Wireless Relay Networks

An assignment on development of Cellular mobile communication Generations, Namely, From 0 G to 5 G. Including a briefing on GSM, EDGE, AMPS, GPRS, And all others categories related to this field. This is totally a briefing that was just created in 15 min. ;)

This paper offers performance analysis of decodeand-forward protocol employing selection combining (SC) at the destination. For an arbitrary number of relays, BER for M PSK of the system is investigated in both independent identically distributed (i.i.d) and independent but not identically distributed (i.n.d.) Rayleigh fading channels. A variety of simulations are performed and show that they match exactly with analytic ones. In addition, our results also show that the optimum number of relays depend not only on channel conditions (operating SNR) but also on modulation scheme which we exploit.

In recent years, Multiple-Input Multiple-Output
(MIMO) systems have emerged as a most promising technology in these measures. MIMO
communication systems can be defined intuitively [GSS+03, PNG03] by considering that
multiple antennas are used at the transmitting end as well as at the receiving end.

This work is part of our final project study conducted in SPIE Morocco. In witch we develop the techni-cal study of the medium-voltage network, protection plan, lighting, electrical installation, instrumentation,and automation of two new facilities in the mining division of the OCP Khouribga intended for preliminarytreatment and storage of phosphate.
In the average voltage studies, we worked on sizing of cables and overhead transmission lines and thecalculation of short-circuits, and finally the protection plan in which we develop our own calculation notesof the protection settings in MV.
The technical study of indoor lighting and outdoor lighting optimizes the positioning of lights and todeterminate their power consumption, after that we did a technical study of the low voltage electrical instal-lation and sizing of power supplies and the cables in order to determinate the protection equipment settings,that taking into account the standards and regulations.
The final step is the establishment of the functional analysis of the hoppers process to develop the Grafcetsof the control of the two stations

Free Space Optical (FSO) communication technology , also known as Optical Wireless Communications (OWC), has regained a great interest over the last few years. In some cases, FSO is seen as an alternative to existing technologies, such as radio frequency. In other cases, FSO is considered as a strong candidate to complement and integrate with next-generation technologies, such as 5G wireless networks. Accordingly, FSO technology is being widely deployed in various indoor (e.g., data centers), terrestrial (e.g., mobile networks), space (e.g., inter-satellite and deep space communication), and underwater systems (e.g., underwater sensing). As the application portfolio of FSO technology grows, so does the need for a clear classification for FSO link configurations. Most existing surveys and classifications are single-level classifications, and thus not inclusive enough to accommodate recent and emerging changes and developments of different FSO link configurations and systems. In this paper, we propose a multi-level classification framework to classify existing and future indoor, terrestrial, space, underwater, and heterogenous FSO links and systems using common and simple unified notation. We use the proposed classification to review and summarize major experimental work and systems in the area until 2017. Using the proposed classification and survey, we aim to give researchers a jump-start to tap into the growing and expanding realm of the FSO technology in different environments. The proposed classification can also help organize and systematically present the progress in the research on FSO technology. This makes the identification of the market needs for standards an easier task. Moreover, different entities involved in the standardization process including academic, industry, and regulatory organizations can use the proposed classification as a unified language to communicate during the early stages of standard development which require ambiguity-free discussions and exchange of ideas between different standardization entities. We use the proposed classification to review existing standards and recommendations in the field of FSO. It is also envisioned that the proposed classification can be used as a unified framework to define different FSO channel models for simulation tools.

International Journal of Computer Networks & Communications (IJCNC)

(Scopus, ERA Listed)


ISSN 0974 - 9322 (Online); 0975 - 2293 (Print)


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New Issue: January 2020, Volume 12, Number 1 --- Table of Contents

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International Journal of Wireless & Mobile Networks (IJWMN) is a bi monthly open access peer-reviewed journal that publishes articles which contribute new results in all areas of Wireless & Mobile Networks. The journal focuses on all technical and practical aspects of Wireless & Mobile Networks. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on advanced wireless & mobile networking concepts and establishing new collaborations in these areas.

