CN103313324B

CN103313324B - The object cell selection method of LTE system and eNB

Info

Publication number: CN103313324B
Application number: CN201210057349.XA
Authority: CN
Inventors: 姚燕玲
Original assignee: Potevio Institute of Technology Co Ltd
Current assignee: Potevio Institute of Technology Co Ltd
Priority date: 2012-03-06
Filing date: 2012-03-06
Publication date: 2016-02-03
Anticipated expiration: 2032-03-06
Also published as: CN103313324A

Abstract

The invention discloses a kind of object cell selection method of LTE system and can realize the eNB of the method, wherein said method comprises: step 1, acquisition adjacent cell Reference Signal Received Power RSRP and cell-of-origin RSRP; Step 2, adjacent cell adjacent cell RSRP and cell-of-origin RSRP difference being greater than the first threshold value are chosen as changeable adjacent cell; Step 3, acquisition adjacent cell resource status; Step 4, in described changeable adjacent cell, the adjacent cell judgement meeting resource status pre-conditioned by choose first according to RSRP order is from big to small Target cell.When the present invention selects switching target small area, the intensity of adjacent cell RSRP and cell-of-origin RSRP and the resource status of adjacent cell are carried out comprehensive consideration simultaneously, using large as far as possible for RSRP intensity and to meet resource status pre-conditioned and ensure that the adjacent cell of nonoverload is as switching cell simultaneously, thus avoid selected switching cell to be the generation of the adjacent cell situation of heavier loads, and then be conducive to the load balancing of LTE system, ensure the stable of LTE system.

Description

The object cell selection method of LTE system and eNB

Technical field

The present invention relates to mobile communication technology, the particularly system of selection of switching target small area in a kind of LTE (LongTermEvolution, Long Term Evolution) system.

Background technology

LTE technology is the evolution technology of 3G (3rd-generation, G mobile communication), and being a transition between 3G and 4G technology, is the global standards of 3.9G, and it improves and enhances the aerial access technology of 3G.The peak rate of descending 326Mbit/s and up 86Mbit/s can be provided under 20MHz spectral bandwidth.Improve the performance of Cell Edge User, improve cell capacity and reduce system delay.

For preventing cell load overweight, UE (UserEquipment, user terminal) needs to switch between cell-of-origin and adjacent cell, to ensure the load balancing of community.The task of load balancing is the unbalanced traffic carrying capacity in the multiple minizone of process, distributed by the traffic carrying capacity of balanced minizone, improve the utilance of Radio Resource, the QoS conversated is remained on a rational level, reduce cutting off rate, also help the capacity and performance that increase LTE system simultaneously.Usually, in LTE system, UE carries out switching process in minizone is divided into four steps: measure, report, adjudicate and perform.Measure: the measurement that the reference signal of the measurement configuration that the UE being in connection status issues according to cell-of-origin eNB (evolvedNodeB, evolved base station) to cell-of-origin and adjacent cell is correlated with.Report: measurement report is reported cell-of-origin eNB by UE.Judgement: according to the measurement result that UE reports, cell-of-origin eNB determines that UE is the need of switching.Perform: when cell-of-origin eNB determines that UE needs to switch, cell-of-origin eNB initiates handoff procedure to UE.

Cell-of-origin eNB initiates in handoff procedure, after cell-of-origin eNB sends handover request message to Target cell eNB, need the call access control receiving Target cell eNB, when the load of Target cell allows this UE to switch, Target cell eNB feeds back handover success message to cell-of-origin eNB just now, otherwise Target cell eNB, by the switching of this UE of refusal, returns switch failure information to cell-of-origin eNB.

In prior art, for the handoff procedure of above-mentioned UE in minizone, the switch decision of measurement report to eNB of UE has key effect, and the handover measurement defined in LTE standard and the respective standard of judgement are:

Reference Signal Received Power (RSRP): namely for the community needing to consider, needing on the measurement frequency band considered, the linear average of Electromagnetic Interference (RE) power contribution (in units of W) of carrying community own reference signal.

Switch delayed difference (HOM): i.e. the RSRP difference of adjacent cell and cell-of-origin, this value can according to communication environment different and sets itself, its size determines handover delay length.

Trigger duration (TTT): namely must continue to meet a certain HOM condition and just can carry out switch decision within this period, TTT effectively can prevent the generation of " ping-pong " in switching.

UE monitors the RSRP of all tested communities (adjacent cell), and sends measurement report to the eNB of cell-of-origin.When condition below continues to be satisfied in given TTT, eNB will switch UE.UE sets TTT parameter according to its speed.

RSRP_T＞RSRP_S+HOM

Wherein, RSRP_T is the Reference Signal Received Power of the Target cell switched, and RSRP_S is the Reference Signal Received Power of cell-of-origin.

