Minimum Hop Count Research Articles

Multi-constraint multi-objective QoS aware routing heuristics for query driven sensor networks using fuzzy soft sets

In this paper, a fuzzy based distributed power aware routing scheme considering both energy and bandwidth constraints, especially for query driven applications in the asynchronous duty-cycled wireless sensor networks are devised. The proposed multi-constraint, multi-objective routing optimization approach under strict resource constraints guarantees reliability and fast data delivery along with efficient power management in spite of unreliable wireless links and limited power supply. In query driven applications, the request from the sink to the individual sensor node will be a broadcast message, whereas the individual sensor nodes replies back to sink as unicast messages. In the proposed work, the fuzzy approach and “A Star” algorithm are utilized for satisfying energy and bandwidth constraints to route the broadcast messages of the sink while querying all the sensor nodes in the network. Every node will be provided with a guidance list, which is used to decide the next best neighbor node with good route quality for forwarding the received multi-hop broadcast messages. The route quality of the every node is estimated with fuzzy rules based on the network parameters such as maximum remaining energy, minimum traffic load and better link quality to increase the network lifetime. The provision of overhearing the broadcast messages and acknowledgements within the transmission range minimizes the effort to search for the active time of nodes while routing the broadcast messages with asynchronous scheduling. Further, in the proposed work only the time slot of its nearest neighbor relay node (to which packets are to be forwarded) is learnt to reduce the number of message transmissions in the network. For the unicast message replies, the fuzzy membership function is modified and devised based on the routing metrics such as higher residual energy, minimum traffic loads and minimum hop count under energy and bandwidth constraints. Also, the multi-hop heuristic routing algorithm called Nearest Neighbor Tree is effectively used to reduce the number of neighbors in the guidance list that are elected for forwarding. This helps to increase the individual sensor node’s lifetime, thereby maximizes the network lifetime and guarantees increased network throughput. The simulation results show that the proposed technique reduces repeated transmissions, decreases the number of transmissions, shortens the active time of the sensor nodes and increases the network lifetime for query driven sensor network applications invariant to total the number of sensor nodes and sinks in the network. The proposed algorithm is tested in a small test bed of sensor network with ten nodes that monitors the room temperature.

End-to-End Link Reliable Energy Efficient Multipath Routing for Mobile Ad Hoc Networks

Among the many multipath routing protocols, the AOMDV is widely used in highly dynamic ad hoc networks because of its generic feature. Since the communicating nodes in AOMDV are prone to link failures and route breaks due to the selection of multiple routes between any source and destination pair based on minimal hop count which does not ensure end-to-end reliable data transmission. To overcome such problems, we propose a novel node disjoint multipath routing protocol called End-to-End Link Reliable Energy Efficient Multipath Routing (E2E-LREEMR) protocol by extending AOMDV. The E2E-LREEMR finds multiple link reliable energy efficient paths between any source and destination pair for data transmission using two metrics such as Path-Link Quality Estimator and Path-Node Energy Estimator. We evaluate the performance of E2E-LREEMR protocol using NS 2.34 with varying network flows under random way-point mobility model and compare it with AOMDV routing protocol in terms of Quality of Service metrics. When there is a hike in network flows, the E2E-LREEMR reduces 30.43 % of average end-to-end delay, 29.44 % of routing overhead, 32.65 % of packet loss ratio, 18.79 % of normalized routing overhead and 12.87 % of energy consumption. It also increases rather 10.26 % of packet delivery ratio and 6.96 % of throughput than AOMDV routing protocol.

Influence of sub-field area on dose distribution in intensity-modulated radiotherapy for cervical cancer

Objective To investigate the optimization of therapeutic regimen through the adjustment of the minimum sub-field area in intensity-modulated radiotherapy (IMRT) for cervical cancer, under the premise of no influence on the dose to target volume or organs at risk. Methods A total of 12 patients with pathologically confirmed cervical cancer were enrolled, and the prescribed dose to the planning target volume (PTV) was 50 Gy in 25 fractions. The Pinnacle 8.0m treatment planning system was used for all patients, and 16 IMRT plans were developed for each patient, with the application of 9 evenly distributed fixed incidence directions (0°, 40°, 80°, 120°, 160°, 200°, 240°, 280°, and 320°), a minimum sub-field number of 80, and a minimum sub-field hop count (MU) of 5 MU.The range of sub-field area was 2-81 cm2.Direct machine parameter optimization was used for inverse-planned optimization calculation, and all the plans met the requirements of the clinical prescribed dose. The dose-volume histogram was used to evaluate the dose distribution in target volume and organs at risk. Results With the sub-field area increasing from 2 cm2 to 81 cm2, the total hop count of IMRT plan was reduced from (1 405±170) MU to (490±47) MU (P=0.000), and when the sub-field area increased above 6 cm×6 cm, the total hop count was reduced significantly (P=0.000). In the IMRT plan with a minimum sub-field area of 2-49 cm2, there was no significant difference in dose between the target volume and the organs at risk (P>0.05). The dose to the rectum, the bladder, and both femoral heads showed no significant differences across the IMRT plans with different minimum sub-field areas (P>0.05). Conclusions When the Pinnacle 8.0m treatment planning system is used to develop IMRT plans for cervical cancer, the requirements for clinical dose can still be met with a minimum sub-field area reaching 7 cm×7 cm, and there are significant reductions in sub-field hop count and total hop count. Key words: Cervix neoplasms/intensity-modulated radiotherapy; Inverse planning optimization; Area of segment field

