How to prolong network lifetime has become an important issue in the design of large scale wireless sensor networks (WSNs). In this paper, a novel power saving scheme for conventional WSNs via simultaneous wireless information and power transfer (SWIPT) based relays is proposed. Unlike conventional relays based communications need extra energy supply for data forwarding, the relay applied in this paper works in an energy-free manner with the support of SWIPT. The power saving model with both power splitting (PS) and time switching (TS) based SWIPT are proposed. Then, we formulate the joint power allocation and splitting problems of SWIPT relay assisted WSNs as non-convex constrained optimization problems. Since the formulated problems are non-convex, semi-positive definite programming (SDP) algorithms are proposed to find the joint optimization on power allocation and splitting with low complexity. The simulation results show that the PS model has more advantages than the traditional direct communication model in long distance transmission. Under the same information receiving strategy, the PS model outperforms the TS model.
The delay-locked loop and other tracking systems derived from it are inadequate for PN code tracking in a frequency selective environment. In this paper a PN code tracking system for frequency selective fading channels is presented. It is shown that the extended Kalman filter, aided by a RAKE receiver, is well suited to estimating the PN code delay after the quadrature down-converted received signal has been pre-processed by early-late structures, similar to the delay-locked loop but excluding any output squaring. The performance of a practical implementation of the tracking system is evaluated using computer simulation. The results show that the system performs well in practice and also highlights the advantages of using a RAKE receiver in frequency selective environments.
Diffusion-based molecular communication (DMC) is a promising technique for nanonetworks. The main objective of this paper is to evaluate the error performance of DMC employing pulse-based modulation scheme. We derive closed-form expressions for error probability using energy detection and amplitude detection techniques. The error performance model accounts for diffusion noise and intersymbol interference (ISI) effects. We compare the performance of both detection techniques along with investigating the effect of different parameters on error performance. We also evaluate the channel capacity of pulse modulated DMC.
In this study, the authors focus on energy-efficient routing in wireless ad hoc and mesh networks. Since the existing energy-efficient routing algorithms are fixed and unaware of the channel fading dynamics, they may be suitable if the antennas at network nodes are situated in very high altitudes and have highly directive links. Although, some physical experimental results suggest that even in such scenarios the effect of fading may not be negligible. Particularly in urban areas, the impact of fading cannot be ignored. Thus, when deployed in real world scenarios, current energy-efficient routing algorithms suffer from severe performance degradation in terms of power consumption. In this study, the authors first introduce fading aware decision metrics that help the current node select the optimal next hop destination. Then, using these metrics, the authors propose a power saving routing (PSR) algorithm that takes into account the multipath fading effect. The algorithm is optimised based on the location knowledge of the nodes and the localised channel condition of each node. Simulation results confirm that the proposed algorithm outperforms the existing well-known PSR algorithm.
Evaluates four handoff priority-oriented channel allocation schemes. These give priority to handoff calls by reserving channels exclusively for handoff calls. The measurement-based handover channel adaptive reassignment scheme (MHAR-A) exclusively uses reserved handover channels for newly originated calls if a certain criterion is satisfied. All four schemes studied differ from the conventional guard channel-based handover priority-oriented channel allocation scheme. To study the schemes, a personal communication network (PCN) based on city street microcells is considered. A teletraffic simulation model accommodating a fast moving vehicle is developed, and the performance parameters are obtained. The performances of all four schemes are compared with the nonpriority scheme and the conventional guard channel-based handover priority-oriented channel allocation scheme. It was found that some of the channel allocation algorithms studied improved the teletraffic capacity over the nonpriority and the conventional guard case. Also, the probability of new call blocking and carried traffic was improved for three of the schemes when compared to the conventional guard scheme. The MHAR-A scheme did not perform up to expectation. Nevertheless, it can be used to finely control the communication service quality equivalent to the control obtained by varying the number of handoff channels in a fraction of one. Increasing the number of reserved handover channels in fraction of one can never be achieved in the conventional guard channel-based handover priority-oriented channel allocation scheme.
An open problem for quality of service routing management is the use of inaccurate metric information. Due to the periodic link-state updates, the router always contains out-of-date information. This paper proposes a novel framework for routing management with inaccurate information. We introduce fuzzy metric representation and the concept of non-dominance or Pareto-optimal fuzzy shortest path routing into our framework. The term fuzzy shortest path routing used here is distinct from the classic sense of fuzzy rule controlled routing. We map the crisp link-state information to a new plane by fuzzification factor, and use fuzzy non-dominated multipath routing algorithm for path selection in order to achieve a better network usage. Under our framework, a network administrator can easily switch between fuzzy or non-fuzzy routing. We will discuss and investigate how this framework could be merged with the current network infrastructure to support better QoS for emerging services and applications. A case study is shown in the paper, and simulation results are also included to validate the network preference enhancement under our framework.
As a new way to design, deploy, and manage network services, network functions virtualization (NFV) decouples the network functions, from one or more physical network infrastructures and black boxes so they can run in software. It therefore comes as no surprise that NFV originated from service providers, who were looking to improve the deployment of new network services to support their revenue and growth objectives. Within the NFV ecosystem, high availability, and low latency are one of the key quality of service (QoS) benefits that service providers can expect from the 5G Cloud and the NFV networks to make delay-critical services such as remote surgery a reality. Therefore, network services should be placed, chained, and routed through the network considering users/tenants stringent QoS and service-level agreement requirements. To this end, routing and placement optimization plays a major role in improving network performance and the overall network cost. In this paper, we study the problem of virtual network functions (VNFs) placement and routing across the physical hosts to minimize overall latency defined as the queuing delay within the edge clouds and in network links. In that respect, this paper takes a holistic view by considering not only VNFs chaining and placement problem but also considering the flows routing aspect since these two problems are inter-related and have a major impact on network latency.
Mobile Internet protocol version 6 (MIPv6) [1] is a proposal for handling routing of IPv6 packets to mobile nodes that have moved away from their home network. We have studied the impact of the basic functionalities of MIPv6 on the performance of TCP when a mobile node (MN) moves between networks. The experiments carried involve a real internetwork connected to the experimental wide area IPv6 backbone and the mobile IPv6 software provided by "Kame" [2].
Cooperative routing and spectrum aggregation are two promising techniques for Cognitive Radio Ad-Hoc Networks (CRAHNs). In this paper, we propose a spectrum aggregation-based cooperative routing protocol, termed as SACRP, for CRAHNs. To the best of our knowledge, this is the first contribution on spectrum aggregation-based cooperative routing for CRAHNs. The primary objective of SACRP is to provide higher energy efficiency, improve throughput, and reduce network delay for CRAHNs. In this regard, we design the MAC and Physical (PHY) layer, and proposed different spectrum aggregation algorithms for cognitive radio (CR) users. We propose two different classes of routing protocols; Class A for achieving higher energy efficiency and throughput, and Class B for reducing end-to-end latency. Based on stochastic geometry approach, we build a comprehensive analytical model for the proposed protocol. Besides, the proposed protocol is compared with the state of the art cooperative and non-cooperative routing algorithms with spectrum aggregation. Performance evaluation demonstrates the effectiveness of SACRP in terms of energy efficiency, throughput, and end-to-end delay.
A novel type of coupled line structure has been used on a GaAs monolithic microwave integrated circuit to realise a 90° coupler operating over 2 to 10 GHz. The multilayer nature of the GaAs IC has been used to realise quasiplanar broadside coupled lines. The coupler has been folded to make it small and measures only 1.0×0.8 mm.
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