Identity-based attacks (IBAs) are one of the most serious threats to wireless networks. Recently, there is an increasing interest in using the received signal strength (RSS) to detect IBAs in wireless networks. However, current schemes tend to generate excessive false alarms in the mobile scenario. In this paper, we propose a stronger Reciprocal Channel Variation-based Identification and classification (RCVIC) scheme for the mobile wireless networks, which exploits the reciprocity of the wireless fading channel and RSS variations naturally incurred by mobility to improve the detection performance. Different from current schemes only detect IBAs, RCVIC scheme conducts a multi-stage detection processes. If the IBAs are detected, RCVIC scheme partitions the received frames into two classes. The frames in the same class should be sent from the same senders, which could benefit the further analysis, such as network forensics, attacker localizing and trajectory analysis, etc. The feasibility of RCVIC are numerically evaluated through theoretical analysis and simulations. It is further validated through experiments using off-the-shelf 802.11 devices under different attacking patterns in real indoor and outdoor mobile scenarios.

In contrast to conventional static fixed-width channel allocation, on-demand dynamic variable-width channel allocation has shown that it can effectively improve the fairness, throughput, and spectrum efficiency of wireless networks. Air-time utilization (the percentage of time spent on transmissions) is often used to characterize the spectrum demand of networks. The higher the airtime utilization of a network is, the more spectrum the network should be allocated to. Normally, if all wireless devices in a network utilize spectrum effectively, the airtime utilization can faithfully reflect the spectrum usage. In practice, however, spectrum can be ineffectively used due to the misconfiguration of wireless devices, such as inappropriate bit rate configuration, conservative transmit power setting, or mismatch between channel-width and bit rate. The misconfiguration not only degrades the performance of its local network, but also causes the inflation of local network's airtime utilization and thus results in an unfair spectrum allocation. To address the problem, we present Pinokio, a system that monitors spectrum usage at access points, detects spectrum misuse and improves spectrum efficiency. Our extensive evaluations suggest that Pinokio can accurately detect spectrum misuse, and limit the inflation of airtime utilization from more than 730% to less than 20%.

Identity-based attacks (IBAs) are one of the most serious threats to wireless networks. Recently, received signal strength (RSS) based detection mechanisms were proposed to detect IBAs in static networks. Although mobility is an inherent property of wireless networks, limited work has addressed IBA detection in mobile scenarios. In this paper, we propose a novel RSS based technique, Reciprocal Channel Variation-based Identification (RCVI), to detect IBAs in mobile wireless networks. RCVI takes advantage of the location decorrelation, randomness, and reciprocity of the wireless fading channel to decide if all packets come from a single sender or more. If the packets are only coming from the genuine sender, the RSS variations reported by the sender should be correlated with the receiver's observations. Otherwise, the correlation should be degraded, then an attack can be flagged. We evaluate RCVI through theoretical analysis, and validate it through experiments using off-the-shelf 802.11 devices under different attacking patterns in real indoor and outdoor mobile scenarios. We show that RCVI can detect IBAs with a high probability even when the attacker is half a meter away from the genuine user.

Multi-radio nodes in wireless mesh networks introduce extra complexity in utilizing channel resources. Depending on the configuration of the radios, bad mappings between radio to wireless frequencies may result in sub-optimal network topologies. Static channel assignments in wireless mesh networks have been studied in theory and through simulation but very little work has been done through experiments. This paper focuses on evaluating static channel assignments on a live wireless mesh network. We chose three popular types of static channel assignment algorithms for implementation and comparison purposes. The three types are breadth-first search, priority-based selection and integer linear programming. We find that there is no single channel assignment algorithm that does well overall. BFS algorithm can create the shortest paths to the gateway and also generate balanced channel usage topologies. The PBS algorithm can use all the best links in the network but have poor performance from each radio to the gateway. Overall, we find the channel assignments given by the algorithms to be suboptimal when applied to a live mesh network because temporal variations in the link quality metrics are not taken into account. Looking at the interflow and intraflow performance of these channel assignment algorithms in a live mesh network, we can conclude that routing protocols must be modified to take advantage of the underlying channel assignment algorithms.

Generating a secret key between two parties by extracting the shared randomness in the wireless fading channel is an emerging area of research. Previous works focus mainly on single-antenna systems. Multiple-antenna devices have the potential to provide more randomness for key generation than single-antenna ones. However, the performance of key generation using multiple-antenna devices in a real environment remains unknown. Different from the previous theoretical work on multiple-antenna key generation, we propose and implement a shared secret key generation protocol, Multiple-Antenna KEy generator (MAKE) using off-the-shelf 802.11n multiple-antenna devices. We also conduct extensive experiments and analysis in real indoor and outdoor mobile environments. Using the shared randomness extracted from measured Received Signal Strength Indicator (RSSI) to generate keys, our experimental results show that using laptops with three antennas, MAKE can increase the bit generation rate by more than four times over single-antenna systems. Our experiments validate the effectiveness of using multi-level quantization when there is enough mutual information in the channel. Our results also show the trade-off between bit generation rate and bit agreement ratio when using multi-level quantization. We further find that even if an eavesdropper has multiple antennas, she cannot gain much more information about the legitimate channel.

