Efficient cellular load balancing through mobility-enriched vehicular communications

Supporting effective load balancing is paramount for increasing network utilization efficiency and improving the perceivable user experience in emerging and future cellular networks. At the same time, it is becoming increasingly alarming that current communication practices lead to excessive energy wastes both at the infrastructure side and at the terminals. To address both these issues, this paper discusses an innovative communication approach enabled by the implementation of device-to-device (d2d) communication over cellular networks. The technique capitalizes on the delay tolerance of a significant portion of Internet applications and the inherent mobility of the nodes to achieve significant performance gains. For delay-tolerant messages, a mobile node can postpone message transmission—in a store–carry and forward manner—for a later time to allow the terminal to achieve communication over a shorter range or to postpone communication to when the terminal enters a cooler cell, before engaging in communication. Based on this framework, a theoretical model is introduced to study the generalized multihop d2d forwarding scheme where mobile nodes are allowed to buffer messages and carry them while in transit. Thus, a multiobjective optimization problem is introduced where both the communication cost and the varying load levels of multiple cells are to be minimized. We show that the mathematical programming model that arises can be efficiently solved in time. Furthermore, extensive numerical investigations reveal that the proposed scheme is an effective approach for both energy-efficient communication and offering significant gains in terms of load balancing in multicell topologies

Continuous Patrolling Games

The continuous patrolling game studied here was first proposed in Alpern et al. (2011), which studied a discrete time game where facilities to be protected were modeled as the nodes of a graph. Here we consider protecting roads or pipelines, modeled as the arcs of a continuous network $Q$. The Attacker chooses a point of $Q$ to attack during a chosen time interval of fixed duration (the attack time, $\alpha$). The Patroller chooses a unit speed path on $Q$ and intercepts the attack (and wins) if she visits the attacked point during the attack time interval. Solutions to the game have previously been given in certain special cases. Here, we analyze the game on arbitrary networks. Our results include the following: (i) a solution to the game for any network $Q$, as long as $\alpha$ is sufficiently short, generalizing the known solutions for circle or Eulerian networks and the network with two nodes joined by three arcs; (ii) a solution to the game for all tree networks that satisfy a condition on their extremities. We present a conjecture on the solution of the game for arbitrary trees and establish it in certain cases

Energy efficient mobile video streaming using mobility

Undeniably the support of data services over the wireless Internet is becoming increasingly challenging with the plethora of different characteristic requirements of each service type. Evidently, about half of the data traffic shifted across the Internet to date consists of multimedia content such as video clips or music files that necessitate stringent real-time constraints in playback and for which increasing volumes of data should be shifted with the introduction of higher quality content. This work recasts the problem of multimedia content delivery in the mobile Internet. We propose an optimization framework with the major tenet being that real-time playback constraints can be satisfied while at the same time enabling controlled delay tolerance in packet transmission by capitalizing on pre-fetching and data buffering. More specifically two strategies are proposed amenable for real time implementation that utilize the inherent delay tolerance of popular applications based on different flavors of HTTP streaming. The proposed mechanisms have the potential of achieving many-fold energy efficiency gains at no cost on the perceived user experience

Optimizing periodic patrols against short attacks on the line and other networks

On a given network, a Patroller and Attacker play the following win-lose game: The Patroller adopts a periodic walk on the network while the Attacker chooses a node and two consecutive periods (to attack there). The Patroller wins if he successfully intercepts the attack, that is, if he occupies the attacked node in one of the two periods of the attack. We solve this game in mixed strategies for line graphs, the first class of graphs to be solved for the periodic patrolling game. We also solve the game for arbitrary graphs when the period is even

Optimal power allocation in block fading Gaussian channels with causal CSI and secrecy constraints

The optimal power allocation that maximizes the secrecy capacity (SC) of block fading Gaussian (BF-Gaussian) networks with causal channel state information (CSI), M-block delay tolerance and a frame based power constraint is examined. In particular, the SC maximization is formulated as a dynamic program. First, the SC maximization without any information on the CSI is studied; in this case the SC is maximized by equidistribution of the power budget, denoted as the 'blind policy'. Next, extending earlier results on the capacity maximization of BF-Gaussian channels without secrecy constraints, transmission policies for the low SNR and the high SNR regimes are proposed. When the available power resources are very low the optimal strategy is a 'threshold policy'. On the other hand when the available power budget is very large a 'constant power policy' maximizes the frame secrecy capacity. Subsequently, a novel universal transmission policy is introduced, denoted in the following as the 'blind horizon approximation' (BHA), by imposing a blind policy in the horizon of unknown events. Through numerical results, the novel BHA policy is shown to outperform both the threshold and constant power policies as long as the mean channel gain of the legitimate user is distinctively greater than the mean channel gain of the eavesdropper. Furthermore, the secrecy rates achieved by the BHA compare well with the secrecy rates of the secure waterfilling policy in the case of acausal CSI feedback to the transmitter

Optimal Power Allocation in Block Fading Channels With Confidential Messages

The optimal power allocation for block fading (BF) networks with confidential messages is investigated under an $M$-block delay and power constraint. First, we study networks without channel state information (CSI) feedback to the transmitter and demonstrate that the optimal power allocation is the equidistribution of the power budget, denoted as the 'blind policy.' In blind scenarios secrecy can be achieved through receiver diversity; the probability of secrecy outage (PSO) is shown to decay exponentially with the diversity order of the legitimate user. Then, we investigate networks with CSI feedback. For comparison purposes, we restate the acausal secure waterfilling algorithm with full CSI before moving to the causal feedback scenario. In the latter, an approximate 'threshold policy' for the low SNR and an approximate 'high power policy' for the high SNR regimes are derived. Furthermore, a novel universal transmission policy is proposed across all SNRs, denoted as the 'blind horizon approximation' (BHA). Through numerical results, the BHA policy is shown to outperform both the threshold and high power policies when the legitimate user has an SNR advantage with respect to the eavesdropper, while it also compares well with the secure waterfilling policy

Patrolling a pipeline

A pipeline network can potentially be attacked at any point and at any time, but such an attack takes a known length of time. To counter this, a Patroller moves around the network at unit speed, hoping to intercept the attack while it is being carried out. This is a zero sum game between the mobile Patroller and the Attacker, which we analyze and solve in certain case

Continuous patrolling games

We study a patrolling game played on a network Q, considered as a metric space. The Attacker chooses a point of Q (not necessarily a node) to attack during a chosen time interval of xed duration. The Patroller chooses a unit speed path on Q and intercepts the attack (and wins) if she visits the attacked point during the attack time interval. This zero-sum game models the problem of protecting roads or pipelines from an adversarial attack. The payo to the maximizing Patroller is the probability that the attack is intercepted. Our results include the following: (i) a solution to the game for any network Q, as long as the time required to carry out the attack is suciently short, (ii) a solution to the game for all tree networks that satisfy a certain condition on their extremities, and (iii) a solution to the game for any attack duration for stars with one long arc and the remaining arcs equal in length. We present a conjecture on the solution of the game for arbitrary trees and establish it in certain cases