The forthcoming 6G technology represents the next evolution in wireless communication, poised to deliver unparalleled speed, capacity, and reduced latency. Building upon the advancements of 5G, 6G will introduce innovative capabilities, ushering in a new era of applications and services. While 5G networks utilize a blend of sub-6 GHz and millimeter wave frequencies, along with cutting-edge technologies like massive MIMO, beamforming, and network slicing to provide high speeds and ultra-reliable low-latency communication, challenges such as spectrum scarcity, energy efficiency, and coverage persist. The primary objective of 6G is to surmount these challenges, pushing the boundaries to achieve even higher performance standards.
In addition to enhancing current 5G applications, experts foresee that 6G will be essential for managing highly challenging scenarios, including holographic communications, expanded virtual reality (XR), extensive digital twinning, and the vast Internet of Things (IoT). These advanced applications will produce enormous data volumes, necessitate ultra-high bitrates in specific locations, and demand a level of network efficiency surpassing the capabilities of 5G. Meeting these requirements will also call for intelligence capabilities beyond what 5G currently provides, enabling real-time decision-making for large volumes of data.
A prospective attribute of upcoming 6G networks involves leveraging the radio spectrum not only for communication but also for sensing purposes. Joint communications and sensing entail a novel paradigm wherein radio hardware and software can concurrently engage in both sensing and communication tasks. Possible applications encompass traffic surveillance and passive object localization, environmental monitoring coupled with human activity/presence detection, and the monitoring of falls along with blood glucose levels.
Reconfigurable Intelligent Surfaces (RIS)
RIS represents groundbreaking techniques that enable the manipulation of the wireless channel, providing exceptionally reliable coverage and superior communication quality. In traditional wireless systems, the propagation environment is considered fixed, and the aim is to optimize communication performance by adjusting transmission schemes and parameters to overcome the challenges posed by the predetermined channel.
The scenario where direct line-of-sight communication between a base station (BS) and user equipment (UE) is obstructed by a building. In such cases, reconfigurable intelligent surfaces (RIS) offer an alternative path for signal transmission.
RIS are flat surfaces composed of reflecting elements with the capability to independently and passively influence the phase of the reflected signal. Through programmable elements, RIS can dynamically alter the wireless channel by adjusting the phase shifts of numerous reflector elements on a surface or antenna array. This active control enables the communication system to manipulate the radio environment, selectively enhancing or eliminating specific signal propagation directions and suppressing interference.
A lofty objective within the realm of 6G is achieving data rates in the range of hundreds of Gbps. The pursuit of such extreme data rates presents various challenges, particularly in connection with heightened power consumption and the utilization of higher carrier frequencies
To attain these extraordinary data rates, a signal bandwidth in the tens of GHz range becomes imperative, even with high spectral efficiency. Consequently, the carrier frequency must venture into the upper mmWave spectrum, surpassing 100 GHz. Higher frequencies pose a significant challenge in terms of RF propagation, primarily due to increased attenuation. Addressing this, the development of new channel models for upper mmWave and sub-THz bands is essential. However, crafting these models based on the conventional stochastic approach used for lower frequencies is intricate. Ray tracing models, proven effective at 60 GHz, offer promising predictive capabilities at higher frequencies, especially for beamforming—a crucial technique in overcoming range limitations.
In the realm of data converters, power consumption rises linearly with the sampling frequency and exponentially with the bit resolution. Coping with increased power consumption stemming from wider bandwidths may necessitate the reengineering of digital-to-analog converters (DAC) and analog-to-digital converters (ADC), potentially involving a reduction in bit resolution.
With data rates surpassing the clock rate for Digital Signal Processing (DSP) circuits, there arises a demand for innovative DSP algorithm designs capable of efficiently processing massively parallel data streams.
Non-Terrestrial Networks (NTNs)
NTNs are anticipated to play a pivotal role in meeting the service availability, continuity, and scalability demands of forthcoming 6G applications. These networks involve non-terrestrial vehicles like commercial drones, high-altitude platforms (HAPs), and satellites functioning as sky-based base stations, either supplementing or partially replacing existing terrestrial networks. By offering coverage and services ubiquitously, NTNs are poised to facilitate crucial applications such as emergency response in the aftermath of natural disasters that disrupt cellular network infrastructure. Additionally, NTNs aim to achieve universal connectivity, thereby addressing the digital divide. Recognizing the significance of NTNs, the 3rd Generation Partnership Project (3GPP) has acknowledged their potential for NR in 5G and has initiated an NTN work item for 3GPP Rel-17 in 2019, with further items identified for Rel-18 and Rel-19.