基于负载均衡的DSR路由协议改进*

动态源路由DSR路由协议以最短路径优先为原则,但是没考虑负载均衡,产生拥塞区域、连接失败等不利结果.为减轻路由负载,提高协议性能,提出了一种基于负载均衡的DSR路由算法.在路由发现过程中节点根据自身负载情况决定接收或丢弃请求分组,从而避开负载过高节点;中间节点采用不应答路由请求分组策略;目的节点根据路径总负载选择合适的...     

使用新判据的改进型DSR协议

传统的无线Mesh网络路由协议都集中于寻找具有最小跳数的路径,但是,这样的路径可能会包含高损耗的链路,从而导致网络吞吐量的大幅度降低。因此,新的路由算法通过进一步考虑链路质量来选择更好的路由。首先,为方便新的路由判据的使用,局部优化了传统的DSR协议为改进的DSR协议。然后,为实现路径链路质量最优与最小跳数之间的均衡,提出一种新的路由判据O-WCETT,将其与WCETT（累计期望传输时间）、HOP（最小跳数）分别应用于改进后的DSR（动态源路由）协议中,采用NS2仿真软件对其性能进行评估。仿真结果表明,在相同的无线传输和网络规模条件下,使用新路由判据O-WCETT的改进型DSR协议使得网络的分组投递率性能更高,端到端平均时延和路由开销都明显减小,并且随着节点移动速度的加快,使用新判据的DSR协议带来的网络性能改善更为显著。     

Intelligent multicast routing for multimedia over cognitive radio networks: a probabilistic approach

Cognitive radio (CR) technology has been demonstrated as one of the key technologies that can provide the needed spectrum bands for supporting the emerging spectrum-hungry multimedia applications and services in next-generation wireless networks. Multicast routing technique plays a significant role in most of wireless networks that require multimedia data dissemination to a group of destinations through single-hop or multi-hop communication. Performing multimedia multicasting over CR networks can significantly improve the quality of multimedia transmissions by effectively exploiting the available spectrum, reducing network traffic and minimizing communication cost. An important challenge in this domain is how to perform a multi-cast transmissions over multiple hops in a dynamically varying CR environment while maintaining high-quality received video streaming to all multi-case CR receivers without affecting the performance of legacy primary radio networks (PRNs). In this paper, we investigate the problem of multicast multimedia streaming in multi-hop CR networks (CRNs). Specifically, we propose an intelligent multicast routing protocol for multi-hop ad hoc CRNs that can effectively support multimedia streaming. The proposed protocol consists of path selection and channel assignment phases for the different multi-cast receivers. It is based on the shortest path tree (SPT) that implements the expected transmission count metric (ETX). The channel selection is based on the ETX, which is a function of the probability of success (POS) over the different channels that depends on the channel-quality and availability. Simulation results verify the significant improvement achieved by the proposed protocol compared to other existing multicast routing protocols under different network conditions.

     

Probabilistic quality-aware routing in cognitive radio networks under dynamically varying spectrum opportunities

In this paper, we introduce a probabilistic routing metric that considers the peculiar characteristics of the operating environment of cognitive radio networks (CRNs). This metric captures the dynamic changes in channel availabilities due to the randomness of primary user’s activity and the rich channel diversity due to the fact that a CRN is expected to operate over highly separated frequency channels with different propagation characteristics. Our metric, Probability of Success (PoS), statistically quantifies the chances of a successful cognitive radio (CR) packet transmission over a given channel. Based on the PoS metric, we propose a joint probabilistic routing and channel assignment protocol for multi-hop CRNs that attempts at selecting the path with the maximum probability of success among all possible paths for a given CR source-destination pair. Selecting such a path results in minimizing the number of disruptions to CR packet transmissions, which consequently improves network throughput. Simulation results verify the significant throughput improvement achieved by our protocol compared to reference CRN routing protocols.     

Performance study of multiple route dynamic source routing protocols for mobile ad hoc networks

Design and analysis of routing protocols are the key issues for a mobile ad hoc network (MANET). The Dynamic Source Routing (DSR) protocol is one of the important on-demand routing protocols. In this paper, we develop a comprehensive analytic model for the performance study of the DSR protocol with multiple routes. Two performance metrics, called probability of a successful data transmission and probability that the multiple routes can support the next data transmission, are introduced. We derive both of the two probabilities for the general case over n multiple routes for the DSR protocol. These analytic results provide insights into the mechanics of the multiple DSR routing protocol. It is also useful for the design and implementation of the on-demand routing for MANET.     

