The invention of wireless communication technologies is one of the breakthrough discoveries of mankind. The technological advancements in the field of wireless communications are significantly visible over the past 50-60 years. Beginning with black rotary dial sets to the smart mobiles, only voice generation to generation of internet, progress in satellite communications etc has credited wireless technology for connecting people around the globe like never before.
Among various fields, cellular communications have progressed quickly in the recent past from the first generation (1G) to fourth-generation (4G) and is ready to embrace the next generation (5G) advancements. 5G is not just about data speed but rather encompasses many sub-technologies like machine-to-machine (M2M) communications, smart cities, e-health, IoT etc. Behind any breakthrough in technology, the contributions of many great minds are the backbone. There are many open challenges in the wireless field to be tackled. We at SPCRC work on cutting edge technologies in the wireless domain and is contributing significantly to the scientific community.
The existing cellular systems are deployed in the sub-3GHz spectral band, which is very much congested due to the tremendous rise in mobile users. In order to provide quality of service to all the users, researchers and communication engineers are focussing on the higher frequency spectrum. The mmWave band which is in the range around 30 to 300 GHz offers a vast amount of spectrum of which an approximate of 100 GHz spectrum is available for mobile communication use. Coupled with other technologies like Massive MIMO and femtocells, mmWaves is projected as a key solution for future 5G mobile communication. Nevertheless, some issues and challenges are yet to be addressed in order for such a system to become a reality. Following are few of the challenges:
With the mammoth rise in IoT devices and with the diminishing size of wireless devices, there is a challenge of self-reliability. That is because of small sizes batteries with limited capacity are being deployed leading to quick depletion of power stored. In certain applications, sensors and devices are often deployed at hazardous or inaccessible locations, which makes the battery replacement or recharging impossible. This could often lead to interruptions in the operation of the network. In such scenarios, transferring power to these devices wirelessly plays a significant role in prolonging the life of the sensor networks. Since most of these devices perform wireless communication, it is of practical interest to consider the transfer of energy to the device using the same electromagnetic wave that is used for communication. This technique, termed ‘simultaneous wireless information and power transmission (SWIPT)’, holds great promise in many applications. SWIPT enables the joint transfer of data and energy to the receiver, which performs both information decoding and energy harvesting simultaneously from the same received electromagnetic wave. This technique will be central to various emerging technologies and has gathered considerable attention recently. Many current and future technologies like wearable devices, sensors used in hazardous areas, 5G and beyond, etc., are expected to use SWIPT technique.
It is estimated that by 2025 number of devices connecting internet is 20 billion [ref]. But limited resources like time, frequency etc are challenging to be shared by all. Thus there is a need for effective multiple access schemes which can handle major challenges posed by next-generation requirements. Existing orthogonal multiple access (OMA) schemes like time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA) and orthogonal frequency division multiple access (OFDMA) suffers spectral inefficiency. Besides this, challenges such as ultra-low latency, connection-density requirements are difficult to be handled by OMA techniques. Hence, in order to tackle these issues NOMA with its potential features is envisaged to be a promising multiple access scheme.
Many of the most hazardous and high-paying jobs within the commercial sector are ripe for displacement by drone technology. The use cases for safe, cost-effective solutions range from data collection to delivery. These unmanned aerial marvels ignite the imaginations of people the world over — and the truth is that we are only scratching the surface of their potential. Efficient and most optimal algorithms are need of the hour for critical applications, thus paving way for a potential research problem in the domain of UAV communications.
Fully digital solutions for a multiple antenna system is costly and consumes more power. Hybrid analog/digital precoding can potentially achieve high spectral efficiencies while requiring less cost and power consumption than fully-digital solutions. This makes it an attractive candidate architecture for millimetre-wave systems, which requires deploying large antenna arrays at both the transmitter and receiver to guarantee sufficient received signal power. Most of the prior work though on hybrid precoding focuses on narrow-band channels and assumes a fully-connected hybrid architecture. Millimetre-wave systems, though, are expected to employ wideband with frequency selectivity. Hybrid precoding, a combination of analog and digital precoding, is an attempt to reach a compromise between complexity and performance. By exploiting more than one radio frequency chain, hybrid precoding enables a millimetre-wave (mmWave) system to take advantage of both spatial multiplexing and beamforming gain. A major challenge with hybrid precoding is its configuration in wideband systems because the analog beamforming weights should be the same across the entire band.
Spectrum scarcity has been a long-standing problem in wireless communication networks with a tremendous increase in the users of mobile data. Cognitive radio (CR) technology handles spectrum access dynamically and helps to solve the spectrum scarcity problem. In CR networks, secondary users (SUs) operate under a power constraint environment to limit the interference to the primary user (PN) below the permissible level. The SUs can operate when PN is inactive as well as when PN is active, but with a strict constraint on transmit power. Thus, SUs and PN can operate at the same in the same frequency band thereby improving spectral efficiency.
Other potential areas for 5G and beyond are Massive MIMO, Full Duplex Communications, femto cells, FBMC etc.
The true laboratory is the mind, where behind illusions we uncover the laws of truth.
Necessity is the cause of many inventions but the best ones are born of desire.
It is of great advantage to the student of any subject to read the original memoirs on that subject, for science is always most completely assimilated when it is in the nascent state.
When wireless is perfectly applied the whole earth will be converted into a huge brain, which in fact it is, all things being particles of a real and rhythmic whole. We shall be able to communicate with one another instantly, irrespective of distance.
One cannot escape the feeling that these mathematical formulae have an independent existence and an intelligence of their own, that they are wiser than we are, wiser even than their discoverers, that we get more out of them than was originally put into them.