WO2006090457A1

WO2006090457A1 - Base station of mobile communication system

Info

Publication number: WO2006090457A1
Application number: PCT/JP2005/003023
Authority: WO
Inventors: Genya Kotani
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2005-02-24
Filing date: 2005-02-24
Publication date: 2006-08-31

Abstract

There are included a receiver that receives an upstream signal from a first mobile station; a sync signal detection timing measuring means that measures a detection timing of an upstream sync signal included in the received upstream signal; and a reception tolerance control means that decides a reception tolerance of the sync signal of the sync signal detecting means, based on the measurement results of the latest detection timing and of a plurality of past detection timings. Thus, even when the distance between the base station and the mobile station increases due to a movement of the mobile station and hence the propagation delay of the radio signals increases, the communication can be performed with less erroneous detection of the sync signal and without any control of transmission timing at the mobile station.

Description

Specification

Base station for mobile communication system

Technical field

TECHNICAL FIELD [0001] The present invention relates to a transmission / reception timing correction process required when a radio signal propagation delay caused by a distance between a base station and a mobile station changes due to movement of a terminal in a TDMA mobile communication system having a large cell radius. is there.

Background art

[0002] In a conventional TDMA communication system, when a base station compensates for a radio signal propagation delay caused by a distance between base stations and mobile stations, for example, the allowable reception range on the base station side is set as in Patent Document 1 below. By spreading, it was possible to receive signals from distant terminals. In this case, the permissible reception range is fixed for each base station and cannot be varied for each TDMA slot. Also, there is a method that adjusts the reception timing on the base station side as described in Patent Document 2 below, and when the distance between base stations and mobile stations is long and the amount of delay is large, the corresponding slot is extended to the adjacent TDM lot. There are some that delay the reception timing. At this time, the condition for delaying the slot to the adjacent TDM lot is that the adjacent TDMA slot is not used, and that the communication can be delayed in the adjacent TDMA slot and the reception timing can be delayed. And it was a natural thing.

[0003] According to the method of Patent Document 1, communication with a distant terminal having a large radio signal propagation delay is possible between base stations and mobile stations. However, since the reception allowable range is uniformly expanded for all slots, synchronization is achieved. The probability that the communication quality is instantaneously deteriorated due to erroneous detection of the signal increases. In addition, since the permissible reception range is fixed for each base station, operation is performed within the same permissible reception range as that of a distant terminal during a call with a nearby terminal. Disadvantageous.

[0004] Further, according to the method of Patent Document 2, the distance between base stations and mobile stations becomes long, and the possibility that communication can be continued even when the radio signal propagation delay becomes large increases. When the MA slot is in use, communication cannot be continued unless the same reception timing delay as that slot is generated. [0005] Further, in Patent Document 3, the time alignment value of the frame to be received next by the base station based on the propagation delay time and the amount of change in the propagation delay time for a predetermined past time is used for TDMA communication. It is described that the mobile station adjusts the transmission timing by transmitting the determined value to the mobile station side.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-191068

[0007] Patent Document 2: Japanese Patent Laid-Open No. 11 340934

Patent Document 3: Japanese Patent Laid-Open No. 2001-358638

Disclosure of the invention

Problems to be solved by the invention

[0009] In a wireless communication system, the radio signal propagation delay increases as the cell radius increases and the distance between the base station and the terminal increases. When this delay increases, the uplink transmission signal from the terminal is defined by TDMA and deviates from the base station reception timing, and cannot be received by the base station. Therefore, if the terminal moves beyond a certain distance, communication with the previous base station cannot be continued, and if the handover destination base station cannot find it, the communication itself is disconnected. It was.

[0010] The present invention has been made to solve the above-described problems, and in a mobile communication system, particularly a TDMA communication system, when a radio signal propagation delay due to a distance between base stations is large. In addition, the purpose is to construct a system that can continue communication between base stations without performing transmission timing correction on the terminal side and cover a large area with as little transmission output as possible in an area where traffic is small.

Means for solving the problem

[0011] A base station according to the present invention is a synchronization that calculates a time difference between a receiver that receives an uplink control signal of mobile station power, a detection timing of a synchronization signal from the mobile station, and a detection timing expected by the base station. A signal detection time difference measurement unit; and a reception allowable range control unit that determines a reception allowable range of the synchronization signal detection unit based on the latest measurement result of the synchronization signal detection timing and a plurality of past synchronization signal detection timings. Is. The invention's effect [0012] A base station according to the present invention is a synchronization that calculates a time difference between a receiver that receives an uplink control signal from a mobile station, a detection timing of a synchronization signal of mobile station power, and a detection timing expected by the base station. A signal detection time difference measurement means; and a reception tolerance range control means for determining a reception tolerance range of the synchronization signal detection means based on the latest measurement result of the synchronization signal detection timing and a plurality of past synchronization signal detection timings. Therefore, even when the propagation delay of a radio signal is long and the distance between the base station and the mobile station is long, communication with less false detection of the synchronization signal can be performed without controlling the transmission timing in the mobile station. Brief Description of Drawings

FIG. 1 is a diagram showing a system configuration of a TDMA communication system according to the present invention.

