Showing papers on "Bit error rate published in 2009"

Hardware-Efficient Coherent Digital Receiver Concept With Feedforward Carrier Recovery for $M$ -QAM Constellations

Abstract: This paper presents a novel digital feedforward carrier recovery algorithm for arbitrary M-ary quadrature amplitude modulation (M-QAM) constellations in an intradyne coherent optical receiver. The approach does not contain any feedback loop and is therefore highly tolerant against laser phase noise. This is crucial, especially for higher order QAM constellations, which inherently have a smaller phase noise tolerance due to the lower spacing between adjacent constellation points. In addition to the mathematical description of the proposed carrier recovery algorithm also a possible hardware-efficient implementation in a parallelized system is presented and the performance of the algorithm is evaluated by Monte Carlo simulations for square 4-QAM (QPSK), 16-QAM, 64-QAM, and 256-QAM. For the simulations ASE noise and laser phase noise are considered as well as analog-to-digital converter (ADC) and internal resolution effects. For a 1 dB penalty at BER = 10-3, linewidth times symbol duration products of 4.1 x 10-4 (4-QAM), 1.4 x 10-4 (16-QAM), 4.0 x 10-5 (64-QAM) and 8.0 x 10-6 (256-QAM) are tolerable.

Space shift keying modulation for MIMO channels

Abstract: In this paper, we present space shift keying (SSK) as a new modulation scheme, which is based on spatial modulation (SM) concepts. Fading is exploited for multiple-input multiple-output(MIMO) channels to provide better performance over conventional amplitude/phase modulation (APM) techniques. In SSK, it is the antenna index used during transmission that relays information, rather than the transmitted symbols themselves. This absence of symbol information eliminates the transceiver elements necessary for APM transmission and detection (such as coherent detectors). As well, the simplicity involved in modulation reduces the detection complexity compared to that of SM, while achieving almost identical performance gains. Throughout the paper, we illustrate SSK's strength by studying its interaction with the fading channel. We obtain tight upper bounds on bit error probability, and discuss SSK's performance under some non-ideal channel conditions (estimation error and spatial correlation). Analytical and simulation results show performance gains over APM systems (3 dB at a bit error rate of 10-5), making SSK an interesting candidate for future wireless applications. We then extend SSK concepts to incorporate channel coding, where in particular, we consider a bit interleaved coded modulation (BICM) system using iterative decoding for both convolutional and turbo codes. Capacity results are derived, and improvements over APM are illustrated (up to 1 bits/s/Hz), with performance gains of up to 5 dB.

Cross-layer wireless bit rate adaptation

Abstract: This paper presents SoftRate, a wireless bit rate adaptation protocol that is responsive to rapidly varying channel conditions. Unlike previous work that uses either frame receptions or signal-to-noise ratio (SNR) estimates to select bit rates, SoftRate uses confidence information calculated by the physical layer and exported to higher layers via the SoftPHY interface to estimate the prevailing channel bit error rate (BER). Senders use this BER estimate, calculated over each received packet (even when the packet has no bit errors), to pick good bit rates. SoftRate's novel BER computation works across different wireless environments and hardware without requiring any retraining. SoftRate also uses abrupt changes in the BER estimate to identify interference, enabling it to reduce the bit rate only in response to channel errors caused by attenuation or fading. Our experiments conducted using a software radio prototype show that SoftRate achieves 2X higher throughput than popular frame-level protocols such as SampleRate and RRAA. It also achieves 20% more throughput than an SNR-based protocol trained on the operating environment, and up to 4X higher throughput than an untrained SNR-based protocol. The throughput gains using SoftRate stem from its ability to react to channel variations within a single packet-time and its robustness to collision losses.

Optical Wireless Communications With Heterodyne Detection Over Turbulence Channels With Pointing Errors

Abstract: We study the error performance of an heterodyne differential phase-shift keying (DPSK) optical wireless (OW) communication system operating under various intensity fluctuations conditions. Specifically, it is assumed that the propagating signal suffers from the combined effects of atmospheric turbulence-induced fading, misalignment fading (i.e., pointing errors) and path-loss. Novel closed-form expressions for the statistics of the random attenuation of the propagation channel are derived and the bit-error rate (BER) performance is investigated for all the above fading effects. Numerical results are provided to evaluate the error performance of OW systems with the presence of atmospheric turbulence and/or misalignment. Moreover, nonlinear optimization is also considered to find the optimum beamwidth that achieves the minimum BER for a given signal-to-noise ratio value.

