WO2012019449A1

WO2012019449A1 - Method and system for adaptive switching

Info

Publication number: WO2012019449A1
Application number: PCT/CN2011/070899
Authority: WO
Inventors: 姚春峰; 王希维; 张娟; 刘巧艳
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-08-10
Filing date: 2011-02-09
Publication date: 2012-02-16
Also published as: CN102377538B; CN102377538A

Abstract

A method for adaptive switching is disclosed in the present invention. The method includes the steps of: when a Rank Indication(RI) reported most recently by a terminal is not consistent with an RI used by a base station when the base station transmits preceding frame data, estimating the frequency spectrum efficiency of a transmission mode corresponding to the RI reported most recently by the terminal, and if the estimated frequency spectrum efficiency is higher than the frequency spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the preceding frame, transmitting the current frame data by the base station using the RI reported most recently by the terminal. A system for adaptive switching is also disclosed in the present invention. The system applies to a downlink transmission mode 3 of a Long Term Evolution (LTE) system, and includes an RI comparison unit and a switching decision-making unit of the base station. The present invention effectively improves system throughput.

Description

Adaptive switching method and system

TECHNICAL FIELD The present invention relates to the field of communications technologies, and in particular, to an adaptive handover method and system.

Background technique

Multi-input Multi-output (MIMO) technology in Long Term Evolution (LTE) systems is a wireless transmission technology using multiple transmit antennas ( Ν _τ ) and multiple receive antennas ( N _R ) , can effectively improve the capacity of the wireless network and link transmission performance. For the two-antenna LTE system downlink transmission mode 3, two kinds of MIMO technologies, transmit diversity and spatial multiplexing, can be used for transmission. The rank indicator (RI) is equal to 1 corresponding to the transmit diversity mode, and RI is equal to 2 corresponding to the spatial multiplexing mode. Transmit diversity is more robust than spatial multiplexing performance, while spatial multiplexing can achieve higher peak rates relative to transmit diversity. Therefore, two transmit modes need to be selected based on actual channel conditions. A switching algorithm of the transmission mode 3 is provided in the prior art. The basic principle of the algorithm is: when the RI reported by the user equipment (UE) is different from the RI used by the current base station, Switch. For example, if the current base station uses RI=1 and the UE continuously reports 3 times RI=2, it switches to RI=2. The main problem with the above handover algorithm is that the handover of the RI depends only on the characteristics of the RI sequence reported by the UE.

SUMMARY OF THE INVENTION The inventors of the present invention have found that: the switching of the RI in the prior art only depends on the characteristics of the RI sequence reported by the UE, and does not consider the spectral efficiency (the spectral efficiency in this paper is defined as the original number of bits transmitted on the unit subcarrier). The impact of MIMO mode switching, which affects system throughput. The technical problem solved by the present invention is to provide an adaptive switching method and system, which can select a frequency A spectrally efficient MIMO transmission method effectively increases system throughput. In order to solve the above technical problem, the present invention provides an adaptive handover method, where the method includes: when the rank indicator (RI) reported by the terminal last time is inconsistent with the RI used by the base station to transmit data of the previous frame, The spectrum efficiency of the transmission mode corresponding to the RI reported by the terminal last time. If the estimated spectrum efficiency is higher than the spectrum efficiency of the RI corresponding to the RI used by the base station in the previous frame, the base station uses the terminal to report the last time. The RI sends data. The method further includes: when the RI reported by the terminal last time is compared with the RI used by the base station to send data in the previous frame; or the RI reported by the terminal last time is inconsistent with the RI used by the base station to send data in the previous frame. However, when the estimated spectral efficiency is equal to or lower than the spectral efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame, the base station still uses the RI used in the previous frame to transmit data. among them,

When the value of the outer loop adjustment parameter A CS is less than 0, it is determined that the estimated spectral efficiency is higher than the spectrum efficiency of the transmission method corresponding to the RI used by the base station in the previous frame. The method further includes: calculating a block error rate (BLER) and obtaining a value of the A CS according to different values of the RI used by the terminal and the RI used by the base station to transmit data. The method further includes: counting, when the last reported RI of the terminal is equal to 2, and transmitting data by using the previous frame by the base station

