Space-time coding and channel estimation scheme, arrangement and method

A method of space-time encoding comprising:

• (a) receiving a stream of data at an input,
• (b) trellis encoding the data stream using a convolutional encoder operable to sequentially group data to provide coded bits,
• (c) outputting the encoded data to a modulator,
• (d) operating the modulator to map the encoded signals to QPSK symbols to provide modulated signal, and (e) operating a de-multiplexer to switch the modulated signals to a set of signal outputs to provide a series of space-time encoded information symbols which are transmitted by all of the plurality of transmit antennas.

A method of estimating complex channel gain in a space-time communications system comprising the steps of:

• (a) generating an initial estimate of channel gain,
• (b) receiving space-time encoded information symbols over the channels from a plurality of transmit antennas, each of said transmit antennas transmitting the same series of space-time encoded information symbols,
• (c) decoding the information symbols using the initial channel estimate to produce a sequence of symbol estimates,
• (d) refining the channel estimate for each channel, by processing the received symbols to remove an expected effect of the transmissions carried by all other channels by performing cancellation using relevant parts of the sequence of symbol estimates, and to remove an expected effect of modulation on each symbol, and by averaging the channel estimates over all symbols for each respective channel to produce a refined estimate for each channel,
• (e) decoding the information symbols again using the refined channel estimate, to produce a refined sequence of coded symbol estimates, and
• (f) repeating steps (d), (e) and (f) until convergence.

Channel estimation apparatus for a space-time communications system comprising:

• (a) an initial estimator operable to generate an initial estimate of channel gain,
• (b) a receiver operable to receive space-time encoded information symbols from a plurality of transmit antennas, each of said transmit antennas transmitting the same series of space-time encoded information symbols,
• (c) a decoder operable to produce a sequence of coded symbol estimates using a channel estimate, and
• (d) estimate refining means operable to refine the channel estimate for each channel, by processing the received symbols to remove the expected effect of the transmissions carried by all the other channels by performing cancellation using the relevant parts of the sequence of symbol estimates, and to remove the expected effect of modulation on each symbol, and by averaging the channel estimates over all symbols for each respective channel to produce a refined estimate for each channel,
• the apparatus being arranged to iteratively repeat the refining of the channel estimation and the production of symbol estimate functions until convergence of the channel estimates occurs.

A computer program which, when executing on suitably configured hardware, causes the hardware to perform the steps of:

• (a) generating an initial estimate of channel gain,
• (b) receiving space-time encoded information symbols over the channels from a plurality of transmit antennas, each of said transmit antennas transmitting the same series of space-time encoded information symbols,
• (c) decoding the information symbols using the initial channel estimate to produce a sequence of symbol estimates,
• (d) refining the channel estimate for each channel, by processing the received symbols to remove the expected effect of the transmissions carried by all the other channels by performing cancellation using the relevant parts of the sequence of symbol estimates, and to remove the expected effect of modulation on each symbol, and by averaging the channel estimates over all symbols for each respective channel to produce a refined estimate for each channel,
• (e) decoding the information symbols again using the refined channel estimate, to produce a refined sequence of coded symbol estimates, and
• (f) repeating steps (d), (e) and (f) until convergence.

A communications system arranged to use space-time coding, and comprising transmitter apparatus and receiver apparatus, wherein the receiver apparatus includes:

• an initial estimator operable to generate an initial estimate of channel gain,
• (b) a receiver operable to receive space-time encoded information symbols from a plurality of transmit antennas, each of said transmit antennas transmitting the same series of space-time encoded information symbols,
• (c) a decoder operable to produce a sequence of coded symbol estimates using a channel estimate, and
• (d) estimate refining means operable to refine the channel estimate for each channel, by processing the received symbols to remove the expected effect of the transmissions carried by all the other channels by performing cancellation using the relevant parts of the sequence of symbol estimates, and to remove the expected effect of modulation on each symbol, and by averaging the channel estimates over all symbols for each respective channel to produce a refined estimate for each channel, the apparatus being arranged to iteratively repeat the refining of the channel estimation and the production of symbol estimate functions until convergence of the channel estimates occurs.