Media streaming applications have recently attracted a large number of users in the Internet. With the advent of these bandwidth-intensive applications, it is economically inefficient to provide streaming distribution with guaranteed QoS relying only on central resources at a media content provider. Cloud computing offers an elastic infrastructure that media content providers (e.g., Video on Demand (VoD) providers) can use to obtain streaming resources that match the demand. Media content providers are charged for the amount of resources allocated (reserved) in the cloud. Most of the existing cloud providers employ a pricing model for the reserved resources that is based on non-linear time-discount tariffs (e.g., Amazon CloudFront and Amazon EC2). Such a pricing scheme offers discount rates depending non-linearly on the period of time during which the resources are reserved in the cloud. In this case, an open problem is to decide on both the right amount of resources reserved in the cloud, and their reservation time such that the financial cost on the media content provider is minimized. We propose a simple-easy to implement-algorithm for resource reservation that maximally exploits discounted rates offered in the tariffs, while ensuring that sufficient resources are reserved in the cloud. Based on the prediction of demand for streaming capacity, our algorithm is carefully designed to reduce the risk of making wrong resource allocation decisions. The results of our numerical evaluations and simulations show that the proposed algorithm significantly reduces the monetary cost of resource allocations in the cloud as compared to other conventional schemes.

Relaying is a major technique to increase network lifetime in wireless sensor networks (WSNs) and body area networks (BANs). The results of relaying studies highly depend on power consumption model of relay's transmitter and receiver radio, channel and mobility models. In this work, we study the effect of relaying with 2.4GHz IEEE802.15.4 modules on network lifetime. We analytically derive the energy expenditure of relays in which we use the path loss probability distribution function (PDF) over links, which is derived from our link characterization using micaZ motes, and the existing power consumption models. It turns out that in order for relaying to be beneficial to network lifetime and for the same transmitter power amplifier efficiency, receive power consumption of IEEE802.15.4 widely used RF modules, e.g., micaZ motes are required to be decreased. For instance, receive power of 17mW helps us achieve 25% more lifetime with 3-relay scheme than single-hop transmission over ankle-waist link during walking, whereas with the current receiver, we achieve 12% less lifetime compared to single-hop scenario.

Transmission Control Protocol (TCP) is the most widely used protocol for end-to-end data transmissions over inter-networks. However, the congestion control algorithm of TCP was not created to match the special characteristics of satellite links, resulting in a drastically performance degradation. The employment of TCP split connections coupled with link level retransmissions and satellite link tailored TCP versions has been proven effective in hiding corruption losses from TCP to improve end-to-end performance. Using NS-2 simulations, this paper evaluates and compares popularly used TCP versions such as New Reno, Hybla, Vegas, DVegas and Westwood+ over GEO VSAT- and LEO-based satellite links employing performance enhancement proxy (PEP) based on snoop. Simulation results show that with the use of snoop proxy, TCP Hybla outperforms the rest of TCP versions, improving the usage of satellite links that are affected by losses not due to congestion. The second good candidate is DVegas over satellite PEP. When the Explicit Control Protocol (XCP) is employed as TCP PEPs, it would improve TCP performance to get high transfer rates and respond to congestion in a correct and scalable way.

Most recent analyses on IEEE802.11e quality of service (QoS)-aware enhanced distributed coordination function (EDCA) require a large degree of complexity, making it difficult to apply them to a wide range of parameter settings for the evaluation of service differentiation mechanisms supported in EDCA, including the Contention Window (CW) and Arbitration Inter-Frame Space (AIFS) mechanisms. In this paper, we propose an improved analytical model to analyze the throughput of EDCA with AIFS and CW differentiation schemes. The model is simplified by decomposing the problem into two easily solved Markov chains that can jointly be solved by numerical method. We present simulation and analytical results over a broad range of system parameters to demonstrate the accuracy of the proposed model. The model is simple to implement and can be applied to general configuration circumstances for the evaluation of EDCA. The results are valuable to facilitate proper design of parameters in 802.11e enhanced distributed channel access for the QoS support required by specific applications.

Many applications in vehicular networks are context-aware in that the observations of sensing nodes, potentially vehicles, at a target location should be made available to the requesting node possibly at a different location. In order to provision such applications, two phases of packet routing between the requesting node and the target location and packet dissemination within the target location need to be implemented. In this paper, we focus on the second phase and propose an efficient reliable packet dissemination mechanism, Request-adaptive Packet Dissemination Mechanism (RPDM), in target location. RPDM allows for different applications to generate request packets based on their exclusive observation needs and delay requirements and adapts the dissemination mechanism in target location to specific needs of the request packet received. Besides, RPDM also takes the intrinsic characteristics of vehicular environments into account to make sure roadmap and connectivity constraints are considered and broadcast storm is prevented. Finally, RPDM is compared with a best-known state-of-the-art data dissemination mechanism, COR, and the results show that RPDM outperforms COR in terms of both resolution time and packet overhead traffic.

