Spread spectrum communication, and associated devices, systems, and methods
Various embodiments relate to spread spectrum communication. A communication system may include a base station and a user equipment. The base station may be configured to: add a cyclic prefix (CP) to each block of a number of blocks of a first direct sequence spread spectrum (DSSS) signal to generate a first cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal; add artificial noise to the first CP-DSSS signal; and transmit, via a channel, the first CP-DSSS signal. The user equipment is configured to receive the first CP-DSSS signal. Associated methods and communications systems are also disclosed.
1. A communication system, comprising:
a base station configured to:
add a cyclic prefix (CP) to each block of a number of blocks of a first direct sequence spread spectrum (DSSS) signal to generate a first cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal;
add artificial noise to the first CP-DSSS signal such that the artificial noise is orthogonal to data symbols of the first CP-DSSS signal; and
transmit, via a channel, the first CP-DSSS signal including the artificial noise; and
a user equipment configured to receive the first CP-DSSS signal, wherein the base station, the user equipment, or each of the base station and the user equipment, include multiple antennas, wherein an effective channel between the base station and the user equipment is at least partially based on concatenation of various channel impulse responses between different pairs of antennas of the base station and antennas of the user equipment, wherein the various channel impulses responses are concatenated via a circulant matrix D Δ 1 selected such that when the circulant matrix pre-multiplies a transmit signal vector, elements of the transmit signal vector are shifted downward by Δ 1 elements to construct the effective channel.
2. The communication system of claim 1 , wherein the base station is configured to add a vector of samples of white noise to a vector of the first CP-DSSS signal.
3. The communication system of claim 1 , wherein the artificial noise added to the first CP-DSSS signal is orthogonal to the data symbols of the first CP-DSSS signal received at the user equipment.
4. The communication system of claim 1 , wherein, at the user equipment, the artificial noise of the received first CP-DSSS signal is nulled out at sample points including the data symbols.
5. The communication system of claim 1 , wherein the artificial noise is transmitted from the base station to the user equipment in a subspace that is orthogonal to a data symbols subspace.
6. The communication system of claim 1 , wherein the transmitted first CP-DSSS signal includes samples that are uncorrelated and Gaussian.
7. The communication system of claim 1 , wherein the data symbols of the first CP-DSSS signal received at the user equipment are substantially free of inter-symbol interference (ISI).
8. A method, comprising:
adding, at a base station, a cyclic prefix (CP) to each block of a number of blocks of direct sequence spread spectrum (DSSS) signal to generate a cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal;
adding, at the base station, artificial noise to the CP-DSSS signal such that the artificial noise is orthogonal to data symbols of the CP-DSSS signal;
transmitting the CP-DSSS signal including the artificial noise; and
receiving the CP-DSSS signal at a user equipment, wherein the base station, the user equipment, or each of the base station and the user equipment, include multiple antennas, wherein an effective channel between the base station and the user equipment is at least partially based on concatenation of various channel impulse responses between different pairs of antennas of the user equipment, wherein the various channel impulses responses are concatenated via a circulant matrix D Δ 1 selected such that when the circulant matrix pre-multiplies a transmit signal vector, elements of the transmit signal vector are shifted downward by Δ 1 elements to construct the effective channel.
9. The method of claim 8 , wherein transmitting the CP-DSSS signal comprises transmitting the CP-DSSS signal such that, at a receiver, the artificial noise of the CP-DSSS signal is nulled out at sample points including the data symbols.
10. The method of claim 8 , wherein transmitting the CP-DSSS signal comprises transmitting the artificial noise in a subspace that is orthogonal to a data symbols subspace.
11. The method of claim 8 , wherein transmitting the CP-DSSS signal comprises transmitting the CP-DSSS signal including samples that are uncorrelated and Gaussian.
12. The method of claim 8 , wherein adding artificial noise comprises adding a vector of samples of white noise to a vector of the CP-DSSS signal.
13. The method of claim 8 , wherein adding artificial noise comprises adding the artificial noise to the CP-DSSS signal such that the data symbols of the CP-DSSS signal recovered at a receiver are substantially free of inter-symbol interference (ISI).
14. A communication system, comprising:
a base station configured to:
add a cyclic prefix (CP) to each block of a number of blocks of a first direct sequence spread spectrum (DSSS) signal to generate a first cyclic prefix-direct sequence spread spectrum (CP-DSSS) signal;
add artificial noise to the first CP-DSSS signal; and
transmit, via a channel, the first CP-DSSS signal including the artificial noise; and
a user equipment configured to receive the first CP-DSSS signal,
wherein the base station, the user equipment, or each of the base station and the user equipment, include multiple antennas, wherein an effective channel between the base station and the user equipment is at least partially based on concatenation of various channel impulse responses between different pairs of antennas of the base station and antennas of the user equipment, wherein the various channel impulses responses are concatenated via a circulant matrix D Δ 1 selected such that when the circulant matrix pre-multiplies a transmit signal vector, elements of the transmit signal vector are shifted downward by Δ 1 elements to construct the effective channel.
15. The communication system of claim 14 , wherein the base station is configured to add a vector of samples of white noise to a vector of the first CP-DSSS signal.
16. The communication system of claim 14 , wherein the artificial noise added to the first CP-DSSS signal is orthogonal to data symbols of the first CP-DSSS signal received at the user equipment.
17. The communication system of claim 14 , wherein, at the user equipment, the artificial noise of the received first CP-DSSS signal is nulled out at sample points including data symbols.
18. The communication system of claim 14 , wherein the artificial noise is transmitted from the base station to the user equipment in a subspace that is orthogonal to a data symbols subspace.
19. The communication system of claim 14 , wherein data symbols of the first CP-DSSS signal received at the user equipment are substantially free of inter-symbol interference (ISI).