The paper presents a Riverbed simulator implementation with both routing and medium access control (MAC) protocols for mobile ad-hoc network wireless networks with multi-beam smart antennas (MBSAs). As one of the latest promising antenna techniques, MBSAs can achieve concurrent transmissions / receptions in multiple directions/beams. Thus it can significantly improve the network throughput. However, so far there is still no accurate network simulator that can measure the MBSA-based routing/MAC protocol performance. In this paper, we describe the simulation models with the implementation of MBSA antenna model in physical layer, MAC layer, and routing layer protocols, all in Riverbed Modeler. We will compare two routing scenarios, i.e., multi-hop diamond routing scenario and multi-path pipe routing. We will analyze the network performance for those two scenarios and illustrate the advantages of using MBSAs in wireless networks. INDEX TERMS Multi-beam Smart Antennas (MBSAs), Medium Access Control (MAC), Multi-path routing, Riverbed Modeler.

hai teman-teman, modul ini adalah bagian dari tugas sekolah jadi jika teman-teman menemukan nama saya tertera dalam modul saya minta maaf dan modul ini masih banyak kekurangan jadi saya harap teman-teman dapat mengembangkan modul ini, semoga modul ini dapat membantu teman-teman. terima kasih.

Free Space Optical (FSO) communication technology, also known as Optical Wireless Communications (OWC), has regained a great interest over the last few years. In some cases, FSO is seen as an alternative to existing technologies, such as radio frequency. In other cases, FSO is considered as a strong candidate to complement and integrate with next-generation technologies, such as 5G wireless networks. Accordingly, FSO technology is being widely deployed in various indoor (e.g., data centers), terrestrial (e.g., mobile networks), space (e.g., intersatellite and deep space communication), and underwater systems (e.g., underwater sensing). As the application portfolio of FSO technology grows, so does the need for a clear classification for FSO link configurations. Most existing surveys and classifications are single-level classifications, and thus not inclusive enough to accommodate recent and emerging changes and developments of different FSO link configurations and systems. In this paper, we propose a multi-level classification framework to classify existing and future indoor, terrestrial, space, underwater, and heterogenous FSO links and systems using common and simple unified notation. We use the proposed classification to review and summarize major experimental work and systems in the area until 2017. Using the proposed classification and survey, we aim to give researchers a jump-start to tap into the growing and expanding realm of the FSO technology in different environments. The proposed classification can also help organize and systematically present the progress in the research on FSO technology. This makes the identification of the market needs for standards an easier task. Moreover, different entities involved in the standardization process including academic, industry, and regulatory organizations can use the proposed classification as a unified language to communicate during the early stages of standard development which require ambiguity-free discussions and exchange of ideas between different standardization entities. We use the proposed classification to review existing standards and recommendations in the field of FSO. It is also envisioned that the proposed classification can be used as a unified framework to define different FSO channel models for simulation tools.

The new paradigm of cooperative communications is a promising resolution to carry out MIMO technique. In this thesis work, we study the performance of cooperative relay networks in which the transmission from a source to a destination is assisted by one or several relaying nodes employing amplify-and-forward (AF) and decode-and-forward (DF) protocols. The performance of two-way (or bi-directional) AF relay networks, which are proposed to avoid the pre-log factor 1/2 of spectral efficiency, is latter investigated. Specifically, the exact closed-form expressions for symbol error
rate (SER), outage probability, and average sum-rate of bi-directional AF relay systems in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels are derived. Our analyses are verified by comparing with the results from Monte-Carlo simulations.

In this paper, we proposed a novel efficient method of analyzing the ergodic channel capacity of the cooperative amplify-and-forward (CAF) relay system. This is accomplished by employing a very tight approximate moment generating function (MGF) of end-to-end signalto-noise ratio of 2-hop multi-relay system, which is In this paper, we proposed a novel efficient method of analyzing the ergodic channel capacity of the cooperative amplify-andforward (CAF) relay system. This is accomplished by employing a very tight approximate moment applicable to myriad of fading environments including mixed and composite fading channels. Three distinct adaptive source transmission policies were considered in our analysis namely: (i) constant power with optimal rate adaptation (ORA); (ii) optimal joint power and rate adaptation (OPRA); and (iii) fixed rate with truncated channel inversion (TCIFR). The proposed frame work based on the novel approximate MGF method is sufficiently general to encapsulate all types of fading environments (especially for the analysis of the mixed fading case)and provides significant advantage to model wireless system for mixed and composite fading channel. In addition to simplifying computation complexity of ergodic capacity for CAF relaying schemes treated in literature, we also derive closed form expressions for the above three adaptive source transmission policies under Nakagami-m fading with i.n.d statistics. The accuracy of our proposed method has been validated with existing MGF expressions that are readily available for specific fading environments in terms of bounds, and via Monte Carlo simulations.

