WO2012129740A1

WO2012129740A1 - Train-ground wireless communication system for rail transportation and handover method between base stations thereof

Info

Publication number: WO2012129740A1
Application number: PCT/CN2011/000750
Authority: WO
Inventors: 李廷军; 樊勇; 陈峙; 林辉; 何宗锐; 赵明华; 黄文峰
Original assignee: 上海磁浮交通发展有限公司; 电子科技大学
Priority date: 2011-03-25
Filing date: 2011-04-29
Publication date: 2012-10-04

Abstract

A train-ground wireless communication system for rail transportation is provided, and the system includes a vehicle part and a ground part between which wireless communication is implemented; the ground part includes a Mobile service Switching Centre (MSC) and a plurality of zone Base Station Controllers (BSCs); every zone BSC includes a Base Station Controller for loop A (BSC A) and a Base Station Controller for loop B (BSC B), and the zones of the BSC A and the BSC B are arranged mutual-redundantly; the BSC A controls a plurality of fixed Base Transceiver Stations for loop A (BTSs A) via an optical network, and the BSC B controls a plurality of fixed Base Transceiver Stations for loop B (BTSs B) via the optical network; the BTS As and BTS Bs are arranged in a interleaving comb-shape. A handover method between BTSs controlled by BSCs for the same loop is disclosed in the present invention as well. With the present invention, the accuracy of the handover between base stations is improved, and the unnecessary handover is avoided.

Description

Vehicle-ground wireless communication system for rail transit and handover method between base stations thereof

The present invention relates to a vehicle-to-ground wireless communication system for rail transit and a method of switching between base stations. Background technique

With the development of social economy, human needs for high-speed traffic are becoming more and more urgent. Rail transit is one of the most important transportation systems. High-speed rail transit is a complex, large system that includes subsystems such as vehicles, traction power, operational controls, $-line and vehicle-to-ground communications. The vehicle-to-ground communication system provides a channel for large-scale data exchange between other subsystems and is an important part of high-speed rail transportation. There are several ways to implement the car-to-ground communication system, mainly including laying cable loops along the track, leaking cables, cracking waveguides, and installing radio base stations. At present, communication systems based on the 802.11X series of wireless local area networks and based on GSM technical standards are commonly used, and systems based on the GSM technical standards are relatively mature.

GSM-R (Global System for Mobile Communication Railway) has been used in high-speed rail operations. GSM-R services include GSM services, voice dispatch services, railway basic services and railway applications.

In the GSM-R system, the base station handover method is basically the same as the GSM base station handover, mainly to monitor the communication signal level and quality to initiate the base station handover operation. The entire handover process of GSM-R is coordinated by MS (mobile station), BTS (base transceiver station), BSC (base station controller) and MSC (mobile service switching center). In the PSTN (Public Switched Telephone Network), ISDN (Integrated Services Digital Network), PSDN (Packet Switched Data Network) and signaling systems, the MSC controls the corresponding NSS (Network Subsystem) for data exchange. Its related network structure is shown in Figure 1. The handover with the base station in the BSC is the most handover in the GSM-R system.

In the GSM-R system, the base station handover process can be easily divided into four phases: measurement, triggering, selection, and execution. The MS is responsible for measuring the downlink performance of the radio subsystem and the strength of the signal received from the surrounding base stations; the BTS is responsible for monitoring the uplink reception level and quality of each served mobile station. BTS confirmation Send it and the results of the mobile station measurements to the BSC. The initial decision was made by the BSC. For information sent from other BSS (Base Station Subsystem) and MSC, the decision of the measurement result is done by the MSC.

1) Measurement process

In the GSM-R system, the decision of the BSC or MSC to handover depends on the periodic report of the downlink measurement sent by the mobile station to the network, and the report of the base station to the uplink measurement, both measurement reports will be simultaneously Transfer to the BSC or MSC for decision. The measurement report sent by the MS contains the measurement results of the reception performance from the current base station and the neighboring base station.

In the downlink direction of the SACCH channel (slow associated control channel), the BTS transmits a system message including the base station and neighbor base station parameter setting status ' to the MS mobile station. According to the information provided by the system, the MS mobile station reports to the network the reception level and signal quality and timing advance (TA) of the base station, power control, and whether DTX (discontinuous transmission) is used, in addition to the information provided by the system. It is also necessary to pre-synchronize the switching neighbor base stations defined by the system and measure the reception level of their BCCH (Broadcast Control Channel) frequency points. In the uplink direction, the MS mobile station reports the signal status of the neighboring base station and the neighboring base station in the neighboring base station list measured in the measurement period to the system through the SACCH channel. The system will make a handover decision based on these conditions.

