DCR‐MAC: distributed cognitive radio MAC protocol for wireless ad hoc networks

The MAC protocol for a cognitive radio network should allow access to unused spectrum holes without (or with minimal) interference to incumbent system devices. To achieve this main goal, in this paper a distributed cognitive radio MAC (DCR‐MAC) protocol is proposed for wireless ad hoc networks that provides for the detection and protection of incumbent systems around the communication pair. DCR‐MAC operates over a separate common control channel and multiple data channels; hence, it is able to deal with dynamics of resource availability effectively in cognitive networks. A new type of hidden node problem is introduced that focuses on possible signal collisions between incumbent devices and cognitive radio ad hoc devices. To this end, a simple and efficient sensing information exchange mechanism between neighbor nodes with little overhead is proposed. In DCR‐MAC, each ad hoc node maintains a channel status table with explicit and implicit channel sensing methods. Before a data transmission, to select an optimal data channel, a reactive neighbor information exchange is carried out. Simulation results show that the proposed distributed cognitive radio MAC protocol can greatly reduce interference to the neighbor incumbent devices. A higher number of neighbor nodes leads to better protection of incumbent devices. Copyright © 2008 John Wiley & Sons, Ltd.     

A delay‐bounded routing protocol for vehicular ad hoc networks with traffic lights

In vehicular ad hoc networks, vehicles may use a routing protocol to inform emergent events, for example, car accidents or traffic jams. Hence, many of the researchers are focused on minimizing the end‐to‐end delay of the routing protocol. However, some applications, for example, email or ftp, are not time critical, and radio spectrum is a limited resource. Hence, delay‐bounded routing protocol, whose goal is to deliver messages to the destination within user‐defined delay and minimize the usage of radio, has become an important issue. The delay‐bounded routing protocols deliver message to the destination by the hybrid of data muling (carried by the vehicle) and forwarding (transmitted through radio). When the available time is enough, the message will be delivered by muling; otherwise, it will be delivered by forwarding. However, in an urban area, there are many traffic lights, which may greatly affect the performance of the delay‐bounded routing protocols. Existing works do not consider the effect of traffic lights, and hence, it may adopt an improper delivery strategy and thus wastes much available time. To improve previous works, we propose a novel delay‐bounded routing protocol, which has considered the effect of traffic lights. Whenever a vehicle passes an intersection, it will gather the information of the traffic light and traffic load of the next road section, and thus, it can make a more accurate prediction and adopt a more proper strategy to deliver message. Simulation results show that the proposed protocol can make a better usage of the available time and uses less radio resource to deliver the message in time. Copyright © 2013 John Wiley & Sons, Ltd.     

Primary user supported routing protocol for cognitive radio ad hoc networks in search of higher throughput

A routing protocol for cognitive radio ad hoc networks (CRAHNs), namely, primary user supported routing (PSR) is demonstrated in this research. Unlike existing routing protocols for CRAHN, where routing of cognitive users (CUs) is accomplished within CUs, in this proposed protocol, some of the primary users (PUs) support CUs to communicate, by forwarding CU packets. This service provided by PU is of voluntary nature. However, such assistance shall be provided by the PUs, only when they are idle, thereby, preserving the principles of cognitive radio networks (CRNs), which indicates that the operation of PU should not be disturbed by the CU activities. The proposed work is compared with cognitive ad hoc on-demand distance vector (CAODV) protocol. The performance parameters considered are routing overhead, rate of loss of packets, and e2e packet delay. PSR outperforms CAODV in all these performance parameters. There has been on average 26.25% improvement in routing overhead, 34.12% decrease in loss, and 27.01% improvement in e2e delivery in the proposed PSR.     

