KR101085607B1 - Method and system for transmitting/receiving data according to channel state in a wireless communication system - Google Patents

Abstract

The present invention relates to a method and system for transmitting and receiving data according to a channel state using a symbol division multiple access (SDMA) scheme in a wireless communication system. To this end, the present invention, in a wireless communication system comprising a plurality of mobile stations and a base station for providing a service to the plurality of mobile stations, the data transmission method according to the channel state of the mobile stations, the channel information from the mobile stations When receiving the signal, determining a predetermined modulation scheme in accordance with the channel information, configuring symbols of a predetermined bit corresponding to the determined modulation scheme, and data to be transmitted corresponding to the channel information in a predetermined bit of the configured symbols Sequentially mapping the symbols, and transmitting the mapped symbols to the mobile stations.

Symbol Division Multiple Access, Adaptive Modulation, Channel Status, Bit Allocation, Data Transmit and Receive

Description

TECHNICAL AND SYSTEM FOR TRANSMITTING / RECEIVING DATA ACCORDING TO CHANNEL STATE IN A WIRELESS COMMUNICATION SYSTEM}

1 is a diagram schematically showing the structure of a TDMA communication system.

2 is a diagram schematically showing the structure of an FDMA communication system.

3 is a diagram schematically showing the structure of a CDMA communication system.

4 schematically illustrates the structure of a communication system using an adaptive modulation scheme.

5 illustrates constellation mapping of bits using the 16QAM scheme in accordance with an embodiment of the present invention.

6A and 6B illustrate constellation mapping of bits using a 64QAM scheme in accordance with an embodiment of the present invention.

7 schematically illustrates the structure of a communication system using the SDMA scheme according to an embodiment of the present invention.

8 is a diagram illustrating a symbol configuration when a communication system using an SDMA scheme according to an embodiment of the present invention uses the 64QAM scheme.

9 is a diagram schematically illustrating a structure of a data transmission unit of a BS in a communication system using an SDMA scheme according to an embodiment of the present invention.

10 is a diagram schematically showing the structure of a data receiver of an MS in a communication system using an SDMA scheme according to an embodiment of the present invention.

11 is a diagram illustrating a structure of a control message including bit allocation information in a communication system using an SDMA scheme according to an embodiment of the present invention.

12 is a diagram illustrating an operation process of a BS in a communication system using an SDMA scheme according to an embodiment of the present invention.

13 is a diagram illustrating an operation process of an MS in a communication system using an SDMA scheme according to an embodiment of the present invention.

14 is a diagram schematically showing the structure of the system when the communication system using the SDMA scheme according to the embodiment of the present invention uses the 16QAM scheme.

15 is a diagram illustrating a signal flow of a communication system using an SDMA scheme according to an embodiment of the present invention.

The present invention relates to a wireless communication system, and more particularly, to a method and system for transmitting and receiving data according to a channel state using a symbol division multiple access (SDMA) scheme. will be.

In a cellular system based wireless communication system, various methods of multiple access have been used to efficiently allocate downlink resources to various users. For example, in a time division multiple access (TDMA) -type communication system, a time slot is divided for each user for resource allocation between users. Frequency division multiple access (FDMA) type communication system, which is similar to the TDMA type communication system, in that frequency is a unit of resources allocated between users. It is different. In addition, in a code division multiple access (CDMA) type communication system, different users may be assigned different codes for each user, thereby enabling one user to share one radio resource. These multiple access communication systems have time slots or frequencies allocated to each user to guarantee the quality of service (QoS) or the fairness between users with different channel conditions. Or use a different way of assigning code numbers.

1 is a diagram schematically illustrating a structure of a TDMA communication system.

Referring to FIG. 1, the TDMA communication system has a multi-cell structure, that is, a cell 1 (100) and a cell 2 (150), and manages a base station (BS) that manages the cell 1 (100). BS 110), BS2 160 that manages Cell 2 150, and a plurality of mobile stations (MS), that is, MS1. (120), MS2 (130), MS3 (170), MS4 (180). In addition, data transmission and reception between the BSs 110 and 160 and the MSs 120, 130, 170 and 180 is performed using a TDMA scheme. In other words, the TDMA communication system allocates different time slots t1 and t2 at one frequency f1 to BS1 110, MS1 120, and MS2 130 (121, 131), and also BS2. (160) and MS3 (170) and MS (180) also assign different time slots (t1, t2) at one frequency (f1) (171, 181). The data is transmitted and received through the allocated time slots t1 and t2, that is, the allocated resources.

At this time, when each BS (110, 160) transmits data to the corresponding MSs (120, 130, 170, 18) downlink, MS1 (120) and MS2 (130) located in the cell 1 (100) is adjacent to the cell 2 (150) MS2 (170) and MS4 (180) located in BS2 (160) of the cell 2 (150) are affected by interference or attenuation of signals from BS1 (110) of adjacent cell 1 (100) (122, 132, 172, 182). ). Such interference and attenuation depend on the position of the MS, i.e., the distance between the BS and the MS and the geographical characteristics, and as a result, the MS has various channel conditions.

Here, BS (110, 160) that manages each cell (100, 150) of the two MSs located in each of the cells (100, 150), MS1 (120) and MS2 (130), and MS3 (170) and MS4 (180), That is, the MS, MS1 (120) and MS3 (170), which are located close to the serving BS of each cell (100,150), are relatively less affected by signal interference and attenuation from the BS of the adjacent cell. Accordingly, MS1 (120) and MS3 (170), which are located close to BS1 (110) and BS2 (160), serving BSs of each cell (100,150), have a channel state compared to MS2 (130) and MS4 (180). Is better.

2 is a diagram schematically showing the structure of an FDMA communication system.

Referring to FIG. 2, the FDMA communication system has a multi-cell structure, that is, a cell 1 (200) and a cell 2 (250), the BS 1 (210) for managing the cell 1 (200) and the cell 2 BS2 260, which governs 250, and a number of MSs, namely MS1 220, MS2 230, MS3 270, and MS4 280. In addition, signal transmission and reception between the BSs 210 and 260 and the MSs 220, 230, 270, and 280 are performed using an FDMA scheme. In other words, the FDMA communication system allocates different frequencies f1 and f2 to BS1 210, MS1 220, and MS2 230 (221, 231), and also BS2 260 and MS3 270. Also, different frequencies f1 and f2 are allocated to the MS4 280 (271 and 281). Data is transmitted and received through the allocated frequencies f1 and f2, that is, the allocated resources.