When the number of times of the RI is equal to 1, the spectrum efficiency of the transmission mode corresponding to the RI that is last reported by the terminal is greater than the spectrum efficiency of the maximum MCS that can be used in the diversity mode, and the base station uses the frame. The RI that the terminal last reported sent data. To solve the above technical problem, the present invention further provides an adaptive handover system, the system being applied to a Long Term Evolution System (LTE) downlink transmission mode 3, the system comprising a rank indicator comparison unit and a handover decision unit in a base station , among them: The rank indicator comparison unit is configured to: compare whether the rank indicator (RI) reported by the terminal last time is consistent with the RI used by the base station to transmit data, and if not, notify the handover decision unit of the result of the inconsistency; The handover decision unit is configured to: after receiving the result of the inconsistency, estimate a spectrum efficiency of a transmission mode corresponding to the RI reported by the terminal last time, if the estimated spectrum efficiency is higher than that of the RI used by the base station of the previous frame. The spectrum efficiency of the transmission mode determines that the base station transmits the data of the RI that was last reported by the terminal. among them,

The rank indicator comparison unit is further configured to: if it is determined that the RI reported by the terminal last time is compared with the RI used by the base station to send data of the previous frame, the result of the agreement is notified to the handover decision unit;

The handover decision unit is further configured to: according to the result of the consistency, determine that the base station still uses the RI used to transmit data in the previous frame. among them,

The handover decision unit is further configured to: after receiving the result of the inconsistency, if the estimated spectral efficiency is equal to or lower than the spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame, determining the base station frame The data is still sent using the RI used in the previous frame. The system further includes an outer loop adjustment parameter obtaining unit, where the outer loop adjustment parameter obtaining unit is configured to: separately calculate according to different values of the RI reported by the terminal and the RI used by the base station to send data. a block error rate (BLER) and obtaining a value of the outer loop adjustment parameter AMCS; the handover decision unit is further configured to: when the value of the outer loop adjustment parameter A CS is less than 0, determine that the estimated spectral efficiency is higher than before The spectral efficiency of the transmission method corresponding to the RI used by one base station. The switching decision unit is further configured to: count the number of times when the RI of the last time the "RI" of the terminal is equal to 2 and the RI used by the base station to send data in the previous frame is equal to 1, when the number of statistics exceeds a predetermined threshold If the spectrum efficiency of the transmission mode corresponding to the RI reported by the terminal is greater than the spectrum efficiency corresponding to the maximum MCS that can be used in the diversity mode, the base station frame is determined to use the RI transmission data that is last reported by the terminal.

According to the invention, according to the case that the RI of the data transmitted by the base station in the previous frame and the RI reported by the UE are the last time, if the RIs of the two are inconsistent, the spectrum efficiencies corresponding to the two transmission modes are respectively estimated and compared, and whether to perform the handover according to the comparison result is determined. In addition, when estimating the corresponding spectral efficiency, combined with the outer loop adjustment parameters, the transmission mode with higher spectral efficiency is selected, which effectively improves the system throughput.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic flowchart of a method for adaptive handover in an LTE downlink transmission mode 3 according to an embodiment of the present invention.

Preferred embodiment of the invention

The basic idea of the present invention is to provide an adaptive handover method, which is applied to the LTE downlink transmission mode 3, and the core content thereof includes: when the RI of the data transmitted by the base station of the previous frame is inconsistent with the RI reported by the UE last time, respectively, the estimation is performed. The spectral efficiency of the two transmission modes of diversity and spatial multiplexing, and the selection of the MIMO transmission mode with high spectral efficiency, can effectively improve the system throughput. Specifically, the present invention combines the existing Adaptive Modulation and Coding (AMC) outer loop adjustment parameter De/toA/GS (also called A CS ) to estimate two transmission modes: transmit diversity and spatial multiplexing. Spectral efficiency. The basic principle of obtaining the AMC outer loop adjustment parameter A CS is as follows: Step 1: Determine the initial value of A CS, A CS maximum value, A CS minimum value, Block Error Ratio (BLER) upper limit value, and BLER lower limit. The initial value of A CS is 0, the maximum value of A CS (value range 1-10), the minimum value (range -20 to -1), and the upper limit of BLER (value range 15% to 50%) , BLER lower limit (value range 0% to 8%). Step 2: If the BLER sample value (10 to 100 sub-frames of the sample period) is consecutive N (value range 1-10) times lower than the lower limit value, then A CS is increased by 1 but not exceeding the maximum value of A CS If the BLER sample value is consecutive K (value range 1-10) times higher than the upper limit value, A CS is decremented by 1, but not less than A CS minimum; otherwise, A CS remains unchanged. In the present invention, according to the RI of the data transmitted by the base station in the previous frame and the RI reported by the UE last time, four AMC outer ring adjustment parameters are used to switch the MIMO transmission mode, respectively, as A CS1, AMCS2, A CS3 and A CS4, and provide the corresponding outer loop parameter acquisition process. The algorithm principles are consistent between the processes, and the relevant parameters are independent. A CS1, AMCS2, AMCS3, and A CS4 are obtained according to BLER1, BLER2, BLER3, and BLER4, respectively. BLER1, BLER2, BLER3, and BLER4 are calculated by the corresponding Acknowledgement (ACK) / Negative Acknowledgement (NACK).

