| 摘要 |
A method of retransmission comprises providing a series of bits, allocating subsets of the series of bits to symbols, ordering the symbols into a sequence and transmitting the sequence of symbols on a channel. In one embodiment the sequence of symbols is reordered for each transmission. In the case of OFDM, this has the effect of allocating symbols to different sub-carriers to those which they were allocated to at initial transmission. Symbols may also be reallocated to a different time position within a burst at retransmission. The reordering of symbols can be achieved by cyclic shifting. Pseudo-random reordering is also proposed. In an alternative embodiment at retransmission bits are reordered within the series of bits before allocation to symbols so that retransmitted symbols contain different bits from their respective originally transmitted symbols. These methods ensure that if a particular frequency band of the signal is consistently impaired, for example by deep fading of the same sub-carriers, different bits are affected at each retransmission. |