As mentioned above, traditional switching target small area is selected mainly to select according to the RSRP of adjacent cell.Can certainly select according to the RSRQ of adjacent cell (ReferenceSignalReceivedQuality, Reference Signal Received Quality), if number of patent application is the patent " a kind of method of switch decision and device " of 201010131337.8.Technology disclosed in it, by after comparing RSRP and RSRQ of cell-of-origin and adjacent cell, selects reference signal power and the strongest community of quality to switch.

Said method, owing to not estimating the load state of adjacent cell, when adjacent cell is in overload or heavy condition, is easy to be switched by adjacent cell refusal, thus causes handover delay to increase, cause the QoS of survice of connection status to can not get reasonable guarantee; And, when UE is in multiple adjacent cell edge, RSRP and RSRQ of simple dependence adjacent cell selects switching target small area, be easy to the adjacent cell choosing heavier loads, thus increase the load of this community, this community may be triggered and initiate load balancing process, UE be switched go back to cell-of-origin or other neighbor cells again, be unfavorable for the stable of LTE system.

Summary of the invention

In view of this, the invention provides the selecting method of switching target community and eNB that are conducive to load balancing in a kind of LTE system, when selecting switching target small area, not only based on the RSRP intensity of adjacent cell, but also consider based on the load state of adjacent cell, thus be conducive to the load balancing between community.

Technical scheme of the present invention is achieved in that

An object cell selection method for LTE system, comprising:

Step 1, acquisition adjacent cell Reference Signal Received Power RSRP and cell-of-origin RSRP;

Step 2, adjacent cell adjacent cell RSRP and cell-of-origin RSRP difference being greater than the first threshold value are chosen as changeable adjacent cell;

Step 3, acquisition adjacent cell resource status;

Step 4, in described changeable adjacent cell, the adjacent cell judgement meeting resource status pre-conditioned by choose first according to RSRP order is from big to small Target cell.

Further, described resource status comprises: hardware load instruction, the instruction of S1 transport network load and radio resource state instruction.

Further, described resource status is pre-conditioned is: hardware load instruction nonoverload, S1 transport network load instruction nonoverload, and the Physical Resource Block PRB utilance of radio resource state is not more than the second threshold value.

Further, described step 4 comprises:

Step 41, the adjacent cell that the hardware load instruction in resource status or S1 transport network load are designated as overload to be deleted from changeable adjacent cell;

In step 42, changeable adjacent cell remaining after the deletion action through described step 41, according to RSRP order from big to small, the adjacent cell of the PRB utilance of the radio resource state in first resource status chosen more than the second threshold value is adjudicated as Target cell.

Further, described step 42 comprises:

Step 421, from changeable adjacent cell, choose the maximum adjacent cell of unsentenced RSRP, and perform step 422;

Step 422, whether adjudicate the PRB utilance of this adjacent cell radio resource state more than the second threshold value, if it is perform step 421, otherwise perform step 423;

Step 423, to arrange this adjacent cell be Target cell.

Further, described method also comprises:

Step 5, when not meeting the pre-conditioned adjacent cell of resource status in described changeable adjacent cell, judging that whether cell-of-origin RSRP is lower than the 3rd threshold value, if it is performing step 6, otherwise performing step 1;

Step 6, from changeable adjacent cell, choose the maximum adjacent cell of RSRP as Target cell.

Further, described method also comprises:

Step 7, to Target cell send handover request.

Further, described adjacent cell RSRP and cell-of-origin RSRP is obtained by user terminal UE and sends to cell-of-origin evolved base station eNB.

Further, described adjacent cell resource status is obtained to adjacent cell eNB by the X2 interface of cell-of-origin eNB.

An evolved base station eNB for LTE system, comprising:

Reference Signal Received Power RSRP acquisition module, for obtaining adjacent cell RSRP and cell-of-origin RSRP;

Changeable adjacent cell screening module, is chosen as changeable adjacent cell for adjacent cell adjacent cell RSRP and cell-of-origin RSRP difference being greater than the first threshold value;

Resource status acquisition module, for obtaining the resource status of adjacent cell;

Target cell judging module, in the changeable adjacent cell selected by described changeable adjacent cell screening module, meeting the pre-conditioned adjacent cell judgement of resource status according to RSRP order from big to small by choose first is Target cell.

Further, described Target cell judging module comprises:

Changeable adjacent cell filter element, deletes from changeable adjacent cell for the adjacent cell hardware load instruction in resource status or S1 transport network load being designated as overload;

Choose decision unit, for in changeable adjacent cell remaining after deleting through described changeable adjacent cell filter element, according to RSRP order from big to small, the adjacent cell of the PRB utilance of the radio resource state in first resource status chosen more than the second threshold value is adjudicated as Target cell.

