In this paper, we propose to provide throughput guarantees in heterogeneous wireless mesh networks by jointly optimizing routing and Medium Access Control configuration. Our solution is based on the notion of linearized capacity region, which provides a technology-independent way of representing the capacity of a wireless link thereby hiding the technology specifics to the upper layers. From the available capacity of the underlying links as given by the linearized capacity region, we propose two routing algorithms based on multipath and single path that find optimal paths for all the flows in the network given their throughput requirements. The throughput allocation resulting from routing is then provided to each link, which uses this information to optimize its technology-specific Medium Access Control parameters. The proposed approach is evaluated in a heterogeneous scenario comprising Wireless Local Area Networks WLAN and Worldwide Interoperability for Microwave Access WiMAX technologies and is shown to outperform previous solutions by at least a factor of 2.Copyright © 2012 John Wiley & Sons, Ltd.

Femtocells were originally conceived to be deployed in private households and to solve the problem of poor indoor radio coverage as well as to offload traffic from the macrocellular network. The BeFEMTO project investigates and develops technologies that not only vastly improve the radio access capacity of femtocells, but also enables their use in novel scenarios like cooperative femtocell networks, outdoor relay femtocells and mobile femtocells. This paper presents the novel use cases and femtocell services considered in BeFEMTO as well as their enabling technologies and technical requirements.

Key incentives for mobile operators to offer femtocell services are the possibilities to cost-efficiently enhance indoor coverage and to offload traffic from the macro-cellular network. While femtocells were originally conceived for standalone deployments in user homes, there is an increasing interest in exploiting their advantages also in an enterprise context. However, with the current architecture as specified by 3GPP, such deployments face technical and economical challenges. This paper proposes a solution for localizing data and control plane traffic inside "Enterprise Femtocell Networks", which significantly offloads both the mobile core network and the backhaul to the core network.

Wireless communication technologies such as microwave radios are used to provide high-speed mobile backhaul connectivity for radio access networks in cases in which wire-based alternatives, e.g. cable or fiber, are not readily available and cannot be deployed in an economic or timely manner. Current mobile backhauls are predominantly deployed in tree or ring topologies, which simplify traffic management. Yet, with the increasing demand on backhaul capacity and the immense cost pressure on mobile backhaul solutions, meshed wireless mobile backhauls have been identified as a promising evolution. While traffic management in wireless mesh networks have been studied extensively in the literature, so far there is no quantitative analysis comparing the different topology options, i.e. mesh, ring and tree, regarding network performance and deployment cost. This paper fills this gap by studying the minimum cost problem of connecting a set of base station/gateway sites using different topologies while supporting both time- and space-varying traffic demands. Furthermore, we consider the additional constraint of resilience to single link failures. The evaluation results show that meshed wireless backhaul topologies are a cost-effective alternative to trees and rings, in particular in the face of spatial and temporal fluctuation of traffic demand and protection against link failures.

In this paper, we present a novel multipath structure called rope-ladder which combines the advantages of path, node and link protection schemes. We also propose a position-based multipath routing protocol in order to efficiently construct rope-ladders in wireless networks. By design, the paths which are constructed by our protocol are closely together which allows to quickly switch back and forth between them in cases of node or link failures. Hence, the size of loss gaps (i.e. the number of consecutively lost packets) can be minimized. Previous works mostly confine themselves to overall packet loss comparisons. However, the loss gap size is crucial to ensure high quality for gap-sensitive traffic like voice flows. Our multipath structure can also tolerate failures of multiple consecutive nodes on the primary path, and has a superior path diversity and path lifetime compared to even perfect braids. We evaluate the performance of our protocol using analysis and simulations.

