AU742936B2

AU742936B2 - Digital telecommunications system with DECT interface

Info

Publication number: AU742936B2
Application number: AU89407/98A
Authority: AU
Inventors: Klaus Geywitz
Original assignee: Alcatel CIT SA; Alcatel SA
Current assignee: Alcatel Lucent SAS
Priority date: 1997-10-28
Filing date: 1998-10-20
Publication date: 2002-01-17
Anticipated expiration: 2018-10-20
Also published as: JPH11266271A; CA2250580A1; AU8940798A; EP0913984A2; EP0913984A3; CN1230088A; DE19747534A1

Description

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ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "DIGITAL TELECOMMUNICATIONS SYSTEM WITH DECT

INTERFACE"

The following statement is a full description of this invention, including the best method of performing it known to us:- I.

S

This invention relates to a digital telecommunications system c6mprising at least one DECT digital enhanced cordless telephone) control unit which controls at least one DECT base station and on which a switching unit is implemented.

Such a system is known, for example, from the performance specification for the Alcatel 4300 E system, published in the spring of 1997.

A large number of competing telecommunications systems with at least partially wireless signal transmission are on the market. The Alcatel 4200 E system is such a digital telecommunications system with internal and external data transmission capability over wire lines, namely over ISDN. Wireless voice terminals can be connected to the system via DECT. The signal transmission in this system, however, is only in the point-to-point mode, only from a respective terminal connected to the system to a given other terminal which may communicate with the system via a telecommunications network. No provision is made for data communication between data terminals in the point-to-multipoint-connection mode.

15 Point-to-multipoint connections are established in local data networks which are based on the LAN (local area network) principle. Such a network generally comprises a communications medium, such as a coaxial cable or a 4-wire line, to which all LAN subscribers are connected. However, no switching function is provided in such a network, but each transmitted data packet is received by each connected subscriber in the point-to-multipoint mode. At each subscriber, the data packets destined for the latter must then be filtered out of the incoming transmission stream. Therefore, a filter function is implemented in each data terminal connected to the LAN. This is disadvantageous in that the entire data volume must be transported to each individual subscriber. The data transmission rate available in the LAN is limited, however, so that if several logical connections are established simultaneously, all transmissions must share the available transmission rate. This may easily result in the data paths being overloaded.

An improvement over the LAN system is the wireless local area network (WLAN), whose operation corresponds to that of the LAN, but which uses radio links for the transmission medium. This permits a greater mobility of the terminals, but at the expense of a reduced transmission rate as compared with the wireline LAN (effective transmission rate approximately 600 kb in the WLAN as compared to 3 Mb in the LAN). Also, the probability of external interference, particularly radio interference, is very much higher than in a wired LAN.

DE 196 33 919 C1 describes the updating of program parts in a mobile telephone via a GSM interface using a PC, with no LAN function being provided, however.

DE 196 00 961 Al describes a cable television distribution network to which terminals of a telecommunications network can be connected which can also transmit by radio. A WLAN function is not possible, either.

DE 196 01 472 Al discloses a telecommunications facility with a switching 10 function between voice terminals and fax machines in which wireless data transmission can take place in the voice band. Here, too, digital data transmission, particularly a WLAN function, is not possible.

:.DE 195 39 507 Al describes a digital mobile telephone with an additional digital interface for the wireless connection of terminals of various kinds. With a single 15 system of that kind, however, no WLAN operation is possible; WLAN operation is g Oo o possible, if at all, with two such systems using a GSM network. Thus, the system lacks the character of a local data network in which data terminals can intercommunicate via the LAN function.

By contrast, it is an object of the present invention to further develop a digital S 20 telecommunications system of the kind referred to by way of introduction, such as the Alcatel 4200 E system, in such a way as to also permit LAN functions, particularly WLAN functions in the point-to-multipoint connection mode.

According to the invention, this object is attained by implementing on the DECT control unit a filter for filtering destination addresses of data packets which delivers routing information to the switching unit, and by providing at least two data terminals, particularly personal computers, at least one of which can communicate with the DECT base station over a wireless link.

By providing a universally applicable DECT board and a DECT radio link, the cable required in conventional LAN systems can be replaced, so that a WLAN function becomes possible. Such a board with a data interface and modem interface on the interface side of the respective data terminals not only permits wireless data transmission but also can be addressed by the data terminals as a modem Hayes) or a LAN board NE2000). The well-known DECT infrastructure, which is commercially available in many versions and at low cost, can be used direct, i.e., without adaptation.

