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

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

In multi-channel systems, channels are used to separate purposes. A channel may be reserved 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. A second channel may allow road repair crews to communicate with state highway department crews. In a geographic system, a taxi company may use one channel to communicate 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 one frequency (RF channel) at any one time. If two radios attempt to transmit in the same frequency 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 the same frequency which can cause interferences if users are not discipline.

  

 

See examples of conventional mobile radio >>

See examples of conventional portable radio >>

 

 

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Radio communications can utilize one of 3 modes:

1. Simplex

This is a mode where both transmitter and receiver operate on the same frequency. User cannot listen or talk simultaneously and only one radio can talk at any one time, while others listen. This mode is used by the most basic radio communication. Radio to radio communication like the FRS walkie-talkie uses this mode. Another example is aircraft VHF AM and marine radios.

Simplex systems often use open architectures that allow any radio meeting basic standards to be compatible with the system. It allows old radios to work with new ones in a single network. This gives advantages as simplex systems are often legacy systems that 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. User cannot listen or talk simultaneously. This mode of operation requires a pair of two frequencies, one for transmit and one for receive. This mode is commonly used for repeater or base station operation. In repeater operation mode, all mobiles/portables radios in the system can hear the repeater transmission, but mobiles/portables cannot hear 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 can listen 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 where the 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.

 

MPT1327 Analogue Trunking

MPT 1327 is a industry standard for trunked radio communications networks. It was developed in 1988 by the British Department of Trade and Industry (DTI), Although a British standard it is widely used around the world and the most used trunked radio protocol.

• Analogue voice quality
• Fast emergency call set-up
• Comprehensive support to group and individual voice and data communications
• Digital control channnel for fast call setup supports + data services
• Subsriber units support encryption levels (Option Boards)
• Data transmission via MAP27 - AVL, Message Handling Dispatcher and Email gateway.
• Fylde MPT1327 is capabable of 500+ sites over multi-regions and Countries

Data messages between mobiles and the network are exchanged on the control channel at 1200 bits per second. Each subscriber in an MPT-1327 trunked radio network has a unique call number.
For the duration of a call a subscriber is exclusively allocated a traffic channel from the available trunk.

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Future MPT1327 Migration to Digital - DMR & dPMR Protocols

The next generation Fylde trunking controller - Available in 2011

MultiLingo is the next generation Fylde trunking controller. This, our 4th generation controller, will support MPT1327, DMR, dPMR and conventional systems. More than that, MultiLingo has been designed to support these protocols within the same radio site. This allows customers to select their protocol of choice as and when they are ready. Note however that the repeater requirements are much more demanding for DMR (TDMA) than for analogue or indeed dPMR (FDMA)..

 

More details can be found by visiting Fyldemicro.com Click Here

More details can be found by visiting Fyldemicro.com Click Here

 

 

There are three tiers in the DMR standard.

DMR Tier I: Unlicenced

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

Tier I provides for consumer applications and low-power commercial applications, using a maximum of 0.5Watt RF power. With a limited number of channels and no use of repeaters, no use of telephone interconnects, and fixed/integrated antennas, Tier I DMR devices are best suited for personal use, recreation, small retail and other settings that do not require wide area coverage or advanced features.

DMR Tier II: Conventional

DMR Tier II covers licensed conventional radio systems, mobiles and hand portables operating in PMR frequency bands from 66-960MHz. The ETSI DMR Tier II standard is targeted at users who need spectral efficiency, advanced voice features and integrated IP data services in licensed bands for high-power communications. ETSI DMR Tier II specifies two-slot TDMA in 12.5kHz channels.
DMR Tier II products are commercially available today.

DMR Tier III: Trunked

DMR Tier III covers trunking operation in frequency bands 66-960MHz. The Tier III standard specifies two-slot TDMA in 12.5kHz channels. Tier III supports voice and short messaging handling similar to MPT-1327 with built-in 128 character status messaging and short messaging with up to 288 bits of data in a variety of formats. It also supports packet data service in a variety of formats, including support for IPv4 and IPv6.

 

APCO-25 (Association of Public Safety Communication Officials – Project 25) is an open standard for digital radio developed in North America under state, local and federal representatives and Telecommunications Industry Association (TIA) governance. The standard was developed to foster the development and progress of the art of public safety communications.

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

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

As APCO is an association representing users, assistance was sought from industry in developing the standard. The Telecommunication Industry Association (TIA) provided technical support and the mechanics of standard writing, which has made the resulting specification (ANSI/TIA 102) into a national industry standard. Published P25 standards suite is administered by the Telecommunications Industry Association (TIA Mobile and Personal Private Radio Standards Committee TR-8).

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

 

 

 

TETRA Digital Trunking

Tetra is a standard specified by the European Telecommunications Standards Institute (ETSI) during the '90s in response to the need of a common digital trunked standard for PMR. ETSI standard assures the interoperability between various manufacturers terminals that can indistinctly operate on any TETRA network, the user requirements fulfillment and a future-proof technology. Main TETRA features are:

• Digital voice quality
• Fast emergency call set-up
• Comprehensive support to group and individual voice and data communications
• Communications also in fringe or out of coverage areas with direct mode of operation (DMO)
• Multiple security schemes and algorithms (two encryption levels)
• Data transmission at up to 28.8Kbps and simultaneous with voice
• Standard interfaces for data terminal connections (PEI) and for TETRA networks interconnection (ISI)

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 call, etc

Spectrum Utilization
TETRA utilizes Time Division Multiple Access (TDMA) technique to achieve spectrum efficiency. TETRA can achieve up to 4 (four) TDMA time slots in one 25 KHz radio channel

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 specific market.