WO1996039785A2 - Ameliorations de la telephonie sans fil ou la concernant - Google Patents

Ameliorations de la telephonie sans fil ou la concernant Download PDF

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Publication number
WO1996039785A2
WO1996039785A2 PCT/SE1996/000699 SE9600699W WO9639785A2 WO 1996039785 A2 WO1996039785 A2 WO 1996039785A2 SE 9600699 W SE9600699 W SE 9600699W WO 9639785 A2 WO9639785 A2 WO 9639785A2
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WO
WIPO (PCT)
Prior art keywords
radio base
base station
telephone exchange
local telephone
telecommunications system
Prior art date
Application number
PCT/SE1996/000699
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English (en)
Other versions
WO1996039785A3 (fr
Inventor
Peter Olanders
Original Assignee
Telia Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telia Ab filed Critical Telia Ab
Publication of WO1996039785A2 publication Critical patent/WO1996039785A2/fr
Publication of WO1996039785A3 publication Critical patent/WO1996039785A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W92/00—Interfaces specially adapted for wireless communication networks
    • H04W92/04—Interfaces between hierarchically different network devices
    • H04W92/045—Interfaces between hierarchically different network devices between access point and backbone network device
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems

Definitions

  • the present invention relates to a cordless telecommunications system and a procedure to construct it.
  • Cordless telephony is a well nown technology and includes a number of different types of systems inclusive, at one extreme, digital mobile cell systems with complete international roaming, such as the GSM-system, and at the other extreme, simple cordless telephones for use at home which operate according to the ordinary air interface standard CT2.
  • Typical standards for cordless telephony include CT2, CT3, DECT, Bellcore Framework and PHP. A brief explanation of some of these standards can be found in "Communications Technology Handbook" by Geoff Lewis, published by Newnes in 1994. For a more detailed explanation of these standards references should be made to different standard specifications published by such bodies as ETSI (The European Telecommunications Standards Institute) .
  • the present invention relates to cordless telephony based on TDMA/TDD of the general type which is specified in the DECT- standards. Though the invention is described with relation to a DECT-system, it has obvious applications at similar systems which fulfils other standards.
  • DECT can be used for a field of system applications, inclusive home- and plant telephony, for instance cordless telephones and radio-exchanges for companies, public access systems such as Telepoint, and network infrastructure, such as Cordless Local Loop.
  • the present invention can be applied at all four of the above mentioned system applications.
  • a basic DECT-system includes one or more radio base stations, one or more portable stations, and possibly a number of repeaters or slave stations. Transmission between the radio base stations and the portable stations utilizes TDMA/TDD which is used to create a total -number of 120 duplex channels on 10 carrier frequencies, at which each carrier frequency carries 12 uplink channels and 12 downlink channels.
  • the operation frequency band is between 1880 and 1900 MHz.
  • the radio base stations have a radio coverage of about 100 m radius, and the effective range of a given base station can be extended by the use of repeaters.
  • Handover can be performed between different channels and between different radio base stations.
  • Handover between different DECT-systems can only be performed by means of functions which are included in the public switched telecommunications network.
  • DECT-systems can be used for private communication, for instance in a cordless telephone, and for public access systems, for instance in a Telepoint-system.
  • DECT-systems must be sufficiently attractive to subscribers in the public access system so a sufficent customer base is created to support the system.
  • the present invention aims at solving at least some of the above outlined problems.
  • the present invention allows a DECT-system to be established at a comparatively small cost by use of the existing public telephone network. It further makes possible that the construction of the radio base stations can be simplified and their cost be reduced by locating certain functions to a local telephone exchance and ' share these functions between radio base stations. Transmission between radio base stations and a local telephone exchange is simplified by the use of an ISDN-protocol, i.e. a transmission format based on the ISDN-standard which uses two channels with 64 kbit/s, and a D- channel with 16 kbit/s over a simple twisted pair copper connection, It should be emphasized that the present invention does not use an ISDN-system for communication between radio base stations and a local telephone exchange, only an ISDN-transmission format.
  • an ISDN-protocol i.e. a transmission format based on the ISDN-standard which uses two channels with 64 kbit/s, and a D- channel with 16 kbit/s over a simple twisted pair copper connection
  • US patent 5 040 177 is described a Telepoint-service, in which radio base stations are connected to a public ISDN-network. Each radio base station can manage up to 40 speech channels. The use of radio base stations which manage a mixture of private and public traffic is not described.
  • the system relates to the provision of ISDN-circuits at a radio telephone system more than use of an ISDN-protocol to transmit speech and signalling between a radio base station and a local telephone exchange.
  • PCT-application W093/21719 describes a DECT-system which has the ability to cooperate with an ISDN-system.
  • a DECT-format with double slot is modified to allow the DECT-system to at the same time transmit an ISDN B-channel and a D-channel separately. This allows that ISDN outband signalling can be managed by a DECT-system.
