Method of determining the position of a target using transmitters of opportunity
A method of determining the position of a target comprising the steps of: providing a transmitter or a plurality of transmitters to transmit a signal to the target, providing a receiver or a plurality of receivers to receive signals reflected from said target. Determining the time of arrival information of said reflected signal at the or each receiver; using information pertaining to the position of the or each receiver and/or the or each transmitter and with the information obtained determining the target position. Preferably the signal includes a modulated or coded portion unique to the transmitter; and said signal portion is associated with the or each particular transmitter by virtue of said signal portion. The signal maybe a mobile phone transmission, DAB, digital TV, digital Radio or digital satellite transmissions.
1. A method of determining the position of a target using components in a wireless communication system in which pre-stored codes are included in transmissions of communications signals as part of a communication protocol, said method comprising the steps of:
a) providing a transmitter which transmits a communications signal;
b) providing a plurality of receivers, in communication with each other, which receive communications signals reflected from said target, the receivers being disposed at locations which are separate from said transmitter and separate from each other, and being time or phase synchronized;
c) determining a time of arrival information of said received communications signal at each receiver by continuously correlating said code in said received communications signal with the prestored codes in the receiver; and
d) using information pertaining to the location of each receiver, together with the information obtained from step c), to determine the target position.
2. A method of determining the position of a target using components in a wireless communication system in which pre-stored codes are included in transmissions of communications signals as part of a communication protocol, said method comprising the steps of:
a) Providing a plurality of transmitters, each of which transmits a communications signal, said transmitters being time or phase synchronized;
b) providing a receiver which receives communications signals reflected from said target, said signals being sent by said transmitters at pre-set times which are known to the receiver, and said receiver being situated at a location separate from said transmitters, which are situated at locations separate from each other;
c) correlating codes in said received communications signal with pre-stored codes in each receiver to identify the transmitter and time of arrival of each particular communications signal;
d) the receiver determining a time delay in receiving each said communications signal by subtracting the time of arrival of said reflected communications signal from each transmitter from the known time at which time the pre-stored code was sent;
e) using information known to the receiver pertaining to the position of each transmitter, together with the time delay information obtained from step d), to determine the target position.
3. A method as claimed in claim 1 wherein transmitted signals includes a modulated or coded portion unique to the transmitter, which is used to identify the transmitter and hence its location for step (e).
4. A method as claimed in claim 1 , wherein all the receivers communicate said time of arrival information and receiver identification to a central unit.
5. A method as claimed in claim 4 wherein said central unit is one of the receivers.
6. In a wireless communication system having a plurality of transmitters and a plurality of receivers, using combined information obtained via the methods of claim 1 to determine the location of the target.
7. A method as claimed in claim 1 , wherein said wireless communications system comprises a system selected from the group consisting of a mobile phone, DAB, digital TV, digital Radio and a digital satellite system.
8. A method as claimed in claim 1 , wherein said signal includes a mid-amble or a portion thereof or any unique sequence of data that is known to the receiver before transmission.