Anirudh Nanda RC6703B48, 3060070098 B.Tech-M.Tech(ECE) Lovely Professional University

Abstract:- off of 72- or 30-volt DC power. A large ship with 117V AC power might have a mounted on the ship's bridge. The term paper includes a brief introduction to mobile radio communication. This term paper also includes a brief mention 2.Disambiguation: Two-way versus telephone of 2 way comm’n,it’s history, the role that it plays in our everyday life with its various future advancements. It also The distinction between and two-way radio is includes a discussion of antennas , Multiple controls, becoming blurred as the two technologies merge. The microphones,data radio, Walkie talkie converters and it’s main backbone or infrastructure supporting the system defines application Professional Mobile Radio with a feature of which category or taxonomy applies. A parallel to this concept selective calling. is the convergence of computing and telephones.

1. Introduction Radiotelephones are full-duplex (simultaneous talk and listen), circuit switched, and primarily communicate with Mobile radio or mobiles refer to communications telephones connected to the public switched telephone systems and devices which are based on radio frequencies, network. The connection sets up based on the user dialing. and where the path of communications is movable on either The connection is taken down when the end button is pressed. end. There are a variety of views about what constitutes They run on telephony-based infrastructure such as AMPS or mobile equipment. For US licensing purposes, mobiles may GSM. include hand-carried, (sometimes called portable), equipment. An obsolete term is radiophone. Two-way radio is primarily a dispatch tool intended to communicate in simplex or half-duplex modes using push-to- Some mobile radios are mounted in aircraft, (aeronautical talk, and primarily intended to communicate with other radios mobile), shipboard, (maritime mobile), on motorcycles, or rather than telephones. These systems run on push-to-talk- railroad locomotives. Power may vary with each platform. For based infrastructure such as Nextel's iDEN, Specialized example, a mobile radio installed in a locomotive would run Mobile Radio (SMR), MPT-1327, Enhanced (ESMR) or conventional two-way systems. Certain modern two-way radio systems may have full-duplex To transmit a message, the PTT key must be pressed during telephone capability. talk-time to allow the voice message to be dispatched by the sending party. During this period, the sending party cannot 2.1 Mobile Radio hear or receive any incoming messages from the mobile radio. The mobile radio is a two-way communication gadget that Once the PTT button is released, the sender may hear the operates through radio frequencies. As such, the channel of response of the receiving party. information and messages in a mobile radio is variable. Used to be known as radiophone, the earlier versions of the mobile 2.3. Why do we need a mobile radio radio, were one-way communication systems used for The use of mobile radio in transportation, security, and broadcast. general operations makes communication fast, efficient and safe. It allows control centers to monitor location of vehicles Contemporary mobile radio systems can have as much as a and dispatch announcements to several receivers hundred channels and may be controlled by microprocessors. simultaneously. Additionally, the range of its area coverage is These types require the use of software to encode channels very high and is not dependent on a , which and operate their integrated functions. The mobile radio, also may fluctuate during emergency situations. known as a two-way radio system, allows the exchange of messages only with other mobile radios through push-to-talk Different types of mobile radio are portable and capable of (PTT) functions. A mobile radio also features wireless withstanding shock and severe weather conditions. Most transceivers, making mobile radios portable. Mobile radio countries impose certain requirements on the manufacture, systems may be used for communications in aircraft, ships, sale and use of two-radio systems. This helps ensure that the automobiles, and other vehicles. The power supply on which communication gadget functions according to standards and mobile radios run depend on the type of vehicle these are that its use does not interfere with other communication mounted on. systems.

