JP2014239433A - Method and device for adjusting trigger time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for adjusting the trigger time (TTT) for triggering to report the measurement.SOLUTION: When a mobile terminal (UE) is handed over, a target base station (TeNB) acquires 101 the handover auxiliary information of the UE, and determines 102 the handover weight of this time handover on the basis of the handover auxiliary information of the UE. A TeNB transmits a handover command to the UE, and weights 103 the handover command. The UE counts the handover on the basis of the handover weight in the handover command to obtain 104 the number of times of handover after update, and adjusts 105 the TTT on the basis of the number of times of handover after update.

Description

  The present invention relates to mobile communication technology, and more particularly to a method and apparatus for adjusting a trigger time for a mobile communication device to report a measurement report during a handover process.

  Cellular mobile phones have brought great convenience to people communication. The 3rd Generation Partnership Project (3GPP), as an important organization in the mobile communication field, has greatly promoted the progress of standardization of 3G mobile communication technology (3G). Currently, 3GPP has begun standardization of 3G Long Term Evolution (LTE) technology from the end of 2004 to address the challenges of broadband access technology and meet the increasing demand for new services. As a result, the spectrum efficiency is further improved, the performance of the cell edge user is improved, the system delay is reduced, and a higher speed access service is provided to a high speed mobile user. Improved LTE (LTE-A: LTE-Advanced) technology is further based on LTE technology, increasing the spectral bandwidth several times, doubling the data rate, and increasing the number of mobile users Provide services that are faster and have better performance.

  In each type of mobile communication system described above, management of user mobility in a connected state (CONNECTED) is particularly important. In order to realize management of user mobility in a connected state, a concept of handover is defined in a mobile communication system, and when a user in a connected state satisfies a certain condition, a hand is transferred from the current serving cell to another cell. It is allowed to exceed. If there is no handover, when the user leaves the serving cell, a new cell may be re-accessed after the call drop, which greatly affects the user's service satisfaction.

  In general, handover mainly includes four steps: measurement, measurement report, handover decision, and handover execution. Here, the measurement means that the user calculates the reference signal received power (RSRP), the reference signal received quality (RSRQ), or the cell signal strength between the user's serving cell and neighboring cells. Refers to measuring other signal strength parameters that can be displayed. The measurement report refers to reporting the handover measurement report to the serving base station when the handover measurement report reporting condition set by the measurement setting is satisfied. Handover determination means that the serving base station determines whether or not the user needs to perform handover based on the handover measurement report and selects a target base station. Handover execution mainly refers to a process in which a user disconnects from a serving base station and establishes a connection with a target base station.

  As can be seen from the above, in the above handover process, whether the handover measurement report reporting condition and the handover condition for determining whether or not to perform the handover can select the target base station with the best performance. It depends on how. Therefore, the setting of the report condition of the handover measurement report and the handover condition is very important.

  Currently, most of the reporting conditions of the handover measurement report used in the LTE system are the reporting conditions of the measurement report based on the event Event A3, that is, the mobile terminal (UE) has RSRP or RSRQ of a certain neighboring cell, If it is determined that the difference between the serving cell's RSRP or RSRQ is greater than the handover offset HO_margin (generally set to 3 dB) set in the serving cell, the timing is started and the above measurement reports are reported within a predetermined period of time. When all the reporting conditions are satisfied, the UE reports a handover measurement report to which the signal strength parameters of the serving cell and the neighboring cell are attached to the source base station. Thereafter, the source base station performs handover determination based on the signal strength parameters of the serving cell and the neighboring cell attached to the handover measurement report reported by the user. As a result of the handover determination, when the handover needs to be performed, the handover execution process is further completed. The predetermined period mentioned in the above process is also called a trigger time (TTT: Time To Trigger) that triggers reporting a measurement report.

  As will be appreciated by those skilled in the art, the time required for the entire handover process mainly includes the time required for TTT, handover decision and handover execution. Here, the time required for handover determination and handover execution is substantially fixed, but TTT is variable. Therefore, TTT is considered to be the main factor affecting the time required for the entire handover process. In the normal case, if the TTT is too long, the measurement report will be too slow, which greatly increases the handover failure rate when the UE moving speed is relatively fast, while if the TTT is too short, The ping-pong effect becomes serious due to frequent handover of UE.

  In the conventional LTE version 9 (Rel-9) standard, the UE adjusts the size of the TTT by mobility state estimation (MSE). Specifically, the UE estimates the moving speed of the own station based on the number of handovers within a certain period, and adjusts the size of the TTT based on the moving speed of the own station. In normal cases, the faster the UE moves, the smaller the TTT, thereby allowing the UE to access the target cell faster, which reduces the handover failure rate while the UE moves. The slower the speed, the larger the TTT, thereby making the handover conditions more severe and reducing the effect of the ping-pong effect. The above moving state estimation method is widely and effectively applied to a traditional homogeneous network (HomoNet: Homogeneous Network), but is not suitable for application to a heterogeneous network (HetNet: Heterogeneous Network).

  Heterogeneous network HetNet is a technology that significantly improves system throughput and overall network efficiency. A heterogeneous network forms different node types with the same coverage by placing at least one low power node (LPN) within the coverage area of one high power node (HPN). Refers to a heterogeneous system. Here, the HPN refers to a base station (for example, a macro cell base station) having a relatively high transmission power and a relatively large cover radius. The LPN is a base station having a relatively low transmission power and a relatively small cover radius (for example, a small cell base station, a micro cell base station, a milli micro cell base station, a remote radio head (RRH), This refers to relays.