Power-Efficient Modulation Formats in Coherent Transmission Systems

Abstract: Coherent optical transmission systems have a four-dimensional (4-D) signal space (two quadratures in two polarizations). These four dimensions can be used to create modulation formats that have a better power efficiency (higher sensitivity) than the conventional binary phase shift keying/quadrature phase shift keying (BPSK/QPSK) signals. Several examples are given, with some emphasis on a 24-level format and an 8-level format, including descriptions of how they can be realized and expressions for their symbol and bit error probabilities. These formats are, respectively, an extension and a subset of the commonly used 16-level dual-polarization QPSK format. Sphere packing simulations in 2, 3, and 4 dimensions, up to 32 levels, are used to verify their optimality. The numerical results, as the number of levels increases, are shown to agree with lattice-theoretical results. Finally, we point out that the use of these constellations will lead to improved fundamental sensitivity limits for optical communication systems, and they may also be relevant as a way of reducing power demands and/or nonlinear influence.

Subcarrier-index modulation OFDM

Abstract: A new transmission approach, referred to as subcarrier-index modulation (SIM) is proposed to be integrated with the orthogonal frequency division multiplexing (OFDM) systems. More specifically, it relates to adding an additional dimension to the conventional two-dimensional (2-D) amplitude/phase modulation (APM) techniques, i.e. amplitude shift keying (ASK) and quadrature amplitude modulation (QAM). The key idea of SIM is to employ the subcarrier-index to convey information to the receiver. Furthermore, a closed-form analytical bit error ratio (BER) of SIM OFDM in Rayleigh channel is derived. Analytical and simulation results show error probability performance gain of 4 dB over 4-QAM OFDM systems for both coded and uncoded data without power saving policy. Alternatively, power saving policy retains an average gain of 1 dB while using 3 dB less transmit power per OFDM symbol.

Performance analysis of MIMO free-space optical systems in gamma-gamma fading

Abstract: Atmospheric turbulence induced fading is one of the main impairments affecting free-space optics (FSO) communications. In recent years, Gamma-Gamma fading has become the dominant fading model for FSO links because of its excellent agreement with measurement data for a wide range of turbulence conditions. However, in contrast to RF communications, the analysis techniques for FSO are not well developed and prior work has mostly resorted to simulations and numerical integration for performance evaluation in Gamma-Gamma fading. In this paper, we express the pairwise error probabilities of single-input single- output (SISO) and multiple-input multiple-output (MIMO) FSO systems with intensity modulation and direct detection (IM/DD) as generalized infinite power series with respect to the signal- to-noise ratio. For numerical evaluation these power series are truncated to a finite number of terms and an upper bound for the associated approximation error is provided. The resulting finite power series enables fast and accurate numerical evaluation of the bit error rate of IM/DD FSO with on-off keying and pulse position modulation in SISO and MIMO Gamma-Gamma fading channels. Furthermore, we extend the well-known RF concepts of diversity and combining gain to FSO and Gamma-Gamma fading. In particular, we provide simple closed-form expressions for the diversity gain and the combining gain of MIMO FSO with repetition coding across lasers at the transmitter and equal gain combining or maximal ratio combining at the receiver.

Phase Estimation Methods for Optical Coherent Detection Using Digital Signal Processing

Abstract: The advent of digital signal processing (DSP) to optical coherent detection means that more phase estimation options are available, compared to the earlier generation where phase-locked loops (PLLs) were invariably deployed in synchronous coherent receivers. Several phase estimation methods are numerically modeled: the maximum a posteriori (MAP) phase estimate, decision directed estimate, power law-Wiener filter estimate and power law-PLL estimate. An asynchronous coherent detection case is also modeled. The phase estimates are evaluated with respect to their tolerance of finite laser linewidth and their suitability for implementation in a parallel digital processor. Laser phase noise causes transmission system performance to be degraded by excess bit errors and cycle slips. The optimal phase estimate is the MAP estimate, and it is also included as a baseline. The power law-Wiener filter phase estimate is found to perform only marginally worse than the MAP estimate. It must be recast using a look-ahead computation to be implemented in a parallel digital processor, and the impact is investigated of the increase in the number of computations required. Differential logical detection is often used to reduce the impact of cycle slip events, and the implications of this operation on the bit error rate are studied. It is found that by choosing the correct FEC scheme differential logical detection does not increase the Q-factor penalty.