Network calculus has proven as a valuable and versatile methodology for worst-case analysis of communication networks. One issue in which it is still lacking is the treatment of aggregate multiplexing, in particular if the FIFO property cannot be assumed when flows are merged. In this paper, we address the problem of bounding the delay of individual traffic flows in feed-forward networks under arbitrary multiplexing. Somewhat surprisingly, we find that direct application of network calculus results in loose bounds even in seemingly simple scenarios. The reasons for this "failure" of network calculus are discussed in detail and a method to arrive at tight delay bounds for arbitrary (aggregate) multiplexing is presented. This method is based on the solution of an optimization problem. For the special case of sink-tree networks this optimization problem is solved explicitly, thus arriving at a closed-form expression for the delay bound. Numerical experiments illustrate that in sink-tree networks the improvement over bounds based on direct application of network calculus can be considerable.

Current Internet use is evolving, users are becoming mobile and are expecting data services on the go. This fact presents big challenges and opportunities to operators, which see the increase in data services as a big market still to be exploited. However, current cellular technologies cannot accommodate the demand that will arise when the true Mobile Internet evolves. Addressing these challenges, we present the CARMEN project, the vision of which is to extend operators’ infrastructure by providing carrier grade services through a heterogeneous wireless mesh. The CARMEN architecture will provide enough bandwidth to cope with users’ expectations at a reduced cost, thereby generating major benefits to operators and users.

Resource-depletion attacks against IEEE 802.11 access points (APs) are commonly executed by flooding APs with fake authentication requests. Such attacks may exhaust an AP's memory resources and result in denied association service, thus enabling more sophisticated impersonation attacks accomplished by rogue APs.

To improve the already tarnished reputation of WLAN security, the new IEEE 802.11i security standard provides means for an enhanced user authentication and strong data confidentiality. However, the standard focuses on securing higher-layer data, i.e., protecting IEEE 802.11 data frames. Management frames used for connection administration are left unprotected and a wide spectrum of known attacks is still applicable and even extended against the IEEE 802.11i/IEEE 802.1X protocol execution. This work describes DiscoSec, a service pack for “patching” WLANs against the most prominent vulnerabilities resulting in resource-depletion and impersonation attacks. DiscoSec provides DoS-resilient key exchange, an efficient frame authentication, and a performance-oriented implementation. By means of extensive real-world measurements the performance of DiscoSec is evaluated showing that even on very resource-limited devices the throughput is decreased by only 22% compared to the throughput without any authentication, and by 6%on more powerful hardware. To demonstrate its effectiveness, DiscoSec is available as an open-source WLAN device driver.

Today's wireless sensor networks (WSN) focus on energy-efficiency as the main metric to optimize. However, an increasing number of scenarios where sensor networks are considered for time-critical purposes in application sce- narios like intrusion detection, industrial monitoring, or health care systems demands for an explicit support of per- formance guarantees in WSNs and, thus, in turn for a re- spective mathematical framework. In [1], a sensor network calculus was introduced in order to accommodate a worst- case analysis of WSNs. This sensor network calculus fo- cused on the communication aspect in WSNs, but had not yet a possibility to treat in-network processing in WSNs. In this work, we now incorporate in-network processing fea- tures as they are typical for WSNs by taking into account computational resources on the sensor nodes. Furthermore, we propose a simple, yet effective priority queue manage- ment discipline which achieves a good balance of response times across sensor nodes in the field.

Resource management for individual flows can significantly improve quality of service (QoS) in mobile cellular networks. However, its efficiency depends on the availability of information about the movement of mobile terminals. Movement prediction can potentially provide this information, but is costly if performed by the network and usually assumes a certain movement model, which may not adequately reflect each individual user's behavior. Instead, we propose the concept of movement contracts, where a mobile terminal specifies its movement to the network, which in return provides a better QoS as long as the provided specification is sufficiently accurate. We describe approaches to specify the spatial and temporal aspects of movement with a parsimonious parameter set and evaluate these approaches through simulations. We find that movement contracts can significantly reduce both session blocking and handover dropping probability simultaneously, whereas existing approaches have to make a tradeoff between these.