WO1999026436A2

WO1999026436A2 - A data connection device in a transport network

Info

Publication number: WO1999026436A2
Application number: PCT/SE1998/002020
Authority: WO
Inventors: Bernt Johansson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1997-11-14
Filing date: 1998-11-10
Publication date: 1999-05-27
Also published as: SE9704172D0; SE523594C2; JP2001523932A; KR100647406B1; EP1031246A1; SE9704172L; WO1999026436A3; CN1132461C; AU1265899A; CN1278991A; KR20010024607A

Abstract

A data connection device and method in a transport network in a cellular mobile system between a base station controller (BSC) and base station sites (12, 13, 14) which radiate information to and from mobile terminals connected to a radio base system (RBS) in an environment demanding narrow cellular positions. The transport network comprises at distributed cross connect means (DXX) having a network management system (11) for managing the transfer. The distributed cross connect means (DXX) has at least one wireless radiation node intended for a wireless transparent connection to be provided between the wireless radiation node (RN) and a wireless radiation terminal (RT). The wireless radiation node means (RN) for several base station sites (RBS) comprises a wireless radiation network (RNC) controlled by the network management system (11). A central cross connect node (C-DXX) in the wireless radiation node (RN) cooperates with the wireless radiation network means (RNC) and central wireless radiation station means (CRS 16; CRS') functioning as a distributed group switch having a point-to-multipoint system. The wireless radiation terminal (RT) is provided for each base station site (RBS) to be wirelessly connected to the wireless radiation node (RN).

Description

A DATA CONNECTION DEVICE IN A TRANSPORT NETWORK

TECHNICAL FIELD OF THE INVENTION

This invention relates to a data connection device in a transpoπ network between a radio node and a radio teπninal, and is particularly directed to a data connection in a transport network between mobile switching centre with base station controller (MSC/BSC) and base stations.

DESCRIPTION OF RELATED ART

In cellular mobile systems data between MSC/BSC and base stations are transported across a backbone transport network. In micro, i.e. outdoors in a croudy and area limited surrounding, and pico, i.e. indoors, cellular applications a large number of base stations are spread out in order to gain capacity and coverage. Each base station requires a transmission link from MSC/BSC, and therefore a lot of transmission links has to be established. Normally these transmission links are implemented by using copper, fibre or radio based point to point systems technologies, one link to each base station.

The number of links increases with the number of base stations and hence the installation cost. In order to make the distribution easy and cost efficient to run, a cellular transpoπ network having digital cross connect features has proven to provide a service-oriented transport networ

This network, often referred to as flexible multiplexer or "flexmux", comprises intelligent cross-connect nodes (DXX) for the transport of digital signals. A cross- connect node can be described as a digital multiplexer equipped with several trunk interfaces, and as a digital cross-connect equipped with several channel interfaces, cross-connections can be made freely between any of the interface types: trunk-to- trunk, trunk-to-channel, and channel-to-channel. The channel connections are semipermanent, i.e. they can be flexibly reconfigured with the aid of an integrated Network Management System (NMS). Earlier this kind of network has been provided with cross-connect nodes (DXX) having wired connection to cross- connect nodes (DXX) in each base station. The DXX concept is described in the article "The Ericsson DXX cross-connect system in mobile networks" by Tsviatko Ganev, Par Johanson och Joachim Walz, Ericsson Review Nr 2, 1996.

In the recent years it has been a requirement to make the cellular systems more and more condense having base stations positioned at small distances from each other and having a smaller signal range than before in order not to disturb each other. This is due particularly in commercial centres or other kinds of centres where a lot people moves around. It is both time consuming and expensive to lay cables. The desire is often to provide a quick installation which could be provisional in order to be changed after some while.

SUMMARY

Having to lay cables in a data transport network makes installation time consuming, expensive, and unflexible to changes. These problems are solved by using point-to- multipoint transparent connections insead of clables.

An object of the invention is to provide data connection in a transport network which is flexible and adaptable both to totally new installations and to make supplements to already existing transport networks.

