JP4684628B2 - Subcarrier allocation apparatus and multicarrier radio communication system - Google Patents

Description

  The present invention relates to a multicarrier radio communication system and a subcarrier allocation apparatus for allocating subcarriers having different radio frequencies for each mobile station that performs radio communication with a base station.

2. Description of the Related Art Conventionally, a multicarrier wireless communication system that assigns subcarriers having different radio frequencies to each mobile station that performs wireless communication with a base station is known.
12 and 13 are conceptual diagrams of an Orthogonal Frequency Division Multiplexing (OFDM) scheme using frequency hopping in which subcarriers to be allocated to users are hopped in symbol periods in a multicarrier wireless communication system. In the OFDM method using frequency hopping (hereinafter referred to as frequency hopping OFDM), as shown in FIG. 12, communication is performed while independently changing the subcarriers used by each user for each symbol period Ts. Here, independent subcarrier hopping patterns are assigned to individual users within the same cell, and different hopping patterns are assigned to adjacent base stations. Thereby, it becomes possible to reduce the influence of the interference between the same channels in the same frequency.

  Note that the transmitter / receiver configuration in the frequency hopping OFDM system is the same as that in the normal OFDM system, and the receiving side knows the subcarrier allocation pattern in advance, so that only the subcarriers addressed to itself are received and determined. (Fast Fourier Transform (FFT) is a batch process) and converted into a baseband data series.

The prior art related to the above-described frequency hopping OFDM system is described in Patent Documents 1, 2, and 3, for example. Further, conventional techniques related to frequency hopping patterns are described in, for example, Patent Documents 4, 5, and 6. In these conventional techniques, subcarriers to be allocated to individual users are frequency hopped for the purpose of avoiding intra-cell interference, reducing co-channel interference from neighboring cells, and acquiring a frequency diversity effect.
JP 2003-110529 A JP 7-288491 A JP-A-9-321736 JP 2000-286822 A JP 2001-156739 A JP 2001-230753 A

  However, in the technology related to the conventional frequency hopping OFDM method described above, a random hopping pattern is used, or a hopping pattern in which subcarriers of the same frequency are not probabilistically allocated in neighboring cells is used, and radio propagation is performed. The influence of road and inter-cell interference is not taken into account when assigning subcarriers. For this reason, when subcarriers with poor reception quality are allocated, the probability of occurrence of reception errors increases and communication quality deteriorates.

  For example, the wider the channel bandwidth, the more susceptible to multi-path frequency selective fading, and the higher the probability that a symbol error will occur when any subcarrier during hopping drops in level. This symbol error is compensated by an error correction code or ARQ (Automatic Repeat Request). For this purpose, an error correction code with a low coding rate is used, which causes a problem of a decrease in transmission efficiency. . In addition, when coping with quality degradation due to channel distortion by increasing transmission power, interference power given to base stations or users in neighboring cells using the same subcarrier frequency increases, and the overall system performance decreases. Problem arises.

  The present invention has been made in consideration of such circumstances, and an object of the present invention is to assign subcarriers with poor communication quality in a multicarrier radio communication system by assigning subcarriers in accordance with radio propagation path conditions. An object of the present invention is to provide a subcarrier allocation apparatus and a multicarrier radio communication system that can prevent carrier allocation and improve communication quality.

In order to solve the above problems, a subcarrier allocation apparatus according to the present invention is a subcarrier allocation apparatus that allocates subcarriers of different radio frequencies for each mobile station that performs radio communication with a base station. Channel estimation means for estimating a radio propagation path with the base station for each mobile station and for each subcarrier, determination means for determining channel estimation information of the estimation result based on a predetermined condition, and based on the determination result , An effective subcarrier group selection means for selecting, for each mobile station, an effective subcarrier group consisting of good subcarriers on the radio propagation path, and a subcarrier for selecting a subcarrier to be allocated to the mobile station from the effective subcarrier group of the selection result comprising a carrier allocation control means, wherein the subcarrier allocation control means, to make a selection of subcarriers for each predetermined time unit And butterflies.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means includes subcarriers already allocated to other mobile stations other than the mobile station among subcarriers included in an effective subcarrier group of a certain mobile station. The carrier is excluded from the subcarrier candidates of the mobile station.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means, when there is no usable subcarrier in the effective subcarrier group, the subcarrier adjacent to the subcarrier in the effective subcarrier group. A search is made for subcarriers that are unassigned as carriers, and the found subcarriers are selected.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means may be any subcarrier that is not allocated to any mobile station when there is no available subcarrier in the effective subcarrier group. It is characterized by selecting.

