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The IEEE 802.11p/1609.4 standard supports both safety applications and non-safety services for vehicular ad hoc networks (VANETs) via multi-channel operations. In this letter, we establish an analytical model to calculate the optimal bandwidth resource allocation and propose a flexible multi-channel coordination MAC (FMC-MAC) protocol for VANETs. The FMC-MAC protocol allows safety messages broadcasted on service channel and non-safety data transmitted on control channel in a flexible way. It does not only guarantee the reliability of safety applications, but also improve the throughput of non-safety services. The simulation results validate the analytical model and the proposed FMC-MAC protocol.

As the widely adopted IEEE 802.15.4 standard exhibited severe drawbacks when used in multi-hop WSN environment, the IEEE Standards Association Board has released a revised version, IEEE 802.15.4e, which includes Time-Slotted Channel Hopping (TSCH) mechanism as the MAC amendment to IEEE 802.15.4. The key feature of IEEE 802.15.4e TSCH mechanism is to allow the sensors to plan the time-slot schedule for efficient data transmission. However, the standard does not specify how to plan a time-slot schedule so that data collected by the sensors can be received by the base station as soon as possible without being delayed by transmission conflicts. In this paper, we propose a constant-time, distributed time-slot scheduling algorithm to address this problem. Existing works on IEEE 802.15.4e TSCH scheduling depend on one or a few nodes to collect traffic-flow information from their descendants and plan a centralized time-slot schedule for the whole network. In contrast, our algorithm allows every sensor node to compute its time-slot schedule in a simple, truly distributed manner. Simulation results show that our algorithm significantly outperforms a state-of-the-art protocol in terms of the packet transmission delay and yields a smaller duty cycle. HighlightsThe current state of the art of IEEE 802.15.4e standard is reviewed.The minimum TSCH schedule for conflict-free data gathering process in an IEEE 802.15.4e WSN is shown to be NP-hard.A constant-time, distributed scheduling algorithm to address the minimum IEEE 802.15.4e TSCH scheduling problem is proposed.

In a wireless body area network (WBAN), high data reliability and long operating time are important requirements. The retransmission process of the default Automatic Repeat reQuest (ARQ) mechanism in IEEE 802.15.4 is a suitable method to ensure the data reliability of WBAN communications, where frame loss can occur frequently. However, retransmitting the entire DATA frame is energy inefficient due to the fact that the most of payload data within lost frames are only partially corrupted. Therefore, this paper proposes the automatic segment repeat request scheme for the IEEE 802.15.4-based WBANs. The proposed scheme partitions the data payload into segments when the channel condition is bad, and retransmits only the corrupted segment(s). This reduces the size of the retransmitted frames, which improves frame reception rate and decreases the amount of transmitted traffic, and thus energy consumption. Our experiments using a real IEEE 802.15.4-based WBAN test bed show that the proposed method provides higher transmission reliability and lower power consumption than the default IEEE 802.15.4 ARQ mechanism.

Vehicular ad hoc networks (VANETs) employ multichannel to provide a variety of safety and non-safety applications. Safety applications require reliable and timely transmission, while non-safety applications need high network throughput. IEEE 802.11p and IEEE 1609.4 protocol divide the bandwidth into seven channels. One control channel (CCH) is to serve safety applications and the other six service channels (SCHs) to serve non-safety applications. The IEEE 1609.4 protocol specifies an alternating scheme to allow vehicles to switch between two types of applications. However, the IEEE 1609.4 multichannel media access control (MAC) protocol has limitations on its capability of supporting either delay- or throughput-sensitive applications. In this paper, we propose an adaptive multi-priority distributed multichannel (APDM) MAC protocol for VANETs. Considering that in realistic VANETs, the queue of MAC layer is far from saturated. We assume that generated packets with different priorities arrive at the MAC layer in a Poisson manner. A Markov analytical model is conducted to optimize the packet transmission probabilities and adjust the ratio between CCH interval and SCH interval dynamically according to the real-time traffic in a distributed way. An M/M/1 queue model is then adopted to analyze the time performance. Extensive simulation results show that the APDM MAC protocol can ensure prioritized transmission of safety packets, reduce the transmission delay of packets and enhance the unsaturated and saturated throughput of SCHs.

The bi-directional communication system is an indispensable component in smart grid (SG) for monitoring and exchanging essential information among the electrical devices. IEEE 802.11s based wireless mesh networks recently have been proposed as an important networking technology to deploy in SG for data collection and remote control purposes, as the cost of networking equipments decreases and performance increases. In this paper, we focus on analyzing the MAC layer performance for IEEE 802.11s wireless mesh networks in the smart grid based on Markov model, taking into account the impact of hidden nodes and different QoS requirements of smart grid applications. We first develop a new Markov chain model to analyze the back-off process for different applications with hidden nodes problem. Then based on the analytical model, we derive a few MAC layer performance metrics such as MAC layer packet dropping probability, the mean throughput and the mean packet delay which contains the queuing delay. Finally, the proposed analytical model is validated via comparing the analytical results with simulation results by ns-3 in NAN scenarios with various applications. We observe a good match between the analytical model and simulations which confirms the veracity of our model.

