Tuomas Tirronen

Understanding the IoT connectivity landscape: a contemporary M2M radio technology roadmap

This article addresses the market-changing phenomenon of the Internet of Things (IoT), which relies on the underlying paradigm of machine-to-machine (M2M) communications to integrate a plethora of various sensors, actuators, and smart meters across a wide spectrum of businesses. Today the M2M landscape features an extreme diversity of available connectivity solutions which, due to the enormous economic promise of the IoT, need to be harmonized across multiple industries. To this end, we comprehensively review the most prominent existing and novel M2M radio technologies, as well as share our first-hand real-world deployment experiences, with the goal to provide a unified insight into enabling M2M architectures, unique technology features, expected performance, and related standardization developments. We pay particular attention to the cellular M2M sector employing 3GPP LTE technology. This work is a systematic recollection of our many recent research, industrial, entrepreneurial, and standardization efforts within the contemporary M2M ecosystem.

Efficient small data access for machine-type communications in LTE

In this paper, we address the emerging concept of Machine-Type Communications (MTC), where unattended wireless devices send their data over the Long Term Evolution (LTE) cellular network. In particular, we emphasize that future MTC deployments are expected to feature a very large number of devices, whereas the data from a particular device may be infrequent and small. Currently, LTE is not optimized for such traffic and its data transmission schemes are not MTC-specific. To improve the efficiency of small data access, we propose a novel contention-based LTE transmission (COBALT) mechanism and evaluate its performance with both analysis and protocol-level simulations. When compared against existing alternatives, our data access scheme is demonstrated to improve network resource consumption, device energy efficiency, and mean data access delay. We conclude that COBALT has the potential for supporting massive MTC deployments based on the future releases of the LTE technology.

An overview of 3GPP enhancements on machine to machine communications

The broad connection of devices to the Internet, known as the IoT or M2M, requires lowcost power-efficient global connectivity services. New physical layer solutions, MAC procedures, and network architectures are needed to evolve the current LTE cellular systems to meet the demands of IoT services. Several steps have been taken under the 3GPP to accomplish these objectives and are included in the upcoming 3GPP LTE standards release (3GPP Release 13). In this tutorial article, we present an overview of several features included in 3GPP to accommodate the needs of M2M communications, including changes in the physical layer such as enhanced machine type communications, and new MAC and higher-layer procedures provided by extended discontinuous reception. We also briefly discuss the narrowband IoT, which is in the development stage with a target completion date of June 2016.

Analysis of PDCCH performance for M2M traffic in LTE

As Long-Term Evolution (LTE) is starting to be widely deployed, the volume of machine-to-machine (M2M) traffic is increasing very rapidly. From the M2M traffic point of view, one of the issues to be addressed is the overload of the random access channel. The limitation in the physical downlink control channel (PDCCH) resources may severely constrain the number of devices that an LTE Evolved Node B (eNB) can serve. We develop a Markov model that describes the evolution of the Message 4 queue in the eNB formed by several users performing the random access procedure simultaneously, and then, we study its stability and performance. Our model explicitly takes into account the four initial steps in the random access procedure. By utilizing the model, we are able to determine the stability limit of the system, which defines the maximum throughput and the probability of failure of the random access procedure due to different causes. We observe that the sharing of the PDCCH resources between Messages 2 and 4 with different priorities makes the performance of the whole random access procedure deteriorate very rapidly near the stability limit. However, we can extend the maximum throughput and improve the overall performance by increasing the PDCCH resource size. Furthermore, we estimate the upper limit of the number of devices that can be served by an LTE eNB and determine the minimum PDCCH resource size needed to satisfy a given traffic demand.

Machine-to-machine communication with long-term evolution with reduced device energy consumption

We present a method to reduce the device battery consumption to efficiently support battery-operated machine-to-machine (M2M) communication in 3GPP long-term evolution. The long-term evolution discontinuous reception (DRX) is a key mechanism in reducing the device energy consumption, and we discuss how the traffic behaviour of machines in the Internet of things scenarios differs from the typical cellular user of today, for whom the current DRX mechanism is optimised for. We list typical transactions in M2M scenarios and discuss how the DRX operation is affected. We continue by introducing a power consumption model for M2M devices. Our assumption is that the device transmits small amounts of data in the uplink with deterministic intervals. The model takes into account the energy consumption in the active and the nonactive periods of the communication, which alternate depending on the DRX configuration. We use the model with different parameter settings referring to potential future M2M devices and identify the parameters, which contribute most to the device energy consumption. The results indicate that making the current maximum DRX cycle length longer will lead to significant gains in the energy consumption of M2M devices compared with what is possible today. Our key contributions include the discussion of the DRX mechanism in the Internet of things scenarios and the realistic assumptions for the potential of trading the responsiveness of a device for energy consumption gain with very long DRX cycles. Copyright

