Receiver and method of receiving
An arrangement for detecting signaling data from bootstrap Orthogonal Frequency Division Multiplexed (OFDM) symbols in the frequency domain, which can provide a more accurate estimate of the signaling data than other arrangements that operate in the time domain. The arrangement includes detecting a cyclic shift of a signature sequence, which has been applied to represent the signaling data, as an average phase change between each of the sub-carriers of the bootstrap OFDM symbol. As a result the signaling data can be more accurately detected or detected at lower signal to noise ratio.
1. A receiver for detecting and recovering payload data from a received signal, the receiver comprising:
a radio frequency demodulation circuit configured to detect and to recover the received signal, the received signal having been formed and transmitted by a transmitter relative to which the receiver is moving at a speed less than or equal to a predetermined maximum speed, the received signal having been formed and transmitted by the transmitter to carry the payload data as Orthogonal Frequency Division Multiplexed (OFDM) symbols in one or more of a plurality of time divided frames, each frame including a preamble including a plurality of bootstrap OFDM symbols, one or more of the bootstrap OFDM symbols of the preamble carrying a signature sequence, and each of the one or more of the bootstrap OFDM symbols carrying a signature sequence carrying signalling data represented as a relative cyclic shift of the bootstrap OFDM symbol, wherein the signature sequence carried by each of the one or more of the bootstrap OFDM symbols comprises a combination of a Zadoff-chu sequence and a pseudorandom-noise sequence,
a detector circuit configured to detect and to convert a useful part of the bootstrap OFDM symbols into the frequency domain,
a bootstrap processor configured to detect the signalling data from the one or more of the bootstrap OFDM symbols in the frequency domain, and
a demodulator circuit configured to recover the payload data from payload OFDM symbols using the signalling data, wherein the bootstrap processor comprises:
a divider configured to divide a first bootstrap OFDM symbol in the frequency domain by a second bootstrap OFDM symbol in the frequency domain, the first and second bootstrap OFDM symbols being adjacent OFDM bootstrap symbols in the received signal, and one of the first and second bootstrap OFDM symbols being a subject bootstrap OFDM symbol which is one of the bootstrap OFDM symbols carrying signalling data;
a divider and multiplier unit configured to divide the output of the divider by the pseudorandom-noise sequence of the signature sequence of the first bootstrap OFDM symbol and multiply the output of the divider by the pseudorandom-noise sequence of the signature sequence of the second bootstrap OFDM symbol;
a phase change estimator configured to detect an average change in phase between adjacent sub-carriers of the subject bootstrap OFDM symbol on the basis of the output of the divider and multiplier unit, and
a signalling data detector configured to identify the signalling data of the subject bootstrap OFDM symbol based on the detected average change in phase which is representative of the cyclic shift applied to the subject bootstrap OFDM symbol.
2. The receiver according to claim 1 , wherein the predetermined maximum speed is:
1000 *c/f o km/h
wherein c is the speed of light and f o is a centre frequency of a transmission channel in which the received signal is transmitted.
3. The receiver according to claim 1 , wherein the predetermined maximum speed is between approximately 500 to 600 km/h.
4. The receiver according to claim 1 , wherein the predetermined maximum speed is approximately 200 km/h.
5. The receiver according to claim 1 , wherein the first bootstrap OFDM symbol is received by the receiver after the second bootstrap OFDM symbol and the subject bootstrap OFDM symbol is the first bootstrap OFDM symbol.
6. The receiver according to claim 1 , wherein the signature sequence which is carried by the one or more bootstrap OFDM symbols comprises a plurality of coefficients, and each of the coefficients of the signature sequence has been combined with one of the sub-carriers of the OFDM symbol.
7. The receiver according to claim 1 , wherein the phase change estimator comprises
an inverse Fourier transformer, which is configured to receive the subject bootstrap OFDM symbol after the effects of the divider and the divider and multiplier unit, and to transform the subject bootstrap OFDM symbol from the frequency domain into the time domain, and
a peak detector configured to detect a peak sample of the time domain version of the subject bootstrap OFDM symbol, a relative position of the peak being indicative of the average change in phase between the adjacent sub-carriers of the subject bootstrap OFDM symbol, and to output a signal indicative of the average phase change to the signalling data detector.
8. The receiver according to claim 1 , wherein the phase change estimator comprises:
a slope estimator configured to receive the subject bootstrap OFDM symbol after the effects of the divider and the divider and multiplier unit and to detect a slope of a function line of phase against frequency across each of a plurality of subcarriers of the subject bootstrap OFDM symbol in order to determine the average change in phase between adjacent sub-carriers of the subject bootstrap OFDM symbol, and to output a signal indicative of the average phase change to the signalling data detector.