Another object with the invention is to provide data connection means in a transport network which is suitable to be installed when radio stations are to be installed near each other in a near cellular system, for instance in croudy places, such as commercial centres or the like.

Still another object with the invention is to provide data connection in a transport network in which a system having sparsely distributed base stations could be more condense in an easy and rapid way.

These objects are achieved by a device having the features in claim 1, and a method disclosed in claim 9. Further features and improvements of the invention, are disclosed in the dependent claims.

The invention relates to a data connection device and method in a transport network in cellular mobile systems between a base station controller and base station sites to radiate information to and from mobile set means in an environment demanding narrow cellular positions. The technical region for the invention is data connection in a transport network in a cellular mobile system between a base station controller and base station sites which radiate information to and from mobile terminal means in an environment demanding narrow cellular positions, and comprising at distributed cross connect means comprising a network management system for managing the transfer. The invention is characterized in that the distributed cross connect means has at least one node comprising wireless radiation node means for several base station sites and comprising wireless radiation network means controlled by the network management system; cross connect node means cooperating with the wireless radiation network means and central wireless radiation station means functioning as a distributed group switch having a point-to- multipoint system provided in said wireless radiation node means; a wireless radiation terminal for each base station site; a wireless transparent connection being provided between the wireless radiation node mean and the wireless radiation terminal. In order to maintain fast roll out and easy planning a dynamic radio channel allocation scheme in the radio via is preferable but other allocation schemes may be used instead. The wireless transparent connection comprises preferably a dynamic channel allocation which could comprise at least one DECT radio link per base station site to be served by the central radio station. Each pair of wireless radiation node and wireless radiation terminal co-operating with each other could be provided within line of sight from each other. The transparent connection could be provided in a digital cross connect system having several digital cross connect nodes in a distributed network, between a digital cross connect node and a base station site for wireless transfer between them. The network management system, when detecting an incoming information to be directed to a base station site wirelessly, could set a flag to the information informing the cross-connect network that a transparent wireless radiation transmission is due. The digital cross connect node for wireless transfer could divide each incoming package into a package having the informations to be wirelessly transferred to base station sites and a package to be transferred to another digital cross connect node. The digital cross connect node for wireless transfer will provide information being destined to base station sites wirelessly to a wireless radiation node for transmitting the information through adaptable wireless radiation channels transparently to the base station sites in question which in turn transmits the information to the destined mobile terminals.

The invention provides a possibility to make new installations for mobile transmission both quickly and cheap. Provisional installations could be made directly when needed which later on could be permanent by providing wired connections to radio base sites. Existing transport networks could be made more dense in an easy way. LIST OF ABBREVIATIONS USED IN THE SPECIFICATION

AMPS Advanced Mobile Phone Service

B-DXX Back-bone Digital Cross Connect BRS Backbone Radio Station

BSC Base Station Controller

BTN Backbone Technical TS Number

BTS Backbone Technical Station

C-DXX Central Digital Cross Connect CRS Central Radio Station

DCA Dynamic Channel Allocation

D-DXX Distributed Digital Cross Connect

DECT Digital European Cordless Telephony

DXX Digital Cross-Connect GSM Global System for Mobile Communication

NMS Network Management System

NMT Nordic Mobile Telephone

OSS Operations Sub-System

PCM Pulse Code Modulation PCN Personal Communication Network

PSTN Public Switched Telephone Network

BS Base Station

RBS Radio Base Station

RNC Radio Network Control RN Radio Node

RT Radio Terminal BRIEF DESCRIPTION OF THE FIGURES

For a more complete understanding of the present invention and for further objects and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which: FIG 1 is a schematic view illustrating the invention; FIG 2A shows a logical view and FIG 2B the physical view of the signalling transmitted in a part of the network shown in FIG 1; FIG 3 is a signalling scheme for a connection in the network shown in FIG 1 ; FIG 4 is another embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the recent time cellular transport systems for transmitting information from the common telephone network through some kind of distribution network for the mobile information distribution system, a distributed system comprising so called DXX (digital cross-connect) systems in several nodes has been utilised in transport networks between switch devices related to the distribution network for the call and the base stations transmitting and receiving information, such as speech, data traffic or the like, from and to a customer mobile terminal.