Wireless simulators provide full control to researchers in investigating traffic flow behavior, but do not always reflect real-world scenarios. Although previous work pointed out such shortages are due to the limitation of radio propagation models in the simulators, it is still unclear how these imperfect models affect network behavior and to what degree. In this paper, we quantify network behavioral differences between simulations and real-world testbed experiments. We compare and analyze the experimental results from indoor and outdoor experiments with the results from NS-2 and Qualnet simulations. We find that in the PHY layer, the distribution of received signal strength in experiments is usually different from simulation due to the antenna diversity. However, path loss, which is regarded as a dominating factor in simulator channel modeling, can be configured to match the real-world behavior. For the MAC layer, increasing traffic load on a flow may cause significant performance degradation in experiments, but it is not the case in simulations. Interference is inadequately captured in simulations and cannot show the flow level unfairness phenomenon. In the network layer, a few dominant routes exist in testbed experiments while routes in simulations are less stable. These findings give the wireless research community an improved overview about the differences between simulations and testbed experiments. They will help researchers to choose between simulations and experiments according to their particular research requirements.

Despite the increasing number of wireless mesh network deployments and research, there is a lack of understanding on how robust these networks are in practice. In this paper, we perform a systematic experimental study to investigate the impacts of different factors on the unreliability of a mesh network and the sources causing such unreliability. We use packet loss rate as a metric for defining reliability. The factors that we studied include traffic load, number of hops and flows, transmission rates, maximum retransmission limits and the RTS/CTS mechanism. Our results are based on measurements performed on our real- world mesh network testbed. In addition to performing the experiments on multiple hops, we include the results of one hop experiments for comparison. In identifying the sources of packet loss, we developed a tool, FlowPaC, to collect flow-based statistics at different points in the system to understand the effects of the MAC layer parameters and the traffic attributes. We also explore the potential remedies for the system configuration and thereby improve the reliability of wireless mesh networks.

The increased deployment of wireless mesh networks (WMNs) should be complemented by a robust resource management scheme that can provide performance guarantees to mission-critical applications. Several admission control schemes have been presented for wireless LANs and wireless ad-hoc networks. However, wireless mesh networks, with static wireless back-bone and multi-hop communication, pose new design challenges. Evaluation of existing admission control schemes has been done primarily via simulations, which often do not have accurate models for capturing interference between adjacent wireless links and nodes. In this paper, we develop light-weight monitoring modules to measure current network/traffic conditions and estimate end-to-end path delay, which is then incorporated in our admission control decision. We utilize a novel layer-2 packet forwarding mechanism, based on the wireless distribution system (WDS) for WMNs. We evaluate our scheme via experiments conducted on a test-bed consisting of IEEE 802.11a-based nodes that form a wireless mesh. Results show that our proposed scheme can provide performance assurance without incurring too much control overhead.

Wireless Mesh Networks are being deployed everywhere as an alternative to broadband connections. Their ease of setup and large coverage are attractive attributes. However, there are very few performance studies of mesh networks especially in the multiple channel arena. Our objective is to study the performance and characterize the 802.11b wireless mesh backbone as a linear topology with respect to multiple channel usage. We look at the relative performances of single and multiple channels, as well as the number of hops utilized. We introduce a number of communication flows into the network to study the interactions. Finally, we look at the physical placement of the antennas on an access point to determine its impact on performance. Several design decisions for the configuration of wireless mesh network deployments have been inferred from our experimental testbed.

Article Free Access Share on StratOSphere: mobile processing of distributed objects in Java Authors: Daniel Wu Department of Computer Science, University of California, Santa Barbara Department of Computer Science, University of California, Santa BarbaraView Profile , Divyakant Agrawal Department of Computer Science, University of California, Santa Barbara Department of Computer Science, University of California, Santa BarbaraView Profile , Amr El Abbadi Department of Computer Science, University of California, Santa Barbara Department of Computer Science, University of California, Santa BarbaraView Profile Authors Info & Claims MobiCom '98: Proceedings of the 4th annual ACM/IEEE international conference on Mobile computing and networkingOctober 1998 Pages 121–132https://doi.org/10.1145/288235.288267Published:25 October 1998Publication History 11citation456DownloadsMetricsTotal Citations11Total Downloads456Last 12 Months11Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Java offers the basic infrastructure needed to integrate computers connected to the Internet into a seamless distributed computational resource: an infrastructure for running coarse-grained parallel applications on numerous, anonymous machines. First, we sketch such a resource's essential technical properties. Then, we present Javelin, an infrastructure for global computing. The system is based on Internet software that is interoperable, increasingly secure and ubiquitous: Java-enabled Web technology. Ease of participation is seen as a key property for such a resource to realize the vision of a multiprocessing environment comprising thousands of computers. Javelin's architecture and implementation require participants to have access to only a Java-enabled Web browser. The security constraints implied by this, the resulting architecture and the current implementation are presented. The Javelin architecture is intended to be a substrate on which various programming models may be implemented. Different computation servers, each corresponding to a different programming model, are supported by Javelin's architecture. Several are presented briefly. Experimental results are given in the form of micro-benchmarks, a Mersenne Prime application and a ray-tracing application that run on a heterogeneous network of several parallel machines, workstations and PCs. © 1997 John Wiley & Sons, Ltd.

The Alexandria project has been initiated to build a digital library for map and satellite images.Designed for content-based retrieval, the relevant information in each image is encoded in the form of a multi-dimensional feature vector.Though representing images by feature vectors ~eatly facilitates user queries, indexing these vectors degrades performance when the number of dimensions is large.We consider 2 popular techniques (DFT and SVD) to reduce the dimension of feature vectors, and study their retrieval performance with respect to recall and precision.We End that though SVD generally out-performs DFT, DFT compares favorably in a limited range suitable for browsing large image databases.