Further, described selection decision unit comprises:

Choose subelement, for choosing the maximum adjacent cell of unsentenced RSRP from changeable adjacent cell;

Whether judgement subelement, for adjudicating the PRB utilance of the radio resource state of the adjacent cell chosen selected by subelement more than the second threshold value;

Subelement is set, for the judgement of judgement subelement is set to Target cell for PRB utilance more than the adjacent cell of the second threshold value.

Further, described eNB also comprises:

Cell-of-origin RSRP judge module, for do not select in Target cell judging module any meet the pre-conditioned adjacent cell of resource status after, judge that whether cell-of-origin RSRP is lower than the 3rd threshold value;

Module is chosen in Target cell, after judging that cell-of-origin RSRP is lower than the 3rd threshold value at cell-of-origin RSRP judge module, chooses the maximum adjacent cell of RSRP as Target cell from changeable adjacent cell.

Further, described eNB also comprises:

Handover request module, for after Target cell judging module rules out Target cell, or chooses after module selects Target cell in Target cell, sends handover request to described Target cell.

As can be seen from such scheme, the object cell selection method of LTE system provided by the invention and eNB, when switching target small area is selected, the resource status (load state) of the intensity of adjacent cell RSRP and cell-of-origin RSRP and adjacent cell is carried out comprehensive consideration, using large as far as possible for RSRP intensity and to meet resource status (load state) pre-conditioned and ensure that the adjacent cell of nonoverload is as switching cell simultaneously simultaneously.Compared with prior art, because the present invention considers again the resource status (load state) of adjacent cell on the basis considering adjacent cell RSRP simultaneously, by resource status (load state) is arranged pre-conditioned (as: hardware load instruction and S1 transport network load indicate equal nonoverload, and the PRB utilance of radio resource state is not more than the second threshold value etc.), avoid selected switching cell to be the generation of the adjacent cell situation of heavier loads.Utilize the switching cell selected by method of the present invention and eNB can reach certain balance on RSRP and resource status (load state), the RSRP of namely selected switching cell is relatively large and resource status (load state) is relatively better, thus be conducive to the load balancing of LTE system, ensure the stable of LTE system.

Accompanying drawing explanation

Fig. 1 is the object cell selection method flow chart of LTE system of the present invention;

Fig. 2 is the flow chart of step 4 in Fig. 1;

Fig. 3 is the flow chart of step 42 in Fig. 2;

Fig. 4 is object cell selection method second flow chart of LTE system of the present invention;

Fig. 5 is the object cell selection method embodiment flow chart of LTE system of the present invention;

Fig. 6 is the eNB structured flowchart of LTE system of the present invention.

In accompanying drawing, the title represented by each label is as follows:

M1, RSRP acquisition module, M2, changeable adjacent cell screening module, M3, resource status acquisition module, M4, Target cell judging module, M41, changeable adjacent cell filter element, M42, choose decision unit, M421, choose subelement, M422, judgement subelement, M423, subelement is set, M5, cell-of-origin RSRP judge module, module is chosen in M6, Target cell, M7, handover request module.

Embodiment

For making object of the present invention, technical scheme and advantage clearly understand, to develop simultaneously embodiment referring to accompanying drawing, the present invention is described in further detail.

As shown in Figure 1, the object cell selection method of LTE system provided by the invention, mainly comprises:

Step 3, acquisition adjacent cell resource status;

In conjunction with prior art, in step 1, adjacent cell RSRP and cell-of-origin RSRP can be undertaken obtaining by UE and send to cell-of-origin eNB.

In step 2, the first threshold value can be considered the HOM value in background technology.If cell-of-origin RSRP is defined as RSRP_S, adjacent cell RSRP being defined as RSRP_N, so, in step 2, only having when meeting the following conditions, just can using satisfied condition adjacent cell as changeable adjacent cell.

RSRP_N-RSRP_S＞HOM

In the present invention, because the Target cell that will carry out switching is further screening and going out from the changeable adjacent cell selected through above-mentioned condition, therefore the needs that arrange of this HOM value think better of.If this HOM value is arranged less, just cell-of-origin RSRP (RSRP_S) is expressed as and adjacent cell RSRP (RSRP_N) difference is little, the RSRP of Target cell that selects of finishing screen is just suitable with cell-of-origin RSRP so in this case, now be convenient to ping-pong occurs, UE is caused frequently to switch in minizone, be unfavorable for the stable of LTE system, affect the communication quality of UE.Therefore arranging of HOM value needs to consider to avoid the generation of ping-pong.

Compared with prior art, advantage of the present invention is RSRP and the resource status of reference cell simultaneously, thus is conducive to the load balancing between community.Therefore, after filtering out changeable adjacent cell through the process of step 1 and step 2, also need to obtain (as step 3) the resource status of adjacent cell further, and carry out adjudicating (as step 4) according to the resource status of adjacent cell.

