2 Way Radio for Me

8/2/2019 2 Way Radio for Me

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Understanding Two-Way Radio Technology

TETRA, APCO, iDEN, Tetrapol, OpenSky, EDACS, MPT 1327, LTR, SmartNet, Trunked,Conventional, Digital Radio, TDMA, FDMA, VHF, UHF, data over radio, multi slot packet

data, etc, etc. What they are all about? If you are new to the two-way radio world, you may be confused with these terms. Youhave come to the right place to learn two-way radio technology the easiest way.

Introduction

What is Two-Way Radio

A two-way radio is simply a radio that can both transmit and receive (a transceiver). In

broader terms, most of voice wireless communications systems, including cellularsystem, fall into two-way radio definition. In this web site, two-way radio refers to radiosystem mainly used for group call communication. This two-way radio system is alsoknown as Professional Mobile Radio (PMR), Land Mobile Radio (LMR), Private Mobile Radio(PMR), Public Access Mobile Radio (PAMR) system. A portable two-way radios are oftencalled walkie-talkies or handie-talkies. Two-way radios are also available in mobile andbase configurations as well as utilizing radio network infrastructure.

A two- way radio is typically equipped with a Push -To- Talk PTT button to activate thetransmitter. User just simply presses the PTT button and can immediately start to talk.User releases the PTT button to listen to others.

Two- way radio can talk directly to other radios or use radio network infrastructure. Adirect talk among radios (usually also known as direct more operation, talk around mode)has limited range due to limitation of radio power. To overcome this limitation, a radionetwork infrastructure can be utilized to extend communication range.

Why Two-Way Radio

With various wireless technology options and two-way radio being one of the earliest wireless technologies, one may question whether two-way radio is still a viabletechnology today. The answer is yes and the following are the 2 key points that uniquelydifferentiate two-way radio to other wireless technology:

1. Instant communication Two-way radio provides instant communication. User just need to press the

Push -To- Talk (PTT) button and within fraction of a second, this user canimmediately talk to convey his/her messages. This is due to a quick callset-up time imbedded in the technology. This instant communicationcapability is one of key factors of why many organizations rely on two-wayradio for their tactical or operational communications.


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2. Group communication Another distinct feature of two- way radio is its capability to facilitate one -to- many group communication (also known as "grou p call") veryefficiently. By efficient means that one user can talk to one, five, tens,hundreds, thousands of users at the same time. User don t need to repeatthe same message over and over again if he/she need to convey to more

than one user. In addition, two-way radio performs the groupcommunication using minimum RF channel resources. If all of users residein the same area, most of the time, you only need one channel resourcesto talk to these hundreds of users.

Why Not Other Wireless System

Every wireless technology has their advantages and disadvantages. The choice of whichtechnology is the most suitable for one s organization depends on whether that particulartechnology can meet the user requirement.

For those users who need to: Work in a group Communicate instantly, and Mobile

Two-way radio can be considered as appropriate solution compared to other wirelesstechnology. Following are the reason why other wireless technology, such as publiccellular network, may not be able to meet the above requirement:

Communicate Instantly Imagine you are in the field and face an emergency situation and need to communicateimmediately to declare your situation. If you are using a cellular phone, for example, youneed to dial a number, wait for a while when the call is being set-up and connected, ringat the other side and finally answered. This process can take a few second and duringthat valuable time, your emergency situation can become worsen.

With two-way radio, you just press the PTT button and shout out emergency to getattention and immediate help. Of course, this is assuming that RF channel are available.We will discuss later on two-way radio features that can overcome RF channel congestionand give highest priority for emergency users, a feature that are not available in otherwireless technology.

Group communication Say you need to inform your 5 staff that a meeting has been rescheduled. If you callthem one-by-one, it will take sometimes. With two-way radio, you just select yourtalkgroup and press the PTT button and start to talk to your 5 staff at the same time.Now, just imagine if you need to broadcast your message to 1000 staff in the field.

While some wireless system allows a group calling, it typically limits the number of groupmember that you can talk at one time. With two- way radio, you just need to talk onceand heard by many.


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Who Are The Users

Two-way radio has been used for many years by various organizations and industries.Due to the nature of their operational needs, they have to utilize two-way radio toaddress their communication needs. Examples of organizations and industries that relyon two-way radio are:

Public Safety organization : Police, Fire Brigade, Emergency Medical Services /Ambulance, Disaster Recovery agency

Security : Military, Intelligence agencies

Transportation : Railway, Airport, Seaport, Light Rail, Subway

Oil & Gas companies

Utility companies : Electricity, Gas, Water, Telephone, Cable TV

Transport Service companies: Taxi, Limos, Trucking

Construction companies: Commercial, Residential, Road and Bridge

Hospitality industries: Hotel, Resort, Restaurant, Tourism

Government agencies : Ministries, Local government, Municipal, Embassies,Public Works

Services industry : Delivery companies, Towing companies

Manufacturing

Contractors: Electrical, Excavating, Plumbing, Roofing

And many others...

In other words, users of two-way radio are any agencies or businesses with multiple staff or workers who work in group and mobile .

The Basics In general, two-way radio technology can be classified as follows:

Based on channel allocation: Conventional system

Conventional system is the most basic radio communications system. Conventional, as itsname implies, refers to a "traditional" method of frequency utilization. Conventionalradios operate on fixed channels and each user group is permanently assigned a fixedfrequency or a set of frequencies.

In the case of radios with multiple channels, they operate on one channel at a time. Theproper channel is selected by a user. Typically, the user operates a channel selector orbuttons on the radio control panel to select the channel.

In multi-channel systems, channels are used to separate purposes. A channel may bereserved for a specific function or for a geographic area . In a functional channel system,one channel may allow a road repair crews to talk to the road maintenance office. Asecond channel may allow road repair crews to communicate with state highway
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department crews. In a geographic system, a taxi company may use one channel tocommunicate in the northern area and a second channel when taxis are in southern area.

One key basic principal to remember when using radio is that only one radio can use onefrequency (RF channel) at any one time. If two radios attempt to transmit in the samefrequency at the same time, signal collision will happen and cause interferences. Thus, it

is important for radio user to be disciplined when using radio to: Check if no one talking at that particular frequency or channel If channel is occupied, wait until no one talk

More often than not, in congested area with limited frequency, multiple groups share thesame frequency which can cause interferences if users are not discipline.

