Express Forwarding Bypass for Time-Critical Frames in Wireless Mesh
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Solution Overview
Problem
Wireless mesh networks experience increased latency due to correlated channel contention and multi-hop delays, which are not adequately addressed by conventional mechanisms, particularly in VoIP and multimedia applications requiring low end-to-end delays.
Innovation Solution
Implement express forwarding bypass by maintaining timers (NAV) at nodes to prioritize and expedite time-critical frames, using predetermined time increments (DT0 and DTI) to manage channel access and reduce contention, allowing forwarding nodes to seize the channel quickly and minimize delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional channel access methods are used in wireless mesh networks, then channel reservation is maintained through NAV timers, but latency increases due to correlated channel contention and multi-hop delays
Solution Approach 1:
The patent applies preliminary action by having forwarding nodes preemptively seize the channel before the NAV timer expires. Instead of waiting for the NAV to expire and then contending for the channel, forwarding nodes detect when they need to forward a frame and immediately seize the channel if it's available, or wait only for a short period. This eliminates the correlated contention that occurs when all nodes wait for NAV expiration simultaneously, thereby reducing latency while maintaining channel reservation reliability.
2Object-affected harmful factors
If nodes wait for NAV expiration before transmitting, then channel collisions are avoided, but end-to-end delay increases for time-critical frames
Solution Approach 1:
The patent applies dynamics by making the channel access behavior adaptive rather than static. Forwarding nodes dynamically adjust their channel access strategy based on whether they have a frame to forward. When a forwarding node has a time-critical frame and the channel is free, it seizes the channel immediately without waiting for NAV expiration. This dynamic behavior reduces end-to-end delay for time-critical traffic while the NAV timer mechanism continues to prevent collisions with non-forwarding nodes.
3Productivity
If express forwarding is implemented without modifications, then forwarding nodes can seize channel quickly, but time-critical frames from non-forwarding nodes are delayed
Solution Approach 1:
The patent applies local quality by creating different channel access privileges for different types of nodes and traffic. Forwarding nodes transmitting time-critical frames are granted special priority to seize the channel quickly, while non-forwarding nodes must wait for NAV expiration. This localized differentiation in access quality ensures that express forwarding achieves high productivity for forwarding traffic without completely blocking time-critical frames from non-forwarding nodes, as they retain their original collision-avoidance-based access rights.
Data Source
AI summary
A method, apparatus and computer program product for the express forwarding bypass are presented. A timer (NAV) is maintained at each respective node of a wireless LAN, the timer (NAV) set to a corresponding time period during which the respective node must refrain from transmitting on a channel. The first node of said plurality of nodes has a time-critical (TC) frame. The first node detects a frame to be express-forwarded by a second node. The first node decrements the duration field by a first predetermined time increment (DT0) before setting its NAV. The first node attempts transmission of the TC frame or back off countdown when the NAV of said first node expires.