WO2006089456A1

WO2006089456A1 - A method of mobile terminal autonomous handoff

Info

Publication number: WO2006089456A1
Application number: PCT/CN2005/000217
Authority: WO
Inventors: Xuemin Liu; Huiying Fang; Wanshuai Zhang
Original assignee: Zte Corporation
Priority date: 2005-02-23
Filing date: 2005-02-23
Publication date: 2006-08-31
Also published as: CN101084692A; CN100551121C

Abstract

A method of mobile terminal autonomous handoff includes: determining a dispatch area; building channel resource of all adjacent cells in said dispatch area, and normally transmitting and receiving signals in calling procedure; transmitting channel resource of adjacent cells in forward channel; mobile terminal obtaining forward pilot energy and channel resource configuration information of adjacent cells from forward channel; mobile terminal measuring forward pilot energy and comparing it with handoff threshold, and when forward pilot energy meets the conditions of soft handoff , performing soft handoff; when forward pilot energy meets the conditions of hard handoff , performing operation steps of hard handoff etc . The present invention does not need to exchange signaling in advance between mobile terminal and base station and then obtain corresponding resource of adjacent cells in order to realize allocation of channel resource, but enable mobile terminal to directly obtain each pilot parameter of adjacent cells through base station issuing channel resource of all adjacent cells in the form of broadcast in dispatch area, and adjust and update its activate pilot set and pilot set of adjacent cells based on quality state of itself current received signals, consequently mobile terminal realizes autonomous handoff.

Description

Mobile terminal cross-region autonomous switching method

Technical field

The invention relates to a method for autonomous handover of a mobile terminal, in particular, in a mobile cellular communication system, a mobile terminal performs a signaling message broadcast according to a periodicity of a base station, and does not need to perform handover signaling interaction between a base station and a mobile terminal. The method of autonomous switching. Background technique

In the mobile cellular communication system, when the mobile terminal performs the handover, the first is to measure the energy information of the pilot signal of the different cells, and report the pilot energy measurement information of the cell exceeding the handover threshold to the base station, and perform handover resource allocation by the base station. And notifying the mobile terminal to establish corresponding channel resources, and finally implementing handover of the mobile terminal. FIG. 1 is a schematic diagram of handover. During the mobile terminal moving from cell B to cell A, soft handover occurs, and a voice channel is established with cell B and cell A. Usually, the handover process of a mobile terminal is as follows:

When the mobile terminal MS detects that a certain pilot strength in the adjacent pilot set exceeds the soft handover plus threshold T_ADD, the pilot strength measurement message PS is transmitted to the base station BS, and the pilot is moved to the candidate pilot set; Sending a handover indication message; the MS transfers the pilot to the active pilot set and sends a handover complete message.

When the mobile terminal MS detects that a certain pilot strength in the active pilot set is lower than the soft handover de-threshold DROP, the MS initiates a handover de-timer; if the handover-out timer expires, the pilot strength is still lower than T-DROP, The MS transmits the PSMM; the BS transmits a handover indication message; the MS moves the pilot from the active pilot set to the adjacent pilot set and transmits a handover complete message.

In the above handover process, signaling interaction between the base station and the mobile terminal is required, and since the signaling interaction process may be long, the handover may be unsuccessful or even dropped. For example, the signal of the original activated cell is very fast, and the quality of the forward link is already very good before the handover process is completed. Poor, not enough to maintain the link. Especially for CDMA mobile cellular systems (self-interference systems), because the adjacent cells are at the same frequency, the strong pilot in the neighboring area is a strong interference before the handover, and after switching, it can provide a high diversity gain, so it is desirable that the switching time is as short as possible. . Similarly, the weak pilot in the active set occupies more search capabilities of the mobile terminal, affecting the search speed of the strong pilot in the neighboring area, and the probability that the strong pilot interference in the neighboring area is more serious and the forward link is worse. Since the handover is added and removed, it is triggered by the mobile terminal. Therefore, if the mobile terminal can perform the handover autonomously, it does not need to perform signaling interaction with the base station, thereby greatly improving the handover speed, ensuring the link quality, and reducing the dropped call. Probability. In some special systems, such as a cluster system, multiple mobile terminals share the air channel resources in time, then, using autonomous handover, without the handover interaction signaling between the base station and the mobile terminal, the load of the air channel resources can be shared, preventing excessive Signaling collisions and channel congestion.