  In HetNet, there is a possibility that a plurality of small cells covered by a small cell base station exist in a macro cell covered by one macro cell base station, so that the network density is greatly increased. In such a case, even if the UE moves at a relatively low speed in the macro cell, a plurality of handovers may occur. At this time, if the above-described movement state estimation method is applied and only the number of handovers is used as a basis for determining the speed of the UE, the UE's movement speed is severely overestimated. Is adjusted to be too low, which can cause a serious ping-pong effect.

  In order to solve the above problem, in an embodiment of the present invention, a method for adjusting a trigger time for reporting a measurement report is provided to achieve an accurate adjustment of TTT.

  A method for adjusting TTT according to an embodiment of the present invention is such that when a mobile terminal (UE) performs handover, a target base station (TeNB) acquires handover auxiliary information of the UE, and the TeNB This includes determining the handover weight of the current handover based on the handover auxiliary information, and the TeNB transmitting a handover command to the UE and attaching the handover weight to the handover command.

  Here, the handover assistance information of the UE includes handover history information of the UE.

  In the above method, the source base station (SeNB) stores the handover history information of the UE, and transmits the handover history information of the UE stored in the local station to the TeNB after the handover determination. In addition.

  In the above method, the mobility management entity (MME) stores the handover history information of the UE, and transmits the handover history information of the UE stored in the local station to the TeNB after handover determination. In addition.

  Here, the TeNB determines the handover weight of the current handover based on the handover assistance information of the UE, determines the first handover weight based on the handover history information of the UE, Including the determined first handover weight as the handover weight of the current handover.

  The UE handover assistance information includes target cell arrangement information, and the TeNB determines the handover weight of the current handover based on the UE handover assistance information based on the target cell arrangement information. , Determining a second handover weight, and setting the determined second handover weight as the handover weight of the current handover.

  The handover assistance information of the UE includes handover history information of the UE and arrangement information of a target cell, and the TeNB determines a handover weight of the current handover based on the handover assistance information of the UE. Determines the first handover weight based on the previous handover history information of the UE, determines the second handover weight based on the target cell arrangement information, and the first handover weight Including selecting a minimum value of the second handover weights as a handover weight of the current handover.

  The determination of the first handover weight based on the UE's handover history information is performed again after the UE has handed over from the cell A within a predetermined period based on the UE's handover history information. If it is determined that a handover to the cell A is to be performed, the first handover weight is set to 0; otherwise, the first handover weight is set to 1.

  Determining the second handover weight based on the target cell arrangement information includes determining the second handover weight based on the target cell size information.

  The UE handover assistance information further includes source cell location information, and the method has the same coverage of the source cell and the target cell based on the source cell location information and the target cell location information. Or if the source cell coverage is within the target cell coverage and if the source and target cell coverage are the same, or if the source cell coverage is the target cell Further comprising setting the second handover weight to 0.

  A method for adjusting TTT according to another embodiment of the present invention is a method in which a UE performs a handover count based on a handover weight attached to a handover command to obtain an updated number of handovers. , Adjusting the TTT based on the updated number of handovers.

  Performing a handover count based on a handover weight attached to a handover command includes that the UE performs a handover count according to a formula HO_count = HO_count + ω, where HO_count is Represents the recorded number of handovers, and ω represents the handover weight attached to the handover command.

  A method for adjusting TTT according to another embodiment of the present invention is as follows. The UE determines the handover weight of the current handover based on the handover auxiliary information of the local station, and the UE determines the handover weight based on the handover weight. The handover count is performed to obtain the updated number of handovers, and the UE adjusts the TTT based on the updated number of handovers.

  The handover assistance information includes handover history information stored in the UE itself, and the UE determines the handover weight of the current handover based on the handover assistance information of the own station. , Determining the first handover weight based on the handover history information stored in the own station, and setting the determined first handover weight as the handover weight of the current handover.

  The handover auxiliary information includes target cell arrangement information, and the UE determines the handover weight of the current handover based on the handover auxiliary information of the own station. And determining a second handover weight and setting the determined second handover weight as the handover weight of the current handover.

  The handover auxiliary information includes UE handover history information and target cell arrangement information provided from the target base station (TeNB), and the UE performs the current handover based on its own handover auxiliary information. Determining the handover weight of the UE is that the UE determines the first handover weight based on the handover history information stored in the local station, and the UE is the target cell arrangement information provided from the TeNB. , Determining a second handover weight, and selecting a minimum value of the first handover weight and the second handover weight as the handover weight of the current handover.

  The UE determines the first handover weight based on the handover history information stored in the own station, based on the handover history information of the UE, the UE from the cell A within a predetermined period. If it is determined that a handover to the cell A is to be performed again after the handover, the first handover weight is set to 0; otherwise, the first handover weight is set to 1.

  The UE determining the second handover weight based on the target cell arrangement information includes determining the second handover weight based on the target cell size information.

  The UE handover assistance information further includes source cell location information, and the method has the same coverage of the source cell and the target cell based on the source cell location information and the target cell location information. Or if the source cell coverage is within the target cell coverage and if the source and target cell coverage are the same, or if the source cell coverage is the target cell The second handover weight is further set to 0.

