288,850 research outputs found
Scheduling process for the M2M communications system in smart cites
The development of Machine-to-Machine communications systems has been increasing recently, especially considering that they have a wide range of applications in smart cities and the Internet of Things (IoT). However, with the massive number of connected devices in such applications, the problem of message collision becomes a vital factor that significantly affects the reliability of the M2M systems. The research project employs the Weightless-N type M2M communications technology as a case study to focus on the collision problem and to develop an improved scheduling process to mitigate this problem. The Weightless-N utilises a special technique to send multi-copies of the message on different frequencies, which increases the probability of receiving the message correctly. A better performance has been achieved by developing a new frequency selection process, which provides a lower number of collisions than the standard technique for the same number of message copies
SymbioCity: Smart Cities for Smarter Networks
The "Smart City" (SC) concept revolves around the idea of embodying
cutting-edge ICT solutions in the very fabric of future cities, in order to
offer new and better services to citizens while lowering the city management
costs, both in monetary, social, and environmental terms. In this framework,
communication technologies are perceived as subservient to the SC services,
providing the means to collect and process the data needed to make the services
function. In this paper, we propose a new vision in which technology and SC
services are designed to take advantage of each other in a symbiotic manner.
According to this new paradigm, which we call "SymbioCity", SC services can
indeed be exploited to improve the performance of the same communication
systems that provide them with data. Suggestive examples of this symbiotic
ecosystem are discussed in the paper. The dissertation is then substantiated in
a proof-of-concept case study, where we show how the traffic monitoring service
provided by the London Smart City initiative can be used to predict the density
of users in a certain zone and optimize the cellular service in that area.Comment: 14 pages, submitted for publication to ETT Transactions on Emerging
Telecommunications Technologie
A Scalable Hybrid MAC Protocol for Massive M2M Networks
In Machine to Machine (M2M) networks, a robust Medium Access Control (MAC)
protocol is crucial to enable numerous machine-type devices to concurrently
access the channel. Most literatures focus on developing simplex (reservation
or contention based)MAC protocols which cannot provide a scalable solution for
M2M networks with large number of devices. In this paper, a frame-based Hybrid
MAC scheme, which consists of a contention period and a transmission period, is
proposed for M2M networks. In the proposed scheme, the devices firstly contend
the transmission opportunities during the contention period, only the
successful devices will be assigned a time slot for transmission during the
transmission period. To balance the tradeoff between the contention and
transmission period in each frame, an optimization problem is formulated to
maximize the system throughput by finding the optimal contending probability
during contention period and optimal number of devices that can transmit during
transmission period. A practical hybrid MAC protocol is designed to implement
the proposed scheme. The analytical and simulation results demonstrate the
effectiveness of the proposed Hybrid MAC protocol
Assessing and augmenting SCADA cyber security: a survey of techniques
SCADA systems monitor and control critical infrastructures of national importance such as power generation and distribution, water supply, transportation networks, and manufacturing facilities. The pervasiveness, miniaturisations and declining costs of internet connectivity have transformed these systems from strictly isolated to highly interconnected networks. The connectivity provides immense benefits such as reliability, scalability and remote connectivity, but at the same time exposes an otherwise isolated and secure system, to global cyber security threats. This inevitable transformation to highly connected systems thus necessitates effective security safeguards to be in place as any compromise or downtime of SCADA systems can have severe economic, safety and security ramifications. One way to ensure vital asset protection is to adopt a viewpoint similar to an attacker to determine weaknesses and loopholes in defences. Such mind sets help to identify and fix potential breaches before their exploitation. This paper surveys tools and techniques to uncover SCADA system vulnerabilities. A comprehensive review of the selected approaches is provided along with their applicability
Probabilistic Rateless Multiple Access for Machine-to-Machine Communication
Future machine to machine (M2M) communications need to support a massive
number of devices communicating with each other with little or no human
intervention. Random access techniques were originally proposed to enable M2M
multiple access, but suffer from severe congestion and access delay in an M2M
system with a large number of devices. In this paper, we propose a novel
multiple access scheme for M2M communications based on the capacity-approaching
analog fountain code to efficiently minimize the access delay and satisfy the
delay requirement for each device. This is achieved by allowing M2M devices to
transmit at the same time on the same channel in an optimal probabilistic
manner based on their individual delay requirements. Simulation results show
that the proposed scheme achieves a near optimal rate performance and at the
same time guarantees the delay requirements of the devices. We further propose
a simple random access strategy and characterized the required overhead.
Simulation results show the proposed approach significantly outperforms the
existing random access schemes currently used in long term evolution advanced
(LTE-A) standard in terms of the access delay.Comment: Accepted to Publish in IEEE Transactions on Wireless Communication
- …