EXTENDED MOBILITY FOR A DECT-SYSTEM

Abstract: The invention relates to a system at a wireless telecommunications system and data communications system which makes possible terminal mobility by means of utilizing DECT-technology and Internet. DECT-terminals are used today for coverage area restricted mobility. The technology is advantageous from an economic point of view, but the mobility is comparatively restricted. A simple and cheap mobility between DECT-coverage areas is lacking, so such a functionality can be regarded as desirable. The invention consequently is aimed at making an extended mobility for the DECT-system possible by utilizing an Internet protocol. The invention is based on "Mobile IP", which is a standard which is intended to provide Internet-connected computers with a function which makes possible that these can move between different points of connection to Internet without an extensive reconfiguration of terminal and/or network elements.

Description: TITLE OF THE INVENTION: Extended mobility for a DECT-system Field of the invention The present invention relates to system at a wireless tele- or data communications system including DECT- 5 terminals for coverage area restricted mobility within their specific DECT-coverage areas. Prior art DECT telephones today are used for coverage area restricted mobility, typically within an office or within a ID home. The technology is cheap, but the mobility is limited. Simple and cheap mobility between these "DECT islands" (office, home etc), however, is to a great extent lacking. A mobility function which implies that a customer can make and receive calls on the same mobile terminal at home, as 15 well as when visiting the homes of acquiantances, and at the working place (but not while travelling between these places) will have a power of attraction if service and equipment is made sufficiently cheap. However, there are needed cheap base stations and an underlying network o adapted to this type of "not-continuous" limited mobility. The aim of the present invention consequently is to effect above mentioned mobility function for simple and cheap mobility between different DECT-co erage areas. Summary of the invention 5 This aim is achieved by a system according to the patent claim 1. The technology is especially useful in connection with broadband upgrading of the access network because it allows "realization" of a "second telephony subscription" over the 0 broadband IP-equipped channel, based on a comparatively simple and cheap solution. This second subscription also allows a coverage area restricted mobility (For instance the home/the school/the youth centre/...) Further characteristics of the present invention are given in the subclaims. Brief description of the drawings In the following a detailed description of an embodiment of the invention is given with reference to the enclosed drawings. Figure 1 shows the physical architecture of the system according to the present invention; Figure 2 shows the protocol architecture between a DECT-terminal (PP) and a base station (FP) . Detailed description of an embodiment of the invention The DECT-standard actually only defines radio access and belonging signalling. The underlying network for handling of mobility and switching is actually not defined but a number of goal networks, i.a. ISDN, POTS and GSM are indicated. The DECT-standard defines generic mechanisms which the underlying network must have in terms of "Home Database" (HDB) and "Visitor Location Database" (VDB) . These rather well correspond to the HLR/VLR-concept in GSM. The basic idea of this invention instead is to use Internet as goal network and base mobility handling on Mobile-IP, and the voice switching on "Voice-Over- Internef-technology . The DECT-terminal correspond to, in the IP-world, a "proxy" which to Internet just looks like an Internet-telephony-equipped computer. In the following, the invention will be described with reference to Figure 1. The interface II is the ordinary DECT-interface . The interface 12 is an IP-based interface which is identical to the interface which a computer equipped with Internet-based telephony makes use of in order to via a gateway (GW) communicate with terminals in PSTN and/or the ISDN-notwoi k . 13 constitutes a normal POTS-interface . The interface 14 is used by GW for incoming calls from PSTN to convert the "telephone number" of the DECT-terminal to corresponding IP-address. The interface is also used by FP in connection with the "location update"-procedure to translate from IPUI to IP-address (because the DECT-mobile does not know "its" IP-address). Each mobile DECT-terminal consequently must be allocated a unique IP-address. The database has been arranged in order to make calls from PSTN/ISDN as transparent as possible. If the solution is used in the application "2:nd subscription" and "ordinary" DECT- telephone number is 7075560, the DECT-teiminals of the home can be allocated number #7075560n, where n is a digit between 1 and 9 which acccordingly makes possible up to 9 mobile terminals. "#" results in that the call is connected to a POTS-H.323 gateway from which the DECT-terminal can be reached. From the DECT-terminal numbers are "dialled" just as ususal. The number database can be indexed with both telephone number and IPUI (International Portable User Identification) . The mobility function in the DECT-system to great extent utilizes existing technology which will now be subject of an overall discussion. Mobile IP Mobile IP is a standard intended to provide Internet- connected computers with a function which makes possible that these can move between different connection-points to Internet without extensive reconfiguration of terminal and/or network elements. Home Agent At the computer's home network (for instance a LAN) there is a "Home Agent" which picks up IE'-packets intended for the mobile computer if this is not on the home network. "Home Agent" forwards these packets to the network where the mobile computer is at present. Foreign Agent When a computer is connected to a "foreign" network, it will register itself by the there existing "Foreign Agent". "Home Agent" is informed about that the computer's "care-off"-address now is the IP-address for "Foreign Agent". When Home Agent has picked up a packet intended for the mobile terminal (the computer) this packet is encapsulated in another packet addressed to "Foreign Agent". Foreign Agent unpacks the original packet and forwards this to the mobile terminal (the computer) . Voice over IP "Voice over IP" is a generic term for a number of technologies which make possible voice communication over Internet. Such a technology includes in addition to coding/decoding and transport protocol also simple functions for signalling and handling of connections. H.323 is a standard (actually for video conference) which a number of suppliers have announced that they intend to support. H.323 allows negotiation about which voice coding algorithm that shall be used for a session. Internet Voice Gateways Recently products have been launched which bridge Voice-over-IP-technology with ordinary PCTS-technology . Such gateways make voice communication possible between an Internet-connected computer and PSTN-conrected computer. Protocol architecture and procedure The "fixed part" of the DECT-system implements a "gateway function" between DECT-based telephony and Internet-based telephony and serves as a "proxy" for a DECT-portable in "Internet". The protocol architecture is shown in Figure 2. The DECT-portable ' s signalling for establishing of connection is "mapped" on corresponding functions in H.323. H.323 suggests as default the use of "DECT" as voice- encoding technology which, if POTS-Internet gateway supports DECT-encoding, eliminates the need of "recoding" in Fixed Part (FP) . The "location update" function of the DECT-system is mapped on corresponding functions in Mobile IP. Home Agent corresponds in principle to "HLR" of the DECT-standard, and "Foreign Agent" corresponds to VLR. In the following a concrete example is given of how the system according to the invention will function, without going into technical details. If, for instance, Kalle connected to ISDN/PSTN makes a call to Sven's DECT-telephone, Kalle "dials" Sven's ordinary DECT-number. If Sven is within his own ordinary DECT-coverage area, everything will proceed just as usual. If, on the other hand, Sven is in another DECT-coverage area than what he normally has coverage area for, then the call is forwarded from the ordinary DECT-coverage area via Internet (described above) to the other DECT-coverage area where Sven is. After that Sven can answer in usual way. It consequently should be realized that FP keeps count of where Sven is, i.e. if Sven is in ordinary DECT-coverage area, or in another acknowledged DECT-coverage area. It also should be realized that when Sven moves between two DECT-coverage areas, Sven can not be accessed via his telephone. FP in ordinary DECT-coverage area has no knowledge of where Sven is, but just observes that Sven is out of the coverage area. When Sven moves into the coverage area in another acknowledged DECT-coverage area, this is registered in FP in said other DECT-coverage area, at which an identification signal is transmitted via GW (Internet) to FP in ordinary DECT-coverage area. In that way FP in ordinary DECT-coverage area will know in which other acknowledged DECT-coverage area Sven is. It consequently should be realized that, in addition to his ordinary DECT-coverage area, Sven has coverage area in just any number of other acknowledged DECT-coverage areas . By an acknowledged DECT-coverage area is referred to a coverage area which can handle the DECT-i nformation via Internet and which can identify a DECT-terminal belonging to another DECT-coverage area, for instarce Sven's DECT- terminal . The above mentioned is only to be regarded as a preferred embodiment of the invention, and the extent of protection of the invention is only defined by what is indicated in the following patent claims.