Power-aware localized routing in wireless networks

A cost aware metric for wireless networks based on remaining battery power at nodes was proposed for shortest-cost routing algorithms, assuming constant transmission power. Power-aware metrics, where transmission power depends on distance between nodes and corresponding shortest power algorithms were also proposed. We define a power-cost metric based on the combination of both node's lifetime and distance-based power metrics. We investigate some properties of power adjusted transmissions and show that, if additional nodes can be placed at desired locations between two nodes at distance d, the transmission power can be made linear in d as opposed to d^α dependence for α ⩾ 2. This provides basis for power, cost, and power-cost localized routing algorithms where nodes make routing decisions solely on the basis, of location of their neighbors and destination. The power-aware routing algorithm attempts to minimize the total power needed to route a message between a source and a destination. The cost-aware routing algorithm is aimed at extending the battery's worst-case lifetime at each node. The combined power-cost localized routing algorithm attempts to minimize the total power needed and to avoid nodes with a short battery's remaining lifetime. We prove that the proposed localized power, cost, and power-cost efficient routing algorithms are loop-free and show their efficiency by experiments     

Precomputation for intra-domain QoS routing

Quality-of-service routing (QoSR), seeking to find a feasible path with multiple constraints, is an NP-complete problem. We propose a novel precomputation approach to multi-constrained intra-domain QoS routing (PMCP). It is assumed that a router maintains the link state information of the entire domain. PMCP cares each QoS weight to several degrees, and computes a number of QoS coefficients uniformly distributed in the multi-dimensional QoS metric space. Based on each coefficient, a linear QoS function is constructed to convert the multiple QoS metrics to a single QoS value. We then create a shortest path tree with respect to the QoS value by Dijkstra’s algorithm. Finally, according to the multiple coefficients, different shortest path trees are calculated to compose the QoS routing table. We analyze linear QoS functions in the QoS metric space, and give a mathematical model to determine the feasibility of a QoS request in the space. After PMCP is introduced, we analyze its computational complexity and present a method of QoS routing table lookup. Extensive simulations evaluate the performance of the proposed algorithm and present a comparative study.     

On the implications of routing metric staleness in delay tolerant networks

Delay Tolerant Network (DTN) routing addresses challenges of providing end-to-end service where end-to-end data forwarding paths may not exist. The performance of current DTN routing protocols is often limited by routing metric “staleness”, i.e., routing information that becomes out-of-date or inaccurate because of long propagation delays. Our previous work, ParaNets, proposed a new opportunistic network architecture in which the data channel is augmented by a thin end-to-end control channel. The control channel is adequate for the exchange of control traffic, but not data. In this paper we present Cloud Routing, a routing solution for the ParaNets architecture. We motivate the need for such a solution, not only because of stale routing metrics, but also because of congestion that can occur in DTNs. Unable to use up-to-date routing metrics to limit congestion, existing DTN routing solutions suffer from low goodput and long data delivery delays. We show how Cloud Routing avoids congestion by smart use of forwarding opportunities based on up-to-date routing metrics. We evaluate our solution using extensive OPNET simulations. Cloud Routing extends network performance past what is currently possible and motivates a new class of globally cognizant DTN routing solutions.     

Influence of mobility models on the performance of data dissemination and routing in wireless mobile ad hoc networks

Many routing protocols are proposed in the literature on mobile ad hoc networks (MANETs). Some of those protocols which have been investigated under different assumptions are unable to capture the actual characteristics of MANETs. Therefore, there is a necessity to investigate the performance of MANETs under a number of different protocols with various mobility models. This paper evaluates the performance of the single path routing protocols (AODV, DSR, and DSDV), in the presence of different network loads and differing mobility models. Our findings show that DSR routing protocol has a better performance compared to other protocols with respect to various metrics.     

基于非均匀分簇机制的ZigBee混合路由算法

针对现有ZigBee网络路由算法存在节点能量消耗不均衡问题,在树路由算法与无线自组网按需距离矢量路由改进(AODVjr)算法的基础上,提出一种基于非均匀分簇机制的ZigBee混合路由算法。该算法将网络分成若干个非均匀的逻辑簇,使距离协调器越近的簇规模越小,从而减少转发任务,使得能量消耗均衡。在分簇的基础上,将节点之间的传输分为簇内传输与簇间传输。簇内传输采用基于邻居表的树路由算法;簇间传输在基于树路由算法无效的情况下,采用AODVjr算法,找到两个簇首之间的较短路径;同时规定只有簇首节点和网关节点才能广播请求分组(RREQ),可以减少冗余的RREQ分组。仿真结果表明,该算法能有效推迟死亡节点出现的时间,延长网络的生存周期,达到提高网络性能的目的。     