This paper presents a secure beamforming design
to prevent eavesdropping on multiple-input multiple-output
(MIMO) device-to-device (D2D) communication. The devices
communicate via a trusted relay which performs physical layer
network coding (PNC), and multiple eavesdroppers are trying
to intercept the device information. The beamforming design is
based on minimizing mean square error of the D2D communication
while employing signal-to-interference-plus-noise ratio
(SINR) threshold constraints to prevent possible eavesdropping.
The channel state information of the device-to-eavesdropper and
relay-to-eavesdropper channels is imperfect at the devices and
relay. The channel estimation errors are assumed with Gaussian
Markov uncertainty model. Consequently, robust optimization
problems are formulated considering the multiple access and
broadcasting stages of the D2D communication. These problems
are non-convex, and two algorithms are proposed to solve them.
In the numerical analysis, we discuss the convergence of the
proposed algorithms, impact of the number of eavesdroppers on
the performance, and the SINR distributions at eavesdroppers.

Flooding attack is a network attack that sends a large amount of traffic to the victim networks or services to cause denial-of-service. In Software-Defined Networking (SDN) environment, this attack might not only breach the hosts and services but also the SDN controller. Besides, it will also cause a disconnection of links between the controller and the switches. Thus, an effective detection and mitigation technique of
flooding attacks is required. Statistical analysis techniques are widely used for the detection and mitigation of flooding attacks. However, the effectiveness of these techniques strongly depends on the defined threshold. Defining the static threshold is a tedious job and most of the time produces a high false positive alarm .In this paper, we proposed the dynamic threshold which is calculated using modified adaptive
threshold algorithm (MATA). The original ATA is based on the Exponential Weighted Moving Average (EWMA) formula which produces the high number of false alarms. To reduce the false alarms, the alarm signal will only be generated after a minimum number of consecutive violations of the threshold. This, however, has increased the false negative rate when the network is under attack. In order to reduce this
false negative rate, MATA adapted the baseline traffic info of the network infrastructure. The comparative analysis of MATA and ATA are performed through the measurement of false negative rate, and accuracy of detection rate. Our experimental results show that MATA is able to reduce false negative rates up to 17.74% and increase the detection accuracy of 16.11%over the various types of flooding attacks at the transport layer.

"Cooperative communication can improve the performance of cellular mobile networks. The optimization techniques based on
duality theory, decomposition and subgradient method were applied for such wireless cellular cooperative systems. It was
shown that the joint optimization and resource allocation problem can be solved efficiently within a network utility maximization
framework. A concept of proportional fairness was used to achieve fair distribution of quality of service among users. Simulation
results confirm the validity of the theoretical work."

— In this paper, we provide a global framework analysis of a dual-hop mixed radio frequency (RF)/free space optical (FSO) system with multiple branches/relays wherein the first and second hops, respectively, consist of RF and FSO channels. To cover various cases of fading, we propose generalized channels' models for RF and FSO links that follow the Nakagami-m and the double generalized gamma distributions, respectively. Moreover, we suggest channel state information (CSI)-assisted relaying or variable relaying gain based amplifiy-and-forward amplification. Partial relay selection with outdated CSI is assumed as a relay selection protocol based on the knowledge of the RF CSI. In order to derive the end-to-end signal-to-interference-plus-noise ratio statistics, such as the cumulative distribution function, the probability density function, the higher order moments, the amount of fading and the moment generating function, the numerical values of the fading severity parameters are only valid for integer values. Based on these statistics, we derive closed-forms of the outage probability, the bit error probability, the ergodic capacity, and the outage capacity in terms of Meijer-G, univariate, bivariate, and trivariate Fox-H functions. Capitalizing on these expressions, we derive the asymptotic high SNR to unpack valuable engineering insights of the system performance. Monte Carlo simulation is used to confirm the analytical expressions. Index Terms— Nakagami-m, double generalized gamma, co-channel interference, outdated CSI, CSI-assisted relaying, multiple branchs/relays.