At this time, when each BS (210, 260) transmits data to the corresponding MS (220, 230, 270, 280) in the downlink, MS1 (220) and MS2 (230) located in the cell 1 (200) is BS2 of the adjacent cell 2 (250) From 260 and MS3 270 and MS4 280 located in cell 2 250 are affected by interference or attenuation of signals from BS1 210 of adjacent cell 1 200 (222, 232, 272, 282). Such interference and attenuation depend on the position of the MS, i.e., the distance between the BS and the MS and the geographical characteristics, and as a result, the MS has various channel conditions.

Here, BSs 210 and 260 which manage each cell 200 and 250 among the two MSs located in each cell 200 and 250, MS1 220 and MS2 230, and MS3 270 and MS4 280, That is, the MS1 220 and the MS3 270 which are located close to the serving BS of each cell 200 and 250 are relatively less affected by signal interference and attenuation from the BS of the adjacent cell. Accordingly, the MS1 220 and the MS3 270, which are located close to the BS1 210 and the BS2 260 serving BSs of the cells 200 and 250, have a channel state compared to the MS2 230 and the MS4 280. Is better.

3 is a diagram schematically illustrating a structure of a CDMA communication system.

Referring to FIG. 3, the CDMA communication system has a multi-cell structure, that is, a cell 1 (300) and a cell 2 (350), and the BS 1 (310) that manages the cell 1 (300) and the cell 2 BS2 360, which governs 350, and a number of MSs, namely MS1 320, MS2 330, MS3 370, and MS4 380. In addition, signal transmission and reception between the BSs 310 and 360 and the MSs 320, 330, 370 and 380 are performed using a CDMA scheme. In other words, the CDMA communication system allocates different codes c1 and c2 at one frequency f1 to the BS1 310, the MS1 320, and the MS2 330 (321, 331), and also the BS2 ( 360 and MS3 370 and MS4 380 also assign different codes c1 and c2 at one frequency f1 (371 and 381). Data is transmitted and received through the allocated codes c1 and c2, that is, the allocated resources.

At this time, when each BS (310, 360) transmits data to the corresponding MS (320, 330, 370, 380) in the downlink, MS1 (320) and MS2 (330) located in the cell 1 (300) is BS2 of the adjacent cell 2 (350) From 360 and MS3 370 and MS4 380 located in cell 2 350 are affected by interference or attenuation of signals from BS1 310 of adjacent cell 1 300 (322,332,372,382). Such interference and attenuation depend on the position of the MS, i.e., the distance between the BS and the MS and the geographical characteristics, and as a result, the MS has various channel conditions.

Here, BSs 310 and 360 that manage each cell 300 and 350 among the two MSs located in each cell 300 and 350, MS1 320 and MS2 330, and MS3 370 and MS4 380. That is, the MS1 320 and the MS3 370 which are located close to the serving BS of each cell 300 and 350 are relatively less affected by the interference and attenuation of the signal from the BS of the adjacent cell. Accordingly, MS1 320 and MS3 370, which are located close to BS1 310 and BS2 360, serving serving BSs of each cell 300, 350, have a channel state compared to MS2 330 and MS4 380. Is better.

As described above, in the multi-access communication system, an adaptive modulation method has been proposed to adaptively cope with different channel environments for each MS because the channel state, that is, the channel environment varies according to the location of the MS.

4 is a diagram schematically illustrating a structure of a communication system using an adaptive modulation scheme.

Referring to FIG. 4, a communication system using the adaptive modulation scheme may be configured based on channel information allocated to MSs present in one cell, that is, MS1 411, MS2 421, and MS3 431, respectively. The modulation method is used differently. One BS 401 exists in one cell, and as the separation distance between the BS 401 and the MS increases, that is, the MS is located at the edge of the cell in a cell formed around the BS 401. The channel environment becomes poor, and as a result, different modulation schemes are adaptively used according to the channel environment according to the separation distance. As shown in FIG. 4, the MS1 411 having the smallest separation distance from the BS 401 has a good channel environment, and thus has a high QAM (Quadrature Amplitude Modulation, or QAM). Since the MS3 431 which uses a modulation scheme and has the largest separation distance from the BS 401 has a poor channel environment, a low modulation scheme such as a quadrature phase shift key (QPSK) (hereinafter referred to as 'QPSK') is used. The MS2 421 in the middle region uses the 16QAM scheme because the channel environment is normal. Since the channel environment of the MSs 411, 421, 431 is different according to the separation distance from the BS 401, the system has three areas according to the separation distance, that is, an area 410 using the QAM method according to the channel environment. It is divided into a region 420 using the 16QAM scheme and an region 430 using the QPSK scheme to cope adaptively with various channel environments.

However, this adaptive modulation method has a limitation in increasing cell capacity because the MS3 431 located at the cell edge uses a low modulation method, and in order to satisfy the QoS of the MS3 431 located at the cell edge. Since more time slots, frequencies, or codes need to be allocated than MS1 411 located at, there is a problem that scheduling complexity increases.

Accordingly, an object of the present invention is to provide an SDMA scheme that can be mixed with a multiple access communication system.

Another object of the present invention is to provide a method and system for constructing symbols according to various channel states, that is, channel environments using SDMA, and efficiently allocating resources by mapping data to the symbols to transmit and receive data. Is in.

Another object of the present invention is to provide a method for mapping data mapped symbols onto a constellation plane in accordance with various channel environments using the SDMA scheme.

A method of the present invention for achieving the above object, in a wireless communication system comprising a plurality of mobile stations located in one cell and a base station providing a service to the mobile stations, symbol division according to the channel conditions of the mobile stations A method of transmitting data in a multiple manner, when the base station receives channel information indicating a channel state from the mobile stations, determines a modulation scheme according to the channel information, and configures symbols in accordance with the determined modulation scheme. And checking the channel state of the mobile stations based on the channel information, and sequentially mapping different data to be transmitted to the mobile stations in the order in which the channel state is good, starting from the lower bits of each of the configured symbols. Characterized in that it comprises a process of transmitting to.

