Background
The carrier aggregation technology is an important technology in LTE-Advanced. Carrier aggregation means that data of a user can be transmitted simultaneously on multiple Component Carriers (CCs), which corresponds to increasing the transmission bandwidth of the user. In the LTE Rel-10 protocol, one user can use up to 5 CCs at the same time, so that the maximum transmission bandwidth of a single user can reach 100MHz theoretically, which greatly improves the peak rate of user data transmission.
A CC represents an uplink carrier or a downlink carrier, and an uplink CC and a downlink CC are associated together by a correspondence relationship to form a Cell (Cell), so carrier aggregation is also called Cell aggregation. The component carriers are divided into a Primary Component Carrier (PCC) and a Secondary Component Carrier (SCC) to facilitate management of the component carriers, and each UE is specified to have at most one uplink PCC and one downlink PCC. The downlink PCC and the uplink PCC are associated together to form a primary cell (PCell); the downlink SCC and the optional uplink SCC are associated together to form a secondary cell (SCell). In Rel-10, when UE is converted from IDLE state to CONNECTED state, the resident carrier is changed into PCell; PCell is always present and addition and deletion of scells is achieved through RRC connection reconfiguration messages.
Compared with the SCell, the PCell has some specific properties, such as the PCell cannot be deactivated, and the UE only performs an activation/deactivation mechanism on the SCell; transmitting, by a User (UE), physical uplink control information to a base station (eNB) only on a PCell; only the configuration of SPS resources on the uplink and the downlink of the PCell is supported in Rel-10.
In a carrier aggregation system, an LTE-a UE may configure multiple CCs for data transmission. Considering the difference between the PCC and the SCC, the PCC needs to additionally support the transmission of physical uplink control information, partial signaling, and SPS scheduling service data, compared to the SCC.
If one CC accesses too many users or services as PCC, exceeding the maximum limit that the CC can carry may cause control resource reconfiguration to increase a large amount of signaling overhead, and may also cause users or services not to be scheduled in time, affecting the communication quality of users.
Because a user selects a resident carrier according to a certain principle, the user is converted from an IDLE state to a CONNECTED state, and the resident carrier of the user becomes a PCell of the user, so that unbalanced user distribution may occur on each CC under the same eNB, some CCs are already in a saturated state as PCC, and resources of other CCs as PCC are not fully utilized. Therefore, in the carrier aggregation system, there are problems of load imbalance and insufficient resource utilization among CCs in the same eNB. This will increase the workload of system management and optimization, and cause the problems of system congestion, which will seriously affect the communication quality of the system.
Disclosure of Invention
The embodiment of the invention provides a load balancing method in carrier aggregation, which can ensure the load balancing among CCs under the same eNB and fully utilize resources, thereby ensuring the communication quality of a system.
The technical scheme of the embodiment of the invention is as follows:
a method of load balancing in carrier aggregation, the method comprising:
determining overload CCs and non-overload CCs according to the load of the carrier CCs and a preset overload threshold, and determining a load mean value according to the load of the overload CCs and the load of the non-overload CCs;
selecting a target CC and a CC to be adjusted from the overload CC and the non-overload CC according to the load mean value;
and switching the user UE on the CC to be adjusted to the target CC.
The selecting the target CC and the CC to be adjusted according to the load mean value in the overload CC and the non-overload CC comprises the following steps:
and if the load average value is smaller than a preset overload threshold, selecting a target CC and a CC to be adjusted according to the load average value from the overloaded CC and the non-overloaded CC.
The selecting the target CC and the CC to be adjusted according to the load mean value in the overload CC and the non-overload CC comprises the following steps:
and if the load average value is more than or equal to a preset overload threshold and only one overload CC exists, selecting a target CC and a CC to be adjusted according to the load average value from the overload CC and the non-overload CC.
The determining the load mean value from the load of the overloaded CC and the load of the non-overloaded CC comprises:
calculating a load mean value according to the load of the overload CC and the load of the non-overload CC;
and if the load average value is greater than or equal to the preset overload threshold and at least two overload CCs exist, deleting the overload CC with the minimum load and re-determining the load average value.
The selecting the target CC and the CC to be adjusted according to the load mean value in the overload CC and the non-overload CC comprises the following steps:
the CC which is more than or equal to the load mean value in the overload CC and the non-overload CC is the CC to be adjusted; CCs smaller than the load mean value among the overloaded CCs and the non-overloaded CCs are target CCs.
The switching the UE on the CC to be adjusted to the target CC includes:
the current load minimum CC in the target CCs is the target CC to be switched;
according to the Reference Signal Received Power (RSRP) of a target CC to be switched measured by UE on the CC to be adjusted, switching the UE to the target CC to be switched;
and re-determining the current load minimum CC in the target CCs except the target CC to be switched.
The step of measuring the RSRP of the target CC to be switched according to the UE on the CC to be adjusted and switching the UE to the target CC to be switched comprises the following steps:
and when the RSRP of the target CC to be switched measured by the UE on the CC to be adjusted meets a preset switching condition, switching the UE corresponding to the RSRP to the target CC to be switched from the CC to be adjusted.
