Important milestones in wireless and wireline communication.
The requirement of data increases many-fold in recent years to support the newest technologies in B5G and 6G. Wireless is the last mile solution as access with an optical network as the backbone in future communication systems. Over the years in every new generation, the distance between the base station and the user is decreasing and the optical node is coming closer to the user. There are several technologies like AR/VR, AI, holographic communication, holographic telepresence, etc. are the main candidates in B5G and 6G, which are required high-speed connection with low latency. To support these services, it is almost mandatory that transmit data across the network should be smooth and seamless to provide successful communication. Providing a successful and appropriate wireless link among the users simultaneously to achieve the requirements is becoming more complex, hence challenging. The optical backbone of all wireless access networks requires supporting these user’s requirements, needs to evolve continuously with wireless network evolution. This chapter will study the evolution of both networks to understand their cooperation, alignment, and support.
- Wireless network
- Heterogeneous network
- Massive MIMO
- Cognitive radio
- Optical network
- Cognitive optical network
- Ethernet PON
Over the year, the number of connected devices (wirelessly and wired) is ever-increasing, will reach 13 billion by 2023 . To support these always-connected devices, the demand for high speed, high reliability, low-latency, low-cost, dense connectivity, different types of mobility needs, and heterogeneous connectivity is escalating, which forced the telecommunications industry to enter into a new era of the future communication network (FCN) . Furthermore, to unleash the full potential of Industry 4.0, guaranteed real-time communication between humans, robots, factory logistics, and products is a fundamental requirement . The FCN incorporates 5G and beyond 5G network, whose main objectives will be application/service-oriented, which are on-demand and highly heterogeneous in nature . To support ever-increasing devices for application-specific on-demand services, there is a strong requirement to view, design, and optimize the network from an end-to-end perspective.
To supports ever-increasing demand on requirements for different types of usage, applications, services, several technologies have been developed over the year. Table 1 describes the important milestones in both wireline and wireless communication. The development of wireline communication first started in copper and later shifted to the optical domain. In the present day, optical fiber is used in the backhaul network and copper wire is used normally in the access network. In the case of wireless communication, communication first started in the sub-GHz range and slowly it moves towards high-frequency ranges. In the latest, wireless communication is moving towards the 60–100 GHz range (mmWave communication) [4, 5].
|1876||A. G. Bell transmits the first sentence||1894||Transmission through radio demonstrated by J. C. Bose|
|1877||First long-distance telephone line||1986||Marconi demonstrates wireless telegraphy|
|1927||The first transatlantic phone call, from the US to the UK||1901||Send the signal wirelessly across the Atlantic|
|1948||Shannon published Shannon’s formula||1914||first voice communication was established over a radio|
|1956||Kapany invented the glass-coated glass rod, named Fiber||1946||The first public mobile telephone was introduced by AT&T|
|1958||LASER invented by Schawlow and Townes||1973||Motorola makes a mobile call from a handheld mobile phone|
|1960||Kao demonstrate communication through fiber||1992||GSM starts its operation|
|1970||Corning Glass produced a practical fiber||1997||IEEE releases WiFi standard|
|1973||TCP/IP protocol proposed by Kahn and Cerf||2003||Birth of WWWW|
|1977||the first live telephone traffic through fiber optics||2009||Birth of the Internet of Things|
|1992||Birth of WWW||2010||First 4G handset introduced|
|1997||Fiber optic link around the globe||2012||5G focus group created|
|2005||YouTube.com launches||2016||Coined Industry 4.0|
|2006||Cloud computing started||2016||Google unveils Google Assistant|
|2014||Demonstration of software-defined networking||2019||6G Communication coined|
To facilitate 5G capabilities (latency less than 1 ms, more than 5 Gbps data rate for high mobile user, other quality of (QoS) and quality of experience (QoE), enhanced spectral, energy and network efficiency, smart security, etc.) FCNs need to enhance existing services. To fulfill 5G and beyond 5G stringent service requirements, it is essential to have an understanding of all available resources across networks (wireless and optical), across radio-access technologies (RAT) (various frequency domain), across services (different class of services and traffic type), across emerging and disruptive technologies (internet-of-things (IoT), artificial intelligence (AI), augmented reality/virtual reality (AR/VR)), and across cloud domains, and finally different backhaul network technologies. The 5G applications categories into three main domains: ultra-reliable low latency communication (uRLLC), massive machine type communication (mMTC), and enhanced mobile broadband (eMBB) [6, 7]. Moving beyond 5G, 6G communication includes few disrupting technologies, such as machine learning (ML) based communication, augmented reality/virtual reality (AR/VR), holographic communication, high precision service, enhance user experience (towards 5-sense), Industry 4.0, molecular communication and more. Their specifications are futuristic, which include 5 Gbps in data rate, 25 μs in latency, new material for 5-sense experience, etc. Figure 1 provides an overview of the required specifications for three different areas in 5G communication and also in 6G communication .
