Systems, methods and transceivers for wireless communications over discontiguous spectrum segments
View Patent ↗Methods of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band include defining a plurality (N FFT ) of orthogonal subcarriers across the frequency band, defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers. The available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments. The methods further include multiplexing the plurality of communications signals onto the plurality of available physical subcarriers. Multiplexing the plurality of communications signals onto the plurality of available physical subcarriers may include assigning the communications signals to respective ones of a plurality (N) of logical subcarriers, and mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers. Related transmitters, receivers and communications systems are also disclosed.
1. A method of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:
defining a plurality (N FFT ) of orthogonal subcarriers across the frequency band;
defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers, wherein N<N FFT , and wherein the available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments; and
multiplexing the plurality of communications signals onto the plurality of available physical subcarriers;
wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises:
assigning the communications signals to respective ones of a plurality (N) of logical subcarriers;
mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers;
assigning at least one pilot signal to at least one of the plurality of logical subcarriers; and
modulating each of the available physical subcarriers with data from a corresponding logical subcarrier, the method further comprising:
defining a plurality (N FFT -N) of unavailable physical subcarriers within the frequency band; and
setting an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero;
wherein the communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers; and
wherein modulating each of the available physical subcarriers with data from a corresponding logical subcarrier comprises performing an N FFT -point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N FFT -N input data signals corresponding to each of the plurality of unavailable physical subcarriers.
2. The method of claim 1 , further comprising
converting an output of the N FFT -point inverse fourier transform to a serial data stream; and
transmitting the serial data stream.
3. The method of claim 1 , further comprising:
defining a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality of contiguous subcarriers;
defining an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols;
allocating a first plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel; and
allocating a second plurality of subcarriers within the AMC subchannel as data subcarriers.
4. The method of claim 3 , wherein defining the AMC subchannel comprises defining a subchannel comprising two clusters over three symbols.
5. The method of claim 3 , wherein defining the AMC subchannel comprises defining a subchannel comprising one cluster over six symbols.
6. The method of claim 3 , wherein the pilot subcarriers for an AMC subchannel are allocated at locations determined by the indices of logical subcarriers.
7. The method of claim 6 , wherein pilot subcarriers in an AMC channel are offset by two subcarriers in adjacent symbols.
8. The method of claim 6 , wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:
pilot_subs
(
n
,
k
)
=
9
n
+
3
m
+
1
for
n
=
0
,
1
,
…
,
⌈
N
9
⌉
,
wherein:
n is an index number of a pilot subcarrier in a symbol;
k is an index of the symbol;
m is given by k mod 3; and
┌X┐ denotes the largest integer not greater than X.
9. The method of claim 3 , further comprising:
assigning a plurality of data symbols to data subcarriers in the AMC subchannel according to a scrambling sequence.
10. The method of claim 9 , wherein the scrambling sequence is defined by a Galois field and an offset.
11. The method of claim 9 , wherein the scrambling sequence is unique to a particular cell and/or sector of a wireless communications system.
12. A method of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:
defining a plurality (N FFT ) of orthogonal subcarriers across the frequency band;
defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers, wherein N<N FFT , and wherein the available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments; and
multiplexing the plurality of communications signals onto the plurality of available physical subcarriers;
wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises:
spreading the plurality of communications signals using a plurality of corresponding spreading codes;
combining the plurality of spread communications signals to form a combined communications signal;
converting the combined communications signal to parallel communications signals
assigning the parallel communications signals to respective ones of a plurality (N) of logical subcarriers;
mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers;
assigning at least one pilot signal to at least one of the plurality of logical subcarriers; and
modulating each of the available physical subcarriers with data from a corresponding logical subcarrier, the method further comprising:
defining a plurality (N FFT -N) of unavailable physical subcarriers within the frequency band; and
setting an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero;
wherein the parallel communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers; and
wherein modulating each of the available physical subcarriers with data from a corresponding logical subcarrier comprises performing an N FFT -point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N FFT -N input data signals corresponding to each of the plurality of unavailable physical subcarriers.
13. The method of claim 12 , further comprising
converting an output of the N FFT -point inverse fourier transform to a serial data stream; and
transmitting the serial data stream.
14. The method of claim 12 , further comprising:
defining a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers;
defining an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols; and
allocating a plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel.
15. The method of claim 14 , wherein the pilot subcarriers for an AMC subchannel are allocated at locations determined by the indices of logical subcarriers.
16. The method of claim 15 , wherein pilot subcarriers in adjacent symbols of an AMC channel are offset by two subcarriers.
17. The method of claim 15 , wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:
pilot_subs
(
n
,
k
)
=
9
n
+
3
m
+
1
for
n
=
0
,
1
,
…
,
⌈
N
9
⌉
,
wherein:
n is an index number of a pilot subcarrier in a symbol;
k is an index of the symbol;
m is given by k mod 3; and
┌X┐ denotes the largest integer not greater than X.