White Paper Prepared by Titan ICT, 2019  |  Download PDF Version

Comparing the Benefits, Features and Functionality of Digital Mobile Radio Systems in the 400MHz Band.

Regulatory Changes in the 400MHz Band

The Australian government regulatory body for radio communications, ACMA, have undertaken a review of their 400MHz band in 2010 to reduce congestion that currently exists in the band. The objective is to enable the use of modern, spectrally efficient technology
whilst prohibiting use of inefficient systems where appropriate. The following outcomes are currently being implemented by ACMA in a transition plan:

Land mobile radio mandated to 12.5kHz channel raster with further splitting of channels to 6.25kHz permitted. Prohibition of the use of 25kHz channels in high density (greater Brisbane, Sydney and Melbourne) and medium density (greater Perth, Adelaide and Newcastle) areas with the exception of spectrally efficient multi-circuit systems (e.g. TETRA).

Harmonisation of government spectrum to promote interoperability and efficient multi-agency networks within the 403¬430MHz band.

Alteration of the arrangement of the 450470MHz band to allow 10MHz duplex frequency splits to enable the use of cellular type technologies such as TETRA.

These changes are a welcome introduction for highly featured digital mobile radio technologies to be used in the 400MHz band such as TETRA which, due to regulatory restrictions in the past, was not allowed to be licensed in Australia in this band.

Introduction of TETRA and APC0-25

APCO Project 25 (APCO25) is a set of open standards initiated by APCO (Association of Public Safety Communications Officials) and developed by the Telecommunications Industry Association (TIA). One of the important aims in developing the standards was to ensure interoperability between public safety agencies, as proprietary systems had prevented this in the past. The set of standards focuses on voice priority, in particular for use in emergency scenarios. For this reason, the standard mandates that voice traffic takes precedence over data traffic.

TETRA (TErrestrial TRunked RAdio) is a European Telecommunications Standards Institute (ETSI) standard. It has been established as the default standard for public safety networks in the UK and in Europe. TETRA was developed to meet the requirements of diverse kinds of end users (not only public safety users). ETSI envisaged networks provided by national organisations, with nationwide coverage, operating usually in urban environments. Consequently, TETRA is more like a cellular telephone system than other VMR standards and is suited to areas with high volumes of radio traffic. It relies on high user numbers to share the infrastructure cost.

Why Use Digital Radio?

Traditionally, for voice mobile radio (VMR) applications, conventional analogue systems have been used in the 400MHz band to cater for a wide range of industries. In addition, data applications including those such as telemetry, remote control and monitoring have been implemented using analogue data radio technologies. Digital mobile radio technologies serve as an alternative solution for converging voice and data applications in the 400MHz band. Digital mobile radio can potentially be utilised for the following uses as a single convergent system:

  • Voice communication including voice recording
  • Process control
  • GPS tracking for vehicles, terminals etc Telemetry, remote control and monitoring
  • GPS based applications (e.g. incoming call)
  • Email and internet applications such as Wireless Application Protocol (WAP)
  • Automatic train operation
  • Database lookups including image downloads for identification and maintenance purposes
  • Private calling to handheld radios from SIP enabled telephones (via a specialised gateway)

This white paper focuses on two digital voice mobile radio technologies that can provide these combined voice and data capabilities, TETRA and APCO Project 25 (APCO25).

