Sharif Digital Repository

Averaging consensus on the values of nodes in a network is a principal problem in distributed computation. In the presence of erasure channels, conventional averaging consensus algorithms may not converge to the average value if packets are erased in arbitrary order. In this paper, we propose a 'Pseudo-Synchronous Averaging Consensus' (PSAC) algorithm to guarantee averaging consensus over erasure channels by employing tagged packets. We show that the PSAC algorithm has a simple structure and it can work with just two tags '0' and '1'. In asynchronous networks, the PSAC algorithm is a synchronizer in the sense that it keeps the updates of various nodes in step with each other. By exploiting... 

In this letter, we focus on evaluating Peak Age-of-Information (PAoI) in a typical wireless link in which each packet transmission is successful with some probability. The receiver applies a hybrid ARQ (HARQ) scheme such as chase combining to decode each packet. Thus, several transmissions of the same packet lead to a sequence of strictly increasing successful packet reception probabilities. Moreover, the number of transmissions for each packet is limited. In this link, when the packets are generated randomly, we compare two queueing policies at the transmitter, i.e., blocking and preemptive. The former exploits the capability of HARQ to send the packet to the destination sooner, but the... 

This paper presents an analytical study of average delay and throughput in a two-way relay network exploiting network coding to exchange source packets, where arrival and departure of packets are stochastic. In this case, a fundamental problem for the relay node is whether to wait in order to obtain a coding opportunity, leading to reduction of the number of transmissions, or sending a packet (coded/uncoded) whenever it has a transmission opportunity, leading to reduction of the packet delay. In order to address the fundamental trade-off between packet delay and transmission power, we develop three network coding schemes based on power-delay constraint of the application. We devise a... 

In a graphene-based Josephson junction, the Andreev reflection can become specular, which gives rise to propagating Andreev modes. These propagating Andreev modes are essentially charge neutral and therefore they transfer energy but not electric charge. One main result of this work is that when the Dirac theory of graphene is deformed into a tilted Dirac cone, the breaking of charge conjugation symmetry of the Dirac equation renders the resulting Andreev modes electrically charged. We calculate an otherwise zero charge conductance arising solely from the tilt parameters ζâ -=(ζx,ζy). The distinguishing feature of such a form of charge transport from the charge transport caused by normal... 

This paper investigates the performance of epidemic routing in mobile social networks considering several communities which are frequently visited by nodes. To this end, a monolithic Stochastic Reward Net (SRN) is proposed to evaluate the delivery delay and the average number of transmissions under epidemic routing by considering skewed location visiting preferences. This model is not scalable enough, in terms of the number of nodes and frequently visited locations. In order to achieve higher scalability, the folding technique is applied to the monolithic model, and an approximate folded SRN is proposed to evaluate performance of epidemic routing. Discrete-event simulation is used to...