Communication modes

Radio communications can utilize one of 3 modes:

1. Simplex This is a mode where both transmitter and receiver operate on the same frequency. Usercannot listen or talk simultaneously and only one radio can talk at any one time, whileothers listen. This mode is used by the most basic radio communication. Radio to radiocommunication like the FRS walkie-talkie uses this mode. Another example is aircraft VHFAM and marine radios.

Simplex systems often use open architectures that allow any radio meeting basicstandards to be compatible with the system. It allows old radios to work with new ones ina single network. This gives advantages as simplex systems are often legacy systemsthat have existed for years or decades and the large number of radios installed (the

installed base,) can take decades to upgrade.2. Half-Duplex This is a mode where transmitters operate on one frequency, receivers on another. Usercannot listen or talk simultaneously. This mode of operation requires a pair of twofrequencies, one for transmit and one for receive. This mode is commonly used forrepeater or base station operation. In repeater operation mode, all mobiles/portablesradios in the system can hear the repeater transmission, but mobiles/portables cannothear each other. Only the repeater can hear all mobile and portable radios. 3. Full-Duplex In this mode, transmitters operate on one frequency, receivers on another but user canlisten and talk simultaneously. This mode of operation requires a pair of two frequencies,one for transmit and one for receive. One example of this mode is cellular phone wherethe signals flow in two directions simultaneously.

The above three modes of operation (or combination of them) are present in most two-way radio system. Some systems use a mix of simplex/duplex where radios use half-duplex as a default but can communicate simplex on the base station channel if out-of-range. The capability to talk simplex on a duplex channel with a repeater is called talk-around or direct mode operation.


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Scanning in conventional radios

For user who works and belong to multiple groups which use different channels, it isdifficult for them to monitor each channel. Automatic scanning features can be used toassist to scan every assigned channel when his/her current channel is idle and stop in achannel that is in use. This way, the user will be able to automatically follow conversationin different group. Of course, this user can only participate in one group at any one time.

Some conventional radios scan more than one channel. That is, the receivers searchesmore than one channel for a valid transmission. A valid channel is a radio channel butmay also require that a signal have a specific signaling such as CTCSS code. There are awide variety of scan configurations which vary from one system to another.

Trunked System

The concept of trunking is taken from telephone company technology and practice. It

refers to the sharing of common resources among a number of different users on thesame system without overhearing or interfering with each other s conversations. Trunkedtakes advantage of the probability that in any given number of user units, not everyonewill need resources access at the same time. Therefore with a given number of users,fewer discrete resources are required.

In a trunked radio system, the system logic automatically selects the physical radiofrequency channel (the resources) without user interference. There is a protocol thatdefines a relationship between the radios and the radio network which supports them.The protocol allows channel assignments to happen automatically. This arrangementallows multiple groups of users to share a small set of actual radio frequencies without

hearing each others' conversations. Trunked systems primarily conserve limited radiofrequencies and also provide other advanced features to users.

Instead of channels, radios are related by groups which may be called, groups, talkgroups, or divided into a hierarchy such as fleet and sub-fleet, or agency-fleet-sub-fleet.These can be thought of as virtual channels which appear and disappear as conversationsoccur.

"Trunked" radio systems differ from "conventional" radio systems in that a conventionalradio system uses a dedicated channel (frequency) for each individual group of users,while "trunking" radio systems use a pool of channels which are available for a great

many different groups of users.

Systems make arrangements for handshaking and connections between radios by one of these two methods:

A computer assigns channels over a dedicated control channel. The controlchannel sends a continual data stream. All radios in the system monitor the datastream until commanded by the computer to join a conversation on an assignedchannel.
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Electronics embedded in each radio communicate using a protocol of tones or datain order to establish a conversation, (scan-based).

If all physical channels are busy, systems include a protocol to queue or stack pendingrequests until a channel becomes available.

Benefit of Trunked Radio System Efficient use of channel (spectrum) resources

o Shared traffic among communication paths o Increased probabilities of obtaining free channel

Privacy of communications due to each group uses one channel exclusively duringthe duration of the call

Eliminate the need to monitor the channel before transmitting. User just PTT andthe system will take care to find available channel for the call

Redundancy of channel resources. If one channel is down, all reminder channelscan still be used by all groups

As trunked system has intelligence control, there are more features available thatare not found in conventional system. Some examples are queuing when allchannels are occupied, automatic call back when channel is available, multiplepriority level, automatic retry, etc.

Based on signal transmission: Analog system

Analog radio transmit analog signal over-the-air. Our original voice, which is in analog

format, is modulated and amplified inside the radio before transmitted. There is noadditional computer processing (i.e. digitization) inside analog radio. Analog radio systemcontinuously transmits radio waves that are usually modulated by a voice.

One example of analog radios is FM radio broadcasting services. Another is AM aircraftradios used to communicate between control towers and air traffic controllers. A walkie-talkie, like the Family Radio Service available, to the public is another example of analogradio.

Advantages of analog radio system Equipment is less complex than digital. This typically lead to cheaper equipment

price

In certain conditions, still able to communicate in areas where a received signal isalready weak where digital system has already cut-off the signal.

Interoperability among analog radio products from different vendors (forconventional system)
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Disadvantages of analog radio system Voice quality highly depends on the environment and can easily get interference.

As user move away from an analog radio transmitting site, the signal qualitydecreases gradually while noise level increase.

Less functionality and features compared to digital radio Less spectrum efficiency: Only one conversation at a time can occur on each

analog channel

Digital system

Digital radio has additional processing inside the radio to convert the original analog voiceinto digital format (ones and zeros) before transmitting the signal in digital form over -the-air. The receiving radio receives the digital signal and converts it back into analogsignal so the user can hear the voice.

Examples of digital radio are radios that comply to APCO-25 standard or TETRA standard.The Sprint Nextel s iDEN radio is another example of digital radio.

The digitalization is done by sampling the voice frequency and then changing the sampledinformation to ones and zeros. This is done using an electronic circuit called a voicecoder or vocoder. Depending on type of vocoding techniques, the vocoder also

compressed the resulting sample so that it can fit into a narrower bandwidth. Examplesof speech coding (vocoding) technique are IMBE (Improved Multi Band Excitation) usedby APCO-25 standard or VSELP (Vector Sum Excited Linear Prediction) used by TETRA standard.

