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World of Wireless, Mobile and Multimedia Networks & Workshops, 2009. WoWMoM 2009. IEEE International Symposium on a

Date 15-19 June 2009

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Displaying Results 1 - 25 of 100
  • A CDMA-based approach for highly efficient medium access control in mesh wireless networks

    Publication Year: 2009 , Page(s): 1 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (163 KB) |  | HTML iconHTML  

    The code division multiple access (CDMA) technology has been recently introduced into mesh wireless networks for improving channel efficiency. The existing approaches, however, do not maximize the capacity of a CDMA system, because the sender transmits to one receiver only. In this paper, we explore novel approaches to allow multiple data frames be transmitted from a sender to multiple receivers simultaneously by using multi-user detection techniques and efficient power control schemes, thus maximizing network capacity and decreasing data delivery delay. More specifically, we propose two CDMA-based medium access control schemes, the PNO (Pseudo Noise Only) and the PPO (PN Plus Orthogonal) scheme, for highly efficient data transmission in mesh wireless networks, especially for those networks serving as communication backbone and thus experiencing high traffic load. The performance of our proposed schemes is evaluated via simulations, and compared with IEEE 802.11 and other CDMA-based schemes under the same channel bandwidth. Our results show that PPO achieves the highest channel efficiency, because of its use of orthogonal codes for channelization. Both PPO and PNO can significantly improve network throughput and reduce packet delivery delay, without increasing signaling overhead noticeably. View full abstract»

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  • Analytic study of Delay/Fault-Tolerant Mobile Sensor Networks (DFT-MSN's)

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    The delay/fault-tolerant mobile sensor network (DFTMSN) has been proposed recently for pervasive information gathering. A DFT-MSN consists of a number of wearable sensor nodes and high-end sink nodes, forming a loosely connected mobile sensor network. In this paper we introduce a generic queuing analytic model for DFT-MSN, where the inputs are the data delivery scheme employed and the nodal mobility pattern, while the outputs are the queuing characteristics of the network. Based on our analysis of the message arrival and service processes, we find that each individual sensor can be modeled as an M/M/1/K queue, and the whole network can be treated as a network of queues. Following Jackson network theory, major queuing characteristics of the network can thus be obtained. We also exemplify the generic analytic model with several representative data delivery schemes (including direct transmission, ZebraNet, and replication-based data delivery) and nodal mobility patterns (such as uniform and power-law distributions). To validate our analytic model, we have carried out extensive simulations and observed a good match between analytic and simulation results. View full abstract»

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  • Interest-aware content distribution protocol for mobile disruption-tolerant networks

    Publication Year: 2009 , Page(s): 1 - 7
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4520 KB) |  | HTML iconHTML  

    Most of the routing protocols for mobile disruption-tolerant networks (DTNs), are designed to route data from a single source to a single destination. Many real-world applications, however, need to transfer data to a group of recipients rather than individuals. Proposed architectures for multicast communication in mobile DTNs rely on a global knowledge of multicast group memberships that makes them infeasible for infrastructure-less networks. Our interest-aware data distribution protocol distributes data among a community of mobile users in DTNs based on their interests. Our interest-aware algorithm automatically learns users' interests from the history of their cached data and provides them with their preferred data content. We implemented this protocol in the ONE simulator and evaluated its performance using reality-mining mobile traces. Our simulations show that our protocol delivers 30% more relevant data to mobile users' interests than epidemic routing. Furthermore, this superior performance is achieved with 35% lower distribution of irrelevant data content among mobile users. View full abstract»

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  • On the design of k-covered wireless sensor networks: Self-versus triggered sensor scheduling

