Systems, devices and methods for communicating data over circularly pulse-shaped waveforms
Circularly pulse-shaped waveforms for communication systems are disclosed herein, including a single carrier modulation in which pulse-shaping is performed using a circular convolution by the transmitter for various modulation schemes. A transmitter, related method, and corresponding receiver are also disclosed for demodulation of the single carrier circularly pulse-shaped signal and data extraction.
1. A method of generating a block of circularly pulse-shaped waveforms, the method comprising: receiving a string of data symbols with a processor of a transmitter; spreading the string of data symbols across a number of complex-valued sinusoidal tones in the frequency domain with the processor, each complex-valued sinusoidal tone of the number of complex-valued sinusoidal tones associated with a different subcarrier band; summing the complex-valued sinusoidal tones with the processor; circularly shifting and accumulating a result of the summing with the processor; generating an output signal with the processor by serializing a result of the circularly shifting and accumulating; and transmitting the output signal wirelessly via communication elements of the transmitter to a receiving device, wherein spreading the string of data symbols across a number of tones includes: applying an L-point fast Fourier transform (FFT) operation that is repeated K times to generate a vector in the frequency domain; and applying a pulse-shaping filter hf[k] to the vector in the frequency domain at a frequency band of interest.
2. The method of claim 1 , wherein summing the complex-valued sinusoidal tones includes passing the complex-valued sinusoidal tones with the string of data symbols through an inverse fast Fourier transform (IFFT).
3. The method of claim 1 , further comprising adding a cyclic prefix to the result of the circularly shifting and accumulating.
4. The method of claim 1 , wherein the pulse-shaping filter h f [k] is a band-limited filter for the frequency band of interest.
5. The method of claim 4 , wherein the pulse-shaping filter h f [k] satisfies the following constraint 1−ϵ 1 ≤hfk≤1+ϵ 1 , for 0≤k≤L 1 wherein ϵ 1 is a design parameter of the transmitter, and L 1 is a number of frequency domain samples for the pulse-shaping filter h f [k].
6. The method of claim 5 , wherein the pulse-shaping filter in the time domain is defined as:
h
[
n
]
=
1
N
(
h
f
[
0
]
+
2
∑
k
=
1
L
1
h
f
[
k
]
cos
(
2
π
N
kn
)
)
.
7. The method of claim 1 , wherein the pulse-shaping filter is a band-pass filter centered at a predetermined subcarrier band.
8. A receiving device for processing a data signal exhibiting a single carrier modulation waveform, the receiving device comprising:
a receiver including a processor, the receiver configured to:
receive a data signal having a single carrier modulated circularly pulse-shaped waveform;
generate estimates of data symbols □ 0 through s L-1 that are spread across a number of complex-valued sinusoidal signal tones responsive to performing a reverse signal synthesis to the data signal via a fast Fourier transform (FFT) demodulator block of the receiver; and
perform interpolation among multi-tones associated with the data signal having the single carrier modulated circularly pulse-shaped waveform to compensate for carrier frequency offset (CFO) of the FFT demodulator block of the receiver for users of a multi-user network having different CFOs.
9. A receiving device for processing a data signal exhibiting a single carrier modulation waveform, the receiving device comprising:
a receiver including a processor, the receiver configured to:
receive a data signal having a single carrier modulated circularly pulse-shaped waveform;
generate estimates of data symbols □ 0 through s L-1 that are spread across a number of complex-valued sinusoidal signal tones responsive to performing a reverse signal synthesis to the data signal via a fast Fourier transform (FFT) demodulator block of the receiver;
remove cyclic prefix from the data signal;
apply an IFFT to the received data signal; and
apply a single-tap equalizer per each complex-valued sinusoidal signal tone in the frequency domain to reduce channel impact on the complex-valued sinusoidal signal tones of the received signal.
10. A communication system, comprising:
a transmitter including a processor, the transmitter configured to:
receive an input data signal including a vector of data symbols;
expand a length of the vector to be equal to a length of a pulse shaping filter;
generate an output signal exhibiting a single carrier circularly pulse-shaped waveform constructed by using a circular convolution for pulse shaping during synthesis of the data symbols of the input data signal;
reduce peak-to-average-power-ratio (PAPR) of the output signal responsive to performing single carrier modulation of the input data signal using a pulse shaping filter in the frequency domain; and
transmit the output signal including the single carrier modulated circularly pulse-shaped waveform; and
a receiver including a processor, the receiver configured to:
receive the output signal from the transmitter; and
generate estimates of data symbols □ 0 through s L-1 that are spread across a number of complex-valued sinusoidal signal tones responsive to performing a reverse signal synthesis to the output signal via a fast Fourier transform (FFT) demodulator block of the receiver.