Advantage of digital radio system Better and Consistent Voice Quality

Because the receiving radio just need to identify the binary information (ones andzeros), the receiving radio can replicate the original voice as long as it s able toidentify the ones and zeros signal. Thus, a digital signal has fairly consistentquality as it moves away from the transmitter until it reaches a thresholddistance.

Voice Privacy As digital radio systems send voice transmissions in digital form, listeners using anFM analog scanner hear only noise on the channel. This gives an added benefit forprivacy from public news organization or casual listeners.

Improved Encrypted Voice Quality To further secure the over-the-air transmission from listeners who have moresophisticated equipment, an encryption feature is required. Encrypted voiceprotects the voice message from being intercepted and understood by listeners.On analog radio systems, voice scrambling may cause audio quality to vary. Foryears, many users have accepted degraded audio quality for the benefit of securevoice transmissions. With digital radio systems, encrypted voice has no perceived
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degradation of quality where encrypted voice sounds the same as clear voice on adigital radio system.

Integrated Voice and Data Services One of the most significant benefits of digital radio systems is that the integrationbetween voice and data services is greatly improved. Because the voicetransmissions are treated as data, there is much better and tighter integrationbetween voice and external data devices. In addition, digital transmissions over-the-air are further improved for error protection, a great feature for wirelessmobility. The integration of voice and data is one of the compelling reasons whyusers want to upgrade their system to digital.

Enhanced Signaling Features Because digital voice transmissions are already in digital format over-the-air, it isnow possible to imbed more signaling features in the same voicetransmissions. Today, analog radios have signaling features, but these tend to belimited to smaller amounts of data than the digital equivalent. Digital radios allowfor the signaling to be transmitted continuously and concurrently with the voicetransmissions. These signaling features furnish quick and appropriate informationalongside the voice, such as the caller identification in which the recipient canidentify the sender, call alert feature or text message. Other enhanced featuresare also possible using these embedded digital signaling features.

Improved Spectrum Efficiency Digital radio system offers the capability to serve more users than in the samecomparable analog spectrum. This is due to the use of compression duringvocoding process. The resulting compressed information can be then send usingnarrower band with while maintaining similar original quality. By using narrowerbandwidth, it allows more simultaneous talking paths in one analog channelspectrum. This benefit is important in an environment where regulatory bodyconstraints spectrum utilization.

Disadvantages of digital radio system: Need more complex equipment than analog radio which may lead to higher cost to

purchase

Radios must be designed to follow the same digital protocol (i.e. vocoding /compression techniques, access method, digital modulation, etc) to allowsinteroperability among different products. An open standard is usually required indigital radio to ensure products compatibility

As digital radio moves away from the transmitter and reach a threshold distance,the signal quality takes a nose dive and can no longer be understood whereas theanalog radio can still receive the signal even though with high noise level


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Based on access method:

Frequency Division Multiple Access (FDMA)

FDMA or Frequency Division Multiple Access is an access method that is used by radiosystems to share the radio spectrum. The terminology multiple access im plies thesharing of the resource amongst users, and the frequency division describes how thesharing is done: by allocating users with different carrier frequencies of the radiospectrum.

In FDMA the given Radio Frequency (RF) bandwidth is divided into smaller frequencybands called subdivisions. Each subdivision has its own carrier frequency. A controlmechanism is used to ensure that two or more earth stations do not transmit in the samesubdivision at the same time. Essentially, the control mechanism designates a receive

station for each of the subdivisions.

Examples of radio technology that are utilizing FDMA are APCO-25 , EDACS and Tetrapol

Time Division Multiple Access (TDMA)

Note: There are some other access methods such as CDMA (Code Division MultipleAccess), SDMA (Space Division Multiple Access) and CSMA (Carrier Sense MultipleAccess). However, these access methods have not been used in two-way radiotechnology.

TDMA or Time division multiple access is an access method that is used by radio systemsto share the radio s pectrum. The terminology multiple access implies the sharing of theresource amongst users, and the time division describes how the sharing is done: bydividing and allocating users into different timeslots in a carrier frequency of the radiospectrum.

The shared users transmit in rapid succession, one after the other, each using his owntimeslot. This allows multiple users to share the same transmission medium (e.g. radiofrequency) while using only the part of its bandwidth they require.

TDMA is used in the Global System for Mobile Communications (GSM) and PersonalDigital Cellular (PDC). It is also used extensively in satellite systems, local area networks,physical security systems, and combat-net radio systems.

Examples of radio technology that are utilizing TDMA are TETRA, OpenSky and iDEN
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Based on standard acceptance:

Open standard

Open standards in two-way radio refers to technology that has specifications that arepublicly available. These standard is endorsed by an internationally recognized standard

body and supported by multiple manufacturers. By allowing anyone to obtain andimplement the standard, they can increase compatibility between various hardware andsoftware components, since anyone with the necessary technical know-how andresources can build products that work together with those of the other vendors thatbase their designs on the standard (although patent holders may impose "reasonable andnon-discriminatory" royalty fees and other licensing terms on implementers of thestandard).

Currently, there are only 2 open standard for digital two-way radio system:

APCO-25 , a s a standard developed by TIA

TETRA, as standard developed by ETSI

TIA and ETSI are both internationally recognized standard body.

One interesting note for open standard in two-way radio is that currently, the standarddefines only certain interfaces. And both APCO-25 and TETRA standard do not defineinterface between switching system and base station. In other word, manufacturers needto use their proprietary design for switching and base station. For users, this means thatthey can not interchange switching system from one vendor with base station from othervendors.

Proprietary System

Proprietary system in two-way radio refers to technology specifically developed bya manufacturer and specifications are not made publicly available. In some cases,a proprietary system from one manufacturer becomes a de-facto standard asseveral other manufacturers also produce accessories or even product. Sometimesthe proprietor (holder of proprietary system) give a right to other manufacturer toproduce the product. Of course with the commercial terms, etc. This happenswhen the proprietary products have been widely accepted and have a largenumber of user base.
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Frequency Band / Spectrum The Federal Communications Commission (FCC) defined frequency spectrum as follows:

VLF Very Low Frequency < 30 KHz

LF

Low Frequency

30 300 KHz

MF Medium Frequency 300 3,000 KHz

HF High Frequency 3 30 MHz

VHF Very High Frequency 30 300 MHz

UHF Ultra High Frequency 300 3,000 MHz

SHF Super High Frequency 3 30 GHz

EHF Extremely High Frequency 30 3,000 GHz

In Two-Way Radio world, while the generic terms still follow the above definition, there are specificdefinition applies to Land Mobile/Two-Way Radio spectrum. The following table shows frequencyspectrum division commonly known in Land Mobile or Two-Way Radio products. Note that thedefinition is not rigid as various sources may slightly use different terms for the exact frequency band.

