Link SNR Research Articles

Dual Mode Localization Assisted Beamforming for mmWave V2V Communication

This study is motivated by the fact that localization in millimeter wave(mmWave) Vehicle-to-Vehicle communication becomes a more critical problem because both the terminals of the communication link are in motion. The positional awareness merely based on GPS or local sensors has an error margin of around 10 meters, which can worsen in uncertain real-time conditions such as road topology and highway traffic. The paper analyses the relation between vehicle dynamics, beamforming, and beam alignment for highly directive antennas. When the subsystem models presented in this paper are taken into consideration, the joint vehicle dynamics-beamforming approach will optimize the link connectivity and SNR. The vehicle dynamics model is designed to be more realistic considering the non-linear acceleration based on the throttle-brake jerks due to induced noises. The Unscented Kalman Filter based prediction subsystem predicts the alignment values even during non-linear acceleration and jerks. The feasibility of antenna design for the beamforming strategies is supported by the requirements of phase shifters and the number of elements.

Information Rate Optimization for the Non-Regenerative Linear MIMO Relay Channel With a Direct Link and Variable Duty Cycle

We consider the optimization of a two-hop linear relay channel based on an amplify-and-forward Multiple-Input Multiple-Output (MIMO) relay. The relay is assumed to derive the output signal by applying a Relay Transform Matrix (RTM) applied to the input signal. Assuming perfect channel state information about the channel at the relay and iid transmitted symbols, the RTM is optimized according to two different criteria: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i)</i> MIMO information rate; <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ii)</i> information rate based on Orthogonal Space–Time Block Codes. The two assumptions have been addressed in part in the literature. The optimization problem is reduced to a manageable convex form, whose KKT equations are explicitly solved. Then, a parametric solution is given, which yields the power constraint and the information rate achieved with uncorrelated transmitted symbols as functions of a positive indeterminate. The solution for a given average power constraint at the relay is amenable to a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">water-filling-like</i> algorithm, and extends earlier literature results addressing the case without the direct link. The duty cycle of the two-hop relaying process is also addressed in the general form of the achievable rate. Simulation results are reported, which are relevant to a Rayleigh fading MIMO relay channel and the role of the direct link SNR is precisely assessed. Duty cycle optimization is also considered by a numerical example.

An adaptive data rate algorithm for improving energy efficiency for multi-gateway LoRaWANs

The need of the low power, long range, and low cost connectivity for satisfying the requirement of internet of things (IoT) applications for smart city is leading the emergence of low power wide area (LPWA) networking technologies. The resource efficiency plays an important role in realistic application, LoRaWAN allows the static end devices to individually adapt and optimise the data rates and the transmission power, which is referred to as adaptive data rate (ADR) problem. In this paper, we develop a new ADR algorithm for multi-gateway LoRaWAN environment to quickly choose the appropriate LoRa transmission parameter for independent LoRa end device based on LoRaWAN specification. To successfully execute the ADR algorithm, we especially rewrite the firmware of Semtech's SX1276 transceivers to implement our proposed ADR algorithm over multi-gateway LoRaWAN system, including end device, multi-gateways and network server. Our ADR algorithm utilises the radio link quality, including RSSI, SNR, and packet reception ratio (PRR), from multi-gateways, and the network server determines the appropriate LoRa transmission parameter. Finally, the experimental results illustrate that the proposed algorithm improves the energy efficiency, the effective bit rate, and the battery life of the end device.

Multi-beam coverage and beamforming technology for high altitude platform station communication system

Multi-beam antenna technology can effectively mitigate the impact of deep fading caused by multipath propagation on communication quality through spatial diversity and increase the reliability of wireless mobile communication systems. At the same time, the multi-beam antenna with beamforming algorithm as the key technology can realize spatial division multiple access (SDMA) by automatically adapting the weight vector of the antenna array, enhance the expected value, and suppress the interference. A novel beamforming technology increases the inner circle beam width and reduces the outer ring beam width to minimize the difference between the internal and external cell link SNR. This study considers reducing the number of cells by reasonably allocating beams, which satisfies both the requirements of coverage link quality and the difficulty of forming antenna beams. This research subject applies the scheme and strategy of improving multi-beam antenna technology in the same system. Under the requirement of cell coverage and partitioning, the related technologies and strategies combining multi-beamforming technology and space-time block code technology can obtain high coding gain and diversity gain without sacrificing bandwidth and effectivelyx improve the wireless systematic capacity.

