Rechnernetze

DECT Application Profiles

Application profiles contain additional specifications defining how the DECT air interface should be used in specific applications. Standard message and protocol subsets have been derived from the base standard’s tool-box tailored for specific applications with the aim to achieve maximum interoperability between DECT equipment from different manufacturers. In addition to the profiles, profile conformance test specifications have been developed by ETSI that enable harmonised testing of DECT equipment designed to meet the profile requirements.

Generic Access Profile (GAP)

The Generic Access Profile (GAP) [9] is the basic DECT profile and applies to all DECT portable and fixed parts that support the 3.1 kHz telephony service irrespective of the type of network accessed. It defines a mini-mum mandatory set of technical requirements to ensure interoperability between any DECT GAP fixed part and portable part.

Procedures are described to establish, maintain, and release 3.1 kHz speech connections and mobility management procedures are included to support incoming and outgoing calls for roaming users. The GAP is the basis for all other (future) DECT speech profiles.

DECT/GSM Interworking Profile (GIP)

Since DECT is an access technology and networkwide mobility is outside the scope of the standard, the DECT GIP [10] is a powerful addition providing mobility in DECT infrastructures distributed over multiple sites through GSM mobility functions.

The DECT/GSM interworking profile for basic 3.1 kHz speech service ETS 300 370 [10] (together with ETS 300 499 [11] and ETS 300 703 [12]) defines the protocol requirements to interwork a DECT PP - through a DECT FP - to the GSM network where the DECT FP is directly connected to the A-interface of the GSM MSC. Inter-working is done in such a way that the GSM network does not know that it is being ac-cessed through DECT.

When compared with GAP, the DECT/GSM interworking profile contains additional requirements due to:

	the use of GSM cipher keys
	the use of GSM identities
	PP support of GSM authentication procedures (which are different from the DECT procedures)

DECT portables compliant with GIP are able to interoperate with GAP fixed parts.

As an alternative to the GSM A-interface the ETSI CTM working group developed the DSS1+ protocol that allows interworking between GSM mobility functions and DECT through the ISDN. The DSS1+ protocol (DE/SPS-05121) is based on DSS1 with enhancements to support mobility functions.

ISDN interworking Profiles (IAP and IIP)

For interworking between an ISDN network and a DECT system two profiles have been defined, the DECT/ISDN profile for end system configurations ETS 300 434 (IAP) [13] and the DECT/ISDN profile for intermediate system configurations DE/RES-03039 (IIP) [14].

The IAP applies when DECT FP and PP together constitute an ISDN terminal (ISDN services and supplementary services are offered at the DECT PP).

The IIP applies where a DECT FP and a DECT PP together constitute a transparent gateway between an ISDN network and one or more ISDN terminals connected to an S0-interface at the DECT Intermediate Portable System (DIPS). The IIP supports ISDN basic access and all network defined services i.e. 3.1 kHz speech, 64 kbit/s unrestricted, ISDN packet data and supplementary services.

In the DECT/ISDN (and also in the RAP) profiles the use of the spectrum - in terms of efficiency - has been optimised to fit to the needs of the teleservices offered, which means that: a single full slot (basic DECT voice) bearer is used for each 3.1 kHz speech channel only if it is active and a double slot bearer is used for each active “unrestricted 64 kbit/s” channel. The ISDN D-channel (containing signalling or user data) only requires additional spectrum (max. one full slot bearer) if there is no other channel active between the FP (DIFS) and PP (DIPS). If there is an active channel, the ISDN D-channel is incorporated in this channel.

Radio local loop Access Profile (RAP)

The DECT Radio Local Loop provides a cost efficient means to establish the final drop in a public telecommunication network. With DECT RLL technology, telecommunications operators can serve their customers with relatively low investments in comparison with wired local loop technologies. In developing countries, DECT RLL technology can stimulate penetration of public telephony significantly. In developed markets at places where it is not economic or impractical to install wired public telephony, RLL technology can provide a cost effective solution and in countries that allow for competition in the local loop, new operators can easily enter the market by using DECT RLL technology.

The DECT Radio local loop Access Profile ETS 300 765 (RAP) [15] defines the DECT protocol subset needed to deliver public network services to their end users. The RAP is divided into two parts:

Part 1 of the profile defines delivery of the basic telephony service (POTS, 64 kbit/s bearer service and “over-the-air” Operation, Administration and Maintenance (OA&M) services).

Part 2 describes ISDN services and broadband packet services (incl. data port).

In general, the services are provided through a standard telephone socket at a Cordless Terminal Adapter (CTA). The CTA (fixed version of a portable part) employs the radio connections with the DECT fixed part, which is directly connected to the public infrastructure.

When the CTA and the FP are operated under Line Of Sight conditions and equipped with the maximum allowed 12 dBi gain antennae, radio ranges up to 5 km are feasible. Application of a Wireless Relay Station (WRS) - in the same constellation - extends the radio range by another 5 km.

The WRS is a cost effective infrastructure building block providing improved or extended coverage in low traffic density applications (both indoor and outdoor).

A WRS can be equipped with one directional antenna (directed towards the RFP) and one omni-directional antenna to provide cost efficient public network access to users in remote areas. Coverage gaps caused by obstacles or building reconstruction can easily be repaired by using a WRS.

The WRS concept is specified in ETS 300 700 [17], detailed application information can be found in ETR 246 [18].