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    Sensing coverage reflects the quality of surveillance of a field by a wireless sensor network (WSN). This paper investigates the problem of minimum connected k-coverage in WSNs, where each point in a field is covered (or sensed) by at least k active sensors while minimizing the necessary total number of active sensors and ensuring connectivity between them. In this paper, we propose two k-coverage protocols using different scheduling approaches. In the first protocol, called self-scheduling driven k-coverage (SSCk), each sensor turns itself on based on the local information it has about its sensing neighbors in order to k-cover its sensing range. The second protocol, called triggered-scheduling driven k-coverage (TSCk), allows a sensor to trigger a necessary number of its sensing neighbors to become active in order to achieve k-coverage of its sensing range. Then, we relax some commonly used assumptions for coverage configuration protocols in WSNs to promote the use of SSCk and TSCk in realworld sensing applications. Simulation results show that TSCk outperforms SSCk with regard to the number of sensors required for connected k-coverage as well as the network lifetime. We find that SSCk outperforms an existing connected k-coverage protocol for WSNs. View full abstract»

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  • ECTC: Energy effiCient topology control algorithm for wireless sensor networks

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (357 KB) |  | HTML iconHTML  

    Sensor network which operates on battery are used to gather data in a variety of environments. The data collected by each node is communicated through the network to the sink, which uses all reported data to determine characteristics of the environment or detect an event. Prolonging sensor's operable lifetime is a main design challenge of these networks. A good energy saving technique in this direction is to schedule nodes sleep interval with the communication radio turned off. In this paper, we propose a distributed topology control algorithm, termed ECTC, which uses a clustering approach. It is built on the notion that when a region of a shared channel wireless sensor network has a sufficient density of nodes, significant energy saving is obtained by allowing redundant nodes to sleep. Using the two-hop neighborhood information, certain nodes sequentially select a subset of nodes to be active among all nodes in the neighborhood, to ensure connectivity. Moreover, to ensure fairness, the role of active nodes is rotated periodically to ensure energy-balanced operations. Results from stochastic geometry are used to derive solutions for the values of parameters of our algorithm that minimize the total energy spent in the network when all sensor nodes report data through the cluster heads to the sink. View full abstract»

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  • A prevention approach to scrambling attacks in WiMAX networks

    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB) |  | HTML iconHTML  

    WiMAX is a telecommunication technology. It is based on IEEE802.16 family and provides the network service with large coverage, high data rate and mobility. Since IEEE802.16 series are connection-based wireless technologies, WiMAX is exposed to a special kind of DoS attacks which can target a specific victim connection without influencing the others. This paper will introduce this scrambling attack in WiMAX networks in detail and will provide a prevention approach. View full abstract»

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  • High performance, low complexity cooperative caching for Wireless Sensor Networks

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (5)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    During the last decade, Wireless Sensor Networks (WSNs) have emerged and matured at such point that currently support several applications like environment control, intelligent buildings, target tracking in battlefields, and many more. The vast majority of these applications require an optimization to the communication among the sensors so as to serve data in short latency and with minimal energy consumption. Cooperative data caching has been proposed as an effective and efficient technique to achieve these goals concurrently. The essence of these protocols is the selection of the sensor nodes which will take special roles in running the caching and request forwarding decisions. This article introduces a new metric to aid in the selection of such nodes. Based on this metric, we propose a new cooperative caching protocol, which is compared against the state-of-the-art competing protocols. The simulation results attest the superiority of the proposed protocol; the proposed solution achieves on the average 20% improvement w.r.t. the competing method for the examined performance measures. View full abstract»

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  • Optimization of WiMax modulation scheme with a cross layer erasure code

    Publication Year: 2009 , Page(s): 1 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (154 KB) |  | HTML iconHTML  

    WIMAX (Worldwide Interoperability for Microwave Access) is a promising new networking technology that potentially offers high speed and wide area wireless access services that complement consistently the 3G and WiFi access networks capabilities. The standard proposes an adaptive modulation scheme which allows WiMax nodes to communicate from various modulation coding schemes according to the link quality. However, the standard does not define a detailed link adaptation algorithm and currently, the most largely used modulation adaptation technique is based on a channel quality lookup table. We argue that this method is not able to make the best adaptation decisions and delivers a sub-optimal goodput in numerous communication contexts. In this paper, we propose a novel cross layer based modulation adaptation mechanism which incorporates the use of adaptive erasure code with the physical layer information to significantly improve the goodput and transmission efficiency. Simulation results show that our proposal adapts more efficiently to real environments and achieves a significant gain on the goodput delivered to mobile nodes. View full abstract»

