Cloudlets are small self maintained clouds, with hotspot like deployment, to enhance the computational capabilities of the mobile devices. The limited resources of cloudlets can become heavily loaded during peak utilization. Consequently, per user available computational capacity decreases and at times mobile devices find no execution time benefit for using the cloudlet. Researchers have proposed augmenting the cloudlet resources using mobile devices; however, the proposed approaches do not consider the offered service to load ratio while using mobile device resources. In this paper, we propose easy to implement Mobile Device based Cloudlet Resource Enhancement (MobiCoRE) while ensuring that: (i) mobile device always have time benefit for its tasks submitted to the cloudlet and (ii) cloudlet induced mobile device load is a fraction of its own service requirement from the cloudlet. We map MobiCoRE on M/M/c/K queue and model the system using birth death markov chain. Given the arrival rate of λ, c cpu cores in cloudlet, maximum tasks in the cloudlet to be K and P0= f(λ, c, K, μ) be probability of having no user in cloudlet, we derive the condition 1/(P0) = (λK)/(cK-cdμK) 1000 for optimal average service time 1/μ of cloudlet such that the mobile applications have maximum benefit for using cloudlet services. We show that the optimal average service time is independent of the applications service requirement. Evaluation shows that MobiCoRE can accommodate up to 50 percent extra users when operating at optimal service time and sharing mobile resources for remaining task, compared to completing the entire user applications in cloudlet. Similarly, up to 47 percent time benefit can be achieved for mobile devices by sharing only 16 percent computational resources with the cloudlet.

Mobile Cloud Computing (MCC) extends cloud services to the resource-constrained mobile devices. Compute-intensive mobile applications can be augmented using cloud either in client/server model or through cyber foraging. However, long or permanent network disconnections due to user mobility increase the execution time and in certain cases refrain the mobile devices from getting response back for the remotely performed execution. In this paper, we propose use of process state synchronization (PSS) as a mechanism to mitigate the impact of network disconnections on the service continuity of cloud-based interactive mobile applications. To validate the PSS-based execution, we develop a mathematical model that incorporates the disconnection and synchronization intervals, and mobile device capabilities along with that of cloud. The comparison with existing mechanisms shows that PSS reduces the execution time by upto 47% for intermittent network connectivity compared to COMET and by upto 35% for optimized VM-based offloading.

Accurate modeling of the effects of interference on network capacity in two flow topologies is very critical in understanding MAC behaviors and predicting per flow throughput in general multi-hop wireless mesh networks. This understanding is helpful in designing efficient routing and spectrum decision protocols for WMNs. The existing interference models do not consider the difference between carrier sensing and transmission range while considering interfering links. In practical scenarios, links inside carrier sensing range of edge nodes of a particular link induce significantly different interference compared to links within transmission range. In this research, we have classified interference between two flow topologies on the basis of geometric location of the links within transmission and carrier sensing ranges. We have also considered the difference in MAC behavior and resulting throughput imbalances. We compute occurrence probabilities of identified categories and discuss the effect of MAC behavior on throughput imbalances. Subsequent work shall focus on interference model for multi-hop WMN based on our two-flow classification and prediction of per flow throughput in a general multi-hop WMNs.

In a typical wireless mesh network (WMN), the interfering links can broadly be classified as coordinated and non-coordinated links, depending upon the geometric relationship. It is known that compared to coordinated interference, the non-coordinated interference result in significantly lower throughput and an unfair capacity distribution amongst the links. However, identification of non-coordinated interference relationships requires that each node is aware of the precise location of its neighbours, which is impractical. In this paper, we propose a novel two-phase cluster-based channel assignment scheme (CCAS) that minimizes both non-coordinated as well as coordinated interference without requiring the nodes to be aware of the location of its neighbours. CCAS logically partitions the network into non-overlapping clusters. The links within each cluster operate on a common channel which is orthogonal to that used in neighbouring clusters, thus eliminating non-coordinated interference. The inter-cluster links are assigned channels such that any non-coordinated interference that they introduce is minimized. The second phase of CCAS minimizes the coordinated interference by exploiting the channel diversity to sub-divide each cluster into multiple interference domains, thereby increasing the capacity of individual links. Simulation-based evaluations demonstrate that CCAS can achieve twice the aggregate network goodput as compared to existing channel assignment schemes, while ensuring a fair distribution of capacity amongst the links.

