Wireless multi-hop networks such as mobile ad-hoc (MANET) or wireless

mesh networks (WMN) have attracted big research efforts during the last years

as they have huge potential in several areas such as military communications, fast

infrastructure replacement during emergency operations, extension of hotspots or

as an alternative communication system. Due to various reasons, such as characteristics

of wireless links, multi-hop forwarding operation, and mobility of nodes,

performance of traditional peer-to-peer applications is rather low in such networks.

In this book chapter, we provide a comprehensive and in-depth survey on recent research

on various approaches to provide peer-to-peer services in wireless multi-hop

networks. The causes and problems for low performance of traditional approaches

are discussed. Various representative alternative approaches to couple interactions

between the peer-to-peer overlay and the network layer are examined and compared.

Some open questions are discussed to stimulate further research in this area

Existing networks for public safety communications are mostly based on systems such as terrestrial trunked radio (TETRA), TETRAPOL and Project 25. These systems are mainly designed to support voice services. However, public safety communication networks are challenged to expand their scope way beyond their original functions toward more sophisticated devices and support new services including packet data communications. Therefore, governments, public safety agencies and research communities are continuously working together and are making significant progresses toward improving public safety communications capabilities. Next-generation mobile technologies are the enablers for meeting the new requirements of the public safety community. Public safety and commercial systems are typically designed and deployed to fulfill different needs and have different requirements, which are directly affecting the quality of service of the communications. The unique and vital nature of public safety affects the technical decisions that are necessary to guarantee connectivity for everyone, anywhere and anytime. For this reason, recent enhancements of the 4G long term evolution (LTE) in the field of public safety communications, such as device-to-device and group communications for mobiles in physical proximity, accrue a great opportunity to bring new services and a high-level of technological innovation to the public safety workers or first responders. We describe and analyze the evolution of public safety communication systems from the technical standpoint providing a complete overview of what is available in the market and a glimpse of future trends. Furthermore, we discuss the challenges to efficiently deploy, operate and interoperate present and future technologies for public safety communication networks and describe how these technologies can help public safety agencies to meet their expectations.

In this chapter, we first discuss the basic features and recent issues of the SDN control plane, notably the controller element. Then, we present feasible ideas to address the SDN controller-related problems using Big Data analytics techniques. Accordingly, we propose that Big Data can help various aspects of the SDN controller to address scalability issue and resiliency problem. Furthermore, we proposed six applicable scenarios for optimizing the SDN controller using the Big Data analytics: (i) controller scale-up/out against network traffic concentration, (ii) controller scale-in for reduced energy usage, (iii) backup controller placement for fault tolerance and high availability, (iv) creating backup paths to improve fault tolerance, (v) controller placement for low latency between controllers and switches, and (vi) flow rule aggregation to reduce the SDN controller's traffic. Although real-world practices on optimizing SDN controllers using Big Data are absent in the literature, we expect scenarios we highlighted in this chapter to be highly applicable to optimize the SDN controller in the future.

Network Function Virtualization (NFV) is an emerging network architecture to increase flexibility and agility within operator's networks by placing virtualized services on demand in Cloud data centers (CDCs). One of the main challenges for the NFV environment is how to efficiently allocate Virtual Network Functions (VNF) to Virtual Machines (VMs). Although a significant amount of work/research has been already conducted for the generic VNF placement problem, network latency among various network components has not been comprehensively considered yet. To address this concern, in this article, we design a more comprehensive model based on real measurements to capture network latency among VNFs with more granularity to optimize placement of VNFs in CDCs. Experimental results are promising and indicate that our approach, namely VNF Low-Latency Placement (VNF-LLP), can reduce network latency by up to 64.24% (50.33% in average) compared with two generic algorithms. Furthermore, it has a lower lead time (time to find a suitable VM to host a VNF) as compared with two classic approaches.