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  • VAPS: Positioning with spatial constraints

    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (433 KB) |  | HTML iconHTML  

    The proliferation of mobile computing devices and local wireless networks has promoted a growing interest in location-aware systems. The problem with existing positioning techniques is that they are designed to position dimensionless objects. Such an assumption may lead to practical inconsistencies, as objects might overlap in the resulting coordinate system. Moreover, it is usual to neglect the effects of an object volume and its physical characteristics on signal propagation. In the scenario considered throughout this paper (positioning containers in a harbor), such characteristics can be finely estimated. We propose VAPS, a volume-aware positioning system that takes advantage of the waveguide effect generated by containers. Although VAPS is specific to the harbor scenario, its principles can be extended and adapted to other situations. VAPS maps discrete RSSI levels into hop-counts and relies on realistic propagation models to obtain near-perfect positioning at a very low control overhead. Our results demonstrate that, in scenarios where the assumptions made by traditional approaches fail, the new considerations of VAPS do make a difference. View full abstract»

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  • Mediacast for mobile communities: When the web and telecommunications converge

    Publication Year: 2009 , Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (629 KB) |  | HTML iconHTML  

    Social communities are emerging as cloud-based service platforms for communities that also offer communication channels to their users. At the same time, modern telecommunications providers are currently seeking for new sources of revenue by exposing network capabilities to 3rd party providers. Moreover, both mobility and the possibility to access services anyhow, anywhere and at any time are becoming the user's pre-requisites for next generation services. By combining these concepts, it becomes clear that mobile social communities will play a predominate role in our society. This paper presents Mediacast, an innovate service that on the one hand allows users to share and consume multimedia within web social community environments using their mobiles and on the other hand promotes collaboration by providing a set of communication tools for hybrid (web/mobile) communities. View full abstract»

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  • RFID reader and tag multi-hop communication for port logistics

    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1286 KB) |  | HTML iconHTML  

    The RFID technology has attracted much attention these days due to the far better efficiency than the barcode and magnetic card system. As an important usage, the 433 MHz active RFID tag was already adopted to the container ports in the United States and Europe for container loading and unloading automation and equipment location. However, for the complete automation, one problem should be solved before. Current RFID systems support only the direct (single-hop) communication between readers (interrogators) and tags within their RF transmission range. Then besides containers, there are a lot of equipments such as crane, yard tractor, and forklift in ports; and being made of metal, they interfere the RF transmission, resulting in the occurrence of the dead-zone. In the dead-zone, tags cannot receive any signal from readers. Several solutions may be possible to this problem. Among them, this paper suggests the most economical solution where RFID tags in the dead-zone communicate with readers via neighbor tags in the multi-hop manner. The new RFID communication architecture must be carefully designed in order to maintain the compatibility with the previous standard. Our experiment shows that the proposed method works well even in the case where some tags are out of the RF range of reader. View full abstract»

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  • A plant-and-play wireless sensor network system for gate monitoring

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB) |  | HTML iconHTML  

    We present a practical plant-and-play wireless sensor network system for entry-exit monitoring. Our system is easily configurable and robust, making it feasible to be deployed in a wide range of entry-exit monitoring applications. At the core of our system lies a novel MAC protocol that is self-synchronizing. Notably, our MAC protocol allows the nodes to maintain a very low duty cycle (the radios are in sleep mode 100% of the time in the absence of detections), while also enabling quick synchronization of the nodes (when needed) for a consistent classification of entry or exit events. We have deployed this system for monitoring a faculty parking lot at our university and integrated it with an SMS notification system to provide information on the availability of parking spots on demand. We present the parking lot occupancy trends obtained through this deployment and discuss some of the reliability issues encountered. View full abstract»

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  • Discovering spatiotemporal mobility profiles of cellphone users

