Random Propagation Delay Research Articles

Normal Inverse Gaussian Approximation for Arrival Time Difference in Flow-Induced Molecular Communications

In this paper, we consider molecular communications in one-dimensional flow-induced diffusive channels with a perfectly absorbing receiver. In such channels, the random propagation delay, until the molecules are absorbed, follows an inverse Gaussian (IG) distribution and is referred to as first hitting time. Knowing the distribution for the difference of the first hitting times of two molecules is very important if the information is encoded by a limited set of molecules and the receiver exploits their arrival time and/or order. Hence, we propose a moment matching approximation by a normal IG (NIG) distribution and we derive an expression for the asymptotic tail probability. Numerical evaluations show that the NIG approximation matches very well with the exact solution obtained by numerical convolution of the IG density functions. Moreover, the asymptotic tail probability outperforms state-of-the-art tail approximations.

Performance comparison of TDMA variants for underwater acoustic sensor networks

In a network with long and random propagation delay, where sensor nodes communicate to a single receiver, there can be two variants of time division multiple access (TDMA), viz., receiver synchronized TDMA and transmitter synchronized TDMA. In receiver synchronized TDMA (RS-TDMA), the transmitter transmits according to the receiver's time slot and in transmitter synchronized TDMA (TS-TDMA), the transmitter transmits according to the transmitter's time slot.In this paper, we study RS-TDMA and TS-TDMA in the presence of distance dependent propagation delay deviation, which is one of the most important parameters for underwater wireless ad hoc networks. First we analyze RS-TDMA and TS-TDMA using discrete time Markov chain in the presence of distance dependent propagation delay deviation. Further we find the optimum parameters to get the maximum frame utilization and compare RS-TDMA and TS-TDMA with respect to arrival rate, transmission range, distance dependent propagation delay variability constant and slot size. In addition to the frame utilization we also parameterize the delay and blocking probability. Our numerical results are verified by discrete event based simulation results.

Analysis on packet resequencing for reliable network protocols

Packets are sometimes disordered in the network. Reliable protocols such as TCP require packets to be accepted, i.e., delivered to the receiving application, in the order they are transmitted at the sender. In order to do so, the receiver’s transport layer must resequence the packets with the help of a resequencing buffer. Even if the application can consume the packets infinitely fast, the packets may still be delayed for resequencing. In this paper, we model packet disordering by adding an independently and identically distributed (IID) random propagation delay to each packet and analyze the required buffer size for packet resequencing and the resequencing delay for an average packet. We demonstrate that these two quantities can be significant and show how they scale with the network bandwidth.