Network Function Virtualization (NFV) is an emerging network architecture to increase flexibility and agility within operator's networks by placing virtualized services on demand in Cloud data centers (CDCs). One of the main challenges for the NFV environment is how to minimize network latency in the rapidly changing network environments. Although many researchers have already studied in the field of Virtual Machine (VM) migration and Virtual Network Function (VNF) placement for efficient resource management in CDCs, VNF migration problem for low network latency among VNFs has not been studied yet to the best of our knowledge. To address this issue in this article, we i) formulate the VNF migration problem and ii) develop a novel VNF migration algorithm called VNF Real-time Migration (VNF-RM) for lower network latency in dynamically changing resource availability. As a result of experiments, the effectiveness of our algorithm is demonstrated by reducing network latency by up to 70.90% after latency-aware VNF migrations.

Packet/frame 'rebuffering' in wireless video streaming typically considers only connectivity from the mobile terminal to its network access point (AP). However, in the presence of multiple APs with the possibility of handoffs, the overall wireless environment should be considered. We develop a model capturing joint rebuffering & handoff dynamics in wireless video streaming, and design a new channel-aware joint rebuffering & handoff control scheme, aiming to minimize the long-run average cost of video jitters and freezes. We first characterize the optimal control in the general case of multiple wireless APs/channels and multiple states per channel. Subsequently, we evaluate the system performance in key important cases, using experimental traces of wireless channel data. We explore the relationship between optimal rebuffering thresholds and overall channel dynamics, and evaluate the associated joint handoff control. The performance results demonstrate the importance of jointly managing rebuffering and handoff controls to achieve high-performance wireless video streaming.

Wireless hand-off control typically considers only connectivity strength from the mobile terminal to alternative access points. In wireless video streaming, however, where video freezing must be avoided at the mobile terminal, the playout buffer level should also be considered by hand-off control. In this paper, we first develop a model capturing hand-off dynamics under video streaming, and design a new playout buffer aware hand-off control. It aims to avert a video freeze for as long as possible, maximizing the expected time until freezing. We compute the optimal control in the general case of multiple access points and multiple connectivity strength states per channel. The optimal hand-off control is then computationally probed in specific relevant cases. It is demonstrated that there is a certain playout buffer threshold level - a buffer tipping point - above which a hand-off should be attempted. Of course, this tipping point depends on the access point to mobile channel statistics

Reputation systems rate the contributions to participatory sensing campaigns from each user by associatinga reputation score. The reputation scores are used to weedout incorrect sensor readings. However, an adversary can de-anonmyize the users even when they use pseudonyms by linking the reputation scores associated with multiple contributions. Since the contributed readings are usually annotated with spatio-temporal information, this poses a serious breach of privacy for the users. In this paper, we address this privacy threat by proposing a framework called IncogniSense. Our system utilizes periodic pseudonyms generated using blind signature and relies on reputation transfer between these pseudonyms. The reputation transfer process has an inherent trade-off between anonymity protection and loss in reputation. We investigate by means of extensive simulations several reputation cloaking schemes that address this tradeoff differently. Our system is robust against reputation corruption and a proof-of-concept implementation demonstrates that the associated overheads are minimal.

Reputation systems are fundamental for assessing the quality of user contributions inparticipatory sensing. However, naively associating reputation scores to contributionsallows adversaries to establish links between multiple contributions and thus deanonymizeusers. We present the IncogniSense framework as a panacea to these privacythreats. IncogniSense utilizes periodic pseudonyms generated using blind signatureand relies on reputation transfer between these pseudonyms. Simulations are used toanalyze various reputation cloaking schemes that address the inherent trade-off betweenanonymity protection and loss in reputation. Our threat analysis confirms the robustnessof IncogniSense and a prototype demonstrates that associated overheads are minimal.

Today, the most frequently used signaling system for telecommunication is called Signaling System No. 7 (SS7). The growing usage of mobile telephones and mobile data communica-tion, and the development of new services mean that the risk of intrusion and exploitation of the SS7 signaling networks increases. The increasing problem with unauthorized access to sensitive information and the operators’ growing demand for security is the origin of our work. This thesis presents a prototype design and implementation of a Security Gateway (SEG), which is a fundamental part of the TCAP user security (TCAPsec) concept. TCAPsec is a security concept for introducing security mechanisms to the signaling system. The proto-type includes three different protection modes that provide security services, ranging from almost no protection to full protection with the use of encryption algorithms. The thesis also contains an evaluation study of the delay penalties caused by the use of these security services. With regards to the restrictions on the prototype, the conclusion drawn from the evaluation results was that the protection mechanisms in the different protection modes did not inflict any significant time penalties. Instead, the results of the study indicate that the routing process of messages in the network is a more significant delaying part in the communication between different nodes. This result implies that the routing process takes longer time than the security services. The thesis also presents a number of discovered features that will require further investigation and development before the TCAPsec concept can be realized.

