HT Wireless LAN Occupation Signal for Legacy Coexistence
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Solution Overview
Problem
In wireless LAN systems, the coexistence of HT terminals and legacy terminals using the same frequency band leads to frequent packet collisions, resulting in deteriorated throughput due to unrecognized signals and interference.
Innovation Solution
A transmitter is designed to generate an occupation signal compatible with the legacy system, allowing the HT system to occupy the radio medium while notifying the legacy system, thereby preventing collisions and maintaining original transmission speeds by specifying or reserving communication periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If HT terminals use a wider frequency band for high-speed transmission, then transmission speed is improved, but packet collisions increase due to unrecognized signals from legacy terminals
Solution Approach 1:
The patent introduces an occupation signal as an intermediary that bridges the HT system and legacy system. This signal is transmitted by the HT access point using legacy-compatible modulation (DSSS or CCK) so that legacy terminals can recognize it and understand that the radio medium is occupied, thereby preventing them from transmitting and causing collisions during HT high-speed communication periods
Solution Approach 2:
The patent applies preliminary action by having the HT access point transmit the occupation signal before initiating high-speed HT communication. This advance notification allows legacy terminals to set their NAV (Network Allocation Vector) and suppress transmission in advance, preventing packet collisions before they can occur during the HT transmission period
2Productivity
If HT terminals transmit without notifying legacy terminals, then transmission efficiency is improved, but interference to legacy terminals increases
Solution Approach 1:
The occupation signal serves as a mediator that informs legacy terminals of upcoming HT transmissions. By transmitting this signal in legacy-compatible formats, the HT system enables legacy terminals to voluntarily suppress their transmissions, thereby eliminating interference without requiring the HT system to reduce its transmission efficiency or share the medium in a round-robin fashion
Data Source
AI summary
A high-speed wireless LAN system capable of avoiding a collision of packets and maintaining the original transmission speed is provided. A transmitter is applied to an HT terminal using a second frequency band wider than a first frequency band used by a legacy terminal, in which an HT sequence is started after a legacy beacon as an occupation signal and a legacy CTS are transmitted using every frequency in the second frequency band. Due to this, an NAV is set at the legacy terminal and packets are no longer transmitted from the legacy terminal. As a result, a collision of packets is avoided and it becomes possible to perform communication between HT terminals at the original transmission speed.