A Glimpse Beyond 5G in Wireless Networks

The fifth-generation (5G) technology promises to provide agile, scalable, and programmable network services in order to respond to the myriad of applications and connected devices of vertical industries. It aims to boost the network capacity, throughput, energy, and spectral efficiencies while reducing latency for sub-milliseconds. In order to fulfill the diverse requirements of industrial Internet of Things (IIoT) applications, drastic changes have been proposed by several telecommunication bodies for the radio access network (RAN) and core. In this chapter, we aim to study comprehensively the 5G architectural frameworks proposed by telecommunication bodies and standards for public and private 5G networks. Furthermore, this chapter provides an in-depth study on the key 5G enabling technologies such as software-defined network (SDN), network functions virtualization (NFV), network slicing, artificial intelligence/machine learning (AI/ML), and multi-access edge computing (MEC). Moreover, 5G simulators and projects are explored and compared considering features, advantages, and limitations.

Recently, offset quadrature amplitude modulation (OQAM) based filter bank multicarrier (FBMC), due to its reduced out-of-band (OOB) emission, has attracted significant research interests for replacing orthogonal frequency division multiplexing (OFDM) in future wireless communication systems. This chapter analyses and design FBMC-OQAM waveform based multiple-input multiple-output (MIMO) and multi-user massive MIMO systems. It begins by describing key features and differences of FBMC waveform over the widely popular OFDM waveform, followed by the discussion over key challenges in designing FBMC based MIMO and massive MIMO systems. A semi-blind (SB) channel state information (CSI) estimation scheme, which enhances the performance with a limited pilot overhead, is developed for MIMO-FBMC system along with its Cramer-Rao lower bound (CRLB) for benchmarking the performance. To compare the performance of FBMC and OFDM waveforms in the uplink transmission, the achievable sum-rates are derived for multi-user (MU) massive MIMO technology relying on FBMC waveform with maximum ratio combining (MRC) and zero-forcing (ZF) receivers. The corresponding power scaling laws for MU massive MIMO-FBMC are also found. It is shown that in practical impairments such as carrier frequency offset, massive MIMO-FBMC systems significantly outperform their OFDM counterparts.

This chapter will present cutting-edge research on full-duplex massive multi-input multi-output (MIMO) relaying, wherein multiple pairs of full-duplex users are communicating with each other via a full-duplex massive relay. It will cover critical PHY layer issues like signal transmission, reception, and processing (i.e., precoding, combining). Through numerical investigations, the spectral efficiency (SE) performance of full-duplex system will be compared with its half-duplex counterpart. The focus will be to make this chapter self-sufficient, with an aim that target audience can appreciate the content without much difficulty. This chapter content is designed keeping in mind the researchers and graduate students (BTech final year, MTech, PhD students) who desire to work in the field of 5G and beyond technologies.

The explosive growth of wireless subscribers and high data rate demanding multimedia services have pushed the fourth-generation (4G) network to improve and adapt to the emerging issues. This has led to the evolution of cutting-edge fifth-generation (5G) wireless networks. Few of the well-known techniques for boosting 5G networks are non-orthogonal multiple access (NOMA), small cell deployment (a.k.a. HetNets), millimeter-wave (mmWave) communications, intelligent reflecting surfaces (IRSs), etc. One of the basic elements of the physical layer of a wireless network is the multiple access (MA) techniques. The MA techniques deviate in each generation and have grown from frequency division multiple access, used in the first generation, to orthogonal frequency division multiple access, which is adequately accepted in the 4G network. NOMA (MA scheme that violates the criteria of orthogonality) has been considered a promising multiple access technique for the 5G networks. NOMA supports a huge number of connected users (or devices), lowers latency, and boosts spectral efficiency. Accordingly, the application of NOMA is essential in investigating the 5G network and beyond. Furthermore, NOMA is compatible with recent techniques, such as HetNets, device to device (D2D) communication, mmWave, and IRS. This integrates NOMA with the contending 5G and beyond techniques of great research interest and is presented in this chapter. This chapter introduces a scenario in which a heterogeneous cellular network (HCN) is considered with three tiers, namely, macro base station (macroBS) tier underlaid with femto base station (femtoBS) tier, and D2D tier. NOMA principle is applied in the femtoBS tier and the D2D tier, while the macroBS tier does not use NOMA. Offloading from the macroBS tier to the femtoBS tier aids in tackling congestion at the macroBS tier. The cooperation introduced using the D2D tier further supports the offloaded macro user (macroU) from the macroBS tier. This support is primarily helpful when the femtoBS tier is using NOMA, and the femtoBS tier is unable to find a pairing user for the offloaded macroU. We introduce theoretical bounds and analysis for outage probability supported by Monte Carlo simulations.