A network of that kind is schematically illustrated in FIG 1, together with features according to the invention. Even nowadays most customers are connected to the common telephone network PSTN (Public Switched Telephone Network) 1 and this network is used for transmitting calls to the cellular mobile systems of different kinds, such as GSM 2, NMT 3, Paging 4, some kinds of data transmissions 5 or the like, as illustrated at the top part of FIG 1 and also illustrated at the right in FIG 1 for a radio station 13 where also the mobile systems PCN and AMPS have been added. Customers connected to these mobile systems could of course be connected directly through these networks as well. It is important that each customer shall have a possibility to reach a customer terminal using anyone of the different kinds of networks. This is common knowledge and illustrated in the upper part of FIG 1, where the different switching networks and the PSTN are connected to each other through interfaces (not shown) in a conventional way. Most often each network GSM, NMT etc. are directly wired to base stations which means that a huge amount of copper and optic cables are drawn lengthways and crosswise through the towns and landscape.

However, the distributed system having DXX nodes have been more frequently installed in micro/pico, i.e. condensed, cellular environment. The DXX concept is known and will therefore not be described in detail, thus only those parts which are relevant for the invention. The DXX concept is described in the article "The Ericsson DXX cross-connect system in mobile networks" by Tsviatko Ganev, Par Johanson och Joachim Walz, Ericsson Review Nr 2, 1996.

The DXX network provides the operator with a network solution which can be enlarged as the network grows and new services are introduced. The DXX concept makes it easy to introduce access (DXX) nodes acting as consolidation nodes for a number of smaller radio base stations (RBS) 12, 13, each of which in turn being provided with a DXX node A co-operating with the consolidation nodes in the network. The consolidation nodes will also be a natural location for conversion between different media/interfaces.

Each DXX node can be described as a digital multiplexer equipped with several trunk interfaces, and as a digital cross-connect device equipped with several channel interfaces. Cross-connections can be made freely between any of the interface types; trank-to-trunk, trunk-to-channel, and channel-to-channel. The channel connection are semi-permanent, i.e. they can be flexibly reconfigured with the aid of an integrated Network Management System (NMS) 11 which is common to all the DXX nodes 6 to 14 in the system. The networks 2 and 3 are connected to the DXX node 6. and the networks 4 and 5 are connected to DXX node 7. as apparent from FIG 1. Thus the DXX nodes 6 and 7 handle calls to and from two different network systems each. The DXX network comprises intelligent cross-connect nodes and access modems for transport of digital signals. As apparent from the right side of FIG 1 showing the conventional DXX concept, each DXX node A provided at an individual station site 13 is wiredly connected to its supply DXX node 10. Each base station site has a wireless contact with the individual mobile equipments or terminals to be served by it in its cellular environment, such as call through the GSM or NMT network, PCN, AMPS, PAGING, dedicated mobile services or the like to and from the mobile equipments.

Where a tight cellular system is desired this conventional wiring at least between a DXX node at a base station site, such as 13, to a DXX node, such as 10, is expensive and time consuming. Therefore, according to the invention a wireless link is provided between some base station sites 14 in a micro/pico cellular network to a central digital crossconnect C-DXX/RNC node 8 belonging to a network C supporting these base station sites 14. It is also illustrated that a combination DXX/C-DXX/RNC node 9 can serve both wiredly and wirelessly connected base station sites. The wireless link is preferably a radio link RN but could alternatively be a wireless light link, for instance transmitting modulated IR-light.

