JP4351240B2 - COMMUNICATION CONTROL METHOD FOR TDD / OFDMA COMMUNICATION SYSTEM, BASE STATION DEVICE, TERMINAL DEVICE, AND COMMUNICATION CONTROL SYSTEM - Google Patents

Description

  The present invention relates to a communication control method, a base station apparatus, a terminal apparatus, and a communication control system of a TDD / OFDMA communication system in which OFDMA is applied in addition to the TDMA / TDD system.

  The TDMA / TDD system that combines TDMA (Time Division Multiple Access) and TDD (Time Division Duplex) is adopted as a wireless access system for digital cellular phone systems and PHS systems. Yes. In addition to this, a TDD / OFDMA communication scheme using OFDMA (Orthogonal Frequency Division Multiplexing Access) has been proposed.

OFDM (Orthogonal Frequency Division Multiplexing), which is the basis of OFDMA, divides a carrier that modulates data into a plurality of subcarriers (subcarriers) that are orthogonal to each other, and distributes the data signal to each subcarrier. This is a method for transmitting.
The outline of the OFDM system will be described below.

  FIG. 6 is a block diagram showing a configuration of an OFDM modulation apparatus used on the transmission side. Transmission data is input to the OFDM modulator. This transmission data is supplied to the serial / parallel converter 201 and converted into data consisting of a plurality of low-speed transmission symbols. That is, the transmission information is divided to generate a plurality of low-speed digital signals. This parallel data is supplied to an inverse fast Fourier transform (IFFT) unit 202.

  Parallel data is assigned to each subcarrier constituting the OFDM and mapped in the frequency domain. Here, modulation such as BPSK, QPSK, 16QAM, and 64QAM is performed on each subcarrier. The mapping data is converted from transmission data in the frequency domain to transmission data in the time domain by performing an IFFT operation. As a result, a multicarrier modulation signal is generated in which a plurality of subcarriers that are orthogonal to each other are independently modulated. The output of the IFFT unit 202 is supplied to the guard interval adding unit 203.

  As shown in FIG. 7, guard interval adding section 203 uses the rear part of the effective symbol of the transmission data as a guard interval, and adds a copy to the front part of the effective symbol period for each transmission symbol. The baseband signal obtained by the guard interval adding unit is supplied to the quadrature modulation unit 204.

  The quadrature modulation unit 204 performs quadrature modulation on the baseband OFDM signal supplied from the guard interval adding unit 203 by using the carrier signal supplied from the local oscillator 105 of the OFDM modulation device, and outputs an intermediate frequency (IF) Frequency conversion to signal or radio frequency (RF) signal. That is, the quadrature modulation unit frequency-converts the baseband signal into a desired transmission frequency band, and then outputs it to the transmission path.

  FIG. 8 is a block diagram showing a configuration of an OFDM demodulator used on the receiving side. An OFDM signal generated by the OFDM modulation device in FIG. 6 is input to the OFDM demodulation device via a predetermined transmission path.

  The OFDM received signal input to this OFDM demodulator is supplied to the orthogonal demodulator 211. The orthogonal demodulator 211 performs orthogonal demodulation on the OFDM received signal using the carrier signal supplied from the local oscillator 212 of the OFDM demodulator, converts the frequency from the RF signal or IF signal to the baseband signal, and converts the baseband signal. Obtain an OFDM signal. This OFDM signal is supplied to the guard interval removal unit 213.

  The guard interval removing unit 213 removes the signal added by the guard interval adding unit 203 of the OFDM modulation apparatus according to a timing signal supplied from a symbol timing synchronization unit (not shown). The signal obtained by the guard interval removing unit 203 is supplied to a fast Fourier transform (FFT) unit 214.

  The FFT unit 214 converts the input time domain received data into frequency domain received data by performing FFT. Further, mapping is performed in the frequency domain, and parallel data is generated for each subcarrier. Here, demodulation for modulation of BPSK, QPSK, 16QAM, 64QAM, etc. applied to each subcarrier has been performed. The parallel data obtained by the FFT unit 214 is supplied to the parallel / serial conversion unit 215 and output as reception data.