In the present invention, utilize that the hardware load in resource status indicates, the instruction of S1 transport network load and radio resource state instruction choose and meet pre-conditioned Target cell.Specifically, in the present invention, resource status is pre-conditioned is: hardware load instruction nonoverload, S1 transport network load instruction nonoverload, and the PRB utilance of radio resource state is not more than the second threshold value.When not indicating containing hardware load instruction and S1 transport network load in the resource state information that adjacent cell eNB returns, this adjacent cell load can be defaulted as not serious.

Based on the above-mentioned reference to adjacent cell resource status, as shown in Figure 2, step 4 can comprise the steps: further

Wherein, in step 41, when the hardware load instruction in resource status or S1 transport network load are designated as overload, show the adjacent cell heavier loads corresponding to this resource status, be not easy to choose as Target cell, the adjacent cell now these being not easy to carry out choosing as Target cell is deleted from changeable adjacent cell, can not affect and choose Target cell further.For both hardware load instruction and the instruction of S1 transport network load, just the adjacent cell of correspondence can be deleted from changeable adjacent cell as long as one of them is overload, only have when the two meets the condition of nonoverload simultaneously, just can think that this adjacent cell load is not serious and this adjacent cell is retained.In step 42, choose adjacent cell according to RSRP order from big to small, object is to ensure that the adjacent cell that RSRP is relatively high can preferentially be chosen, and is beneficial to load balancing.PRB, i.e. Physical Resource Block are the minimum bandwidth unit that the scheduler of eNB distributes.It is not very high condition that the setting of the second threshold value should meet PRB utilance, thus can search out the relatively low adjacent cell of load preferably, and whether main needs that arrange of the second threshold value transships with reference to radio resource state or heavy duty.In conjunction with the screening of aforesaid RSRP, just can search out that both to have met RSRP relatively large, meet again resource status meet pre-conditioned (load is not very large, namely hardware load nonoverload and S1 transport network load nonoverload and PRB utilance is not very high) adjacent cell as Target cell.

Said method simultaneously with reference to adjacent cell RSRP size and resource status situation, and carries out compromise process: and the adjacent cell that non-selection RSRP is maximum, but the adjacent cell that prioritizing selection RSRP is larger when resource status meets pre-conditioned is as Target cell.This mode is conducive to load balancing, because resource status meets pre-conditioned adjacent cell be the community of not transshipping, therefore the situation being switched to overloaded cells that these non-overloaded cells there will not be mistake is switched to, select the larger adjacent cell of RSRP to switch simultaneously, can also ensure that the communication signal intensity of UE is better.If do not consider adjacent cell resource status situation, probably occur that the maximum adjacent cell of RSRP is the situation of overloaded cells, carried out as Target cell this overloaded cells in this situation switching, pole is unfavorable for load balancing.

Further, as shown in Figure 3, the concrete operations of step 42 can adopt following a few sub-steps to realize.

Step 423, to arrange this adjacent cell be Target cell.

Through the circulation of above-mentioned steps 421, step 422, travel through the maximum adjacent cell of unsentenced RSRP successively and just can search out the adjacent cell that first meets step 422 condition, simple possible in practical operation.

Due to may occur in actual state through above in steps after still fail to search out the situation of Target cell.Such as, all adjacent cell loads are all heavier, cause meeting resource status pre-conditioned (if hardware load instruction overload, S1 transport network load instruction overload or PRB utilance are more than the second threshold value).And now the RSRP of cell-of-origin is also undesirable, need to carry out cell merge.So, after the above step, with reference to Fig. 4, method of the present invention is also further comprising the steps.

Step 5 ', when not meeting the pre-conditioned adjacent cell of resource status in described changeable adjacent cell, judge that whether cell-of-origin RSRP is lower than the 3rd threshold value, if it is perform step 6 ', otherwise perform step 1 ';

Step 6 ', from changeable adjacent cell, choose the maximum adjacent cell of RSRP as Target cell.

Because the low generation that will inevitably cause communication disruption situation to a certain extent of community RSRP, now just handover operation must be carried out, above-mentioned steps 5 ' and step 6 ' as remedial steps, can ensure that UE switches to the maximum adjacent cell of RSRP before producing communication disruption because cell-of-origin RSRP is not enough, to ensure normally carrying out of communication.Wherein, the setting of the 3rd threshold value should ensure that the lowest signal intensity in UE communication process required for transfer of data is met.

Whole steps flow chart shown in Fig. 4 is:

Step 1 ', obtain adjacent cell Reference Signal Received Power RSRP and cell-of-origin RSRP;

Step 2 ', the adjacent cell that adjacent cell RSRP and cell-of-origin RSRP difference is greater than the first threshold value is chosen as changeable adjacent cell;

Step 3 ', obtain adjacent cell resource status;

Step 4 ', in described changeable adjacent cell, the adjacent cell judgement meeting resource status pre-conditioned by choose first according to RSRP order is from big to small Target cell.