Based on the above idea, the present invention provides an adaptive handover method, which specifically uses the following technical solution: When the RI reported by the terminal is not consistent with the RI used by the base station to transmit data in the previous frame, the RI that the terminal last reported is estimated. The spectrum efficiency of the corresponding transmission mode, if the estimated spectrum efficiency is higher than the spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame, the base station transmits the data using the RI reported by the terminal last time. Further, the RI reported by the terminal is the same as the RI used by the base station to transmit data in the previous frame; or the RI reported by the terminal is not consistent with the RI used by the base station to transmit data in the previous frame, but the estimated spectrum efficiency is equal to When the spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame is lower than that of the previous frame, the base station still uses the RI used in the previous frame to transmit data. It should be noted that the terminal does not report the RI every frame. For example, the UE reports RI=1 on the t frame, and the UE reports RI=2 on the t+4 frame. Then, in this paper, it is considered to be t+1 frame to t+. The RI reported by the three-frame terminal is 1, that is, the RI of the UE last time. Further, when the value of the outer loop adjustment parameter A CS is less than 0, it is determined that the estimated frequency efficiency is higher than the frequency efficiency of the transmission method corresponding to the RI used by the base station of the previous frame. Further, according to the last reported RI of the terminal and the data transmitted by the base station in the previous frame, For different values of the RI, the block error rate BLER is separately calculated and the value of the CS is obtained. Further, when the RI of the last time reported by the terminal is equal to 2, the number of times the RI used by the base station to transmit data is equal to 1 when the number of statistics exceeds a predetermined threshold and the spectrum efficiency of the terminal is the most recent. Then, the base station transmits data using the RI reported by the terminal last time. Specifically, according to the RI of the data transmitted by the base station in the previous frame and the value of the last reported RI of the UE, the following four processes are respectively provided (for the first time that the UE is scheduled, the RI of the data transmitted by the base station in the previous frame is the closest to the UE. The value of RI reported once is the same). Flow A: If the RI of the data transmitted by the base station in the previous frame is equal to 1 and the RI reported by the UE last time is equal to 1, the handover procedure A is entered. The process A is divided into the following steps: Step A1: The spectrum efficiency corresponding to an MCS is the closest to the spectrum efficiency corresponding to the reported channel quality indicator (CQI), and the MCS is recorded as MCS _imt . Step A2: The MCS of the final base station transmitting data is: MCS _use = max(min(( C^ _rai + AMCSl), MCS _Max), MCS _Min) where MCS_M«x represents the MCS maximum value specified by the protocol, and for the LTE system is 28 . MCS _M « represents the minimum MCS specified by the protocol, and is 0 for the LTE system. Step A3: The base station transmits data using RI equal to 1 in this frame. Step A4: The UE feeds back the ACK/NACK of the current frame, and is used to calculate and calculate the BLER1 corresponding to the process and obtain the outer ring parameter AMCSI.

Flow B: If the RI of the data transmitted by the base station in the previous frame is equal to 2 and the RI reported by the UE last time is equal to 2, the process B is entered. Process B is divided into the following steps:

Then the MCS is recorded as MC& _m . Step B2: The MCS of the final base station transmitting data is:

MCS _use = max(min(( C^ _rai + AMCS2), MCS _Max), MCS _Min) where MCS_M«x represents the maximum MCS value specified by the protocol, and 28 for the LTE system. MCS _M « represents the minimum MCS specified by the protocol, and is 0 for the LTE system. Step B3: The base station transmits data using RI equal to 2 in this frame. Step B4: The UE feeds back the ACK/NACK information of the current frame for calculating BLER2 and acquiring the outer loop parameter A CS2.