  OFDMA is a scheme in which a carrier wave is divided into a plurality of subcarriers in the same manner as OFDM described above, but differs from OFDM in that the divided subcarriers are grouped. The subcarriers in the group are called “subchannels”, and a single user may occupy these subchannels or may be shared by multiple users.

  By the way, in the wireless transmission path, the signal transmitted from the terminal side propagates through the space and is received by the base station side. However, if there are multiple obstacles such as buildings and mountains in the transmission path, they are reflected on the obstacle. The reflected wave may reach the base station with a delay from the direct wave. This is called a delayed wave, but the delay wave and the direct wave have different transmission distances, so that the base station side widens the reception timing due to the influence of a plurality of paths (multipath). The base station sets a desired timing (for example, the strongest transmission power) among these timings as a desired timing. As a result, undesired timings may be distributed before and after the desired timing.

  Further, in a communication system employing a multi-access scheme in which a plurality of data is simultaneously transmitted from a plurality of terminals to a base station, when the distance from the base station differs for each terminal, the signal for each terminal arriving at the base station is Since the timings are different from each other, intersymbol interference may occur in order to expand the spread in timing in combination with the influence of the plurality of paths (multipaths) described above.

  As a technique for compensating for such inter-carrier interference due to propagation delay, Patent Document 1 discloses a method for supplying a time alignment control signal to each of a plurality of transceivers that repeatedly transmit signals to a common transceiver. Detecting the arrival time at a common transceiver of one signal transmitted from each of the plurality of transceivers such that signals subsequently transmitted from each of the plurality of transceivers are substantially at an arrival time within a predetermined period of time. For each transceiver, determine the advance and delay of the next signal to be transmitted to the common transceiver, and the next transmitted signal from virtually all transceivers is determined by the advance and delay in the timing control signal. For each of the multiple transceivers to be advanced or delayed by Method of supplying control signals, including the step of transmitting is disclosed a timing control signal including the amount of the advance or delay with respect to transceiver.

  Further, Patent Document 2 discloses a plurality of user apparatuses by estimating and calculating the moment when an OFDM symbol is transmitted to the headend apparatus so that the headend apparatus can receive the OFDM symbol at a predetermined moment. A time synchronization between a part of the head end device and the head end device is disclosed.

  In addition to the timing control described in the above-mentioned patent document, a method of adding a guard interval on the terminal side is generally employed as a method of removing inter-carrier interference. As shown in FIG. 8, the guard interval is obtained by copying the same signal as the part X of the second half of the effective symbol to the first half of the effective symbol.

  On the base station side, by ignoring the information of this guard interval section, even if a delay occurs only in a certain carrier, if the delay time is within this guard interval section, the symbol of each subcarrier is removed after the guard interval is removed. Since there is no discontinuity and interference is not given to adjacent subcarriers even after FFT, the delay is ignored and reception can be performed correctly. In addition, since the data in the effective symbol is copied and inserted in the guard interval section, no information is lost even if a certain carrier shifts.

  However, as the transmission distance between the terminal and the base station increases, delay dispersion increases, and a delayed wave may enter the guard interval length. Also, in a system in which random access control is performed between the terminal and the base station, the period during which the base station communicates with the terminal becomes intermittent, the transmission timing deviation at the terminal increases, and the delay time exceeds the guard interval. If this happens, there is a high possibility of interference with adjacent carriers.

  For this reason, it is necessary to control the transmission timing on the terminal device side or to control the reception timing on the base station device side so that the delay time does not exceed the guard interval. As a method of performing transmission timing control by the terminal device, a method of performing timing control by the terminal device based on a transmission timing request included in downlink information transmitted from the base station device after call connection (after entering the communication channel) Can be considered.

