JP4980206B2 - Subcarrier allocation method, transmitter and receiver for OFDM communication system - Google Patents

Description

The present invention relates to a subcarrier allocation method, a transmission apparatus, and a reception apparatus of an OFDM communication system that performs multiple access communication using OFDM (Orthogonal Frequency Division Multiplexing) modulation.
In this specification, an OFDM communication system in which a plurality of base stations perform multiple access communication with a plurality of terminal stations under its control is assumed, and the base station is set as a transmitting station (transmitting apparatus) and the terminal station is received. Although described as a station (receiving device), the radio resource control featured in the present invention is not limited to a base station but may be autonomously performed by a terminal station. In this case, the relationship between the transmitting station and the receiving station is reversed. To do. The present invention is also applicable to an OFDM communication system having no master-slave relationship such as a base station and a terminal station.

  A transmission system using a plurality of subcarriers is generally called a multicarrier transmission system. Among the multi-carrier transmission systems, there is an OFDM modulation system as a modulation system particularly excellent in frequency utilization efficiency. In the OFDM modulation scheme, a plurality of subcarriers are arranged at a minimum frequency interval such that the subcarriers are orthogonal to each other in the frequency domain. In addition, the OFDM modulation method is one of the high-speed wireless transmission methods because it can block the influence of the delayed wave on the next symbol by adding a guard interval, and has excellent resistance to frequency selective fading. Attention has been paid.

  As such multiple access schemes using OFDM modulation, OFDM / TDMA (Time Division Multiple Access) scheme, OFDM / CSMA (Carrier Sense Multiple Access) scheme, OFDMA (Orthogonal Frequency Division Multiple Access) scheme There is. In the OFDM / TDMA scheme, a frame is divided into time slots for each fixed number of OFDM symbols, and the central control station distributes the time slots to a plurality of users. In the OFDM / CSMA scheme, a frame is divided into time slots for each fixed number of OFDM symbols, but the time slots are autonomously distributed in a time-sharing manner by a plurality of stations. These are adopted in IEEE802.11a / g, which is one of the standardization standards for wireless LANs.

  On the other hand, the OFDMA scheme divides the frequency direction into subcarriers, the time direction into time slots, and divides users in a two-dimensional time-frequency region. IEEE802.16, which is one of the standardization standards for wireless broadband access systems. (Non-patent Document 1).

  In general, when an OFDM modulation scheme in which a plurality of base stations share the same frequency band is used, in the OFDM / TDMA scheme or OFDM / CSMA scheme, since all subcarriers are subject to radio wave interference between adjacent base stations, sufficient In areas other than the vicinity of the base station where CIR (Carrier to Interference Ratio) can be secured, there is a high possibility that the communication quality is extremely deteriorated.

On the other hand, in the OFDMA scheme, subcarriers to be used can be varied for each base station by appropriately allocating radio resources. Therefore, even when adjacent base stations share the same frequency band, subcarrier interference between base stations can be avoided by distinguishing subcarriers used by one base station and subcarriers used by the other base station. can do. That is, as shown in segmented PUSC (Partial Usage of SubChannel) shown in FIG. 10 (1), subcarrier interference can be avoided by segmenting and assigning different subcarriers for each base station.

Further, in the OFDMA scheme, there is a method of assigning all subcarriers to each base station without segmenting the subcarrier assignments as in FUSC (Full Usage of SubChannel) shown in FIG. 10 (2).

Here, when subcarriers are divided into a plurality of subchannels by subsetting, the subcarriers are appropriately read as subchannels. For example, in the case of segmented PUSC, in order to reduce the collision probability of subcarriers, there is a case where a set of subcarriers constituting a subchannel is made different for each base station (sector). Note that the set of subcarriers constituting the subchannel is not necessarily combined with adjacent subcarriers, but may be a combination of subcarriers arranged alternately in a comb shape.
IEEE 802.16-2004: Air Interface for Fixed Broadband Wireless Access Systems, IEEE, October 2004, pp.551-576

  Since the segmented PUSC in the OFDMA scheme divides the frequency band in principle so that interference does not occur, there is a problem that the frequency band assigned to each base station becomes narrow and the transmission capacity decreases.

  On the other hand, FUSC can secure 100% of the subcarrier usage rate due to the overlap of frequency bands. However, since subcarrier collision occurs, it ensures sufficient CIR especially around the cell (base station radio area). There is a problem that demodulation errors frequently occur in areas where communication cannot be performed, and communication quality is significantly reduced.

  In addition, since the conventional OFDMA communication device is not configured to easily switch between the two, it is fixed to one of the subcarrier allocation methods.

  The present invention makes it possible to change the subcarrier used for each transmitting station, and to utilize the OFDMA characteristic that allows frequency bands to overlap between transmitting stations, thereby securing a sufficient CIR while increasing the subcarrier usage rate. It is an object of the present invention to provide a subcarrier allocation method, a transmission apparatus, and a reception apparatus of an OFDM communication system that can suppress deterioration in communication quality in an area where communication cannot be performed.