A mobile radio system is composed of a transceiver and 3. History of mobile radio microphone with a push-to-talk key. It has an that links to the transceiver. Since most types of mobile radio are Early users of mobile radio equipment included transportation used in moving vehicles, where the surrounding noise can be and government. These systems used one-way broadcasting loud, some mobile radio types come with an external speaker. instead of two-way conversations. Railroads used medium Other models have headsets and microphones with noise- frequency range (MF) communications (similar to the AM reduction capabilities. broadcast band) to improve safety. Instead of hanging out of a locomotive cab and grabbing train orders while rolling past a 2.2. How does a mobile radio work? station, voice communications with rolling trains became Most mobile radios operate on a single band of frequency. possible. Radios linked the caboose with the locomotive cab. The radio transceiver contains transmit and receive Early police radio systems were initially one way using MF frequencies. Very high frequency (VHF) and ultra high frequencies above the AM broadcast band, (1.7 MHz). Some frequency (UHF) allow a mobile radio to operate on early systems talked back to dispatch on a 30-50 MHz link, maximum coverage. This means that its average operating (called crossband). range is from 150 to 470 MHz. Early mobile radios used amplitude modulation (AM) to so they could not transmit unless the vehicle ignition was on. convey intelligence through the communications channel. In Persons without a key to the vehicle could not transmit. time, problems with sources of electrical noise showed that Equipment had to be "type accepted", or technically approved, frequency modulation (FM) was superior for its ability to cope by the FCC before it could be offered for sale. In order to be with vehicle ignition and power line noise. The frequency type accepted, the radio set had to be equipped with an range used by most early radio systems, 25 to 50 MHz (vhf indicator light, usually green or yellow, that showed power "low band") is particularly susceptible to the problem of was applied and the radio was ready to transmit. Radios were electrical noise. This plus the need for more channels led to also required to have a lamp (usually red) indicating when the the eventual expansion of two-way radio communications into transmitter was on. These traits continue in the design of the VHF "high band" (150 to 174 MHz) and UHF (450 to 470 modern radios. MHz). The UHF band has since been expanded again. Early tube-type radios operated on 50 kHz channel spacing One of the major challenges in early mobile radio technology with plus-or-minus fifteen kilohertz modulation deviation. was that of converting the six or twelve volt power supply of This meant that the number of radio channels that could be the vehicle to the high voltage needed to operate the vacuum accommodated in the available radio frequency spectrum were tubes in the radio. Early tube-type radios used dynamotors - limited to a certain number, dictated by the of the essentially a six or twelve volt motor that turned a generator to signal on each channel. 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 6V or 12V direct current (DC) to alternating current (AC) which could be passed through a In the early 1970s, the California Department of Forestry transformer to make high voltage. requirement for 6-frequency transmit, 3-frequency receive, scanning, and a 5-tone burst encoder was unusual, leading to Examples of US 1950s-1960s tube-type mobile radios with no this custom-built mobile radio. transistors: Solid state equipment arrived in the 1960s, with more efficient • FMTRU-140D (dynamotor powered) circuitry and smaller size. Channel spacing narrowed to 20-30 • Motorola Twin-V, named for its "universal" 6 or 12 kHz with modulation deviation dropping to plus-or-minus five Volt power supply kilohertz. This was done to allow more radio spectrum • General Electric Progress Line (Early models without availability to accommodate the rapidly growing national "T-Power" power supply) group of two-way radio users. By the mid 1970s, tube-type • Kaar Engineering Model 501 transmitter power amplifiers had been replaced with high- power transistors. From the 1960s to the 1980s, large system The requirement that unauthorized persons be prohibited from users with specialized requirements often had custom built using the radio transmitter meant that many radios were wired radios designed for their unique systems. Systems with multiple tone encoders and more than two channels are • Motorola Astro Digital Spectra W9 unusual. Examples of US hybrid partially solid state mobile • Kenwood TK-690 radios: As use of mobile radio equipment has virtually exploded, • Motorola Motrac. channel spacing has had to be narrowed again to 12.5-15 kHz • Motorola MJ IMTS Car Telephone (1963) with modulation deviation dropping to plus-or-minus 2.5 • General Electric Transistorized Progress Line kilohertz. In order to fit into smaller, more economical • General Electric MASTR Professional and MASTR vehicles, today's radios are trending toward radically smaller Executive sizes than their tube-type ancestors. • RCA Super Carfone. 5. Description of Mobile radio comm’n

