JP2008193550A - Allocation method and base station device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an influence of deterioration in estimation precision of a frequency offset. <P>SOLUTION: The base station device 10 generates a frame by time multiplexing of a plurality of time slots while generating time slots by frequency multiplexing of a plurality of subchannels. A communication quality decision unit 34 detects precision of a frequency offset estimated by a terminal device. A time slot specifying unit 36 specifies one of the plurality of time slots forming the frame according to the detected precision. A radio resource allocating unit 38 allocates at least one of the plurality of subchannels forming the specified time slot to the terminal device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an allocation technique, and more particularly to an allocation method for allocating time slots to terminal apparatuses and a base station apparatus using the allocation method.

In a wireless communication system, a base station device may connect a plurality of terminal devices. One of the forms when the base station apparatus connects a plurality of terminal apparatuses is TDMA / TDD. In TDMA / TDD, a frame is formed by a plurality of time slots, and a plurality of frames are continuously arranged. Further, some of the plurality of time slots included in one frame are used for the uplink, and the remaining time slots are used for the downlink. In the prior art using such TDMA / TDD, the number of time slots used for the uplink in one frame and the number of time slots used for the downlink are determined as traffic. It is set according to the difference (see, for example, Patent Document 1).
JP-A-8-186533

  In general, effective use of limited frequency resources is desired in wireless communication. In particular, as the communication speed increases, the demand is further increased. One technique for meeting this demand is the OFDMA (Orthogonal Frequency Division Multiple Access) scheme, which can be combined with the TDMA / TDD described above. OFDMA is a technique for frequency-multiplexing a plurality of terminal devices using OFDM.

  In such OFDMA, a subchannel is formed by a plurality of subcarriers, and a multicarrier signal is formed by a plurality of subchannels. Further, the base station apparatus performs communication with the terminal apparatus by assigning at least one subchannel to the terminal apparatus. In general, there is a frequency offset between a signal output from a local oscillator provided in a terminal device and a signal output from an oscillator provided in a base station device. In order to reduce the influence of such a frequency offset, when receiving a signal from the base station apparatus, the terminal apparatus estimates a frequency offset for the received signal. Further, the terminal device corrects the received signal and the signal to be transmitted with the estimated frequency offset. Note that the frequency offset estimation accuracy differs for each terminal device.

  On the other hand, the base station apparatus receives signals from each of a plurality of terminal apparatuses multiplexed by OFDMA. At this time, if the accuracy of estimation of the frequency offset in a predetermined terminal apparatus deteriorates, orthogonality between subchannels is not established, and interference with other subchannels increases. When the interference increases, not only the reception characteristic for the terminal apparatus deteriorates, but also the reception characteristic for the terminal apparatus to which the subchannel affected by the interference is assigned deteriorates.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an allocation technique that reduces the influence of deterioration of the estimation accuracy of the frequency offset.

  In order to solve the above problems, a base station apparatus according to an aspect of the present invention is a base station apparatus that forms a frame by time multiplexing of a plurality of time slots while forming a time slot by frequency multiplexing of a plurality of subchannels. A detection unit that detects the accuracy of the frequency offset estimated in the terminal device, and a specification unit that specifies any of a plurality of time slots forming a frame according to the accuracy detected by the detection unit And an allocating unit that allocates at least one of the plurality of subchannels forming the time slot identified by the identifying unit to the terminal device.

  According to this aspect, since the subchannel included in the time slot is assigned after specifying the time slot according to the detected estimation accuracy, the influence of the terminal device whose estimation accuracy has deteriorated can be reduced.

  The specifying unit predefines a time slot in which terminal devices whose accuracy has deteriorated below the threshold are to be aggregated, and specifies the time slot when the accuracy detected by the detecting unit has deteriorated below the threshold. May be. In this case, since the terminal devices whose estimation accuracy has deteriorated below the threshold are concentrated in a predetermined time slot, the influence of the terminal devices whose estimation accuracy has deteriorated can be reduced.

  The specifying unit predetermines a range of accuracy for each of a plurality of time slots, specifies a range including the accuracy detected by the detecting unit, and then specifies a time slot associated with the specified range. May be. In this case, since the time slot is associated with each of the estimation accuracy ranges, the influence of the terminal device whose estimation accuracy has deteriorated can be reduced.

