Multi-hop routing with cooperative transmission: a cross-layer approach

Cooperative diversity techniques have received a lot of attention recently due to their ability to provide spatial diversity in fading wireless environment without the requirement of implementing multiple antenna on the same device. It increases link reliability, provides higher capacity, reduces transmit power, and extends transmission range for the same level of performance and modulation rate. In this paper, we study the achievable gain of cooperative communications from a wireless cross-layer point of view in multi hop networks. We propose two routing algorithms applicable for wireless ad hoc networks. First, we propose an edge node based on a greedy cooperative routing (ENBGCR) algorithm, where we modify the geographic routing algorithm to incorporate the cooperative transmission and extend the coverage range of the nodes. The main objective of ENBGCR algorithm is to minimize the number of hops that messages transverse to reach their destination. Then the energy-efficient cooperative routing algorithm is proposed to minimize the end-to-end total transmission power subject to end-to-end target data rate. Simulation results for both algorithms show that the proposed strategies have great improvement in terms of delay and power saving respectively for the same quality of service requirement as compared to traditional algorithms.     

大规模输电线路状态监测传感器网络的周期性低功耗通信技术方案

为了实现输电线路监测的功耗低、寿命长、绿色发展的目的，提出大规模输电线路状态监测传感器网络周期性低功耗通信技术方案。依据网络中传感器网络组网特征以及节点运行状态转换特点，设置睡眠定时器，以周期性运行方式使传感器网络通信节点在初始化、睡眠、激活状态间转换，通信节点在输电线路状态监测数据无传递需求时进入睡眠状态，节省通信功耗；传感器网络汇聚（sink）节点利用梯度创建上行路由，通过源路由的方式创建下行路由，以跳数和剩余能量为依据进行上、下行路由数据分组传递，降低节点功耗，延长通信运行时间。实验显示，大规模输电线路状态监测传感器网络应用该技术方案后，通信功耗明显降低，运行时间明显延长，且不会影响监测传感器网络的数据传输性能，延长了监测传感器网络的使用寿命。     

Low Complexity Modified Viterbi Decoder with Convolution Codes for Power Efficient Wireless Communication

To attain high quality of service (QoS) with efficient power consumption with minimum delay through Wireless Local Area Network (WLAN) through mesh network is an important research area. But the existing real-time routing system involves multiple hops with time varying mobility channels for fastest data propagation is greatly degraded with power utilization factor through congestion traffic queue. Required allocation and resource management through desired access points plays vital roles in which multiple hops demands delay rates by interconnected data nodes. In order to achieve high throughput with minimum delay the QoS in real-time data communication have to be concentrated by using Viterbi decoder with convolution codes. By undertaking IEEE 802.11 WLAN physical layers afford multiple transmission rates by engaging various modulations and channel coding schemes, major point arises to pinpoint the desired transmission rate to enhance the performance. Because each node exhibits different dynamic characteristics based on the token rings passed from the server to the end links. In order to validate the real-time traffic with power consumption and average delay communication, an improved Viterbi decoder is designed with convolution codes to determine accurate channel estimation based on learning the utilization ration of the needed to execute the current wireless channel optimization. The proposed methodology can attain accurate channel estimation without additional implementation effort and modifications to the current 802.11 standard. And each node is capable to choose the optimized transmission rate, so that the system performance can be improved with very minimum power with high packet transmission ratio with minimum traffic rate to improve QoS. The proposed scheme also offers an appealing combination of the allocation of transmission rate and the current link condition. Based on the basic relationship between them, the proposed decoding scheme maximizes the throughput with periodic learning of channel variation and system status.

     

Joint Power Minimization in Wireless Relay Channels

Energy-constrained multihop wireless links are considered, where the total power consumption is minimized under given requirements on the end-to-end bit error rate (BER). As multihop transmissions are known to be able to save transmission energy in a wireless environment, we study the optimal power scheduling schemes over intermediate hops when the source- relays-destination link can be modeled as cascaded binary symmetric channels. The problem is formulated with an end- to-end BER constraint, and the resulting power consumption is compared with that of the individual link requirement strategy where each hop assigns power under a per-link BER constraint. Results show that the proposed joint power scheduling strategy can achieve a maximum power reduction factor of M in an M-hop route.     

