_ac, and information for making an order to allocate bursts for terminals a and d in a subburst region ad UL_subburst_ad. With use of the subburst region, the base station can allocate different amount of bursts for C-MIMO-capable terminals, thereby increasing resource utilization.

[69] FIG. 9 is diagram illustrating pilot patterns being applied to a UL PUSC mode in an

OFDM/OFDMA-based 2x2 C-MIMO system according to the present invention. In the UL PUSC mode, the pilot patterns shown in FIG. 9 is transmitted by an antenna TxAnt of a first terminal and an antenna TxAnt of a second terminal, respectively.

[70] Referring to FIG. 9, the antenna TxAnt of the first terminal transmits pilot and data with pilot pattern A 900 and the antenna TxAnt of the second terminal transmits pilot and data with pilot pattern B 950. Then a first receive antenna RxAntO of the base station receives first and second received signals (i.e., received signals on a first channel and a second channel) via first and second channels HOO and HOl, respectively, and a second receive antenna RxAntl receives third and fourth received signals (i.e., received signals on a third channel and a fourth channel) via third and fourth channels HlO and HI l, respectively. In this way, the base station can receive all signals (UL frame) transmitted by the first and second terminals.

[71] Referring back to the example of FIG. 8, the resource allocator 540 allocates the pilot pattern A 900 for the terminal a, and allocates the pilot pattern B 950 for the terminals b, c and d. As a result, the terminals perform spatial multiplexing through the same subcarriers during data transmission. Of course, the base station may exchange the pilot patterns A 900 and B 950 for their allocation. In this case, the burst allocation information and the pilot pattern allocation information for each terminal are included in a MAP IE.

[72] The MAP IE can be, for example, MIMO_UL_Basic_IE defined in Table 1 below. [73] [Table 1] [74]

[75] Where an Uplink Interval Usage Code (UIUC) is used for defining an uplink access form and a burst form associated with the corresponding access. When a value of UIUC is 15 in UL-MAP, it corresponds to Extended UIUC, and this means that the current MAP IE [MIMO_UL_Basic_IE()] delivers particular information (i.e. MIMO). Such MIMO_UL_Basic_IE() includes data region, Connection Identifier (CID) for each terminal, and pilot pattern allocation information, for C-MIMO. In Table 1, 'Num_Assign' indicates the number of burst allocations, and allocates CIDs of terminals corresponding to the number of burst allocations and pilot patterns of the corresponding terminals through a 'for' syntax.

[76] FIG. 10 is a diagram illustrating a burst allocation method according to the present invention. Shown in FIG. 10 are a burst allocation for terminals (e.g., the terminal a and the terminal c in FIG. 8) determined in the current frame, and a burst allocation method for terminals re-grouped in the next frame.

[77] Referring to FIG. 10, the resource allocator 540 receives, from C-MIMO grouper

530, information obtained by re-grouping the optimal terminals searched for in the current frame through the method of FIG. 8, with the remaining terminals except for the optimal terminals, for transmission of the next frame, and allocates bursts based on the information obtained by re-grouping.

[78] In the illustrated example, since the terminals a and c are allocated the greatest amount of bursts in the current frame, the resource allocator 540 generates a UL-MAP message so that it allocates bursts in the next frame as shown in FIG. 8, for example, allocates bursts for terminal b and terminal d, terminal b and terminal e, ..., and terminal b and terminal z except for the terminals a and c. That is, in FIG. 8, the resource allocator 540 includes, in the UL-MAP message, information used for allocating bursts for the terminals b and d in a subburst region bd UL_subburst_bd, information used for allocating bursts for the terminals b and e in a subburst region be UL_subburst_be, and information used for allocating bursts for the remaining terminals in corresponding subburst regions, in this manner. Further, the resource allocator 540 includes, in the UL-MAP message, information used for allocating the pilot pattern A 900 for the terminal b, and information used for allocating the pilot pattern B 950 for the terminals d, e, f, ..., z. Of course, it is also possible to allocate the pilot patterns in the opposite way. In a similar method, it is possible to generate the UL-MAP message so as to allocate the bursts in the same way as described above, even for the terminal d.