Special table 2003-528483 gazette JP-T-2004-533769

  However, since the transmission timing from the terminal device is shifted according to the transmission distance even at the first channel allocation request time (before entering the communication channel), in this situation, the probability of interference between carriers due to delay dispersion exceeding the guard interval Will increase.

  Therefore, the present invention has been made to solve the above problems, and by suppressing the delay time caused by the transmission timing deviation at the time of channel allocation request within the guard interval, inter-carrier interference due to delay dispersion is reduced. The purpose is to prevent it from occurring.

In response to a channel allocation request included in uplink information from the terminal device, channel allocation is performed using downlink information from the base station device by a TDD / OFDMA communication scheme between the base station device and a plurality of terminal devices. A communication control method for responding,
The base station device
When confirming a channel assignment request from the terminal device, estimating whether reception timing for receiving the uplink information is earlier or later than a reference based on a pilot symbol included in the channel assignment request;
If the reception timing of the channel assignment request is not within a reference range based on the estimation result of the reception timing, a transmission timing shift amount is added to a response related to the channel assignment that rejects the channel assignment, and the channel assignment is performed. when the reception timing of the request is in the reference range, and executes the steps of: transmitting a response for the channel assignment to perform the channel assignment to the terminal device. (Claim 1)

Further, in the present invention, when transmitting a channel allocation request from the terminal device, the transmission power is increased stepwise from a small level to a large level and transmitted to the base station device;
The base station device includes a step of transmitting a response related to the channel assignment when confirming a channel assignment request from the terminal device. (Claim 2)

Further, in the present invention, the base station apparatus,
Recording the reception timing estimation result in a timing recording means;
Upon transmission of response for the channel assignment reject the channel assignment from the base station apparatus, further perform the steps of: by adding the transmission timing shift amount based on the recorded contents of said timing recording means for transmitting to said terminal device And
The terminal device,
Extracting the received transmission timing shift amount and recording it in a transmission timing recording means;
When transmitting a channel assignment request again from the terminal device, and transmitting the to the base station apparatus at the indicated timing transmission timing the transmission timing shift amount recorded in the recording means, further executes Features. (Claim 3)

Further, the present invention also includes a step of estimating reception timing for uplink information transmitted from the terminal apparatus using a channel allocated from the base station apparatus;
Adding a transmission timing control bit to downlink information based on the reception timing estimation result;
Adjusting the transmission timing of uplink information according to the transmission timing control bit added to the downlink information, and transmitting the uplink information on the allocated channel. (Claim 4)

Further, the present invention capable of solving the above problems is a base station apparatus that performs communication in a TDD / OFDMA communication scheme with a plurality of terminal apparatuses,
When transmitting the channel allocation request from the terminal device, when the channel allocation request transmitted by checking the transmitted channel allocation request stepwise from a small level to a large level is confirmed, based on the pilot symbol included in the channel allocation request Timing estimation means for estimating whether the timing for receiving the channel assignment request is earlier or later than a predetermined timing preset in the base station device;
Timing recording means for recording the transmission timing shift amount based on the estimation result;
Based on the recorded contents of the timing recording means, if the reception timing of the channel assignment request is not within a reference range, the transmission timing shift amount recorded in the timing recording means in response to the channel assignment rejecting channel assignment is And a transmission timing shift amount adding means to be added. (Claim 5)

Further, the present invention is a terminal device that performs communication of the TDD / OFDMA communication method with the above base station device ,
In the terminal device, when transmitting a channel allocation request, transmission power adjustment means for transmitting by increasing the transmission power stepwise from a small level to a large level;
A transmission timing recording means for recording received the transmission timing shift amount,
Transmission timing adjustment means for transmitting to the base station apparatus at a timing indicated by the transmission timing shift amount when transmitting uplink information from the terminal apparatus. (Claim 6)