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (769 KB) |  | HTML iconHTML  

    Mobility path information of cellphone users play a crucial role in a wide range of cellphone applications, including context-based search and advertising, early warning systems, city-wide sensing applications such as air pollution exposure estimation and traffic planning. However, there is a disconnect between the low level location data logs available from the cellphones and the high level mobility path information required to support these cellphone applications. In this paper, we present formal definitions to capture the cellphone users' mobility patterns and profiles, and provide a complete framework, Mobility Profiler, for discovering mobile user profiles starting from cell based location log data. We use real-world cellphone log data (of over 350 K hours of coverage) to demonstrate our framework and perform experiments for discovering frequent mobility patterns and profiles. Our analysis of mobility profiles of cellphone users expose a significant long tail in a user's location-time distribution: A total of 15% of a user's time is spent on average in locations that each appear with less than 1% of time. View full abstract»

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  • A framework for interference mitigation in multi-BSS 802.11 wireless LANs

    Publication Year: 2009 , Page(s): 1 - 11
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    This paper proposes a framework for interference mitigation in multi-BSS infrastructure 802.11 WLANs. Our interference mitigation approach is based on access point (AP) coordination. With this approach, interfering BSSs negotiate and switch from the 802.11 CSMA/CA to a time slotted mechanism if users' QoS is observed to be degraded, diagnoses conclude that the cause is high interference, and the switch to the time slotted modus is expected to be useful and feasible. The proposed algorithms within the framework are driven by measurements. We utilize the wireless bandwidth and improve the fairness among WLAN users. We present results of detailed simulation experiments as well as real implementation. View full abstract»

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  • Delivering improved QoS and cell throughput in UMTS based HSDPA networks

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB) |  | HTML iconHTML  

    One of the main challenges in cellular wireless data networks is to meet the stringent quality of service (QoS) requirements of voice over IP (VoIP) and video streaming traffic whilst attaining high total cell throughput. In this paper, a novel two layered scheduling approach that addresses this challenge in a UMTS based HSDPA network is presented. The first layer carries out resource reservation for different traffic classes while the second layer dequeues packets on the basis of the reported channel quality indicator value and buffer occupancy. Simulation results show that the algorithm has low latency and jitter for VoIP services, whilst achieving better total cell throughput and fairness properties in comparison to several other well known scheduling algorithms. The performance of the algorithm for video streaming has also been evaluated in terms of peak signal to noise ratio (PSNR). View full abstract»

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  • Efficient data collection in wireless sensor networks with path-constrained mobile sinks

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    Recent work shows that sink mobility along a constrained path can improve the energy efficiency in wireless sensor networks. However, due to the path constraint, a mobile sink with constant speed has limited communication time to collect data from the sensor nodes deployed randomly. This poses significant challenges in simultaneously improving the amount of data collected and reduction in energy consumption. To address this issue, we propose a novel data collection scheme, called the maximum amount shortest path (MASP), that increases network throughput as well as conserves energy to optimize the assignment of sensor nodes. MASP is formulated as an integer linear programming problem and then solved with the help of a genetic algorithm. A two-phase communication protocol is designed to implement the MASP scheme. Simulations experiments using OMNET++ show that MASP outperforms the shortest path tree (SPT) and static sink methods in terms of system throughput and energy efficiency. View full abstract»

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  • A novel analytical framework to model malware diffusion in heterogeneous wireless networks

    Publication Year: 2009 , Page(s): 1 - 10
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    Now that smart phones can interact with computers through numerous interface technologies such as Bluetooth, infrared, or the 802.11 family of IEEE specifications, they are working in an environment where malware can propagate. While many studies have modeled malware proliferation, little has been done to take into account the different types of devices that may exist in an ad hoc wireless network. We have therefore developed two novel models that consider diversity of entity as well as interactions between different classes of network items to see how those features affect the spread of a disease. Our models, based on a 4-compartment epidemic method, also have taken into consideration various states that a device may undergo when it gets infected by the malware. We propose these analytical models as an aid to understanding the spread of malware through a network. A huge result space is producible by our framework thus makes it appropriate to describe many viral proliferating scenarios. In addition, we have developed a formula to calculate the possible average number of newly infected devices in the considered system. An important contribution of our work is the comprehension of item diversity, which has influence on the viral propagation. We have found that more types of network item cause a higher risk that malware spreads wider. View full abstract»

