«ETSI TR 102 021-10 V1.1.1 (2010-12) Technical Report Terrestrial Trunked Radio (TETRA); User Requirement Specification TETRA Release 2.1; Part 10: Local ...»
Regarding the reliability of the coverage, the users expect that the coverage is as predictable as possible. This means that the signal strength should change a slowly as possible in function of the distance from the transmitter and preferable almost only in function of the distance from the transmitter. This is especially important for indoor communication. The user expects that also indoor the signal strength is (very) slowly changing and also preferable mainly based on distance to the transmitter. E.g. going around a corner wall should not result in a sudden complete loss of the communication. Moving indoor in a closed room (no new walls or corners) should certainly not suddenly affect the available services (communication). E.g. physical dimensions of indoor objects should not create unreliable communication when small movements are made.
8 Data rate As already indicated, the "data-throughput" of the LMB is expected to at least support the TETRA 1 (voice, SDS, IP) and TETRA 2 (wide-band applications introduced with TEDS) services and throughputs. If the used frequencies allow high bandwidth ("channels") the LMB is expected to support real broadband services and throughputs.
For the already mentioned LMW version this means that the data rate is comparable with the TEDS data rates.
For the "real" LMB the data rate should be comparable with what is currently available and under development in the commercially wireless local area technologies.
9 Voice LMB (and LMW) is expected to support all TETRA voice services.
LMB (and LMW) is expected to behave like a TETRA base station, which means that multiple simultaneous TETRA voice call are supported, (pre-emptive) emergency call is supported, group scanning is supported.
It is expected that GoS for these TETRA voice services are comparable (at least those) of the current TETRA.
10 Data LMB (and LMW) is expected to support all TETRA data services, including SDS.
LMB (and LMW) is expected to behave like a TETRA base station, which means that multiple simultaneous TETRA data services are supported.
It is expected that GoS for these TETRA data services are comparable (at least those) of the current TETRA.
11 Voice and data interaction LMB (and LMW) is expected to support all TETRA services simultaneously.
LMB (and LMW) mobiles are expected to support TETRA voice and data simultaneously.
12 Service transparency between TMO and LMB to allow seamless operation LMB is expected to behave like a TETRA base station. This means that the users can continue to use all their current TETRA services when being in LMB.
If the LMB is in isolated mode (no connection to a non-ad hoc TETRA network), some mobiles or applications could of course be unreachable.
13 LMB gateway The LMB network should be capable of being securely connected, extended and integrated into the non ad-hoc fixed TETRA network.
It is expected that this can happen automatically based on preconfigured settings in the LMB equipment.
It is expected that this integrated LMB can support communications of independent organisations: support all fixed TETRA network communications over the LMB area, whilst maintaining the existing private "VPN" communications.
14 Security The LMB network should be as secure as current TETRA networks.
The LMB network should be made robust and redundant, securely supporting intervention teams of different disciplines within the same incident area.
TETRA World Congress 2007 workshop A.1 TETRA World Congress 2007 workshop enhancement area's TC TETRA organised a workshop at the TETRA World Congress 2007 to discuss the candidate TETRA enhancement areas for TETRA Release 2 evolution.
The objectives of TC TETRA for the workshop were:
• to provide a clear indication to TC TETRA of the weighting and relative importance of all candidate TETRA enhancement areas identified;
• to produce a set of User Requirement Specifications (URSs) for use in TC TETRA to initiate new standardisation work by the technical Working Groups as required;
• to further enhance the portfolio of TETRA standards with new services and facilities, as well as performance enhancements, to ensure the continued evolution, success and longevity of TETRA as the technology of choice for traditional PMR user organisations.
Regarding to Local Mode Broadband, 2 enhancement areas were identified and specified as:
• Local Mode Broadband:
Even though the TETRA standard has been enhanced for "wide-band" applications with the introduction of TEDS, some suggestions have been made to further increase data throughput to match that offered by broadband data services. For example, some suggestions have been to provide access to broadband services in certain "hot zones" within a TETRA TMO network coverage area. It was also suggested that "hot zone" coverage should dynamically increased and/or decreased as required for communication purposes.
• Networking capability for Local Mode Broadband area to Local Mode Broadband area To further enhance the capability of broadband services in certain "hot zones" as suggested above, there have also been suggestions to increase "hot zone" coverage by interconnecting different "hot zones" together via the TMO network.
