WO2005122448A1

WO2005122448A1 - Wireless communication apparatus

Info

Publication number: WO2005122448A1
Application number: PCT/JP2005/008957
Authority: WO
Inventors: Shimpei To; Seiichi Sampei
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2004-06-09
Filing date: 2005-05-17
Publication date: 2005-12-22

Abstract

According to a communication technique of a block controlled subcarrier adaptive modulation scheme, in a case of blocking some successive subcarriers requiring like reception levels, such blocking is performed not by use of any block size but by selecting one of predetermined block sizes that is close to the number of the successive subcarriers, thereby eliminating necessity of notifying the front subcarrier number of each block to reduce modulation information. In addition, the number of the blocks in each frame is kept constant so as to keep the length of the modulation information constant, thereby eliminating necessity of notifying information indicative of the modulation information length to a receiving end to reduce the control information indicative of the modulation information length. In this way, the control information is reduced so as to provide a wireless communication system having an excellent frame efficiency.

Description

Specification

Wireless communication device

Technical field

The present invention relates to a communication method and a communication device, and more particularly to a control technique of a control signal and a subsequent data signal.

Background art

[0002] In recent years, the number of users seeking high-speed transmission in wireless communication systems has increased. A multi-carrier transmission scheme has attracted attention as one of the communication schemes capable of realizing high-speed and large-capacity dani. The multicarrier transmission method is a method of transmitting information signals in parallel by frequency division multiplexing using a plurality of subcarriers having a narrow bandwidth arranged at a certain frequency interval. Fig. 19 shows an example of the spectrum at the time of transmission (codes 200 and 202) and the received spectrum (codes 201 and 203) subjected to the propagation path fluctuation when high-speed transmission is performed by single-carrier transmission and multi-carrier transmission. As shown in Fig. 19 (a), when high-speed transmission is performed by single-carrier transmission, the frequency characteristics of the entire band are not flat due to the influence of frequency selective fusing. This is equivalent to the occurrence of intersymbol interference in the time domain, and causes a significant deterioration in transmission quality. On the other hand, in multicarrier transmission, even in a frequency selective fading environment, the propagation path fluctuation of each subcarrier can be regarded as uniform fading, and the effect of frequency selective fading can be reduced.

[0003] As shown in Fig. 19 (b), in multicarrier transmission, the received power of each subcarrier (or received SNR: Signal to Noise power Ratio or received SINR: Signal to Interference plus Noise Power Ratio) is different. Therefore, compared to the case where modulation parameters such as transmission power, modulation method, and coding rate are commonly applied to all subcarriers, the adaptive modulation method (which provides appropriate modulation parameters for each subcarrier according to the propagation path conditions) By using the subcarrier adaptive modulation method), highly efficient communication can be performed.

[0004] FIG. 20 shows an outline of subcarrier adaptive modulation in which a different modulation scheme is assigned to each subcarrier. Based on the received spectrum, the modulation method (multi-valued number) Select). However, when using the subcarrier adaptive modulation scheme, the receiving side cannot correctly demodulate the received data unless the receiving side knows in advance the modulation scheme used for each subcarrier. Therefore, it is necessary to notify the receiving side of the modulation scheme identification information indicating which modulation scheme is used by each subcarrier. So figure

As shown in FIG. 21, the modulation scheme is obtained by adding control information (hereinafter, referred to as modulation information: indicated by reference numeral 204) indicating the modulation scheme of each subcarrier before data. Can be notified of the identification information.

[0005] While performing the modulation using different modulation schemes for each subcarrier as shown in FIG. 21, the modulation scheme identification information 206 corresponding to the number of subcarriers is required. If the number is large, the ratio of the modulation information 204 to one entire frame increases, the area for transmitting the actual data 205 decreases, and the frame efficiency decreases.

[0006] To cope with such a problem, a scheme has been proposed in which several adjacent subcarriers having the same level of received power are divided into blocks, and the modulation scheme of each subcarrier is set in block units (for example, And Patent Document 1). This is because, in general, in multicarrier transmission, the reception power of adjacent subcarriers is unlikely to change significantly, and the reception power of subcarriers fluctuates to some extent.Therefore, the same modulation method is used for adjacent subcarriers. This is often the case.

[0007] Such a system is hereinafter referred to as a block control type subcarrier adaptive modulation system, and FIG. 22 shows an outline of the block control type subcarrier adaptive modulation system. In the technique described in Patent Document 1, as shown in FIG. 22, adjacent subcarriers having reception power not exceeding a preset threshold are divided into blocks, and the reception power of the subcarriers in the block is reduced. Based on this, control is performed to allocate a block modulation method. Here, the modulation information also includes modulation scheme identification information 209 indicating a modulation scheme corresponding to the reception power of each block, a head subcarrier number 210 of each block, a modulation information length 211, and power. In this way, if adjacent subcarriers having the same level of received power are divided into blocks and the modulation scheme is set in units of blocks, the modulation scheme identification information for the number of blocks may be notified, thereby reducing the modulation information. Becomes possible. Patent Document 1: JP 2003-169036 A

Disclosure of the invention

Problems to be solved by the invention

[0008] As described above, by using the block control type subcarrier adaptive modulation scheme, compared to a case where block control is not performed, modulation information can be reduced and frame efficiency can be improved. However, in the control method described in Patent Document 1, since a subcarrier number 210 at the head of each block and modulation scheme identification information 209 used in each block are notified as modulation information, a system having a large number of subcarriers is used. In, the number of bits required for notification of the subcarrier number 210 increases. For example, when the number of subcarriers is 7 bits, information indicating a subcarrier number of 7 bits per block is required, and when the number of subcarriers is 1024, information indicating a 10-bit subcarrier number is required for each block. If the number is large, the frame efficiency decreases. Further, in the control shown in Patent Document 1, since the block size (the number of subcarriers to be blocked) is not fixed and the number of blocks is variable, the length of modulation information differs for each frame. . If the length of the modulation information varies from frame to frame in this way, the length of the modulation information must be notified to the receiving side, so that information indicating the modulation information length 211 is newly needed in the frame. This causes a reduction in frame efficiency (Figure 22).