To this end, a method is disclosed in U.S. Patent No. 006 725 043 B2, which does not require signaling interaction to achieve autonomous switching of the mobile terminal. In this patent, when the mobile terminal receives a certain number of forward error frames, the transmission is turned off, and on the base station side, it is found that the received energy is less than a certain threshold (because the mobile terminal turns off the transmission), and the pilot measurement is reported according to the mobile terminal. Information such as messages, neighboring cells, dropped call history information, etc., determines that some neighboring base stations (called rescue base stations) establish resources to search for reverse signals of the mobile terminal. After the transmission is turned off for a period of time, the mobile terminal re-opens the transmission, and after the rescue base station captures the reverse signal of the mobile terminal, the mobile station transmits a signal in the forward direction to establish a link with the mobile terminal.

The foregoing method is directed to the case where the forward link is insufficient to maintain signal quality. At this time, the mobile terminal and the base station are basically unable to perform signaling interaction. For the handover success, determining the rescue base station is very critical. If the judgment is wrong, the link cannot be recovered. If there are too many rescue base stations specified, the resources are wasted. Moreover, the rescue base station establishes channel resources and the search takes time, which inevitably affects the user's feelings. If the time is too long, the user will hang up because there is no voice for a long time.

Under normal circumstances, if the forward signal can also maintain the link quality, the handover can be completed through signaling interaction. Only when the switching processing time is too long, and the forward link signal becomes very weak during processing, at this time, the autonomous switching method described in the patent prevents the call drop, actually only A remedy. It can be seen from this that the method disclosed in the above patent does not fundamentally eliminate the problem of system performance degradation due to handover delay. Therefore, the autonomous switching mode can be adopted at any time, thereby avoiding the long-term signaling interaction between the base station and the mobile terminal, and realizing fast switching in a true sense, which is very meaningful for improving voice quality and reducing call drop rate. . Summary of the invention

The purpose of the present invention is to prevent the communication quality from being degraded or dropped due to the excessive signaling interaction time during the handover process, and the autonomous handover of the mobile terminal cannot be fundamentally eliminated because of the handover delay. The system performance is degraded, and a method for autonomous handover of a mobile terminal is provided. The method can select a corresponding neighboring channel resource to implement an autonomous handover by using a handover decision and a mobile terminal sharing the same channel resource. Switch. To achieve the above object, the present invention adopts a method for autonomous handover of a mobile terminal, including the following steps: Step 1: Determine a scheduling area, where the scheduling area includes a plurality of geographically adjacent cells; Step 2: In the dispatching area, at the beginning of the call, the base station side establishes channel resources of all neighboring cells, and normally sends and receives signals during the call until the call is released;

Step 3: In each of the cells, the base station sends channel resources of neighboring cells on a forward channel.

Step 4: The mobile terminal acquires the pre-channel energy and the channel resource configuration information of the neighboring cell from the forward channel during the call and the mobile in the scheduling area. Step 5: The mobile terminal measures the front The frequency energy is compared, and compared with the switching threshold, when the front pilot energy meets the soft switching condition, the soft handover is performed; when the front pilot energy meets the hard handover condition, the hard handover is performed.

