12.3.4.4 Infrastructure-less Peer-to-peer networks
In the case of a peer-to-peer network of N mobile nodes where each node wants to find its distance to every
other peer node as part of solving their relative location then this is ½N(N-1) distance measurements. For
example, for a 5 node system, this is 10 distance measurements.
With symmetric double-sided ranging this needs 3 messages per distance measurement. There may also be
a need to send an additional message to communicate the results, which could be 1 per distance
measurement or just 1 per node containing all the results which that node calculated. This is then a total of
35 to 40 messages in the 5 node example case.
With the asymmetric ranging scheme the ranging exchanges can be combined and completed with just two
transmissions per node, i.e. 10 messages in the case of the 5 node example. Again this represents a
substantial saving in message traffic thereby saving battery power and air-time. However the ranging
exchanges are highly asymmetric.
Further details on these various schemes and the derivation of the associated formulae are available from
Decawave.
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