Another method of the present invention for achieving the above object is, in a wireless communication system comprising a plurality of mobile stations located in one cell and a base station providing a service to the mobile stations, according to the channel state of the mobile stations In the method of receiving data in a division multiplexing method, after the mobile stations transmit channel information indicating a channel state to the base station, a control message including bit allocation information corresponding to the transmitted channel information is received from the base station. And receiving, from the base station, symbols in which data to be received by the mobile stations corresponding to the bit allocation information are mapped to predetermined bits, and by each mobile station in the received symbols based on the bit allocation information. Extracting and decoding only the data to be received; DONGKUK are data to be received, is characterized in that the channel state is sequentially mapped from the low-order bit of each of said symbols in accordance with a preferred order.

An apparatus of the present invention for achieving the above object, in a wireless communication system comprising a plurality of mobile stations and a base station providing services to the mobile stations, the data in a symbol division multiplexing manner according to the channel state of the mobile stations; In the apparatus for transmitting, when receiving channel information indicating a channel state from the mobile stations, the encoders for encoding different data to be transmitted to the mobile stations corresponding to the channel information, respectively, and the mobile station based on the channel information And a multiplexer for checking a channel state and sequentially mapping the encoded data starting from the lower bits of each symbol according to the order in which the channel state is good.
Another apparatus of the present invention for achieving the above object is, in a wireless communication system comprising a plurality of mobile stations located in one cell and a base station providing a service to the mobile stations, according to the channel state of the mobile stations An apparatus for receiving data in a division multiplexing method, the apparatus comprising: a receiver configured to transmit channel information indicating the channel state to the base station, and then receive a control message including bit allocation information corresponding to the transmitted channel information from the base station And receiving, from the base station, symbols in which data to be received by the mobile stations are mapped to predetermined bits corresponding to the bit allocation information, and extracting only data to be received by each mobile station from the received symbols based on the bit allocation information. A demultiplexer and a demodulator for decoding the extracted data And the data to be received by the mobile stations is sequentially mapped from the lower bits of each of the symbols in order of good channel condition.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention uses symbol division multiple access (SDMA) in a wireless communication system to efficiently transmit and receive data by allocating resources according to various channel environments, that is, channel states. Suggest ways to do it. In this case, the SDMA scheme is used by dividing a bit string constituting one symbol by a plurality of users, for example, a mobile station (hereinafter, referred to as MS). In particular, the present invention includes Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), hereinafter referred to as "FDMA", The SDMA method can be used in a multiple access communication system such as code division multiple access (CDMA) (hereinafter, referred to as "CDMA"). The present invention also provides a method for constructing symbols corresponding to various channel environments, mapping and transmitting data to be transmitted to the MSs to the configured symbols, and mapping the data-mapped symbols to constellations. Suggest how to.

Herein, the present invention maps symbols to constellations so as to differentiate error robustness of bits constituting one symbol in order to use one symbol for different MSs in a channel environment. To this end, in the embodiment of the present invention, two bits of the most significant bit (MSB) of the bit string corresponding to each symbol are referred to as 1,2,3 or 4 in the constellation plane. Used to distinguish between quadrants. The next 2 bits of the MSB 2 bits indicate which quadrant in each corresponding quadrant, and the subsequent 2 bit strings are repeated as described above. In other words, two bits of the MSB serve to distinguish symbols at the largest level, while the least significant bit (LSB) refers to distinguishing the nearest symbols. Accordingly, the bit string located on the left side like the MSB is strong against the channel error among the bit strings constituting one symbol, but the bit string positioned on the right side like the LSB is weak against the channel error.

As described above, according to the present invention, since bits constituting arbitrary symbols have various robustness to errors depending on the position of each bit, each bit is allocated to meet the needs of MSs having different channel environments. Therefore, each MS has only bits that are similar to an error condition, so that detailed bit allocation and channel coding can be performed according to the channel environment of each MS.

FIG. 5 is a diagram illustrating constellation mapping of bits using 16QAM (Quadrature Amplitude Modulation (QAM)) according to an embodiment of the present invention.

Referring to FIG. 5, the constellation mapping using the 16QAM scheme is set such that only one bit is different from each adjacent symbol, such as a gray mapping scheme, and two bits of MSB are selected from 1,2,3 and 4 quadrants. It indicates which quadrant it belongs to. The next two bits of the MSB two bits indicate which one of the quadrants of the corresponding quadrant. For example, if the MSB 2 bits are "00", it represents one quadrant, "01" represents a quadrant, "11" represents a quadrant, and "10" represents a quadrant. In the first quadrant, if the next two bits of the MSB two bits, that is, the LSB two bits are "00", the first quadrant is displayed; if the "01" is a quadrant, if the "11" is a third quadrant, "10" In this case, the quadrant 4 represents the quadrant LSB 2 bits represent the quadrants by gray mapping, for example, in the quadrant 4, the quadrant LSB represents the first quadrant. In case of "11", the second quadrant is represented, in case of "01", the third quadrant is represented, and in case of "00", the fourth quadrant is represented, where the 2 bits of the MSB are bits that are robust to errors, and the LSB 2 bits are errors. Is a weak bit.

6A and 6B illustrate constellation mapping of bits using a 64QAM scheme according to an embodiment of the present invention. 6A is a diagram illustrating uniform constellation mapping, and FIG. 6B is a diagram illustrating non-uniform constellation mapping.

6A and 6B, constellation mapping using the 64QAM scheme is configured such that only one bit is different between each adjacent symbol by gray mapping scheme as in the 16QAM scheme described above, and MSB 2 bits are 1,2,3. And which of the four quadrants belongs to which quadrant. The next two bits of the MSB two bits indicate which one of the quadrants in each corresponding quadrant, and the next two bits indicate which one of the quadrants in each corresponding quadrant. That is, the MSB 2 bits are bits that are error resistant and become weaker bits toward the LSB bit.

In addition, in the case of non-uniform constellation mapping as shown in FIG. 6B, differentiation between bits that are error-resistant and bits that are less robust may be increased compared to the uniform constellation mapping of FIG. 6A. In other words, the non-uniform constellation mapping of FIG. 6B increases the spacing between the quadrants to prevent the occurrence of symbol errors between the first, second, third, and fourth quadrants in each region. It can be taken similarly to the constellation of using a level. Accordingly, the non-uniform constellation mapping can further differentiate the robustness of each bit by obtaining an effect in which the bits that are error-resistant are more error-resistant and the bits that are weak in error are relatively weaker in error. Can be.