  The UE performing the handover count based on the handover weight includes that the UE performs the handover count according to the formula HO_count = HO_count + ω, where HO_count is the number of handovers recorded by the UE. Ω represents the handover weight of the current handover.

Method of adjusting the TTT according to still another embodiment of the present invention is to preset the initial value TTT ₀ of _{TTT, 0 <thre 1 <thre} 2 <... <thre n and _{1> factor 1> factor 2>} ... > Factor _n > 0 (n is a natural number), n threshold values thre ₁ , thre ₂ ,..., Thre _n and n coefficients factor ₁ , factor ₂ , corresponding to the n threshold values, ..., factor _n is set in advance, the UE performs a handover count, and each time a handover occurs, 1 is added to the handover counter value HO_count, and the UE is based on the handover assistance information of the UE. If n thresholds or the n coefficients are adjusted and thre _k <HO_count <thre _{k + 1} is satisfied, TTT = TTT ₀ × factor _k , and HO_count> thre _n is satisfied, TTT = TTT ₀ × factor _n (k <n and k is a natural number) ), Including that.

  A base station according to an embodiment of the present invention determines a handover weight of a current handover based on a handover assistance information acquisition module that obtains handover assistance information of a user terminal (UE) and the handover assistance information of the UE. And a handover command transmission module that transmits a handover command to the UE and assigns the handover weight to the handover command.

  The UE according to the embodiment of the present invention performs a handover count based on a handover weight receiving module that extracts a handover weight from a received handover command and a handover weight in the handover command, and after updating And a trigger time adjustment module for adjusting a trigger time (TTT) based on the updated number of handovers.

  Another base station according to an embodiment of the present invention includes a handover command transmission module that transmits a handover command to the UE and adds the location information of the local station to the handover command.

  Another UE according to an embodiment of the present invention performs a handover weight determination module for determining a handover weight of the current handover based on the handover auxiliary information of the own station, and a handover count based on the handover weight. A handover count module that obtains the updated number of handovers, and a trigger time adjustment module that adjusts the trigger time (TTT) based on the updated number of handovers.

Yet another UE according to an embodiment of the present invention, the initialization module for setting an initial value TTT ₀ triggers time (TTT) in _{advance, 0 <thre 1 <thre 2} <... <thre n and _1> factor 1> In _order to satisfy factor ₂ >...> factor _n > 0 (n is a natural number), n threshold values thre ₁ , thre ₂ ,..., thre _n and n factor factors ₁ corresponding to the n threshold values are provided. , Factor ₂ ,..., Factor _n in advance, a handover count module that performs a handover count and adds 1 to the handover counter value HO_count each time a handover occurs, and a hand of the local station If the threshold adjustment module for adjusting the n thresholds or the n coefficients based on over auxiliary information and thre _k <HO_count <thre _{k + 1} are satisfied, TTT = TTT ₀ × factor _k , HO_count> If thre _n is satisfied, the trigger time adjustment module is set such that TTT = TTT ₀ × factor _n (k <n and k is a natural number).

  As can be seen from the above embodiments, the above method adjusts the TTT based on the network location information and / or the handover history information of the UE to realize an accurate estimation of the moving speed of the UE. Effect of over-estimation of UE movement speed due to excessive cell density in environment and over-estimation of UE movement speed caused when UE performs round-trip handover at adjacent cell edge Can be solved. Based on the above causes, according to the above method, it is possible to estimate the moving speed of the UE relatively accurately and adjust an appropriate TTT, thereby improving the handover performance and lowering the handover failure rate. As a result, the influence of the ping-pong effect can be reduced.

3 is a flowchart of a TTT adjustment method according to an embodiment of the present invention. It is a figure which shows the concrete implementation method of step 102 in FIG. It is a flowchart of the adjustment method of TTT which concerns on another Example of this invention. It is a figure which shows the concrete implementation method of step 301 in FIG. It is a flowchart of the adjustment method of TTT which concerns on another Example of this invention. It is a figure which shows the internal structure of the base station which concerns on one Example of this invention. It is a figure which shows the internal structure of UE which concerns on one Example of this invention. It is a figure which shows the internal structure of the base station which concerns on another Example of this invention. It is a figure which shows the internal structure of UE which concerns on another Example of this invention. It is a figure which shows the internal structure of UE which concerns on another Example of this invention.

  In order to solve the above problem, the embodiment of the present invention provides a method for adjusting TTT, and more accurate movement state estimation can be realized by using UE's handover assistance information. The UE handover assistance information may include UE handover history information, source cell and / or target cell arrangement information, and the like. Here, the arrangement information includes one of information such as a cell position, a cell size, and a cell type, or any combination thereof.

  Hereinafter, various implementation methods of the present invention will be described in detail with reference to specific examples and drawings.

Example 1
FIG. 1 is a flowchart of a TTT adjustment method according to an embodiment of the present invention. As shown in FIG. 1, the method mainly includes a step 101 in which a target base station (TeNB) acquires handover auxiliary information of the UE when a mobile terminal (UE) performs handover, and a TeNB of the UE Step 102 for determining the handover weight of the current handover based on the handover auxiliary information, Step 103 for transmitting the handover command to the UE by the TeNB and attaching the above-mentioned handover weight to the handover command, Step 104 for performing handover count based on the handover weight in the handover command to obtain the updated number of handovers, and Step 105 for adjusting the TTT based on the updated number of handovers by the UE. Including.

  Hereinafter, the specific execution method of each step in FIG. 1 will be described in detail with reference to the drawings.