Wherein, step 1 ', step 2 ', step 3 ' with step 4 ' and abovementioned steps 1, step 2, step 3 are identical with the process of step 4, increase step 5 ' and step 6 ' after, make the present invention program more perfect.

Through above steps, Target cell is just selected.Now, just can perform:

Step 7, to Target cell send handover request.

To realize cell merge.

Below in conjunction with Fig. 5, a specific embodiment operating process of the object cell selection method of LTE system of the present invention is introduced.The concrete steps of this embodiment comprise as follows.

The adjacent cell RSRP that step S01, cell-of-origin eNB reception UE reports and cell-of-origin RSRP, performs step S02 afterwards.

The adjacent cell that received adjacent cell RSRP and cell-of-origin RSRP difference are greater than the first threshold value is chosen as changeable adjacent cell by step S02, eNB, performs step S03 afterwards.

Wherein, the setting of the first threshold value should meet the generation effectively preventing pingpang handoff situation.For different manufacturers and varying environment, the first threshold value may adopt different values, and in general, the first threshold value can be taken at about 3dB.

Step S03, by changeable adjacent cell by RSRP sort from big to small form changeable adjacent cell list, afterwards perform step S04.

Setting steps S03, to form changeable adjacent cell list, mainly for the ease of carrying out poll to each changeable adjacent cell in list according to predetermined rule (RSRP from big to small), improves the execution efficiency of each step subsequently.

Step S04, send resource status request message to adjacent cell, perform step S05 afterwards.

The resource status updating message of step S05, reception adjacent cell, performs step S06 afterwards.

In LTE system, X2 interface is the communication interface between eNB and eNB.The execution of above-mentioned steps S04 and step S05 is that cell-of-origin eNB carries out the transmission of resource status request message and the reception of resource status updating message by its X2 interface.Equally, the transmission of the adjacent cell eNB reception and resource status updating message of carrying out resource status request message is also undertaken by its X2 interface.

In the present embodiment, step subsequently is mainly carried out consideration to S1 interface (being the communication interface between eNB and packet-based core networks (EPC)) transport network layer (TNL) load information of the eNB hardware load information in resource status, eNB and the radio resource state information of eNB and is adjudicated, and in radio resource state information, the utilance of Main Basis PRB (Physical Resource Block) is considered again.Above-mentioned each load information, state information are all included among the resource status updating message of adjacent cell.

Step S06, the adjacent cell that the hardware load instruction in resource status updating message or S1 interface TNL load are designated as overload to be deleted from changeable adjacent cell queue, perform step S07 afterwards.

If the hardware load instruction of adjacent cell eNB or S1 interface TNL load are designated as overload, then show that corresponding adjacent cell eNB transships, now just should not initiate handover request to the adjacent cell of overload.Therefore, the adjacent cell of overload is just not changeable adjacent cell, and the selection carrying out switching cell afterwards just can further be considered, therefore needs to delete from changeable adjacent cell queue.Delete after these judge the adjacent cell of having transshipped, the changeable adjacent cell quantity in changeable adjacent cell queue can also be reduced, accelerate polling speeds.Adjacent cell eNB feeds back in the resource status updating message of cell-of-origin eNB, if when the hardware load instruction not containing eNB and S1 interface TNL load instruction, can be defaulted as this adjacent cell eNB load not serious.

The above-mentioned step S03 carrying out sequence work, except can performing between step S02 and step S04, is arranged on and performs all passable between step S05 and step S06 or between step S06 and step S07, do not affect the execution of each step subsequently.

Step S07, from changeable adjacent cell list, select the adjacent cell that unsentenced RSRP is the strongest, perform step S08 afterwards.

Because changeable adjacent cell is sorted according to RSRP order from big to small in step S03, therefore just can from the adjacent cell of first in changeable adjacent cell list poll.Article 1 in changeable adjacent cell list is recorded as the strongest adjacent cell of RSRP, if Article 1 the adjacent cell of record is adjudicated, Article 2 then in changeable adjacent cell list is recorded as the strongest adjacent cell of unsentenced RSRP, if Article 2 record is also adjudicated, then Article 3 is recorded as the strongest adjacent cell of unsentenced RSRP, the rest may be inferred then can according to each the changeable adjacent cell in the RSRP changeable adjacent cell list of order poll from big to small, until find suitable adjacent cell as switching cell.

Step S08, judge that whether PRB utilance in this adjacent cell radio resource state is more than the second threshold value, if it is perform step S10, otherwise perform step S09.

Wherein the second threshold value arrange Primary Reference radio resource state whether transship or heavy duty, rule of thumb, when it has been generally acknowledged that PBR utilance more than 0.8, community just enters heavy duty or overload, therefore the scope that the second threshold value can be arranged is no more than 0.8 (such as can arrange certain value between 0.6 to 0.8), but also should not arrange too low, otherwise can occur that RSRP is comparatively large and load is lighter community cannot be chosen as the generation of switching cell situation, and affect the load balancing of LTE system.

