JP2005323403A - Communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication method by which communication between terminal equipment and a base station can be properly made, according to a position, etc. of the terminal equipment at the time. <P>SOLUTION: A proper control, according to the position of the terminal equipment in an area, can be made by performing a process of reducing the communication capacity between the terminal equipment and the base station by a control from the base station, when it is determined that the terminal equipment is located near the boundary part of a communication area of the base station in communication at the present. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication method, a transmission method and a reception method suitable for application to, for example, a cellular radiotelephone system, and a base station and a terminal device based on these methods, and in particular, a TDMA method (Time Division Multiplex Access method: The present invention relates to a method suitable for applying a time division multiple access method.

  Various wireless telephone systems that wirelessly transmit digitalized signals have been put into practical use. As one of systems that can be efficiently connected, a system to which the TDMA system is applied has been put into practical use. In this method, one transmission band (frequency channel) is divided by a time axis to form a time slot, and each time slot is assigned to a plurality of terminal devices (mobile stations). Can be connected to the base station.

  FIG. 8 is a diagram showing a channel configuration example of a cellular radio telephone system to which a conventional TDMA scheme is applied, in which the vertical axis indicates frequency and the horizontal axis indicates the passage of time. On the frequency axis, one band slot is formed for each predetermined frequency band (for example, every several KHz), and a number (here, a continuous number) is assigned to each band slot. In the time axis, one time slot is formed every predetermined time (for example, every several hundreds of microseconds), and a number (here, a continuous number) is assigned to each time slot.

  A predetermined band slot (the 13th band slot and the 23rd band slot in the example of FIG. 8) is allocated as a band slot dedicated to control channel CCH (Commom Control Channel) transmission. In the band slot for the control channel CCH, all time slots are occupied for the control channel. In general, different band slots are allocated for control channels between adjacent base stations. For example, a certain base station transmits a control channel CCH in the thirteenth band slot, and another base station adjacent to the base station. Is configured to transmit the control channel CCH in the 23rd band slot.

  Then, other band slots (1st to 12th band slots, 14th to 22nd band slots, 24th to 37th band slots in the example of FIG. 8) are used for calling voice data, various data, etc. The transmission band of the information transmission channel TCH (Traffic Channe) through which user information is transmitted. The setting of the information transmission channel TCH in this transmission band is notified from the base station to each terminal device through the control channel. Accordingly, when each terminal apparatus is connected to the base station, first, a band slot in which the control channel CCH is transmitted is received, and user information is obtained from the control information indicated by the control channel CCH transmitted in this band slot. A band slot and a time slot assigned to this terminal device for transmission of the terminal are determined, and communication with the base station in the band slot and time slot is started.

  The 36th band slot in FIG. 8 is a diagram showing an example of the communication state between the base station and one terminal device. In FIG. 9, in this example, communication is performed in a period of 3 time slots. In the case where the 1TDMA frame to be performed is composed of 3 slots, the transmission slot Tx such as user information from the base station to the terminal apparatus is 1 time slot period at the position of time slot number 1, and the next time slot number 2 At the position, the receiving slot Rx such as user information from the terminal device to the base station has one time slot period, and transmission / reception is stopped at the position of the next time slot number 3 for one time slot period. Thereafter, the processing for this three time slot period (that is, processing of 1 TDMA frame) is repeated. Here, the transmission slot and the reception slot are viewed from the base station side, and when viewed from the terminal device, the positions of the transmission slot and the reception slot are reversed.

  In a period in which transmission / reception of user information is suspended (time slot numbers 3, 6, 9, etc.), the base station search process is performed. That is, in the cellular radio telephone system, the communication area of each base station is arranged continuously in a cell shape in principle, and each terminal device needs to determine which base station is an area where a call can be made. is there. Specifically, the terminal device side receives the control channel CCH transmitted from the base station, determines which base station can communicate with the received electric field strength, etc., and issues a connection request to the base station capable of communication. . For this reason, each terminal device side needs a search process for searching for a cell of a base station that can communicate at that time. In addition, even after the start of communication, if the position of the terminal device moves and moves to another area, a handoff process is required to switch the base station with which the call is to be made. Even if it exists, the search process of the base station is necessary at any time.

