Scheduling Request Enhancements For 5G NR-U Networks
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Solution Overview
Problem
Current 5G networks face challenges in scheduling requests, particularly in unlicensed spectrum, due to listen-before-talk (LBT) requirements that can lead to increased latency and reduced throughput, as UEs may struggle to detect available channels, resulting in repeated connection reestablishments and inefficient resource allocation.
Innovation Solution
The implementation of enhanced scheduling request techniques, including the use of RRC signaling to configure SR timers and counters, separate LBT timers, and multiple PUCCH resources across different bandwidth parts and cells, to manage and optimize SR transmissions, thereby reducing the impact of LBT failures and increasing transmission opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen-before-talk (LBT) requirements are implemented in unlicensed spectrum, then channel access reliability is improved, but transmission latency increases and throughput decreases
Solution Approach 1:
The patent implements preliminary actions by configuring SR timers and counters before actual scheduling request transmissions. The sr-ProhibitTimer prevents excessive SR transmissions during channel access attempts, while sr-TransMax sets a preliminary limit on transmission retries. This preliminary configuration reduces latency by avoiding unnecessary repeated connection reestablishments while maintaining reliability through structured LBT failure handling.
Solution Approach 2:
The patent introduces intermediary mechanisms including separate LBT timers (lbt-Sr-ProhibitTimer, lbt-Sr-TransMax) that mediate between the LBT procedure and SR transmission. These intermediaries buffer the impact of LBT failures by providing dedicated timing control, allowing the system to maintain reliable channel access while reducing the latency impact through controlled retry behavior rather than immediate reestablishment.
2Productivity
If multiple PUCCH resources across different bandwidth parts and cells are configured, then SR transmission opportunities increase, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing PUCCH resources across multiple bandwidth parts (BWPs) and serving cells. Instead of a single SR transmission resource, the system segments resources into multiple options that can be selectively used based on channel conditions and LBT outcomes. This segmentation increases transmission opportunities by providing alternative paths while managing complexity through structured organization of resources across different frequency and cell domains.
Solution Approach 2:
The patent introduces additional dimensions for SR transmission by utilizing multiple serving cells and bandwidth parts. Rather than relying solely on time-domain resources, the system adds spatial (different cells) and frequency (different BWPs) dimensions. This multi-dimensional resource allocation increases transmission opportunities through diverse pathways while managing complexity through standardized configuration procedures across the additional dimensions.
3Reliability
If separate LBT timers and SR counters are implemented, then LBT failure management is improved, but signaling overhead increases
Solution Approach 1:
The patent extracts LBT-specific timing parameters from the general SR configuration by introducing separate LBT timers (lbt-Sr-ProhibitTimer, lbt-Sr-TransMax) distinct from traditional SR parameters. This extraction allows independent optimization of LBT failure management without affecting core SR functionality. The separated parameters enable targeted control of LBT-related behavior, improving reliability through specialized timing control while managing signaling overhead by keeping the extracted parameters confined to LBT-specific contexts.
Data Source
AI summary
An apparatus of user equipment (UE) includes processing circuitry coupled to memory, where to configure the UE for communication of data in a New Radio-Unlicensed (NR-U) spectrum, the processing circuitry is to decode RRC signaling from a base station. The RRC signaling includes configuration information to configure a listen-before-talk (LBT) timer and a scheduling request (SR) prohibit timer. An LBT procedure is performed while the LBT timer is activated. An SR is encoded for transmission to the base station, based on detecting an unoccupied transmission resource within the NR-U spectrum during the LBT procedure. The SR transmission activates the SR prohibit timer. An uplink grant from the base station is decoded in response to the SR, the uplink grant received while the SR prohibit timer is activated. A buffer status report (BSR) is encoded for transmission to the base station based on the uplink grant.