2) Trigger process,

The base station sends the collected uplink and downlink measurement reports to the BSC, as shown in Figure 2.

The BSS (Base Station Subsystem) processes the base station's measurement report for the uplink and the mobile station's measurement report for the downlink and performs a base station handover decision. The BSS performs an arithmetic average and a weighted average of the measured sample values of the signal level, signal quality, and timing advance obtained according to the associated parameter settings.

Within each SACCH multiframe, the BSS compares the preprocessed measurement with its associated threshold to determine whether to trigger the handover process. The reasons for triggering the switching process mainly include:

A quality switch,

If the current link signal quality is greater than the signal quality switching threshold, quality switching can be performed; B-level switching,

If the current received signal level is less than the signal level switching threshold, level switching can be performed; C distance switching,

If the distance between the mobile station and the base station is greater than the maximum allowable distance threshold, the distance can be executed. Switch.

3) Selection process

The GSM-R selection process is much simpler than GSM. The mobile station and the base station eliminate the measurement of several neighbor base stations and do not have to queue and select a large number of qualified base stations. If the target base station designation method is adopted, the BSC or the MSC only needs to send the corresponding parameters of the designated target base station from the pre-stored neighbor base station table and wait for the handover permission to be transmitted. If the target base station designation method is not used, the BSC or MSC needs to be queued according to the measurement results of two neighboring base stations, and the first one will be used as the target base station.

4) Implementation process

The main task of the handover execution process is to allocate and activate a new channel to switch the MS mobile station's call to the new channel. The signaling flow between base stations in the BSC is shown in Figure 3.

The BSC performs handover according to the measurement report decision, and after triggering the handover, sends a channel activation message to the target base station, and requests a traffic channel (TCH) to prepare for receiving handover. If the target base station has an idle traffic channel, TCft will send back to the BSC (Channel activation). Ack) message. The BSC sends a (Handover command) message to the old BTS, including parameters such as the frequency, time slot, and transmit power of the new channel. The BTS sends the parameters to the MS.

The MS adjusts the frequency to the new channel, and sends a handover access burst to the new channel. After receiving the new BTS, the TA value is sent back to the MS MS to send the handover complete message to the BSC through the new BTS. The BSC then requests the old BTS to release the channel.

By describing the base station handover procedure in the above conventional GSM-R mobile communication system, the base station handover fundamentally solves two problems: the determination of the handover target base station and the trigger timing of the handover (ie, when to switch).

The determination of the target base station is generally adopted in the neighboring base station list mode, and the BSC selects the optimal base station as the target base station according to the neighbor base station list in the process of handover;

The traditional method of triggering handover is to compare the received signal level and signal quality of the neighboring base station and the current base station with the switching threshold and the lag margin. A switching method based on signal strength, distance, signal-to-noise ratio, bit error rate, system load, and combinations thereof has emerged. These methods are based on an ideal physical platform, ie without regard to the reliability of the actual wireless channel.

In fact, due to the complexity, variety, and openness of the wireless communication environment, it is impossible to use A precise single mathematical model to represent the wireless transmission link. For example, the strength of the signal, the size of the interference, etc., represent a fuzzy concept, and it is difficult to achieve high-precision real-time measurement, which is easy to generate erroneous handover decisions. In particular, when the mobile station is just at the junction of two base stations, it will frequently switch, that is, "ping-pong effect", which will be very disadvantageous for the communication of trains running at speeds of up to 500 km/h. Disclosure of invention

The invention provides a vehicle-to-ground wireless communication system for rail transit and a method for switching between the base stations, which does not need to monitor the receiving level, the signal quality and the timing advance, but uses the train running direction and the position parameter to perform base station switching.

In order to achieve the above object, the present invention provides a vehicle-to-vehicle wireless communication system for rail transit, which system includes an in-vehicle portion and a ground portion, and wireless communication is performed between the in-vehicle portion and the ground portion.

The in-vehicle portion includes a head moving station respectively provided at the front of the vehicle, a rear mobile station provided at the rear of the vehicle, and an in-vehicle mobile base station controller that connects the front mobile station and the rear mobile station.