[0009] The present invention provides a multi-carrier transmission system using block-controlled subcarrier adaptive modulation, which reduces the modulation information required for subcarrier adaptive modulation by blocking using a simple method, and improves the frame efficiency. The aim is to provide technology that prevents the decline of the market.

Means for solving the problem

[0010] The present invention provides a multicarrier transmission system using block-controlled subcarrier adaptive modulation, in which several continuous subcarriers requiring the same level of reception are blocked. Prepare a block of the default block size in advance as an option not to block into an arbitrary block size as in, and select a block size from among the preset block size options prepared in advance. Then, the number of continuous subcarriers is adjusted so as to have the block size, and the block is formed. This allows each block This eliminates the need to notify the first subcarrier number, thereby reducing modulation information.

[0011] Further, by keeping the number of blocks in each frame constant and keeping the length of modulation information constant, there is no need to notify the reception side of information indicating the length of modulation information, and control indicating the length of modulation information is performed. Reduce information.

As described above, for block control type subcarrier adaptive modulation, control information such as a subcarrier number at the head of each block and a modulation information length, which need to be notified from the transmission side to the reception side, is reduced. Thus, it is possible to prevent a decrease in frame efficiency.

The invention's effect

[0013] According to the present invention, in a multicarrier transmission system using a subcarrier adaptive modulation scheme, when block control for setting the modulation scheme of each subcarrier in block units is performed, control information The IJ point is that it is possible to reduce the frame rate and prevent the frame efficiency from decreasing.

Brief Description of Drawings

FIG. 1 is a diagram illustrating an example of a configuration of a radio communication system using a block-controlled subcarrier adaptive modulation scheme according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a frame configuration and an example of modulation information when performing block control type subcarrier adaptive modulation according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a detailed configuration example of a wireless communication system according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an example of subcarriers and modulation schemes blocked by the wireless communication system according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing a flow of a blocking control process in the wireless communication system according to the first embodiment of the present invention.

FIG. 6 is a flowchart showing a flow of a sub-control process for reblocking in the wireless communication system according to the first embodiment of the present invention.

FIG. 7 is a flowchart showing a flow of sub-control processing for reblocking by a plurality of candidates in the wireless communication system according to the first embodiment of the present invention.

FIG. 8 is a flowchart showing the flow of a re-blocking process using a single candidate in the sub-control process flow. FIG.

FIG. 9 is a flowchart showing a sub-control process (process A) according to the present invention.

FIG. 10 is a flowchart showing a flow of a main control process (process B) according to the present invention.

FIG. 11 is a flowchart showing a flow of a main control process (process C) according to the present invention.

FIG. 12 is a flowchart showing a sub-control flow (process D) according to the present invention.

FIG. 13 is a flowchart showing a sub-control flow (process E) according to the present invention.

FIG. 14 is a diagram showing an example (64 subcarriers) of fluctuation of a propagation path and a reception spectrum.

FIG. 15 is a diagram showing a process of setting a modulation scheme based on the reception power of each subcarrier and initial blocking.

FIG. 16 is a diagram showing a process of reblocking.

FIG. 17 is a diagram comparing a conventional technology and a technology according to the present embodiment with a frame configuration.

FIG. 18 is a diagram showing a detailed configuration example of a radio communication system of a block control type subcarrier adaptive modulation system according to a second embodiment of the present invention, showing a configuration example in consideration of transmission power control. .

FIG. 19 is a diagram showing transmission / reception spectra of a single carrier (FIG. 19 (a) and a multi-carrier (FIG. 19 (b)).

FIG. 20 is a diagram showing an outline of subcarrier adaptive modulation.

FIG. 21 is a diagram illustrating a frame configuration and a configuration of modulation information when performing subcarrier adaptive modulation.

FIG. 22 is a diagram showing a frame configuration and a configuration of modulation information when performing conventional block-controlled subcarrier adaptive modulation.

BEST MODE FOR CARRYING OUT THE INVENTION

In this specification, the multicarrier transmission scheme refers to a scheme in which information signals are transmitted in parallel by frequency division multiplexing using a plurality of subcarriers having a narrow bandwidth arranged at a certain frequency interval. In the multicarrier transmission scheme, a subcarrier that divides a plurality of subcarriers on the frequency axis and generates a plurality of subcarrier blocks including one or more subcarriers corresponding to the divided frequency in one block. Block generator A stage in which at least one of the number of subcarriers of each subcarrier block and the transmission power or modulation scheme of each subcarrier block is transmitted as adaptive modulation information, and for each subcarrier block, the transmission power or modulation scheme Is referred to as a block control type subcarrier adaptive modulation method.

First, a radio communication technique of a block control type subcarrier adaptive modulation scheme according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present invention. As shown in FIG. 1, radio communication system 302 according to the present embodiment includes transmitting apparatus 300 and receiving apparatus 301 each having antenna ANT. Hereinafter, the present embodiment will be described in detail. First, the frame configuration when subcarriers are blocked, particularly the content of modulation information, will be described with reference to FIG. As shown in FIG. 2, a frame according to the present embodiment is configured to include modulation information 1 and data 2 subsequent thereto. Modulation information 1 is composed of block size identification information 3 indicating a block size, modulation scheme identification information 4 indicating a modulation scheme, and the like. However, in the present embodiment, the TDD (Time Division Duplex) method is targeted as the duplex method.

[0017] In the case of targeting an FDD (Frequency Division Duplex) system which is another duplex system, after notifying the receiving side of the received power of each measured subcarrier to the transmitting side, A procedure for setting the modulation method for each subcarrier on the transmitting side is required. Therefore, when targeting the FDD scheme, the difference is that the signal for notifying the received power of each subcarrier must also be transmitted to the transmitting side on the receiving side.

As shown in FIG. 2, subcarriers are blocked based on respective power spectrum thresholds that define subcarriers to be modulated by 64QAM, 16QAM, QPSK, and BPSK modulation schemes.

