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This paper proposes a MAC protocol for ad hoc networks using In-band Full-duplex (IBFD) wireless communications, which are named as AdHoc-FDMAC. To utilize IBFD communications in ad hoc networks, this protocol modifies a number of control frames in the IEEE 802.11 Distributed Coordination Function (DCF) MAC standard. Here, the detailed time sequences for all types of IBFD communications are shown for the data transmission and routing. In this paper, the probability and throughput equations for IBFD communications in different situations have been derived. The performance of the proposed AdHoc-FDMAC has been analysed in terms of probability, throughput, and routing time. The Maximum throughput of AdHoc-FDMAC has been found to be 48.34 Mbps, and it is compared with a recently published ad hoc MAC as well as with the conventional HD MAC. The AdHoc-FDMAC outperforms the recently published ad hoc MAC and conventional HD MAC by 16.80% and 66.50% throughput gain, respectively. AdHoc-FDMAC incorporates the existing Ad hoc On-demand Distance Vector (AODV) routing protocol, but this AODV routing is utilized here using IBFD communications. This paper also compares the routing time of the IBFD-based AODV with the conventional AODV. The result shows that the IBFD-based AODV requires 33.33% less routing time than that of the conventional AODV for 3-hop distance between the transmitter and receiver. This paper suggests that the AdHoc-FDMAC protocol provides much more throughput in ad hoc networks by utilizing IBFD communications. [ABSTRACT FROM AUTHOR]

In view of the security threats posed inside and outside the network due to the weaknesses of network protocols and systems, power line and wireless converged communications have security problems in communication connections that appear in environments where heterogeneous networks overlap. In order to cope with the problems of network delay and data transmission security in smart grid, this paper proposes an online monitoring security protection method based on edge nodes, which manages user trust under the premise of not leaking grid user data, and establishes a personalized machine learning model. This method not only guarantees users a secure communication experience, but also ensures users' real-time network connection and content acquisition, and can obtain a fast and personalized user experience. [ABSTRACT FROM AUTHOR]

Copyright of Information Sciences / Informacijos Mokslai is the property of Vilnius University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An opportunistic network is a wireless ad hoc network that has frequently intermittent connectivity due to nodes’ mobility. These spare, unpredictable networks aim to solve the prolonged delay paths by a store-carry-forward scheme. It is difficult to determine the appropriate nodes to forward the messages since there are few opportunistic contacts. The nodes might decide based on the obtained data of the network as a guide to reach a destination. The aforementioned technique is not helpful in case the rate of change in the network topology is higher than the rate of data gathering due to usage restrictions and uncertain available information/knowledge of the future contacts. In this paper, to cope with the challenges imposed by the un-deterministic environment, a risk assessment strategy is considered to evaluate the short and long-term impact of each decision to find the optimal node/paths. This routing scheme can take advantage of the unanticipated connection to make the routing more flexible in short time and with less buffer usage. Our proposed risk assessment algorithms that are based on MALP are mixed with the knowledge about buffer management and network capacity. The prioritized messages to be disseminated as well as better decision to take a risk are the main contributions of this paper. Moreover, the self-adaptive threshold, distributed PID controller, is considered to tackle different threshold levels for each node individually. Numerical results prove that the proposed method drastically increases the delivery ratio and also minimizes the risk of exceeding resource consumption and packet loss. [ABSTRACT FROM AUTHOR]

A cooperative wireless-powered communication network protocol is proposed, in which user far away from a hybrid access point (H-AP) is capable of harvesting wireless powers by overhearing the uplink signals of users that are relatively nearer to the H-AP, in addition to downlink signal broadcast by the H-AP. In this setting, time allocations for the downlink transmission of the H-AP and the uplink transmission for the users are jointly optimized for two different purposes. First, the weighted sum-rate maximization problem is solved for a given total transmission time. Then, the total transmission time is minimized under a minimum rate constraint, and an efficient algorithm is also presented to solve the optimal solution by a line search strategy. Numerical results demonstrate that the proposed schemes significantly increase the far user's rate, which in turn improves user fairness and transmission delay. [ABSTRACT FROM PUBLISHER]

Mobile ad hoc networks (MANETs) are mobile networks, which are automatically outspread on a geographically limited region, without requiring any preexisting infrastructure. Mostly, nodes are both self-governed and self-organized without requiring a central monitoring. Because of their distributed characteristic, MANETs are vulnerable to a particular routing misbehavior, called wormhole attack. In wormhole attack, one attacker node tunnels packet from its position to the other attacker nodes. Such wormhole attack results in a fake route with fewer hop count. If source node selects this fictitious route, attacker nodes have the options of delivering the packets or dropping them. For this reason, this paper proposes an improvement over AODV routing protocol to design a wormhole-immune routing protocol. The proposed protocol called defending against wormhole attack (DAWA) employs fuzzy logic system and artificial immune system to defend against wormhole attacks. DAWA is evaluated through extensive simulations in the NS-2 environment. The results show that DAWA outperforms other existing solutions in terms of false negative ratio, false positive ratio, detection ratio, packet delivery ratio, packets loss ratio and packets drop ratio. [ABSTRACT FROM AUTHOR]

Abstract: Full duplex wireless communication is one of the enabling technologies of the fifth generation (5G) mobile telecommunication networks. It boosts up the bandwidth by enabling simultaneous data transmission and reception on a single channel. In this paper, we design a suitable medium access control (MAC) protocol for 5G networks to realize the benefit of full duplex communication. We also develop an analytical model to evaluate the performance of our proposed MAC protocol. [ABSTRACT FROM AUTHOR]

