Venkatesh T.G.

Massive machine type communication (mMTC) is a key use case that is expected to be supported by 5G NR. One of the key challenges in 5G NR communications for mMTC use case is to enhance the initial access procedure to overcome the problem of congestion and overloading from mMTC devices. The intermittent blockages in the mmWave frequency range of 5G further degrade the random access performance significantly. 5G NR introduces the concept of numerology where multiple types of sub-carrier spacing is allowed. To circumvent the problem of random access performance enhancement, we propose a blockage aware adaptive numerology to maximize the number of devices that can be connected to the cellular network. In this paper, the problem of selecting optimal numerology for random access is modelled as a contextual multi-arm bandit framework while taking the blockages and their mobility pattern in the cell at a given time into account. We consider the upper confidence bound (UCB) action selection method to take the uncertainty of rewards of numerologies at a given instance into account. The proposed adaptive numerology solution maximizes the number of devices joining the network per RACH occasion and also minimizes the average joining time of a device when compared to fixed numerology schemes.

Stochastic delay differential equations play an important role in modelling scientific and engineering systems. In this paper the partial differential equation satisfying the time evolution of the probability density function of the state variable governed by the stochastic delay differential equation (SDDE) with additive white noise and coloured noise perturbation is obtained under small time delay and small correlation time approximation using path integral formalism. This partial differential equation reduces to a Fokker–Planck equation for particular linear and non-linear SDDE. Fokker–Planck equation is then solved with reflecting boundary conditions to get the analytical solutions for Stationary Probability Density Function (SPDF). The analytical solutions for SPDF is compared with the SPDF obtained using simulation. Further the Mean First Passage Time (MFPT) of the bistable system is calculated for various values of time delay and noise strength and compared with that of the simulation. The MFPT for the time delayed system for the case of cubic potential driven by Gaussian and Levy noise as well as asymmetric bistable potential driven by a noise and periodic driving force has been investigated.

Simultaneous transmission and reception of data packets in Full-Duplex (FD) communication can theoretically double the system throughput. However, efficient self-interference mitigation and symbol detection at the receiver is required to realize the full potential of FD communication in practical scenarios. In this paper, we propose a constellation-based FD medium access control (MAC) protocol (C-FD) for wireless local area networks (WLAN). In the proposed C-FD MAC protocol, the node and Access Point (AP) can exchange packets simultaneously by transmitting the symbols and using different modulation schemes. The superimposed constellation diagram has been used to decode the symbols efficiently at both ends. The novel feature of the C-FD MAC protocol is that it does not require any complicated interference cancellation techniques. The analytical results for Symbol Error Rate (SER), Packet Error Rate (PER), and throughput have been derived for the symmetrical and asymmetrical FD link considering the additive white Gaussian noise (AWGN) with Rayleigh fading. The proposed C-FD MAC protocol achieves nearly twice the throughput compared to Half duplex (HD) communication without compromising the SER. The analytical results have been validated with extensive simulation.

Today, we witness an explosion in wireless networks that are accessed by high-performance mobile devices running a wide variety of demanding applications. The IEEE 802.11ad is a standard targeted at meeting these design requirements. Analytical modeling and performance evaluation is a crucial step needed for the evolution of any standard. In this paper, we model the service periods (SPs) of the IEEE 802.11ad hybrid medium access control as a special case of periodically gated queueing system (PGQS) with Bernoulli scheduling. We first state and prove some basic theorems related to the probability generating functions of the PGQS. Using these results, we derive the average delay and the delay variations (jitter) of packets belonging to SP of IEEE 802.11ad. We show that as the arrival rates increases, the delay increases linearly until the critical arrival rate, and beyond that, it becomes unbounded. Further, a practical scheme for the admission control mechanism of 802.11ad is also presented. To validate the model, analytical results are compared with simulation results.