Next, an example of the configuration of the transceiver according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, in the receiver 19 according to the present invention, the signal received by the antenna (ANT) is input to the FFT unit 7 via the RF unit 5 and the transmission / reception switch 6. In the FFT unit 7, the time domain signal is converted into a frequency domain signal, converted into a serial signal by the PZS converter 8, and then the received data is extracted by the demodulator 9 and the decoder 10. At this time By feeding back the modulation scheme identification information obtained from the modulation information added before the data from the decoder 10 to the demodulator 9, the modulation scheme used in each block (each subcarrier) is identified.正 Correct demodulation can be performed.

In control section 20, received power measuring apparatus 11 measures the power of each subcarrier after FFT, and modulating scheme determining section 12 determines the modulation scheme of each subcarrier based on the measurement result. . Next, the block control unit 13 performs a process of blocking continuous subcarriers having substantially the same reception power into a predetermined block size and a predetermined number of blocks. In this blocking process, the modulation method of the subcarrier is changed to the modulation method with the previously determined modulation method, power modulation, and low multi-level number in order to block the data into the predetermined block size and number of blocks. There is. In such a case, the amount of data that can be transmitted by one symbol is slightly reduced. Therefore, at the time of blocking processing, such blocking is performed that the amount of data that can be transmitted by one symbol is not reduced as much as possible. . Here, the memory 14 is a memory for storing information of each block and the like.

[0021] Information of each block obtained in control section 20 is reported to modulator 16 of transmitter 21, and each subcarrier is modulated according to a modulation scheme set for each block. Next, the signal is transmitted from the antenna (ANT) via the SZP converter 17, the IFFT unit 18, the transmission / reception switching switch SW6, and the RF unit 5. With the transceiver configuration shown in FIG. 3, subcarriers can be blocked into a predetermined block size and a predetermined number of blocks, and subcarrier power data that has been blocked can be demodulated.

[table 1]

Block size Number of blocks Block identification information

16 subcarriers 1 000

8 subcarrier 2 001

4 subcarrier 5 010

2 subcarrier 4 01 1

1 subcarrier 4 100

[Table 2]

Here, examples of the block size and the modulation scheme used in the present embodiment are shown in Tables 1 and 2, respectively. For example, it is assumed that a total of 64 subcarriers are used as the number of subcarriers, and as shown in Tables 1 and 2, there are 5 types of block sizes, a total of 16 blocks, and a non-transmission (carrier hole) modulation method. It is assumed that different types of modulation are used. Tables 1 and 2 also show the block size identification information corresponding to each block and the modulation method identification information corresponding to each modulation method, and in the examples given here, the block size identification information And 3 bits each for modulation format identification information It turns out that it is necessary. In the communication device shown in FIG. 3, since control is performed to form a block so as to correspond to the block size in the options shown in Table 1, a total of 64 subcarriers has 16 subcarrier blocks (block size: 16). One, eight subcarrier blocks (block size: 8), two four subcarrier blocks (block size: 4), five, two two subcarrier blocks (block size: two), one subcarrier Block (block size: 1) is divided into 4 blocks, totaling 16 blocks. Each of these blocks is modulated by one of the modulation methods shown in Table 2. This is illustrated in FIG. In FIG. 4, the horizontal axis represents frequency, and the vertical axis represents a modulation method (modulation degree) .There are 64 white circles indicating subcarriers in total, and the position on the vertical axis of the white circle is for each subcarrier. It shows the modulation method set by the user. As shown in FIG. 4, all of the 64 subcarriers are divided into one block of 16 subcarriers of block size 16 and block 2 of 8 subcarriers of block size 8 by the communication device (particularly, the block control unit 13) shown in FIG. Each block is divided into 16 blocks: 5 blocks of 4 subcarriers of block size 4, 4 blocks of 2 subcarriers of block size 2, and 4 blocks of 1 subcarrier of block size 1.

FIG. 5 is a flowchart showing a control flow relating to the blocking process according to the present embodiment. As shown in FIG. 5, based on the received power of each subcarrier of the previous frame measured on the transmitting side, the subcarriers having the received power are set to high! The subcarriers having low received power are subjected to subcarrier adaptive modulation for assigning the low modulation level and the modulation scheme, respectively (steps 001 to 002). Here, continuous subcarriers to which the same modulation scheme is assigned are temporarily blocked. This processing is hereinafter referred to as initial blocking (step 003). When the number of blocks thus initialized and the block size of each block match the predetermined ones (Table 1), the block processing is completed without the need for further block processing (step 004). On the other hand, if the number of blocks subjected to the initial blocking and the block size of each block are different from the predetermined ones (Table 1), it is necessary to perform the re-blocking process so that the predetermined number of blocks and the block size are obtained. (Steps 004, 005). In this re-blocking process, the modulation scheme of the subcarriers is changed from the previously determined modulation scheme to a modulation scheme with a low number of modulation levels and a modulation scheme in order to block the data into a predetermined block size and the number of blocks. change At this time, control is performed so that the amount of data that can be transmitted in one symbol is not reduced as much as possible. By this re-blocking, the blocking process is completed, and each subcarrier is subjected to the predetermined number of blocks and block size.

[0024] In the following, a procedure of subcarrier blocking will be described for the case where the received power of each subcarrier is as shown in FIG. Here, as the subcarrier reblocking procedure, a reblocking process using the control flows shown in FIGS. 6 to 13 will be described. The control flows shown in FIGS. 6 to 13 show an example of a blocking algorithm that does not reduce the amount of data that can be transmitted in one symbol as much as possible. However, here, the TDD system is targeted as the duplex system.

