Multi-hop Relay Research Articles

On Bit Error Probability and Power Optimization in Multihop Millimeter Wave Relay Systems

5G networks are expected to provide gigabit data rate to users via the millimeter-wave (mmWave) communication technology. One of the major problems faced by mmWaves is that they cannot penetrate buildings. In this paper, we utilize multihop relaying to overcome the signal blockage problem in an mmWave band. The multihop relay network comprises a source device, several relay devices, and a destination device and uses device-to-device communication. Relay devices redirect the source signal to avoid the obstacles existing in the propagation environment. Each device amplifies and forwards the signal to the next device, such that a multihop link ensures the connectivity between the source device and the destination device. We consider that the relay devices and the destination device are affected by external interference and investigate the bit error probability (BEP) of this multihop mmWave system. Note that the study of the BEP allows quantifying the quality of communication and identifying the impact of different parameters on the system reliability. In this way, the system parameters, such as the powers allocated to different devices, can be tuned to maximize the link reliability. We derive exact expressions for the BEP of $M$ -ary quadrature amplitude modulation and $M$ -ary phase-shift keying in terms of multivariate Meijer’s G-function. Due to the complicated expression of the exact BEP, a tight lower bound expression for the BEP is derived using a novel Mellin-approach. Moreover, an asymptotic expression for the BEP at high SIR regime is derived and used to determine the diversity and the coding gain of the system. In addition, we optimize the power allocation at different devices subject to a sum power constraint such that the BEP is minimized. Our analysis reveals that optimal power allocation allows achieving more than 3-dB gain compared with the equal power allocation. This paper can serve as a framework for designing and optimizing mmWave multihop relaying systems to ensure link reliability.

Mobility-Aware Caching Scheduling for Fog Computing in mmWave Band

As an extension of cloud computing, fog computing at the edge of networks provides low latency, location awareness, and real-time interactions. At the same time, millimeter wave (mmWave) communications are able to provide directional multi-gigabit transmission rates with large available bandwidth. Based on the user mobile trajectories in a region, several activity hotspots that users pass by frequently can be obtained. By caching popular content at the edge nodes near the hotspots, users can download the cached content directly at a short distance, and the user experience can be significantly improved. Considering multiple hotspots in a region, how to efficiently schedule the transmission for the caching at edge nodes becomes a key problem. In this paper, we focus on the problem of mobility aware transmission scheduling for caching at edge nodes near hotspots, and utilize multi-hop relaying and concurrent transmissions to achieve better performance. After formulating the optimal scheduling problem as a stochastic nonlinear mixed integer program, we propose a mobility aware caching scheduling scheme, called MHRC (Multi-Hop Relaying based Caching), where multi-hop D2D paths are established for edge nodes, and concurrent transmissions are exploited in the scheduling of caching at edge nodes. Extensive performance evaluation demonstrates MHRC achieves more than 1x higher expected cached data amount compared with state-of-the-art schemes.

Analysis of Average Packet Loss Rate in Multi-Hop Broadcast for VANETs

Multi-hop relay can effectively improve the average packet loss rate (PLR) of vehicular ad hoc networks within a particular zone of interest. Challenges arise from analyzing the average PLR affected by distributed relay selections, which depend on the mobility of vehicles, the wireless channel conditions, and media access control (MAC). In this letter, we propose an average PLR analysis model taking into account the above three factors. However, the closed-form expression for the average PLR is intractable mainly due to the multiple integral of the joint distance distribution integrating with the channel conditions and vehicle mobility. An explicit expression for the upper bound of the average PLR is obtained by using Taylor series expansion, Holder's inequality, and the relay probability relaxation, which can facilitate the selection of the parameters at the physical and MAC layers for a better PLR. Simulation results validate our analyses.

