Maaz Rehan

A comprehensive survey on multichannel routing in wireless sensor networks

Multi-channel based routing approach may utilize more than one channel for communication and has the ability to provide high performance by more rigorously countering interference, collisions and re-transmissions than the single-channel routing methodology. This research work aims to establish guidelines for future research and development in the area of Wireless Sensor Networks (WSNs) based on the critical analysis of the prevalent multi-channel based routing protocols for WSNs. Due to extensive ongoing research in this domain, a significant number of multi-channel routing strategies have been presented which need to be discussed. To explore, this work not only reviews a variety of single/multi-path and single/multi-radio multichannel routing protocols for WSNs under a novel taxonomy, but also outlines their relevant pros and cons. In order to help design new multi-channel routing strategies for WSNs, an insightful review on the applications, current design issues and associated challenges of multichannel routing in WSNs are in-depth scrutinized. Towards the end, some prospect trends are put forth regarding multi-channel routing for WSNs which may provide a road map for future investigation.

Reliability-constrained routing for traffic load balancing in Wireless Sensor Networks

In recent years, a notable progress has been observed in the field of Wireless Sensor Networks (WSNs) due to their enormous number of applications. In this paper, a routing problem has been considered in a static WSN. Traditionally, routing mechanisms are based on a single objective optimisation function, e.g., the cost in terms of distance to find the shortest End-to-End (ETE) path from a source (S) to a destination (D). This behaviour may not be appropriate for long term reliable communication. We have considered a reliability-constrained multi-objective optimisation problem that implicitly captures the traffic load based on the Packet Delivery Ratio (PDR) along with the hop-count. The proposed technique selects an optimum ETE reliable path. The reliability is achieved by selecting the nodes with least congestion along the path from S to D that eventually balance the traffic load in the network. The result shows that the PDR and the hop count have a significant impact to select the best reliable ETE path.

ZGLS: a novel flat quorum-based and reliable location management protocol for VANETs

In location management services, a destination advertises its position attributes to a set of vehicles called location servers while, a source obtains these attributes from such location servers to track destination. The location management techniques in VANET have been categorized into flooding-based, flat hashing-based, hierarchical hashing-based and hierarchical quorum-based techniques. In flooding-based location service, destination information is flooded to the entire network which results into high congestion, low throughput and non-scalable network. In flat hashing, a global hash function is applied to compute location servers of each destination which results into higher delay, drop and signaling overhead in large VANETs. In hierarchical hashing, global hash function computes location servers of destination in hierarchical order. It therefore suffers from handover signaling between servers, high load on the top hierarchy and location query delay when source and destination are apart. In hierarchical quorum-based, location servers are identified cluster-wise and therefore it also suffers from the problems similar to hierarchical techniques. To overcome these problems, ZoomOut Geographic Location Service (ZGLS) protocol is proposed which introduces flat quorum-based location management service. In contrast to the aforementioned techniques, the novelty of ZGLS lies in the fact that it has shifted the location server role from hashing-based or clustering-based geographic areas to few 1-hop neighbours, called relatives. The proposed protocol creates a chain of relatives to provide positioning and tracking service. To evaluate signalling overhead, timeliness and the reliability of update and query packets, ZGLS is compared with RLSMP and HRHLS through ns-2 simulations. The results reveal that ZGLS stands out as a better choice for large-scale sparse and dense VANETs.

Machine-Learning Based Channel Quality and Stability Estimation for Stream-Based Multichannel Wireless Sensor Networks

Wireless sensor networks (WSNs) have become more and more diversified and are today able to also support high data rate applications, such as multimedia. In this case, per-packet channel handshaking/switching may result in inducing additional overheads, such as energy consumption, delays and, therefore, data loss. One of the solutions is to perform stream-based channel allocation where channel handshaking is performed once before transmitting the whole data stream. Deciding stream-based channel allocation is more critical in case of multichannel WSNs where channels of different quality/stability are available and the wish for high performance requires sensor nodes to switch to the best among the available channels. In this work, we will focus on devising mechanisms that perform channel quality/stability estimation in order to improve the accommodation of stream-based communication in multichannel wireless sensor networks. For performing channel quality assessment, we have formulated a composite metric, which we call channel rank measurement (CRM), that can demarcate channels into good, intermediate and bad quality on the basis of the standard deviation of the received signal strength indicator (RSSI) and the average of the link quality indicator (LQI) of the received packets. CRM is then used to generate a data set for training a supervised machine learning-based algorithm (which we call Normal Equation based Channel quality prediction (NEC) algorithm) in such a way that it may perform instantaneous channel rank estimation of any channel. Subsequently, two robust extensions of the NEC algorithm are proposed (which we call Normal Equation based Weighted Moving Average Channel quality prediction (NEWMAC) algorithm and Normal Equation based Aggregate Maturity Criteria with Beta Tracking based Channel weight prediction (NEAMCBTC) algorithm), that can perform channel quality estimation on the basis of both current and past values of channel rank estimation. In the end, simulations are made using MATLAB, and the results show that the Extended version of NEAMCBTC algorithm (Ext-NEAMCBTC) outperforms the compared techniques in terms of channel quality and stability assessment. It also minimizes channel switching overheads (in terms of switching delays and energy consumption) for accommodating stream-based communication in multichannel WSNs.