This article gives an overview of the IEEE 802.15.10 standard specifying a layer 2 routing (L2R) protocol enabling communication over multiple hops in IEEE 802.15.4 networks. IEEE 802.15.4 is expected to be a predominant technology as we move toward an increasingly interconnected society. IEEE 802.15.10 allows increasing the range of an IEEE 802.15.4 network while maintaining low-power transmission. This new standard is suitable for applications such as smart metering, intelligent transportation systems, and automation, where a varying number of devices are deployed in an area ranging from a few square meters to entire cities or countries.

In this paper we provide a model for analyzing the saturation throughput of the ieee 802.15.4 mac protocol, which is the de-facto standard for wireless sensor networks, ensuring fair access to the channel. To this end, we introduce the concept of a natural layer, which reflects the time that a sensor node typically has to wait prior to sending a packet. The model is simple and provides new insight how the throughput depends on the protocol parameters and the number of nodes in the network. Validation experiments with simulations demonstrate that the model is highly accurate for a wide range of parameter settings of the mac protocol, and applicable to both large and small networks. As a byproduct, we discuss fundamental differences in the protocol stack and corresponding throughput models of the popular 802.11 standard.

The IEEE 802.11s Wireless Mesh Networks (WMN) is a new multi-hop technology increasing the coverage of IEEE 802.11 Wireless Network and providing Internet access. In order to increase the mesh network capacity, the WMN has evolved from single-radio single-channel architecture to Multi-Channel MultiRadios (MC-MR) architecture. In MC-MR the main challenge of the WMN is the channel assignment. In this article, we propose a new channel assignment method based on channel diversity. This new method named ODCAM (On Demand channel Assignment Method for channel diversity ) defines a channel diversity mechanism used to select a new channel along the path between the source and the destination. The best path between the source and the destination is provided by the HWMP (Hybrid Wireless Mesh Protocol) protocol using MWCETT (Modified Weighted Cumulative Expected Transmission Time) an extension of the WCETT metric. The simulation results show the ODCAM performance compared with an hybrid approach.

To implement WMN, IEEE 802.11s has been developed. The routing protocol for selecting a path between two mesh stations in IEEE 802.11s is hybrid wireless mesh protocol (HWMP). But mobility of external stations has not been considered in IEEE 802.11s. For handling movement of clients, many mobility management schemes have been proposed. Some of such schemes are: ANT, Mesh Mobility Management (M $$^{3})$$ , Infrastructure Mesh (iMesh), SMesh, MEsh networks with MObility management (MEMO), Wireless mesh Mobility Management (WMM), Static Anchor Scheme, Dynamic Anchor Scheme, LMMesh, Session-to-Mobility-Ratio based Scheme and Forward Pointer-Based Mobility Management Scheme (FPBR). But none of the schemes except FPBR have been integrated with IEEE 802.11s for providing mobility support to the external stations. FPBR has been proposed to enhance IEEE 802.11s for providing mobility support to external stations, but it can support internet traffic only. In WMN both internet and intranet traffic to and from the external station is important. In this paper, an improved version of FPBR named Enhanced FPBR (EFPBR) Scheme has been introduced to handle both internet and intranet traffic. Both EFPBR and HWMP have been numerically analyzed. HWMP and EFPBR schemes are simulated and the performances are compared. From the performance comparison, it can be observed that EFPBR performs better than that of IEEE 802.11s concerning throughput, end-to-end delay, routing overhead and average handoff cost. The number of route management packets transferred per handoff measured from numerical analysis and simulation has also been compared.

Energy consumption has been a critical factor for mobile video applications. The quality of content delivery over wireless mesh networks consisting of such devices is also considered important. Existing energy-aware research and industrial effort focuses on reducing high-energy-consuming working periods of mesh devices at the expense of decreasing the quality of video content. This paper proposes AOC-MAC, an energy-quality-balanced solution, deployed at the medium access control (MAC) layer, which works in conjunction with an energy-aware routing algorithm for wireless mesh devices. The simulation and perceptual test results are also presented to investigate the performance of the proposed solution. In particular, the impacts of content delivery data rate, mesh network topology scale, and mesh device mobility are studied. Results demonstrate that AOC-MAC obtains up to 23% energy savings at roughly the same content delivery quality level in comparison with the IEEE 802.11s MAC protocol.

