Two modified blind equalization algorithms are analyzed for performance. These algorithms add a constellation-matched error term to the cost functions of the generalized Sato and multimodulus algorithms. The dynamic convergence behavior and steady-state performance of these algorithms, and of a related version of the constant modulus algorithm, are characterized. The analysis establishes the improved performance of the proposed algorithms.

Blind source separation (BSS) techniques allow recovery of individual source signals from observed mixtures, exploiting only the assumption of mutual independence of sources. Generally, complex signals are recovered with an arbitrary phase rotation. In this letter, we propose two BSS algorithms to separate complex sources that have independent in-phase and quadrature (I/Q) parts. The proposed algorithms allow source phase recovery as well as separation. Simulation results demonstrate that the algorithms are effective in recovering source phases without affecting source separation.

A dual-mode blind equalization technique for adaptive channel equalization of quadrature amplitude modulation signals is introduced. The equalizer uses the constant modulus algorithm (CMA) in the initial phase and then switches to a proposed constellation-matched error (CME) minimization algorithm at appropriate values of the mean-square error. The proposed CME cost function can be constructed using finite- or infinite-order polynomials with desirable properties over the constellation region. This dual-mode equalization technique is applied to a linear equalizer and is shown to provide superior performance or simplicity over the conventional CMA and some other dual-mode schemes.

This paper proposes an effective hybrid multilevel error control (HMEC) with an early-stop automatic repeat request (ARQ) scheme for wireless asynchronous transfer mode (ATM) networks. In this scheme, the source traffic is segmented into a number of blocks, each with m cells, then encoded into k(k>m) cells. The transmission of one block may be finished as long as m out of the k cells are received correctly. The ARQ protocol is applied only when too many cells are dropped or corrupted due to uncorrectable error in the radio channel. This paper also provides a detail study of the proposed scheme. In particular, the throughput efficiency with parameters (m,k) are derived analytically for the white Gaussian and Rayleigh fading channels. Simulation results show a very close match with theoretical results. All the results show that the HMEC scheme can reduce cell-retransmission probability and improve network throughput over a wide range of channel error rates when appropriate values of parameters m and k are chosen.

An adaptive gradient technique is applied for the minimization of a hybrid cost function that consists of amplitude-dependent and constellation-dependent terms. A time-varying weighting coefficient is induced in the combined cost function to emphasize/de-emphasize the role of the two terms in determining the gradient during initializations, convergence, and steady state conditions. This coefficient is recursively updated and leads to improved global and local convergence properties. It is shown that the proposed technique is superior to the method in which the cost function involves fixed weighting.