WO2000074360A1

WO2000074360A1 - Connection device with real time and non-real time data ports

Info

Publication number: WO2000074360A1
Application number: PCT/EP1999/003754
Authority: WO
Inventors: Uwe Rademacher
Original assignee: Nortel Networks Limited
Priority date: 1999-05-31
Filing date: 1999-05-31
Publication date: 2000-12-07

Abstract

Connection device for a telecommunication system, comprising: at least one real time port (12) connectable to a real time terminal (14) which is specifically adapted for handling real time data, at least one network port (20, 22) connectable to a data network for transmitting and receiving data packets which each include control information specifying at least the destination of the packet; and relay means (36) for feeding data from the real time port to the network port and vice versa, characterized in that it further comprises at least one data port (16) connectable to a data processing unit (18) capable of processing non-real time data, said relay means (36) is further adapted to feed data from the data port (16) to the network port (20, 22) and to direct data from the network port either to the real time port (14) or to the data port (16), depending on the specified destination, and control means (30, 34) are provided for handling the real time data with a higher priority than non-real time data.

Description

CONNECTION DEVICE WITH REAL TIME AND NON-REAL TIME

DATA PORTS

DESCRIPTION

The invention relates to a connection device for a telecommunication system, compnsing at least one real time port connectable to a real time terminal which

5 is specifically adapted for handling real time data, at least one network port connectable to a data network for transmitting and receiving data packets which each include control information specifying at least the destination of the packet, and relay means for feeding data from the real time port to the network port and vice versa

10

More specifically, the invention relates to a connection device which offers the possibility to use a data network such as the Internet or a local area network (LAN) for making a telephone call. Since, in case of a telephone call, the voice of the speaker should be made audible on the side of the listener without any noti-

15 ceable delay, it is essential that the voice data are transmitted and processed in real time. Data of this type, I e data which need to be transmitted and processed without any substantial delay, will be termed "real time data ' herein Although voice data are the most prominent example for such real time data, it will be understood, that real time data occur also in other applications, e g m video,

20 multimedia or remote control applications

In contrast to this, the data that are normally transmitted through a data network, for example, text data sent as an e-mail, are normally buffered on the side of the receiver, so that real time processing is not essential Data of this 25 kind will be termed "non-real time data' herein

In general, the standards or transmission protocols used for data transmission through a network, such as the Internet protocol (IP), are optimised for non-real time data The continuous stream of digital data of a file to be transmitted

30 through the network is subdivided into a plurality of packets, and a header is added to each packet This header includes information on the destination to which the packet is to be sent and may also include additional information on the type of the data, depending on the transmission standard that is being used Thanks to the information provided in the header, each packet can individually

35 be routed through the network from the sender to the receiver Thus, the time required for transmitting a packet from the sender to the receiver may vary from packet to packet, depending on the load on the network In addition, each packet first needs to be compiled on the side of the sender, before it can be sent through the network. As a result, it is only w th a certain delay that the original file can be re-assembled on the side of the receiver

Nevertheless, several standards have been developed which permit the transmission of voice data through a network of this type practically in real time On the side of the sender, the analogue voice data are at first converted into digital data and are sampled over a certain period of time which will determine the length of the data packet. Preferably, data compression is applied in order to reduce the number of bits that need to be transmitted. Then, the header is added to each packet and the packet is sent through the network On the side of the receiver, the voice data included in the packets are decompressed and re-assembled to form a continuous data stream which is then reconverted into analogue data. It will be understood that the time delay between the recording of the voice data on the side of the sender and the reproduction of these data on the side of the receiver cannot be smaller than the sample time for an individual packet Thus, in order to keep the delay as small as possible and to provide a good quality of the telephone connection, the packets should be made as small as possible However, small packets are inefficient in terms of bandwidth, because a header has to be transmitted with each packet and, as a result, the ratio between useable voice data and the overhead of control data becomes worse when the number of packets increases Thus, a suitable compromise has to be made for the time intervals in which the packets are sent In case of non-real time data, the optimal packet length is considerably larger

In many known standards for the transmission of voice data, additional processing routines are applied to the digital data In particular, it is advantageous to provide a routine for echo cancellation A certain amount of echo is inevitably produced in an any telephone connection However, in a normal telephone call, this echo is not noticeable because the time delay between the echo and the original signal is too small to be resolved by the human ear When the delay between the original signal and the echo becomes larger due to the packet-wise transmission, echo cancellation becomes important