The DCF (Distributed Coordination Function) is the basic MAC (Medium Access Control) protocol of IEEE 802.11 wireless LANs and compatible with various IEEE 802.11 PHY extensions. The performance of the DCF degrades exponentially as the number of nodes participating in the DCF transmission procedure increases. To deal with this problem, we propose a simple, however efficient modification of the DCF by which the performance of the DCF is greatly enhanced.

Hybrid Wireless Mesh Protocol (HWMP) has been specified for routing of packets in Wireless Mesh Network (WMN) for IEEE 802.11s. But external STAs’ movement is not supported by IEEE 802.11s. There are many existing techniques for managing mobility of mobile nodes. But IEEE 802.11s is not integrated with any of these techniques. The paper proposes adaptive mobility management technique to support movement of external STA in WMN. The scheme is combined with IEEE 802.11s. NS-2 has been used to simulate both the schemes. Performance comparison shows that the proposed technique performs better than HWMP in respect of average handoff cost, average end to end delay, normalized routing overhead, and throughput in different network conditions.

With the proliferation of drones in our daily lives, there is an increasing need for handling their numerous challenges. One of such challenge arises when a swarm-of-drones are deployed to accomplish a specific task which requires coordination and communication among the drones. While this swarm-of-drones is essentially a special form of mobile ad hoc networks (MANETs) which has been studied for many years, there are still some unique requirements of drone applications that necessitates re-visiting MANET approaches. These challenges stem from 3--D environments the drones are deployed in, and their specific way of mobility which adds to the wireless link management challenges among the drones. In this paper, we consider an existing routing standard that is used to enable meshing capability among Wi-Fi enabled nodes, namely IEEE 802.11s and adopt its routing capabilities for swarm-of-drones. Specifically, we propose a link quality metric called SrFTime as an improvement to existing Airtime metric which is the 802.11s default routing metric to enable better network throughput for drone applications. This new metric is designed to fit the link characteristics of drones and enable more efficient routes from drones to their gateway. The evaluations in the actual 802.11s standard indicates that our proposed metric outperforms the existing one consistently under various conditions.

In the field of wireless communication, zigbee is a latest technology in wireless network based on IEEE 802.15.4 standard. On IEEE 802.15.4 standard based zigbee network uses low power sensor nodes to ensure reliable, process, collect, and store the data. The sensor nodes have low cost, smaller in memory size and used in lower coverage area first two layers based on IEEE 802.15.4 standard are PHY and MAC layer. Routing protocols are divided in two categories that are reactive protocol and proactive protocol. AODV routing protocol comes under reactive protocol. It creates route between source and destination when needed. When source node has data to transmit to the destination node then it will create RREQ (route request message) and send to all neighbors in the network, when the destination node found or neighbor node found the route to destination then they will generate a RREP (route reply message) and forward back to source node. After the creation of route between source node and destination node they can exchange the data.

Multicasting is an efficient data transmission approach for group communication applications in multi-channel multi-radio wireless mesh networks. In this paper we have studied the problem of accepting on-line multicast requests, which is quite important for supporting multimedia applications. Our proposed algorithm investigates the acceptance of an arrived call in two phases. In the first phase, a loop-free mesh backbone is constructed. In this mesh, the set of possible parents of each node is limited to the neighbors that are one hop closer to the source node. The neighbors with the same distance from the source node are also acceptable under the circumstance that two neighboring nodes cannot be the possible parents of each other. Next, a sub-optimal mathematical model has been proposed for tree construction over the obtained mesh. The derived multicast trees utilize the minimum amount of bandwidth; are load-balanced; and exploit wireless broadcast advantage. The results show that the proposed algorithm improves the rate of multicast call acceptance by 40% on average compared to previous algorithms in a short running time.

Wireless mesh networks (WMNs) extend the limited transmission coverage of wireless LANs by enabling users to connect to the Internet via a multi-hop relay service provided by wireless mesh routers. In such networks the quality of experience (QoE) depends on both the user location relative to the Internet gateway and the traffic load. Various channel access or queue management schemes have been proposed for achieving throughput fairness among WMN users. However, delay and bandwidth utilization efficiency of such schemes may be unacceptable for real-time applications. Accordingly, the present study proposes a proportional bandwidth allocation scheme with a delay constraint consideration for enhancing the QoE of users of WMNs based on the IEEE 802.11e standard. An analytical model of the proposed scheme is provided. Moreover, the performance of the proposed scheme is systematically compared with that of existing bandwidth allocation methods. The simulation results show that the proposed scheme outperforms previously proposed schemes in terms of both an improved throughput fairness among the WMN users and a smaller end-to-end transmission delay.