The vehicle mobile base station controller has an external interface for accessing data of the vehicle equipment. The in-vehicle mobile base station controller includes mutually redundant A-ring controllers and B-ring controllers for controlling the head mobile station and the tail mobile station, respectively.

The front mobile station and the rear mobile station are respectively provided with antennas, and the distance between the front and the rear antenna is between 25 and 200 meters.

The ground part comprises a mobile service switching center and a plurality of partitioned base station controllers, wherein the mobile service switching center and the plurality of partitioned base station controllers have external interfaces, and the plurality of partitioned base station controllers are connected to the mobile services switching center by running the control core network. .

Each of the partitioned base station controllers includes an A-ring base station controller and a B-ring base station controller, and the A-ring base station controller and the B-ring base station controller area are mutually redundant.

The A-ring base station controller controls a plurality of A-ring fixed base stations through a fiber-optic network, and the B-ring base station controller controls a plurality of B-ring fixed base stations through a fiber-optic network.

The A-ring fixed base station and the B-ring fixed base station are arranged in an interlaced comb arrangement.

The interval between the adjacent A-ring fixed base station and the B-ring fixed base station is generally less than 1000 m, and the overlapping coverage area of the adjacent fixed base station in the same ring is generally greater than 50 m, and the fixed base station is blind (the base station) Cannot be covered, covered by neighboring base stations) The length is about 40m.

The present invention further provides a handover method between fixed base stations controlled by the same ring base station controller. The handover method between the A-ring fixed base stations and the train length is smaller than the fixed base station blind zone length. The handover method includes the following steps:

Step 1. The in-vehicle mobile base station controller collects the train positioning data sent by the positioning system on the train, and transmits the data to the A-ring base station controller.

Step 2: The A-ring base station controller compares the received train positioning data with the base station handover position parameter to determine whether the train has entered the base station handover preparation area in the overlapping coverage area of the current A-ring fixed base station and the next A-ring fixed base station. 1 (The position between the beginning of the overlapping coverage area and the beginning of the blind area), if yes, go to step 3.

Step 3: The A-ring base station controller reads the operating parameters of the next A-ring fixed base station and the standby parameters of the current A-ring fixed base station from the working parameter table of the base station, so that the transmitting and receiving modules of the A-ring base station controller enter the base station handover. status.

Step 4: The partition base station controller determines whether the train passes the blind zone of the B-ring fixed base station located between the current fixed ring base station of the A ring and the fixed base station of the next A ring, and passes the position 2 just passing the blind zone, and if yes, steps are performed. 5.

Step 5: The fixed base station switches, the A-ring base station controller releases the channel of the current fixed-base station of the A-ring through the base station control channel of the optical network, opens the channel of the fixed base station of the next A-ring, and the mobile station and the vehicle of the train at the next communication The tail mobile station communicates with the next A-ring fixed base station.

Step 6: The partitioning base station controller determines whether the base station handover is successful. If successful, the process returns to step 1. If the failure occurs, the mobile service switching center reports that the next A-ring fixed base station is faulty.

Under normal circumstances, the location where the base station handover is successful should be before the location 3 (the location where the overlapping coverage area is about to end) in the overlapping coverage area of the adjacent base station.

If the handover fails, the vehicle-to-ground communication at this time is not interrupted, and the B-ring fixed base station is responsible for the vehicle-ground information exchange.

The method of switching between the B-ring fixed base stations is the same as the method of switching between the A-ring fixed base stations. The method is also applicable to base station handover where the length of the train is greater than the length of the dead zone of the base station, and is also applicable to the distribution of the single-ring base station.

The invention can effectively improve the accuracy of handover of the base station, reduce unnecessary handover, enhance the reliability of data transmission of the wireless communication, save the cost of the base station equipment, reduce the operation cost, and help A new description of the wireless coverage method, enriching the content of the wireless network solution

1 is a schematic diagram of a network structure of a GSM-R system of the prior art;

2 is a schematic diagram of a channel monitoring result reporting process in a GSM-R system of the prior art; FIG. 3 is a schematic diagram of a base station handover procedure in a GSM-R system of the prior art;

4 is a schematic structural view of a vehicle-mounted portion of a vehicle-to-ground wireless communication system for rail transit provided by the present invention;

Figure 5 is a block diagram showing the structure of a ground portion of a vehicle-to-ground wireless communication system for rail transit provided by the present invention;

6 is a schematic diagram of transmission of train positioning information for a handover method between fixed base stations controlled by the same ring base station controller according to the present invention;

7 is a schematic diagram of a base station handover before handover of a fixed base station controlled by the same ring base station controller according to the present invention;

FIG. 8 is a schematic diagram of a base station handover after a handover method between fixed base stations controlled by the same ring base station controller according to the present invention. The best way to implement the invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be specifically described with reference to FIGS. 4 to 8.