FIG. 2 is a diagram for explaining a permissible reception range of a synchronization signal of a base station before establishing synchronization with a mobile station in Embodiment 1 of the present invention.

FIG. 3 is a diagram for explaining a permissible range of receiving a synchronization signal of a base station after establishing synchronization with a mobile station in Embodiment 1 of the present invention.

[Fig. 4] Fig. 4 is a diagram for explaining fluctuations in the reception timing of a synchronization signal according to movement of a mobile station after synchronization is established in Embodiment 1 of the present invention.

FIG. 5 is a flowchart showing the processing contents of adjustment of the allowable reception range of the uplink synchronization signal of the base station according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining a case where a signal propagation delay fluctuates due to movement of a mobile station, and a received signal interferes with an adjacent slot.

FIG. 7 is a flowchart showing processing contents when a received signal interferes with an adjacent slot due to a propagation delay variation during communication according to Embodiment 1 of the present invention.

FIG. 8 is a diagram showing transmission / reception timings of synchronization signals of a base station and a mobile station after synchronization is established according to Embodiment 2 of the present invention.

FIG. 9 is a flowchart showing processing contents of transmission timing control according to the second embodiment of the present invention.

FIG. 10 is a flowchart showing processing contents of transmission timing control according to the second embodiment of the present invention.

FIG. 11 is a flowchart showing the processing contents when adjusting transmission / reception timing according to the third embodiment of the present invention. It is a chart.

FIG. 12 is a flowchart showing another processing content when adjusting transmission / reception timing according to the third embodiment of the present invention.

FIG. 13 is a flowchart showing details of transmission / reception timing adjustment processing according to the fourth embodiment of the present invention.

FIG. 14 is a flowchart showing details of transmission / reception timing adjustment processing according to the fourth embodiment of the present invention.

Explanation of symbols

[0014] 1 Mobile station

2 Base station

3 Transceiver

4 TDMA controller

5 Sync signal detector

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Embodiment 1.

FIG. 1 is a diagram showing a configuration of the TDMA communication system according to the first exemplary embodiment of the present invention. For convenience of explanation, only one mobile station 1 is shown, but there are multiple mobile stations in the base station cell. Here, the base station 2 includes a transmission / reception unit 3 that communicates with the mobile station 1, a TDMA control unit 4 that controls radio signal transmission / reception timing, and a synchronization signal detection unit that detects an uplink signal from the base station. And 5. The TDMA control unit 4 controls one or more transmission / reception units 3 provided in the base station 2. Based on the synchronization signal detection timing report from the synchronization signal detection unit 5, the TDMA control unit 4 sends an adjustment signal for adjusting the next synchronization signal reception allowable range to the synchronization signal detection unit 5, and the transmission / reception unit Determine the timing for sending a transmission / reception control signal to switch between transmission and reception for 3. Each transceiver 3 is connected to an antenna and communicates with a mobile station.

FIG. 2 shows an example of synchronization signal reception timing at the base station before synchronization is established. Figure 2 (a) is a TDMA transmission frame, (b) is a TDMA reception frame, (c) is a format of the reception signal, (d) is a TDMA reception slot, and (e) is a synchronization signal before synchronization is established. (F) is a diagram showing a reception signal at the limit timing at which synchronization can be established. As shown in FIG. 2 (c), the received signal according to the present invention is also a synchronization signal, followed by data and power. In addition, it is assumed that the part before the synchronization signal contains, for example, a bit string such as a start symbol or preamble for demodulation by the transceiver 3, and the part after the control data contains, for example, an error detection or correction bit. is doing.

Here, A in Fig. 2 (c) is the allowable reception range of the synchronization signal when no fluctuation of the signal propagation delay is assumed, and B is the allowable reception range considering the delay due to the distance between the base stations and mobile stations to the maximum. It is. The permissible reception range B is defined by the TDMA frame, and the end of the received signal is placed within the guard bits, and is extended to the maximum range that does not affect the adjacent TDMA slot. As a result, the uplink control signal from the distant mobile station 1 can also be received.

