Optimum Receiver Performance Research Articles

BER and Capacity Improvement for Multiuser MIMO System by MRT Precoding Technique

In recent years several of endeavors have been conducted in various papers to improve capacity and bit error rate performance of multiuser MIMO system. Every effort tried to increase gain of the individual stream between base station and users’ antennas while reducing the interference among multiple users and interference between streams of single user itself. All these papers adopted precoding techniques for beam forming of individual stream. Various papers have compared precoding techniques such as DPC, BD-ZF, BD-MMSE, BD-QR-MRL, and BD-QR-LRL. Block diagonalization technique is capable to reduce multiuser interference, but not able to combat interference between antennas of single user itself. BD combines with other techniques to overcome this problem. This paper also proposes a precoding technique called modified maximum ratio transmission, which is able to deal with the problem without much complexity. Simulation is done to compare all precoding technique with MRT. The paper tests the precoding techniques on the parameters of BER and capacity, to achieve optimum receiver performance. BER curve and capacity curve are plotted to conclude the paper.

Optimum Receiver Performance With Binary Phase-Shift Keying for Decode-and-Forward Relaying

Cooperative diversity through decode-and-forward (DF) relaying is an effective method for improving the performance of mobile wireless systems. We consider here the performance of a cooperative diversity system in which the relay employs the DF protocol to transmit data from a source to a destination using binary phase-shift keying (BPSK). A flat Rayleigh fading environment with statistically independent links is assumed. The optimum receiver for this system is presented, and from the decision rule, the end-to-end symbol error probability (SEP) is derived. Numerical results on the SEP are obtained and compared with those for a suboptimum receiver, which does not need the channel state information of the source-to-relay link.

Optimum receiver performance of TH-PPM ultra wideband system in multiple user interference

This paper demonstrates optimum receiver performance in terms of bit error rate (BER) for time hopping pulse position modulation (TH-PPM) ultra wideband (UWB) system in multiple user interference environment for indoor radio communication. Equal gain combining and selective gain combining have been demonstrated in terms of ideal RAKE (ARAKE), selective RAKE (SRAKE) and partial RAKE (PRAKE) receiver performances. The recently accepted IEEE 802.15.3a model of the UWB channel has been used to describe UWB propagation in indoor environment. Two channel scenarios named CM-1 and CM-3 for IEEE 802.15.3a channel model have been investigated principally. Finally, this paper concludes with an approximation of equivalence of number of fingers in SRAKE and PRAKE receivers as well as an indication of SNR gains achievable as the RAKE finger number is increased, espe- cially with multiple user interference (MUI), for a 16.6 Mbit/s UWB system.

A Unified Approach to BER Analysis of Synchronous Downlink CDMA Systems with Random Signature Sequences in Fading Channels with Known Channel Phase

A detailed analysis of the multiple access interference (MAI) for synchronous downlink CDMA systems is carried out for BPSK signals with random signature sequences in Nakagami-m fading environment with known channel phase. This analysis presents a unified approach as Nakagami-m fading is a general fading distribution that includes the Rayleigh, the one-sided Gaussian, the Nakagami-q, and the Rice distributions as special cases. Consequently, new explicit closed-form expressions for the probability density function (pdf) of MAI and MAI plus noise are derived for Nakagami-m, Rayleigh, one-sided Gaussian, Nakagami-q, and Rician fading. Moreover, optimum coherent reception using maximum likelihood (ML) criterion is investigated based on the derived statistics of MAI plus noise and expressions for probability of bit error are obtained for these fading environments. Furthermore, a standard Gaussian approximation (SGA) is also developed for these fading environments to compare the performance of optimum receivers. Finally, extensive simulation work is carried out and shows that the theoretical predictions are very well substantiated.

