Profitable Task Allocation in Mobile Cloud Computing

We propose a game theoretic framework for task allocation in mobile cloud computing that corresponds to offloading of compute tasks to a group of nearby mobile devices. Specifically, in our framework, a distributor node holds a multidimensional auction for allocating the tasks of a job among nearby mobile nodes based on their computational capabilities and also the cost of computation at these nodes, with the goal of reducing the overall job completion time. Our proposed auction also has the desired incentive compatibility property that ensures that mobile devices truthfully reveal their capabilities and costs and that those devices benefit from the task allocation. To deal with node mobility, we perform multiple auctions over adaptive time intervals. We develop a heuristic approach to dynamically find the best time intervals between auctions to minimize unnecessary auctions and the accompanying overheads. We evaluate our framework and methods using both real world and synthetic mobility traces. Our evaluation results show that our game theoretic framework improves the job completion time by a factor of 2-5 in comparison to the time taken for executing the job locally, while minimizing the number of auctions and the accompanying overheads. Our approach is also profitable for the nearby nodes that execute the distributor's tasks with these nodes receiving a compensation higher than their actual costs

Reliable multicast in multi-access wireless lans

Abstract—Multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. In this paper, we focus on multicast in single channel multi–access wireless local area networks (LANs) comprising several small cells. In such a system, a receiver cannot correctly receive a packet if two or more packets are sent to it at the same time, because the packets “collide. ” Therefore, one has to ensure that only one node sends at a time. We look at two important issues. First, we consider the problem of the sender acquiring the multi–access channel for multicast transmission. Second, for reliable multicast in each cell of the wireless LAN, we examine ARQ–based approaches. The second issue is important because the wireless link error rates can be very high. We present a new approach to overcome the problem of feedback collision in single channel multi–access wireless LANs, both for the purpose of acquiring the channel and for reliability. Our approach involves the election of one of the multicast group members (receivers) as a “leader ” or representative for the purpose of sending feedback to the sender. For reliable multicast, on erroneous reception of a packet, the leader does not send an acknowledgement, prompting a retransmission. On erroneous reception of the packet at receivers other than the leader, our protocol allows negative acknowledgements from these receivers to collide with the acknowledgement from the leader, thus destroying the acknowledgement and prompting the sender to retransmit the packet. Using analytical models, we demonstrate that the leader–based protocol exhibits higher throughput in comparison to two other protocols which use traditional delayed feedback–based probabilistic methods. Last, we present a simple scheme for leader election. I

Securing Ad Hoc Wireless Networks Against Data Injection Attacks Using

Abstract — We propose to secure ad hoc networks against data injection attacks by placing firewall functionality at strategic locations in the ad hoc network. We first show that, given the location of the attackers and the victims, the problem of placement of firewall functionality at a fixed number of ad hoc nodes while minimizing the impact of the data injection attack is identical to the k-Coverage problem [1]. This problem is known to be NP-hard. Then, we develop a near-optimal approximate algorithm for placing firewall functions. We also incorporate the loss behavior of wireless links in our algorithm. Next, we develop an architecture to determine the location of the attackers. Our architecture uses a separate control network (a cellular network in this paper) in conjunction with ad hoc networks to provide a provable attack detection mechanism. We evaluate our firewall placement algorithm for various topologies obtained from ns-2 simulations. Our results show that our algorithm can find near-optimal solutions. Based on simple analyses and measurement results, we also find that the overhead of our provable attack detection mechanism is low. I