A 52 $\mu$ W Wake-Up Receiver With $-$ 72 dBm Sensitivity Using an Uncertain-IF Architecture

Abstract: A dedicated wake-up receiver may be used in wireless sensor nodes to control duty cycle and reduce network latency. However, its power dissipation must be extremely low to minimize the power consumption of the overall link. This paper describes the design of a 2 GHz receiver using a novel ldquouncertain-IFrdquo architecture, which combines MEMS-based high-Q filtering and a free-running CMOS ring oscillator as the RF LO. The receiver prototype, implemented in 90 nm CMOS technology, achieves a sensitivity of -72 dBm at 100 kbps (10-3 bit error rate) while consuming just 52 muW from the 0.5 V supply.

1.28 terabit/s (32x40 Gbit/s) wdm transmission system for free space optical communications

Abstract: We review a novel free space optical (FSO) system that represents a significant breakthrough in the area of FSO communications. The system encompasses a pair of novel terminals: these allow direct and transparent optical connection to common single mode fibers and include a dedicated electronic control unit that effectively tracks the signal beam wandering due to atmospheric turbulence and mechanical vibrations. Further improvement in the signal power stabilization is achieved by means of saturated EDFAs. These solutions allow to realize a new FSO system, which is tested in a double-pass FSO link between two buildings in Pisa, Italy. When the terminals are fed by common WDM signals they allow enough power budget and margins to support a record high capacity transmission (32times40 Gbit/s), with a enormous improvement of stability (six hours with no error burst). During day-long transmission, the system behavior has been deeply characterized to correlate any increase of bit error ratio (BER) to the FSO control parameters.

Fading Reduction by Aperture Averaging and Spatial Diversity in Optical Wireless Systems

Abstract: Atmospheric turbulence can cause a significant performance degradation in free-space optical communication systems. It is well known that the effect of turbulence can be reduced by performing aperture averaging and/or employing spatial diversity at the receiver. In this paper, we provide a synthesis on the effectiveness of these techniques under different atmospheric turbulence conditions from a telecommunication point of view. In particular, we quantify the performance improvement in terms of average bit error rate (BER) and outage capacity, which are among important parameters in practice. The efficiency of channel coding and the feasibility of exploiting time diversity in aperture averaging receivers are discussed as well. We also compare single- and multiple-aperture systems from the point of view of fading reduction by considering uncorrelated fading on adjacent apertures for the latter case. We show that when the receiver is background noise limited, the use of multiple apertures is largely preferred to a single large aperture under strong turbulence conditions. A single aperture is likely to be preferred under moderate turbulence conditions, however. When the receiver is thermal noise limited, even under strong turbulence conditions, the use of multiple apertures is interesting only when working at a very low BER. We also provide discussions on several practical issues related to system implementation.

On unbounded path-loss models: effects of singularity on wireless network performance

Abstract: This paper addresses the following question: how reliable is it to use the unbounded path-loss model G(d) = d-alpha, where alpha is the path-loss exponent, to model the decay of transmitted signal power in wireless networks? G(d) is a good approximation for the path-loss in wireless communications for large values of d but is not valid for small values of d due to the singularity at 0. This model is often used along with a random uniform node distribution, even though in a group of uniformly distributed nodes some may be arbitrarily close to one another. The unbounded path-loss model is compared to a more realistic bounded path-loss model, and it is shown that the effect of the singularity on the total network interference level is significant and cannot be disregarded when nodes are uniformly distributed. A phase transition phenomenon occurring in the interference behavior is analyzed in detail. Several performance metrics are also examined by using the computed interference distributions. In particular, the effects of the singularity at 0 on bit error rate, packet success probability and wireless channel capacity are analyzed.

Which is the most power-efficient modulation format in optical links?

Abstract: By exploiting the electromagnetic wave's four-dimensional signal space, we find that for the additive white Gaussian noise channel, the modulation format with best sensitivity to be an 8-level format with 1.76 dB asymptotic gain over BPSK, for uncoded optical transmission with coherent detection. Low-complexity modulators are presented for the format, as well as an interpretation in terms of quantum-limited sensitivity.

