In this paper, we propose an adaptive forward error correction (FEC) and rate control technique to improve service quality in a wireless gaming environment. In particular, we concentrate on a centralized server gaming architecture (our results can be extended to peer-to-peer architectures as well), where wireless users can also connect to the gaming service. Our models are well-suited for last-hop wireless link users, but can also guarantee service improvement for other wireless scenarios through small modifications. It is assumed that the game server and clients (mobile devices) can switch between different prediction levels having different data rates. We introduce a new scheme for estimating the packet loss rates due to congestion and wireless channel conditions and use this information in a cross-layer design to improve the overall service quality. The congestion packet loss probability is used to devise a simple TCP-friendly rate control algorithm for sending downlink data packets from the game server. We also propose a novel adaptive FEC and dynamic packetization algorithm to alleviate the effects of wireless channel packet losses based on this chosen data rate. The simulation results show the efficacy of our scheme in achieving higher throughput

Because of their pervasiveness and autonomy in operation, mesh-based wireless sensor networks (WSNs) are an ideal candidate in offering sustained monitoring functions at reasonable cost over a wide area. However, devising an energy-efficient, cost-effective and reliable communication strategy for WSNs requires tight collaboration of all of the sublayers, which introduces new technical challenges in the areas of data, network and power management. This paper proposes a cross-layer sleep-scheduling-based organizational approach, called SS-Trees, that aims to harmonize the various engineering issues and provides a method of increasing monitoring coverage and operational lifetime of mesh-based WSNs engaged in wide-area surveillance applications. An integer linear programming (TLP) formulation based on Dijkstra's algorithm and an iterative algorithmic approach are also suggested to determine the feasible SS-Tree structures for achieving such design goals

Demand for broadband access networks has grown rapidly with the increased demand for Internet connectivity and multimedia services. Fixed broadband wireless access systems based on the IEEE 802.16 standard may become a viable alternative to wired systems. In particular, the mesh networking capability added into the standard will potentially provide significantly wider broadband wireless coverage without requiring line-of-sight. In this paper, we present a transmission scheduling algorithm for the IEEE 802.16 mesh mode standard. To the best of the authors' knowledge, this is the first scheduling algorithm for a multihop network based on the 802.16 standard. Simulation results show that the proposed algorithm achieves high channel efficiency while providing equal transmission opportunity (i.e., fair access) to all nodes in the network. This study will aid network designers in fine-tuning the details of the communication system for satisfactory performance in the field

Designed for high data rate wireless personal area networks (WPANs), the IEEE 802.15.3 medium access control (MAC) protocol fits well with emerging technologies such as ultra-wideband (UWB). In an 802.15.3 piconet, all MAC frames are exchanged in a peer-to-peer manner between devices (DEVs) to allow efficient ad hoc operations while the piconet coordinator (PNC) only provides timing synchronization in the piconet; thus peer discovery is an essential function. If two peer DEVs in a piconet are out of transmission range, the standard peer discovery method will fail, and a costly upper layer routing procedure is required to complete the peer connection. In this paper, we propose a third-party handshake protocol (3PHP) at the 802.15.3 MAC layer to provide reliable and prompt peer discovery between out of range DEVs in a piconet via the PNC. It removes the overhead of unsuccessful peer discovery in the standard method, and completely eliminates costly upper layer routing between these DEVs by means of a simple and efficient MAC layer PNC forwarding. The performance of the proposed scheme is evaluated by a novel CSMA/CA delay analysis for the contention access period (CAP). Analytical and simulation results show that for uniformly distributed DEVs over the maximum coverage of a piconet, up to 41.3% of intra-piconet peer discovery procedures may fail if the standard method is used. The cost of unsuccessful MAC peer discovery and consequent routing is very high. The expected peer discovery time for 3PHP is 100 mum lower than that of the standard method when the latter is successful in peer discovery, and up to 10 times faster than the standard method with network layer routing when the standard method is unsuccessful in connecting the peer DEVs. 3PHP also significantly reduces the peer discovery failure probability. Therefore, the proposed 3PHP scheme brings huge performance gain with minimum cost, and successfully resolves the potential connectivity issue in an IEEE 802.15- - 3 piconet