In the subcarrier allocation apparatus according to the present invention, a threshold for determining the channel estimation information is prepared in a plurality of stages, and the subcarrier allocation control means applies the determination threshold in stages to subcarrier candidates. It is characterized by obtaining.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means randomly selects a subcarrier.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means performs selection of a subcarrier for each symbol.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means performs subcarrier selection every k symbols (1 <k <M; M is the number of symbols corresponding to one frequency hopping block). Features.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means performs selection of a subcarrier for each one or a plurality of frequency hopping blocks.

  In the subcarrier allocation apparatus according to the present invention, the subcarrier allocation control means performs selection of a subcarrier every arbitrary time unit.

  In the subcarrier allocation apparatus according to the present invention, the effective subcarrier group selection means updates the effective subcarrier group according to the state of the radio propagation path.

  In the subcarrier allocation apparatus according to the present invention, the effective subcarrier group selection means updates the effective subcarrier group for each one or a plurality of frequency hopping blocks.

  A multicarrier radio communication system according to the present invention includes the above-described subcarrier allocation apparatus in a multicarrier radio communication system in which subcarriers having different radio frequencies are allocated to each mobile station that performs radio communication with a base station, The mapping information indicating the correspondence between the mobile station and the subcarrier, which is the allocation result by the subcarrier allocation apparatus, is configured to be shared between the mobile station and the base station.

  According to the present invention, in a multicarrier radio communication system, subcarriers can be allocated according to the state of a radio propagation path, so that it is possible to prevent subcarriers with poor communication quality from being allocated. This makes it possible to improve communication quality.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of a base station 100 of a frequency hopping OFDM multi-carrier wireless communication system according to an embodiment of the present invention. This base station 100 corresponds to a time division duplex (TDD) system, and FIG. 1 shows a configuration related to a transmission / reception function of the TDD system.

First, the transmission function of the base station 100 will be described.
In FIG. 1, each data series 1-1 to L addressed to users 1 to L is input to the data mapping circuit 2. The data mapping circuit 2 assigns a subcarrier number to each of the data series 1-1 to L based on the mapping information input from the mapping control circuit 10. Each set of the data series 1-1 to L and the subcarrier number is input to an IFFT (Inverse Fast Fourier Transform) circuit 3. The mapping information is information indicating a correspondence relationship between a user (mobile station) and a subcarrier.

  The IFFT 3 performs IFFT on each of the data series 1-1 to L, and based on the subcarrier numbers associated with the signals corresponding to the converted data series 1-1 to L, respectively. Multiply the corresponding subcarrier frequency. As a result of the multiplication, n signals f1 to fn corresponding to the number n of subcarrier frequencies are obtained. These signals f1 to fn are input to the adder 4.

The adder 4 adds the inputted signals f <b> 1 to fn and outputs them to the guard interval adding circuit 5.
The guard interval adding circuit 5 adds a guard interval to the input signal. The signal (baseband signal) to which the guard interval is added is input to the multiplier 7 via the switch 6.
The multiplier 7 multiplies the input baseband signal by the carrier signal output from the high frequency oscillator 8. The multiplication result signal is wirelessly transmitted via the antenna 9.

Next, the reception function of the base station 100 will be described.
In FIG. 1, a radio signal received by an antenna 9 is input to a multiplier 7 and multiplied by a carrier signal output from a high frequency oscillator 8. The multiplication result signal (baseband signal) is input to the guard interval removal circuit 11 via the switch 6. The guard interval removal circuit 11 removes the guard interval from the input baseband signal. The signal resulting from the removal is input to an FFT (Fast Fourier Transform) circuit 12.

  The FFT circuit 12 performs FFT on the input signal. Thereby, a baseband received signal for each subcarrier is obtained. The baseband received signal for each subcarrier is input to the channel estimation circuit 13 and the data determination circuit 14.

  Based on the input baseband received signal for each subcarrier, the channel estimation circuit 13 determines the mobile station and its own base station for each user by using a symbol period, a leading preamble portion, or a pilot symbol periodically inserted. Estimate the radio propagation path with the station 100. In this radio channel estimation process, a parameter representing the characteristics of the radio channel between the mobile station and the base station 100 is measured for each user and for each subcarrier. For example, measurement of received signal power, interference signal power, noise power, ratio of received signal power and interference signal power, ratio of received signal power and noise power, or ratio of combined power of interference power and noise power and received signal power To do. The measurement result data (channel estimation information) for each user and each subcarrier is input to the data determination circuit 14 and the mapping control circuit 10.

  Based on the channel estimation information input from the channel estimation circuit 13, the data determination circuit 14 performs data determination on the baseband received signal for each subcarrier input from the FFT circuit 12. The baseband received signal for each subcarrier of the data determination result is input to the data demapping circuit 15.

