NAVT-Based Distributed Wireless Access Method for Collision Avoidance
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Solution Overview
Problem
In distributed wireless networks, the hidden terminal and exposed terminal problems lead to packet collisions and inefficient resource utilization, limiting system throughput and resource utilization rates.
Innovation Solution
A distributed wireless medium access control method using a Network Allocation Vector Table (NAVT) with a packet type field and duration field, where nodes determine the presence of RTS or CTS items to manage channel access, reducing collisions and optimizing resource use by allowing concurrent transmissions without disturbing ongoing communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If nodes independently control transmission in distributed MAC mode, then system flexibility and adaptability are improved, but packet collisions occur due to hidden terminal problems
Solution Approach 1:
The patent introduces RTS (Request to Send) and CTS (Clear to Send) control packets as intermediaries between data transmitting nodes. These control packets enable nodes to sense channel occupancy and coordinate transmissions, preventing hidden terminal collisions while preserving distributed control flexibility. The RTS/CTS handshaking mechanism acts as a mediator that resolves the conflict between independent node operation and collision avoidance.
2Reliability
If nodes sense ambient transmissions to avoid collisions, then packet collision avoidance is improved, but resource utilization deteriorates due to exposed terminal problems
Solution Approach 1:
The patent enables nodes to make localized transmission decisions based on their specific sensing results and NAVT table status. Instead of uniformly inhibiting all transmissions upon sensing ambient activity, nodes evaluate local conditions (NAVT emptiness, packet type) to determine whether transmission is safe. This localized decision-making allows exposed terminal nodes to transmit when appropriate, improving resource utilization while maintaining collision avoidance where needed.
3Reliability
If RTS/CTS handshaking is performed to solve hidden terminal problem, then packet collision avoidance is improved, but system complexity and transmission overhead increase
Solution Approach 1:
The patent implements selective RTS/CTS handshaking rather than requiring it for all transmissions. Nodes perform the handshaking procedure only when the NAVT table is empty or contains only RTS items, and skip it when NAVT contains CTS items or is otherwise occupied. This partial application of the handshaking mechanism reduces protocol complexity and overhead while maintaining collision avoidance effectiveness in critical scenarios.
4Reliability
If channel is sensed busy, then collision avoidance is improved, but transmission delays increase due to backoff procedures
Solution Approach 1:
The patent performs preliminary channel sensing and NAVT table checking before initiating transmission or backoff procedures. By evaluating the NAVT status and packet type in advance, nodes can determine whether the channel is truly occupied or if transmission is permitted, avoiding unnecessary backoff delays. This preliminary assessment action reduces wasted time in the transmission process while maintaining collision avoidance.
Data Source
AI summary
Embodiments of the present invention include a wireless access method based on a NAVT (Network allocation vector table), which is applied to a distributed wireless mobile communication system comprising a plurality of nodes, the NAVT comprises a packet type field and a duration field and is stored in the respective nodes of the communication system, comprising: on a transmitting side, determining whether only a RTS (request to send) item is contained in the NAVT when a packet arrives; sensing channel to judge whether the channel is busy after determining that only the RTS item is contained in the NAVT; sending a RTS packet based on the RTS item to the receiving side after determining that the channel is busy; and on a receiving side, determining whether the NAVT is empty or not when the RTS packet is received; sending a CTS (clear to send) packet back to the transmitting side after determining that the NAVT is empty.