Tandem Queue Models with Applications to QoS Routing in Multihop Wireless Networks

We consider the problem of quality of service (QoS) routing in multi-hop wireless networks where data are transmitted from a source node to a destination node via multiple hops. The routing component of a QoS-routing algorithm essentially involves the link and path metric calculation which depends on many factors such as the physical and link layer designs of the underlying wireless network, transmission errors due to channel fading and interference, etc. The task of link metric calculation basically requires us to solve a tandem queueing problem which is the focus of this paper. We present a unified tandem queue framework which is applicable for many different physical layer designs. We present both exact and approximated decomposition approaches. Using the queueing framework, we can derive different performance measures, namely, end-to-end loss rate, end-to-end average delay, and end-to-end delay distribution. The proposed decomposition approach is validated and some interesting insights into the system performance are highlighted. We then present how to use the decomposition queueing approach to calculate the link metric and incorporate this into the route discovery process of the QoS routing algorithm. The extension of the queueing and QoS routing framework to wireless networks with class-based queueing for QoS differentiation is also presented.     

交通路灯监控系统的无线传感网链状路由算法

在交通路灯监控系统中为节省网络节点能耗和降低数据传输时延,提出一种无线传感网链状路由算法（CRASMS）。该算法根据节点和监控区域的信息将监控区域分成若干个簇区域,在每一个簇区域中依次循环选择某个节点为簇头节点,通过簇头节点和传感节点的通信建立簇内星型网络,最终簇头节点接收传感节点数据,采用数据融合算法降低数据冗余,通过簇头节点间的多跳路由将数据传输到Sink节点并将用户端的指令传输到被控节点。仿真结果表明：CRASMS算法保持了PEGASIS算法在节点能耗方面和LEACH算法在传输时延方面的优点,克服了PEGASIS 算法在传输时延方面和LEACH算法在节点能耗方面的不足,将网络平均节点能耗和平均数据传输时延保持在较低水平。在一定的条件下,CRASMS算法比LEACH和PEGASIS算法更优。     

一种基于蚁群的新型按能需求路由算法研究

提出了一种基于蚁群的新型按能需求路由算法(ARADE),针对移动网络节点剩余能量分布不均而导致网络生命周期短和蚁群算法收敛速度慢这两种缺陷做了相应的改进.存有路由信息的反向信息素表的引入简化了路由请求数据包的数据结构,将节点剩余能量、路径消耗能量以及跳数通过相应的影响因子归一化成一个参数作为路由性能评价值,以此来达到均衡整个网络节点剩余能量的目的.此外,迭代过程中信息素的最大值Гhigh可以当作参数进行一次自我迭代,使得当前节点维护在反向信息素表中的信息素值得到正反馈变化,从而加快整个算法的收敛速度.整个实验仿真是在NS-2平台上进行,随着数据包的传输速率的增加,它的生命周期、平均能量消耗和端到端延迟都会优于AODV.     

储能-发送模式的单天线两跳中继系统保密速率的优化

该文研究节点具有能量收集能力的两跳中继系统的物理层安全传输方案。考虑窃听节点与源和中继节点间都有直接链路的情况。每个数据传输时隙分为能量收集和数据传输两个阶段,各节点用收集的能量发送信号。中继采用放大转发方式,目的节点发送人工噪声进行协作干扰,保护在两跳传输中传输的保密信息。以最大化保密速率为目标,采用迭代算法优化能量吸收和数据传输两阶段的时间分配比例系数和协作干扰功率分配因子。仿真结果表明优化算法准确,优化后的协作干扰方案能显著提高系统的保密传输速率。由于考虑了窃听节点在两跳传输中都能接收到信号的可能性,文中方案更贴近实际,并解决了一个复杂的优化问题。     

