NAV Segmentation for Collision-Free Wireless LAN Reservations
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Solution Overview
Problem
Conventional mechanisms for start-to-end reservations in wireless LANs face deficiencies, particularly in resetting the NAV (Network Allocation Vector), which can cause collisions due to outstanding reservation requests, leading to inefficient channel management and potential transmission conflicts.
Innovation Solution
Implementing a method where each node maintains a NAV set by the larger of RRQ and RRS values, declining channel reservations and transmissions when the NAV is non-zero, and resetting RRQ NAV while decrementing RRS NAV upon cancellation or expiration to prevent collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If NAV is reset when reservation is cancelled, then channel utilization is improved, but collisions may occur due to outstanding NAV setting requests
Solution Approach 1:
The NAV value is segmented into two separate components: RRQ_NAV (set by reservation requests) and RRS_NAV (set by reservation responses). This segmentation allows independent management and resetting of each component, enabling the system to reset RRQ_NAV when a reservation is cancelled without affecting RRS_NAV, thus preventing collisions while improving channel utilization.
Solution Approach 2:
The NAV management mechanism becomes dynamic by allowing selective resetting of RRQ_NAV based on reservation cancellation events, while RRS_NAV continues to operate independently. This dynamic approach enables the system to adapt NAV settings to current channel conditions and reservation states, resolving the contradiction between channel utilization and collision avoidance.
2Adaptability or versatility
If frame-by-frame reservation extension is used, then transmission flexibility is improved, but reservation cancellation complexity increases
Solution Approach 1:
The patent extracts the cancellation complexity from the frame-by-frame extension mechanism by introducing a separate start-to-finish reservation mechanism. When a reservation is cancelled, only the RRQ_NAV component needs to be reset without affecting the ongoing frame-by-frame extensions, thus reducing cancellation complexity while maintaining transmission flexibility.
Solution Approach 2:
The RRQ_NAV component acts as an intermediary that mediates between reservation cancellation requests and the actual NAV settings. By resetting only RRQ_NAV upon cancellation, the system maintains flexibility in ongoing transmissions while simplifying the cancellation process, as the RRS_NAV component continues to manage active reservations without interference.
3Reliability
If NAV is set by both RRQ and RRS, then collision avoidance is improved, but NAV management complexity increases
Solution Approach 1:
The NAV setting mechanism is segmented into two independent components: RRQ_NAV set by reservation requests and RRS_NAV set by reservation responses. Each component operates independently with its own setting and resetting rules, which simplifies the management logic compared to a monolithic NAV system. This segmentation maintains comprehensive collision avoidance while reducing management complexity through modular operation.
Solution Approach 2:
Different parts of the NAV management system have different functions: RRQ_NAV handles reservation request-related collision avoidance, while RRS_NAV handles reservation response-related collision avoidance. This local specialization allows each component to be managed independently with simple, targeted rules, reducing overall system complexity while maintaining comprehensive collision protection.
Data Source
AI summary
A method, apparatus and computer program product for providing start-to-finish reservations in distributed MAC protocols for wireless LANs. Each node maintains a corresponding time period (NAV) during which the node must refrain from transmitting on a channel of a plurality of traffic channels. Each NAV is set by detecting a reservation request (RRQ) or a reservation response (RRS), each corresponding NAV comprising the larger of a RRQ NAV value and a RRS NAV value. Each node declines to reserve a traffic channel while the NAV is non-zero, and declines to transmit on a channel when the node detects the occurrence of a transmission on the channel or that the NAV is non-zero. The RRQ NAV is reset while a corresponding RRS NAV is decremented when a reservation is cancelled, and the RRS NAV is reset while a corresponding RRQ NAV is decremented when the reservation time period expires.