HF High Frequency 3 25 MHz

VHF Very High Frequency - VHF comes with various sub-bandsuch as:

Low Band : 25 50 MHz Mid Band : 72 76 MHz High Band : 132 174 MHz

25 174 MHz

UHF Ultra High Frequency

UHF comes with various sub-bandsuch as:

380 MHz band : 380 400 MHz 400 MHz band : 400 430 MHz 450 MHz band : 450 470 MHz 470 MHz band : 470 512 MHz

350 512 MHz

800 MHz UHF 800 MHz Band

In many countries, 800 MHz bandhas been allocated with 45 MHzseparation so the typical 800 MHzspectrum is:

806 825 MHz / 851 870 MHz

806 870 MHz


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The Technology There are many two-way radio technology available today. The following lists the mostwell known radio technology. The table shows each of technology in terms of whether itis analog or digital, and whether it is conventional or trunked. Note that the analog

conventional is the most basic and well known technology. We will not discuss analogconventional system in this site.

Conventional Trunked

Analog

Analog conventional radio

APCO-16

EDACS

LTR

MPT 1327

Digital

DMR

APCO-25

APCO-25

DMR

EDACS

iDEN

OpenSky TETRA

Tetrapol
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ANALOG

APCO-16 Association of Public Safety Communications Officials - Project 16

Open Standard/Proprietary See note below

Analog/Digital Analog

FDMA/TDMA FDMA

Conventional/Trunked Trunked

Typical frequency band VHF/UHF/800

Channel bandwidth 25/30 kHz (typical)

* APCO-16 defines operational / functional requirement for a trunked system but doesnot restrict manufacturers to develop their own design

What is APCO-16

APCO-16 (Association of Public Safety Communications Officials Project 16) was aneffort to establish basic requirements for a typical public safety communicationssystem. The result was an operational/functional (non-technical) standard to whichmany manufacturers have responded. The recommendation was established in 1979. Itwas the foundation for the further efforts of Project 25, which continued beyond Project16 to define technical standards.

APCO-16 addressed specific characteristics and functional capabilities of trunked radio

systems. The intention was to create a system concept that would satisfy the minimumneeds of all potential users and permit the inclusion of more complex requirementsneeded by some communities then or in the future. APCO-16 published documents definethe mandatory and desirable functional capabilities for a public safety analogtrunked radio system .

The specifications include recommendations for analog voice modulations and trunkingfunctions for use of the RF spectrum. As APCO-16 recommendations focus more ontrunking functional specification, it does not specify how manufacturer should design thesystem. Manufacturers are not restricted to develop their own design to meet therequired functionalities in APCO-16 recommendation. Many APCO-16 compliant productsuses 3600 baud control channel for its signaling protocol.

Examples of products that complies to APCO-16 definition are SmartNet and SmartZonetrunked system developed by Motorola.

Features and Capabilities

Project 16 addressed such characteristics and capabilities as: Channel access times Automated priority recognition


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Data systems interfaces Individuality of system users Command and control flexibility System growth capability Frequency utilization, and Reliability

These capabilities bring improved features compared to previously available analogtrunked system.

Spectrum Utilization

As this is an analog technology, typically, APCO-16 products follow 25 or 30 KHz radiochannel utilization. Thus, one 25 KHz radio channel supports one voice conversation.

Frequency Band

Following are the APCO-16 frequency bands that are typically found in the market today: 136 174 MHz (VHF)

403 512 MHz (UHF) 800 MHz Band


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LTR Logic Trunked Radio

Open Standard/Proprietary Proprietary


FDMA/TDMA FDMA


Typical frequency band UHF/800/900

Channel bandwidth 25 kHz

What is LTR

LTR (Logic Trunked Radio) is a signaling protocol for analog trunked radio systemdeveloped by the E. F. Johnson Company in the late 1970s. It was primarily used by

private companies such as taxicabs, utilities, delivery trucks, and repair services and it isnot very popular with public safety agencies.

LTR is distinguished from some other common Trunked Radio Systems in that it does nothave a dedicated control channel. It uses distributed control concept. Each repeater hasits own controller and all of these controllers are coordinated together. Even though eachcontroller monitors its own channel, one of the channel controllers is assigned to be amaster and all the other controllers report to it. The signaling protocol for LTR uses 300baud control channel.

Typically on LTR systems, each of these controllers periodically sends out a data burst(approximately every 10 seconds on LTR Standard systems) so that the subscriber unitsknow that the system is there. The idle data burst can be turned off if desired by thesystem operator. Some systems will broadcast idle data bursts only on channels used ashome channels and not on those used for "overflow" conversations. To a listener, the idledata burst will sound like a short blip of static like someone keyed up and unkeyed aradio within about 1/2 second. This data burst is not sent at the same time by all thechannels but happen randomly throughout all the system channels.

Note: the product has been discontinued.


From end user point of view, LTR provides: Group call Individual call Telephone Interconnect Call
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LTR utilizes Frequency Division Multiple Access (FDMA) technique to utilize spectrum. LTRutilizes 25 KHz bandwidths. Thus, one 25 KHz radio channel supports one voiceconversation.

Frequency Band

The current available product in the market today offers the following frequency bands: UHF Band 800 MHz Band 900 MHz Band


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MPT 1327 Ministry of Posts and Telegraph 1327

Open Standard/Proprietary Open


FDMA/TDMA FDMA



Channel bandwidth 25, 20, 12.5, 10 kHz

What is MPT 1327

MPT 1327 (Ministry of Posts and Telegraph 1327) is a signaling protocol standard foranalog trunked radio. It was developed in 1988 by the British Department of Trade and

Industry (DTI).

The standard defines the protocol rules for communication between a trunking systemcontroller (TSC) and users' radio units and it defines only the over-air signaling andimposes only minimum constraints on system design. The signaling protocol for MPT1327uses 1200 baud control channel.