The present invention provides a vehicle-to-vehicle wireless communication system for rail transit, the system comprising a vehicle-mounted portion and a ground portion, wherein the vehicle-mounted portion and the ground portion communicate wirelessly.

As shown in FIG. 4, the vehicle-mounted portion includes a mobile station MS-A respectively disposed at the front of the vehicle, a mobile station MS_B disposed at the rear of the vehicle, and a vehicle connected to the front mobile station MS-A and the rear mobile station MS-B. Mobile base station controller MBSC:. The vehicle mobile base station controller MBSC has an external interface for accessing data of the vehicle equipment. The in-vehicle mobile base station controller MBSC includes mutually redundant A-ring controller MBSC A and B-ring controller MBSC B, respectively controlling the head mobile station MS-A and the rear mobile station MS-B. The front mobile station MS-A and the rear mobile station MS-B are respectively provided with antennas, and the distance between the front and the rear antenna is between 25 and 200 meters.

As shown in FIG. 5, the terrestrial part includes a mobile services switching center MSC and a plurality of partitioned base station controllers BSC, the mobile services switching center MSC and a plurality of partitioned base station controllers BSC. With an external interface, several partitioned base station controllers BSC are connected to the mobile services switching center MSC through the operational control core network (WAN #1, WAN #2).

Each of the partitioned base station controllers BSC includes an A-ring base station controller BSC A and a B-ring base station controller BSC B, and an A-ring base station controller BSC A and a B-ring base station controller BSC B-area are mutually redundant.

The A-ring base station controller BSC A controls a plurality of A-ring fixed base stations BTS A through a fiber-optic network, and the B-ring base station controller BSC B controls a plurality of B-ring fixed base stations BTS B through a fiber-optic network. The A-ring fixed base station BTS A and the B-ring fixed base station BTS B are interlaced in a comb-like arrangement on the track side. The interval between the adjacent A-ring fixed base station BTS A and the B-ring fixed base station BTS B is generally less than 1000 m, and the overlapping coverage area of the adjacent fixed base station in the same ring is generally greater than 50 m, and the fixed base station is blind (the base station cannot cover, The adjacent base station covers) the length is about 40m.

When a train enters the coverage area of another base station BTS from a base station BTS coverage area managed by the same sub-base station controller BSC, it is necessary to switch the communication base station in order to ensure uninterrupted communication.

The present invention provides a handover method between fixed base stations suitable for control by the same ring base station controller.

The process of the base station switching method (similar to the B-ring fixed base station) is described by taking the case where the A-ring is switched and the length of the car is smaller than the length of the dead zone of the fixed base station.

As wrong! The reference source was not found. As shown, the train is placed in the coverage area of the ground A ring fixed base station An, and is operated to the ground A ring fixed base station An+1. Due to the uniqueness of the railway environment, wireless coverage is mainly covered along the railway line. For each fixed base station, only two adjacent fixed base stations can be switched. For example, in this example, only the fixed base station An-1 and the fixed base station An+1 can be switched. After the train positioning parameter is used to determine the running direction of the train, It can be determined that the handover target base station of the train is an An+1 base station. When the train length is less than the length of the fixed base station blind zone, the base station switching position and interval are selected in the A-ring fixed base station overlapping coverage area after the train passes the B-ring fixed base station blind zone.

