Jesus Alonso-Zarate

Is the Random Access Channel of LTE and LTE-A Suitable for M2M Communications? A Survey of Alternatives

The 3GPP has raised the need to revisit the design of next generations of cellular networks in order to make them capable and efficient to provide M2M services. One of the key challenges that has been identified is the need to enhance the operation of the random access channel of LTE and LTE-A. The current mechanism to request access to the system is known to suffer from congestion and overloading in the presence of a huge number of devices. For this reason, different research groups around the globe are working towards the design of more efficient ways of managing the access to these networks in such circumstances. This paper aims to provide a survey of the alternatives that have been proposed over the last years to improve the operation of the random access channel of LTE and LTE-A. A comprehensive discussion of the different alternatives is provided, identifying strengths and weaknesses of each one of them, while drawing future trends to steer the efforts over the same shooting line. In addition, while existing literature has been focused on the performance in terms of delay, the energy efficiency of the access mechanism of LTE will play a key role in the deployment of M2M networks. For this reason, a comprehensive performance evaluation of the energy efficiency of the random access mechanism of LTE is provided in this paper. The aim of this computer-based simulation study is to set a baseline performance upon which new and more energy-efficient mechanisms can be designed in the near future.

Challenges of massive access in highly dense LTE-advanced networks with machine-to-machine communications

Machine-to-machine wireless systems are being standardized to provide ubiquitous connectivity between machines without the need for human intervention. A natural concern of cellular operators and service providers is the impact that these machine type communications will have on current human type communications. Given the exponential growth of machine type communication traffic, it is of utmost importance to ensure that current voice and data traffic is not jeopardized. This article investigates the limits of machine type communication traffic coexisting with human communication traffic in LTE-A networks, such that human customer churn is minimized. We show that under proper design, the outage probability of human communication is marginally impacted whilst duty cycle and access delay of machine type communications are reasonably bounded to ensure viable M2M operations.

Persistent RCSMA: A MAC Protocol for a Distributed Cooperative ARQ Scheme in Wireless Networks

The persistent relay carrier sensing multiple access (PRCSMA) protocol is presented in this paper as a novel medium access control (MAC) protocol that allows for the execution of a distributed cooperative automatic retransmission request (ARQ) scheme in IEEE 802.11 wireless networks. The underlying idea of the PRCSMA protocol is to modify the basic rules of the IEEE 802.11 MAC protocol to execute a distributed cooperative ARQ scheme in wireless networks in order to enhance their performance and to extend coverage. A closed formulation of the distributed cooperative ARQ average packet transmission delay in a saturated network is derived in the paper. The analytical equations are then used to evaluate the performance of the protocol under different network configurations. Both the accuracy of the analysis and the performance evaluation of the protocol are supported and validated through computer simulations.

Device-to-device communications and small cells: enabling spectrum reuse for dense networks

In the evolution of communication networks, there has always been a need to increase the capacity to cope with the continuous growing demand for data transmission. However, with the arrival of the Internet-of-Things and the commoditization of broadband access through smartphones, tablets, smart-watches, and all types of connecting devices, future networks must be capable of providing higher bandwidth and Quality of Experience, as wellas operating in dense networks with a massive number of simultaneous connections. This high number of connections will be very heterogeneous, spanning from highly-demanding data rate applications to low-complexity and high energy-efficient Machine-to-Machine communications. In such a dense and complex scenario, a more flexible use of spectrum resources is deemed to be the way to meet the growing requirements for data transmission. In particular, this article focuses on Device-to-Device communications and small cell deployments as emerging facilitators of such a demanding and heterogeneous scenario. The pros and cons of both complementary strategies are identified from both a technical and a business point of view, and main standardization activities are discussed. The aim of this article is to identify and describe open challenges and to inspire new areas for research that make viable the next generation of dense networks.