First, control flows of FIGS. 6 to 13 will be briefly described. As shown in FIG. 6, from step 004 in FIG. 5, the process proceeds to the reblocking 005 process, and in step 006 in FIG. 6, the reblock counter is set to “0”. In step 007, in Table 1, the block having the largest size among the blocks still used for reblocking is set as the allocated block. In step 008, among the initial blocks that have not been reblocked, the block of the maximum size is set as a candidate block. In step 009, it is determined whether there are a plurality of candidate blocks. If there are a plurality of candidates, the process proceeds to step 010 to perform re-blocking processing for a plurality of candidates (steps 016 to 020). If there is not a plurality, the process proceeds to step 011 to perform a re-blocking process for a single candidate (steps 021 to 025). In either case, the process proceeds to step 012, and it is determined whether or not reblocking has succeeded. If not successful, the process proceeds to step 013, where the next largest block after the current candidate block among the initial blocks that have not been reblocked is set as a new candidate block, and the process returns to step 009. If the reblocking is successful, the process proceeds to step 014, and the value of the reblock counter is incremented by "1". Next, the routine proceeds to step 015, where it is determined whether or not the reblock counter is 16 (16 is the total number of blocks in Table 1). If not, the process returns to step 007. If it is the total number of blocks, this processing ends.

FIG. 7 is a flowchart showing the flow of a reblocking control process using a plurality of candidates. First, from step 009 (FIG. 6), it is determined whether or not the candidate block size is equal to the allocation block size, and if they are equal, the process proceeds to step 020 (process G: step 049 to be described later). Go to 052). If the candidate block size is not equal to the allocation block size, the process proceeds to step 017 to determine whether the candidate block size is equal to the allocation block size. If it is the candidate block size and the allocation block size, the process proceeds to step 019 (process B: steps 037 to 048 described later). If it is not the candidate block size and the allocated block size, the process proceeds to step 018 (process A: steps 026 to 036 described later). Thereafter, the process proceeds to step 012.

FIG. 8 is a flowchart showing the flow of a reblocking control flow using a single candidate. As shown in FIG. 8, the process proceeds from step 009 (FIG. 6) to step 021, where it is determined whether or not the candidate block size is equal to the allocation block size. If the candidate block size is equal to the allocation block size, the process proceeds to step 022 to reblock the candidate block, and then proceeds to step 012. If the candidate block size is not equal to the allocation block size, the process proceeds to step 023 to determine whether the candidate block size is equal to the allocation block size. If it is the candidate block size and the allocation block size, the process proceeds to Step 025 (Process E: Steps 064 to 075 to be described later). If the size is not the candidate block size or the allocated block size, the process proceeds to step 024 (process D: steps 053 to 063 described later). Thereafter, the process proceeds to step 012.

FIG. 9 is a flowchart showing the flow of the process regarding process A. From step 017, the process proceeds to step 026, where it is determined whether or not there is a reblocked candidate block in both adjacent blocks. In the case of Yes, the process proceeds to step 027, where the re-blocking is performed from the leftmost subcarrier among the blocks of the minimum size among the candidate blocks in which both adjacent blocks have been re-blocked. In the case of No, the process proceeds to step 028, and it is determined whether or not a reblocked candidate block exists in one adjacent block. In the case of Yes, the process proceeds to step 029, and reblocking is performed for the smallest size block among the candidate blocks in which one adjacent block has been reblocked, starting from the subcarrier on the adjacent block side that has been reblocked. If No, the process proceeds to step 030 to calculate the difference between the M-ary modulation values of the candidate block and its adjacent block.

[0029] Then, the process proceeds to step 031, where it is determined whether or not there is one candidate block in which the difference between the M-ary modulation values is the smallest. If yes, go to step 032 and select In addition, re-blocking is also performed on the subcarrier power on the side where the difference of the modulation multi-level number from the adjacent block becomes large. In the case of No, the process proceeds to step 033, and it is determined whether or not there is one block having the lowest modulation multi-level number among the candidate blocks having the minimum difference between the modulation multi-level numbers. In the case of Yes, the process proceeds to step 034, in which the subcarrier power of the adjacent block having a higher modulation level among the blocks satisfying the left condition is also reblocked. If the modulation level of both adjacent blocks is the same, the left subcarrier power is also reblocked. If No, the process proceeds to step 035, and it is determined whether or not one of the candidate blocks satisfying the above condition has the smallest size. In the case of Yes here, in step 036, the subcarrier power of the adjacent block having the higher M-ary modulation value among the blocks corresponding to the above conditions is re-blocked. If the modulation level of both adjacent blocks is the same, the left subcarrier power is also reblocked. If No, the process proceeds to step 037, and the leftmost block among candidate blocks satisfying the above conditions is re-blocked from the left subcarrier. After the processing of steps 027, 029, 032, 034, 036, 037, the process proceeds to step 012 (FIG. 6).

FIG. 10 is a flowchart showing the flow of the processing relating to the processing B. The process proceeds from step 017 to step 038 to determine whether both adjacent blocks of all the candidate blocks have been reblocked. If yes, the process proceeds to step 039, and reblocking fails. In the case of No, the process proceeds to step 040, and it is determined whether or not there is a candidate block in which one adjacent block has been reblocked. In the case of Yes, the process proceeds to step 041, and the following equation (1) is calculated for the candidate block in which one of the adjacent blocks has been reblocked, and reblocking is performed so that K becomes the minimum. In the case of No, the process proceeds to step 042 to calculate the following equation (1) for the candidate block, and then proceeds to step 043 to determine whether or not there is one candidate block with the minimum K. In the case of Yes, the process proceeds to step 044, and re-blocking is performed so that K becomes the minimum for the block corresponding to the left condition. In the case of No, the process proceeds to step 045, and it is determined whether or not there is one block having the lowest modulation multilevel number among the candidate blocks having the smallest K. In the case of Yes, the process proceeds to step 046, and reblocking is performed so that K becomes the minimum for the block corresponding to the left condition. If No, proceed to step 047, and select the block with the smallest size among the candidate blocks that meet the above conditions. It is determined whether the force exists. Here, in the case of Yes, the process proceeds to step 048, and re-blocking is performed so that K becomes the minimum for the block corresponding to the condition of step 047. In the case of No, the process proceeds to step 049, and the left subcarrier force is re-blocked for the leftmost block among the candidate blocks satisfying the condition of step 047. Steps 039, 041, 044, 046, 048, 049 go to step 012.