In public applications (RLL and CTM) DECT RFPs are installed in a DECT Access Site (DAS), which may comprise 6 to 12 DECT radios equipped with sectorised antennae. In a multi site environment a DAS can support 40 to 60 Erlang (see note 1) at 1% Grade Of Service. This enables a single DAS to serve 400 to 600 subscribers with 100 mE (milli Erlang) average traffic each. An extensive study on traffic capacity and spectrum requirements for multi-system and multi-service DECT applications is reported in ETR 310 [19].

CTM Access Profile (CAP)

The Cordless Terminal Mobility (CTM) service allows users of cordless terminals to roam within and between networks. Where radio coverage is provided and the cordless terminal has appropriate access rights the user is able to make and receive calls at any location within the fixed public and/or private networks, and may move without interruption of a call in progress. CAP is similar to the DECT-GSM interworking with the difference that CAP is not limited to the mobility functions of the existing GSM network but may interwork - in a standardised manner - with any network providing mobility functions.

The CAP profile aims at maintaining compatibility with GAP; in fact, it can be seen as an extension to GAP stimulating the use of DECT for public applications.

Data Service Profiles -( A, B, C, D, E, F, Internet interworking)

A family of data transfer profiles is developed by ETSI to ensure interoperability for data communication equipment being connected through the DECT air interface. Each member of the profile family is optimised for a specific service. The table below shows a list of data profiles as currently planned.

Profile	Reference	Application
A/B.1	ETS 300 435	Generic frame relay for interworking with Ethernet and Token ring LANs at up to 552 kbit/s. Forms the basis for the C and F profiles.
A/B.2	ETS 300 701	Supports similar services as ETS 300 435 for mobile applications and provides direct interworking with the Internet Protocol (IP).
C.1	ETS 300 699	Generic data link service built upon the generic frame relay service of the A/B profile for applications that need a high degree of data integrity. It includes interworking with V.24 interfaces.
C.2	ETS 300 651	The C.2 profile extends the Data Stream service into environments where mobility is required. It contains interworking with V.24 and connection oriented bearer services.
D.1	not yet finalised	Provides transparent and isochronous transfer of synchronous data services for Closed User Groups.
D.2	not yet finalised	Similar to D.1 for mobile applications.
E.2	ETS 300 757	Low Rate Messaging service for roaming applications. Providing both point-to-point and point-to-multipoint messaging (e.g. alphanumeric pag-ing) using the signalling channels.
F.2	ETS 300 755	Multimedia Messaging Service for mobile applications (Fax, E-mail, WWW access, SMS).
Table 2. DECT data profiles

Two mobility classes have been defined for the data profiles; Class 1 supporting no mobility and class 2 providing mobility functions across FP’s enabling private and public roaming applications.

Application areas and markets

DECT handsets and base stations are available on the market since summer 1993; GAP compliant DECT equipment is available since spring 1996. The DECT product shipments were

	0.5 M until the end of 1994,
	1.5 M in 1995, and
	5 M in 1996 (Source: DECT Forum meeting in Paris, January 1997).

The majority of DECT product shipments are in the residential and business applications. DECT has proven to be cost effective for the lowend consumer market, showing potential for further cost reductions. Most of the shipments in this market segment concern single base station and single handset configurations. The prices for these configurations have reached a level at which DECT becomes extremely interesting for the consumer market. Consumers start to replace their old inferior quality (CT0 and CT1) cordless phones by a DECT product or buy their first fully digital DECT cordless phone because they feel confident about its quality, security level and flexibility. The perspective that a DECT cordless telephone can easily be transformed in a “home PABX” by just adding extra handsets is extremely attractive.

The initial interest in DECT has come from the wireless PABX market. Superior Dynamic Channel Selection and Handover procedures of DECT have proven to be efficient and reliable for large office and industrial installations both indoor and outdoor with 4000 to 5000 users per installation.

The main benefits experienced in this application area are cordlessness and transparency of DECT for PABX features offering increased productivity, lower call back costs because there are no unnecessary unanswered calls and reduced reconfiguration costs.

A large number of DECT RLL installations with totally several 100,000s of subscribers are in operation all over the world. Line Of Sight ranges beyond 5 km with perfect speech are consistently reported. Booked orders have passed 0.5 M lines at the end of 1996. Growth rates indicate that RLL may become a dominant DECT application.

DECT products can efficiently provide public pedestrian cordless type of services wherever the need arises. Test installations are currently in operation in several countries showing excellent performance, Finland already runs systems in commercial operation. During the last year, DECT industry received substantial orders for DECT public pedestrian systems. This is now speeding up the delivery and development of DECT infrastructure, base stations and handsets especially designed for outdoor pedestrian environments.

Future developments and evolutions

Future developments of the DECT standard will be initiated by the market for DECT equipment and services as encountered by those involved in the standardisation process. Evolution of DECT due to new applications may lead to additions to the existing toolbox or new standard subsets (pro-files).

Applications that have been recognised for the near future are:

	Modifications to the DECT radio part definition to achieve higher data rates. A study has been started on a modified radio (with 2 Mb/s capability) that co-exists with the “normal” DECT radio without decreasing the overall performance.
	Dual mode terminals supporting DECT and GSM, DECT and DCS1800 (or even triple mode terminals).
	Use of DECT in the evolution towards UMTS.
	Interworking with primary rate ISDN and broadband ISDN.