In this paper, we propose a sounding control scheme for IEEE 802.11ac multiuser multiple-input multiple-output (MU-MIMO). The proposed scheme comprehensively considers the long-term characteristics of a network environment, including the downlink traffic loads and channel coherence times of wireless links, and jointly determines the sounding node set and sounding interval to maximize the long-term expected MU-MIMO throughput gain in consideration of sounding overhead. To this end, we analytically formulate an MU-MIMO throughput gain maximization problem, considering the network environment and sounding overhead. We conduct MIMO channel measurement in practical wireless local area network (WLAN) environments and evaluate the performance of the proposed scheme by employing the real channel data traces. Simulation results verify that the proposed scheme adaptively determines the sounding node set and sounding interval, according to the network environment, and outperforms the existing scheme, which considers the channel coherence times only.

Wireless local area networks (WLANs) are widely deployed for internet-centric data applications. It is predicted that by 2018, about two-thirds of the world's internet traffic will be video, and mo...

In this paper, we propose an adaptive medium access control (MAC) solution for a fully connected mobile ad hoc network (MANET), supporting homogeneous best-effort data traffic. The MAC scheme achieves consistently high network performance by adapting to the ever-varying network traffic load. Based on the detection of a current network load condition, nodes can make a switching decision between IEEE 802.11 distributed coordination function (DCF) and dynamic time-division multiple access (D-TDMA), when the network traffic load reaches a threshold, referred to as MAC switching point. The adaptive MAC solution determines the MAC switching point to maximize network performance. Approximate and closed-form performance analytical models for both MAC protocols are established, which facilitate the computation of MAC switching point in a tractable way. Extensive analytical and simulation results demonstrate that the adaptive MAC solution provides consistently maximal network performance in the presence of traffic load dynamics.

IEEE 802.15.4 is a promising standard that can provide efficient communication quality at low cost and low data rates. This standard has been studied for vehicle-to-infrastructure (V-I) communication in wireless sensor network (WSN)-based vehicular ad hoc network (VANET) applications. To adopt this standard for vehicular communications, link quality metrics must be investigated for topology design and network optimization. In this study, a series of measurements were made with IEEE 802.15.4 radios to identify wireless channel characteristics with regard to antenna height, vehicle velocity, and distance in various vehicular scenarios. The empirical behavior of link communication quality was also investigated in terms of received signal strength, packet error rate (PER), and packet loss distribution (PLD). The empirically measured and experimental results, which have been validated through appropriate analytical modeling, provide valuable insights, as well as guide design decisions and tradeoffs for WSN-based VANET applications.

As the growth of mobile data traffic places significant strain on cellular networks, plans for exploiting under-utilized network resources become increasingly attractive. In this paper, we propose, design, and evaluate a data offloading architecture, where mobile users are offloaded to mesh networks, which are built and managed by residential users. Such networks are often developed in the context of community networks or, recently, as commercial services. Mobile network operators can lease capacity from these networks and offload traffic to reduce their servicing costs. We introduce an analytical framework that determines the offloading policy, i.e., which mobile users should be offloaded, based on the energy cost induced to the cellular base stations. Accordingly, we design a minimum-cost servicing policy for the mesh networks. Clearly, such architectures are realizable only if the mesh nodes agree with each other to jointly serve the offloaded traffic. To achieve this, we employ the Shapley value rule for dispensing the leasing payment among the mesh nodes. We evaluate this paper by simulating the operation of the LTE-A network, and conducting test bed experiments for the mesh network. The results reveal significant savings for eNBs power consumption and reimbursements for mesh users.

IEEE 802.11-based wireless networks are becoming more popular, and a lot of research is done to enhance the performance of the distributed control function (DCF) found in the IEEE 802.11 standard. Many researchers utilized jamming to further enhance the performance of the contention resolution in DCF. However, jamming-based protocols follow elimination schemes based on the use of jam signals which add to the complexity of wireless devices, add new types of errors like falsely detecting noise as a jam, and are not compatible with the IEEE 802.11 standard. In this paper we propose a self-elimination MAC protocol, called SEMP, for wireless networks to achieve a high performance like that of jamming-based protocols but without the use of jamming signals. SEMP requires no changes to the IEEE 802.11 physical layer, is fully compatible with the IEEE 802.11 wireless devices, and is designed to work without any prior knowledge of the number of nodes. Through extensive simulation, we evaluate SEMP and compare it to the IEEE 802.11 DCF and CONTI (a jamming-based protocol that was shown to highly improve the performance of the IEEE 802.11 wireless networks). Simulation results demonstrate that SEMP outperforms the IEEE 802.11 DCF in terms of the throughput, delay, fairness, and jitter. In addition, results show that SEMP provides throughput and delay gains over CONTI, and that both schemes have comparable fairness and jitter measures. Hence, results reveal that SEMP actually does achieve a high performance like CONTI even though no jamming is used.