We analyze the performance of dual-hop multiple-input multiple-output (MIMO)
amplify-and-forward (AF) relay systems by considering the source-to-relay and
relay-to-destination channels undergo Rayleigh and Rician fading, respectively.
Several MIMO techniques and practical relaying scenarios are considered to investigate
the effect of such asymmetric fading on the MIMO AF relaying systems.

Sekitar akhir tahun 1995, saya dan istri saya sering dibuat pusing karena hujan yang turun hampir tiap hari. Bukan hanya pusing karena kehujanan saja, melainkan pusing karena cucian yang tidak kunjung kering. Maklum, kalau sedang musim hujan matahari sering hanya nongol 1-2 jam saja dalam sehari. Yang lebih bikin pusing lagi, dalam cuaca seperti itu semua orang

Considering a symmetric Gaussian multi-way relay channel (MWRC) with K users, this work compares two transmission strategies, namely one-way relaying (OWR) and multi-way relaying (MWR), in terms of their achievable rates. While in OWR, only one user acts as data source at each time and transmits in the uplink channel access, users can make simultaneous transmissions in MWR. First, we prove that for MWR, lattice-based relaying ensures a gap less than 1 2(K−1) bit from the capacity upper bound while MWR based on decode-and-forward (DF) or amplify-and-forward (AF) is unable to guarantees this rate gap. For DF and AF, we identify situations where they also have a rate gap less than 1 2(K−1) bit. Later, we show that although MWR has higher relaying complexity, surprisingly, it can be outperformed by OWR depending on K and the system SNR. Summarily speaking, for large K and small users' transmit power, OWR usually provides higher rates than MWR.

Distributed Information SHaring (DISH) is a new cooperative approach to designing multichannel MAC protocols. It aids nodes in their decision making processes by compensating for their missing information via information sharing through neighboring nodes. This approach was recently shown to significantly boost the throughput of multichannel MAC protocols. However, a critical issue for ad hoc communication devices, viz. energy efficiency, has yet to be addressed. In this paper, we address this issue by developing simple solutions that reduce the energy consumption without compromising the throughput performance and meanwhile maximize cost efficiency. We propose two energy-efficient strategies: in-situ energy conscious DISH, which uses existing nodes only, and altruistic DISH, which requires additional nodes called altruists. We compare five protocols with respect to these strategies and identify altruistic DISH to be the right choice in general: it 1) conserves 40-80 percent of energy, 2) maintains the throughput advantage, and 3) more than doubles the cost efficiency compared to protocols without this strategy. On the other hand, our study also shows that in-situ energy conscious DISH is suitable only in certain limited scenarios.

In the last decade, there has been a great technological advance in the infrastructure of mobile technologies. The increase in the use of wireless local area networks and the use of satellite services are also noticed. The high utilization rate of mobile devices for various purposes makes clear the need to track wireless networks to ensure the integrity and confidentiality of the information transmitted. Therefore, it is necessary to quickly and efficiently identify the normal and abnormal traffic of such networks, so that administrators can take action. This work aims to analyze classification techniques in relation to data from Wireless Networks, using some classes of anomalies pre-established according to some defined criteria of the MAC layer. For data analysis, WEKA Data mining software (Waikato Environment for Knowledge Analysis) is used. The classification algorithms present a success rate in the classification of viable data, being indicated in the use of intrusion detection systems for wireless networks.

Optimal power allocation in a multi-hop cognitive radio network is investigated. Information transmitted from the source passes through several wireless relay nodes before reaching the destination. At each hop, the received signal is decoded, re-encoded and retransmitted to the following node. Transmissions at every hop are overheard by nearby nodes and therefore cause interference. We study optimal power allocation strategies that maximize the end-to-end throughput of the network under the constraint of strictly limited interference to external users. We show that for networks that can be modeled as a line topology the optimal solution is achieved when the capacities of every intermediate link are equal and the interference power constraint is satisfied with equality. High- and low-SNR approximations that simplify the problem of finding the optimal power allocation are presented as well. The numerical results show good performance compared to schemes with equal power allocation.