A first invention is a subcarrier allocation method in an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of the transmitting stations, and the plurality of transmitting stations are the same Dividing into a shared band in which a part of a plurality of subcarriers in the frequency band is shared and allowing mutual interference and an occupied band in which a part of the plurality of subcarriers in the same frequency band is occupied and not interfered with each other, FEC or The data encoded by the CDM is distributed in the shared band and the occupied band, and the data encoded by the FEC or CDM is distributed in priority in the frequency direction of the frame and distributed to a plurality of subcarriers. Subcarrier allocation is performed so that the subcarrier usage rate decreases or increases in the axial direction.

A second invention is a subcarrier allocation method in an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of the transmitting stations, and the plurality of transmitting stations are the same A plurality of subcarriers in the frequency band are divided into priority bands to be preferentially used for each transmitting station, and data encoded by FEC or CDM is arranged in each priority band, and data having a capacity exceeding this priority band It was evenly distributed non-priority zone area which is a priority band of the other transmitting station, with a sequence corresponding to the frequency into a plurality of sub-carriers of the same frequency band, and the order of allocation subcarriers priority bandwidth, non priority bandwidth The subcarriers are allocated so that the subcarrier allocation order is reversed.

A third invention is an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under its control, wherein the plurality of transmitting stations are a plurality of the same frequency band. The subcarrier is divided into priority bands to be preferentially used for each transmission station, and data encoded by FEC or CDM is arranged in each priority band, and data having a capacity exceeding the priority band is transmitted to other transmission stations. evenly arranged in the non-priority zone is preferentially band, you assign preferentially initial transmission data or retransmission data used for ARQ transmission priority band.

A fourth invention is an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of the transmitting stations, and the plurality of transmitting stations include a plurality of transmitting stations in the same frequency band. The subcarrier is divided into priority bands to be preferentially used for each transmission station, and data encoded by FEC or CDM is arranged in each priority band, and data having a capacity exceeding the priority band is transmitted to other transmission stations. The FEC or CDM encoded data is preferentially distributed in a plurality of subcarriers and distributed to a plurality of subcarriers, and the subframe is subordinately arranged in the time axis direction of the frame. It intends row subcarrier allocation as the carrier utilization decreases or increases.

According to a fifth aspect of the present invention, in a transmission apparatus of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under their control, data to be transmitted is encoded by FEC or CDM. And an information encoding modulator that modulates with a predetermined modulation method, a transmission data buffer that receives data encoded and modulated by the information encoding modulator, and stores at least one frame of the OFDMA method, and the same frequency band A shared band that allows part of multiple subcarriers to be shared with other transmitting stations and allows mutual interference, and an occupied part that does not interfere by occupying a part of multiple subcarriers in the same frequency band for each transmitting station divided into bands, occupation data to be read from the transmission data buffer to control the read address of the transmission data buffer and shared bandwidth Comprising a transmission control means for controlling so as to be distributed in frequency, and OFDM modulator for generating a transmission signal by OFDM modulation data read from the transmission data buffer by the control of the transmission control unit, transmission control unit The data read from the transmission data buffer is preferentially distributed in a plurality of subcarriers in the frequency direction of the frame, and the subcarriers are allocated so that the subcarrier usage rate decreases or increases in the time axis direction of the frame. Do.

According to a sixth aspect of the present invention, in a transmission apparatus of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under their control, data to be transmitted is encoded by FEC or CDM. And an information encoding modulator that modulates with a predetermined modulation method, a transmission data buffer that receives data encoded and modulated by the information encoding modulator, and stores at least one frame of the OFDMA method, and the same frequency band with a plurality of sub-carriers divided into priority bands to be preferentially utilized for each transmission station, place the data to be read from the transmission data buffer to control the read address of the transmission data buffer in the priority band, exceeds the priority bandwidth are evenly spaced data capacity non-priority band is the priority band of the other transmission station And transmission control means for controlling the, OFDM modulator and a transmission control means for generating a transmission signal by OFDM modulation data read from the transmission data buffer by the control of the transmission control means, a plurality of the same frequency band The subcarriers are assigned an order corresponding to the frequency, and the subcarriers are allocated so that the subcarrier allocation order of the priority band and the subcarrier allocation order of the non-priority band are reversed.
According to a seventh aspect of the present invention, in a transmission apparatus of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA system perform multiple access communication with a plurality of receiving stations under their control, data to be transmitted is encoded by FEC or CDM. And an information encoding modulator that modulates with a predetermined modulation method, a transmission data buffer that receives data encoded and modulated by the information encoding modulator, and stores at least one frame of the OFDMA method, and the same frequency band The subcarriers are divided into priority bands that are preferentially used for each transmitting station, and the data read from the transmission data buffer is arranged in the priority band by controlling the read address of the transmission data buffer, and this priority band is exceeded. Capacity data is evenly allocated to the non-priority band that is the priority band of other transmitting stations A transmission control means that controls the data read from the transmission data buffer under the control of the transmission control means, and an OFDM modulator that generates a transmission signal. Transmission data or retransmission data is preferentially assigned to a priority band.
According to an eighth aspect of the present invention, there is provided an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under their control, and data to be transmitted is encoded by FEC or CDM. And an information encoding modulator that modulates with a predetermined modulation method, a transmission data buffer that receives data encoded and modulated by the information encoding modulator, and stores at least one frame of the OFDMA method, and the same frequency band The subcarriers are divided into priority bands that are preferentially used for each transmitting station, and the data read from the transmission data buffer is arranged in the priority band by controlling the read address of the transmission data buffer, and this priority band is exceeded. Capacity data is evenly allocated to the non-priority band that is the priority band of other transmitting stations A transmission control means for controlling the data, and an OFDM modulator for generating a transmission signal by OFDM modulating the data read from the transmission data buffer under the control of the transmission control means, and the transmission control means reads from the transmission data buffer Data is preferentially distributed in a plurality of subcarriers in the frequency direction of the frame, and subcarriers are allocated so that the subcarrier usage rate decreases or increases in the time axis direction of the frame.

