JP5058873B2 - Wireless communication system and communication method - Google Patents

Description

  The present invention relates to a wireless communication system and a communication method.

  Currently, in a wireless communication system such as PHS (Personal Handy-phone System), a time division multiple access (TDMA) system and a time division duplex (TDD) system are adopted as multiple access systems. Yes. In a base station in this wireless communication system, a carrier is divided into time slots having a predetermined time interval, and various types of information are transmitted to and received from a mobile terminal using this time slot. In this wireless communication system, a data communication service based on a packet communication method for transmitting packet data by time slots has been put into practical use.

  The base station in the wireless communication system transmits / receives various information to / from the mobile terminal by alternately switching the downlink (transmission) and the uplink (reception) every four consecutive time slots. One frame is composed of 4 time slots of the downlink and uplink, that is, 8 time slots. In such a base station, when there are few mobile terminals in its own cell, in data communication, for example, the downlink and uplink time slots in each frame are allocated to the same mobile terminal. That is, each mobile terminal is assigned a time slot at the same position in each frame.

  In addition, in such a base station, when there are many mobile terminals in its own cell, the communication speed per mobile terminal decreases, but the same time slot is shared by a plurality of mobile terminals. . For example, when two mobile terminals share the same time slot, the frequency of time slot allocation to each mobile terminal is halved compared to the case of one mobile terminal, that is, each mobile terminal has a normal communication speed (full rate). ) Communication at half the communication speed (half rate). In such a case, the two portable terminals communicate using the same time slot alternately frame by frame.

Further, in such a base station, four mobile terminals can share the same time slot. When sharing the same time slot with four mobile terminals, the frequency of time slot allocation to each mobile terminal is set to 1/4 of the case of one mobile terminal, that is, each mobile terminal has a full rate of 4 minutes. The communication is performed at a communication speed (quarter rate) of 1. In such a case, the four mobile terminals perform communication using the same time slot while changing one frame at a time. Non-Patent Document 1 describes a method for specifying a time slot in communication at the above half rate and quarter rate.
“Second Generation Cordless Telephone System Standard RCR STD-28” 5.0, P89-90 Radio Industry (ARIB)

  By the way, in the above prior art, the same slot is shared by two or four portable terminals for the purpose of assigning as many time slots as possible to the portable terminals. However, this enables, for example, when the mobile terminal a connected to the base station occupies the first slot of the downlink and uplink in each frame and performs data communication, the new mobile terminal b When connected to the base station, the mobile terminal b has to share the slot, so that data communication has to be performed at a communication speed lower than before. In such a case, even if the mobile terminal a is handed over to a base station with a small number of mobile terminals present in the cell, in the data communication, the data communication that has been executed so far is once terminated due to the occurrence of the handover. In other words, data communication cannot be continued from the base station newly connected by handover. Therefore, when the new mobile terminal b is connected to the base station, the mobile terminal a cannot improve the communication speed even if it is handed over.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a wireless communication system and a communication method capable of improving the communication speed as compared with the related art.

In order to achieve the above object, in the present invention, as a first solving means related to a radio communication system, a plurality of base stations connected to a higher-level communication network and a plurality of mobile terminals communicate with each other by a time division multiple access method. A communication system, wherein a first base station communicates with a first portable terminal using a first time slot of a first carrier from a second portable terminal. When the time slot limitedly specified to be required to establish a link, search the base station near which is not used for communication with the first time slot of the first carrier (second base station) and, wherein in said first base station instead of its own to the second base station requests to communicate with the first mobile terminal, the second base station receives the request, the first base of the base station identification information in the communication of the mobile station Adopting means of communicating with the first mobile terminal by said first time slot of the first carrier as well as changes to those.

In the present invention, as the second solving means relating to the radio communication system, in the first solving means, the first base station has a plurality of second base stations when a plurality of the second base stations exist. Base station to measure the reception strength from the first portable terminal, and based on the measurement results of the plurality of second base stations, the second base station with the strongest reception strength adopting means that requests to communicate with the first base station instead of its own.

  In the present invention, as the third solving means relating to the radio communication system, in the first or second solving means, the second base station transmits communication data for transmission to the first portable terminal. A means is adopted in which communication data received from the network via the one base station and further received from the first portable terminal is transmitted to the upper communication network via the first base station.