A Low-Latency Communication Scheme for Mobile Wireless Sensor Control Systems

Millions of dedicated sensors are deployed in smart cities to enhance quality of urban living. Communication technologies are critical for connecting these sensors and transmitting events to sink. In control systems of mobile wireless sensor networks (MWSNs), mobile nodes are constantly moving to detect events, while static nodes constitute the communication infrastructure for information transmission. Therefore, how to communicate with sink quickly and effectively is an important research issue for control systems of MWSNs. In this paper, a communication scheme named first relay node selection based on fast response and multihop relay transmission with variable duty cycle (FRAVD) is proposed. The scheme can effectively reduce the network delay by combining first relay node selection with node duty cycles setting. In FRAVD scheme, first, for the first relay node selection, we propose a strategy based on fast response, that is, select the first relay node from adjacent nodes in the communication range within the shortest response time, and guarantee that the remaining energy and the distance from sink of the node are better than the average. Then for multihop data transmission of static nodes, variable duty cycle is introduced novelty, which utilizes the residual energy to improve the duty cycle of nodes in far-sink area, because nodes adopt a sleep-wake asynchronous mode, increasing the duty cycle can significantly improve network performance in terms of delays and transmission reliability. Our comprehensive performance analysis has demonstrated that compared with the communication scheme with fixed duty cycle, the FRAVD scheme reduces the network delay by 24.17%, improves the probability of finding first relay node by 17.68%, while also ensuring the network lifetime is not less than the previous researches, and is a relatively efficient low-latency communication scheme.

Performance Analysis of Multihop Relaying Caching for Internet of Things under Nakagami Channels

Performance analysis is studied in this paper for the wireless transmissions in Internet of Things (IoT) system, where both the direct link and the multihop relaying caching wireless transmission from the source node to the destination node are taken into the consideration. The key feature is the Nakagami channels of the wireless channel from the source node to the destination node, which results in the difficulty of the theoretical analysis over the system performance. To tackle this difficulty, the probability distribution function (PDF) of the received signal‐to‐noise ratio (SNR) at the destination node is derived by exploiting the function and integral properties. Then, the outage probability and bit error rate (BER) of the whole wireless IoT system are derived in the analytical expression without any approximation. Numerical simulations demonstrate the accuracy of the derived theoretical analysis for this system.

Real-time web-cast system by multihop WebRTC communications

A software system is developed for casting the screen images and voices from a host PC to the client web browsers on many other PCs in real time. This system is intended to be used in the classrooms. Students have only to bring their own PCs and connect to the teacher's host PC by a web browser via a wireless network to see and listen to the teaching materials presented on the host PC. Then the client web-browsers are organised in the shape of a binary tree along which the video and audio data are relayed in the multihop fashion by the Web Real-Time Communication (WebRTC) protocol. This structure of binary multihop relay is adopted in order not to burden the host PC with communications load. A test has shown that voice and the motion pictures in a rather small size of 320 × 240 pixels on a teacher's PC have been presented at the rate of 5 frames per second without any conceivable delays on the web browsers running on 38 client devices for students under a local WiFi network. To host more client devices, we have to lower the frame rate as slow as the slide show of still pictures.

Sequential Closed-Form Semiblind Receiver for Space-Time Coded Multihop Relaying Systems

In this letter, we present a sequential closed-form semi-blind receiver for a one-way multi-hop amplify-and-forward (AF) relaying system. Assuming Khatri-Rao space-time (KRST) coding at each relay, it is shown that the system with K relays can be modeled by means of a generalized nested PARAFAC model. Decomposing this model into K +1 third-order PARAFAC models, we develop a closed-form semi-blind receiver for jointly estimating the information symbols and the individual channels, at the destination node. Each step consists of a Khatri-Rao factorization. Parameter identifiability conditions are given, and simulation results are provided to illustrate the effectiveness of the proposed semi-blind receiver. Index Terms—Multi-hop relaying, sequential closed-form semi-blind receiver, space time (ST) coding, amplify-and-forward, generalized nested PARAFAC model. I. INTRODUCTION Relay nodes will play an important role in 5G communication systems. In such systems, the high-capacity wireless backhaul offers operators an alternative solution to conventional backhauling using multi-hop short-distance communications [1]–[4]. Tensor decompositions have been widely exploited for point-to-point wireless communication systems. The practical motivation for tensor modeling comes from the fact that one can simultaneously benefit from multiple (more than two) signal diversities, like space, time and frequency diversities, for instance. In the context of cooperative wireless communications, few results have been published on tensor-based receivers, and most of them are limited to a single relay scenario. In previous works [5]–[8], the problem of channel estimation for multiple input multiple output (MIMO) relaying systems was considered under a supervised approach. The works [5]–[7] considered one-way two-hop systems, while [8] addressed two-way MIMO relaying systems. In [9] and [10], three-hop relaying systems were studied. Recent works proposed semi-blind receivers for joint symbol and channel estimation. For instance, one can cite the PARAFAC-PARATUCK [11] and the nested PARAFAC receivers [12], [13]. However, the generalization of tensor-based semi-blind receivers to the multi-hop relaying scenario has not been addressed so far to the best of authors' knowledge.

