Receiver apparatus using maximum-likelihood-determination

A receiving apparatus that uses a maximum-likelihood-determination method as a method of determining reception data, and executes a determination process using an analog-to-digital-converted reception signal, the receiving apparatus comprising:

• a transmission-path estimating unit that estimates a transmission-path response matrix of a radio transmission path based on the reception signal;
• a matrix processing unit that decomposes the transmission-path response matrix into an upper triangular matrix, and multiplies the reception signal by an inverse matrix of the transmission-path response matrix;
• a provisional determining unit that provisionally determines a transmission signal based on a result of multiplication of the reception signal by the inverse matrix of the transmission-path response matrix;
• a metric calculating unit that calculates a metric based on a result of the provisional determination, the decomposed transmission-path response matrix, and the result of the multiplication;
• a comparing unit that compares a metric obtained as a result of the calculation by the metric calculating unit with an updated metric, and outputs a smaller metric;
• an estimate-symbol determining unit that forms a hypersphere centering around a reception signal point based on a specific value representing a radius of the hypersphere or the updated metric, from a result of comparison by the comparing unit, generates a candidate of an estimate symbol based on the decomposed transmission-path response matrix and the result of the multiplication, and determines whether the candidate of the estimate symbol is present within the hypersphere;
• and
• a metric updating unit that calculates a metric based on the candidate of the estimate symbol obtained as a result of the determination by the estimate-symbol determining unit and the result of the multiplication, stores a minimum metric from among metrics calculated in the past and the candidate of the estimate symbol corresponding to the minimum metric, compares a newly calculated metric with a currently stored metric every time when the metric is newly calculated, and updates stored information when the newly calculated metric is smaller than the currently stored metric, wherein
• the metric updating unit repeats the update process until the estimate-symbol determining unit determines that no candidate of the estimate symbol is present within the hypersphere, and sets the candidate of the estimate symbol that corresponds to a final minimum metric as a maximum-likelihood-determination value.