  In the example of FIG. 9, one frequency channel (band slot) is occupied by one terminal device. However, depending on the setting state of the period in which the transmission slot Tx and the reception slot Rx are arranged, a plurality of terminals are used. It is also possible to connect the device to one channel. For example, in the example shown in FIG. 10, a 1 TDMA frame is configured by 8 time slots, and a reception slot Rx for user information from the terminal apparatus is provided in the first time slot among the 8 time slots in the 1 TDMA frame. In the fourth time slot, there is a transmission slot Tx for user information from the base station. In this configuration, when transmission and reception have the same frequency, four transmission slots and reception slots can be set in one TDMA frame, and one band slot can be shared by four terminal devices. Even in the case of FIG. 10, in a predetermined slot period (here, the sixth time slot and the seventh time slot) in each TDMA frame in which each terminal device does not transmit or receive user information, Search processing is performed.

  Even in the case of the example of the communication state shown in FIG. 9, when the uplink and downlink are set to different frequency bands, 3 time slots are obtained for each uplink and downlink. Communication is performed between one terminal device and a base station in a cycle, and three terminal devices can be shared by one frequency channel (one band slot).

  As described above, in any of the configurations, each terminal device side prepares a period for performing cell search for each TDMA frame and performs a process of receiving a control channel during that period. In this way, for each TDMA frame, If the cell search process is always performed, it is difficult to flexibly cope with the case where it is desired to perform cell search frequently or when cell search is not required. Further, when performing a cell search in each TDMA frame, as shown in FIG. 9, it is the minimum configuration that 1 TDMA frame is composed of 3 time slots, and 1 TDMA frame is composed of 2 time slots. Was impossible.

  In addition, when performing communication between the base station and the terminal device with the above-described configuration, if the power of the signal transmitted from the terminal device can be appropriately controlled, the communication state becomes good and the power consumption of the terminal device, etc. This is also preferable. That is, in the case of a wireless telephone system, the position of each terminal device is not constant, so that the terminal device may communicate near the base station, or the terminal device may communicate at a location away from the base station. For this reason, it is not preferable to perform transmission with constant power. If the transmission power from the terminal device can be controlled appropriately, set a small transmission power when communicating near the base station, and set a large power when communicating far away from the base station. Thus, unnecessary power is not consumed for transmission processing on the terminal device side, and the amount of interference with other communications can be minimized. However, in order to appropriately control the transmission power on the terminal device side, complicated processing is required, and in general, the transmission power is not generally controlled.

  An object of the present invention is to enable appropriate communication between a terminal device and a base station according to the position of the terminal device at that time.

  When it is determined that a terminal device is located in the vicinity of the boundary of the communication area of the currently communicating base station, the present invention communicates between the corresponding terminal device and the base station under the control of the base station. The processing for reducing the capacity is performed.

  By performing such processing, appropriate control according to the position in the area of the terminal device becomes possible.

  According to the present invention, when it is determined that the terminal device is located in the vicinity of the boundary portion of the communication area of the currently communicating base station, the control between the base station and the corresponding terminal device By performing the process of reducing the communication capacity, the communication capacity in each terminal apparatus is appropriately set according to the position of the terminal apparatus, and good communication can be performed wherever communication is performed.

  In this case, by making the transmission output from the base station or the terminal device variable according to the communication state at that time, the communication capacity setting and the transmission output setting make it even better to communicate in any situation You can communicate.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  In this example, the present invention is applied to a cellular radio telephone system. First, the configuration of a communication system to which this example is applied will be described. The configuration of the communication system of this example is basically a system in which communication is performed by the TDMA system, but is a multicarrier signal as a signal transmitted in each time slot. That is, there is a so-called multi-carrier system in which a plurality of subcarriers are continuously arranged in a band (Band) allocated in advance, and a plurality of subcarriers in one band are simultaneously used in one transmission path (path). Further, a plurality of subcarriers in one band are modulated by time division (Division) and modulated, and here it is referred to as a band division multiple access (BDMA) system.