Optimum filter bandwidths for optically preamplified NRZ receivers

We present a comprehensive treatment of optically preamplified direct detection receivers for non-return-to-zero (NRZ) and return-to-zero (RZ) on/off keying modulation, taking into account the influence of different (N)RZ optical pulse shapes, specified at the receiver input, and filter transfer functions; optical Fabry-Perot filters (FPFs) and Bragg gratings as well as electrical fifth-order Bessel and first-order RC low-pass filters are considered. We determine optimum optical and electrical filter bandwidths and analyze the impact of bandwidth deviations on receiver sensitivity. Optimum receiver performance relies on a balance between noise and intersymbol interference (ISI) for NRZ transmission, while for RZ reception detection noise has to be traded against filter-induced signal energy rejection. Both for NRZ and 33% duty cycle RZ, optical filter bandwidths of around twice the data rate are found to be optimum. Receivers using RZ coding are shown to closely approach the quantum limit, and thus to outperform NRZ-based systems by several decibels. We further analyze the impact of important degrading effects on receiver sensitivity and optimum receiver bandwidths, including receiver noise, finite extinction ratio, chirp, and optical carrier frequency (or optical filter center frequency) fluctuations.

System Temperatures, Single Versus Double Sideband Operation, and Optimum Receiver Performance

This paper discusses the relative observing efficiency of single sideband (SSB) and double sideband (DSB) receiver systems in the presence of atmospheric and antenna losses. We use the antenna parameters currently specified for the NRAO Millimeter Array (MMA) antennas and atmospheric opacities appropriate to an excellent site such as Mauna Kea or the MMA site on the Llano de Chajnantor in northern Chile. We find that for spectroscopic observations in one sideband, SSB measurements are always more efficient. Below 400 GHz, the observing time advantage is 50-80%. Above 400 GHz, the advantage is over a factor of 2, indicating that SSB-mode observing is more efficient even if spectral lines of interest are present in both sidebands. We discuss the goals for the ultimate, practical receiver performance that one should aim for in the presence of atmospheric and telescope losses. Observing efficiencies are displayed as a function of frequency using atmospheric opacity models as input. We also develop some analytic expressions for SSB and DSB observing.

Performance of optimum and suboptimum receivers in the presence of impulsive noise modeled as an alpha-stable process

Impulsive noise bursts in communication systems are traditionally handled by incorporating in the receiver a limiter which clips the received signal before integration. An empirical justification for this procedure is that it generally causes the signal-to-noise ratio to increase. Recently, very accurate models of impulsive noise were presented, based on the theory of symmetric /spl alpha/-stable probability density functions. We examine the performance of optimum receivers, designed to detect signals embedded in impulsive noise which is modeled as an infinite variance symmetric /spl alpha/-stable process, and compare it against the performance of several suboptimum receivers. As a measure of receiver performance, we compute an asymptotic expression for the probability of error for each receiver and compare it to the probability of error calculated by extensive Monte-Carlo simulation. >

Theory of polarization spreading techniques-Part II

This paper, together with a companion one [l], constitute a thorough presentation and analysis of a series of techniques grouped under the denomination “Polarization Spreading,” the intent of which is that of making the performance of a coherent optical receiver insensitive to the polarization transformations occurring along the optical fiber, without resorting to polarization compensation or control. The principle on which Polarization Spreading operates is that of spreading the signal power over different states of polarization, so that heterodyning of at least half of the optical incident bit energy is always ensured. The main obtained results concern (presented in [l]) a condition that guarantees the maximum heterodyned signal energy, some classes of spreading waveforms satisfying the above condition, the derivation of the structure and performance of optimum receivers in Gaussian noise; and, presented in this paper, the analysis of a suboptimum but easily implementable receiver and a detailed comparative analysis of the spectral broadening induced by the different spreading techniques. The results encompass most of the binary optical coherent modulation schemes proposed and experimented, such as ASK, FSK and DPSK.