Energy Efficient, Lifetime Improving and Secure Periodic Data Collection Protocol for Wireless Sensor Networks

The most emerging prominent sensor network applications collect data from sensor nodes and monitors periodically. Resource constraint Sensor motes sense the environment and transit data to the remote sink via multiple hops. Minimum energy dissipation and secure data transmission are crucial to such applications. This paper delivers an energy efficient, lifetime improving, secure periodic Data Gathering scheme that is a hybrid of heuristic path establishment and secure data transmission. This protocol uses artificial intelligence (AI) based A* heuristic search algorithm to establish energy efficient admissible optimal path to sink in terms of high residual energy, minimum hop counts and high link quality. This scheme also adopts block encryption Rivest Cipher (RC6) Algorithm to secure the transmission of packets. This code and speed optimized block encryption provides confidentiality against critical data and consumes less energy for encryption. This proposed method increases the network lifetime there by reducing the total traffic load. Evaluation of performance analysis of this algorithm using Network Simulator (NS2) shows the superiority of the proposed scheme.

다중 홉 무선 네트�p에서 지연을 고려한 멀티케스트 루팅

Static wireless multi-hop networks, such as wireless mesh networks and wireless sensor networks have proliferated in recent years because of they are easy to deploy and have low installation cost. Two key measures are used to evaluate the performance of a multicast tree algorithm or protocol : end-to-end delay and the number of transmissions. End-to-end delay is the most important measure in terms of QoS because it affects the total throughput in wireless networks. Delay is similar to the hop count or path length from the source to each destination and is directly related to packet success ratio. In wireless networks, each node uses the air medium to transmit data, and thus, bandwidth consumption is related to the number of transmission nodes. A network has many transmitting nodes, which will cause many collisions and queues because of congestion. In this paper, we optimize two metrics through a guaranteed delay scheme. We provide an integer linear programming formulation to minimize the number of transmissions with a guaranteed hop count and preprocessing to solve the aforementioned problem. We extend this scheme not only with the guaranteed minimum hop count, but also with one or more guaranteed delay bounds to compromise two key metrics. We also provide an explanation of the proposed heuristic algorithm and show its performance and results.

An Efficient Next Hop Selection Algorithm for Multi-Hop Body Area Networks.

Body Area Networks (BANs) consist of various sensors which gather patient’s vital signs and deliver them to doctors. One of the most significant challenges faced, is the design of an energy-efficient next hop selection algorithm to satisfy Quality of Service (QoS) requirements for different healthcare applications. In this paper, a novel efficient next hop selection algorithm is proposed in multi-hop BANs. This algorithm uses the minimum hop count and a link cost function jointly in each node to choose the best next hop node. The link cost function includes the residual energy, free buffer size, and the link reliability of the neighboring nodes, which is used to balance the energy consumption and to satisfy QoS requirements in terms of end to end delay and reliability. Extensive simulation experiments were performed to evaluate the efficiency of the proposed algorithm using the NS-2 simulator. Simulation results show that our proposed algorithm provides significant improvement in terms of energy consumption, number of packets forwarded, end to end delay and packet delivery ratio compared to the existing routing protocol.