[79] Each terminal loads data on its allocated subburst region depending on the UL-MAP where the resource allocation information is recorded, and then transmits the data to the base station using the same subcarriers for the consecutive OFDMA symbols. Therefore, the base station can receive a UL frame transmitted through the same sub- carriers for each terminal, and estimate the corresponding channel using pilots included in at least one tile, thereby restoring the data.

[80] With reference to the above-stated grouping method and resource allocation method, a description will now be made of a method for supporting C-MIMO according to the present invention. For reference, for a detailed process and/or operating principle of the method for supporting C-MIMO according to the present invention, reference can be made to the description of the above-stated apparatus for supporting C-MIMO, so the repeated description will be omitted, and the following description will be given herein, focusing on the steps occurring on a time -by-time basis.

[81] FIG. 11 is a signaling diagram illustrating a method for supporting C-MIMO according to the present invention.

[82] Referring to FIG. 11, terminals each notify their own capacities to a base station by carrying the capacities on an SS (Subscriber Station) Basic Capability Request (SBC-REQ) message, and the base station determines basic capacity of the terminals and the base station, and responds to the notification by carrying the determined basic capacity on an SS Basic Capability Response (SBC-RSP) message (Sl I lO).

[83] Upon receipt of the SBC-RSP message from each of the terminals, the base station registers the corresponding terminal (Sl 120). The term registration as used herein refers to an operation in which the base station connects terminals to the network, receives secondary management CIDs from the terminals, and switches the terminals in a manageable state. To this end, the terminals each send a Registration Request (REG-REQ) message to the base station, and the base station responds thereto using a Registration Response (REG-RSP) message. In this case, the REG-REQ message includes the secondary management CIDs, and the REQ-RSP message includes Right based on which the terminals can deliver traffics to the communication network.

[84] Thereafter, the base station performs scheduling for data transmission on the terminals (S 1130). Herein, the scheduling includes grouping terminals for C-MIMO, and determining resources to be allocated to the grouped terminals, and the determining of resources includes designating a burst region for each terminal in the UL frame, and generating a UL-MAP message so as to allocate pilot patterns. A description of such scheduling has been given based on FIGs. 6 to 10, and its brief description will be made below with reference to FIG. 12.

[85] Subsequently, the base station sends resource allocation information determined for each terminal according to the scheduling, to the terminals on UL-MAP during DL transmission (Sl 140). That is, the base station sends a UL-MAP message so that in a burst region allocated to one terminal supporting C-MIMO, selected based on the terminal information, the one terminal and another one terminal supporting C-MIMO may use at least one subburst region in the same way. In this case, in the UL-MAP message, different pilot patterns are allocated to the one terminal and the another one terminal.

[86] The terminals each receive the frame, decode their data, allocate data synchronized to

UL Bursts indicated by the UL-MAP during UL transmission, and transmit the data to the base station (Sl 150 and Sl 160). In this case, the grouped terminals transmit pilots and data in different pilot patterns.

[87] FIG. 12 is a flowchart illustrating a scheduling method for supporting C-MIMO according to the present invention.

[88] Referring to FIG. 12, a base station searches for C-MIMO-capable terminals in the

SISO/MIMO-mixed system environment depending on the basic capacity exchanged between terminals and the base station (S 1210).

[89] Thereafter, the base station acquires parameters for the searched terminals (Step

S 1220). Such parameters can include, for example, positions of terminals, CINRs based on CQI channels of terminals, allocated power of terminals, etc.

[90] Next, the base station sorts the terminals using the parameters or a combination of the parameters (Step S 1230). For example, the base station sorts the terminals in order of a terminal located closest to the base station when it performs the sorting using the position information of terminals; sorts the terminals in order of a terminal, low interference and good signal state of which is detected through a CQI channel of the terminals, i.e., in order of a terminal having a high CINR, when it performs the sorting using the CINR information of terminals; and sorts the terminals in order of a terminal having higher allocated power when it performs the sorting using the power allocation information of terminals. In this case, it is also possible to sort the terminals taking at least two parameters into consideration.

