Improved-performance noncoherent weighted-coefficients diversity combiner for DPSK and NC-FSK signals in nonidentical Nakagami fading channels

It is well-known that noncoherent equal-gain combining (NC-EGC) is the simplest combining technique for noncoherent and differentially coherent communication systems. However, for nonidentical Nakagami-m channels (channels having nonuniform multipath intensity profile (MIP) and/or arbitrary non-integer fading parameters), the use of NC-EGC has three main disadvantages. First, its performance serves as a lossy upper bound to that of the optimum diversity combiner. Second, it results in complicated expressions for the system average error performance. Third, it incurs noncoherent combining loss (does not aid the use of diversity) at relatively low average signal-to-noise ratio (SNR). In this letter, we propose a modified version of the NC-EGC, which is a noncoherent combiner with weighting coefficients, to overcome the disadvantages of the conventional one. We show that this alternative combiner does provide improvements over the conventional N.C-EGC for all values of average SNRs, it does not incur any noncoherent combining loss, and it leads to a design of the receiver whose average error performance can be evaluated easily.     

Average Error Performance of M-ary Modulation Schemes in Nakagami-q (Hoyt) Fading Channels

Presented are exact-form expressions for the average error performance of various coherent, differentially coherent, and noncoherent modulation schemes in Nakagami-q (Hoyt) fading channels. The expressions are given in terms of the Lauricella hypergeometric function, F_D ⁽ⁿ⁾; for nges1, which can be evaluated numerically using its integral or converging series representation. It is shown that the derived expressions reduce to some existing results for Rayleigh fading as special cases     

Hybrid frequency-polarization shift-keying Modulation for optical transmission

In this paper, we propose a new modulation scheme based on combining frequency and polarization modulated signals, which we will refer to as hybrid frequency-polarization shift keying (FPolSK). The FPolSK modulation is basically an extension of the conventional M-PolSK modulation over orthogonal domains. This expansion enables representing signal constellation points over multidimensional space, which ensures increasing the geometric distances between these points, and in turn, improving the system power efficiency. On the other hand, compared with M-FSK modulation, FPolSK improves the bandwidth efficiency by employing less number of orthogonal frequencies to represent information symbols. Moreover, FPolSK is extremely useful for implementing communication systems that have limitations in power and bandwidth usage. This advantage comes from the fact that FPolSK inherently enables selecting the appropriate number of orthogonal frequencies that convey with system constraints. The contribution in this paper is threefold. First, we propose a design for the transmitter and the receiver of the FPolSK technique. Second, we perform analysis for the system power and bandwidth efficiencies. Third, we derive an expression for the system power spectral density (PSD). A performance comparison between the FPolSK modulation technique and previously developed techniques is also presented in this paper. Our results reveal that the proposed modulation scheme performs better than M-PolSK, M-DPSK, and M-FSK modulation schemes in terms of both power and bandwidth efficiencies. We have also found that same bandwidth efficiency can be obtained using different FPolSK modulation formats, and the PSD of the FPolSK modulation does not contain discrete components that are considered as a waste of power. Finally, the effects of the laser phase noise and fiber dispersion on the performance of the proposed modulation are also discussed in detail.     

Non-coherent improved-gain diversity reception of binary orthogonal signals in Nakagami-q (Hoyt) mobile channels

A novel non-coherent receiver with diversity reception for binary orthogonal signals in non-identical Nakagami-g (Hoyt) fading channels (channels having arbitrary average fading powers and arbitrary fading parameters) is proposed. A closed-form expression for the average bit error probability of the proposed receiver is derived, which is given in terms of elementary functions, and can be readily evaluated numerically. In addition, the results clarify that the proposed receiver does not incur non-coherent combining loss, and at the same time, lower bounds the performance of the conventional non-coherent equal-gain combining (NC-EGC) receiver. Simulation results are provided to validate the mathematical analysis.     