This paper provides a concise modeling and performance evaluation of the iSCSI storage area network (SAN) architecture and protocol. SANs play a key role in business continuity, enterprise-wide storage consolidation and disaster recovery strategies in which storage resources are most often distributed over many distant data center locations. In the future, SAN traffic will be transported over IP-based networks, e.g., enterprise virtual private networks, to benefit from converged networks and save cost. In these scenarios, the impact of end-to-end delay and QoS of broadband networks on SAN performance is critical and has to be well understood by IT departments when deploying IP-storage solutions and network operators when designing transport network services for SAN applications. In this context, we propose models for iSCSI write requests over TCP/IP networks, e.g., as used in asynchronous mirroring applications. In addition to the analysis for individual requests we present - to the best of our knowledge for the first time - the evaluation of an iSCSI session under a realistic request traffic model with and without interleaving. We analyze the throughput and total request write times for different network dimensions, i.e., round-trip times, and QoS levels, processing delays in the iSCSI layer as well as request characteristics

Service providers today are constantly seeking to offer multiple services on a single common infrastructure. For instance, it is desirable sometimes to provide transport services transparently to data traffic encapsulated over different network layers. Tunneling is a technique for encapsulating a packet or frame within another packet of the same or a different network layer. One of the motivations for tunneling is bridging various heterogeneous networks that use different protocols for communication. Tunneling is also used for providing private and secure communications over a publicly shared network. This article investigates the interactions between different tunneling technologies in order to provide end-to-end virtual connectivity to end clients. Particularly, the article describes the technical details of the implementation of various layer-2 tunneling techniques-such as L2TP, GRE, and MPLS-based tunnels- in order to establish an end-to-end virtual connection-service as a concatenation of services offered by the different network domains along the path between end users

Internet computing is emerging as an important new paradigm in which resource intensive computing is integrated over Internet-scale networks. Over these large networks, different users and organizations share their computing resources, and computations take place in a distributed fashion. In such an environment, a framework is needed in which the resource providers are given incentives to share their resources. CompuP2P is a light weight architecture for enabling Internet computing. It uses peer-to-peer networks for sharing of computing resources. CompuP2P create dynamic markets of network accessible computing resources, such as processing power, memory storage, disk space, etc., in a completely distributed, scalable, and fault-tolerant manner. This paper discusses the system architecture, functionality, and applications of the proposed CompuP2P architecture. We have implemented a Java based prototype, and our results show that the system is light-weight and can provide almost a perfect speedup for applications that contain several independent compute-intensive tasks

The peer-to-peer technology offers many advantages, but at the same time, it poses many novel challenges for the research community. Modern peer-to-peer systems are characterized by large scale, poor reliability, and extreme dynamism of the participating nodes, with a continuous flow of nodes joining and leaving the systems. Selection of an optimal network requires estimation of its rank using attributes such as storage, average load, cost, reliability etc. There are multiple networks, each vying for users business by providing them novel services. The user in turn has to decide which network best meets its service requirements and accordingly join a network. In this paper, we propose a model with two ranking schemes, one being network-specific and the other user-specific. The schemes use fuzzy logic to rank different networks based on their attributes. The difference between the two ranking schemes lie in the dynamism offered by them. The user-specific ranking criteria is flexible while the network-specific scheme uses a fixed criteria. The network-specific scheme helps in providing a structure to visualize the overall performance index of the networks. The user-specific scheme is adaptive in the sense that it caters to the specific needs of the users. The simulations performed by us show that the two schemes are light-weight, highly accurate and easily implementable

We consider live continuous broadcast (such as radio or TV) to which users can join with time-shifting. They can join the broadcast at time t and receive the broadcast of time t - w for some offset parameter w ges 0. The simplest implementation that supports such a feature allocates a dedicated channel for each arrival time t and offset value w. Using such a technique, the server bandwidth quickly becomes a bottleneck. We adapt the stream merging technique to the time-shifting model, which allows us to greatly reduce the required server bandwidth. In addition to the application of distributing popular media, there are many other applications such as distance learning and large Internet events that could benefit from the use of time-shifting

This paper presents the application of multidimensional multiple-choice knapsack problem (MMKP) to admission control and QoS adaptation of multimedia sessions to maximize revenue from multimedia services for distributed video on demand service (DVoDS) over the Internet. We have discussed different distributed admission control and QoS adaptation architectures and their request handling policies. We have introduced the mapping of utility model-distributed (UM-D) by different admission controllers to the MMKP, a variant of the classical 0-1 knapsack problem. An exact solution of MMKP, an NP-hard problem, is not applicable for the online admission control problem in the VoD system. Therefore we have applied heuristics, IHEU and C-HEU for solving the MMKP for online real-time admission control and QoS adaptation. We present a qualitative analysis of the performance of these heuristics as well as greedy approach to solve admission control problems based on the worst-case complexity analysis and the experimental results from different sized data sets. The performance of different distributed admission control architectures applied in a simulated environment over a set of media server farm has been discussed detail using the experimental outcome