[91] Subsequently, the base station groups the sorted terminals (Step S1240). That is, as described in FIG. 6, the base station groups the highest-priority terminal among the sorted terminals with the remaining lower-priority terminals. Thereafter, as described in FIG. 7, the base station groups the terminals having the greatest amount of allocated bursts in the next frame based on the fed-back burst allocation information, and regroups the remaining terminals.

[92] The base station allocates resources for the grouped terminals (S 1250). That is, as described in FIG. 8, the base station includes burst allocation information for the grouped terminals in UL-MAP. In this case, the base station segments the burst region to be allocated to any one terminal in the grouped terminals into a plurality of subburst regions, allocates bursts for the remaining terminals except for the any one terminal in at least one subburst region among the plurality of subburst regions, and then allocates a different pilot pattern to each terminal in the grouped terminals. In addition, the base station receives information obtained by re-grouping the optimal terminals searched for in the current frame through the method of FIG. 8, with the remaining terminals except for the optimal terminals, for transmission of the next frame, and allocates resources based on the information obtained by re-grouping as described in FIGs. 9 and 10. [93] While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

[1] A method for supporting Collaborative Multiple Input Multiple Output

(C-MIMO) in wireless communication system, the method comprising: sorting a plurality of C-MIMO-capable terminals using at least one of position information and channel quality information; grouping a highest-priority terminal among the sorted terminals with each of a plurality of terminals selected except for the highest-priority terminal; and transmitting a message including burst allocation information for the grouped terminals.

[2] The method of claim 1, wherein the burst allocation information is information indicating at least one subburst region in a burst region for the highest-priority terminal.

[3] The method of claim 1, wherein the message includes information used for allocating different pilot patterns to the highest-priority terminal and the plurality of terminals.

[4] The method of claim 3, wherein the message is an Up-Link MAP (UL-MAP).

[5] A method for scheduling in Collaborative Multiple Input Multiple Output

(C-MIMO) wireless communication system, the method comprising: sorting, in a current frame, a plurality of C-MIMO-capable terminals, grouping a first-priority terminal with each of a first plurality of terminals selected except for the first-priority terminal, and transmitting first burst allocation information for the grouped terminals; and selecting, in a next frame of the current frame, a first terminal group having a greatest amount of allocated bursts among the grouped terminals, re-grouping a second-priority terminal except for the first terminal group with each of a second plurality of terminals selected except for the second-priority terminal, and transmitting second burst allocation information for the first terminal group and the re-grouped terminals.

[6] The method of claim 5, wherein the first burst allocation information is information indicating at least one subburst region in a burst region for the first- priority terminal.

[7] The method of claim 5, wherein the step transmitting first burst allocation information comprises: transmitting information used for allocating different pilot patterns to the first- priority terminal and the first plurality of terminals.

[8] The method of claim 5, wherein the second burst allocation information is information indicating at least one subburst region in a burst region for the second- priority terminal.

[9] The method of claim 8, wherein the step transmitting second burst allocation information comprises: transmitting information used for allocating different pilot patterns to the second- priority terminal and the second plurality of terminals.

[10] The method of claim 8, wherein the first burst allocation information and the second burst allocation information are transmitted using Up-Link MAP (UL-MAP) message.

[11] A method for supporting Collaborative Multiple Input Multiple Output

(C-MIMO), the method comprising: receiving a registration message including terminal information from each of a plurality of terminals; and transmitting an Up-Link MAP (UL-MAP) message to be allocated the same at least one subburst region in a burst region allocated to a first terminal supporting C-MIMO, selected based on the terminal information by the first terminal and another terminal.

[12] The method of claim 11, wherein the UL-MAP message is transmitted to the plurality of terminals during a Down-Link (DL) transmission interval.

[13] The method of claim 11, wherein the UL-MAP message includes information used for allocating different pilot patterns to the first terminal and another one terminal.

