Mesh Network Medium Access Control Using Reservation Allocation Vectors
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Solution Overview
Problem
In mesh wireless communication networks, existing reservation mechanisms like NAVs are inefficient in preventing collisions during multiple overlapping reservations, leading to interference and airtime wastage, especially when stations have reserved the medium but have no data to transmit.
Innovation Solution
The method introduces Reservation Allocation Vectors (RAVs) that are set based on detected reservations, updating the Network Allocation Vector (NAV) expiration timer to ensure collision-free medium access, allowing access only when all reservations have ended, and adapting RAVs when reservations are foreshortened to save airtime, with optional simplification by limiting RAV timer management to a predetermined number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the NAV is made permanent to prevent interference with ongoing transmissions, then collision avoidance is improved, but airtime utilization deteriorates due to wasted airtime when reserved stations have no data to transmit
Solution Approach 1:
The invention segments the single NAV mechanism into multiple RAVs (Reservation Allocation Vectors), each corresponding to a specific reservation. This allows independent tracking of multiple reservations without requiring a permanent NAV, enabling the system to release medium access when reservations are foreshortened while still preventing collisions during active reservations.
Solution Approach 2:
The invention introduces dynamic RAV expiration timers that can be updated based on actual transmission status. When a station foreshortens its transmission, the corresponding RAV is updated to reflect the new expiration time, allowing other stations to access the medium sooner. This dynamic adjustment optimizes airtime utilization while maintaining collision avoidance through the timer-based mechanism.
2Loss of energy
If the NAV is reset when stations foreshorten their transmission, then airtime utilization is improved, but collision avoidance deteriorates as stations can access the medium during ongoing transmissions
Solution Approach 1:
The invention uses RAV expiration timers that provide continuous feedback about reservation status. When a station foreshortens transmission, it updates its RAV timer and notifies other stations, creating a feedback loop that maintains accurate medium access control information without requiring permanent NAV settings. This feedback mechanism prevents collisions while enabling timely medium access when reservations are completed or foreshortened.
3Reliability
If multiple RAV timers are managed to track all reservations, then collision avoidance is improved, but device complexity increases
Solution Approach 1:
The invention makes each station maintain and manage its own RAV timers based on reservations it is party to, rather than requiring centralized management. Each RAV timer serves multiple functions: tracking reservation duration, detecting foreshortened transmissions, and controlling medium access. This universal approach distributes the complexity across all stations rather than concentrating it in a single controller.
Data Source
AI summary
The present invention relates to Method for controlling medium access in a mesh network comprising the following steps: a station of the network receiving a Network Allocation Vector (NAV) setting frame indicating a period of time during which the station cannot access the medium,—the station setting a Network Allocation Vector expiration timer based on the received setting frame, the station detecting a least one reservation made by two other stations in the network, and setting a respective Reservation Allocation Vector (RAV) expiration timer based on the duration of the detected reservation, and storing the identity of the two stations as owners of the reservation, the station updating the NAV expiration timer as the latest of the NAV expiration time of the NAV setting frame and all set respective RAV expiration timers.