  As described above, the handover auxiliary information may include handover history information of the UE. The handover history information of the UE includes a list of serving eNBs after the establishment of the radio resource control (RRC) connection of the UE, a time when each eNB serves the UE, and the like.

  In actual application, the source base station (SeNB) stores the UE handover history information, and in step 101 above, the SeNB stores the UE handover history stored in itself after the handover determination. Information may be transmitted to the TeNB. Normally, when the SeNB determines a handover, it will transmit a handover request message to the TeNB. In the present embodiment, the SeNB transmits a handover request and also transmits UE handover history information to the TeNB, for example, via the X2 interface.

  Alternatively, as an alternative to the above scheme, another entity other than the SeNB in the network, for example, the mobility management entity (MME) stores the UE's handover history information, and after the handover determination in step 101 above, The MME may transmit the UE handover history information stored in its own station to the TeNB.

  Further, as described above, the handover assistance information may include source cell arrangement information and / or target cell arrangement information. Normally, after the network arrangement is completed, the arrangement information of each cell is stored in the core network, and each eNB obtains the arrangement information of the own station and its neighboring cells from the core network at once. Can do.

  Specifically, when only the UE handover history information is included in the handover auxiliary information in Step 102 above, the TeNB determines the first handover weight based on the UE handover history information. , The first handover weight may be the handover weight of the current handover, and when only the target cell arrangement information is included in the handover auxiliary information, the TeNB, based on the target cell arrangement information, The second handover weight may be determined and the second handover weight may be used as the handover weight of the current handover. The handover history information of the UE is also included in the handover auxiliary information and the target cell arrangement information. , The handover of the current handover according to the method shown in FIG. It may be determined only. Specifically, the method shown in FIG. 2 includes a step 1021 in which the TeNB determines the first handover weight based on the handover history information of the UE, and the TeNB determines the first handover weight based on the location information of the target cell. A step 1022 of determining a handover weight of 2; a step 1023 in which the TeNB selects a minimum value of the first handover weight and the second handover weight as a handover weight of the current handover; including.

  Here, a specific method for the TeNB to determine the first handover weight based on the UE handover history information is that the UE makes a round trip between neighboring cells based on the UE handover history information. If it is determined to be handed over, the first handover weight is set to 0; otherwise, the first handover weight is set to 1. For example, if it is determined based on the UE's handover history information that the UE will hand over from cell A within a predetermined period and then hand over to cell A again, the first handover weight is set to 0 Otherwise, the first handover weight may be set to 1. The predetermined period may be defined in advance by the eNB and the UE, and may be set by the eNB for the UE via RRC signaling. Its typical value may be, for example, 1 second.

  In addition, the method in which the TeNB determines the second handover weight based on the target cell arrangement information includes determining the second handover weight based on the target cell size information. Here, the size of the target cell can be represented by the diameter of the target cell or the transmission power of the TeNB. A specific method may include the following two methods.

  In the method 1, the second handover weight is determined based on the correspondence relationship between the preset cell size of the target cell and the second handover weight. In a normal case, the larger the cell where the TeNB is located, the smaller the corresponding second handover weight.

  Table 1 below shows an example of the correspondence relationship between the diameter of the cell where the TeNB is located and the second handover weight. In actual application, the second handover weight can be determined directly based on Table 1 below. It should be noted that only one example is provided in Table 1, but the specific values in the table below can be adaptively adjusted in actual application, and as an alternative the table below The cell diameter parameter in 1 may be replaced with the TeNB transmission power parameter.

  In Method 2, the second handover weight is calculated according to Equation 1 below. As a matter of explanation, when the second handover weight calculated by the following formula 1 is larger than 1, the second handover weight is set to 1.

[Formula 1]
ω2 = cell_size × γ

  Here, ω2 represents the second handover weight, cell_size represents the size of the target cell, specifically, can be represented by the diameter of the target cell or the transmission power of the TeNB, and γ The set coefficient is, for example, 0.002.

  If the handover auxiliary information further includes the location information of the source cell, in step 102, the second handover weight may be updated based on the location information of the source cell. Determine whether the coverage of the source cell and the target cell is the same based on the placement information of the source cell and the placement of the target cell, or the coverage of the source cell is within the coverage of the target cell If the coverage of the source cell and the target cell is the same, or if the coverage of the source cell is within the coverage of the target cell, the second handover weight is further set to 0 , Including that.

  In step 103 described above, in order to add a handover weight to the handover command, it is necessary to add a new information element (IE) to the handover command and mount the handover weight.

  In step 104 above, the UE performs a handover count according to Equation 2 below, and updates the number of handovers.

[Formula 2]
HO_count = HO_count + ω

  Here, HO_count represents the number of handovers recorded by the UE, and ω represents the handover weight of the current handover.

  As should be explained, in the present embodiment, the above-mentioned counter for performing the handover count calculates the number of handovers weighted within a predetermined period set by the system. Each time the predetermined period passes, the counter is cleared.

  In step 105 described above, the UE may adjust the TTT based on the updated number of handovers. A specific method may include the following two methods.