Reducing energy consumption of LTE devices for machine-to-machine communication

We present a method to reduce the device battery consumption to efficiently support machine-to-machine (M2M) communication in LTE. We first introduce a model for calculating energy consumption of a LTE device. We assume that the M2M device transmits small amounts of data with deterministic intervals. Our model takes into account the energy consumption in active and nonactive periods which alternate depending on the configuration of discontinuous reception (DRX). We use the model with different parameter settings referring to potential future M2M devices. The results indicate that making the current maximum DRX cycle length longer would lead to significant gains in the energy consumption of M2M devices. Thus, our key contribution is to show the potential of trading the responsiveness of a device for energy consumption gain with very long DRX cycles.

Effects of Heterogeneous Mobility on D2D- and Drone-Assisted Mission-Critical MTC in 5G

mcMTC is starting to play a central role in the industrial Internet of Things ecosystem and have the potential to create high-revenue businesses, including intelligent transportation systems, energy/ smart grid control, public safety services, and high-end wearable applications. Consequently, in the 5G of wireless networks, mcMTC have imposed a wide range of requirements on the enabling technology, such as low power, high reliability, and low latency connectivity. Recognizing these challenges, the recent and ongoing releases of LTE systems incorporate support for lowcost and enhanced coverage, reduced latency, and high reliability for devices at varying levels of mobility. In this article, we examine the effects of heterogeneous user and device mobility -- produced by a mixture of various mobility patterns -- on the performance of mcMTC across three representative scenarios within a multi-connectivity 5G network. We establish that the availability of alternative connectivity options, such as D2D links and drone-assisted access, helps meet the requirements of mcMTC applications in a wide range of scenarios, including industrial automation, vehicular connectivity, and urban communications. In particular, we confirm improvements of up to 40 percent in link availability and reliability with the use of proximate connections on top of the cellular-only baseline.

Machine-to-machine communications over FiWi enhanced LTE networks : A power-saving framework and end-to-end performance

To cope with the unprecedented acceleration of machine-to-machine (M2M) services over cellular networks, this paper envisions a highly converged network architecture based on the integration of high-capacity and reliable Ethernet fiber-wireless (FiWi) access networks with flexible and cost-effective 4G long term evolution (LTE) technology to support M2M connectivity in an end-to-end fashion, i.e., from air interface to transport (backhaul) network. In such emerging architecture, energy efficiency must be addressed in a comprehensive way, in which both wireless front-end and optical backhaul segments are considered at the same time to maximize the battery life of battery-constrained M2M devices as well as reduce operational expenditures for network operators, while maintaining acceptable network performance. Toward this end, an end-to-end power-saving framework is introduced in this paper that devises a timeout driven discontinuous reception (DRX) mechanism for LTE-enabled M2M devices and a polling-based power-saving mechanism for optical network units (ONUs) to improve the overall energy efficiency. End-to-end performance in terms of energy saving and packet delay is analytically modeled based on a semi-Markov process for the front-end and an M/G/1 queue for the backhaul. The obtained results indicate that the device battery life is significantly prolonged by extending the DRX cycle, whereas the backhaul energy consumption is minimized by incorporating the ONU power-saving modes into the dynamic bandwidth allocation process of the optical backhaul.

Analyzing the overload of 3GPP LTE system by diverse classes of connected-mode MTC devices

As massive deployments of autonomous MTC devices jeopardize current mobile access networks with their excessive signaling, wireless industry is taking decisive steps to protect future technology from such overloads. Whereas efficient mechanisms for overload control of 3GPP Long Term Evolution (LTE) system are now in place when the devices are connecting to the network, we investigate the situation when the connection has already been established and a large number of devices send their meaningful data. In this paper, we intend to identify whether a surge in simultaneous transmission attempts by numerous connected-mode MTC devices actually threatens 3GPP LTE and characterize an overloaded scenario with a mixture of diverse device classes (e.g., low and high priority devices). Our approach combines both analysis and protocol-level simulations to conclude that appropriate overload control mechanisms may also be necessary for connected-mode devices.

NB-IoT Technology Overview and Experience from Cloud-RAN Implementation

The 3GPP has introduced a new narrowband radio technology called narrowband Internet of Things (NB-IoT) in Release 13. NB-IoT was designed to support very low power consumption and low-cost devices in extreme coverage conditions. NB-IoT operates in very small bandwidth and will provide connectivity to a large number of low-data-rate devices. This article highlights some of the key features introduced in NB-IoT and presents performance results from real-life experiments. The experiments were carried out using an early-standard-compliant prototype based on a software defined radio partial implementation of NB-IoT that runs on a desktop computer connected to the network. It is found that a cloud radio access network is a good candidate for NB-IoT implementation.