Cross-Carrier Scheduling Timing Alignment in TDD Carrier Aggregation
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Solution Overview
Problem
In the LTE-A system, defining timing relationships between PDCCH and cross-carrier scheduled PUSCH, between cross-carrier scheduled PUSCH and PHICH, and between cross-carrier scheduled PDSCH and uplink HARQ ACK/NACK is challenging, especially when TDD uplink-downlink configurations of aggregated carriers differ, leading to difficulties in data and control channel transmission errors and delays.
Innovation Solution
A method is provided where the base station transmits scheduling information on a control channel of a first cell and data on a shared channel of a second cell, using downlink subframes with differing subframe configuration information, allowing for cross-carrier scheduling to mitigate errors and delays by aligning transmission timings across aggregated carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cross-carrier scheduling is implemented with different TDD uplink-downlink configurations on aggregated carriers, then bandwidth and data rate are improved, but timing relationship definition becomes complex and error-prone
Solution Approach 1:
The patent changes the parameter of subframe configuration by introducing a new parameter 'k' that indicates the offset between the subframe carrying scheduling information and the subframe carrying the scheduled data or control channel. This parameter-based approach allows flexible timing relationship definition across different TDD configurations without requiring complex configuration tables, thereby resolving the contradiction between high data rate and timing definition complexity.
Solution Approach 2:
The patent segments the timing relationship definition into multiple independent parameters: 'k' for the offset between scheduling subframe and data/control subframe, and 'm' for the offset between scheduled data subframe and HARQ ACK/NACK subframe. This segmentation allows each parameter to be independently configured and managed, simplifying the overall timing relationship definition while supporting cross-carrier scheduling with different TDD configurations.
2Reliability
If detailed transmission timings are defined for cross-carrier scheduling, then transmission errors and delays are reduced, but system complexity increases
Solution Approach 1:
The patent introduces compact parameters 'k' and 'm' to represent complex timing relationships. Instead of defining detailed timing configurations for each scenario, the patent uses these parameters to concisely specify the timing offsets, thereby reducing transmission errors and delays while avoiding excessive system complexity.
3Area of stationary object
If carrier aggregation with different TDD configurations is used, then bandwidth is expanded, but synchronization and timing alignment become difficult
Solution Approach 1:
The patent uses parameter 'k' to define the timing offset between the control channel subframe on one carrier and the scheduled data or control channel subframe on another carrier with different TDD configuration. This parameter-based approach enables easy timing alignment across carriers with different configurations, allowing bandwidth expansion through carrier aggregation while maintaining operational simplicity.
Data Source
AI summary
A method, base station, and terminal employing time division duplex and carrier aggregation are disclosed. The method by the base station includes transmitting, to a terminal, scheduling information on a control channel of a first cell, and transmitting, to the terminal, data on a shared channel of a second cell based on the scheduling information. The scheduling information is transmitted in a first downlink subframe or a first subframe including downlink pilot time slot (DwPTS) based on first subframe configuration information of the first cell. The data is transmitted in a second downlink subframe or a second subframe including DwPTS corresponding to the first downlink subframe or the first subframe. The first subframe configuration information of the first cell is different from second subframe configuration information of the second cell.