Biblio

We study the problem of randomized Leader Election in synchronous distributed networks with indistinguishable nodes. We consider algorithms that work on networks of arbitrary topology in two settings, depending on whether the size of the network, i.e., the number of nodes \$n\$, is known or not. In the former setting, we present a new Leader Election protocol that improves over previous work by lowering message complexity and making it close to a lower bound by a factor in \$$\backslash$widetildeO($\backslash$sqrtt\_mix$\backslash$sqrt$\backslash$Phi)\$, where $\Phi$ is the conductance and \textsubscriptmix is the mixing time of the network graph. We then show that lacking the network size no Leader Election algorithm can guarantee that the election is final with constant probability, even with unbounded communication. Hence, we further classify the problem as Leader Election (the classic one, requiring knowledge of \$n\$ - as is our first protocol) or Revocable Leader Election, and present a new polynomial time and message complexity Revocable Leader Election algorithm in the setting without knowledge of network size. We analyze time and message complexity of our protocols in the CONGEST model of communication.

As networks continue to grow in complexity using wired and wireless technologies, efficient testing solutions should accommodate such changes and growth. Network simulators provide a network-independent environment to provide different types of network testing. This paper is motivated by the observation that, in many cases in the literature, the success of developed network protocols is very sensitive to the initial conditions and assumptions of the testing scenarios. Network services are deployed in complex environments; results of testing and simulation can vary from one environment to another and sometimes in the same environment at different times. Our goal is to propose mutation-based integration testing that can be deployed with network protocols and serve as Built-in Tests (BiT).This paper proposes an integrated mutation testing framework to achieve systematic test cases' generation for different scenario types. Scenario description and variables' setting should be consistent with the protocol specification and the simulation environment. We focused on creating test cases for critical scenarios rather than preliminary or simplified scenarios. This will help users to report confident simulation results and provide credible protocol analysis. The criticality is defined as a combination of network performance metrics and critical functions' coverage. The proposed solution is experimentally proved to obtain accurate evaluation results with less testing effort by generating high-quality testing scenarios. Generated test scenarios will serve as BiTs for the network simulator. The quality of the test scenarios is evaluated from three perspectives: (i) code coverage, (ii) mutation score and (iii) testing effort. In this work, we implemented the testing framework in NS2, but it can be extended to any other simulation environment.

We revisit Physical-Layer Network Coding (PLNC) and the reasons preventing it from becoming a staple in wireless networks. We identify its strong coupling to the Two-Way Relay Channel (TWRC) as key among them due to its requiring crossing traffic flows and two-hop node coordination. We introduce SE-PLNC, a Source-Encoded PLNC scheme that is traffic pattern independent and involves coordination only among one-hop neighbors, making it significantly more practical to adopt PLNC in multi-hop wireless networks. To accomplish this, SE-PLNC introduces three innovations: it combines bit-level with physical-level network coding, it shifts most of the coding burden from the relay to the source of the PLNC scheme, and it leverages multi-path relaying opportunities available to a particular traffic flow. We evaluate SE-PLNC using theoretical analysis, proof-of-concept implementation on a Universal Software Radio Peripherals (USRP) testbed, and simulations. The theoretical analysis shows the scalability of SE-PLNC and its efficiency in large ad-hoc networks while the testbed experiments its real-life feasibility. Large-scale simulations show that TWRC PLNC barely boosts network throughput while SE-PLNC improves it by over 30%.

When cellular networks collapse (e.g. due to disaster scenarios), it is vital to quickly establish new communication channels. The worldwide spread of smartphones, which support multiple communication standards, offers a great potential to solve this problem with commodity hardware. On the software side, Disruption-tolerant Network technologies may be leveraged to transmit messages between devices, even if there is no direct connection between them. However, DTNs are vulnerable to black-hole attacks. Therefore, mechanisms have to be available to address this problem in order to provide reliable networks. In this paper, we present a concept for an ad-hoc smartphone-based DTN which is robust against packet drop attacks as network nodes are able to identify attackers and exclude them from the network. The overall concept has been practically evaluated using an implementation for the Android platform. Our results show that the approach is capable to mitigate black-hole attacks effectively with high detection rate and short convergency time.

Vehicular Ad-hoc Networks (VANETs) are a subset of Mobile Ad-hoc Networks (MANETs). They are deployed to introduce the ability of inter-communication among vehicles in order to guarantee safety and provide services for people while driving. VANETs are exposed to many types of attacks like denial of service, spoofing, ID disclosure and Sybil attacks. In this paper, a novel lightweight approach for preventing Sybil attack in VANETs is proposed. The presented protocol scheme uses symmetric key encryption and authentication between Road Side Units (RSUs) and vehicles on the road so that no malicious vehicle could gain more than one identity inside the network. This protocol does not need managers for Road Side Units (RSUs) or Certification Authority (CA) and uses minimum amount of messages exchanged with RSU making the scheme efficient and effective.

In ad-hoc networks, data messages are transmitted from a source wireless node to a destination one along a wireless multihop transmission route consisting of a sequence of intermediate wireless nodes. Each intermediate wireless node forwards data messages to its next-hop wireless node. Here, a wireless signal carrying the data message is broadcasted by using an omni antenna and it is not difficult for a eavesdropper wireless node to overhear the wireless signal to get the data message. Some researches show that it is useful to transmit noise wireless signal which collide to the data message wireless signal in order for interfering the overhearing. However, some special devices such as directional antennas and/or high computation power for complicated signal processing are required. For wireless multihop networks with huge number of wireless nodes, small and cheap wireless nodes are mandatory for construction of the network. This paper proposes the method for interfering the overhearing by the eavesdropper wireless nodes where routing protocol and data message transmission protocol with cooperative noise signal transmissions by 1-hop and 2-hop neighbor wireless nodes of each intermediate wireless node.

Mobile users access location services from a location based server. While doing so, the user's privacy is at risk. The server has access to all details about the user. Example the recently visited places, the type of information he accesses. We have presented synergetic technique to safeguard location privacy of users accessing location-based services via mobile devices. Mobile devices have a capability to form ad-hoc networks to hide a user's identity and position. The user who requires the service is the query originator and who requests the service on behalf of query originator is the query sender. The query originator selects the query sender with equal probability which leads to anonymity in the network. The location revealed to the location service provider is a rectangle instead of exact co-ordinate. In this paper we have simulated the mobile network and shown the results for cloaking area sizes and performance against the variation in the density of users.