Performance–lifetime tradeoff for source extraction in multihop sensor networks

This paper intends to reveal the performance–lifetime tradeoff for source extraction in a multihop sensor network. The randomly deployed sensor network consists of multiple independent branches. The leaf node in each branch takes an observation from the sensing field. The observation is assumed to be a noisy instantaneous linear mixture of the sources. To account for the bandwidth constraint, each leaf node quantizes its observation and sends the quantized data to the sink in a multihop fashion. The observed mixtures are reconstructed at the sink and are utilized to extract the sources. The accumulated bit error probability in each branch depends on the number of hops and the bit error probability of each channel in that branch. The communication errors affect the accuracy of reconstructing mixtures, and hence affect the performance of source extraction. Network lifetime is defined and analyzed under both per‐sensor energy constraint and network energy constraint. The tradeoff between performance and network lifetime is described by optimization problems and the conditions for optimization are identified. As a by‐product, the conditions for maximizing the network lifetime are also identified. Simulation results demonstrate that the tradeoff exists under certain situations. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimization and realization of SWIPT relay channel transmission rate based on rateless code

The optimization of the transmission rate and implementation of the simultaneous wireless information and power transfer in a relay system were studied.In a three-node two-hop system,the decode-and-forward protocol was employed by the relay node.One transmission period was divided into two phases.The first phase was the simultaneous transmission of the information and energy from the source to the relay.The received signal at the relay node was split to two parts.One part was used for information decoding,and the other was converted into energy for information forwarding in the second phase.In the second phase,the information was forwarded according to the decode-and-forward protocol by the relay.The power splitting factor was optimized to minimize the total time of the two hops for the transmission of a certain amount of information when the durations of the two hops were unequal.Furthermore,Raptor codes were combined with different modulation modes to realize different transmission rates on the two hops for the efficient utilization of the different channel capacities in the two hops.The selection mechanism of the codeword length of Raptor codes and modulation mode was given.The simulation proves that the two hops with unequal durations can achieve a higher throughput,and the capacity of the relay channel can be efficiently used by employing Raptor codes,and an efficient and reliable transmission is realized.     

A Delay-Tolerant Virtual Tunnel Scheme for Asynchronous MAC protocols in WSN

Typically, asynchronous MAC protocols are used to monitor a significant facility for rare events or to detect an intrusion in wireless sensor networks. Moreover, asynchronous MAC protocols can achieve high energy efficiency due to the fact that there is no periodic control frame. However, asynchronous MAC protocols have the problem of long end-to-end delay time caused by the absence of precedent time synchronization per link. This paper proposes a new scheme, called virtual tunnel (VT), which can reduce the delivery delay of asynchronous MAC protocols in multi-hop environment. The VT scheme can achieve approximated duty cycle synchronization with on-demand approach. In this scheme, through the estimation of next wakeup time of peer node, without exceptional process, each node on the transmission path can improve end-to-end delay in multi-hop topologies. And it becomes low power consumption by reducing unnecessary retransmissions. Additionally, we devise the protection method of VT. In our simulation results, end-to-end delay according to hop counts and traffic amount is compared with the X-MAC that is an asynchronous protocol recently developed. Furthermore, it is shown that the VT scheme decreases energy consumption due to the lower end-to-end delay than the X-MAC in multi-hop topologies.     

Distributed Transmit Power Control for Maximizing End-to-End Throughput in Wireless Multi-hop Networks

Wireless multi-hop networks have a solidarity property, in which each multi-hop link interferes mutually and so an increase in one link’s rate results in a decrease of the other links’ rate. In a multi-hop link, the end-to-end throughput between a source and destination is restricted by the lowest link rate, so the max-min fair allocation on the link rates is an optimal strategy to maximize the end-to-end throughput. In this paper, we verify that if the wireless links have a solidarity property, the max-min fair allocation has all link rates equal, so we propose a transmit power control (TPC) algorithm that decides the transmit power of multi-hop nodes to equalize all link rates. The proposed algorithm operates in a distributed manner, where each node averages the recognized link rates around itself, allocates its transmit power to achieve this average rate, and iterates this operation until all link rates become equal. Intensive simulation shows that the proposed TPC algorithm enables all link rates to converge on the same value, and thus maximizes the multi-hop end-to-end throughput while decreasing the power consumption of multi-hop nodes.     

