Method and system of identifying wireless units

A method for wireless communication between an interrogator (26) and at least one device (12) identifier radio frequency to identify the device (12) identifier radio frequency in an environment containing multiple identifiers RF devices, comprising: providing at least a device (12), wherein at least one device (12) is configured to generate a random value for use in an arbitration system; sending a first order from the interrogator (26) to at least one device (12), where the first order comprises a set of bits, at least one of which indicates that at least one device is selected to participate in this system arbitration, and characterized by: using as part of the arbitration system, an interval chosen at random from a first number of intervals to determine at least in part when said at least one device (12) can communicate a first response to that first order; send a second command from the interrogator (26) to at least one device (12); use as part of the arbitration system, an interval chosen at random from a second number of intervals to determine at least in part when said at least one device (12) can communicate a second reply to said second order, said second number of intervals other than said first number of slots; and communicating the second response from at least one device (12) to the interrogator (26), wherein the second response comprises it said random value generated by the device (12).