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The authors assume a linear equidistance antenna array as the receiver for a fixed frame-length multiple-access system, which employs variable-gain receiver power and repetition encoding. They propose a robust maximum a posteriori probability (MAP) blind bit-rate detector (BBRD). This detector considers the rate detection (RD) as a multi-hypothesis test and maximises the likelihood functions (LFs) to find the true bit-rate, whereas the complex amplitude of the received signal, the noise variance and the direction of arrival are unknown parameters. First, assuming that the location parameter is known and the information sequence are independent and uniformly distributed random variables, the authors propose a hybrid likelihood ratio test (HLRT). The proposed HLRT requires to solve a set of non-linear equations that have no closed-form solution. Thus, an iterative numerical algorithm is proposed. In addition, a quasi-HLR detector which has a significantly lower computational complexity is also proposed. In the case of unknown location parameter, the authors develop two quasi-HLR methods. They use fast Fourier transform and search to estimate the unknown location. In Q-HLRT-Method-I, the non-linear equation similar to the one in known location parameter is iteratively solved. In Q-HLRT-Method-II, a low complexity solution is proposed. Simulation examples evaluate and compare the performances of the proposed BBRDs.
Inspec keywords: direction-of-arrival estimation; antenna arrays; nonlinear equations; encoding; iterative methods; multi-access systems; computational complexity
Other keywords: rate detection; fixed frame-length multiple-access system; repetition encoding; information sequence; linear equidistance antenna array; direction of arrival; maximum a posteriori probability; fast Fourier transform; quasiHLR detector; Q-HLRT-Method-II; hybrid likelihood ratio test; nonlinear equations; hybrid likelihood ratio bit-rate detectors; iterative numerical algorithm; true bit-rate; blind bit-rate detector; variable-gain multiple-access systems; variable-gain receiver power; MAP; computational complexity; low complexity solution; likelihood functions; BBRD; quasiHLR methods; unknown noise variance; multihypothesis test
Subjects: Signal processing and detection; Multiple access communication; Codes; Antenna arrays; Nonlinear and functional equations (numerical analysis); Interpolation and function approximation (numerical analysis)