Directional Wireless Medium Reservation Protocol
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Solution Overview
Problem
In wireless networks operating in congested environments, such as the 60 GHz band, directional transmissions and receptions can lead to communication conflicts and interference due to the lack of central scheduling, causing some communications to fail, as devices cannot transmit and receive simultaneously on different links without a central controller.
Innovation Solution
A protocol is introduced that uses directional Request to Send (DRTS) and Clear to Send (DCTS) messages to reserve time for data communication, preventing interference by setting Network Allocation Vectors (NAV) to ensure only specific devices can transmit during reserved periods, allowing simultaneous operation of different links without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ad hoc scheduling is used by devices without a central controller, then device autonomy and flexibility are improved, but communication conflicts and interference increase
Solution Approach 1:
Each device autonomously manages its own directional links and scheduling without requiring a central controller. Devices independently send DRTS messages, manage NAV counters, and coordinate transmissions based on local conditions, enabling self-service operation while maintaining communication reliability through distributed conflict avoidance.
2Productivity
If multiple directional links operate simultaneously, then network throughput and productivity are improved, but interference between links increases
Solution Approach 1:
Before actual data transmission occurs, devices perform preliminary reservation by exchanging DRTS and DCTS messages. This preliminary action establishes time slots and directional constraints that prevent interference during subsequent simultaneous transmissions, allowing multiple links to operate concurrently without harmful interactions.
Solution Approach 2:
The NAV (Network Allocation Vector) counter acts as an intermediary mechanism that mediates between simultaneous transmissions. When a device receives a DRTS or DCTS message, it sets its NAV counter to indicate the duration of the reserved transmission, thereby mediating conflict avoidance without requiring direct coordination between all simultaneous transmitters.
3Reliability
If a central controller schedules all communications, then interference is reduced, but device complexity and control overhead increase
Solution Approach 1:
The patent extracts the scheduling function from a centralized controller and distributes it to individual devices. Each device independently manages its own transmission reservations using DRTS/DCTS messages and NAV counters, eliminating the need for complex central control while maintaining effective interference reduction through distributed coordination.
4Use of energy by moving object
If directional transmissions are used to reduce interference, then spectral efficiency is improved, but scheduling conflicts and communication failures increase
Solution Approach 1:
The protocol implements feedback mechanisms where receiving devices respond to DRTS messages with DCTS messages indicating whether they can accept the reservation. This feedback loop ensures that directional transmissions are only established when they will not cause or result from interference, maintaining both spectral efficiency and communication reliability simultaneously.
Data Source
AI summary
Two wireless communications devices in a wireless network may reserve a period of time for directional data communications between themselves during a Contention Access Period. The technique may include transmitting Clear-to-Send messages to each other, and to any other devices with which either has established a directional link, to prevent interfering transmissions from these other devices. Other devices that have not established a directional link with either of these two may overhear the CTS messages and also refrain from transmitting interfering signals during the reserved time period.