Transmission of system-critical control information plays a key role in efficient management of limited wireless network resources and successful reception of payload data information. This paper uses an orthogonal frequency division multiplexing (OFDM) architecture to investigate the detection performance of a time-domain approach used to detect deterministic control signalling information. It considers a type of control information chosen from a finite set of information, which is known at both transmitting and receiving wireless terminals. Unlike the maximum likelihood (ML) estimation method, which is often used, the time-domain detection technique requires no channel estimation and no pilots as it uses a form of time-domain correlation as the means of detection. Results show that when compared with the ML method, the time-domain approach improves detection performance even in the presence of synchronisation error caused by carrier frequency offset. [ABSTRACT FROM AUTHOR]

VANETs have emerged as an exciting research and application area. Increasingly vehicles are being equipped with embedded sensors, processing and wireless communication capabilities. This has opened a myriad of possibilities for powerful and potential life-changing applications on safety, efficiency, comfort, public collaboration and participation, while they are on the road. Although, considered as a special case of a Mobile Ad Hoc Network, the high but constrained mobility of vehicles bring new challenges to data communication and application design in VANETs. This is due to their highly dynamic and intermittent connected topology and different application’s QoS requirements. In this work, we survey VANETs focusing on their communication and application challenges. In particular, we discuss the protocol stack of this type of network, and provide a qualitative comparison between most common protocols in the literature. We then present a detailed discussion of different categories of VANET applications. Finally, we discuss open research problems to encourage the design of new VANET solutions. [ABSTRACT FROM AUTHOR]

Buffer sizing is an important network configuration parameter that impacts the quality of service characteristics of data traffic. With falling memory costs and the fallacy that "more is better," network devices are being overprovisioned with large buffers. This may increase queueing delays experienced by a packet and subsequently impact stability of core protocols such as TCP. The problem has been studied extensively for wired networks. However, there is little work addressing the unique challenges of wireless environments such as time-varying channel capacity, variable packet inter-service time, and packet aggregation, among others. In this article we discuss these challenges, classify the current state-of-the-art solutions, discuss their limitations, and provide directions for future research in the area. [ABSTRACT FROM PUBLISHER]

There is a significant interest in new wireless multiple access protocols that adaptively split a wide frequency channel into multiple sub-channels—perhaps of varying widths—and assign these sub-channels to competing transmissions. Existing protocols suffer from various limitations such as considerable protocol overhead, dependence on a centralized controller, and use of fixed-size channels. We introduce Ez-Channel, a novel MAC protocol that parsimoniously utilizes the OFDM sub-carriers to perform channelization and assignment of sub-channels to competing links. In addition to circumventing hidden and exposed terminal problems, Ez-Channel adapts channel assignments to the network topology. To eliminate the need for a centralized controller and to avoid an overwhelming amount of information exchange, the protocol uses a randomization technique enabling provably efficient localized decision making. Our extensive analytical and simulation studies show that Ez-Channel yields significant throughput improvements as compared to the state-of-the-art protocols. [ABSTRACT FROM AUTHOR]

Liu, Y.; Xu, Y.; Zhang, K., and Feng, Y., 2019. Hardware design of marine buoy data communication terminal based on the 1st generation Beidou navigation positioning system. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 639–645. Coconut Creek (Florida), ISSN 0749-0208. Aiming at the actual situation of marine buoy data monitoring and the problems of poor anti-interference performance, low fault tolerance coefficient and high energy consumption in current communication system, the hardware design of marine buoy data communication terminal based on the 1st generation Beidou navigation positioning system is proposed. Based on the marine buoy system, the overall structure of communication terminal is designed. The main components of the hardware are Beidou communication module and wireless network communication module, and the auxiliary parts are antenna and power supply module. The long-distance part uses the inherent data transmission mode of Beidou navigation system to communicate, while the short-range part uses the radio network communication protocol to complete the data transmission. There are two UART interfaces in the hardware, one is connected with the auxiliary cabin, which is responsible for receiving the related data of the auxiliary cabin, including azimuth, attitude and pressure sensing, and the other UART interface is connected with the Beidou communication module, which is responsible for receiving positioning and navigation data and transmitting remote data. The experimental results show that the design has high signal-to-noise ratio, strong fault-tolerant performance, high positioning accuracy and communication success rate, low energy consumption and perfect performance. [ABSTRACT FROM AUTHOR]

It is widely known that Control Area Networks (CAN) are used in real-time, distributed and parallel processing which cover manufacture plants, humanoid robots, networking fields, etc., In applications where wireless conditions are encountered it is convenient to continue the exchange of CAN frames within the Wireless CAN (WCAN). The WCAN considered in this research is based on wireless token ring protocol (WTRP); a MAC protocol for wireless networks to reduce the number of retransmissions due to collision and the wired counterpart CAN attribute on message based communication. WCAN uses token frame method to provide channel access to the nodes in the system. This method allow all the nodes to share common broadcast channel by taken turns in transmitting upon receiving the token frame which is circulating within the network for specified amount of time. This method provides high throughput in bounded latency environment, consistent and predictable delays and good packet delivery ratio. The most important factor to consider when evaluating a control network is the end-to-end time delay between sensors, controllers, and actuators. The correct operation of a control system depends on the timeliness of the data coming over the network, and thus, a control network should be able to guarantee message delivery within a bounded transmission time. The proposed WCAN is modeled and simulated using QualNet, and its average end to end delay and packet delivery ratio (PDR) are calculated. The parameters boundaries of WCAN are evaluated to guarantee a maximum throughput and a minimum latency time, in the case of wireless communications, precisely WCAN. [ABSTRACT FROM AUTHOR]