  • the invention relates to the cooperation between DECT and ISDN rather than the use of an ISDN-protocol for transmission between a local telephone exchange and a radio base station.
  • US patent 5 325 419 describes a PCS with complete ISDN- interface.
  • the invention utilizes intelligent radio base stations. None of the documents relating to the prior art, which has been discussed above, describes the use of an ISDN-protocol to transmit at least three independent speech channels in an ADPCM-format, per ISDN-channel, between a radio base station and a local telephone exchange.
  • radio base stations manage a mixture of private and public traffic; that the control functions of the system, inclusive encryption, decryption, encoding and decoding are localized to a local telephone exchange; that radio base stations are supplied with power from a local telephone exchange; data compression, interleaving and signal filtering to reduce the bit rate of the D-channel; and that repeaters are linked to the radio base stations via the public telecommunications network.
  • One of the ideas according to the invention which lies behind a WACA-system according to present invention is that much of the higher control layers, for instance NWK and DLC, can be placed in a central control unit, for instance located in an LX. In this way these system layers can be made comparatively powerful. This allows that subscriber equipment which includes a radio base station can be simplified, for instance by reduction of the MAC-layer. Consequently the subscriber equipment will not be completely independent because its fixed part FP at least partly is remote-controlled.
  • a cordless telecommunications system for transmission of speech, inclusive at least one radio base station and at least one portable station, in which data, inclusive signalling and encoded speech, is transmitted between said at least one base station and said at least one portable station by use of TDMA/TDD, and in which the speech is encoded, by use of ADPCM, characterized in that said radio base station is linked to a local telephone exchange, in that signalling and speech is transmitted between said radio base station and said local telephone exchange with an ISDN-protocol, in that speech is transmitted between said radio base station and said local telephone exchange in the same data format as said speech is received by said radio base station from a portable station or transmitted from said radio base station to a portable station, and in that at least three speech channels per ISDN-protocol channel are accessible for transmission between said radio base station and said local telephone exchange.
  • Preferably four compressed speech channels with 32 kbit/s are accessible per ISDN-protocol channel for transmission of speech between said radio base station and said local telephone exchange.
  • Said radio base station can be arranged to manage both private traffic and public traffic.
  • Said radio base station can be connected to said local telephone exchange with a local loop connection in the public telecommunications network.
  • a control device for said system is located at said local telephone exchange.
  • Signalling between said control device and said base station can be digitally compressed.
  • the signalling between said control device and said base station, intended for or received from different portable stations, can be interleaved.
  • said radio base station can be arranged to, from the signalling between said control device and said base station, delete each part of it which is only needed for operation of said radio base station, which by that reduces the signal traffic levels between said radio base station and said control device.
  • Functions for encryption, decryption, encoding and decoding are located in said local telephone exchange and arranged to be shared between a number of radio base stations.
  • a method to construct a cordless telecommunications system characterized in the steps: to localize a control device for said cordless telecommunications system at a local telephone exchange; to localize radio base stations at selected subscribers; and to connect said local telephone exchange to said radio base stations via an existing public local loop network, . by use of an ISDN-transmission protocol.
  • Said method can include the step to, at a subscriber, install a radio base station arranged to serve a number of subscribers. Preferably a sufficient number of radio base stations are installed, localized in a way that their radio coverages overlap each other, to provide essentially complete radio coverage, over a predetermined geographical area, substantially larger than a radio coverage for one single radio base station.
  • Said method can include the steps: to install radio base stations at some subscribers; to, at other subscribers, install repeater stations; to link repeater stations to radio base stations by connections established over an existing public local loop.
  • a cordless telecommunications system which has a number of radio base stations, which each is arranged to provide telecommunications services to a number of portable stations, characterized in that said cordless teleconmmunications system is arranged to at least in some radio base stations combine functionality with public access and functionality with private access, resulting in that one single base station can be used to provide private home service and a public Telepoint-service.
  • Figure 1 illustrates the relation between the cost for providing cordless telephony and a number of subscribers, for small and big cell units.
  • FIG. 2 is a schematic illustration of a communication link established with a cordless telephone system, in accordance to the present invention, between a portable station and the public telecommunications network via a radio base station and local telephone exchange.
  • Figure 3 is a schematic illustration of the frame structure for a DECT-system.