Step S09, to arrange this adjacent cell be switching cell.

In the present invention, the adjacent cell after each step screening before have passed through step S09, can think that RSRP is comparatively large and the adjacent cell that load is lower, just in step S09, this adjacent cell can be set to switching cell.

Step S10, judge in changeable adjacent cell list, whether to there is other unsentenced adjacent cells, if it is return and perform step S07, otherwise perform step S11.

Not after step S08, select the qualified adjacent cell of judgement surely as switching cell with regard to one.After the PRB utilance of adjudicating current changeable adjacent cell in step S08 is more than the second threshold value, this adjacent cell is not just re-used as changeable adjacent cell, and the adjacent cell now just needing again to find unsentenced RSRP the strongest is adjudicated again.The arranging to solve of step S10 judges whether that all changeable adjacent cells have been adjudicated complete all, and carries out the problem of process step subsequently according to this judged result.When finding in step S10 to still have unsentenced adjacent cell in changeable adjacent cell list, just flow process is pointed to step S08, if when finding in step S10 that adjacent cells all in changeable adjacent cell list is all adjudicated complete (now still not finding switching cell), just remedial steps subsequently can be pointed to, as step S11.

Step S11, judge that whether cell-of-origin RSRP is lower than the 3rd threshold value, if it is perform step S12, otherwise return step S01.

Because still do not find switching cell after step each before step S11, illustrate and each changeable adjacent cell all do not meet the condition of switching cell (RSRP is too low, overload), and once cell-of-origin RSRP is too small, the communicating interrupt of UE also can be caused.And to ensure that the communication of UE is not interrupted be the most basic requirement, so arrange this step S11, the 3rd threshold value is set for cell-of-origin RSRP.Under general status, when RSRP is less than-110dB, UE can often occur the going offline situation of (communicating interrupt) occurs, that is RSRP must meet and is greater than-110dB and could ensures that the communication of UE may not be interrupted substantially, once lower than-110dB, just cell merge (when there is changeable adjacent cell) must be carried out.Therefore, the 3rd threshold value can with reference to the RSRP value reducing to cause UE to go offline due to RSRP, such as-110dB.In the middle of practice, choosing of the 3rd threshold value is relevant with the application scenarios of reality, so the 3rd threshold value also will consider it is actual conditions, also can be greater than-110dB or be less than the value of-110dB.

Step S12, from changeable adjacent cell list, select adjacent cell that RSRP is the strongest as switching cell.

When after each step before step S12, (the switching requirement of RSRP has been met in each changeable adjacent cell, see step S02) in find the adjacent cell that requires less than the load state meeting switching cell, also find in step S11 that cell-of-origin RSRP is lower than the 3rd threshold value, the communication of UE in cell-of-origin may be interrupted at any time.Now just have to abandon the consideration to changeable adjacent cell load state, using adjacent cell the strongest for RSRP in changeable adjacent cell as switching cell, to ensure that the communication of UE can be carried out smoothly.

After step S09 or step S12, just completed the selection of Target cell, cell-of-origin eNB just can perform subsequently:

Step S13, to this switching cell send handover request.

To perform cell merge flow process.

Above step S01 to step S13 is further illustrating the object cell selection method of LTE system of the present invention.Wherein step S01 and step 1 (step 1 ') are corresponding, step S02 and step 2 (step 2 ') corresponding, step S04 and step S05 and step 3 (step 3 ') corresponding, step S06 to step S10 and step 4 (step 4 ') corresponding, step S11 and step 5 ' corresponding, step S12 and step 6 ' corresponding, step S13 is corresponding with step 7.Further, step S06 is corresponding with step 41, and step S07 to step S10 is corresponding with step 42 (step 421 is to step 423).

Below in conjunction with an application scenarios, said method is further described.

Suppose that the cell-of-origin residing for user UE is community A, adjacent cell is respectively community B, community C, community D, community E, community F, and the eNB that user UE is meeting certain trigger condition (cycle triggers or event triggers) Shi Xiang community A sends measurement report.

The eNB of community A receives the measurement report that user UE reports, and which includes the RSRP measured value RSRP_A of community A, the RSRP measured value RSRP_B of community B, the RSRP measured value RSRP_C of community C, the RSRP measured value RSRP_D of community D, the RSRP measured value RSRP_E of community E, the RSRP measured value RSRP_F of community F.

RSRP_A compares with RSRP_B, RSRP_C, RSRP_D, RSRP_E, RSRP_F by eNB respectively.Wherein, the first threshold value HOM1 is set as benchmark, finds out the adjacent cell being greater than HOM1 with the difference of RSRP_A, add changeable adjacent cell list.Suppose that comparative result is as follows:

RSRP_B-RSRP_A＞HOM1

RSRP_C-RSRP_A＞HOM1

RSRP_D-RSRP_A＞HOM1

RSRP_E-RSRP_A＜HOM1

RSRP_F-RSRP_A＞HOM1

Ze Jiang community B, community C, community D, community F add changeable adjacent cell list.