Time-frequency packing for linear modulations: spectral efficiency and practical detection schemes

Abstract: We investigate the spectral efficiency, achievable by a low-complexity symbol-by-symbol receiver, when linear modulations based on the superposition of uniformly time- and frequency-shifted replicas of a base pulse are employed. Although orthogonal signaling with Gaussian inputs achieves capacity on the additive white Gaussian noise channel, we show that, when finite-order constellations are employed, by giving up the orthogonality condition (thus accepting interference among adjacent signals) we can considerably improve the performance, even when a symbol-by-symbol receiver is used. We also optimize the spacing between adjacent signals to maximize the achievable spectral efficiency. Moreover, we propose a more involved transmission scheme, consisting of the superposition of two independent signals with suitable power allocation and a two-stage receiver, showing that it allows a further increase of the spectral efficiency. Finally, we show that a more involved equalization algorithm, based on soft interference cancellation, allows to achieve an excellent bit-error-rate performance, even when error-correcting codes designed for the Gaussian-noise limited channel are employed, and thus does not require a complete redesign of the coding scheme.

Channel Estimation for OFDM Modulated Two-Way Relay Networks

Abstract: In this work, we introduce the model of employing orthogonal-frequency-division multiplexing (OFDM) for transmission over time-dispersive channels in the two-way relay network (TWRN), where two source terminals exchange their information through a relay terminal using the amplify-and-forward (AF) relaying scheme. We propose a two-phase training protocol for the channel estimation, which is compatible with the two-phase data transmission scheme. In the first phase, the two source terminals send their individual training sequences concurrently to the relay, while in the second phase the relay amplifies the received training sequences and broadcasts them to both source terminals. We propose two different types of training methods as well as develop their corresponding channel estimation algorithms at each of the two source terminals. The first type of training is block based, for which we first estimate the cascaded source-relay-source channels, and then design algorithms to recover the individual channels between sources and relay. The second type of training is pilot-tone (PT) based, for which we propose to directly estimate the individual channels between sources and relay. Moreover, the identifiability issues on the nonambiguous estimate of the channels in both types of proposed training are carefully addressed. Finally, various numerical examples are presented to corroborate our analytical results.

An overview of peak-to-average power ratio reduction schemes for OFDM signals

Abstract: Orthogonal frequency division multiplexing (OFDM) has been adopted as a standard for various high data rate wireless communication systems due to the spectral bandwidth efficiency, robustness to frequency selective fading channels, etc. However, implementation of the OFDM system entails several difficulties. One of the major drawbacks is the high peak-to-average power ratio (PAPR), which results in intercarrier interference, high out-of-band radiation, and bit error rate performance degradation, mainly due to the nonlinearity of the high power amplifier. This paper reviews the conventional PAPR reduction schemes and their modifications for achieving the low computational complexity required for practical implementation in wireless communication systems.

Path loss modeling and performance trade-off study for short-range non-line-of-sight ultraviolet communications

Abstract: We consider outdoor non-line-of-sight deep ultraviolet (UV) solar blind communications at ranges up to 100 m, with different transmitter and receiver geometries. We propose an empirical channel path loss model, and fit the model based on extensive measurements. We observe range-dependent power decay with a power exponent that varies from 0.4 to 2.4 with varying geometry. We compare with the single scattering model, and show that the single scattering assumption leads to a model that is not accurate for small apex angles. Our model is then used to study fundamental communication system performance trade-offs among transmitted optical power, range, link geometry, data rate, and bit error rate. Both weak and strong solar background radiation scenarios are considered to bound detection performance. These results provide guidelines to system design.

Error control in wireless sensor networks: a cross layer analysis

Abstract: Error control is of significant importance for Wireless Sensor Networks (WSNs) because of their severe energy constraints and the low power communication requirements. In this paper, a cross-layer methodology for the analysis of error control schemes in WSNs is presented such that the effects of multi-hop routing and the broadcast nature of the wireless channel are investigated. More specifically, the cross-layer effects of routing, medium access, and physical layers are considered. This analysis enables a comprehensive comparison of forward error correction (FEC) codes, automatic repeat request (ARQ), and hybrid ARQ schemes in WSNs. The validation results show that the developed framework closely follows simulation results. Hybrid ARQ and FEC schemes improve the error resiliency of communication compared to ARQ. In a multi-hop network, this improvement can be exploited by constructing longer hops (hop length extension), which can be achieved through channel-aware routing protocols, or by reducing the transmit power (transmit power control). The results of our analysis reveal that for hybrid ARQ schemes and certain FEC codes, the hop length extension decreases both the energy consumption and the end-to-end latency subject to a target packet error rate (PER) compared to ARQ. This decrease in end-to-end latency is crucial for delay sensitive, real-time applications, where both hybrid ARQ and FEC codes are strong candidates. We also show that the advantages of FEC codes are even more pronounced as the network density increases. On the other hand, transmit power control results in significant savings in energy consumption at the cost of increased latency for certain FEC codes. The results of our analysis also indicate the cases where ARQ outperforms FEC codes for various end-to-end distance and target PER values.