The invention provides a handover method between fixed base stations controlled by the same ring base station controller, which comprises the following steps:

Step 1. The vehicle mobile base station controller BSC collects the train positioning data transmitted by the positioning system on the train, and transmits the data to the A-ring base station controller BSC A. (As shown in Figure 6)

Step 2: The A-ring base station controller BSC A compares the received train positioning data with the base station handover position parameter to determine whether the train has entered the current A-ring fixed base station BTS An and the next A. The base station handover preparation area 1 in the overlapping coverage area of the ring fixed base station BTS An+1 (the position between the beginning of the overlapping coverage area and the beginning of the blind area), and if yes, step 3 is performed. (as shown in Figure 7)

Step 3: The A-ring base station controller BSC A reads the operating parameters of the next A-ring fixed base station BTS An+1 and the standby parameters of the current A-ring fixed base station BTS An from the operating parameter table of the base station, so that the A-ring base station controller The transmitting and receiving modules of BSC A enter the base station switching state.

Step 4: The partition base station controller BSC determines whether the train passes the blind zone of the B-ring fixed base station BTS Bn+1 located between the current A-ring fixed base station BTS An and the next A-ring fixed base station BTS An+1, and has passed Pass the position 2 of the dead zone, and if yes, go to step 5.

Step 5: The fixed base station switches, the A-ring base station controller BSC A releases the channel of the current A-ring fixed base station BTS An through the base station control channel of the optical network, and opens the channel of the next A-ring fixed base station BTS An+1, the next communication At the time, the head mobile station MS_A and the rear mobile station MS-B of the train communicate with the next fixed-base station Ant+1 of the A-ring.

Step 6: The partitioned base station controller BSC determines whether the base station handover is successful. If successful, returns to step 1. If the failure occurs, the mobile service switching center MSC reports that the next A-ring fixed base station BTS An+1 is faulty.

As wrong! The reference source was not found. As shown, under normal circumstances, the location where the base station handover is successful should be before the location 3 (the location where the overlapping coverage area is about to end) in the overlapping coverage area of the adjacent base station.

The determination of positions 1, 2 and 3· is related to the distribution of the field base stations, obtained through simulation calculations and actual tests. Firstly, the dead zone and overlapping coverage area of the base station are obtained through simulation calculation and actual test. Considering the environmental and other changing factors, the blind zone can be expanded by 20% and the overlapping coverage zone can be reduced. Position 1 is the position just entering the overlapping coverage area of the base station; position 2 is the position just emerging from the blind spot of the base station; and position 3 is the position just after the overlapping coverage area of the base station. '

In order to ensure uninterrupted communication when the fixed base station is switched, the location and interval of the base station handover are related to the overlapping coverage area length of the same base station, the length of the base station blind zone, the train running speed and the length of the train. If the length of the train is less than the length of the dead zone of the base station, the location of the fixed base station handover should avoid the dead zone of the base station. Otherwise, the communication failure of the A and B loops will occur when the base station fails to switch. When the length of the train is longer than the length of the dead zone of the base station, the train head/tail antenna will not enter the dead zone of the base station at the same time. When the base station fails to switch, the A/B ring will not be interrupted at the same time. Due to the redundancy, the vehicle communication signal will not be interrupted. , and so In this case, the handover of the fixed base station may not consider the influence of the dead zone of the base station. At this time, the handover process is the same as the process in which the train length is smaller than the base station blind zone length, except that the base station handover preparation, the start handover, and the handover end position are sequentially distributed in the base station overlap coverage area without being bound by the base station blind zone.

The present invention has an advantage in that a vehicle-to-ground wireless communication base station switching method for high-speed rail transit is proposed by using the train running direction and position parameters, which can improve the vehicle-to-ground communication performance of a train running at a speed of up to 500 km/h.

The invention patent is also applicable to base station handover where the length of the train is greater than the length of the dead zone of the base station, and is also applicable to the distribution of the single-ring base station.

Although the present invention has been described in detail by the preferred embodiments thereof, it should be understood that the foregoing description should not be construed as limiting. Various modifications and alterations of the present invention will be apparent to those skilled in the art. Therefore, the scope of the invention should be limited by the appended claims.

Claims

Rights request

A vehicle-to-vehicle wireless communication system for rail transit, characterized in that the system includes an in-vehicle portion and a ground portion, and wireless communication is performed between the in-vehicle portion and the ground portion;

The terrestrial portion includes a mobile services switching center (MSC) and a plurality of partitioned base station controllers (BSCs);

Each of the partitioned base station controllers (BSCs) includes an A-ring base station controller (BSC A) and a B-ring base station controller (BSC B), an A-ring base station controller (BSC A), and a B-ring base station controller (BSC). B) The zones are mutually redundant;

The A-ring base station controller (BSC A) controls a number of A-ring fixed base stations (BTS A) through a fiber-optic network, and the B-ring base station controller (BSC B) controls a number of B-ring fixed base stations (BTS B) through a fiber-optic network. );

The A-ring fixed base station (BTS A) and the B-ring fixed base station (BTS B) are arranged in an interlaced comb arrangement.

