Uplink Synchronization Maintenance via Sync Reference Signal
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Solution Overview
Problem
Current wireless cellular communication systems face challenges in efficiently maintaining uplink synchronization of a large number of user equipment (UEs) in LTE networks, particularly due to high overhead associated with contention-based Random Access procedures, which limits spectral efficiency and increases latency.
Innovation Solution
The implementation of a contention-free scheduling request channel using a Sync Reference Signal (sync-RS) and Scheduling Request Indicator (SRI) allows UEs to request uplink resources without contention, enabling efficient synchronization maintenance with reduced overhead by allocating specific resources for timing adjustments and scheduling requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contention-based Random Access procedures are used for uplink synchronization maintenance, then UEs can request uplink resources, but overhead increases and spectral efficiency decreases
Solution Approach 1:
The patent segments the random access procedure by introducing a two-stage process: first, UEs send scheduling requests on a dedicated uplink control channel (PUCCH) without contention; only UEs needing timing adjustments proceed to the second stage using PRACH. This segmentation reduces overall overhead by filtering out UEs that don't require full random access procedures.
Solution Approach 2:
The patent introduces an intermediary scheduling request mechanism on the PUCCH channel that acts as a filter before the contention-based PRACH. This intermediary allows the base station to identify which UEs actually need timing adjustments, reducing unnecessary PRACH transmissions and associated overhead.
2Reliability
If contention-based Random Access procedures are used for uplink synchronization maintenance, then UEs can request uplink resources, but latency increases
Solution Approach 1:
The patent implements preliminary action by having UEs send scheduling requests on the PUCCH channel before potentially needing full random access. This preliminary step allows the base station to prepare and potentially provide timing adjustments earlier, reducing the overall latency for UEs that need synchronization maintenance.
Solution Approach 2:
By segmenting the procedure into an initial low-latency PUCCH request stage and a subsequent PRACH stage only when necessary, the patent reduces the average latency for uplink synchronization maintenance, as most UEs can be served through the faster PUCCH mechanism.
3Quantity of substance
If a large number of UEs are supported in connected mode, then network capacity increases, but synchronization maintenance becomes more difficult
Solution Approach 1:
The patent introduces an intermediary PUCCH-based scheduling request mechanism that simplifies synchronization maintenance for large numbers of UEs. By filtering through this intermediary, the base station can efficiently identify which UEs need attention without managing complex contention-based procedures for all connected UEs.
Solution Approach 2:
The patent segments UE management into two groups: those using the simplified PUCCH request mechanism and those requiring full PRACH procedures. This segmentation allows the base station to handle large numbers of UEs efficiently by applying different procedures based on their specific needs, reducing overall system complexity.
Data Source
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AI summary
A cell within cellular network includes user equipments (UEs) that transmit data to a base station (eNB). UEs are synchronized to the eNB upon entry to the cell. If a particular UE has data to transmit, it will be placed in a connected state and scheduled for transmission. Over a period of time, not all of the UEs will have data to transmit. The UEs are tracked (402) as a scheduled portion and an unscheduled portion, wherein a UE is included in the scheduled portion in response to receiving a scheduling request from the UE. Synchronization is maintained (404) between the eNB and each UE in the scheduled portion by sending a timing adjustment (TA) command if needed in response to receiving a scheduled transmission from each respective UE in the scheduled portion; Synchronization is maintained (406) between the eNB and each UE in the unscheduled portion by allocating a periodic reference signal (sync-RS) to each UE in the unscheduled portion and by sending a respective timing adjustment (TA) command if needed to each respective UE in the unscheduled portion in response to a respective sync-RS received from each UE in the unscheduled portion.