TETRA

APCO – 25

Voice CommunicationIndividual, group, broadcast, emergency & priority callingIndividual, group, broadcast, emergency & priority calling
Process ControlTETRA enabled remote data modems available supporting RS-232, RS-485, Ethernet, ModbusAPCO-25 is designed as a voice priority system. Dedicated data channels (i.e.standalone base station) required
GPS Applications (e.g. vehicle tracking & logging)Terminals SupportGPS interface and Application Programming Interface (API) which enables GPS based applicationsTerminals SupportGPS interface and Application Programming Interface (API) which enables GPS based applications
Remote Control  & Monitoring, TelemetryTETRA enables remote data modems available supporting RS-232, RS-485, Ethernet Modbus etc serial interfacesAPCO-25 is designed as a voice priority system. Dedicated data channels i.e. standalone base station) required
Automatic Train OperationOne dedicated 25 kHz TETRA carrier can provide approx. 9kbps raw data throughput for ATO applications. Can operate in full duplex to allow efficient use of automatic repeat requests (ARQ) for data integrity under RF fadingOne dedicated 25 kHz APCO-25 carrier can provide approx. 4kbps raw data throughput for ATO applications. Simplex data only, inefficient compared to TETRA for transmission of ARQ data repeat requests
E-mail/ Internet (WAP)Many TETRA enabled PDA and terminals available enabling WAP browsing applications and e-mail capabilityLimited APCO-25 devices currently available which support these applications
Image Sharing (e.g. photographs for identification or diagnostic purposes)Many TETRA enabled PDA and terminals available enabling photographic image sharing between TETRA devicesLimited APCO-25 devices currently available which support these applications
Database Lookup (e.g. for remote diagnostic access)Many TETRA enabled PDA and terminals available enabling information downloads to devices from server databasesLimited APCO-25 devices currently available which support these applications
Voice Recording/ LoggingDevices can be integrated to TETRA network to record and log transmissions and devices within the networkDevices can be integrated to APCO-25 network to record and log transmissions and devices within the network
SIP Telephone IntegrationGateway devices available which enable private voice calls between a SIP enables telephone and TETRA terminalGateway devices available which enable private voice calls between a SIP enables telephone and APCO-25 terminal

 

Table 1: Comparison of applications and uses for TETRA and APCO-25 networks

 

CONVENTIONAL

TRUNCKED

Simple topology, networks consist of repeater sites consist of a base station unit, multicoupling and antennas. To form channel groups consisting of multiple sites, voting unit(s) are required at each site or at a centralised locationFor a given number of users, fewer discrete radio channels required compared to conventional. From another perspective, with a given number of radio channels, a greater quantity of users can be accommodated
Fast call set-up time. There is no delay incurred for channel assignment as in trunked networksIntelligence in the trunking controller makes it possible for any available channel to be assigned to any user. For calls involving more than one site, the controller only includes those sites which have participants in the call. If one traffic channel (base station) fails, the capacity of the network will only decrease by one call slot; no users lose service
For smaller numbers of users it is cost effective as networks can consist of a single standalone base stationGreater impact on cost due to the requirements for additional trunking controllers at each site in addition to the network core controller located at the master site.

 

Table 2: Considerations for Conventional and Trunked Networks

Consideration for Implementation of Systems

TETRA and APCO-25 provide varying levels of operation and selection of any one of these technologies depends on end user requirements of the network including number of users, capacity, coverage area, applications and uses (required capacity).

Scale of Mobile Radio Network

The number of users accessing a mobile radio network within the required coverage area can influence the selection of an appropriate network topology and ultimately, the digital radio technology.

Conventional radio is a system in which each group of users is assigned one frequency. If one user is occupying a channel, other users willing to make a call must queue or wait until the channel is free.

In contrast, a trunked radio system is where user groups share an allocated group of frequencies. Trunking is a system option for larger networks. Instead of allocating each channel to a set of users, trunking intelligence makes it possible for any available channel to be assigned to any user.

The APCO-25 technology may be configured in either conventional and/or trunked mode. TETRA may only be configured as a trunked network. The table below compares the implementation considerations for conventional and trunked networks.

Refer to Table 2: Considerations for Conventional and Trunked Networks on page 7.

Equipment Capacity

Dependent on the scale of the network and required data applications, TETRA and APCO-25 offer varying levels of voice and data capacity per frequency carrier.

A single TETRA transmitter utilising 25 kHz of spectral bandwidth can offer 4 channels (or timeslots), where one channel will be dedicated to control purposes (subsequent transmitters at one site will support the full 4 channels for voice and data). In comparison, an APCO-25 system requires 4 transmitters utilising 12.5 kHz of bandwidth each to achieve the same number of channels.

TETRA utilises half of the required spectrum to achieve an equivalent number of channels when compared to APCO-25. In addition, the use of four timeslots in a TETRA carrier enables the use of full duplex communication (transmission in both directions) for voice and data which is not supported with a single APCO-25 carrier.

The future release of APCO-25 Phase II will address these issues where 2 channels will be supported per 12.5 kHz of bandwidth.