Impact of routing parameters on route diversity and path inflation

Years after the initial development of the current routing protocols we still lack an understanding of the impact of various parameters on the routes chosen in today’s Internet. Network operators are struggling to optimize their routing, but the effectiveness of those efforts is limited.In this article, we study sensitivity of routing stretch and diversity metrics to factors such as policies, topology, IGP weights, etc. using statistical techniques. We confirm previous findings that routing policies and AS size (in number of routers) are the dominating factors. Surprisingly, we find that intra-domain factors only have marginal impact on global path properties.Moreover, we study path inflation by comparing against the paths that are shortest in terms of AS-level/router-level hops or geographic distances. Overall, the majority of routes incur reasonable stretch. From the experience with our Internet-scale simulations, we find it hard to globally optimize path selection with respect to the geographic length of the routes, as long as inter-domain routing protocols do not include an explicit notion of geographic distance in the routing information.     

用于Ad Hoc网络的改进的动态源路由协议

为了提高源路由协议(DSR)的性能,平衡整个网络的能量,减少拥塞,提高伸缩性和延长网络生存时间,对发送的RREP和RREQ包结构做了改进,加入了新的延迟发送机制,提出了一种新的协议IDSR,并用仿真对改进后的IDSR路由协议进行了性能评估。     

Efficient use of route requests for loop-free on-demand routing in ad hoc networks

On-demand routing protocols flood a route request (RREQ) identified by a unique source-sequenced label (SSL) to build directed acyclic graphs (DAG) consisting of possible paths to destinations, and use reverse paths along such DAGs to send route replies from the destinations. We present the first framework that uses only the SSL of the RREQ to establish loop-free paths without requiring additional mechanisms or information, e.g., per destination-sequence numbers or source routing. We present the Labeled Successor Routing (LSR) protocol, which stores the SSL of the RREQ as a route request label (RRL) at the nodes that participated in the creation of the RREQ DAG. The RRLs allow the source of the RREQ to identify neighbors as loop-free successors to the destination, which reduces network-wide RREQ flooding. Simulations results for scenarios consisting of networks of 50 and 100 mobile nodes show that LSR performs comparably or better than the Dynamic Source Routing (DSR) protocol, the Ad hoc On-demand Distance Vector (AODV) routing protocol, and the Optimized Link State Routing (OLSR) protocol.     

A multi-objective evolutionary algorithm based QoS routing in wireless mesh networks

The huge demand for real time services in wireless mesh networks (WMN) creates many challenging issues for providing quality of service (QoS). Designing of QoS routing protocols, which optimize the multiple objectives is computationally intractable. This paper proposes a new model for routing in WMN by using Modified Non-dominated Sorting Genetic Algorithm-II (MNSGA-II). The objectives which are considered here are the minimization of expected transmission count and the transmission delay. In order to retain the diversity in the non-dominated solutions, dynamic crowding distance (DCD) procedure is implemented in NSGA-II. The simulation is carried out in Network Simulator 2 (NS-2) and comparison is made using the metrics, expected transmission count and transmission delay by varying node mobility and by increasing number of nodes. It is observed that MNSGA-II improves the throughput and minimizes the transmission delay for varying number of nodes and higher mobility scenarios. The simulation clearly shows that MNSGA-II algorithm is certainly more suitable for solving multiobjective routing problem. A decision-making procedure based on analytic hierarchy process (AHP) has been adopted to find the best compromise solution from the set of Pareto-solutions obtained through MNSGA-II. The performance of MNSGA-II is compared with reference point based NSGA-II (R-NSGA-II) in terms of spread.     

Complexity results on labeled shortest path problems from wireless routing metrics

Metrics to assess the cost of paths through networks are critical to ensuring the efficiency of network routing. This is particularly true in multi-radio multi-hop wireless networks. Effective metrics for these networks must measure the cost of a wireless path based not only on traditional measures such as throughput, but also on the distribution of wireless channels used. In this paper, we argue that routing metrics over such networks may be viewed as a class of existing shortest path problems, the formal language constrained path problems.On this basis, we describe labeled path problems corresponding to two multi-radio wireless routing metrics: Weighted Cumulative Expected Transmission Time (WCETT), developed by Draves et al., and Metric for Interference and Channel-switch (MIC), developed by Yang et al. For the first, we give a concise proof that calculating shortest WCETT paths is strongly NP-Complete for a variety of graph classes. We also show that the existing heuristic given by Draves et al. is an approximator. For the second, we show that calculating loop-free (simple) shortest MIC paths is NP-Complete, and additionally show that the optimization version of the problem is NPO PB-Complete. This result implies that shortest simple MIC paths are only poorly approximable in the worst case.Furthermore, we demonstrate how the polynomial-time algorithm for shortest MIC paths is derivable from an existing language constrained shortest path algorithm. We use this as a basis to exhibit the general utility of viewing multi-channel wireless routing metrics as labeled graph problems, and discuss how a class of related polynomial-time computable metrics are derivable from this algorithm.     

