Distributed MAC Protocol for Collaborative Ranging
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Solution Overview
Problem
Traditional round-trip time based range measurement in communications networks requires a large number of communication rounds, leading to substantial overhead, especially in large and densely deployed networks, due to the need for pair-wise MAC procedures using unicast communications.
Innovation Solution
A distributed MAC protocol utilizing multi-cast communication for RTS-TOA/CTS-TOA ranging, where nodes send and receive multi-cast messages to reduce the number of communication rounds, allowing simultaneous transmission to multiple nodes and reducing the total number of rounds by approximately 50%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pair-wise MAC procedure using unicast communication is used for round-trip time based range measurement, then ranging accuracy is achieved, but communication overhead increases substantially
Solution Approach 1:
The patent merges multiple unicast communication rounds into a single multi-cast communication round. Instead of requiring separate RTS/CTS exchanges between each node pair, all nodes simultaneously participate in a coordinated multi-cast transmission sequence, where a source node sends an RTS message that is received by multiple destination nodes, and all destinations simultaneously send CTS messages back, achieving pair-wise ranging for multiple pairs in parallel
Solution Approach 2:
The patent introduces dynamic role assignment where nodes transition between source and destination roles within the same ranging protocol. A node that sends an RTS message becomes a source node, receives CTS messages as a destination, then can become a source in subsequent rounds. This dynamic role switching enables flexible adaptation to different ranging requirements while maintaining protocol efficiency
2Loss of information
If pair-wise MAC procedure is used for network-wide ranging, then complete node location information is obtained, but number of communication rounds increases
Solution Approach 1:
The patent implements continuous useful action by eliminating idle communication rounds. In traditional protocols, nodes wait for their turn to transmit, creating idle time. In this patent, every communication round involves all nodes actively participating - either as sources sending RTS or as destinations sending CTS - ensuring continuous utilization of the communication medium for productive ranging operations
Solution Approach 2:
The patent segments the network-wide ranging process into multiple phases or rounds, where each round focuses on a specific subset of node pairs. By organizing nodes into groups and systematically rotating source nodes through different groups, the protocol ensures complete coverage of all node pairs across multiple segmented rounds, maintaining information completeness while reducing total communication time
Data Source
AI summary
A method for reducing communications in a peer-to-peer wireless network having nodes includes sending an RTS-TOA ranging communication from a first node (N0) in a node group to another node (Nr, I) in the group, receiving the RTS-TOA communication with the second node (Nr, I) and sending a multi-cast CTS-TOA/RTS-TOA ranging communication from the second node (Nr, I) as a reply to the received RTS-TOA communication, and successively and sequentially repeating the multi-cast sending step for each of the nodes. A CTS-TOA message is a reply to the received RTS-TOA message and, simultaneously, is an RTS-TOA ranging communication to a new destination node (J). The method applies for a randomized communications approach when node identifications are not sequenced and to a sequential approach where nodes are sequenced, and also applies to completely connected and multi-hop networks. Also provided is a node for carrying out the method of the present invention.