Contention-Based Uplink Channel Access Rule for Latency Reduction
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Solution Overview
Problem
Current wireless communication systems face latency issues during the transition of a dormant wireless transmit receive unit (WTRU) to an active state, particularly in LTE systems, which affects quality of service due to inefficient use of uplink channels and signaling overhead.
Innovation Solution
Implementing a rule-based restriction on access to contention-based uplink channels, ensuring the use of contention-free channels when available, and dynamically managing the size of allocated resources to optimize uplink transmissions, thereby reducing latency and improving resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a dormant WTRU uses contention-based uplink channel for data transmission, then latency is reduced and resource utilization is improved, but collision probability increases and transmission reliability deteriorates
Solution Approach 1:
The WTRU dynamically switches between dormant and active states based on data transmission needs. When data arrives, the WTRU transitions from dormant to active state and selects between contention-based and contention-free channels dynamically, rather than using a fixed channel access method. This dynamic adaptation allows the system to exploit contention-based channels for low latency when appropriate while falling back to reliable contention-free channels when needed.
Solution Approach 2:
The system changes the channel access parameter from always using contention-free channels to conditionally using contention-based channels. The WTRU monitors buffer status and data arrival patterns, and adjusts its channel selection behavior accordingly. This parameter change enables the system to achieve lower latency by utilizing contention-based channels while maintaining reliability through intelligent selection criteria.
2Reliability
If a dormant WTRU transitions to active state using traditional SR-based method, then transmission reliability is maintained, but latency increases due to multiple time components
Solution Approach 1:
The WTRU performs preliminary checks and preparations before transitioning to active state. It checks for available contention-free resources in advance and only transitions when necessary. The WTRU also pre-configures its channel selection logic and buffer status reporting mechanisms to enable rapid transition when data arrives, reducing the overall transition time while maintaining reliability.
Solution Approach 2:
The buffer status report (BSR) acts as an intermediary mechanism that bridges the dormant and active states. Instead of directly transitioning through multiple SR exchanges, the WTRU uses BSR to inform the network of its data buffer status, which triggers appropriate uplink grant allocations. This intermediary mechanism streamlines the transition process and reduces latency.
3Reliability
If contention-free uplink channels are always used for uplink transmissions, then transmission reliability is ensured, but resource utilization efficiency deteriorates and latency increases
Solution Approach 1:
The uplink channel access method is segmented into multiple paths: contention-free channel for reliable transmissions and contention-based channel for efficient resource utilization. The WTRU segments its transmission strategy based on data characteristics, buffer status, and network conditions. This segmentation allows the system to achieve both reliability and efficiency by using the appropriate channel for each transmission scenario.
Solution Approach 2:
The channel selection mechanism is made dynamic, allowing the WTRU to switch between contention-free and contention-based channels based on real-time conditions. The WTRU continuously monitors its transmission performance, buffer status, and network responses, and adjusts its channel selection dynamically. This dynamic approach optimizes resource utilization efficiency while maintaining transmission reliability.
4Speed
If the WTRU frequently transitions between dormant and active states, then responsiveness to data arrivals is improved, but power consumption increases
Solution Approach 1:
The WTRU performs preliminary assessments before transitioning to active state, checking for available contention-free resources and evaluating the urgency of data transmission. This preliminary action allows the WTRU to make informed decisions about when to transition, avoiding unnecessary state changes that would consume power. The WTRU also pre-configures its transmission parameters to enable rapid activation when needed.
Solution Approach 2:
The WTRU adjusts its DRX cycle parameters and channel selection behavior based on transmission patterns and network conditions. When data arrivals are frequent and urgent, the WTRU shortens its DRX cycle and becomes more responsive. When traffic is light, it extends the DRX cycle to conserve power. This parameter adaptation allows the system to balance responsiveness and power consumption dynamically.
Data Source
AI summary
A method and apparatus for a wireless transmit receive unit (WTRU) to use a contention-based uplink communications channel, applies a rule-based restriction of access to the contention-based uplink channel that attempts to use at least one contention-free uplink channel allocation for uplink transmissions on a condition that at least one contention-free uplink channel allocation has been granted.