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  • Simple and practical rate adaptation algorithms for wireless networks

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    Wireless devices can exploit the knowledge of channel conditions to their advantage in achieving high throughput and robust communication. Current systems support multiple transmission rates and the ability to select a desirable rate. Higher transmission rates can be chosen when the channel quality is good thereby maximizing the throughput. Lower transmission rates can be selected when the channel quality is poor ensuring reliable message delivery. In order to achieve this, a wireless device needs some intelligence so it can assess the channel quality and adapt its transmission rate accordingly. This paper presents two novel algorithms to achieve throughput maximization and robust communication using intelligent link rate adaptation algorithms in the wireless device. The first of the two algorithms operates entirely at the sender and uses current channel quality information to guide the rate adaptation decision in finding the next transmission rate. The second algorithm relies on sender-receiver coordination in which feedback on current channel conditions at the recipient is provided to the sender via the rate used to transmit an acknowledgement (ACK). These algorithms were implemented in the ns-2 network simulator and their performance was evaluated against the classic Auto Rate Fallback (ARF) algorithm. Results from this study indicate that the proposed algorithms attain up to twice the throughput attained by ARF in certain scenarios. The results also confirm the limitations of ARF highlighted by previous studies. View full abstract»

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  • Routing with transmission buffer zones in MANETs

    Publication Year: 2009 , Page(s): 1 - 10
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB) |  | HTML iconHTML  

    Dealing with link breaks in MANETs is a challenge for the routing protocol. This paper proposes a mechanism to reduce the negative impact of link breaks on the routing. The transmission area of a node is divided into a safe zone close to the node and an unsafe zone (i.e. buffer zone) near the end of the transmission range. The probability is high that link breaks occur with neighboring nodes located in the buffer zone, while links to neighboring nodes in the safe zone are expected to be more stable. Thus, neighbors in the safe zone are preferred as relay nodes, while neighbors in the buffer zone are only used if necessary to avoid network partitioning. The main cost of this mechanism is that the mean number of hops between two nodes is higher than without the mechanism, but simulations show that the solution offers increased throughput. View full abstract»

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  • Enhanced Ripple (E-Ripple) protocol for chain-based multihop wireless networks

    Publication Year: 2009 , Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    It has been shown that IEEE 802.11 DCF medium access control (MAC) protocol may not be suitable for multihop wireless networks due to its relatively low throughput and severely unfairness problems. A tokenpassing MAC protocol, named Ripple, has been proposed to enhance the throughput of DCF by utilizing spatial reuse. However, two perfect assumptions of dasiafixed-length data packetpsila and dasiaidentical interference range and transmission rangepsila in Ripple make it less practical in the real world. This paper proposes an Enhanced Ripple (E-Ripple) protocol aiming to remove the two restrictions. An analytical model is presented to estimate the performance of E-Ripple and the accuracy of the analysis is then verified via computer simulations. The results indicate that E-Ripple performs well in such a non-perfect environment. View full abstract»

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  • Admission control based on OFDMA channel transformations

    Publication Year: 2009 , Page(s): 1 - 11
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    It is well known that channel-dependent OFDMA resource assignment algorithms provide a significant performance improvement compared to static (i.e. channel-unaware) approaches. Such dynamic algorithms constantly adapt resource assignments to current channel states according to some objective function. Due to these dynamics, it is difficult to predict the resulting performance for such schemes given a certain scenario (characterized by the number of terminals in the cell and their average channel gains). Hence, previous work on admission control for OFDMA systems neglects the performance improvement from channel-dependent resource assignments and bases analysis on the average channel gains instead. In this paper we provide for the first time an analytical framework for admission control in OFDMA systems applying channel-dependent resource assignments. The framework is based on fundamental transformations of the channel gains caused by the channel-dependent assignment algorithms. We provide closed-form expressions for these transformations and derive from them probability functions for the rate achieved per terminal and frame. These functions can then be used for admission control as demonstrated in this paper for Voice-over-IP streams in IEEE 802.16e systems. View full abstract»