Joint load balanced stable routing and communication segment assignment in mobile cognitive radio ad‐hoc networks

The fundamental issues in mobile cognitive radio ad‐hoc networks are the selection of the optimal stable paths between nodes and proper assignment of the frequency channels/time slots (communication segments) to the links. In this paper, a joint load balanced stable routing and communication segment assignment algorithm is proposed that considers jointly the mobility prediction, mitigating the co‐channel interference and energy consumption. The novelty of the proposed algorithm lies in the increasing of the path stability, which benefits from the maximum link lifetime parameter and introduced weighting function to keep routes away from the PU's region. This avoids the negative impacts on the PUs' operations and decreases the conflict of the cognitive nodes. In the proposed algorithm, the concept of load balancing is considered that yields in the balancing energy consumption in the network, improving the network performance and distributing traffic loads on all available channels. The effectiveness of the proposed algorithm is verified by evaluating the aggregate interference energy, average end‐to‐end delay, goodput, and the energy usage per packet under 6 scenarios. The results show that the performance of the proposed algorithm is significantly better than the recently proposed joint stable routing and channel assignment protocol.     

Practical cross‐layer routing and channel assignment in cognitive radio ad hoc networks

In the heterogeneous and unreliable channel environment of cognitive radio ad hoc networks (CRAHNs), a multipath route with channel assigned is preferable in both throughput and reliability. The cross‐layer multipath routing and channel assignment in CRAHNs is becoming a challenging issue. In this paper, this problem is characterized, formulated, and shown to be in the form of mixed integer programming. For this Non‐deterministic Polynomial‐time (NP)‐hard problem, the deficiency of the widely used linearization and sequential fixing algorithm is first analyzed. The main contribution of this paper is the development of a new backtracking algorithm with feasibility checking to search optimal solutions and a heuristic algorithm with high feasible solution‐obtained probability (HHFOP) for distributed application in CRAHNs. Through feasibility checking and solution bounds validating, backtracking algorithm with feasibility checking cuts off unnecessary searching space in early stage without loss of optimal solutions, making it much more efficient than brute searching. For practical application in CRAHNs with polynomial complexity, HHFOP first computes the maximal‐supported throughput through link‐channel assignment and link‐capacity coordination for each candidate path. Then the paths are combined, and the route throughput is optimized. Extensive simulation results demonstrate that HHFOP can achieve a high feasible solution‐obtained probability with little throughput degradation compared with linearization and sequential fixing algorithm, indicating its practicability for distributed applications in CRAHNs. Copyright © 2013 John Wiley & Sons, Ltd.     

感知无线电ad hoc网络基于干扰的路由

感知无线电技术作为一种新兴技术,通过时间和空间维度上的频谱空洞的利用能很好地提高频谱利用率。感知无线电的路由不同于传统的路由度量,因为次用户从时间和空间上都不能对主用户造成干扰。在感知无线电ad hoc网络环境下,选取了干扰作为路由的度量,并将干扰分为系统内干扰(次用户自身之间的干扰)和系统间干扰(次用户对主用户的干扰)。在已有的ad hoc网络干扰路由协议的基础上对干扰权重做出改进,并提出新的基于系统间路由干扰(对主用户干扰最小化)和基于联合系统内和系统间干扰的路由协议。仿真结果表明,该干扰模型符合感知无线电移动ad hoc网络的特性。     

Delay constraint multipath routing for wireless multimedia ad hoc networks

According to the disadvantages of real time and continuity for multimedia services in ad hoc networks, a delay constraint multipath routing protocol for wireless multimedia ad hoc networks, which can satisfy quality of service (QoS) requirement (QoS multipath optimized link state routing [MOLSR]), is proposed. The protocol firstly detects and analyzes the link delay among the nodes and collects the delay information as the routing metric by HELLO message and topology control message. Then, through using the improved multipath Dijkstra algorithm for path selection, the protocol can gain the minimum delay path from the source node to the other nodes. Finally, when the route is launched, several node‐disjoint or link‐disjoint multipaths will be built through the route computation. The simulation and test results show that QoS‐MOLSR is suitable for large and dense networks with heavy traffic. It can improve the real time and reliability for multimedia transmission in wireless multimedia ad hoc networks. The average end‐to‐end delay of QoS‐MOLSR is four times less than the optimized link state routing. Copyright © 2014 John Wiley & Sons, Ltd.     