2. Technology evolution over the years
In today’s telecommunication world, user access the services through different transmission media (copper, wireless, and fiber), however, backbone are predominantly optical. Most of the time, the access network is wireless, as the number of devices increases over the years due invent of IoT). In this work, users use the wireless networks for access purposes with the backbone network as optical. Figure 2 gives an idea of how the evolution of optical networks makes an impact on the wireless network. As the requirements of high data rate and low latency are increasing, the availability of optical networks (fronthaul) is coming closer to the home and access distance through wireless is decreasing. In the following, the development of technologies will be discussed in both domains.
2.1 Development of wireless network
Over the years, wireless communication evolved generation-wise, started from 1G analog to 5G digital and moving towards 6G communication. The focus of 5G and 6G technologies is to connect people, society seamlessly along with applications, services, data, and geographical area in a smart networked environment. The present wireless network is heterogeneous in terms of infrastructure (Macrocell to femtocell), spectrum usage (licensed and unlicensed, sub-GHz to THz), coverage (multi-tier), antenna (single to the massive number of antennas), cooperation (user to eNB), and power usage (mW to 100 W).
The technologies developed for supporting these heterogeneous characteristics are co-existing together. These technologies are used to serve their purpose and produce interference on other services while in use, due to this their performance is somehow limited. To enhance performance by increasing awareness and cooperation, 5G technologies proposed several new solutions. These include technologies (as shown in Figure 3) like massive multiple-input multiple-output (MIMO) for higher data rate and better coverage, coordinated multipoint transmission (CoMP) for a lower outage, distributed antenna system (DAS) for better connectivity, software-defined radio (SDR) for reconfigurability, cognitive radio (CR) for better spectrum utilization, cloud computing for better usage, software-defined network (SDN) for an optimized network, and mmWave communication for high bandwidth. These technologies differ in channel characteristics, usage specification, operational requirement, application supports, etc. The 5G communication stipulates to support a data rate of more than 5 Gbps, less than 1 ms latency for high mobility users . Several important developments in 5G wireless networks are.
Having understood these technologies of 5G wireless communication, FCN is planning to have the communication system that can achieve data rates of about 100 Tb/s high speed, low latency, and reliable communications are essential for supporting ML/AI at the edge; giving rise to the research field entitled Communication over machine learning. Incorporation of holographic telepresence, holographic communication, virtual reality, and augmented reality in future communication, boost the requirement of wireless communication .
2.2 Development of optical network
In the present network scenario, the data generated by the wireless devices are transported through an optical network. In general, optical fiber is connected between wireless base stations (BSs/eNB), and their controlling, switching, and monitoring centers. Due to the enormous available bandwidth, the optical fiber can carry data up to 100 Tbps for networking in the optical network. By using appropriate technology, the capacity can be increased further. Similar to the evolution of the wireless network, the optical networks also evolved generation-wise. During the process of evolution, the optical network incorporated optical cross-connect (OXC), a synchronous digital hierarchy (SDH) /synchronous optical network (SONET) rings, optical add-drop multiplexers (OADMs), Software-defined network/network function virtualization (SDN/NFV). Today’s long-haul backbone networks of 10/40 Gbps wavelength channels use wavelength-division multiplexing (WDM) transmission systems. Further increase in capacity, the optical network uses a dense WDM (DWDM) frequency grid (12.5, 25, 50, and 100 GHz by G.694.1). Further development of WDM transmission systems makes the system an adaptable DWDM grid.