It can be seen from the foregoing technical solution that the present invention does not require signaling interaction between the mobile terminal and the base station, and then acquires corresponding resources in the neighboring area to implement channel resource allocation, but In the scheduling area, the base station broadcasts channel resources of all neighboring cells in a broadcast manner, so that the mobile terminal can directly acquire various resource parameters of the neighboring cell, and adjust and update the activated pilot set according to the quality status of the current received signal. The pilot set of the neighboring area realizes the autonomous switching of the area. The present invention is useful for some specific functions of a mobile communication system, such as a trunking communication system, to achieve autonomous switching of a mobile terminal. In a dispatching area of the trunking communication system (usually a plurality of cells adjacent to each other in a geographical location, the service range of the group call in the designated cluster system is provided, and the group call service is provided in the dispatching area, and not provided outside the dispatching area ), the mobile terminal shares the same channel resources to implement communication between all mobile terminals. Generally, in the scheduling area in which the mobile terminal is located, the channel resources of each neighboring cell are already established, and therefore, the channel resource allocation between the mobile terminal and the base station is not required. Therefore, as long as the mobile terminal can acquire the channel resource information of the neighboring cell, there is no need for the handover signaling interaction between the mobile terminal and the base station, and there is no need

The mobile terminal required by the US006725043B2 patent closes the transmission, determines the rescue base station, and the mobile terminal retransmission process. Hereinafter, the present invention will be further described in detail through a specific implementation process of a handover process of a mobile terminal in a trunking communication system and in conjunction with the accompanying drawings. DRAWINGS

Figure 1 Schematic diagram of the handover.

Figure 2 Mobile terminal autonomous handover process.

Figure 3 Autonomous soft handoff plus flow of the forward voice channel.

Figure 4 Autonomous soft handoff of the forward voice channel.

Figure 5 Autonomous hard handoff procedure for the signaling channel. detailed description

When the mobile terminal performs the autonomous handover, it mainly goes through the following steps:

Step 1: Determine a scheduling area that contains multiple geographically adjacent cells. In the trunking communication system, a scheduling area including a plurality of geographically adjacent cells is first defined, and the mobile terminals of the cluster are dispersed in a PTT group call in a fixed or mobile state within a range of the scheduling area.

Step 2: In the scheduling area, at the beginning of the call, the base station side establishes channel resources of all neighboring cells, and normally sends and receives signals during the call until the call is placed.

The corresponding channel resources are established, including a forward voice channel and a forward signaling channel, and a reverse signaling channel. Under the adjacent cells, all the mobile terminals of the listening user share the channel resources.

Step 3: In each cell, the base station transmits channel resources of the neighboring cell on the forward channel. The base station periodically transmits channel resource configuration information of the neighboring cell on the forward signaling channel. Since the neighboring cell lists of different neighboring cells are different, the mobile terminal can only implement hard handover on the forward signaling channel, and the forward voice On the channel, different neighboring areas send the same content, which can implement soft handover, thereby improving voice quality. On the reverse signaling channel, since all mobile terminals of the listening user share in the scheduling area, when adopting autonomous handover, the reverse signaling transmission can be reduced, and the load of the reverse shared signaling channel is also reduced. Reduce collisions and avoid signalling congestion. Therefore, for a system using a shared channel, the mobile terminal autonomously switches, not only can improve the switching speed, but also can reduce the signal collision on the shared channel.

The flow provided in FIG. 2 is a principle flow of the mobile terminal performing autonomous handoff. In the unit 201, the mobile terminal performs step 4: the mobile terminal acquires the foregoing from the forward channel during the call and move in the scheduling area. Pre-channel energy and channel resource configuration information of adjacent cells.

In unit 202, the mobile terminal performs step 5: the mobile terminal measures the pre-guided energy, and compares with the handover threshold, when the current pilot energy meets the soft handover condition, performs a soft handover, and the autonomous handover can be subdivided into a voice channel. Soft handoff, soft handoff plus; when the current pilot frequency energy meets the hard handoff condition, the hard handoff is performed. The hard handover of the handover is a hard handover of the signaling channel.

FIG. 3 to FIG. 5 respectively show specific operational procedures for the mobile terminal to perform the autonomous soft handover of the voice channel and the autonomous hard handover of the signaling channel by using the method provided by the present invention.

