Emerging Communications Landscape
Over the last three decades, mobile communication networks have undergone significant revolutionary development. The 5G mobile network is already implemented in most parts of the world. Approximately 65 % of the world's population is expected to access the 5G network by the end of 2025 . The continuous progress of the 5G mobile communication system is constantly revealing significant restrictions to this network. Its original principle was to empower the Internet of Everything (IoE). However, due to limited capacity, the 5G system is unable to achieve a fully intelligent and automated network that enables IoE as a service . Several emerging applications and sectors have rapidly grown to include virtual augmented reality (VAR), three-dimensional (3D) media, AI, machine-to-machine (M2M) and Brain to Machine (B2M) communications, enhanced mobile broadband (eMBB), etc. These developments require Tbps-data rate and ultra-low latency, which cannot be met even with the new frequency bands of the 5G system. The increase in industrial automation and the transition from Industry 4.0 to Industry X.0 will further increase massive connectivity far beyond the specifications that 5G was originally planned for. Increased connection density will further raise the demand for enhanced energy efficiency, which is not possible in 5G.

Washington has already started to sketch out the 6G battle lines. US telecommunications standards developer known as ATIS (Alliance for Telecommunications Industry Solutions) launched the Next G Alliance (NGA) in October 2020 to “advance North American leadership in 6G.

Global mobile data traffic is expected to increase by 55 % per year between 2020 and 2030 . The anticipated traffic growth will generate 5,016 exabytes (EBs) of monthly data by 2030. The rapid deve lopment of da t a - c entri c and automated systems may eventually overtake the capacity of 5G and existing mobile networks. 5G will reach its limit by 2030, prompting the development of new paradigms to overcome the challenges in previous mobile network generations. The 6G infrastructure will be extremely complicated due to massive connectivity. As far as military applications are concerned - gathering intelligence, visualizing combat operations, and delivering precise logistical support have been identified to be fit areas for 6G intervention. The US and China have commenced exploring the potential of 6G technolog y and its vastly superior bandwidth, extremely low latency, and high connectivity properties and expect that the future of combat will be autonomous (based on Internet of Military Things,IoMT) and reliant on data driven AI for modernised militaries.

6G Technologies: Features and Promises
To meet the 6G targets, overcome the limitations of 5G and support new challenges, mobile communication systems in 5G and beyond must be enhanced with new and sophisticated features. The features of 6G mobile technology go beyond the intelligence, reliability, scalability, and security of ground mobile networks. They will empower satellite and undersea communication integration to form a ubiquitous mobile network, in line with the need to have a truly global wireless network presence . The 6G mobile network is expected to attain high practical standards that meet the performance requirements of IoE, VAR, 3D applications, AI, M2M and B2M communications, eMBB and their supplementary technological directions. It is expected that the 6G network will provide a 100x increment in energy and volume tri c spe c tr a l e ffic i enc y compared to the 5G network. The 6G network will enhance the 5G system lag by introduc ing a nove l s e t of technologies that include: a THz-band operating system, ubiquitous AI, massive networkaut omation , intelligent network environments, ambient backscatter communication, internet of space things (IoST), massive Multiple Input Multiple Output (MIMO) cellular networks, and human-to-human (H2H) and Brain-to-Machine (B2M) communication . Three upcoming features are also expected to change future mobile networks, but they will not be mature enough for 6G. These features are quantum communications, the internet of nano things (IoNT), and the internet of bio-nano things (IoBNT) .

The 6G target is to provide global cove rage. AI applications will distinguish 6G from previous generations. Although it is still in its early stages, the autonomous 6G network is expected to serve as the backbone of 6G technology. High transmission rates are indicated by the THz frequency. Because of 6G, latency will be in the range of 10–100 µs, connectivity density will be in the range of 10 million devices/km2, and traffic capacity will be in the range of 1 Gb/s/m2. Spectrum efficiency and energy efficiency will exponentially increase compared to 5G. 6G promises an unlimited wireless connection. It will be a communication network that will host numeroussystemssuchas communication, metering, storage, computing, control, Global Positioning System (GPS), radar, imaging, and navigation.