Wireless sensor networks with mobile sinks, mWSNs, have attracted a lot of attention recently. This is because sink mobility can greatly alleviate the hotspot issue in WSNs and further prolong the network lifetime. However, sink mobility also causes unexpected changes in network topology and data routing paths, which can largely affect the routing performance in such networks. Design of efficient routing protocols for mWSNs has been a critical issue, and much work has been carried out in this aspect. In this article, we first classify existing protocols based on different design criteria and then present a survey of the state-of-the-art routing protocols in this area. We illustrate how each of the protocols works, and discuss their advantages and disadvantages. Finally, we point out some future directions for efficient routing in mWSNs. [ABSTRACT FROM AUTHOR]

Abstract: DCCP (Datagram Congestion Control Protocol) is a transport layer protocol that provides congestion control for unreliable data transmission. The congestion control mechanism embedded in DCCP adjusts the packet sending rate according to network condition. However, DCCP does not discriminate congestion losses and wireless link errors resulted from fading and thus it leads to unnecessary rate adjustment. In this paper, we proposed a mechanism to enhance bandwidth utilization of DCCP over wireless network. We employed a cross-layer loss discrimination scheme to distinguish congestion loss and fading loss. The cross-layer based mechanism detects frame loss in the data link layer in real-time to infer the actual fading loss rate. Thereafter, the fading loss can be excluded from the packet loss observed in the transport layer. Once the accurate congestion loss rate is calculated, the sender can make appropriate adjustment on the transmission rate that reflects the current congestion state along the transmitting path using the DCCP rate control procedure. Simulation results show that DCCP with our proposed CCID 3 rate control scheme can discriminate fading loss and achieve from 4.7% to 15.5% improvement on transmission throughput when the fading loss rate varies from 5% to 15% in wireless network. [Copyright &y& Elsevier]

We consider an erasure multi-way relay channel (EMWRC) in which several users share their data through a relay over erasure links. Assuming no feedback channel between the users and the relay, we first identify the challenges for designing a data sharing scheme over an EMWRC. Then, to overcome these challenges, we propose practical low-latency and low-complexity data sharing schemes based on fountain coding. Later, we introduce the notion of end-to-end erasure rate (EEER) and analytically derive it for the proposed schemes. EEER is then used to calculate the achievable rate and transmission overhead of the proposed schemes. Using EEER and computer simulations, the achievable rates and transmission overhead of our proposed schemes are compared with the ones of one-way relaying. This comparison implies that when the number of users and the channel erasure rates are not large, our proposed schemes outperform one-way relaying. We also find an upper bound on the achievable rates of EMWRC and observe that depending on the number of users and channel erasure rates, our proposed solutions can perform very close to this bound. [ABSTRACT FROM AUTHOR]

Abstract: Security protocols operating over wireless channels can incur significant communication costs (e.g., energy, delay), especially under adversarial attacks unique to the wireless environment such as signal jamming, fake signal transmission, etc. Since wireless devices are resource constrained, it is important to optimize security protocols for wireless environments by taking into account their communication costs. Towards this goal, we first present a novel application of a signal-flow-based approach to analyze the communication costs of security protocols in the presence of adversaries. Our approach models a protocol run as a dynamic probabilistic system and then utilizes Linear System theory to evaluate the moment generating function of the end-to-end cost. Applying this technique to the problem of secret key exchange over a wireless channel, we quantify the efficiency of existing families of key exchange cryptographic protocols, showing, for example, that an ID-based approach can offer an almost 10-fold improvement in energy consumption when compared to a traditional PKI-based protocol. We then present a new key exchange protocol that combines traditional cryptographic methods with physical-layer techniques, including the use of “ephemeral” spreading codes, cooperative jamming, and role-switching. Utilizing signal flow analysis, we demonstrate that this new protocol offers performance advantages over traditional designs. [Copyright &y& Elsevier]

We study the capacity scaling laws for the cognitive network that consists of the primary hybrid network (PhN) and secondary ad hoc network (SaN). PhN is further comprised of an ad hoc network and a base station-based (BS-based) network. SaN and PhN are overlapping in the same deployment region, operate on the same spectrum, but are independent with each other in terms of communication requirements. The primary users (PUs), i.e., the ad hoc nodes in PhN, have the priority to access the spectrum. The secondary users (SUs), i.e., the ad hoc nodes in SaN, are equipped with cognitive radios, and have the functionalities to sense the idle spectrum and obtain the necessary information of primary nodes in PhN. We assume that PhN adopts one out of three classical types of strategies, i.e., pure ad hoc strategy, BS-based strategy, and hybrid strategy. We aim to directly derive multicast capacity for SaN to unify the unicast and broadcast capacities under two basic principles: 1) The throughput for PhN cannot be undermined in order sense due to the presence of SaN. 2) The protocol adopted by PhN does not alter in the interest of SaN, anyway. Depending on which type of strategy is adopted in PhN, we design the optimal-throughput strategy for SaN. We show that there exists a threshold of the density of SUs according to the density of PUs beyond which it can be proven that: 1) when PhN adopts the pure ad hoc strategy or hybrid strategy, SaN can achieve the multicast capacity of the same order as it is stand-alone; 2) when PhN adopts the BS-based strategy, SaN can asymptotically achieve the multicast capacity of the same order as if PhN were absent, if some specific conditions in terms of relations among the numbers of SUs, PUs, the destinations of each multicast session in SaN, and BSs in PhN hold. [ABSTRACT FROM AUTHOR]