Next, FIG. 3 shows an example of synchronization signal detection timing in the base station after establishment of synchronization. Fig. 3 (a) shows the format of the TDMA received signal, Fig. 3 (b) shows the mth slot received for the reception timing of this TDMA received signal, and Fig. 3 (c) shows the mth slot received before synchronization is established. It is a reception tolerance range. As shown in Fig. 3 (c), the synchronization signal reception allowable range is set to the maximum range that can be received using the guard bit before synchronization is established. Next, FIG. 3 (d) shows the actual reception timing of the first TDMA reception signal, and FIG. 3 (e) shows the detection timing of the synchronization signal included in this reception signal. Thus, when the first received signal is actually received, synchronization between the base station and the mobile station is established when the synchronization signal is detected. Then, in accordance with the detection timing of the sync signal, the allowable reception range is narrowed as shown in Fig. 3 (f). By narrowing the allowable reception range of the synchronization signal in this way, erroneous detection of the synchronization signal can be prevented. In this case, the allowable reception range is set in a range longer than the length of the synchronization signal, assuming that the mobile station moves and the timing is shifted. Specifically, it depends on a system to which the present invention is applied, that is, an assumed moving speed, the number of synchronization signal bits, a data transmission speed, and the like.

[0018] Here, when the call continues, the delay time of the received signal changes with the movement of the mobile station. Therefore, the first bit of the slot expected on the base station side according to the delay time Figure 4 illustrates the adjustment of the final bit position. Figure 4 (a) is a diagram comparing the first allowable reception range after synchronization and the actual control signal reception frame. is there. (B), (c), (d), and (e) are the detection timings of the first, second, third, and nth synchronization signals, respectively. (F) is the (n + 1) th synchronization signal estimation detection timing, and (g) is the (n + 1) th reception tolerance range determined based on the estimation timing. FIG. 5 is a flowchart for explaining the operation at that time. First, when the synchronization signal from mobile station 1 is received at base station 2, base station 2 and mobile station 1 are synchronized (step SO), and counting is started with count P = l (step Sl ). Next, the reception allowable range of the first synchronization signal is determined from the detection timing of the synchronization signal in step SO (step S2). The reception allowable range at that time is as described above.

Next, the count is incremented by 1 (P = P + 1, step S3), and the count is compared with a predetermined parameter n to determine the magnitude (step S4). When the count P is smaller than n and the P-th uplink synchronization signal is detected (step S5), the detection timing force is also estimated for the next synchronization signal detection timing (step S6). It is determined whether or not the next synchronization signal estimated position is within the current reception allowable range (step S7).

[0020] That is, if the moving speed of mobile station 1 is not large, the next synchronization signal estimation position should be within the current reception allowable range. In this case (S7: Yes), the reception allowable range is Return to step S3. On the other hand, if it is estimated that the next synchronization signal whose movement speed is high does not fall within the current allowable reception range (S7: No), the next synchronous signal reception allowable range is newly determined in step S8, and the step S3 Return to. This process increases the possibility of following the mobile station.

[0021] The loop of steps S3—S8 above is repeated to gather a sufficient number of samples. When the count P reaches n in step S4, the (n + 1) th time from the latest n synchronization signal detection timings. The synchronization signal detection timing is estimated (step S9), and the (n + 1) th synchronization signal reception allowable range is determined from the estimated detection timing (step S10). Then, when the (n + 1) th synchronization signal is detected, the process returns to step S9 to estimate the (n + 2) th synchronization signal detection timing from the past n synchronization signal detection timings! Repeat n + 3), (n + 4) ... and so on until communication is completed.

[0022] For the timing estimation method, for example, for each n detection timings, a difference between a certain detection timing and the previous detection timing is taken, and an average value of the differences is taken. Estimate the detection timing. Also, the estimation in step S8 above takes the difference from the previous detection timing according to the number of samples so far, and calculates the difference from the reference timing by taking the average value of the difference, and the next synchronization Estimate signal reception tolerance.

[0023] The number of samples n determined in advance is determined by the specifications of the system to which the present invention is applied. However, in a system with a short synchronization signal, if the reception tolerance is widened, the probability of false detection increases, so the tolerance is exceeded. If it is assumed that the moving speed of the mobile station is high, n is relatively small so that the mobile station can follow the movement. On the other hand, in the case of a false detection probability with a long synchronization signal, the allowable reception range can be accurately estimated by increasing n.

[0024] With the above, the mobile station does not adjust the transmission timing while reducing the possibility of erroneous detection by narrowing the allowable reception range of the synchronization signal within the guard bit range within the reception TDMA slot. In the following, we explain the case where the detection timing is delayed beyond the guard bit range.

