Evolution Of Mobile Radio Communication Fundamentals Pdf
Our wireless communication system has changed significantly since the first wireless network was created over four decades ago. When the first generation mobile network was introduced in the early 1980s, the demand for more connections worldwide grew, leading to the rapid evolution of mobile communication.
Evolution Of Mobile Radio Communication Fundamentals Pdf
The second generation in the evolution of wireless communication introduced a new digital technology known as Global System for Mobile communication (GSM), which became the standard in future generations of wireless communication.
3G mobile communication enabled the global popularity of smartphones. Specific applications were developed to utilize newer capabilities, such as multimedia chat, email, video calling, social media and mobile games.
As the latest stage in the evolution of mobile communication, 5G addresses one of the biggest challenges of wireless technology: latency, or the time it takes for an amount of data to be transmitted from one point to another.
Mobile radio or mobiles refer to wireless communications systems and devices which are based on radio frequencies(using commonly UHF or VHF frequencies), and where the path of communications is movable on either end. There are a variety of views about what constitutes mobile equipment. For US licensing purposes, mobiles may include hand-carried, (sometimes called portable), equipment. An obsolete term is radiophone.[a]
A sales person or radio repair shop would understand the word mobile to mean vehicle-mounted: a transmitter-receiver (transceiver) used for radio communications from a vehicle. Mobile radios are mounted to a motor vehicle usually with the microphone and control panel in reach of the driver. In the US, such a device is typically powered by the host vehicle's 12 Volt electrical system.
Some mobile radios are mounted in aircraft (aeronautical mobile), shipboard (maritime mobile), on motorcycles, or railroad locomotives. Power may vary with each platform. For example, a mobile radio installed in a locomotive would run off of 72 or 30 Volt DC power. A large ship with 117 V AC power might have a base station mounted on the ship's bridge.
Early users of mobile radio equipment included transportation and government. These systems used one-way broadcasting instead of two-way conversations. Railroads used medium frequency range (MF) communications (similar to the AM broadcast band) to improve safety. Instead of hanging out of a locomotive cab and grabbing train orders while rolling past a station, voice communications with rolling trains became possible. Radios linked the caboose with the locomotive cab. Early police radio systems were initially one way using MF frequencies above the AM broadcast band, (1.7 MHz). Some early systems talked back to dispatch on a 30-50 MHz link, (called crossband).
One of the major challenges in early mobile radio technology was that of converting the six or twelve volt power supply of the vehicle to the high voltage needed to operate the vacuum tubes in the radio. Early tube-type radios used dynamotors - essentially a six or twelve volt motor that turned a generator to provide the high voltages required by the vacuum tubes. Some early mobile radios were the size of a suitcase or had separate boxes for the transmitter and receiver. As time went on, power supply technology evolved to use first electromechanical vibrators, then solid-state power supplies to provide high voltage for the vacuum tubes. These circuits, called "inverters", changed the 6 or 12 V direct current (DC) to alternating current (AC) which could be passed through a transformer to make high voltage. The power supply then rectified this high voltage to make the high voltage DC required for the vacuum tubes, (called valves in British English). The power supplies needed to power vacuum tube radios resulted in a common trait of tube-type mobile radios: their heavy weight due to the iron-core transformers in the power supplies. These high voltage power supplies were inefficient, and the filaments of the vacuum tubes added to current demands, taxing vehicle electrical systems. Sometimes, a generator or alternator upgrade was needed to support the current required for a tube-type mobile radio.
Custom design for a particular customer is a thing of the past. Modern mobile radio equipment is "feature rich". A mobile radio may have 100 or more channels, be microprocessor controlled and have built-in options such as unit ID. A computer and software is typically required to program the features and channels of the mobile radio. Menus of options may be several levels deep and offer a complicated array of possibilities. Some mobile radios have alphanumeric displays that translate channel numbers (F1, F2) to a phrase more meaningful to the user, such as "Providence Base", "Boston Base", etc. Radios are now designed with a myriad of features to preclude the need for custom design. For example, Hytera's HM68X mobile radio, which was introduced in September 2022, offers a variety of features, including GPS location, emergency alarm, noise cancellation, and more.