Abstract: In many wireless sensor network applications, nodes are mobile, while many protocols proposed for these networks assume a static network. Thus, it is important to evaluate if a traditional protocol designed for a static network can tolerate different levels of mobility. This paper provides an analytic model to investigate the effect of mobility on a well-known cluster-based protocol, LEACH. The model evaluates data loss after construction of the clusters due to node mobility, which can be used to estimate a proper update interval to balance the energy and data loss ratio. Thus, the results can help the network designer to adjust the topology update interval given a value of acceptable data loss threshold. A practical approach to increase the mobility tolerance of the protocol is applying a buffer zone to the transmission ranges of the nodes. The model is extended in order to consider the effect of buffer zone. To validate the analytic evaluations, extensive simulations are conducted and correctness of the evaluations is tightly verified. [Copyright &y& Elsevier]

Abstract: This paper reports a feasibility analysis of the use of a hybrid control network based on the Common Industrial Protocol (CIP). For this feasibility analysis, the message service time between DeviceNet and the wireless devices is investigated. The feasibility of hybrid control networks is analyzed using a mathematical analysis and experimental tests. The experimental results show the feasibility of the hybrid control networks in terms of the polling/COS service time and the average end-to-end delays. [Copyright &y& Elsevier]

In this paper, we develop an analytical energy efficiency model using dual switched branch diversity receiver in wireless sensor networks in fading environments. To adapt energy efficiency of sensor node to channel variations, the optimal packet length at the data link layer is considered. Within this model, the energy efficiency can be effectively improved for switch-and-stay combiner (SSC) receiver with optimal switching threshold. Moreover, to improve energy efficiency, we use error control of Bose-Chaudhuri-Hochquengh (BCH) coding for SSC-BPSK receiver node compared to one of non-diversity NCFSK receiver of sensor node. The results show that the BCH code for channel coding can improve the energy efficiency significantly for long link distance and various values of high energy consumptions over Rayleigh fading channel. [ABSTRACT FROM AUTHOR]

Wireless self-organizing networks (WSONs) have attracted considerable attention from the network research community; however, the key for their success is the rigorous validation of the properties of the network protocols. Applications of risk or those demanding precision (like alert-based systems) require a rigorous and reliable validation of deployed network protocols. While the main goal is to ensure the reliability of the protocols, validation techniques also allow the establishment of their correctness regarding the related protocols' requirements. Nevertheless, even if different communities have carried out intensive research activities on the validation domain, WSONs still raise new issues for and challenging constraints to these communities. We thus, advocate the use of complementary techniques coming from different research communities to efficiently address the validation of WSON protocols. The goal of this tutorial is to present a comprehensive review of the literature on protocol engineering techniques and to discuss difficulties imposed by the characteristics of WSONs on the protocol engineering community. Following the formal and nonformal classification of techniques, we provide a discussion about components and similarities of existing protocol validation approaches. We also investigate how to take advantage of such similarities to obtain complementary techniques and outline new challenges. [ABSTRACT FROM AUTHOR]

In a secure message transmission (SMT) scenario, a sender wants to send a message in a private and reliable way to a receiver. Sender and receiver are connected by n wires, t of which can be controlled by an adaptive adversary with unlimited computational resources. In Eurocrypt 2008, Garay and Ostrovsky considered an SMT scenario where sender and receiver have access to a public discussion channel and showed that secure and reliable communication is possible when n \geq t+1. In this paper, we will show that a secure protocol requires at least three rounds of communication and two rounds invocation of the public channel and hence give a complete answer to the open question raised by Garay and Ostrovsky. We also describe a round optimal protocol that has constant transmission rate over the public channel. [ABSTRACT FROM AUTHOR]

Abstract: In traditional wireless sensor network (WSN) applications, energy efficiency may be considered to be the most important concern whereas utilizing bandwidth and maximizing throughput are of secondary importance. However, recent applications, such as structural health monitoring, require high amounts of data to be collected at a faster rate. We present a multi-channel MAC protocol, MC-LMAC, designed with the objective of maximizing the throughput of WSNs by coordinating transmissions over multiple frequency channels. MC-LMAC takes advantage of interference and contention-free parallel transmissions on different channels. It is based on scheduled access which eases the coordination of nodes, dynamically switching their interfaces between channels and makes the protocol operate effectively with no collisions during peak traffic. Time is slotted and each node is assigned the control over a time slot to transmit on a particular channel. We analyze the performance of MC-LMAC with extensive simulations in Glomosim. MC-LMAC exhibits significant bandwidth utilization and high throughput while ensuring an energy-efficient operation. Moreover, MC-LMAC outperforms the contention-based multi-channel MMSN protocol, a cluster-based channel assignment method, and the single-channel CSMA in terms of data delivery ratio and throughput for high data rate, moderate-size networks of 100 nodes at different densities. [ABSTRACT FROM AUTHOR]

Copyright of Gerencia Tecnologica Informatica is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The recent advances in wireless client devices and the crucial role of multimedia communications in our society have motivated relevant standardization efforts, such as the IP multimedia subsystem, to support session control, mobility, and interoperability in all-IP next-generation networks. IMS has already driven the design of commercial mobile multimedia, but exhibits limited support for service continuity during handoffs. In particular, it omits advanced techniques to reduce/eliminate handoff delays, especially during vertical handoffs (i.e., change of the wireless technology employed by a client to access the wired Internet, e.g., from UMTS to WiFi). We propose an original solution for session continuity based on the primary design guideline of cleanly and effectively separating the signaling plane (for session reconfiguration via SIP) from the media delivery plane (data transmission and related handoff management operations). Our optimized handoff management techniques exploit terminal-based decentralized predictions to minimize service-level handoff delays. Different from other recent related work, our proposal fully complies with the standard IMS infrastructure and works at the application level. The reported experimental results point out that our solution, available as an open source tool for the IMS community, reduces playout interruption times relevantly by introducing a limited and scalable signaling overhead. [ABSTRACT FROM AUTHOR]