  In the present invention, as the fourth solving means relating to the radio communication system, in the first or second solving means, the second base station has received and accumulated from the higher-level communication network by the first base station. After receiving communication data for transmission to the first mobile terminal from the first base station, communication data for transmission to the first mobile terminal without going through the first base station A means for transmitting communication data received from the network and further received from the first portable terminal to the upper communication network is employed.

The present invention provides a wireless communication system in which a plurality of base stations connected to a higher-level communication network and a plurality of mobile terminals communicate with each other by a time division multiple access method as a first solving means related to a communication method, When the base station communicates with the first mobile terminal using the first time slot of the first carrier, the base station specifies the first time slot from the second mobile terminal in a limited manner. When requesting the establishment of a link, to explore the surrounding base stations that are not used for communication with the first time slot of the first carrier (second base station), to the second base station requests to communicate with the first base station instead of its own,
The second base station receives the request, the second by the first of the first time slot of the carrier as well as changing the base station identification information in the communication of the mobile station, to that of the first base station A means of communicating with one mobile terminal is adopted.

  According to the present invention, a wireless communication system is a wireless communication system in which a plurality of base stations connected to a higher-level communication network and a plurality of mobile terminals communicate by a time division multiple access method, wherein the first base station is When communicating with the first mobile terminal using the first time slot of the first carrier, the second mobile terminal specifies the first time slot in a limited manner to establish a link. When requested, a search is made for a neighboring base station (second base station) that is not using the first time slot of the first carrier for communication, and the second base station instead of itself The second base station requests to communicate with the first base station, and when the second base station receives the request, the base station identification information in the communication is that of the first base station and the first time of the first carrier Communicates with the first mobile terminal by slot Thus, in the past, the first mobile terminal and the second slot shared the first slot for communication, that is, the communication speed had to be set at a half rate. Since the second base station can communicate with the first mobile terminal instead of the base station, that is, the first mobile terminal can communicate at the full rate, the communication speed can be improved as compared with the prior art. . This also allows the second mobile terminal to communicate with the first base station at full rate.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a base station that communicates with a PHS (Personal Handy-phone System) terminal. FIG. 1 is a system configuration diagram of a radio communication system configured by the base station A1 according to the present embodiment.

  As shown in FIG. 1, this wireless communication system is composed of base stations A 1 and A 2, PHS terminals B 1 and B 2, a dedicated IP (Internet Protocol) network C, an Internet switching center D, and a public Internet network E. The base stations A1 and A2 and the PHS terminals B1 and B2 communicate with each other by a communication method combining a time division multiple access (TDMA) method and a time division duplex (TDD) method. Device.

  A slot, frame, and superframe in a carrier in TDMA-TDD communication between the base stations A1, A2 and PHS terminals B1, B2 will be described in detail with reference to FIG. FIG. 2 is a schematic diagram showing slots, frames, and superframes in a carrier of TDMA-TDD communication between the base stations A1, A2 and PHS terminals B1, B2. Carriers in communication between the base stations A1, A2 to PHS terminals B1, B2 are divided into slots which are the minimum units by the TDMA method. The slot length of this slot is 0.625 secm. Further, in the carrier in the communication between the base stations A1, A2 to PHS terminals B1, B2, transmission (downlink) and reception (uplink) are switched every 4 slots by the TDD method. A frame is composed of slots, that is, eight slots.

  The frame length of the frame is 5 mSec. Furthermore, a super frame is composed of a plurality of frames, and the super frame length of this super frame is 100 mSec. Each lattice shown in FIG. 2 represents each slot, and “C”, “T1”, “T2”, “T3”, and “T4” described in each slot represent channels assigned to each slot. “C” indicates a control channel, and “T1”, “T2”, “T3”, and “T4” indicate communication channels.

The base stations A1 and A2 are discretely arranged with a predetermined interval, and communicate with the PHS terminals B1 and B2 in the cells assigned to them. The base stations A1 and A2 are connected to the Internet switching center D via the dedicated IP network C, and transmit / receive various information to / from the public Internet network E via the Internet switching center D. The base stations A1 and A2 can directly communicate with each other via the dedicated IP network C.
The Internet switching center D transmits the data received from the public Internet network E to the base station A1 or A2 according to the link destination of the destination PHS terminal B1 or B2. The base station A1 or A2 transmits the data received from the Internet exchange D to the PHS terminal B1 or B2.