A ninth invention is an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA system perform multiple access communication with a plurality of receiving stations under their control, and any one of the fifth to eighth inventions In the receiving device that receives the OFDM signal transmitted by the transmitting device, the OFDM demodulator that demodulates the received OFDM signal and the demodulated data output from the OFDM demodulator are input, and the address is divided into subcarrier units. Received data buffer to be stored, information demodulating decoder for inputting and demodulating and decoding data encoded by FEC or CDM from the received data buffer, and demodulated and decoded by the information demodulating decoder Subcarriers that interfere with each other by measuring the error rate for each subcarrier of the received data. Was identified, the data demodulated and decoded by information demodulation decoder re-coding and modulating, and suppress interference signals by overwriting the data corresponding to the interfering sub-carrier in the corresponding buffer area of the received data buffer, Receiving control means for repeating the process of inputting to the information demodulating decoder again a predetermined number of times or until the error rate reaches a predetermined value, and then outputting the demodulated and decoded data.

Further, the reception control means of the ninth invention may be configured to identify subcarriers that interfere with each other from a plurality of transmitting stations from predetermined control information notified from the transmitting apparatus.

  According to the present invention, as a subcarrier allocation method in the OFDMA scheme, a part of frequency bands are overlapped between a plurality of transmitting stations, so that the transmission capacity can be improved as compared with a case where the frequency bands are completely divided.

  Also, the data encoded by FEC or CDM is divided into an occupied band that does not interfere and a shared band that allows interference, or a priority band that has a small interference ratio and a non-priority band that has a large interference ratio (priority bands of other transmitting stations). ). Accordingly, it is possible to suppress the occurrence of an error at a receiving station with low reception quality (for example, away from the transmitting station) by the error correction effect by FEC decoding or the processing gain by CDM decoding (despreading process) on the receiving side. In particular, data with a capacity exceeding the priority band of the local station is evenly distributed in the non-priority band (priority band of other transmitting station), and the allocation order of the subcarriers in the priority band and the non-priority band is reversed. As a result, the ratio that the priority band becomes an occupied band that does not interfere increases, and interference of subcarriers assigned to the non-priority band can be minimized.

  Further, in the vicinity of a transmitting station where CIR can be sufficiently secured, even if all subcarriers interfere, transmission without error is possible. Therefore, data encoded by FEC or CDM is preferentially distributed in a plurality of subcarriers in the frequency direction, and subcarrier allocation is performed by changing the subcarrier usage rate in the time axis direction. Interference proof strength can be changed according to the usage rate. That is, for example, it is possible to arrange a user near the transmitting station in the first half of the frame and assign a user far from the transmitting station in the second half of the frame, or vice versa, and efficiently accommodate users in one frame. be able to. In addition, depending on the distance between the transmitting station that is the target of interference and its own station, it is possible to selectively use overlap of all frequency bands, partial overlap of frequency bands, and complete separation of frequency bands. Throughput can be maximized.

(First Embodiment of Subcarrier Allocation Method in the Present Invention)
FIG. 1 shows a first embodiment of a subcarrier allocation method in the OFDM communication system of the present invention. Here, subcarrier allocation in three base stations that share the same frequency band and are adjacent to each other will be described as an example. A plurality of subcarriers may be replaced with subchannel allocation.