In Method 1, the initial value TTT _{0 of} TTT is satisfied so that 0 <thre ₁ <thre ₂ <... <thre _n and 1> factor ₁ > factor ₂ >...> Factor _n > 0 (n is a natural number). n threshold values thre ₁ , thre ₂ ,..., thre _n and n coefficients factor ₁ , factor ₂ ,..., factor _n corresponding to the n threshold _values are preset. When HO_count is larger than the kth threshold value and smaller than the k + 1th threshold value, that is, when thre _k <HO_count <thre _{k + 1} is satisfied, TTT = TTT ₀ × factor _k and HO_count If> thre _n is satisfied, TTT = TTT ₀ × factor _n (k <n and k is a natural number).

In one illustration of the invention, n may be equal to 2. That is, when HO_count is larger than a preset _first threshold thre _{1 and} smaller than a preset second threshold thre ₂ , the UE is considered to be a medium speed device, and TTT = TTT ₀ × factor _When HO_count is greater than the second threshold thre ₂ , it is considered that the UE is a high-speed device and TTT = TTT ₀ × factor ₂ is set. Here, factor ₁ > factor ₂ .

In Method 2, TTT is directly calculated by the following Equation 3. However, the condition TTT ≦ TTT ₀ needs to be satisfied.

  Here, δ is a preset coefficient larger than 0, and δ can be set by RRC signaling.

  Both of the above two methods can realize dynamic adjustment to the TTT, and satisfy that the larger the HO_count, the smaller the TTT.

  After this, during the next handover process, the UE can apply a dynamically adjusted TTT to trigger a measurement report.

(Example 2)
FIG. 3 shows a TTT adjustment method according to another embodiment of the present invention. As shown in FIG. 3, the method mainly includes the following steps.

  In step 301, the UE determines the weight of the current handover based on the handover assistance information of the local station.

  In step 302, the UE performs a handover count based on the handover weight to obtain the updated number of handovers. Here, the execution method of step 302 is the same as that of step 104 in the first embodiment, and the description thereof is omitted here.

  In step 303, the UE adjusts the TTT based on the updated number of handovers. Here, the execution method of step 303 is also the same as step 105 in the first embodiment, and the description thereof is omitted here.

  Hereinafter, the execution method of step 301 in FIG. 4 will be described in detail with reference to the drawings.

  As described above, the UE handover assistance information may include UE handover history information. In this embodiment, the UE's handover history information may be stored in the UE.

  Further, the handover assistance information may include target cell arrangement information provided from the TeNB. In a present Example, TeNB transmits the arrangement | positioning information of a target cell to UE with the handover command transmitted to UE. The UE extracts target cell arrangement information from the received handover command. In this step, in order to attach the target cell arrangement information to the handover command, it is necessary to add the new IE to the handover command and mount the target cell arrangement information.

  Specifically, when only the UE handover history information is included in the handover auxiliary information in the above step 301, the UE determines the first handover weight based on the UE handover history information, The first handover weight is set as the handover weight of the current handover. If only the target cell arrangement information is included in the handover auxiliary information, the UE determines the second handover weight based on the target cell arrangement information, and sets the second handover weight to the hand of the current handover. An overweight may be used.

  If the handover assistance information includes UE handover history information and target cell arrangement information, the handover weight of the current handover may be determined according to the method shown in FIG. The method shown in FIG. 4 includes a step 3011 in which the UE determines a first handover weight based on the handover history information stored in the own station, and the UE determines the first handover weight based on the location information of the target cell. A step 3012 of determining a second handover weight, and a step 3013 of selecting a minimum value of the first handover weight and the second handover weight as the handover weight of the current handover.

  Here, the execution method of step 3011 is the same as that of step 1021, and description thereof is omitted here.

  The execution method of step 3012 is similar to step 1022. Specifically, in step 3012, the second handover weight may be determined based on information on the cell size of the TeNB (eg, the diameter of the target cell or the transmission power of the TeNB). Can include the following two.

  In the method 1, the second handover weight is determined based on the correspondence between the preset target cell size and the second handover weight. In a normal case, the larger the target cell, the smaller its corresponding second handover weight. Table 1 above can be referred to for the correspondence between the diameter of the target cell and the second handover weight.

  In method 2, the second handover weight is calculated according to Equation 1 above. If the second handover weight calculated according to Equation 1 is greater than 1, the second handover weight is set to 1.

  Further, if the handover auxiliary information further includes source cell arrangement information, in step 301, the second handover weight may be updated based on the source cell arrangement information. Determines whether the coverage of the source cell and the target cell is the same based on the placement information of the source cell and the placement information of the target cell, or the coverage of the source cell is within the coverage of the target cell. If the coverage of the source cell and the target cell is the same, or if the coverage of the source cell is within the coverage of the target cell, the second handover weight is set to 0. Including.

  After this, during the next handover process, the UE can apply a dynamically adjusted TTT to trigger a measurement report.

  As can be seen from the above embodiment, on the other hand, the above method can sufficiently consider the handover history information of the UE when counting the number of handovers, and the UE can handover to the same cell within a certain period of time. Is repeatedly executed, it is possible to effectively solve the problem that the UE moving speed is overestimated, which is caused when these handovers are not counted, and the UE moves back and forth at the cell edge. On the other hand, the above method can sufficiently consider the location information of the source cell and the target cell when counting the number of handovers, thereby realizing an accurate estimation of the moving speed of the UE in a HetNet network environment. It is possible to effectively solve the problem that the UE moving speed is overestimated due to the cell density being too high in the HetNet network environment. Based on the above cause, according to the above method, the UE moving speed can be estimated relatively accurately and the appropriate TTT can be adjusted, thereby improving the handover performance and realizing a lower handover failure rate In addition, the influence of the ping-pong effect can be reduced.