4. Mobile radio in everyday routine 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 . Some models may have an external, separate speaker which can be

Custom design for a particular customer is a thing of the past. positioned and oriented facing the driver to overcome ambient Modern mobile radio equipment is "feature rich". A mobile road noise present when driving. The installer would have to radio may have 100 or more channels, be microprocessor locate this equipment in a way that does not interfere with the controlled and have built-in options such as unit ID. A vehicle's sun roof, electronic engine management system, computer and software is typically required to program the vehicle stability computer, or air bags. features and channels of the mobile radio. Menus of options Mobile radios installed on motorcycles are subject to extreme may be several levels deep and offer a complicated array of vibration and weather. Professional equipment designed for possibilities. Some mobile radios have alphanumeric displays use on motorcycles is weather and vibration resistant. Shock that translate channel numbers (F1, F2) to a phrase more mounting systems are used to reduce the radio's exposure to meaningful to the user, such as "Providence Base", "Boston vibration imparted by the motorcycle's modal, or resonant, Base", etc. Radios are now designed with a myriad of features shaking. to preclude the need for custom design.

Mobile radio equipment is manufactured to specifications Examples of US microprocessor-controlled mobile radios: developed by the Electronics Industries Association/ Industries Association Though initially relatively inexpensive mobile radio system (EIA/TIA). These specifications have been developed to help components, frequently damaged antennas can be costly to ensure that mobile radio equipment not only performs as replace since they are usually not included in maintenance expected by the user, but also to prevent the sale and contracts for mobile radio fleets. Some types of vehicles in distribution of inferior equipment which could degrade 24-hour use, with stiff suspensions, tall heights, or rough communications. All specifications should be reviewed by diesel engine idle vibrations may damage antennas quickly. radio system engineers to ensure that appropriate equipment is The location and type of antenna can affect system used to meet the end user's needs. performance drastically. Large fleets usually test a few vehicles before making a commitment to a certain antenna 6. Antenna location or type.

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 7. Multiple radio sets antenna length: length relates to frequency and cannot be arbitrarily lengthened or shortened (more likely) by the end Dispatch-reliant services, such as tow cars or ambulances, user. The standard "quarter wave" antenna in the 25-50 MHz may have several radios in each vehicle. For example, tow range can be over nine feet long. A 900 MHz antenna may be cars may have one radio for towing company communications three inches long for a quarter wavelength. A transit bus may and a second for emergency road service communications. have a ruggedized antenna, which looks like a white plastic Ambulances may have a similar arrangement with one radio blade or fin, on its roof. Some vehicles with concealed radio for government emergency medical services dispatch and one installations have antennas designed to look like the original for company dispatch. 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 These early mobile telephone systems can be distinguished being determined by frequencies used. Microwave antennas from earlier closed systems in that they were may look like flat panels on the aircraft's skin. Temporary available as a commercial service that was part of the public installations may have antennas which clip on to vehicle parts switched telephone network, with their own telephone or are attached to steel body parts by a strong magnet. numbers, rather than part of a closed network such as a police radio or taxi dispatch system.

These mobile telephones were usually mounted in cars or trucks, though briefcase models were also made. Typically, the transceiver (transmitter-receiver) was mounted in the vehicle trunk and attached to the "head" (dial, display, and handset) mounted near the driver seat.

8. Applications 8.1 Multiple controls, microphones Intended as a cost savings, some systems employ vehicular chargers instead of a mobile radio. Each radio user is issued a walkie talkie. Each vehicle is equipped with a charger system console. The walkie talkie inserted into a vehicular charger or converter while the user is in the vehicle. The charger or converter :-

1) connects the walkie talkie to the vehicle's two-way radio antenna, 2) connects an amplified speaker,

A mobile radio in a US ambulance often has two sets of 3) connects a mobile microphone, and controls: one in the patient area and another near the driver. 4) charges the walkie talkie's battery. The weak point of these US ambulances often have radios with dual controls and dual systems has been connector technology which has been microphones allowing the radio to be used from the patient proven unreliable in some installations. Receiver performance care area in the rear or from the vehicle's cab. is a problem in congested radio signal and urban areas. These installations are sometimes referred to as jerk-and-run 8.2 Data radio systems.