Moralism: mobility prediction with link stability based multicast routing protocol in MANETs

In recent research, link stability is getting tremendous attention in mobile adhoc networks (MANETs), because of several impediments that occur in a reliable and robust network. Link stability metric is used to improve network performance in terms of end-to-end delay, data success delivery ratio (DSDR) and available route time (ART). Energy consumption, bandwidth and communication delay of major concern in ad hoc networks. A high mobility of MANET nodes reduces the reliability of network communication. In a dynamic networks, high mobility of the nodes makes it very difficult to predict the dynamic routing topology and hence cause route/link failures. Multicast in MANETs is an emerging trend that effectively improves the performance while lowering the energy consumption and bandwidth usage. Multicast routing protocol transmits a packet to multicast a group at a given time instant to achieve a better utilization of resources. In this paper, node mobility is considered to map better their movement in the network. So, the links with long active duration time can be identified as a stable link for route construction. Variation in signal strength is used to identify whether the direction of the node is towards or away from estimating node. We consider signal strength as QoS metric to calculate link stability for route construction. Efforts are made to identify the link with highly probable longer lifetime as the best suitable link between two consecutive nodes. We predict the movement time of nodes that define the route path to the node destination. Exata/cyber simulator is used for network simulation. The simulation results of the proposed routing protocol are compared with on-demand multicast routing protocol and E-ODMRP, which works on minimum hop count path. Analysis of our simulation results has shown improvement of various routing performance metrics such as DSDR, ART, routing overhead and packet drop ratio.

Ant based routing algorithm over clustering technique to provide better communication for manets with minimum hop count

Ant based routing algorithm over clustering technique to provide better communication for manets with minimum hop count

Trust Based Fuzzy Aided ACO for Optimal Routing with Security in MANET

The mobile ad hoc network is basically a self-configurable network scheme in which there is no fixed infrastructure available. Because of the regular mobility and dynamic topology, the network is imposed with several issues such as energy and security. In order to surpass these issues, the existing scenario proposed Multivariate Auto regressive models (MAR) and hybrid ACO-MGA algorithms for the cluster head selection and optimal path selection correspondingly. But the present mechanism has not entirely dealt with the performance issues associated with security by taking the shortest path into consideration. In order to resolve this issue, the proposed technique proposed Fuzzy aided ACO algorithm, utilized for optimal path selection along with lesser energy consumption. In this work, Fuzzy Relevance Degree algorithm is utilized for cluster head (CH) selection. Any node in the cluster, which has more power and signal strength, obtained from the RS will be chosen to bea CH. For establishing the secure means of transmission, trust aware model is employed. Fuzzy aided ACO isfocused over the selection of the optimal paths. The path information by ants will be provided to FIS (Fuzzy Interference system) for computing the score values of the available path, and on the basis of this score value from the FIS system, the optimal paths will be chosen having minimal hop counts. At last, the packets are transmitted along this path. This new system attains a better performance with respect to packet delivery ratio, bandwidth, end to end delay, energy consumption, throughput and network lifetime when compared with the already available techniques.

A new unequal clustering protocol with local re-clustering mechanism for wireless sensor networks

A new unequal clustering protocol with local re-clustering mechanism is proposed to mitigate the 'hot spot' problem and thereby prolong the network lifetime of a wireless sensor network WSN. In the setup phase, the network is partitioned into several unequal-size layers based on the minimum hop count of each node to the base station BS. Then each layer is further partitioned into several layer-dependent-size clusters by a weight-based cluster head CH competition, where candidate nodes participating in CH election are selected by the BS with a new exploration approach. In addition, we propose a local re-clustering mechanism to further mitigate the uneven energy load during the data transmission phase, that is, different layers reselect their CHs at different frequencies according to their relative distances to the BS. Furthermore, for local re-clustering, a simplified CH rotation approach is proposed to lessen the communication and computation overhead. The simulation results demonstrate that our proposed protocol is effective in prolonging the network lifetime and in balancing the energy consumption.

An Energy-Efficient Clustering Algorithm for Edge-Based Wireless Sensor Networks

To employee clustering algorithms in multi-hop data forwarding mechanism, Hot-spot problem will cause unbalanced energy dissipation among the cluster heads in the network. Unequal clustering technique promotes even energy dissipation only in inter-cluster communications not in intra-cluster communication. An Energy-efficient Clustering Algorithm (EECA) is introduced to avoid these problems in edge-based wireless sensor networks. The main aim of the presented algorithm is to avoid hot-spot problem by balancing uniform energy utilization among networked cluster heads. EECA constructs uneven size clusters in different levels to enable uniform energy expenditure among cluster heads. Data delivery is one of the important and unavoidable energy consuming operation in any sensor networks. To balance energy consumption load among data transmission routes, a multi-hop data forwarding protocol is introduced. Here, source node selects a relaying node who has minimum hop count to base station with more energy reserves and relayed less number of packets. Extensive experimental results prove that the presented algorithm overcome the congestion problem in the network by uniform distribution of energy consumption and enhances network's lifetime.