Multiuser two-way relaying: detection and interference management strategies

Abstract: We consider a multiuser two-way relay network where multiple pairs of users communicate with their preassigned partners, using a common intermediate relay node, in a two-phase communication scenario employing code division multiple access (CDMA). By taking advantage of the bidirectional communication structure, we first propose that each pair of partners share a common spreading signature and design a jointly demodulate-and-XOR forward (JD-XOR-F) relaying scheme, where all users transmit to the relay simultaneously followed by the relay broadcasting an estimate of the XORed symbol for each user pair. We derive the decision rules and the corresponding bit error rates (BERs) at the relay and at the users' receivers. We then investigate the joint power control and receiver optimization problem for each phase for this multiuser two-way relay network with JD-XOR-F relaying. We solve each optimization problem by constructing the iterative power control and receiver updates that converge to the corresponding unique optimum. Simulation results are presented to demonstrate the performance of the proposed multiuser two-way JD-XOR-F relaying scheme in conjunction with the joint power control and receiver optimization algorithms. Specifically, we observe significant power savings and user capacity improvement with the proposed communication scheme as compared to the designs with a "one-way" communication perspective.

Two hop amplify-and-forward transmission in mixed rayleigh and rician fading channels

Abstract: The performance of a two hop amplify-and-forward relay system, where the source-relay and the relay-destination channels experience Rayleigh and Rician fading respectively, is investigated. We derive exact and lower bound expressions for the outage probability and average bit error probability, where the bounds become tight at high signal-to-noise ratios (SNR). Our results are verified through comparison with Monte Carlo simulations, where we also illustrate the positive impact of the Rician factor on the system performance.

Selected mapping without side information for PAPR reduction in OFDM

Abstract: Selected mapping (SLM) is a technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. SLM requires the transmission of several side information bits for each data block, which results in some data rate loss. These bits must generally be channel-encoded because they are particularly critical to the error performance of the system. This increases the system complexity and transmission delay, and decreases the data rate even further. In this paper, we propose a novel SLM method for which no side information needs to be sent. By considering the example of several OFDM systems using either QPSK or 16-QAM modulation, we show that the proposed method performs very well both in terms of PAPR reduction and bit error rate at the receiver output provided that the number of subcarriers is large enough.

Optimal resource allocation in the OFDMA downlink with imperfect channel knowledge

Abstract: Previous research efforts on OFDMA resource allocation have typically assumed the availability of perfect channel state information (CSI). Unfortunately, this is unrealistic, primarily due to channel estimation errors, and more importantly, channel feedback delay. In this paper, we develop optimal resource allocation algorithms for the OFDMA downlink assuming the availability of only partial (imperfect) CSI. We consider both continuous and discrete ergodic weighted sum rate maximization subject to total power constraints, and average bit error rate constraints for the discrete rate case. We approach these problems using a dual optimization framework, allowing us to solve these problems with O(MK) complexity per symbol for an OFDMA system with K used subcarriers and M active users, while achieving relative optimality gaps of less than 10-5 for continuous rates and less than 10-3 for discrete rates in simulations based on realistic parameters.

Performance analysis of the dual-hop asymmetric fading channel

Abstract: In real wireless communication environments, it is highly likely that different channels associated with a relay network could experience different fading phenomena. In this paper, we investigate the end-to-end performance of a dual-hop fixed gain relaying system when the source-relay and the relay-destination channels experience Rayleigh/Rician and Rician/Rayleigh fading scenarios respectively. Analytical expressions for the cumulative distribution function of the end-to-end signal-to-noise ratio are derived and used to evaluate the outage probability and the average bit error probability of M-QAM modulations. Numerical and simulation results are presented to illustrate the impact of the Rician factor on the end-to-end performance. Furthermore, these results confirm that the system exhibits an improved performance in a Rician/Rayleigh (source-relay link/relay-destination link) environment compared to a Rayleigh/Rician environment.