  Based on the mapping information input from the mapping control circuit 10, the data demapping circuit 15 rearranges the data symbols included in the baseband received signal for each subcarrier input from the data determination circuit 14 for each user. By this rearrangement, data series 16-1 to 16-L from the users 1 to L are obtained.

  Further, the mapping control circuit 10 determines which subcarrier is optimally allocated to which user based on the channel estimation information for each user and each subcarrier input from the channel estimation circuit 13, and this Mapping information based on the determination result is generated.

  In FIG. 1, general components such as a low-pass filter and a timing recovery circuit necessary for frequency conversion are omitted.

FIG. 2 is a block diagram showing the configuration of the mapping control circuit 10 shown in FIG.
In FIG. 2, channel estimation information for each user and for each subcarrier is input to the mapping control circuit 10 from the channel estimation circuit 13 of FIG. In addition, priority allocation control information set in advance in the base station 100 is input. This priority allocation control information is information indicating the priority of the user.

  In the mapping control circuit 10 of FIG. 2, the threshold determination unit 21 determines channel estimation information based on the threshold for each user and for each subcarrier. Specifically, a pass / fail decision is made by comparing a parameter related to radio channel characteristics included in the channel estimation information with a predetermined threshold. The determination result for each user and each subcarrier is notified to the effective subcarrier group selection unit 22.

  The effective subcarrier group selection unit 22 selects an effective subcarrier group U composed of good subcarriers on the radio propagation path for each user based on the determination result for each user and for each subcarrier notified from the threshold determination unit 21. To do. The effective subcarrier group U for each user is notified to the subcarrier allocation control circuit 23.

  The subcarrier allocation control circuit 23 selects subcarriers to be allocated to the corresponding users from the effective subcarrier groups U for each user notified from the effective subcarrier group selection unit 22. In this subcarrier allocation process, one or a plurality of subcarriers are selected and allocated from the corresponding effective subcarrier group U in order from the user with the highest priority based on the priority allocation control information. At this time, the same subcarrier is not duplicated between users. Information on the result of this allocation, that is, information (mapping information) mapping users and subcarriers is input to the data mapping circuit 2 and the data demapping circuit 15 in FIG. Further, the mapping information is input to the control frame generation unit 31, stored in the control frame, and wirelessly transmitted to all users.

  Various methods can be considered for selecting a subcarrier from the effective subcarrier group U. For example, select at random. Alternatively, the selection is made according to a certain standard (for example, in descending order of frequency). Alternatively, a good subcarrier is selected based on channel estimation information.

FIG. 3 is a flowchart showing a procedure of subcarrier allocation processing according to the present embodiment.
In FIG. 3, first, for each user, a channel estimation result (channel estimation information) is compared with a predetermined threshold Th0 (step S1). This threshold comparison is performed individually for all subcarriers (number of subcarriers Ns).

  Next, an effective subcarrier group U composed of good subcarriers is selected on the radio propagation path for each user based on the comparison result of step S1 (step S2). The effective subcarrier group U is a set of subcarrier candidates for the user. Thereby, subcarriers with poor characteristics on the radio propagation path are excluded from the subcarrier candidates.

In FIG. 3, a set of subcarrier numbers U _i = {a _i1 , a _i2 ,..., A _ix } that can be used in units of users is defined. However, i represents a user number, a _ix represents an available subcarrier number (where x is an integer of 1 ≦ x ≦ Ns, and Ns is the number of all subcarriers). At this time, U _i is an independent set for each user, but the elements may overlap.

  Next, one or a plurality of subcarriers are selected from the corresponding effective subcarrier group U for each user from the effective subcarrier group U for each user selected in step S2 (step S3). Here, when selecting a subcarrier for a certain user, a subcarrier already selected for another user is excluded from the subcarrier candidates of the user. In addition, the order of users selecting subcarriers follows the user priority of the priority assignment control information.

For example, when the number of users is N (N is an arbitrary positive integer) and the number of simultaneously allocated subcarriers is n (n is an integer of 1 ≦ n ≦ Ns), the first user can use the own station. From the set of subcarrier numbers U ₁ = {a ₁₁ , a ₁₂ ,..., A _1x }, the first to n-th subcarrier numbers used for wireless communication are random or a fixed reference (for example, received signal) Next, the second user selects a set U of subcarrier numbers that can be used by the user station, such as selecting from subcarriers with higher power sequentially, selecting at regular intervals, selecting using a formula, etc. ₂ = {a ₂₁ , a ₂₂ ,..., A _2x }, from the remaining subcarrier numbers excluding the subcarrier number selected by the first user, from the first to the first used for wireless communication nth subcarrier number is random or constant The selection is made based on the reference (same as above), and the subcarrier numbers of all users are selected in the same manner.