Systems based on MPT 1327 generally consist of several radio channels. At least one of these channels is defined as the control channel (CC) and all other channels are trafficchannels (TCs). Data messages between mobiles and the network are exchanged on thecontrol channel at 1200 bits per second. Each subscriber in an MPT-1327 trunked radionetwork has a unique call number. It consists of a prefix (3 digits), the fleet number (4digits) and the subscriber s call number within the fleet (2 or 3 digits). After it has beenentered the call number will be converted in the mobile to a 20-bit address. For theduration of the call a subscriber is exclusively allocated a traffic channel from theavailable trunk.


The different types of communications on an MPT-1327 network and their definitions: Traffic types:

- Mobile-mobile in a cell- Mobile-mobile in different cells- Mobile-line access unit via landline or radio- Mobile-dispatcher station via landline or radio- Mobile-PABX, Mobile-PSTN

Short Data Communication: - Status messages on the CC (5-bit data length)- Short data messages on the CC (186-bit data length)- Transparent data transmission on the TC (data communication).

Calls: - Point to point connections- Group calls


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MPT1327 utilizes Frequency Division Multiple Access (FDMA) technique to utilizespectrum. MPT1327 utilizes 25, 20, 12.5, 10 KHz bandwidths. Thus, MPT1327 hasflexibility in utilizing available spectrum. Systems using 10kHz, 12.5kHz and 25kHzchannel spacing have been deployed in North America.

Frequency Band

The current available product in the market today offers the following frequency bands: VHF UHF 800 MHz Band


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DIGITAL

APCO-25 Association of Public Safety Communications Officials - Project 25


Analog/Digital Digital

FDMA/TDMA FDMA

Conventional/Trunked Both


Channel bandwidth 25/12.5 kHz

* The standard allows analog mode in radio terminal for backward compatibility withanalog radio

What is APCO-25

APCO-25 (Association of Public Safety Communication Officials Project 25) is an openstandard for digital radio developed in North America under state, local and federalrepresentatives and Telecommunications Industry Association ( TIA ) governance. Thestandard was developed to foster the development and progress of the art of publicsafety communications.

In 1989, APCO formed a Working Group, called APCO Project 25, to work on developmentof a digitally trunked radio system specifications tailored to public safety needs. Project25 was established to provide an industry-wide effort to set standards for uniform digitaltwo way radio communications for public safety and emergency services .

APCO-25 brings together representatives from various associations and agencies toobtain as many contributions as possible to make the resulting specification a worldstandard for digital land public safety mobile radio. The objective is to find solutions thatbest serve the needs of the public safety marketplace. In addition, the committee hasencouraged the participation of numerous international public safety organizations,making this a worldwide recommended standard-setting initiative. Worldwide interest hasbeen generated due to the standards process being pursued by users working closelywith the industry.

As APCO is an association representing users, assistance was sought from industry indeveloping the standard. The Telecommunication Industry Association (TIA) providedtechnical support and the mechanics of standard writing, which has made the resultingspecification (ANSI/TIA 102) into a national industry standard. Published P25 standards


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suite is administered by the Telecommunications Industry Association (TIA Mobile andPersonal Private Radio Standards Committee TR-8).

APCO-25, APCO-Project 25, APCO-P25 are all refer to the same standard name. APCO P25 Capabilities and Features

From end user point of view, APCO-25 provides, among others: Group call Individual call Telephone Interconnect Call Wireless data Integrated Voice and Data Secured network with encryption Talk Around mode Backward compatibility with analog Advanced radio features and capabilities such as Dynamic Grouping, emergency

call, etc


APCO P25 utilizes Frequency Division Multiple Access (FDMA) techniques to achievespectrum efficiency. At present, APCO can achieve up to 2 (two) voice channels in one25 KHz radio channel.

Frequency Band

Frequency bands for APCO-25 products that are typically found in the market today: 136 174 MHz (VHF) 403 512 MHz (UHF) 800 MHz Band

Backward Compatibility with Analog

APCO-25 standard allows backward compatibility with analog system. APCO-25 radio candirectly interoperate with analog radios that are using the same frequency (note: directinteroperation here means direct communication among radios without using networkinfrastructure). With this capability, APCO-25 allows some smooth migration from analogsystem to digital. Users who already own analog system can migrate to digital by phases.Thus, users can decide to upgrade to digital system based on their needs, timing andresources.

Trunked and Conventional in One Network

APCO-25 supports combination of conventional and/or trunked system in one network.This gives user an advantage to have an option to deploy trunked system in high densityarea and conventional in less density area.


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DMR Digital Mobile Radio

Open Standard/Proprietary Open Standard


FDMA/TDMA FDMA/TDMA

Conventional/Trunked Both

Typical frequency band 446/VHF/UHF

Channel bandwidth 12.5/6.25 kHz

What is DMR

DMR (Digital Mobile Radio) is a digital radio standard for Professional Mobile Radio (PMR)users developed by ETSI under its ERM Technical Committee. The standard is designed tooperate within the existing channel spacing used in land mobile frequency bands inEurope. DMR is specifically targeted at small to medium sized PMR systems whereanalogue PMR is currently applied today. The primary goal of the DMR standardization isto specify a digital system with low complexity and low cost levels. It will provide voice,data and other supplementary services.

The first release of the DMR Standard has been approved by ETSI . It is released as aTechnical Standard TS 102 361 covering the Air interface (Part I) and Services andFacilities (Part II) for voice and data calls, for the 12.5 KHz TDMA protocol for Tier I andTier II products.

There are 3 tiers in the DMR standard:

DMR Tier I products are for license-free use in the 446MHz band.

Under Tier I, ETSI has also defined two Tier-1 protocols:

o DMR Tier-1 protocol utilizes 12.5kHz FDMA

o dPMR protocol utilizes 6.25kHz FDMA

Both protocols provide for consumer applications and low-power commercialapplications, using a maximum of 0.5 watt RF power. With a limited number of channels and no use of repeaters, no use of telephone interconnects, andfixed/integrated antennas, Tier-1 DMR/dPMR devices are best suited for personal

use, recreation, small retail and other settings that don t require wide area coverageand advanced features.

DMR Tier II covers hand portables, mobiles and base stations operating in the VHFand UHF allocations for PMR.