Further, in order to more accurately estimate the moving state in the above method, when the system sets the initial value TTT ₀ of TTT, further consider the average inter-site distance (ISD) or network density. Can do. For example, if the average base station distance is relatively small or the network density is relatively high, a lower TTT initial value TTT ₀ is set, while the average base station distance is relatively large or the network density is relatively low Set a higher TTT initial value TTT ₀ .

Example 3
FIG. 5 shows a TTT adjustment method according to still another embodiment of the present invention. As shown in FIG. 5, the method mainly includes the following steps.

In step 501, an initial value TTT ₀ of TTT is preset.

As mentioned above, the average inter-base station distance or network density can be further taken into account when the system sets the initial TTT value TTT ₀ . For example, if the average base station distance is relatively small or the network density is relatively high, a lower TTT initial value TTT ₀ is set, while the average base station distance is relatively large or the network density is relatively low Set a higher TTT initial value TTT ₀ .

In step 502, n threshold values thre ₁ , n satisfying 0 <thre ₁ <thre ₂ <... <thre _n and 1> factor ₁ > factor ₂ >...> factor _n > 0 (n is a natural number). thre ₂ ,..., thre _n and n coefficients factor ₁ , factor ₂ ,..., factor _n corresponding to the n threshold _values are preset.

  In step 503, the UE performs a handover count, and adds 1 to the handover counter value HO_count each time a handover occurs.

  In step 504, the UE adjusts the n thresholds or the n coefficients based on the handover assistance information.

  In this step, the UE can adjust the above n thresholds based on the network location information in the handover auxiliary information, for example, network density information or the average distance between base stations, thereby increasing the network density or the average base station. The smaller the inter-station distance, the larger the n threshold values. Alternatively, the UE adjusts the above n threshold values based on the UE's historical handover information in the handover auxiliary information, for example, the UE moves between neighboring cells based on the UE's handover history information. If it is determined that the handover is to be made in a round trip (the UE tries to hand over to the cell A again after handing over from the cell A within a predetermined period), the above n threshold values are increased, for example, 1 is added. .

  As an alternative to the above scheme, in this step, the UE may adjust the n coefficients based on network location information in the handover auxiliary information, for example, network density information or average base station distance. Thus, the larger the network density or the smaller the average distance between base stations, the larger the value of the n coefficients. Alternatively, the UE may adjust the above n coefficients based on the UE's historical handover information in the handover auxiliary information. For example, based on the UE's handover history information, the UE When it is determined that handover is performed in a round trip between adjacent cells (within a predetermined period, the UE tries to hand over to cell A again after handing over from cell A), the values of the above n coefficients are To increase.

In step 505, if HO_count is larger than the kth threshold value and smaller than the k + 1th threshold value, that is, if thre _k <HO_count <thre _{k + 1} is satisfied, TTT = TTT ₀ × factor _k Then, if HO_count> thre _n is satisfied, TTT = TTT ₀ × factor _n (k <n and k is a natural number).

  As can be seen from the above embodiments, the above method can adjust the TTT based on network location information and / or UE hand-over history information, which results in relatively high network density, inter-base station distance. If the UE is relatively small or if it is handed over to and from neighboring cells, the rate at which the TTT is adjusted to be reduced is reduced, and an accurate estimation of the UE's moving speed is achieved, and the cell density in a HetNet network environment. The problem is that the UE's moving speed is overestimated due to the fact that it is too high, and the UE's moving speed is overestimated, which is caused when the UE is handed over to and from the neighboring cell edge, resulting in a low TTT. It is possible to effectively solve the problem of being adjusted too early. Based on the above causes, according to the above method, it is possible to estimate the moving speed of the UE relatively accurately and adjust an appropriate TTT, thereby improving the handover performance and realizing a lower handover failure rate. In addition, the influence of the ping-pong effect can be reduced.

  Corresponding to the method of the first embodiment, the embodiment of the present invention also provides a base station eNB and a user terminal UE that implement the method.

  FIG. 6 shows an internal configuration of the base station. As shown in FIG. 6, the base station is based on the handover auxiliary information acquisition module 601 for acquiring the handover auxiliary information of the UE, and the handover auxiliary information of the UE. A handover weight determining module 602 that determines a handover weight of the current handover, and a handover command transmitting module 603 that transmits a handover command to the UE and adds the above-described handover weight to the handover command.

  Here, the handover auxiliary information acquisition module 601 receives the UE handover history information from another entity (for example, MME) in the network for storing the SeNB or UE handover history information. It's okay.

  The handover auxiliary information acquisition module 601 may acquire source cell arrangement information and / or target cell arrangement information by the method of step 101.

  The handover weight determination module 602 may determine the handover weight of the current handover based on the handover auxiliary information by the method of step 102.

  The handover command transmission module 603 may add a handover weight to the handover command and transmit the handover command with the handover weight to the UE.

  FIG. 7 shows the internal configuration of the user terminal. As shown in FIG. 7, the user terminal includes a handover weight receiving module 701 that extracts a handover weight from the received handover command, and a handover command. A handover count module 702 that performs a handover count based on the attached handover weight and obtains the updated number of handovers; a trigger time adjustment module 703 that adjusts the TTT based on the updated number of handovers; ,including.

  Here, the handover count module 702 may perform the handover count by the method of step 104, and the trigger time adjustment module 703 adjusts the TTT by the method of step 105 in FIG. The description may be omitted here.