Access link can often be the bottleneck for application performance. In this paper, we propose to augment wired connections using cellular ones, that we term "3G onloading (3GOL)". 3GOL utilizes available mobile devices and alreadypaid-for data volumes to augment and improve performance of applications on wired network. We motivate 3GOL by understanding bottlenecks present in the wired and the cellular networks. In order to understand the potential benefits of 3GOL, we conduct active experiments using mobile devices. We show that capacity gains can scale linearly with the number of devices on the downlink while also seeing improvements on the uplink. Using real traces we show how video on demand can benefit with 3GOL, even when volume caps are in place. We design 3GOL as an over the top service, and highlight research challenges.

International Journal of Wireless Networks Systems (IJWNS)is a bi monthly open access peer-reviewed journal that publishes articles which contribute new results in all areas of Wireless & Mobile Networks. The journal focuses on all technical and practical aspects of Wireless Networks Systems .

In this paper, we have proposed a Relay based Improved Throughput and Energy-efficient Multi-hop Routing Protocol (Rb-IEMRP) for the Intra Wireless Body Sensor Network (Intra-WBSN). Moreover, mathematical analysis has been presented, to calculate the minimum number of relay nodes require to be deployed corresponding to the bio-sensor nodes in Intra-WBSN. Normal sensing data from bio-sensor nodes forwarded to BNC through relay nodes while emergency data is directly transmitted to BNC. Relays nodes are placed in the patients' cloth. It can be easily replaced or recharged that facilitates effective health monitoring. The proposed routing protocol has achieved better network stability, network lifetime, energy efficiency and throughput as compared to Stable Increased Throughput Multi-Hop Protocol for Link Efficiency in Wireless Body Area Networks (SIMPLE) and Reliable Energy Efficient Critical Data Routing in Wireless Body Area Networks (REEC) routing protocols. It has been validated through simulation results. KEYWORDS Intra wireless body sensor network (Intra-WBSN), Body node coordinator (BNC), Relay, Wireless body sensor network (WBSN), Energy efficiency.

Broadcasting has a main importance in Wireless Sensor Networks (WSNs). Effectively, the sink node has
to collect periodically, data from the environment supervised by sensors. To perform this operation, it
sends requests to all nodes. Furthermore, WSNs have a dynamic behaviour due to their evolution. At any
time, a node can be retrieved from the network due to an exhausting energy or a node problem. In fact,
WSNs are prone to failure such as software or hardware malfunctioning, exhaustion of energy,
wireless interference and environmental hazards. Thus, an appropriate broadcasting method should
take into consideration this aspect and uses the less possible amount of energy to accomplish the task. In
this paper, a robust tree-based scheme is proposed which is called Robust Tree Broadcasting (RTB). The
new scheme has a load-balanced behaviour which induces an efficient use of energy. In addition, RTB
has a high-quality fault tolerant performance.

The increase of cheaper, smaller and more powerful mobile devices have made wireless Ad Hoc networks [4, 5] to become one of the fastest growing areas of research. This new type of self-deploying network may combine wireless communication with high degree node mobility. Unlike conventional wired networks they have no fixed infrastructure. This flexibility makes them attractive for many applications for a situation where either supporting structure is unavailable or deployment is unfeasible such as military networks and disaster recovery operationsThe adhoc self-organisation also makes them suitable for virtual conferences, where setting up a traditional network infrastructure is a time consuming high-cost task.

IEEE 802.15.4 refers to a standard meant for short range wireless sensor networks (WSNs). Recently, the standard has gained huge popularity due to its simplicity, scalability, and low power consumption. In this paper, we investigate the energy efficiency of relay assisted dual hop communication between two 802.15.4 compliant wireless nodes. Novel energy consumption models for both amplify-and-forward (AF) and decode-andforward (DF) selective relaying protocols have been formulated and energy efficiency of these two protocols have been assessed by comparing the respective energy requirement per successful bit transmission. Small scale fading introduces outage during transmission over 802.15.4 links. The results show that although under moderate to high channel outage probability, DF relaying offers better energy efficiency than AF relays, when the outage is low, their performances become identical. Next, variation of energy consumption with data payload size is elaborated for both DF and AF relays. It was found that, under moderate outage, there exists an optimum value for the payload size where energy saving is maximum. For similar channel conditions, the optimum payload size is more for DF relays. When the outage value is very high energy consumption increases exponentially with payload size. The trend reverses when the outage is low.