  Next, as a result of the subcarrier selection in step S3, for users who have no usable subcarriers in the effective subcarrier group U (the determination result in step S4 is NO), the effective subcarrier group U of the user An unassigned subcarrier that is adjacent to the middle subcarrier is searched, and the found subcarrier is assigned to the user (step S5).

  Next, based on the subcarrier allocation result for each user in step S3 or S5, a subcarrier number for specifying a subcarrier to be used is determined for each user (step S6).

  Next, mapping information indicating the correspondence relationship between the determined subcarrier number and the user is generated (step S7).

  The execution cycle of the subcarrier allocation process of FIG. 3 described above is (1) every symbol, (2) k symbols (1 <k <M; M is the number of symbols corresponding to one frequency hopping block), ( 3) Every 1 frequency hopping block (M symbol), (4) Every m frequency hopping block (m is an integer of 2 or more), (5) Arbitrary time unit, etc.

  In addition, although various methods can be considered as a method for prioritizing users, the present invention does not necessarily require a restriction.

  In addition, in the process when there is no usable subcarrier in the effective subcarrier group (step S5 in FIG. 3), as described above, the subcarriers adjacent to the subcarriers in the effective subcarrier group are sequentially ordered. Methods other than searching and selecting empty subcarriers in the order in which they are found are also applicable. For example, an arbitrary subcarrier that is not assigned to any station may be selected. Alternatively, the threshold Th0 is prepared in two or more stages, and when there are no subcarrier candidates in the effective subcarrier group obtained with the first threshold Th0, the second threshold Th0 is used. A new effective subcarrier group may be selected. Further, if the threshold Th0 is set extremely low, selection for all subcarriers is performed for all users, and in this case, for example, selection is performed in order from the first user, starting with subcarriers with high received signal power. You may do it.

4 and 5 are conceptual diagrams for explaining the subcarrier allocation method according to the present embodiment.
FIG. 4 shows a state in which subcarriers assigned to each user are hopped for each symbol period Ts.
In FIG. 4, in the period from time t = 0 to 3Ts,
User 1 effective subcarrier group U ₁ = {f ₁ , f ₂ , f ₃ , f ₄ , f ₅ , f ₆ , f ₇ },
User L's effective subcarrier group U _L = {f ₄ , f ₅ , f ₆ , f ₇ , f ₈ , f ₉ , f ₁₀ },
User i's effective subcarrier group U _i = {f _n−5 , f _n−4 , f _n−3 , f _n−2 , f _n−1 , f _n },
Are selected based on the channel estimation information of each user. Here, in the effective subcarrier group _{U L} of the effective subcarrier groups _{U 1} and the user L of the user 1, contains subcarriers _{f 4, f 5, f 6} , f 7 overlapping each other.

Then, for example, when attention is paid to user 1, the user 1 of the subcarriers, the effective subcarrier group U _1,
In the period from time t = 0 to Ts, the subcarrier f ₂ is
In the period from time t = Ts to 2Ts, subcarrier f ₃ is
In the period from time t = 2Ts to 3Ts, the subcarrier f ₄ is
Each is selected.

Similarly, the subcarrier effective subcarrier group U _L user L, also, the sub-carrier of the user i from the effective subcarriers U _i, are respectively selected. At this time, a different subcarrier from user 1 is selected as the subcarrier of user L.

  In the period from time t = kTs to (k + 1) Ts, the effective subcarrier group of each user is updated. As described above, it is preferable that the effective subcarrier group is appropriately updated according to the state of the radio propagation path.

FIG. 5 shows an example of frequency hopping related to one user (user 1).
5, the effective subcarrier group U ₁ of the user 1 is partially selected from the M subcarriers. In the example of FIG. 5, a periodic block (a block surrounded by a broken line) corresponding to one period of frequency hopping is divided into three. That is, three blocks surrounded by a broken line are one cycle of frequency hopping. Effective subcarrier group U ₁ of the user 1, and a sub-carrier corresponding to the period block.

FIG. 5 shows two types of subcarrier frequency hopping patterns (first and second hopping patterns) for user 1. The first hopping pattern is a subcarrier sequence U ₁₁ selected from the effective subcarrier group U _{1 of} user 1. The second hopping pattern is a subcarrier sequence U ₁₂ selected from the effective subcarrier group U _{1 of} user 1.

As shown in FIG. 5, the same subcarrier is used a plurality of times in one hopping pattern. For example, subcarrier sequence U _11, sub-carrier 1, the second sub-carrier 2 in a large frequency of the maximum frequency, such as sub-carrier M minimum frequency is used multiple times. However, since these subcarriers are all good for the user 1 on the radio propagation path, the communication quality can be improved.

  Note that, by updating the effective subcarrier group for each periodic block or for each integer multiple of the periodic block, it is possible to smoothly follow the time variation of the radio propagation path.