In addition, the present invention that can solve the above-described problem responds to a channel assignment request included in uplink information from the terminal device by a TDD / OFDMA communication scheme between the base station device and a plurality of terminal devices. A communication control system for responding to channel assignment with downlink information from the base station device,
The base station device
When transmitting the channel allocation request from the terminal device, when the channel allocation request transmitted by checking the transmitted channel allocation request stepwise from a small level to a large level is confirmed, based on the pilot symbol included in the channel allocation request Timing estimation means for estimating whether the timing for receiving the channel assignment request is earlier or later than a predetermined timing preset in the base station device;
Timing recording means for recording the transmission timing shift amount based on the estimation result;
Based on the recorded contents of the timing recording means, if the reception timing of the channel assignment request is not within a reference range, the transmission timing shift amount recorded in the timing recording means in response to the channel assignment rejecting channel assignment is Transmission timing shift amount adding means for adding,
The terminal device
Transmission power adjusting means for transmitting the channel allocation request by increasing the transmission power stepwise from a small level to a large level when transmitting the channel assignment request;
Transmission timing recording means for recording the received transmission timing request;
Transmission timing adjusting means for transmitting to the base station apparatus at a timing instructed by the transmission timing request when uplink information is transmitted from the terminal apparatus. (Claim 7)

  According to the present invention, it is possible to prevent inter-carrier interference due to delay dispersion by suppressing a delay time caused by a shift in transmission timing at the time of channel allocation request within a guard interval. Further, by increasing the transmission power for requesting the first channel allocation in order from the smallest power, it is possible to reduce uplink adjacent channel interference and other cell interference.

  Hereinafter, embodiments of a communication control method, a base station apparatus, and a terminal apparatus of a TDD / OFDMA communication system according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram of a base station apparatus according to an embodiment of the present invention.

The base station apparatus 10 of the present embodiment includes a transmission / reception unit 1 (PA / RF unit / IF unit / BB unit) and a signal processing unit 2 that processes received signals.
In the transmission / reception unit 1, an OFDMA signal as a baseband signal can be obtained via a signal received from an antenna via an RF unit and an IF unit.

  The signal processing unit 2 includes a symbol synchronization unit 2-1, a memory 2-2, an FFT unit 2-3, a frequency estimation unit (channel estimation unit) 2-4, a timing estimation unit 2-5 (timing estimation unit), and a demodulation unit (Decoding unit) 2-6, physical layer frame forming unit 2-7 (transmission timing request adding means), modulation encoding unit 2-8, and IFFT unit 2-9.

  The symbol synchronization unit 2-1 performs symbol synchronization of the OFDMA signal obtained from the transmission / reception unit 1, removes the guard interval (GI), and performs the FFT by the FFT unit 2-3, so that the OFDMA signal is changed for each user. Take out the symbol. Thereafter, the timing estimation unit 2-5 performs timing estimation, and based on the timing estimation result, stores in the memory 2-2 (timing recording means) how early or late the reception timing for receiving the channel assignment request is from the reference. .

  A frequency estimator (channel estimator) 2-4 performs frequency estimation and channel estimation, and a demodulator (decoder) 2-6 demodulates and decodes data to extract data, performs error checking, and passes it to the upper layer. Thereafter, the transmission timing shift amount stored in the memory 2-2 is set in the response information related to channel assignment. Note that the responses related to the channel assignment include a channel assignment response in which the base station apparatus 10 assigns a channel to the terminal apparatus 20 and a channel assignment rejection in which the base station apparatus 10 refuses a channel assignment to the terminal apparatus 20.

  The physical layer frame forming unit 2-7 forms a physical layer frame of the subchannel, and the modulation coding unit 2-8 performs coding and modulation. IFFT part 2-9 applies IFFT, adds a guard interval (GI), passes through DA and converts it to an analog signal, then converts it to an RF frequency signal through the IF part and RF part of transceiver 1, and passes through the PA part. Sent from antenna.

  Next, the functional configuration of the terminal device according to the embodiment of the present invention will be described. FIG. 2 is a functional block diagram of the terminal device.

