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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]

Most existing network communication systems, such as the Internet, are built around the TCP/IP protocol stack. However, TCP/IP cannot effectively support the upcoming network communication systems with more wireless communication links and higher requirements in terms of throughput, latency, and reliability. In this article, we introduce a general network communication protocol design based on batched network coding (BNC), which includes the existing framework as a special case and whose design can be guided by channel coding theory. BNC-based protocols can have significant throughput gain for single-hop or multihop wireless communications and provide better trade-off among throughput, latency and reliability. [ABSTRACT FROM AUTHOR]

Machine-to-machine (M2M) communication devices communicate and exchange information with each other in an independent manner to perform necessary tasks. The machine communicates with another machine over a wireless network. Wireless communication opens up the environment to huge vulnerabilities, making it very easy for hackers to gain access to sensitive information and carry out malicious actions. This paper proposes an M2M communication system through the internet in Tele-Robotics and provides network performance security. Tele-robotic systems are designed for surgery, treatment and diagnostics to be conducted across short or long distances while utilizing wireless communication networks. The systems also provide a low delay and secure communication system for the tele-robotics community and data security. The system can perform tasks autonomously and intelligently, minimizing the burden on medical staff and improving the quality and system performance of patient care. In the medical field, surgeons and patients are located at different places and connected through public networks. So the design of a medical sensor node network with LEACH protocol for secure and reliable communication ensures through the attack and without attack performance. Finally, the simulation results show low delay and reliable secure network transmission. [ABSTRACT FROM AUTHOR]

Global Mobility Networks(GLOMONETs) in wireless communication permits the global roaming services that enable a user to leverage the mobile services in any foreign country. Technological growth in wireless communication is also accompanied by new security threats and challenges. A threat-proof authentication protocol in wireless communication may overcome the security flaws by allowing only legitimate users to access a particular service. Recently, Lee et al. found Mun et al. scheme vulnerable to different attacks and proposed an advanced secure scheme to overcome the security flaws. However, this article points out that Lee et al. scheme lacks user anonymity, inefficient user authentication, vulnerable to replay and DoS attacks and Lack of local password verification. Furthermore, this article presents a more robust anonymous authentication scheme to handle the threats and challenges found in Lee et al.’s protocol. The proposed protocol is formally verified with an automated tool(ProVerif). The proposed protocol has superior efficiency in comparison to the existing protocols. [ABSTRACT FROM AUTHOR]

Driven by the increasing demand on marine exploration, UWANs are confronted with the rigorous challenge of improving network throughput. To deal with this challenge, this article proposes to apply the IBFD technique to UWANs. The IBFD technique can potentially double link capacity by simultaneously transmitting and receiving on the same frequency band, which has been recently demonstrated to be feasible for wireless communications. In this article, novel MAC protocols are specifically proposed for the acoustic IBFD network to overcome the inherent issues in underwater acoustic communications, such as long packet delay, large node collision probability, and high power consumption. Numerical results verify that our proposals can effectively mitigate these effects and improve the overall performance of the UWANs. [ABSTRACT FROM AUTHOR]

Current networking technologies are not perfectly equipped to support Quality of Service (QoS), which is vital for real-time multimedia applications in Wireless Community Mesh Networks (WCNs). Therefore, there is a need to devise innovative routing algorithms to support QoS on top of existing standards. Thus, this paper presents a cross layer relay node selection model for routing protocols in order to offer optimal routes to real-time applications. To the best of our knowledge, our two proposed routing metrics, Packet Priority-Oriented routing metric (PPO) and Packet Priority-oriented QoS routing metric (PP-QoS) , are the first to provide differentiated priorities and service levels to applications with different needs. PPO considers the application priority. Moreover, PP-QoS also considers the channel busy level to improve the performance of path selection. The simulation confirms the superiority of the proposed model against a number of existing counterparts. [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]

