Bit allocation method and apparatus for multicarrier modulation signal, and system
A bit allocation method and apparatus for a multicarrier modulation signal and a system where the method includes: determining a signal to noise ratio margin according to a predefined probability of a maximum clipping noise that can be allowed by the system; and allocating the number of modulating bits and power in each subcarrier for a multicarrier modulation signal according to the signal to noise ratio margin. By presetting a signal to noise ratio margin for a clipping noise, tolerance of the signal for the clipping noise is increased, and bit error rate is efficiently lowered.
1. A bit allocation apparatus in a multicarrier communication system, comprising:
a determining unit configured to determine a signal to noise ratio margin according to a predefined probability of a maximum clipping noise allowed by the multicarrier communication system; and
an allocating unit configured to allocate a number of modulating bits and power in each subcarrier for a multicarrier modulation signal according to the signal to noise ratio margin,
wherein the determining unit comprises:
a waveform processing module configured to obtain a waveform of a time domain signal according to the number of modulating bits and power in each subcarrier allocated for the multicarrier modulation signal, and perform a clipping operation on the waveform of the time domain signal;
a calculating module configured to calculate power of clipping noise of the waveform of the time domain signal within a predefined time window, and calculate a probability distribution of the power of the clipping noise; and
a reading module configured to read maximum power of clipping noise corresponding to a probability of a maximum clipping noise from the probability distribution according to the predefined probability of the maximum clipping noise allowed by the system, and set the maximum power as the signal to noise ratio margin.
2. The bit allocation apparatus according to claim 1 , wherein the allocating unit comprises:
a determining module configured to determine a new signal to noise ratio of each subcarrier according to the read maximum power of the clipping noise and an original signal to noise ratio of each subcarrier; and
an allocating module configured to allocate a new number of bits and new power for each subcarrier according to the new signal to noise ratio of each subcarrier and a number of bits to which a rate of the multicarrier communication system corresponds.
3. The bit allocation apparatus according to claim 2 , wherein the new signal to noise ratio of each subcarrier is:
SNR
m
,
i
=
1
1
SNR
o
,
i
+
α
P
clip
;
where, i is an index of a subcarrier, i=1, 2, . . . k, k being the number of the subcarriers, P clip is the signal to noise ratio margin, SNR o,i is the original signal to noise ratio of an i-th subcarrier, SNR m,i is the new signal to noise ratio of the i-th subcarrier, and a is a correction coefficient of the signal to noise ratio margin.
4. A transmitter in a multicarrier communication system, comprising a bit allocation apparatus, the bit allocation apparatus being configured to:
determine a signal to noise ratio margin according to a predefined probability of a maximum clipping noise allowed by the multicarrier communication system; and
allocate a number of modulating bits and power in each subcarrier for a multicarrier modulation signal according to the signal to noise ratio margin,
wherein the bit allocation apparatus is further configured to:
obtain a waveform of a time domain signal according to the number of modulating bits and power in each subcarrier allocated for the multicarrier modulation signal, and perform a clipping operation on the waveform of the time domain signal;
calculate power of clipping noise of the waveform of the time domain signal within a predefined time window, and calculate a probability distribution of the power of the clipping noise; and
read the maximum power of the clipping noise corresponding to the probability of a maximum clipping noise from the probability distribution according to the predefined probability of the maximum clipping noise allowed by the system, and set the maximum power as the signal to noise ratio margin.
5. The transmitter according to claim 4 , wherein the bit allocation apparatus is further configured to:
determine a new signal to noise ratio of each subcarrier according to the read maximum power of the clipping noise and an original signal to noise ratio of each subcarrier; and
allocate a new number of bits and new power for each subcarrier according to the new signal to noise ratio of each subcarrier and a number of bits to which a rate of the multicarrier communication system corresponds.
6. The transmitter according to claim 5 , wherein the new signal to noise ratio of each subcarrier is:
SNR
m
,
i
=
1
1
SNR
o
,
i
+
α
P
clip
;
where, i is an index of a subcarrier, i=1, 2, . . . k, k being the number of the subcarriers, P clip is the signal to noise ratio margin, SNR o,i is the original signal to noise ratio of an i-th subcarrier, SNR m,i is the new signal to noise ratio of the i-th subcarrier, and a is a correction coefficient of the signal to noise ratio margin.
7. A receiver in a multicarrier communication system, comprising a bit allocation apparatus, the bit allocation apparatus being configured to:
determine a signal to noise ratio margin according to a predefined probability of a maximum clipping noise allowed by the system; and
allocate a number of modulating bits and power in each subcarrier for a multicarrier modulation signal according to the signal to noise ratio margin
wherein the bit allocation apparatus is further configured to:
obtain a waveform of a time domain signal according to the number of modulating bits and power in each subcarrier allocated for the multicarrier modulation signal, and perform a clipping operation on the waveform of the time domain signal;
calculate power of clipping noise of the waveform of the time domain signal within a predefined time window, and calculate probability distribution of the power of the clipping noise; and
read the maximum power of the clipping noise corresponding to the probability of a maximum clipping noise from the probability distribution according to the predefined probability of the maximum clipping noise allowed by the system, and set the maximum power as the signal to noise ratio margin.
8. The receiver according to claim 7 , wherein the bit allocation apparatus is further configured to:
determine a new signal to noise ratio of each subcarrier according to the read maximum power of the clipping noise and an original signal to noise ratio of each subcarrier; and
allocate a new number of bits and new power for each subcarrier according to the new signal to noise ratio of each subcarrier and a number of bits to which a rate of the multicarrier communication system corresponds.
9. The receiver according to claim 8 , wherein the new signal to noise ratio of each subcarrier is:
SNR
m
,
i
=
1
1
SNR
o
,
i
+
α
P
clip
;
where, i is an index of a subcarrier, i=1, 2, . . . k, k being the number of the subcarriers, P clip is the signal to noise ratio margin, SNR o,i is the original signal to noise ratio of an i-th subcarrier, SNR m,i is the new signal to noise ratio of the i-th subcarrier, and a is a correction coefficient of the signal to noise ratio margin.