Random phase multiple access system with location tracking
A method of determining the location of a communication tag in a random phase multiple access communication network is disclosed. A ranging request signal that is spread using a first pseudo-noise code and offset with a first random timing offset is transmitted at a first time. A ranging response signal that is spread using a second pseudo-noise code and offset with a second random timing offset is received at a second time. A propagation delay that is dependent on the first time and the second time is calculated.
1. A method of determining the location of a communication device in a communication network, the method comprising:
transmitting a ranging request signal at a first time from a transmitter, wherein the ranging request signal is spread using a first predetermined pseudo-noise (PN) code;
receiving a ranging response signal at a second time at a receiver, wherein the ranging response signal is spread using a second predetermined pseudo-noise (PN) code and further wherein the ranging response signal has a random timing offset; and
calculating a propagation delay at a controller coupled to the transmitter and the receiver based on the first time and the second time.
2. The method of claim 1 , wherein:
the ranging response signal further comprises a notification of a random delay in the transmission made before the second time; and
the propagation delay is calculated based on the first time, the second time and the received random delay.
3. The method of claim 1 , wherein:
the ranging response signal further comprises a notification of a pseudo-random delay in the transmission made before the second time; and
the propagation delay is calculated based on the first time, the second time and the received pseudo-random delay.
4. The method of claim 1 , wherein:
the ranging request signal is transmitted at the first time, wherein the transmission is delayed by a predetermined value; and
the propagation delay is calculated based on the first time, the second time and the predetermined value.
5. The method of claim 1 , wherein:
the ranging request signal is transmitted at the first time, wherein the first time is delayed by a random value; and
the propagation delay is calculated based on the first time, the second time and the random value.
6. The method of claim 5 , wherein the ranging request signal is transmitted only at a predetermined time interval corresponding to a slot for a receiving device.
7. The method of claim 1 , wherein calculating the propagation delay occurs at a remote device.
8. The method of claim 1 , wherein the ranging request signal is transmitted only at a predetermined time interval corresponding to a slot for a receiving device.
9. The method of claim 1 , wherein the second predetermined pseudo-noise (PN) code is the same as the first predetermined pseudo-noise (PN) code.
10. An apparatus for determining the location of a communicating device, the apparatus comprising:
a transmitter configured to transmit a ranging request signal at a first time, wherein the ranging request signal is spread using a first predetermined pseudo-noise (PN) code;
a receiver configured to receive a ranging response signal at a second time, wherein the ranging response signal is spread using a second predetermined pseudo-noise (PN) code and further wherein the ranging response signal has a random timing offset; and
a controller coupled to the transmitter and the receiver and operable to trigger the transmission of the ranging request signal, to wait for the reception of the ranging response signal, and to calculate a propagation delay based on the first time and the second time.
11. The apparatus of claim 10 , wherein:
the ranging response signal further comprises a notification of a random delay in the transmission made at the second time; and
the propagation delay is calculated based on the first time, the second time and the random delay.
12. The apparatus of claim 10 , wherein:
the ranging response signal further comprises a notification of a pseudo-random delay in the transmission made at the second time; and
the propagation delay is calculated based on the first time, the second time and the pseudo-random delay.
13. The apparatus of claim 10 , wherein:
the ranging request signal is transmitted at the first time, wherein the transmission is delayed by a predetermined value; and
the propagation delay is calculated based on the first time, the second time and the predetermined value.
14. The apparatus of claim 10 , wherein:
the ranging request signal is transmitted at the first time, wherein the transmission is delayed by a random value; and
the propagation delay is calculated based on the first time, the second time and the random value.
15. The apparatus of claim 10 , wherein calculation of the propagation delay occurs at a remote device.
16. The apparatus of claim 10 , wherein the ranging request signal is transmitted only at a predetermined time interval corresponding to a slot for a receiving device.
17. The apparatus of claim 10 , wherein the second predetermined pseudo-noise (PN) code is the same as the first predetermined pseudo-noise (PN) code.