International Journal of Computer Networks and Applications

Number V-6-I-4, 2019

55 - 64
Evaluation of Optimum NPRACH Performance in NB-IoT Systems

Authors: Maha Medhat, Khaled ElShafey, Ali Rashed

Abstract

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Narrowband-internet of Things (NB-IoT) is a low power wide area network that contributes strongly to the revolution and expansion of the internet of things (IoT). Here, we aim at improving the performance and reliability of NB-IOT. Given than random access is one of the most influential characteristics of NB-IoT system performance, a detailed study of the NB-IOT random access was conducted, taking into account random access channel (NPRACH) periodicity, number of collisions, number of users, random access preamble repetitions and time taken for all system users to finalize a random access procedure. Simulation results have shown that appropriately choosing NPRACH periodicity values can efficiently achieve uplink channel optimization between its two signals NPRACH and NPUSCH with an acceptable number of collisions and a high number of delivered packets. Short periodicities (40ms and 80ms) show optimal results in reducing the number of collisions for both low and high traffic while all users win NPRACH and start to send data to the base station after approximately 2 second. However, short periodicities waste more uplink resources in random access, minimizing resources remaining for data transmission. Medium-length periodicities (such as 160ms and 320ms) show a promising performance that balances the two uplink physical channels. Our results demonstrate that doubling the number of users (from 40 to 80) is not a considerable factor in choosing NPRACH periodicity with different repetition values. We further showed how to maximize the system performance by selecting certain NPRACH periodicity value for every preamble repetition scheme.

65 - 72
Lane Id based Selective Emergency Message Forwarding Scheme for VANET

Authors: Getamesay Haile, Dereje Yohannes, Kebebew Ababu

Abstract

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Number of views: 192

In this paper we proposed a novel emergency message forwarding scheme for VANET (Vehicular Ad-hoc Network) which can capable of tackling broadcast storm problem by reducing unwanted network traffic. Safety application of VANET by its nature is time critical and it needs low delay and needs to be disseminated on time. So applying broadcasting technique is the best option in safety application for VANET. But applying simple broadcasting causes broadcast storm problem due to high number of unwanted network traffic. Unwanted network traffic happens when the number of nodes to rebroadcast the emergency message is increased. The numbers of forwarder node to re-transmit the emergency message have high effect on the network. So, one of the solution to reduce unwanted traffic is applying selective forwarding scheme to broadcast emergency message and minimize the number of forwarder node which rebroadcast the emergency message. The aim of this paper is to design lane Id based selective emergency message forwarding scheme (LSEMF) which can minimize the number of forwarder node without affecting the notified vehicles with high data delivery ratio and low overhead. The proposed forwarding scheme is a multi-hop selective forwarding scheme in which vehicles found in the same lane with the source of emergency message and found behind the accident can have high priority to be selected as a forwarder node. To select forwarder node we combine distance, lane id and travel direction of vehicle. To simulate this work, we use SUMO simulator for generating mobility and OMNeT++ for network simulator by using Veins framework. Finally we compare our result with counter based scheme and distance based scheme. From the simulation result the proposed scheme has better performances than the existing schemes in terms of data delivery ratio, overhead and forwarder node ratio.