Thus, in the WLAN mode, in contrast to the prior-art solutions discussed above, in which data transfer to an air interface takes place without protocol conversion, a substantially lower transmission capacity is necessary for the same transmission efficiency. Each dat a terminal connected to the digital telecommunications system according to the invention has its own DECT link. By the filtering function implemented on the DECT control unit, any unnecessary reception of data packets not 10 destined for the respective terminal is blocked at an early stage, so that the transmission links are substantially less loaded.

The switching unit and the filter in the digital telecommunications system according to the invention may be implemented in hardware. Preferably, however, the switching unit and/or the filter are implemented in software, which permits greater 15 flexibility and simpler retrofitting than hardware solutions and greatly reduces the cost of manufacture.

In a preferred embodiment, a data bus is provided which interconnects two or more DECT control units. This bus system can control the entire data traffic, particularly the transfer of data packets. In this manner, the number of possible 20 connections for base stations in the system can be significantly increased, so that a greater geographical coverage becomes possible. In the above-mentioned Alcatel 4200 E system, for example, the existing signalling bus, which has so far been used only for signalling voice calls, can also be used for data transfers between the DECT control units.

In another preferred embodiment, the DECT base station is spatially separated from the DECT control unit and connected to'the latter by a line. Compared to priorart solutions, such as the digital mobile telephone disclosed in the above-cited DE 195 39 507 Al, the spatial separation permits a significantly greater geographical coverage. If fiber optic cables are used, for example, the cable length can be several kilometers.

In a further preferred embodiment of the telecommunications system according to the invention, a bus system is provided for transmitting digital voice signals which interconnects two or more DECT control units. This makes it possible to couple voice terminals, such as telephones, fax machines, etc., to the system.

In a further development, digital interfaces are provided for the telecommunications terminals, such as ISDN telephones, analog telephones, fax machines, personal computers with ISDN interface, or added feature telephones.

Advantageously, a trunk junctor providing the connection to a wireline telephone network is connected to the bus system for transmitting digital speech signals. This makes it possible to implement a connection to a widely branching wireline network, and thus, for example, an access to the Internet, a remote data 10 transmission system, etc.

0 Further advantages of the invention will become apparent from the following description and the accompanying drawings. The aforementioned features of the invention and the features mentioned in the following can be used singly or in arbitrary combinations. While particular embodiments of the invention will be shown and 1 5 described, it is to be understood that the description is made only by way of example and not as a limitation to the scope of the invention.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the accompanying drawings, in which: Figure. l a is a schematic representation of a simple embodiment of the 20 telecommunications system in accordance with the invention; Figure. 1 b is a functional diagram of a telecommunications system of the Alcatel 4200 E type incorporating the inventive modification of Figure. 1 a; Figure. 2 shows an embodiment in which data packets are exchanged over an ISB bus; Figure. 3 shows an embodiment using an HSB bus; and Figure. 4 shows an embodiment in which the switching function and the filter function are implemented in hardware.

Referring to Figure. 1 a, which shows a simple embodiment of the digital telecommunications system in accordance with the invention, the system comprises a DECT digital enhanced cordless telephone) control unit 1 on which a switching unit 2 for establishing data calls and a filter 3 for filtering destination addresses of data packets are implemented. The filter 3 supplies routing information to the switching unit 2.

Also connected to the filter 3 are various MAC-ASIC medium access control application-specific integrated circuit) units 5, multiplexed application-specific integrated circuits, which each serve a DECT base station 4 via a signal line 7 and grant the respective data packets to be transmitted access to the DECT time slots.

Each of the MAC-ASIC units 5 is controlled by a cell site processor (CSP) 6, which controls the DECT cell site functions.

In the embodiment of Figure. la, two data terminals 9 and 9' in the form of personal computers communicate with the DECT base station 4 over radio links 8 and 10 respectively. Communication is in the WLAN (wireless local area network) mode o using the point-to-multipoint method; through the use of the filter 3, however, the MAC-ASIC units 5 not involved as well as the DECT base stations connected thereto o. (not shown) and the associated radio links are not loaded with the transport of these data packets, as only a connection between the two data terminals 9 and 91 is to be 15 maintained.

The switching unit 2 and/or the filter 3 may be implemented in either hardware or software.

By varying the length of the line 7, different requirements for the coverage by the base stations 4 can be implemented.

20 In Figure. Ib, the digital telecommunications system according to the invention is shown incorporated in a larger system which comprises further digital interfaces for other telecommunications terminals, namely an analog interface 15 for analog telephones, an ISDN S o interface 16 for connecting, besides telephones and fax machines, a personal computer 19" for example, and an interface 17 for addedfeature telephones. Via a trunk junctor 18, the system is linked to a wired telephone network 100.