Wireless sensor networks are mainly designed for environment surveillance, wherein wireless sensor nodes cooperate to get their job done. Generally, wireless sensors are battery powered; therefore, it is crucial for them to efficiently use their battery resources. Most of the existing power-saving protocols achieve power savings by periodically putting sensor nodes to sleep. Such a regular sleep/awake mechanism fails to adjust a sensor node's sleep duration based on its traffic load, thus causing either lower power efficiency or higher latency. Furthermore, sensors may be deployed in hostile environments and may thus unexpectedly fail. Most power-saving protocols do not promptly react to such link breakage, resulting in long transmission delays. In this paper, we propose a quorum-basedmedium access control (QMAC) protocol that enables sensor nodes to sleep longer under light loads. Since traffic flows toward the sink node in wireless sensor networks, a new concept, i.e., the next-hop group, is also proposed to reduce transmission latency. Simulation results verify that the proposed QMAC saves more energy and keeps the transmission latency low. [ABSTRACT FROM AUTHOR]

Existing work has shown that random coding across multicast sessions can significantly reduce system delay. However, such a scheme requires the strong assumption that each source has priori information of other sources' messages. The broadcasting nature of radio propagation can provide an opportunity to realize collaboration across sessions without causing much system overhead. In this paper, we propose the application of network coding to multisource-multidestination (MSMD) scenarios and provide formal analysis for the improvement of system delay. In particular, two types of analytical results have been developed, with one based on the outage probability and the other based on the use of practical convolutional codes. Monte Carlo simulation results have also been provided to demonstrate the delay performance of the proposed network-coded protocol. [ABSTRACT FROM AUTHOR]

A method to improve the reliability of data transmission between two terminals without using multiple antennas is cooperative communication, where spatial diversity is introduced by the presence of a relay terminal. The Quantize and Forward (QF) protocol is suitable to implement in resource constraint relays, because of its low complexity. In prior studies of the QF protocol, all channel parameters are assumed to be perfectly known at the destination, while in reality these need to be estimated. This paper proposes a novel quantization scheme, in which the relay compensates for the rotation caused by the source-relay channel, before quantizing the phase of the received M-PSK data symbols. In doing so, channel estimation at the destination is greatly simplified, without significantly increasing the complexity of the relay terminals. Further, the destination applies the expectation maximization (EM) algorithm to improve the estimates of the source-destination and relay-destination channels. The resulting performance is shown to be close to that of a system with known channel parameters. [ABSTRACT FROM AUTHOR]

We propose a novel channel model to be used for simulating indoor wireless propagation environments. An extensive measurement campaign was carried out to assess the performance of different transport protocols over 802.11 links. This enabled us to better adjust our approach, which is based on an autoregressive filter. One of the main advantages of this proposal lies in its ability to reflect the "bursty" behavior which characterizes indoor wireless scenarios, having a great impact on the behavior of upper layer protocols. We compare this channel model, integrated within the Network Simulator (ns-2) platform, with other traditional approaches, showing that it is able to better reflect the real behavior which was empirically assessed. [ABSTRACT FROM AUTHOR]

IEEE802.11 access protocol uses CSMA/CA in its Medium Access control layer as the main access function, which carries several deficiencies. In these networks, as the number of active stations increases, delay and throughput degrade severely. As far as throughput and service delay are vital elements in Quality of Service (QoS) determination, such degradation could lead to intolerable situations and reduce the efficiency of WLANs. Networks (WLANs). Studies proved this problemarises due to constant initial backoff windows size (CWmin), which is an important parameter in determination of network behavior. In this paper, we introduce a new method to tune this parameter adaptively according to changes in channel load. In this method, we do tune this parameter after every transmission using a feedback from transmission channel. Later it will be proven that applying this method in MAC layer enhances network stability; delay trend in all traffic classes exhibits a considerable reduction when compared with simple Enhanced Distributed Coordination Access (EDCA) scenarios. Also throughput exhibits a salient improvement in level. In other word, QoS improves. Especially, with the aid of this method, delay variations in all decrease considerably and more smoothen delay trends are achieved. [ABSTRACT FROM AUTHOR]

This paper proposes a novel framework for the cross-layer analysis and design of wireless networks combining adaptive modulation and coding (AMC) at the physical layer with an automatic repeat request (ARQ) protocol at the data-link layer. Most previous works rely on first-order amplitude-based finite-state Markov chains (AFSMCs) to model the physical layer. It is shown that these models present several deficiencies that could compromise the design of higher layer protocols. Thus, a physical-layer first-order 2-D Markov model using both the amplitude and the rate of change of the fading envelope is presented. Based on this multidimensional physical-layer Markov model, the quality-of-service (QoS) performance at the data-link layer is investigated through the use of two different approaches. The first one relies on an analytical framework based on a discrete-time Markov chain (DTMC) that jointly describes the statistical behavior of the arrival process, the queueing system, and the physical layer. The second one is based on the effective-bandwidth and effective-capacity theories. Both the DTMC-based and the effective-bandwidth/capacity-based approaches are analyzed and compared in combination with our proposed physical-layer first-order 2-D Markov model in a cross-layer design aiming to satisfy the required average packet loss `probability constraint by maximizing the average throughput of the system. Numerical results show that our proposed framework represents a significant improvement over previous models. [ABSTRACT FROM AUTHOR]