Next, the flow of the process C will be described with reference to FIG. As shown in FIG. 11, the process proceeds from step 016 (FIG. 7) to step 050 to compare the modulation multi-level numbers of the candidate blocks. Next, the process proceeds to step 051, where it is determined whether or not there is only one block in which the number of modulation levels is the minimum. In the case of Yes, the process proceeds to step 052, and the candidate block having the minimum number of modulation levels is re-blocked. In the case of No, the process proceeds to step 053, and the block on the left side among the candidate blocks corresponding to the above conditions is re-blocked. Step 05 2-step or Step 053 Force to Step 012.

Next, the flow of the processing D will be described with reference to FIG. From step 023 (FIG. 8), the process proceeds to step 054, where it is determined whether or not both adjacent blocks have already been reblocked. In the case of Yes, the process proceeds to step 055, and the subcarrier force on the left end of the candidate block is re-blocked by the allocated block size. In the case of No, the process proceeds to step 056, and it is determined whether or not one of the adjacent blocks has already been re-blocked. In the case of Yes, the process proceeds to step 057 to reblock the subcarrier power allocation block size of the reblocked adjacent block. If No, the process proceeds to step 058, and it is determined whether or not the difference between the M-ary modulation values of the candidate block and its adjacent blocks is different. Here, in the case of Yes, the process proceeds to step 059 to reblock the allocated block size from the subcarriers on the adjacent block side where the difference of the modulation multi-value number becomes large. In the case of No, the process proceeds to step 060, and it is determined whether or not the modulation schemes of both adjacent blocks are different. In the case of Yes here, the process proceeds to the step 061, the modulation multi-value number is high, and the subcarrier power on the adjacent block side is also allocated and the block size is re-blocked. If No, the process proceeds to step 062, and it is determined whether the sizes of both adjacent blocks are different. In the case of Yes here, the process proceeds to a step 063 to reblock the subcarrier power allocation block size of the adjacent block having the smaller size. If No, go to step 064, where the leftmost subcarrier The power is harmed. Steps 055, 057, 059, 061, 063, and 064 proceed to step 012.

Next, the flow of the process E will be described with reference to FIG. The process proceeds from step 016 (FIG. 7) to step 065, where it is determined whether or not both adjacent blocks have already been reblocked. Here, in the case of Yes, the process proceeds to step 066, and reblocking fails. In the case of No, the process proceeds to Step 067, and it is determined whether or not one of the adjacent blocks has already been re-blocked. Here, in the case of Yes, the process proceeds to step 068, where the subcarriers of the adjacent blocks that have not been reblocked are also reblocked. If No, proceed to step 069, calculate the following equation (1) for the candidate block and both adjacent blocks, and proceed to step 070 to judge whether there is a difference in the value of K. Here, in the case of Yes, the process proceeds to Step 071 to re-block together the subcarriers of the adjacent block in which the value of K becomes small. In the case of No, the process proceeds to step 072, and it is determined whether or not the modulation methods of the two adjacent blocks are different. Here, in the case of Yes, the process proceeds to Step 073 to re-block together the subcarriers of the adjacent block having a low modulation multilevel number. If No, the process proceeds to step 074, and it is determined whether or not the sizes of both adjacent blocks are different. Here, in the case of Yes, the process proceeds to Step 075, and re-blocking is performed together with subcarriers of adjacent blocks having a small size. In the case of No, the process proceeds to step 076, and the subcarrier of the adjacent block on the left side of the candidate block is re-built together. Steps 066, 068, 071, 073, 075, 076 and the like proceed to step 112. Blocking (re-blocking) is performed by the above processing.

Next, FIG. 15 shows the modulation scheme of each subcarrier set based on the received power, taking as an example a case where each subcarrier has the received power shown in FIG. Here, there are 64 white circles indicating the subcarriers in FIG. 15, and the position on the vertical axis indicates the modulation scheme set for each subcarrier. Also, in FIG. 15, adjacent subcarriers that are once set to the same modulation scheme are blocked (initial blocking: step 003 in FIG. 5), and numbers (1) to (16) are assigned to them. Waving. Here, the blocks that are initially blocked to an arbitrary block size as shown in FIG. 15 are different from those shown in Table 1 in both the block size and the number of blocks. It is necessary to perform re-blocking to achieve the indicated block size and number of blocks (Figure 5: Steps 004 to 005). As described above, since the re-blocking process is performed to block the block size and the number of blocks shown in Table 1, the number of blocks that can be formed by the re-blocking is shown in Table 1 When the number of blocks becomes 16, that is, when the number of blocks becomes 16, the re-blocking process ends. Therefore, a counter called a re-block counter is provided, and the number of blocks for which re-blocking has been completed is counted (FIG. 6: steps 006 and 014). At this time, block assignment (re-blocking) is performed in order from the largest block size in the options shown in Table 1 (block sizes 16, 8, 4, 2, 1).

Here, as shown in steps 007 to 008 in FIG. 6, among the blocks not used for reblocking in Table 1, the largest block is allocated, and the block that is not reblocked is allocated. Is referred to as the candidate block. First, in allocating the block size 16, the block with the largest block size (block (10): candidate block) is selected from the blocks (Fig. 15) that have been initialized to an arbitrary size first. ) Is compared with the block size 16 (allocated block) (steps 007 to 011). Since the block size of the block (10) shown in FIG. 15 is 15, it is obvious that one subcarrier is insufficient to re-block the block (10) into a block of size 16. In such a case, in this embodiment, control is performed to form a block of a desired size by combining subcarriers of adjacent blocks. In this control, the candidate block and the neighboring block's subcarrier modulation scheme are set to the same modulation scheme in order to create a block of the same size as the allocation block by combining the candidate block with the subcarriers of the neighboring block and re-block the blocks. Perform the adjustment process.

In the case of FIG. 15, the modulation method of all subcarriers in block (10) is changed to QPSK, and the force combined with one subcarrier on the right end of block (11) or the left end of block (9) is changed. There are two control patterns to change the modulation method of one subcarrier to 16QAM and combine it with block (10). (Change to a modulation method with a low modulation power is also performed because it causes bit errors. Absent).

