Adaptive Backbone and Link Correlation based Data Transmission Schemes for Wireless Sensor Networks

Masteroppgave informasjons- og kommunikasjonsteknologi - Universitetet i Agder, 2015One of the main challenges faced by modern wireless sensor networks (WSN) is rapid energy depletion of individual sensor nodes. In many applications, sensor nodes are deployed in outdoor environments and it is difficult to replace or recharge node batteries. Depending on network topology and the transmission schemes implemented, certain nodes could have higher energy consumption compared with other nodes. In highly unbalanced load distributions this could lead to early total energy depletion of a critical node in the topology resulting in what is known as an energy hole in the network. Considering these factors it is vital that the transmission schemes employed in WSNs are designed to address these energy constraints. At the same time transmission schemes should be able to achieve the expected levels of reliability and latency requirements of the applications. This thesis proposes one basic scheme (BS) and an advanced scheme (AS) considering aforementioned requirements for efficient and reliable data transmissions. AS scheme would be employed if 100% reliability is required in the network while BS could be employed otherwise. The proposed schemes utilize the concept of wireless link correlation to minimize the number of transmissions and hence to reduce the energy consumption. The BS proposes 3 main components, backbone selection criteria, hop count based back-off algorithm and the selective re-transmission (SR) phase . The backbone selection method extends the ideas from connected dominating set (CDS) to achieve more balanced load distribution and the hop count based back-off algorithm aims to reduce the number of intermediate re-transmissions. In addition,the selective re-transmission (SR) helps to improve the reliability of BS. The proposed schemes are implemented along with two other transmission schemes in MATLAB based environment and extensive simulations are carried out for performance evaluation and comparison. The results show that BS and AS are capable of achieving higher level of reliability with comparatively low levels of energy consumption and number of transmissions. Furthermore, BS and AS have better performance in weak correlations than their counter parts like Collective Flooding (CF). The AS is capable of reaching 100 % reliability in all scenarios for a slightly higher energy consumption compared with BS. The results reveal also the trade off between energy consumption and reliability in a WSN. Overall, the proposed schemes could contribute towards the energy conservation of the network while providing a higher reliability when required

Priority-based initial access for URLLC traffic in massive IoT networks: Schemes and performance analysis

At a density of one million devices per square kilometer, the10’s of billions of devices, objects, and machines that form a massive Internet of things (mIoT) require ubiquitous connectivity. Among a massive number of IoT devices, a portion of them require ultra-reliable low latency communication (URLLC) provided via fifth generation (5G) networks, bringing many new challenges due to the stringent service requirements. Albeit a surge of research efforts on URLLC and mIoT, access mechanisms which include both URLLC and massive machine type communications (mMTC) have not yet been investigated in-depth. In this paper, we propose three novel schemes to facilitate priority-based initial access for mIoT/mMTC devices that require URLLC services while also considering the requirements of other mIoT/mMTC devices. Based on a long term evolution-advanced (LTEA) or 5G new radio frame structure, the proposed schemes enable device grouping based on device vicinity or/and their URLLC requirements and allocate dedicated preambles for grouped devices supported by flexible slot allocation for random access. These schemes are able not only to increase the reliability and minimize the delay of URLLC devices but also to improve the performance of all involved mIoT devices. Furthermore, we evaluate the performance of the proposed schemes through mathematical analysis as well as simulations and compare the results with the performance of both the legacy LTE-A based initial access scheme and a grant-free transmission scheme.acceptedVersio

Towards a scalable routing approach for mobile ad-hoc networks

The Internet is evolving towards a two-fold architecture that will comprise of traditional infrastructure based networks as well as emerging self organised autonomic peripheral networks. Such Internet peripheral networks are being termed as the Internet of things (IoT) whereby smart objects and devices will be connected together in a fully distributed fashion to provide ubiquitous services through pervasive networking. Mobile Ad hoc Networks (MANETs) is regarded as one of the pervasive self-organised networks that will play a major role in autonomic future internet communication. There are several well- known challenges to be addressed in order to enable MANET deployments of large islands of interconnected smart devices. Therefore, in this paper, we present a mathematical model based analysis of various well-known routing protocols for MANETs in order to determine the scalability of these protocols. This paper analyses the scalability of the routing protocols with respect to routing overhead required by approaches while also considering the packet delivery latency, which is an important Quality of Service (QoS) metric

Priority Enabled Grant-Free Access With Dynamic Slot Allocation for Heterogeneous mMTC Traffic in 5G NR Networks

Although grant-based mechanisms have been a predominant approach for wireless access for years, the additional latency required for initial handshake message exchange and the extra control overhead for packet transmissions have stimulated the emergence of grant-free (GF) transmission. GF access provides a promising mechanism for carrying low and moderate traffic with small data and fits especially well for massive machine type communications (mMTC) applications. Despite a surge of interest in GF access, how to handle heterogeneous mMTC traffic based on GF mechanisms has not been investigated in depth. In this paper, we propose a priority enabled GF access scheme which performs dynamic slot allocation in each 5G new radio subframe to devices with different priority levels on a subframe-by-subframe basis. While high priority traffic has access privilege for slot occupancy, the remaining slots in the same subframe will be allocated to low priority traffic. To evaluate the performance of the proposed scheme, we develop a two-dimensional Markov chain model which integrates these two types of traffic via a pseudo-aggregated process. Furthermore, the model is validated through simulations and the performance of the scheme is evaluated both analytically and by simulations and compared with two other GF access schemes.publishedVersio

Preamble Transmission Prediction for mMTC Bursty Traffic : A Machine Learning based Approach

Author's accepted manuscript.© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.acceptedVersio

Topology Design to Increase Network Lifetime in WSN for Graph Filtering in Consensus Processes

Graph filters, which are considered as the workhorses of graph signal analysis in the emerging field of signal processing on graphs, are useful for many applications such as distributed estimation in wireless sensor networks. Many of these tasks are based on basic distributed operators such as consensus, which are carried out by sensor devices under limited energy supply. To cope with the energy constraints, this paper focuses on designing the network topology in order to maximize the network lifetime and reduce the energy consumption when applying graph filters. The problem is a complex combinatorial problem and in this work, we propose two efficient heuristic algorithms for solving it. We show by simulations that they provide good performance in terms of the network lifetime and the total energy consumption of the filtering process.acceptedVersionnivå