The digital interfaces 15, 16, 17, the trunk junctor 18, and the DECT control units 11, 11' are interconnected by a data bus 12, to which a central control unit 10 is connected and over which data packets can be transferred at a rate of, 2 Mb. If a system of the Alcatel 4200 E type is used, the data bus 12 may be physically implemented by the signalling bus of that system.

Figure. 1 b further includes a bus system 13 which also interconnects the digital 6 interfaces 15, 16, 17, the trunk junctor 18, and the DECT control units 11, 11'. This bus system will, as a rule, be designed as a high-speed bus (HSB) and can transport speech information at a transmission rate of 16 Mb.

In the embodiment shown in Figure. Ib, the two data terminals 19 and 19', which are connected by radio links to the same DECT base station 14, can communicate with one another, but the data terminal 19, for example, can also communicate via the DECT base station 14, the DECT control unit 11, the data bus 12, the DECT control unit 11', the DECT base station 141, and a corresponding radio link with another data terminal 19".

10 The second party to the connection, as in the case of the data terminal can also communicate directly with the data terminal 19 via a suitable interface (in the example shown the ISDN SO interface 16) and the DECT control unit 11.

In Figures. 2, 3, and 4, the normal data path within a DECT board is shown by continuous lines, while the path for continuous data is shown dotted.

Figure. 2 shows an embodiment in which two DECT control units 21, 21'are interconnected by an ISB bus 22.

This configuration can be implemented, for example, with a system of the Alcatel 4200 E type without hardware modification. The DECT control units 21 and 21' have interface chips 20 and 20', respectively, which enable access to the data bus 20 22. The central processing unit in each of the DECT control units 21, 21' is an 80C188 microprocessor of Intel, which can perform the control and filtering functions.

Connections to base stations 24 and 241 are again provided by MAC-ASIC units and 25', which are controlled by cell site processors 26 and 26', respectively. Via an ADPCM highway implemented as a data link with ADPCM time slots, the MAC-ASIC units 25 and 25' are connected with one another and with the interface chips 20 and respectively.

As described in the example of Figure. la, each of the MAC-ASIC units 25, enables access to DECT time slots in a respective one of the DECT base stations 24, 24', to which a data terminal 29, 29' is connected via a radio link 28, 28'.

In the embodiment shown in Figure. 2, at the very beginning, when the PC 29 is started and the network adaptor is initialized, a specifically marked DECT link to one of the Alcatel 4200 E interface boards is established. This link is not reported to the central control unit, but the data for it is stored in the DECT control unit 21. Thus, the central control unit has no knowledge of this link. During the establishment of this specific link, the address of the PC 29, which may be derived from the IPUI-N like an ethernet address, is transmitted to and stored in the DECT control unit 21. This address will be needed later to filter out all data packets for this PC 29.

Data packets are transmitted in a single slot (32 kb) or a double slot (64 kb).

The packets are extracted from or injected into the B-fields by the DECT control unit 21 by accessing the receive and transmit buffers of the MAC-ASIC The data packets are exchanged between the boards 21, 21'via the ISB bus 22 10 using the ISB broadcast mechanism. Each of the DECT control units 21, 21' receives *999 all data packets but filters out only those packets which are destined for its "clients".

This reduces the data traffic on the DECT air interfaces.

For continuous 64-kb connections (such as video transmissions), a direct pointto-point connection can be used. In that case, the data will not be extracted from the 15 B-field, but will be switched via two adjacent time slots on the ADPCM highway to the interface chip 20 and from there via the HSB time to the other board 21'.

This embodiment requires no changes to existing hardware. The central control unit is not loaded with the user data, so that the number of voice sets in the Alcatel 4200 E system is not reduced. Furthermore, the cost and complexity of the implementation on the side of the DECT control unit is kept low.

Another advantage is that no configuration data are needed on the DECT control units 21, 21'. Since a broadcast mechanism (DECT group) is used on the ISB bus, it is not necessary for the DECT control units to know each other. The DECT control units 21, 21' and the ISB bus 22 are transparent to the data packets, so there is no dependence-on the network protocol used.

In addition, no switching effort is needed for the data packets. Furthermore, it is possible to select the transmission rate on the air interface (32/64 kb). Finally, the software used in the central control unit is not affected, so that it is "releaseindependent".