The terminal device 20 according to the present embodiment includes a transmission / reception unit 11 (PA / RF unit / IF unit / BB unit) and a signal processing unit 22 that processes a received signal.
In the transmission / reception unit 11, the signal received from the antenna can obtain an OFDMA signal as a baseband signal via the RF unit and the IF unit.

  The signal processing unit 12 includes a symbol synchronization 12-1, a memory 12-2, an FFT unit 12-3, a frequency estimation unit (channel estimation unit) 12-4, a timing estimation unit 12-5, a demodulation unit (decoding unit) 12- 6, physical layer frame forming unit 12-7, modulation coding unit 12-8, IFFT unit 12-9, timing request extraction 12-10, timing shift unit 12-11 (transmission timing adjusting means), transmission power control unit 12- 12 (transmission power adjusting means).

  The transmission power control unit 12-12 sets the strength of the transmission power of the channel allocation request to be transmitted to the base station apparatus 10 at the CCH (control channel) stage before entering the communication channel. In this embodiment, the transmission power can be increased stepwise from a small level to a large level.

  The symbol synchronization unit 12-1 performs symbol synchronization of the OFDMA signal obtained from the transmission / reception unit 11, removes the guard interval (GI), and the FFT unit 12-3 performs FFT to extract a symbol from the OFDMA signal. . Thereafter, the timing estimation unit 12-5 performs timing estimation, and the frequency estimation unit (channel estimation unit) 12-4 performs frequency estimation and channel estimation. Then, the demodulation unit (decoding unit) 12-6 demodulates and decodes to extract data, and the timing request extraction 12-10 extracts the transmission timing shift amount added to the channel assignment response, and the memory 12-2 It is recorded in (transmission timing recording means), checked for errors, and passed to the upper layer.

  The physical layer frame forming unit 12-7 forms a physical layer frame of the subchannel, and the modulation encoding unit 12-8 performs encoding and modulation. Thereafter, the timing shift unit 12-11 controls the transmission timing of uplink information from the terminal device 20 according to the transmission timing shift amount (transmission timing request) stored in the memory 12-2, and the IFFT unit 12-9 applies IFFT. After adding a guard interval (GI) and passing through the DA and converting it into an analog signal, it is converted into an RF frequency signal through the IF unit and RF unit of the transmission / reception unit 11 and transmitted from the antenna through the PA unit.

Next, the format of subchannels constituting an OFDMA frame will be described with reference to FIG. FIG. 3 is an explanatory diagram showing the format of the subchannel.
As shown in FIG. 3, one frequency band is composed of four downlink subchannels and four uplink subchannels.

  Each subchannel is further divided into OFDM subcarriers on the frequency axis and OFDM symbols on the time axis. Subcarriers include subcarriers that carry information necessary for communication, guard subcarriers that reduce the influence of other carriers on the frequency axis, and DC subcarriers that are DC components that are not necessary for communication. being classified. A subcarrier for each symbol includes a preamble, a pilot symbol, a guard time, a guard interval, data, and the like. Each symbol includes a time length (FFT range in FIG. 3) necessary for performing FFT and a guard interval.

PR is a preamble: (PRiamble), and is a signal for recognizing the start of frame transmission and giving timing for synchronization.
PS is a pilot symbol: PS (Pilot Symbol), which is a known signal waveform or known data for obtaining a phase reference for correctly identifying and recognizing the absolute phase of each carrier subcarrier.
TS is a training symbol.
Sub channel payload is a sub channel payload and is a part that accommodates physical layer (PHY) data.
GT (guard interval: GI) is a guard time: GT (Guard Time), and prevents bursts from each terminal apparatus from overlapping due to a difference in distance between each terminal apparatus and the base station apparatus or a transmission timing error. It is a part for.
Guard interval: GI (Guard Interval) is used to prevent inter-subcarrier interference by appropriately selecting the FFT timing even when adjacent waves overlap due to overlapping of arrival waves due to multiple different timings. It is a part of.

