Zero tail and unique word based waveforms for DFT-s OFDM and OFDM
Methods and systems for operation in a wireless network are provided, the methods including receiving modulated data symbols and zeros in a frequency-domain, and mapping in the frequency-domain the modulated data symbols and zeros in an interleaved manner to sub-carriers within a resource allocation. The methods and systems further include generating a time-domain data signal based on the mapped sub-carriers, and generating a time domain cancellation signal by sign inverting and repeating a predetermined number of time-domain samples at a tail portion of the data signal. The methods and systems further include combining the time-domain data signal and the time domain cancellation signal to generate an exact zero tail data signal such that the exact zero tail data signal has a zero tail length equal to the predetermined number of time-domain samples, and transmitting the exact zero tail data signal.
1. A wireless transmit/receive unit (WTRU) comprising:
an antenna; and
a processor operatively coupled to the antenna; wherein:
the processor is configured to receive modulated data symbols and zeros in a frequency-domain;
the processor is further configured to map, in the frequency-domain, the modulated data symbols and zeros in an interleaved manner to sub-carriers within a resource allocation;
the processor is further configured to generate a time-domain data signal based on the mapped sub-carriers;
the processor is further configured to generate a time-domain cancellation signal by sign inverting and repeating a predetermined number of time-domain samples at a tail portion of the time-domain data signal;
the processor is further configured to combine the time-domain data signal and the time-domain cancellation signal to generate an exact zero tail data signal, wherein the exact zero tail data signal has a zero tail length equal to the predetermined number of time-domain samples; and
the processor and the antenna are configured to transmit the exact zero tail data signal.
2. The WTRU of claim 1 , wherein the processor is further configured to generate the time-domain cancellation signal by inverting a sign of the time-domain samples and repeating a sequence of the inverted time-domain samples.
3. The WTRU of claim 1 , wherein the processor is further configured to generate the time-domain cancellation signal by inverting a vector comprising the tail time-domain samples and repeating the inverted vector a plurality of times to generate a string of the inverted vectors such that the time-domain cancellation signal comprises the string of the inverted vectors.
4. The WTRU of claim 1 , wherein the processor is further configured to generate the time domain cancellation signal by inverting the time-domain samples, converting the sign inverted time-domain samples into a plurality of frequency-domain symbols, and mapping the plurality of frequency-domain symbols in an interleaved manner to a plurality of allocated sub-carriers.
5. The WTRU of claim 4 , wherein the plurality of frequency-domain symbols are uniformly interleaved over the plurality of allocated sub-carriers.
6. The WTRU of claim 1 , wherein the processor is further configured to generate an exact zero tail data signal by shifting at least one time-domain sample from a tail portion of the exact zero tail data signal to a head portion of the exact zero tail data signal.
7. The WTRU of claim 1 , wherein the exact zero tail data signal comprises a plurality of data blocks each having a zero-tail portion, and wherein the processor is further configured to insert, in the time-domain, a unique word at each zero tail portion of the exact zero tail data signal.
8. The WTRU of claim 1 , wherein the processor is further configured to insert guard bands into the exact zero tail data signal.
9. The WTRU of claim 1 , wherein the processor is further configured to:
sign invert the tail time-domain samples;
convert the tail time-domain samples into an inverted plurality of tail frequency-domain symbols with an Nzt size discrete Fourier transform (DFT);
map the inverted plurality of tail frequency-domain symbols to a plurality of allocated sub-carriers in an interleaved manner such that another plurality of zeros are inserted on
M
N
zt
-
1
consecutive sub-carriers of the plurality of allocated sub-carriers between each output of the Nzt size DFT, wherein M is a number of the plurality of allocated sub-carriers, Nzt is a number of the selected plurality of tail time-domain samples, and
M
N
zt
is an integer; and
generate the time domain cancellation signal by converting the mapped inverted plurality of tail frequency-domain symbols into the time-domain such that the time-domain cancellation signal is a replica of the inverted plurality of tail time-domain samples, repeated
M
N
zt
times.
10. The WTRU of claim 1 , wherein the exact zero tail data signal is an orthogonal frequency-division multiplexing (OFDM) signal.