The Playground for 6G Technologies
To understand the importance of 6G technology, it is relevant to examine where 6G will be used. In addition to phones, it is estimated that the density of mobile communication devices will increase. Higher quality devices, such as wearable devices, integ rated headsets, and implantable sensors require more advanced environmental conditions, and these conditions are only available in 6G. 6G technology will be effective in undeveloped rural areas as well as in busy and developed cities. This largescale communication network will be enabled by terrestrial, airborne, and satellite communications. 6G technology must participate in Industry 4.0. Building and factory automation, production, e-health, transportation, agriculture, surveillance, and smart networks all require 6G for enhanced reliability, latency, and broad bandwidth. Another contribution of the 6G generation will be the transfer of the five senses (taste, smell, touch, vision, and hearing) to users. This transfer will include a neurological process that will be made possible thanks to wireless brain-computer interactions. The system, known as the braincomputer interface (BCI), will be used to establish a connection between the brain and other devices connected to this system. AI, virtual reality, 3D media, and IoE-based systems are based on 6G. 6G will be much more secure than current generations. The defence industry will also benefit from 6G technology since high data rates in wireless connections are required for UAVs. Submarines are also included in the concept of global coverage. This is crucial since most of the world is covered by water.

Geopolitics of 6G: The Next Tech Race
Washington has already started to sketch out the 6G battle lines. US telecommunications standards developer known as ATIS (Alliance for Telecommunications Industry Solutions) launched the Next G Alliance (NGA) in October 2020 to “advance North American leadership in 6G.” The alliance's members include technology giants like Apple Inc, AT&T Inc, Qualcomm Inc, Google and Samsung Electronics Co. The alliance reflects the way the world has been fractured into opposing camps as a result of 5G rivalry. The US has demonstrated that it has the ability to seriously handicap Chinese companies, as in the case of ZTE, which almost collapsed after the Commerce Department banned it for three months in 2018 from buying American technology. Japan, Australia, Sweden and the UK which are part of NGA have shut out Huawei from their 5G networks which hampers Huawei's 6G ambitions. But, Huawei is welcomed in Russia, the Philippines, Thailand, and other countries in Africa and the Middle East.

In December 2020, the European Union also unveiled a 6G wireless project led by Nokia, which includes companies like Ericsson AB and Telefonica SA, as well as universities. Notwithstanding the above developments, as of Aug 2021 the state of patent applications filed are given in Figure above.

The Ministry of Communications in India has evolved a Bharat 6G Vision Document in March 2023 highlighting how India can realize its mission of becoming a global leader in this field. The Technology Innovations Group has set up six task forces to explore the major pillars of the 6G Vision. These task forces will look into their respective areas covering Multi-platform Next Generation Networks, 6G Spectrum, 6G Devices, International Standard Contribution and R&D Finance. The Bharat 6G mission is divided into two phases: Phase 1 (2023-25) and Phase 2 (2025-2030). In Phase 1, support will be provided to explorative ideas, risky pathways, and proof-of-concept tests. Further, ideas and concepts that show promise and potential for acceptance by the global peer community will be adequately supported to develop them to completion, establish their use cases and benefits, and create implementation IPs and testbeds leadingto commercialization as part of Phase 2.

Way Ahead
The 6G in THz fr equency spectrumrange will support a large numberof promising applications as computing power concurrently grows to approach the processing power of the human brain. Many applications of THz wireless will enable novel cognition,sensing, imaging, communications, and positioning capabilities that will be used by automated machinery, autonomous cars, and new human interfaces, all enabled by the ultra-wide bandwidth and ultra-short wavelength at THz which appears to be a promising spectrum forfuture wireless communications. Simult aneous imaging and sensing with location capabilities may be enabled by the move to above 100 GHz. THz positioning will support centimetre level accuracy and may also support imaging, even in non - line of sight ( N L O S ) environments. Challenges such as power-efficient devices, cost-effective integrated circuit solutions, and practical phased arrays that may be interconnected with minimal loss loom as impediments to 6G and THz product development, and offer open research and development problems that are being investigated by DARPA and other global research agencies. Today, the most important limitation that must be addressed is the economic factor. A global technological revolution such as 6G can be defined as a high-scale, costly business. 6G technology can be cost efficient if integrated with the 5G infrastructure. Making neutral hosting and location-based spectrum licensing would possibly reduce the total cost by 50 %.