  • FIG. 4 is a schematic illustration of the radio coverage provided by a cordless telecommunications system in accordance to the present invention.
  • A/D Analog/digital conversion ADPCM Adaptive Differential Pulse Code Modulation.
  • VPN+ Virtual Private Network with mobility support sometimes called M-VPN.
  • a cordless telecommunications system in accordance to the present invention can be described as a WACA, i.e. the system provides cordless access to telecommunications services over a wide geographical area, for certain an area which is considarably larger than the radio coverage for one single radio base station.
  • the invention is not restricted to WACA-systerns.
  • a telecommunications network operator must ensure that acceptable surface coverage is produced by the system as rapidly and economically as possible.
  • the initial costs for small cell systems are essentially larger than for large cell systems, i.e. when the number of users of the system is small.
  • DECT- systems are generally small cell systems. Typically a DECT radio base station has a radio coverage of about 100 m radius or less. It is cost effective for a telecommunications operator which establishes a new system, to maximally utilize installed network infrastructure. At installation of a WACA-system one should ideally utilize the existing twisted copper network to establish connection between radio base stations and local telephone exchanges.
  • FIG. 2 illustrates in schematic form the way in which a portable DECT-station can be connected, via a radio base station an local telephone exchange, to the public telecommunications network in the so called U-plane.
  • a system can be illustrated schematically in a number of ways, for instance by use of block diagrams or circuit diagrams.
  • the user plane is a simplified schematic illustration of a system which shows how a user "sees" or experiences the system in operation.
  • the PP i.e. the portable unit, is physically located to a portable station or cordless handset.
  • Th PP includes a number of layers - NWK, DLC, MAC and PHL.
  • a radio connection can be established between the physical layer PHL of the portable handset and the physical layer of a fixed radio unit RFP.
  • the fixed radio unit is of course physically located to a base station or a radio base station.
  • a wire connection which utilizes a ISDN-protocol can then be established between the physical layer of the fixed radio unit and the physical layer of the central fixed unit CFP.
  • the CFP is normally located to a radio base station, but the present invention suggests that it can be located to a local telephone exchange.
  • the CFP is then connected via the local telephone exchange LX to the public telecommunications network.
  • Radio base stations can be located at the subscriber and connected to the local telephone exchange via the existing local wire network. This implies for the DECT-system according to the present invention that the RFP and the CFP are connected with twisted copper pairs which are used in the local network.
  • connection media can be used if they are available, for instance optical fibre.
  • the connection between the RFP and the CFP must be able to transfer a 32 kbit/s ADPCM-signal, as has been specified in the DECT-standards, together with the belonging DECT-signalling.
  • the protocol and the signalling between the RFP and the CFP should be digital. This facilitates the use of repeaters.
  • the use of digital transmission further avoids the need for analog/digital conversion between the transport network of the headbit of the public network and the subscriber, which consequently reduces the unavoidable distorsion and the noise which is produced at each A/D or D/A-step.
  • the protocol which is used at the present invention for transmission between the RFP and the CFP is an ISDN-protocol which is utilized for communication between station equipment and subscriber equipment.
  • ISDN can successfully be transmitted via twisted copper pairs between a local telephone exchange and subscriber equipment, and is consequently suitable for use in the present invention to link the RFP at a radio base station to the CFP at a local telephone exchange.
  • the ISDN-protocol includes two B- channels, i.e. two speech channels with 64 kbit/s, and one D- channel, i.e. a channel with 16 kbit/s, which is used for signalling and normally is used in packet transmission mode.
  • each B-channel can be used in the present invention to carry two speech channels instead of the only speech channel which is normally used in ISDN.
  • the use of an ISDN protocol link between the RFP and the CFP is shown in Figure 2.
  • the ISDN-protocol allows simultaneous transmission of four ADPCM speech channels with 32 kbit/s over the two ISDN B-channels. There is however one problem with the signalling and this is discussed later in this application.
  • the separation of the RFP and the CFP and the use of an ISDN-link means that the MAC-layer, see Figure 2, in the RFP can be made very "thin", because it only needs to manage the separation of the signalling and the speech and distribute these between the two B- channels and the D-channel in the ISDN-protocol. (The MAC-layer distributes and makes free physical channels depending on what higher layers request) .
  • the MAC-layer or the media access layer, exists in most telecommunications systems, but not in OSI-based systems.
  • the MAC-layer is located above the physical layer which it principally controls.
  • the "thickness" of the MAC-layer, i.e. its content, is decided by the amount of controlling it has to perform.
  • the MAC-layer is "thin" because of the amount of controlling which is performed in higher layers, for instance NWK and DLC, and the demands from PHL.
  • DECT-specific signalling is transmitted over the ISDN-channel which connects the RFP and the CFP.