  Hereinafter, the configuration of the connection method will be described. FIG. 3 is a diagram showing the slot configuration of the transmission signal of this example, with the vertical axis representing frequency and the horizontal axis representing time. In the case of this example, an orthogonal basis is obtained by dividing the frequency axis and the time axis into a lattice shape. That is, one transmission band (one band slot) is set to 150 KHz, and 24 subcarriers are arranged in one transmission band of 150 KHz. The 24 subcarriers are continuously arranged at equal intervals at intervals of 6.25 kHz, and subcarrier numbers from 0 to 23 are assigned to each carrier. However, there are actually 22 subcarriers from subcarrier numbers 1 to 22, and subcarrier numbers 0 and 23 at both ends in one band slot are guard bands that do not raise subcarriers. Is 0. Then, for example, the user information is modulated and transmitted by the phase difference of each of the 22 subcarriers.

  A plurality of band slots each having a predetermined number of one band slot configured as described above are used as one transmission unit on the frequency. For example, when a 32 band slot is defined as one transmission unit on the frequency, as shown in FIG. 4A, a continuous 32 band slot is used as one transmission unit on the frequency. As shown in B, a multicarrier signal by 22 subcarrier signals is used for transmission. A frequency channel for each predetermined band slot (here, one frequency channel for every eight band slots) is used as a channel for transmitting control information. Details of the transmission configuration of the control information will be described later.

  Returning to FIG. 3, the structure of the time axis will be described. One time slot is defined at intervals of 200 μs, and a burst signal is modulated and transmitted on 22 subcarriers per time slot. Here, a state in which 16 time slots are arranged is defined as one frame. Successive time slot numbers are given to the 16 time slots in one frame. The range indicated by hatching in FIG. 3 indicates one time slot section of one band slot.

  Using the orthogonal base obtained by dividing the frequency axis and the time axis in a grid pattern, the base station performs multiple access for communicating with a plurality of terminal devices at the same time. By setting the communication state in this way, signals transmitted between each terminal apparatus and the base station are kept orthogonal to other signals, and interference of other signals is prevented. Only the corresponding signal can be taken out without receiving.

  Next, the configuration of the base station that communicates with the terminal device in the system configuration described above will be described with reference to FIG.

  FIG. 1 is a block diagram showing the overall configuration of the base station of this example. A transmission / reception antenna 11 is connected to a high-frequency circuit 12, and a signal in a predetermined frequency band (frequency here) received by the antenna 11 is shown. A band is a signal of one transmission unit composed of, for example, 32 band slots) converted into an intermediate frequency signal, and the intermediate frequency signal is converted into digital data by the analog / digital converter 13 and then supplied to the modulation / demodulation processing unit 14 To do. The modem unit 14 demodulates the supplied intermediate frequency signal. As the demodulation processing here, for example, demodulation processing such as orthogonal transformation in which data transmitted by being distributed and modulated on 22 subcarriers described in the above-described transmission method (BMDA method) is converted into one series of data. I do. Then, the demodulated data is supplied to the demultiplexer 15 and separated for each data transmitted from each terminal device, and each separated data is separated into another decoder 16a, 16b,... 16n (n is an arbitrary number). ). At the time of separation by the demultiplexer 15, the frequency position (band slot) to be separated is changed as needed in consideration of the above-described frequency hopping and supplied to the decoders 16a to 16n.

  The decoders 16a to 16n are prepared in a number corresponding to the number of terminal devices that can be connected to one base station at the same time, and each decoder 16a to 16n performs a decoding process of data supplied from the terminal device. Then, the data decoded by each of the decoders 16a to 16n is supplied to another communication system (not shown) connected to the base station, and transmitted to the other party connected to the terminal device via the telephone line. . However, control data such as a connection request transmitted from the terminal device to the base station is supplied to the control unit 20 of the base station after being decoded by one of the decoders 16a to 16n.