  Next, the configuration of the base station A1 and the base station A2 will be described with reference to FIG. In FIG. 3, the base station A1 of the base station A1 and the base station A2 includes a wireless communication unit 1, a storage unit 2, a dedicated IP network communication I / F unit 3, and a control unit 4, and the base station A2 It comprises a unit 11, a storage unit 12, a dedicated IP network communication I / F unit 13 and a control unit 14. The wireless communication unit 1 and the wireless communication unit 11, the storage unit 2 and the storage unit 12, the dedicated IP network communication I / F unit 3 and the dedicated IP network communication I / F unit 13, and the control unit 4 and the control unit 14 are respectively Has the same function. Below, each part of base station A1 is demonstrated in detail.

Under the control of the control unit 4, the wireless communication unit 1 transmits and receives various signals such as voice signals, data signals, and control signals to and from the PHS terminals B1 and B2 through the control channel and the communication channel.
The storage unit 2 is a non-volatile memory, and stores various information such as a call information management table under the control of the control unit 4.
FIG. 4 is a schematic diagram showing a call information management table. As shown in FIG. 4, in the call information management table, for each call number, as the first communication channel information, the slot number, carrier number, communication method, communication rate, etc., and the second communication as in the first communication channel information. It is a data table in which a slot number, a carrier number, a communication method, a communication rate, etc., and a call time are registered as channel information. This call number is an identification number assigned to the PHS terminals B1, B2 and other PHS terminals that have successfully established a link with the base station A1.

The dedicated IP network communication I / F unit 3 is an interface for connecting to the dedicated IP network C, and is connected to the Internet switching center D and the base station A2 via the dedicated IP network C.
The control unit 4 includes an internal memory including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), the wireless communication unit 1, the storage unit 2, and a dedicated IP network communication I / F unit. 3 and an interface circuit for inputting / outputting signals respectively, and a base station based on a control program stored in the ROM and signals received by the wireless communication unit 1 and the dedicated IP network communication I / F unit 3 Controls the overall operation of A1. The control program stored in the ROM includes a base station switching control program, and the control unit 4 controls switching of base stations that perform data communication based on the base station switching control program. The details of the control process executed by the control unit 4 will be described below as the operation of the base station A1.

Next, operations of the base station A1 and the base station A2 in the wireless communication system configured as described above will be described with reference to the sequence diagram of FIG. FIG. 5 is a sequence diagram showing operations of the base station A1 and the base station A2.
First, the PHS terminal B1 transmits a link establishment request to the base station A1 through the control channel in order to start data communication. (Step S1)

When the wireless communication unit 1 receives a link establishment request from the PHS terminal B1 through the control channel, the control unit 4 of the base station A1 determines a communication channel carrier used by the PHS terminal B1 for communication and a slot in the carrier, and determines The wireless communication unit 1 is transmitted as a link establishment response to communicate using the communication channel assigned to the slot of the carrier (step S2). Here, it is assumed that the carrier determined by the control unit 4 is the carrier C1, the slot in the carrier is the slot S1, and the channel of the slot is the communication channel T1.
The PHS terminal B1 establishes a link with the communication channel T1 assigned to the slot S1 in the carrier C1 based on the link establishment response received through the control channel, and performs data communication with the base station A1 using the communication channel T1. (Step S3).

  Then, the PHS terminal B2 that has moved into the cell of the base station A1 transmits a link establishment request to the base station A1 through the control channel to request that a link be established at the timing of the slot S1 in the base station A1. (Step S4). Requesting establishment of a link by limiting slots to the base station A1 as in this PHS terminal B2 is called a slot limited call. In this slot limited call, when the PHS terminal B2 performs communication using a plurality of slots, a slot other than the timing at which the link has already been established is limitedly designated to establish a link with the base station A1. It is caused by requesting.

  When the wireless communication unit 1 receives the link establishment request from the PHS terminal B1, the control unit 4 of the base station A1 uses the communication channel T1 assigned to the slot S1 of the carrier C1 from the surrounding base stations for communication. In order to search for a non-existing base station, a communication channel investigation request is transmitted to the peripheral base station A2 and other base stations (not shown) via the dedicated IP network C to the dedicated IP network communication I / F unit 3 ( Step S5).

  When the dedicated IP network communication I / F unit 13 receives the communication channel investigation request, the control unit 14 of the base station A2 determines whether the communication channel T1 of the slot S1 in the carrier C1 is used for communication. The dedicated IP network communication I / F unit 13 is transmitted to the base station A1 as a survey response (step S6). In the base station A2, it is assumed that the communication channel T1 assigned to the slot S1 of the carrier C1 is not used for communication.

