Partial response signaling techniques for single and multi-carrier nonlinear satellite systems
New partial response signaling systems and methods for high spectral efficiency communications are described. In a first implementation, a communication system includes a partial response signaling transmitter and a nonlinear satellite transponder. The partial response signaling transmitter includes a partial response transmit filter configured to convert complex-valued data symbols to a transmit signal using a partial response pulse shaping function; and a modulator configured to modulate the transmit signal onto a carrier wave. The transponder receives and non-linearly amplifies the modulated transmit signal for broadcast to receivers. In a second implementation, a receiver includes circuitry for downconverting a received input signal; a partial response filter with a partial response impulse function for filtering the downconverted signal; circuitry for downsampling the partial response filtered signal; circuitry for equalizing the downsampled signal; and a linear and non-linear interference cancellation module including circuitry for removing linear and non-linear ISI in the input signal.
1. A communication system, comprising:
a transmitter comprising:
a partial response transmit filter configured to convert complex-valued data symbols to a transmit signal using a partial response pulse shaping function; and
a modulator configured to modulate the transmit signal onto a carrier wave for transmission as a modulated transmit signal; and
a nonlinear satellite transponder configured to receive the modulated transmit signal and comprising a nonlinear amplifier for amplifying the modulated the modulated transmit signal to be broadcast to one or more receivers,
wherein the pulse shaping function is given by
PT
(
t
)
=
∑
l
-
0
L
-
1
f
l
·
sin
c
(
t
-
lT
s
T
s
)
Where L is an integer, single-sided memory span of the transmit filter, T s is the symbol duration, and f l is a coefficient associated with a memory l.
2. The system of claim 1 , wherein L is 2 or 3.
3. The system of claim 1 , wherein the transponder further comprises: an input multiplexing (IMUX) filter and an output multiplexing (OMUX) filter, and wherein the coefficient f t is based at least in part on the IMUX filter and the OMUX filter.
4. The system of claim 1 , wherein the amplifier is a power amplifier.
5. The system of claim 1 , further comprising: a downlink receiver configured to receive the broadcasted amplified modulated transmit signal, the receiver comprising a partial response receiver filter matched to the partial response transmit filter.
6. A communication system, comprising:
a transmitter comprising:
a first partial response transmit filter configured to convert a first set of complex-valued data symbols to a first transmit signal using a partial response pulse shaping function:
a second partial response transmit filter configured to convert a second set of complex-valued data symbols to a second transmit signal using a partial response pulse shaping function;
a first modulator configured to modulate the first transmit signal onto a carrier wave for transmission as a first modulated transmit signal;
a second modulator configured to modulate the second transmit signal onto a second carrier wave for transmission as a second modulated transmit signal; and
an adder configured to add the first and second modulated transmit signals to generate a composite signal; and
a nonlinear satellite transponder configured to receive the composite signal and comprising a nonlinear amplifier for amplifying transmit signals to be broadcast to one or more receivers.
7. The system of claim 6 , wherein the transponder is configured to receive the composite signal at an input multiplexing (IMUX) filter.
8. A method, comprising:
converting complex-valued data symbols to a transmit signal using a partial response pulse shaping function of a partial response transmit filter;
modulating the transmit signal onto a carrier wave for transmission as a modulated transmit signal;
receiving the modulated transmit signal at a nonlinear satellite transponder; amplifying the received modulated transmit signal using a nonlinear amplifier of the satellite transponder; and
broadcasting the amplified modulated transmit signal from the satellite transponder to one or more downlink receivers,
wherein the pulse shaping function is given by
PT
(
t
)
=
∑
l
-
0
L
-
1
f
l
·
sin
c
(
t
-
lT
s
T
s
)
Where L is an integer, single-sided memory span of the transmit filter, T s is the symbol duration, and f l is a coefficient associated with a memory l.
9. A method, comprising:
converting a first set of complex-valued data symbols to a first transmit signal using a partial response pulse shaping function of a partial response transmit filter;
modulating the first transmit signal onto a carrier wave for transmission as a first modulated transmit signal using a first modulator;
converting a second set of complex-valued data symbols to a second transmit signal using a partial response pulse shaping function of a second partial response transmit filter;
modulating the second transmit signal onto a second carrier wave for transmission as a second modulated transmit signal using a second modulator;
adding the first and second modulated transmit signals to generate a composite signal; and
transmitting the composite signal to a nonlinear satellite transponder, wherein the nonlinear satellite transponder comprises a nonlinear amplifier for amplifying transmit signals to be broadcast to one or more receivers.
