Communication device and method in the cellular band
A wireless communication method in a network comprising a plurality of nodes including ranging masters, broadcasting a chirp-modulated ranging requests, and ranging slaves slave, replying with thereto with chirp-modulated ranging responses, whereby mobile nodes can locate themselves passively by listening to the request/reply exchanges, based on the respective time differences of arrival.
1. A wireless communication network including a plurality of nodes, each node having a time reference, and being arranged for receiving and transmitting chirp-modulated radio signals, wherein the phase of the chirps is a continuous function, such that a node receiving the radio signal can align its time reference with that of a node transmitting the radio signal, wherein at least a subset of the nodes, acting as master, are arranged to broadcast a chirp-modulated ranging request, and at least a subset of the nodes, acting as slave, are arranged to receive the ranging requests and reply with a chirp-modulated ranging response, and at least one mobile node is operatively arranged to receive both the ranging requests of the masters and the ranging responses of the slaves, and determine for each pair of one ranging request and one ranging reply, a difference of the propagation time between the master and the mobile node minus the propagation time between the slave and the mobile node, whereby the position of the mobile node is determined, based on said difference of propagation times and on the positions of said masters and slaves.
2. The wireless communication network of claim 1 , wherein the ranging requests and ranging replies are exchanged between the masters and the slaves repeatedly over time, and/or through different antennas, and/or frequencies.
3. The wireless communication network of claim 1 , wherein the ranging request includes an identification of the master and an identification of the slave.
4. The wireless network of claim 1 , in which a plurality of the subset of nodes acting as slave are arranged to reply to one ranging request transmitted by one master.
5. The wireless network of claim 4 , wherein the plurality of slaves replying to one ranging request are arranged to insert a predetermined or algorithmically derivable delay before the ranging reply.
6. The wireless network of claim 1 , wherein the mobile node is arranged for determining the times of arrival of said ranging requests and ranging replies, and for transmitting said times of arrival, or differences between said times of arrival, to a network infrastructure for localization.
7. The wireless network of claim 6 , wherein the mobile node (E) is arranged to transmit received signal strength indicator values to the network infrastructure.
8. The wireless network of claim 1 , wherein the broadcasting of ranging requests is planned such that the ranging requests are not broadcast at the same time by nodes that so close as to be simultaneously receivable by a mobile node.
9. The wireless network of claim 1 , wherein the broadcast of ranging requests is planned such that the master and slave nodes in a pair are along a plurality of baselines, differently oriented at a right angle.