Error performance of maximal-ratio combining with transmit antenna selection in flat Nakagami-m fading channels

Abstract: In this paper, the performance of an uncoded multiple-input-multiple-output (MIMO) scheme combining single transmit antenna selection and receiver maximal-ratio combining (the TAS/MRC scheme) is investigated for independent flat Nakagami-m fading channels with arbitrary real-valued m. The outage probability is first derived. Then the error rate expressions are attained from two different approaches. First, based on the observation of the instantaneous channel gain, the binary phase-shift keying (BPSK) asymptotic bit error rate (BER) expression is derived, and the exact BER expression is obtained as an infinite series, which converges for reasonably large signal-to-noise ratios (SNRs). Then the exact symbol error rate (SER) expressions are attained as a multiple infinite sum based on the moment generating function (MGF) method for M-ary phase-shift keying (M-PSK) and quadrature amplitude modulation (M-QAM). The asymptotic SER expressions reveal a diversity order equal to the product of the m parameter, the number of transmit antennas and the number of receive antennas. Theoretical analysis is verified by simulation.

Transmit processing with low resolution D/A-converters

Abstract: We study the transmitter optimization for the flat multi-input multi-output (MIMO) channel under nonlinear distortion from the digital-to-analog converters (DACs). Our design is based on a minimum mean square error (MMSE) approach, taking into account the effects of the transmitter nonlinearities. Our derivation does not make use of the assumption of uncorrelated white distortion (quantization) errors and considers the correlations of the quantization error with the other signals of the system. Through simulation, we compare the new optimized linear transmitter to previously proposed linear transmitter designs when operating under DACs in terms of uncoded BER.

A study of LED nonlinearity effects on optical wireless transmission using OFDM

Abstract: Orthogonal frequency division multiplexing (OFDM) is a promising technique to realize high-speed indoor optical wireless (OW) links through the exploitation of the high peak-to-average power ratio (PAPR) for intensity modulation (IM). However, non-linear distortions in the transmission chain can significantly compromise the performance of OFDM as they incur inter-channel interference. The light emitting diode (LED) is the main source for such distortions due to its nonlinear behavior. Distortion levels can be controlled when the LED operates in a quasi-linear segment of its characteristic around a bias point. The severity of non-linear distortions and the dependence of the bias point on the chosen digital modulation scheme are analyzed in this paper. In this context, the bit-error performance is determined as a function of the bias point and the applied power back-offs.

Effect of Channel-Estimation Error on BER Performance in Cooperative Transmission

Abstract: In this paper, a framework for evaluating the bit-error-rate (BER) performance of amplify-and-forward (AF) relay-assisted cooperative transmission is provided in the presence of imperfect channel estimation. First, the AF relaying is classified into two cases - a variable gain and a fixed gain. For each case, the closed-form average BER is derived by using the moment-generating function (MGF) of the effective output SNR, which quantifies the SNR penalty due to the noisy channel estimate. Moreover, the asymptotic BER bound is also provided at a high SNR regime for the insight of our approach. In particular, the effect of the feedforward delay on informing the source-relay channel estimate as to the destination is presented in the variable-gain relay. Numerical investigation shows that the analytic result makes an exact match with the simulation, and the comparative superiority between the fixed- and variable-gain relay is discussed.

5.6 Gbps optical intersatellite communication link

Abstract: A 5.6 Gbps optical communication link has been verified in-orbit. The intersatellite link uses homodyne BPSK (binary phase shift keying) and allows to transmit data with a duplex data rate of 5.6 Gbps and a bit error rate better than 10-9 between two LEO satellites, NFIRE (U.S.) and TerraSAR-X (Germany). We report on the terminal design and the link performance during the measurement campaign. As an outlook we report on the flight units adapted to LEO-to-GEO intersatellite links that TESAT currently builds and on plans to study GEO-to-ground links.

Performance analysis of incremental opportunistic relaying over identically and non-identically distributed cooperative paths

Abstract: In this paper, we consider an incremental relaying protocol based on an amplify-and-forward transmission in conjunction with the best relay selection scheme over non-identically distributed relay channels. In order to satisfy the spectral efficiency and the bit error rate (BER) requirements, adaptive modulation is applied to our proposed scheme. We derive the average spectral efficiency, average BER and outage probability for the performance analysis of our proposed scheme. For a more tractable analysis, we start with an upper bound for the combined signal-to-noise ratio at the destination and provide closed-form expressions for independent non-identically distributed Rayleigh fading conditions. Our analytical-based numerical results are validated by some computer-based simulations. These results show that our proposed scheme leads to a considerable improvement in the performance of cooperative diversity systems.