HARQ Retransmission Slot Permutation for Recurring Interference
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Solution Overview
Problem
Synchronous HARQ and persistent scheduling in wireless communication systems are susceptible to recurring interference, particularly at the cell edge, leading to packet loss and performance degradation due to fixed resource allocation patterns.
Innovation Solution
A modified scheduling scheme that permutes retransmission slots in both time and frequency to avoid periodic interference, using cell-specific or sector-specific scheduling functions that change resource allocation patterns to prevent collisions, while maintaining the overhead advantages of periodic scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If synchronous HARQ or persistent scheduling is employed with fixed resource allocation patterns, then resource allocation efficiency is improved and signaling overhead is reduced, but recurring interference occurs leading to packet loss and performance degradation
Solution Approach 1:
The patent applies dynamics by making the resource allocation pattern variable rather than fixed. Specifically, it introduces time-varying shifts to the resource allocation pattern for synchronous HARQ retransmissions, where the shift amount changes with each retransmission attempt. This dynamic adjustment breaks the recurring interference pattern while maintaining the efficiency benefits of predetermined resource locations, thereby resolving the contradiction between resource allocation efficiency and reliability.
2Ease of operation
If fixed resource allocation patterns are used for synchronous HARQ retransmissions, then resource reservation is simplified, but interference from neighboring cells with same patterns causes repeated packet loss
Solution Approach 1:
The patent applies asymmetry by introducing asymmetric shifts to the resource allocation pattern. Instead of using identical resource patterns across all retransmissions, the system applies different time shifts to each retransmission attempt. This asymmetric modification to the otherwise symmetric fixed pattern breaks the interference alignment with neighboring cells while maintaining operational simplicity through predetermined shift values.
3Loss of information
If periodic resource allocation is used for persistent scheduling, then MAP overhead is reduced for predictable traffic, but recurring interference patterns cause performance degradation at cell edge
Solution Approach 1:
The patent applies periodic action with a twist - it maintains the periodic nature of resource allocation for persistent scheduling but introduces varying phase shifts to the periodic pattern. The resource allocation remains periodic to maintain low MAP overhead, but the phase shift varies with each transmission interval, breaking the recurring interference pattern while preserving the efficiency benefits of periodic scheduling for predictable traffic patterns.
Data Source
AI summary
A method of avoiding periodic interference by permuting periodic transmissions by a base station (BS) may include transmitting a frame of data to a subscriber station (SS). The BS may check for an acknowledgement of the frame of data from the SS and may schedule a next frame of data for transmission or retransmission based on whether the acknowledgement was received from the SS. The scheduling may include permuting traffic within the next frame in time or in frequency relative to similar traffic in a prior frame according to a predetermined function. The BS may generate media access protocol (MAP) information for the next frame based on the permuting.