Smart homes and environments will consist of a large number of low power wireless devices such as sensors and actuators. Recently IETF standardized a network protocol called RPL that is designed to run on these nodes. In this article, we study the performance of RPL on a variety of scenarios that these nodes will encounter when they are deployed in practice. We deploy a network of 23 sensor nodes in a computer lab to monitor energy used by each computer across the applications and users. We subject the network to four different levels of interference that are representative of the types and levels of interference that these networks might encounter in deployment. Our study finds that RPL?s reliability degrades even with an access point in overlapping channel under normal network traffic. With high interference, the packet delivery reliability goes down to 10 percent. The scenario that resulted in this performance is not unimaginable in smart home or environment. This performance degradation is partly due to lack of coordination across the layers of the protocol stack: RPL is unaware of the changes in the wireless environment underneath and proceeds as usual. As other research has shown, coordination across the network stack is essential for network protocols to work reliably in the presence of interference. This will require a more coordinated approach to standards across the bodies. [ABSTRACT FROM PUBLISHER]

The groundbreaking transformations triggered by the Industry 4.0 paradigm have dramatically reshaped the requirements for control and communication systems within the factory systems of the future. The aforementioned technological revolution strongly affects industrial smart and distributed measurement systems as well, pointing to ever more integrated and intelligent equipment devoted to derive accurate measurements. Moreover, as factory automation uses ever wider and complex smart distributed measurement systems, the well-known Internet of Things (IoT) paradigm finds its viability also in the industrial context, namely Industrial IoT (IIoT). In this context, communication networks and protocols play a key role, directly impacting on the measurement accuracy, causality, reliability and safety. The requirements coming both from Industry 4.0 and the IIoT, such as the coexistence of time-sensitive and best effort traffic, the need for enhanced horizontal and vertical integration, and interoperability between Information Technology (IT) and Operational Technology (OT), fostered the development of enhanced communication subsystems. Indeed, established technologies, such as Ethernet and Wi-Fi, widespread in the consumer and office fields, are intrinsically non-deterministic and unable to support critical traffic. In the last years, the IEEE 802.1 Working Group defined an extensive set of standards, comprehensively known as Time Sensitive Networking (TSN), aiming at reshaping the Ethernet standard to support for time-, mission- and safety-critical traffic. In this paper, a comprehensive overview of the TSN Working Group standardization activity is provided, while contextualizing TSN within the complex existing industrial technological panorama, particularly focusing on industrial distributed measurement systems. In particular, this paper has to be considered a technical review of the most important features of TSN, while underlining its applicability to the measurement field. Furthermore, the adoption of TSN within the Wi-Fi technology is addressed in the last part of the survey, since wireless communication represents an appealing opportunity in the industrial measurement context. In this respect, a test case is presented, to point out the need for wirelessly connected sensors networks. In particular, by reviewing some literature contributions it has been possible to show how wireless technologies offer the flexibility necessary to support advanced mobile IIoT applications. [ABSTRACT FROM AUTHOR]

Opportunistic Spectrum Access (OSA) in distributed cognitive radio networks (CRNs) has been well studied in the literature from a theoretical perspective. However, such theoretically-optimized distributed OSA approaches are challenged by several practical implementation issues. In this paper, we design a custom cross-layer framework that enables the: (i) clean-slate implementation of a wide variety of OSA mechanisms; (ii) experimental evaluation of the individual practical OSA components of the Rate-Adaptive Probabilistic (RAP) framework; and (iii) detailed comparison of the performance of such a practical OSA approach against theoretical OSA approaches developed for fully-capable CRNs. Our evaluation reveals the multi-fold goodput improvement and remarkable fairness characteristics of the practical RAP OSA approach compared to the OSA approaches that overlook the OSA and CR practical limitations. However, the superior performance of practical OSA comes at the expense of more outages to the primary licensed networks but within the permissible bounds. Another key finding is that the wide family of existing theoretically-optimized OSA protocols can benefit from the gains available to the individual components of the practical RAP approach, namely, the random spectrum sensing and the probabilistic non-greedy access. [ABSTRACT FROM AUTHOR]

In this paper, we describe a framework for designing a discrete-bandwidth nonblocking network. The theoretical foundation of the framework combines theories from both networking and switching. While the conventional Clos theory must assume a particular topology, the new theory allows us to design a nonblocking network with an arbitrary topology. Thus it can be considered as a generalization of the Clos theory. In addition to the design of WDM or SONET networks, applications such as grid computing and supercomputing can also benefit from the results developed in the paper. [ABSTRACT FROM AUTHOR]