CWDM combines multiple optical signals at various wavelengths for transmission in optical fiber cables. Up to 18 channels are allowed to be connected over a dark fiber pair. Unlike 0.4 nm spacing for DWDM, CWDM systems have channels at wavelengths spaced 20 nanometers (nm) apart. CWDM works well in two prominent wavelength regions, 1310 nm, and 1550 nm.
TWDM is a WDM technique, where TDMA is applied to a set of wavelengths instead of just one wavelength. It requires strict coordination with the radio equipment to guarantee low latency, as with TDMA and provides more bandwidth than TDMA. In a passive optical network (PON), TWDM can be used as an alternative for transmitting 5G traffic .
3. Performance requirement for end-to-end services
Nowadays, end-to-end performance is based on customer experience. As the data is sent over a heterogeneous network combination of wireless and wired (as shown in Figure 4), passing through several autonomous systems. These are operated by the same or different operators, which are using various networking technologies. These connections are inter-technical, inter-national, and inter-continental. Thus end-to-end performance is measured by the quality of experience (QoE) along with other metrics like quality of service (QoS), quality of resilience (QoR), quality of transmission (QoT), etc.
QoS/QoE parameters are different for different applications. Varies in latency, connectivity, data rate, etc. QoE evaluation by the user depends on several independent factors, such as service type, user profile (details of user personal information), type of equipment, type of content or service pricing policy (free, paid), screen size, etc. QoE is influenced not only by QoS but also by the grade of service (GoS) and QoR, as shown in Figure 5. The most popular measure of QoE is based on the Mean Opinion Score (MOS) .
User experience varied QoE while using the service from a different operator. At the technology level, operators are launching new services, which can work with virtualized, software-based, cloud-native, and more agile networks. In general, customer’s QoS/QoE needs to be monitored across physical. In virtualized networks, this becomes even more critical where services will be activated in real-time and need to be tested, fulfilled, and assured in an automated fashion.
The specification of 5G communication is different for different applications, like M2M, high broadband, and uRLLC. All these applications have different requirements (see Figure 2). Apart from these, in 6G communication, several new applications have been proposed, such as holographic telepresence, AR/VR, etc. The transmission requirements of these applications are quite futuristic in terms of data rate, latency, and BER. Thus, maintaining QoE in FCN will be very complex and challenging, as there are different types of CoS asking for separate GoS working in various environments, policies, and networks.
4. Behavior of evolved wireless technologies with corresponding evolved optical techniques to satisfy user QoE
In the present day, users require appropriate supports from the network infrastructure as per the service usages. In general, users are connected to the network through wireless access and the wireless access point is connected to the optical fronthaul node. Depending on the application, the user required variable BW, the latency of wireless access to satisfy its QoE. Optical network technologies will play an important role in addressing these requirements within the radio access network (RAN). Through the deployed network technologies, such as backhaul networks, metro networks, and PONs, etc., optical networks continuously support their QoS. The optical network used an eCPRI fronthaul interface to support the 5G specification. For example, eCPRI of 100 Gb/s supports a 5G system of 200 MHz BW (below 6 GHz frequency) with 64 (8X8) antenna arrays. It can also support mmWave communication of 400 MHz radio bandwidth in 60 GHz frequency range with 256 (16x16) radiating elements by 400–800 Gb/s capacity [21, 22].
Every component of the optical network participated in the data transports and consumes energy. The CAPEX amount is more at the beginning, however, usage of massive MIMO along with small cells in dense networks can impact more on OPEX. Usage of NFV decreases the OPEX costs by reducing the conventional purposed hardware, installation, and up-grading for new services and Virtual network functions (VNF) are virtualized tasks implemented by the NFV platform, providing security, load balancing, and other EPC functions . A WDM transmitter/receiver (TX/RX) pair at the interface between each link provides regenerated signals at each wavelength for injection in the next link of the system. Energy consumption exists at many levels in optical transmission systems, from inefficiencies at the device level in optical amplifier pump lasers and their cooling systems, at the circuit level in the tradeoff of efficiency for speed in high-speed electronic circuits used in transmitters and receivers, and at the system level in terms of multiplexing and management overheads [34, 35].
This chapter provides an overview of telecommunication networks while considering both wireless and optical networks. The technologies in both the networks were evolved in such that they can assist each other for better performance of users and network as a whole. The chapter provides an overview of the main technologies in 5G and analyses how the optical network technologies are beneficial and cooperative to wireless technologies.