Energy efficient topology control for multi-hop relay cellular networks based on flow management

The rapid expansion of mobile communication networks has led to a significant increase of energy consumption, and the energy consumption of wireless access networks accounted for nearly 90%. As an important form of the wireless access networks, multi-hop relay networks have been widely deployed in the existing cellular networks. Consequently, improving the energy efficient of multi-hop relay cellular networks is crucial for communication networks. In this paper, we design an energy flow management framework for multi-hop relay cellular networks, which contains routing planning, traffic adjustment and power allocation. In order to reduce the energy consumption and guarantee the system capacity, a heuristic algorithm is designed in this paper, which mixes the ant colony algorithm with convex optimization theory. In order to verify the effect of the proposed algorithm, we make numerical simulation and compare it with other network management strategies, such as ant colony algorithm, shortest path routing strategy and greedy algorithm. Simulation results show that by our algorithm, the energy consumption can be reduced compared with the ant colony algorithm, shortest path and greedy algorithm while ensuring the demand of quality of service (QoS).

Energy efficient constrained shortest path first-based joint resource allocation and route selection for multi-hop CRNs

Cognitive radio networks (CRNs) are expected to improve spectrum utilization efficiently by allowing secondary users (SUs) to opportunistically access the licensed spectrum of primary users (PUs). In CRNs, source and destination SUs may achieve information interaction in an ad hoc manner. In the case that no direct transmission link between the SU transmission pairs is available, multi-hop relay SUs can be applied to forward information for the source and destination SUs, resulting in multi-hop CRNs. In this paper, we consider a multi-hop CRN consisting of multiple PUs, SU transmission pairs and relay SUs. Stressing the importance of transmission hops and the tradeoff between data rate and power consumption, we propose an energy efficient constrained shortest path first (CSPF)-based joint resource allocation and route selection algorithm, which consists of two sub-algorithms, i.e., CSPF-based route selection sub-algorithm and energy efficient resource allocation sub-algorithm. More specifically, we first apply CSPF-based route selection sub-algorithm to obtain the shortest candidate routes (SCRs) between the SU pair under the transmission constraints. Then, an energy efficient resource allocation problem of the SCRs is formulated and solved by applying iterative algorithm and Lagrange dual method. Simulation results demonstrate the effectiveness of the proposed algorithm.

Security-Reliability Analysis of Noma-Based Multi-Hop Relay Networks in Presence of an Active Eavesdropper with Imperfect Eavesdropping CSI

In this paper, we evaluate system performances of a multi-hop relay protocol with presence of an active eavesdropper. In the proposed protocol, a source attempts to transmit its data to a destination with assistance of multiple intermediate relays. From the eavesdropping Channel State Information (CSI) estimated, the source and relays adjust their transmit power so that the eavesdropper cannot overhear the transmitted data. Moreover, to enhance throughput for the proposed system, Non-Orthogonal Multiple Access (NOMA) technique with a simple power allocation is also proposed. We derive exact closed-form expressions of the Outage Probability (OP) and throughput for the data transmission over Rayleigh fading channel. In addition, when the CSI estimation is imperfect, Intercept Probability (IP) at the eavesdropper is derived. Finally, Monte Carlo simulations are presented to verify the theoretical derivations.

Highly Efficient Multi Channel Packet Forwarding with Round Robin Intermittent Periodic Transmit for Multihop Wireless Backhaul Networks.