Monitoring and transforming smart grid (SG) assets in a timely manner is highly desired for emerging smart grid applications. This critically requires the design of a neighborhood area network (NAN) which is capable of providing high-efficiency and reliable two-way last mile communication from meters to other SG domains. For this demand, IEEE 802.11s based wireless mesh network (WMN) is anticipated to be utilized in a NAN as it can provide high scalability, high-speed and cost-effective wireless transmission. In this paper, we propose a NAN QoS-aware and load-balance routing scheme (NQA-LB) based on the default hybrid wireless mesh protocol (HWMP) of IEEE 802.11s, which aims to address multiple QoS requirements from different NAN applications, and guarantee the highly reliability transfer of NAN traffic data towards gateway. With the NQA-LB, various QoS requirements can be satisfied through sufficient differentiated services as well as network congestion is mitigated by achieving load balance between multiple transmission paths. In order to improve the reliability of NQA-LB, we present an EDCA based adaptive priority adjustment scheme, called AP-EDCA, which dynamically adjusts packet's priority to increase the throughput under low load condition and to mitigate the collision under heavy load condition to improve the reliability of applications with high QoS requirements. Extensive simulation experiments demonstrate the superiority of the proposed scheme in terms of packet delivery ratio, end-to-end delay and throughput while satisfies various QoS requirements much better at the same time.

Wireless mesh networks are being considered as the most adequate topology for deployment in the neighborhood area network NAN domain in the smart-grid infrastructure, because its features such as self-organizing, scalability, and cost-efficiency complement to the NAN requirements. To provide security functionality to the NAN, the key refreshment strategy of the simultaneous authentication of equals or the efficient mesh security association protocol is an efficient way to make the network more resilient against various cyberattacks. However, it is discovered that when the key refreshment strategy is used, the efficient mesh security association protocol demonstrates a security vulnerability, leading to denial of service attacks. In this paper, a simple hash-based encryption scheme is proposed to prevent the unprotected messages from being replayed by the adversary with an enhancement to the key refreshment scheme to improve the resilience of the mesh key holder security handshake. The Protocol Composition Logic is used to describe the logical correctness of the proposed scheme, while the Process Analysis Toolkit is used to formally verify the security functionality against the malicious attacks. The efficiency analysis and the simulation results prove that the proposed scheme is reliable and efficient. Copyright © 2016 John Wiley & Sons, Ltd.

Opportunistic routing (OR) is a promising paradigm that has been proposed for wireless mesh networks. This routing paradigm takes advantage of the broadcast nature of the wireless medium to increase the reliability of transmissions in multihop wireless networks. The selection of a set of candidates involves satisfying the basic requirements of the model, in which packets are forwarded toward the destination. In OR, if one of the selected candidates does not receive the packet, another candidate might be able to continue forwarding the packet. The decision of which forwarder to choose is made by coordination between candidates that have successfully received the transmitted packet. In this paper, we propose a discrete-time Markov chain as a general model for OR and demonstrate how it can be used to evaluate the performance of OR protocols. We also review three well-known OR protocols that we have selected as a study case. Our study demonstrates how our model facilitates better understanding of the combination of a number of candidates and retransmissions and their significant contributions to the successful delivery of data packets. Thus, this shows that our model can help in the design of future OR protocols and efficient candidate selection algorithms.

Recently, as IoT (Internet of Things) becomes more important, low cost implementation of sensor nodes also becomes critical issues for two well-known standards, IEEE 802.15.4 and IEEE 802.15.6 which stands for WPAN (Wireless Personal Area Network) and WBAN (Wireless Body Area Network), respectively. This paper presents the area-optimized AES-CCM (Advanced Encryption Standard - Counter with CBC-MAC) hardware security engine which can support both IEEE 802.15.4 and IEEE 802.15.6 standards. First, for the low cost design, we propose the 8-bit AES encryption core with the S-box that consists of fully combinational logic based on composite field arithmetic. We also exploit the toggle method to reduce the complexity of design further by reusing the AES core for performing two operation mode of AES-CCM. The implementation results show that the total gate count of proposed AES-CCM security engine can be reduced by up to 42.5% compared to the conventional design.