Commercial and professional mobile radios are often purchased from an equipment supplier or dealer whose staff will install the equipment into the user's vehicles. Large fleet users may buy radios directly from an equipment manufacturer and may even employ their own technical staff for installation and maintenance.
A modern mobile radio consists of a radio transceiver, housed in a single box, and a microphone with a push-to-talk button. Each installation would also have a vehicle-mounted antenna connected to the transceiver by a coaxial cable. Some models may have an external, separate speaker which can be positioned and oriented facing the driver to overcome ambient road noise present when driving. The installer would have to locate this equipment in a way that does not interfere with the vehicle's sun roof, electronic engine management system, vehicle stability computer, or air bags.
Some mobile radios use noise-canceling microphones or headsets. At speeds over 100 MPH, the ambient road and wind noise can make radio communications difficult to understand. For example, California Highway Patrol mobile radios have noise-canceling microphones which reduce road and siren noise heard by the dispatcher. Most fire engines and radios in heavy equipment use noise-canceling headsets. These protect the occupant's hearing and reduce background noise in the transmitted audio. Noise-canceling microphones require the operator speak directly into the front of the microphone. Hole arrays in the back of the microphone pick up ambient noise. This is applied, out-of-phase, to the back of the microphone, effectively reducing or canceling any sound which is present both in front and back of the microphone. Ideally, only the voice present on the front side of the microphone goes out on the air.
Mobile radio equipment is manufactured to specifications developed by the Electronic Industries Association/Telecommunications Industry Association (EIA/TIA). These specifications have been developed to help assure the user that mobile radio equipment performs as expected and to prevent the sale and distribution of inferior equipment which could degrade communications.
A mobile radio must have an associated antenna. The most common antennas are stainless steel wire or rod whips which protrude vertically from the vehicle. Physics defines the antenna length: length relates to frequency and cannot be arbitrarily lengthened or shortened (more likely) by the end user. The standard "quarter wave" antenna in the 25-50 MHz range can be over nine feet long. A 900 MHz antenna may be three inches long for a quarter wavelength. A transit bus may have a ruggedized antenna, which looks like a white plastic blade or fin, on its roof. Some vehicles with concealed radio installations have antennas designed to look like the original AM/FM antenna, a rearview mirror, or may be installed inside windows, or hidden on the floor pan or underside of a vehicle. Aircraft antennas look like blades or fins, the size and shape being determined by frequencies used. Microwave antennas may look like flat panels on the aircraft's skin. Temporary installations may have antennas which clip on to vehicle parts or are attached to steel body parts by a strong magnet.
Though initially relatively inexpensive mobile radio system components, frequently damaged antennas can be costly to replace since they are usually not included in maintenance contracts for mobile radio fleets. Some types of vehicles in 24-hour use, with stiff suspensions, tall heights, or rough diesel engine idle vibrations may damage antennas quickly. The location and type of antenna can affect system performance drastically. Large fleets usually test a few vehicles before making a commitment to a certain antenna location or type.
Dispatch-reliant services, such as tow cars or ambulances, may have several radios in each vehicle. For example, tow cars may have one radio for towing company communications and a second for emergency road service communications. Ambulances may have a similar arrangement with one radio for government emergency medical services dispatch and one for company dispatch.
Both tow cars and ambulances may have an additional radio which transmits and receives to support a mobile data terminal. A data terminal radio allows data communications to take place over the separate radio. In the same way that a facsimile machine has a separate phone line, this means data and voice communication can take place simultaneously over a separate radio. Early Federal Express (FedEx) radio systems used a single radio for data and voice. The radio had a request-to-speak button which, when acknowledged, allowed voice communication to the dispatch center.
Each radio works over a single band of frequencies. If a tow car company had a frequency on the same band as its auto club, a single radio with scanning might be employed for both systems. Since a mobile radio typically works on a single frequency band, multiple radios may be required in cases where communications take place over systems on more than one frequency band. 041b061a72