10. A transmitter for a satellite communication system, comprising:
a partial response transmit filter configured to convert complex-valued data symbols to a transmit signal using a partial response pulse shaping function; and
circuitry for modulating the transmit signal onto a carrier wave for transmission as a modulated transmit signal, wherein the transmitter transmits the modulated transmit signal to a satellite transponder,
wherein the pulse shaping function is given by:
PT
(
t
)
=
∑
l
-
0
L
-
1
f
l
·
sin
c
(
t
-
lT
s
T
s
)
Where L is an integer, single-sided memory span of the transmit filter, T s is the symbol duration, and f l is a coefficient associated with a memory l.
11. The transmitter of claim 10 , further comprising:
a second partial response transmit filter configured to convert a second set of complex valued data symbols to a second transmit signal using the partial response pulse shaping function;
circuitry for modulating the second transmit signal onto a second carrier wave for transmission as a second modulated transmit signal; and
circuitry for adding the first and second modulated transmit signals to generate a composite signal.
12. The transmitter of claim 10 , wherein the coefficient f t is based at least in part on an input multiplexing (IMUX) filter and an output multiplexing (QMUX) filter of a satellite transponder.
13. The transmitter of claim 10 , wherein L is 2 or 3.
14. A partial response signaling receiver, comprising:
circuitry for downconverting a received input signal, wherein the partial response signaling receiver receives signals from a satellite transponder; and
a partial response receive filter with impulse function PR(t) for filtering the downconverted signal;
wherein the impulse function is given by PR(t)=PR*(−t), wherein PT(t) is a pulse shaping function of a matched partial response transmit filter, wherein
PT
(
t
)
=
∑
l
-
0
L
-
1
f
l
·
sin
c
(
t
-
lT
s
T
s
)
Where L is an integer, single-sided memory span of the transmit filter, T s is the symbol duration, and f l is a coefficient associated with a memory l.
15. A partial response signaling receiver, comprising:
circuitry for downconverting a received input signal, wherein the received input signal is received from a satellite transponder comprising an input multiplexing (IMUX) filter and an output multiplexing (QMUX) filter;
a partial response receive filter with an impulse function for filtering the downconverted signal;
a downsampler for downsampling the partial response filtered signal; and
a linear equalizer for equalizing the downsampled signal and configured to compensate for a group delay resulting from the IMUX filter and OMUX filter.
16. A partial response signaling receiver, comprising:
circuitry for downconverting a received input signal, wherein the partial response signaling receiver receives signals from a satellite transponder;
a partial response filter with a partial response impulse function for filtering the downconverted signal;
a downsampler for downsampling the partial response filtered signal; a linear equalizer for equalizing the downsampled signal; and
circuitry for removing linear inter-symbol interference (ISI) and non-linear ISI in the input signal, wherein the circuitry for removing linear and non-linear ISI comprises an interference estimate filter configured to estimate interference in the input signal by creating a polynomial representation of a nonlinear satellite system with memory.
17. The receiver of claim 16 , wherein the polynomial representation is based on a Volterra series.
18. The receiver of claim 17 , wherein the interference estimate may be expressed as
[ h ( n )· E{a NL (1,3) ( n )| L A (E) ( a n )}− E{ρ centroid ( a n )| L A (E) ( a n )}]
Where h (n) is a set of Volterra filter coefficients, chosen to model an amplifier and partial response induced distortion in the nonlinear satellite system, ρ centroid (a n ) is the centroid associated with symbol a n , of the clusters at the fractionally-spaced equalizer output, found during training mode, a NL (1,3) (n) is a vector of 1st- and 3rd-order symbol combinations, the term [ h (n)·E{a NL (1,3) (n)|L A (E) (a n )} estimates a received signal, and the term E{ρ centroid (a n )|L A (E) (a n )} estimates a transmitted signal.
19. The receiver of claim 16 , wherein the received input signal is received from a satellite transponder comprising an input multiplexing (IMUX) filter and output multiplexing (QMUX) filter, and wherein the linear equalizer compensates for a group delay resulting from the IMUX filter and OMUX filter.
20. A method, comprising:
downconverting an input signal received at a partial response signaling receiver, wherein the partial response signaling receiver receives the input signal from a satellite transponder;
filtering the downconverted signal using a partial response filter of the receiver with a partial response impulse function;
downsampling the partial response filtered signal using a downsampler of the receiver;
equalizing the downsampled signal using a linear equalizer of the receiver; and
removing linear inter-symbol interference (ISI) and non-linear ISI in the input signal,
wherein removing linear ISI and non-linear ISI in the input signal comprises using an interference estimate filter to estimate interference in the input signal by creating a polynomial representation of a nonlinear satellite system with memory.