For the use of digital mobile radio to provide data applications, it is possible for both TETRA and APCO-25 to support combined voice and data. As TETRA supports full duplex, it uses this to its advantage for automatic repeat requests (ARQ) to be communicated allowing for higher efficiency in data throughput. Typical data rates for each standard are as follows:

  • APCO-25 – 9.6kbps maximum throughput per 12.5kHz carrier. Actual packet data rate following error correction and overheads of 4kbps
  •  TETRA – 7.2kbps maximum per channel (or timeslot) totalling 28.8kbps maximum per 25 kHz carrier. Actual packet data rate following error correction and overheads of 3.5kbps per timeslot, or a total of 9kbps when combining all four timeslots.

Impact on Site Infrastructure

Site infrastructure to support a digital mobile radio network includes three basic elements being equipment accommodation, power source and antenna support structures. Radio repeater sites that are located in a remote location may be in an area without access to mains power and utilise solar power as the primary power source. Utilising solar power creates an increased site infrastructure cost and it is important in any design to minimise communications equipment power consumption to minimise the cost of implementing solar power systems. The following considerations should be noted when implementing a digital radio system:

  • Trunking based systems (whether they are APCO-25 or TETRA) typically require site controllers to be co-located at each repeater site. Site controllers can be power hungry devices dependent on the vendor or system type.
  • Typically base stations are rugged and operate under extreme climate conditions. Site controllers in some trunking based systems are highly intolerant to these conditions and require active cooling to overcome this. The use of air conditioning is highly wasteful on power generated at solar sites.
  • For APCO-25 trunked based systems, each channel requires its own base station. Each channel that is added to a site will increase the power consumption considerably. In contrast, each TETRA base station supports 4 channels resulting in lower transmitter power consumption when compared to 4 APCO-25 base stations. Conventional APCO-25 systems typically consumes less average power in contrast to trunked APCO-25 as the base stations are only drawing maximum power when transmitting (e.g. when users are operating radios)

Terminal Devices

Many data applications are device based and selection of terminals (i.e. mobiles and portable handhelds) may be based on its proposed uses. In addition to traditional mobile radio devices, TETRA enabled PDA’s are also available on the market. Both APCO¬25 and TETRA devices support an Application Programming Interface (API) which enables numerous feature rich data applications to be enabled on its various devices. Some of these advanced features include:

    • GPS based applications (e.g. incoming call location, tracking & logging)
    • Email and WAP based internet browsing
    • Image sharing (e.g. photographs for person identification or equipment diagnostics)
    • Database query (e.g. for remote diagnostic access to data)

    Modern digital mobile radio networks also permit the transmission data in process control, monitoring or telemetry applications. SCADA units are available which are TETRA capable and support a number of serial data interfaces including RS-232, Modbus etc or Ethernet interfaces.

    Security of Network

    Trunked networks provide a number of features which provide increased security to private mobile radio networks. Trunked networks store information of terminal units that are registered and/or make calls centrally on the network controller. Some of features this enables include:

    • Restrict access to the network to only terminals which are registered for use
    • Restrict individual terminals to certain features and functionality of the network
    • Define the user groups which have individual access
    • The dynamic and random allocation of channels makes it more difficult for a casual eavesdropper to monitor conversations
    • The identity of all users along with the time and duration of messages are known to trace and/or
      ban abusers of the network
    • Supports end to end encryption of channels to prevent eavesdropping

    Migration from Analogue Networks

    Careful planning is required when migrating from conventional analogue mobile radio networks to digital mobile radio. Some critical issues that will impact the planned upgrade path include:

