LTE-A Mobile Station TAG Identifier Handling
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Solution Overview
Problem
In LTE-A R11, the setting of Timing Advance Groups (TAGs) leads to issues in wireless communication systems, particularly due to misidentification of TAG identifiers by mobile stations when connected to base stations of different release numbers, resulting in incorrect adjustment of upstream transmission timings.
Innovation Solution
The solution involves modifying the format of the Timing Advance Command (TAC) to include a TAG identifier, allowing mobile stations to correctly identify and apply the appropriate Timing Advance values to cells within specific TAGs, even when connected to base stations of different release numbers, by using specific bit configurations to distinguish between primary and secondary TAGs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier aggregation with multiple TAGs is implemented in LTE-A R11, then transmission timing accuracy for different cell groups is improved, but compatibility with base stations of different release numbers deteriorates due to misidentification of TAG identifiers
Solution Approach 1:
The mobile station performs preliminary determination of TAG identifier interpretation based on the release number of the base station before processing TAC. When connected to an R11 base station, the mobile station interprets the most significant bit according to R11 rules (indicating sTAG). When connected to pre-R11 base stations, it interprets the bit according to R10 rules (ignoring TAG differentiation). This preliminary action based on release number detection resolves the compatibility issue while maintaining timing accuracy for both scenarios
Solution Approach 2:
The interpretation parameter of the TAG identifier bit is changed dynamically based on the base station's release number. The mobile station adjusts how it reads the most significant bit of the TAG identifier: in R11 mode, it treats the bit as indicating sTAG membership; in pre-R11 mode, it treats the same bit as part of the original R10 TAC format without TAG differentiation. This parameter change enables the system to maintain both timing accuracy for R11 and compatibility with older releases
2Reliability
If TAG identifier is included in TAC format, then correct identification of target TAG is improved, but complexity of message format increases
Solution Approach 1:
The TAG identifier is segmented into two parts: the most significant bit (which changed in R11) and the remaining bits (which maintain backward compatibility). The mobile station only needs to interpret the most significant bit differently based on release number, while the other bits remain unchanged. This segmentation reduces the complexity of format changes while maintaining reliable TAG identification
Solution Approach 2:
The TAC message format serves multiple functions: it maintains compatibility with pre-R11 base stations (where the most significant bit is interpreted as in R10) while simultaneously supporting R11 functionality (where the same bit indicates sTAG). This multi-functionality allows a single message format to serve both legacy and advanced scenarios, reducing the need for separate message formats and thereby reducing overall system complexity
Data Source
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AI summary
[Object] To provide a wireless communication system, a mobile station, and a base station that are able to resolve problems associated with the setting of a TAG in LTE-A Rl1. [Solution] A mobile station that performs wireless communication using a plurality of cells, the mobile station includes: a reception unit that receives a first control signal transmitted from a base station, the first control signal including first information used to adjust a transmission timing of the mobile station with the cells and second information that is different from the first information, and a second control signal transmitted from the base station; and a control unit that uses the first information to adjust the transmission timing of the mobile station with a cell specified by the second information among the cells when the second control signal includes information indicating whether the second information is used to specify the cell.