7 is a diagram schematically illustrating a structure of a communication system using an SDMA scheme according to an embodiment of the present invention.

Referring to FIG. 7, in a communication system using the SDMA scheme, MSs present in one cell, that is, MS1 711, MS2 721, MS3 731, and MS4 733 may be selected from a base station (BS: Base). The channel environment is different depending on the distance from the station (hereinafter, referred to as 'BS') 701. That is, as the separation distance between the BS 701 and the MS increases, the channel environment becomes worse. As shown in FIG. 7, the MS1 711 having the smallest separation distance from the BS 701 has a good channel environment. The MS3 731 and the MS4 733 having the largest separation distance from the BS 701 have a poor channel environment, and the MS2 721 having the separation distance between the MS1 711 and the MS3 731 is The channel environment is normal. Here, the MS1 711, the MS2 721, and the MS3 731 perform signal transmission and reception directly with the BS 701, but the MS4 733 is referred to as a relay station (RS). Signal transmission and reception is performed with the BS 701 through 703.

Corresponding to such a channel environment, the communication system divides the cell region into three regions 710, 720, and 730, that is, the region 710 having a good channel environment, the region 720 having a normal channel environment, and the poor region 730. . As the cell is divided into three regions, the 64QAM scheme is used as a modulation scheme in all three regions, and if the cell is divided into two regions, the 16QAM scheme is used in all divided regions. The case in which the cell is divided into two regions and uses the 16QAM scheme will be described later, and thus a detailed description thereof will be omitted.

The communication system, which divides a cell into three regions according to the channel environment of the MSs 711, 721 and 731, allocates bits having different degrees of robustness to errors for each of the MSs 711, 721 and 731 using the SDMA scheme. In other words, the bits 710, 720, and 730 in which the MSs 711, 721, 731 are located, that is, bits having different degrees of robustness to errors are allocated according to the channel environment. In more detail, the MS3 731 located in the region 730 having a poor channel environment is allocated to the MS3 731 having the most robust error by using the SDMA method, and the region 720 having a normal channel environment is allocated. ) Allocates the next 2 bits 743 of the MSB 2 bits 741 to the MS2 721 located in the C2), and the LSB 2 having the smallest error tolerance to the MS1 711 located in the region 710 having a good channel environment. Allocates bit 745.

In addition, in the above-described adaptive modulation scheme of FIG. 4, different modulation schemes are used according to channel environments, so that MSs receive all bits having different degrees of robustness to errors. In this case, the robustness of the error is small, so that when an error occurs in the bit in which the error occurs, the MSs use an averaging method of recovering through channel coding. Here, the level of error recovery is determined according to a modulation and coding scheme (MCS) level, so the MCS level should be optimized in an adaptive modulation scheme.

On the other hand, in the communication system using the SDMA scheme according to the embodiment of the present invention, the robustness to error for each MS allocates different bits to correspond to the channel environment of the MSs. In this case, since each MS is assigned only bits that are similar to the robustness of the error according to the channel environment, that is, only the bits that meet the error robustness of each MS are allocated. Accordingly, in the embodiment of the present invention, more detailed adaptive resource allocation is possible than the conventional adaptive modulation scheme. That is, since the robustness of the error is divided up to the bit level rather than the symbol level, more optimized adaptive resource allocation is possible.

In addition, in the communication system using the SDMA scheme according to an embodiment of the present invention, MSBs having high error resistance are allocated to MSs located at the edge of a cell having a poor channel environment, that is, having a large separation distance from the BS, and are robust against errors. These small LSBs are allocated to MSs located inside a cell having a good channel environment, that is, a small distance from the BS. In this case, in the conventional adaptive modulation scheme, different demodulation schemes are used for each MS having various channel environments. However, in the communication system of the present invention, the average cell capacity is increased because data is transmitted to the MSs using a high modulation scheme. .

In particular, the communication system further differentiates the robustness against errors of each bit by using the non-uniform constellation mapping scheme of FIG. 6B described above, and allocates a large bit that is robust to errors to an MS having a poor channel environment. Maintain similar performance to the constellation when using the method. As a result, the communication system prevents performance degradation of the system. In addition, when the non-uniform constellation mapping method of FIG. 6B is used, a bit having a small error robustness may be additionally allocated to an MS having a sufficiently good channel environment to receive the small bit. As the capacity is improved by the allocation, the capacity of the entire cell also increases.

Here, when the communication system according to the embodiment of the present invention uses the SDMA scheme, when the bit that is robust to the error of the MS is large, for example, when the request for the MSB is large, the request for the MSB is too high in the resource allocation process. There may be limits to the allocation. At this time, as shown in FIG. 7, the RS 703 or a low rate error code (Low Code Rate) are used to bit bits that are less robust to errors to the MS 733 that require bit allocation. By allocating, the above limitation can be overcome.

8 is a diagram illustrating a symbol configuration when a communication system using the SDMA scheme according to an embodiment of the present invention uses the 64QAM scheme.

Referring to FIG. 8, the communication system is referred to as Media Access Control (MAC) of each of the MSs, that is, MS1, MS2, and MS3, in order to allocate bits corresponding to the channel environment of each MS. Layer protocol data units (PDUs) (hereinafter referred to as 'MAC PDUs'), that is, MS1 MAC PDUs, MS2 MAC PDUs, and MS3 MAC PDUs. The encoding process is performed to perform physical (PHY) layer PDUs (hereinafter, referred to as PHY PDUs), that is, MS1 PHY PDU, MS2 PHY PDU, and MS3 PHY PDU. Create Here, for convenience of explanation, it is assumed that the channel environment of MS3 is the worst among the MSs, the channel environment of MS2 is normal, and the channel environment of MS1 is good. Each MAC PDU (MS1 MAC PDU, MS2 MAC PDU, MS3 MAC PDU) includes a Cyclic Redundancy Check (CRC) bit. The CRC bit allows each MS to perform an error check of the received MAC PDU when it receives the MAC PDU.