Round Robin based Intermittent Periodic Transmit (RR-IPT) has been proposed which achieves highly efficient multi-hop relays in multi-hop wireless backhaul networks (MWBN) where relay nodes are 2-dimensionally deployed. This paper newly investigates multi-channel packet scheduling and forwarding scheme for RR-IPT. Downlink traffic is forwarded by RR-IPT via one of the channels, while uplink traffic and part of downlink are accommodated in the other channel. By comparing IPT and carrier sense multiple access with collision avoidance (CSMA/CA) for uplink/downlink packet forwarding channel, IPT is more effective in reducing packet loss rate whereas CSMA/CA is better in terms of system throughput and packet delay improvement.

A multi-hop relay path selection algorithm considering path channel quality and coordinating with bandwidth allocation

A multi-hop relay path selection algorithm considering path channel quality and coordinating with bandwidth allocation

A multi-hop relay path selection algorithm considering path channel quality and coordinating with bandwidth allocation

Many multi-hop relay path selection algorithms were proposed. However, these algorithms do not consider the channel condition of the overall path and coordinate with the bandwidth allocation algorithm. In this paper, we proposed a greedy based multi-hop relay path selection algorithm considering channel quality and available bandwidth of overall path to provide high throughput in varying channel conditions. From the simulation results, our proposed algorithm actually provides higher throughput and outperforms the previous works.

EEECARP

WSN is a promising approach for variety of different real time applications. Different Routing protocols for WSNs are very effective challenge in present days because of scalability, efficient energy utilization and robustness in large number of wireless sensor networks with consists of more number of sensor nodes. LEATCH is a traditional routing protocol for energy optimization in WSNs. However, LEATCH cannot scale performance for large scale wireless sensor networks and difficulty to apply effective utilization of real time wireless sensor networks. So, in this paper the authors propose to develop a novel Energy Efficiency and Event Clustering Adaptive Routing Protocol (EEECARP) for WSN. The main designing feature of their proposed approach is as follows: Energy Efficiency, Dynamic Event Clustering and multi hop relay configuration with residual energy available on relay nodes in wireless sensor networks. The simulation results show that authors' routing protocol achieves convenient and effective better performance in formation of clusters with relay sensor nodes in wireless sensor networks.

Effects of threshold based relay selection algorithms on the performance of an IEEE 802.16j mobile multi-hop relay (MMR) WiMAX network

IEEE 802.16j MMR WiMAX network introduces multi-hop relay architecture, which involves cooperative relay stations focusing on increasing the network throughput and coverage. Relay selection algorithms can be used to choose the optimal relay, which help in reducing the computational complexity during the signal processing operation of the wireless network. In this research work, a conventional Amplify-Forward (AF)/Decode-Forward (DF) assisted multi-relay IEEE 802.16j WiMAX network is considered. The effects of relay selection algorithms on the performance metrics such as Symbol Error Rate (SER) and channel capacity are investigated in detail through simulation-based study. Further, the performance of this network utilizing the proposed relay selection algorithms, namely threshold based max_min and threshold based harmonic mean of SNR, are compared with the existing max_min and harmonic mean of SNR based algorithms. Standard diversity combining techniques such as Maximal Ratio Combining (MRC) and Selection Combining (SC) are used for combining the transmitted signal at the receiver. In addition, the impact of relay locations on the performance metrics are explored. It is observed that both the proposed threshold based max_min and threshold based harmonic mean of SNR based relay selection algorithms outperform the max_min and harmonic mean of SNR based algorithms, as both the SER and channel capacity for the considered multi-relay WiMAX network is improved significantly. Further, this extensive study and analysis will be beneficial for the design of MMR WiMAX networks.

Energy Harvesting Based Multihop Relaying in Cognitive Radio Network

In this paper, a multihop cognitive radio network using a series of multiple decode and forward (DF) energy harvesting relays is proposed to enhance the spectrum utilization and lifetime of the network. A time switching based energy harvesting scheme is considered for the DF relays. An analytical expression has been derived for evaluating the transmission power of the secondary source and secondary relays (SR) as well as SNR at SRs and secondary destination. The corresponding transmission power and signal to noise ratio (SNR) profiles are also analyzed for several numbers of relays under various locations of the primary transmitter (PT). An expression for a critical number of relays, for which the performance of the network is worst, has also been derived. It is seen that upto a critical number of relays the SNR decreases. However the SNR again increases with further increase in number of relays. Further secondary outage probabilities have been compared for several locations of PT. Analytical results following our development are presented and validated by MATLAB based simulation.

