SDR, DVB-T, DAB, FM, ADS-B, ETC 

SDR - Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which used to be only theoretically possible.
DVB-T  - "Digital Video Broadcasting — Terrestrial"; it is the DVBEuropean-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998.[1] This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation. It is also the format widely used worldwide (including North America) for Electronic News Gatheringfor transmission of video and audio from a mobile newsgathering vehicle to a central receive point.
DAB - Digital audio broadcasting (DAB) is a digital radio standard for broadcasting digital audio radio services, used in countries across Europe, the Middle East and Asia Pacific.The DAB standard was initiated as a European research project in the 1980s. The Norwegian Broadcasting Corporation(NRK) launched the first DAB channel in the world on 1 June 1995 (NRK Klassisk),[2] and the BBC and Swedish Radio (SR) launched their first DAB digital radio broadcasts in September 1995. DAB receivers have been available in many countries since the end of the 1990s.
DAB is more efficient in its use of spectrum than analogue FM radio, and thus may offer more radio services for the same given bandwidth. DAB is more robust with regard to noise and multipath fading for mobile listening, since DAB reception quality first degrades rapidly when the signal strength falls below a critical threshold, whereas FM reception quality degrades slowly with the decreasing signal.
The original version of DAB used the MP2 audio codec. An upgraded version of the system was released in February 2007, called DAB+, which uses the HE-AAC v2 audio codec. DAB is not forward compatible with DAB+, which means that DAB-only receivers are not able to receive DAB+ broadcasts. However, broadcasters can mix DAB and DAB+ programs inside the same transmission and so make a progressive transition to DAB+. DAB+ is approximately twice as efficient as DAB, and more robust.
FM - a method of radio broadcasting using frequency modulation(FM) technology. Invented in 1933 by American engineer Edwin Armstrong, it is used worldwide to provide high-fidelity sound over broadcast radio. FM broadcasting is capable of better sound quality than AM broadcasting, the chief competing radio broadcasting technology, so it is used for most music broadcasts. FM radio stations use the VHF frequencies. The term "FM band" describes the frequency band in a given country which is dedicated to FM broadcasting.
ADS-B -  Automatic dependent surveillance – broadcast (ADS–B) is a surveillance technology in which an aircraft determines its position via satellite navigation and periodically broadcasts it, enabling it to be tracked. The information can be received by air traffic control ground stations as a replacement for secondary radar. It can also be received by other aircraft to provide situational awareness and allow self separation.ADS–B is "automatic" in that it requires no pilot or external input. It is "dependent" in that it depends on data from the aircraft's navigation system.

ADS–B is an element of the US Next Generation Air Transportation System (NextGen), Airports Authority of India upgrade plans in line with ICAO Global Plan Initiatives and Aviation System Block Upgrade (ASBU) and the Single European Sky ATM Research (SESAR). 

​ADS–B equipment is currently mandatory in portions of Australian airspace, the United States requires some aircraft to be equipped by 2020 and the equipment will be mandatory for some aircraft in Europe from 2017. Canada is currently using ADS-B for rather limited air traffic control, mainly in the Hudson Bay area.