The ETSI DMR Tier-2 standard is targeted to those users who need spectralefficiency, advanced voice features and integrated IP data services in licensed bandsfor high-power communications. ETSI DMR Tier-2 calls for two slot TDMA in 12.5 kHzchannels.
http://www.etsi.org/http://www.etsi.org/http://www.etsi.org/http://www.etsi.org/


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DMR Tier III products will support trunking operation.

The newly formed DMR MOU group is working on the interoperability specification forDMR radios. Manufacturers including Motorola, Vertex Standard, Kenwood, Icom andothers are working on the development of products.

As this standard is relatively new, there are not many products available in the marketyet.


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EDACS Enhanced Digital Access Communication System

Open Standard/Proprietary Proprietary Analog/Digital Both

FDMA/TDMA FDMA


Typical frequency band VHF/UHF/800/900

Channel bandwidth 25/12.5 kHz

What is EDACS

EDACS (Enhanced Digital Access Communication System) is a trunked system that isavailable in both analog and digital air interface. This technology was invented by GeneralElectric Corporation in mids 1980s. This system is based on a number of proprietaryinterfaces and protocols, for example, the air interface is proprietary as well as the digitalvocoder, known as the Aegis Vocoder. EDACS is used in trunked repeater systems thatinclude wide-area simulcast operation.

EDACS was manufactured by ComNet Ericsson, headquarter in the US, and eventuallywas sold after the telecom meltdown. M/A-COM Inc, a holding of Tyco Electronics,acquired the asset and continue to support the product family.


EDACS utilizes Frequency Division Multiple Access (FDMA) technique to utilize spectrum.EDACS support both 25 KHz and 12.5 KHz bandwidths. Thus, EDACS can achieve up to 2voice channel in a 25 KHz radio channel.

Frequency Band The current available product in the market today offers the following frequency bands:

VHF UHF 800 Band 900 Band


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iDEN Integrated Digital Enhanced Network

Open Standard/Proprietary Proprietary Analog/Digital Digital

FDMA/TDMA TDMA


Typical frequency band 800


What is iDEN

iDEN (integrated Enhanced Digital Network) is a digital trunked radio developed byMotorola which provides its users the benefits of a trunked radio and a cellular-liketelephone services. It was first introduced in 1994. The technology supports multipleservices in single devices. The Four-in-one service allows business users to takeadvantage of advanced wireless technologies with one pocket-sized digital handset thatcombines: two-way digital radio; digital wireless phone; short message services; anddata capabilities leveraging Internet access technology.

iDEN places more users in a given spectral space, compared to analog cellular and two-way radio systems, by using speech compression and time division multiple access TDMA. Using these technique, iDEN can achieve 6 time slots in one 25 KHz.

iDEN handsets use SIM cards, just like GSM, and, in fact, the interconnect-side of thenetwork uses GSM signaling for call set-up and mobility management, with the protocolstack modified to support iDEN's additional features. With its sleek and compact formfactor, the iDEN handset looks similar to cellular handset. Various handset model areavailable. The iDEN handset features include color display, built-in GPS, WAP support,ruggedized (for some model), dual mode GSM/iDEN (some model) and other featurescomparable to cellular handset.

iDEN Capabilities and Features

From end user point of view, iDEN provides, among others, the following features and

services: Group call Individual call Telephone Interconnect Call High Speed Wireless packet data (96 kbps over-the-air) Short Data Services Integrated Voice and Data
http://en.wikipedia.org/w/index.php?title=Trunked_Radio_System&action=edithttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/TDMAhttp://en.wikipedia.org/wiki/TDMAhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/w/index.php?title=Trunked_Radio_System&action=edit


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iDEN is the most spectrally efficient radio technology. iDEN utilizes Time Division MultipleAccess (TDMA) techniques to achieve spectrum efficiency. iDEN can achieve up to 6 (six)TDMA time slots in one 25 KHz radio channel.

Frequency Band

At present, iDEN supports frequency band in 800 MHz Band


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OpenSky

Open Standard/Proprietary Proprietary


FDMA/TDMA TDMA


Typical frequency band 700/800/AMPS Band


What is OpenSky

OpenSky is a wireless communication system, developed by a team of M/A-COM Inc.,now a division of Tyco International's Electronics unit. OpenSky received the directattention of Tyco when they acquired it along with Amp Corporation. The technology was

originally developed for Federal Express in mid 1990s for its urban operations. Thetechnology was developed to meet the requirement of higher message data speedcompared to its previous system. It was initially designed as a wireless data system butthe system can support both voice and data services. OpenSky technology applies voice-over-IP transport to radio communications applications in a unique architecture.


OpenSky utilizes TDMA with 4 (four) time slots to support both voice and data. The fourtime slots can be used for both voice and data simultaneously or can be aggregated tosupport 19.2 kbps throughput on a 25 KHz channel.

Frequency Band

Frequency bands for OpenSky products that are typically found in the market today: 700/800 Band AMPS Band
http://en.wikipedia.org/wiki/Voice-over-IPhttp://en.wikipedia.org/wiki/Voice-over-IPhttp://en.wikipedia.org/wiki/Voice-over-IPhttp://en.wikipedia.org/wiki/Voice-over-IP


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TETRA Terrestrial Trunked Radio



FDMA/TDMA TDMA


Typical frequency band UHF/800


What is TETRA

TETRA (Terrestrial Trunked Radio) is a digital trunked radio standard developed by theEuropean Telecommunications Standards Institute ( ETSI ) . ETSI is a standardization bodyfor Information and Communication Technology in Europe. The purpose of the TETRA

standard was to meet the needs of Professional Mobile Radio (PMR) user organizations.The first version of TETRA standard was published in 1995.

Because the TETRA standard has been specifically developed to meet the needs of a widevariety of PMR user organizations, it has a scaleable architecture allowing networkdeployments ranging from single site - local area coverage to multiple site - wide areanational coverage. Besides meeting the needs of PMR user organizations, the TETRAstandard has also been developed to meet the needs of Public Access Mobile Radio(PAMR) operators.

Recognizing that important market requirements outside the responsibility of ETSIneeded to be addressed to ensure the success of TETRA, a number of organizationsformed the TETRA MoU (Memorandum of Understanding) Association in December1994. The main objectives of the TETRA Association are to promote the TETRA standardand to ensure multi-vendor equipment interoperability. This forum acts on behalf of allinterested parties, representing users, manufacturers, application providers, integrators,
http://www.etsi.org/http://www.etsi.org/http://www.etsi.org/http://www.etsi.org/http://www.etsi.org/


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operators, test houses and telecom agencies who are involved in the development and ordeployment of the TETRA standard. Today the TETRA Association represents over 135organizations, from all continents of the world.