In information security and network management, attacks based on vulnerabilities have grown in importance. Malicious attackers break into hosts using a variety of techniques. The most common method is to exploit known vulnerabilities. Although patches have long been available for vulnerabilities, system administrators have generally been reluctant to patch their hosts immediately because they perceive the patches to be annoying and complex. To solve these problems, we propose a security vulnerability evaluation and patch framework called PKG-VUL, which evaluates the software installed on hosts to decide whether the hosts are vulnerable and then applies patches to vulnerable hosts. All these operations are accomplished by the widely used simple network management protocol (SNMP). Therefore, system administrators can easily manage their vulnerable hosts through PKG-VUL included in the SNMP-based network management systems as a module. The evaluation results demonstrate the applicability of PKG-VUL and its performance in terms of devised criteria. [ABSTRACT FROM AUTHOR]

String matching is a fundamental element of an important category of modern packet processing applications which involve scanning the content flowing through a network for thousands of strings at the line rate. To keep pace with high network speeds, specialized hardware-based solutions are needed which should be efficient enough to maintain scalability in terms of speed and the number of strings. In this paper, a novel architecture based upon a recently proposed data structure called the Bloomier filter is proposed which can successfully support scalability. The Bloomier filter is a compact data structure for encoding arbitrary functions, and it supports approximate evaluation queries. By eliminating the Bloomier filter's false positives in a space efficient way, a simple yet powerful exact string matching architecture is proposed that can handle several thousand strings at high rates and is amenable to on-chip realization. The proposed scheme is implemented in reconfigurable hardware and we compare it with existing solutions. The results show that the proposed approach achieves better performance compared to other existing architectures measured in terms of throughput per logic cells per character as a metric. [ABSTRACT FROM AUTHOR]

Internet Protocol TV (IPTV), an emerging internet application, provides more flexibility and interactivity for users because of its embedded return channel. Wireless 802.11 networks, used as the last hop of IPTV networks, would add another dimension of mobility, which is of great value for hot spot deployment and is increasingly required for in-home content distribution. However, a wireless channel may suffer from multi-path fading and interference, which may cause random and burst packet loss and impact users' quality of experience of an IPTV program. We report the design, implementation and evaluation of Merged Hybrid Adaptive FEC and ARQ (MHARQ) system for IPTV multicast over wireless LANs. In MHARQ, an IPTV cache server is introduced to improve the reliability for the last hop wireless distribution. MHARQ combines the advantages of receiver-driven staggered FEC and hybrid ARQ schemes to compensate the large dynamic range of WLAN channels and to achieve high reliability, scalability and wireless bandwidth efficiency for IPTV multicast. We also address backward compatible FEC encoding and decoding, audio and video synchronization issues in practical system implementation. Using the ORBIT radio grid test bed, we have investigated the performance of the proposed MHARQ system with various numbers of users per AP and different numbers of APs per IPTV cache server. It is demonstrated via real system implementation on ORBIT that MHARQ improves wireless bandwidth efficiency and scalability for reliable IPTV multicast, compared with existing reliable multicast schemes. [ABSTRACT FROM AUTHOR]

In this paper, we introduce and outline the concept of channel code-division multiple access using a design example based on the recently proposed multilevel-structured (MLS) low-density parity-check (LDPC) codes. We succeeded in making the memory requirements of the multiuser transceiver to become practically independent of the total number of users supported by the system, as well as ascertain that each user benefits from the same level of protection. Finally, we will demonstrate that despite their beneficial compact structure, the proposed MLS LDPC codes do not suffer from any bit-error-ratio or block-error-ratio performance degradation, when compared to an otherwise identical benchmarker scheme using significantly more complex LDI'C codes having pseudorandom parity-check matrices. [ABSTRACT FROM AUTHOR]

In this paper, we propose a Cooperative Transmission Strategy using Entropy-based Relay Selection in Mobile Ad-hoc Wireless Sensor Networks (MAWSN) with Rayleigh Fading Environments. The main features and contributions of the proposed cooperative transmission strategy are as follows. First, entropy-based relay selection is used to improve data transmission reliability from a source node to a destination node. Second, we present a theoretical analysis model for the proposed cooperative transmission strategy with the outage probability of the end-to-end performance. The performance of our protocol is evaluated using analysis and simulation. [ABSTRACT FROM AUTHOR]

Interference is a serious problem in wireless communications. In a wireless network, the signal sent by a terminal will be received by all its neighboring nodes. If a neighbor (except the destinations) is receiving data from some other terminals at the same time, the signals will collide, and the useful signal will be destroyed, which may result in transmission failure. Previous solutions to this problem focused on the avoidance of signal collisions through careful medium access control (MAC) and/or scheduling. However, this needs some sophisticated protocols and may waste system resources such as bandwidth. In this paper, we shall put forward some practical schemes to recover the useful signal from the collided signals for different types of wireless channels; thus, the throughput and network efficiency can greatly be increased. The proposed schemes are based on the network coding technique and performed on the physical layer. One feature of our schemes is that neither strict synchronization nor power control is needed among the different terminals; thus, it is very fit for distributed networks. Simulation results will show that the bit error rate (BER) of the recovered signal by our developed schemes is almost the same as that of the signal with no collision, which proves their efficiency in eliminating the interference. [ABSTRACT FROM AUTHOR]

This article investigates distributed cooperative medium access control protocol design for multihop wireless networks. Cooperative communication has been proposed recently as an effective way to mitigate channel impairments. With cooperation, single-antenna mobile terminals in a multi-user environment share antennas from other mobiles to generate a virtual multiple-antenna system that achieves more reliable communication with a higher diversity gain. However, more mobiles conscribed for one communication inevitably induces complex medium access interactions, especially in multihop wireless ad hoc networks. To improve the network throughput and diversity gain simultaneously, we investigate the issues and challenges in designing an efficient MAC scheme for such networks. Furthermore, based on the IEEE 802.11 DCF, a cross-layer designed cooperative MAC protocol is proposed. The MAC scheme adapts to the channel condition and payload length. [ABSTRACT FROM AUTHOR]