It needs to be clear that the active pilot set of the voice channel and the activation of the adjacent pilot set and signaling channel The pilot set and the neighbor pilot set are different. Since the voice channel supports soft handover, the signaling channel adopts a hard handover manner. Therefore, the activated pilot set of the voice channel may include multiple activated pilots, and the neighboring pilot set is a combination of all adjacent regions of the activated pilots. The active pilot set of the signaling channel has only one active pilot, and the neighbor pilot set can be either the neighbor pilot of the active pilot or the neighbor pilot set of the voice channel.

In the process of performing autonomous handover, the mobile terminal corresponds to the processes shown in FIG. 3, FIG. 4 and FIG. 5, respectively, and cyclically performs the above soft channel switching and signaling channel hard handover steps during the entire call.

In Fig. 3, the mobile terminal first performs soft handover of the voice channel, the complete process of which is as follows: From unit 301, the steps described in the following units are performed.

The unit 302 is configured to select a previous pilot frequency energy of the first neighboring cell (assumed to be D) and obtain channel resource configuration information.

Unit 303, obtaining the pre-guided energy S (t);

The unit 304 determines whether the condition of the handover is satisfied, that is, whether S (t) is greater than or equal to the soft handover threshold T-ADD, and if yes, enters the 305 unit, and determines whether the activated pilot number in the activated pilot set has reached the system setting. The upper limit (for example, the system sets the four-party soft handover, and the number of activated pilots reaches four). If the upper limit is not reached, the unit 306 and the unit 310 are transferred to the mobile terminal according to the identifier of the neighboring cell and the channel resource configuration information obtained in the unit 302. The corresponding channel resources are established, and the activated pilot set and the neighboring pilot set are updated to implement soft handover of the voice channel. S (t) is smaller than the soft handover threshold T-ADD, and the direct mega-transfer unit 311 selects the previous pilot frequency energy of the next adjacent cell. In the foregoing unit 305, if the activated pilot number reaches the upper limit, the weakest activated pilot mode is adopted, and the access terminal 307 is used, and the mobile terminal acquires the leading pilot energy P of the neighboring cell E that activates the pilot with the smallest pilot energy. t); unit 308: determining whether a difference S (t) - P (t) between the current pilot signal energy and the pilot energy of the smallest neighboring cell is greater than or equal to a preset threshold T_C0MP of the system If yes, proceed to unit 309 and unit 310, first release the channel resources of the smallest neighboring cell, and then perform a soft handover plus operation; if not, execute the steps in unit 311. If the difference between S (t) - P (t) is less than T_C0MP, jump directly to unit 311. Unit 311 determines if there are still no other neighboring cells for processing, if any, then proceeds to unit 312, the mobile terminal selects the next neighboring cell and returns to unit 303 for the neighboring cell; if not, enters the voice channel Soft switch (A in the figure), the flow is shown in Figure 4.

In Figure 4, unit 401, the mobile terminal selects the first active pilot in the active pilot set, and sets it to F; unit 402, obtains the energy Sf(t) of the activated pilot;

The unit 403 performs a handover decision. If the energy Sf (t) of the activated pilot is less than the soft handover threshold T_DROP, the process proceeds to the unit 406 to determine whether the previous time Sf (t) is greater than or equal to T_DROP. After the switch-off timer (element 407) is started, the unit 408 determines whether the switch-off timer expires. If so, after the switch-off timer is reset at unit 409, it is determined in unit 410 whether the activated pilot number is not less than 2, if Then, the channel resource corresponding to the first neighboring cell F is released in the unit 411, and the activated pilot set and the neighboring pilot set are updated, and then at the unit 412, it is determined whether there are other activated pilots in the activated pilot set. Then, in unit 413, the mobile terminal selects the next active pilot, and obtains the energy of the activated pilot for the activated pilot return unit 402, otherwise, the hard handover procedure of the signaling channel (B in the figure) .

