Wireless Packet Spoofing for Mixed 802.11b/g NAV
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Solution Overview
Problem
The coexistence of IEEE 802.11g and IEEE 802.11b wireless communication systems poses challenges due to differences in transmission rates, leading to collisions and increased overhead, as conventional stations cannot decode high-speed data packets and set Network Allocation Vectors (NAV) appropriately.
Innovation Solution
A wireless communication system where packets are composed of a first portion receivable by IEEE 802.11b stations and a second portion by IEEE 802.11g stations, with the second portion containing spoofed information about packet length and transmission rate, allowing IEEE 802.11g stations to perform packet transmission while avoiding collisions by setting NAVs correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If IEEE 802.11g stations transmit high-speed data packets, then transmission rate is improved, but IEEE 802.11b stations cannot decode the packets and set NAV appropriately, leading to collisions
Solution Approach 1:
The patent segments the packet structure into a first portion (containing spoofed packet length and transmission rate information) and a second portion (containing actual high-speed data). This segmentation allows 802.11b stations to correctly interpret the first portion and set appropriate NAV values, preventing collisions, while 802.11g stations can process both portions for high-speed transmission.
Solution Approach 2:
The patent changes the parameters (packet length and transmission rate) in the first portion of the packet to values that are compatible with 802.11b station decoding capabilities. By spoofing these parameters, the patent ensures that 802.11b stations calculate correct NAV durations based on the modified parameters, thereby maintaining collision avoidance across mixed 802.11b/g networks.
2Reliability
If IEEE 802.11g stations use RTS/CTS procedure for collision avoidance, then reliability is improved, but overhead increases
Solution Approach 1:
The patent extracts the collision avoidance function from the RTS/CTS procedure and implements it directly through spoofed packet length and transmission rate information in the first portion of data packets. This extraction eliminates the need for separate RTS/CTS exchange, reducing overhead and transmission delay while maintaining collision avoidance reliability in mixed 802.11b/g networks.
3Speed
If packets are transmitted in a format decodable only by IEEE 802.11g stations, then transmission rate is improved, but compatibility with IEEE 802.11b stations is lost
Solution Approach 1:
The patent makes the first portion of the packet universally decodable by both 802.11b and 802.11g stations by using a format and parameter set compatible with 802.11b capabilities. The second portion contains high-speed data intended for 802.11g stations. This multi-functionality allows the same packet structure to serve both legacy and advanced stations, maintaining compatibility while enabling high-speed transmission.
Data Source
AI summary
Random access operation is performed under a communication environment in which a plurality of communication modes having different transmission rate coexist with small overhead. A high-grade communication station spoofs information of a packet length and a rate in a decoding portion so that a value of (packet length)/(rate) corresponds to a duration where the communication is hoped to be stopped. The other station receiving the spoofed information receives the rest of the packet with the designated rate during the interval designated by the value of (packet length)/(rate). In this case, the packet length and the rate are not those of actually transmitted packet so that this packet is discarded.