  FIG. 6 is a block diagram showing a configuration of the mobile station 200 of the multicarrier wireless communication system according to the present embodiment. This mobile station 200 corresponds to the TDD system, and FIG. 6 shows a configuration related to the transmission / reception function of the TDD system. A user of the multicarrier wireless communication system can perform wireless communication by wirelessly connecting to the base station 100 using the mobile station 200.

First, the transmission function of the mobile station 200 will be described.
In FIG. 6, the transmission data series 201 is input to the data mapping circuit 202. The data mapping circuit 202 assigns a subcarrier number to the transmission data sequence 201 based on the mapping information input from the mapping information detection circuit 210. This set of transmission data series 201 and subcarrier number is input to IFFT circuit 203.

  IFFT 203 performs IFFT on transmission data sequence 201 and multiplies the converted signal by the corresponding subcarrier frequency based on the subcarrier number associated with transmission data sequence 201. As a result of the multiplication, n signals f1 to fn corresponding to the number n of subcarrier frequencies are obtained. These signals f1 to fn are input to the adder 204.

The adder 204 adds the input signals f <b> 1 to fn and outputs them to the guard interval adding circuit 205.
The guard interval adding circuit 205 adds a guard interval to the input signal. A signal (baseband signal) to which the guard interval is added is input to the multiplier 207 via the switch 206.
Multiplier 207 multiplies the input baseband signal by the carrier signal output from high frequency oscillator 208. The multiplication result signal is wirelessly transmitted via the antenna 209.

Next, the reception function of the mobile station 200 will be described.
In FIG. 6, the radio signal received by the antenna 209 is input to the multiplier 207 and multiplied by the carrier signal output from the high frequency oscillator 208. The multiplication result signal (baseband signal) is input to the guard interval removal circuit 211 via the switch 206. The guard interval removal circuit 211 removes the guard interval from the input baseband signal. The signal resulting from the removal is input to an FFT (Fast Fourier Transform) circuit 212.

  The FFT circuit 212 performs FFT on the input signal. Thereby, a baseband received signal for each subcarrier is obtained. The baseband received signal for each subcarrier is input to channel estimation circuit 213 and subcarrier selection / determination circuit 214.

  Based on the input baseband received signal for each subcarrier, the channel estimation circuit 213 uses the base station 100, the mobile station 200, and the base station 100 and the leading preamble portion or periodically inserted pilot symbols. Is estimated. In this radio channel estimation process, based on the mapping information input from the mapping information detection circuit 210, a subcarrier to be estimated for the radio channel is selected, and the radio channel characteristics for the selected subcarrier are selected. Measure the parameters. For example, measurement of received signal power, interference signal power, noise power, ratio of received signal power and interference signal power, ratio of received signal power and noise power, or ratio of combined power of interference power and noise power and received signal power To do. The measurement result data (channel estimation information) is input to the subcarrier selection / determination circuit 214.

  The subcarrier selection / determination circuit 214 performs data determination of the baseband reception signal for each subcarrier input from the FFT circuit 212 based on the channel estimation information input from the channel estimation circuit 213. In this data determination process, based on the mapping information input from the mapping information detection circuit 210, a subcarrier to be a data determination target is selected, and data determination is performed for the selected subcarrier. The baseband reception signal for each subcarrier of the data determination result is input to the parallel / serial conversion circuit 215.

  The parallel / serial conversion circuit 215 converts the input parallel signal into a serial signal and outputs it as a serial data series. The output serial data sequence is input to the mapping information detection circuit 210 by the switch 216 or output as the reception data sequence 217 according to the reception timing of the reception frame.

  Of the received frames, a control frame is input to the mapping information detection circuit 210. The mapping information detection circuit 210 extracts mapping information from the input control frame. This mapping information is generated by the mapping control circuit 10 of the base station 100 and distributed to all users by a control frame. That is, the mapping information is shared between the base station 100 and all users.

  In FIG. 6, general components such as a low-pass filter and a timing recovery circuit necessary for frequency conversion are omitted.

  Next, a frequency hopping OFDM system and a frequency division duplex (FDD) system multi-carrier wireless communication system will be described as another embodiment of the present invention.

  In the case of the TDD scheme in the above-described embodiment, the base station 100 uses the same radio frequency for transmission and reception, and performs transmission to the mobile station 200 and reception from the mobile station 200 in a time division manner. Therefore, the radio propagation path between the base station 100 and the mobile station 200 is the same for transmission and reception. For this reason, the channel estimation information measured based on the signal received by the base station 100 is effective for the bidirectional radio propagation path between the base station 100 and the mobile station 200. Thereby, based on the channel estimation information, common subcarrier allocation can be performed for the bidirectional radio propagation path between the base station 100 and the mobile station 200. That is, the mapping information generated by the base station 100 described above is common to the bidirectional radio propagation path between the base station 100 and the mobile station 200.