9. A method of detecting and recovering payload data from a received signal at a receiver, the method comprising:
detecting and recovering the received signal, the received signal having been formed and transmitted by a transmitter relative to which the receiver is moving at a speed less than or equal to a predetermined maximum speed, the received signal having been formed and transmitted by the transmitter to carry the payload data as Orthogonal Frequency Division Multiplexed (OFDM) symbols in one or more of a plurality of time divided frames, each frame including a preamble including a plurality of bootstrap OFDM symbols, one or more of the bootstrap OFDM symbols of the preamble carrying a signature sequence, and each of the one or more of the bootstrap OFDM symbols carrying a signature sequence carrying signalling data represented as a relative cyclic shift of the bootstrap OFDM symbol, wherein the signature sequence carried by each of the one or more of the bootstrap OFDM symbols comprises a combination of a Zadoff-chu sequence and a pseudorandom-noise sequence,
detecting and converting a useful part of the bootstrap OFDM symbols into the frequency domain,
detecting the signalling data from the one or more of the bootstrap OFDM symbols in the frequency domain, and
recovering the payload data from payload OFDM symbols using the signalling data, wherein the detecting of the signalling data from the one or more of the bootstrap OFDM symbols in the frequency domain comprises:
a first step of dividing a first bootstrap OFDM symbol in the frequency domain by a second bootstrap OFDM symbol in the frequency domain, the first and second bootstrap OFDM symbols being adjacent OFDM bootstrap symbols in the received signal, and one of the first and second bootstrap OFDM symbols being a subject bootstrap OFDM symbol which is one of the bootstrap OFDM symbols carrying signalling data;
a second step of dividing the output of the first step by the pseudorandom-noise sequence of the signature sequence of the first bootstrap OFDM symbol and multiplying the output of the first step by the pseudorandom-noise sequence of the signature sequence of the second bootstrap OFDM symbol;
a third step of detecting an average change in phase between adjacent sub-carriers of the subject bootstrap OFDM symbol on the basis of the output of the second step, and
a fourth step of identify the signalling data of the subject bootstrap OFDM symbol based on the detected average change in phase which is representative of the cyclic shift applied to the subject bootstrap OFDM symbol.
10. A non-transitory computer readable medium including computer program instructions, which when executed by a computer causes the computer to perform the method of claim 9 .
11. A receiver for detecting and recovering payload data from a received signal, the receiver comprising:
radio frequency demodulation circuitry configured to detect and to recover the received signal, the received signal having been formed and transmitted by a transmitter relative to which the receiver is moving at a speed less than or equal to a predetermined maximum speed, the received signal having been formed and transmitted by the transmitter to carry the payload data as Orthogonal Frequency Division Multiplexed (OFDM) symbols in one or more of a plurality of time divided frames, each frame including a preamble including a plurality of bootstrap OFDM symbols, one or more of the bootstrap OFDM symbols of the preamble carrying a signature sequence, and each of the one or more of the bootstrap OFDM symbols carrying a signature sequence carrying signalling data represented as a relative cyclic shift of the bootstrap OFDM symbol, wherein the signature sequence carried by each of the one or more of the bootstrap OFDM symbols comprises a combination of a Zadoff-chu sequence and a pseudorandom-noise sequence,
detector circuitry configured to detect and to convert a useful part of the bootstrap OFDM symbols into the frequency domain,
bootstrap processor circuitry configured to detect the signalling data from the one or more of the bootstrap OFDM symbols in the frequency domain, and
demodulator circuitry configured to recover the payload data from payload OFDM symbols using the signalling data, wherein the bootstrap processor comprises:
divider circuitry configured to divide a first bootstrap OFDM symbol in the frequency domain by a second bootstrap OFDM symbol in the frequency domain, the first and second bootstrap OFDM symbols being adjacent OFDM bootstrap symbols in the received signal, and one of the first and second bootstrap OFDM symbols being a subject bootstrap OFDM symbol which is one of the bootstrap OFDM symbols carrying signalling data:
divider and multiplier circuitry configured to divide the output of the divider circuitry by the pseudorandom-noise sequence of the signature sequence of the first bootstrap OFDM symbol and multiply the output of the divider circuitry by the pseudorandom-noise sequence of the signature sequence of the second bootstrap OFDM symbol;
phase change estimator circuitry configured to detect an average change in phase between adjacent sub-carriers of the subject bootstrap OFDM symbol on the basis of the output of the divider and multiplier circuitry, and
signalling data detector circuitry configured to identify the signalling data of the subject bootstrap OFDM symbol based on the detected average change in phase which is representative of the cyclic shift applied to the subject bootstrap OFDM symbol.