[14] A method for supporting Collaborative Multiple Input Multiple Output

(C-MIMO), the method comprising: receiving, by a first terminal supporting C-MIMO, a message to allocat the same Up-Link (UL) subburst region as that of a second terminal supporting C-MIMO, from a base station; and transmitting, by the first terminal, data and pilots with a pilot pattern different from that of the second terminal using the subburst region according to the message.

[15] The method of claim 14, wherein the subburst region is a part of a two- dimensional burst region allocated to the first terminal in frequency and time.

[16] An apparatus for scheduling in Collaborative Multiple Input Multiple Output

(C-MIMO) wireless communication system, the apparatus comprising: a grouper for grouping a first terminal selected based on information on C- MIMO-capable terminals with each of a first plurality of C-MIMO-capable terminals selected except for the first terminal; and an allocator for allocating a burst region for the grouped terminals.

[17] The apparatus of claim 16, wherein the allocator comprises: a burst segmentation unit for segmenting a burst region for the first terminal into a plurality of subburst regions; a burst allocator for allocating bursts for the first plurality of terminals in at least one of the subburst regions, respectively; a pattern allocator for allocating different pilot patterns for the first terminal and the first plurality of terminals; and a recorder for recording, in UL-MAP, burst allocation information for the first terminal and the first plurality of terminals, and the pilot pattern allocation information.

[18] The apparatus of claim 16, wherein the allocator comprises feedback unit for feeding back burst allocation information for the first terminal and the first plurality of terminals to the C-MIMO grouper.

[19] The apparatus of claim 18, wherein the grouper comprises: a selector for selecting a first terminal group occupying a greatest burst region among the grouped terminals using the fed-back burst allocation information for the first terminal and the first plurality of terminals; and a re-grouper for re-grouping another one second terminal except for the selected first terminal group with each of a second plurality of terminals except for the second terminal.

[20] The apparatus of claim 19, wherein the burst segmentation unit segments a burst region for the second terminal into a plurality of subburst regions; the burst allocator allocates bursts for the first terminal group and bursts for the second plurality of terminals in at least one of the subburst regions, respectively; the pattern allocator allocates different pilot patterns for terminals in the first terminal group and different pilot patterns for the second terminal and the second plurality of terminals; and the recorder records, in the UL-MAP, burst allocation information for the first terminal group, the second terminal and the second plurality of terminals, and the pilot pattern allocation information.

[21] A base station in a Collaborative Multiple Input Multiple Output (C-MIMO) wireless communication system, the base station comprising: a receiver for receiving a registration message including terminal information from each of a plurality of terminals; and a transmitter for transmitting a burst allocation message to be allocated the same at least one subburst region in a burst region allocated to a first terminal supporting C-MIMO, selected based on the terminal information by the first terminal and another terminal.

[22] The base station of claim 21, wherein the transmitter transmits the burst al- location message together with pilot pattern information used for allocating different pilot patterns to the first terminal and another one terminal.

[23] A terminal in a Collaborative Multiple Input Multiple Output (C-MIMO) wireless communication system, the terminal comprising: a receiver for receiving, from a base station, a message to allocat the same Up- Link (UL) subburst region as that of a separate C-MIMO-capable terminal; and a transmitter for transmitting data and pilots with a pilot pattern different from that of the separate C-MIMO-capable terminal using the UL subburst region according to the message.

[24] The terminal of claim 23, wherein the subburst region is a part of a two- dimensional burst region allocated in frequency and time.

[25] A method for processing Collaborative Multiple Input Multiple Output

(C-MIMO) by a terminal in wireless communication system, the method comprising: pairing the terminal and a first terminal, and transmitting data and pilots of the terminal to a base station using a first Up-Link (UL) burst region in a UL frame; and pairing the terminal and a second terminal, and transmitting data and pilots of the terminal to the base station using a second UL burst region in the UL frame; wherein a pilot pattern for the terminal is equal in the first UL burst region and the second UL burst region.

[26] The method of claim 25, wherein the first UL burst region and the second UL burst region each are a subburst region in a burst region for the terminal.