Today, the most frequently used signaling system for telecommunication is called Signaling

System No. 7 (SS7). The growing usage of mobile telephones and mobile data communication,

and the development of new services mean that the risk of intrusion and exploitation of

the SS7 signaling networks increases. The increasing problem with unauthorized access to

sensitive information and the operators’ growing demand for security is the origin of our

work. This thesis presents a prototype design and implementation of a Security Gateway

(SEG), which is a fundamental part of the TCAP user security (TCAPsec) concept. TCAPsec

is a security concept for introducing security mechanisms to the signaling system. The prototype

includes three different protection modes that provide security services, ranging from

almost no protection to full protection with the use of encryption algorithms. The thesis also

contains an evaluation study of the delay penalties caused by the use of these security services.

With regards to the restrictions on the prototype, the conclusion drawn from the evaluation

results was that the protection mechanisms in the different protection modes did not inflict

any significant time penalties. Instead, the results of the study indicate that the routing process

of messages in the network is a more significant delaying part in the communication between

different nodes. This result implies that the routing process takes longer time than the security

services. The thesis also presents a number of discovered features that will require further

investigation and development before the TCAPsec concept can be realized.

Software in computers control many important functions in today's society and are widely used for communication but also to control equipment. For the software to work reliably it needs to be built correctly and tested extensively. To achieve reliability, a build server can be used to automatically build and test the software. This report describes how a prototype of a monitoring system for the build servers was created. The system will be monitored by a monitoring service that retrieves information from a build server using the CruiseControl.NET [10] software. The information gathered by the monitoring service will be presented on a web portal. The information retrieved from build the server goes from a high level of abstraction down to the smallest detail that is based on the log files from the build server, for example, information about compilation errors.

The development of the monitoring system has been focused on making it possible to use cloud services and thus not restrict where a build server is located. One of the cloud services used is the Service Bus Relay [27] that handles the communication between a monitoring service and the web portal. The web portal is developed to be responsive [34] and provide support for mobile devices which give the user the freedom to visit the web portal from whatever device. The web portal uses a database to store information which enables monitoring of multiple build servers. A well-developed user management system is used on the web portal which provides administrators with an effective tool for user management. There have been several lessons learned, including the discovery of a bug in the Microsoft implementation of message handling in the Service Bus Relay.

Mobila lösningar blir allt vanligare och appar kan utvecklas för att hjälpa mobilanvändare

med det mesta. Att utveckla appar är populärt och kan göras i en mängd olika språk och

utvecklingsmiljöer, och projektet har haft som mål att både utveckla en användbar app

och utvärdera en sådan utvecklingsmiljö.

PaddelAppen som utvecklats i projektet fyller ett tomrum genom att vara en resurs för

paddelintresserade. Samtidigt har utvecklingsarbetet resulterat i en utvärdering av utveck-lingsmiljön Xamarin, som använts tillsammans med Visual Studio för att plattformsobe-roende utveckla appen för både Android och Windows Phone.

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.

The impact of transmission impairments such as loss and latency on user perceived quality(QoE) depends on the service type. In a real network, multiple service types such as audio,video, and data coexist. This makes resource management inherently complex and difficultto orchestrate. In this paper, we propose an autonomous Quality of Experience managementapproach for multiservice wireless mesh networks, where individual mesh nodes apply rein-forcement learning methods to dynamically adjust their routing strategies in order to maxi-mize the user perceived QoE for each flow. Within the forwarding nodes, we develop a novelpacket dropping strategy that takes into account the impact on QoE. Finally, a novel sourcerate adaptation mechanism is designed that takes into account the expected QoE in order tomatch the sending rate with the available network capacity. An evaluation of our mechanismsusing simulations demonstrates that our approach is superior to the standard approaches,AODV and OLSR, and effectively balances the user perceived QoE between the service flows.

