Cross-layer aided energy-efficient routing design for ad hoc networks

In this treatise, we first review some basic routing protocols conceived for ad hoc networks, followed by some design examples of cross-layer operation aided routing protocols. Specifically, cross-layer operation across the PHYsical layer (PHY), the Data Link layer (DL) and even the NETwork layer (NET) is exemplified for improving the energy efficiency of the entire system. Moreover, the philosophy of Opportunistic Routing (OR) is reviewed for the sake of further reducing the system's energy dissipation with the aid of optimized Power Allocation (PA). The system's end-to-end throughput is also considered in the context of a design example

Reliable routing scheme for indoor sensor networks

Indoor Wireless sensor networks require a highly dynamic, adaptive routing scheme to deal with the high rate of topology changes due to fading of indoor wireless channels. Besides that, energy consumption rate needs to be consistently distributed among sensor nodes and efficient utilization of battery power is essential. If only the link reliability metric is considered in the routing scheme, it may create long hops routes, and the high quality paths will be frequently used. This leads to shorter lifetime of such paths; thereby the entire network's lifetime will be significantly minimized. This paper briefly presents a reliable load-balanced routing (RLBR) scheme for indoor ad hoc wireless sensor networks, which integrates routing information from different layers. The proposed scheme aims to redistribute the relaying workload and the energy usage among relay sensor nodes to achieve balanced energy dissipation; thereby maximizing the functional network lifetime. RLBR scheme was tested and benchmarked against the TinyOS-2.x implementation of MintRoute on an indoor testbed comprising 20 Mica2 motes and low power listening (LPL) link layer provided by CC1000 radio. RLBR scheme consumes less energy for communications while reducing topology repair latency and achieves better connectivity and communication reliability in terms of end-to-end packets delivery performance

A Joint Model for IEEE 802.15.4 Physical and Medium Access Control Layers

Many studies have tried to evaluate wireless networks and especially the IEEE 802.15.4 standard. Hence, several papers have aimed to describe the functionalities of the physical (PHY) and medium access control (MAC) layers. They have highlighted some characteristics with experimental results and/or have attempted to reproduce them using theoretical models. In this paper, we use the first way to better understand IEEE 802.15.4 standard. Indeed, we provide a comprehensive model, able more faithfully to mimic the functionalities of this standard at the PHY and MAC layers. We propose a combination of two relevant models for the two layers. The PHY layer behavior is reproduced by a mathematical framework, which is based on radio and channel models, in order to quantify link reliability. On the other hand, the MAC layer is mimed by an enhanced Markov chain. The results show the pertinence of our approach compared to the model based on a Markov chain for IEEE 802.15.4 MAC layer. This contribution allows us fully and more precisely to estimate the network performance with different network sizes, as well as different metrics such as node reliability and delay. Our contribution enables us to catch possible failures at both layers.Comment: Published in the proceeding of the 7th International Wireless Communications and Mobile Computing Conference (IWCMC), Istanbul, Turkey, 201

An efficient scalable scheduling mac protocol for underwater sensor networks

Underwater Sensor Networks (UWSNs) utilise acoustic waves with comparatively lower loss and longer range than those of electromagnetic waves. However, energy remains a challenging issue in addition to long latency, high bit error rate, and limited bandwidth. Thus, collision and retransmission should be efficiently handled at Medium Access Control (MAC) layer in order to reduce the energy cost and also to improve the throughput and fairness across the network. In this paper, we propose a new reservation-based distributed MAC protocol called ED-MAC, which employs a duty cycle mechanism to address the spatial-temporal uncertainty and the hidden node problem to effectively avoid collisions and retransmissions. ED-MAC is a conflict-free protocol, where each sensor schedules itself independently using local information. Hence, ED-MAC can guarantee conflict-free transmissions and receptions of data packets. Compared with other conflict-free MAC protocols, ED-MAC is distributed and more reliable, i.e., it schedules according to the priority of sensor nodes which based on their depth in the network. We then evaluate design choices and protocol performance through extensive simulation to study the load effects and network scalability in each protocol. The results show that ED-MAC outperforms the contention-based MAC protocols and achieves a significant improvement in terms of successful delivery ratio, throughput, energy consumption, and fairness under varying offered traffic and number of nodes

