Dedicated Scheduling Request Resources for VoIP Latency Reduction
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Solution Overview
Problem
In wireless communication systems, particularly in UMTS-based packet data systems using OFDMA, there is a significant latency issue for VoIP calls due to collisions and delays when transmitting scheduling requests over random access channels, resulting in unacceptable latency periods of up to 50-60 ms for time-sensitive applications.
Innovation Solution
Allocating dedicated resources for transmitting scheduling requests in packet data systems, allowing for immediate resource allocation without the delays associated with collisions on random access channels, thereby reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If scheduling requests are transmitted over random access channels, then resource allocation can be performed, but latency increases due to collisions and delays
Solution Approach 1:
The patent segments the random access channel transmission process into multiple attempts with backoff mechanisms. When collisions occur on the random access channel, the system divides the resource allocation process into retry attempts separated by predetermined time intervals, allowing successful transmission eventually while managing collision impacts.
Solution Approach 2:
The patent implements preliminary actions by establishing predetermined time intervals and backoff mechanisms before actual transmission attempts. The system prepares retry schedules and time interval parameters in advance, so when collisions occur, the retransmission process can proceed systematically without additional decision delays.
2Loss of time
If dedicated resources are allocated for scheduling requests, then latency is reduced, but system complexity increases
Solution Approach 1:
The patent applies local quality by allocating dedicated resources specifically for scheduling requests from UEs with active data sessions, while maintaining random access channel usage for other scenarios. This targeted approach reduces latency for time-sensitive applications without requiring dedicated resources for all transmission types, thereby limiting the increase in system complexity to only where it provides maximum benefit.
Solution Approach 2:
The patent implements dynamic resource allocation where the transmission channel type (dedicated vs. random access) is selected based on the UE's current state. UEs with active data sessions use dedicated resources for scheduling requests, while other UEs use the random access channel. This dynamic adaptation allows the system to optimize latency for specific scenarios without permanently increasing complexity across all operations.
3Reliability
If random access channels are used for scheduling requests, then resource allocation flexibility is maintained, but transmission reliability decreases due to collisions
Solution Approach 1:
The patent segments the scheduling request transmission into multiple attempts with systematic backoff intervals. When collisions occur on the random access channel, the system divides the retry process into discrete time intervals, ensuring that eventually the transmission succeeds without permanently failing the resource allocation process.
Solution Approach 2:
The patent implements feedback mechanisms where the system monitors transmission outcomes on the random access channel and adjusts retransmission timing based on detected collisions. The Node B provides feedback about successful preamble detection, and the UE uses this information along with predetermined time intervals to determine when to retry scheduling requests, improving overall transmission reliability.
Data Source
AI summary
Disclosed is a method of allocating resources in a packet data system to a User Equipment (UE) with an active data session, such as a Voice over Internet Protocol (VoIP) call, using dedicated resources to transmit scheduling requests, thereby reducing latency which may occur as a result of collisions associated with transmitting scheduling requests over a random access channel. The method comprises the step of transmitting over dedicated resources a scheduling request, and receiving a scheduling grant in response thereto. The scheduling request indicates that a transmitter in a data session has a data packet to transmit. The scheduling grant indicates resources allocated for transmitting the data packet.