  Base stations # 1, # 2, and # 3 share some subcarriers with respect to a plurality of subcarriers in the same frequency band, allow mutual interference, and occupy some subcarriers so as not to interfere. It is characterized by being divided and allocated. In the example shown in FIG. 1, the same frequency band shared by each base station is divided into six frequency bands according to the respective data amounts, and the subcarriers in frequency band 1 are shared by base station # 1 and base station # 3. The subcarrier of frequency band 2 is occupied by base station # 1, the subcarrier of frequency band 3 is shared by base station # 1 and base station # 2, and the subcarrier of frequency band 4 is occupied by base station # 2. The subcarrier of frequency band 5 is shared by base station # 2 and base station # 3, and the subcarrier of frequency band 6 is occupied by base station # 3. Here, the shared subcarriers are two base stations at the maximum, but there may be subcarriers shared among the three base stations.

  In base station # 1, data encoded by FEC (Forward Error Correction) or CDM (Code Division Multiplexing) is allocated to subcarriers in frequency bands 1, 2, and 3, and in base station # 2, it is encoded in the same manner. The base station # 3 assigns the same encoded data to the subcarriers in the frequency bands 1, 5, and 6, and each of the subbands in which the interference is allowed and the interference. Distribute them in a band with no noise.

  Since the receiving stations in the radio areas of the base stations # 1, # 2, and # 3 perform reception processing including subcarriers that do not interfere and subcarriers that allow interference, the error correction effect by FEC decoding or Due to the processing gain by CDM decoding (despreading processing), it is possible to suppress the occurrence of errors at a receiving station with low reception quality (for example, away from the base station). In addition, unlike conventional segmented PUSC, some subcarriers are shared by a plurality of base stations, so that the user throughput can be increased by increasing the subcarrier usage rate.

(Second Embodiment of Subcarrier Allocation Method in the Present Invention)
FIG. 2 shows a second embodiment of the subcarrier allocation method in the OFDM communication system of the present invention. Here, subcarrier allocation in three base stations that share the same frequency band and are adjacent to each other will be described as an example. A plurality of subcarriers may be replaced with subchannel allocation.

  The base stations # 1, # 2, and # 3 set a frequency band (priority band) to be preferentially used for each base station, and allocate, for example, data with a high QoS (Quality of Services) request to the subcarriers of the priority band. Furthermore, when transmitting data with a capacity exceeding this priority band, the probability of occurrence of interference to subcarriers between non-priority bands (priority bands of other base stations) between base stations Allocate evenly.

  For example, in the example of FIG. 2 (1), when data from the priority band at the base station # 1 is over, it is assigned to a subcarrier in the priority band of the base station # 2, and data from the priority band is over at the base station # 2. The base station # 3 is assigned to the subband of the priority band, and when the data exceeds the priority band at the base station # 3, the base station # 1 is assigned to the subcarrier of the priority band of the base station # 1, thereby reducing the probability of occurrence of interference. Equalize. In the example of FIG. 2 (2), when data exceeds the priority band at the base station # 1, it is divided and assigned to the subcarriers of the priority bands of the base stations # 2 and # 3, and the base station # 2 If the data exceeds the priority band, the substations of the priority bands of the base stations # 1 and # 3 are divided and assigned. If the data exceeds the priority band of the base station # 3, the base station # 1 , # 2 is divided into subcarriers of each priority band and assigned to equalize the probability of occurrence of interference.

  In the receiving station, subcarriers that do not interfere and subcarriers that allow interference are distributed, so that error generation can be suppressed by the error correction effect by FEC decoding or the processing gain by CDM decoding (despreading processing), and the priority band Since the data arranged only inside is not easily affected by interference, high quality QoS can be provided.

(Third embodiment of subcarrier allocation method in the present invention)
FIG. 3 shows a third embodiment of the subcarrier allocation method in the OFDM communication system of the present invention. Here, subcarrier allocation in three base stations that share the same frequency band and are adjacent to each other will be described as an example. A plurality of subcarriers may be replaced with subchannel allocation.

  Compared with the second embodiment, the third embodiment is devised to secure more bands that do not interfere with each other. The third embodiment assigns subcarriers in the priority band and subbands in the non-priority band. Setting is made so that the carrier allocation order is reversed (for example, the former is in descending order and the latter is in ascending order). Hereinafter, the subcarrier number will be used for convenience. Further, subcarriers in the same frequency band shared by the three base stations are assumed to be f1 to f15, and explanation will be made in correspondence with the example of FIG.

  First, a priority band is equally allocated to each base station, the priority band of the base station # 1 is subcarriers f1 to f5, the priority band of the base station # 2 is subcarriers f6 to f10, and the priority band of the base station # 3 is sub The carriers are f11 to f15. If base station # 1 has a data allocation request of 8 subcarriers, base station # 2 has 3 subcarriers, and base station # 3 has 9 subcarriers, the priority band is in descending order and the non-priority band is in ascending order. In the base station # 1, the subcarrier numbers are paid out in the order of f5, f4, f3, f2, f1, f6, f11, and f7. Similarly, base station # 2 pays out subcarrier numbers in the order of f10, f9, f8, and base station # 3 has subcarrier numbers of f15, f14, f13, f12, f11, f1, f6, f2, f7. It is paid out in order.

