Directional RTS Signaling for Beam Sweep Detection in Dense WLANs
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Solution Overview
Problem
In wireless communication systems, especially those compliant with the IEEE 802.11ad standard, network congestion arises due to interference from multiple devices transmitting Request to Send (RTS) messages simultaneously, leading to increased overhead in RTS/CTS signaling and overall network congestion, as intended recipients may not respond to RTS messages due to overestimated interference.
Innovation Solution
The receiving device performs a beam sweep in determined spatial directions to detect RTS messages by transmitting the same RTS message multiple times or with extended duration, allowing detection during the beam sweep interval, while transmitters send RTS messages in specific spatial directions without knowing the receiver's beam sweeping pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple devices transmit RTS messages simultaneously in a dense wireless system, then the system supports more concurrent communications, but interference increases causing intended recipients to fail to detect RTS messages and transmit CTS responses
Solution Approach 1:
The transmitting device sends the RTS message multiple times in a periodic manner during the beam sweep interval. The receiver performs directional listening in multiple spatial directions at different time intervals, increasing the probability that at least one RTS transmission will be detected despite simultaneous transmissions from other devices causing interference.
Solution Approach 2:
The system introduces spatial dimensionality to the RTS message transmission and reception process. Instead of omnidirectional transmission, the receiver performs beam sweeping across multiple spatial directions, and transmitters send RTS messages in specific spatial directions. This spatial differentiation allows the receiver to distinguish between RTS messages from different directions, reducing the impact of interference from simultaneous transmissions.
2Reliability
If the receiver performs omnidirectional reception to detect RTS messages from any direction, then all RTS messages can be received, but network congestion increases due to inability to filter directional interference
Solution Approach 1:
Instead of uniform omnidirectional reception, the receiver applies directional quality filtering by performing beam sweeping. The receiver selectively listens in specific spatial directions at different time intervals, matching the directional transmission patterns of potential transmitters. This allows the receiver to focus on relevant signals while filtering out interference from other directions, improving both detection reliability and network efficiency.
3Reliability
If RTS messages are transmitted with longer duration or multiple times, then detection probability during beam sweep increases, but transmission overhead increases
Solution Approach 1:
The system transmits RTS messages multiple times or with extended duration, which is more than the minimum single transmission. This excessive action ensures that at least one transmission will coincide with the receiver's beam sweep in the correct spatial direction, achieving reliable detection. The overhead is accepted as necessary to overcome the uncertainty of beam sweep timing and directional alignment.
Data Source
AI summary
Methods and apparatus that support controlled transmission and directional reception of RTS and/or CTS messages, are described. Controlled transmission may include transmitting a same RTS message multiple times in the same direction and/or transmitting an RTS message with a length that is multiple times longer than a standard RTS message. In an aspect, a receiver may determine spatial directions of a plurality of transmitters including a first transmitter and at least one other transmitter, and may perform a beam sweep in the determined spatial directions for receiving one or more RTS messages. A transmitter may determine that a receiver is to perform a beam sweep in K different spatial directions, and may transmit a same RTS message for a data transmission K times in the same direction or an RTS message with a length approximately K times longer than a standard RTS message, during a duration of the beam sweep.