The aggregate capacity of wireless mesh networks can be improved significantly by equipping each node with multiple interfaces and by using multiple channels in order to reduce the effect of interference. Efficient channel assignment is required to ensure the optimal use of the limited channels in the radio spectrum. In this paper, a cluster-based multipath topology control and channel assignment scheme (CoMTaC), is proposed, which explicitly creates a separation between the channel assignment and topology control functions, thus minimizing flow disruptions. A cluster-based approach is employed to ensure basic network connectivity. Intrinsic support for broadcasting with minimal overheads is also provided. CoMTaC also takes advantage of the inherent multiple paths that exist in a typical WMN by constructing a spanner of the network graph and using the additional node interfaces. The second phase of CoMTaC proposes a dynamic distributed channel assignment algorithm, which employs a novel interference estimation mechanism based on the average link-layer queue length within the interference domain. Partially overlapping channels are also included in the channel assignment process to enhance the network capacity. Extensive simulation based experiments have been conducted to test various parameters and the effectiveness of the proposed scheme. The experimental results show that the proposed scheme outperforms existing dynamic channel assignment schemes by a minimum of a factor of 2.

In order to fully exploit the aggregate bandwidth available in the radio spectrum, future wireless mesh networks (WMN) are expected to take advantage of multiple orthogonal channels, where the nodes have the ability to communicate with multiple neighbours simultaneously using multiple radios (NICs) over orthogonal channels. Dynamic channel assignment is critical for ensuring effective utilization of the non-overlapping channels. Several algorithms have been proposed in recent years, which aim at achieving this. However, all these schemes inherently assume that the mesh nodes are well-behaved without any malicious intentions. A recent work has exposed the vulnerabilities in channel assignment algorithms. In this paper, a mechanism is proposed to secure the channel assignment algorithms, addressing the security vulnerabilities in the existing algorithms. The proposed mechanism successfully prevents the WMN from the recently exposed attacks. The simulation based experiments show the effectiveness of the proposed solution. The experiments also show that the incurred overhead because of security is negligible.

In order to fully exploit the aggregate bandwidth available in the radio spectrum, future wireless mesh networks (WMN) are expected to take advantage of multiple orthogonal channels, with nodes having the ability to communicate with multiple neighbors simultaneously using multiple radios (NICs) over orthogonal channels. Dynamic channel assignment is critical for ensuring effective utilization of the non-overlapping channels. Several algorithms have been proposed in recent years, which aim at achieving this. However, all these schemes inherently assume that the mesh nodes are well-behaved without any malicious intentions. In this paper, we expose the vulnerabilities in channel assignment algorithms and unveil three new security attacks: Network Endo-Parasite Attack (NEPA), Channel Ecto-parasite Attack (CEPA) and low-cost ripple effect attack (LORA). These attacks can be launched with relative ease by a malicious node and can cause significant degradation in the network performance. We also evaluate the effectiveness of these attacks through simulation based experiments and briefly discuss possible solutions to counter these new threats.

Currently, denial of service (DoS) attacks remain amongst the most critical threats to Internet applications. The goal of the attacker in a DoS attack is to overwhelm a shared resource by sending a large amount of traffic thus, rendering the resource unavailable to other legitimate users. In this paper, we expose a novel contrasting category of attacks that is aimed at exploiting the adaptive behavior exhibited by several network and system protocols such as TCP. The goal of the attacker in this case is not to entirely disable the service but to inflict sufficient degradation to the service quality experienced by legitimate users. An important property of these attacks is the fact that the desired adversarial impact can be achieved by using an non-suspicious low-rate attack stream, which can easily evade detection. Further by tuning various parameters of the attack traffic stream, the attacker can inflict varying degrees of service degradation and at the same time making it extremely difficult for the victim to detect attacker presence. Our simulation based experiments validate our observations and demonstrate that an attacker can significantly degrade the performance of the TCP flows by inducing lowrate attack traffic which is co-ordinated to exploit the congestion control behavior of TCP