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]

The heterogeneous mobile terminals coexist in the next generation wireless networks. The most common routing schemes for mobile ad hoc networks are designed for homogeneous wireless networks. The heterogeneous wireless network routing protocols are needed urgently in many important applications. This paper im- proves the routing scheme utilizing different capability of terminals and the Hybrid Grid Routing Protocol (HGRP) is proposed. The network is organized in the grid form, that is, the network deployment area is divided into square cells according to the location. Each cell contains one backbone node and several ordinary nodes. This proposed protocol consists of four parts: grid construction, local routing, global routing, and routing correction. Analysis and simulation results indicate that the proposed protocol has the advantages of lower routing cost, lower energy consumption, smaller delay and higher throughput, compared to AODV and ZRP. [ABSTRACT FROM AUTHOR]

Vehicular delay-tolerant networks (VDTNs) are opportunistic networks that enable connectivity in challenged scenarios with unstable links where end-to-end communications may not exist. VDTN architecture handles non-real time applications using vehicles to relay messages between network nodes. To address the problem of intermittent connectivity, network nodes store messages on their buffers, carrying them through the network while waiting for transfer opportunities. The storage capacity of the nodes affects directly the network performance. Therefore, it is important to incorporate suitable network protocols using self-contained messages to improve communication that supports store-carry-and-forward operation procedures. Clearly, such procedures motivate content caching and retrieval. This paper surveys the state-of-the art on intelligent caching and retrieval mechanisms focusing on ad-hoc and delay tolerant networks (DTN). These approaches can offer important insights for upcoming proposals on intelligent caching and retrieval mechanisms for VDTNs. [ABSTRACT FROM AUTHOR]

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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]

A Bayesian game-theoretic model is developed to design and analyze the resource allocation problem in K-user fading multiple access channels (MACs), where the users are assumed to selfishly maximize their average achievable rates with incomplete information about the fading channel gains. In such a game-theoretic study, the central question is whether a Bayesian equilibrium exists, and if so, whether the network operates effiiently at the equilibrium point. We prove that there exists exactly one Bayesian equilibrium in our game. Furthermore, we study the network sum-rate maximization problem by assuming that the users coordinate according to a symmetric strategy profile. This result also serves as an upper bound for the Bayesian equilibrium. Finally, simulation results are provided to show the network efficiency at the unique Bayesian equilibrium and to compare it with other strategies. [ABSTRACT FROM AUTHOR]

More and more applications and protocols are now running on wireless networks. Testing the implementation of such applications and protocols is a real challenge as the position of the mobile terminals and environmental effects strongly affect the overall performance. Network emulation is often perceived as a good trade-off between experiments on operational wireless networks and discrete-event simulations on Opnet or ns-2. However, ensuring repeatability and realism in network emulation while taking into account mobility in a wireless environment is very difficult. This paper proposes a network emulation platform, called W-NINE, based on off-line computations preceding online pattern-based traffic shaping. The underlying concepts of repeatability, dynamicity, accuracy, and realism are defined in the emulation context. Two different simple case studies illustrate the validity of our approach with respect to these concepts. [ABSTRACT FROM AUTHOR]

A new class of multiple access algorithms for systems without feedback is introduced and analyzed. A finite population of users is assumed, where each user transmits a packet R times within the next N time slots (and all packets have an equal length of one slot). To improve the performance achieved by randomly selecting these R slots, user codes are invoked such that any two users will only transmit simultaneously in at most one slot, i.e., 2-(N, R, 1) designs. We argue that in most cases, the set of user codes can be generated easily using cyclic designs and provide a method to select T user codes from the set of user codes SN,R in case the user population consists of T < ∣ SN,R∣ users. We further demonstrate how larger populations, with T > ∣SN,R∣ can still benefit from these user codes in two different manners. Closed formulas that express the success probability of a packet are provided for all population setups. Finally, a comparison with the random selection strategy demonstrates the performance gain realized by the new multiple access algorithms and some engineering rules to optimize the performance are provided. [ABSTRACT FROM AUTHOR]