The system according to the invention uses a central wirelessly radiation station, below called central radio station CRS, preferably having DECT air interface (DECT = Digital European Cordless Telephony), in radio signalling between the nodes 8 and 14. A DECT radio link provide transparent n*64 kbps connections between a radio node (RN) and a radio terminal (RT). The major advantage with DECT is that a DECT air interface uses dynamic channel allocation (DCA). There is thus no need for cell planning (frequency planning). However, a line of sight is required between the transmitter and the receiver in order to provide sufficient quality of service. It is to be noted, however, that other air interface providing transparent connections than DECT could be used. The C-DXX/RNC node 8 is combined with radio network control RNC and is connected to a central radio station node CRS 16 functioning as a distributed group switch in the radio node RN transforming incoming information from the DXX network into radio signals to be transmitted to the sites 14 and incoming bit stream information from the sites 14 into signals adapted to be transmitted through the DXX network. The central digital cross connect and radio network control node is below called C-DXX RNC 8.

The access backbone digital cross connect B-DXX nodes B at the base station sites 14 need be adapted to be wirelessly supported and comprises the backbone radio station BRS. The B-DXX are in an amended form in relation to the DXX A and will be described further below.

Also the integrated Network Management System (NMS) 11 need be adapted to a system which can transmit information signals both to wired and wireless transmittance to and from sites A and B such that it for the system does not matter to which kind of site an information signal is to be transmitted. Therefore specific network managing functions are integrated in the NMS 11. The advantage with this is that no extra management system has to be involved for the wireless transmitting features according to the invention. The customer will see every site as a part of the DXX concept.

The NMS can in turn be connected to an operation sub-system OSS which can be connected to a base station controller BSC in order to have a centralised operation.

Incoming bit streams from the DXX network are within the C-DXX/RNC node 8 cross connected to virtual output ports in the CRS 16, as will be described below.

FIG 2A shows a logical view and FIG 2B a physical view of the signalling transmitted in the DXX network between the C-DXX/RNC 8 and the DXX 6, and between the C-DXX/RNC 8 and the B-DXXs B. Even though the signalling is provided in both directions through the network the pathway will now be described for a call coming from the PSTN 1 to one of the mobile sets connected to a radio base station RBS in the system. The calls to all the sets to be connected through the C-DXX/RNC 8 are mapped into packets PI , where each call has been allotted an individual time slot in the packet.

One of the functions in the NMS 11 is to set up roting information in the DXX network to reach the aimed destination for a particular radio base station. One of the functions for the specific managing functions provided to support the invention when having a DXX network is to provide a particular wireless-flag on such calls which are to be handled to a RBS 18 served by a B-DXX wirelessly connected to a C-DXX/RNC.

As shown in FIG 2A, the C-DXX/RNC selects the time slots having the wireless- flag from the packet PI, puts them together to a second packet P2 also including a control slot CCS on time slot #16 in a way common in the art for control signalling for internal control between the CRS and the C-DXX/RNC node, as shown in FIG 2B, and sends it to the CRS 16. It is to be noted that the C-DXX/RNC 8 and the CRS 16 could be comprised in the same box, but are preferably mapped, i.e. wired, to each other, for instance through a physical 2 Mbps port connected to the CRS 16. The reason for this is that the CRS 16 comprises the antenna for Iransrmtting and receiving which must be positioned outdoors. The most practical way is then to have the whole box including the circuitry for the CRS outdoors.

The time slots not having the wireless-flag, or another wireless-flag indicating that it is to be sent via another C-DXX/RNC, is provided in a packet P3 which is sent to another DXX in the system, for instance having wired connection, such as the DXX 9 in FIG 1. Each B-DXX is provided with a backbone radio station (BRS) 17A - 17N. This BRS is adapted to wireless transceiving and is included in a radio terminal (RT) in the contrary to the access units provided in the DXXs A. The C-DXX RNC node 8 including the CRS 16 has one virtual output port for each BRS/B-DXX 17A - 17N. Each of these virtual output ports are connected to the appropriate CRS and from there to the selected mobile RBS set on a conventional PCM (PCM = Pulse Code Modulation) channel. In the conventional way the subscriber is allocated an available radio channel at calling in a multiple access, the most common one being time division multiple access (TDMA).