Reliable and efficient communications in sensor networks

Wireless sensor networks are inherently plagued by problems of node failure, interference to communications from environmental noise and energy-limited sensor motes. These problems pose conflicting issues in the design of suitable routing protocols. Several existing reliable routing protocols exploit message broadcast redundancy and hop count as routing metrics and their performance trade-offs are revealed during simulation. In this paper, we study and analyse related design issues in proposed efficient and reliable routing protocols that attempt to achieve reliable and efficient communication performance in both single- and multi-hub sensor networks. Simulation results of four such routing protocols show that routing performance depends more on optimal (near-optimal) routing in single hub than in multi-hub networks. Our work also shows that optimal (near-optimal) routing is better achieved when historical metrics like packet distance traversed and transmission success are also considered in the routing protocol design.     

Scalability of MANET routing protocols for heterogeneous and homogenous networks

In Mobile Ad hoc Network (MANET), mobility, traffic and node density are main network conditions that significantly affect performance of routing protocols. Much of the previous research in MANET routing have focused on developing strategies, which suit one specific networking scenario. Therefore, there is no existing protocol that can work well in all different networking scenarios. This paper reviews characteristics of several different classes of routing protocols. Moreover, most of current routing protocols assume homogeneous networking conditions where all nodes have the same capabilities and resources. This paper presents extensive studies simulations for DSR, AODV, LAR1, FSR and WRP in homogenous and heterogeneous networks that consist of different nodes with different resources. The results showed that while all protocols perform reasonably well in homogenous networking conditions, their performance suffer significantly over heterogonous networks.     

Full-duplex routing with low-complexity sequential-decision for throughput enhancement in dynamic access networks

Integrating the Full-Duplex (FD) communication technology in multi-hop Cognitive Radio Networks (CRNs) can significantly enhance routing decisions such that overall network performance is improved. Unfortunately, when employing the FD technology in multi-hop routing, the channel assignment becomes very challenging due to the possible simultaneous transmissions/reception. Hence, careful low-complexity channel assignment over the various hops along a path is needed to avoid hop-to-hop interference and enhance network performance. In this paper, we propose a low-complexity sequential-decision routing protocol, referred to as Sequential FD (SFD)-aware protocol. The SFD protocol identifies a set of possible routes between any source–destination communicating pair. For each discovered route, SFD successively assigns channels for each hop along the router such that the maximum route capacity is achieved. Then, SFD selects the routes with the highest capacity. Unlike most of existing FD-CRN channel assignment/routing protocols, which require optimization procedures with NP-hard time complexity with the number of channels and hops, the time-complexity of the proposed SFD protocol is polynomial. Compared to the optimal FD-aware routing (obtained using the brute-force search method) and maximum per-hop rate FD-unaware routing protocols, the simulation results confirm the effectiveness of our proposed protocol and its superiority over the existing FD-unaware baseline routing protocol in terms of the end-to-end network throughput. The results also confirm that the SFD protocol provides solutions within 5% of the optimal ones.     

A routing-table-based adaptive and minimal routing scheme on network-on-chip architectures

In this paper, we present a routing algorithm that combines the shortest path routing and adaptive routing schemes for NoCs. In specific, routing follows the shortest path to ensure low latency and low energy consumption. This routing scheme requires routing information be stored in a series of routing tables created at the routers along the routing path from the source to the destination. To reduce the exploration space and timing cost for selecting the routing path, a routing list and routing table for each node are created off-line. Routing table is updated on-line to reflect the dynamic change of the network status to avoid network congestion. To alleviate the high hardware implementation cost associated with the routing tables, a method to help reduce the size of the routing tables is also introduced. Compared to the existing routing algorithms, the experimental results have confirmed that the proposed algorithm has better performance in terms of routing latency and power consumption.     

Improving source routing reliability in mobile ad hoc networks

In this paper, we propose a novel on-demand routing protocol called backup source routing (BSR) to establish and maintain backup routes that can be utilized after the primary path breaks. The key advantage of BSR is the reduction of the frequency of route discovery flooding, which is recognized as a major overhead in on-demand protocols. We define a new routing metric, called the route reliability, and use it to provide the basis for the backup path selection. We use a heuristic cost function to develop an analytical model and an approximation method to measure this metric. Various algorithms for our BSR protocol in the route discovery phase and route maintenance phase have been designed based on this cost function. Extensive simulations demonstrated that our routing strategy has two interesting features: 1) in less stressful situations of lower mobility, BSR has similar performance to DSR, 2) in more challenging situations of high mobility, BSR can improve the performance significantly.