2. The vehicle-to-vehicle wireless communication system for rail transit according to claim 1, wherein said vehicle-mounted portion includes a front mobile station (MS-A) respectively disposed at a front end of the vehicle and a vehicle disposed at the rear of the vehicle. Tail mobile station (MS-B), and connected head mobile station (MS-A) and rear mobile station

(MS-B) Vehicle Mobile Base Station Controller (MBSC).

3. The vehicle-to-vehicle wireless communication system for rail transit according to claim 2, wherein said in-vehicle mobile base station controller (MBSC) has an external interface for accessing data of the in-vehicle device.

4. The vehicle-to-vehicle wireless communication system for rail transit according to claim 3, wherein said in-vehicle mobile base station controller (MBSC) comprises mutually redundant A-ring controllers (MBSC A) and The B-ring controller (MBSC B) controls the head mobile station (MS-A) and the rear mobile station (MS-B), respectively.

5. The vehicle-to-vehicle wireless communication system for rail transit according to claim 2, wherein the front mobile station (MS-A) and the rear mobile station (MS-B) are respectively provided with antennas .

6. The vehicle-to-vehicle wireless communication system for rail transit according to claim 5, wherein the front and rear antennas are between 25 and 200 meters apart.

7. The vehicle-to-vehicle wireless communication system for rail transit according to claim 1, wherein said mobile services switching center (MSC) and a plurality of partitioned base station controllers (BSCs) have external interfaces, and a plurality of partitioned base stations The controller (BSC) is connected to the mobile services switching center (MSC) through the operational control core network.

8. The vehicle-to-ground wireless communication system for rail transit according to claim 1, wherein an interval between adjacent A-ring fixed base stations (BTS A) and B-ring fixed base stations (BTS B) is less than 1000 m The length of the overlapping coverage area of the adjacent fixed base station in the same ring is greater than 50 m, and the length of the fixed base station blind zone is 40 m.

9. A method for switching between fixed base stations controlled by the same ring base station controller, taking an example of switching between A-ring fixed base stations and a train length smaller than a fixed base station dead zone length, wherein the handover method comprises the following steps:

Step 1. The in-vehicle mobile base station controller (MBSC) collects the train positioning data sent by the positioning system on the train, and transmits the data to the A-ring base station controller (BSC A);

Step 2: The A-ring base station controller (BSC A) compares the received train positioning data with the base station handover position parameter to determine whether the train has entered the current A-ring fixed base station (BTS An) and the next A-ring fixed base station (BTS). An +1 overlap coverage area of the base station switching preparation area 1, and if so, step 3;

Step 3: The A-ring base station controller (BSC A) reads the operating parameters of the next base station (BTS An+1) and the standby parameters of the current base station (BTS An) from the operating parameter table of the base station, so that the A-ring base station controller The transmitting and receiving module of (BSC A) enters the base station switching state;

Step 4: The partition base station controller (BSC) determines whether the train passes the B-ring solid between the current fixed-base station (BTS An) and the next fixed-base station (BTS An+1). a dead zone of the base station (BTSBn+1), and passed the position 2 just passed through the blind zone, and if so, step 5;

Step 5: The fixed base station handover, the A-ring base station controller (BSCA) releases the channel of the current A-ring fixed base station (BTSAn) through the base station control channel of the optical network, and opens the channel of the next A-ring fixed base station (BTSAn+1). In the case of secondary communication, the head mobile station (MS-A) and the rear mobile station (MS-B) of the train communicate with the next fixed-base station (BTSAn+1) of the A-ring; Step 6. The base station controller (BSC) judges If the base station handover is successful, if it is successful, it returns to step 1; if it fails, it reports the failure of the next A-ring fixed base station (BTSAn+1) of the mobile services switching center (MSC);

The method of switching between the B-rings and the fixed base stations is the same as the method of switching between the A-ring fixed base stations. The method for switching between fixed base stations controlled by the same ring base station controller according to claim 9, wherein the method is also applicable to base station handover where the train length is greater than the base station blind zone length, and is also applicable to the single ring base station distribution. .