TETRA Capabilities and Features

From end user point of view, TETRA provides the following features and services:

Group call Individual call Telephone Interconnect Call Wireless data: Circuit switch and/or packet data Integrated Voice and Data Secured network with authentication and encryption Direct Mode Operation Advanced radio features and capabilities such as Dynamic Grouping, emergency


TETRA utilizes Time Division Multiple Access (TDMA) technique to achieve spectrumefficiency. TETRA can achieve up to 4 (four) TDMA time slots in one 25 KHz radiochannel

Frequency Band

Frequency bands for TETRA products that are typically found in the market today: 380 - 400 MHz 410 430 MHz 800 MHz Band

Some vendors have promised to provide some other band to meet requirement in specificmarket.


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TETRAPOL Open Standard/Proprietary See below*


FDMA/TDMA FDMA


Typical frequency band UHF

Channel bandwidth 12.5/10 kHz

* Tetrapol is not endorsed as standard by international standard body but it offersPublicly Available Specifications (PAS) . This means that document specifyingTetrapol is available for any manufacturer that wants to develop Tetrapol compliantequipment.

What is Tetrapol

TETRAPOL is a digital trunked radio solution, originally developed in Europe. It wasdesigned to meet the growing needs and expectations of Professional Mobile Radio (PMR)users such as Public Safety Forces, Transport or Industry.

Publicly Available Specifications

The Publicly Available Specifications (PAS) comprise 3,000 pages of technicalspecifications of Tetrapol open interfaces. This means that any manufacturer can usethese specifications to develop equipment that is fully compatible with TETRAPOLnetworks. The document is managed by the TETRAPOL Forum's technical committee.


From end user point of view, Tetrapol provides the following features and services:

Group call


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Individual call Telephone Interconnect Call Wireless data Integrated Voice and Data Secured network with authentication and encryption Advanced radio features and capabilities such as Dynamic Grouping, emergency

call

Spectrum Efficiency

Tetrapol utilizes Frequency Division Multiple Access (FDMA) technique to achievespectrum efficiency. Each Tetrapol channel is divided into 12.5 KHz or 10 KHz radiochannel thus Tetrapol can achieve up to 2 voice channel within a 25 KHz radio channel.

Frequency Band

At present, Tetrapol products in the market supports frequency band in 380 450 MHz

Most Installed Digital Radio Technology

The following list of the most installed digital radio technology are based solely on theauthor observation. The list shown are based on alphabetical order.

Technology Why

APCO-25 Many implementation worldwide; Populardue to Open Standard

iDEN Largest user base; Worldwideimplementation

TETRA Many implementation worldwide; Populardue to Open Standard
http://about2wayradio.com/About2WayRadio/APCO_25.htmhttp://about2wayradio.com/About2WayRadio/APCO_25.htmhttp://about2wayradio.com/About2WayRadio/iDEN.htmhttp://about2wayradio.com/About2WayRadio/TETRA.htmhttp://about2wayradio.com/About2WayRadio/TETRA.htmhttp://about2wayradio.com/About2WayRadio/TETRA.htmhttp://about2wayradio.com/About2WayRadio/iDEN.htmhttp://about2wayradio.com/About2WayRadio/APCO_25.htm


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The Components

The following diagram illustrates major components in two-way radio system. The diagramshows a typical wide area network.

Typical Network Component

In a typical configuration, a wide area radio network consists of 3 major components: - Switching system - Base Stations - Radio Terminal

Note that the above configuration applies to a wide area radio network. For a single siteradio network, typically there is no centralized switching system. Its switching orcommonly known as controller resides in the same physical location as Base Station. Thus,a single-site radio network consists of:

- Base station or site repeater (which includes site controller)

- Radio Terminal


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Radio Terminal

Also known as: Subscribers Unit, Radio Unit, Mobile Station, Portable Radio, Mobile Radio,Fixed-Station Radio

This is a device for the user to communicate and interface to the network. For end-users,they will mostly see these devices more often than the radio infrastructure itself. Thus, theergonomics and performance of radio terminal (i.e. size, weight, battery life, user interfaceand ease of use) plays important role for end- user s acceptance of radio system.

In general, radio terminal can be classified into:

- Portable Radio

This is the device that users can carry while in the move. Since users carry thisdevice most of the time, the ergonomics of portable radio (i.e. size and weight) isone of important factors for users. However, size, weight and battery life are, amongothers, factors that limit the performance of radio unit. Portable radios usually havelower power output compared to mobile or fixed-station radio due to the abovelimitation factors. Thus, the range of portable radio is typically smaller than mobileor fixed-station radio. In many cases, portable radio with higher power comes withbigger form factors. Usually there will be a trade-off between the size of portable andpower output. Either you can have smaller form factor radio but lower power orhigher power but bigger form factor.

- Mobile Radio

This is the device that permanently installed in a vehicle or a car. The size andweight of this mobile radio is bigger than portable radio but it usually does not reallymatter to user because mobile radio is permanently fixed into the vehicle (i.e. users

do not have to carry a mobile radio). Typically, mobile radio has higher poweroutput than portable radio due to its form factor which facilitate more components toproduce higher power as well as it does not have issue with battery life (it usesvehicle battery for its power). Thus, the range of a mobile radio is usually greaterthan portable radio.

- Fixed-Station Radio

This device is usually installed in a fixed location such as a branch office or a fieldpost. Typically, a fixed-station radio is a mobile radio with a power supply, externalmicrophone or speaker and better antenna system (such as directional antenna).Thus, the range of fixed-station radio is greater than mobile and portable radio.

Base Station or Repeater

Also known as: Site repeater, RF Repeater, Site

This is a network component that provides RF coverage in a radio network. In typicalconfiguration, a base station can consist of RF Repeater(s), Controller(s), antennadistribution system (i.e. duplexer, combiner, etc) and Power Supply.


