Distributed Radio Head Collision Detection via Waveform Monitoring
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Solution Overview
Problem
Conventional collision avoidance strategies in CSMA/CA wireless communication systems, such as IEEE 802.11 networks, waste air time due to the need for message exchanges like RTS/CTS protocols, which are inefficient in maximizing throughput and minimizing frame collisions.
Innovation Solution
A distributed multi-user MIMO system using central processor subsystems and distributed radio heads to detect collisions by monitoring receive waveforms and modifying transmit waveforms in real-time to reduce or avoid collisions, employing adaptive digital beamforming and multiple collision thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional collision avoidance strategies (RTS/CTS protocol) are used, then frame collisions are avoided, but air time is wasted due to message exchange overhead
Solution Approach 1:
The system uses each transceiver's own transmit signal as a reference to detect collisions on the channel, eliminating the need for separate RTS/CTS message exchanges. Each transceiver independently monitors its own transmitted waveform to detect collisions, thereby avoiding the overhead of conventional collision avoidance protocols while maintaining collision detection capability
Solution Approach 2:
The system implements continuous feedback by monitoring receive waveforms during transmission and using this information to dynamically adjust or terminate ongoing transmissions. The central processor subsystem receives waveforms from transceivers, detects collisions in real-time, and provides feedback to modify transmit waveforms, creating a closed-loop collision avoidance mechanism that eliminates the need for separate acknowledgment messages
2Reliability
If client devices listen to beacon transmissions for transmit window opportunities, then collision avoidance is achieved, but air time is wasted
Solution Approach 1:
The system eliminates idle listening periods by enabling transceivers to continuously transmit useful data without requiring periodic beacon transmissions or transmit window announcements. The distributed transceivers operate continuously, with each transceiver independently detecting collisions and adjusting its transmissions, thereby eliminating the air time wasted on non-data beacon messages while maintaining continuous useful communication
3Productivity
If distributed transceivers transmit simultaneously to maximize throughput, then productivity increases, but frame collisions increase
Solution Approach 1:
The system performs preliminary collision detection by monitoring the channel during the transmission process itself. Rather than waiting for collision to occur and then reacting, the central processor subsystem continuously monitors receive waveforms and detects collisions in real-time, allowing for immediate intervention to prevent complete frame corruption while maintaining high throughput through parallel transmissions
Data Source
AI summary
A central processor subsystem controls multiple transceivers. Each transceiver transmits protocol data units from antennas of that transceiver and produces receive waveforms from wirelessly received signals at the one or more antennas. A transmit waveform, including a frame addressed to one or more wireless client devices, is sent through a first transceiver to be transmitted wirelessly by the first transceiver on a frequency channel. A receive waveform, representative of the transmission by the first transceiver and wirelessly received at a second transceiver, is received from the second transceiver. While the transmit waveform is being sent to the first transceiver: a level of collision between the receive waveform and another transmission on the frequency channel is detected; and if the level of collision exceeds a threshold prior to an end of the receive waveform, the transmit waveform being sent to the first transceiver is modified to reduce the collision.