  In this way, when the data allocation request band is larger than the priority band, interference occurs due to the sharing of the subcarriers in the priority band, but by reversing the allocation order of the subcarriers in the priority band and the non-priority band, Thus, the probability of occurrence of interference is reduced, and even when interference occurs, it occurs evenly in all base stations. In the present embodiment, subcarriers f10, f9, and f8 of priority bands are assigned in descending order at base station # 2, resulting in an occupied band that does not interfere, and the remaining subcarriers f6 and f7 are assigned to base stations # 1 and # 3. It can be seen that the merit of this method is utilized.

(Fourth Embodiment of Subcarrier Allocation Method in the Present Invention)
FIG. 4 shows a fourth embodiment of the subcarrier allocation method in the OFDM communication system of the present invention.

  In the fourth embodiment, when the subcarrier allocation method having the priority band shown in FIGS. 2 to 3 is adopted, initial transmission data or retransmission data used for ARQ (Automatic Repeat reQuest) transmission is preferentially allocated to this priority band. . For example, when initial transmission data is assigned to a non-priority band, when there is a retransmission request for the transmission data, control is performed to assign the retransmission data to a priority band and an occupied band that does not interfere. In addition, the receiving station uses a retransmission signal synthesizer to combine the initial transmission data transmitted in the non-priority band and the retransmission data transmitted in the priority band (occupied band), thereby achieving a high SIR (Signal Interference Ratio). ) Can be secured.

(Fifth Embodiment of Subcarrier Allocation Method in the Present Invention)
FIG. 5 shows a fifth embodiment of a subcarrier allocation method in the OFDM communication system of the present invention.

  Here, it is assumed that a frame is represented in two dimensions, a time axis and a frequency axis, and in this embodiment, a radio resource indicated by one OFDM symbol length and one subcarrier is called a slot. For example, when one frame is composed of 15 OFDM symbols and 15 subcarriers, there are 225 slots of radio resources in one frame. In this embodiment, as shown in the embodiments of FIGS. 2 and 3, subcarriers f1 to f5 are assigned to the priority band of base station # 1 among subcarriers f1 to f15, and the subbands are assigned to the priority band of base station # 2. When the carriers f6 to f10 are allocated, the subcarriers f11 to f15 are allocated to the priority band of the base station # 3, and the data allocation request band is larger than the priority band, the sub-band of the non-priority band (priority band of the adjacent base station) Assign to a carrier. The frequency axis may be a subchannel in which a plurality of subcarriers are collected.

  In the present embodiment, slots for allocating data encoded by FEC or CDM are preferentially arranged in the frequency direction and straddle a plurality of subcarriers (subcarriers without interference and subcarriers that allow interference). And, from the top of the frame in the time axis direction, are assigned in order from the user with high reception quality. The example shown in FIG. 5 shows an example in which each base station accommodates 5 users. In the time axis direction, the subcarrier usage rate decreases toward the second half of the frame, and the user with the lowest reception quality is assigned to be positioned at the end of the frame. As a result, the number of subcarriers that collide is averagely distributed at each base station for each OFDM symbol, and it is assumed that the number of collisions decreases as the distance from the rear end of the frame decreases and the interference tolerance increases.

(Embodiment of transmission apparatus of OFDM communication system of the present invention)
FIG. 6 shows an embodiment of a transmission apparatus of the OFDM communication system of the present invention.
In the figure, a base station (transmitting apparatus) 100 inputs binary data of one or a plurality of users to an information encoding modulator 101, encodes it with FEC or CDM, and then performs PSK (Phase Shift Keying) or Modulation is performed by a modulation method such as QAM (Quadrature Amplitude Modulation). The encoded and modulated data is stored in the data buffer 102 for at least one frame. The data amount counter 103 refers to the address information of the data buffer 102 and the like to grasp the data amount for each user. The radio resource control unit 104 inputs the data amount for each user, and arranges the data in one frame corresponding to the subcarrier assigned to the base station according to the subcarrier allocation algorithm described with reference to FIGS. As described above, the data in the data buffer 102 is exchanged (address conversion) using the address mapper 105. The data buffer 102 sequentially reads data in the address section designated by the address controller 106 and outputs the data to the OFDM modulator 107. The OFDM modulator 107 generates a transmission signal by OFDM modulation processing.

  In the subcarrier allocation algorithm of this embodiment, as shown in FIG. 6, subcarriers f1 to f4 are allocated to the first base station # 1 among the subcarriers f1 to f6, and the subcarriers are allocated to the second base station # 2. By assigning carriers f3 to f6, it is possible to divide into subcarriers f3 and f4 that allow interference and subcarriers f1, f2, f5, and f6 that do not interfere. The frequency axis may be a subchannel in which a plurality of subcarriers are collected.

