Wireless transmission system and reception device

A Multi Input Multi Output (MIMO) reception method, comprising:

• receiving a signal having been subjected to error correction coding on a transmission side, performed with first interleaving of performing rearrangement over frames that are predetermined transmission units, thereafter performed with second interleaving of performing rearrangement within a frame, and transmitted while mapped to a symbol and performing turbo equalization;
• detecting, by a detection process, each reception signal received by a plurality of antennae;
• calculating, by a demapping process, each received bit log-likelihood ratio (LLR) by performing separation detection and interference removal of a substream from a plurality of signals detected in the detection process and prior information;
• performing, by a frequency deinterleaving process, on the received bit LLR of each of the plurality of antennae, rearrangement of an order of data having been rearranged by the second interleaving into an original order;
• performing, by a bit deinterleaving process, on output from the frequency deinterleaving process, rearrangement of an order of data having been rearranged by the first interleaving into an original order;
• storing, by a storing process, in a frame buffer, the received bit LLR having been rearranged in the bit deinterleaving process into the original order with respect to a frame to be decoded and a part of a frame preceding or following the frame;
• reading, by a decoding process, the received bit LLR stored in the frame buffer, and performing on the received bit LLR, maximum a posteriori possibility decoding based on a Bahl, Cocke, Jelinek and Raviv (BCJR) algorithm, and outputting an external LLR;
• and
• performing the first interleaving and the second interleaving on the external LLR and providing the external LLR to the demapping process as the prior information,
• wherein, a decoding bit sequence length of the frame is denoted as a real number L, a trellis learning period is denoted as a real number K, a maximum value of delay over the frames due to the first interleaving is denoted as a real number M′ symbols, a number of bits allotted to a symbol is denoted as a real number Q, and a real number M is represented as M=M′Q,
• wherein to decode a real number Nth frame represented by bit sequence numbers 1 from 1 (N−1)L to 1=NL, the decoding process includes:
• calculating a transition state probability γ and a forward metric α from 1=(N−1)L−(K+M) to 1=(N−1)L by reading the received bit LLR from 1=(N−1)L−(K+M) to 1=(NL+K) from the frame buffer and regarding the received bit LLR as a prior LLR;
• calculating a transition state probability γ and a backward metric β from 1=NL+K to 1=NL;
• calculating a decoded bit LLR and a coded bit LLR by decoding from 1=(N−1)L−M to 1=NL based on the BCJR algorithm using specified states where 1=(N−1)L−M and 1=NL;
• and
• outputting the external LLR obtained by subtracting the received bit LLR input thereto from the coded bit LLR in a length from 1=(N−1)L−M to 1=NL.