[0038] When the former is selected from these two patterns, re-blocking is performed to obtain 15 (the number of subcarriers) x 2 (modulation multi-level number of 16QAM-variation of QPSK per symbol). (Multi-value number) = 30-bit information amount is reduced. On the other hand, if you choose the latter, 1 Per symbol, 1 (the number of subcarriers) X 2 (the number of modulation levels of 64QAM—the number of modulation levels of 16QAM) = The amount of 2-bit information can be reduced. Therefore, in order to prevent a decrease in the amount of information that can be transmitted in one symbol, the modulation method for the leftmost subcarrier of block (9) should be changed to 16QAM and combined with block (10). Is good. Figure 16 shows how the modulation scheme of the subcarrier is changed when re-blocking to a predetermined block size is performed by a procedure based on this concept. The white circles in Fig. 16 do not change, the modulation method for each subcarrier, the black circles show the modulation method for each subcarrier before the change, and the hatched circles show the modulation method for each subcarrier after the modulation method is changed by reblocking. Is represented. FIG. 16 shows the re-blocked block of size 16 as a new block (a) (FIG. 8: Steps 021 to 025). As can be seen by comparing FIGS. 15 and 16, for example, block (15) is changed to 16QAM and combined with block (14) to form a new block (g). Other blocks are similarly re-blocked.

As described above, according to the block control technique according to the present embodiment, when performing re-blocking of subcarriers, if there is no candidate block having the same size as the allocated block, By changing the power or the modulation scheme of the adjacent block, and combining the candidate block with the subcarriers of the adjacent block, the size is adjusted to be the same as the allocated block size. As described above, when the modulation scheme of a candidate block or an adjacent block is changed, simple control is performed in a direction to prevent a decrease in the amount of information that can be transmitted as much as possible. Here, a discriminant for preventing a decrease in the amount of information that can be transmitted is shown below.

[0040] K = L X (lb-la) Equation (1)

Where L in equation (1) is the number of subcarriers for which the modulation scheme must be changed when re-blocking, and lb is the number of bits that can be transmitted per subcarrier according to the modulation scheme before the change. la indicates the number of bits that can be transmitted per subcarrier according to the changed modulation scheme. That is, (lb-la) represents the difference between the M-ary modulation values in adjacent blocks. Also, K represents the amount of reduction in information due to the change in modulation scheme. When re-blocking is performed by combining subcarriers of adjacent blocks, control is performed to reduce the value of K (Figure 8: Step 023). Step 025, FIG. 13 steps 065 to 071).

Here, if there are a plurality of blocks having the same block size, For each, the amount of information degradation is evaluated using equation (1), and re-blocking is performed so that K is minimized (Fig. 7: Step 019, Fig. 10: Steps 038 to 044). When there are a plurality of blocks of the same block size having the same value of K, the blocks are modulated by a low M-ary modulation value, and the blocks are re-blocked by giving priority to the blocks with a small block size! / (Figure 10: Steps 045 to 049).

[0042] By the above-described control, the largest block of size 16 in Table 1 is allocated.

Allocation of the block of size 8 with the next largest block size is performed. From Figure 15, block (7) has the largest block size other than block (10) (already re-blocked), and its block size is 9, so it is re- It can be seen that one subcarrier is left when blocking. In such a case, first, the subcarrier force at the end where the adjacent block has already been reblocked is reblocked (Figure 8: Step 024, Figure 12: Steps 053 to 057). Here, since the blocks adjacent to block (7) (blocks (6) and (8)) have not been re-blocked, the process proceeds to step 058 in FIG. 12 to compare the modulation schemes of the adjacent blocks. .

According to FIG. 15, the modulation scheme of block (7) is QPSK, the modulation scheme of adjacent block (6) is BPSK, the modulation scheme of block (8) is 16QAM, and block (7) The difference between the M-ary modulation values for (6) and (6) is 1, and the difference between the M-ary modulation values for blocks (7) and (8) is 2. When the difference between the modulation levels is different from the neighboring blocks on both sides in this way, the subcarrier force at the end where the difference between the modulation levels is larger is re-blocked to reduce the difference between the modulation levels. Provide a fraction on the smaller side. In this embodiment, this control re-blocks the block (7) into a block of size 8 counting from the rightmost subcarrier. The block of size 8 thus re-blocked is shown in FIG. 16 as block (b). Here, if the difference in the modulation level between adjacent blocks on both sides is the same, the modulation level in the adjacent block is high, and the subcarrier power at the end is reblocked. If the modulation level of the adjacent block is also the same, the subcarrier force at the end with the smaller adjacent block size is also reblocked (steps 060 to 064).

As shown in Table 1, another size 8 block remains, so that the size 8 block is re-formed as shown in Table 1. Figure 15 The block with the next largest block size is block (13) (block size 6), and there are two subcarriers short to re-block into block of size 8. Therefore, consider combining the subcarriers of the blocks (12) or (11) adjacent on both sides into a block of size 8, and calculate Equation (1) as described above. As a result of the calculation of equation (1), in this case, the block (13) is used as a carrier hole (no transmission) and combined with the subcarriers of the block (12) reduces the amount of information to be reblocked. It turns out that there are few. Therefore, re-blocking is performed by using the block (13) as a carrier hole and combining the sub-carrier with the block (12). The block of length 8 thus reblocked is shown in FIG. 16 as block (c).

Next, a block of size 4 is allocated. The largest block size among the remaining initial blocks in Fig. 15 is block (9) (the block size is 5 because the subcarrier at the right end has been moved to the adjacent block by the previous processing). Therefore, when re-blocking is performed using a block of size 4, only one subcarrier is left. At this time, of the adjacent blocks, block (10) (block (a) in FIG. 14) has already been re-blocked, so the size of the block (10) -side subcarrier (rightmost subcarrier) is reduced. Block 4 is performed (Figure 8: Step 024, Figure 12: Steps 054 to 057). The block of size 4 thus re-blocked is shown in FIG. 16 as block (d).