Error control coding in wireless sensor networks

Wireless Sensor Networks (WSN) are usually a set of battery-supplied small devices. One of the main challenges in deploying WSN is to improve energy-efficiency and lifetime of the nodes while keeping communication reliability. Transmissions over the wireless channel may experience many impairments, like random noise and fading, increasing the bit error rate at reception, causing several retransmissions, and consuming extra energy from the node. In order to minimize the harmful effects of the radio channel, error control strategies using packet retransmission and error correcting codes are commonly utilized. In this work we investigate the trade-off between transmission and processing energy consumption in a sensor node employing convolutional codes. Through this study we can identify and select the appropriate complexity of the error control code to be used in each sensor node, in order to maximize the network lifetime.     

Energy-efficient protocols for wireless networks with adaptive MIMO capabilities

Transmission power control has been used in wireless networks to improve the channel reuse and/or reduce energy consumption. It has been mainly applied to single-input single-output (SISO) systems, where each node is equipped with a single antenna. In this paper, we propose a power-controlled channel access protocol for MIMO-capable wireless LANs with two antennas per node. Our protocol, called E-BASIC, extends the classic CSMA/CA access scheme by allowing for dynamic adjustment of the transmission mode and the transmission power on a per-packet basis so as to minimize the total energy consumption. By transmission mode we mean one of the four possible transmit/receive antenna configurations: 1 × 1 (SISO), 2 × 1 (MISO), 1 × 2 (SIMO), and 2 × 2 (MIMO). Depending on the transmitter-receiver distance, any of the four modes can be the optimal one in terms of minimizing the total energy consumption. We study the performance of E-BASIC in both ad hoc and access point topologies. We also incorporate E-BASIC in the design of a power-aware routing (PAR) scheme that selects minimum-energy end-to-end paths. Our adaptive designs are first conducted assuming fixed-rate transmission, but later extended to multi-rate systems. To account for the energy-throughput tradeoff in our designs, we impose a constraint on the average packet delivery time. Simulations indicate that the proposed adaptations achieve a significant reduction in the overall energy consumption relative to non-adaptive MIMO systems.     

Tradeoff between energy efficiency and spectral efficiency in a delay constrained wireless system

Because of the inevitable trend of green networking, energy efficiency (EE) is quickly becoming one of the key performance metrics to evaluate wireless communication systems, together with spectrum efficiency (SE) and quality of service (QoS) that have been traditionally used. This paper studies the fundamental tradeoff between EE and SE in the presence of statistical QoS requirements in wireless transmission systems. Earlier studies have shown that the performance with QoS requirements in the wireless transmission can be measured through effective capacity, which can capture the physical layer fading channel characteristics in the link layer QoS requirements, such as delay and data rate. Under this context, SE is defined as effective capacity per unit frequency bandwidth, and EE is defined as energy consumed per effective capacity bit. Both circuit power and transmission power are considered in the energy model, based on which we derive the quasi‐convex generalized EE formulation. To exploit the tradeoff between EE and SE with QoS considerations, we propose a generic close‐form approximation for EE–SE formulation by employing a curve fitting approach. The impacts of QoS and circuit power consumption on EE–SE tradeoff are respectively analyzed. QoS requirement and circuit power consumption affect the EE–SE tradeoff differently. In the low‐SNR regime, circuit power shows more impact on the EE–SE tradeoff, whereas QoS impacts EE–SE tradeoff more in the high‐SNR regime. Copyright © 2014 John Wiley & Sons, Ltd.     