In this paper, we study an amplify-and-forward OFDM-based wireless relay network and provide an exact analysis of the system achievable average throughput and probability of outage. It is assumed that the users transmits their data over a Rayleigh fading channel. Further, to increase the system throughput and use the channel more efficiently, adaptive modulation is applied on each subcarrier and the relaying strategy is selective OFDMA. Our analysis shows that how the system performance enhances by using selective OFDMA relaying scheme in terms of both average throughput and probability of outage. Simulation results verifies the accuracy of our proposed analysis.

Massive multiple-input multiple-output (MIMO) avails of simple transceiver design which can tackle many drawbacks of relay systems in terms of complicated signal processing, latency, and noise amplification. However, the cost and circuit complexity of having one radio frequency (RF) chain dedicated to each antenna element are prohibitive in practice. In this paper, we address this critical issue in amplify-and-forward (AF) relay systems using a hybrid analog and digital (A/D) transceiver structure. More specifically, leveraging the channel long-term properties, we design the analog beamformer which aims to minimize the channel estimation error and remain invariant over a long timescale. Then, the beamforming is completed by simple digital signal processing, i.e., maximum ratio combining/maximum ratio transmission (MRC/MRT) or zero-forcing (ZF) in the baseband domain. We present analytical bounds on the achievable spectral efficiency taking into account the spatial correlation and imperfect channel state information at the relay station. Our analytical results reveal that the hybrid A/D structure with ZF digital processor exploits spatial correlation and offers a higher spectral efficiency compared to the hybrid A/D structure with MRC/MRT scheme. Our numerical results showcase that the hybrid A/D beamforming design captures nearly 95% of the spectral efficiency of a fully digital AF relaying topology even by removing half of the RF chains. It is also shown that the hybrid A/D structure is robust to coarse quantization, and even with 2-bit resolution, the system can achieve more than 93% of the spectral efficiency offered by the same hybrid A/D topology with infinite resolution phase shifters.

Energy efficiency has become an encouragement, and more than this, a requisite for the design of next-generation wireless communications standards. In current work, a dual-hop cognitive (secondary) relaying system is considered, incorporating multiple amplify-and-forward relays, a rather cost-effective solution. First, the secondary relays sense the wireless channel, scanning for a primary network activity, and then convey their reports to a secondary base station (SBS). Afterwards, the SBS, based on these reports and its own estimation, decides cooperatively the presence of primary transmission or not. In the former scenario, all the secondary nodes start to harvest energy from the transmission of primary node(s). In the latter scenario, the system initiates secondary communication via a best relay selection policy. Performance evaluation of this system is thoroughly investigated, by assuming realistic channel conditions, i.e., non-identical link-distances, Rayleigh fading, and outdated channel estimation. The detection and outage probabilities as well as the average harvested energy are derived as new closed-form expressions. In addition, an energy efficiency optimization problem is analytically formulated and solved, while a necessary condition in terms of power consumption minimization for each secondary each node is presented. From a green communications standpoint, it turns out that energy harvesting greatly enhances the resources of secondary nodes, especially when primary activity is densely present.

Although relaying can be very beneficial for wireless systems, understanding which relaying schemes can achieve specific performance objectives under realistic fading is crucial. In this paper we present a general framework for modeling and evaluating the performance of dual-hop decode-and-forward (DF) relaying schemes over independent and not necessarily identically distributed (INID) Nakagami-m fading channels. We obtain closed-form expressions for the statistics of the instantaneous output signal-to-noise ratio of repetitive transmission with selection diversity. Furthermore, we present a unified statistical overview of other three significant relaying schemes with DF, one based on repetitive transmission with maximal-ratio diversity and the other two based on relay selection (RS). To compare the considered schemes, we present closed-form and analytical expressions for the outage probability and the average symbol error probability under various modulation methods, respectively. Importantly, it is shown that when the channel state information for RS is perfect, RS-based schemes always outperform repetitive ones. Furthermore, when the direct link between the source and the destination nodes is sufficiently strong, relaying may not result in any gains, and it should be switched off.

