Sassan Iraji

Machine-type communications: current status and future perspectives toward 5G systems

Machine-type communications (MTC) enables a broad range of applications from mission- critical services to massive deployment of autonomous devices. To spread these applications widely, cellular systems are considered as a potential candidate to provide connectivity for MTC devices. The ubiquitous deployment of these systems reduces network installation cost and provides mobility support. However, based on the service functions, there are key challenges that currently hinder the broad use of cellular systems for MTC. This article provides a clear mapping between the main MTC service requirements and their associated challenges. The goal is to develop a comprehensive understanding of these challenges and the potential solutions. This study presents, in part, a roadmap from the current cellular technologies toward fully MTC-capable 5G mobile systems.

System performance of LTE and IEEE 802.11 coexisting on a shared frequency band

This paper presents the system performance analysis of 3GPP Long-Term Evolution (LTE) and IEEE 802.11 Wireless Local Area Networks (WLAN) in a situation where LTE downlink (DL) has been expanded over to unlicensed frequency band usually used by WLAN. Simple fractional bandwidth sharing mechanism is used to allow both technologies to transmit. The system performance is evaluated by means of fully dynamic network simulations.

Analysis of transmission methods for ultra-reliable communications

Fifth generation of cellular systems is expected to widely enable machine-type communications (MTC). The envisioned applications and services for MTC have diverse requirements which are not fully supported with current wireless systems. Ultra-reliable communications (URC) with low-latency is an essential feature for mission-critical applications, such as industrial automation, public safety, and vehicular safety applications. This feature guarantees a communication service with a high level of reliability. This paper investigates the feasibility and efficiency of URC over wireless links. It also analyzes the effectiveness of different transmission methods, including spatial diversity and support of hybrid automatic repeat request (HARQ). Finally, the importance of reliable feedback information is highlighted.

Performance of Low-Cost LTE Devices for Advanced Metering Infrastructure

Machine type communications (MTC) is defined as data communication among devices without the need for human interaction. With the decommissioning of legacy cellular systems, migration of MTC devices to LTE is under investigation by many operators. It is desirable that the cost of LTE MTC devices is similar to that of existing GSM devices. Several cost reduction techniques have been studied. This paper summarizes cost reduction techniques for MTC devices and examines system impacts from such devices being introduced in LTE. Performance is evaluated for the Advanced Metering Infrastructure used in smart grid. It is seen that LTE offers significant capacity for smart metering even with low-cost devices. For a system with 10 MHz bandwidth, approximately 2% of the system resource is required to support AMI in an urban deployment scenario.

Link adaptation design for ultra-reliable communications

The fifth generation (5G) of cellular networks is expected to provide connectivity for a wide range of services. This requires the network to encounter novel features. Ultra-reliable communications (URC) is one of the considered features, which provides a certain level of communication service almost all the time. This is essential in order to support mission-critical applications, such as industrial automation, public safety, and vehicular communications. This paper studies link adaptation optimization for URC, considering errors in both data and feedback channels. As the implementation of optimal link adaptation is challenging, particularly, for downlink transmissions due to the limited feedback channel, a simple link adaption scheme is also proposed. Results reveal that the performances of the proposed and optimal link adaptation schemes are close. Hence, the proposed scheme can be utilized to efficiently support URC in cellular networks.

Reducing signaling overload: Flexible capillary admission control for dense MTC over LTE networks

The increasing adoption of Machine-Type Communication (MTC) applications on existing Long Term Evolution (LTE) brings new challenges for traditional signaling mechanism and system capacity. MTC is related to high number of devices; which represents a challenge when performing control and signaling procedures required for getting resource grant, since these processes are inefficient compared to the actual resource usage for small data transmissions. Solutions based on device grouping propose a static grouping approach, which does not perform well in low load scenario. This paper introduces the notion of a flexible admission/connection that can give granular group device control to Core network. With the proposed approach devices can be grouped for a certain period of time under supervision and control of a gateway and they can be ungrouped when there is no need for grouping them together. In this way, a finer control can be achieved on prioritizing certain services and load balancing. Our simulation results demonstrate significant signaling reduction by using this simple scheme compared to conventional connection procedure.

Delay analysis of network architectures for machine-to-machine communications in LTE system

Machine-to-machine communications has emerged to provide autonomic communications for a wide variety of intelligent services and applications. Among different communication technologies available for connecting machines, cellular-based systems have gained more attention as backhaul networks due to ubiquitous coverage and mobility support. The diverse ranges of service requirements as well as machine constraints require adopting different network architectures. This paper reviews three M2M network architectures to integrate machines into the LTE system and analyzes their associated communication delays. It also presents how the appropriate networks can be selected for some machine-to-machine applications, fulfilling their latency constraints.

Data aggregation in capillary networks for machine-to-machine communications

As machine-to-machine applications using cellular systems become pervasive, it is an important concern that their deployment does not jeopardize the performance of the cellular systems. Support for a massive number of machines brings technical challenges affecting the performance of the random access channel and efficiency of radio resource allocation. Capillary networks are considered as an extensions to the cellular systems for providing large-scale connectivity. This paper proposes an aggregation scheme for capillary networks connected to the LTE network to improve their communication efficiency. A gateway, an intermediate unit between machines and the base station, aggregates packets from the machines during a predefined time, and then delivers them to the LTE network. In addition, this paper analyzes the trade-offs between random access interaction, resource allocation, and communication latency. Results reveals that accepting the extra latency for accumulating packets can significantly reduce the random access requests and the required resources for the data transmissions.

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.

Optimized transmission and resource allocation strategies for ultra-reliable communications

Fifth generation (5G) wireless systems will provide connectivity for a wide range of new applications with diverse requirements. In part, the network needs to support ultra-reliable communications with low-latency (URLLC) for mission-critical applications. For these applications, the generated data should be delivered with a limited number of transmission attempts with high success probability. This paper considers the optimal transmission and resource allocations for URLLC in cellular systems. The resource allocations are derived for the fixed and adaptive transmission attempt assignments. The analysis results reveal that both fixed and adaptive transmission assignments, applicable to automatic repeat request (ARQ) and hybrid ARQ (HARQ) schemes, can reduce the required resources compared to the equal transmission assignment.