The widespread use of mobile devices in the IP network has lead to a new attempt to apply a power-saving mode (PSM) to real-time traffic such as Voice over IP (VoIP). This paper evaluates the performance of the PSM when the PSM is used for VoIP services of mobile devices. Taking the activity of each conversational party into account, we consider two different kinds of PSMs: one is employed during the talk-spurt periods and the other is employed during the mutual silence periods of two conversational parties. The performance of each PSM is analyzed with respect to buffering delay, the probability of packet drop, and power consumption of a mobile VoIP device. Thereafter, the maximum bound of sleep interval in each period is derived, which minimizes the power consumption of the mobile device without violating the quality-of-service (QoS) of VoIP. In the various network environments, the analysis and simulation results show that the proposed PSM for VoIP significantly decreases the power consumption while satisfying the end-to-end delay and packet drop probability constraints of a VoIP connection. [ABSTRACT FROM AUTHOR]

Content or service delivered through IPTV is high quality and of high economic value accordingly. As digital technologies progress, illegal copy and redistribution of IPTV content become easier and simpler. Therefore it is required to protect IPTV content or service. In this paper, following the approaches taken by ITU-T IPTV Focus Group, we analyze the security threats and requirements. We also discuss related issues and solutions for IPTV. Specially, interoperability issues among different content and service protection systems are addressed. [ABSTRACT FROM AUTHOR]

In this paper, we propose an Adaptive Hybrid Transmission (AHT) scheme for on-demand mobile IPTV service over broadband wireless access network (i.e. mobile WiMAX, 802.16e). Proposed algorithm utilizes hybrid mechanism which combines multi-channel multicasting and unicast scheme to enhance not only service blocking probability but also reduce overall bandwidth consumption of the wireless system which has very limited resources compared to wired networks. An adaptive resource allocation algorithm is also proposed, and is shown to achieve minimum blocking probability. In order to evaluate the performance, we compare proposed algorithm against traditional unicast and multicast schemes. [ABSTRACT FROM AUTHOR]

IPTV is becoming a serious alternative to traditional broadcast schemes, such as cable, satellite or terrestrial, to deliver TV to the home. However, the expectation of the user is that IPTV provides the same or even better Quality of Experience (QoE). An important part of QoE for linear TV services is the Channel Change Time (CCT) also known as zapping time. Due to its relevance many ideas and concepts have been published which describe how to optimize or speed up the CCT. First, to be able to judge the challenges and benefits of the available concepts, a common understanding of the contributors to the CCT is necessary. This article provides an overview of all elements in the IPTV end-to-end chain influencing the CCT from the head end down to the Set-Top Box (STB) and finally to the display. Second, various techniques for reducing the CCT are presented and discussed. [ABSTRACT FROM AUTHOR]

Internet Protocol Television (IPTV) over IEEE 802.11 Wireless LANs, which are considered today as the de-facto wireless access network for local distribution (home networks, hotspots), brings forth a big challenge to guarantee high quality multicast/broadcast delivery over unreliable and time-variant wireless channels. However, in IEEE 802.11 Wireless LANs, current standard MAC layer protocols do not provide any error correction scheme for broadcast/multicast. In our previous work, we enhanced a Leader Based Protocol (LBP) and proposed a Beacon-driven Leader Based Protocol (BLBP) for the MAC layer multicast error control. However, as pure Automatic Repeat reQuest (ARQ) schemes, both LBP and BLBP are not efficient for large multicast groups. In this paper, we combine BLBP and packet level Forward Error Correction (FEC) and propose a Hybrid Leader Based Protocol (HLBP) for the MAC layer multicast error control. HLBP transmits the original data packets using raw broadcast and retransmits parity packets using an improved BLBP which is based on block feedback. To guarantee the required Packet Loss Ratio (PLR) under strict delay constraints for multicast delivery over a Gilbert-Elliott (GE) channel, we analyze LBP, BLBP and HLBP, develop analytic performance models that allow optimizing the configurations. The performance models are verified via simulation experiments. Both the theoretical analysis and simulation results show that HLBP is much more efficient than LBP and BLBP especially for large multicast groups and is also more efficient than the best application layer multicast error correction scheme. BLBP needs the minimum number of redundancy transmissions among all pure ARQ based schemes while HLBP needs the near-minimum number of redundancy transmissions among all schemes. Due to the simplicity and efficiency, BLBP is a good choice for IPTV multicast delivery for small groups in Wireless LANs while HLBP is a better choice for large multicast groups. [ABSTRACT FROM AUTHOR]