We consider a spectrum sharing scenario where a secondary transmitter (ST) communicates with its destination via a decode-and-forward secondary relay (SR) in the presence of interference from multiple primary transmitters. The SR harvests energy from received radio-frequency signals that include primary interference and uses it to forward the information to the secondary destination. The relay adopts a time switching policy that switches between energy harvesting and information decoding over the time. Under the primary outage constraints and the peak power constraints at both ST and SR, to determine the average secondary throughput, we derive exact analytical expressions for the secondary outage probability and the ergodic capacity, which characterize the delay-limited and the delay-tolerant transmissions, respectively. We also investigate the effects of the number of primary transceivers and the peak power constraints on the optimal energy harvesting time that maximizes the secondary throughput. By utilizing the primary interference as an energy source, the secondary network achieves a better throughput performance compared to the case where the primary interference is ignored for energy harvesting purpose. Finally, we consider a case where ST also harvests energy from primary transmissions and compare its throughput performance with that of the non-energy harvesting ST case.

— This paper investigates the effectiveness of a cross-layer design that combines adaptive modulation (AM) at the physical layer with an adaptive truncated automatic repeat request (ARQ) protocol at the data link layer to maximize the throughput of cooperative amplify-and-forward (CAF) relay networks under prescribed delay and/or error performance constraints. A by-product of our proposed analytical framework, that involves evaluation of the marginal moment generating function (MGF) of the end-to-end signal-to-noise ratio (SNR), for computing the average throughput and average packet error rate performance metrics is the unification and generalization of existing studies on cross-layer combining of AM and truncated ARQ for non-cooperative diversity systems to generalized fading channels. Our analytical methodology is motivated by the fact that the MGF of end-to-end SNR for multi-relay CAF networks is either available in the research literature (for certain fading environments) or it can be computed much more conveniently than its PDF, while the desired marginal MGF can be evaluated efficiently using a multi-precision Laplace inversion formula of an auxiliary MGF function. The efficacy of an adaptive R max (maximum retransmission limit) strategy over the classical fixed R max scheme is also examined. Index Terms — adaptive modulation, adaptive ARQ, cooperative diversity, cross-layer PHY/MAC design I. MOTIVATION It is well-known that link adaptation techniques (e.g., adaptive modulation/coding) could dramatically enhance the spectral utilization efficiency of wireless networks that employ " fixed-transmission " methods. But to improve the transmission reliability/robustness at the physical (PHY) layer, one has to either increase the transmit power (thereby, decreasing the battery-life) or reduce the transmission rate (e.g., by selecting a smaller constellation size or decreasing the code rate of forward error correction coding). Moreover, spatial/polarization diversity solutions at the PHY layer (by packing multiple antenna elements at the transmitter and/or receiver) may not be practically feasible on small-sized handheld portable devices or sensor nodes. An alternative way to mitigate the deleterious effects of multipath fading is to exploit " diversity " mechanisms at higher layers of the protocol stack. For instance, ARQ is an effective strategy to achieve a high reliability of packet transmissions at the data link layer (especially in slowly time varying channels) and unlike FEC, the redundancy (packet retransmissions) are only introduced when necessary. Similarly, the number of collaborating nodes in a CAF network (i.e., distributed spatial diversity order) could be increased to satisfy the prescribed average packet error rate constraint (but the reliability improvement is attained at the expense of the network capacity owing to the half-duplex operation of CAF networks, although this technique could overcome the practical implementation issue of packing multiple antenna elements on small-sized sensor nodes). Instead of considering AM at the PHY layer, ARQ at the data link layer, and cooperative diversity at the network layer separately, in this article we pursue a cross-layer design that combines these three layers judiciously to maximize the spectral efficiency or throughput subject to delay and/or error performance constraints. Cross-layer design breaks away from traditional network design where each layer of the protocol stack is optimized and operates independently. In particular, we exploit the channel knowledge at transmitter and explore the potential synergies between different protocol layers to maximize the end-to-end throughput while satisfying the prescribed delay and average packet error rate (APER) constraints. For instance, by achieving a higher packet success probability with cooperative diversity and ARQ, the stringent error control requirement is alleviated for the AM at the PHY layer. This enables a considerable spectral efficiency gain especially at low mean SNR values. Given the maximum allowable number of retransmissions R max (that depends on the delay constraint) in a CAF relay network, we design AM transmissions that guarantee the required APER performance. The benefits of adapting R max and the number of cooperating relay nodes are also investigated. Literature Review/Prior Work While the literature on performance analysis of non-adaptive (i.e., fixed-rate and/or fixed-power) cooperative diversity systems and adaptive transmission techniques for non-cooperative wireless networks are quite extensive that span over four decades, most prior works have only aimed to improve the link layer performance, and the art of adaptive link layer for cooperative wireless networks especially in a cross-layer design framework is still in its infancy. For instance, in [1]-[3] (and references therein), the authors have studied extensively the design and implementation of AM and coding at the PHY layer, wherein the transmission rates are matched to the time-varying channel conditions in a non-cooperative wireless system. Ref. [4] examines the efficacy of a truncated ARQ protocol for a non-cooperative system with fixed modulation. Ref. [5]-[7] have considered AM and/or optimal power allocation among collaborating nodes in cooperative relay networks. Ref. [8] studied the efficacy of cross-layer combining of ARQ and AM for non-cooperative diversity systems in a Nakagami-m fading environment.