After the UE corresponding to the RSRP is switched to the target CC to be switched from the CC to be adjusted, the method further includes:
and after updating, the load of the CC to be adjusted is equal to the average load value, and the UE on the CC to be adjusted does not perform load balancing any more.
After the UE corresponding to the RSRP is switched to the target CC to be switched from the CC to be adjusted, the method further includes:
and the load of the target CC to be switched is equal to the average load value after updating, and the target CC to be switched is not subjected to load balancing any more.
After the UE corresponding to the RSRP is switched to the target CC to be switched from the CC to be adjusted, the method further includes:
and when the updated load of the target CC to be switched is smaller than the load mean value, and the RSRP of the target CC to be switched measured by the UE on the CC to be adjusted meets the preset switching condition, switching the UE corresponding to the RSRP to the target CC to be switched from the CC to be adjusted.
A is the RSRP of the current maximum target CC to be switched measured by the UE, and B is the RSRP of the CC to be adjusted corresponding to the UE;
the preset switching conditions include: b is less than or equal to A, or B-A is more than 0 and less than or equal to T, and T is a preset threshold value.
The step of measuring the RSRP of the target CC to be switched by the UE on the CC to be adjusted to meet the preset switching condition comprises the following steps:
selecting UE corresponding to the maximum value of the current RSRP as UE to be switched;
and adjusting the preset switching condition when the current RSRP maximum value does not meet the preset switching condition.
The preset switching condition is adjusted by using a step length α to adjust T, wherein the T is more than 0 and less than α and less than 1, the preset switching condition comprises that B is less than or equal to A, or more than 0 and B-A are less than or equal to T (1+ α), and T is a preset threshold value.
It can be seen from the above technical solutions that, in the embodiment of the present invention, an overloaded CC and a non-overloaded CC are determined according to a load of the CC and a preset overload threshold, and a load mean value is determined according to the load of the overloaded CC and the load of the non-overloaded CC; selecting a target CC and a CC to be adjusted from the overload CC and the non-overload CC according to the load mean value; and switching the user UE on the CC to be adjusted to the target CC. Because the load balance among all CCs under the same eNB can be ensured, resources are fully utilized, and the communication quality of the system is ensured.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
In the embodiment of the invention, overload CCs and non-overload CCs are determined according to the load of the CCs and a preset overload threshold, and the load mean value is determined according to the load of the overload CCs and the load of the non-overload CCs; selecting a target CC and a CC to be adjusted from the overload CC and the non-overload CC according to the load mean value; and switching the user UE on the CC to be adjusted to the target CC. Because the load balance among all CCs under the same eNB can be ensured, resources are fully utilized, and the communication quality of the system is ensured.
Referring to fig. 1, a schematic flow chart of a method for load balancing in carrier aggregation specifically includes the following steps:
101. and determining overload CCs and non-overload CCs according to the load of the CCs and a preset overload threshold, and determining a load mean value according to the load of the overload CCs and the load of the non-overload CCs.
And counting and evaluating the load condition of each CC. The load that may be considered includes the maximum number of users, available radio resources, hardware load indication, etc. The number of users is used in the present invention to characterize the load of the CC. And respectively counting the number of users as PCC under each CC in the eNB.
Let N CCs be C respectively1,C2,...,CNThe current load value statistical conditions of each CC are respectively L1,L2,...,LN. Each CC has a certain bearer capability and if this bearer capability is exceeded, it is overloaded. The bearer capability may be reduced to a certain number of users supported by one CC according to the limitations of the configuration of available air interface radio resources and device hardware resources.
An overload threshold is preset. If the load value of a CC exceeds a preset overload threshold, the CC is overloaded, otherwise, the CC is not overloaded. And judging the load condition of each CC according to a preset overload threshold, and correspondingly classifying the CC into an overload CC queue or a non-overload CC queue.
And determining whether load balancing is needed or not according to the load evaluation condition. If all CCs are overloaded or all CCs are not overloaded, load balancing is not performed; otherwise, load balancing is carried out. In other words, the load values L of N CCs1,L2,...,LNAnd if any one of the following conditions is met, not performing load balancing:
(1) and the load values of all CCs are less than or equal to a preset overload threshold.
(2) And the load values of all CCs are greater than or equal to a preset overload threshold.
And respectively sequencing the overloaded CC queue and the non-overloaded CC queue according to the load value of each CC, wherein A is a preset overload threshold. There are M (M < N) CC overloads, two queues are ordered as
Overload CC: a is less than L'1≤L'2≤...≤L'M
Non-overload CC: l'M+1≤L'M+2≤...≤L'N≤A
102. And selecting a target CC and a CC to be adjusted according to the load mean value in the overload CC and the non-overload CC.
And calculating the load average value according to the current whole load condition. And dividing the overloaded CC and the non-overloaded CC into two queues, namely a target CC and a CC to be adjusted according to the load average value.
103. And switching the UE on the CC to be adjusted to the target CC.
Because the UE on the CC to be adjusted is switched to the target CC, the load of the CC to be adjusted is correspondingly reduced, the load of the target CC is increased, the load balance among the CCs is realized, the resources are fully utilized, and the communication quality of the system is ensured.