The related identified DMO enhancement areas:
• Increased frequency efficiency Some users have expressed a need to increase the number of independent DMO channels within the limited frequency spectrum available.
• Increased call service reliability/availability Some users in particular DMO communication scenarios have experienced difficulties in setting up long range DMO calls.
• Increased data rate Requirement for DMO Data rates matching those already available on TMO.
• Duplex voice Full duplex DMO voice communications as provided on TMO
• Concurrent voice and data Even though available in the TETRA V+D standard (though not yet provided by suppliers) a requirement for "concurrent voice and data" in DMO has also been requested.
• Increased service transparency between TMO and DMO to allow seamless operation Requirements have been mentioned for increased service transparency between TMO and DMO in, for
example, the following areas:
• Improved performance behaviour of gateways and repeaters Some members of the TETRA community have expressed a need to provide improved performance behaviour of gateways and repeaters, in areas of, for example, call set-up times, increased range, call set-up reliability, etc.
• Multiple call support on gateways and gateway/repeaters This enhancement area refers to the capability of a single gateway, repeater or gateway/repeater to support more than one DMO call simultaneously.
• Application Programming Interface (API) The API is required in both DMO and TMO terminals to provide a standard interface for use by application providers to supply, for example, internet/intranet access, location information or services applications, etc.
• Accessory interface standard (hardwire and wireless) Although this is not a DMO specific enhancement area, it has been placed in this category grouping as it was not considered appropriate to have a separate MS only category. This suggested interface standard covers for example, the type, size, location, appearance of such items as displays, buttons, switches, as well as the type of connectors, pin usages and electrical/electronic levels, impedances and RF signalling protocols and also the type of batteries.
• Networking capability This networking capability is the same as that mentioned in the TMO Enhancement grouping under "Networking capability for DMO area to DMO area" and has been placed in the DMO Enhancement area grouping to assess its relevant importance compared with other DMO enhancement areas.
• Mesh Type Enhancement TMO/DMO. (suggested by a participant during the workshop, no description).
• Dual Scanning (suggested by a participant during the workshop, no description).
The related identified TMO enhancement areas:
• Enhancing DMO with the use of TMO. (suggested by a participant during the workshop, no description).
A.2 TETRA World Congress 2007 workshop results The results are presented in TR 102 621 [i.1].
A.3 Analysis current situation
Currently TETRA radios support 2 methods of operation:
• Trunking Mode Operation (TMO): communication between radios uses a fixed infrastructure with a centralised intelligence (SwMI).
• Direct Mode operation (DMO): communication between radios happens without usage of the fixed infrastructure and without using a centralised intelligence (SwMI).
During interventions TMO is preferred because this offers most features and facilities like voice and data (SDS and IP).
It offers of course also connection to remote teams and control rooms. The problem is however that if the base stations are at some distance from the buildings on the incident area, coverage in those areas is not anymore guaranteed. The only more or less guaranteed operation mode becomes then DMO. A disadvantage of having to use DMO is that (with most current implementations) all users have to switch to DMO. Not only is this a cause of human errors, but it also means that a lot of the wanted services are lost (connection towards remote users, control rooms, crisis centre, SDS, IP).
There is the DMO gateway that was supposed to bridge the gap between DMO and TMO but up to now has not succeeded to do so. Not only is the DMO gateway not supporting all wanted services (IP, SDS, scanning of talk groups of remote users, etc.) but also the performance and reliability of the basic service "voice group call" has not been perceived as good. Call setup times seems to be too long, random access collisions seem to cause call setup problems, coverage differences between DMO gateways and DMO radios cause problems.
Currently DMO suffers from trying to be two things at a time and it succeeds in neither of them:
• DMO tries to offer a basic two-way radio (walky-talky service) like available in the ("old") analogue equipment. However, because of the complex modulation it can't offer the range of the "old" analogue equipment. And because of the "non-transparency" between TMO and DMO it can't offer the seamless integration between on site communication and "remote" communication.
• DMO tries to offer data services, but these are very limited and/or not implemented.
Instead of trying to improve the current DMO (including DMO gateways and repeaters) which is based on narrowband technology from more than a decade ago it is probably easier and more efficient to start with a new approach based on the current broadband IP technologies.