In this paper we investigate the potential gain that can be obtained in DVB-H using application layer forward error correction (AL-FEC) to perform a multi-burst protection of the transmission for improving the reception of streaming services for mobile terminals. Compared to the conventional approach with link layer multi protocol encapsulation FEC (MPE-FEC), this technique allows to increase the robustness of the DVB-H transmission not only as a function of the capacity devoted for error repair (FEC overhead), but also as a function of the number of bursts jointly encoded. The main drawback of this approach is an increase of the network latency, that can be translated into a larger service access time, and, in the case of mobile TV, a larger zapping time between channels, which is currently seen as a crucial parameter for DVB-H usability. In this paper the performance of the proposed approach is evaluated using field measurements. We evaluate the gain compared to MPE-FEC in terms of reduced IP packet error rate of the streaming service as a function of the FEC overhead and the latency introduced. Moreover, simulations have been performed to quantify feasible link margin gains. We also discuss techniques to reduce and hide the zapping time from the perception of the users. [ABSTRACT FROM AUTHOR]

Fieldbus systems are well known in the industrial automation world. Due to the increasing demand for scalability and capability of working in harsh environment, the use of wireless communication is gaining in importance. In the past, some efforts were pursued to encapsulate wired standards over wireless link, but their diffusion is limited by reliability and predictability requirements. In addition, event-driven protocols borrowed from the consumer world (as IEEE802.11 or IEEE802.15.4) are not well suited for some industrial applications. In this paper, authors present the design and the experimental evaluation of a wireless real-time communication protocol that tries to overcome these limits. It exploits standard hardware to lower cost and implements a hybrid medium access strategy. Time Division Multiple Access scheduling is used to ensure time deadlines respect, while Carrier Sense Multiple Access with Collision Avoidance is used for acyclic communications, as those involved in network management. It has been successfully adopted for temperature monitoring in plastic machineries. The prototype network adopts star topology and can manage up to 16 nodes with a refresh time of 128 ms. [ABSTRACT FROM AUTHOR]

The article presents the recent developments on Internet Protocol (IP) authentication that can reduce the re-authentication delay. These newly developed protocols are the IEEE 802.11 r and the Extensible Authentication Protocol (EAP) Re-authentication Protocol (ERP) for handover keying (HOKEY). These two protocols utilize the key hierarchies to avoid full authentication. The control and provisioning of wireless access points (CAPWAP) architecture was introduced to illustrate different optimizations.

Modeling and simulation methods are employed by scientists and engineers to gain insight into system behavior that can lead to faster product time-to-market and more robust designs. These advantages come at the cost of model development time and the potential for questionable results because the model represents limited attributes of the actual system. M&S techniques are used to characterize complex interactions and performance at various layers of the protocol stack. This article provides a discussion of M&S for wireless network designers and developers, with particular attention paid to the architectural issues, as well as a discussion of the various communication M&S tools available today. The topics presented span the protocol stack, including radio-frequency-propagation M&S tools, physical-layer and waveform M&S, network-layer M&S, and distributed simulation, as well as waveform generation for test and evaluation. [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]

Cooperative networking, by leveraging the broadcast nature of the wireless channel, significantly improves system performance and constitutes a promising technology for next-generation wireless networks. Although there is a large body of literature on cooperative communications, most of the work is limited to theoretical or simulation studies. To impact the next generation of wireless technologies and standards, it is essential to demonstrate that cooperative techniques indeed work in practice. This article describes two programmable cooperative communication testbeds built at Polytechnic Institute of NYU to achieve this goal. The testbeds are based on open- source platforms and enable implementation of cooperative networking protocols in both the physical and the medium access control layer. Extensive experiments carried out using the testbeds suggest not only that cooperative communication techniques can be integrated into current wireless technologies, but also that significant benefits of cooperation can be observed in terms of network throughput, delay, and video quality in real applications. [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]

