Encoding or decoding communication data

1 . A method of decoding a received communication signal, the method comprising:

converting the received communication signal to a frequency domain to provide frequency domain data;

combining amplitudes of one or more selected frequency components of the frequency domain data, the one or more frequency components being selected according to a predefined communication symbol comprising one or more selected frequency tones corresponding to the one or more selected frequency components; and

detecting the predefined communication symbol in the received communication signal depending on the combined amplitudes of the one or more selected frequency components of the frequency domain data,

wherein the combining is based on a plurality of combiners, each of the plurality of combiners having associated symbol indicator data, wherein the symbol indicator data associated with each of the combiners is updated based on amplitudes of selected frequency components of the frequency domain data corresponding to the respective selected frequency tones of the symbol, and

wherein the respective combiners of the plurality of combiners are to capture the predefined communication symbol at times which are temporally offset from each other.

2 . The method of claim 1 comprising decoding the received communication signal based on the symbol indicator data of each of the plurality of combiners.

3 . The method of claim 1 wherein the predefined communication symbol comprises a plurality of selected frequency tones.

4 . The method of claim 3 wherein the plurality of selected frequency tones comprise temporally overlapping orthogonal or pseudo-orthogonal frequency tones.

5 . The method of claim 3 wherein the predefined communication symbol comprises a plurality of selected frequency tones provided sequentially in a predefined time sequence.

6 . The method of claim 1 wherein the respective combiners of the plurality of combiners are to capture different instances of the predefined communication symbol which are temporally offset from each other in the received communication signal.

7 . The method of claim 6 comprising updating the symbol indicator data associated with the respective combiners based on frequency components of the frequency domain data corresponding to the respective selected frequency tones of the symbol obtained from respective portions of the communication signal received for respective time periods which are offset from each other.

8 . The method of claim 1 wherein each of the combiners of the plurality of combiners comprises a plurality of combiner bins, each of the combiner bins of each of the combiners having an associated symbol indicator value, wherein the symbol indicator values associated with the respective combiner bins of each of the combiners are updated based on respective frequency components of the frequency domain data corresponding to the respective selected frequency tones of the symbol.

9 . The method of claim 8 wherein, for each of said respective frequency tones of the symbol, the symbol indicator values of the respective combiner bins of each of the combiners of the plurality of combiners are updated based on portions of the communication signal received in respective detection time windows into which the received communication signal is apportioned, wherein said detection time windows are temporally offset from each other and temporally overlap each other.

10 . The method of claim 8 further comprising determining that the received communication signal comprises the predefined communication symbol by determining, for each of a plurality of detection time windows, a combiner bin of the plurality of combiners having a highest associated symbol indicator value, and determining that the received communication signal comprises the predefined communication symbol based on the symbol indicator values associated with the combiner bins of the plurality of combiners having the highest symbol indicator values over the plurality of detection time windows.

11 . The method of claim 1 comprising outputting symbol indicator data associated with different individual combiners of the plurality of combiners in order of increasing detection time offset.

12 . The method of claim 11 , further comprising decoding data in the received communication signal based on the output symbol indicator data.

13 . The method of claim 1 wherein the method comprises: analysing, prior to the combining amplitudes of the one or more frequency components of the frequency domain data corresponding to the selected frequency tones of the predefined communication symbol, phases, amplitudes or phases and amplitudes of the one or more frequency components of the frequency domain data corresponding to the selected frequency tones of the predefined communication symbol the amplitudes of which are to be combined to determine one or more amplitude, phase or amplitude and phase compensation factors or pre-compensation factors; and applying the one or more amplitude, phase or amplitude and phase compensation factors to one or more selected frequency components of the frequency domain data or causing a signal indicative of the amplitude, phase or amplitude and phase pre-compensation factors to be transmitted.

14 . The method of claim 1 , wherein the combining amplitudes of the one or more selected frequency components of the frequency domain data, the one or more frequency components being selected according to a predefined communication symbol comprising one or more selected frequency tones corresponding to the one or more selected frequency components comprises:

for each of a plurality of different portions of the received communication signal, combining amplitudes of one or more selected frequency components of the frequency domain data selected according to the predefined communication symbol and corresponding to that portion of the received communication signal to thereby generate respective symbol indicator data for that portion;

and wherein the method comprises:

decoding a message depending on the symbol indicator data for the said portions;

determining a validity of the message; and

generating an indication of a suitability of the predefined communication symbol for communication depending on the determined validity of the message.

15 . The method of claim 1 , wherein the predefined communication symbol is one of a plurality of predefined communication symbols, the method further comprising:

decoding, in the received communication signal, a respective message for each predefined communication symbol of the plurality of predefined communication symbols; and

determining a validity of each of the decoded messages.

16 . The method of claim 15 , wherein decoding the respective message for each predefined communication symbol of the plurality of predefined communication symbols comprises:

performing the said combining amplitudes for each of a plurality of different portions of the received communication signal by combining amplitudes of one or more selected frequency components of the frequency domain data selected according to that predefined communication symbol and corresponding to that portion of the received communication signal to thereby generate respective symbol indicator data for that portion; and

decoding the message for that predefined communication symbol in the plurality of different portions of the received communication signal depending on the symbol indicator data for the said portions.

17 . The method of claim 16 , wherein decoding the said message for that predefined communication symbol in the plurality of different portions of the received communication signal depending on the symbol indicator data for the said portions comprises:

detecting a keying pattern of that predefined communication symbol in the plurality of different portions of the received communication signal depending on the symbol indicator data for the said portions.

18 . The method of claim 1 wherein each of the plurality of combiners has an associated symbol indicator value, wherein the symbol indicator value associated with each of the combiners is updated depending on amplitudes of selected frequency components of the frequency domain data corresponding to the respective selected frequency tones of the symbol, and wherein the method comprises determining whether the received communication signal comprises the predefined communication symbol depending on a variation over time of an onset value, wherein the onset value comprises or consists of a highest symbol indicator value of the symbol indicator values of the plurality of combiners at a given time.

19 . The method of claim 1 wherein each of the plurality of combiners comprises a plurality of combiner bins, each of the combiner bins of each of the combiners having an associated symbol indicator value, wherein the symbol indicator values associated with the respective combiner bins are updated depending on respective frequency components of the frequency domain data corresponding to the respective selected frequency tones of the symbol, wherein the method comprises determining whether the received communication signal comprises the predefined communication symbol depending on a variation over time of an onset value, wherein the onset value comprises or consists of a highest symbol indicator value of the symbol indicator values of the plurality of combiner bins of the plurality of combiners at a given time.

20 . Apparatus for decoding a received communication signal, the apparatus comprising processing circuitry communicatively coupled to a memory, the processing circuitry to:

convert the received communication signal to a frequency domain to provide frequency domain data;

combine amplitudes of one or more selected frequency components of the frequency domain data, the one or more frequency components being selected according to a predefined communication symbol comprising one or more selected frequency tones corresponding to the one or more selected frequency components; and

detect the predefined communication symbol in the received communication signal depending on the combined amplitudes of the one or more selected frequency components of the frequency domain data,

wherein the combining is based on a plurality of combiners, each of the plurality of combiners having associated symbol indicator data, wherein the symbol indicator data associated with each of the combiners is to be updated based on amplitudes of selected frequency components of the frequency domain data corresponding to the respective selected frequency tones of the symbol, and

wherein the respective combiners of the plurality of combiners are to capture the predefined communication symbol at times which are temporally offset from each other.