Dynamic NAV Setting in Wireless Communication Systems
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Solution Overview
Problem
In wireless communication systems, particularly in ad-hoc networks, the hidden terminal problem leads to transmission collisions due to incomplete access control, resulting in reduced throughput and inefficient use of bandwidth, especially when neighboring stations fail to correctly estimate the completion time of RTS/CTS transmission/reception preparation processes.
Innovation Solution
A wireless communication system that stores two types of duration information in the header of preparation packets, allowing neighboring stations to set and reset Network Allocation Vectors (NAV) based on this information to prevent unnecessary transmission-disabled states and improve throughput by enabling timely resumption of transmission operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If neighboring stations set NAV based on RTS/CTS duration information to avoid hidden terminal collisions, then collision avoidance is improved, but transmission efficiency deteriorates due to unnecessary transmission-disabled states when RTS/CTS preparation fails
Solution Approach 1:
The NAV setting mechanism is made dynamic by introducing two different duration values (first duration for CTS reception, second duration for ACK reception) and selectively applying them based on whether the RTS/CTS preparation process succeeds or fails. This allows the system to adapt between conservative NAV setting (when successful) and liberal transmission access (when failed), resolving the contradiction between collision avoidance and transmission efficiency
Solution Approach 2:
The patent changes the NAV duration parameter based on the state of the RTS/CTS preparation process. When the process succeeds, NAV is set to the second duration (longer, for ACK protection). When the process fails, NAV is set to the first duration (shorter, allowing quicker retransmission). This parameter adaptation resolves the contradiction by optimizing NAV length for each specific scenario
2Device complexity
If a single duration value is used in RTS packets for NAV setting, then packet structure simplicity is maintained, but accurate NAV management deteriorates when RTS/CTS preparation fails
Solution Approach 1:
The duration information in the RTS packet is segmented into two distinct values: first duration information (for CTS reception timing) and second duration information (for ACK reception timing). This segmentation allows the receiving station to make accurate NAV decisions based on the specific phase of the transmission process, improving NAV management accuracy without significantly complicating the packet structure
Solution Approach 2:
The patent adds a temporal dimension to the duration information by providing different duration values for different time phases (CTS phase and ACK phase). This multi-dimensional approach to duration information enables accurate NAV management throughout the entire transmission process, resolving the contradiction between simple packet structure and accurate NAV management
3Reliability
If neighboring stations wait for the full Duration period before resetting NAV, then communication quality is maintained, but bandwidth utilization deteriorates due to prolonged transmission-disabled states
Solution Approach 1:
The NAV reset timing is made dynamic by introducing a monitoring mechanism that detects RTS/CTS preparation failures. When failure is detected, the NAV is reset after the first duration (shorter time). When success is confirmed, the NAV is maintained until the second duration (longer time). This dynamic approach resolves the contradiction between communication quality and bandwidth utilization
Solution Approach 2:
The system implements feedback by monitoring whether the RTS/CTS preparation process succeeds or fails. Based on this feedback, the neighboring station adjusts its NAV reset timing accordingly. This feedback mechanism enables the system to maintain communication quality when necessary while improving bandwidth utilization when the preparation fails, resolving the contradiction
Data Source
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AI summary
In a wireless communication system where packet transmission begins after a preparation process is performed between a source and a destination, the source stores, in a header of a preparation packet, first duration information corresponding to an end of a first response packet sent from the destination and second duration information corresponding to an end of a second response packet sent from the destination. A neighboring station having received the preparation packet sets a first NAV relating to a scheduled reception completion time of the first response packet based on the first duration information and a second NAV relating to a scheduled reception completion time of the second response packet based on the second duration information and ignores the second NAV when no packet transmission is detected within the first NAV period or within a predetermined time after the scheduled reception completion time of the first response packet.