In the above processing, when the decision result of the unit 403 is that the energy Sf (t) of the activated pilot is not less than T_DR0P, the process jumps to the unit 404, and determines whether the energy Sf (t) of the activated pilot is less than T at the previous moment. – DROP, if yes, the reset switch to timer (unit ⁴ 05) is required to go to unit 41 ² ; if not, jump directly to unit 412. When Sf(t) at the last moment in unit 406 is less than T-DROP, it is directly transferred to unit 408. In unit 408, if there is no timeout, then jump to unit " ^2. " In unit 410, if the number of activated pilots is not less than 2, then jump to unit 412.

When the energy of the pilot is activated for soft switching, two conditions need to be met, one is less than the switching threshold T-DROP, and the other is required to remain for a period of time. Therefore, it is necessary to determine at unit 408 whether the timer has expired. In addition, the mobile terminal must maintain at least one active pilot, and if so, the weak activated pilot can be removed by switching.

The hard handover process of the signaling channel is shown in FIG. 5. In the figure, unit 501 acquires an activated pilot (only There is a) energy set to P(t), and unit 502 selects the first neighboring cell to be set to G. The unit 503 acquires the leading pilot energy S _g (t) of the neighboring cell G. Since the decision of the hard handover is that the pilot cell energy of the neighboring cell exceeds the amount of the activated pilot energy, T-C0MPG is used as the difference. The decision of the unit 504 is: if the pilot energy difference obtained by S _g (t) - P (t) is not less than T_C0MPG, then the unit 50 ^{5 is obtained} , and the channel resource corresponding to the currently activated pilot is released first, and then the neighboring cell is established. The pilot energy corresponds to the channel resource of the neighboring cell G. In block 506, P (t) = S _g (t) is updated and the active pilot set is updated; at unit 507, new from the established channel resource The signaling channel acquires and maintains a list of new neighboring cells G and corresponding channel resource configuration information; at unit 508, a new neighboring pilot search list is set.

In unit 504, if the pilot energy difference obtained by Sg(t)-P(t) is less than T-COMPG, then jump to unit 509 to determine if there is still another neighbor cell, and if so, at unit 510. The next neighbor cell pilot is selected and returned to the unit 503, otherwise, the exit is ended. So far, the mobile autonomous handover process of the mobile terminal is completed, and starts from the next cycle, that is, starting from the unit 301 of FIG. 3, and enters a new measurement handover autonomous handover process.

In summary, by implementing the channel resources of each neighboring cell and transmitting the neighboring cell channel resource configuration of the mobile terminal to the mobile terminal on the forward channel, the mobile terminal can adopt the autonomous handover method. Speed up switching. For cluster systems, etc., the switching performance can be optimized, and the load of the shared channel and its collision probability can be reduced to better meet the specific performance requirements of the system.

Claims

Rights request

A method for autonomous handover of a mobile terminal, characterized in that it comprises the following steps: Step 1: Determine a scheduling area, the scheduling area includes a plurality of geographically adjacent cells; Step 2: In the scheduling In the area, at the beginning of the call, the base station side establishes channel resources of all neighboring cells, and normally sends and receives signals during the call until the call is released;

Step 3: In each of the cells, the base station sends channel resources of a neighboring cell on a forward channel.

Step 4: The mobile terminal obtains the pre-channel energy and channel resource configuration information of the neighboring cell from the forward channel during the call and the mobile in the scheduling area;

Step 5: The mobile terminal measures the front pilot frequency energy, and compares with the switching threshold. When the front pilot frequency energy satisfies the soft switching component, performing a soft handover; when the front pilot energy meets the hard When the condition is switched, a hard handoff is performed.