Theory of polarization spreading techniques. I

Presents an analysis of a series of techniques grouped under the denomination "polarization spreading", the intent of which is that of making the performance of a coherent optical receiver insensitive to the polarization transformations occurring along the optical fiber, without resorting to polarization compensation or control. The principle on which Polarization spreading operates is that of spreading the signal power over different states of polarization, so that heterodyning of at least half of the optical incident bit energy is always ensured. The main results obtained concern a condition that guarantees the maximum heterodyned signal energy, some classes of spreading waveforms satisfying the above condition, the derivation of the structure and the performance of optimum receivers in Gaussian noise. The results encompass most of the binary optical coherent modulation schemes proposed and experimented, such as ASK, FSK and DPSK.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimum and Suboptimum Detector Performance for Signals in Cyclostationary Noise

The detection of known and partially known signals in additive white Gaussian uonstationary noise is considered, with primary attention to the ease where the time-varying noise intensity parameter N_{o}(t) is a periodic function. Optimum receiver structures are derived for three detection cases, namely completely known signals, sinusoids with random phase, and sinusoids with both random amplitude and phase. It is demonstrated that optimum receiver performance can be achieved only if proper synchronization to the noise intensity N_{o}(t) is accomplished. Large performance penalties can be demonstrated when an improperly synchronized receiver is used. Consequently, suboptimum receivers that ignore the noise intensity time variations and therefore require no synchronization, have been considered, and their performance compared to their optimum counterparts. Depending on the type of time-varying noise intensity being considered, results show that performance differences between optimum and suboptimum receivers can be negligible in some cases, and yet can be substantial in other cases. Several examples have been worked out using two different forms for N_{o}(t) and corresponding performance evaluations have been carried out and presented graphically in terms of receiver error probability as a function of signal-to-noise ratio.

Correlative Phase Shift Keying--A Class of Constant Envelope Modulation Techniques

Correlative phase shift keying (CORPSK) is described. CORPSK is a constant envelope modulation technique with smooth transitions between fixed phase positions with successive transitions correlated. A number of CORPSK members for 2 and 4 input levels are analyzed, including tamed frequency modulation (TFM). Main lobe bandwidth is the same or less than in other constant envelope modulation techniques such as MSK, QPSK, and CPFSK, but the out-of-band radiation is much lower. Carrier extraction can be realized with simple techniques, so that coherent detection with optimum receiver performance is practically feasible. Simulation results are presented for coherent as well as noncoherent detection. A power efficiency 2 dB better than four MSK and DQPSK can be obtained for CORPSK with no more than for phase positions. A wide variety of modulations exists within the CORPSK class, with ample opportunity for tradeoffs between power, bandwidth, and complexity. Practical results for TFM are reported.

Distributed-parameter state-variable model for time-variant channels

Signals transmitted over certain randomly time-varying linear channels undergo spreading both in time and in frequency. This paper considers a particular class of doubly spread channels: those with an impulse response that can be represented as the output of a distributed linear system, the dynamics of which are governed by partial differential state equations driven by a white noise process. The model is shown to include channels characterized by wide-sense stationary scattering (WSS), uncorrelated scattering (US), or both (WSSUS). When reception takes place in white Gaussian noise, the optimum, quadratic detector can be realized as an estimator-correlator. For the doubly spread channels encompassed by the model, the causal least-squares estimator of the channel response is obtained in the form of a linear filter with a distributed-parameter state-variable description. Certain error probability bounds and approximations can be evaluated upon solution of the receiver equations. Numerical results are given for an example: binary frequency-shift-keying (FSK) signaling over a particular WSSUS channel. The effects of the channel's frequency-time spread factor (BL) and the signaling interval on the optimum receiver performance, as measured by the Bhattacharyya distance, are investigated.

Limitations in the Use of Dielectric Interference Filters in Wide Angle Optical Receivers

Along a clear line-of-sight optical signal path through the atmosphere, the usefulness of interference filters in rejecting unwanted background light is limited mainly by the technology of fabrication. If the signal to be observed is strongly scattered by fog or aerosols, the received signal appears to come from a wide angular subtense. In such a case it is found that the interference filter is not a very useful device for separating signal and background. The optimum photoelectron counting receiver equipped with such a filter performs not much better than a receiver without any filter. The difficulty is an interdependence between the effective bandwidth and field of view of such filters, which results in an optimum receiver performance in which neither parameter specifically appears. The results also apply to other wavelength-dependent filters, such as the liquid crystal, and filters using polarization anisotropy along a path between polarizers.