  Corresponding to the method of the second embodiment, the embodiment of the present invention also provides a base station eNB and a user terminal UE that implement the method.

  FIG. 8 shows the internal configuration of the base station. As shown in FIG. 8, the base station transmits a handover command to the UE, and adds the location information of the own station to the handover command. 801 is included.

  FIG. 9 shows an internal configuration of the user terminal. As shown in FIG. 9, the user terminal determines a handover weight for this time based on its own handover auxiliary information, a handover weight determination module 901, A handover count module 902 that performs a handover count based on the handover weight and obtains the updated number of handovers, and a trigger time adjustment module 903 that adjusts the TTT based on the updated number of handovers are included.

  Here, the handover weight determination module 901 may determine the handover weight of the current handover in step 301, and the handover count module 902 may determine the handover count by the method in step 302. The trigger time adjustment module 903 may adjust the TTT by the method of step 303, and the description thereof is omitted here.

  Corresponding to the method of the third embodiment, the embodiment of the present invention also provides a user terminal UE that realizes the method.

FIG. 10 shows an internal configuration of the user terminal. As shown in FIG. 10, the user terminal includes an initialization module 1001 that presets an initial value TTT ₀ of TTT, and 0 <thre ₁ <thre ₂ <. thre _n and 1> factor ₁ > factor ₂ >...> factor _n > 0 (n is a natural number), n threshold values thre ₁ , thre ₂ ,..., thre _n and the n threshold values A threshold setting module 1002 for presetting corresponding n coefficients factor ₁ , factor ₂ ,..., Factor _n , and a hand that performs a handover count and adds 1 to the handover counter value HO_count each time a handover occurs An overcount module 1003; a threshold adjustment module 1004 that adjusts the n thresholds or the n coefficients based on handover auxiliary information; Ri large, smaller than the k + 1 th threshold of which, that is, if the _{thre k <HO_count <thre k +} 1 is satisfied, then the _{TTT = TTT 0 × factor k,} HO_count> thre _{if n} is satisfied , TTT = TTT ₀ × factor _n (k <n and k is a natural number) trigger time adjustment module 1005.

  Here, for the specific processing of each module, each step in FIG. 5 can be referred to, and the description thereof is also omitted here.

  As described above, the method and apparatus of the present invention can adjust the TTT more accurately, thereby achieving better handover performance.

  As a matter of explanation, when the method according to the embodiment of the present invention is applied to HetNet, a better effect can be obtained, but the above method is not limited to being applied to HetNet. Can also be applied to the traditional HomoNet.

The above are only preferred embodiments of the present invention and do not limit the protection scope of the present invention. Various modifications, equivalent replacements, improvements and the like made within the spirit and principle of the present invention should all be included in the protection scope of the present invention.

Claims (26)