FIG. 6 shows a case where the detection timing of the uplink synchronization signal in the base station goes out of the guard bit range of the TDMA slot. For example, when mobile station 1 moves away from base station 2, the detection timing of the synchronization signal from mobile station 1 at base station 2 gradually delays and the specified guard bit is used up. When I interfere with the slot.

[0026] FIG. 7 is a flowchart for explaining the processing in the case of going out of the above guard bit range. During communication in the m-th slot (step S100), if it is determined that the next detection timing interferes with the adjacent (m + 1) slot (step S101), the (m + 1) slot moves to another position. Check whether it is used for communication with the station (step S 10 2). If the (m + 1) slot is not used by this check, the process proceeds to step S103, the detection timing is delayed to the (m + 1) slot at the next detection, the communication of the mth slot is continued, The (m + 1) th slot is blocked (unusable) so that the terminal does not use it (step S104). When the communication of the first lot is completed (step S105), the block of the (m + 1) th slot is also released and usable (step S106).

When using the (m + 1) th slot with the detection timing delayed in step S103 However, as described above, the allowable reception range of the synchronization signal is made as narrow as possible only by providing a margin for the number of bits determined by the system specifications in addition to the length of the synchronization signal. In this way, by continuing communication while estimating the next detection timing, false detection of synchronization signals is reduced.

[0027] On the other hand, if it is determined in step S102 that the (m + 1) slot is used, the mobile station that is communicating in the (m + 1) slot is within the same base station. The slot switching is instructed (step S107). If the slot in the base station is empty and switching is successful (step S108: Yes), the reception timing is delayed to the empty (m + 1) slot and the subsequent communication is performed (step S103). On the other hand, if switching is not possible because there is no free space, the mobile station in communication in the (m + 1) th slot is instructed to perform handover to another base station (step S109).

[0028] If handover to another base station is successful due to this handover instruction (step S110: Yes), the process proceeds to step S103, and communication is performed by delaying the detection timing to the (m + 1) slot. Continue. On the other hand, when there is no suitable base station or when handover to another base station fails, the communication in the m-th slot is terminated in an out-of-synchronization state (step S111).

In the above description, the case where the propagation delay is gradually increased has been described. However, it is natural that the same processing is performed when the propagation delay gradually decreases and the interference with the (m-1) th slot occurs. It can respond by.

[0029] As described above, the synchronization signal reception allowable range after establishment of synchronization is limited, the reception allowable range is sequentially shifted according to the movement of the mobile station, and adjacent slots are also used as necessary. Thus, even in a situation where the propagation delay of the radio signal is long due to the long distance between the base station and the mobile station, it is possible to perform communication with less misdetection of the synchronization signal without performing transmission timing control in the mobile station. In particular, even in a mobile communication system such as PHS that was originally designed on the assumption that the cell radius is small, the cell radius can be increased.

[0030] Embodiment 2.

In Embodiment 1 above, radio signal propagation delay was supported by controlling the reception timing of the base station (the position of the first bit and the last bit of the received signal). Describes a TDMA communication system that enables communication by controlling the transmission timing of the base station, thereby reducing the number of false detections of synchronization signals that are not transmitted to the mobile station! .

[0031] In Embodiment 2, the maximum allowable reception range is established before synchronization is established, and after synchronization is established, a range slightly longer than the length of the synchronization signal is received based on the reception timing received at the time of establishment of synchronization. This is the same as in the first embodiment up to the point where the allowable range is determined, the detection timing force is estimated n times and the detection timing of the next synchronization signal is estimated. The second embodiment is characterized in that the transmission timing of the base station is adjusted based on the estimated reception timing.

The system configuration diagram of the second embodiment is the same as that of FIG. 1 of the first embodiment.

Here, when a base station power is transmitted to a mobile station and a synchronization signal of the mobile station power is returned and received at the base station, the time difference between them, that is, the delay time is the distance between the base station and the mobile station. It is determined based on internal processing in the mobile station. If the internal processing in the mobile station that received the radio wave is constant, the delay time will eventually change based on the distance. Therefore, the timing at which the signal from the mobile station is received by the base station can be adjusted by adjusting the transmission timing of the previous base station.

FIG. 8 is a diagram showing transmission / reception timings according to the second embodiment of the present invention. Figure 8 (a) shows the structure of the TDMA received frame of the base station. FIG. 8 (b) shows the reception timing of the received signal in the m-th reception slot for the TDMA reception frame in FIG. 8 (a). D shows the case where the optimal timing force is also delayed by D. Figure 8 (c) shows the structure of the TDMA transmission frame of the base station. (d) shows the transmission signal when the transmission timing is uncorrected for the mth transmission slot. (E) shows the transmission signal when the transmission timing can be adjusted optimally. If there is a delay amount D as shown in (b), if the transmission timing can be advanced by the amount of delay D as shown in (e), the base station will receive the mth received signal. Slots can be received at the optimal timing.