IEEE 802.15.4 targets low data rate communication with limited power devices and cheap wireless networking solutions. In recent years both industry and academia are attracted to IEEE 802.15.4 because of its applicability in wireless sensor networks and wireless body area networks. An important feature of IEEE 802.15.4 is its very low duty cycle operation for conserving energy consumption of sensor device. Super-frame structure of IEEE 802.15.4 defines the duty cycle of nodes. The super-frame structure is based on two parameters: beacon order (BO) and super-frame order (SO). The performance of an IEEE 802.15.4 network depends on the values of BO and SO. These values depict the energy consumption, throughput, node discovery and latency of communication. IEEE 802.15.4 uses fixed BO and SO values which can be carefully chosen to meet the network requirements. In this paper, an extensive survey of dynamic super-frame adjustment algorithms is presented. The survey focuses on beacon-enabled star topology of IEEE 802.15.4 and studies the impact of aforementioned algorithms for various applications. Also, the survey categorizes common IEEE 802.15.4 applications based on their requirements for super-frame adjustment. A brief simulation analysis is included in this survey to highlight the impact of BO and SO on the network performance.

To cope with the increasing demand of multimedia applications, new IEEE 802.11 wireless local area networks devices have been defined such as IEEE 802.11aa and IEEE 802.11ac. The former proposes new intra-access categories (AC) differentiation based on stream classification service (SCS) scheme. The latter standard allows simultaneous downlink transmissions thanks to downlink multi-user MIMO technology and sharing transmission opportunity (TXOP) period scheme. In this paper, we focus on the basis of this technique and the behavior of the access point (AP) to manage the multi-user access. Then, we propose a hybrid access mechanism entitled multi-user multi-cast access mechanism (MUMAM) that supports downlink multi-user transmissions while considering intra-AC differentiation. MUMAN considers SCS scheme to prioritize between multicast and unicast flows of an AC and follows transmissions based on IEEE 802.11ac TXOP sharing technique. Extensive simulation and analysis show that MUMAM has a significant positive impact on delay and throughput performance of different AC(s).

Relay technology is one of the key technologies for long-term evolution advanced (LTE-A) project. The introduction of relay will not only bring a wider coverage and higher capacity to the system but also lower the cost of network building. Multihop wireless relay technology plays an important role in next-generation mobile and wireless communication systems. Nowadays, we are witnessing the formation of a new technological marvel: Internet of Things (IoT). This formation is able to combine in a particular operational entity, all the bits and pieces of the world around us. In this paper, we perform queuing modeling of a two-hop wireless relay network and carry out performance analysis of end-to-end packet delay. In the two-hop wireless relay network, two groups of wireless nodes (WNs) and a single relay node (RN) are considered. A Poisson packet arrival process and IEEE 802.11 distributed coordination function are assumed in the network for the network traffic model and for regulating the nodes’ access to the shared channel, respectively. We model a node as a single-server queuing system, whose service time of a packet is unknown and dependent on the probabilistic parameters of IEEE 802.11 DCF medium access control (MAC). A system of equations is then obtained for numerically computing the probabilistic parameters of IEEE 802.11 DCF MAC through discretization of the continuous-time network operations, based on which we construct semi-Markov processes and derive an analytic result for the expectation of the end-to-end packet delay. As a key performance indicator in evaluation of wireless networks, the packet delay result helps measure the efficiency of IEEE 802.11 MAC in two-hop wireless relay networks.

The goal of the SmartGrid is to maximize energy efficiency by exchanging bi-directional real-time power information with the help of ICT(Information and Communication Technology). In this paper, we propose a “JRS-MS” (Joint Routing and Scheduling for Multi-channel SmartGrid) algorithm that uses numerical modeling methods in IEEE 802.11s based STDMA multi-channel SmartGrid NAN networks. The proposed algorithm controls the amount of data transmission adaptively at the link layer and finds a high data-rate path which has the least interference between traffic flows in multi-channel SmartGrid NAN networks. The proposed algorithm improve transmission performance by enhancing network utilization. By comparing the results of performance analysis between the proposed algorithm and the JRS-SG algorithm [11] in the previous paper, we showed that the JRS-MS algorithm can improve transmission performance by maximally utilizing given network resources when the number of flows are increasing in the multi-hop NAN wireless mesh networks.

The IEEE 802.11s wireless mesh networking standard supports power save mode where a mesh station can switch from the awake state to the doze state when there is no data to transmit. In the standard, the doze state is peer specific and has two different modes of operations—light sleep mode and deep sleep mode. This paper analytically evaluates the performance of a mesh basic service set under the operation of different power save modes, with the help of a queuing petri net modeling. The analytical model gives several insights of the power save mode operations, which are further validated using simulation results as well as results from a practical mesh networking testbed. Our analysis reveals that there exists interesting performance tradeoffs among light sleep mode and deep sleep mode, that can be explored to design an efficient power profile for mesh networks.

