Despreading spread spectrum data
A method for de-spreading spread data includes receiving a data stream by multiple access communication where the received data stream is spread using a pseudo-noise (PN) code; multiplying a first portion of the received data stream including data from a first user by a first portion of a PN signal to obtain a first product; providing the first product to a first counter; multiplying a second portion of the received data stream including data from a second user by the first portion of the PN signal to obtain a second product; providing the second product to a second counter; and determining whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.
1. A method for de-spreading spread data, the method comprising:
receiving a data stream by multiple access communication, wherein the spread data is spread using a pseudo-noise (PN) code;
multiplying a first portion of the received data stream including data from a first user by a first portion of a PN signal to obtain a first product;
providing the first product to a first counter;
multiplying a second portion of the received data stream including data from a second user by a second portion of the PN signal to obtain a second product;
providing the second product to a second counter; and
determining whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.
2. The method of claim 1 , wherein the spread data is spread using the PN code with a randomly selected chip offset.
3. The method of claim 2 , further comprising determining whether the data stream is valid using a cyclic redundancy checking check.
4. The method of claim 1 , further comprising iterating the PN signal over multiple spreading factors until valid sequences are determined.
5. The method of claim 1 , wherein the second portion of the PN signal is obtained by imposing a delay on the first portion of the PN signal.
6. The method of claim 1 , further comprising utilizing a plurality of contiguous timing hypothesis until valid sequences are determined.
7. The method of claim 1 , further comprising iterating over fine automatic frequency control (AFC) hypothesis until valid sequences are determined.
8. A system for de-spreading spread data, the system comprising:
a first de-spread element comprising
a first combiner configured to multiply a first portion of a data stream from a first user by first portion of a pseudo-noise (PN) signal to obtain a first product, wherein the spread data is spread with a PN code; and
a first counter configured to receive the first product from the first combiner;
a second de-spread element comprising
a second combiner configured to multiply a second portion of the data stream from a second user by a second portion of the PN signal to obtain a second product; and
a second counter configured to receive the second product from the second combiner; and
a multiplexer configured to receive outputs of the first and second counters, wherein the multiplexer is used at least in part to determine whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.
9. The system of claim 8 , wherein the spread data is spread using the PN code with a randomly selected chip offset.
10. The system of claim 9 , wherein the PN signal is iterated over multiple spreading factors until valid sequences are determined.
11. The system of claim 9 , further comprising a delay module configured to impose a delay on the PN signal such that the second portion of the data stream is multiplied by the second portion of the PN signal.
12. The system of claim 8 , wherein the first product is part of a first timing hypothesis and the second product is part of a second timing hypothesis.
13. The system of claim 12 , wherein the first timing hypothesis and the second timing hypothesis are simultaneously determined.
14. An access point configured to de-spread spread data, the access point comprising:
a receiver configured to receive a data stream that is spread with a pseudo-noise (PN) code; and
a de-spreader in communication with the receiver, wherein the de-spreader comprises
a first de-spread element comprising
a first combiner configured to multiply a first portion of the data stream from a first user by a first portion of a pseudo-noise (PN) signal to obtain a first product; and
a first counter configured to receive the first product from the first combiner;
a second de-spread element comprising
a second combiner configured to multiply a second portion of the data stream from a second user by a second portion of the PN signal to obtain a second product; and
a second counter configured to receive the second product from the second combiner; and
a multiplexer configured to receive outputs of the first and second counters, wherein the multiplexer is used at least in part to determine whether the first portion of the PN signal and the second portion of the PN signal produce valid sequences based at least in part on the first product and the second product.
15. The access point of claim 14 , wherein the data stream is spread using the PN code with a randomly selected chip offset.
16. The access point of claim 14 , wherein the de-spreader further comprises a delay module configured to impose a delay on the PN signal such that the second portion of the data stream is multiplied by the second portion of the PN signal.
17. The access point of claim 14 , wherein the first product is part of a first timing hypothesis and the second product is part of a second timing hypothesis, and further wherein the first timing hypothesis and the second timing hypothesis are a chip apart.
18. The access point of claim 14 , wherein the PN signal is iterated over multiple spreading factors until valid sequences are determined.