  Next, the configuration of the transmission system of the base station will be described. Data transmitted from the individual counterpart side to the base station for each connected terminal device is converted into separate encoders 17a, 17b,. Supply). The encoders 17a to 17n are prepared in a number corresponding to the number of terminal devices that can be connected to one base station at the same time as the decoder, and perform encoding processing of data supplied by the encoders 17a to 17n. Then, the data encoded by the encoders 17 a to 17 n is supplied to the multiplexer 18, and all transmission data handled by the base station is set as one system transmission data and supplied to the modulation / demodulation processing unit 14. The modulation / demodulation processing unit 14 performs processing to distribute and modulate the supplied data to 22 subcarriers, and supplies the modulated data to the high-frequency circuit 12 as an analog signal by the digital / analog converter 19. The frequency is converted into a signal of a predetermined frequency band (here, the frequency band is a signal of one transmission unit composed of 32 band slots), and wirelessly transmitted from the antenna 11. Note that control data transmitted from the control unit 20 of the base station to the terminal device is also supplied to one of the encoders 17a to 17n and encoded, and then transmitted by a transmission system from the multiplexer 18 to the high frequency system circuit 12. Process and send wirelessly.

  The base station performs wireless communication with the terminal device with the configuration described above, and the communication control is performed by the control unit 20 of the base station. This control part 20 is comprised by control means, such as a microcomputer, and control of communication with each terminal device is performed by wirelessly transmitting the control data generated by this control unit 20 to the terminal device side. Even in the case of performing handoff processing for switching the base station with which each terminal device performs communication, it is executed based on the control of the control unit 20 of the base station.

  Next, the configuration of a terminal apparatus that performs radio communication with the base station will be described with reference to FIG.

  FIG. 2 is a block diagram showing the overall configuration of the terminal device of this example. A transmission / reception antenna 31 is connected to a high-frequency circuit 32, and a signal in a predetermined frequency band (frequency here) received by the antenna 31 is shown. 1 band slot signal) is converted into an intermediate frequency signal, and the intermediate frequency signal is converted into digital data by the analog / digital converter 33 and then supplied to the modulation / demodulation processing unit 34. The modulation / demodulation processing unit 34 demodulates the supplied intermediate frequency signal. As the demodulation processing here, for example, demodulation processing such as orthogonal transformation in which data transmitted by being distributed and modulated on 22 subcarriers described in the above-described transmission method (BMDA method) is converted into one series of data. I do. Then, the demodulated data is supplied to the decoder 35, and the data transmitted from the base station side is decoded. Then, the data decoded by the decoder 35 is supplied to the voice processing system circuit 36, the voice data for call is processed, and the obtained voice signal is emitted from the speaker 37. When the decoded data is control data from the base station, the decoded data is supplied to the control unit 41 of this terminal apparatus.

  Next, the configuration of the transmission system of the terminal device will be described. When the data to be transmitted is a voice for calling, the audio signal picked up by the microphone 38 is supplied to the audio processing system circuit 36, and the audio data of a predetermined system is used. After that, the audio data is supplied to the encoder 39 to perform encoding processing and the like. Then, the data encoded by the encoder 39 is supplied to the modulation / demodulation processing unit 34. The modulation / demodulation processing unit 34 performs processing to distribute and modulate the supplied data to 22 subcarriers, and supplies the modulated data to the high frequency system circuit 32 as an analog signal by the digital / analog converter 40. The frequency is converted into a signal of a predetermined frequency band and wirelessly transmitted from the antenna 31. Control data such as a connection request transmitted from the control unit 41 of the terminal device to the base station is also supplied to the encoder 39 and encoded, and then transmitted in the transmission system from the modulation / demodulation processing unit 34 to the high frequency system circuit 32. Transmission processing is performed and wireless transmission is performed. Further, during transmission processing in the high-frequency circuit 32, the transmission power amplifier 32a amplifies the signal to a predetermined output for wireless transmission. The gain of the transmission power amplifier 32a can be variably set under the control of the control unit 41. An appropriate gain is set according to the communication state with the base station.

  The reception state and transmission state in this terminal device are controlled by a control unit 41 configured by control means such as a microcomputer. The control unit 41 determines control data transmitted from the base station, and determines a frequency channel (band slot) for transmission / reception and a transmission / reception timing (that is, a time slot for transmission and reception) in the frequency channel. Then, control is performed so that each unit in the terminal device performs processing in a corresponding state. The control unit 41 is configured to receive operation information from a key 42 such as a dial key. Further, a display unit 43 constituted by a liquid crystal display panel or the like is connected to the control unit 41 and displays an operation state and the like.

  The terminal device shown in FIG. 2 has been described as a configuration for transmitting and receiving voice data for calls, but it may be configured as a terminal device for transmitting or receiving various other data. For example, it may be a terminal device configured to transmit or receive some character data or numeric data, or to transmit or receive data such as electronic mail or the Internet.

