What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.

What Will 5G Be

Wireless communication with unmanned aerial vehicles (UAVs) is a promising technology for future communication systems. In this paper, assuming that the UAV flies horizontally with a fixed altitude, we study energy-efficient UAV communication with a ground terminal via optimizing the UAV’s trajectory, a new design paradigm that jointly considers both the communication throughput and the UAV’s energy consumption. To this end, we first derive a theoretical model on the propulsion energy consumption of fixed-wing UAVs as a function of the UAV’s flying speed, direction, and acceleration. Based on the derived model and by ignoring the radiation and signal processing energy consumption, the energy efficiency of UAV communication is defined as the total information bits communicated normalized by the UAV propulsion energy consumed for a finite time horizon. For the case of unconstrained trajectory optimization, we show that both the rate-maximization and energy-minimization designs lead to vanishing energy efficiency and thus are energy-inefficient in general. Next, we introduce a simple circular UAV trajectory, under which the UAV’s flight radius and speed are jointly optimized to maximize the energy efficiency. Furthermore, an efficient design is proposed for maximizing the UAV’s energy efficiency with general constraints on the trajectory, including its initial/final locations and velocities, as well as minimum/maximum speed and acceleration. Numerical results show that the proposed designs achieve significantly higher energy efficiency for UAV communication as compared with other benchmark schemes.

Energy-Efficient UAV Communication With Trajectory Optimization

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Recent developments and technological advancements in wireless communication, MicroElectroMechanical Systems (MEMS) technology and integrated circuits has enabled low-power, intelligent, miniaturized, invasive/non-invasive micro and nano-technology sensor nodes strategically placed in or around the human body to be used in various applications, such as personal health monitoring. This exciting new area of research is called Wireless Body Area Networks (WBANs) and leverages the emerging IEEE 802.15.6 and IEEE 802.15.4j standards, specifically standardized for medical WBANs. The aim of WBANs is to simplify and improve speed, accuracy, and reliability of communication of sensors/actuators within, on, and in the immediate proximity of a human body. The vast scope of challenges associated with WBANs has led to numerous publications. In this paper, we survey the current state-of-art of WBANs based on the latest standards and publications. Open issues and challenges within each area are also explored as a source of inspiration towards future developments in WBANs.

Wireless Body Area Networks: A Survey

Massive multiple-input multiple-output MIMO is one of themost promising technologies for the next generation of wirelesscommunication networks because it has the potential to providegame-changing improvements in spectral efficiency SE and energyefficiency EE. This monograph summarizes many years ofresearch insights in a clear and self-contained way and providesthe reader with the necessary knowledge and mathematical toolsto carry out independent research in this area. Starting froma rigorous definition of Massive MIMO, the monograph coversthe important aspects of channel estimation, SE, EE, hardwareefficiency HE, and various practical deployment considerations.From the beginning, a very general, yet tractable, canonical systemmodel with spatial channel correlation is introduced. This modelis used to realistically assess the SE and EE, and is later extendedto also include the impact of hardware impairments. Owing tothis rigorous modeling approach, a lot of classic "wisdom" aboutMassive MIMO, based on too simplistic system models, is shownto be questionable.

https://www.nowpublishers.com/article/DownloadSummary/SIG-093

Massive MIMO Networks: Spectral, Energy, and Hardware Efficiency

Hybrid ARQ (HARQ) combines Automatic Repeat Request (ARQ) and Forward Error Correction (FEC) to exploit information from erroneous packets after retransmissions. Due to its superior reliability, HARQ became a crucial component of several important 3G and 4G systems such as Long Term Evolution (LTE) and LTE-Advanced. Although the performance advantage is very attractive, implementing HARQ is challenging with emerging high throughput communication systems. Knowing that LTE and LTE-A systems would provide Gbps or hundreds of Mbps, a straightforward implementation would require around 10 Mbit memory for a HARQ buffer. With cost and power-limited wireless terminals, the available memory size to support HARQ requires an efficient implementation. In this paper we propose a novel method to exploit the time coherence of the wireless channel in order to reduce the memory storage for HARQ. This method has been evaluated with a full LTE MIMO simulation chain. Compared to state-of-the-art solutions, we show a promising memory compression factor close to 4, whereas performance degradation is marginal.

Reduction of HARQ memory in low mobility LTE systems

Image processing for multimedia terminals and related architectures

We address the problem of IQ imbalance in OFDM radars. IQ imbalance is known to cause severe distortion in OFDM receivers, manifesting itself as interference from one side of the received spectrum to the other side and vice versa. Various methods have been designed in the wireless communications context to estimate and compensate the receiver IQ imbalance. We adopt here an approach where the radar waveform is designed to be robust against IQ imbalance. We derive an analytical criterion to achieve this robustness. We validate the effectiveness of our method with simulation results.

IQ Imbalance Robust OFDM Radar Waveform

In many joint source-channel coding applications, there is a need to assess the performance of a system on a given channel, with different combinations of channel codes What is interesting is to know some measure of the overall bit error rate, in order to design the source and/or channel codes accordingly We propose here an approximation of the bit error rate of the cascade of a linear block code and a memoryless binary channel With this approximation, both of these components can be considered in this respect as a single binary symmetric channel, with known transition probability, and can be used as such for further processing We also show some possible applications in joint source-channel coding schemes

Approximating the protection offered by a channel code in terms of bit error rate

Massive MIMO is a promising technology for 5G. While its advantages of increasing capacity and reducing output power are clear, understanding its SNR requirements in practical cases lacks sufficient theoretical support. This paper computes the relative power levels of the different signal, interference and noise terms in a Massive MIMO system using Maximum-Ratio Transmission (MRT). This brings light on the operational region of the system. The MRT operation is shown to support a maximum number of users, which is function of the selected modulation and coding scheme. The related expression also leads to a bound for other linear precoders. The impact of channel estimation is shown to be related to the number of orthogonal pilot sequences and users. When both are equal it leads to a 3 dB degradation. At system level, this model directly impacts output power requirements and hence system trade-offs when determining the number of antennas to use.

Claude Desset

Papers

Reduction of HARQ memory in low mobility LTE systems

Image processing for multimedia terminals and related architectures

IQ Imbalance Robust OFDM Radar Waveform

Approximating the protection offered by a channel code in terms of bit error rate

Signal, noise and interference power analysis in MRT-based Massive MIMO systems