  In this way, in order to assign subcarriers f1 to f4 to base station # 1 and to assign subcarriers f3 to f6 to base station # 2, each data amount counter 103 between radio resource control units 104 of each base station. The amount of data for each user detected in (1) is mutually referred through the control path, and control is performed so that the band in which interference is allowed and the band without interference are distributed accordingly. Or it is good also as a structure which isolate | separates the radio | wireless resource control part 104 with which each base station was equipped from each base station, and performs collective centralized control from the radio | wireless resource control part connected to each base station via a bark bone line. In addition, when the radio resource control unit 104 provided in each base station performs radio resource control independently without exchanging the data amount for each user, the average subcarrier usage rate or the maximum subcarrier usage rate in the frame And subcarriers used in each base station may be distributed and set so that the presence of subcarriers without interference can be expected.

  Also, a retransmission control unit is provided, and the radio resource control unit 104 performs allocation control to the subcarrier as described in the fourth embodiment of the subcarrier allocation method for the retransmission data specified by the retransmission control unit. May be.

  FIG. 7 shows an example of address translation of the address mapper 105 of the base station # 1. FIG. 7 (1) shows valid data stored in the data buffer 102. Data 1 to 24 correspond to buffer addresses a1 to a24, and buffer addresses a25 to a36 are empty. When the address controller 106 of the base station # 1 sequentially reads the addresses a1 to a6 at the time t1 and sequentially reads the addresses a7 to a12 at the time t2, the addresses a1, a2, and a3 as shown in FIG. , a4, a25, a26, a5, a6, a7, a8, a27, a28,..., and finally, data 1 to 24 are transferred to subcarriers f1 to f4 as shown in FIG. To be mapped. The above subcarrier allocation method can also be handled by the same address conversion.

(Embodiment of receiving apparatus of OFDM communication system of the present invention)
FIG. 8 shows an embodiment of the receiving apparatus of the OFDM communication system of the present invention.
In the figure, a terminal station (receiving device) 200 demodulates a received OFDM signal by an OFDM demodulator 201 and accumulates demodulated data in a data buffer 202. The buffer area of the data buffer 202 is divided into addresses in units of subcarriers. A plurality of subcarriers may be combined into subchannel units (the same applies hereinafter).

  The data stored in the data buffer 202 is input to the information demodulator / decoder 203 and demodulated / decoded in reverse processing with the information encoding modulator 101 of the base station 100. This demodulated / decoded data is measured by a CINR measuring device 204 for each carrier with a CINR (Carrier to Interference and Noise Ratio) value, and it is determined that interference occurs for a subcarrier that does not satisfy a certain CINR value. To do. The control switch 205 inputs the measurement result of the CINR measuring device 204 and inputs the demodulated / decoded data to the information encoding modulator 206 until all the subcarriers satisfy a certain CINR value. The same code modulation as that of the information code modulator 101 is performed. The address controller 207 inputs the encoded and modulated data and performs address division in units of subcarriers, and also inputs the measurement result of the CINR measuring unit 204, and outputs data corresponding to subcarriers that do not satisfy a certain CINR value. The corresponding buffer area of the data buffer 202 (subcarriers f3 and f4 in the example of FIG. 6) is overwritten.

  Thereafter, reading from the data buffer, demodulation / decoding processing, CINR measurement, encoding / modulation processing, and partial overwriting of the data buffer are repeated. The control switch 205 stops this repetitive processing when all the subcarriers satisfy a certain CINR value, and outputs demodulated / decoded data as restored data. Note that the control switch 205 may stop the repetition process when the number of repetitions reaches a predetermined upper limit number.

  Further, when control information including used subcarrier information for each base station is transmitted using a different subcarrier for each base station, it is possible to recognize subcarriers that interfere with the control information. For example, when control information indicating that slots to be restored exist in subcarriers f1 to f4 and slots not to be restored exist in subcarriers f3 to f6, interfering subcarriers are f3 and f4. It can be specified that there is. The CINR measuring unit 204 obtains this information from the OFDM demodulating base station 201 and measures the CINR value for the interfering subcarriers f3 and f4. The control switch 205 and the address controller 207 determine the CINR of the subcarriers f3 and f4. You may make it perform the process according to a value.

  Through the above processing, the terminal station 200 performs reception processing including subcarriers without interference and subcarriers that allow interference, thereby obtaining an error correction effect by FEC decoding or processing gain by CDM decoding (despreading processing). Further, the demodulation / restoration process is repeated while accurately updating the received data of the subcarriers that allow interference, so that the occurrence of errors can be reliably suppressed.