However, in practice, the mobile station cannot receive the downlink synchronization signal unless the transmission timing is adjusted within the allowable reception range of the downlink synchronization signal from the base station in the mobile station. The transmission timing is adjusted within the maximum value range that the mobile station can follow. Figure 8 (f) shows the transition. This is the allowable reception range of the downlink synchronization signal of the mobile station. Fig. 8 (g) shows the synchronization signal detection position this time, that is, the synchronization signal detection position when the transmission signal is received by the mobile station in the mth slot of the base station. FIGS. 8 (h) and 8 (i) are diagrams showing the maximum ranges when the detection timing of the downlink synchronization signal is shifted due to the movement of the mobile station in the next frame. In the figure, E indicates the maximum allowable detection range in the next frame. The mobile station reception tolerance range is adjusted so that when a downlink synchronization signal is detected, its frame timing is corrected based on the detection timing, and the detection timing is positioned at the center of the reception tolerance range. . Figure 8 (j) shows the transmission timing after correction of the mth transmission slot. Since there is a limit on the synchronization signal reception allowable range on the mobile station side, the transmission signal is transmitted earlier than the delay amount D by the adjustment amount E.

FIG. 8 (k) shows the TDMA reception frame of the base station again! /, But shows the reception mth slot of the frame next to the reception mth slot in FIG. 8 (a). Fig. 8 (1) shows the reception timing of the received signal after the transmission timing correction for the mth slot. As described above, since the adjustment amount is E, which is smaller than the delay amount D, the optimal timing force is still delayed by F = D-E. Note that the example in FIG. 8 is a case where the distance of the mobile station to the base station changes between FIGS. 8 (a) to (k), and the mobile station moves as if it is separated from the base station power. Of course, if you continue, the amount of delay will be larger than D—E.

FIG. 9 is a flowchart showing processing contents of transmission timing control according to the second embodiment of the present invention. First, the base station 2 receives the synchronization signal from the mobile station 1 (step S200). The synchronization signal reception count P = l (step S201), and the synchronization signal reception allowable range is determined based on the timing at which synchronization is established (step S202). As described above, this allowable reception range is set to a range longer than the length of the synchronization signal after synchronization is established.

[0037] Next, the count P is incremented by one (step S203). It is determined whether the count P exceeds the parameter n! /! (Step S204). If it does not exceed the parameter n, the synchronization signal is received as it is (step S205). The next synchronization signal detection timing is estimated for both the synchronization establishment start force and the transition force of the detection timing until now (step S206). As a result, it is determined whether or not the next synchronization signal detection timing is within the allowable reception range (step S207). [0038] When the mobile station moves faster and the reception allowable range force detection timing falls off during n sample collections, based on the detection timing estimated in step S206, Advance the transmission timing and adjust it to be within the allowable reception range (step S208). On the other hand, if the reception permissible range power does not deviate, the process returns to step S204, and sampling of the detection timing is continued up to n times.

[0039] When n times of sample collection are completed and the count P = n in step S204, the process proceeds to step S209, and the past n synchronization signal detection timings are compared with the synchronization signal detection timing when synchronization is established. Force Estimate the next synchronization signal detection timing. Using this estimated detection timing, the transmission timing of the (n + 1) -th base station power is adjusted (step S210). After receiving the (n + 1) th synchronization signal (step S211), transmission is performed at the adjusted transmission timing (step S212), and the (n + 1) th detection timing is used to estimate the next detection timing (step Return to S209).

[0040] Furthermore, the base station operation when the next transmission timing interferes with the transmission (m-1) slot as a result of adjusting the transmission timing during communication using the transmission and reception mth slots Will be described with reference to the flowchart of FIG. During communication using the first transmission lot, it is determined whether the next transmission timing interferes with the transmission (m-1) slot (S213). It is further determined whether the slot is communicating with another mobile station (S214). If the transmission (m-1) slot is not used, the transmission timing is advanced to the transmission (m-1) slot timing, and communication is continued (S215). At that time, the transmission (m-1) slot is blocked (unusable) so that other mobile stations do not use it (S216). Thereafter, when the communication is completed (S217), the transmission slot (m-1) is unblocked (S218).

