505 research outputs found
Near-Capacity Turbo Coded Soft-decision Aided DAPSK/Star-QAM
Low-complexity non-coherently detected Differential Amplitude and Phase-Shift Keying (DAPSK) schemes constitute an ideal candidate for wireless communications. In this paper, we derive the soft-output probability formulas required for the soft-decision based demodulation of DAPSK, which are then invoked for Turbo Coded (TC) transmissions. Furthermore, the achievable throughput characteristics of the family of M-ary DAPSK schemes are provided. It is shown that the proposed 4-ring based TC assisted 64-ary DAPSK scheme achieves a coding gain of about 4.2 dBs in comparison to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme at a bit error ratio of 10?5
MIMO Networks: the Effects of Interference
Multiple-input/multiple-output (MIMO) systems promise enormous capacity
increase and are being considered as one of the key technologies for future
wireless networks. However, the decrease in capacity due to the presence of
interferers in MIMO networks is not well understood. In this paper, we develop
an analytical framework to characterize the capacity of MIMO communication
systems in the presence of multiple MIMO co-channel interferers and noise. We
consider the situation in which transmitters have no information about the
channel and all links undergo Rayleigh fading. We first generalize the known
determinant representation of hypergeometric functions with matrix arguments to
the case when the argument matrices have eigenvalues of arbitrary multiplicity.
This enables the derivation of the distribution of the eigenvalues of Gaussian
quadratic forms and Wishart matrices with arbitrary correlation, with
application to both single user and multiuser MIMO systems. In particular, we
derive the ergodic mutual information for MIMO systems in the presence of
multiple MIMO interferers. Our analysis is valid for any number of interferers,
each with arbitrary number of antennas having possibly unequal power levels.
This framework, therefore, accommodates the study of distributed MIMO systems
and accounts for different positions of the MIMO interferers.Comment: Submitted to IEEE Trans. on Info. Theor
Performance Analysis of Coherent and Noncoherent Modulation under I/Q Imbalance
In-phase/quadrature-phase Imbalance (IQI) is considered a major
performance-limiting impairment in direct-conversion transceivers. Its effects
become even more pronounced at higher carrier frequencies such as the
millimeter-wave frequency bands being considered for 5G systems. In this paper,
we quantify the effects of IQI on the performance of different modulation
schemes under multipath fading channels. This is realized by developing a
general framework for the symbol error rate (SER) analysis of coherent phase
shift keying, noncoherent differential phase shift keying and noncoherent
frequency shift keying under IQI effects. In this context, the moment
generating function of the signal-to-interference-plus-noise-ratio is first
derived for both single-carrier and multi-carrier systems suffering from
transmitter (TX) IQI only, receiver (RX) IQI only and joint TX/RX IQI.
Capitalizing on this, we derive analytic expressions for the SER of the
different modulation schemes. These expressions are corroborated by comparisons
with corresponding results from computer simulations and they provide insights
into the dependence of IQI on the system parameters. We demonstrate that the
effects of IQI differ considerably depending on the considered system as some
cases of single-carrier transmission appear robust to IQI, whereas
multi-carrier systems experiencing IQI at the RX require compensation in order
to achieve a reliable communication link
A universal space-time architecture for multiple-antenna aided systems
In this tutorial, we first review the family of conventional multiple-antenna techniques, and then we provide a general overview of the recent concept of the powerful Multiple-Input Multiple-Output (MIMO) family based on a universal Space-Time Shift Keying (STSK) philosophy. When appropriately configured, the proposed STSK scheme has the potential of outperforming conventional MIMO arrangements
MGF Approach to the Analysis of Generalized Two-Ray Fading Models
We analyze a class of Generalized Two-Ray (GTR) fading channels that consist
of two line of sight (LOS) components with random phase plus a diffuse
component. We derive a closed form expression for the moment generating
function (MGF) of the signal-to-noise ratio (SNR) for this model, which greatly
simplifies its analysis. This expression arises from the observation that the
GTR fading model can be expressed in terms of a conditional underlying Rician
distribution. We illustrate the approach to derive simple expressions for
statistics and performance metrics of interest such as the amount of fading,
the level crossing rate, the symbol error rate, and the ergodic capacity in GTR
fading channels. We also show that the effect of considering a more general
distribution for the phase difference between the LOS components has an impact
on the average SNR.Comment: 14 pages, 8 Figures and 2 Tables. This work has been accepted for
publication at IEEE Transactions on Wireless Communications. Copyright (c)
2014 IEEE. Personal use of this material is permitted. However, permission to
use this material for any other purposes must be obtained from the IEEE by
sending a request to [email protected]
A Belief Propagation Based Framework for Soft Multiple-Symbol Differential Detection
Soft noncoherent detection, which relies on calculating the \textit{a
posteriori} probabilities (APPs) of the bits transmitted with no channel
estimation, is imperative for achieving excellent detection performance in
high-dimensional wireless communications. In this paper, a high-performance
belief propagation (BP)-based soft multiple-symbol differential detection
(MSDD) framework, dubbed BP-MSDD, is proposed with its illustrative application
in differential space-time block-code (DSTBC)-aided ultra-wideband impulse
radio (UWB-IR) systems. Firstly, we revisit the signal sampling with the aid of
a trellis structure and decompose the trellis into multiple subtrellises.
Furthermore, we derive an APP calculation algorithm, in which the
forward-and-backward message passing mechanism of BP operates on the
subtrellises. The proposed BP-MSDD is capable of significantly outperforming
the conventional hard-decision MSDDs. However, the computational complexity of
the BP-MSDD increases exponentially with the number of MSDD trellis states. To
circumvent this excessive complexity for practical implementations, we
reformulate the BP-MSDD, and additionally propose a Viterbi algorithm
(VA)-based hard-decision MSDD (VA-HMSDD) and a VA-based soft-decision MSDD
(VA-SMSDD). Moreover, both the proposed BP-MSDD and VA-SMSDD can be exploited
in conjunction with soft channel decoding to obtain powerful iterative
detection and decoding based receivers. Simulation results demonstrate the
effectiveness of the proposed algorithms in DSTBC-aided UWB-IR systems.Comment: 14 pages, 12 figures, 3 tables, accepted to appear on IEEE
Transactions on Wireless Communications, Aug. 201
Spatial Modulation with Partial-CSI at the Receiver: Optimal Detector and Performance Evaluation
International audienceSpatial Modulation (SM) is a novel and recently proposed transmission technology for Multiple–Input–Multiple–Output (MIMO) wireless communication systems, which has been shown to be a promising alternative to several popular MIMO schemes. So far, only optimal or heuristic transceivers with Full Channel State Information (F–CSI) at the receiver have been investigated, and their performance analyzed over fading channels. However, in several circumstances, channel fading might be sufficiently rapid to preclude the availability of the perfect knowledge of CSI at the receiver, and, in particular, the estimation of a stable phase reference. Motivated by this consideration, in this paper we develop the optimal detector for SM with unknown phase reference at the receiver (i.e., Partial–CSI, P–CSI, knowledge), which inevitably leads to a sub–optimal receiver design. An analytical framework will be developed for the accurate performance analysis of this novel detector over fading channels, and its performance will be compared to the optimal receiver design with F–CSI. Numerical results will point out that, unlike ordinary modulation schemes, there is a substantial performance loss when the receiver cannot exploit the phase information for optimal detection operations. This result highlights the importance of accurate and reliable channel estimation mechanisms for the efficient operation of SM over fading channels. Analytical frameworks and theoretical findings will also be substantiated via Monte Carlo simulations
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