Flow C: If the RI of the data transmitted by the base station in the previous frame is equal to 1 and the RI reported by the UE last time is equal to 2, the process C is entered. Flow C is divided into the following steps: Step C1: C - R1R2 = C - R1R2 + 1; where C - R1R2 has an initial value of 0.

Mark the MCS as MC, ― _M , then

MCS _SM = max(min(( C^ _ira , _SM + AMCS2), MCS _Max), MCS _Min) where MCS _SM represents the corresponding MCS when RI=2, MCS_Max represents the MCS maximum value specified by the protocol, for the LTE system Is 28. MCS _M indicates the minimum MCS specified by the protocol, and is 0 for the LTE system. Calculate the frequency efficiency of MC3⁄4 _M and multiply by 2 (because RI=2), denoted as T-R2-tmpl. Step C3: Calculate the mean value of T-R2-tmpl in the window, denoted as T-R2, and use the sliding window method, and the window length is M (value range 5-100). Perform steps C4, C5, and C6 if one of the following conditions is met, otherwise perform steps C7, C8, and C9. Condition 1: If C—R1R2 is greater than or equal to M and T—R2 is greater than the maximum MCS that can be used The spectral efficiency T-SFBC (ie the spectral efficiency corresponding to the diversity mode MCS=28). Where T-R2 is greater than T-SFBC, it means that the frequency efficiency estimated by RI=2 is higher than the highest efficiency of RI=1, so it can be directly switched to RI=2. Condition 2: A CS4 is less than 0. Among them, A CS4 is less than 0, which means that the frequency efficiency of RI=1 is lower than the estimated spectral efficiency of RI=2. Step C4: The base station uses RI equal to 2 for this frame, and uses MC _{M to} transmit data. Step C5: Initialize the outer loop parameters, that is, A CS4=0, BLER4 re-statistics, and the corresponding ACK/NACK is cleared, C—R1R2=0, T_R2=0, and the window data in step C3 is cleared. Step C6: The UE feeds back the ACK/NACK information of the current frame to calculate the BLER2 and outer ring parameters.

A CS2 acquisition. Step C7: The base station uses the RI equal to 1 to transmit data. Step C8: Determine MG^., according to T_R2_tmpl in step C2, the principle is that the spectral efficiency corresponding to a certain MCS is closest to T-R2-tmpl. Further, the MCS of the transmitted data is determined according to the following formula.

MCS _use = max(min(( C^ _ira , AMCS4), MCS_Max), MCS _Min) where MCS_M«x represents the maximum MCS specified by the protocol, and 28 for the LTE system. MCS_M « represents the minimum MCS specified by the protocol, and is 0 for the LTE system. Step C9: The UE feeds back the ACK/NACK information of the current frame, and is used to calculate the acquisition of the BLER4 and the outer ring parameter A CS4.

Flow D: If the RI of the data transmitted by the base station in the previous frame is equal to 2 and the RI reported by the UE last time is equal to 1, the handover procedure D is entered. The process D is divided into the following steps: Step D1: further judge according to the value of A CS3. If A CS3 is greater than or equal to 0, perform steps D2 to D7. If A CS3 is less than 0, perform steps D8 to D1 l. Step D2: The base station transmits data using RI equal to 2 in this frame. Step D3: The spectrum efficiency corresponding to an MCS is closest to the spectrum efficiency corresponding to the reported CQI, and the MCS is recorded as MCS _init . MCS _SFBC is obtained by:

MCS max(min(( C^. _ra , AMCS\), MCS _Max), MCS _Min) where MCS_M«x represents the maximum MCS specified by the protocol, and 28 for the LTE system.

MCS_M« represents the minimum MCS specified by the protocol and is 0 for the LTE system. Step D4: Calculate the spectral efficiency corresponding to MC^ _BC , and divide it by 2 and record it as r. Step D5: The spectrum efficiency corresponding to an MCS is closest to ^, and the MCS is recorded as

MCS _{init SM} . Step D6: The MCS of the final base station transmitting data is:

MCS _use = max(min(( C^. _ra , _SM + AMCS3), MCS_Max , MCS _Min) where MCS_M«x represents the maximum MCS specified by the protocol, and for the LTE system is 28. MCS_M« represents the MCS specified by the protocol The minimum value is 0 for the LTE system. Step D7: The UE feeds back the ACK/NACK information of the current frame for calculating the acquisition of the BLER3 and the outer ring parameter A CS3. Step D8: The base station transmits the data using RI equal to 1 in the current frame. Step D9: The outer loop parameter is initialized, that is, A CS3 =0, BLER3 is re-statisticed, and the corresponding ACK/NACK is cleared. Step D10: The spectrum efficiency corresponding to an MCS is the closest to the spectrum efficiency corresponding to the reported CQI, and the MCS is recorded as MCS. _Imt The MCS of the final base station to send data is:

