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Abstract

An adaptive tree-based contention resolution media access control protocol for a local area network using orthogonal frequency division multiplexing. The invention uses constant tones in frequency bins to resolve contention between multiple transmitting nodes. All nodes are synchronized to transmit 'contention tones' in a 'contention frame.' Each node is assigned a unique identification (ID) number, and this ID number is mapped to frequency bins by transmitting a tone in each bin corresponding to each 1-bit in the binary representation of the node's ID number. The result of multiple nodes each transmitting its unique ID during a contention frame is a complex frequency signal which each participating node decodes. The nodes then participate in a 'resolution frame' in which all nodes again transmit tones in frequency bins. The resolution frame tones correspond only to tones in which the result of the contention frame indicated the presence of a tone where such node had 0-valued ID bits. All nodes receive the results of the resolution frame and record the results ('resolution bits') in a reasonably-balanced binary tree. If the resolution frame contained no tones in any frequency bin, only one node is contending and can transmit. Otherwise, the contending nodes utilize the resolution bits to continue with another cycle of contention and resolution frames. Each node follows a tree-traversal algorithm to determine the order of transmission among all contending nodes. The contention process continues until all contending nodes have transmitted their frames.

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First Claim