[0041] On the other hand, when the transmission (m-1) slot is in use, a different slot in the same base station is used for the mobile station communicating in the transmission (m-1) slot. A switching instruction is issued (S21 9). If this switching is successful (S220), communication is continued using the mth slot to the (m-1) slot as it is (S215-S218). (m-1) Instructs the mobile station in communication in the slot to perform handover to another base station (S221). [0042] When the handover is successful (S222), communication is continued using the transmission (m-1) slot as it is (S215-S218). The slot communication is terminated (S223).

[0043] As described above, in Embodiment 2, by adjusting the transmission timing of the base station so that the synchronization signal is received within the allowable reception range, the radio signal having a long distance between the base station and the mobile station is obtained. Even in situations where the signal propagation delay is large, the mobile station can perform communication with less misdetection of the synchronization signal without controlling the transmission timing. In particular, even in a mobile communication system such as PHS that was originally designed on the assumption that the cell radius is small, the cell radius can be increased.

[0044] Embodiment 3.

In Embodiments 1 and 2 above, even if the propagation timing of the radio signal is long due to the long distance between the base stations and the base station by adjusting either the reception timing or the transmission timing of the base station, the transmission timing in the mobile station Although the TDMA communication system that can perform communication with less synchronization signal misdetection without performing control of the TDMA has been described, in Embodiment 3, the reception timing is adjusted and this adjustment can be performed. At this stage, we will explain a TDMA communication system that can cope with situations where the radio signal propagation delay is larger by adjusting the transmission timing of the base station.

[0045] In Embodiment 3, in step S110 of FIG. 7 of Embodiment 1, when the handover cannot be performed to other CSs that have slots that can move within the same base station, the transmission timing of the base station By adjusting the frequency, the base station can follow the movement of the mobile station further than in the first embodiment.

FIG. 11 is a flowchart showing the processing contents in the transmission / reception timing adjustment of the third embodiment. In FIG. 11, the processing contents up to step S110 are the same as those in FIG. If handover to another base station is not successful in step S110, the base station adjusts the transmission timing of the base station based on the estimation result of the reception timing of the synchronization signal of the mth slot, The adjustment amount is determined (step S112). The adjustment amount is adjusted so that the end of the received signal does not protrude from the guard bit of the mth slot and does not enter the (m + 1) th slot. [0047] As described above, in Embodiment 3, the reception timing of the synchronization signal is controlled, and when the slot adjacent to the communicating slot is in use and handover is not possible, By adjusting the transmission timing of the station, a TDMA communication system that can cope with situations where the propagation delay of radio signals becomes longer is obtained. In particular, the cell radius can be increased even in a mobile communication system such as PHS that was originally designed with the assumption that the cell radius was small! /.

[0048] In the above, the transmission timing of the base station is adjusted after the handover failure. As yet another example, as shown in FIG. 12, the (m + 1) th slot is communicating in step S102. If determined, the transmission timing of the base station in the m-th slot may be adjusted (step S 114). If the delay of the received signal is further increased and the transmission timing cannot be adjusted any further due to deviation from the mobile station reception tolerance (step S115), the (m + 1) Instruct the mobile station that is communicating in the slot to switch to another slot in the same base station (step S107), and if the switch is not successful, further instruct handover (step S110) Anyway!

[0049] When the switching of the slot of the mobile station in use of the (m + 1) slot is successful, or when the handover to another base station is successful, the reception timing is delayed until the (m + 1) slot timing. The point of continuing communication in the mth slot is the same as steps S103 to S106 in FIG. 5 of the first embodiment.

Also, in the above description, the case where the delay time is long and the communication in the mth slot interferes with the communication in the (m + 1) th slot has been described, but when the mobile station approaches, the communication in the mth slot is not performed. Even in the case of interference with the (m-1) th slot, adjustment is possible by increasing the reception timing or delaying the transmission timing.

[0050] Embodiment 4.

In the third embodiment, after adjusting the reception timing, the transmission timing of the base station is further adjusted. However, in the fourth embodiment, the transmission timing of the base station is adjusted and the adjustment can no longer be performed. This section describes a TDMA communication system that adjusts the reception timing at each stage and has a larger radio signal propagation delay and can cope with the situation.

FIG. 13 is a flowchart showing details of transmission / reception timing adjustment processing according to the fourth embodiment. It is. In the fourth embodiment, as shown in FIG. 9, the transmission timing is adjusted in the same way as in the second embodiment to cope with fluctuations in the signal propagation delay of the mobile station. However, in step S222, other base stations are contacted. If the handover of this is unsuccessful, the reception timing is further adjusted and communication is continued. That is, in step S224, the amount of adjustment of the detection timing of the synchronization signal of the base station in the m-th reception slot is determined by estimating the detection timing power of the last n synchronization signals. If interference can be avoided by adjusting the reception timing (S225), continue communication and return to step S213 again to check whether the next transmission timing is strong enough to interfere with the transmission (m-1) slot. To do. On the other hand, if interference avoidance is impossible due to adjustment of the reception timing, the communication using the transmission and reception mth slot is terminated.