Figure. 3 shows a further embodiment of the invention which can also be implemented in a system of the Alcatel 4200 E type without hardware changes. The PC side is identical to that shown in Figure. 2.

8 In this embodiment, the data packets can only be transmitted in a double slot (64 kb). The packets are switched on to the ADPCM highway, bypassed by a ADPCM transcoder [sic], and sent from the DECT control unit 31 to another DECT control unit 31'via an HSB bus system 33. The data packets are exchanged between the DECT control units 31, 31'via the HSB bus system 33 by means of interface chips 30, with a suitable switching matrix. Only the addressed DECT control units 31, 31' receive the data packets. Before each connection or each data packet, a switching operation must be performed on the HSB bus.

In addition, the above-described connection between the DECT control units 31, 10 31'via an ISB bus 32 is provided. Between the DECT base stations 34, 34' and the data terminals 39, 39', the data packets are again transmitted over radio links 38, 38'.

Some of the HSB time slots must be reserved for data services. This requires software changes in the central control unit, so that the data applications are no longer independent of the software version used in the central control unit.

In this embodiment, too, the central control unit need not know the user data, so that in a system of the Alcatel 4200 E type, the number of possible voice sets is unaffected.

Also, no configuration data are needed in the central control unit, but some reserved HSB time slots cannot be used for the normal transmission of data packets.

S"The DECT control units 31,31' are again only transparent to data packets of known protocols.

Figure. 4 shows schematically an embodiment which is suitable for higher data rates (64 kb, but more packets per unit of time) but necessitates major changes to the hardware of the DECT control units 41, 41', which, as in the embodiment of Figure. 3, are granted access to the ISB bus 42 and the HSB bus system 43 via an interface chip In this embodiment, the data packets are not extracted from the B-fields by the processors but switched to specific network chips 45, 45' which are normally used as network routers. These network chips 45, 45' contain the switching and filtering functions in hardware form, are able to filter out addresses of data packets, and can "listen into" more than one B channel. They only need support from the processor for 9 their configuration.

The exchange of data packets between data terminals 49, 49', as described above, takes place via radio links 48, 48', DECT base stations 44, 44', and DECT control units 41, 41', between which the packets are normally transmitted on the HSB bus system 43. No extra switching is performed. There is at'least one HSB time slot from each board to all other boards. This means that there is at least one time slot per board in which all data coming from this board are transmitted. All other boards will read these time slots, and the chips mentioned above will extract the data packets if they are needed. In this manner, no switching is required in the control unit and no 10 processing power is needed for filtering processes.

In this embodiment, too, the central control unit need not know the user data, so that the number of possible voice sets is again unaffected. Again, no configuration data are needed on the central control unit, with some HSB time slots having to be reserved. The DECT control units are again only transparent to data packets of known 15 protocols. There are no influences on data rates because of.high-rate telephone traffic and vice versa. The 80C188 processor is not particularly loaded, since most of the job is done by the ethernet chip set.

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Claims

1. A digital telecommunications system comprising at least one DECT digital enhanced cordless telephone) control unit which controls at least one DECT base station and on which a switching unit is implemented, wherein on the DECT control unit, a filter for filtering destination addresses of data packets is implemented which provides routing information to the switching unit, and wherein at least two data terminals are provided, at least one of which can communicate with the DECT base station over a wireless link.

2. A digital telecommunications system as claimed in claim 1, wherein the 10 switching unit and/or the filter are implemented in software.

3. A digital telecommunications system as claimed in claim 1 or 2, wherein a data bus is provided which interconnects two or more DECT control units.

4. A digital telecommunications system as claimed in any one of the preceding claims, wherein the DECT base station is spatially separated from, and connected by a 15 line to, the DECT control unit.

5. A digital telecommunications system as claimed in any one of the preceding claims, wherein a bus system is provided for transmitting digital speech signals which interconnects two or more DECT control units.

6. A digital telecommunications system as claimed in claim 5, wherein digital 20 interfaces for telecommunications terminals, such as ISDN telephones, analog telephones, fax machines, personal computers with an ISDN interface, or added- feature telephones, are connected to the bus system for transmitting digital speech signals.

7. A digital telecommunications system as claimed in claim 5 or 6, wherein a trunk junctor providing the connection to a wired telephone network is connected to the bus system for transmitting digital speech signals.

8. A digital telecommunications system as claimed in any one of the preceding claims, wherein said data terminals are personal computers. 11

9. A digital telecommunications system substantially as herein described with reference to Figures 1-4 of the accompanying drawings. DATED THIS FIFTEENTH DAY OF OCTOBER 1998 ALCATEL a a a