  Next, a state in which communication is performed between the base station and the terminal device configured as described above will be described with reference to FIGS. FIG. 5 is a diagram illustrating a channel configuration of communication between the base station and the terminal device in this example, where the vertical axis indicates the frequency by the band slot number, and the horizontal axis indicates the passage of time by the time slot number. A consecutive number is assigned to the band slot and the time slot.

  Here, one band slot (ie, first band slot, ninth band slot, seventeenth band slot, twenty-fifth band slot, thirty-third band slot,...) For every eight band slots is designated as a dedicated channel for control information communication ( That is, it is used as a control information channel CCH). In other band slots (second to eighth band slots, tenth to sixteenth band slots, eighteenth to twenty-fourth band slots, twenty-sixth to thirty-second band slots, etc.), an information transmission channel that is a transmission channel for user information TCH transmission is performed.

  In the control information channel CCH for every eight band slots, control information is not transmitted in all time slots, but the base station is intermittently transmitted according to a predetermined rule (or an irregular order generated based on a random number sequence). The control unit 20 of the base station controls transmission so as to be transmitted from the station. However, in the case of this example, one transmission of control information is performed continuously for two time slot periods. Further, the intermittent transmission state of the control information CCH prepared in one base station in each transmission channel is set to be different in each transmission channel. Information regarding the transmission timing of the time slot of the control information CCH in each transmission channel is configured to be transmitted by being added to the control information CCH under the control of the control unit 20 of the station, and the control unit 41 on the terminal device side By receiving the control information CCH of any transmission channel, the transmission timing of the time slot of the control information CCH on each transmission channel of the station can be determined.

  In the case of this example, the frequency channel used as the control information channel CCH is set to the same channel in all base stations for this telephone system (or at least all base stations in a certain area). The setting state of the timing at which the control information CCH is transmitted on the same channel is changed at least between adjacent base stations. In this case, in the control information CCH transmitted from each base station, information on the transmission timing of the control information CCH in the base station adjacent to the base station (for example, information on which frequency channel is transmitted in which time slot) The control unit 41 of each terminal apparatus also determines the transmission timing of the control information CCH in each transmission channel at the base station in the area adjacent to the area of the base station currently communicating. I can do it.

  In the band slot in which the information transmission channel TCH such as the second to eighth band slots is transmitted, communication is performed using 4 time slots as 1 TDMA frame. Accordingly, one transmission slot and one reception slot are set for every four time slots. In this way, when 1 TDMA frame is set to 4 time slots, when the same frequency is used for transmission and reception, one transmission channel can be shared by two terminal devices, and when different frequency bands are used for transmission and reception One transmission channel can be shared by four terminal devices.

  The 36th band slot in FIG. 5 shows an example of the communication state between a certain terminal device and the base station, and the transmission slot Tx from the base station (to the terminal device) and the base (transmitted from the terminal device). The reception slots Rx at the station are alternately set, and bidirectional communication is performed between the base station and the terminal device. Here, in this example, 32 time slots (that is, 8 TDMA frames) are defined as one data frame, and at least 1 TDMA frame period (that is, 4 time slot periods) in this one data frame, communication between the transmission slot Tx and the reception slot Rx is performed. The terminal device is stopped and a so-called cell search is performed in which the terminal device searches for a base station.

  FIG. 6 shows the state of communication with the base station of one data frame in each terminal apparatus. One data frame is composed of 8 TDMA frames. Basically, reception slots are arranged within 4 time slot periods of each TDMA frame. Rx and transmission slot Tx are set for each time slot. 6 is the timing seen from the terminal device, the relation between the reception slot Rx and the transmission slot Tx in the 1TDMA frame is opposite to FIG. 5 seen from the base station side.

An arbitrary 1 TDMA frame period (seventh TDMA frame period in FIG. 6) in one data frame is set as a cell search period. During this cell search period, a control information channel CCH in which control information is transmitted from a base station arranged in an area adjacent to the communication area of the currently communicating base station is received. For example, as shown in FIG. 6, in a first one time slot period of a 1 TDMA frame period in which cell search is performed, reception of a predetermined band slot X ₁ in which the control information channel CCH is transmitted is attempted, and in the next one time slot period. A process of switching the reception channel is performed, and reception of another band slot X ₂ in which the control information channel CCH is transmitted in the next one time slot period is attempted. Then, in the last one time slot period, a process of switching to the channel that receives the reception slot Rx in the next TDMA frame period is performed.