Performance analysis of mixed RF/FSO cooperative systems with wireless power transfer

This paper investigates the performance of mixed radio frequency-free space optical (RF/FSO) systems where the battery-limited RF nodes can harvest the required energy for information transmission. The analysis takes into account the Rayleigh fading caused by signal propagation in the RF link and Gamma–Gamma atmospheric turbulence with the effect of pointing errors in the FSO link. Two different scenarios have been considered; in the first scenario, the source uses an RF random power provided by a relay for information transmission in a dual-hop cooperative configuration; whereas in the second scenario there is also a direct RF link between the source and destination. We provide closed-form expressions for the outage probability, bit error probability and ergodic capacity for the dual-hop amplify-and-forward relaying system that performs energy harvesting. Asymptotic expressions are also provided for the high SNR regime where the diversity order of the system is calculated. The accuracy of the proposed analytical formulations is proved by means of a set of numerical results. For instance, for the second scenario, fixing the average electrical SNR of the FSO link, we show that the link diversity order is equal to one. However, when fixing the average SNR of the RF links, the link diversity order equals zero, resulting in an error floor due to the dominant effect of the RF link.

Robust and Efficient Energy Harvested-Aware Routing Protocol With Clustering Approach in Body Area Networks

Wireless body area network (WBAN) is one of the specialized branches of wireless sensor networks (WSNs), which draws attention from various fields of science, such as medicine, engineering, physics, biology, and computer science. It has emerged as an important research area contributing to sports, social welfare, and medical treatment. One of the most important technologies of WBANs is routing technology. For efficient routing in WBANs, multiple network operations, such as network stability, throughput, energy efficiency, end-to-end delay, and packet delivery ratio, must be considered. In this paper, a robust and efficient Energy Harvested-aware Routing protocol with Clustering approach in Body area networks (EH-RCB) is proposed. It is designed with the intent to stabilize the operation of WBANs by choosing the best forwarder node, which is based on optimal calculated Cost Function (C.F). The C.F considers the link SNR, required transmission power, the distance between nodes, and total available energy, i.e., harvested energy and residual energy. Comprehensive simulation has been conducted, supported by NS-2 and C++ simulations tools to compare EH-RCB with existing protocols named DSCB, EERP, RE-ATTEMPT, and EECBSR. The results indicate a significant improvement in the EH-RCB in terms of the end-to-end delay network stability, packet delivery ratio, and network throughput.

A Novel Equivalent Definition of Modified Bessel Functions for Performance Analysis of Multi-Hop Wireless Communication Systems

A statistical model is derived for the equivalent signal-to-noise ratio of the Source-to-Relay-to-Destination (S-R-D) link for Amplify-and-Forward (AF) relaying systems that are subject to block Rayleigh-fading. The probability density function and the cumulated density function of the S-R-D link SNR involve modified Bessel functions of the second kind. Using fractional-calculus mathematics, a novel approach is introduced to rewrite those Bessel functions (and the statistical model of the S-R-D link SNR) in series form using simple elementary functions. Moreover, a statistical characterization of the total receive-SNR at the destination, corresponding to the S-R-D and the S-D link SNR, is provided for a more general relaying scenario in which the destination receives signals from both the relay and the source and processes them using maximum ratio combining (MRC). Using the novel statistical model for the total receive SNR at the destination, accurate and simple analytical expressions for the outage probability, the bit error probability, and the ergodic capacity are obtained. The analytical results presented in this paper provide a theoretical framework to analyze the performance of the AF cooperative systems with an MRC receiver.

End-to-End Data Rate Performance of Decode-and-Forward Relaying with Different Resource Allocation Schemes

This paper studies the end-to-end (e2e) data rate of dual-hop Decode-and-Forward (DF) infrastructure relaying under different resource allocation schemes. In this context, we first provide a comparative analysis of the optimal resource allocation scheme with respect to several other approaches in order to provide insights into the system behavior and show the benefits of each alternative. Then, assuming the optimal resource allocation, a closed form expression for the distribution of the mean and outage data rates is derived. It turns out that the corresponding mean e2e data rate formula attains an expression in terms of an integral that does not admit a closed form solution. Therefore, a tight lower bound formula for the mean e2e data rate is presented. Results can be used to select the most convenient resource allocation scheme and perform link dimensioning in the network planning phase, showing the explicit relationships that exist between component link bandwidths, SNR values, and mean data rate.

Upper Bound for Average Outage Probability of BT-ADF relay networks Over Quasi-Static Rayleigh Fading channels

In this paper, we propose the analytical approach for burst transmission (BT) adaptive decode-and-forward (ADF) relaying schemes consisting of burst transmission over quasistatic Rayleigh fading channels. At first, we focus on the error-event at relay nodes for symbol burst transmission, whereas previous researches considered one data symbol transmission so that they showed the best performance bounds. By considering symbol burst for ADF relay systems, we derive an exact outage probability expression which can be the performance of practical systems. Furthermore, the average outage probability is derived in approximated closed-form upper bound for an arbitrary link SNR. The derived analytical approach is verified based on the number of relays and burst symbols. Its accuracy is confirmed by comparison with simulation results.