The generated PHY PDUs (MS1 PHY PDU, MS2 PHY PDU, MS3 PHY PDU) are mapped to symbols corresponding to each channel environment. That is, MS1 PHY PDU, MS2 PHY PDU, and MS3 PHY PDU to be transmitted to each MS according to the channel environment of the MSs are mapped to bits having different degrees of robustness for errors in one symbol. In more detail, as described above with reference to FIG. 7, the data to be transmitted to the MS3 having a poor channel environment, that is, the MS3 PHY PDU, is mapped to the MSB 2 bits having the greatest robustness to an error in each symbol, and the channel environment is usually The data to be transmitted to MS2, that is, the MS2 PHY PDU, is mapped to the next two bits of the MSB 2 bits, and the data to be transmitted to MS1 with good channel environment, that is, the MS1 PHY PDU is mapped to LSB 2 bits.

Here, one symbol is composed of 6 bits, and as described above, data to be transmitted to MSs (MS1 PHY PDU, MS2 PHY PDU, MS3 PHY PDU) is mapped to MSs, and thus MS3, which is data to be transmitted to MS3, is mapped to each symbol. The PHY PDU is most robust to errors, and the PHY PDUs are robust to errors in the order of MS2 PHY PDUs, which are data to be transmitted to MS2, and MS1 PHY PDUs, which are data to be transmitted to MS1. As a result, the MS3 PHY PDU transmitted through any channel environment has a higher reception probability than the MS2 PHY PDU or the MS1 PHY PDU. At this time, MSs present in the channel environment, for example, MS1, MS2, and MS3, receive all data mapped to the symbols, that is, MS1 PHY PDU, MS2 PHY PDU, and MS3 PHY PDU. Extract only the data corresponding to itself from PHY PDU, MS2 PHY PDU, and MS3 PHY PDU. The process of the MS receiving the data-mapped penalties will be described later, and thus a detailed description thereof will be omitted.

9 is a diagram schematically illustrating a structure of a data transmission unit of a BS in a communication system using an SDMA scheme according to an embodiment of the present invention. In the following description, it is assumed that the transmitter is included in the BS in the wireless communication system, and the receiver that receives the symbol configured and transmitted by the transmitter is assumed to be included in the MS. Shall be.

First, referring to FIG. 9, the transmitter includes a MAC PDU transmit buffer 910, a CRC adder 920, an encoder 930, a PHY PDU transmit buffer 940, and a multiplexer 950. Include.

The MAC PDU transmission buffer 910 receives a MAC PDU to be transmitted to a plurality of MSs from the MAC layer and delivers the MAC PDU to the CRC adder 920 corresponding to each MS. The CRC adder 920 includes a plurality of CRC adders 921, 923, 925, and 927 corresponding to each MS, and each of the CRC adders 921, 923, 925, and 927 corresponds to an MS corresponding to the MS from the MAC PDU transmission buffer 910. Receive each of the MAC PDU. Each of the CRC adders 921, 923, 925, and 927 adds a CRC bit to the received MAC PDU of each MS and transmits the CRC bit to the encoder 930. Here, the CRC bit is a bit for performing error checking on the information bit when each MS receives the information bit transmitted by the transmitter.

The encoder 930 includes a plurality of encoders 931, 933, 935, and 937 that receive MAC PDUs of respective MSs to which the CRC bit has been added, and each of the encoders 931, 933, 935, and 937 is provided to itself from the CRC adders 921, 923, 925, and 927. Receive each MAC PDU of the corresponding MS. Then, the encoders 931, 933, 935 and 937 generate a PHY PDU by performing an encoding process on the received MAC PDUs of the MSs. That is, the encoders 931, 933, 935, 937 perform an encoding process corresponding to the channel environment of each of the MSs MS1, MS2, MS3,..., PHY to be transmitted to each of the MSs MS1, MS2, MS3,... After generating the PDU, the PHY PDU transmit buffer 940 stores the PHY PDU to be transmitted to each of the MSs MS1, MS2, MS3, ....

The multiplexer 950 transmits a PHY PDU to each MS (MS1, MS2, MS3, ...) stored in the PHY PDU transmission buffer 940, as described above with reference to each MS (MS1, MS2). After mapping to each symbol according to the channel environment of MS3, ...), the PHY PDU transmits each mapped symbol. Here, since a method of mapping data to be transmitted to each MS (MS1, MS2, MS3, ...), that is, the PHY PDU to each symbol corresponding to a channel environment has been described above, a detailed description thereof will be omitted.

10 is a diagram schematically illustrating a structure of a receiver of an MS in a communication system using an SDMA scheme according to an embodiment of the present invention.

Referring to FIG. 10, the receiver includes a demultiplexer 1001, a PHY PDU reception buffer 1003, a decoder 1005, a CRC checker 1007, and a MAC PDU reception buffer 1009.

When the demultiplexer 1001 receives the symbols transmitted by the BS transmitter of FIG. 9, the demultiplexer 1001 extracts only PHY PDUs corresponding to the PHY PDUs corresponding to the received symbols. In other words, the demultiplexer 1001 extracts only data corresponding to an MS including its own, that is, PHY PDU, among data of each MS mapped to each symbol, that is, PHY PDUs, corresponding to the channel environment of each MS. The PHY PDU is transferred to the PHY PDU reception buffer 1003. Then, the PHY PDU reception buffer 1003 stores the PHY PDU.

The decoder 1005 generates a MAC PDU by decoding the PHY PDU stored in the PHY PDU reception buffer 1003, and transfers the generated MAC PDU to the CRC checker 1007. The CRC checker 1007 checks an error of the MAC PDU, that is, the information bit, through the CRC bit included in the MAC PDU received from the decoder 1005. The MAC PDU which does not generate an error as a result of the error checking is delivered to the MAC PDU receiving buffer 1009, and the MAC PDU receiving buffer 1009 transmits the received MAC PDU to the MAC layer.

On the other hand, in the communication system using the SDMA scheme according to an embodiment of the present invention, since a plurality of MSs are used by dividing one symbol, the BS should inform the plurality of MSs of resource allocation related information, that is, bit allocation information. In other words, the BS should inform the MSs of bits that each MS should extract from among the bits constituting the punishments, and the MSs extract only bits allocated only to themselves without extracting all bits of received symbols. Organize your data.