Certificate Transparency (CT) logs are append-only tamper-evident data structures that can be verified by anyone. For example, it is possible to challenge a log to prove certificate inclusion (membership) and log consistency (append-only, no tampering) based on partial information. While these properties can convince an entity that a certificate is logged and not suddenly removed in the future, there is no guarantee that anyone else observes the same consistent view. To solve this issue a few gossip protocols have been proposed, each with different quirks, benefits, assumptions, and goals. We explore CT gossip below the application layer, finding that packet processors such as switches, routers, and middleboxes can aggregate gossip passively or actively to achieve herd immunity: (in)direct protection against undetectable log misbehaviour. Throughout the thesis we describe, instantiate, and discuss passive aggregation of gossip messages for a restricted data plane programming language: P4. The concept of active aggregation is also introduced. We conclude that (i) aggregation is independent of higher-level transparency applications and infrastructures, (ii) it appears most prominent to aggregate Signed Tree Heads (STHs) in terms of privacy and scalability, and (iii) passive aggregation can be a long-term solution if the CT ecosystem adapts. In other words, not all sources of gossip must be encrypted to preserve privacy.

Today's computer logs are like smoking guns and treasure maps in case of suspicious system activities: they document intrusions, and log crucial information such as failed system updates and crashed services. An adversary thus has a clear motive to observe, alter, and delete log entries, considering that she could (i) start by using the log's content to identify new security vulnerabilities, and (ii) exploit them without ever being detected. With this in mind we consider syslog standards and open source projects that safeguard events during the storage and transit phases, and examine how data compression effects security. We conclude that there are syslog standards in place that satisfy security on a hop-by-hop basis, that there are no such standards for secure storage, and that message compression is not recommended during transit.

Throughout the years the Swedish local history societies have collected a large quantity of material, consisting of photos, documents and items, among others. As the society has become more computerized, the need has increased for these collections to become digitalized. This is a way to make their media more easily accessible to the general public, but also to easily be able to archive and preserve for example photos and videos electronically.This thesis concerns itself with the work we have done for the local history society of Nyed in Molkom. The task set before us consisted of creating both a website for the society, and a reliable database from witch the website draws its information. This project allows anyone with administrator privileges to upload new files and any additional information. Beyond that, general users van then search through and view these files. The following is an explanation ofout methodology, concluding with an assessment of out performance bases on the standards set by the requestor.

In today's information society, privacy-enhanced identity management can help users to control their personal spheres when makinguse of e-services. However, privacy is a difficult concept to visualise, and comprehensible and intuitive user interfaces are needed to make such systems usable and informative for normal users. Typically, usability tests are used as a means to achieve this. This paper describes how the concept of identity management was introduced to the test subjects before a series of tests on prototypes and mock-ups of user interfaces were conducted. One reason why this was necessary was to provide the test subjects with enough context information to be able to perform the tests. Both oral and written introductions have been used, as well as introductory films. This paper discusses how these introductions have evolved during the usability testing process, and it further elaborates on which kinds of introductions are most suitable for which kind of usability test.

This deliverable provides a first overview of the state of the art on wireless security metrics and algorithms,

which are particularly very important with respect to the intrinsic vulnerability of the wireless

medium. The first part deals with building practical physical layer information-theoretic secure schemes.

Indeed, Shannon formalized the concepts of capacity (as a transmission efficiency measure) and equivocation

(as a measure of secrecy). While the concept of capacity has been extended to fading channels

with the introduction of concepts like the outage capacity or the ergodic capacity, similar paths are yet to

be developed concerning equivocation. In the second part, we present a taxonomy of threats for wireless

networks, and particularly for wireless sensor networks, in terms of the affected protocol layers. Besides,

an overview to attack tree and attack graph techniques as formal means for describing and measuring

vulnerabilities and thus also for assessing also the security level of wireless sensor networks is provided.

Finally, an overview to suitable security concepts for wireless networks is given

When using Voice over IP (VoIP) in Wireless Mesh Networks the overhead induced by the IEEE 802.11 PHY and MAC layer accounts for more than 80% of the channel utilization time, while the actual payload only uses 20% of the time. As a consequence, the Voice over IP capacity is very low. To increase the channel utilization efficiency and the capacity several IP packets can be aggregated in one large packet and transmitted at once. This paper presents a new hop-by-hop IP packet aggregation scheme for Wireless Mesh Networks.