With the evolution of wireless communication technologies, the growth of data-centric multi-rate multimedia services is exponentially impeccable. As per the Cisco report by 2022, there will be 28.5 billion networked devices and connections. Out of which 12.3 billion are the mobile-ready devices and connections. It is expected that the mobile data traffic is expected to grow sevenfold over 2017 by 2022 with a growth rate of 77 exabytes per month by 2022 Forecast (Update 2017:2022, 2019). The primary concern of the data-hunger devices is the energy efficiency (Singya et al. (IEEE Open J Commun Soc 2:617–655, 2021)). Green communications is one such prominent technology to address the energy needs of the devices to comply with the standards of 5th generation (5G) and beyond communication systems in attaining the key performance indicator of 10-year battery life (Series (Recommen ITU 2083:0, 2015)). In this chapter we address the energy harvesting (EH) in terms of linear and nonlinear methods. Non-depleting resources such as radio frequency (RF) electromagnetic signals find a prominent source for the battery-dependent nodes to draw the energy while simultaneous wireless information and power transfer (SWIPT), and wired powered communication networks. We further discuss the EH implementation protocols. Next, we introduce the device-to-device (D2D) multiple-input and multiple-output (MIMO) relays along with SWIPT. We also examine the practical constraints such as feedback errors and imperfect channel state information on the system performance, and useful insights in system design are provided accordingly by considering the impacts of channel conditions, multiple antennas, and energy harvesting parameters.

In this chapter, the requirements and challenges in the design and analysis of advanced wireless communication systems for vehicular communications (from V2V to V2X) will be presented. The characteristics and challenges in wireless channel behavior will be described, from RF-mmWave to future THz frequency bands. Different types of vehicular network configurations, in terms of antenna subsystems and transceivers, will be described, as well as in relation with the impact of dense urban and urban and rural scenarios on system implementation. Examples of coverage/capacity relations for vehicular communication scenarios will be presented, based on volumetric geometric/stochastic modeling techniques. Future beyond 5G (B5G) network architectures, as the evolution of present 5G networks, and current developments will be presented. The role of the satellite segment in the future of B5G vehicular communications will be outlined.

In this chapter, we will describe the framework for IoT evolution, from current LPWAN/5G connectivity to future B5G systems, taking advantage of sub-THz (mainly in the 100–300 GHz frequency range) and THz bands (up to 10 THz). The requirements in terms of device integration, node density, interference, and energy handling will be described. Coverage/capacity estimations for different case uses within dense urban/urban/suburban settings will be presented, based on deterministic volumetric wireless channel estimation. Different application scenarios, such as the evolution of current IoT applications towards sensing networks, will be discussed, based on the description of three realistic use case scenarios.

The future wireless network aims to accommodate new forms of services arising from the large-scale inclusion of the internet of things (IoT). This inclusion of IoT and ever-increasing users will require the future network to possess higher system capacity and manage heterogeneity in the service requirement. Layer division multiplexing (LDM) is a potential technology that can enhance network capacity by taking advantage of this inherent heterogeneity of future wireless networks. This chapter presents a transmission framework where the LDM layer serves IoT-user pairs. The IoT devices are served using an LDM upper layer (UL), and the users are served using a lower layer (LL). We have developed a physical layer model incorporating LDM and tested its performance for the intended usages scenario. Both UL and LL performance show the capability to serve IoT devices and users to justify our proposed transmission scenario. Mobility management for LDM LL is a crucial challenge as it was initially developed for static receivers. Moreover, the mobility of both IoT devices and the user impacts the LDM pair sustainability. To test our system’s robustness against receiver mobility, we have developed an analytical model to test the link sustainability for LDM pairs when both receivers have different levels of mobility. We have also included massive multiple-input multiple-output transmission and beamforming in the system model, focusing on the future wireless network. For simulation, we have considered three different mobility models for both types of receivers, and link sustainability for LDM pairs belonging to different mobility groups is compared to determine the more suitable LDM pair from receiver mobility. The achieved results show that LDM can enhance the system capacity in future wireless networks.

The future 6G wireless communications will need the definition of new spectral bands and the employment of novel advanced physical layer solutions. The millimeter-wave (mmWave) frequency bands have been allocated for the fifth generation (5G) of cellular systems, while additional mmWave sub-bands have been assigned as well. The need to support higher data rates than 5G in the order of terabits per second requires more bandwidth. However, the total consecutive available bandwidth in mmWave bands is still less than 10 GHz, so such data rates cannot be supported. In this context, future 6G communication systems require the use of the terahertz communication band (0.1–10 THz). The THz band is envisioned as a critical wireless technology for meeting future demands in 5G and beyond. For several years, there has been a lack of THz transceivers and antennas, so that the THz band has become one of the electromagnetic (EM) spectrum’s least studied frequency ranges in terms of wireless communication. However, the need for 6G communication systems has redefined the requirements for THz antennas. In this book chapter, we provide a complete framework for circular polarized antenna design in the low THz band. This optimization framework is based on a swarm intelligence algorithm, namely, the salp swarm algorithm (SSA). The numerical results show that the SSA has been successfully applied in designing antenna with wide band operation and circular polarization.