For example, in the case of the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system, the MAP information element (IE), which indicates information of an arbitrary PHY burst, may be used. By sequentially listing connection identifiers (CIDs) (hereinafter, referred to as' CIE's), each MS can know, from the order of listed CIDs, bits to extract from among bits constituting any symbol. . As such, the BS informs the MSs of the bit allocation information through the CID enumeration order, and the BS transmits a control message including the bit allocation information to each MS.

11 is a diagram illustrating a structure of a control message including bit allocation information in a communication system using an SDMA scheme according to the present invention.

Referring to FIG. 11, the control message includes a field 1110 indicating PHY burst allocation information and a field 1120 indicating bit allocation information according to the present invention as in the IEEE 802.16 system.

The field 1110 indicating the PHY burst allocation information includes a field 1111 indicating a symbol offset, a field 1113 indicating the number of subchannels, a field 1115 indicating the number of symbols, and a coding level. Field 1117. Here, the field 1111 indicating the symbol offset indicates how many symbols from the start of the frame the allocated data region starts, and the field 1113 indicating the number of subchannels indicates the number of server channels used. . In addition, the field 1115 indicating the number of symbols indicates the number of symbols used in the allocated data region, and the field 1117 indicating the coding level indicates the channel coding scheme used in the allocated data region.

In addition, the field 1120 indicating the bit allocation information includes CIDs sequentially listed to inform bit allocation information for each MS, a field 1121 indicating the number of the listed CIDs, and a CID for each MS. Field 1123. For example, when the field 1121 indicating the number of CIDs is 2 bits, the 2 bits have one of "00", "01", "10", and "11", and these values indicate the CID. This means that there are one, two, three, or four CIDs in the field 1123 indicated. If the two bits have a value of "00", the field 1123 indicating the CID includes one CID, which means that data is transmitted using a QPSK scheme. In addition, if the two bits are "01", it consists of two CIDs, which means that data is transmitted using the 16QAM scheme. That is, the field 1121 indicating the number of CIDs indicates the number of divided channel environment regions, and thus means a modulation scheme of the communication system.

Here, when the two bits of the field 1121 indicating the number of the CID is "01", since the field 1123 indicating the CID is composed of two CIDs, the field 1123 indicating the CID is 16QAM. The method is 4 bits. The first 2 bits of the 4 bits of the field 1123 indicating the CID, that is, the MSB 2 bits, indicate the CID of the MS having a poor channel environment, and the next 2 bits of the MSB 2 bits, that is, the LSB 2 bits, indicate the channel environment. Good CID is shown. When the 2 bits are '10', the CID is composed of three CIDs, which means that data is transmitted using the 64QAM scheme. Thus, the field 1123 indicating the CID is 6 bits using the 64QAM scheme.

Of the 6 bits, as in the 16QAM scheme described above, MSB 2 bits represent the CID of the MS having a poor channel environment, the next 2 bits represent the CID of the MS having a normal channel environment, and LSB 2 bits represent the channel environment. Good CID is shown. In addition, when the two bits are '11', four CIDs are used to transmit data using the 256QAM scheme, and the field 1123 indicating the CID is 8 bits using the 256QAM scheme. In addition, as in the 16QAM and 64QAM schemes, the 8-bit bits indicate MS CIDs of the MS having the poorest channel environment, and the LSB bits 2 indicate CIDs of the MS having the best channel environment. Each bit represents the CID of the MS having a good channel environment. In this way, the control message informs each MS of a modulation scheme through a field 1121 indicating the number of CIDs, and a bit of a field 1123 indicating a CID corresponding to a value of the field 1121 indicating the number of CIDs. The number is determined and the determined bit tells the CIDs of the respective MSs.

In addition, all MSs present in one cell may receive the control message, and each of the MSs receiving the control message recognizes a modulation scheme through a field 1121 indicating the number of CIDs. Note how many channels are divided into environmental areas. Each of the MSs recognizes the channel environment region to which it belongs and its CID through the field 1123 indicating the CID to know the location of the bit assigned to it among the bits of the symbols. Accordingly, each of the MSs extracts only data corresponding to itself from among data of all MSs mapped to each symbol as shown in FIG. 8.

12 is a diagram illustrating an operation process of a BS in a communication system using an SDMA scheme according to an embodiment of the present invention. As described above, the BS includes the data transmitter of FIG. 9.

Referring to FIG. 12, in step 1201, if the BS receives downlink channel information from MSs present in a cell managed by the BS, the BS proceeds to step 1203. In step 1203, the control message as shown in FIG. 11 is transmitted to the MSs according to the channel environment of the MSs included in the channel information. That is, the BS transmits PHY burst allocation information and bit allocation information according to the channel environment to the MSs. Then, in step 1205, the MAC PDU transmission buffer of the data transmission unit of the BS receives the MAC PDU from the MAC layer, and adds a CRC bit for error checking to the received MAC PDU, and then proceeds to step 1207.

In step 1207, the encoder of the data transmitter of the BS encodes the MAC PDU of each MS to which the CRC bit is added. After generating a PHY PDU to be transmitted to each MS through the encoding process, and stores each generated PHY PDU in the PHY PDU transmission buffer of each MS proceeds to step 1209. In step 1209, the stored PHY PDU is multiplexed to correspond to each symbol by multiplexing to correspond to the channel environment of each MS through a multiplexer, and then in step 1211, the PHY PDU mapped to each symbol is transmitted. When the transmission is completed as described above, each MS has mobility, so the process proceeds to step 1201 again to perform the above-described process.

13 is a diagram illustrating an operation process of an MS in a communication system using an SDMA scheme according to an embodiment of the present invention. Here, as described above, the MS includes a control message transmitted by the BS including the transmitter of FIG. 9 and a receiver of FIG. 10 for receiving each symbol.

Referring to FIG. 13, in step 1301, when the MS transmits channel allocation information corresponding to the channel environment in which the MS is located, the MS receives a control message as shown in FIG. 11 from the BS. Then proceed to step 1303. Herein, the control message includes PHY burst allocation information and bit allocation information as described above. When receiving data symbols configured using the SDMA scheme from the BS again in step 1303, the MS in step 1305, among the data mapped to the received symbols, that is, PHY PDUs of all MSs located in the cell Extract only the data corresponding to the PHY PDU.