QoS multicast routing in cognitive radio ad hoc networks

In this paper, we discussed the issues of QoS multicast routing in cognitive radio ad hoc networks. The problem of our concern was: given a cognitive radio ad hoc network and a QoS multicast request, how to find a multicast tree so that the total bandwidth consumption of the multicast is minimized while the QoS requirements are met. We proposed two methods to solve it. One is a two‐phase method. In this method, we first employed a minimal spanning tree‐based algorithm to construct a multicast tree and then proposed a slot assignment algorithm to assign timeslots to the tree links such that the bandwidth consumption of the tree is minimized. The other is an integrated method that considers the multicast routing together with the slot assignment. Extensive simulations were conducted to show the performance of our proposed methods. Copyright © 2011 John Wiley & Sons, Ltd.     

On‐demand flow regulated routing for ad hoc wireless networks

In this paper, we present an on‐demand flow regulated routing algorithm (OFRA) for ad hoc wireless networks. The OFRA consists of two parts: an intermediate node load evaluation process and a routing path selection process. The intermediate node load evaluation process evaluates the load efficiency of the intermediate nodes according to bandwidth, data packets and computing capability. The routing path selection process selects the routing path with lower flow and fewer intermediate nodes. The OFRA can prevent intermediate nodes to be overcrowded and distribute traffic load over routing paths more evenly. The simulation result shows that the percentage of blocked routing paths is reduced and the total flow is more balanced and distributed. Copyright © 2006 John Wiley & Sons, Ltd.     

Multi‐interface cognitive radio for enhanced routing in multi‐hop cellular networks

Multi‐hop cellular network (MCN) is a wireless communication architecture that combines the benefits of conventional single‐hop cellular networks and multi‐hop ad hoc relaying networks. The route selection in MCN depends on the availability of intermediate nodes and their neighborhood connectivity. Cognitive radio (CR) is an emerging communication paradigm that exploits the available radio frequencies opportunistically for the effective utilization of the radio frequency spectrum. The incorporation of CR and mobile ad hoc network routing protocols in MCN could potentially improve the spectrum utilization and the routing performance of MCN. This paper firstly presents the proposed model for the multi‐interface CR mobile node with transceiver synchronization and then investigates its opportunistic spectrum utilization and routing performance in MCN. Copyright © 2015 John Wiley & Sons, Ltd.     

A mobicast routing protocol with carry‐and‐forward in vehicular ad hoc networks

In vehicular networks, safety and comfort applications are two quite different kinds of applications to avoid the emergency traffic accident and enjoy the non‐emergency entertainment. The comfort application drives the challenges of new non‐emergency entertainments for vehicular ad hoc networks (VANETs). The comfort application usually keeps the delay‐tolerant capability; that is, messages initiated from a specific vehicle at time t can be delivered through VANETs to some vehicles within a given constrained delay time λ. In this paper, we investigate a new mobicast protocol to support comfort applications for a highway scenario in VANETs. All vehicles are located in a geographic zone (denoted as zone of relevance (ZOR)) at time t; the mobicast routing must disseminate the data message initiated from a specific vehicle to all vehicles that have ever appeared in ZOR at time t. This data dissemination must be performed before time t + λ through the carry‐and‐forward technique. In addition, the temporary network fragmentation problem is considered in our protocol design. Also, the low degree of channel utilization is kept to reserve the resource for safety applications. To illustrate the performance achievement, simulation results are examined in terms of message overhead, dissemination success rate, and accumulative packet delivery delay. Copyright © 2012 John Wiley & Sons, Ltd.     