ENHANCING VARYING OVERHEAD AD HOC ON DEMAND DISTANCE VECTOR WITH ARTIFICIAL ANTS

A cluster of mobile hosts installed with a wireless transceiver form a Mobile Adhoc Network (MANET), without base stations. Wireless ad hoc networks routing protocols usually focus on finding paths with minimum hop count. In a MANET, a route may suddenly be broken when a host roams away. Even if a route is connected, it may worsen due to host mobility or a better route being formed new in the system. Current protocols stick to a fixed route between a source - destination pair when discovered and it continues till it expires or is broken. A routing algorithm chooses better paths by considering wireless links quality. However, in large networks link quality from source to destination provides multiple options in space domain and finding local minima is crucial for successful routing implementation. This study extends the Varying Overhead Ad hoc On demand Distance Vector (VO-AODV) by introducing an optimization parameter using Ant Colony Optimization (ACO).

Load Balanced Fuzzy Control based Adaptive Gateway Discovery for Ubiquitous Internet Access in MANET

Integrating MANETs (Mobile Ad-hoc Networks) nodes to the Internet require either a connection to the Internet or they can connect to the Internet through the Internet gateways. For the second case if a node in a MANET has discover the gateway to connect to the fixed hosts in the Internet and it can be done either by broadcasting a gateway discovery request message initiated by nodes itself or by broadcasting periodic gateway advertisement messages from the gateways. End to end packet delay and throughput are strongly dependent on the time needed to discover the gateways.Nodes in a MANET use number of hops as metric to select a path to a gateway, if all the nodes select its nearest gateway to access the Internet then there may be situations when the network performance degrades because some nodes along the path have too many packets waiting in the queue.This paper presents a novel solution to access internet through mobile nodes in ad hoc network. Here the gateway replies with an advertisement message which is broadcasted to the whole network instead of sending a unicast reply to the requesting node. The traffic load taken into account along a path in addition with minimum hop count to select an efficient gateway. The AODV routing protocol has been used for routing in the MANET domain.A new strategy of gateway discovery was investigated and impact of new metric on the gateway selection in NS-2 was observed. Simulation results show that the proposed scheme outperforms over the existing scheme with high throughput and lower end to end delay.

Routing in delay tolerant networks with periodic connections

In delay tolerant networks (DTNs), the network may not be fully connected at any instant of time, but connections occurring between nodes at different times make the network connected through the entire time continuum. In such a case, traditional routing methods fail to operate because there are no contemporaneous end-to-end paths between sources and destinations. This study examines the routing in DTNs where connections arise in a periodic nature. We analyze various levels of periodicity in order to meet the requirements of different network models. We propose different routing algorithms for different kinds of periodic connections. Our proposed routing methods guarantee the earliest delivery time and minimum hop-count, simultaneously. We evaluate our routing schemes via extensive simulation experiments and compare them to some other popular routing approaches proposed for DTNs. Our evaluations show the feasibility and effectiveness of our schemes as viable routing methods for delay tolerant networks.

Link quality estimation in static wireless networks with high traffic load

Effective link quality estimation is a vital issue for reliable routing in wireless networks. This paper studies the performance of expected transmission count (ETX) under different traffic loads. Although ETX shows good performance under light load, its performance gets significantly worse when the traffic load is high. A broadcast packet storm due to new route discoveries severely affects the link ETX values under high traffic load, which makes it difficult to find a good path. This paper presents the design and implementation of a variation of ETX called high load - ETX (HETX), which reduces the impact of route request broadcast packets to link metric values under high load. We also propose a reliable routing protocol using link quality metrics, which is called link quality distance vector (LQDV). We conducted the evaluation of the performance of three metrics - HETX, ETX and minimum hop-count. The simulation results show that HETX improves the average route throughput by up to 25% over ETX under high traffic load. Minimum hop-count has poor performance compared with both HETX and ETX at all of the different traffic loads. Under light load, HETX and ETX show the same performance.

Routing Mechanism in Mobile Ad hoc Network with Improved Security and Channel Adaptivity under Fading

Mobile Ad Hoc Network is a type of wireless network without a fixed topology consist a set of self organized nodes which are randomly, frequently and unpredictably mobile. In MANETs packet transmission is affected by radio link fluctuations. Hop count is a simple routing metric that calculate the distance between a source and destination on the number of routers in the path. Routing protocols for ad hoc networks have less channel fading. The minimum hop count is not enough for a routing protocol to achieve a good performance. MANET is an open environment and it is susceptible to many security attacks due to dynamic topology and lack of centralized monitoring authority. Anonymous routing protocols conceal the identities about the route, source and destination to provide security and privacy from intruder’s attacks. So in this paper, channel adaptive protocol with improved node security, extensions to a multipath routing protocol to accommodate channel fading and node security is introduced. The resulting protocol is referred to as Channel Adaptive routing protocol with node security (CARNS). Using channel state information (CSI), a preemptive handoff strategy is applied to maintain reliable and stable connections. Paths are reusable, rather than simply regarding them as useless. In this paper we provide performance analysis of CARNS, as well as comparison between CARNS with AODV and AOMDV. The simulation results which confirms the improved network performance of CARNS, both in terms of node security and channel fading.