In step 1305, the MS extracts only PHY PDUs corresponding to itself from PHY PDUs of all MSs mapped to each symbol by performing a symbol division demodulation method, and stores the PHY PDU data in step 1306. . In this case, the MS extracts only the PHY PDU corresponding to the self from the PHY PDUs mapped to each symbol through the control message received in step 1301. After performing demultiplexing on the PHY PDU data stored in step 1306, the process proceeds to step 1307.

In step 1307, the MS generates a MAC PDU by decoding the demultiplexed PHY PDU, and in step 1309, the MS checks the error of the MAC PDU through the CRC bit included in the MAC PDU. Then, in step 1311, the MAC PDU successfully transmitted through the error check is transmitted to the MAC layer.

14 is a diagram schematically showing the structure of the communication system when the communication system using the SDMA scheme according to the embodiment of the present invention uses the 16QAM scheme. Here, the cell region is divided into three regions in FIG. 7, but the cell region is divided into two regions in FIG. 14. Accordingly, the communication system of FIG. 7 uses the 64QAM scheme, which will be described later. The communication system uses the 16QAM scheme.

Referring to FIG. 14, in the communication system using the SDMA scheme, the channel environments of MSs in one cell, that is, MS1 1411 and MS2 1421 differ from each other according to a distance from the BS 1401. . That is, as the separation distance between the BS 1401 and the MS increases, the channel environment becomes worse. As illustrated in FIG. 14, the MS1 1411 having a small separation distance from the BS 1401 has a good channel environment. The MS2 1421, which has a large separation distance from the BS 1401, has a poor channel environment. Corresponding to such a channel environment, the communication system divides a cell area into two areas 1410 and 1420, that is, an area 1410 having a good channel environment and an area 1420 having a poor channel environment. As the cell is divided into two regions, all two regions use the 16QAM scheme as a modulation scheme.

The communication system that divides a cell into two areas according to the channel environment of the MSs 1411 and 1421 may include bits having different degrees of robustness to errors for the MSs 1411 and 1421 using the SDMA scheme. It allocates correspondingly to the area where the MSs 1411 and 1421 are located, that is, the channel environment. In more detail, the MS2 1421 located in the region 1420 having a poor channel environment is allocated an MSB 2 bit 1431 having high error robustness to the MS1 1421 using the SDMA scheme, and the region 1410 having a good channel environment. The MS1 1411 located is allocated a LSB 2 bit 1433 which is less prone to error.

That is, in the communication system using the SDMA scheme according to the embodiment of the present invention as described above, bits that are robust to errors for each MS are allocated to correspond to channel environments of the MSs. In this case, since each MS is allocated only bits that are similar to the robustness of the error in the channel environment, that is, only the bits that meet the requirements of the error robustness of each MS are allocated, so that delicate adaptive resource allocation is possible. That is, since the robustness of the error is divided up to the bit level rather than the symbol level, more optimized adaptive resource allocation is possible.

15 illustrates a signal flow of a communication system using an SDMA scheme according to an embodiment of the present invention. For convenience of explanation, it is assumed that the BS 1510 transmits data to the MS1 1520 and the MS2 1530 as shown in FIG. 14, and the MS1 1520 has a good channel environment and the MS2 ( 1530 assumes that the channel environment is poor. In addition, since the cell is divided into two regions as described above, the 16QAM scheme is used as the modulation scheme.

Referring to FIG. 15, the BS 1510 receives downlink channel information from MSs, ie, MS1 1520 and MS2 1530, present in a cell that it manages (steps 1501 and 1503). Then, the BS 1510 corresponds to the received channel information, that is, corresponding to the channel environment of the MS1 1520 and the MS2 1530, as described above, a control message including PHY burst allocation information and bit allocation information. Send to MSs 1520 and 1530 (steps 1505 and 1507).

In this case, as previously assumed, the MS1 1520 having a good channel environment is allocated an LSB 2 bit having low robustness to an error using the 16QAM scheme, and the MS2 1530 having a poor channel environment has a high robustness against an error. Sends information indicating that MSB 2 bits are allocated. Then, the MS1 1520 and the MS2 1530 receive the bit allocation information of the control message, thereby recognizing the corresponding bit among the bits constituting each symbol to which the data is mapped (steps 1509 and 1511). ). That is, the MSs 1520 and 1530 recognize bits to which data to be extracted and demodulated are mapped among the bits of each symbol transmitted from the BS 1510 through bit allocation information.

Then, the BS 1510 maps the data to symbols using the SDMA scheme to correspond to the channel environment of the MSs 1520 and 1530 to transmit data to the MSs 1520 and 1530. The mapped symbols are transmitted to the MSs 1520 and 1530 (steps 1513 and 1515). Then, each of the MSs 1520 and 1530 receives the symbols transmitted by the BS 1510, and extracts, i.e., demodulates only the data corresponding to the received symbols using the SDMA scheme (step 1517). Step 1519). At this time, the MS1 1520 extracts the LSB 2 bits allocated to it from the bits of the received symbols through the control message, and the MS2 1530 extracts the MSB 2 bits. Then, errors of the demodulated data are respectively checked.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention can efficiently transmit and receive data by configuring symbols by using the SDMA scheme and mapping and transmitting data to be transmitted to the MSs in each bit of the symbols corresponding to various channel environments of the MSs. have. In addition, the present invention, when the MS receives the data, so that the robustness to the error receives only similar bits, and accordingly differentiating the robustness to the error up to the bit level, it is possible to allocate radio resources in accordance with various channel environments Do. In addition, the present invention can reduce the complexity of the system by using one modulation and demodulation scheme in one cell, and increase the average cell capacity by transmitting and receiving data using a high level modulation and demodulation scheme.