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In the traditional Two-way Radio world, the term Base Station is also known as a fixedstation that receives a signal but do not re-broadcast the signal to other radio users in thesystem. This configuration allows an operator, commonly known as the dispatcher, sitting inthe office to communicate with the radio terminals in the field. The term Repeater is usedreferring to a transceiver that receive a signal and re-transmit it at the same time. Theprimary purpose of repeaters is to extend coverage. The main difference between base

station and repeater is that a repeater repeats a signal that it receives, a base stationdoesn t.

Nowadays, the term of Base Station and Repeaters are often mixed referring to networkcomponent that provides RF coverage.

In one radio network, there can be multiple base stations or repeaters to provide necessarycoverage. In a wide area configuration, these base stations are connected to a centralswitch that manages the entire network. The connection from the base stations to switch iscalled a Site Link.

Switching System or Controller

Also known as: Central controller, central switch, Mobile Switching Office (MSO)

This is a network component that manages the entire network. The switching system, forexample, manages the traffic in and out and route the communication to and from basestations. Switching system is the brain of the network without which the network will not beable to handle wide area network calls.

In typical configuration, a switching system can consist of multiple devices or equipments.Each equipment handles specific function. For example, one equipment handles the routingof the calls while the other handles interaction with base stations. More often than not,these devices or equipments are placed in rack(s) or cabinet(s). Depending on the

complexity of the network, the switching system can have from one to tens of racks.

Mobile Switching Office (MSO)

Also known as: Switching system, Controller, Central controller, central switch

This refers to physical location where all of network switching or controller is placed. Thisterm is derived from cellular network for a common term to refer to its switching system.Since the switching system is located in one physical location, the generic term is MobileSwitching Office (MSO) with a n office word added to emphasize a location thataccommodates various equipment of the switch.

In two-way radio, this term is sometimes also used to refer to the radio switching system,especially for radio network with complex switching system. A digital trunked radio systemlike iDEN , for example, has an architecture similar to a cellular system. Its switching systemis as complex as the cellular system. Thus, the iDEN switching system sometimes refers toiDEN MSO.
http://about2wayradio.com/iDEN.htmhttp://about2wayradio.com/iDEN.htmhttp://about2wayradio.com/iDEN.htmhttp://about2wayradio.com/iDEN.htm


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Site Link

This is a facility to connect base station(s) to its switching system. Depending on thetechnology and products, site link can be E1, partial E1, microwave, 4W, fiber-optic networkand any other means to connect base station to its switching with necessary bandwidth andperformance. In many radio network installations, site link(s) can be leased from a telecomprovider (i.e. E1 line) or owned by the organization (i.e. microwave). Leased line willtypically incur a monthly recurring cost but has lower maintenance cost while privatelyowned link will need a higher capital expenditure to buy the equipment and maintenanceexpenses but organizations do not to need to pay monthly subscription like leased line.

There are several discussions on the use of satellite as site link. The long delay of satellitelink is one of the main factors that need to be considered for two-way radio networkimplementation, especially for group call type of communication.

Antenna System

This is a device connected to the base station / repeater to propagate the Radio Frequency(RF) energy. Antenna system plays an important role to determine the efficiency of converting electrical energy into RF energy. Thus, determine the area of coverage.

There are several antenna configurations to meet various condition and terrain.

A typical antenna parameters are:

Frequency Band : This is the range of the band that the antenna will operate in (i.e.806-870 MHz). This only means that the antenna will operate within this band. Itusually does not necessarily mean that the antenna will operate over the entireband.

Bandwidth : The maximum frequency separation that this antenna will operatewithin the frequency band.

Gain : Antenna gain is proportional to the product of directivity and the antenna sefficiency. Directivity is a measure of how an antenna focuses energy. Antenna sefficiency accounts for loss associated with antenna. Gain is achieved in an antennaby re-directing energy from some directions into the desired directions. The higherthe gain of the antenna, the further the coverage obtained. However, a higher gainantenna typically means higher cost.

Radiation Pattern : In Two-Way Radio, there are usually uni-directional antenna oromni-directional antenna. The names reflect the radiation pattern produced by eachtype of antenna.

Maximum Input Power : Look for the specs with the maximum input power ratingof the antenna is greater than the RF power output rating of the transmitter(s).

VSWR (Voltage Standing Wave Ratio) : A high VSWR (Voltage Standing WaveRatio) implies a large amount of reflected power. This means that the amount of forward power is less. Therefore, the higher the VSWR, the less efficient theantenna.


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Length : This refers to the physical length of the antenna. A long antenna iscumbersome to ship, store or install.

Wind Loading : In windy areas, the load of the wind on the antenna must be takeninto account.

Dispatcher or Console System

This is a network sub-system where an operator, commonly known as dispatcher, interfacewith the netwo rk to monitor users activities and communicate with users in the field. Thedispatcher acts as the central focus of the most two-way radio system and usually has morepowerful features to allow the dispatcher operator to effectively monitor and manage theusers in the field. The dispatcher is usually located at organization s control center (alsoknown as: Command and Control room or Monitor room).

In traditional two-way radio system, console or dispatcher system has various buttons andLEDs to facilitate monitoring and managing various talk group. In a modern two-way radio

system, these buttons and LEDs are replaced with Personal Computer equipped withspecialized Digital Sound Processing (DSP) card and other specialized equipment to facilitatemonitoring and managing users effectively. Many dispatcher and console system has aGraphical User Interface (GUI) for ease of use.

Network Management System

This is a network sub-system to monitor and manage all related components in the entirenetwork. Depending on the products, Network Management System can vary in term of functionalities and performance. An industry standard for network management whichfollows the Open System Interconnection (OSI) reference model will have, at least, thefollowing functional management known as FCAPS:

- Fault management

- Configuration management

- Accounting management

- Performance management, and

- Security management

In modern two-way radio system, the Network Management System uses computerized

system, such as Personal Computer with specialized hardware and software to perform thefunction. The use of Personal Computer with Graphical User Interface (GUI) will make iteasier for network manager to monitor and manage the network.

Area of Coverage

Area of coverage indicates the area where the radio terminals have usable signal (uplinkand downlink) to use the radio network. The usable signal means an acceptable signal levelthat allows user to communicate. A term that is mostly used in area of coverage is coverage


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reliability. A 95% coverage reliability means that there is 95% chance that user will havethe acceptable signal level in particular area of coverage. The higher the number, the betterthe coverage but it usually comes with higher cost due to the need to build more basestation or repeater sites.

Source: Google

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