  The specifying unit may specify a time slot associated with the highest accuracy range for the control signal. In this case, since the control signal is assigned to the time slot associated with the range of the highest estimation accuracy, the influence of the terminal device whose estimation accuracy has deteriorated on the control signal can be reduced.

  Another aspect of the present invention is an allocation method. In this method, a time slot is formed by frequency multiplexing of a plurality of subchannels, and a frame is formed by time multiplexing of a plurality of time slots. Depending on the accuracy, one of a plurality of time slots forming a frame is specified, and at least one of the plurality of subchannels forming the specified time slot is allocated to the terminal device.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to reduce the influence of the deterioration of the frequency offset estimation accuracy.

  Before describing the present invention specifically, an outline will be given first. Embodiments of the present invention relate to a communication system including a base station device and at least one terminal device. In the communication system, each frame is formed by time-division multiplexing a plurality of time slots, and each time slot is formed by frequency-division multiplexing a plurality of subchannels. Each subchannel is formed by a multicarrier signal. Here, OFDM signals are used as multicarrier signals, and OFDMA is used as frequency division multiplexing.

  The base station apparatus performs communication with the plurality of terminal apparatuses by assigning each of the plurality of subchannels included in each time slot to the terminal apparatus. As described above, since OFDMA is performed for each of the plurality of subchannels, orthogonality is required between the plurality of subchannels. To cope with this, the terminal apparatus estimates a frequency offset based on the downlink signal from the base station apparatus, and corrects the uplink signal to be transmitted by the estimated frequency offset. Note that the frequency offset estimation accuracy differs for each terminal device. On the other hand, uplink signals included in a predetermined time slot are transmitted from a plurality of terminal apparatuses. Therefore, the base station apparatus receives the signal corrected with the frequency offset having different estimation accuracy while being synthesized. If the estimation accuracy of the frequency offset in a predetermined terminal device is deteriorated, the uplink signal from the terminal device interferes with other subchannels. As a result, reception characteristics in other subchannels are deteriorated. In order to cope with this, the base station apparatus according to the present embodiment executes the following processing.

  The base station apparatus measures the accuracy of the frequency offset estimated in the terminal apparatus. Also, the base station apparatus assigns a subchannel included in a specific time slot to a terminal apparatus whose estimation accuracy has deteriorated. On the other hand, a terminal device whose estimation accuracy has not deteriorated is assigned to a subchannel included in another time slot. As a result, the terminal devices whose estimation accuracy has deteriorated interfere with each other, but the influence of interference received by the terminal devices whose estimation accuracy has not deteriorated is reduced.

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. The communication system 100 includes a first terminal device 12a, a second terminal device 12b, and a third terminal device 12c, which are collectively referred to as a base station device 10 and a terminal device 12.

  The base station device 10 has a terminal device 12 connected to one end via a wireless network and a wired network (not shown) connected to the other end. Further, the terminal device 12 is connected to the base station device 10 via a wireless network. The base station apparatus 10 performs communication with the plurality of terminal apparatuses 12 by assigning communication channels to the plurality of terminal apparatuses 12. Specifically, the terminal apparatus 12 transmits a channel allocation request signal to the base station apparatus 10, and the base station apparatus 10 allocates a communication channel to the terminal apparatus 12 in response to the received request signal.

  In addition, the base station apparatus 10 transmits information on the communication channel assigned to the terminal apparatus 12, and the terminal apparatus 12 performs communication with the base station apparatus 10 while using the assigned communication channel. As a result, the data transmitted from the terminal device 12 is output to the wired network via the base station device 10 and finally received by a communication device (not shown) connected to the wired network. Data is also transmitted in the direction from the communication device to the terminal device 12.

  The terminal device 12 receives the downlink signal from the base station device 10. A frequency offset exists between the local oscillator provided in the terminal device 12 and the local oscillator provided in the base station device 10. The terminal device 12 estimates a frequency offset from the received downlink signal by a known technique. Further, the terminal device 12 corrects the received downlink signal with the estimated frequency offset. Further, the terminal device 12 corrects the uplink signal to be transmitted with the estimated frequency offset. That is, in the communication system 100, the frequency offset is estimated and corrected in the terminal device 12.