A near-optimum cross-layered distributed queuing protocol for wireless LAN

Distributed queuing collision avoidance (DQCA) is a distributed MAC protocol for WLAN systems that offers near optimum performance. The protocol implements a reservation scheme that ensures collision-free data transmissions for high traffic load and switches smoothly and automatically to a random access mechanism when the traffic load is light, improving the delay performance for this situation. In this article the DQCA protocol operation is thoroughly described, and its algorithm rules are given. Furthermore, an enhanced cross-layer scheduling mechanism is also proposed for inclusion in the protocol procedure. This mechanism employs a virtual priority function to reschedule transmissions according to a cross-layer design. Two possible configurations are described in this article by including a PHY-MAC dialog involving channel stale information and the waiting time of the packets in the system, offering a trade-off between throughput maximization and fairness. The performance in terms of throughput and mean delay of DQCA and the two cross-layer schemes has been evaluated through simulations, and a significant enhancement over legacy IEEE 802.11 operation is achieved. The obtained results emphasize the advantages of the proposed schemes and the importance of cross-layer design in wireless communication systems.

Machine-to-machine: An emerging communication paradigm

In recent years, the number of networked machines and/or devices, such as those encountered in automatic meter readers, smart plants, vending machines or in remote monitoring applications, has dramatically increased. As a result, we have witnessed the emergence of the so-called machine-to-machine (M2M) communication paradigm. M2M devices are often characterised by very modest data rates, low mobility and stringent cost and energy efficiency requirements, along with the need to communicate over a wide area. Besides, in the coming years, M2M devices are expected to significantly outnumber voice and (often bandwidth-hungry) data terminals. All this entails a major redesign of future (low power) wireless and cellular networks, which were originally conceived with human-to-human communications in mind. This opens a wide research area for M2M communications, including investigations on scalability, wide area coverage, energy efficiency, spectral efficiency, heterogeneity, cooperation, security and inter-networking architectures. To this end, the European Telecommunication Standards Institute’s M2M Technical Committee has proposed a hybrid architecture whereby cellular-enabled gateways can act as traffic aggregation and protocol translation points for their capillary (i.e. wireless sensor) networks. Capillary networks, in turn, are composed of a potentially high number of devices (namely, sensors and actuators) equipped with short-range radio interfaces, often compliant with IEEE802.15.4 and IEEE 802.11-related standards. Current standardisation activities in Third Generation Partnership Project (3GPP) encompass a number of optimisations specifically addressing machine-type communication needs. Moreover, IP for smart objects is assembling a protocol stack from standards being finalised at the IEEE and IETF. This special issue aims at gathering recent advances in the areas of advanced M2M communication systems, and technologies, with the perspective of current M2M-related standardisation activities in 3GPP, ETSI, IEEE, IETF and IP for smart objects. In addition to the submissions from the open call, we invited authors of a number of selected papers from the International Workshop on M2M Communications held in conjunction with IEEE Globecom’12 (Anaheim, CA), and the International Workshop on M2M Communication Technologies and Systems (Wuxi, China) to produce extended versions of their manuscripts. After extensive and careful reviews of the numerous manuscripts we received, we accepted eight papers that, in our opinion, bear the highest quality and the best fit with the topic of this Special Issue. The accepted papers address three main research areas: random access and scheduling, energy consumption and energy efficiency, and architectural aspects. The first group of papers report on recent advances on random access and scheduling methods for Machine-Type Communications (MTC). In their contribution, Thomsen, Pratas, Stefanovic and Popovski investigate a novel random access method, inspired in that of LTE, which significantly increases the amount of contention resources without increasing system resources, such as contention sub-frames and preambles. This, as it is shown in the paper, enables a massive support of MTC users that is beyond the reach of current systems. Complementarily, Gerasimenko, Petrov, Galinina and Andreev analyse the impact of MTC on the performance of random access channels in a 3GPP LTE-advanced context. To that aim, the authors propose a novel evaluation methodology, fully compatible with the 3GPP test cases, to analyse, on the one hand, the performance of RACH channels in overloaded MTC scenarios and, on the other, that of regular MTC operation. Both energy consumption and latency aspects are explicitly taken into account in this work. Still in a context of LTE/LTE-A cellular networks, Gotsis, Lioumpas and Alexiou focus on time-controlled scheduling strategies to support diverse M2M traffic characteristics and quality of service requirements. First, the authors propose analytical models to predict system performance in scenarios with multiple traffic classes and diverse quality of service requirements. Then, they modify an existing scheduling algorithm to improve the performance of low priority M2M device groups. Finally, the proposed scheme is validated through extensive system-level simulations. The applicability of compressed sensing techniques for joint detection of sensor node activity and transmitted data is the main research topic addressed in the paper by Bockelmann, Schepker and Dekorsy. Such an approach facilitates the design of low overhead communication schemes not requiring additional control signaling for resource allocation and management. Computer simulation results reveal that activity detection and, in particular, the missed detection rate (rather than false alarm rate) determines the performance of the overall system. The next group of papers revolve around energy consumption and energy efficiency aspects. Specifically, Bartoli, Hernández-Serrano, León, Kountouris and Barthel focus on authentication schemes capable of discarding non-intended and/or non-legitimate packets just after the