Community B, community C, community D, community F are sorted by RSRP measured value size, suppose RSRP_D > RSRP_B > RSRP_C > RSRP_F, then putting in order of four adjacent cells in changeable adjacent cell list is followed successively by community D, community B, community C, community F.

Send resource status solicited message respectively to community B, community C, community D, community F, and receive the resource status updating message of these adjacent cells feedback.Suppose, in the resource status updating message that community D feeds back, comprise hardware overload and the instruction of S1 transmission network overload, and in the resource status updating message of community B, community C, community F feedback, there is no these overload instructions, Ze Jiang community D deletes from changeable adjacent cell list, now only remains community B, community C, community F and RSRP_B > RSRP_C > RSRP_F in changeable adjacent cell list.

Afterwards, from the adjacent cell that RSRP is the strongest, judge that whether the PRB utilance of each adjacent cell in changeable adjacent cell list is more than the second threshold value successively, to find out the adjacent cell that first PRB utilance is no more than the second threshold value.Suppose, the PRB utilance in the resource status updating message that community B feeds back has exceeded the second threshold value, and the PRB utilance of community C and community F is not all more than the second threshold value.Because RSRP_B > RSRP_C > RSRP_F, so judge that order is as community B, community C, community F.First judge community B, because the PRB utilance of community B has exceeded the second threshold value, community B has not considered, and judges community C in turn, because the PRB utilance of community C is not more than the second threshold value, so select community C as switching cell.Although the PRB utilance of community F is not also more than the second threshold value, but sort according to the strong and weak order of RSRP, so although the community C selected before and community F meets the condition of PRB utilance more than the second threshold value, but RSRP_C > is RSRP_F, so above-mentioned deterministic process have also contemplated that the size of RSRP, between community C and community F, optimum selecting community C is as switching cell, and this is also that method of the present invention is better than a now methodical embodiment.Find out community C as after switching cell, just can send handover request to enter switching flow to community C.

The embodiment of the present invention additionally provides a kind of eNB of LTE system, as shown in Figure 6, mainly comprises RSRP acquisition module M1, the screening of changeable adjacent cell module M2, resource status acquisition module M3 and Target cell judging module M4.Wherein, RSRP acquisition module M1, for obtaining adjacent cell RSRP and cell-of-origin RSRP, RSRP acquisition module M1 by obtaining adjacent cell RSRP and cell-of-origin RSRP the measurement report from UE reception.Changeable adjacent cell screening module M2, is chosen as changeable adjacent cell for adjacent cell adjacent cell RSRP and cell-of-origin RSRP difference being greater than the first threshold value.Resource status acquisition module M3, for obtaining the resource status of adjacent cell, resource status acquisition module M3 is by sending resource status request message to adjacent cell eNB and receiving the resource status updating message of adjacent cell from adjacent cell eNB, to obtain the resource status of adjacent cell.Target cell judging module M4, in the changeable adjacent cell selected by changeable adjacent cell screening module M2, meeting the pre-conditioned adjacent cell judgement of resource status according to RSRP order from big to small by choose first is Target cell.

Target cell judging module M4 also comprises further: changeable adjacent cell filter element M41 and choose decision unit M42.Wherein, changeable adjacent cell filter element M41, deletes from changeable adjacent cell for the adjacent cell hardware load instruction in resource status or S1 transport network load being designated as overload.Choose decision unit M42, for in changeable adjacent cell remaining after deleting through changeable adjacent cell filter element M41, according to RSRP order from big to small, the adjacent cell of the PRB utilance of the radio resource state in first resource status chosen more than the second threshold value is adjudicated as Target cell.

Decision unit 42 is wherein selected also to comprise further: choose subelement M421, judgement subelement M422 and subelement M423 is set.Wherein, choose subelement M421, for choosing the maximum adjacent cell of unsentenced RSRP from changeable adjacent cell.Whether judgement subelement M422, for adjudicating the PRB utilance of the radio resource state of the adjacent cell chosen selected by subelement M421 more than the second threshold value.Subelement M423 is set, for judgement subelement M422 judgement is set to Target cell for PRB utilance more than the adjacent cell of the second threshold value.