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  • Joint routing and scheduling in WiMAX-based mesh networks: A column generation approach

    Publication Year: 2009 , Page(s): 1 - 10
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (218 KB) |  | HTML iconHTML  

    The problem of scheduling and tree routing in WiMAX/802.16 based mesh networks were not defined in the standard and are thus subject to extensive research. In this paper, we consider the problem of joint routing and scheduling in 802.16-based wireless mesh network, with the objective of determining a minimum length schedule that satisfies a given (uplink/downlink) end-to-end traffic demand. Minimizing the schedule length amounts to maximizing the spectrum spatial reuse by concurrently transmitting on as many links as possible, which we refer to as a transmission configuration (a group of links that can simultaneously transmit without violating the signal-to-interference-plus- noise ratio (SINR) requirement). Our model is referred to as maximum spatial reuse (MSR). Since there is an overwhelming number of possible transmission configurations to be assigned to time slots, we adopt the column generation technique to construct our MSR model. We present two formulations for modeling MSR, namely the link-based column generation (CGLink) formulation and the path-based column generation (CGPath) formulation. These two formulations differ mainly in the number of routing decision variables. Our experimental results indicate that the path-based formulation needs much less computational (CPU) time than the link-based formulation in order to determine the (same) optimized solution with the same spatial reuse gain. View full abstract»

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  • Habit: Leveraging human mobility and social network for efficient content dissemination in Delay Tolerant Networks

    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (181 KB) |  | HTML iconHTML  

    This paper proposes Habit, an efficient multi-layered approach to content dissemination in Delay Tolerant Networks (DTN) that leverages information about nodes' colocation (physical layer) and their social network (application layer). More precisely, the regularity of users' colocation is learned based on historical colocation observations; also, the users' social network (or `network of interest') is dynamically propagated during periods of colocation; finally, these distinct pieces of information are locally combined and used to compute the paths that content should follow, in a way that maximises both precision (i.e., nodes receive only content they are interested in) and recall (i.e., all relevant content is received by interested nodes). View full abstract»

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  • Highly efficient multipoint relay selections in link state QoS routing protocol for multi-hop wireless networks

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB) |  | HTML iconHTML  

    In this paper, we propose three heuristics for high-efficiency selections of MPRs (multipoint relays) in link state QoS routing protocol: MIMS (maximizing integration metric selection), MQES (maximizing QoS-efficiency selection), and MCIS (minimizing cost-inefficiency selection). The basic approach of these selections is to determine a smaller set of MPRs that provide better QoS paths between any two nodes. The main objective in doing so is to maximize the QoS (quality of service) effect while limiting routing overhead for flooding control traffic. In addition, we evaluate the performance of the routing protocols with the proposed selections by simulation. The results indicate that the proposed methods achieve high-efficiency selection; as compared to an existing MPR selection taking into account the QoS requirements, MIMS reduces the maintenance cost by 30%, while the throughput of the resultant path is decreased by 13%, and MCIS reduces the cost by 21% without any decrease in the throughput. View full abstract»

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  • Distributed user authentication in wireless LANs

    Publication Year: 2009 , Page(s): 1 - 9
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (294 KB) |  | HTML iconHTML  

    An increasing number of mobile devices, including smartphones, use WLAN for accessing the Internet. Existing WLAN authentication mechanisms are either disruptive, such as presenting a captive web page prompting for password, or unreliable, enabling a malicious user to attack a part of operator's infrastructure. In this paper, we present a distributed authentication architecture for WLAN users providing instant network access without manual interactions. It supports terminal mobility across WLAN access points with the Host Identity Protocol (HIP), at the same time protecting the operator's infrastructure from external attacks. User data sent over a wireless link is protected by the IPsec ESP protocol. We present our architecture design and implementation experience on two OpenWrt WLAN access points, followed by measurement results of the working prototype. The system is being deployed into pilot use in the city-wide panOULU WLAN. View full abstract»

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