Managing Overlapping PRACH and SR Uplink Transmissions
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Solution Overview
Problem
Current 3GPP specifications for New Radio (NR) medium access control do not provide adequate state updates when PRACH and SR resources overlap, leading to additional latency as UE cannot immediately send the next SR or PRACH due to unaddressed skipped procedures.
Innovation Solution
The proposed solution involves a processor determining to skip UL transmissions for either a SR or PRACH procedure, adjusting associated parameters, and signaling this decision to the MAC to allow parallel procedures while avoiding overlapped transmissions, ensuring SR has higher priority over PRACH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If SR and PRACH resources are overlapped in time, then UE implementation determines which to transmit, but the skipped procedure's state is not updated, causing additional latency
Solution Approach 1:
The patent implements feedback mechanisms where the MAC layer updates the state of skipped procedures. When SR is skipped, SR_COUNTER is decremented and sr-prohibitTimer is stopped. When PRACH is skipped, the preamble transmission counter is decremented and RAR window is stopped. This feedback ensures proper state management and prevents unnecessary delays.
Solution Approach 2:
The patent performs preliminary state updates before the skipped procedure would naturally complete. By decrementing counters and stopping timers in advance when overlap is detected, the system prepares the UE to immediately resume the skipped procedure without waiting for counter expiration or timer completion, thereby reducing latency.
2Reliability
If SR is skipped due to overlap, then PRACH can be transmitted, but SR_COUNTER is not decremented and sr-prohibitTimer keeps running, preventing immediate SR resumption
Solution Approach 1:
When the MAC layer determines to skip SR transmission due to resource overlap with PRACH, it immediately provides feedback by decrementing SR_COUNTER by 1 and stopping the sr-prohibitTimer. This feedback mechanism ensures the SR procedure state is properly updated, allowing the UE to resume SR transmission immediately after PRACH completion without unnecessary delays.
3Reliability
If PRACH is skipped due to overlap, then SR can be transmitted, but preamble counter is not decremented and RAR window remains active, delaying next PRACH
Solution Approach 1:
When the MAC layer determines to skip PRACH transmission due to resource overlap with SR, it immediately updates the PRACH procedure state by decrementing the preamble transmission counter and stopping the RAR window timer. This feedback ensures proper state management, allowing the UE to resume PRACH transmission immediately after SR completion without waiting for counter expiration or window completion.
4Adaptability or versatility
If UE implements autonomous selection between SR and PRACH, then flexibility is improved, but additional latency occurs due to unupdated skipped procedure states
Solution Approach 1:
The patent maintains UE autonomy in selecting which procedure to transmit while adding MAC layer feedback mechanisms. When a procedure is skipped, the MAC layer immediately updates its state (decrementing counters, stopping timers) and notifies the PHY layer. This feedback system preserves UE flexibility while eliminating the latency caused by unupdated states, as the UE can immediately resume the skipped procedure after the transmitted procedure completes.
Data Source
AI summary
Techniques and examples of handling of simultaneous transmission of physical random access channel (PRACH) and other uplink (UL) channels in mobile communications are described. An apparatus (e.g., user equipment (UE)) determines to skip an UL transmission to a wireless network for either a first procedure or a second procedure. Responsive to determining to skip transmission of the first procedure, the apparatus performs the second procedure and also adjusts one or more parameters associated with the first procedure.