MCS _use = max(min(( C^ _rai + AMCSl), MCS _Max), MCS _Min) where MCS_M«x represents the maximum MCS specified by the protocol, and 28 for the LTE system. MCS_M« represents the minimum MCS specified by the protocol and is 0 for the LTE system. Step D1: The UE feeds back the ACK/NACK information of the current frame for calculating the acquisition of the BLER1 and the outer loop parameter A CS1. The implementation of the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the case of no conflict, the features of the embodiments and the embodiments of the present invention may be arbitrarily combined with each other. 1 is a schematic flowchart of an adaptive handover method in an LTE downlink transmission mode 3 according to an embodiment of the present invention. Referring to FIG. 1, the adaptive handover method in this embodiment is specifically described as follows: Step 101: Parameter initialization includes outer loop adjustment parameters, BLER, T_R2_tmpl value in the window, C_R1R2 and T_R2; Step 102, determining whether the RI of the upper frame is equal to the RI reported by the UE at the current time, if yes, executing step 103; if not, Step 104: Step 103: Send data using the RI reported by the UE last time; Step 104: Determine whether the base station of the previous frame uses RI=1 and the RI=2 reported by the UE last time. If yes, execute step 105. If not, perform step 108; Step 105, determine whether the corresponding DeltaMCS is non-negative, and RI The frequency efficiency of =2 does not exceed the maximum spectral efficiency of RI=1, if yes, step 106 is performed, if not, step 107 is performed; step 106, it is decided not to perform handover, and the base station continues to use RI=1 to transmit data; End. In step 107, it is decided to perform handover, and the base station transmits data by using RI=2 in the current frame; Step 108, that is, the base station uses the RI=2 and the last reported RI=1 of the UE, and then determines whether the corresponding DeltaMCS is non-negative. If yes, step 109 is performed. If not, step 110 is performed; , decide not to perform handover, the base station continues to use RI=2 to send data; the end. Step 110: Determine to perform handover, and the base station transmits data by using RI=1 in the current frame, and ends.

In addition, an embodiment of the present invention further provides an adaptive handover system (not shown), which is applied to the LTE downlink transmission mode 3. The adaptive handover system in this embodiment includes a rank indicator comparison unit and a handover decision in the base station. Unit, where: The rank indicator comparison unit is configured to: compare whether the RI reported by the terminal last time is consistent with the RI used by the base station to transmit data of the previous frame, and if not, notify the handover decision unit of the result of the inconsistency;

The handover decision unit is configured to: after receiving the result of the inconsistency, estimate a spectrum efficiency of a transmission mode corresponding to the RI reported by the terminal last time, if the estimated spectrum efficiency is higher than an RI used by the base station of the previous frame The spectrum efficiency of the corresponding transmission mode determines that the base station uses the RI transmission data that is last reported by the terminal. Further, the rank indicator comparing unit is further configured to: if it is determined that the RI reported by the terminal last time is compared with the RI used by the base station to send data of the previous frame, notify the handover decision unit of the result of the consistency; The handover decision unit is further configured to: according to the result of the agreement, determine that the base station still uses the RI transmission data used in the previous frame. Further, the handover decision unit is further configured to: after receiving the result of the inconsistency, if the estimated spectral efficiency is equal to or lower than a spectrum efficiency of a transmission mode corresponding to the RI used by the base station in the previous frame, The base station still uses the RI used in the previous frame to transmit data. Further, the system further includes an outer loop adjustment parameter obtaining unit, where the outer loop adjustment parameter obtaining unit is configured to: according to different values of the RI reported by the terminal and the RI used by the base station to send data in the previous frame. Calculating the block error rate BLER and obtaining the value of the outer loop adjustment parameter AMCS; the handover decision unit is further configured to: when the value of the outer loop adjustment parameter A CS is less than 0, determine that the estimated spectrum efficiency is higher than The spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame. Further, the handover decision unit is further configured to: count the number of times when the RI of the last time the terminal is up to 2 and the RI used by the base station to transmit data is equal to 1 when the number of statistics exceeds a predetermined threshold When the spectrum efficiency of the transmission mode corresponding to the RI reported by the terminal is greater than the spectrum efficiency corresponding to the maximum MCS that can be used in the diversity mode, the base station frame is determined to use the RI transmission data that is last reported by the terminal. The adaptive switching method of the present invention will be more specifically described below in conjunction with an application example. The application example 1 sets AMCSl = -1, AMCS2 = -2, AMCS3 = 0, AMCS4 = 0, C_R1R2=0, the sliding window length M is 5, there is no value in the window; the base station sends data to the UE on one frame. RI=1, and RI=1 reported by the UE in the current frame, and CQI=5 reported last time. According to the usage of the RI of the previous frame and the latest reporting of the RI, the process A of the switching algorithm is entered, and the process A is divided into the following four steps: Step A1: First, according to the correspondence between the CQI and the spectrum efficiency, the CQI=5 corresponding is found. The frequency efficiency is 0.8770; among them, according to the LTE protocol, the correspondence between CQI and spectrum efficiency is as shown in Table 1:

