Random phase multiple access communication interface system and method
A method for communicating through a multiple access communication interface includes receiving a first signal from a first tag, where the first signal is spread using a predetermined pseudo-noise (PN) code, and further where the first signal includes first payload data. A second signal is received from a second tag. The second signal is spread using the predetermined PN code, and the second signal includes second payload data. The first payload data from the first signal is identified at least in part with a PN array despreader. The second payload data from the second signal is also identified at least in part with the PN array despreader.
1. A method for communicating through a multiple access communication interface, the method comprising:
receiving a first signal from a first tag during a time slot, wherein the first signal is spread using a predetermined pseudo-noise (PN) code, wherein the first signal has a first random timing offset in that the first signal is transmitted at a first random time in an uplink portion of a half duplex system, and further wherein the first signal includes first payload data;
receiving a second signal from a second tag during the time slot, wherein the second signal is spread using the predetermined PN code, wherein the second signal has a second random timing offset in that the second signal is transmitted at a second random time in the uplink portion of the half duplex system, and further wherein the second signal includes second payload data, and further wherein at least a portion of the second signal is received while at least a portion of the first signal is received;
identifying the first payload data from the first signal; and
identifying the second payload data from the second signal.
2. The method of claim 1 , wherein the first payload data is identified using a PN array despreader, and further wherein the second payload data is identified using the PN array despreader.
3. The method of claim 1 , wherein the first signal and the second signal are both received at a predetermined power level.
4. The method of claim 1 , further comprising demodulating a plurality of chip hypotheses to identify the first signal.
5. The method of claim 4 , wherein the demodulating further comprises using a cyclic redundancy check (CRC) to validate the first payload data.
6. The method of claim 1 , further comprising providing a third signal to the first tag, wherein the third signal is spread with a second PN code, and further wherein the second PN code is specific to the first tag.
7. A system for communicating through a multiple access communication interface, the system comprising:
a first tag having a first transmitter configured to transmit first payload data in a first signal during a time slot, wherein the first signal is spread using a predetermined pseudo-noise (PN) code, and further wherein the first signal has a first random timing offset in that the first signal is transmitted at a first random time in an uplink portion of a half duplex system;
a second tag having a second transmitter configured to transmit second payload data in a second signal during the time slot, wherein the second signal is spread using the predetermined PN code, and further wherein the second signal has a second random timing offset in that the second signal is transmitted at a second random time in the uplink portion of the half duplex system, and further wherein at least a portion of the second signal is received while at least a portion of the first signal is received; and
an access point in communication with the first tag and with the second tag, wherein the access point comprises a receiver configured to receive the first signal and the second signal.
8. The system of claim 7 , wherein the access point further comprises a despread array configured to despread the first signal and the second signal.
9. The system of claim 7 , wherein the access point further comprises a demodulator configured to demodulate a plurality of chip hypotheses to identify the first signal.
10. The system of claim 9 , wherein the demodulator includes a cyclic redundancy check configured to validate the first payload data.
11. The system of claim 7 , wherein the first transmitter is configured to transmit the first signal such that the first signal is received by the receiver of the access point at a predetermined power level, and further wherein the second transmitter is configured to transmit the second signal such that the second signal is received by the receiver of the access point at the predetermined power level.
12. The system of claim 7 , wherein the access point further comprises a third transmitter configured to provide a third signal to the first tag, wherein the third signal is spread with a second PN code, and further wherein the second PN code is specific to the first tag.
13. The system of claim 7 , wherein the first tag further comprises a second receiver, and further wherein the first transmitter of the first tag is configured to re-transmit the first signal if a response is not received by the second receiver.
14. An access point for use in a multiple access communication system, the access point comprising;
a processor;
a receiver in communication with the processor and configured to receive a first signal from a first tag during a time slot, wherein the first signal includes first payload data, wherein the first signal has a first random timing offset in that the first signal is transmitted at a first random time in an uplink portion of a half duplex system, and further wherein the first signal is spread using a predetermined pseudo-noise (PN) code; and
receive a second signal from a second tag during the time slot, wherein the second signal includes second payload data, wherein the second signal has a second random timing offset in that the second signal is transmitted at a second random time in the uplink portion of the half duplex system, and further wherein the second signal is spread using the predetermined PN code, and further wherein at least a portion of the second signal is received while at least a portion of the first signal is received; and
a transmitter in communication with the processor and configured to transmit a third signal to the first tag, wherein the third signal is spread with a second PN code, and further wherein the second PN code is specific to the first tag.
15. The access point of claim 14 , further comprising a demodulator having a despread array, wherein the despread array is configured to despread the first signal and the second signal.
16. The access point of claim 14 , wherein the transmitter is further configured to transmit a fourth signal to the second tag, wherein the fourth signal is spread with a third PN code, and further wherein the third PN code is specific to the second tag.
17. The access point of claim 16 , wherein the fourth signal comprises an acknowledgement message that verifies receipt by the access point of the second signal.
18. The access point of claim 14 , wherein the first signal is received at a predetermined power level, and further wherein the second signal is received at the predetermined power level.
19. The access point of claim 14 , wherein the access point further comprises a demodulator configured to demodulate a plurality of chip hypotheses, wherein the demodulator includes a cyclic redundancy check configured to validate the first payload data.