IEEE 802.16, also known as Worldwide Interoperability for Microwave Access, is a standardization effort carried out by the IEEE to provide last-mile broadband access to end users. The IEEE 802.16 standard supports two medium access control modes--a mandatory point to multipoint mode and an optional mesh mode. In this paper, we propose an asymmetric interference aware routing algorithm and a new multipointer approach in implementing scheduling algorithms for IEEE 802.16 mesh networks. We modify three different centralized scheduling algorithms, fixed scheduling, ordered scheduling and per-slot scheduling using multipointer approach to allow for spatial reuse in IEEE 802.16 mesh networks. Simulation results reveal that fixed scheduling with SR provides the best performance.

As one of the most widely used wireless network technologies, IEEE 802.11 wireless local area networks (WLANs) have found a dramatically increasing number of applications in soft real-time networked control systems (NCSs). To fulfill the real-time requirements in such NCSs, most of the bandwidth of the wireless networks need to be allocated to high-priority data for periodic measurements and control with deadline requirements. However, existing QoS-enabled 802.11 medium access control (MAC) protocols do not consider the deadline requirements explicitly, leading to unpredictable deadline performance of NCS networks. Consequentially, the soft real-time requirements of the periodic traffic may not be satisfied, particularly under congested network conditions. This paper makes two main contributions to address this problem in wireless NCSs. Firstly, a deadline-constrained MAC protocol with QoS differentiation is presented for IEEE 802.11 soft real-time NCSs. It handles periodic traffic by developing two specific mechanisms: a contention-sensitive backoff mechanism, and an intra-traffic-class QoS differentiation mechanism. Secondly, a theoretical model is established to describe the deadline-constrained MAC protocol and evaluate its performance of throughput, delay and packet-loss ratio in wireless NCSs. Numerical studies are conducted to validate the accuracy of the theoretical model and to demonstrate the effectiveness of the new MAC protocol.

Wireless mesh networking extends the communication range among cooperating multiple low-power wireless radio transceivers and is useful for collecting data from sensors widely distributed over a large area. By integrating an off-the-shelf wireless design, such as the XBee module, development of sensor systems with mesh networking capability can be accelerated. This study introduces an open-source wireless mesh network (WMN) module, which integrates the functions of network discovery, automatic routing control, and transmission scheduling. In addition, this design is open source in order to promote the use of wireless mesh networking for environmental monitoring applications. Testing of the design and the proposed networking module is reported. The proposed wireless mesh networking module was evaluated and compared with XBee. The average package delivery ratio and standard deviation of the proposed WMN module and the XBee are 94.09%, 91.19%, 5.14%, and 10.25%, respectively, in a 20 node experiment. The proposed system was demonstrated to have the advantages of low-cost combined with high reliability and performance, and can aid scientists in implementing monitoring applications without the complications of complex wireless networking issues.

In this paper, we propose a cross-layer optimization technique for multi-radio Wireless Mesh Networks (WMNs) using new routing metric and load balancing mechanism. WMNs are an emerging technology and are used as a backhaul network to connect various types of networks to the internet. These networks consist of mesh routers with multi-radio support to enhance the capacity. As the traffic density is very high from the client mesh to the gateways, load balancing in these networks has become an important research issue. For this, multipath routing which can exploit the multi-radio capabilities to balance the traffic simultaneously through mesh routers is required. To address this, we analytically derive the routing metric using IEEE 802.11 Distributed Coordination Function (DCF) delay model. Using this model, we propose a routing metric called Passive Interference and Delay Aware (PIDA) metric for multipath routing to find the interference free paths. We extend the work by performing load balancing on multiple paths as well as on multiple interfaces using the proposed metric. We implement our techniques using popular Ad hoc On-demand Multipath Distance Vector (AOMDV) routing protocol in NS2. The results reveal that PIDA performs better in terms of throughput and average delay compared to recently proposed routing metrics with minimal routing overhead. In addition, load balancing mechanism with PIDA metric shows better results depending on the congestion level in the network.

This paper concentrates on the IEEE 802.11p MAC sublayer to analyze its performance in the presence of hidden terminals. An analytical model for the throughput of the IEEE 802.11p in the presence of hidden terminal is presented in this paper. A 3-D Markov chain is created to model the backoff procedure for each access category. The different contention windows and arbitration interframe space are considered for each access category. The model also takes into consideration control packets and data packets separately. The probabilities of frame blocking, successful transmission, collisions and hidden terminals have been derived and used to calculate the throughput. The simulation results are presented to validate the analytical results of the proposed model. The results of the proposed model are compared with the existing model IEEE 802.11 EDCA (Kosek-Szott et al. in Comput Netw 55(3):622---635, 2011). The results of the proposed model outperform the existing model.

