Method and system for providing code cover to OFDM symbols in multiple user system
The present disclosure discloses a method and a system for providing a code cover to Orthogonal Frequency Division Multiplexing (OFDM) symbols in a multiple user system. A data sequence is received from each of a plurality of users. Further, a reference sequence is generated for the data sequence of each of the plurality of users. Each of the reference sequence is multiplied with a code cover which are orthogonal to each other. Each of the reference sequence is time-multiplexed with corresponding data sequence, to generate a corresponding multiplexed sequence. Further, a Discrete Fourier Transform (DFT) is performed on each of the multiplexed sequence to generate a corresponding DFT-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) symbol. Lastly, the corresponding DFT-s-OFDM symbol is processed for transmitting over corresponding one or more channels.
1. A method for generating a waveform by one or more transmitters in a communication network, the method comprising:
generating, by the one or more transmitters, at least one data sequence, at least one reference sequence (RS) and at least one phase tracking reference sequence (PT-RS), wherein the at least one of the data sequence, the at least one RS and at least one PT-RS are applied with a corresponding transmitter specific code cover;
time-multiplexing, by the one or more transmitters, the at least one data sequence, at least one RS, and the at least one PT-RS to generate a multiplexed sequence; and
generating, by the one or more transmitters, a filtered DFT-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) waveform using the multiplexed sequence.
2. The method of claim 1 , wherein each of the plurality of code covers is one of a binary phase shift keying (BPSK) sequence and a Walsh Hadamard sequence.
3. The method of claim 1 , wherein the at least one data sequence is one of a pi/2 BPSK sequence, quadrature phase shift keying (QPSK) sequence and a quadrature amplitude modulation (QAM) sequence.
4. The method of claim 1 , wherein the at least one of the data sequence, the RS and the PT-RS is converted by performing one of a spreading operation and a multiplication operation, using the corresponding transmitter specific code cover from a plurality of code covers.
5. The method of claim 1 , wherein the RS is a binary phase shift keying reference sequence (BPSK-RS).
6. The method of claim 1 , wherein the method comprises applying a cover code to the BPSK-RS, and rotating the BPSK-RS by 90 degrees between successive elements to generate a rotated BPSK-RS.
7. The method of claim 1 , wherein generating the filtered DFT-s-OFDM waveform using the multiplexed sequence comprises:
performing a Discrete Fourier Transform (DFT) on the multiplexed sequence to generate a corresponding DFT-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) symbol; and
mapping the filtered DFT-s-OFDM symbol associated with each of the one or more transmitters with at least one of localized subcarriers and distributed subcarriers to generate a mapped signal; and
performing an Inverse Fast Fourier Transform (IFFT) on the mapped signal to produce a time domain waveform.
8. The method of claim 1 , wherein generating the filtered DFT-s-OFDM waveform using the multiplexed sequence comprises:
performing one of a plurality of operation sequences, wherein:
a first operation sequence comprises transforming the multiplexed sequence using a Discrete Fourier Transform (DFT) to generate a transformed multiplexed sequence, and applying a frequency domain pulse shaping filter on the transformed multiplexed sequence,
a second operation sequence comprises precoding the multiplexed sequence to produce a precoded multiplexed sequence, and transforming the precoded multiplexed sequence using a Discrete Fourier Transform (DFT), and
a third operation sequence comprises transforming the multiplexed sequence using a Discrete Fourier Transform (DFT);
mapping the DFT-s-OFDM symbol associated with each of the one or more transmitters with at least one of localized subcarriers and distributed subcarriers to generate a mapped signal; and
performing an Inverse Fast Fourier Transform (IFFT) on the mapped signal to produce a time domain DFT-s-OFDM waveform.
9. The method of claim 8 , wherein the precoding is performed using one of a 1+D precoder and a Q-tap polynomial precoder and wherein D is the delay unit and Q is one of 1, 2 and 3.
10. The method of claim 8 , wherein the frequency domain pulse shaping filter is one of DFT of a 1+D precoder and DFT of a Q-tap polynomial precoder, wherein D is the delay unit and Q is one of 1, 2 and 3.
11. A system, the system comprising:
one or more transmitters operable to:
generate at least one data sequence, at least one reference sequence (RS) and at least one phase tracking reference sequence (PT-RS), wherein the at least one of the data sequence, the at least one RS and at least one PT-RS are applied with a corresponding transmitter specific code cover;
time-multiplex the at least one data sequence, at least one RS, and the at least one PT-RS to generate a multiplexed sequence; and
generate a filtered DFT-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) waveform using the multiplexed sequence.
12. The system of claim 11 , wherein each of the plurality of code covers is one of a binary phase shift keying (BPSK) sequence and a Walsh Hadamard sequence.
13. The system of claim 11 , wherein the at least one data sequence is one of a pi/2 BPSK sequence, quadrature phase shift keying (QPSK) sequence and a quadrature amplitude modulation (QAM) sequence.
14. The system of claim 11 , wherein the at least one of the data sequence, the RS and the PT-RS is converted by performing one of a spreading operation and a multiplication operation, using the corresponding transmitter specific code cover from a plurality of code covers.
15. The system of claim 11 , wherein the RS is a binary phase shift keying reference sequence (BPSK-RS).
16. The system of claim 11 , wherein the method comprises applying a cover code to the BPSK-RS, and rotating the BPSK-RS by 90 degrees between successive elements to generate a rotated BPSK-RS.
17. The system of claim 11 , wherein the one or more transmitters are operable to:
perform a Discrete Fourier Transform (DFT) on the multiplexed sequence to generate a corresponding DFT-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) symbol; and
map the filtered DFT-s-OFDM symbol associated with each of the one or more transmitters with at least one of localized subcarriers and distributed subcarriers to generate a mapped signal; and
perform an Inverse Fast Fourier Transform (IFFT) on the mapped signal to produce a time domain waveform.
18. The system of claim 11 , wherein the one or more transmitters are operable to:
perform one of a plurality of operation sequences, wherein:
a first operation sequence comprises transforming the multiplexed sequence using a Discrete Fourier Transform (DFT) to generate a transformed multiplexed sequence, and applying a frequency domain pulse shaping filter on the transformed multiplexed sequence,
a second operation sequence comprises precoding the multiplexed sequence to produce a precoded multiplexed sequence, and transforming the precoded multiplexed sequence using a Discrete Fourier Transform (DFT), and
a third operation sequence comprises transforming the multiplexed sequence using a Discrete Fourier Transform (DFT);
map the DFT-s-OFDM symbol associated with each of the one or more transmitters with at least one of localized subcarriers and distributed subcarriers to generate a mapped signal; and
perform an Inverse Fast Fourier Transform (IFFT) on the mapped signal to produce a time domain DFT-s-OFDM waveform.
19. The system of claim 18 , wherein the precoding is performed using one of a 1+D precoder and a Q-tap polynomial precoder and wherein D is the delay unit and Q is one of 1, 2 and 3.
20. The system of claim 18 , wherein the frequency domain pulse shaping filter is one of DFT of a 1+D precoder and DFT of a Q-tap polynomial precoder, wherein D is the delay unit and Q is one of 1, 2 and 3.