FIG. 9 shows an example of improved transmission characteristics according to the present invention.
In the figure, the vertical axis indicates frequency utilization efficiency, and the vertical axis indicates the distance from the base station. The distance 1 on the horizontal axis is the farthest point that the base station should cover. When the subcarrier usage rate is 100%, the farthest point cannot be covered, and the segmented PUSC has a problem that the throughput near the base station cannot be secured.

  In the system of the present invention, frequency utilization efficiency equivalent to or higher than that of FUSC and segmented PUSC with a subcarrier usage rate of 100% can be realized within a normalized distance of 0.1 to 1 from the base station. In the system of the present invention, the subcarrier usage rate can be set to 100% in the vicinity of the base station, and in that case, high frequency utilization efficiency can be realized over the entire range.

  The radio resource control of the present invention described above is to increase the transmission capacity by providing subcarriers that allow interference, but replace the subcarriers described above with OFDM symbols to allow interference in the time axis direction. The transmission capacity may be increased.

The figure which shows 1st Embodiment of the subcarrier allocation method of this invention. The figure which shows 2nd Embodiment of the subcarrier allocation method of this invention. The figure which shows 3rd Embodiment of the subcarrier allocation method of this invention. The figure which shows 4th Embodiment of the subcarrier allocation method of this invention. The figure which shows 5th Embodiment of the subcarrier allocation method of this invention. The figure which shows embodiment of the transmitter of the OFDM communication system of this invention. The figure which shows the example of an address conversion of the address mapper 105 of base station # 1. The figure which shows embodiment of the receiver of the OFDM communication system of this invention. The figure which shows the example of improvement of the transmission characteristic by this invention. The figure which shows the example of subcarrier allocation in the conventional OFDM communication system.

Explanation of symbols

100 Base station (transmitter)
DESCRIPTION OF SYMBOLS 101 Information coding modulator 102 Data buffer 103 Data amount counter 104 Radio | wireless resource control part 105 Address mapper 106 Address controller 107 OFDM modulator 200 Terminal station (receiving apparatus)
201 OFDM demodulator 202 Data buffer 203 Information demodulation decoder 204 CINR measurement device 205 Control switch 206 Information coding modulator 207 Address controller

Claims (10)