However, in the case of the FDD scheme, since different radio frequencies are used for transmission and reception, the radio propagation path between the base station and the mobile station is different for transmission and reception. Therefore, channel estimation information measured based on radio signals received by the mobile station is required for subcarrier allocation when transmitting from the base station to the mobile station. Moreover, channel estimation information measured based on a radio signal received by the base station is necessary for subcarrier allocation when transmitting from the mobile station to the base station.
Hereinafter, a base station and a mobile station applicable to such an FDD system will be described. In the following description, the direction from the mobile station to the base station is referred to as “uplink”, and the direction from the base station to the mobile station is referred to as “downlink”.

  FIG. 7 is a block diagram showing a configuration of the base station 100a according to the embodiment of the FDD scheme of the present invention. FIG. 7 shows a configuration relating to an FDD transmission / reception function. In FIG. 7, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  In the base station 100a of FIG. 7, the channel estimation circuit 13 measures uplink channel estimation information (uplink channel estimation information) based on the signal received by the base station 100a. Further, the data determination circuit 14a extracts downlink channel estimation information transmitted from each user from the signal received by the base station 100a. The downlink channel estimation information is downlink channel estimation information measured based on a signal received by the mobile station. The uplink channel estimation information and the downlink channel estimation information are input to the mapping control circuit 10a.

  The mapping control circuit 10a performs uplink subcarrier allocation based on the uplink channel estimation information, and performs downlink subcarrier allocation based on the downlink channel estimation information.

  FIG. 8 is a block diagram showing a configuration of the mapping control circuit 10a shown in FIG. As shown in FIG. 8, the mapping control circuit 10a includes an uplink subcarrier allocation threshold determination unit 21-1, an effective subcarrier group selection unit 22-1, and a downlink subcarrier allocation threshold determination. Unit 21-2, effective subcarrier group selection unit 22-2, and subcarrier allocation control circuit 23a.

  In FIG. 8, the threshold determination unit 21-1 performs threshold determination on the uplink channel estimation information of each user. The effective subcarrier group selection unit 22-1 selects an effective subcarrier group Uu for each user's uplink based on the threshold determination result. The subcarrier allocation control circuit 23a selects uplink subcarriers for each user from the effective subcarrier group Uu for uplink of each user, and generates uplink mapping information. The uplink mapping information is input to the control frame generator 31.

  Similarly, the threshold determination unit 21-2 performs threshold determination on the downlink channel estimation information of each user. The effective subcarrier group selection unit 22-2 selects the effective subcarrier group Ud for downlink of each user based on the threshold determination result. The subcarrier allocation control circuit 23a selects a downlink subcarrier for each user from the effective subcarrier group Ud for downlink of each user, and generates downlink mapping information. The downlink mapping information is input to the data mapping circuit 2 and the data demapping circuit 15 and the control frame generator 31 shown in FIG.

  The uplink mapping information and the downlink mapping information input to the control frame generation unit 31 are stored in the control frame and wirelessly transmitted to all users.

  FIG. 9 is a block diagram showing a configuration of the mobile station 200a according to the FDD scheme of the present invention. FIG. 9 shows a configuration related to an FDD transmission / reception function. 9, parts corresponding to those in FIG. 6 are assigned the same reference numerals and explanations thereof are omitted. A user of the multicarrier wireless communication system can perform wireless communication by wirelessly connecting to the base station 100a using the mobile station 200a.

  In the mobile station 200a of FIG. 9, multipliers 207-1 and 207-2, high-frequency oscillators 208-1 and 208-2, and antennas 209-1 and 209-2 are provided for uplink and downlink, respectively. Also, a downlink channel estimation information control circuit 220 is provided.

  In the mobile station 200a of FIG. 9, the data mapping circuit 202 assigns a subcarrier number to the transmission data series 201 based on the uplink mapping information input from the mapping information detection circuit 210.

  The mapping information detection circuit 210a extracts uplink mapping information and downlink mapping information from the control frame received by the mobile station 200a. The uplink mapping information and the downlink mapping information are generated by the mapping control circuit 10a of the base station 100a and distributed to all users by the control frame. That is, the uplink mapping information and the downlink mapping information are shared between the base station 100a and all users.

  Based on the baseband received signal for each subcarrier input from the FFT circuit 212, the channel estimation circuit 213a is self-moving with the base station 100a in accordance with each symbol period, the leading preamble portion, or periodically inserted pilot symbols. Estimate the radio propagation path with the station 200a. In this radio channel estimation process, a subcarrier to be estimated for a radio channel is selected based on downlink mapping information input from the mapping information detection circuit 210, and a radio channel for the selected subcarrier is selected. Measure parameters related to characteristics. The measurement result data (downlink channel estimation information) is input to the subcarrier selection / determination circuit 214 and the downlink channel estimation information control circuit 220.