[0052] As another example, when the next transmission timing interferes with the (m-1) slot and the transmission (m-1) slot is communicating, another slot in the same base station is used. It is also possible to adjust the reception timing rather than switching to. FIG. 14 is a flowchart showing the processing contents in such a case.

If the (m−1) th transmission slot is communicating in step S214, the reception timing of the base station in the mth reception slot is adjusted in step S224. If interference can be avoided by adjusting the reception timing (S225), the process returns to step S213 again. On the other hand, if interference cannot be avoided by adjusting the reception timing, the mobile station in communication at the (m-1) transmission slot is instructed to switch to a slot in the same base station. (S219). As a result, when the slot switching is successful (S220), communication is continued using the transmission (m-1) slot from the transmission mth slot as it is. On the other hand, if the switching fails, the mobile station in communication in the transmission (m-1) slot is instructed to perform handover to another base station (S221). If the handover to another base station succeeds (S222), the communication is continued using the transmission lot and the transmission (m-1) slot as it is. If the handover fails, the transmission is performed. Communication using the mth slot is terminated (S223).

As described above, in the fourth embodiment, when the transmission timing cannot be adjusted, the reception timing is further adjusted, so that the propagation delay of the radio signal with a long base station-to-mobile station distance is further increased. Even in large situations, the mobile station does not control transmission timing Therefore, it is possible to perform communication with less erroneous detection of the synchronization signal.

[0054] In the above description, the reception timing is adjusted after transmission timing adjustment becomes impossible. However, the reception timing may be adjusted simultaneously with the transmission timing adjustment. With this configuration, the amount of transmission timing that can be adjusted with a single adjustment increases, so that the same effect as described above can be obtained without performing transmission timing control in the mobile station.

Industrial applicability

[0055] The TDMA communication system according to the present invention can be applied to a mobile phone or PHS.

Claims

The scope of the claims

[1] a receiver that receives an upstream signal from the first mobile station;

Synchronization signal detection timing measuring means for measuring the detection timing of the uplink synchronization signal included in the received uplink signal;

And a reception allowable range control means for determining a reception allowable range of the synchronization signal of the synchronization signal detection means based on the latest detection timing and a plurality of past detection timing measurement results. A communication system base station.

[2] The reception allowable range control means sets the reception allowable range to a maximum range that can be used in one reception slot before the synchronization between the base station and the first mobile station is established. The base station of the mobile communication system according to claim 1, wherein after the synchronization is established, the reception allowable range is determined based on the measured latest detection timing and a plurality of past detection timings.

[3] Receiving slot interference determining means for determining whether a terminal end or front end of the uplink signal deviates from a current receiving slot and interferes with a receiving slot adjacent to the receiving slot when receiving within the determined allowable reception range;

When the reception slot interference determination means determines that interference occurs, the reception slot use determination means for determining whether the adjacent reception slot is in communication with other mobile stations, and the determination by the reception slot use determination means As a result, when the adjacent receiving slot is not communicating, the adjacent receiving slot is also used for communication, and when the adjacent receiving slot is communicating, the other mobile station receives another reception. A communication control means for issuing an instruction to use another receiving slot instructing to perform communication using the slot, and controlling the first mobile station to perform communication using an adjacent receiving slot vacated by this instruction; The base station of the mobile communication system according to claim 2, further comprising:

[4] The communication control means further instructs a handover to another base station when the other mobile station cannot use another reception slot according to the instruction to use another reception slot, and performs this handover. If successful, the first mobile station communicates using the adjacent receiving slot, and if this handover fails, the first mobile station is controlled to terminate communication. The mobile communication according to claim 3, System base station.

[5] Further comprising transmission timing control means for determining the next transmission timing of the transmitter based on the latest detection timing measured by the synchronization signal detection timing measurement means and the plurality of past detection timings,

4. The communication control unit according to claim 3, wherein, when the handover fails, the communication control unit further adjusts a transmission timing so that communication can be continued in the current reception slot by the transmission timing control unit. A base station for a mobile communication system.