The air interface A i/f transports only user data between the CRS 16 and each BRS/B-DXX node and acts as a cross connect with limited cross connection functionality in order to connect an appropriate BRS B-DXX 17A to 17N to the C- DXX/RNC 8 through the CRS 16. Logical transmission channels are established for each BRS/B-DXX 17A to 17N. Virtual transmission channels having a rate of for instance 2 Mbps are achieved in this way.

Connections are considered semi -permanent, i.e. no dynamic call handling is performed. Connections are always set up on request from the radio network control RNC. As illustrated in FIG 3, an incoming connection request is defined as a connection request originating from the DXX NMS 11 for the DXX network. On receiving an incoming connection request the radio network control RNC checks its data base to verify that the RBS is within its cellular area. If this is the case the RNC checks to which backbone station the connection shall be directed and where the destination backbone station is registered in the system.

If the backbone station is of the broadcast kind, i.e. provided in a BRS/B-DXX B, a broadcast message containing the Backbone Technical TS Number (BTN) of the backbone station is sent on all traffic and beacon channels. In the DECT- transmission system the BRS/B-DXXs are identified by their BTN. The address

CRS selects the best available transmission channel (Physical channel request). The CRS must authenticate and then the connection request is transmitted to the CRS. for instance having a rate of 64 kbps. At least one data^' channel is established for each BRS/B-DXX.

After that all wanted channels are established the CRS is connected to appropriate input TS from the base station controller BSC (see FIG 1) and the system changes mode to operating mode.

One CRS 16 could for instance have six radio ports. Each radio port may handle six data channels.

The C-DXX/RNC 8 routes each incoming bit stream, aimed for a connected BRS in a B-DXX B, to the appropriated time slot on the pulse code modulated link connected to the CRS 16. The routing is performed by the cross connect block within the C-DXX/RNC 8. The C-DXX/RNC is configured from the NMS 11 through the control channel. The control channel is also managed by the cross connect block.

As mentioned earlier the invention could be provided in order to make a cellular environment more dense. In a case like that an existing DXX node having wired transmission to some radio base station sites could be provided with additional wireless transparent transmission to some additional radio base station sites. This is illustrated in the middle of FIG 1 where the combined DXX/C-DXX/RNC node 9 supports both A-DXX nodes A at sites 12 and through a CRS 20 B-DXX nodes 21.

It is also possible to have a data connection device of the intelligent kind according to the invention as a link stand alone from a network system, for instance GSM, having its own remote NMS. This is illustrated in FIG 4. The base station controller BSC is connected to a radio network control RNC which controls a number of radio access nodes CRS '. The radio transmission is preferably of the DECT kind. Each CRS' may be connected to a number of backbone access units BRS/B-DXX' by the use of for instance DECT air interface. It is to be noted that one BRS/B-DXX^" could co-operate with several CRS's, and one CRS' could co-operated with several BRS/B-DXX' s. In order to achieve a spectrum efficient system only valid data within each time slot is transmitted across the air interface. The pulse code modulated link is recovered at the BRS/B-DXX' and the RNC and synchronised to the interface El/Tli between the BSC and the RNC at the BSC side. From the BSC point of view, the system then acts as virtual, semi permanent pulse code modulated links to the radio base station sites RBS which are synchronised to the interface E1/T1₂ between the RBS and the BRS/B-DXX^'.

An example of dimensioning the system

One DECT radio port can handle up to 12 simultaneous 32 kbps connections or 6*64 kbps time slots. In order to handle a full Mbps pulse code modulated link six DECT radio ports may be used within one BAU. Time slot 0 is used for synchronisation purposes and may thus be generated within the BAU. Each 32 kbps DECT time slot is allocated to one of up to 120 available channels.

