Apparatus and method for decoding a bit sequence from QPSK or QAM symbols
View Patent ↗A bit sequence (b, b′) from QPSK or QAM symbols is decoded, in which an associated receive probability (w, w′) is assigned to each receive bit (b, b′). The receive probability (w, w′) is adaptively determined taking into account the transfer properties of the channel.
1. A method of decoding a bit sequence (b, b′) in a decoder system from QPSK or QAM symbols received following transmission over a channel, in which an associated receive probability (w, w′) is assigned to each receive bit (b, b′), the method performed in a decoder comprising:
adaptively determining the receive probability (w, w′) as a function of the transfer properties of the channel; and
weighting the receive probability (w, w′) with an adaptive weighting value set as a function of the channel transfer properties, where the function is indicative of a signal to noise and interference ratio;
wherein the step of adaptively determining the receive probability (w, w′) comprises determining the receive probability as a function of carrier energy (S), noise energy (N), and the interference energy (IF).
2. The method of claim 1 , comprising estimating channel transfer properties when determining the receive probability (w, w′) for each carrier (i).
3. The method of claim 1 , wherein decoding of bits (b, b′) of differing significance is implemented sequentially.
4. A method of decoding a bit sequence (b, b′) in a decoder system from QPSK or QAM symbols received following transmission over a channel, in which an associated receive probability (w, w′) is assigned to each receive bit (b, b′), the method performed in a decoder comprising:
adaptively determining the receive probability (w, w′) as a function of the transfer properties of the channel;
weighting the receive probability (w, w′) with an adaptive weighting value set as a function of the channel transfer properties, where the function is indicative of a signal to noise and interference ratio;
wherein the step of adaptively determining the receive probability (w, w′) comprises determining the receive probability as a function of carrier energy (S), noise energy (N), and the interference energy (IF); and
wherein to determine the receive probability for low-order bits, higher-level constellations are transformed into constellations of lower level, and that for bit significances a uniform function is employed to determine the receive probability.
5. A method of decoding a bit sequence (b, b′) in a decoding system from QPSK or QAM symbols, in which an associated receive probability (w, w′) is assigned to each receive bit (b, b′), the method performed in a decoder comprising:
transforming higher-level constellations into constellations of lower level; and
shifting characteristics for bits of different significance from the lower level constellation such that a uniform function or characteristic is obtained representing an approximation of both most and least significant bits;
determining the receive probability for bit significances using the uniform function or characteristic.
6. An apparatus for decoding a bit sequence containing QPSK or QAM symbols, said apparatus comprising:
a hard decision output mapper that receives the bit sequence and provides a hard decision output signal and a Euclidean distance signal indicative of the bit sequence relative to a decision threshold;
a soft decision logic unit that receives and processes the Euclidean distance signal to provide a receive probability signal for the bit sequence as a function of carrier energy (S), noise energy (N), and the interference energy (IF); and
a weighting unit that weights the receive probability signal by applying a function indicative of a signal to noise and interference ratio, and provides a weighted receive probability signal.
7. A method of decoding a bit sequence (b, b′) in a decoder system from QPSK or QAM symbols received following transmission over a channel, in which an associated receive probability (w, w′) is assigned to each receive bit (b, b′), the method performed in a decoder comprising:
adaptively determining the receive probability (w, w′) as a function of the transfer properties of the channel; and
weighting the receive probability (w, w′) with an adaptive weighting value set as a function of the channel transfer properties, where the function is indicative of a signal to noise and interference ratio;
wherein the step of adaptively determining the receive probability (w, w′) comprises determining the receive probability as a function of carrier energy (S) and noise energy (N).
8. A method of decoding a bit sequence (b, b′) in a decoder system from QPSK or QAM symbols received following transmission over a channel, in which an associated receive probability (w, w′) is assigned to each receive bit (b, b′), the method performed in a decoder comprising:
adaptively determining the receive probability (w, w′) as a function of the transfer properties of the channel; and
weighting the receive probability (w, w′) with an adaptive weighting value set as a function of the channel transfer properties, where the function is indicative of a signal to noise and interference ratio;
wherein the step of adaptively determining the receive probability (w, w′) comprises determining the receive probability as a function of at least two of carrier energy (S), noise energy (N), and the interference energy (IF).