Performance analysis of a persistent relay carrier sensing multiple access protocol

The Persistent Relay Carrier Sensing Multiple Access (PRCSMA) has been recently presented in the literature as a novel Medium Access Control (MAC) protocol based on the IEEE 802.11 and modified to cope with the contention among the relays in a Cooperative ARQ (C-ARQ) scheme. We present in this paper a theoretical model to calculate the average cooperation delay of PRCSMA. Computer simulations have been carried out to assess the accuracy of the model.

Energy-efficiency of LTE for small data machine-to-machine communications

In this paper, we evaluate the energy-efficiency of LTE for Machine-to-Machine (M2M) communications with small data transmissions. We quantify the minimum resources that can be allocated in LTE for the uplink and we show that the energy-efficiency of the transmissions of small blocks of data strongly depends on the transmission power and the Adaptive Modulation and Coding (AMC) procedure. Indeed, when an aggressive Modulation and Coding Scheme (MCS) is used thanks to good channel quality, the energy-efficiency of LTE decreases for the transmission of small amounts of data, as the physical resource blocks are under-utilized. In addition, we propose a solution to deal with this drawback by selecting an optimal MCS and utilizing the LTE Uplink Power Control (UPC) mechanism. The results presented in this paper are based on open-source ns-3 computer-based simulations.

Cellular Communications for Smart Grid Neighborhood Area Networks: A Survey

This paper surveys the literature related to the evolution of cellular communications as a key enabling technology for fundamental operations of smart grid neighborhood area networks (NANs). The latest releases of the LTE standard, representing the recent advancements in cellular technology, offer significant benefits to the modernization of the aging power distribution grid compared with other communication technologies. However, since LTE was not originally designed for smart grid applications, important challenges remain unsolved before it can efficiently support advanced NAN functionalities. This survey identifies the limitations of LTE and provides a comprehensive review of the most relevant proposed architectural and protocol enhancements for the communication infrastructure associated with smart grid NANs that can be found in the literature to date. As device-to-device (D2D) communications in LTE standards are a promising technology for reducing delay and boost reliability, this paper dwells on the potential gains that can be achieved by enabling direct communication using cellular networks, and also discusses in detail LTE-D2D applicability in representative NAN use cases in the power distribution grid. We conclude by stating open issues and providing research directions for future research in the field. This paper constitutes the first comprehensive survey of proposed LTE-enhancement and D2D solutions for smart grid NANs.

Converged wireless networking and optimization for next generation services

The Next Generation Network (NGN) vision is tending towards the convergence of internet and mobile services providing the impetus for new market opportunities in combining the appealing services of internet with the roaming capability of mobile networks. However, this convergence does not go far enough, and with the emergence of new coexistence scenarios, there is a clear need to evolve the current architecture to provide cost-effective end-to-end communication. The LOOP project, a EUREKA-CELTIC driven initiative, is one piece in the jigsaw by helping European industry to sustain a leading role in telecommunications and manufacturing of high-value products and machinery by delivering pioneering converged wireless networking solutions that can be successfully demonstrated. This paper provides an overview of the LOOP project and the key achievements that have been tunneled into first prototypes for showcasing next generation services for operators and process manufacturers.