The papers deals with a modeling of a Time- Difference of Arrival system for a subscriber station localization, based on the 802.11 standard wireless network. In the case of severe multipath effects the standard TDOA estimation methods, based on correlation of signals, received by conveniently displaced receiving stations show large errors. Thus, a new algorithm is proposed using received signals decomposition to a set of delayed replicas. This represents a linear estimation of reflected signals amplitudes. The described method leads to a better estimation of time differences of the signals, propagating on the direct paths between the emitter and the receiving stations. [ABSTRACT FROM AUTHOR]

Research on vehicular ad hoc networks has focused mainly on efficient routing protocol design under conditions where there are relatively large numbers of closely spaced vehicles. These routing protocols are designed principally for urban areas with high node density and fully connected networks and are not suitable for packet delivery in a sparse, partially connected VANET. In this article, we examine the challenges of VANETs in sparse network conditions, review alternatives including epidemic routing, and propose a border node-based routing protocol for partially connected VANETs. The BBR protocol can tolerate network partition due to low node density and high node mobility. The performance of epidemic routing and BBR are evaluated with a geographic and traffic information-based mobility model that captures typical highway conditions. The simulation results show that under rural network conditions, a limited flooding protocol such as BBR performs well and offers the advantage of not relying on a location service required by other protocols proposed for VANETs. [ABSTRACT FROM AUTHOR]

IEEE 802.15.4 is the global standard protocol designed for low-power and low-rate wireless personal area networks. When applied to sensor networks, extra care should be taken due to their requirements for multihop communication with minimum energy consumption. In this article we first discuss potential problems with the energy consumption in sensor networks using IEEE 802.15.4. Then six representative categories of algorithms are presented. The algorithms reside in between the MAC and a network layer. All operations of the MAC are performed through the standard interfaces of IEEE 802.15.4 without altering the standard protocol. The energy consumption and latency of the algorithms are evaluated by analysis and experiments, and the feasibility of real implementations is also discussed. [ABSTRACT FROM AUTHOR]

The article discusses the study which advocates the design of a new network layer that can support multihop communications efficiently in Worldwide Interoperability for Microwave Access (WiMAX) networks and that can fully exploit the features of the WiMAX standards. The study identifies services that are important for broadband wireless network providers and investigates the requirements for different services. It also illustrates how to design WiMAX networks by considering issues of efficiency, security, and reliability.

The article discusses the study that focuses on wireless mesh networking and the insights into the related standardization efforts in IEEE 802. The study illustrates the draft wireless local area network (WLAN) mesh standard IEEE 802.11s and identifies challenges for medium access control in multihop communication. Derived from the study's proposal to 802.11s, its draft incorporates an optional medium access scheme that circumvents a performance gap. It also compares the performance of both solutions and provide an outlook for future 802 wireless systems that will be more reliable.

Recent technological innovations allow mobile devices to be equipped with multiple wireless interfaces. Moreover, the trend in fourth-generation or next-generation wireless networks (4G/NGWNs) is the coexistence of diverse but complementary architectures and wireless access technologies. In this context, an appropriate mobility management scheme, as well as the integration and interworking of existing wireless systems, is crucial. Several proposals for solving these issues are available in the literature. However, these proposals cannot guarantee seamless roaming and service continuity. This paper proposes a novel architecture called Integrated InterSystem Architecture (lISA), which is based on the Third-Generation Partnership Project/Third-Generation Partnership Project 2 requirements that enables the integration and interworking of current wireless systems, and investigates mobility management issues. An efficient handoff protocol based on localized mobility management, access networks discovery, and fast handoff concepts called Handoff Protocol for Integrated Networks (HPINs) is proposed. It alleviates service disruption during handoff in IPv6-based heterogeneous wireless environments. Numerical results show that HPIN performs better in terms of signaling cost, handoff latency, handoff-blocking probability, and packet loss compared to existing schemes. [ABSTRACT FROM AUTHOR]