The guard interval is a portion obtained by cyclically expanding the output signal from the IFFT unit 2-9 or IFFT unit 12-9, and is added for each symbol. By adding a guard interval, it is possible to demodulate any part of the OFDM part including the guard interval without degradation, as long as the timing to cut the signal periodically input to the FFT part 2-3 or the FFT part 12-3 is within the OFDM symbol. it can. That is, even if the delay time component is included in one symbol, if the delay time is shorter than the guard interval, the adjacent symbol component does not enter, so that intersymbol interference does not occur.
In the present embodiment, the total delay time including the delay time due to multipath and the delay time due to the difference in distance from the base station for each terminal can be kept within the guard interval. It has become.

The timing estimation unit 2-5 of the base station apparatus 10 performs a correlation operation between a known symbol such as a pilot symbol: PS or preamble: PR of each subchannel and the received signal, thereby requesting a channel assignment from the terminal apparatus 20. Is estimated to be earlier or later than a reference timing of the base station apparatus 10, that is, a desired timing. Further, the timing extraction unit 12-10 of the terminal device 20 extracts the transmission timing shift amount added to the channel assignment response from the base station device 10.
Note that timing detection using known symbols can also be performed by performing a correlation operation on a known time axis waveform in a timing detection block before FFT (including before GI removal), for example, symbol synchronization 2-1. .

(First embodiment)
Next, a communication control method between the base station terminal 10 and the terminal device 20 according to the present embodiment will be specifically described with reference to FIG. FIG. 4 is a flowchart illustrating a first timing control process performed between the base station terminal 10 and the terminal device 20 according to the present embodiment.

  First, the terminal device 20 performs frame synchronization with the broadcast channel of the base station device 10 in advance (step S11), and sends a channel assignment request to the base station device 10 (step S12). At that time, the transmission power is increased in order from the lowest level (step S13 to step S15), and a channel assignment response from the base station apparatus 10 is awaited. When the base station apparatus 10 confirms the channel allocation request from the terminal apparatus 10 (step S15), the shift between the reception timing and the reference timing is measured, and added to the downlink information of the channel allocation response as a transmission timing shift amount. 20 (step S16).

  At the time of call connection, the terminal apparatus 20 transmits the downlink communication quality state of each channel to the base station apparatus 10. The base station apparatus 10 also monitors the uplink communication quality state, and assigns the channel with the best communication quality to the anchor subchannel according to the mutual communication quality state. Here, the anchor subchannel is used to notify each terminal device which subchannel is used by which terminal device, and whether the base station device and the terminal device have correctly exchanged data by retransmission control. This is a subchannel used for negotiation.

  The terminal device 20 adjusts the timing to be transmitted earlier according to the transmission timing shift amount in the information in the channel assignment response, and transmits uplink information on the allocated channel (step S17).

  Steps S11 to S17 are timing control at the stage of the control channel before entering the communication channel. However, after the call connection is completed, the terminal device 20 is set to perform timing control even after entering the communication channel. It is also possible. The following is a description of the timing control process in the communication channel.

  The base station apparatus 10 estimates the average reception timing of the terminal apparatus 20 based on the pilot symbol of the uplink information. When the estimated timing is late, it is set as a transmission timing control bit in the anchor subchannel of the downlink information of the terminal device 20 so as to transmit to the terminal device 20 early. When the estimated timing is early, the transmission timing control bit is set in the anchor subchannel of the downlink information of the terminal device 20 so that the terminal device 20 transmits the information late. The base station apparatus 10 adds this transmission timing control bit to the terminal apparatus 20 and transmits it together with other downlink information (step S18).

  It should be noted that the transmission timing control bit is configured to include not only a single determination level of whether transmission is early or late, but also a plurality of determination levels of how early or late transmission is performed. Is also possible.

  The terminal device 20 receives the downlink information, adjusts the uplink information transmission timing in accordance with the transmission timing bits of the anchor subchannel, and transmits the uplink information on the allocated channel (step S19). Note that for the uplink information (step 19) transmitted from the terminal apparatus 20 using the assigned channel after step S17, the reception timing for receiving the uplink information is earlier than the reference based on the pilot symbols included in the uplink information. It can also be configured to estimate whether it is slow or not and repeat the same processing as step S18 (step S20).