  • the frame structure which is used for DECT-transmission is illustrated in Figure 3. From this we conclude that a data packet is preceded by a synchronization sequence of 32 bits, followed by a data packet which contains 388 bits. The data packet can be followed by four bits which repeates the last four bits in the data packet, to facilitate detection of slot drift and by that avoid packet collision.
  • the data packet includes 48 bits signalling data, followed by 16 error detection/correction bits.
  • the packet includes 320 bits user data, followed by further four error detection bits. Consequently are 48 bits signalling data per channel produced per time frame. The length of the time frame is 10 milliseconds.
  • the ISDN-link can however be arranged to support four DECT speech channels by: using data compression; - signal interleaving; coordination and reduction of the signal needs; or a combination of the above mentioned.
  • the DECT-signalling does not utilize data compression technologies.
  • the data compression level which is required to compress the 4,8 kbit/s DECT-signalling to the accessible 4 kbit/s on the ISDN-channel is not high - 1:1,2. Because BER for wire connections is essentially lower than on radio links, with a number of magnitudes, the low data compression which is required to squeeze in the DECT-signalling on the ISDN D-channel does not cause any problems.
  • a lot of suitable data compression technologies to achieve this data compression level is well known to experts in the field.
  • the signalling need can be reduced by coordination and reduction of the total signal traffic.
  • Parts of the radio specific signalling need not be transmitted to the CFP.
  • Parts of the radio specific signalling and other signalling can be shared between speech channels. This can be used to reduce the requirements on the D- channel, making it land up within the transmission capacity.
  • Embodiments of the present invention have a number of advantages, inclusive: low costs of production for the RFP; simple connection of the RFP; sufficiently simple for a subscriber to connect the RFP him/herself; the provision of services to a number of subscribers, up to four, over the same connection;
  • FIG. 4 illustrates the way in which the radio coverages, which correspond to the individual radio base stations, are combined to give almost total radio coverage for a given area.
  • a Telepoint- system can be built up by use of existing local loops and radio base stations located at subscribers.
  • Use of radio base stations at subscribers also facilitates the accessibility to Telepoint on private property, for instance an industrial plant, to advantage both to the network operator and the subscriber.
  • telephony i.e. telephony with private access/restricted access
  • telephony with public access for instance Telepoint
  • the present invention provides a DECT-based system in which comparatively high traffic capacity, two speech channels with 64 kbit/s, plus a signalling channel with 16 kbit/s, can be made accessible to subscribers.
  • Different developments of the present invention will be realized be experts in the field.
  • Speech encoders and encryption equipment can be centrally placed in the CFP. This dramatically reduces the costs and the power consumption for the RFP. This makes it possible that the RFP can be supplied with power from a central power source, for instance located at the local telephone exchange.
  • Slave base stations i.e. repeaters
  • the use of repeaters will add to the radio surface coverage.
  • Handover can be controlled from a master base station with comparatively small additions. Control of handover between a radio base station and a repeater, from the radio base station, will reduce the load on the CFP.
  • the RFP Since the RFP is constructed to operate with an ISDN-protocol, it is especially simple to arrange that the RFP operates directly with ISDN in accordance to DECT/ISDN IWP.
  • ISDN-services can be distributed from the RFP via a DECT-radio interface and/or a "fixed" outlet, i.e. the common ISDN-outlet.
  • a "fixed outlet” i.e. the common ISDN-outlet.
  • the requirements on the RFP is increased due to, among other things, the need to include a speech encoder.
  • the RFP becomes a part of an ISDN- terminal. It should be noticed that the function of an RFP, as an
  • ISDN-terminal falls outside the scope of the present invention even if the characteristics of the present invention facilitates an upgrading to complete ISDN-operation.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne des améliorations de la téléphonie sans fil ou la concernant, grâce auxquelles on peut installer un système DECT, pour un prix relativement bas, en utilisant le réseau public existant de télécommunications. L'invention permet en outre de simplifier la construction des stations radio de base, de réduire leur coût de production, par la mise en place de certaines fonctions dans un central téléphonique local, et de répartir ces fonctions entre plusieurs stations radio de base. Les transmissions entre les stations radio de base et un central téléphonique local sont simplifiées par l'emploi d'un protocole RNIS, c'est-à-dire d'un format de transmission fondé sur la norme RNIS qui utilise deux canaux B à 64 kbits/s, et un canal D à 16 kbits/s, passant par une seule liaison en fils de cuivre toronnés. Dans un système WACA selon la présente invention, une grande partie des couches de commande supérieures, par exemple NWK et DLC, est placée dans une unité centrale de commande, par exemple dans un central téléphonique local. De cette façon, les couches du système peuvent être rendues relativement puissantes. Cela permet de simplifier l'équipement d'abonné qui prévoit une station radio de base, par exemple en rendant la couche MAC plus mince. Par conséquent, l'équipement d'abonné n'est pas entièrement indépendant puisque son unité fixe et, au moins en partie, télécommandée.
PCT/SE1996/000699 1995-06-06 1996-05-30 Ameliorations de la telephonie sans fil ou la concernant WO1996039785A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9502052-5 1995-06-06
SE9502052A SE514244C2 (sv) 1995-06-06 1995-06-06 Förbättringar av eller avseende trådlös telefoni