Dynamic Spectrum Sharing for OFDMA-Based Multi-hop Cognitive Radio Networks with Priority

In this paper, we propose a resource assignment scheme of a secondary user (SU) for a multi-hop cognitive radio network. In multi-hop networks, since each link has different SNR because of their different distance between stations and multipath fading, the link of the smallest SNR is the bottleneck. For overcoming this problem, it is proposed to give a priority to each link based on the link SNR and to assign the resource blocks (RBs) in ordering of instantaneous SNR on the link. This link priority information is shared among nodes through a control channel. Then, we assign the selected SU RB to each SU node according to the SNR ordering with distributed manner. We confirm the effectiveness of the proposed SU RB assignment by using computer simulation.

Adaptive narrowband interference mitigation by designing UWB waveforms based on radial basis function neural networks

In order to mitigate the mutual interference between ultra-wideband (UWB) impulse radio and other existing wireless systems, a novel adaptive interference-avoiding UWB pulse, in the context of the appealing cognitive radio, is presented based on the radial basis function neural networks. Theoretical and implementation architecture for UWB pulse generator is addressed. Transmission performance in the presence of narrowband interference including tone interference is comprehensively analyzed. The presented generator can adaptively change the spectrum shape of UWB signals according to the authorized users’ working states, and hence the mutual interference between UWB and other systems sharing the frequency bands can efficiently be avoided. The critical performance indication parameters, such as the SNR, SIR, and BER of UWB communication links, are also derived. Performance evaluations and comparisons between the proposed scheme and other pulse optimization methods have been provided based on the extensive numerical simulations. It is demonstrated that the presented pulse can indeed achieve much superior performance in terms of either single-link BER or anti-jamming capability.

On the achievable rates of multiple antenna broadcast channels with feedback-link capacity constraint

In this paper, we study a MIMO fading broadcast channel where each receiver has perfect channel state information while the channel state information at the transmitter is acquired by explicit channel feedback from each receiver through capacity-constrained feedback links. Two feedback schemes are considered, i.e., the analog and digital feedback. We analyze the achievable ergodic rates of zero-forcing dirty-paper coding (ZF-DPC), which is a nonlinear precoding scheme inherently superior to linear ZF beamforming. Closed-form lower and upper bounds on the achievable ergodic rates of ZF-DPC with Gaussian inputs and uniform power allocation are derived. Based on the closed-form rate bounds, sufficient and necessary conditions on the feedback channels to ensure nonzero and full downlink multiplexing gain are obtained. Specifically, for analog feedback in both AWGN and Rayleigh fading feedback channels, it is sufficient and necessary to scale the average feedback link SNR linearly with the downlink SNR in order to achieve the full multiplexing gain. While for the random vector quantization-based digital feedback with angle distortion measure in an error-free feedback link, it is sufficient and necessary to scale the number of feedback bits B per user as where M is the number of transmit antennas and is the average downlink SNR.

A bandwidth‐efficient cooperative relaying scheme with hard interference cancellation and iterative decoding

AbstractThis paper considers a coded cooperative relaying scheme in which all successfully decoded signals from multiple sources are simultaneously forwarded by a multi‐antenna relay to a common multi‐antenna destination to increase bandwidth efficiency. Iterative decoding with hard interference cancellation is used at destination to recover user information. By using orthogonal transmission from sources to avoid their mutual interference, the multi‐antenna relay offers receive space diversity that greatly enhances the decoding performance at the relay. This makes the source‐relay transmission more robust, less sensitive to the source‐relay link SNR, and hence increases the contribution of the relay in cooperative transmission. Simulation results show that the proposed scheme significantly outperforms direct transmission under the same transmit power and bandwidth efficiency. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Optical frequency modulation links: Theory and experiments

In this paper, the first theoretical analysis and experimental realization of an optical frequency modulation coherent detection (FMCD) link working at microwave frequencies is reported. Advantages over conventional optical intensity modulation direct detection (IMDD) links in terms of reduced effects of fiber nonlinearity, facilitation of multichannel operation, and bandwidth/signal-to-noise ratio (SNR) tradeoffs are identified. A detailed theoretical analysis of the SNR of FMCD links is carried out and compared to that for IMDD links. In the experimental FMCD link, a novel source laser tuning technique, based on the quantum confined Stark effect, is used. The experimental results are presented and compared with the predictions of the theoretical analysis.

Pulse-coded multiple access in space optical communications

There is interest in space-based wireless optical networks with nonsynchronous multiple access capability. Since space links are usually power-limited, pulsing is necessary to accomplish the multiple accessing and data transmission. In this paper, a nonsynchronous pulsed multiple-access optical-space system using code sequences for identifying stations is considered. Both OOK and PPM data encoding is considered and the link data rates and bit error probabilities (PE) are examined. It is shown that the achievable data rates are limited by the multiple access coding and the link SNR, while the PE can be either crosstalk or power-limited. It appears that moderate data rates (tens of Mb/s) are feasible with networks of about 5-20 stations even with low-link SNR. >