(Second Embodiment)
Next, the 2nd timing control process performed between the base station apparatus 10 and the terminal device 20 of this embodiment is demonstrated. FIG. 5 is a flowchart for explaining the second timing control process.

In the second timing control process, the description of the steps overlapping with the first timing control process is omitted, and different process steps are described.
When the base station apparatus 10 confirms the channel assignment request from the terminal apparatus 10 in step S15, the base station apparatus 10 does not issue a state transition permission to the communication channel at that time (without issuing a channel assignment response). A channel allocation refusal is transmitted to the terminal device 20 (step S31). At this time, the difference between the reception timing of the channel allocation request received in step S15 and the reference timing is measured, added to the downlink information of channel allocation rejection as a transmission timing shift amount, and transmitted to the terminal device 20 (step S31).

  The terminal device 20 that has received the channel assignment rejection adjusts the timing in accordance with the transmission timing shift amount added to the channel assignment rejection, and transmits the channel assignment request again (step S32). The base station apparatus 10 confirms the channel allocation request again, detects the signal timing after timing adjustment, confirms whether it falls within the expected range, and if it falls within the expected range, permits to the communication channel and the channel An allocation response is given (step S33).

  As described above, according to the timing control process of the present embodiment, it has been confirmed that the reception timing of the channel allocation request transmitted from the terminal device 20 is within the assumed range set in the base station device 10. Thereafter, the channel assignment response can be transmitted to the terminal device 20. Therefore, by matching the communication timing between the base station apparatus 10 and the terminal apparatus 20 from the stage of the control channel before entering the communication channel, the expansion of the signal reception timing is suppressed as much as possible, and the delay time is set within the guard interval range. Therefore, the occurrence of intersymbol interference can be prevented.

It is a functional block diagram of the base station apparatus which concerns on embodiment of this invention. It is a functional block diagram of the terminal device of this embodiment. It is explanatory drawing which shows the format of a subchannel. It is a flowchart explaining the 1st timing control processing performed between the base station apparatus and terminal device of this embodiment. It is a flowchart explaining the 2nd timing control processing performed between the base station apparatus and terminal device of this embodiment. It is a block diagram which shows the structure of the conventional OFDM modulation apparatus used for the transmission side. It is a schematic diagram explaining the state which copied the guard interval to the effective symbol. It is a block diagram which shows the structure of the conventional OFDM demodulation apparatus used for the receiving side.

Explanation of symbols

1: Transmission / reception unit, 2: Signal processing unit, 2-1: Symbol synchronization unit, 2-2: Memory, 2-3: FFT unit, 2-4: Frequency estimation unit (channel estimation unit), 2-5: Timing Estimation unit, 2-6: Demodulation unit (decoding unit), 2-7: Physical layer frame forming unit, 2-8: Modulation coding unit, 2-9: IFFT unit, 10: Base station device, 22: Signal processing unit 12-1: Symbol synchronization, 12-2: Memory, 12-3: FFT unit, 12-4: Frequency estimation unit (channel estimation unit), 12-5: Timing estimation unit, 12-6: Demodulation unit (decoding) Part), 12-7: physical layer frame forming part, 12-8: modulation code part, 12-9: IFFT part, 12-10: timing request extraction, 12-11: timing shift part, 12-12: transmission power Control unit, 20: terminal device

Claims (7)