    • Upgrade of network wide mobile fleet. The APCO-25 standard supports backwards compatibility with conventional analogue terminals whilst TETRA does not. Utilising APCO-25 base infrastructure will allow gradual upgrade of analogue devices to APCO-25 devices.
    • Upgrade of analogue base stations. For a multiple site network, legacy analogue base stations can be interconnected to an APCO-25 based network via analogue gateways. This allows analogue base stations to be upgraded in a staged process.
    • The APCO-25 standard specifies dual mode (analogue and digital mode operation) for both
      base stations and terminals. Upgrading the mobile fleet to APCO-25 terminals allows interoperability between conventional analogue and APCO-25 base stations.
    • Upgrading from an analogue radio network to a TETRA based network. TETRA terminals are
      not backwards compatible with legacy analogue networks. A defined planning strategy is required to upgrade both site infrastructure and the mobile fleet to TETRA.
    • Antenna, feeder and multi-coupling upgrades. Typically, conventional analogue base stations are licensed to run at 25 kHz. Upgrading to equivalent APCO-25 base stations requires re-tuning or
      upgrade of multi-coupling systems to support 12.5kHz channelling arrangements. TETRA systems typically utilise receive diversity antennas and will require upgrades to antenna installations at base sites.
    • Site DC power and accommodation capacity. Individual site analysis is required to ensure sufficient power source, battery backup, rack space and/or floor space is available to accommodate new base equipment.

    Selecting the Right Standard for your Requirements

    The common perception is that APCO-25 based systems are most suitable for low and medium capacity deployments which require large coverage areas while TETRA systems are suitable for small coverage area, high capacity applications. These perceptions were due to characteristics of TETRA systems including base stations and terminals with low RF power output and poor dynamic sensitivity of the TETRA receivers due to the modulation scheme (non constant envelope). In addition, the restrictions enforced by the ACMA of frequency license allocations for TETRA in the 400MHz band reinforced the preference for APCO-25 systems as they offer wider coverage being attractive for industries such as mining, oil and gas, utilities and rail.

    Latest developments in the TETRA marketplace driven by demand and improvements in technology led to the introduction of compact TETRA systems with improved receive sensitivity, higher power base station and terminals with similar characteristics to APCO-25 systems. In addition, a recent change to the 400 MHz band plan by ACMA now enables the use of TETRA as an alternative to APCO-25 in the 400 MHz band. The table below summarises some of the key features and functionality of TETRA and APCO-25 for Phase I systems.

    Refer to Table 3: Key features and functionality of TETRA and APCO-25 systems below.

    Future development of TETRA and Project 25 standards Currently, both the APCO and TETRA organisational bodies are developing next generation standards named APCO-25 Phase II and TETRA Release 2 respectively.

    The mandated developments and objectives for APCO-25 Phase II include:

    • Increase of spectral efficiency utilising TDMA techniques to provide two time slots within a 12.5 kHz RF channel. This will enable equivalent spectral efficiency to TETRA systems
    • The control channel will support FDMA techniques to enable backward compatibility with Phase I systems.
    • An improved voice encoder (vocoder) shall be implemented to further compress the required to 4800bps per voice channel.
    • Improved modulation techniques to increase data throughput within an equivalent channel width.

    Current developments within the TETRA Release 2 include:

    • Increase of the current maximum coverage range of 58km to 83km. Note that this is the theoretical maximum and actual range is limited by RF losses and terrain.
    • TETRA Enhanced Data Service (TEDS) is a new high speed data service using different RF channel bandwidths and data rates for flexible use of PMR frequency bands. TEDS is fully compatible with TETRA Release 1 and allows for ease of migration. TEDS will support adaptive selection of modulation schemes, RF channel bandwidths and coding according to propagation conditions and QoS negotiation for real-time class data applications.

     

    TETRA

    APCO-25

    Trunked system, highly feature rich with more advanced functionalityOperates in both conventional and trunked modes. The use of conventional network is more cost effective for a small number of users or small systems
    Higher spectral efficiency. Half of the RF spectrum required to provide the same number of channels as APCO-25 systemsDeveloped primarily for public safety radio networks. As a result emergency calls and voice calls take absolute priority over data
    Only one base station required to provide four channels. Savings on base station cost, power consumption and rank spaceOne base station required per channel. Higher overall capital cost and power power consumption compared to TETRA
    Typical coverage area of modern TETRA systems is 30-40km (rural)Typical  base coverage area of APCO-25 systems is 40-50km (rural)
    Cellular based standard. One carrier provides full duplex communications enabling higher data efficiency, duplex voice communication. Base station allow call handover betweem cellsFull duplex capability for trunked APCO-25 systems. half duplex for conventional systems
    Concurrent voice and data. As one carrier supports four timeslots, two timeslots can be used for data whilst one is assignmed for voice. Alternatively, all timeslots can be combined for up to 9kbps of data throughputBase stations support combined voice and data, however concurrent capability only in trunked APCO-25 systems Data throughput per base station or channel is approximately 4kbps