For multihop and ad hoc networks, a conventional 1-D channel model cannot capture the spatial correlation of the shadowing processes. This paper investigates the joint spatial correlation property of the shadowing process for peer-to-peer (P2P) radio links in urban environments. When a fixed base station is assumed, statistical analysis reveals that the shadowing process is mainly a result of spatial displacement at the mobile station (MS). Furthermore, the joint correlation property of the MS-MS channel shows that MS displacements at each end of the P2P link have an independent and equal effect on the correlation coefficient. A sum-of-sinusoids simulation model is proposed to generate the joint correlation shadowing process for urban P2P radio channels. The performance of the proposed channel simulator is analyzed in terms of the autocorrelation and joint correlation function of the simulated shadowing process. Simulations illustrate that the proposed model is able to output deterministic shadowing with a normal distribution (in decibels) and the desired correlation properties. It is thus suitable for use in system-level simulations, such as the evaluation of routing and radio resource management algorithms in ad hoc or mesh networks. [ABSTRACT FROM AUTHOR]

We propose a high-throughput random access protocol for 2 × 2 multiuser multiple-input multiple-output (MIMO) systems. The cross-layer mechanism utilizes the packets combining technique to exploit the advantages of both spatial multiplexing and multipacket reception. Analytical result indicates that the proposed scheme achieves 0.669 per spatial degree of freedom in stable throughput, which is much higher than those in the existed studies. [ABSTRACT FROM AUTHOR]

A novel random access protocol combining a tree algorithm (TA) with successive interference cancellation (SIC) has been introduced recently. To mitigate the deadlock problem of SICTA arising in error-prone wireless networks, we put forth a SICTA with first success (SICTA/FS) protocol, which is capable of high throughput while requiring limited-sensing and gaining robustness to errors relative to SICTA. [ABSTRACT FROM AUTHOR]

This paper presents an optimized spatial signal shaping for multiple-input-multiple-output (MIMO) "ad hoc"-like networks. It is adopted for maximizing the information throughput of pilot-based multiantenna systems that are affected by spatially colored multiple access interference (MAI) and channel estimation errors. After deriving the architecture of the minimum mean square error (MMSE) MIMO channel estimator, closed-form expressions for the maximum information throughput that is sustained by the MAI-affected MIMO links are provided. Then, we present a novel power allocation algorithm for achieving the resulting link capacity. Several numerical results are provided to compare the performance achieved by the proposed power-allocation algorithm with that of the corresponding MIMO system that works in MAI-free environments and is equipped with error free (e.g., perfect) channel estimates. By so doing, we are able to give an insight on the ultimate performance loss that is induced in MIMO systems by spatially colored MA! and imperfect channel estimates. Finally, we point out some implications about space- division multiple access strategies arising from the proposed power allocation algorithm. [ABSTRACT FROM AUTHOR]

The article discusses the proposed generic analytical model for medium access control (MAC) protocol in wireless broadband access networks. The model is based on a hierarchical three-level renewal process mechanism which directs to some significant MAC protocol performance metrics. The model is a very general analytical framework that can be also applied to protocols with various types of backoff policies and widely used in several wireless broadband access networks. It has been tested to the recent work of the performance analysis of the prioritized channel access MAC protocol in multiband orthogonal-frequency-division-multiplexing-based ultra wideband.

In this paper, we develop a physical/medium- access-control (PHY/MAC) cross-layer analytical model to investigate the throughput performance of the wireless local-area network (WLAN) in a lossy wireless environment. From the PHY-layer perspective, the developed model incorporates the effects of capture and directional antennas, while from the MAC-layer perspective, our approach takes into account the carrier-sense multiple access with collision-avoidance (CSMA/CA) MAC protocol and the effect of the backoff process in the IEEE 802.11 WLAN. We derive explicit analytical expressions for the frame outage and capture probabilities of a directional antenna system in the presence of shadowing and Rayleigh fading. Applying this analysis, we can model the interaction between the PHY and MAC layers more accurately for the infrastructure-based WLAN. The numerical results show that our analytical model can approach that attained by simulations. The proposed cross-layer analytical model not only provides insights into the PHY layer impacts on the throughput of the CSMA/CA MAC protocol but also indicates to how directional antennas can improve the CSMA/CA-based WLAN in terms of antenna beamwidth and the number of radio transceivers. [ABSTRACT FROM AUTHOR]