Correspondence between CQI and spectral efficiency

15 64QAM 948 .5547 According to the principle of spectral efficiency, MCS _m 7; where the spectral efficiency of each MCS ( 0-28 ) is {0.1970, 0.2424, 0.3106, 0.4167, 0.5227, 0.6439, 0.7652, 0.9167, 1.0379 , 1.1894, 1.1894, 1.3106, 1.5227, 1.7045, 1.9167, 2.1591, 2.3409, 2.3409, 2.4621, 2.7045, 2.9470, 3.3106, 3.5530, 3.7955, 4.0379, 4.3409, 4.7045, 4.8864, 5.6742}. Step A2: The MCS of the final base station transmitting data is:

MCS max(min((7 + (-1)), 28), 0) = 6 Step A3: The base station uses the RI equal to 1 to transmit data. Step A4: The UE feeds back the ACK/NACK of this frame to calculate the BLER1 and outer ring parameters.

The application example 2 sets AMCSI = 0, AMCS2 = -2, AMCS3 = 0, AMCS4 = -1, C_R1R2=20, the sliding window length M is 5, and the five values in the window are {2.4621, 2.4621, 2.9470, respectively. , 3.3106, 3.5530}. The RI=1 used by the base station to send data to the UE on one frame, and the RI=2 reported by the UE last time, and the reported CQI=3. According to the usage of the previous frame RI and the latest report of the RI, the process flow C is entered, and the process C is divided into the following steps: Step C1: C - R1R2 = C_R1R2 + 1 = 21; Step C2: CQI = 3 The spectral efficiency is 0.3770, according to the principle of spectral efficiency

Mcs _{Mt SM} ^ , further seeking

MCS _SM = max(min((3 + (-2)),28),0) = 1

The frequency efficiency of MCS1 is 0.2424, and the result after multiplying by 2 is 0.4848, namely: T—R2—tmpl is 0.4848. Step C3: Calculate T—R2 by sliding window. The average value of D-1, equal to {2.4621, 2.9470, 3.3106, 3.5530, 0.4848} is 2.5515. Contrast conditions, satisfying condition 2, so continue to execute C4, C5 and C6. Step C4: The base station uses RI equal to 2 for this frame, and sends data using MC _M = 1. Step C5: Initialize the outer loop parameters, that is, A CS4=0, BLER4 re-statistics, and the corresponding ACK/NACK is cleared, C—R1R2=0, T_R2=0, and the window data in step C3 is cleared. Step C6: The UE feeds back the ACK/NACK information of the current frame for calculating BLER2 and acquiring the outer loop parameter A CS2.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. The present invention may be embodied in various other embodiments without departing from the spirit and scope of the invention. Various changes and modifications may be made to the invention, and such changes and modifications are intended to be included within the scope of the appended claims. One of ordinary skill in the art will appreciate that all or a portion of the above steps may be accomplished by a program instructing the associated hardware, such as a read-only memory, a magnetic disk, or an optical disk. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each module/unit in the above embodiment may be implemented in the form of hardware or in the form of a software function module. The invention is not limited to any specific form of combination of hardware and software.

