Soft-Persistent Uplink Scheduling for Interference Management
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Solution Overview
Problem
The existing uplink scheduling methods in 3GPP LTE wireless networks face interference variation issues due to frequency selective gain, which complicates modulation and coding scheme (MCS) adaptation, leading to performance degradation. Current persistence scheduling approaches restrict resource allocation, limiting frequency selective gain and increasing complexity.
Innovation Solution
A soft-persistent scheduling scheme is implemented, where a bonus is added to the priority of user equipment (UE) for resource blocks allocated in previous transmission time intervals (TTIs), allowing for more consistent resource allocation while still enabling frequency selective gain by adjusting priorities based on recent resource block allocations and interference variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency selective scheduling is used to allocate UEs to RBs with best quality, then frequency selective gain is achieved, but interference variation at neighboring BS increases making MCS adaptation difficult
Solution Approach 1:
The patent applies preliminary action by pre-allocating resource blocks to UEs based on their channel quality indicators (CQIs) before actual data transmission. The base station identifies suitable RBs for each UE in advance, considering both the UE's channel conditions and the interference impact on neighboring base stations. This preliminary allocation allows the system to prepare modulation and coding schemes (MCS) ahead of time, reducing the negative impact of interference variation on MCS adaptation while maintaining frequency selective gain.
2Reliability
If persistent scheduling is used to reduce interference variation, then MCS adaptation improves, but frequency selective gain is limited due to restricted resource allocation
Solution Approach 1:
The patent applies dynamics by implementing a flexible persistent scheduling mechanism where resource block allocations are maintained across multiple transmission time intervals (TTIs) but can be dynamically adjusted. The base station continues to allocate the same RBs to a UE over several TTIs to provide persistence and reduce interference variation, but simultaneously monitors channel conditions and allows re-allocation when significant changes occur. This dynamic approach maintains the benefits of persistent scheduling for MCS adaptation while preserving the ability to capture frequency selective gain when channel conditions warrant it.
3Productivity
If resource blocks are frequently reallocated to capture best channel conditions, then frequency selective gain is maximized, but interference volatility increases
Solution Approach 1:
The patent applies parameter changes by modifying the allocation parameters (such as the persistence factor or allocation frequency) based on channel conditions and interference measurements. Instead of using a fixed allocation strategy, the base station adjusts the degree of persistence in resource block allocation - sometimes maintaining the same allocation over multiple TTIs to reduce interference volatility, and sometimes changing allocations more frequently to capture frequency selective gain when channel conditions indicate it is beneficial. This adaptive parameter adjustment resolves the contradiction between maximizing frequency selective gain and minimizing interference volatility.
Data Source
AI summary
A method embodiment for transmission scheduling includes implementing, by a first base station (BS), a soft-persistent scheduling scheme. The soft-persistent scheduling scheme includes allocating a first resource block to a first UE and other resource blocks to other UEs for a first transmission time interval (TTI), calculating a first priority of the first UE for the first resource block for a second TTI, wherein calculating the first priority involves including a first bonus in the first priority, and wherein the second TTI is later than the first TTI, calculating other priorities for the other UEs and the other resource blocks for the second TTI, and allocating the first and the other resource blocks to the first and other UEs for the second TTI in accordance with the first priority of the first UE as modified by the first bonus and the other priorities of the other UEs.