  The control unit 4 of the base station A1 determines that the communication channel T1 assigned to the slot S1 of the carrier C1 is based on the communication channel investigation response received by the dedicated IP network communication I / F unit 3 from the base station A2 and other base stations. A base station that is not used for communication is determined (step S7), and the base station (including the base station A2) among these base stations (including the base station A2) receives from the base station with the best communication state with the PHS terminal B1, that is, the PHS terminal B1. In order to determine the base station with the strongest reception intensity of the control channel, the dedicated IP network communication I / F unit 3 is caused to transmit a reception intensity measurement request to those base stations (including the base station A2) (step S8).

When the dedicated IP network communication I / F unit 13 receives the reception strength measurement request, the control unit 14 of the base station A2 measures the control channel reception strength received by the wireless communication unit 1 from the PHS terminal B1 and The measurement result is transmitted as a received intensity measurement response to the base station A1 to the dedicated IP network communication I / F unit 13 (step S9).
The control unit 4 of the base station A1 starts from the base station with the best communication state, that is, the PHS terminal B1, based on the reception strength measurement response received by the dedicated IP network communication I / F unit 3 from the base station A2 and other base stations. A base station having the strongest reception strength of the control channel to be received is determined (step S10). Here, the strongest reception intensity of the control channel received from the PHS terminal B1 is defined as the base station A2.

  The control unit 4 of the base station A1 uses the packet data to be transmitted to the PHS terminal B1 in the data communication and the slot of the carrier C1 instead of the base station A1 in order to cause the base station A2 to execute the data communication with the PHS terminal B1. The base station A2 is transmitted to the dedicated IP network communication I / F section 3 to the base station A2 instructing data communication through the communication channel T1 assigned to S1 (step S11).

  Then, when the dedicated IP network communication I / F unit 3 receives the packet data and the base station replacement instruction from the base station A2, the control unit 14 of the base station A2 uses the communication channel T assigned to the slot S1 of the carrier C1 to change the PHS terminal. A link with B1 is established and a link establishment success notification is sent to the base station A1 to the dedicated IP network communication I / F unit 13 (step S12), and the base station ID which is one of the information possessed by the control channel of the carrier C1 Is changed from the base station A2 to that of the base station A1, and the packet data is transmitted to the PHS terminal B1 via the communication channel T1 in the slot S1 of the carrier C1, that is, data communication with the PHS terminal B1 is executed. (Step S13).

  In general, the PHS terminal B1 can accept a delayed wave up to a certain extent in addition to the direct wave of the radio wave transmitted from the base station A1. Accordingly, if the PHS terminal B1 has a radio wave transmitted from the base station A2 through the communication channel T1 of the slot S1 of the carrier C1 in step 13 within an allowable range as a delayed wave of the radio wave transmitted from the base station A1, Packet data can be received, that is, data communication can be performed. Further, even when the PHS terminal B1 cannot normally receive the packet data when the base station that transmits the packet data to the PHS terminal B1 is switched from the base station A1 to the base station A2, data communication is not possible. Since there is a mechanism for retransmitting packet data that could not be normally received by the PHS terminal B1, there is no problem.

  When the dedicated IP network communication I / F unit 13 receives the link establishment success notification from the base station A2, the control unit 4 of the base station A1 communicates with the PHS terminal B1 through the communication channel T1 assigned to the slot S1 of the carrier C1. Is stopped (step S14), and the fact that communication is performed using the communication channel T1 of the slot S1 in the carrier C1 is transmitted to the PHS terminal B2 to the wireless communication unit 1 as a link establishment response (step S15).

  The PHS terminal B2 establishes a link with the communication channel T1 assigned to the slot S1 in the carrier C1 based on the link establishment response received through the control channel, and performs data communication with the base station A1 using the communication channel T1. (Step S16). At this time, the communication speed in communication between the base stations A1 to PHS terminal B2 is a full rate.