The core-based approach in multipoint communication enhances the solution space in terms of QoS-efficiency of solutions in inter and intra-domain routing. In an earlier work (A. Karaman and H.S. Hassanein, 2004), we showed that the constrained cost minimization solutions in core-based approach proposed to date are restrictive in their search to a subrange of solutions, and we proposed SPAN, a generic framework to process in our identified extended solution space. In this paper, we study the core selection component of SPAN and propose two novel algorithms, SPAN/COST and SPAN/ADJUST, which define the core-selection component of SPAN. SPAN/COST mainly optimizes the cost distances to be traveled between the source-core and core-receiver pairs on the multicast trees, while SPAN/ADJUST selects the cores based on the numbers of nodes they dominate and adjusting the set based on cost. Our algorithms consistently outperform their counterparts proposed to date and can be considered pioneering in their optimization range of multiple metrics and processing in the extended solution space

Multicast enables efficient data transmission from one source to multiple destinations, and has been playing an important role in Internet multimedia applications. Although several multicast scheduling schemes for packet switches have been proposed, they usually consider only short delay and high throughput but not bandwidth guarantees. However, fair bandwidth allocation is critical for the quality of service (QoS) of the network, and is necessary to support multicast applications requiring guaranteed performance services, such as online audio and video streaming. This paper addresses the issue of bandwidth guaranteed multicast scheduling on virtual output queued (VOQ) switches. We propose the credit based multicast fair scheduling (CMF) algorithm, which aims at achieving not only short multicast latency but also fair bandwidth allocation. CMF uses a credit/balance based strategy to guarantee the reserved bandwidth of an input port on each output port of the switch. It keeps track of the difference between the reserved bandwidth and actually received bandwidth, and minimizes the difference to ensure fairness. Moreover, CMF supports multicast scheduling by allowing a multicast packet to send transmission requests to multiple output ports simultaneously. As a result, a multicast packet has more chances to be delivered to all its destinations in the same time slot, and thus shortens its multicast latency. Extensive simulations are conducted to compare the performance of CMF with other existing scheduling algorithms, and the results demonstrate that CMF achieves the two design goals: short multicast latency and fair bandwidth allocation

Prolonging lifetime is a key challenge in wireless sensor networks comprising unattended, limited resource sensor nodes. As sensors are usually densely deployed, redundant data is produced by multiple observations on the same event, which decreases the network lifetime. With each observing sensor acting as a source of data, we schedule the time when these sources are allowed to send data to prolong the network lifetime with the guarantee that the total data provided satisfies the application requirement at any time. Considering k-coverage of each target as the application requirement, we propose the observation time scheduling for network lifetime maximization (OSLM) problem and solve it for two observation scenarios: a) a sensor node can distinguish the targets in its sensing range and selects a subset of targets to observe and b) a sensor node has to simultaneously observe all the targets in its sensing range as it cannot distinguish targets. We develop an optimal solution using a linear programming (LP) problem formulation for OSLM problem for the first observation scenario and solve it using CPLEX package. We prove that OSLM problem for the second observation scenario is NP-complete. A heuristic algorithm for the second scenario is then proposed. The performance is evaluated by the numerical results obtained from CPLEX and extensive simulation results

Video-based wireless sensor networks continue to gain increasing interest due to their ability to collect visual information for a wide range of applications. However, knowledge about these types of networks is mostly related to visual algorithms, leaving the networking perspective aside. In this work, we analyze how an algorithm designed for traditional wireless sensor networks, which integrates the coverage and routing problem, behaves in video-based networks. Our results show that because of the unique way that cameras capture data, the sensor network algorithm does not give the expected results in terms of coverage preservation of monitored areas. We discuss the main differences between traditional wireless sensor networks and video-based networks that lead to such a result, and we provide ideas for how protocols should be designed for the unique features of video-based networks

