HARQ Subframe Alignment in Multi-Cell HSDPA Networks
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Solution Overview
Problem
In multi-cell wireless networks, particularly in Single Frequency Dual-Cell (SFDC)-HSDPA systems, the lack of synchronization between cells leads to mis-aligned subframes, causing challenges in Hybrid Automatic Repeat Request (HARQ) timing alignment, which affects the efficiency of feedback messaging and data transmission.
Innovation Solution
The implementation of a method to align subframes between mis-aligned cells by determining which subframes to associate, allowing for the distribution of the HARQ timeline burden between User Equipment (UE) and Node B, using RRC messages and NBAP signaling to inform UE and Node B of the associated subframes, and adjusting for timing drifts to maintain synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cells operate independently without synchronization, then each cell can transmit data autonomously, but subframes become mis-aligned causing HARQ timing conflicts
Solution Approach 1:
The patent segments the HARQ feedback process by introducing separate feedback channels (first HARQ feedback channel for first cell, second HARQ feedback channel for second cell) and separate downlink assignment channels. This allows each cell to operate autonomously while maintaining independent HARQ timing, resolving the conflict between autonomous operation and timing alignment.
2Productivity
If subframes are mis-aligned between cells, then flexible cell operation is maintained, but feedback message timing becomes uncertain affecting processing efficiency
Solution Approach 1:
The patent applies preliminary action by establishing predetermined timing relationships and associations between subframes of different cells before data transmission begins. The network configures and signals the associations between first subframes and second subframes in advance, allowing UE and Node B to prepare their processing schedules beforehand, thereby eliminating timing uncertainty while maintaining flexible operation.
3Adaptability or versatility
If HARQ feedback timing is not standardized, then autonomous transmission is possible, but processing burden on UE and Node B increases
Solution Approach 1:
The patent segments the processing burden by creating separate HARQ feedback channels and downlink assignment channels for each cell. This allows UE and Node B to process each cell's HARQ timing independently according to standardized rules, rather than managing complex cross-cell timing relationships, thereby reducing overall processing complexity while maintaining autonomous transmission capability.
Data Source
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AI summary
A method, apparatus, processing system, and computer program product enable association of mis-aligned subframes (802) (804) from a first and second downlink (1114) with one another, such that a HARQ acknowledgment message (1116) including jointly encoded feedback for the respective subframes can be correctly interpreted by the corresponding cells. Here, an RNC (1108) may provide an RRC message (1110) to the UE (1102) to associate particular subframes with one another. Further, the RNC (1108) may provide NBAP messages (1112) to the cells (1104) (1106) transmitting the downlink signals, so that the cells can associate the HARQ acknowledgment message (1116) with the appropriate subframe. Still further, additional signaling provides for changing the set of associated subframes when needed due to a drift in the timing offset between cells.