In response to a channel allocation request included in uplink information from the terminal device, channel allocation is performed using downlink information from the base station device by a TDD / OFDMA communication scheme between the base station device and a plurality of terminal devices. A communication control method for responding,
The base station device
When confirming a channel assignment request from the terminal device, estimating whether reception timing for receiving the uplink information is earlier or later than a reference based on a pilot symbol included in the channel assignment request;
If the reception timing of the channel assignment request is not within a reference range based on the estimation result of the reception timing, a transmission timing shift amount is added to a response related to the channel assignment that rejects the channel assignment, and the channel assignment is performed. when the reception timing of the request is in the reference range, a communication control method characterized by performing the steps of: transmitting a response for the channel assignment to perform the channel assignment to the terminal device. When transmitting a channel allocation request from the terminal device, gradually increasing the transmission power from a small level to a large level, and transmitting to the base station device;
  The communication control method according to claim 1, wherein the base station device includes a step of transmitting a response related to the channel assignment when confirming a channel assignment request from the terminal device. The base station apparatus,
Recording the reception timing estimation result in a timing recording means;
Upon transmission of response for the channel assignment reject the channel assignment from the base station apparatus, further perform the steps of: by adding the transmission timing shift amount based on the recorded contents of said timing recording means for transmitting to said terminal device And
The terminal device,
Extracting the received transmission timing shift amount and recording it in a transmission timing recording means;
When transmitting a channel assignment request again from the terminal device, and transmitting the to the base station apparatus at the indicated timing transmission timing the transmission timing shift amount recorded in the recording means, further executes the communication control method according to claim 1 or 2, characterized. Estimating reception timing for uplink information transmitted from the terminal device using a channel allocated from the base station device; and
Adding a transmission timing control bit to downlink information based on the reception timing estimation result;
4. The communication control method according to claim 3, further comprising: adjusting transmission timing of uplink information according to a transmission timing control bit added to the downlink information, and transmitting the uplink information on the assigned channel. . A base station apparatus that performs communication in a TDD / OFDMA communication scheme with a plurality of terminal apparatuses,
When transmitting the channel allocation request from the terminal device, when the channel allocation request transmitted by checking the transmitted channel allocation request stepwise from a small level to a large level is confirmed, based on the pilot symbol included in the channel allocation request Timing estimation means for estimating whether the timing for receiving the channel assignment request is earlier or later than a predetermined timing preset in the base station device;
Timing recording means for recording the transmission timing shift amount based on the estimation result;
Based on the recorded contents of the timing recording means, if the reception timing of the channel assignment request is not within a reference range, the transmission timing shift amount recorded in the timing recording means in response to the channel assignment rejecting channel assignment is And a transmission timing shift amount adding means to be added. A terminal apparatus that performs communication in a TDD / OFDMA communication scheme with the base station apparatus according to claim 5 ,
In the terminal device, when transmitting a channel allocation request, transmission power adjustment means for transmitting by increasing the transmission power stepwise from a small level to a large level;
A transmission timing recording means for recording received the transmission timing shift amount,
And a transmission timing adjusting means for transmitting to the base station apparatus at a timing indicated by the transmission timing shift amount when uplink information is transmitted from the terminal apparatus. In response to a channel allocation request included in uplink information from the terminal device, channel allocation is performed using downlink information from the base station device by a TDD / OFDMA communication scheme between the base station device and a plurality of terminal devices. A communication control system for responding,
The base station device
When transmitting the channel allocation request from the terminal device, when the channel allocation request transmitted by checking the transmitted channel allocation request stepwise from a small level to a large level is confirmed, based on the pilot symbol included in the channel allocation request Timing estimation means for estimating whether the timing for receiving the channel assignment request is earlier or later than a predetermined timing preset in the base station device;
Timing recording means for recording the transmission timing shift amount based on the estimation result;
Based on the recorded contents of the timing recording means, if the reception timing of the channel assignment request is not within a reference range, the transmission timing shift amount recorded in the timing recording means in response to the channel assignment rejecting channel assignment is Transmission timing shift amount adding means for adding,
The terminal device
Transmission power adjusting means for transmitting the channel allocation request by increasing the transmission power stepwise from a small level to a large level when transmitting the channel assignment request;
Transmission timing recording means for recording the received transmission timing request;
A transmission control system comprising: a transmission timing adjustment unit that transmits to the base station apparatus at a timing instructed by the transmission timing request when transmitting uplink information from the terminal apparatus.

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