Forward Control Channel Subchannel Partitioning for Rate Adaptation
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Solution Overview
Problem
The existing control channel structure in wireless local area networks (WLANs) is inefficient as it is dictated by the worst-case user's data rate, limiting the performance and efficiency of the forward control channel (FCCH) even for users capable of operating at higher rates.
Innovation Solution
The FCCH is partitioned into multiple subchannels, each operating at specific data rates, allowing the access point to select the appropriate subchannel for each user terminal based on selection criteria, enabling efficient resource allocation and decoding of control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the FCCH operates at a single data rate dictated by the worst-case user, then all users can decode control information reliably, but the overall system efficiency and resource utilization deteriorate because users capable of higher rates are limited
Solution Approach 1:
The FCCH is segmented into multiple subchannels, each operating at a different data rate. Users can selectively decode subchannels at rates matching their capabilities, allowing the system to serve both worst-case and best-case users efficiently without forcing a uniform rate on all users.
Solution Approach 2:
Different portions of the control channel (subchannels) are assigned different data rates according to local user requirements. Each user terminal can decode control information at the appropriate rate for its specific channel conditions, rather than being constrained by a globally imposed worst-case rate.
2Productivity
If the FCCH operates at a higher data rate to improve productivity, then system throughput increases, but reliability deteriorates for worst-case users who cannot decode at higher rates
Solution Approach 1:
By dividing the FCCH into multiple subchannels with different data rates, the system enables reliable reception for worst-case users on lower-rate subchannels while simultaneously achieving higher overall productivity through higher-rate subchannels that users with better channel conditions can exploit.
Solution Approach 2:
The data rate parameter of the control channel is made variable across different subchannels rather than fixed. This allows the system to adapt the effective data rate to match user-specific channel conditions, achieving both reliability for vulnerable users and high productivity for capable users.
3Device complexity
If a single control channel structure is used for all users, then device complexity is reduced, but adaptability deteriorates because the structure cannot accommodate users with different data rate capabilities
Solution Approach 1:
The control channel is divided into multiple subchannels with different characteristics. Each user terminal adapts by selecting and decoding the appropriate subchannel based on its capabilities, providing adaptability without requiring complex per-user channel structures at the transmitter.
Solution Approach 2:
The multi-subchannel FCCH structure serves multiple functions simultaneously: it provides reliable service to worst-case users, high-rate service to best-case users, and enables rate adaptation for intermediate users. This universal structure handles diverse user requirements without requiring separate specialized channels for each user type.
Data Source
AI summary
According to one aspect of the invention, a method is provided in which a control channel used for transmitting control information is partitioned into a plurality of subchannels each of which is operated at a specific data rate. For each of one or more user terminals, one of the subchannels is selected based on one or more selection criteria for transmitting control information from an access point to the respective user terminal. Control information is transmitted from the access point to a user terminal on a particular subchannel selected for the respective user terminal. At the user terminal, one or more subchannels are decoded to obtain control information designated for the user terminal.