The size of the aggregation packets is a very important performance factor. Too small packets yield poor aggregation efficiency; too large packets are likely to get dropped when the channel quality is poor. Two novel distributed protocols for calculation of the optimum respectively maximum packet size are described. The first protocol assesses network load by counting the arrival rate of routing protocol probe messages and constantly measuring the signal-to-noise ratio of the channel. Thereby the optimum packet size of the current channel condition can be calculated. The second protocol, which is a simplified version of the first one, measures the signal-to-noise ratio and calculates the maximum packet size.

The latter method is implemented in the ns-2 network simulator. Performance measurements with no aggregation, a fixed maximum packet size and an adaptive maximum packet size are conducted in two different topologies. Simulation results show that packet aggregation can more than double the number of supported VoIP calls in a Wireless Mesh Network. Adaptively determining the maximum packet size is especially useful when the nodes have different distances or the channel quality is very poor. In that case, adaptive aggregation supports twice as many VoIP calls as fixed maximum packet size aggregation.

Wireless Mesh Networks (WMNs) have emerged as a promising network technology, which combines the benefits of cellular networks and Wireless Local Area Networks (WLANs). In a WMN mesh routers wirelessly relay traffic on behalf of other mesh routers or clients and thereby provide coverage areas comparable to cellular networks, while having the low complexity and low costs of WLANs. As Voice over IP (VoIP) is a very important Internet service, it is critical for the success of WMNs to support high quality VoIP. However, currentWMNs are not adapted well for VoIP. The capacity and scalability of single-radio WMNs is low, especially for small packet transmissions of VoIP calls, because the MAC and PHY layer overhead for small packets is high. The scalability of multiradio/multi-channel WMNs is usually higher, since fewer nodes contend for a channel. However channel scheduling might be required, which can lead to excessive delay and jitter and result in poor VoIP quality. In this thesis we investigate how to deliver high quality VoIP in single radio and multi-radio networks by using cross-layer optimization. For single radio WMNs, we consider the use of IP packet aggregation and IEEE 802.11e transmission opportunities. We conclude that IP packet aggregation greatly improves the capacity and thereby the scalability of WMNs. We show that the key for providing good quality is to artificially delay packets prior to aggregation. We propose a distributed cross-layer optimization system, which, based on Fuzzy Logic Inference, derives an aggregation delay that enhances the capacity and quality. For multi-radio/multi-channel WMNs, we demonstrate the importance of qualityof- service-aware channel scheduling. We develop a quality-of-serviceaware channel scheduler that compared to a basic round-robin scheme significantly reduces jitter and in that way increases VoIP quality. Our analysis shows that there is a trade-off between the jitter of high priority VoIP traffic and the throughput of background TCP traffic. The proposed optimizations significantly increase the capacity of singleradio and multi-radio WMNs. This allows network operators to serve more users with an existing mesh infrastructure or provide better service delivery to existing users.

Abstract--- In multi-radio wireless mesh networks (WMNs) several radios can operate within one node simultaneously on different channels. Due to frequency selective fading and varying output powers of WLAN cards the received signal strength on channels in the U-NII band can differ by several dB. Furthermore, power leakage from neighboring channels in the frequency spectrum can cause adjacent channel interference (ACI). Using a IEEE 802.11a testbed, we experimentally evaluate the achievable throughput of a multi-radio mesh network in a string topology under the impact of ACI and channel heterogeneity. Our results show that for low PHY rates the channel separation is a good indicator for throughput. However, for high PHY rates the propagation properties of a specific channel also need to be considered. Based on the results we provide recommendations for designing channel assignment algorithms for IEEE 802.11-based WMNs