  In the above description, the communication channel is specified by the combination of the subchannel and the time slot described above. In addition, since the base station apparatus 10 has a plurality of time slots and a plurality of subchannels, the base station apparatus 10 executes OFDMA using a plurality of subchannels while executing TDMA using the plurality of time slots.

  2A to 2C show a frame configuration in the communication system 100. FIG. The horizontal direction in the figure corresponds to the time axis. The frame is formed by 8 time slots. The eight time slots are composed of four upstream time slots and four downstream time slots. Here, four uplink time slots are indicated as “first uplink time slot” to “fourth uplink time slot”, and four downlink time slots are indicated as “first downlink time slot” to “fourth downlink time slot”. . Further, the illustrated frame is repeated continuously. The configuration of the frame is not limited to that shown in FIG. 2A. For example, the frame configuration may be configured by four time slots or 16 time slots. The configuration will be described with reference to FIG. For the sake of brevity, it is assumed that the upstream time slot and the downstream time slot have the same configuration. For this reason, only one of the uplink time slot and the downlink time slot may be described, but the same description is valid for the other time slot.

  FIG. 2B shows the configuration of one time slot in FIG. The vertical direction in the figure corresponds to the frequency axis. As shown in the figure, one time slot is formed by “16” subchannels from “first subchannel” to “16th subchannel”. In addition, the plurality of subchannels are frequency division multiplexed. Since each time slot is configured as shown in FIG. 2B, the above-described communication channel is specified by the combination of the time slot and the subchannel. Also, the frame configuration corresponding to one subchannel in FIG. 2B may be as shown in FIG. Note that the number of subchannels arranged in one time slot may not be “16”.

  FIG. 2 (c) shows the configuration of one subchannel in FIG. 2 (b). Similar to FIG. 2A and FIG. 2B, the horizontal direction in the figure corresponds to the time axis, and the vertical direction in the figure corresponds to the frequency axis. Further, numbers “1” to “29” are assigned to the frequency axis, and these indicate subcarrier numbers. In this way, the subchannel is composed of multicarrier signals, and in particular is composed of OFDM signals. “TS” in the figure corresponds to a training symbol and is constituted by a known value. Further, it is assumed that a control signal may be included in “TS”. “GS” corresponds to a guard symbol, and no substantial signal is arranged here. “PS” corresponds to a pilot symbol, and is configured by a known value. “DS” corresponds to a data symbol and is data to be transmitted. “GT” corresponds to a guard time, and no substantial signal is arranged here.

  FIG. 3 shows an arrangement of subchannels in the communication system 100. In FIG. 3, the frequency axis is shown on the horizontal axis, and the spectrum for the time slot shown in FIG. 2B is shown. As described above, 16 subchannels from the first subchannel to the 16th subchannel are frequency division multiplexed in one time slot. Each subchannel is configured by a multicarrier signal, here, an OFDM signal.

  FIG. 4 shows the configuration of the base station apparatus 10. The base station apparatus 10 includes a first RF unit 20a, a second RF unit 20b, an NRF unit 20n, a baseband processing unit 22, a modem unit 24, an IF unit 26, a radio control unit 28, and a storage unit 30. including. The radio control unit 28 includes a control channel determination unit 32, a communication quality determination unit 34, a time slot identification unit 36, and a radio resource allocation unit 38.

  As a reception process, the RF unit 20 performs frequency conversion on a radio frequency multicarrier signal received from a terminal device 12 (not shown) to generate a baseband multicarrier signal. Here, the multicarrier signal is formed as shown in FIG. 3, and corresponds to the uplink time slot of FIG. Further, as described above, the frequency offset is corrected by each of the plurality of terminal devices 12 in the multicarrier signal received from each of the plurality of terminal devices 12. Further, the RF unit 20 outputs a baseband multicarrier signal to the baseband processing unit 22. In general, a baseband multicarrier signal is formed by an in-phase component and a quadrature component, and therefore should be transmitted by two signal lines. For the sake of clarity, a single signal line is used here. Only. The RF unit 20 also includes an AGC, an A / D conversion unit, and a local oscillator.