一种新的无线传感器网络定位算法研究

针对传统无线传感器网络定位算法平均误差大、节点能耗过高、定位精度不够理想等缺陷,提出了一种新的无线传感器网络定位算法IMDV-Hop.该算法引进了局部跳数Si和修正因子δ-i,用修正因子-δi对局部跳数进行修正,使待定位节点到锚节点的平均跳数更加符合实际情况;通过权衡定位精度和能耗,分三种情况计算了平均每跳间距,使得平均每跳间距更接近于真实值.仿真实验结果表明IMDV-Hop算法平均定位误差低,具有较小的通信开销,在非规则网络中可达到较好的定位精度.     

面向能量受限传感网的最优数据收集策略

本文研究了能量受限条件下无线传感器网络(wireless sensor networks,WSNs)的最优数据收集策略问题.首先,传感器节点周期性采集数据并通过卡尔曼滤波器(Kalman filter,KF)对信息进行预处理以滤除噪声.其次,考虑到通信为主要耗能环节,设计最优数据发送策略令节点在特定轮内发送数据,使得满足网络生存周期前提下,基站获得的数据精度最高.具体来说,针对单跳网络,给出可使基站误差方差最小化的数据发送策略;在此基础上,进一步提出面向多跳网络的改进数据发送策略.最后,利用仿真和原型实验验证所提策略的有效性.     

Adaptive bandwidth mechanism using dual rate OLT for energy efficient WDM–TDM passive optical network

This paper reviews various energy efficient approaches in existence and proposes a Hybrid WDM–TDM PON architecture that allows the adaptive bandwidth allocation mechanism to reduce central office power consumption with acceptable performance. Our proposed architecture allows sending two signals, one broadband and other narrowband to each optical networking unit so an appropriate signal can be utilized according to the traffic demand. In case of very low traffic, only narrowband signal is used and a significant amount of energy consumption and OPEX is reduced. By using \(2\times \hbox {N}\) power splitter and interleaver, proposed architecture provides broadcasting at both broadband and narrowband signal depending on the required link rate. This further reduces energy consumption and OPEX by avoiding the transmission of same signal from multiple sources. Offered data rates to the optical distribution networks (ODNs) may also be varied by doubling the wavelength spacing of remote node AWG so that two contiguous wavelengths can be transmitted at each port or ODN. This provides the geographical dynamic bandwidth allocation. Proposed architecture also support simultaneous transmission of both broadband and narrowband signals to the ODN to provide bandwidth scalability and network extensibility for supporting future access network in terms of new users and data rates. As two signals are reaching to any ODN, resiliency against OLT TRx and line card failure is also achieved. The performance of the proposed design is verified by simulation results in terms of bit error rate and receiver sensitivity to demonstrate its feasibility for the next-generation optical access network.     

水下传感网络中基于链路质量和位置的协作路由

水下传感网络是开发水域环境的有效技术手段。但在水下环境传输数据,信号衰减快,通信链路质量差,降低了数据包传递率。提出基于链路质量和位置的协作(LQLC)路由。LQLC路由引用协作路由思想,利用链路质量和节点能量信息,构建候选转发节点集;再从候选转发节点集中选择具有最优链路质量的节点作为转发节点;最后在候选转发节点集中选择离转发节点最近的节点作为协作节点。仿真结果表明,提出的LQLC路由提高了数据包传递率。     

紫外光无线传感器网络节能的研究与仿真

为了减少无线传感器网络节点的能量消耗,采用紫外光作为无线传感器网络的信息载体,研究了紫外光传感器节点的能量模型。理论分析了单跳节能和多跳节能,得出了计算最优跳数的数学表达式,并对单跳通信、多跳通信和最优跳通信的平均能量消耗进行了计算机仿真,仿真结果与理论分析一致;对于多跳通信带来的能量消耗不均匀的问题,利用移动sink节点来解决,通过仿真对比了sink节点不同移动速率对网络平均能量消耗、丢包率和端到端时延的影响。结果表明,借助移动sink节点可以降低网络的平均能量消耗,但要根据场景选择合适的移动速率。