Owing to the self organizing, self configuring and self healing capabilities, Wireless Mesh Nwetworks (WMN) have emerged as most powerful architectures in recent times. Wireless Mesh Networks operate with limited battery resources. In 802.11s, a mobile station(STA) can act as router as well as client that results in increased energy consumption during routing process. The degradation of energy at STA can result in low network performance due to relay STA failure. In order to increase network performance there is a need to reduce the energy consumption rate of STA. To save energy, 802.11s has introduced a mechanism called power save mode(PSM) which switches STA mode from active to light sleep or deep sleep mode when STA is not involved in transmission. This ensures saving of energy at each STA during routing process. Several models have been proposed by researchers to improve the energy saving mechanisms in 802.11s. Adhoc On Demand Distance Vector (AODV) routing algorithm is used for routing purpose in WMN. In this routing protocol, regular usage of the same node during routing may lead to battery failure and result in low network lifetime. Hence in this work we propose a novel Energy Aware Power Save Mode-AODV (EAPSM-AODV) routing model that switches among power save modes based on battery status of a node before participating in AODV routing. Our proposed routing model refers to the mechanism that takes available remaining energy and energy draining rate of a node into account to decide on relaying traffic. It consist of four units namely Routing, Path choosing, Mode selector and Energy units. Experiments have been conducted using NS3 simulator by considering various situations such as keeping nodes in static position and moving nodes dynamically in a simulation area. The results shows that our proposed model significantly improves network performance and increase in network lifetime.

Low-altitude unmanned aerial vehicles (UAVs) combined with WLAN mesh networks (WMNs) have facilitated the emergence of airborne network-assisted applications. In disaster relief, they are key solutions for 1) on-demand ubiquitous network access and 2) efficient exploration of sized areas. Nevertheless, these solutions still face major security challenges as WMNs are prone to routing attacks. Consequently, the network can be sabotaged, and the attacker might manipulate payload data or even hijack the UAVs. Contemporary security standards, such as the IEEE 802.11i and the security mechanisms of the IEEE 802.11s mesh standard, are vulnerable to routing attacks as we experimentally showed in previous works. Therefore, a secure routing protocol is indispensable for making feasible the deployment of UAV-WMN. As far as we know, none of the existing research approaches have gained acceptance in practice due to their high overhead or strong assumptions. Here, we present the position-aware, secure, and efficient mesh routing approach (PASER). Our proposal prevents more attacks than the IEEE 802.11s/i security mechanisms and the well-known, secure routing protocol ARAN, without making restrictive assumptions. In realistic UAV-WMN scenarios, PASER achieves similar performance results as the well-established, nonsecure routing protocol HWMP combined with the IEEE 802.11s security mechanisms.

Wireless systems continue to rapidly gain popularity. This fact is extremely true for data networks in the local and personal areas. Media Access Control (MAC) layer protocols have a critical role in making a typical Mobile ad hoc network and Personal ad hoc network more reliable and efficient. Choice of MAC layer protocol and other factors including number of nodes, mobility, traffic rate and playground size dictates the performance of a particular WLAN and WPAN. The aim of this paper is to analysis the performance of mobility models in IEEE802.11 MAC and IEEE 802.15.4 ZigBee MAC using NS2.34.These mobility models are RPGM, RWM, Freeway mobility and city section mobility model. Then extraction of the simulation results based on the performance metrics to calculate a Packet Delivery Ratio, data loss, end-to-end delay and Throughput.

The IEEE 802.11e enhanced distributed channel access (EDCA) protocol follows class-based service differentiation for providing differentiated quality-of-service (QoS). However, its collision avoidance mechanism using backoff algorithm can be inefficient for providing improved performance with respect to throughput and channel access delay, especially in a high network configuration (i.e. number of stations) with imperfect wireless channel. The existing and emerging works have devoted considerable attention on tuning the backoff parameters for achieving optimal throughput only. The prior works do not consider the channel access delay and throughput metrics altogether for performance improvement. Additionally, in most of the cases, the optimal configuration of backoff parameters are performed by a centralized controller. In this paper, we propose a delay-aware distributed dynamic adaptation of contention window scheme, namely D2D , for the cumulative improvement of both the throughput and the channel access delay at runtime. The D2D scheme requires two ad-hoc, distributed, and easy-to-obtain estimates— delay deviation ratio and channel busyness ratio —of the present delay level and channel congestion status of the network, respectively. A key advantage of the D2D scheme is that it is compliant with the IEEE 802.11 standard, and, thus, can be seamlessly integrable with the existing wireless card. We show the integrated model of the medium access control protocol, namely D2D Channel Access ( D2DCA ), for the IEEE 802.11e networks. We further propose a two-dimensional Markov chain model of the D2DCA protocol for analyzing its theoretical performance in saturated networks with imperfect wireless channel. Theoretical comparison with the benchmark protocols establishes the effectiveness of the D2DCA protocol.