In this paper, opportunistic cooperative amplify-and-forward networks in conjunction with three different adaptive policies, namely optimal simultaneous power and rate adaptation (OPRA), constant power with optimal rate adaptation (OPA) and truncated channel inversion with fixed rate (TIFR), are investigated and compared in terms of Rayleigh channel capacity where the source adapts its rate and/or power level according to channel conditions while the best relay simply amplifies and then forwards the received signals. Furthermore, the effect of diversity combining on the network is studied by investigating two cases of maximal ratio combining (MRC) and selection combining (SC) equipped at the destination. To this end, the mathematically tractable form of the upper and lower bound of the end-to-end effective signal-to-noise ratio (SNR) is provided and then used to derive the closed-form expression of the Shannon capacity. Our results are verified through comparison with Monte Carlo simulations in some representative scenarios where we also illustrate that, among them, for an arbitrary number of cooperative relays, OPRA slightly outperforms ORA, which, in turn, outperforms TIFR.

This paper investigates optimal relay selection schemes for orthogonal space-time block coded multiple-input multiple-output system with non-coherent amplify-and-forward relays, where channel state information is not available at the source and relays. The source-relay and relay-destination channels undergo Rayleigh and Rician fading, respectively. Two possible relay selection schemes are proposed, and both are statistically characterised by deriving exact closed form expression for the cumulative distribution function and probability density function of the instantaneous signal-to-noise ratio (SNR) at the destination. In the first relay selection method, maximizing instantaneous SNR at the destination is considered to select the best relay. In the second scheme, maximizing relay-destination channel is considered. The derived statistical results are used to analyse the performance of the system with outage probability, average bit error rate and ergodic capacity. Finally, we compare both relay selection schemes with respect to the relay pool size and Rician factor.

In this paper we study the end-to-end outage performance of multi-hop cooperative communication systems employing amplify and forward (AaF) relaying under Rayleigh, Nakagami, Rician and Weibull fading channels. The outage probability performances of multi-hop systems with fixed gain and variable gain relays is compared. The outage probability for multi-hop systems under Rayleigh, Nakagami and Weibull fading models can be determined only by combining analytical results with numerical integration techniques. We show that fixed gain system has a better outage performance compared to the variable gain for all fading scenarios. This performance gap increases by increasing the number of hops.

International Journal of Wireless Networks Systems (IJWNS)is a bi monthly open access peer-reviewed journal that publishes articles which contribute new results in all areas of Wireless & Mobile Networks. The journal focuses on all technical and practical aspects of Wireless Networks Systems .

An optimal logical topology of a wireless sensor network (WSN) facilitates the deployed sensor nodes to
communicate with each other with little overheads, lowers energy consumption, lengthens lifetime of the
network, provides scalability, increases reliability, and reduces latency. Designing an optimal logical
topology for a WSN thus needs to consider numerous factors. Chain oriented topologies have been found
to offer a number of improvements in energy consumptions, lifetime, and load balancing than other
topologies of WSNs. However, they usually suffer from latency, scalability, reliability and interference
problems. In this paper, we present a chain oriented logical topology, which offers solutions to those
problems. The proposed topology is designed such that it retains the advantages of the chain oriented
topologies, and at the same time, overcomes the problems of the chain oriented topology such as latency,
scalability, and data reliability. The proposed topology provides a communication abstraction, which can
be easily used to devise a range of application protocols. Moreover, the logical topology offers node
management, resource management, and other services. The performance of the proposed topology is
compared with other topologies in respect to total energy consumption and lifetime of the network.