A method for adjusting a trigger time (TTT),
When the mobile terminal (UE) is handed over, the target base station (TeNB) obtains handover assistance information of the UE,
The TeNB determines the handover weight of the current handover based on the handover assistance information of the UE,
The TeNB sends a handover command to the UE and attaches the handover weight to the handover command.
A method comprising:   The method of claim 1, wherein the UE handover assistance information includes handover history information of the UE. The source base station (SeNB) stores the handover history information of the UE, and transmits the handover history information of the UE stored in the local station to the TeNB after the handover determination.
The method of claim 2 further comprising: The mobility management entity (MME) stores the handover history information of the UE, and transmits the handover history information of the UE stored in the local station to the TeNB after handover determination.
The method of claim 2 further comprising: The TeNB determines the handover weight of the current handover based on the UE's handover assistance information,
Determining a first handover weight based on the UE's handover history information, and using the determined first handover weight as the handover weight of the current handover.
The method according to claim 2. The UE handover assistance information includes target cell location information,
The TeNB determines the handover weight of the current handover based on the UE's handover assistance information,
Including determining a second handover weight based on the arrangement information of the target cell, and setting the determined second handover weight as the handover weight of the current handover.
The method according to claim 1. The UE handover assistance information includes the UE handover history information and target cell arrangement information,
The TeNB determines the handover weight of the current handover based on the UE's handover assistance information,
Determining a first handover weight based on the UE's handover history information;
Determining a second handover weight based on the target cell placement information;
Selecting a minimum value of the first handover weight and the second handover weight as the handover weight of the current handover,
The method according to claim 1. Determining a first handover weight based on the UE's handover history information,
Based on the UE's handover history information, if it is determined that the UE will hand over to cell A after handing over from cell A within a predetermined period, the first handover weight is set to 0 Otherwise, setting the first handover weight to 1
The method according to claim 5 or 7, characterized in that Determining the second handover weight based on the target cell location information is
Determining a second handover weight based on target cell size information,
The method according to claim 6 or 7, characterized in that The UE handover assistance information further includes source cell arrangement information,
The method determines whether the coverage of the source cell and the target cell is the same based on the placement information of the source cell and the placement information of the target cell, or the coverage of the source cell is the coverage of the target cell. If the coverage of the source cell and the target cell is the same, or if the coverage of the source cell is within the coverage of the target cell, the second handover weight is set to 0 Including further,
The method according to claim 6 or 7, characterized in that A method for adjusting a trigger time (TTT),
The UE performs a handover count based on the handover weight attached to the handover command, obtains the updated number of handovers,
The UE adjusts the TTT based on the updated number of handovers,
A method comprising: The UE performs the handover count based on the handover weight attached to the handover command,
The UE performs a handover count according to the formula HO_count = HO_count + ω, where
HO_count represents the number of handovers recorded at the UE, ω represents the handover weight attached to the handover command,
The method according to claim 11. A method for adjusting a trigger time (TTT),
UE determines the handover weight of the current handover based on the handover assistance information of its own station,
The UE performs a handover count based on the handover weight, obtains the updated number of handovers,
The UE adjusts the TTT based on the updated number of handovers,
A method comprising: The handover auxiliary information includes handover history information stored in the UE own station,
The UE determines the handover weight of the current handover based on the handover assistance information of its own station,
The UE determines a first handover weight based on the handover history information stored in the own station, and uses the determined first handover weight as the handover weight of the current handover. including,
The method according to claim 13. The handover assistance information includes target cell arrangement information,
The UE determines the handover weight of the current handover based on the handover assistance information of its own station,
The UE determines a second handover weight based on the TeNB arrangement information, and uses the determined second handover weight as the handover weight of the current handover.
The method according to claim 13. The handover auxiliary information includes UE handover history information and target cell arrangement information provided from a target base station (TeNB),
The UE determines the handover weight of the current handover based on the handover assistance information of its own station,
The UE determines a first handover weight based on the handover history information stored in the local station,
The UE determines the second handover weight based on the target cell location information provided from the TeNB,
Selecting a minimum value of the first handover weight and the second handover weight as the handover weight of the current handover,
The method according to claim 13. The UE determines the first handover weight based on the handover history information stored in the local station,
Based on the UE's handover history information, if it is determined that the UE will hand over to cell A after handing over from cell A within a predetermined period, the first handover weight is set to 0 Otherwise, setting the first handover weight to 1
17. A method according to claim 14 or 16, characterized in that The UE determines the second handover weight based on the location information of the target cell,
Determining a second handover weight based on target cell size information,
The method according to claim 15 or 16, characterized in that: The UE handover assistance information further includes source cell arrangement information,
The method determines whether the coverage of the source cell and the target cell is the same based on the placement information of the source cell and the placement information of the target cell, or the coverage of the source cell is the coverage of the target cell. And if the coverage of the source cell and the target cell is the same, or if the coverage of the source cell is within the coverage of the target cell, set the second handover weight to 0 Further including
The method according to claim 15 or 16, characterized in that: The UE performs the handover count based on the handover weight,
The UE performs a handover count according to the formula HO_count = HO_count + ω, where
HO_count represents the number of handovers recorded at the UE, ω represents the handover weight of the current handover,
The method according to claim 13. A method for adjusting a trigger time (TTT),
The initial value TTT ₀ of TTT is set in advance,
0 <thre ₁ <thre ₂ <... <thre _n and 1> factor ₁ > factor ₂ >...> factor _n > 0 (n is a natural number) n threshold values thre ₁ , thre ₂ ,. , thre _n and said n n coefficients factor _1, factor ₂ corresponding to the threshold, ..., set the factor _n in advance,
The UE performs a handover count, and every time a handover occurs, 1 is added to the handover counter value HO_count,
The UE adjusts the n thresholds or the n coefficients based on the UE handover assistance information,
When thre _k <HO_count <thre _{k + 1} is satisfied, TTT = TTT ₀ × factor _k , and when HO_count> thre _n is satisfied, TTT = TTT ₀ × factor _n (k <n And k is a natural number)
A method comprising: A base station,
A handover auxiliary information acquisition module for acquiring handover auxiliary information of a user terminal (UE);
A handover weight determination module for determining a handover weight of the current handover based on the handover assistance information of the UE;
A handover command transmission module for transmitting a handover command to the UE and attaching the handover weight to the handover command;
A base station comprising: A user terminal (UE),
A handover weight receiving module for extracting a handover weight from the received handover command;
A handover count module that performs a handover count based on the handover weight in the handover command and obtains the updated number of handovers;
A trigger time adjustment module that adjusts a trigger time (TTT) based on the number of handovers after the update;
A user terminal comprising: A base station,
A handover command transmission module for transmitting a handover command to the UE and attaching the location information of the local station to the handover command;
A base station comprising: A user terminal (UE),
A handover weight determination module for determining the handover weight of the current handover based on the handover auxiliary information of the own station;
A handover count module that performs a handover count based on the handover weight and obtains the updated number of handovers;
A trigger time adjustment module that adjusts the trigger time (TTT) based on the number of handovers after the update;
A user terminal comprising: A user terminal (UE),
An initialization module for presetting an initial value TTT ₀ of the trigger time (TTT);
0 <thre ₁ <thre ₂ <... <thre _n and 1> factor ₁ > factor ₂ >...> factor _n > 0 (n is a natural number) n threshold values thre ₁ , thre ₂ ,. , thre _n and said n coefficients factor ₁ which corresponds to n thresholds, factor _2, ..., and a threshold setting module for setting a factor _n in advance,
A handover count module that performs a handover count and adds 1 to the handover counter value HO_count each time a handover occurs;
A threshold adjustment module that adjusts the n thresholds or the n coefficients based on handover assistance information of the local station;
When thre _k <HO_count <thre _{k + 1} is satisfied, TTT = TTT ₀ × factor _k , and when HO_count> thre _n is satisfied, TTT = TTT ₀ × factor _n (k <n , And k is a natural number)
A user terminal comprising:

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