[6] Transmission timing control means for determining the next transmission timing of the transmitter based on the latest detection timing measured by the synchronization signal detection timing measurement means and a plurality of the past detection timings;

As a result of the determination by the reception slot use determination means, when adjacent reception slots are communicating, the transmission timing control means adjusts the transmission timing so that communication can be continued in the current reception slot. When the adjustment cannot be performed, the mobile station communicating with the adjacent reception slot is instructed to communicate using another reception slot, and the adjacent reception slot vacated by this instruction is used. The base station of the mobile communication system according to claim 2, further comprising communication control means for controlling the first mobile station to perform communication.

[7] When the communication control means further instructs the handover to another base station if the other mobile station cannot use another reception slot according to the instruction, and the handover succeeds. The first mobile station communicates using the adjacent reception slot at the same time, and if the handover fails, the first mobile station is controlled to terminate the communication. The base station of the mobile communication system according to claim 6.

[8] a transmitter for transmitting a downlink signal including a synchronization signal for establishing synchronization with the first mobile station;

A receiver that receives the uplink signal of the mobile station power that receives the downlink signal of the transmitter power and performs internal processing for a fixed time and then returns the uplink signal;

Synchronization signal detection timing measuring means for measuring the detection timing of the uplink synchronization signal included in the received uplink signal; A base station for a mobile communication system, comprising: transmission timing control means for determining a next transmission timing of the transmitter based on the latest measured detection timing and a plurality of past detection timings.

[9] If transmission is performed at the transmission timing determined by the transmission timing control means, it is determined whether or not the downlink signal can be received within the reception allowable range of the first mobile station. 9. The base station of the mobile communication system according to claim 8, further comprising transmission timing adjustment means for adjusting so as to be within a reception allowable range of one mobile station.

[10] Transmission slot interference determination means for determining whether or not the terminal or front end of the transmission signal deviates from the current transmission slot when transmitting at the determined transmission timing and interferes with a transmission slot adjacent to the transmission slot. ,

A transmission slot use determining means for determining whether or not the adjacent transmission slot is communicating with another mobile station when the transmission slot interference determining means determines that the adjacent transmission slot interferes;

As a result of the determination by the transmission slot use determining means, if the adjacent transmission slot does not communicate, the adjacent transmission slot is also used for communication, and if the adjacent transmission slot is communicating, An instruction to use another transmission slot is issued to instruct the other mobile station to perform communication using another transmission slot, and the first mobile station performs communication using an adjacent transmission slot vacated by this instruction. 9. The base station of the mobile communication system according to claim 8, further comprising communication control means for performing control.

[11] The communication control means further instructs the handover to another base station when another mobile station cannot use another transmission slot according to the instruction to use another transmission slot, and succeeds in this handover. 11. The base station of the mobile communication system according to claim 10, further comprising communication control means for performing control so that communication is performed using the adjacent slot in the case of being performed.

[12] A reception tolerance range control means for determining a reception tolerance range of the synchronization signal of the synchronization signal detection means based on the latest detection timing measured by the synchronization signal detection timing measurement means and a plurality of past detection timings. Prepared,

When the communication control means fails in the handover, the reception control further 12. The base station of the mobile communication system according to claim 11, wherein the reception tolerance range of the synchronization signal in the reception slot is adjusted by adjusting the reception tolerance range of the downlink synchronization signal by range control means. .

[13] Transmission slot interference determination means for determining whether or not the terminal or front end of the transmission signal deviates from the current transmission slot when transmitting at the determined transmission timing and interferes with a transmission slot adjacent to the transmission slot. ,

A reception tolerance range control means for determining a reception tolerance range of the downlink synchronization signal of the synchronization signal detection means based on the latest detection timing and a plurality of past detection timings measured by the synchronization signal detection timing measurement means;

As a result of this determination, adjacent transmission slots communicate with each other, in which case the adjacent transmission slots are also used for communication, and when adjacent transmission slots are communicating, instead of controlling transmission timing. 9. The base station of the mobile communication system according to claim 8, further comprising communication control means for adjusting a reception allowable range of the downlink synchronization signal in a reception slot by the reception allowable range control means.

[14] When the communication control means cannot adjust the reception timing by adjusting the reception allowable range, it communicates in an adjacent transmission slot and uses another transmission slot for the mobile station. 9. The mobile communication system according to claim 8, wherein the communication is instructed to perform communication, and the first mobile station performs communication using an adjacent transmission slot vacated by this instruction. base station.

[15] The communication control means further instructs a handover to another base station when the other mobile station cannot use another transmission slot according to the instruction to use another transmission slot. If successful, the first mobile station communicates using the adjacent transmission slot, and if this handover fails, the first mobile station is controlled to terminate communication. The base station of the mobile communication system according to claim 13,