Abstract: The invention relates to an arrangement and method for enhancing a search through a trellis in connection with decoding or channel correction, for instance. When searching through the trellis, the state indexes being processed are divided into more than one subset at each stage of the trellis, the path metrics of the state indexes are defined in the subsets, and a predefined number of state indexes are selected for continuation from each subset on the basis of the metrics.

Abstract: An arrangement for transmitting information between a transmitter and a receiver in a mobile system, the transmitter comprising mapping means (704A-704B) for mapping bits of the information to be transmitted to channel symbols, and at least two transmitting antennas (500-A500B) for transmitting the channel symbols to a radio channel of the mobile system. The mobile system comprises measuring means (622) for measuring the status of the radio channel used for the transmission of information, and the mapping means (704A-704B) of the transmitter are arranged to map the bits to channel symbols by means of a mapping scheme that is dependent on the radio channel status measured by the measuring means (622).

Abstract: A method and arrangement for performing Viterbi decoding by means of a trellis is provided. According to one embodiment, the arrangement comprises one or more ACS units. Connections between the inputs and outputs of the ACS units are implemented in such a manner that in calculating the consecutive metrics of the trellis, the calculated metrics of the previous stage of the trellis obtained from the outputs of the ACS units are directly connected to the inputs of the ACS units to be used in the calculation of the next stage of the trellis.

Abstract: A suboptimal method for searching for a symbol sequence, the method comprising the steps of: determining a channel impulse response; sampling a received signal; selecting at least one of the highest and/or most reliable impulse response values; determining a reference signal using at least one impulse response value and a symbol sequence assumed as transmitted; determining differential terms corresponding to the selected impulse response values for the signal sample and the reference signal; using the determined differential terms in a transition metric for searching for a symbol sequence; forming a survivor path by adding the symbol sequence provided by the transition metric to the survivor path formed so far.