Mobile relay deployment in multihop relay networks

In multihop relay networks such as LTE-Advanced and the mobile WiMAX network, subscribers move in and out of the Fixed Relays’ (FRs) coverage in different periods. Frequent handover requests generated by population mobility lead to low data rate and load imbalances among FRs. To fulfill the requirement of subscribers, Mobile Relays (MRs), are considered to patrol FRs to offload their relay task which can improve the efficiency of the access network. In this paper, we define and study the Minimum Mobile Relay Path selection problem (MMRP), whose objective is to deploy minimum MRs to patrol FRs when they are “busy”. First, Markov chains are used to predict FRs’ busy period which is then transformed into a busy period graph. Based on this busy period graph, we propose solutions to different relaying scenarios. Maximum matching and the maximum flow technologies are adopted to find heuristic algorithms for these different scenarios respectively. Theoretical analysis and simulation results show that, compared with traditional search algorithms, solutions based on the maximum matching and the maximum flow technologies have O(n2) complexity, where n is the number of FRs, and they perform better than traditional ways on the number of paths and system overhead. Moreover, the solution using predicted busy periods is more efficient than that when FRs’ busy periods are presupposed.

Performance Analysis of Multihop Relaying Systems in an $\alpha$-Ginibre Field of Interferers

In this paper, we consider multihop relaying systems, where nodes experience cochannel interference and where interferers are randomly distributed. Although modeling the locations of the interferers as a Poisson point process (PPP) allows us to readily characterize the performance of the systems, the PPP may not be suitable in practical scenarios, since the interferers, such as cellular base stations, exhibit repulsion behaviors, and thus, there exists a form of correlation among the interferers. In order to take the correlation into account, we model the spatial distribution of the interferers as an $\alpha$ -Ginibre point process (GPP), which reflects the repulsion among the interferers and includes the PPP as a special case. We first derive a closed-form expression for the Laplace transform of the interference. Then, we analyze the outage probability and the ergodic capacity of the multihop relaying systems by considering two protocols: decode-and-forward (DF) and amplify-and-forward (AF). As the $\alpha$ -GPP contains the PPP as a special case, our analytical results can be seen as a generalization of prior works on the relaying systems with the PPP distributed interferers. From simulation results, we verify the accuracy of our analysis.

A Congestion Aware, Energy Efficient, on Demand Fuzzy Logic Based Clustering Protocol for Multi-hop Wireless Sensor Networks

Node clustering or simply clustering provides an effective way of organizing the network to achieve energy efficiency, efficient distribution of workload, maintain a connected hierarchy and accomplish data aggregation. On the other hand multi-hop communication significantly reduces the energy required for communication and multi-path communication helps in distributing the relay load and it also increases reliability of the network. The proposed methodology in this paper is a combination of these three features. In addition to that, we have used fuzzy logic in cluster head (CH) selection to blend different parameters to select the set of best possible CHs and to handle the uncertainties in parametric quantities. There are five main aspects of the proposed algorithm (a) on demand based clustering (b) fuzzy logic based CH selection (c) dynamic unequal cluster range for CHs’ (d) a cost function based multi-hop relay selections (e) Fibonacci sequence based relay load distribution. The proposed approach creates more balanced cluster by means of fuzzy logic and inequality in cluster range. It saves energy by conducting CH selection on demand basis. Finally, the cost function based multi-hop relay selections along with Fibonacci sequence based relay load distribution create an optimal structure for relaying data.The proposed approach is implemented and compared with the well known approaches like LEACH, ECPF, CHEF and UCR. Simulation results have shown that the proposed approach performs better, in every aspect of network life time and other metrics.

Secure and Scalable Group Rekeying for Mobile Multihop Relay Network

Secure and Scalable Group Rekeying for Mobile Multihop Relay Network