Likelihood Bit Research Articles

A New Constellation Diagram-Based Signal Detection for GSM-MIMO Systems

The generalized spatial modulation is a multi-input multi-output modulation technique that improves spectral and energy efficiency, but also increases receivers’ detection complexity. In this letter, we first propose a new constellation diagram, and then realize: a joint detection of modulated and zero-power signals and a companion detection algorithm based on this new diagram. Simulation results show that our algorithm can achieve near maximum likelihood bit error rate performance and reduce complexity at a maximum rate of 42% compared with the conventional ordered block minimum mean-squared error algorithm.

A VLSI 8 × 8 MIMO Near-ML Detector with Preprocessing

Multiple-input multiple-output (MIMO) systems are of significant interest due to their ability to increase the capacity of wireless communications systems, but for these to be useful they must also be practical for implementation in VLSI circuits. A particularly difficult part of these systems is the detector, where the optimal maximum-likelihood solution is desirable, but cannot be directly implemented due to its exponential complexity. This paper addresses this challenge and presents a digital circuit design for an 8×8 MIMO detection problem. A key feature is the integrated channel preprocessing unit, which performs the channel decomposition functions that are either omitted or performed "off-line" in other designs. The proposed device achieves near maximum likelihood bit error rate results at 57.6 Mbps. Other novelties include a high speed sorting mechanism and power saving features.

The Minimum Likelihood--A New Concept for Bit Synchronization

A new bit synchronization concept based on the "minimum likelihood" criterion instead of the conventional "maximum likelihood" concept is developed. The minimum likelihood situation is even easier to reach than the maximum likelihood because the derivative of the log likelihood function becomes identically zero there. Minimum likelihood implies "least likely" for synchronization (the worst case synchronization error) or an "orthogonal" timing condition which simply means that the locally generated clock is synchronized correctly, but with a delay of a half bit period. The structure and performance of the minimum likelihood bit synchronizer are discussed in detail in this paper. The results indicate that the minimum likelihood bit synchronizer has a much simpler structure, but with performance very close to the optimal maximum likelihood synchronizer.

Generalized decision feedback equalizer for approximate maximum likelihood bit detection of digital signals

A new type of non-linear equalizer which gives the maximum Likelihood (ML) bit estimates approximately is presented and its error rate performance is discussed. The structure of the non-linear equalizer is derived by introducing the idea of the decision feedback to the ML bit estimation. Since it is implemented by simple digital filters and decision slicers, we can greatly reduce this computation and storage required in the ML bit estimation and significantly improve the bit error probability as compared to the conventional decision feedback equalizer.