14 research outputs found
Multiple Access for Massive Machine Type Communications
The internet we have known thus far has been an internet of people, as it has connected people with one another. However, these connections are forecasted to occupy only a minuscule of future communications. The internet of tomorrow is indeed: the internet of things. The Internet of Things (IoT) promises to improve all aspects of life by connecting everything to everything. An enormous amount of effort is being exerted to turn these visions into a reality. Sensors and actuators will communicate and operate in an automated fashion with no or minimal human intervention. In the current literature, these sensors and actuators are referred to as machines, and the communication amongst these machines is referred to as Machine to Machine (M2M) communication or Machine-Type Communication (MTC). As IoT requires a seamless mode of communication that is available anywhere and anytime, wireless communications will be one of the key enabling technologies for IoT. In existing wireless cellular networks, users with data to transmit first need to request channel access. All access requests are processed by a central unit that in return either grants or denies the access request. Once granted access, users' data transmissions are non-overlapping and interference free. However, as the number of IoT devices is forecasted to be in the order of hundreds of millions, if not billions, in the near future, the access channels of existing cellular networks are predicted to suffer from severe congestion and, thus, incur unpredictable latencies in the system. On the other hand, in random access, users with data to transmit will access the channel in an uncoordinated and probabilistic fashion, thus, requiring little or no signalling overhead. However, this reduction in overhead is at the expense of reliability and efficiency due to the interference caused by contending users. In most existing random access schemes, packets are lost when they experience interference from other packets transmitted over the same resources. Moreover, most existing random access schemes are best-effort schemes with almost no Quality of Service (QoS) guarantees. In this thesis, we investigate the performance of different random access schemes in different settings to resolve the problem of the massive access of IoT devices with diverse QoS guarantees. First, we take a step towards re-designing existing random access protocols such that they are more practical and more efficient. For many years, researchers have adopted the collision channel model in random access schemes: a collision is the event of two or more users transmitting over the same time-frequency resources. In the event of a collision, all the involved data is lost, and users need to retransmit their information. However, in practice, data can be recovered even in the presence of interference provided that the power of the signal is sufficiently larger than the power of the noise and the power of the interference. Based on this, we re-define the event of collision as the event of the interference power exceeding a pre-determined threshold. We propose a new analytical framework to compute the probability of packet recovery failure inspired by error control codes on graph. We optimize the random access parameters based on evolution strategies. Our results show a significant improvement in performance in terms of reliability and efficiency. Next, we focus on supporting the heterogeneous IoT applications and accommodating their diverse latency and reliability requirements in a unified access scheme. We propose a multi-stage approach where each group of applications transmits in different stages with different probabilities. We propose a new analytical framework to compute the probability of packet recovery failure for each group in each stage. We also optimize the random access parameters using evolution strategies. Our results show that our proposed scheme can outperform coordinated access schemes of existing cellular networks when the number of users is very large. Finally, we investigate random non-orthogonal multiple access schemes that are known to achieve a higher spectrum efficiency and are known to support higher loads. In our proposed scheme, user detection and channel estimation are carried out via pilot sequences that are transmitted simultaneously with the user's data. Here, a collision event is defined as the event of two or more users selecting the same pilot sequence. All collisions are regarded as interference to the remaining users. We first study the distribution of the interference power and derive its expression. Then, we use this expression to derive simple yet accurate analytical bounds on the throughput and outage probability of the proposed scheme. We consider both joint decoding as well as successive interference cancellation. We show that the proposed scheme is especially useful in the case of short packet transmission
MBMS—IP Multicast/Broadcast in 3G Networks
In this article, the Multimedia Broadcast and Multicast Service (MBMS) as standardized in 3GPP is presented. With MBMS, multicast and broadcast capabilities are introduced into cellular networks. After an introduction into MBMS technology, MBMS radio bearer realizations are presented. Different MBMS bearer services like broadcast mode, enhanced broadcast mode and multicast mode are discussed. Streaming and download services over MBMS are presented and supported media codecs are listed. Service layer components as defined in Open Mobile Alliance (OMA) are introduced. For a Mobile TV use case capacity improvements achieved by MBMS are shown. Finally, evolution of MBMS as part of 3GPP standardization is presented
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin
On delay-sensitive communication over wireless systems
This dissertation addresses some of the most important issues in delay-sensitive
communication over wireless systems and networks. Traditionally, the design of communication
networks adopts a layered framework where each layer serves as a “black
box” abstraction for higher layers. However, in the context of wireless networks with
delay-sensitive applications such as Voice over Internet Protocol (VoIP), on-line gaming,
and video conferencing, this layered architecture does not offer a complete picture.
For example, an information theoretic perspective on the physical layer typically ignores
the bursty nature of practical sources and often overlooks the role of delay in
service quality. The purpose of this dissertation is to take on a cross-disciplinary
approach to derive new fundamental limits on the performance, in terms of capacity
and delay, of wireless systems and to apply these limits to the design of practical
wireless systems that support delay-sensitive applications. To realize this goal, we
consider a number of objectives.
1. Develop an integrated methodology for the analysis of wireless systems that
support delay-sensitive applications based, in part, on large deviation theory.
2. Use this methodology to identify fundamental performance limits and to design
systems which allocate resources efficiently under stringent service requirements.
3. Analyze the performance of wireless communication networks that takes advantage of novel paradigms such as user cooperation, and multi-antenna systems.
Based on the proposed framework, we find that delay constraints significantly
influence how system resources should be allocated. Channel correlation has a major
impact on the performance of wireless communication systems. Sophisticated power
control based on the joint space of channel and buffer states are essential for delaysensitive
communications
Secure protocols for wireless availability
Since wireless networks share a communication medium, multiple transmissions
on the same channel cause interference to each other and degrade the
channel quality, much as multiple people talking at the same time make for
inefficient meetings. To avoid transmission collision, the network divides
the medium into multiple orthogonal channels (by interleaving the channel
access in frequency or time) and often uses medium access control (MAC)
to coordinate channel use. Alternatively (e.g., when the wireless users use
the same physical channel), the network users can emulate such orthogonal
channel access in processing by spreading and coding the signal. Building
on such orthogonal access technology, this dissertation studies protocols that
support the coexistence of wireless users and ensure wireless availability.
In contrast to other studies focusing on improving the overall e fficiency
of the network, I aim to achieve reliability at all times. Thus, to study the
worst-case misbehavior, I pose the problem within a security framework and
introduce an adversary who compromised the network and has insider access.
In this dissertation, I propose three schemes for wireless availability:
SimpleMAC, Ignore-False-Reservation MAC (IFR-MAC), and Redundancy
O ffset Narrow Spectrum (RONS). SimpleMAC and IFR-MAC build on MAC
protocols that utilize explicit channel coordination in control communication.
SimpleMAC counters MAC-aware adversary that uses the information being
exchanged at the MAC layer to perform a more power e fficient jamming
attack. IFR-MAC nulli ffies the proactive attack of denial-of-service injection
of false reservation control messages. Both SimpleMAC and IFR-MAC
quickly outperform the Nash equilibrium of disabling MAC and converge to
the capacity-optimal performance in worst-case failures. When the MAC
fails to coordinate channel use for orthogonal access or in a single-channel
setting (both cases of which, the attacker knows the exact frequency and time
location of the victim's channel access), RONS introduces a physical-layer, processing-based technique for interference mitigation. RONS is a narrow
spectrum technology that bypasses the spreading cost and eff ectively counters
the attacker's information-theoretically optimal strategy of correlated
jamming