EEAODR: An energy‐efficient ad hoc on‐demand routing protocol for mobile ad hoc networks

Mobile ad hoc networks (MANETs) are characterized by random, multi‐hop topologies that do not have a centralized coordinating entity or a fixed infrastructure that may change rapidly over time. In addition, mobile nodes operate with portable and finite power sources. In this work, we propose an energy‐efficient routing protocol for MANETs to minimize energy consumption and increase the network's consistency. Traditional works mainly focused on the shortest path‐based schemes to minimize energy, which might result into network failure because some nodes might exhaust fast as they are used repetitively, while some other nodes might not be used at all. This can lead to energy imbalance and to network life reduction. We propose an energy‐efficient ad hoc on‐demand routing protocol that balances energy load among nodes so that a minimum energy level is maintained among nodes and the network life increases. We focused on increasing the network longevity by distributing energy consumption in the network. We also compared the simulation results with a popular existing on‐demand routing protocol in this area, AODV, to establish the superiority of our approach. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis and enhancement of multi‐channel MAC protocol for ad hoc networks

In this paper, an analytical model is proposed to calculate the network throughput of dedicated control channel protocols that are designed to schedule multiple packets to be transmitted on different data channels simultaneously. Based on the analytical model, a scheme by tuning the initial contention window size is proposed to maximize the network throughput. We also present a novel multi‐channel MAC protocol for single‐hop scenario. Simulation results show that the proposed model is capable of modeling the behaviors of dedicated control channel protocols accurately. Furthermore, the proposed scheme can reduce the cost of collisions and enhance the network throughput up to 22% for 1 kB packet size and 80 nodes. Compared with other dedicated control channel protocols, the proposed protocol can schedule more control packets and use multiple channels more efficiently. Copyright © 2010 John Wiley & Sons, Ltd.     

QoS‐aware routing and power control algorithm for multimedia service over multi‐hop mobile ad hoc network

This paper presents a QoS (quality of service) aware routing and power control algorithm consuming low transmission power for multimedia service over mobile ad hoc network. Generally, multimedia services need stringent QoS over the network. However, it is not easy to guarantee the QoS over mobile ad hoc network since its network resources are very limited and time‐varying. Furthermore, only a limited amount of power is available at mobile nodes, which makes the problem more challenging. We propose an effective routing and power control algorithm for multimedia services that satisfies end‐to‐end delay constraint with low transmission power consumption. The proposed algorithm supports the required bandwidth by controlling each link channel quality over route in a tolerable range. In addition, a simple but effective route maintenance mechanism is implemented to avoid link failures that may significantly degrade streaming video quality. Finally, performance comparison with existing algorithms is presented in respect to traditional routing performance metrics, and an achievable video quality comparison is provided to demonstrate the superiority of the proposed algorithm for multimedia services over mobile ad hoc network. Copyright © 2010 John Wiley & Sons, Ltd.     

Ad hoc网络中带宽保证路由协议

研究ad hoc网络中无线链路存在邻近链路干扰及隐藏终端和暴露终端问题，提出新的带宽预留模型及带宽保证路由协议(BGRP)，旨在按需探测符合带宽需要的路由路径并预留可靠的带宽资源。理论分析证明，BGRP探测的路由路径能满足带宽需要，而且预留的带宽资源准确有效。仿真结果表明，就有效带宽而言，BGRP较INSIGNIA和BGSR算法有效，而且消息复杂性较小，具有良好的网络扩展性。     

车载自组织网中基于蚁群算法的延迟感知路由协议

针对城市道路环境下车载自组织网( VANETs)中通信性能下降以及数据传输失败的问题,提出了一种基于蚁群算法的延迟感知路由( ACDR)协议。首先,建立双向车道的数学延迟模型;然后,根据提出的端点十字路口( EI)的概念,ACDR利用蚁群优化( ACO)寻找最佳路线,其中前向蚂蚁根据本地路段延迟以及当前十字路口与目的节点的端点十字路口之间的全局时延来选择路径,后向蚂蚁则负责在返回路径时更新信息素,同时,相邻十字路口之间利用贪婪转发算法进行数据包的传递。最后仿真比较了ACDR协议与连通性感知路由( CAR)协议的性能,结果表明提出的ACDR协议的数据包的传输延迟小,丢包率低,通信性能好。     