The eNB of the LTE system that the embodiment of the present invention provides also comprises further: module M6 is chosen in cell-of-origin RSRP judge module M5 and Target cell.Wherein, cell-of-origin RSRP judge module M5, for do not select at Target cell judging module M4 any meet the pre-conditioned adjacent cell of resource status after, judge that whether cell-of-origin RSRP is lower than the 3rd threshold value.In the judging module M4 of Target cell, the unit whether conclusive judgement meets the pre-conditioned adjacent cell of resource status is judgement subelement M422 wherein, after the PRB utilance of the radio resource state of all adjacent cells of judgement subelement M422 judgement is all more than the second threshold value, just can start the work of cell-of-origin RSRP judge module M5.Module M6 is chosen in Target cell, for after cell-of-origin RSRP judge module M5 judges that cell-of-origin RSRP is lower than the 3rd threshold value, chooses the maximum adjacent cell of RSRP as Target cell from changeable adjacent cell.If cell-of-origin RSRP judge module M5 judges that cell-of-origin RSRP is not less than the 3rd threshold value, lowest signal intensity then between expression UE and cell-of-origin eNB can also ensure the needs of transfer of data, now just do not need to choose Target cell immediately, after again can obtaining adjacent cell RSRP and cell-of-origin RSRP by RSRP acquisition module M1, carry out screening again.

Further, the eNB of the LTE system that the embodiment of the present invention provides also comprises handover request module M7, for rule out Target cell (namely the Target cell set by subelement M423 is set) at Target cell judging module M4 after, or choose in Target cell after module M6 selects Target cell, send handover request to Target cell.

The object cell selection method of LTE system provided by the invention and eNB, when switching target small area is selected, the resource status (load state) of the intensity of adjacent cell RSRP and cell-of-origin RSRP and adjacent cell is carried out comprehensive consideration, using large as far as possible for RSRP intensity and to meet resource status (load state) pre-conditioned and ensure that the adjacent cell of nonoverload is as switching cell simultaneously simultaneously.Compared with prior art, because the present invention considers again the resource status (load state) of adjacent cell on the basis considering adjacent cell RSRP simultaneously, by resource status (load state) is arranged pre-conditioned (as: hardware load instruction and S1 transport network load indicate equal nonoverload, and the PRB utilance of radio resource state is not more than the second threshold value etc.), avoid selected switching cell to be the generation of the adjacent cell situation of heavier loads.Utilize the switching cell selected by method of the present invention and eNB can reach certain balance on RSRP and resource status (load state), the RSRP of namely selected switching cell is relatively large and resource status (load state) is relatively better, thus be conducive to the load balancing of LTE system, ensure the stable of LTE system.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within the scope of protection of the invention.

Claims

1. an object cell selection method for LTE system, comprising:

Step 3, acquisition adjacent cell resource status;

Step 4, in described changeable adjacent cell, the adjacent cell judgement meeting resource status pre-conditioned by choose first according to RSRP order is from big to small Target cell;

Wherein, described step 4 comprises:

2. the object cell selection method of LTE system according to claim 1, is characterized in that, described resource status comprises: hardware load instruction, the instruction of S1 transport network load and radio resource state instruction.

3. the object cell selection method of LTE system according to claim 1, it is characterized in that, described resource status is pre-conditioned is: hardware load instruction nonoverload, S1 transport network load instruction nonoverload, and the Physical Resource Block PRB utilance of radio resource state is not more than the second threshold value.

4. the object cell selection method of LTE system according to claim 1, is characterized in that, described step 42 comprises:

Step 423, to arrange this adjacent cell be Target cell.

5. the object cell selection method of LTE system according to claim 1, is characterized in that, described method also comprises:

6. the object cell selection method of the LTE system according to any one of claim 1 to 5, is characterized in that, described method also comprises:

Step 7, to Target cell send handover request.

7. the object cell selection method of the LTE system according to any one of claim 1 to 5, is characterized in that: described adjacent cell RSRP and cell-of-origin RSRP is obtained by user terminal UE and sends to cell-of-origin evolved base station eNB.

8. the object cell selection method of the LTE system according to any one of claim 1 to 5, is characterized in that: described adjacent cell resource status is obtained to adjacent cell eNB by the X2 interface of cell-of-origin eNB.

9. an evolved base station eNB for LTE system, is characterized in that, comprising:

Target cell judging module, in the changeable adjacent cell selected by described changeable adjacent cell screening module, meeting the pre-conditioned adjacent cell judgement of resource status according to RSRP order from big to small by choose first is Target cell;

Wherein, described resource status comprises: hardware load instruction, the instruction of S1 transport network load and radio resource state instruction;

Described Target cell judging module comprises:

10. the eNB of LTE system according to claim 9, it is characterized in that, described resource status is pre-conditioned is: hardware load instruction nonoverload, S1 transport network load instruction nonoverload, and the Physical Resource Block PRB utilance of radio resource state is not more than the second threshold value.

The eNB of 11. LTE system according to claim 9, is characterized in that, described selection decision unit comprises:

The eNB of 12. LTE system according to claim 9, is characterized in that, described eNB also comprises:

The eNB of 13. LTE system according to any one of claim 9 to 12, it is characterized in that, described eNB also comprises: