150 research outputs found
Design of Block Transceivers with Decision Feedback Detection
This paper presents a method for jointly designing the transmitter-receiver
pair in a block-by-block communication system that employs (intra-block)
decision feedback detection. We provide closed-form expressions for
transmitter-receiver pairs that simultaneously minimize the arithmetic mean
squared error (MSE) at the decision point (assuming perfect feedback), the
geometric MSE, and the bit error rate of a uniformly bit-loaded system at
moderate-to-high signal-to-noise ratios. Separate expressions apply for the
``zero-forcing'' and ``minimum MSE'' (MMSE) decision feedback structures. In
the MMSE case, the proposed design also maximizes the Gaussian mutual
information and suggests that one can approach the capacity of the block
transmission system using (independent instances of) the same (Gaussian) code
for each element of the block. Our simulation studies indicate that the
proposed transceivers perform significantly better than standard transceivers,
and that they retain their performance advantages in the presence of error
propagation.Comment: 14 pages, 8 figures, to appear in the IEEE Transactions on Signal
Processin
GTD-based transceivers for decision feedback and bit loading
We consider new optimization problems for transceivers with DFE receivers and linear precoders, which also use bit loading at the transmitter. First, we consider the MIMO QoS (quality of service) problem, which is to minimize the total transmitted power when the bit rate and probability of error of each data stream are specified. The developments of this paper are based on the generalized triangular decomposition (GTD) recently introduced by Jiang, Li, and Hager. It is shown that under some multiplicative majorization conditions there exists a custom GTD-based transceiver which achieves the minimal power. The problem of maximizing the bit rate subject to the total power constraint and given error probability is also considered in this paper. It is shown that the GTD-based systems also give the optimal solutions to the bit rate maximization problem
Joint optimization of transceivers with decision feedback and bit loading
The transceiver optimization problem for MIMO
channels has been considered in the past with linear receivers as
well as with decision feedback (DFE) receivers. Joint optimization
of bit allocation, precoder, and equalizer has in the past been
considered only for the linear transceiver (transceiver with linear
precoder and linear equalizer). It has also been observed that
the use of DFE even without bit allocation in general results in
better performance that linear transceivers with bit allocation.
This paper provides a general study of this for transceivers
with the zero-forcing constraint. It is formally shown that when
the bit allocation, precoder, and equalizer are jointly optimized,
linear transceivers and transceivers with DFE have identical
performance in the sense that transmitted power is identical
for a given bit rate and error probability. The developments of
this paper are based on the generalized triangular decomposition
(GTD) recently introduced by Jiang, Li, and Hager. It will be
shown that a broad class of GTD-based systems solve the optimal
DFE problem with bit allocation. The special case of a linear
transceiver with optimum bit allocation will emerge as one of
the many solutions
Optimal channel equalization for filterbank transceivers in presence of white noise
Filterbank transceivers are widely employed in data communication networks to cope with inter-symbol-interference (ISI) through the use of redundancies. This dissertation studies the design of the optimal channel equalizer for both time-invariant and time-varying channels, and wide-sense stationary (WSS) and possible non-stationary white noise processes. Channel equalization is investigated via the filterbank transceivers approach. All perfect reconstruction (PR) or zero-forcing (ZF) receiver filterbanks are parameterized in an affine form, which eliminate completely the ISI. The optimal channel equalizer is designed through minimization of the mean-squared-error (MSE) between the detected signals and the transmitted signals. Our main results show that the optimal channel equalizer has the form of state estimators, and is a modified Kalman filter. The results in this dissertation are applicable to discrete wavelet multitone (DWMT) systems, multirate transmultiplexers, orthogonal frequency division multiplexing (OFDM), and direct-sequence/spread-spectrum (DS/SS) based code division multiple access (CDMA) networks. Design algorithms for the optimal channel equalizers are developed for different channel models, and white noise processes, and simulation examples are worked out to illustrate the proposed design algorithms
Orthogonal transmultiplexers : extensions to digital subscriber line (DSL) communications
An orthogonal transmultiplexer which unifies multirate filter bank theory and communications theory is investigated in this dissertation. Various extensions of the orthogonal transmultiplexer techniques have been made for digital subscriber line communication applications.
It is shown that the theoretical performance bounds of single carrier modulation based transceivers and multicarrier modulation based transceivers are the same under the same operational conditions. Single carrier based transceiver systems such as Quadrature Amplitude Modulation (QAM) and Carrierless Amplitude and Phase (CAP) modulation scheme, multicarrier based transceiver systems such as Orthogonal Frequency Division Multiplexing (OFDM) or Discrete Multi Tone (DMT) and Discrete Subband (Wavelet) Multicarrier based transceiver (DSBMT) techniques are considered in this investigation.
The performance of DMT and DSBMT based transceiver systems for a narrow band interference and their robustness are also investigated. It is shown that the performance of a DMT based transceiver system is quite sensitive to the location and strength of a single tone (narrow band) interference. The performance sensitivity is highlighted in this work. It is shown that an adaptive interference exciser can alleviate the sensitivity problem of a DMT based system. The improved spectral properties of DSBMT technique reduces the performance sensitivity for variations of a narrow band interference. It is shown that DSBMT technique outperforms DMT and has a more robust performance than the latter. The superior performance robustness is shown in this work.
Optimal orthogonal basis design using cosine modulated multirate filter bank is discussed. An adaptive linear combiner at the output of analysis filter bank is implemented to eliminate the intersymbol and interchannel interferences. It is shown that DSBMT is the most suitable technique for a narrow band interference environment.
A blind channel identification and optimal MMSE based equalizer employing a nonmaximally decimated filter bank precoder / postequalizer structure is proposed. The performance of blind channel identification scheme is shown not to be sensitive to the characteristics of unknown channel. The performance of the proposed optimal MMSE based equalizer is shown to be superior to the zero-forcing equalizer
- …