In Wireless mesh networks mesh access points (MAPs) forward traffic wirelessly towards users or Internet gateways. A user device usually connects to the MAP with the strongest signal, as such MAP should guarantee the best quality of service. However, this connection policy may lead to: (i) unfairness towards users that are distant from gateways; (ii) uneven distribution of users to MAPs; and (iii) inefficient use of network paths. We present a new model and solution approach to the problem of assigning users to MAPs and routing the data within the mesh network with the objective of providing max–min fair throughput. The problem is formulated as a mixed-integer linear programming problem (MILP). Because of the inherent complexity of the problem, real size instances cannot be solved to optimality within the time limits for online optimization. Therefore, we propose an original heuristic solution algorithm for the resulting MILP. Both numerical comparisons and network simulations demonstrate the effectiveness of the proposed heuristic. For random networks, the heuristic achieves 98% of the optimal solution. Network simulations show that in medium-sized networks, the number of users with at least 1Mbit/s minimum end-to-end rate increases by 550% when compared with the classical signal-strength based association.

In this demo, we will present KAUMesh, an experimental Wireless Broadband Mesh Network based on 802.11a/b/g WLAN devices that has been deployed at the Karlstad University Campus. KAUMesh comprises currently 20 mesh nodes, which are permanently installed to cover large areas inside the new House 21. Standard 802.11b/g based clients can be used to connect to the mesh as they would to any given normal WLAN access point. KAUMesh features multiple gateways that connect the mesh network towards the internet. By deploying multiple radio cards in mesh nodes, KAUMesh is able to fully exploit available spectrum in the mesh backbone. One radio card interface is used for transparent client access, using typically 802.11b/g mode. The mesh backhaul connectivity is established using multiple radio interfaces per mesh node. The interfaces involved in the backhaul use a hybrid channel assignment mechanism, which rebalances channel usage according to user demand. As the hybrid channel assignment involves channel switching, a novel scheduling approach for making the channel switching QoS aware has been developed. KAUMesh also supports 802.11e standard on the mesh interface to provide service differentiation on the mesh backhaul

In Wireless Local Area Network (WLAN) hotspots the coverage areas of Access Points (APs) often overlap considerably. Current state of the art optimization models find the optimal AP for each user station by balancing the load across the network. Recent studies have shown that in typical commercial WLAN hotspots the median connection duration is short. In such dynamic network settings the mentioned optimization models might cause many handovers between APs to accommodate for user arrivals or mobility. We introduce a new mixed integer linear optimization problem that allows to optimize handovers but takes into account the costs of handovers such as signaling and communication interruption. Using our model and extensive numeric simulations we show that disregarding the handover costs leads to low performance. Based on this insight we design a new optimization scheme that uses estimates of future station arrivals and mobility patterns. We show that our scheme outperforms current optimization mechanisms and is robust against estimation errors

System and method for deriving an aggregation delay for a packet aggregation in a wireless network comprising a controller for deriving an optimal aggregation delay at a network node depending on information relating to the channel quality related parameters at the network node in the wireless network.

Wireless mesh networks (WMNs) are wireless multi-hop backhaul networks in which mesh routers relay traffic on behalf of clients or other routers. Due to large MAC layer overhead, applications such as Voice over IP, which send many small packets, show poor performance in WMNs. Packet aggregation increases the capacity of IEEE 802.11-based WMNs by aggregating small packets into larger ones and thereby reducing overhead. In order to have enough packets to aggregate, packets need to be delayed and buffered. Current aggregation mechanisms use fixed buffer delays or do not take into account the delay characteristics of the saturated IEEE 802.11 MAC layer. In this work, we present FUZPAG, a novel packet aggregation architecture for IEEE 802.11-based wireless mesh networks. It uses fuzzy control to determine the optimum aggregation buffer delay under the current channel utilization. By cooperation among neighboring nodes FUZPAG distributes the buffer delay in a fair way. We implemented and evaluated the system in a wireless mesh testbed. For different network topologies we show that FUZPAG outperforms standard aggregation in terms of end-to-end latency under a wide range of traffic patterns.