Industrial Applicability According to the present invention, according to the case where the RI of the data transmitted by the base station in the previous frame and the RI reported by the UE last time, if the RIs of the two are inconsistent, the spectrum efficiencies corresponding to the two transmission modes are respectively estimated and compared, and the comparison result is determined according to the comparison result. Whether to perform handover; In addition, when estimating the corresponding spectrum efficiency, combined with the outer loop adjustment parameters, the transmission mode with higher spectral efficiency is selected, and the system throughput is effectively improved.

Claims

Claim

An adaptive handover method, the method includes: when the rank indicator (RI) reported by the terminal is inconsistent with the RI used by the base station to transmit data, estimating the RI corresponding to the last reported RRC of the terminal The spectrum efficiency of the transmission mode. If the estimated spectrum efficiency is higher than the spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame, the base station transmits data using the RI reported by the terminal last time.

2. The method according to claim 1, further comprising: RI when the terminal recently reported the RI and the RI used by the base station to transmit data in the previous frame; or the RI reported by the terminal last time and the previous one The RI used by the frame base station to transmit data is inconsistent, but when the estimated spectrum efficiency is equal to or lower than the spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame, the base station still uses the RI used in the previous frame to transmit data. .

3. The method according to claim 1, wherein, when the value of the outer loop adjustment parameter A CS is less than 0, it is determined that the estimated spectral efficiency is higher than the spectrum of the transmission method corresponding to the RI used by the base station of the previous frame. effectiveness.

4. The method of claim 3, further comprising, according to the last time the terminal was reported

RI and the different values of the RI used by the base station to transmit data in the previous frame, respectively calculate the block error rate (BLER) and obtain the value of the A CS.

The method according to claim 3 or 4, further comprising: counting the number of times when the RI of the last time reported by the terminal is equal to 2 and the RI used by the base station to transmit data in the previous frame is equal to 1, when the number of statistics exceeds a predetermined number If the spectrum efficiency of the transmission mode corresponding to the RI that the terminal has reported last time is greater than the spectrum efficiency of the maximum MCS that can be used in the diversity mode, the base station transmits data using the RI reported by the terminal last time.

6. An adaptive handover system, the system being applied to a long-term evolution system (LTE) downlink transmission In the mode 3, the system includes a rank indicator comparing unit and a handover decision unit in the base station, where: the rank indicator comparing unit is configured to: compare the last reported rank indicator (RI) of the terminal with the previous frame base station Whether the RIs used for sending data are consistent. If they are inconsistent, the result of the inconsistency is notified to the handover decision unit. The handover decision unit is configured to: after receiving the result of the inconsistency, estimate the transmission corresponding to the RI reported by the terminal last time. The spectral efficiency of the mode, if the estimated spectrum efficiency is higher than the spectrum efficiency of the transmission mode corresponding to the RI used by the base station in the previous frame, determines that the base station uses the RI transmission data that the terminal last reported.

7. The system according to claim 6, wherein the rank indicator comparing unit is further configured to: if it is determined that the RI reported by the terminal last time is compared with the RI used by the base station to transmit data of the previous frame, Notifying the handover decision unit of a consistent result;

The handover decision unit is further configured to: according to the result of the consistency, determine that the base station still uses the RI used to transmit data in the previous frame.

8. The system according to claim 6, wherein the handover decision unit is further configured to: after receiving the result of the inconsistency, if the estimated spectral efficiency is equal to or lower than an RI used by a base station of a previous frame The spectral efficiency of the corresponding transmission mode determines that the base station still uses the RI transmission data used in the previous frame.

9. The system of claim 6, 7 or 8, further comprising an outer loop adjustment parameter acquisition unit,

The outer loop adjustment parameter obtaining unit is configured to: calculate a block error rate (BLER) and obtain an outer loop adjustment parameter according to different values of the RI used by the terminal and the RI used by the base station to send data. The value of the AMCS is further set to: when the value of the outer loop adjustment parameter A CS is less than 0, it is determined that the estimated spectrum efficiency is higher than the frequency of the transmission method corresponding to the RI used by the base station of the previous frame. Spectral efficiency.

10. The system according to claim 9, wherein the handover decision unit is further configured to: count the number of times when the RI of the last time the terminal is equal to 2 and the RI used by the base station to transmit data in the previous frame is equal to 1 When the number of times of the statistic exceeds the predetermined threshold and the spectrum efficiency of the RI corresponding to the latest reporting of the terminal is greater than the spectrum efficiency of the maximum MCS that can be used in the diversity mode, the base station is determined to use the terminal most recently. The RI sent by one report sends data.