Recent studies demonstrated that dynamic spectrum access can improve spectrum utilization significantly by allowing secondary unlicensed users to dynamically share the spectrum that is not used by the primary licensed users. Cognitive radio was proposed to promote the spectrum utilization by opportunistically exploiting the existence of spectrum "holes." Meanwhile, cooperative relay technology is regarded widely as a key technology for increasing transmission diversity gain in various types of wireless networks, including cognitive radio networks. In this article, we first give a brief overview of the envisioned applications of: cooperative relay technology to CRNs, cooperative transmission of primary traffic by secondary users, cooperative transmission between secondary nodes to improve spatial diversity, and cooperative relay between secondary nodes to improve spectrum diversity. As the latter is a new direction, in this article we focus on this scenario and investigate a simple wireless network, where a spectrum-rich node is selected as the relay node to improve the performance between the source and the destination. With the introduction of cooperative relay, many unique problems should be considered, especially the issue for relay selection and spectrum allocation. To demonstrate the feasibility and performance of cooperative relay for cognitive radio, a new MAC protocol was proposed and implemented in a universal software radio peripheral-based testbed. Experimental results show that the throughput of the whole system is greatly increased by exploiting the benefit of cooperative relay. [ABSTRACT FROM AUTHOR]

In this paper, we propose an empirical framework for modeling and emulating interference in multi-hop wireless ad-hoc networks. Wireless interference causes wide variation in the frame delivery rate at a link, and thus we cannot represent the state of the link with only two states, connected state and disconnected state, as in wired networks. We first investigate wireless interference in detail, in order to accurately calibrate the interference and identify its underlying attributes, and then we simulate the diverse occurrences and effects of interference, after incorporating the scheme into a simulation tool. Based on these observations, we devise a modeling and simulation framework with several control parameters, and perform an extensive set of simulation studies. The simulation results indicate that the proposed framework enables us to examine various attributes of wireless interferences and their effects on wireless network protocols and systems. [ABSTRACT FROM AUTHOR]

We address two issues of contemporary interest in the area of enhancing the performance of ad hoc networks, where the IEEE 802.11 distributed coordination function (DCF) is the adopted medium-access control (MAC). We investigate the effects that transmission power control and tuning carrier sensing (CS) threshold have on network throughput, and we study the inter- play between them. To accomplish this, we develop a realistic analytical model that characterizes the transmission activities that are governed by the IEEE 802.11 DCF in a single-channel power-aware multihop wireless network. We observe that selecting a smaller CS threshold will severely impact the spatial reuse, whereas a larger CS threshold will yield excessive interference among concurrent transmissions. Accordingly, we discovered that performing power control has either a minor or negligible effect in both situations, respectively. Furthermore, when the CS threshold is selected appropriately, power control shows its effectiveness in reducing collisions and, hence, improving system performance. Finally, using our model, we demonstrate the potential adverse impacts of request-to-send/clear-to-send (RTS/CTS) control packets on the network capacity and compare its performance with the two-way basic access method. [ABSTRACT FROM AUTHOR]

In this paper, we consider the binary-distributed hypothesis testing problem, where a wireless sensor network (WSN) is used to determine the true state of nature. We propose a novel signaling scheme where signature vectors (SVs) are used to transmit censored sensor decisions to the fusion center (FC). In particular, the length of the SVs is chosen to be smaller than the number of sensors, resulting in nonorthogonal sensor channels and allowing a desirable tradeoff between bandwidth and power efficiency in WSNs. We consider deterministic SVs that are assumed to be known to the FC and random SVs that are unknown to the FC. For both cases, the optimum noncoherent fusion rules are derived, assuming independent Ricean fading sensor-FC channels. Since the complexity of these optimum fusion rules is prohibitively large, even for WSNs of moderate size, we also consider a low-complexity suboptimum energy-based fusion rule and show that it is equivalent to the optimum fusion rules under certain conditions. Furthermore, we calculate the system probabilities of detection and false alarm for the energy-based fusion rule for both deterministic and random SVs. Numerical and simulation results show that with the proposed nonorthogonal signaling scheme, significant improvements in bandwidth efficiency are possible at the expense of only a small loss in power efficiency. [ABSTRACT FROM AUTHOR]

Despite significant research effort, the performance of distributed medium access control methods has failed to meet theoretical expectations. This paper proposes a protocol named "Channel MAC" performing a fully distributed medium access control based on opportunistic communication principles. In this protocol, nodes access the channel when the channel quality increases beyond a threshold, while neighbouring nodes are deemed to be silent. Once a node starts transmitting, it will keep transmitting until the channel becomes "bad." We derive an analytical throughput limit for Channel MAC in a shared multiple access environment. Furthermore, three performance metrics of Channel MAC-throughput, fairness, and delay-are analysed in single hop and multihop scenarios using NS2 simulations. The simulation results show throughput performance improvement of up to 130% with Channel MAC over IEEE 802.11. We also show that the severe resource starvation problem (unfairness) of IEEE 802.11 in some network scenarios is reduced by the Channel MAC mechanism. [ABSTRACT FROM AUTHOR]

Transmission control protocols have to overcome common problems in wireless networks. TCP employing both packet loss discrimination mechanism and available bandwidth estimation algorithm, known as the good existing solution, shows significant performance enhancement in wireless networks. For instance, TCP New Jersey which exhibits high throughput in wireless networks intends to improve TCP performance by using available bandwidth estimation and congestion warning. Even though it achieves 17% and 85% improvements in terms of goodput over TCP Westwood and TCP Reno, respectively, we further improve it by exploring maximized available bandwidth estimation, handling bit-error-rate error recovery, and effective adjustment of sending rate for retransmission timeout. Hence, we propose TCP NJ+, showing that for up to 5% packet loss rate, it outperforms other TCP variants by 19% to 104% in terms of goodput when the network is in bi-directional background traffic. [ABSTRACT FROM AUTHOR]