As described above, when the base station A1 is performing data communication with the PHS terminal B1 through the communication channel T1 assigned to the slot S1 of the carrier C1, a link establishment request that specifies the slot S1 from the PHS terminal B2 in a limited manner. When received, the PHS terminal B1 and PHS terminal B2 share the slot, that is, instead of executing half-rate communication, instead of the base station A1 from the base stations in the vicinity of the base station A1 and the PHS terminal B1. By searching for a base station A2 that can perform data communication with the PHS terminal B1, that is, the communication channel T1 is not used for communication, and causing the base station A2 to perform data communication with the PHS terminal B1, Terminal B1 performs data communication at full rate instead of half rate It can reason, it is possible to improve the communication speed than conventional.
Further, since the communication speed of data communication can be improved by improving the base station A1 and the base station A2 without improving the PHS terminal B1, the PHS terminal B2, and the Internet switching center D, the burden of the improvement is reduced. I can do it.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the base station A2 transmits the packet data received from the base station A1 to the PHS terminal B1, but the present invention is not limited to this.
For example, after receiving the packet data to be transmitted to the PHS terminal B1 stored in the base station A1, the base station A2 receives the packet data directly from the Internet switching center D without passing through the base station A1. Data may be transmitted to the PHS terminal B1. Further, when receiving data from the PHS terminal B1, the base station A2 may transmit the data to the Internet exchange D via the base station A1 or directly to the Internet exchange D.

(2) In the above embodiment, the base station A1 and the base station A2 are connected by a dedicated IP network, but may be connected by an ISDN (Integrated Services Digital Network).

It is a system configuration | structure figure of the radio | wireless communications system comprised by base station A1 and base station A2 which concern on this embodiment. It is a schematic diagram which shows the slot in the carrier of the communication of the TDMA-TDD system between base station A1, A2-PHS terminal B1, B2 which concerns on this embodiment, and a super frame. It is a functional block diagram of base station A1 and base station A2 which concern on this embodiment. It is a schematic diagram which shows the call information management table of base station A1 and base station A2 which concerns on this embodiment. It is a sequence diagram which shows operation | movement of base station A1 and base station A2 which concern on this embodiment.

Explanation of symbols

A1, A2 ... base station, B1, B2 ... PHS terminal, C ... dedicated IP network, D ... internet exchange, E ... public internet network, 1,11 ... wireless communication unit, 2,12 ... storage unit, 3,13 ... Dedicated IP network communication I / F unit, 4, 14 ... Control unit

Claims (5)

A wireless communication system in which a plurality of base stations connected to a higher-level communication network and a plurality of mobile terminals communicate by a time division multiple access method,
When the first base station is communicating with the first mobile terminal using the first time slot of the first carrier, the first base station restricts the first time slot from the second mobile terminal. When requesting the establishment of a link specification to the first base station near you are not used to communicate the first time slot of the carrier (second base station) to explore, the second wherein the base station instead of its own as the first base station requests to communicate with the first mobile terminal,
The second base station receives the request, the second by the first of the first time slot of the carrier as well as changing the base station identification information in the communication of the mobile station, to that of the first base station A wireless communication system characterized by communicating with one mobile terminal. The first base station, when there are a plurality of the second base stations, requests a plurality of second base stations to measure the reception strength from the first mobile terminal, based on the measurement results of the plurality of second base stations, characterized in that requests to communicate with the first base station instead of its most reception strength strong second base station The wireless communication system according to claim 1.   The second base station receives communication data for transmission to the first mobile terminal from the higher-level communication network via the one base station, and further receives communication data received from the first mobile terminal in the first mobile station. The wireless communication system according to claim 1, wherein the wireless communication system transmits to a higher-level communication network via a base station.   The second base station receives the communication data to be transmitted to the first mobile terminal from the first base station after the first base station receives and stores the first base station from the upper communication network. Receiving communication data for transmission to the first mobile terminal without going through a base station from the higher-level communication network, and further transmitting communication data received from the first mobile terminal to the higher-level communication network The wireless communication system according to claim 1 or 2. A wireless communication system in which a plurality of base stations connected to a higher-level communication network and a plurality of mobile terminals communicate by a time division multiple access method,
When the first base station is communicating with the first mobile terminal using the first time slot of the first carrier, the first base station restricts the first time slot from the second mobile terminal. When requesting the establishment of a link specification to the first base station near you are not used to communicate the first time slot of the carrier (second base station) to explore, the second wherein the base station instead of its own as the first base station to request to communicate,
The second base station receives the request, the second by the first of the first time slot of the carrier as well as changing the base station identification information in the communication of the mobile station, to that of the first base station A communication method characterized by communicating with one portable terminal.

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