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Bit rate and power are two commonly used optimality criteria for MIMO transceiver design. In the literature, bit rate maximization and power minimization problems are viewed as different problems and solved independently. In this paper, we derive the duality between these two problems for both the cases with and without integer constraint on bit allocation. We will show that if a transceiver is optimal for the power-minimizing problem, it is also optimal for the rate maximizing problem, and the converse is true. Such a duality has not been stated and proved in the literature to the best of our knowledge. The derivation does not involve any existing optimal solution and we can establish duality result even for the rate maximization problem with integer bit constraint, which the optimal solution is not known. The duality also allows us to develop an algorithm for finding the rate-maximizing transceiver with integer bit allocation using the solution of power-minimizing system. We will also consider some possible generalizations of the problem, for example, when there is a constraint on the maximal constellation size and when the subchannel bit error rates (BERs) are constrained. For each of these cases, we will see that the duality between the two problems continued to hold. In the simulations, we will compute the optimal solutions for these two problems and demonstrate the duality between these two. [ABSTRACT FROM PUBLISHER]

The performance of a multiuser orthogonal frequency-division multiplexing (OFDM) transceiver, called the precoded multiuser OFDM (PMU-OFDM), with time asynchronous access is investigated in this paper. It is shown that multiaccess interference (MAI) due to time asynchronism is asymptotically zero as the number of parallel input symbols N becomes large in the PMU-OFDM system. Then, we show that PMU-OFDM with even or odd Hadamard—Walsh codewords can significantly suppress the MAI effect due to time asynchronism. For the half-loaded case, no sophisticated signal processing technique is needed by PMU-OFDM for MAI suppression. For the fully loaded situation, PMU-OFDM demands less complexity than does conventional OFDMA for interference suppression since PMU-OFDM deals with only one half of interferers. [ABSTRACT FROM AUTHOR]

The carrier frequency offset (CFO) effect of a new multiaccess orthogonal frequency division multiplexing (OFDM) transceiver is analyzed. We show that multiaccess interference (MAI) due to CFO can be mitigated by choosing a proper set of orthogonal codes. That is, if we use M/2 symmetric or antisymmetric codewords of the M Hadamard-Walsh codewords, MAI can be greatly reduced to a negligible amount. The new OFDM system has been shown to be approximately MAI-free when there is no CFO. The new result developed here shows that the system continues to be approximately MAI-free even in the presence of CFO. Furthermore, we derive a close form for the reduced MAI, which reveals an interesting property of the system. That is, when the number of users increases, the reduced MAI and the inter carrier interference (ICI) due to self-CFO will decrease. Finally, it is demonstrated by simulation that the proposed OFDM scheme with proper code selection outperforms the OFDMA and the multicarrier code division multiplexing access (MC-CDMA) systems in a CFO environment. [ABSTRACT FROM AUTHOR]

In this paper, we consider window designs for discrete Fourier transform (DFT) based multicarrier transceivers without using extra cyclic prefix. As in previous works of window designs for DFT based transceivers, a postprocessing matrix that is generally channel dependent, is needed to have a zero-forcing receiver. We show that postprocessing is channel independent if and only if the window itself has the cyclic-prefixed property. We design optimal windows with minimum spectral leakage subject to the cyclic-prefixed condition. Moreover, we analyze how postprocessing affects the signal-to-noise ratio (SNR) at the receiver, which is an aspect that is not considered in most of the earlier works. The resulting SNR can be given in a closed form. Join optimization of spectral leakage and SNR are also considered. Furthermore, examples demonstrate that we can have a significant reduction in spectral leakage at the cost of a small SNR loss. In addition to cyclic-prefixed systems, window designs for zero-padded DFT-based transceivers are considered. For the zero-padded transceivers, windows that minimize spectral leakage can also be designed. [ABSTRACT FROM AUTHOR]

Discusses the implementation of orthogonal frequency division multiplexing (OFDM) transmitters. Analog versus discrete Fourier transform (DFT)-based transmitters; Conditions for equivalence of analog representation and digital implementation.

Derives the minimum redundancy required for the existence of finite impulse response (FIR) transceivers for a given channel. Polyphase representation of filterbank transceivers; Properties of filterbank transceivers with no redundancy; Presentation of block-based transceivers with reduced redundancy.

Presents information on a study which considered the general block-based DMT transceivers for distorted channel with colored noise. Problem formulation; Class of zero padding DMT systems; Comparison of different DMT systems with zero padding; Conclusions.

Presents information on a study which developed design methods for intersymbol interference-free finite impulse response (FIR) filterbank transceivers with effective band separation. Polyphase representation of filterbank transceivers; Types of FIR systems with FIR inverses; Minimum mean squared error receivers for orthogonal transmitters; Conclusions.

The orthogonal frequency-division multiplexing (OFDM) transceiver has enjoyed great success in many wideband communication systems. It has low complexity and robustness against channel-induced intersymbol interference (ISI). When the channel order does not exceed the length of cyclic prefix, any frequency-selective channel is converted to a set of frequency-nonselective subchannels. This channel-independent ISI-free property is useful for many applications. In this correspondence, we study general block transceiver with such a property. We will show that the solutions of channel-independent ISI-free block transceivers are given in a closed form. It is found that except for some special cases, the solutions are identical to the Lagrange-Vandermonde and Vandermonde-Lagrange transceivers. [ABSTRACT FROM AUTHOR]