Claims (27)

In a wireless communication system comprising a plurality of mobile stations located in one cell and a base station providing services to the mobile stations, the method for transmitting data in a symbol division multiplexing scheme according to the channel state of the mobile stations, When the base station receives channel information indicating a channel state from the mobile stations, determining a modulation scheme according to the channel information, and configuring symbols according to the determined modulation scheme; Checking the channel state of the mobile stations based on the channel information, and sequentially mapping different data to be transmitted to the mobile stations from the lower bit of each of the configured symbols in order of good channel state to the mobile stations. And transmitting the data. The method of claim 1, Mapping the data to be transmitted, Mapping data to be transmitted to the mobile station having the best channel state to the least significant bit of each of the symbols, and mapping data to be transmitted to the mobile station having the worst channel state to the most significant bit of each symbol. . The method of claim 1, And mapping each symbol to which the data to be transmitted is mapped to a constellation. The method of claim 3, The process of mapping to the constellation, The most significant bit of each symbol, two bits, represents the quadrant in which each of the four quadrants of the constellation are located, and the next two bits of the most significant bit represent each quadrant when the quadrant in which each of the symbols is located is divided into four quadrants. And mapping to indicate the quadrant where they are located. The method of claim 1, Determining a modulation scheme in accordance with the channel information, and configuring the symbols in accordance with the determined modulation scheme, And dividing the one cell into a plurality of areas according to the channel state, and determining the modulation scheme according to the number of the divided areas. The method of claim 1, And transmitting a control message to the mobile stations, the control message including bit allocation information for bits to which data to be transmitted to the mobile stations is mapped. The method of claim 6, The control message, And an identification information field including a field indicating the number of mobile stations and a number of identification information corresponding to the number of mobile stations. The method of claim 7, wherein And mapping identification information of the mobile stations sequentially from an upper bit of the identification information field in order of good channel status. In a wireless communication system comprising a plurality of mobile stations located in one cell and a base station providing a service to the mobile stations, the method for receiving data in a symbol division multiplexing scheme according to the channel state of the mobile stations, Receiving, by the mobile stations, channel information indicating a channel state to the base station, and then receiving a control message from the base station, the control message including bit allocation information corresponding to the transmitted channel information; Receiving symbols from the base station in which data to be received by the mobile stations mapped to predetermined bits corresponding to the bit allocation information; Each mobile station extracts and decodes only data to be received from the received symbols based on the bit allocation information; And the data to be received by the mobile stations is sequentially mapped from the lower bits of each of the symbols in the order in which the channel state is good. 10. The method of claim 9, The data to be received by the mobile stations is the data to be received by the mobile station having the best channel state is mapped to the least significant bit of each of the symbols, and the data to be received by the mobile station having the poorest channel state is the most significant bit of each symbol. Data receiving method characterized in that mapped to. 10. The method of claim 9, The most significant bit of each symbol, two bits, represents the quadrant in which each of the four quadrants of the constellation are located, and the next two bits of the most significant bit represent each quadrant when the quadrant in which each of the symbols is located is divided into four quadrants. Data receiving method, characterized in that indicating the quadrant is located. 10. The method of claim 9, The symbols are data receiving method, characterized in that the one cell is modulated in a modulation scheme corresponding to the number of areas divided according to the channel state. 10. The method of claim 9, The control message, And an identification information field comprising a field indicating the number of mobile stations and a number of identification information corresponding to the number of mobile stations. The method of claim 13, And identification information of the mobile stations is sequentially mapped from an upper bit of the identification information field in order of good channel status. A wireless communication system comprising a plurality of mobile stations and a base station providing a service to the mobile stations, the apparatus for transmitting data in a symbol division multiplexing scheme according to the channel state of the mobile stations, Receiving channel information indicating a channel state from the mobile stations, the encoders encoding different data to be transmitted to the mobile stations in correspondence with the channel information; And a multiplexer for identifying the channel state of the mobile stations based on the channel information, and sequentially mapping the encoded data starting from the lower bits of each symbol to the mobile stations in the order of the good channel state. Data transmission apparatus. The method of claim 15, The multiplexer, And mapping data to be transmitted to the mobile station having the best channel state to the least significant bit of each of the symbols, and mapping data to be transmitted to the mobile station having the worst channel state to the most significant bit of each symbol. . The method of claim 15, The multiplexer, And mapping each symbol to which the data to be transmitted is mapped to a constellation. The method of claim 15, The multiplexer, The most significant bit of each symbol, two bits, represents the quadrant in which each of the four quadrants of the constellation are located, and the next two bits of the most significant bit represent each quadrant when the quadrant in which each of the symbols is located is divided into four quadrants. And mapping to indicate the quadrant where they are located. The method of claim 15, And a transmitter for transmitting a control message to the mobile stations, the control message including bit allocation information for bits mapped with data to be transmitted to the mobile stations. The method of claim 19, The control message, And an identification information field including a field indicating the number of mobile stations and a number of identification information corresponding to the number of mobile stations. 21. The method of claim 20, And the transmitting unit maps the identification information of the mobile stations sequentially from the upper bits of the identification information field in order of good channel condition. In a wireless communication system comprising a plurality of mobile stations located in one cell and a base station providing services to the mobile stations, the apparatus for receiving data in a symbol division multiplexing scheme according to the channel state of the mobile stations, A receiving unit for receiving, from the base station, a control message including bit allocation information corresponding to the transmitted channel information after transmitting the channel information indicating the channel state to the base station; The demultiplexer receives symbols from the base station in which data to be received by the mobile stations is mapped to predetermined bits corresponding to the bit allocation information, and extracts only data to be received by each mobile station from the received symbols based on the bit allocation information. Wow, A demodulator for decoding the extracted data, And data to be received by the mobile stations is sequentially mapped from the lower bits of each of the symbols in the order in which the channel state is good. The method of claim 22, The data to be received by the mobile stations is the data to be received by the mobile station having the best channel state is mapped to the least significant bit of each of the symbols, and the data to be received by the mobile station having the worst channel state is the most significant bit of each symbol. Data receiving apparatus, characterized in that mapped to. The method of claim 22, The most significant bit of each symbol, two bits, represents the quadrant in which each of the four quadrants of the constellation are located, and the next two bits of the most significant bit represent each quadrant when the quadrant in which each of the symbols is located is divided into four quadrants. Data receiving device, characterized in that indicating the quadrant is located. The method of claim 22, The symbols are data receiving apparatus, characterized in that the one cell is modulated in a modulation scheme corresponding to the number of areas divided according to the channel state. The method of claim 22, The control message, And an identification information field including a field indicating the number of mobile stations and a number of identification information corresponding to the number of mobile stations. The method of claim 26, And identification information of the mobile stations is sequentially mapped from an upper bit of the identification information field in order of good channel status.

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