The method of claim 1, wherein the step 5 specifically includes:

Step 5a: The mobile terminal measures the front pilot frequency energy. When the front pilot frequency energy is greater than or equal to the soft handover plus threshold, the mobile terminal performs soft handover plus; the specific process of the soft handover is based on And determining, by the identifier of the neighboring cell and the channel resource configuration information obtained in step 4, a corresponding channel resource, and updating an active pilot set and a neighboring pilot set; Step 5b: the mobile terminal is activated The pilot set selects the activated pilot and acquires the activated pilot energy of the activated pilot. When the activated pilot energy is less than the soft handover threshold, the mobile terminal starts the handover to the timer, and the timer directly releases after the timer expires. Activating a channel resource corresponding to the pilot energy and updating its activated pilot set and the neighboring pilot set;

Step 5c: The mobile terminal acquires the energy of the currently activated pilot in the activated pilot set, and acquires the pre-guided energy of a neighboring cell in the neighboring pilot set to determine the energy of the currently activated pilot. Whether the difference from the pilot energy of the neighboring cell is greater than or equal to a preset reference And when the value is greater than or equal to, the channel resource corresponding to the currently activated pilot is released, and then the channel resource of the neighboring cell corresponding to the pilot energy of the neighboring cell is established, and the currently activated pilot is used. The energy is replaced by the pilot energy of the neighboring cell and the activated pilot set is updated, and a new neighbor list and corresponding channel resource configuration information are acquired and saved from the new signaling channel in the established channel resource; Setting a new neighbor pilot search list; when less than, determining whether there is another next neighbor cell, and if so, acquiring the previous pilot frequency energy of the next neighbor cell, returning to determine the activated pilot energy and Whether the difference of the front pilot frequency energy is greater than or equal to the operation performed by the preset reference value; if not, completing the handover hard handover once.

The method for autonomous handover of a mobile terminal according to claim 2, wherein: the step 5a further comprises the following specific steps: Step 5a-1, when the front pilot frequency energy is greater than or equal to soft When the threshold is added, it is determined whether the activated pilot number in the activated pilot set has reached the upper limit set by the system, and if not, the soft handover plus operation is performed; if it is reached, the following steps are continued; When the pilot energy is less than the soft switching plus threshold, jump to step 5a - 4;

Step 5a-2: The mobile terminal acquires pilot energy of an adjacent cell with the smallest pilot energy in the activated pilot set;

Step 5a-3: determining whether a difference between the current pilot signal energy and a pilot energy of the smallest neighboring cell is greater than or equal to a threshold value preset by the system, and if yes, releasing the minimum neighbor The channel resource of the cell is followed by the soft handover plus operation; if not, the following steps are continued;

Step 5a-4: Determine whether there are other neighboring cells. If yes, the mobile terminal returns to step 5a-1 for the next neighboring cell; if not, step 5b is performed.

The method for autonomous handover of a mobile terminal according to claim 2, wherein: the step 5b is specifically: Step 5b-1: The mobile terminal selects a first activated pilot in the activated pilot set and acquires energy of the activated pilot. When the energy of the activated pilot is less than the soft handover threshold, Determining whether the energy of the activated pilot is greater than or equal to the soft handover de-blocking threshold at the previous moment. If yes, the mobile terminal starts the handover de-timer and performs step 5b-2; if not, directly executes step 5b-2 When the energy of the activated pilot is not less than the soft handover de-threshold, determining whether the energy of the activated pilot is less than the soft handover de-threshold at the previous moment, and if yes, resetting the handover-out timer Then, step 5b-5 is performed; if not, step 5b-5 is directly executed; step 5b-2, determining whether the switch-off timer expires, and if so, resetting the switch-off timer and executing step 5b- 3; if not, directly perform steps 5b-5; step 5b-3, determine whether the number of activated pilots is not less than 2, if yes, perform step 5b-4; if not, perform steps 5b-5 ; Step 5b-4, straight And the activation pilot described in the releasing step 5b-1 corresponds to the channel resource of the neighboring cell and updates the activated pilot set and the neighboring pilot set;

Step 5b-5: Determine whether there are other activated pilots in the activated pilot set. If yes, the mobile terminal returns to step 5b-1 for the next activated pilot; if not, proceed to step 5c.