Random orthogonal frequency division multiplexing
Methods, systems, and apparatuses, including computer programs encoded on computer-readable media, for receiving a first modulated signal on a first sub-channel, wherein a first transmitter randomly selects the first sub-channel from a plurality of sub-channels and for receiving, at the receiver, a second modulated signal on a second sub-channel, wherein the second sub-channel is orthogonal to the first sub-channel, wherein a second transmitter randomly selects the second sub-channel from the plurality of sub-channels. At least a portion of the first signal overlaps with a portion of the second signal. For each of the plurality of sub-channels, a plurality of symbols are stored in a buffer and a plurality of potential data frames are determined based upon the symbols in the buffer. A signal detection algorithm is applied to the potential data frames to detect the first modulated signal and the second modulated signal.
1. A method for receiving signals in a multiple access communication system comprising:
receiving, at a receiver, a first modulated signal on a first sub-channel, wherein a first transmitter randomly selects the first sub-channel from a plurality of sub-channels;
receiving, at the receiver, a second modulated signal on a second sub-channel, wherein the second sub-channel is orthogonal to the first sub-channel, wherein a second transmitter randomly selects the second sub-channel from the plurality of sub-channels, and wherein at least a portion of the first signal overlaps with a portion of the second signal;
storing, for each of the plurality of sub-channels, a plurality of potential symbols in a buffer;
determining a plurality of potential data frames based upon the potential symbols in the buffer; and
applying a signal detection algorithm to the potential data frames to detect the first modulated signal and the second modulated signal.
2. The method of claim 1 , wherein the buffer comprises a plurality of buffers, wherein each buffer corresponds to one sub-channel.
3. The method of claim 1 , wherein the first sub-channel is given by the formula e j2π(RF*ΔF+CF) , wherein RF comprises the first random frequency offset, ΔF comprises a frequency spacing and CF comprises a base carrier frequency.
4. The method of claim 1 , wherein the first transmitter transmits a frame of symbols on the first sub-channel.
5. The method of claim 1 , wherein each of the potential data frames is spread across multiple sub-channels.
6. The method of claim 5 , wherein the first transmitter transmits symbols of a first data frame across multiple sub-channels according to a known hopping sequence.
7. The method of claim 6 , wherein the known hopping sequence satisfies a requirement for spreading a transmission power per unit time across a frequency spectrum.
8. The method of claim 1 , wherein the signal detection algorithm comprises:
calculating, for each potential data frame, a hash value on the potential data frames; and
determining if the hash value matches a previously calculated hash value contained in the potential data frame.
9. The method of claim 8 , wherein the hash value is a cyclic redundancy check value.
10. The method of claim 1 , wherein the first modulated signal and the second modulated signal are both received at a predetermined power level.
11. An access point comprising:
a receiver configured to:
receive a first modulated signal on a first sub-channel, wherein a first transmitter randomly selects the first sub-channel from a plurality of sub-channels; and
receive a second modulated signal on a second sub-channel, wherein the second sub-channel is orthogonal to the first sub-channel, wherein a second transmitter randomly selects the second sub-channel from the plurality of sub-channels, and wherein at least a portion of the first signal overlaps with a portion of the second signal; and
a processor operatively coupled to the receiver and configured to:
store, for each of the plurality of sub-channels, a plurality of potential symbols in a buffer;
determine a plurality of potential data frames based upon the potential symbols in the buffer; and
apply a signal detection algorithm to the potential data frames to detect the first modulated signal and the second modulated signal.
12. The access point of claim 11 , wherein the buffer comprises a plurality of buffers, wherein each buffer corresponds to one sub-channel.
13. The access point of claim 11 , wherein the first frequency is given by the formula e j2π(RF*ΔF+CF) , wherein RF comprises the first pseudo-random frequency offset, ΔF comprises a frequency spacing and CF comprises a base carrier frequency.
14. The access point of claim 11 , wherein the first transmitter transmits a frame of symbols on the first sub-channel.
15. The access point of claim 11 , wherein each of the potential data frames is spread across multiple sub-channels.
16. The access point of claim 15 , wherein the first transmitter transmits symbols of a first data frame across multiple sub-channels according to a known hopping sequence.
17. The access point of claim 16 , wherein the known hopping sequence satisfies a requirement for spreading a transmission power per unit time across a frequency spectrum.
18. The access point of claim 11 , wherein the signal detection algorithm comprises:
calculating, for each potential data frame, a hash value on the potential data frames; and
determining if the hash value matches a previously calculated hash value contained in the potential data frame.
19. The access point of claim 18 , wherein the hash value is a cyclic redundancy check value.
20. The access point of claim 11 , wherein the first modulated signal and the second modulated signal are both received at a predetermined power level.