  The subcarrier selection / determination circuit 214 performs data determination of the baseband received signal for each subcarrier input from the FFT circuit 212 based on the downlink channel estimation information input from the channel estimation circuit 213.

  Further, the downlink channel estimation information control circuit 220 processes the downlink channel estimation information input from the channel estimation circuit 213 into control information and outputs the control information to the data mapping circuit 202. The data mapping circuit 202 stores the input downlink channel estimation information in the control header of the uplink signal. Thereby, the downlink channel estimation information measured based on the signal received by the mobile station 200a is wirelessly transmitted to the base station 100a.

  Thus, in the case of the FDD scheme, since the uplink and downlink use different frequencies, it is necessary to perform channel estimation independently. That is, for the uplink, the base station measures the communication quality (received signal power, etc.) of the uplink signal transmitted from each user, and determines the frequency hopping pattern for each user at the base station based on the state. The information is notified to the user. On the other hand, for the downlink, each user measures the communication quality (received signal power, etc.) of the downlink signal transmitted from the base station, and the channel information itself or information on the subcarrier group selected on the user side is obtained. It feeds back to the base station side, determines a frequency hopping pattern on the base station side based on the information, and informs each user as control information.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

For example, in the case of the TDD scheme, the upper and lower links use the same frequency, and thus are considered to basically have the same channel characteristics (radio propagation path characteristics). Therefore, channel estimation may be performed in either the upper or lower direction, a subcarrier group may be selected based on the result, and a frequency hopping pattern may be determined.
That is, as in the above-described embodiment, the communication quality (received signal power, etc.) of the uplink signal transmitted from each user is measured, and the frequency hopping pattern of each user is determined by the base station based on the state. The information is notified to the user. Alternatively, as another embodiment, each user selects a subcarrier group based on the communication quality (received signal power, etc.) of the downlink signal received by the mobile station, and feeds back the information to the base station. The station may determine the frequency hopping pattern and notify the user of the information.

Note that subcarrier switching control may be performed by applying the concept of code spreading. 10 and 11 are conceptual diagrams showing an embodiment of a subcarrier switching control method to which the concept of code spreading is applied.
In FIG. 10, within the block that performs time / frequency spreading surrounded by a broken line, the same information data 301 is copied and assigned to the subcarriers to be hopped, and a plurality of spreading codes are superimposed on the time axis and the frequency axis simultaneously. Spread spectrum processing. In this way, by performing the diffusion process on the subcarriers to be hopped, interference resistance can be obtained simultaneously on the time axis and the frequency axis. In addition, by performing despreading processing by MMSEC, it can be expected to obtain a time / frequency diversity effect at the same time.

  FIG. 11 shows a method of increasing the number of users who can communicate simultaneously by performing N multiplexing when the spreading code length is set to N, or increasing the transmission rate per user by multi-coding. By applying this method, it is possible to maximize the frequency utilization efficiency.

  In this way, by assigning a spreading code to a subcarrier that performs frequency hopping, it is possible to provide a radio system that has resistance to co-channel interference and has excellent characteristics for obtaining a time / frequency diversity effect. . Furthermore, by assigning spreading codes that are orthogonal to each other, it is possible to perform communication while simultaneously using the same subchannel for multiple users, and communication is simple compared to the frequency hopping OFDM system that simply performs time and frequency spreading. The capacity can be increased.

  Note that the present invention can be applied to various wireless communication systems. For example, digital wireless communication systems such as digital cellular systems, digital mobile communication systems, high-speed wireless access, subscriber wireless access, fixed microwave transmission, wireless LAN, personal area networks, digital satellite communications, mobile satellite systems, sensor networks, etc. Applicable.

It is a block diagram which shows the structure of the base station 100 of the multicarrier radio | wireless communications system of the frequency hopping OFDM system which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the mapping control circuit 10 shown in FIG. It is a flowchart which shows the procedure of the subcarrier allocation process which concerns on one Embodiment of this invention. It is a conceptual diagram for demonstrating the subcarrier allocation method which concerns on one Embodiment of this invention. It is a conceptual diagram for demonstrating the subcarrier allocation method which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the mobile station 200 of the multicarrier radio | wireless communications system which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the base station 100a which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the mapping control circuit 10a shown in FIG. It is a block diagram which shows the structure of the mobile station 200a which concerns on other embodiment of this invention. It is a conceptual diagram which shows the Example of the subcarrier switching control method to which the concept of the code spreading which concerns on this invention is applied. It is a conceptual diagram which shows the Example of the subcarrier switching control method to which the concept of the code spreading which concerns on this invention is applied. It is a conceptual diagram of the conventional frequency hopping OFDM system. It is a conceptual diagram of the conventional frequency hopping OFDM system.