This paper investigates the hidden-node phenomenon (HN) in IEEE 802.11 wireless networks. HN occurs when nodes outside the carrier-sensing range of each other are nevertheless close enough to interfere with each other. As a result, the carrier- sensing mechanism may fail to prevent packet collisions. HN can cause many performance problems, including throughput degradation, unfair throughput distribution among flows, and through-put instability. The contributions of this paper are threefold. 1) This is a first attempt to identify a set of conditions-which we called Hidden-node-Free Design (HFD)—that completely remove HN in 802.11 wireless networks. 2) We derive variations of HFD for large-scale cellular WiFi networks consisting of many wireless LAN cells. These HFDs are not only HN-free, but they also reduce exposed nodes at the same time so that the network capacity is improved. 3) We investigate the problem of frequency-channel assignment to adjacent cells. We find that with HFD, careful assignment in which adjacent cells use different frequency channels does not improve the overall network capacity (in unit of bits per second per frequency channel). Indeed, given f frequency channels, a simple scheme with f overlaid cellular WiFi networks in which each cell uses all f frequencies yields near-optimal performance. [ABSTRACT FROM AUTHOR]

In this article we study two representative mobility management schemes for mobile hotspots with heterogeneous multihop wireless links: the NEMO basic support protocol at the network layer and the SIP-based network mobility support protocol at the application layer. We evaluate their salient features and quantify their handoff latency. It is shown that the SIP-based network mobility support protocol can easily be deployed and reduce the tunneling overhead incurred in the NEMO basic support protocol. However, it increases handoff latency due to longer message length. We also discuss several open research issues for seamless mobility support in mobile hotspots. [ABSTRACT FROM AUTHOR]

Routing in wireless sensor networks is a demanding task. This demand has led to a number of routing protocols which efficiently utilize the limited resources available at the sensor nodes. All these protocols typically find the minimum energy path. In this paper we take a view that, always using the minimum energy path deprives the nodes energy quickly and the time taken to determine an alternate path increases. Multipath routing schemes distribute traffic among multiple paths instead of routing all the traffic along a single path. Two key questions that arise in multipath routing are how many paths are needed and how to select these paths. Clearly, the number and the quality of the paths selected dictate the performance of a multipath routing scheme. We propose an energy efficient adaptive multipath routing technique which utilizes multiple paths between source and the sink, adaptive because they have low routing overhead. This protocol is intended to provide a reliable transmission environment with low energy consumption, by efficiently utilizing the energy availability and the received signal strength of the nodes to identify multiple routes to the destination. Simulation results show that the energy efficient adaptive multipath routing scheme achieves much higher performance than the classical routing protocols, even in the presence of high node density and overcomes simultaneous packet forwarding. [ABSTRACT FROM AUTHOR]

With recent developments in ad hoc networks and sensor networks, random-access protocol without feedback is a technique that deserves a closer look. This paper is based on Massey's model on random-access channel without feedback. A central concept of this model is the idea of protocol sequences. For these sequences, it is desirable that their cross correlation should be as low as possible and that the length of their period should not be too long, even if there is a large number of active users. Another useful feature is to be able to support multirate communication. Based on these considerations, a new family of protocol sequences is proposed in this paper. These new protocol sequences are built on the concept of prime sequences. It is shown that these sequences possess properties that make them suitable candidates for designing random access protocols for certain ad hoc or sensor networks. [ABSTRACT FROM AUTHOR]

Tag identification is an important tool in RFID systems with applications for monitoring and tracking. A RFID reader recognizes tags through communication over a shared wireless channel. When multiple tags transmit their IDs simultaneously, the tag-to-reader signals collide and this collision disturbs a reader's identification process. Therefore, tag collision arbitration for passive tags is a significant issue for fast identification. This paper presents two adaptive tag anticollision protocols: an Adaptive Query Splitting protocol (AQS), which is an improvement on the query tree protocol, and an Adaptive Binary Splitting protocol (ABS), which is based on the binary tree protocol and is a de facto standard for RFID anticollision protocols. To reduce collisions and identity tags efficiently, adaptive tag anticollision protocols use information obtained from the last process of tag identification. Our performance evaluation shows that AQS and ABS outperform other tree-based tag anticollision protocols. [ABSTRACT FROM AUTHOR]