Design of rate-adaptive MAC and medium aware routing protocols for multi-rate, multi-hop wireless networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The IEEE 802.11 standard conformant wireless communication stations have multi-rate transmission capability. To achieve greater communication efficiency, multi-rate capable stations use rateadaptation to select appropriate transmission rate according to variations in the channel quality. The thesis presents two rate-adaptation schemes, each belonging to one of the two classes of rateadaptation schemes i.e.(1) the frame-transmission statistics based schemes, and (2) Signal-to-Noise Ratio (SNR) based, closed loop schemes. The SNR-based rate-adaptation scheme, proposed in this thesis uses a novel mechanism of delivering a receiver’s feedback to a transmitter; without requiring any modification in the standard frames as suggested by existing research. The frame-transmissionstatistics based rate adaptation solution uses an on-demand incremental strategy for selecting a rate-selection threshold. This solution is based on a cross-layer communication framework, where the rate-adaptation module uses information to/from the Application layer along with relevant information from the Medium Access Control (MAC) sub-layer. The proposed solutions are highly responsive when compared with existing rate-adaptation schemes; responsiveness is one of the key factors in the design of such protocols. The novel feedback mechanism makes it possible to achieve frame-loss differentiation with just three frames, avoiding the use of Request To Send/ Clear To Send (RTS/CTS) frames and further delays in this process. Performance tests have affirmed that the proposed rate-adaptation schemes are energy efficient; with efficiency up to 19% in specific test scenarios. In terms of throughput and frame loss-differentiation mechanisms, the proposed schemes have shown significantly better performance.Routing protocols for Mobile Ad-Hoc Networks (MANETs) use broadcast frames during the route discovery process. The 802.11 mandates the use of different transmission rates for broadcast and unicast (data-) frames. In many cases it causes creation of communication gray zones, where stations which are marked as ‘reachable neighbours’ using the broadcast frames (using lower transmission rate) are not accessible during normal, unicast communication (mainly at a higher rate). Similarly, higher device density, interference and mobility cause variable medium access delays. The IEEE 802.11e introduces four different MAC level queues for four access categories, maintaining service priority within the queues; which implies that frames from a higher priority queue are serviced more frequently than those belonging to lower priority queues. Such an enhancement at the MAC sub-layer introduces uneven queuing delays. Conventional routing protocols are unaware of such MAC specific constraints and as a result these factors are not considered which result in severe performance deterioration. To meet such challenges, the thesis presents a medium aware distance vector (MADV) routing protocol for MANETs. MADV uses MAC and physical layer (PHY) specific information in the route metric and maintains a separate route per-AC-per-destination in its routing tables. The MADV-metric can be incorporated into various routing rotocols and its applicability is determined by the possibility of provision of MAC dependent arameters that are used to determine the hop-by-hop MADV-metric values. Simulation tests and omparison with existing MANET protocols demonstrate the effectiveness of incorporating the medium dependent parameters and show that MADV is significantly better in terms of end-to-end delay and throughput

