Digital video broadcast service discovery
View Patent ↗Embodiments are directed to binary phase shift key modulating a first pilot symbol according to a reference sequence, and differentially binary phase shift key modulating a second pilot symbols. The original reference sequence and the delayed differentially modulated sequence are then combined before performing an Inverse Fast Fourier Transform and inserting a guard interval. Receiver operations are an inverse of the transmitter operations, which were just discussed. The receiver does not have to know the reference sequence. Embodiments are directed to specifying a plurality of seeds that are bit patterns each having r bits not all of which have a value of zero, extending the seeds into respective sequences by applying to each seed a recurrence formula; and using one of the sequences as a comb sequence and using the sequences other than the comb sequence as binary phase shift keying patterns.
1. A method comprising:
transmitting a first pilot orthogonal frequency division multiplexing (OFDM) symbol comprising a plurality of sparsely distributed active subcarriers;
selecting a set of pseudorandom signaling sequences that is configured to provide signaling information within the plurality of sparsely distributed active subcarriers; and
modulating, using differential binary phase shift keying, the plurality of sparsely distributed active subcarriers by the set of pseudorandom signaling sequences such that the signaling information is provided within the plurality of sparsely distributed active subcarriers.
2. The method of claim 1 , wherein the plurality of sparsely distributed active subcarriers is selected from a middle of a frequency band.
3. The method of claim 1 , wherein the sparse distribution of the plurality of sparsely distributed active subcarriers forms an identifiable pattern indicating frequency shift.
4. The method of claim 1 , wherein sequences of the set of pseudorandom signalling sequences are orthogonal to each other.
5. An apparatus comprising:
a processor; and
a memory storing executable instructions configured to, with the processor, cause the apparatus to at least:
cause to be transmitted a first pilot orthogonal frequency division multiplexing (OFDM) symbol comprising a plurality of sparsely distributed active subcarriers;
select a set of pseudorandom signaling sequences that is configured to provide signaling information within the plurality of sparsely distributed active subcarriers; and
modulate, using differential binary phase shift keying, the plurality of sparsely distributed active subcarriers by the set of pseudorandom signaling sequences such that the signaling information is provided within the plurality of sparsely distributed active subcarriers.
6. The apparatus of claim 5 , wherein the plurality of sparsely distributed active subcarriers is selected from a middle of a frequency band.
7. The apparatus of claim 5 , wherein the sparse distribution of the plurality of sparsely distributed active subcarriers forms an identifiable pattern indicating frequency shift.
8. The apparatus of claim 5 , wherein sequences of the set of pseudorandom signalling sequences are orthogonal to each other.
9. The apparatus of claim 5 , wherein the first pilot OFDM symbol uses a 1 k fast Fourier Transform.
10. The apparatus of claim 5 , wherein the first pilot OFDM symbol occupies approximately one half of subcarriers available in a middle of a frequency band.
11. A method comprising:
receiving a first pilot orthogonal frequency division multiplexing (OFDM) symbol;
performing a fast fourier transform on the first pilot OFDM symbol;
detecting a frequency offset at least in part by finding a shifted subcarrier pattern; and
differentially demodulating the first pilot OFDM symbol, by a processor, to generate an estimated pseudo random binary sequence.
12. The method of claim 11 , wherein receiving the first pilot OFDM symbol indicates that a desired signal is present.
13. The method of claim 11 , wherein subcarrier power is used to detect the frequency offset.
14. The method of claim 11 , wherein signaling sequences are decoded from a phase difference between adjacent subcarriers.
15. An apparatus comprising:
a processor; and
a memory storing executable instructions configured to, with the processor, cause the apparatus to at least:
receive a first pilot orthogonal frequency division multiplexing (OFDM) symbol;
perform a fast fourier transform on the first pilot OFDM symbol;
detect a frequency offset at least in part by finding a shifted subcarrier pattern; and
differentially demodulate the first pilot OFDM symbol to generate an estimated pseudo random binary sequence.
16. The apparatus of claim 15 , wherein the memory further stores executable instructions configured to, with the processor, cause the apparatus to: use the first pilot OFDM symbol as an indication that a desired signal is present.
17. The apparatus of claim 16 , wherein the memory further stores executable instructions configured to, with the processor, cause the apparatus to: use subcarrier power to detect the frequency offset.
18. The apparatus of claim 15 , wherein signaling sequences are decoded from a phase difference between adjacent subcarriers.
19. One or more computer readable media comprising computer-executable instructions configured to, when executed, cause an apparatus to at least:
cause to be transmitted a first pilot orthogonal frequency division multiplexing (OFDM) symbol comprising a plurality of sparsely distributed active subcarriers;
select a set of pseudorandom signaling sequences that is configured to provide signaling information within the plurality of sparsely distributed active subcarriers; and
modulate, using differential binary phase shift keying, the plurality of sparsely distributed active subcarriers by the set of pseudorandom signaling sequences such that the signaling information is provided within the plurality of sparsely distributed active subcarriers.
20. The one or more computer readable media of claim 19 , wherein the memory further stores executable instructions configured to, with the processor, cause the apparatus to: select the plurality of sparsely distributed active subcarriers from a middle of a frequency band.
21. The one or more computer readable media of claim 19 , wherein the sparse distribution of the plurality of sparsely distributed active subcarriers forms an identifiable pattern indicating frequency shift.
22. The one or more computer readable media of claim 19 , wherein sequences of the set of pseudorandom signalling sequences are orthogonal to each other.
23. One or more computer readable media comprising computer-executable instructions configured to, when executed, cause an apparatus to at least:
receive a first pilot orthogonal frequency division multiplexing (OFDM) symbol;
perform a fast fourier transform on the first pilot OFDM symbol;
detect a frequency offset at least in part by finding a shifted subcarrier pattern; and
differentially demodulate the first pilot OFDM symbol to generate an estimated pseudo random binary sequence.
24. The one or more computer readable media of claim 23 , wherein receiving the first pilot OFDM symbol indicates that a desired signal is present.
25. The one or more computer readable media of claim 23 , wherein signaling sequences are decoded from a phase difference between adjacent subcarriers.
26. The one or more computer readable media of claim 23 , wherein subcarrier power is used to detect the frequency offset.
27. The method of claim 1 , wherein the signaling information is frequency offset information.
28. The apparatus of claim 5 , wherein the signaling information is frequency offset information.
29. The one or more computer readable media of claim 19 , wherein the signaling information is frequency offset information.