An Energy-Efficient Hybrid Clustering Mechanism for Wireless Sensor Network

Valuable energy resources of sensor network should be utilized wisely to prolong network's lifetime. Clustering technique helps wireless sensor network (WSN) to enhance its lifetime by reducing energy consumption on every individual sensor node in the network. In multi-hop data forwarding model, difference in energy consumption among cluster heads (HS) causes hot-spot problem in the network. While data is being transferred, the CH close to base station are burdened with heavy relay traffic from several data routes and tend to die early. Unequal clustering avoids this hot-spot problem by establishing different sized clusters at various levels in the network. Since unequal clustering technique does not control number of CHs it creates, it forms huge number of clusters in the network. This increases hop count between source and destination, and leads to impose more over head on each data forwarding route in the network. Also, rapid variation in cluster size causes imbalance in energy dissipation among clustered nodes in the network. This uneven energy consumption influences network performance and lifetime. In this paper, we present an energy-efficient hybrid clustering mechanism for wireless sensor network using equal and unequal clustering techniques to create limited number of clusters in varied sizes at various level of the network. This avoids hot-spot problem with minimum hop count between the source and destination and achieves uniform energy dissipation between intra- and inter-cluster communication. Simulation results show that the proposed clustering mechanism balances the energy consumption among clusters with its hybrid cluster formation mechanism and elevates sensor network lifetime.

Impact of Limiting Hop Count on the Lifetime of Wireless Sensor Networks

In this study, we present a novel family of mixed integer programming (MIP) models to analyze the effects of limiting hop count on Wireless Sensor Network (WSN) lifetime. We performed analysis to uncover the trade-off between minimizing the number of hops and maximizing the network lifetime by exploring the parameter space through numerical evaluations of the optimization models. Our results reveal that minimum hop routing leads to significant decrease in network lifetime (up to 40%) when compared to the maximum network lifetime obtained without any restrictions on hop count. However, the decrease in network lifetime is negligible if the minimum hop routing criterion is modestly relaxed ( e.g ., 3% decrease in network lifetime is possible if the minimum hop count is increased by 15%).

A Range-free Node Localization Algorithm Based on Potential Space Self-definition and Local Neighbor Selection in WSN

A range-free 3D node localization algorithm based on potential space self-definition and local neighbor selection in Wireless Sensor Network (WSN) is proposed in this paper. This algorithm needs only three anchors in space without extra information exchange between unknown nodes and position estimation is completed by using triangle method. Only three anchors are placed in the specified positions of a cube space in advance, named as A1, A2 and A3. Unknown sensors will compute the minimum hop counts to A1, A2 and A3 respectively and a potential sub-space will be defined whose hop counts are the same in which unknown sensors may most possibly locate. By using this sub-space the positions of unknowns will be computed roughly and then more accurate position estimations will be given according to its other local neighbors in the adjacent potential sub-space which is called local neighbor selection. Simulations are finished in MATLAB to explore the effects of different parameters on the proposed method and it is proved this method has better robustness and stability in extremely bad environment. Also comparisons are made with classic DV-Hop method and the results prove the proposed algorithm is better than the DV-Hop method in localization accuracy.

Link Reliable Energy Efficient AOMDV routing protocol for mobile ad hoc networks

Reliable data transmission has been an emerging issue in ad hoc on-demand multipath distance vector (AOMDV) routing since the nodes are prone to link failures and route breaks in highly dynamic ad hoc networks owing to the selection of multiple routes between any source and destination pair based on minimal hop count. For eliminating such problems, a novel node disjoint multipath routing protocol called link reliable energy efficient AOMDV (LR-EE-AOMDV) routing protocol, the extension of AOMDV is proposed. The LR-EE-AOMDV finds multiple link reliable energy efficient paths between any source and destination pair for data transmission using three metrics such as path length, path-link quality estimator (P-LQE) and a novel path-node energy estimator (P-NEE). The performance of LR-EE-AOMDV is evaluated using NS2.34 with varying network flows and number of nodes under random waypoint mobility model in terms of quality-of-service (QoS) metrics. Simulation results reveal the effectiveness of LR-EE-AOMDV routing protocol.