Further, reblocking of size 4 is performed. Block (2) has the largest block size among the remaining initial blocks, but since the block size is exactly 4, it is re-blocked as it is (Figure 8: Steps 021 to 022) and the block ( This is shown in Fig. 16 as e).

Next, among the remaining initial blocks, the blocks having the largest block sizes are blocks (3), (6),

(11), (14), and (16), since these blocks are all of size 3, one subcarrier is insufficient for re-blocking with size 4 blocks. Therefore, it is determined whether the sub-carriers of the adjacent blocks can be re-blocked together. Since both adjacent blocks of block (11) have already been reblocked, they cannot be reblocked into block (11) size 4 blocks. Therefore, the above equation (1) is calculated for blocks (3), (6), (14), and (16), and the value of K is obtained for each block. As a result, the modulation method of block (6) is changed to BPSK, and the remaining one of block (7) is changed. By combining with subcarriers, reblocking of size 4 is performed (Fig. 10: steps 038 to 044). The block of length 4 thus re-blocked is shown in FIG. 16 as a block (!).

Next, the blocks having the largest block size among the remaining initial blocks are blocks (3) and (1).

I), (14), and (16). The value of K is obtained by performing the calculation of equation (1) in the same manner as above. As a result, the modulation method of block (15) is changed to 16QAM and size 4 is reblocked together with block (14) (Fig. 10: steps 038 to 044). The block of length 4 thus reblocked is shown in FIG. 16 as block (g).

[0049] Further, in order to perform re-blocking of size 4, the same processing as described above is performed for blocks (3), (11), and (16). Since both adjacent blocks have already been reblocked, blocks (11) and (16) cannot be reblocked into size 4 blocks. Therefore, the modulation scheme of block (3) is changed to BPSK, and re-blocking of size 4 is performed together with block (4). The block of length 4 thus re-blocked is shown in FIG. 16 as block (h).

[0050] Since the reblocking of the block of size 4 has been completed by the above processing, reblocking of the block of size 2 is performed next. Here, blocks (11) and (16) have the largest block sizes among the remaining initial blocks, but these two blocks are blocks of size 3 using the same modulation scheme, and V, Both blocks may be re-blocked because the blocks adjacent to the shifted block have already been re-blocked. In such a case, in the present embodiment, it is assumed that the left block power is re-blocked (FIG. 38: step 049), and the size 2 re-block is first performed from the leftmost subcarrier of the block (11). Then, in the next! サイズ, re-blocking of size 2 is performed from the leftmost subcarrier of the block (16). The blocks of length 2 reblocked in this way are shown in Fig. 16 as blocks (0, (j), respectively. Furthermore, for blocks (1) and (8), reblocking of size 2 is also performed. The re-blocked blocks of length 2 are shown in Fig. 16 as blocks (k) and (1), respectively. Then, re-blocking is performed using the block of the leftmost subcarrier, and the remaining subcarriers at the left end of block (5) and block (7)

II) and the rightmost subcarrier of block (16). Since the size is 1, the block having a low modulation level (5) is re-blocked in order! FIG. 16 shows the blocks of length 1 thus re-blocked as blocks (m), (n), (o), and (p).

[0051] Through the above processing, all 64 subcarriers can be reblocked into blocks having the sizes shown in Table 1. Each subcarrier thus re-blocked is transmitted after being modulated by the modulation method of each block.

Here, the conventional block control (based on the technology described in the above-mentioned Japanese Patent Application Laid-Open No. 2003-169036) and the block control according to the present embodiment will be described with reference to the case of the propagation path condition shown in FIG. The amount of data that can be calculated is calculated, and the effect of the block control according to the present embodiment will be described.

First, the amount of modulation information in the conventional block control is calculated. In the conventional block control, in the case of the propagation path condition shown in FIG. 14, blocking is performed as shown in FIG. In this case, since a total of 64 subcarriers are used, a subcarrier number needs 6 bits per block, and as shown in Table 2, 3 bits per block are required as modulation scheme identification information. Become. Furthermore, since it is necessary to notify the length of the modulation information to the receiving side, if 8 bits are allocated as the modulation information length, 152 bits are required as the modulation information for all 16 blocks. Usually, such control information is modulated by the modulation method having the lowest modulation multilevel number. Therefore, if this modulation information is modulated by BPSK, one bit of information can be transmitted per subcarrier, and a multi-carrier signal of three symbols is required. From FIG. 15, the data following this modulation information is 196 bits per symbol.

On the other hand, the modulation information in the block control according to the present embodiment is composed of block identification information of 3 bits per block (see Table 1) and modulation scheme identification information of 3 bits per block. 96 bits are required for 16 blocks. As described above, when this modulation information is modulated by BPSK, a two-symbol multicarrier signal is obtained. From FIG. 16, the data following this modulation information is 182 bits per symbol.

As described above, when the block control according to the present embodiment is performed, the number of bits that can be transmitted in one symbol is slightly reduced as compared with the case where the conventional block control is performed. However, while the conventional block control required three symbols for modulation information, the present embodiment In the block control according to the state, it becomes possible to use one symbol that is surplus of two symbols as a data symbol. Figure 17 shows this situation. As shown in Fig. 17, the modulation information is reduced from code 22 to code 24, and the amount is used for data transmission (code 23 to code 25), so that the number of symbols in one frame is 10 When a short frame is transmitted, the amount of data that can be transmitted in one frame increases, indicating that highly efficient communication can be achieved.

[0056] As described above, the difference between the block control according to the present embodiment and the conventional block control appears more strongly as the number of subcarriers used increases. In addition, the frame efficiency can be further improved by setting the block size as shown in Table 1 in consideration of the specified frequency band of the system and the usage environment. As described above, with the block control according to the present embodiment, frame efficiency can be improved by performing control to block subcarriers into a block size and the number of blocks determined in advance. .