Explanation of symbols

2, 202 ... data mapping circuit, 3, 203 ... inverse fast Fourier transform circuit (IFFT), 4, 204 ... adder (Σ), 5, 205 ... guard interval addition circuit, 6, 206, 216 ... switch, 7 , 207 ... Multiplier, 8, 208 ... High frequency oscillator (fc), 9, 209 ... Antenna, 10, 10a ... Mapping control circuit, 11, 211 ... Guard interval removal circuit, 12, 212 ... Fast Fourier transform circuit (FFT) , 13, 213, 213a ... channel estimation circuit, 14, 14a ... data decision circuit, 15 ... data demapping circuit, 21 ... threshold decision unit, 22 ... effective subcarrier group selection unit, 23, 23a ... subcarrier allocation control Circuit, 31 ... control frame generation unit, 100, 100a ... base station, 200, 200a ... mobile station, 210, 210a Mapping information detection circuit, 214 ... subcarrier selection / determination circuit, 215 ... parallel / serial conversion circuit, 220 ... downlink channel estimation information control circuit.

Claims (4)

In a subcarrier allocation apparatus that allocates subcarriers of different radio frequencies for each mobile station that performs radio communication with a base station,
Channel estimation means for estimating a radio propagation path between a mobile station and a base station for each mobile station and for each subcarrier;
Determining means for determining the channel estimation information of the estimation result based on a predetermined condition;
Based on the determination result, effective subcarrier group selection means for selecting, for each mobile station, an effective subcarrier group consisting of good subcarriers on the radio propagation path;
Subcarrier allocation control means for selecting a subcarrier to be allocated to a mobile station from the effective subcarrier group of the selection result,
The subcarrier allocation control means, have the row selection of subcarriers for each predetermined time unit,
A threshold for determining the channel estimation information is prepared in a plurality of stages,
The subcarrier allocation control means obtains subcarrier candidates by applying the determination threshold step by step ,
The subcarrier allocation control means randomly selects a subcarrier. In a subcarrier allocation apparatus that allocates subcarriers of different radio frequencies for each mobile station that performs radio communication with a base station,
Channel estimation means for estimating a radio propagation path between a mobile station and a base station for each mobile station and for each subcarrier;
Determining means for determining the channel estimation information of the estimation result based on a predetermined condition;
Based on the determination result, effective subcarrier group selection means for selecting, for each mobile station, an effective subcarrier group consisting of good subcarriers on the radio propagation path;
Subcarrier allocation control means for selecting a subcarrier to be allocated to a mobile station from the effective subcarrier group of the selection result,
The subcarrier allocation control means, have the row selection of subcarriers for each predetermined time unit,
The subcarrier allocation control means excludes subcarriers already allocated to other mobile stations other than the mobile station from among subcarriers included in an effective subcarrier group of a mobile station from the subcarrier candidates of the mobile station. If there is no usable subcarrier in the effective subcarrier group, a subcarrier that is adjacent to the subcarrier in the effective subcarrier group and that is not allocated is searched for and found. A subcarrier allocating device, wherein: In a subcarrier allocation apparatus that allocates subcarriers of different radio frequencies for each mobile station that performs radio communication with a base station,
Channel estimation means for estimating a radio propagation path between a mobile station and a base station for each mobile station and for each subcarrier;
Determining means for determining the channel estimation information of the estimation result based on a predetermined condition;
Based on the determination result, effective subcarrier group selection means for selecting, for each mobile station, an effective subcarrier group consisting of good subcarriers on the radio propagation path;
Subcarrier allocation control means for selecting a subcarrier to be allocated to a mobile station from the effective subcarrier group of the selection result,
The subcarrier allocation control means, have the row selection of subcarriers for each predetermined time unit,
The subcarrier allocation control means excludes subcarriers already allocated to other mobile stations other than the mobile station from among subcarriers included in an effective subcarrier group of a mobile station from the subcarrier candidates of the mobile station. A subcarrier allocation apparatus that selects an arbitrary subcarrier that is not allocated to any mobile station when there is no usable subcarrier in the effective subcarrier group. In a multicarrier radio communication system in which subcarriers of different radio frequencies are allocated to each mobile station that performs radio communication with a base station,
A subcarrier allocation apparatus according to any one of claims 1 to 3 , comprising:
A multicarrier wireless communication system configured to share mapping information indicating a correspondence relationship between a mobile station and a subcarrier, which is an allocation result by the subcarrier allocation apparatus, between the mobile station and the base station .

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