     

    Table 3: Key features and functionality of TETRA and APCO-25 systems

    How Titan ICT can add value when implementing Mobile Radio Systems

    Titan ICT has a long involvement in mobile radio networks for rail and mining industries throughout Perth and country WA. Titan ICT has also been involved in designing and implementing mobile radio networks for a number of ‘greenfield’ and ‘brownfield’ for some of WAs biggest resource projects.

    Our experience includes:

    • Silcar Communications – Titan ICT designed the communications elements of the Public Transport Authority’s Southern Suburbs Rail Project including the private mobile radio (PMR) component.
    • Rio Tinto Simandou – Design of the Simandou P25 PMR system for the 800km rail network connecting mine to port in West Africa
    • Rio Tinto Iron Ore – Titan ICT designed the upgrade to Rio Tinto’s PMR system in the Pilbara. This project involved the design for 3 ports, 14 mines and 1300km rail. Titan ICT was also engaged to project manage the implementation and commissioning of the system which included radio upgrades, implementation of SINAD voters and the associated consoles
    • WestNet Rail – Detailed Design and implementation of the PMR system on the Midwest network from Geraldton to Perenjori
    • Australia Premium Iron JV (API JV) – West Pilbara Iron Ore Project (WPIOP) Phase 1 definitive feasibility study (DFS) voice mobile radio network review.

    Titan ICT has the expertise to advise and engineer the most appropriate fit-for-purpose designs and systems for mobile radio networks. Titan ICT can assist in the following ways:

    • Facilitate business decisions regarding implementation of services and mobile radio technologies (e.g. an over arching strategy)
    • Develop standards and specifications for network infrastructure and service delivery equipment to ensure consistency across your business
    • Engineering design for mobile radio networks and site infrastructure
    • Tender package development and evaluation services
    • Project management of the implementation up to and including commissioning and final acceptance.

    Involving Titan ICT in the early stages of planning for new or upgraded mobile radio networks will allow any project to benefit from this experience and expertise and avoid pitfalls in design or implementation that might cause significant project delays or lead to ‘band¬aid’ solutions.

    Choosing the right implementation strategy will ensure the required services are delivered in a reliable manner at the lowest cost. Titan ICT’s experienced consultants will be happy to discuss how we might assist at any stage of your mobile radio project.

    About Titan ICT

    Titan ICT is an Australian-owned company specialising in strategic ICT advice, systems integration and technical support services to deliver high quality integrated technology and business solutions. With a proud record of delivery since 2003, we have a national footprint with offices located Perth, Brisbane, Melbourne and Sydney.

    From the outset the decision was made to focus purely on ICT disciplines providing trusted advice and engineered solutions that tackle technology transformation and maximise the potential of any project, big or small.

    As a result, we are at the forefront of new technologies by constantly turning to innovation and ingenuity for the development of tailored, leading-edge solutions that support the operational and strategic objectives of the companies we work with.

    By working with us, you too can enjoy the success that results from the bringing together of world-class skills, best in breed products and practical know-how in planning, managing and delivering complex scopes of work.

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    Disclaimer

    The author only represents himself as competent professional in the planning, design and implementation of Telecommunications and Information Technology systems, networks and practice. Any statement provided which may be of a legal nature is only offered as an opinion based on the author’s understanding of the law and how it may apply. The author has made every effort to identify all relevant and available source data in the preparation of this document. All surveys, forecasts, projections and recommendations are made in good faith on the basis of information available at the time. The author, its agents, licensee and/or other representatives disclaims any liability for loss of damage caused by errors or omissions, whether such errors or omissions resulted from negligence, accident or other causes. Neither the author, its agents, licensee nor representatives will be liable for any loss or other consequences (whether or not due to the negligence of the author or their agents) arising out of the use of information in this report. No responsibility is taken for the accuracy of this information in relation to pricing or functionality of products and services described in this report. Readers should confirm with the appropriate service provider as to the validity of the information and any variations which may have taken place since publishing.