A wireless sensor-actuator network (WSAN) is composed of sensor modes and actuator modes which are interconnected in wireless networks. A sensor node collects information on the physical world and sends a sensed value in a wireless network. Another sensor node forwards the sensed value to deliver to an actuator node. A sensor node can deliver messages with sensed values to only nearby nodes due to weak radio. Messages are forwarded by sensor nodes to an actuator node by a type of flooding protocol. A sensor mode senses an event and sends a message with the sensed value. In addition, on receipt of a message with a sensed value from another sensor mode, a sensor node forwards the sensed value. Messages transmitted by sensor nodes might be lost due to noise and collisions. In this paper, we discuss a redundant data transmission (RT) protocol to reliably and efficiently deliver sensed values sensed by sensor nodes to an actuator node. Here, a sensor node sends a message with not only its sensed value but also sensed values received from other sensor nodes. The more number of sensed values are included in a message, the more frequently the message is lost. Each message carries so many number of sensed values that the message loss ratio is not increased. Even if a message with a sensed value v is lost in the wireless network, an actuator node can receive the sensed value v from a message sent by another sensor node. Thus, each sensed value is redundantly carried in multiple messages. The redundancy of a sensed value is in nature increased since the sensed value is broadcast. In order to reduce the redundancy of sensed value, we take a strategy that the farther sensor nodes from an actuator node forward the fewer number of sensed values. We evaluate the RT protocol in terms of loss ratio, redundancy, and delay time of a sensed value. We show that about 80% of sensed values can be delivered to an actuator node even if 95% of messages are lost due to noise and collision. [ABSTRACT FROM AUTHOR]

The paper presents a detailed discussion of various issues involved in designing a medium access control (MAC) protocol for multihop wireless networks with nodes employing multiple beam smart antennas. Multiple beam smart antennas can form several beams simultaneously and can initiate concurrent transmissions or receptions in them, thereby increasing the throughput of the bottleneck nodes. Traditional on-demand MAC protocols for omnidirectional and single beam directional antennas based on the IEEE 802.11 distributed coordination function (DCF) mechanism cannot take advantage of this unique capability of multiple beam antennas as they do not facilitate concurrent transmissions or receptions by a node. This paper introduces a novel protocol, hybrid MAC .(HMAC), which enables concurrent packet reception (CPR) and concurrent packet transmission (CPT) at a node equipped with multiple beam antennas and is backward compatible with IEEE 802.11 DCF. Simulation results show the superior performance of HMAC in most ad hoc scenarios. Moreover, in some sample topologies, the throughput of HMAC is close to the theoretical maximum. The paper also presents a wireless mesh network architecture with heterogeneous antenna technologies and illustrates the advantages of employing multiple beam smart antennas and HMAC in such networks. [ABSTRACT FROM AUTHOR]

In the last decade, process instrumentation field devices such as sensors and actuators that have a direct contact with industrial processes have become increasingly intelligent. An important property of such intelligent field devices is their ability to be networked. The Foundation fieldbus (FF) is one of the most widely used fieldbus protocols for process instrumentation and control systems applications. This paper presents a study that validates the effectiveness of a new scheduling method that satisfies the performance requirements for a scheduled message using an FF protocol. Our scheduling method generates a schedule list that records the scheduled starting time and the scheduled period of each scheduled message. Then, it allocates scheduled message traffic to a bandwidth-limited fieldbus medium. As part of this study, an experimental model of an FF network was developed. The experimental results from our model confirmed that our scheduling method restricts the delay of a scheduled message to a prespecified bound. [ABSTRACT FROM AUTHOR]

A random access protocol named ALLow Improved Access in the Network via Cooperation and Energy Savings (ALLIANCES) was recently proposed, that achieves high throughput by resolving collisions in wireless networks. ALLIANCES exploits diversity provided by user cooperation. In this paper we propose a multichannel extension of ALLIANCES that in addition to cooperation diversity can exploit multipath diversity. The total bandwidth is divided into noninterfering subchannels and each packet occupies one subchannel for its transmission. First, two schemes are proposed for rate-limited traffic. Users transmit packets on all subchannels. Collisions on a subchannel are resolved via cooperative transmissions, involving either the subchannel on which they occurred only, or all subchannels in a shared fashion. Second, for the case of bursty traffic, a random subchannel selection scheme is proposed to adaptively control the number of transmitted packets for each active user and, thus, keep collision orders small. Third, to accommodate heterogeneous traffic with diverse quality of service requirements, a fixed subchannel selection scheme is presented, where packets with the same traffic type are allocated to the same cluster of subchannels and predefined traffic priorities are taken into account. Analytical performance characterization of the proposed schemes at the physical layer is provided. The analysis provides insight on the relationship between achievable diversity and parameters such as collision order, number of relays, channel length, and number of carriers per subchannel. [ABSTRACT FROM AUTHOR]

The article offers information on the proposed quality of service differentiation scheme for the Institute of Electrical and Electronics Engineers (IEEE) 802.16 wireless mesh networks. According to the article, WMN is becoming an important architecture of future generations of wireless communications systems wherein the quality of service provisioning provides an essential role in optimizing its performance. It provides a detailed discussion on the system model, frame structure, different scheduling schemes and collocated topology. It also discusses the different relevant issues and potential performances associated with the approach.