Congestion-aware and traffic load balancing scheme for routing in WSNs

Congestion in a Wireless Sensor Network (WSN) is one of the causes of performance degradation due to severe packet loss that leads to excessive energy consumption. Solutions in WSNs try to avoid and overcome congestion by selecting sensor nodes with sufficient buffer space and adjusting the traffic rate at the source node over the shortest discovered route that usually decreases the End-to-End (ETE) throughput. On-demand routing protocols have the potential to discover the least congested route when it is required. In a WSN, most of the on-demand routing protocols replace the routing metric of the prevalent routing protocol with their proposed routing metric and keep the route discovery mechanism intact, which is not sufficient to increase the performance of the WSN. To address these problems, a novel Congestion-aware and Traffic Load balancing Scheme (CTLS) for routing has been proposed. The CTLS proactively avoids congestion through a novel route discovery mechanism to select the optimum node based on a composite metric. If congestion occurs, CTLS tries to detect it in a timely manner and alleviates it reactively using a novel ripple-based search approach. The simulation results show that the CTLS performs better as compared to the congestion avoidance, detection and alleviation and no congestion control schemes in terms of packet delivery ratio, ETE delay, throughput, and energy consumption per data packet in a resource constraint wireless network.

A Critical Review of Surveys Emphasizing on Routing in Wireless Sensor Networks—An Anatomization under General Survey Design Framework

A large number of routing-related surveys are published so far for Wireless Sensor Networks (WSNs) that exhibit either complete or partial emphasis on routing in WSNs. These surveys classify and discuss the relevant routing protocols published mainly in the fields of classical, energy efficient, secure, hierarchical, geographic, intelligent, Quality of Service (QoS)-based and multipath WSNs. However, to the best of our knowledge, no study is presented so far which may clearly categorize the routing-related survey literature for WSNs.To fill this gap, an effort is made in this paper for presenting an in-depth review of already published routing-related survey literature in WSNs. Our review initially proposes a generalized survey design model and afterwards analyzes the routing-related survey literature in the light of the devised General Survey Design Framework (GSDF). Such an analysis describes the design soundness of the published routing-related surveys. Therefore, our review puts forth an original classification based on the frequency-of-survey-publication and taxonomizes the corresponding routing-related fields into high, medium and low focused areas of survey publication in WSNs. Furthermore, the surveys belonging to each main category are sub-categorized into various sub-classes and briefly discussed according to their design characteristics. On the one hand, this review is useful for beginners who may easily explore the already published routing-related survey literature in WSNs in a single document and investigate it by spending less effort. On the other hand, it is useful for expert researchers who may explore the trends and frequency of writing surveys in different areas of routing in WSNs. The experts may explore those areas of routing which are either neglected or least focused or lack in design soundness as per general survey design framework. In the end, insights and future research directions are outlined and a reasonable conclusion is put forth which may outline guiding principles for routing-related survey research in future.

ZoomOut HELLO: A Novel 1-Hop Broadcast Scheme to Improve Network QoS for VANET on Highways

On highways, each vehicle uses periodic 1-hop broadcast messages to advertise its position and other information so that vehicles in the vicinity and those which are hops away can find the advertising vehicle for information exchange. During destination discovery, a vehicle issues broadcast messages, which travel hop by hop in search of destination. We argue that since periodic 1-hop messages are sent on regular intervals, so these can be manipulated in such an intelligent way that routing protocols may not need to execute broadcast destination discovery procedure. The continuous periodic HELLO broadcast mechanism can assist the routing protocol in this regard. The proposed ZoomOut HELLO (ZOH) technique introduces a neighbour-cum-forwarding (NF) table. In this scheme, periodic ZOH mechanism will populate the NF table, while the forwarding mechanism will use it. We introduce the concepts of Front and Behind relatives, which are selected out of 1-hop neighbours based on the typed HELLO messages exchanged between 1-hop neighbours. ZOH is a broadcast suppression technique and implicitly provides chain of relatives in the front and behind direction of each vehicle. A routing protocol can therefore use this chain. We have developed analytical model for ad-hoc on-demand distance vector (AODV), preferred group broadcast (PGB), reliable opportunistic broadcast (R-OB-VAN) and ZoomOut HELLO, and implemented them in MATLAB. The results show that ZoomOut HELLO generates least number of RREQ rebroadcast messages and has minimum network delay due to RREQ messages.