Claims: PATENT CLAIMS 1. System at a wireless tele- or data communications network including DECT-terminals for coverage area restricted mobility within their specific DECT-coverage areas, c h a r a c t e r i z e d in that an Internet protocol is arranged to effect a mobility function for handling of DECT-information between said DECT-coverage areas . 2. System according to patent claim 1, c h a r a c t e r ! z e d in that said mobility handling is based on a Mobile Internetprotocol (Mobile-IP) and "voice switching" based on "Voice-Over-Internet"-technology . 3. System according to patent claim 2, c h a r a c t e r i z e d in that a DECT-terminal in Mobile-IP corresponds to a "proxy" which towards Internet is experienced as an Internet-telephony equipped computer. 4. System according to patent claim 3, c h a r a c t e r i z e d in that when a DECT-terminal is connected to a foreign network, it will register itself by means of the there existing "Foreign Agent" corresponding to "VLR" of the DECT-standard, at which the "Home Agent" of said DECT-terminal, corresponding to "HLR" of the DECT- standard, is informed about that the "care of address" of the DECT-terminal now is the IP-address for "Foreign Agent". 5. System according to patent claim 4, c h a r a c t e r i z e d in that when "home Agent" in ordinary DECT-coverage area receives a telephony packet intended for said mobile terminal which is in another DECT- coverage area, said telephony packet is encapsulated in another packet addressed to "Foreign Agent" in said other DECT-coverage area, at which "Foreign Agent" unpacks original telephony packet and forwards it to said mobile terminal . 6. System according to any of the patent claims 2-5, c h a r a c t e r i z e d in that it includes a DECT- interface (II) for communication between just any DECT- terminal and a DECT base station (FP), an IP-based interface (12) for communication between said DECT base station (FP) and a gateway (GW) , which gateway communicates with terminals in PSTN/ISDN via a POTS-interface (13) . 7. System according to any of the patent claims 2-6, c h a r a c t e r i z e d in that it includes an interface (14) between said gateway (GW) and a number database (DB), and an interface (14) between said number database (DB) and said DECT base station (FP) for conversion of DECT-numbers to corresponding IP-addresses and vice versa.

Inventors: ALMGREN GUNNAR, NYCANDER CLAS, ALMGREN, GUNNAR, NYCANDER, CLAS
Applicants: TELIA AB
Application year: 1998
Main classification: H04Q7
IPC codes: H04M7, H04W8, H04W80, H04W84