  As a transmission process, the RF unit 20 performs frequency conversion on the baseband multicarrier signal input from the baseband processing unit 22 to generate a radiofrequency multicarrier signal. Further, the RF unit 20 transmits a radio frequency multicarrier signal. The RF unit 20 transmits a multicarrier signal while using the same radio frequency band as the received multicarrier signal. That is, as shown in FIG. 2A, TDD (Time Division Duplex) is used. The RF unit 20 also includes a PA (Power Amplifier) and a D / A conversion unit.

  The baseband processing unit 22 inputs a baseband multicarrier signal from each of the plurality of RF units 20 as a reception operation. Since the baseband multicarrier signal is a time domain signal, the baseband processing unit 22 converts the time domain signal to the frequency domain by FFT and performs adaptive array signal processing on the frequency domain signal. To do. Further, the baseband processing unit 22 executes timing synchronization, that is, FFT window setting, and also deletes the guard interval. Since a known technique may be used for timing synchronization and the like, description thereof is omitted here. The baseband processing unit 22 outputs the result of adaptive array signal processing to the modem unit 24. As a transmission operation, the baseband processing unit 22 receives a multi-carrier signal in the frequency domain from the modulation / demodulation unit 24 and performs dispersion processing using weight vectors.

  As a transmission operation, the baseband processing unit 22 converts the frequency domain signal to the time domain by IFFT on the frequency domain multicarrier signal input from the modem unit 24, and converts the converted time domain signal to the RF unit. 20 output. The baseband processing unit 22 also adds a guard interval, but the description is omitted here. Here, the frequency domain signal includes a plurality of subchannels as shown in FIG. 2B, and each of the subchannels includes a plurality of subcarriers as in the vertical direction of FIG. 2C. For the sake of clarity, it is assumed that the signals in the frequency domain are arranged in the order of subcarrier numbers to form a serial signal.

  The modem unit 24 performs demodulation on the multi-carrier signal in the frequency domain from the baseband processing unit 22 as reception processing. The multicarrier signal converted into the frequency domain has components corresponding to each of the plurality of subcarriers as shown in FIGS. Demodulation is performed in units of subcarriers. The modem unit 24 outputs the demodulated signal to the IF unit 26. Further, the modem unit 24 performs modulation as transmission processing. The modem unit 24 outputs the modulated signal to the baseband processing unit 22 as a multi-carrier signal in the frequency domain.

  The IF unit 26 receives the demodulation result from the modulation / demodulation unit 24 as a reception process, and separates the demodulation result for each terminal device 12. That is, the demodulation result is composed of a plurality of subchannels as shown in FIG. Therefore, when one subchannel is assigned to one terminal apparatus 12, the demodulation result includes signals from a plurality of terminal apparatuses 12. The IF unit 26 separates such a demodulation result for each terminal device 12. The IF unit 26 outputs the separated demodulation result to a wired network (not shown). At that time, the IF unit 26 performs transmission according to information for identifying the destination, for example, an IP (Internet Protocol) address.

  Further, the IF unit 26 inputs data for the plurality of terminal devices 12 from a wired network (not shown) as a transmission process. The IF unit 26 assigns data to subchannels and forms a multicarrier signal from a plurality of subchannels. That is, the IF unit 26 forms a multicarrier signal composed of a plurality of subchannels as shown in FIG. The subchannel to which data is to be assigned is determined in advance as shown in FIG. 2 (c), and an instruction related thereto is received from the radio control unit 28. The IF unit 26 outputs the multicarrier signal to the modem unit 24.

  The communication quality determination unit 34 receives a frequency domain multicarrier signal from the baseband processing unit 22 via a signal line (not shown). Here, the frequency domain multi-carrier signal may be a result of adaptive array signal processing. Further, the communication quality determination unit 34 derives the accuracy of the frequency offset estimated in each of the plurality of terminal devices 12 based on the frequency domain multicarrier signal. Here, the estimated accuracy of the frequency offset corresponds to the residual component of the frequency offset included in the signal corrected in the terminal device 12.

  FIG. 5 shows a configuration of the communication quality determination unit 34. The communication quality determination unit 34 includes a delay unit 62, a multiplication unit 64, and a measurement unit 66. The processing of the delay unit 62 and the multiplication unit 64 is performed on the subcarrier in which the pilot symbol is arranged among the plurality of subcarriers included in the multicarrier signal shown in FIGS. The There are a plurality of such subcarriers. In order to clarify the explanation, here, processing for one subcarrier will be described. The delay unit 62 delays the input pilot symbol. Multiplier 64 derives the phase difference between the input pilot symbol and the pilot symbol delayed in delay unit 62. The measurement unit 66 receives the phase difference from the multiplication unit 64. In addition, the measurement unit 66 derives an average value of phase differences in subcarriers corresponding to one terminal apparatus 12.