In this paper, a new method is proposed utilizing a diversity scheme to reduce power consumption in large scale sensor networks. Sensor networks are composed of large number of battery powered nodes. Energy consumption is the most important design objective in sensor networks while delay and throughput are taken less into account. Wireless transmission is the other important characteristic of these networks. Small-scale fading decreases wireless communication performance. In a fading channel higher SNRs is needed and consequently more energy is consumed in fading channels. Another important characteristic of sensor networks is the necessity of fault tolerant protocols. Node-to-node links are unreliable because of the insatiability of nodes and therefore the corresponding end-to-end links are unreliable. Most of the sensor network routing protocols propose path redundancy in order to guarantee a reliable packet delivery. Path redundancy makes some copies of a packet to receive to destination. This is a type of diversity and we benefit from this diversity to reduce transmit power and consequently decrease average network power consumption which it results in prolonging network life timeIn this paper, a new method is proposed utilizing a diversity scheme to reduce power consumption in large scale sensor networks. Sensor networks are composed of large number of battery powered nodes. Energy consumption is the most important design objective in sensor networks while delay and throughput are taken less into account. Wireless transmission is the other important characteristic of these networks. Small-scale fading decreases wireless communication performance. In a fading channel higher SNRs is needed and consequently more energy is consumed in fading channels. Another important characteristic of sensor networks is the necessity of fault tolerant protocols. Node-to-node links are unreliable because of the insatiability of nodes and therefore the corresponding end-to-end links are unreliable. Most of the sensor network routing protocols propose path redundancy in order to guarantee a reliable packet delivery. Path redundancy makes some copies of a packet to receive to destination. This is a type of diversity and we benefit from this diversity to reduce transmit power and consequently decrease average network power consumption which it results in prolonging network life time

Routing in ad hoc sensor networks is a complicated task because of many reasons. For traffic engineering, multipath capabilities are important. This paper, a source routing based multi-path OLSR (SR-MPOLSR) protocol is proposed. In this protocol, MPRs (multi-point relays) are used to obtain the network topology effectively and multiple Dijkstra algorithms are used to calculate multiple routes and to allocate the loads in a weighted round-robin fashion. Data transmission at the source is carried out through predetermined multiple paths (hence source routing). Our experiments have shown that SR-MPOLSR can, to some extent, increase the utility of network resources and network throughput, improve robustness and reliability of the transmission service, and reduce the average transmission delay

With the availability of cheap computing technology and the standardization of different wireless communication paradigms, wireless sensor networks (WSNs) are becoming a reality. This is visible in the increasing amount of research being done in the WSN area, and the growing number of companies offering commercial WSN solutions. In this regard, we realize that there is a need for an unambiguous classification and definition of WSN devices. Such a classification scheme would benefit the WSN research and industrial community. We consider the spectrum of wireless devices ranging from passive RF devices to gateway devices for the classification. The classification scheme is based on functionality of the devices. This scheme is analogous to an object-oriented classification, where an object is classified on the basis of its functionality and is described by its attributes. Attributes of the wireless devices are grouped into five broad categories: communication, sensing, power, memory, and "other features". Each of these are further classified to provide sufficient details that are required for a typical WSN application

We envision the emergence of general-purpose, well-provisioned sensor networks - which we call "Sensoria" - that are embedded in (or overlayed atop) physical spaces, and whose use is shared amongst autonomous users of that space for independent and possibly conflicting missions. Our conception of a Sensorium stands in sharp contrast to the commonly adopted view of an embedded sensor network as a special-purpose infrastructure that serves a well-defined, fixed mission. The usefulness of a Sensorium will not be measured by how highly optimized its various protocols are, or by how efficiently its limited resources are being used, but rather by how flexible and extensible it is in supporting a wide range of applications. To that end, in this paper, we overview and present a first-generation implementation of SNBENCH: a programming environment and associated run-time system that support the entire life-cycle of programming sensing-oriented applications. The components of SNBENCH are analogous to those commonly found in traditional, stand-alone general-purpose computing environments. SNAFU (sensornet applications as functional units) is a high-level strongly-typed functional language that supports stateful, temporal, and persistent computation. SNAFU is compiled into an intermediate, abstract representation of the processing graph, called a STEP (Sensorium task execution plan). The STEP graph is then linked to available Sensorium execution environments (SXEs). A Sensorium service dispatcher (SSD) decomposes the STEP graph into a linked execution plan, loading STEP sub-graphs to appropriate individual SXEs and binding those loaded sub-graphs together with appropriate network protocols. The SSD may load many such programs onto a Sensorium simultaneously, taking advantage of programs' shared computation and dependencies to make more efficient use of sensing, computation, network, and storage resources

This paper describes the architecture and programming model of a semantic-service-oriented sensor information system platform. We argue that the key to enabling scalable sensor information access is to define an ontology and associated sensor information hierarchy for interpretation of raw data streams. The ontological abstraction allows a sensing system to optimize its resource utilization in collecting, storing, and processing data. We describe the SONGS architecture that uses an automatic service planning to convert declarative user queries into a service composition graph, and performs compile-time and run-time optimizations for resource-aware execution of the service composite in a sensor network, building on the sensor information hierarchy. We motivate and demonstrate the SONGS platform using a parking garage example

