Radio Spectrum, Signal Processing, and Beamforming

- 5G Spectrum Bands

The U.S. economy will benefit from the establishment of a pipeline of spectrum auctions in the 3-8 GHz range. However, new spectrum allocations should meet certain criteria to maximize economic benefits. 

First, the new spectrum allocation should allow base station power limits to apply to macro coverage across the mid-band to ensure efficient use of spectrum in wide-area use cases and indoor penetration. Second, large-scale contiguous spectrum allocation is required to ensure maximum performance and global competitiveness. 

We must ensure that new allocations do not limit or limit 5G use case support and achieve the IMT-2020 performance vision.

- Radio Waves

Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications.

Radio waves can travel long distances and can penetrate buildings. Radio waves have omnidirectional antennas, i.e. antennas that can send signals in all directions. The properties of radios waves vary according to their frequencies. However, radio waves at all frequencies are prone to interference from electrical equipments like motors etc. 

Low and medium frequency radio waves can pass through obstacles and have ground propagation. However, the power diminishes rapidly depending upon the distance from the source. This attenuation in power is called the path loss. High frequency radio waves travel in straight lines and have sky propagation. However, they are affected by interferences and are affected by rains. The military communicates in the HF and VHF bands. They are also used for long distance broadcasting and FM radio. 

- Signal Processing

Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as sound, images, and scientific measurements. Signal processing techniques can be used to improve transmission, storage efficiency and subjective quality and to also emphasize or detect components of interest in a measured signal. 

Signal transmission using electronic signal processing. Transducers convert signals from other physical waveforms to electric current or voltage waveforms, which then are processed, transmitted as electromagnetic waves, received and converted by another transducer to final form. 

Connectivity in recent wireless communication is accessible anywhere because of the large footprints of both cellular and Wi-Fi networks. Yet, the broadcasting in wireless technology increases the susceptibility of signals to contemporary challenges such as interference, fading, and distortion. In addition, the energy of signals is lost because of Doppler effects and scattering caused by the obstacles in the channel. 

- The Beamforming

The beamforming is achieved via new signal processing methods. These methods involve the processing of multi-user digital signals via the special new silicon chip. The evolution of communications systems inherently relies on integrated microelectronic circuits. 

Beamforming is a powerful technique which has been widely used in signal processing, radar and sonar, biomedical, and particularly in communications. Beamforming offers a significantly improved solution to reduce the interference levels and improve the system capacity. 

In applications of beamforming in communications systems, the basic idea is to optimally process signals received over different antennas, or the signals which are to be transmitted over different paths, by adjusting the signal amplitudes and phases, to form a strong beam toward the direction of interest, and at the same time, to avoid receiving or creating interference. Both receive beamforming and transmit beamforming have been extensively studied in the literature leading to numerous innovative and interesting beamforming schemes.