Next, a communication technique of the block-controlled subcarrier adaptive modulation scheme according to the second embodiment of the present invention will be described with reference to the drawings. In the control described so far, since the block size and the number of blocks of the initial block do not always match the predetermined ones, it is necessary to change the modulation scheme set first to a modulation scheme with a lower modulation level. Therefore, the adjustment was performed so that the default block size and the number of blocks were obtained. In this way, when re-blocking, when changing from a modulation scheme with a high modulation level to a modulation scheme with a low modulation level, the subcarriers to be changed are transmitted with a transmission power larger than the required power. It is transmitted by electric power (surplus power). This is due to the use of a modulation scheme with a low modulation multi-level, although transmission is possible using a modulation scheme with a high modulation multi-level.

[0058] The transmitter according to the present embodiment has a configuration in which surplus power generated at the time of reblocking is evenly distributed to subcarriers of the same block. The reblocking procedure is the same as the procedure described in the first embodiment (FIGS. 5 to 13), and can be realized by adding a transmission power control unit after the modulator of the transmitter. Figure 18 shows an example of the configuration of this transceiver. In FIG. 18, they are indicated by reference numerals 26 to 43 (except reference numeral 38). Each of the functional blocks may be the same as the functional block indicated by reference numerals 5 to 21 in FIG. That is, the difference between the configuration of FIG. 18 and the configuration of FIG. 1 is that the transmitter 43 according to the present embodiment shown in FIG. 18 performs transmission power control on the basis of the output from modulator 37. It has 38 points. The transmission power control unit 38 evenly distributes surplus power generated due to re-blocking of subcarriers to subcarriers of the same block. As a result, there is an IJ point that transmission with excellent resistance to noise can be performed.

[0059] As described above, by using the block control type subcarrier adaptive modulation wireless communication technique according to the present embodiment, a simple multicarrier transmission system using block control type subcarrier adaptive modulation can be used. By blocking using the technique, modulation information required for subcarrier adaptive modulation can be reduced, and a decrease in frame efficiency can be prevented.

Industrial applicability

[0060] The present invention is applicable to various wireless communication devices using a multicarrier transmission system.

Claims

The scope of the claims

[1] A block control type subcarrier adaptive modulation transmission apparatus

When blocking continuous subcarriers that require the same level of reception, select a preset block size option that is prepared in advance, select a block size, and adjust the number of subcarriers in the direction that is the block size. A transmission device characterized by having a block control unit for performing blocking.

[2] The block control unit determines all subcarriers in a direction such that the number of subcarrier blocks having the number of subcarriers equal to or greater than the minimum number of subcarriers defined as an arbitrary threshold becomes the predetermined number of subcarrier blocks. 2. The transmitting apparatus according to claim 1, further comprising subcarrier allocation means for allocating to each subcarrier block.

3. The transmission device according to claim 1, wherein the block control unit performs control so as to keep the length of modulation information constant while keeping the number of blocks in each frame constant.

[4] The subcarrier allocating means allocates the blocks in the direction of changing a predetermined first modulation scheme to a second modulation scheme having a low modulation multi-level when performing blocking. The transmission device according to any one of claims 1 to 3, wherein:

[5] Further, when performing re-blocking to change the configuration of the subcarrier block according to a change in the number of subcarrier blocks or the minimum number of subcarriers configuring each subcarrier block, 5. The transmission device according to claim 1, further comprising a transmission power distribution updating unit that updates distribution of transmission power to carrier blocks.

[6] Further, in the re-blocking, transmission power control for allocating surplus power generated when the modulation level of a subcarrier is changed to a lower one to other subcarriers in a block to which the subcarrier belongs. The transmitting device according to claim 5, further comprising:

[7] When performing the re-blocking, if there is no candidate block used for re-blocking having the same size as the allocated block, if the candidate block or an adjacent block adjacent to the candidate block is not used. By changing the modulation method and adding the subcarriers of the adjacent block to the candidate block, the size becomes the same as the allocated block size. 7. The transmission device according to claim 6, wherein adjustment is performed.

[8] When performing the re-blocking, if there are a plurality of blocks of the same block size having the same value of the following K, the block modulated by the low modulation multi-level number or 7. The transmitting apparatus according to claim 6, wherein a block having a small block size is re-blocked with priority.

However, the value of K is represented by K = LX (Ib−Ia), where L is the modulation method that must be changed when re-blocking, the number of subcarriers, and lb is the value before the change. The number of bits that can be transmitted per subcarrier by the modulation method, and la is the number of bits that can be transmitted per subcarrier by the changed modulation method.

[9] When the difference between the modulation levels is different from the neighboring blocks on both sides, the difference between the modulation levels is large V, and the subcarrier force at the end is re-blocked. 7. The transmitting apparatus according to claim 6, wherein the difference is small, and a fraction is provided on one side.

[10] If the difference between the modulation levels of adjacent blocks on both sides is the same, the modulation level of the adjacent block is high, and the subcarrier force at the end is reblocked. 7. The transmitting apparatus according to claim 6, wherein when the modulation multi-level numbers of the adjacent blocks are the same, reblocking is performed from the subcarrier at the end with the smaller adjacent block size.

[11] A radio communication system comprising the transmission device according to any one of claims 1 to 10.

[12] In the block control type subcarrier adaptive modulation method,

In a subcarrier block generation procedure of dividing a plurality of subcarriers by frequency and generating a plurality of subcarrier blocks corresponding to the divided frequencies,

Sub-carrier block power with the number of sub-carriers equal to or greater than the minimum number of sub-carriers Sub-carrier allocation step of allocating sub-carriers to each sub-carrier block in the direction of the predetermined number of sub-carrier blocks is provided. Transmission method characterized by the above-mentioned.

[13] Further, when changing the configuration of the subcarrier block according to the change in the number of subcarrier blocks or the minimum number of subcarriers constituting each subcarrier block, the transmission power for updating the transmission power allocation to the subcarrier block is changed. 13. The transmission method according to claim 12, comprising a distribution update procedure. [14] A program for causing a computer to execute the procedure according to claim 12 or 13.