Both tow cars and ambulances may have an additional radio 9. Professional Mobile 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 Motorola HT1000 hand-held two-way radio one frequency band. Professional Mobile Radio (also known as Private Mobile 8.3 Walkie talkie converters in place of mobile radios Radio (PMR) in the UK and Land Mobile Radio (LMR) in North America) are field radio communications systems The relevant code consisting of one or more digits is sent and which use portable, mobile, base station, and dispatch console the station programmed to respond to the number, typically radios. Operation of PMR radio equipment is based on such one or two digits responds by opening the on the standards as MPT-1327, TETRA and APCO 25 which are receiver to let the audio through. The disadvantage of this designed for dedicated use by specific organizations, or system is that if the receiver does not pick up the code at the standards such as NXDN intended for general commercial instant the DTMF signalling takes place then it will not use. Typical examples are the radio systems used by police respond to any of the message. This can be a significant forces and fire brigades. Key features of professional mobile disadvantage because mobile stations often lose the signal for radio systems can include: short periods as they are on the move.

• Point to multi-point communications (as opposed to cell phones which are point to point communications) 9.3 CTCSS • Push-to-talk , release to listen — a single button press opens communication on a radio frequency channel Another widely used system is CTCSS, also referred to as • Large coverage areas subaudible tones or PL tones (a Motorola trademark). As the • Closed user groups name suggests it uses subaudible tones (below about 250 Hz) • Use of VHF or UHF frequency bands. to carry the selection information. These are transmitted in addition to the normal voice channel, but as they appear below 9.1 Selective calling the audio range passed by most mobile radios (roughly 300- 3000Hz), they are filtered out and therefore not heard. Many systems operate with the remote or mobile stations being able to hear all the calls being made. This may not Only when the correct tone for the required station is always be satisfactory and a system of selective calling may transmitted will the squelch for that receiver be opened and be required. There are several ways of achieving this, the transmitted audio will be heard. The advantage of this including Dual Tone Multiple Frequency (DTMF) signalling system is that the subaudible tones are transmitted for the and Continuous Tone Coded Squelch System (CTCSS). whole period of the transmission so if the signal fades at the beginning of the transmission is lost but later then increases in 9.2 DTMF strength, the continuously transmitted tones will enable the

DTMF is a system that is widely used for telephone signalling squelch to open and the audio to be heard. Systems typically and is almost universally used for touch tone dialing for are able to provide up to 37 different tones, the lowest landline telephones today. It uses set pairs of tones that are frequency of which is 67 Hz and the highest 254.1 Hz. This used to carry the information. The eight frequencies used are enables a variety of different mobiles to be called selectively.. 697, 770, 852, 941 Hz which are termed the "low tones" and 9.4 Modulation 1209, 1336, 1477, and 1633 Hz which are "high tones". One high and one low tone is used together and the various In general narrow band frequency modulation is the chosen combinations are used to represent different numbers and form of modulation, although airport services use amplitude symbols. modulation. Typically a deviation of 2.5 kHz is used for FM and this enables a channel spacing of 12.5 kHz to be This term paper reveals all the aspects of mobile radio. implemented. As the demands for PMR are high, it is Though mentioned in the above term paper, mobile radio has necessary to make effective use of the channels available. This evolved a lot but it is an ever growing field and has its is achieved by re-using the frequencies in different areas. Base technology being advanced in near future. It is ever growing stations must be located sufficiently far apart so that in private sector and giving room to an blooming industry. interference is not experienced, and also selective calling Hence, in near future, it will increase to ever lasting heights techniques such as CTCSS and DTMF are used to ensure that as many mobiles as possible can use a given channel. 11. References:- http://en.wikipedia.org/wiki/Mobile_radio. http://en.wikipedia.org/wiki/Mobile_radio_telephone. 10. Conclusion www.flipkart.com/.../mobile-radio-communications