Energy-efficient communication protocols in resource-constrained networks and specifically wireless body area networks (WBANs) has been of significant importance since they emerged nearly last decade. In this work, we use the periodic nature of body actions to propose an action-based scheduling technique in which time-slot allocations are adapted to the periodic connectedness of on-body links. In other words, the periodicity of on-body links is employed to predict the future behaviours of links to help develop energy-efficient communications between on-body nodes, thereby elongating the network lifetime. Analysis and measurement with 2.4GHz IEEE 802.15.4/ZigBee compliant micaZ motes in a fitness environment serve as our tool to do action recognition and subsequently scheduling. The proposed technique helps us reach within less than 7% of power consumption lower bound while it does not have complexity of most channel prediction algorithms that can result in excessive process power consumption.

In this paper, we propose a novel routing protocol, WLAN-WiMAX Double-Technology Routing (WWDTR), for routing packets in the heterogeneous vehicular network. Any given route in the protocol can be generally formed of a combination of WLAN and WiMAX hops. WWDTR uses the position-based routing approach over the parts of the route in which packets are forwarded via WLAN radios, in order to handle relatively fast changes of the topology with respect to the shorter transmission ranges of WLAN-enabled vehicles. On the other hand, topology-based routing is employed over the parts of the route in which packets are forwarded via WiMAX radios, given the more stable routes comprised of WiMAX-enabled vehicles, thus overall yielding a hybrid routing scheme. The route selection logic takes both operators' and subscribers' preferences such as QoS and network utilization into account. Furthermore, we propose network architecture to facilitate forwarding packets towards the access network of a given operator over routes that partly utilize relaying over other operators' links. To the best of our knowledge, WWDTR is the first multi-technology multi-operator routing solution for heterogeneous vehicular networks.

This paper addresses the problem of optimal vertical handoff (VHO) in a vehicular network setting. The VHO objective can be minimizing the data transfer time or alternatively minimizing the cost of transmitting traffic. As a framework for performance evaluations, we first analyze a heterogeneous network consisting of a wide-area cellular network interworking with wireless local area networks (WLAN) with fixed inter-distance between access points (APs) placed along roadsides. We further analyze a scenario with random inter-distance between WLAN APs. In both aforementioned cases, only Vehicle-to-Infrastructure (V2I) capability is assumed. We show that in order to minimize the cost of transmission or alternatively transmission time, performing VHOs is an appropriate choice at lower speeds, whereas it would be better to avoid VHO and stay in the cellular network at higher speeds. We further generalize our study, to investigate the VHO strategies in a random inter-distance scenario with both V2I and Vehicle-to-Vehicle (V2V) communication capabilities. We demonstrate that the combination of WLAN plus cellular plus ad hoc networking outperforms any other networking strategies considered in this work in terms of transmission times and transmission costs. The presented results provide insightful guidelines for optimal VHO decision making based on the characteristics of the network as well as the user mobility profile.

As the traffic situations on highways and streets become more variable and more complex every day, the deployment of a traffic information system (TIS) becomes inevitable. In this paper, we develop an advanced wireless mesh architecture for TIS (WMTIS) which provides vehicles with the least delay routes to their destinations. The contributions of the paper are twofold. First, we propose an efficient communication framework for a TIS based on wireless mesh networking, i.e., WMTIS, and shed light on the mechanisms and the functional elements of WMTIS that are required to be deployed over the wireless mesh topology in order to support traffic applications. The performance improvements of WMTIS over fully ad-hoc TISs are verified via simulations. Second, we propose an approach to minimize the deployment cost of WMTIS while keeping the round trip delays of traffic information messages below the maximum tolerable delay in traffic applications. We use simulations to demonstrate the effectiveness of the proposed cost minimization approach.

Routing of data packets in vehicular ad hoc networks (VANETs) is challenging due to dynamic changes in the network topologies. As nodes in VANETs can obtain accurate position information from onboard Global Positioning System receivers, position-based routing is considered to be a very promising routing strategy for VANETs. This paper presents a novel position-based directional vehicular routing (PDVR) method. To make sure the packets can be sent to the destination in an efficient and stable route, PDVR selects the next-hop from vehicles traveling in the same direction as the forwarding vehicle based on their angular directions relative to the destination. We analyze the straight and the curve highway scenarios, and present the realizing algorithm based on position and velocity vectors. The method is evaluated using NS2 and compared with typical ad hoc routing protocol ad hoc on-demand distance vector (AODV), the position-based routing protocol distance routing effect algorithm for mobility (DREAM), and VANETs routing based on the Cartesian space method. Simulation results show that PDVR can find and maintain more stable routes compared with the other routing protocols.

In this paper, we propose an analytical framework in order to compute the throughput capacity of a multi-hop ad hoc network with a finite number of mobile wireless nodes. The proposed framework consists of two related queueing networks; a closed BCMP queueing network to represent the mobility model of the wireless nodes and an open BCMP queueing network comprising symmetric M/G/l nodes to represent the multi-hop packet routing process from sources to destinations. In this respect, we consider very simple MAC and routing schemes and then map the related parameters onto several components of the queueing network. By solving the linear traffic equations corresponding to concerned queueing networks and the stability requirement of each node, we obtain throughput capacity, i.e., the maximum throughput with which the packets can be successfully received with finite delay. Finally, we compute the throughput capacity for different number of nodes and several mobility patterns and verify our approach by simulation.