In this vision paper we propose the creation of sensor networks based on custom designed multifunction imagers that can directly pick out events of interest from a scene. We argue that with a suitable learning framework such sensors have great potential for realizing sensor networks that can interpret and subsequently orchestrate behaviors in physical space. This paper provides an overview of the research challenges followed by a brief description of our current research efforts towards creating a functional experimental system for investigating these intelligent networks

We study the behavior of the maximum likelihood (ML) estimator for localization via triangulation, under Gaussian noise. Likelihood maximization is a non-convex problem, with possibly multiple solutions. In this paper we present an algorithm for solving this non-convex problem, which under some reasonable assumptions, is guaranteed to produce the exact ML estimate. A nice feature of our algorithm is that it is readily amenable to analysis: we give (a) a characterization of a domain in which, if the algorithm is started with an initial estimate within that domain, a standard steepest descent method is guaranteed to converge to a global minimum; (b) the distribution of the estimate; and (c) a measure of sensitivity to noise of the estimate. Many numerical examples and plots are included to illustrate these concepts

We investigate the use of distributed image sensing for network localization, dynamic routing, and load balancing in wireless sensor networks. In particular, the image sensors are first used to obtain angular bearing information between each network node and a set of other nodes, mobile agents, or targets. This data is used to construct the relative geographic topology of the network. The image sensors are then employed to make periodic measurements, which are reported to the destination via multihop routing. Nodes may also infrequently detect an event from which a set of image frames need to be reported. These high-bandwidth event reports may cause packet queues to develop at the routing nodes along paths to the destination. We propose a distributed routing scheme that employs a cost function based on location data, in-node queue sizes, and energy levels at neighboring nodes. Our scheme also implements a set of relative priority levels for the event-based and periodic data packets. Simulation results are presented and indicate improved network lifetime, lower end-to-end average and maximum delays, and significantly reduced buffer size requirements for the network nodes

A wireless ambulatory ECG system with an Internet based telemedicine service was developed by the authors. Some new solutions of all the three main aids - remote sensing, decision making, and the patients' real time management - of a telemedicine solution were applied. Using more sophisticated math analysis - wavelet for heart rate variability and ventricular late potentials, correlation dimension, data mining with piecewise aggregate approximation (PAA) - the indication of conventional ambulatory (Holter) registrations was expanded. The well-defined indications of Holter monitoring do not permit to extend the applications to a greater population for cardiovascular risk prediction. This "inflexibility" was changed with a rapid, frequent Internet ECG monitoring of our HeartSpy, heart observer systems. The clinical studies were performed in various patients' groups to predict the recurrence of paroxysmal atrial fibrillation and the occurrence of malignant ventricular arrhythmias and/or sudden cardiac death. The analysis showed some promising results in the prediction of these two diseases, where the conventional methods have only a poor prognostic value

The next generation wireless communication devices are expected to be capable of communicating with the best possible last mile networks as well as to utilize multiple networks simultaneously. Existing solutions such as the interoperability mechanisms and the always best connected (ABC) paradigm limit the access of wireless devices to only one, preferably the best possible network. Such schemes, though found to be better than the traditional single interface communication, are limited in their ability to utilize the services in the best possible way. Existing work focuses mainly on network layer or transport layer bandwidth aggregation mechanisms which either need to change the existing TCP protocol or require proxy nodes to perform the bandwidth scheduling process. We, in this paper, propose a new wireless access paradigm for multi-homed hosts based on a session layer bandwidth aggregation mechanism. The major advantages of our solution are the high end-to-end throughput, glitch free transition during both mobility and interface changes, dynamic selection of number of end-to-end paths, and above all our solution can work with existing transport and network layer protocols in today's Internet. In this paper, we provide the architectural and protocol solutions for the proposed scheme and results from extensive simulations and a Linux based implementation

Ethernet passive optical network (EPON) was proposed to overcome the bandwidth bottleneck at the access networks due to its simplicity, cost effectiveness and wide spread deployment. A failure in access networks can cause serious problems, because access networks transmit aggregated high-speed traffic from hundreds of subscribers. Protection and restoration mechanisms have been applied in backbone networks, but access networks are not considered significantly in the scope of survivability. In this paper, we propose a cost effective protection scheme for a novel ring-based EPON architecture. The protection scheme is capable of fault detection within 2 ms, assuring zero packet loss. Furthermore, this novel approach also has the potential of inter-ONU connectivity, which can bring LAN support in access environment