Performance analysis of the forward link cdma2000 1xEV‐DO evolution for multirate services in cellular wireless system

In this paper, we propose a combined analytical and simulation framework for performance evaluation of the forward link in the cdma2000 evolution for data only (1xEV‐DO) cellular systems with throughput and spectral efficiency being used as performance metrics. A closed form expression for the aggregate average throughput is derived in terms of system‐dependent parameters and a discrete random process that reflects the stochastic behavior of the transmission channel. The random process is expressed in terms of the cumulative distribution function (CDF) of the users signal‐to‐interference‐plus‐noise ratio (SINR). Quantitative results for throughput and spectral efficiency are presented for a variety of users distribution models, base station antenna types and frequency reuse factors for the cases of sectorized and non‐sectorized cells. Furthermore, we study the impact of the cell radius on the system performance. Copyright © 2006 John Wiley & Sons, Ltd.     

Average SEP of Rectangular QAM in Rayleigh Fading with GSC

This letter presents an exact-form expression for the average symbol error probability (SEP) of general rectangular quadrature amplitude modulation (QAM) in Rayleigh fading channels with generalized selection combining (GSC). Expressions for the system average SEP with maximal ratio combining (MRC) and selection combining (SC) are obtained as limiting cases. It is shown that the results herein reduce to some existing ones as special cases.     

Impact of delayed arbitrary transmit antenna selection on the performance of rectangular QAM with receive MRC in fading channels

Constrained switching rate imposes practical limitations on the effectiveness of selection combining diversity algorithms. This paper investigates the impact of delayed arbitrarilyordered transmit antenna selection on the average symbol error probability (SEP) performance of arbitrary rectangular quadrature amplitude modulation (QAM) with receive maximal ratio combining (MRC) diversity. New closed form expression is presented for the system average SEP considering the case of statistically independent diversity branches over which the instantaneous fading-to-noise power ratios follow Gamma distributions.     

Performance analysis of rectangular quadrature amplitude modulation with combined arbitrary transmit antenna selection and receive maximal ratio combining in nakagami-m fading

The average symbol error probability (SEP) performance of arbitrary rectangular quadrature amplitude modulation in the context of arbitrarily ordered transmit antenna selection and receive maximal ratio combining diversity system is analysed. The channel gains are assumed to follow Nakagami-m fading distribution with in general arbitrary fading parameters. Exact expressions for the average SEP performance are derived for the general case of unequal in-phase and quadrature decision distances as well as distinct in-phase and quadrature modulation orders. The results generalise many previous case studies, and can be used to investigate the impact of various diversity-combining schemes and different modulation and channel parameters on the system average SEP performance.     

Performance of W-CDMA systems with rectangular signalling in OSTBC MIMO generalised nakagami-m fading channels

The performance of combined temporal multipath diversity with statistically independent branches and spatial antenna diversity with arbitrarily correlated branches is investigated. A downlink wide-band code-division multiple access system employing orthogonal space-time block coding multiple-input-multiple-output communications is considered. The performance is quantified in terms of the average symbol error probability (SEP) of coherent arbitrary rectangular quadrature amplitude modulation in Nakagami-m fading with arbitrary statistics. Through the analysis, new expressions for the average SEP are derived under the generalised system model described above. Specifically, the considerations of the combined path and space diversity model, the arbitrary correlation profile among spatial diversity branches, and the arbitrary statistics of Nakagami-m fading processes are the main aspects that make the system model herein generalised as compared to previous ones. Furthermore, for this generalised system model, the consideration of distinct in-phase and quadrature decision distances as well as modulation orders in the rectangular signalling constellation through the analysis provide additional enhancements on some existing results. Numerical and simulation results are presented to demonstrate the enhanced validity of the analytical development.     

Series Resistance Compensation in PTAT Temperature Sensors and Bandgap Reference Circuits

A general compensation technique for the extrinsic series resistor in the pn diode has been proposed in this paper. Proportional-to-absolute-temperature (PTAT) temperature sensors and bandgap reference circuits using diodes have been also proposed. In the design of bandgap reference circuits, the most common method used to produce an output voltage that is independent of temperature variations is the curvature correction method. The series resistance compensation technique represents part of this curvature. Several designs of PTAT temperature and bandgap circuits have been proposed in this work. For illustration, the PTAT sensor and bandgap circuits are numerically simulated, using the proposed algorithm.