In an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
The plurality of transmitting stations share a part of the plurality of subcarriers in the same frequency band and allow mutual interference, and a part of the plurality of subcarriers in the same frequency band occupy each interference. And divide the data encoded by FEC (Forward Error Correction) or CDM (Code Division Multiplexing) into the shared band and the occupied band ,
The data encoded by the FEC or CDM is preferentially distributed in a plurality of subcarriers in the frequency direction of the frame, and the subcarrier usage is reduced or increased in the time axis direction of the frame. A subcarrier allocation method for an OFDM communication system, characterized by performing allocation. In an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
The plurality of transmitting stations divide the plurality of subcarriers in the same frequency band into priority bands to be preferentially used for each transmitting station, and arrange data encoded by FEC or CDM in the respective priority bands, the data capacity that exceeds the priority bandwidth evenly disposed in the non-priority zone area which is a priority bandwidth of other transmitting stations,
The plurality of subcarriers in the same frequency band are ordered according to the frequency, and the subcarrier allocation is performed so that the subcarrier allocation order in the priority band and the subcarrier allocation order in the non-priority band are reversed. subcarrier allocation method of an OFDM communication system, which comprises carrying out. In an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
The plurality of transmitting stations divide the plurality of subcarriers in the same frequency band into priority bands to be preferentially used for each transmitting station, and arrange data encoded by FEC or CDM in the respective priority bands, Distribute data with a capacity that exceeds this priority band evenly in the non-priority band that is the priority band of other transmitting stations,
A subcarrier allocation method in an OFDM communication system, wherein initial transmission data or retransmission data used for ARQ (Automatic Repeat reQuest) transmission is preferentially allocated to the priority band. In an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
The plurality of transmitting stations divide the plurality of subcarriers in the same frequency band into priority bands to be preferentially used for each transmitting station, and arrange data encoded by FEC or CDM in the respective priority bands, Distribute data with a capacity that exceeds this priority band evenly in the non-priority band that is the priority band of other transmitting stations,
The data encoded by the FEC or CDM is preferentially distributed in a plurality of subcarriers in the frequency direction of the frame, and the subcarrier usage is reduced or increased in the time axis direction of the frame. A subcarrier allocation method for an OFDM communication system, characterized by performing allocation. In a transmitter of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
An information encoding modulator for encoding data to be transmitted by FEC or CDM and modulating the data by a predetermined modulation method;
A transmission data buffer for inputting data encoded and modulated by the information encoding modulator and storing at least one frame of the OFDMA scheme;
A part of a plurality of subcarriers in the same frequency band is shared with other transmitting stations to allow mutual interference, and a part of a plurality of subcarriers in the same frequency band is occupied for each transmitting station. does not interfere divided into occupied band Te, and transmission control means for data to be read from the transmission data buffer to control the read address of the transmission data buffer is controlled to be distributed to the occupied band and the shared spectrum,
An OFDM modulator that generates a transmission signal by OFDM-modulating data read from the transmission data buffer under the control of the transmission control means , and
The transmission control means includes
Data to be read from the transmission data buffer is preferentially distributed in a plurality of subcarriers in the frequency direction of the frame, and subcarrier allocation is performed so that the subcarrier usage rate decreases or increases in the time axis direction of the frame. An OFDM communication system transmitter characterized by the above. In a transmitter of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
An information encoding modulator for encoding data to be transmitted by FEC or CDM and modulating the data by a predetermined modulation method;
A transmission data buffer for inputting data encoded and modulated by the information encoding modulator and storing at least one frame of the OFDMA scheme;
Together with the multiple subcarriers of the same frequency band is divided into priority bands to be preferentially utilized for each transmission station, place the data to be read from the transmission data buffer to control the read address of the transmission data buffer to the priority band, Transmission control means for controlling data having a capacity exceeding the priority band so as to be evenly arranged in a non-priority band that is a priority band of another transmitting station;
An OFDM modulator that generates a transmission signal by OFDM-modulating data read from the transmission data buffer under the control of the transmission control means , and
The transmission control means includes
The plurality of subcarriers in the same frequency band are ordered according to the frequency, and the subcarrier allocation is performed so that the subcarrier allocation order in the priority band and the subcarrier allocation order in the non-priority band are reversed. transmitting device of the OFDM communication system, which comprises carrying out. In a transmitter of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
An information encoding modulator for encoding data to be transmitted by FEC or CDM and modulating the data by a predetermined modulation method;
A transmission data buffer for inputting data encoded and modulated by the information encoding modulator and storing at least one frame of the OFDMA scheme;
Dividing the plurality of subcarriers of the same frequency band into priority bands that are preferentially used for each transmission station, controlling the read address of the transmission data buffer and arranging the data read from the transmission data buffer in the priority band, Transmission control means for controlling data having a capacity exceeding the priority band so as to be evenly arranged in a non-priority band that is a priority band of another transmitting station;
An OFDM modulator for generating a transmission signal by OFDM-modulating data read from the transmission data buffer under the control of the transmission control means;
With
The transmission control means includes
First transmission data or retransmission data used for ARQ (Automatic Repeat reQuest) transmission is preferentially allocated to the priority band.
An OFDM communication system transmitter characterized by the above. In a transmitter of an OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of them,
An information encoding modulator for encoding data to be transmitted by FEC or CDM and modulating the data by a predetermined modulation method;
A transmission data buffer for inputting data encoded and modulated by the information encoding modulator and storing at least one frame of the OFDMA scheme;
Dividing the plurality of subcarriers of the same frequency band into priority bands that are preferentially used for each transmission station, controlling the read address of the transmission data buffer and arranging the data read from the transmission data buffer in the priority band, Transmission control means for controlling data having a capacity exceeding the priority band so as to be evenly arranged in a non-priority band that is a priority band of another transmitting station;
An OFDM modulator for generating a transmission signal by OFDM-modulating data read from the transmission data buffer under the control of the transmission control means;
With
The transmission control means includes
Data to be read from the transmission data buffer is preferentially distributed in a plurality of subcarriers in the frequency direction of the frame, and subcarrier allocation is performed so that the subcarrier usage rate decreases or increases in the time axis direction of the frame.
An OFDM communication system transmitter characterized by the above. 9. An OFDM communication system in which a plurality of transmitting stations sharing the same frequency band in the OFDMA scheme perform multiple access communication with a plurality of receiving stations under each of the transmitting stations, and the transmitting apparatus according to claim 5, In a receiving apparatus that receives an OFDM signal to be transmitted,
An OFDM demodulator that demodulates the received OFDM signal;
Received data buffer that receives demodulated data output from the OFDM demodulator, stores the address divided in subcarrier units, and
An information demodulator / decoder for inputting and demodulating and decoding data encoded by FEC or CDM and modulated by a predetermined modulation method from the reception data buffer;
By measuring an error rate for each subcarrier of data demodulated and decoded by the information demodulation decoder, subcarriers that interfere between the plurality of transmitting stations are identified, and demodulated and decoded by the information demodulation decoder A process of re-encoding and modulating data, overwriting data corresponding to the interfering subcarrier in a corresponding buffer area of the reception data buffer to suppress an interference signal, and inputting the data again to the information demodulation decoder A reception apparatus for an OFDM communication system, comprising: a reception control unit that repeats a predetermined number of times or until the error rate reaches a predetermined value, and thereafter outputs the data as demodulated and decoded data. The receiving apparatus of the OFDM communication system according to claim 9 ,
The reception apparatus of an OFDM communication system, wherein the reception control means is configured to identify subcarriers that interfere between the plurality of transmission stations from predetermined control information notified from the transmission apparatus.

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