Sparsely‐deployed relay node assisted routing algorithm for vehicular ad hoc networks

In this paper, we study the issue of routing in a vehicular ad hoc network with the assistance of sparsely deployed auxiliary relay nodes at some road intersections in a city. In such a network, vehicles keep moving, and relay nodes are static. The purpose of introducing auxiliary relay nodes is to reduce the end‐to‐end packet delivery delay. We propose a sparsely deployed relay node assisted routing (SRR) algorithm, which differs from existing routing protocols on how routing decisions are made at road intersections where static relay nodes are available such that relay nodes can temporarily buffer a data packet if the packet is expected to meet a vehicle leading to a better route with high probability in certain time than the current vehicles. We further calculate the joint probability for such a case to happen on the basis of the local vehicle traffic distribution and also the turning probability at an intersection. The detailed procedure of the protocol is presented. The SRR protocol is easy to implement and requires little extra routing information. Simulation results show that SRR can achieve high performance in terms of end‐to‐end packet delivery latency and delivery ratio when compared with existing protocols. Copyright © 2013 John Wiley & Sons, Ltd.     

一种应急通信中业务感知的宽带自组网路由协议

随着科技进步,我国在应急通信系统建设上也正高速发展,当前应急通信网络对多媒体业务有着迫切需求,对网络带宽要求更高。而当网络存在多种不同业务时,传统通用的路由协议不再适用,它们大多以最小跳数为路由度量或者是某个单一度量,未能考虑不同业务的服务质量(Quality of Service, QoS)需求,因而无法同时兼顾不同业务流的传输要求。提出了一种应急通信中业务感知的宽带自组网路由策略,对不同类型业务在路由和转发优先级上进行区分。经多次仿真验证,该策略能使网络在满足应急语音业务QoS需求的同时,也能兼顾承载的视频、数据等其他业务的性能。     

Research on multi-channel routing threats and defense for cognitive ad hoc network

In the environment of scarce spectrum resources,cognitive ad hoc network which is independent with infrastruc-ture and fixed spectrum allocation policy,has been also developed quickly.Due to the characteristic of multi-channel routing,cognitive ad hoc network is commonly perceived as an environment offering both opportunities and threats.To further un-derstand the multi-channel routing threats,the current research situation and development trend,the types of threats were analyzed in terms of the node routing and the multi-channel selection,and several typical security methods were concluded.Meanwhile,the most important solution to keep the security of cognitive radio network was found to build trust relationship among cognitive users.Trust management was just the basic technology to solve the security problems of multi-channel routing.Finally,the current problems of related works and research trends in this area were discussed.     

Energy‐aware virtual multi‐input‐multi‐output‐based routing for wireless ad hoc networks

Virtual multi‐input‐multi‐output (vMIMO) technology is becoming a promising way to improve the energy efficiency of wireless networks. Previous research always builds up the vMIMO‐based routing on the fixed structure such as clusters, and the MIMO mode is omitted in most cases. So, they cannot fully explore the advantage of vMIMO in routing. In this paper, we study a general routing scheme in which no fixed structure is required, and any communication mode of vMIMO is allowed for sake of the energy efficiency. We define two vMIMO‐based routing problems aiming to energy‐minimization and lifetime‐optimization. The first problem can be solved by our distributed energy‐minimum vMIMO‐based algorithm. The algorithm constructs the virtual cooperative graph, and applies the shortest path method on the virtual cooperative graph to solve this problem. The second problem is non‐deterministic polynomial‐time hard, and we design the distributed lifetime‐oriented vMIMO‐based algorithm, which is based on the modified Bellman‐Ford method. It can reach approximation ratio of four. The simulations show that our algorithms can work well in many situations. For example, distributed lifetime‐oriented vMIMO‐based algorithm can prolong the lifetime about 20.2% in dense topologies compared with the cooperative routing algorithm on average. Copyright © 2015 John Wiley & Sons, Ltd.