Relay Station HARQ Timing Coordination for Collision Avoidance
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Solution Overview
Problem
Conventional wireless communication systems face challenges in performing Hybrid Automatic Repeat Request (HARQ) for relay stations, as they typically consider only one-to-one situations between base stations and mobile terminals, making it difficult to maintain compatibility with existing synchronous HARQ and avoid collisions.
Innovation Solution
A method for a relay station to perform HARQ using a fixed period with mobile stations and a series of HARQ periods with base stations, where the HARQ period series includes elements (xk, yk) indicating the timing of ACK/NACK signal receipt and retransmission, with at least one of xk and yk differing across periods, ensuring compatibility with synchronous HARQ and avoiding collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional one-to-one HARQ between base station and mobile terminal is used, then system simplicity is maintained, but relay station functionality and coverage extension cannot be achieved
Solution Approach 1:
The patent segments the HARQ process into separate uplink and downlink HARQ procedures. The relay station performs independent HARQ with the mobile terminal in uplink and with the base station in downlink, allowing each HARQ process to be optimized separately while maintaining overall system functionality
Solution Approach 2:
The relay station acts as an intermediary that bridges the base station and mobile terminal. It receives downlink data from the base station, performs HARQ operations, and forwards to the mobile terminal, enabling coverage extension while managing HARQ complexity at the relay level
2Loss of information
If synchronous HARQ is used between base station and mobile terminal, then signaling overhead is reduced, but collisions occur when relay station is involved
Solution Approach 1:
The patent introduces dynamic timing adjustments where the relay station can flexibly determine HARQ timing based on its processing capabilities and buffer status. The timing between receiving downlink data from base station and transmitting uplink data to mobile terminal is dynamically optimized to prevent collisions while maintaining synchronous HARQ benefits
Solution Approach 2:
The relay station performs preliminary HARQ operations with the mobile terminal before receiving downlink data from the base station. By preparing uplink transmissions in advance and managing buffers proactively, the relay station avoids collisions between uplink and downlink HARQ processes
3Area of stationary object
If relay station performs HARQ with both base station and mobile terminal, then coverage is extended, but HARQ collision and timing coordination become problematic
Solution Approach 1:
The patent separates HARQ operations into different time dimensions, creating distinct uplink and downlink HARQ processes that operate independently. The relay station manages timing in the time domain by scheduling uplink HARQ transmissions in different time slots from downlink HARQ receptions, eliminating collisions while extending coverage
Data Source
AI summary
A method for performing HARQ includes: receiving information to determine downlink subframes used for a relay station to receive scheduling information from a BS; determining uplink subframes for performing a HARQ with the DL subframes, each of the UL subframes corresponding to each of the DL subframes; assigning sequentially each of a plurality of HARQ processes to each of the UL subframes one by one; and performing HARQ with the BS at at least one of the HARQ processes. An n-th subframe is configured for a corresponding UL subframe if an (n−4)-th subframe is configured for one of the DL subframes, n denoting an integer. The HARQ processes are equal in number to the UL subframes. The DL subframes are configured in at least one radio frame having 10 subframes indexed from 0 to 9. Subframes having indexes 0, 4, 5 and 9 are not configured as a DL subframe.