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Internet of Things (IoT) is pushing the Internet to the next level, bringing the number of connected devices to an unprecedented amount, creating new services and improving old services like the metering system. The advanced meter infrastructure (AMI) measures, collects and analyzes the distribution and consumption of utilities such as water, electricity, and gas, which are of vital importance for the implementation of smart cities. In this paper, we employ LoRa, which is a low power wide area network technology (LPWAN), for the communication of meter devices and network server, and we study the coexistence of two kinds of messages: regular and alarm events. Our focus is on the analysis of the alarm events, which can be characterized by emergency situations and require ultra-reliability. We investigated the feasibility of the alarms for a smart metering scenario through simulation campaigns and a mathematical model. By assigning a different spreading factor (SF) to the device depending on whether the event is regular or alarm, we assessed the system performance. We evaluate the availability, reliability, and quantity of alarms that satisfy the restricted requirements of alarms events and do not compromise the performance of regular events. The best performance for regular events at SF-7 was obtained when alarm events are allocated to SF-8, whereas the other combinations are affected for a stronger interference.

This paper analyzes the feasibility of the coexistence of telemetry and alarm messages employing Long-Range Wide-Area Network (LoRaWAN) technology in industrial environments. The regular telemetry messages come from periodic measurements from the majority of sensors while the alarm messages come from sensors whose transmissions are triggered by rarer (random) events that require highly reliable communication. To reach such a strict requirement, we propose here strategies of allocation of spreading factor, by treating alarm and regular (telemetry) messages differently. The potential of such allocation strategies has also been investigated under retransmission and diversity of gateways. Both indoor industrial plant and open-field scenarios are investigated. We compare the proposed solution with a benchmark scenario&mdash, where no alarm is considered&mdash, by using system level simulation. Our results show that it is possible to achieve high reliability with reasonably low delay for the alarm messages without significantly affecting the performance of the regular links.

Interference Alignment (IA) is a technique for mitigating the interference in wireless networks. While previous studies have mainly focused on theoretical gains and algorithms, this paper goes a step further, by assessing IA incorporated to a Coordinated Multi-Point (CoMP)-like network. IA algorithms have been well studied in terms of transmissions performance and signaling cost, albeit for fixed number of users. In the current paper we evaluate the IA technique in more realistic scenarios, in which a scheduling policy is required towards providing service for a whole population of users while the sheer number of involved channels change all the time. The IA performance is shown to be in between the joint processing and conventional transmission schemes, which are distinguished by the coordination (or the lack of it) among the transmitters. By analyzing the impact of different scheduling policies based on distances between subspaces, it is concluded that the channel gains should not be disregarded by the schedulers when trying to improve system capacity.

The paper builds up on the idea of separating, in the time dimension, between conventional uncoordinated MIMO and IA transmission. The former usually utilizes all available dimensions (antennas) to send useful information, while the latter mitigates inter-cell interference. Due to the multitude of users in cellular networks, the transmission schemes are suitable for different groups of users. Therefore, in order to take advantage of both schemes, the users are classified into two groups: one with those users that supposedly benefit from cooperation and the other with those that should not cooperate. The proposed method for grouping the users has the advantage of being based on a simple decision metric, which avoids having to calculate precoders for all different possible combinations. Since each group must apply the proper transmission scheme, a fraction of the temporal resources is dedicated to each type of transmission. An automatic reservation of the temporal resources and an adaptive adjustment of the grouping threshold for each user, which avoids having to empirically determine a single threshold, are also proposed. These proposed mechanisms are shown to provide performance gains of up to 30% over the conventional transmissions.

This chapter revisits many of the issues concerning radio resource management with a focus on the upcoming systems embodying the Coordinated Multipoint (CoMP) technology. Nowadays CoMP-based systems have attracted special attention due to their potential benefits in terms of spectral efficiency and coverage. As a part of 3GPP Long Term Evolution—Advanced, CoMP technology promises substantial improvement of the users’ experience at the expense of requiring a reliable and efficient connection among the evolved Node Bs (eNBs). If multiple users and eNBs are coordinated using a suitable technique, the concerns about interference can be greatly alleviated and, consequently, also the restrictions on sharing the radio resources. In this chapter, the grouping of users and eNBs is explored in two different occasions. First, coordinated strategies process the Channel State Information (CSI) for scheduling users in order to improve the system performance; afterwards, clustering of eNBs is described as an attractive approach to deal with the processing and signaling overheads brought by CoMP. The chapter presents an analysis of different algorithms, as well as case studies illustrating some key concepts through computer simulations.

More and more Coordinated Multi-Point (CoMP) systems are attracting interest as a means to improve the performance of conventional cellular networks, particularly thanks to the joint processing approach. However, the large amount of signaling and computer operations required deserves special attention regarding both backhaul and radio resources constraints. Partitioning the set of transmission points into clusters is likely to reduce this coordination cost, but the search for the best formations of clusters may lead to expressive further computational efforts. Herein we introduce a novel approach, the Clustering-based Assignment Algorithm (CbAA), to cluster dynamically the transmission points on the downlink in order to transmit coherently to multiple users. When compared to static clustering, the proposed CbAA provided expressive gains in terms of system spectral efficiency. Compared to state-of-the-art dynamic clustering approaches, CbAA can waive the exhaustive search over all possible formations as well as the repetitive precoder calculations during the clustering procedure.

In the context of Long Term Evolution (LTE)-Advanced, the transmission points responsible for Coordinated Multi-Point (CoMP) transmission can be arranged in a distributed way and each one can be equipped with multiple antennas. In such scenario, efficient Radio Resource Allocation (RRA) strategies are required to exploit the available spatial degrees of freedom, coordinate the resources usage and manage the interference. This work provides system-level analyses for several RRA strategies in multi-antenna CoMP systems. The results show significant benefits in terms of system spectral efficiency for different spatial transmission strategies, including the combination of spatial multiplexing and spatial diversity.

This article considers the two-way bidirectional relaying scenario, in which it is crucial to improve the transmission efficiency to make up for the extra hop in the communication. Single-antenna two-way relaying can be implemented through a Self-Interference (SI) cancellation scheme known as Bidirectional Amplification of Throughput (BAT). This paper analyzes the impact that an imperfect cancellation has on the system performance. Additionally, some insights are provided on the achievable gains when multi-antenna relay stations are employed. An extension of the BAT concept to this multi-antenna case is formulated and compared to a Zero-Forcing (ZF) approach.

This article introduces a software development framework, which amasses object-oriented programming (OOP) concepts and designed procedures, intended to systematize the implementation of link-level simulation tools. This development framework is fully implemented in C++ programming language providing modularity and reusability (improving the coding activity). This framework then constitutes remarkable tool for quickly creating link-level applications. Aiming to evaluate the applicability of this software structure, the conversational service class transmitting at 12.2 kbps and over the Wideband CDMA (WCDMA) Downlink (DL) dedicated channel (DCH) is addressed as a case-study and therefore potential benefits of utilizing such development library are identified. It is shown that the development framework provides flexibility for the software development of link-level simulators remarkably reducing the design, programming and testing stages.