Method for detection of symbols in communication signals

A method for detection of symbols carried in received communication signals, the method comprising:

• receiving at least one communication signal y transmitted over a radio channel H, wherein said received signal y comprises encoded radio channel symbol inputs x;
• receiving a priori Log Likelihood Ratios (LLRs) of said channel inputs x;
• computing soft symbol estimates μ and variance D of said channel inputs x based on LLRs of said channel inputs x, wherein the LLRs of said channel inputs x are obtained from a decoder;
• filtering and interference cancelling said received signal y by using a first filter and filtered soft symbol estimates μ to obtain a filtered and interference cancelled received signal, wherein a kth element of said filtered and interference cancelled received signal has a form rk=E(xk|y,μl), l∉Ik, where E is the expectation operator and Ik is a set of indices that depends on k in a pre-determined fashion, and wherein the vector comprising rk, ∀k , is denoted as E(x|y,μ);
• estimating the Mean Square Error (MSE) matrix B of said filtered and interference cancelled received signal;
• computing an optimal matrix Gopt for a Bahl-Cook-Jelinke-Raviv (BCJR) algorithm based on said MSE estimate B, wherein said optimal matrix Gopt specifies the BCJR algorithm;
• further filtering said filtered and interference cancelled received signal by using a second filter to obtain an input signal r to the BCJR algorithm, wherein the second filter is derived from said optimal matrix Gopt;
• and
• feeding said input signal r into the BCJR algorithm to obtain extrinsic LLRs of said channel inputs xl;
• feeding said extrinsic LLRs into the decoder to obtain updated LLRs of said channel inputs x;
• and
• repeating said computing the soft symbol estimates μ and variance D, filtering and interference cancelling, estimating the MSE matrix B, computing the optimal matrix Gopt, filtering said filtered and interference cancelled received signal, feeding said input signal r, and feeding said extrinsic LLRs into the decoder i number of times by using said updated LLRs to compute soft symbol estimates μ and variance D.

A non-transitory computer readable medium having computer-executable instructions stored thereon for detection of symbols carried in received communication signals, the computer executable instructions comprising instructions for:

• receiving at least one communication signal y transmitted over a radio channel H, wherein said received signal y comprises encoded radio channel symbol inputs x;
• receiving a priori Log Likelihood Ratios (LLRs) of said channel inputs x;
• computing soft symbol estimates μ and variance D of said channel inputs x based on LLRs of said channel inputs x;
• filtering and interference cancelling said received signal y by using a first filter and filtered soft symbol estimates μ to obtain a filtered and interference cancelled received signal, wherein a kth element of said filtered and interference cancelled received signal has a form rk=E(xk|y,μl), l∉Ik, where E is the expectation operator and Ik is a set of indices that depends on k in a pre-determined fashion, and wherein the vector comprising rk, ∀k , is denoted as E(x|y,μ);
• estimating the Mean Square Error (MSE) matrix B of said filtered and interference cancelled received signal;
• computing an optimal matrix Gopt for a Bahl-Cook-Jelinke-Raviv (BCJR) algorithm based on said MSE estimate B, wherein said optimal matrix Gopt specifies the BCJR algorithm;
• further filtering said filtered and interference cancelled received signal by using a second filter to obtain an input signal r to the BCJR algorithm, wherein the second filter is derived from said optimal matrix Gopt;
• and
• feeding said input signal r into the BCJR algorithm to obtain extrinsic LLRs of said channel inputs x.

A detection device arranged for detection of symbols carried in received communication signals, the detection device comprising a processor arranged to:

• receive at least one communication signal y transmitted over a radio channel H, wherein said received signal y comprises encoded radio channel symbol inputs x;
• receive a priori Log Likelihood Ratios (LLRs) of said channel inputs x;
• compute soft symbol estimates μ and variance D of said channel inputs x based on LLRs of said channel inputs x;
• filter and interference cancel said received signal y by using a first filter and filtered soft symbol estimates μ to obtain a filtered and interference cancelled received signal, wherein a kth element of said filtered and interference cancelled received signal has a form rk=E(xk|y,μl), l∉Ik, where E is the expectation operator and Ik is a set of indices that depends on k in a pre-determined fashion, and wherein the vector comprising rk, ∀k, is denoted as E(x|y,μ);
• estimate the Mean Square Error (MSE) matrix B of said filtered and interference cancelled received signal;
• compute an optimal matrix Gopt for a Bahl-Cook-Jelinke-Raviv (BCJR) algorithm based on said MSE estimate B, wherein said optimal matrix Gopt specifies the BCJR algorithm;
• further filter said filtered and interference cancelled received signal by using a second filter to obtain an input signal r to the BCJR algorithm, wherein the second filter is derived from said optimal matrix Gopt;
• and
• feed said input signal r into the BCJR algorithm to obtain extrinsic LLRs of said channel inputs x.