Real-Time Cross-Layer Routing Protocol for Ad Hoc Wireless Sensor Networks

Reliable and energy efficient routing is a critical issue in Wireless Sensor Networks (WSNs) deployments. Many approaches have been proposed for WSN routing, but sensor field implementations, compared to computer simulations and fully-controlled testbeds, tend to be lacking in the literature and not fully documented. Typically, WSNs provide the ability to gather information cheaply, accurately and reliably over both small and vast physical regions. Unlike other large data network forms, where the ultimate input/output interface is a human being, WSNs are about collecting data from unattended physical environments. Although WSNs are being studied on a global scale, the major current research is still focusing on simulations experiments. In particular for sensor networks, which have to deal with very stringent resource limitations and that are exposed to severe physical conditions, real experiments with real applications are essential. In addition, the effectiveness of simulation studies is severely limited in terms of the difficulty in modeling the complexities of the radio environment, power consumption on sensor devices, and the interactions between the physical, network and application layers. The routing problem in ad hoc WSNs is nontrivial issue because of sensor node failures due to restricted recourses. Thus, the routing protocols of WSNs encounter two conflicting issue: on the one hand, in order to optimise routes, frequent topology updates are required, while on the other hand, frequent topology updates result in imbalanced energy dissipation and higher message overhead. In the literature, such as in (Rahul et al., 2002), (Woo et al., 2003), (TinyOS, 2004), (Gnawali et al., 2009) and (Burri et al., 2007) several authors have presented routing algorithms for WSNs that consider purely one or two metrics at most in attempting to optimise routes while attempting to keep small message overhead and balanced energy dissipation. Recent studies on energy efficient routing in multihop WSNs have shown a great reliance on radio link quality in the path selection process. If sensor nodes along the routing path and closer to the base station advertise a high quality link to forwarding upstream packets, these sensor nodes will experience a faster depletion rate in their residual energy. This results in a topological routing hole or network partitioning as stated and resolved in and (Daabaj 2010). This chapter presents an empirical study on how to improve energy efficiency for reliable multihop communication by developing a real-time cross-layer lifetime-oriented routing protocol and integrating useful routing information from different layers to examine their joint benefit on the lifetime of individual sensor nodes and the entire sensor network. The proposed approach aims to balance the workload and energy usage among relay nodes to achieve balanced energy dissipation, thereby maximizing the functional network lifetime. The obtained experimental results are presented from prototype real-network experiments based on Crossbow’s sensor motes (Crossbow, 2010), i.e., Mica2 low-power wireless sensor platforms (Crossbow, 2010). The distributed real-time routing protocol which is proposed In this chapter aims to face the dynamics of the real world sensor networks and also to discover multiple paths between the base station and source sensor nodes. The proposed routing protocol is compared experimentally with a reliability-oriented collection-tree protocol, i.e., the TinyOS MintRoute protocol (Woo et al., 2003). The experimental results show that our proposed protocol has a higher node energy efficiency, lower control overhead, and fair average delay

Development of an efficient Ad Hoc broadcasting scheme for critical networking environments

Mobile ad hoc network has been widely deployed in support of the communications in hostile environment without conventional networking infrastructure, especially in the environments with critical conditions such as emergency rescue activities in burning building or earth quick evacuation. However, most of the existing ad hoc based broadcasting schemes either rely on GPS location or topology information or angle-of-arrival (AoA) calculation or combination of some or all to achieve high reachability. Therefore, these broadcasting schemes cannot be directly used in critical environments such as battlefield, sensor networks and natural disasters due to lack of node location and topology information in such critical environments. This research work first begins by analyzing the broadcast coverage problem and node displacement form ideal locations problem in ad hoc networks using theoretical analysis. Then, this research work proposes an efficient broadcast relaying scheme, called Random Directional Broadcasting Relay (RDBR), which greatly reduces the number of retransmitting nodes and end-to-end delay while achieving high reachability. This is done by selecting a subset of neighboring nodes to relay the packet using directional antennas without relying on node location, network topology and complex angle-of-arrival (AoA) calculations. To further improve the performance of the RDBR scheme in complex environments with high node density, high node mobility and high traffic rate, an improved RDBR scheme is proposed. The improved RDBR scheme utilizes the concept of gaps between neighboring sectors to minimize the overlap between selected relaying nodes in high density environments. The concept of gaps greatly reduces both contention and collision and at the same time achieves high reachability. The performance of the proposed RDBR schemes has been evaluated by comparing them against flooding and Distance-based schemes. Simulation results show that both proposed RDBR schemes achieve high reachability while reducing the number of retransmitting nodes and end-to-end delay especially in high density environments. Furthermore, the improved RDBR scheme achieves better performance than RDBR in high density and high traffic environment in terms of reachability, end-to-end delay and the number of retransmitting nodes

On the benefits of Cross Layer Feedback in Multi-hop Wireless Networks

Wireless networks operate under harsh and time-varying channel conditions. In wireless networks the time varying channel conditions lead to variable SINR and high BER. The wireless channel is distinct from and more unpredictable than the far more reliable wireline channel. {\em Cross layer feedback} is a mechanism where layers provide {\em selective} information to other layers to boost the performance of wireless networks. {\em Cross layer feedback} can lead to a tremendous increase in the performance of the TCP/IP stack in wireless networks, and an increase in the user's satisfaction level. However, it is possible that naive feedbacks (or optimizations) can work non-coherently; therefore, these can negatively effect the performance of the TCP/IP stack. In this paper, we holistically analyze each layer of the TCP/IP stack, and propose possible Cross layer feedbacks which work coherently. The proposed Cross layer feedbacks can greatly enhance the performance of the TCP/IP stack in wireless networks