Wireless mesh networks (WMNs) are wireless multihop networks comprised of mesh routers, which relay traffic on behalf of clients and other nodes. Using the standard IEEE 802.11 distributed coordination function (DCF) as MAC layer, a node needs to contend for the medium each time it wants to transmit a packet. This creates high overhead in particular for small packets and leads to poor performance for real-time applications such as Voice over IP (VoIP) or online gaming. Burst packet transmission can increase the efficiency. For example, with the Transmission Opportunity limit (TXOPlimit) in IEEE 802.11e, a station may transfer several packets without contending for the channel in between. Similarly, IP packet aggregation combines several IP packets together and sends them as one MAC Service Data Unit. Originally, both schemes have been developed for singlehop networks only. Thus the impact on WMNs is unclear if the packets need to contend over multiple hops. In this paper, we use measurements from a 9-node WMN testbed to compare TXOPs and IP packet aggregation for VoIP in terms of fairness, network capacity and quality of user experience. We show that for low networks loads, both TXOPs and IP packet aggregation increase the VoIP quality compared to IEEE 802.11 DCF. However, in highly loaded networks IP packet aggregation outperforms the other schemes.

We present a software framework for channel assingment and routing experiments in multi-channel/multi-radio wireless mesh networks.Based on a plug-in architecture we develop a traffic demand-aware channel assignment algorithm. The evaluation in KAUMesh - an experimental multi-radio mesh network - shows around 30% throughput improvement with respect to a traffic un-aware channel assignment scheme

Optimizing the operation of IEEE 802.11 networks requires to estimate the load of the wireless channel. The channel busy fraction, which is the fraction of time in which the wireless channel is sensed busy due to successful or unsuccessful transmissions, can be used as such indicator. It can be obtained from e.g. the IEEE 802.11k channel load report or hardware-specific interfaces. Previously, the channel busy fraction has been used as a metric for different purposes such as routing and admission control. However, a thorough evaluation of the relationship between the busy fraction and other important characteristics such as the collision probability and throughput is missing. In this paper, we present an analytical model to study the channel busy fraction in non-saturated IEEE 802.11 networks. We validate the model with measurements in a testbed. The predictions from the model match measurements well. Furthermore, we demonstrate how to apply the model to estimate the available link bandwidth. Using measurements obtained from a testbed operated at 6 Mbit/s, we show that the channel busy fraction allows an accurate prediction of the available bandwidth with an error smaller than 70 Kbit/s.

Wireless Mesh networks are multi-hop networks mostly based on IEEE 802.11 technology and are considered as a viable alternative for providing broadband wireless Internet access. As a consequence, they require support for Quality of Service or advanced mechanisms for selecting Internet gateways. One important requiredinformation is the one-way delay between different nodes. In this paper, we have developed, implemented, and evaluated an one-way delay estimation technique for wireless mesh networks which is based on estimating intra node queuing and inter node forwarding delay. An IP-header option field is used to accumulate the per hop delay estimate to provide an end-to-end estimate. We also outline problems with the implementation and compare results with real one-way delays obtained from a 14 node mesh testbed.We show how estimation accuracy depends on network load and provide insights into further improvements

With ubiquitous use of digital camera devices, especially in mobile phones, privacy is no longer threatened by governments and companies only. The new technology creates a new threat by ordinary people, who could take and distribute pictures of an individual with no risk and little cost in any situation in public or private spaces. Fast distribution via web based photo albums, online communities and web pages expose an individual's private life to the public. Social and legal measures are increasingly taken to deal with this problem, but they are hard to enforce in practice. In this paper, we proposed a model for privacy infrastructures aiming for the distribution channel such that as soon as the picture is publicly available, the exposed individual has a chance to find it and take proper action in the first place. The implementation issues of the proposed protocol are discussed. Digital rights management techniques are applied in our proposed infrastructure, and data identification techniques such as digital watermarking and robust perceptual hashing are proposed to enhance the distributed content identification.

he advances in mobile technologies enable mobile devices to perform tasks that are traditionally run by personal computers as well as provide services to the others. Mobile users can form a service sharing community within an area by using their mobile devices. This paper highlights several challenges involved in building such service compositions in mobile communities when both service requesters and providers are mobile. To deal with them, we first propose a mobile service provisioning architecture named a mobile service sharing community and then propose a service composition approach by utilizing the Krill-Herd algorithm. To evaluate the effectiveness and efficiency of our approach, we build a simulation tool. The experimental results demonstrate that our approach can obtain superior solutions as compared with current standard composition methods in mobile environments. It can yield near-optimal solutions and has a nearly linear complexity with respect to a problem size.