Claims

We claim

1. A data connection device in a transport network in a cellular mobile system between a base station controller (BSC) and base station sites (12, 13, 14) which radiate information to and from mobile terminal means connected to a radio base station (RBS) in an environment demanding narrow cellular positions, and comprising at distributed cross connect means (DXX) comprising a network management system (11) for managing the transfer, characterized in that the distributed cross connect means (DXX) has at least one node comprising: a) wireless radiation node means (RN) for several base station sites (RBS) and comprising wireless radiation network means (RNC) controlled by the network management system (11); b) cross connect node means (C-DXX) cooperating with the wireless radiation network means (RNC) and central wireless radiation station means (CRS 16; CRS') functioning as a distributed group switch having a point-to-multipoint system provided in said wireless radiation node means (RN); c) a wireless radiation terminal (RT) for each base station site (RBS); d) a wireless transparent connection being provided between the wireless radiation node mean (RN) and the wireless radiation terminal (RT).

2. A data connection device according to claim 1, characterized in that the wireless transparent connection comprises a dynamic channel allocation.

3. A data connection device according to claim 1 or 2, characterized in that the wireless transparent connection comprises at least one DECT radio link per base station site to be served by the central radio station (CRS 16; CRS').

4. A data connection device according to any one of the preceding claims, characterized in that each pair of wireless radiation node (RN) and wireless radiation terminal (RT) co-operating with each other are provided within line of sight from each other.

5. A data connection device according to anyone of the preceding claims, characterized in that the distributed cross connect means (DXX) consist of the wireless radiation node means (RN).

6. A data connection device according to anyone of the claims 1 to 4, characterized in that the transparent connection is provided in a digital cross connect system having several digital cross connect nodes in a distributed network, between a digital cross connect node (C-DXX RNC) and a base station site (BRS/B-DXX) for wireless transfer between them.

7. A data connection device according to claim 6, characterized in that the network management system (NMS 11), when detecting an incoming information to be directed to a base station site (B-DXX) wirelessly, sets a flag to the information informing the cross-connect network that a transparent wireless radiation transmission is due.

8. A data connection device according to claim 6 or 7, characterized in that the digital cross connect node (C-DXX/RNC) for wireless transfer for each incoming package (P 1 ) of information divides it into a package (P2) having the informations to be wirelessly transferred to base station sites and a package (P3) to be transferred to another digital cross connect node (DXX).

9. A data connection device according to anyone of the claims 6 to 8, characterized in that the digital cross connect node (C-DXX/RNC) for wireless transfer provides informations being destined to base station sites wirelessly to a wireless radiation node (CRS 16; CRS') for transmitting the information through adaptable wireless radiation channels transparently to the base station sites in question which in turn transmits the information to the destined mobile terminals.

10. A data connection method in a transport network in a cellular mobile system between a base station controller (BSC) and base station sites (12, 13, 14) which radiate information to and from mobile terminal means connected to a radio base station (RBS) in an environment demanding narrow cellular positions, and comprising at least one distributed cross connect means (DXX) comprising a network management system (11) for managing the transfer, characterized by a) providing central wireless radiation station means (CRS 16; CRS') functioning as a distributed group switch having a point-to-multipoint system comprising wireless radiation node means (RN) for several base station sites (RBS); b) connecting a wireless radiation network controller means (RNC) at a distributed cross connect node (C-DXX); c) controlling the central wireless radiation station means and the wireless radiation network controller means by the network management system (11) d) providing a wireless radiation terminal (RT) for each base station site (RBS); and e) providing a wireless transparent connection between the wireless radiation node and the wireless radiation terminal.

11. A data connection method according to claim 10, characterized by providing each pair of wireless radiation node (RN) and wireless radiation terminal (RT) co- operating with each other within line of sight from each other.

12. A data connection method according to claim 10 or 11, characterized by providing the distributed cross connect node (C-DXX) as the only node in the distributed cross connect system.

13. A data connection method according to claim 10 or 11 for a distributed cross connect system having several digital cross connect nodes in a distributed network, characterized by providing the transparent connection between at least one digital cross connect node (C-DXX RNC) and a base station site (BRS/B-DXX) for wireless transfer between them.

14. A data connection method according to claim 13, characterized by setting a flag to the information to be transmitted at the network management system (11) when detecting that the incoming information is to be directed to a base station site (B-DXX) wirelessly.