  For example, assuming that control information CCH is transmitted from the own station and neighboring cells in the state shown in FIG. 5, and assuming that the time slot numbers 13 to 16 of communication in the channel of the 36th band slot are the search period. By receiving the first band slot during the time slot number 13, the control information CCH of this channel can be received. During the time slot number 15, by receiving the 17th band slot, The control information CCH of this channel can be received.

  In this way, a process of attempting to receive control information on at least two channels is performed during the 1TDMA frame period in which cell search is performed. If channel switching can be performed at high speed, reception of channels in which different control information channels CCH are transmitted in all time slot periods constituting one TDMA frame (that is, four band slots in one TDMA frame) is attempted. May be. Then, in the cell search period of each data frame, the channel to which the reception is attempted is changed, and every several data frame periods, the control information channel CCH from all the base stations existing adjacent to the currently communicating base station Try to receive. In the terminal device, the frequency channel in which the slot of the control information CCH exists is determined based on the control information transmitted from the base station during the cell search period, and the determined frequency channel is received. The

  When reception of the slot of the control information CCH is made when the reception is attempted during the cell search period, the control unit 41 of the terminal device determines the reception state (reception level, etc.) at that time, and the received reception thus determined. The status data is added to information to be transmitted to the base station (such as user data transmission slot accompanying data).

  The control unit 20 on the base station side determines whether or not the current position of the terminal device is within the communication area of the own station from the data on the reception state of the control information transmitted from the terminal device. As described above, each terminal apparatus sets a cell search period only once in one data frame, and determines the communication state based on the data obtained in the cell search period, so that an efficient cell search can be performed. it can. That is, compared to the case where cell search is always performed within 1 TDMA frame as in the prior art, the frequency of cell search can be reduced, so that a longer period can be used for transmission of user information, and the communication capacity is increased. In addition, the power required for cell search on the terminal device side can be saved.

  In such a process, when it is determined that the position of the terminal device is in the vicinity of the boundary between the communication area of the own station and the communication area of another base station (for example, the signal of the terminal device at the terminal device When it is determined that the reception level and the reception level of the signal of the other base station at the terminal device are substantially equal), it is determined whether or not handoff processing for switching communication to the other base station is necessary.

  When it is determined whether or not this handoff process is necessary, the cell search period is increased and the cell search period is increased with the associated data of the user information transmission slot for the corresponding terminal device. In response to this increase, control data is transmitted to reduce the amount of user information transmitted. FIG. 7 is a diagram showing the communication timing of one data frame on the terminal device side when the cell search period is increased. In this example, the fifth of 8TDMA frames constituting one data frame is shown. The TDMA frame and the seventh TDMA frame are set as the period for performing the cell search, and the cell search process is executed in each period.

  By processing in this way, the cell search period is doubled, the current communication state of the terminal device can be detected with higher accuracy, and handoff processing for switching communication to another base station is required. It is possible to quickly determine whether or not handoff processing is necessary, and the base station can quickly respond. That is, in the case of this example, the cell search is performed only once in one data frame in the normal state, and the frequency of performing the cell search is reduced compared to the case where the cell search is performed every 1 TDMA frame. When it is important to perform a cell search, the frequency of performing a cell search is increased. Therefore, the cell search is performed at the same frequency as the conventional one or at a frequency higher than the conventional one, and the handoff process can be executed well. Although FIG. 7 shows an example in which the cell search period of one data frame period is doubled, the cell search period may be increased depending on the communication state at that time.

  In addition, in a state where it is possible to determine that the communication state with the own station is sufficiently better than the communication state with other base stations in a state where the period for performing the cell search is increased in this way, You may make it return to the original cell search frequency.