The process of selecting the target CC and the CC to be adjusted according to the load mean will be described with reference to fig. 2.
201. And calculating a load average value, and averaging the load values of each CC in the non-overload CC queue and the overload CC queue to obtain the load average value.
202. If the load average value is smaller than the preset overload threshold, it indicates that load balance can be achieved between the overloaded CC and the non-overloaded CC, and 204 is executed; if the load average is greater than or equal to the predetermined overload threshold, it means that the load average cannot be achieved between the overloaded CC and the non-overloaded CC, so the number of overloaded CCs needs to be adjusted, and step 203.
203. If only one overloaded CC remains and the number of overloaded CCs cannot be adjusted, 204 is performed.
204. The CC which is more than or equal to the load mean value in the overload CC and the non-overload CC is the CC to be adjusted; CCs smaller than the load mean value among the overloaded CCs and the non-overloaded CCs are target CCs.
205. The number of overloaded CCs is adjusted by removing the overloaded CC with the least load, and then returning to 201 to recalculate the load mean.
The following describes in detail the handover of the UE on the CC to be adjusted to the target CC with reference to fig. 3.
301. Comparing and sequencing the CC to be adjusted and the target CC, and dividing the CC to be adjusted and the target CC into the following two queues, wherein the load mean value is B:
if the load mean value is larger than CC, the CC to be adjusted is: b < L1≤L''2≤...≤L''P。
And the load mean value CC is less than or equal to the target CC: l'P+1≤L''P+2≤...≤L''P+Q≤B。
And selecting a first CC in the CC queue less than or equal to the load mean value as a target CC to be switched, namely selecting the CC with the minimum load from the target CCs as the target CC to be switched.
302. According to the Reference Signal Received Power (RSRP) of the target CC to be switched measured by the UE on the CC to be adjusted, the UE is switched to the target CC to be switched, and the specific process is shown in fig. 4 and 401-410.
303. In the target CCs except the target CC to be switched, the current load minimum CC can be determined again, and then the operation returns to 301; otherwise, ending.
The switching of the UE to the target CC according to the RSRP of the UE is described in detail below with reference to fig. 4.
401. And performing descending sequencing according to the RSRP corresponding to the target CC to be switched measured by the UE of the CC to be adjusted, wherein the UE refers to a user using the CC to be adjusted as PCC.
402. And reading the first user information in the RSRP sequencing queue.
403. If the user meets the switching condition, then 404 is executed; if the user does not satisfy the handover condition, 405 is performed.
A is the RSRP of a target CC to be switched measured by the UE of the CC to be adjusted, and B is the RSRP of the CC to be adjusted corresponding to the UE of the CC to be adjusted;
the switching conditions include: b is less than or equal to A, or B-A is more than 0 and less than or equal to T, and T is a preset threshold value.
If the first user in the RSRP sorting queue does not meet the switching condition, namely the maximum value of the current RSRP does not meet the preset switching condition, the switching condition needs to be adjusted, T is adjusted by the step length α, wherein T is more than 0 and less than α and less than 1, the switching condition is adjusted, B is less than or equal to A, or more than 0 and B-A and less than or equal to T (1+ α), and T is a preset threshold value.
404. And switching the UE of the CC to be adjusted, namely switching the CC to be adjusted to the target CC to be switched.
405. If the UE is not the last user in the RSRP queue, 406 is performed; if the UE is the last user in the RSRP queue, 407 is performed.
406. And reading next user information in the RSRP queue, namely reading user information corresponding to the maximum RSRP in the RSRP except the maximum value of the current RSRP.
407. Modify the RSRP preset threshold, i.e., modify T, adjust T with step α, 0 < α < 1.
408. And updating the load of the CC to be adjusted. Since the UE switches from the CC to be adjusted to the target CC to be switched, the load of the CC to be adjusted changes. If the load of the CC to be adjusted is equal to the average load value after updating, 409 is executed; otherwise, 410 is performed.
409. Since the load of the CC to be adjusted after the update is equal to the load average value, the CC to be adjusted has already reached load balance, and therefore the CC to be adjusted is deleted in the queue of the CC to be adjusted.
410. And updating the load of the target CC to be switched. Since the UE is switched from the CC to be adjusted to the target CC to be switched, the load of the target CC to be switched changes. If the load of the target CC to be switched is equal to the load mean value after updating, the load of the target CC to be switched reaches load balance, and then the operation is finished; otherwise, executing 405, and continuing to switch the UE of the CC to be adjusted to the target CC to be switched.
It should be noted here that, in the switching process of 401-410, only one target CC to be switched and at least one CC to be adjusted are included. When the load of the CC to be adjusted is equal to the load average value and the load of the target CC to be switched does not reach the load average value, the target CC to be switched can also bear the UE, so that the UE meeting the switching condition can be continuously determined to be switched. When the load of the CC to be adjusted is equal to the load average value, the load of the target CC to be switched is also equal to the load average value, which indicates that both the CC to be adjusted and the target CC to be switched reach load balance, so that the CC with the minimum current load is re-determined in 303, that is, the target CC to be switched is re-determined.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.