  As shown in FIG. 2 (c), pilot signals are arranged on a plurality of subcarriers in one subchannel. Therefore, a plurality of phase differences corresponding to one terminal device 12 are also derived. In general, since the frequency offset is common to different subcarriers, the measurement unit 66 performs, for example, averaging processing over one subchannel to reduce the influence of noise. In addition, correspondence between the average value and the estimation accuracy is stored in advance as a table in the storage unit 30 described later, and the communication quality determination unit 34 derives the estimation accuracy from the average value while referring to the table. For example, the table defines a relationship in which the estimation accuracy deteriorates as the average value increases.

  When subchannel allocation is executed for a new terminal device 12, the communication quality determination unit 34 derives estimation accuracy based on the channel allocation request signal received from the terminal device 12. On the other hand, when switching the subchannel to the terminal device 12 to which the subchannel has already been assigned, the communication quality determination unit 34 derives the estimation accuracy based on the data signal received from the terminal device 12.

  The storage unit 30 stores information regarding the frame. As described above, a frame is formed by time multiplexing of a plurality of time slots, and the time slot is formed by frequency multiplexing of a plurality of subchannels, and information on the frame is, for example, a predetermined subchannel is allocated. This is information regarding the terminal device 12. In addition, the storage unit 30 stores the result of carrier sense performed for each subchannel. Here, the carrier sense is performed in the RF unit 20 by a known technique. Furthermore, the storage unit 30 predefines a range of estimation accuracy for each of a plurality of time slots.

  FIG. 6 shows the relationship between the conditions stored in the storage unit 30 and the time slots. As illustrated, a condition column 200 and a time slot column 202 are stored. In the condition column 200, a plurality of threshold values “a”, “b”, and “c” are defined to have a relationship of “a” <“b” <“c”. These threshold values define the range of estimation accuracy. Here, the lower the condition column 200, the lower the estimated accuracy range. In addition, a decrease in estimation accuracy corresponds to a decrease in estimation accuracy. Since the estimation accuracy is associated with the above-described average value, the estimation accuracy decreases as the estimation accuracy value in the condition column 200 increases. In the time slot column 202, time slots associated with the estimation accuracy range are defined. The range of estimation accuracy that has deteriorated most is associated with the fourth time slot. Returning to FIG.

  The time slot specifying unit 36 receives the estimated accuracy value from the communication quality determining unit 34. The time slot specifying unit 36 specifies one of a plurality of time slots forming a frame according to the received estimation accuracy. That is, the time slot specifying unit 36 specifies a time slot associated with the specified range after specifying the range including the estimation accuracy while referring to the table stored in the storage unit 30. The time slot specifying unit 36 outputs the specified time slot to the radio resource allocating unit 38.

  The radio resource allocation unit 38 allocates at least one of the plurality of subchannels forming the time slot specified by the time slot specifying unit 36 to the terminal device 12. At that time, the radio resource allocating unit 38 extracts empty subchannels included in the identified time slot while referring to information on the frame stored in the storage unit 30. In addition, the radio resource allocation unit 38 specifies the subchannel with the lowest interference wave level among the extracted free subchannels while referring to the carrier sense result stored in the storage unit 30.

  Here, in order to reduce the influence of interference, the radio resource allocation unit 38 allocates subchannels preferentially from the subchannel “16” having the highest frequency and the subchannel “1” having the lowest frequency. Also good. Note that carrier sense may be performed when a subchannel is specified. The radio resource allocation unit 38 determines the allocation of the identified subchannel and transmits the result as a notification of allocation to the terminal device 12 via the modem unit 24, the baseband processing unit 22, and the RF unit 20. Further, the radio resource allocation unit 38 reflects the allocated result in the storage unit 30.

  When there is no empty subchannel in the time slot specified by the time slot specifying unit 36, the radio resource allocating unit 38 specifies again the time slot specified so that the estimation accuracy range is higher than that of the time slot. . Further, the time slot specifying unit 36 extracts empty subchannels included in the specified time slot. Here, the time slot defined so that the estimation accuracy range is higher than that of the time slot corresponds to the third time slot when “the time slot” is the fourth time slot of FIG. . If there is an empty subchannel, the time slot specifying unit 36 performs subchannel allocation as described above. If the allocation is impossible, the time slot specifying unit 36 may transmit the allocation rejection to the terminal device 12 via the modem unit 24, the baseband processing unit 22, and the RF unit 20.

  The control channel determination unit 32 assigns control signals to subchannels. Here, the control signal is a signal including information used for controlling communication with the terminal device 12. Such a control signal is more important than a data signal. Therefore, the control channel determination unit 32 identifies the time slot associated with the highest estimation accuracy range with respect to the control signal while referring to the storage unit 30, and a plurality of times included in the identified time slot. Select one of the subchannels. In addition, the control channel determination unit 32 notifies the radio resource allocation unit 38 of the selected subchannel. The radio resource allocation unit 38 allocates a subchannel to the control signal according to the notification from the radio resource allocation unit 38.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The operation of the communication system 100 configured as above will be described. FIG. 7 is a sequence diagram showing a subchannel assignment procedure in communication system 100. The first terminal apparatus 12a transmits a subchannel allocation request signal to the base station apparatus 10 (S10). The base station apparatus 10 measures the accuracy of the frequency offset estimated in the first terminal apparatus 12a based on the allocation request signal (S12), and identifies the time slot based on the measured estimation accuracy ( S14). The base station apparatus 10 allocates the subchannel included in the identified time slot to the first terminal apparatus 12a (S16). The base station apparatus 10 transmits an allocation notification of the allocated result to the first terminal apparatus 12a (S18). Thereafter, the base station apparatus 10 and the first terminal apparatus 12a perform communication while using the assigned subchannel.

  FIG. 8 is a flowchart showing a subchannel allocation procedure in the base station apparatus 10. The communication quality determination unit 34 measures the frequency offset estimation accuracy (S30). The time slot specifying unit 36 specifies a time slot based on the measured estimation accuracy (S32). If there is an empty subchannel in the identified time slot (Y in S34), the RF unit 20 performs carrier sense (S36). If subchannel allocation is possible (Y in S38), the radio resource allocation unit 38 executes allocation and notifies the result (S40). On the other hand, when there is no empty subchannel in the specified time slot (N in S34) or when subchannel allocation is not possible (N in S38), if there is a higher group (Y in S42), the time slot specifying unit 36 Specifies a time slot (S44).

  Here, the upper group corresponds to a range where the estimation accuracy is higher than that at present. If there is an empty subchannel in the identified time slot (Y in S46), the RF unit 20 performs carrier sense (S48). If subchannel allocation is possible (Y in S50), the radio resource allocation unit 38 executes allocation and notifies the result (S52). If there is no empty subchannel in the identified time slot (N in S46) or if subchannel allocation is not possible (N in S50), the process returns to step 42. On the other hand, if there is no higher group (N in S42), the radio resource allocation unit 38 rejects the allocation (S54).

  Hereinafter, modifications of the present invention will be described. In the embodiment, the storage unit 30 associates time slots with each of the estimation accuracy ranges. However, in the modification, the storage unit 30 predefines time slots in which the terminal devices 12 whose estimation accuracy is worse than the threshold value should be aggregated. In other words, there is a rule that only the terminal devices 12 that are likely to interfere with other terminal devices 12 are grouped into one time slot. The base station apparatus 10 according to the modification is the same type as that in FIG.

  FIG. 9 shows the relationship between the conditions and the time slots stored in the storage unit 30 according to the modification of the present invention. As illustrated, a condition column 200 and a time slot column 202 are stored. In the condition column 200, one threshold value “c” is defined. In the time slot column 202, a time slot associated with the condition in the condition column 200 is defined. A fourth time slot is associated with the terminal device 12 whose estimation accuracy is worse than the threshold value. Returning to FIG. The time slot specifying unit 36 specifies the fourth time slot when the estimation accuracy is worse than the threshold value.

  According to the embodiment of the present invention, since the subchannel included in the time slot is assigned after the time slot is specified according to the measured estimation accuracy, the influence of the terminal device whose estimation accuracy has deteriorated can be reduced. In addition, since the time slot is associated with each estimation accuracy, it is possible to specify different time slots for the terminal device with high estimation accuracy and the terminal device with low estimation accuracy. Further, since different time slots are specified for the terminal device with high estimation accuracy and the terminal device with low estimation accuracy, the influence of the terminal device with low estimation accuracy on the terminal device with high estimation accuracy can be reduced. In addition, since terminal devices whose estimation accuracy has deteriorated below the threshold are concentrated in a predetermined time slot, the influence of the terminal devices whose estimation accuracy has deteriorated can be reduced. In addition, since the control signal is assigned to the time slot associated with the highest estimation accuracy, the influence of the terminal device with low estimation accuracy on the control signal can be reduced.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the communication quality determination unit 34 measures the estimation accuracy of the frequency offset from the received signal. However, the present invention is not limited to this. For example, the terminal device 12 may estimate the frequency offset, measure the estimation accuracy of the frequency offset, and notify the base station device 10 of the measurement result. The communication quality determination unit 34 receives the notified measurement result. The measurement at the terminal device 12 is performed in the same manner as the processing at the communication quality determination unit 34 in the embodiment. According to this modification, the degree of freedom in design can be improved.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the frame structure in the communication system of FIG. It is a figure which shows the frame structure in the communication system of FIG. It is a figure which shows the frame structure in the communication system of FIG. It is a figure which shows arrangement | positioning of the subchannel in the communication system of FIG. It is a figure which shows the structure of the base station apparatus of FIG. It is a figure which shows the structure of the communication quality determination part of FIG. It is a figure which shows the relationship between the conditions memorize | stored in the memory | storage part of FIG. 4, and a time slot. FIG. 2 is a sequence diagram showing a subchannel allocation procedure in the communication system of FIG. 1. 6 is a flowchart showing a subchannel allocation procedure in the base station apparatus of FIG. It is a figure which shows the relationship between the conditions memorize | stored in the memory | storage part which concerns on the modification of this invention, and a time slot.

Explanation of symbols

  10 base station apparatus, 12 terminal apparatus, 20 RF section, 22 baseband processing section, 24 modulation / demodulation section, 26 IF section, 28 radio control section, 30 storage section, 32 control channel determination section, 34 communication quality determination section, 36 time A slot identifying unit; 38 a radio resource allocating unit; 100 a communication system;

Claims (6)

A base station apparatus that forms a frame by time multiplexing of a plurality of time slots while forming a time slot by frequency multiplexing of a plurality of subchannels,
A detection unit for detecting the accuracy of the frequency offset estimated in the terminal device;
A specifying unit for specifying any one of a plurality of time slots forming a frame according to the accuracy detected by the detection unit;
A base station apparatus comprising: an allocating section that allocates at least one of a plurality of subchannels forming a time slot identified by the identifying section to the terminal apparatus.   The specifying unit predefines a time slot in which terminal devices whose accuracy has deteriorated below a threshold are to be aggregated, and when the accuracy detected by the detection unit deteriorates below a threshold, the time slot The base station apparatus according to claim 1, wherein:   The specifying unit predetermines a range of accuracy for each of a plurality of time slots, specifies a range including the accuracy detected by the detecting unit, and then associates the time slot associated with the specified range The base station apparatus according to claim 1, wherein:   The base station apparatus according to claim 3, wherein the specifying unit specifies a time slot associated with the highest accuracy range for the control signal.   While a time slot is formed by frequency multiplexing of a plurality of subchannels, a frame is formed by time multiplexing of a plurality of time slots, and when the accuracy of the frequency offset estimated in the terminal device is detected, Allocating one of a plurality of time slots forming a frame and allocating at least one of a plurality of subchannels forming the specified time slot to the terminal device Method. Detecting the accuracy of the frequency offset estimated in the terminal device;
A time slot is formed by frequency multiplexing of a plurality of subchannels, and a frame is formed by time multiplexing of a plurality of time slots. According to the detected accuracy, a time slot is formed out of a plurality of time slots forming the frame. A step to identify one,
Assigning at least one of a plurality of subchannels forming a specified time slot to the terminal device;
A program that causes a computer to execute.

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