Effect of reinforcement learning on routing of cognitive radio ad-hoc networks

Todays network control systems have very limited ability to adapt the changes in network. The addition of reinforcement learning (RL) based network management agents can improve Quality of Service (QoS) by reconfiguring the network layer protocol parameters in response to observed network performance conditions. This paper presents a closed-loop approach to tuning the parameters of the protocol of network layer based on current and previous network state observation for user and channel interference, specifically by modifying some parameters of Ad-Hoc On-Demand Distance Vector (AODV) routing protocol for Cognitive Radio Ad-Hoc Network (CRAHN) environment. In this work, we provide a self-contained learning method based on machine-learning techniques that have been or can be used for developing cognitive routing protocols. Generally, the developed mathematical model based on the one RL technique to handle the route decision in channel switching and user mobility situation so that the overall end-to-end delay can be minimized and the overall throughput of the network can be maximized according to the application requirement in CRAHN environment. Here is the proposed self-configuration method based on RL technique can improve the performance of the original AODV protocol, reducing protocol overhead and end-to-end delay for CRAHN while increasing the packet delivery ratio depending upon the traffic model. Simulation results are shown using NS-2 which shows the proposed model performance is much better than the previous AODV protocol.

ZLS: A next-door lightweight QoS aware location service technique for VANET on highways

In VANET, a Location service technique comprises of location update and location request. In location update, a destination vehicle advertises its services and location to a set of vehicles called location servers. In location request, a source vehicle queries location servers in its broadcast range about the location and services of destinations. During location update, separate control messages are exchanged to periodically update location servers which create delay and congestion in the network. Similarly, after location request, pre-loaded digital maps at source vehicle are used to find the shortest path towards destination which does not give vehicle density on road at that moment in time. Other than digital maps, Dijkstra or Bellmen ford algorithms at source or intermediate nodes are also used to find shortest path, which is a computationally time consuming activity leading to an extra delay during path finding and before packet transmission. We therefore propose QoS and traffic density aware location service technique called ZoomOut Location Service (ZLS). We have implemented ZLS in NS2.33. The simulation results for highway traffic show that ZLS updates its location servers in a uni-cast fashion such that the location servers have up-to-date information of advertised services and destination position. Similarly, a source can reach destination in the quickest possible way by sending uni-cast messages without using digital map or shortest path finding algorithms.

Anatomizing the robustness of multichannel MAC protocols for WSNs: An evaluation under MAC oriented design issues impacting QoS

Abstract Traditional Wireless Sensor Networks (WSNs) are single-channel based and mainly focus on energy-efficiency and scalability. Therefore, they may readily suffer from issues such as bandwidth insufficiency, interference, jamming and so on. With the deployment of dense sensor networks and the outset of multimedia technology, the intensity of the above-mentioned issues is further aggravated. To address those challenges, the researchers have employed multichannel technology in WSNs that focuses on increasing bandwidth/throughput while decreasing collision/congestion, delay, and energy consumption. For ascertaining a comprehensive exploration of multichannel technology in WSNs, this paper discusses in detail the important issues that are indispensable for providing high-performance and achieving Quality of Service (QoS) in multichannel WSNs. Further on, it evaluates a variety of multichannel MAC protocols under the stated design issues and classifies them into the categories Highly, Medium and Least-Robust, based upon aggregate-of-the-design-issues addressed by the corresponding multichannel MAC protocols for WSNs. Besides on the basis of channel access mechanism, each main category is sub-categorized into Time Division Multiple Access (TDMA), Carrier Sense Multiple Access (CSMA), Composite and Other-Novel classes whereby the functionality of the MAC protocols belonging to each class is briefly discussed along with relevant pros & cons. In addition to that, the survey delineates the implementation of the multichannel methodology in the emerging smart technologies of WSNs. In the end, future research directions are anticipated and a reasonable conclusion is put forth.