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WO1996039785A2 true WO1996039785A2 (fr) 1996-12-12
WO1996039785A3 WO1996039785A3 (fr) 1997-02-13

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19717365C1 (de) * 1997-04-24 1998-11-26 Siemens Ag ISDN-Netz mit DECT-Zwischensystem

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992004796A1 (fr) * 1990-09-04 1992-03-19 Motorola, Inc. Systeme de telephone sans fil a usage residentiel, commercial ou public
WO1993011625A1 (fr) * 1991-12-06 1993-06-10 Motorola Inc. Controleur de systeme radiotelephonique
US5257410A (en) * 1991-03-22 1993-10-26 Motorola, Inc. Communication device with ISDN interface
WO1995005720A1 (fr) * 1993-08-12 1995-02-23 Nokia Telecommunications Oy Systeme telephonique ct2
EP0643543A2 (fr) * 1993-09-10 1995-03-15 Alcatel SEL Aktiengesellschaft Système téléphonique de proximité
GB2288104A (en) * 1994-03-31 1995-10-04 Plessey Telecomm Call point base stations interconnected by CT2 radio
WO1995033350A1 (fr) * 1994-06-01 1995-12-07 Airnet Communications Corp. Station de base sans fil a large bande utilisant un bus a acces multiple a repartition dans le temps pour effectuer des connexions commutables avec des ressources modulateur/demodulateur

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992004796A1 (fr) * 1990-09-04 1992-03-19 Motorola, Inc. Systeme de telephone sans fil a usage residentiel, commercial ou public
US5257410A (en) * 1991-03-22 1993-10-26 Motorola, Inc. Communication device with ISDN interface
WO1993011625A1 (fr) * 1991-12-06 1993-06-10 Motorola Inc. Controleur de systeme radiotelephonique
WO1995005720A1 (fr) * 1993-08-12 1995-02-23 Nokia Telecommunications Oy Systeme telephonique ct2
EP0643543A2 (fr) * 1993-09-10 1995-03-15 Alcatel SEL Aktiengesellschaft Système téléphonique de proximité
GB2288104A (en) * 1994-03-31 1995-10-04 Plessey Telecomm Call point base stations interconnected by CT2 radio
WO1995033350A1 (fr) * 1994-06-01 1995-12-07 Airnet Communications Corp. Station de base sans fil a large bande utilisant un bus a acces multiple a repartition dans le temps pour effectuer des connexions commutables avec des ressources modulateur/demodulateur

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19717365C1 (de) * 1997-04-24 1998-11-26 Siemens Ag ISDN-Netz mit DECT-Zwischensystem
US6567412B1 (en) 1997-04-24 2003-05-20 Siemens Aktiengesellschaft Holding a connection in an ISDN network with a DECT intermediate system

Also Published As

Publication number Publication date
SE514244C2 (sv) 2001-01-29
SE9502052L (sv) 1996-12-07
SE9502052D0 (sv) 1995-06-06
WO1996039785A3 (fr) 1997-02-13

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