  In the case of this example, the gain of the transmission power amplifier 32a in the high-frequency circuit 32 on each terminal device side is variably set. For example, in the above-described process, the communication area of the own station and other base stations If it is determined that the signal is in the vicinity of the boundary with the communication area, the gain of the transmission power amplifier 32a is set to a relatively large value so that the transmission output is increased so that the communication with the base station can be performed satisfactorily. It is conceivable to set to Further, when the transmission output from the base station can also be adjusted, the transmission output may be set large when it is determined that it is in the vicinity of the boundary portion of the communication area.

  In the case of this example, when the cell search period is increased as shown in FIG. 7, the data amount of user information transmitted between the base station and the terminal device is reduced based on the control of the base station. Then, a process of reducing the transmission slot period of the user information by the reduced amount is performed. Specifically, since the transmission slot and the reception slot in one data frame period are reduced from 7 time slots to 6 time slots, respectively, processing for reducing the data amount of user information to 6/7 is performed. Further, when the cell search period becomes short, a process for returning to the original data amount is performed. Such fluctuations in the amount of data that can be transmitted can be dealt with, for example, by changing the compression rate of voice data when the user information to be transmitted is voice data, and in the case of various data such as e-mail data. This can be dealt with by temporarily changing the data transfer rate.

  Further, the transmission amount of user information may be changed by factors other than the fluctuation of the transmission amount based on the increase / decrease of the cell search period. For example, the current communication state between the base station and the terminal device is relatively poor, such as when it is determined that it is near the boundary between the communication area of the local station and the communication area of another base station. When the base station determines that the user information can be transmitted by reducing the transmission rate of data transmitted in one time slot based on the control of the base station. As a process for reducing the data transmission rate, for example, it can be dealt with by changing the encoding method or changing the modulation method.

  In the above-described embodiment, the frequency channel (band slot) for transmitting user information between the base station and the terminal device is described as being fixed to a fixed frequency channel for communication. It may be configured to perform processing called frequency hopping that changes the frequency channel transmitted for each frame. In this way, the prepared transmission band is used almost uniformly, and a good cell search can be performed in a state where a good transmission state is secured, and a good transmission of user information is possible. In addition to ensuring the characteristics, the handoff process when the terminal device moves is also processed well, and a good communication state is obtained.

  Further, in the above-described embodiment, details such as the communication configuration and the frame configuration are shown as examples, and the present invention is not limited to the above-described embodiment. In particular, in the above-described embodiments, the present invention is applied to transmission of a multicarrier signal as a signal to be transmitted. However, the processing of the present invention can also be applied to transmission of signals of other modulation schemes. In the above-described embodiment, the present invention is applied to the cellular radio telephone system, but can also be applied to other communication systems.

It is a block diagram which shows the structure of the base station by embodiment of this invention. It is a block diagram which shows the structure of the terminal device by embodiment of this invention. It is explanatory drawing which shows the slot structure of the transmission signal by embodiment of this invention. It is explanatory drawing which shows the band slot arrangement | positioning by embodiment of this invention. It is explanatory drawing which shows the channel structure by embodiment of this invention. It is explanatory drawing which shows the example (at the time of the search of normal frequency) of the communication timing by embodiment of this invention. It is explanatory drawing which shows the example (at the time of high frequency search) of the communication timing by embodiment of this invention. It is explanatory drawing which shows the example of a channel structure of the conventional cellular system. It is explanatory drawing which shows an example of the conventional communication timing. It is explanatory drawing which shows another example of the conventional communication timing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... High frequency system circuit, 14 ... Modulation / demodulation processing circuit, 15 ... Demultiplexer, 16a-16n ... Decoder, 17a-17n ... Encoder, 18 ... Multiplexer, 20 ... Control part, 32 ... High frequency system circuit, 32a ... Power amplifier for transmission 34. Modulation / demodulation processing circuit, 35 ... Decoder, 36 ... Audio system circuit, 39 ... Encoder, 41 ... Control unit

Claims (2)

In a communication method in which a plurality of base stations arranged in a predetermined state and a terminal device communicate with each other,
Processing to reduce the communication capacity between the corresponding terminal device and the base station by the control from the base station when it is determined that the terminal device is located in the vicinity of the boundary of the communication area of the currently communicating base station Do the communication method. The communication method according to claim 1,
A communication method in which a transmission output from the base station or the terminal device is variable depending on a communication state at that time.

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