A connection device of the type indicated above serves as an adapter between the telephone set and the data network may not only be used for making telephone calls through a wide area network (WAN), but also offers the possibility to integrate a telephone system with one or more telephone sets into an existing local area network Since computer networks such as Ethernet or the like are available in many offices or companies, this removes the necessity to install a separate wiring for the telephone system Instead, the telephone sets are simply plugged to the computer network just like personal computers, printers or other equipment Then, the telephone sets are connected among each other only through the cables of the computer network If the computer network itself is connected to a public telephone network through an ISDN switch or the like, then it is possible to make not only internal calls but also external calls In addi- tion to a reduction installations costs, the integration of the telephone system into the computer network has the advantage that all the functionality of the computer network becomes available for administrating the telephone system Thus, all the service functions of an advanced telephone system such as a data base for telephone numbers, voice mail, automatic telephone responder and the like, can easily be implemented as software m one or more of the computers of the network

Examples of known telecommunication systems of this type are disclosed in DE 94 18 959 U and in the publication "NetServe VoiceServer Telefonanlage der II Generation , published by Netserve Systementwicklung und Projektierung GmbH, Berlin. Germany In these systems, a device that is marketed under the trade name voice hub serves as a connection device for connecting one or more telephone sets to a LAN (e g Ethernet) and a so-called voice server provides the administration and service software for the telephone svstem and can be con- nected to a public telephone network by means of. for example, an ISDN board, so that the telephone sets are connected to each other and to the public telephone network through the LAN

Most commonly used LANs, such as, for example, coax Ethernet, have a bus ar- chitecture, which means that all network components, e g a server, a number of client computers and also the above-mentioned voice hubs are directly connected to a LAN bus, and the data transmitted through the bus are, in principle, available for each component This architecture has the advantage that the wiring scheme is comparatively simple and, accordingly, the costs for installing a network of this type within a building, a factory or the like are relatively small However, the bus architecture imposes certain requirements on the hardware configuration of the cable connections

In this respect, it may therefore be preferable to use a network that is based on end-to-end connections, such as twisted-pair Ethernet In this case, a specific connection device, e g a so-called Ethernet hub, is connected to all the components of the network through end-to-end cable connections and serves as a relay for the data traffic among the various components Of course, the above mentioned voice hub ' can also be connected to such an Ethernet hub. but then the wiring scheme becomes relatively complex and no substantial savings are achieved in comparison to a conventional installation m which separate wirings are provided for the LAN and the telephone system

It is accordingly an object of the invention to provide a connection device of the type specified in the preamble of claim 1 which is more efficient when the real time terminal is to be integrated m a data network based on end-to-end connections

In order to achieve this object, the connection device according to the invention is characterized in that it further comprises at least one data port connectable to a data processing unit capable of processing non-real time data, said relay means is further adapted to feed data from the data port to the network port and to direct data from the network port either to the real time port or to the data port, depending on the specified destination, and control means are provided for handling the real time data with a higher pπonty than non-real time data

With the connection device according to the invention, at least one real time terminal, e g an analogue or digital telephone set. and at least one processing unit, e g a personal computer for processing non-real time data can be connected to the data network through one and the same port As a result, one or more tele- phone sets and one or more computers can easily be connected to the data network, no matter whether the data network has a bus architecture or an end-to- end architecture

The device according to the invention is particularly useful for a typical desk top environment in which one or two computers and one or two telephone sets are installed on the desk top within a limited area, e g within the same office room Then, onlv one cable needs to be installed and to be connected to the network port of the connection device installed in this room, and the connection device has intelligence for routing both the voice data and the computer data to their respective destinations. Since the connection device is also capable of handling the voice data and the computer data with different pπoπties, it is possible to suspend the transmission of computer data when voice data are received or are to be sent, so that the transmission time intervals between the voice packets will not become unacceptably long and a telephone connection with high quality is achieved even though the voice data and the computer data share the same transmission line.

Useful details of the invention are specified in the dependent claims

Preferably, the connection device has at least two network ports The second network port can then be used for connecting another connection device of the same type, so that the data network can be established or extended by forming a cascade of connection devices interconnected only through end-to-end connections.

If the data network is a LAN, any known standard such as the ITU standard H.323 may be used for managing internal telephone calls, I e telephone calls among the various telephone sets connected to the LAN In addition, the LAN may of course have a gateway or interface to a wide area network (WAN) or a public telephone network, so that external telephone calls are also possible

On the other hand, the connection device according to the invention is not limited to use within a LAN, but it can also be connected directly to a WAN. Likewise, the data network may be a hybπd fiber cable network (HFC network) In this case, the network port of the connection device includes or is connected to a cable modem suitable for data transmission over a broadband cable (CATV)

The connection device according to the invention may be configured as a standalone component, but it may also be physically integrated into the telephone set or into the computer to which it is connected. In the latter case, it is preferable however that the connection device is operable independently of the computer, so that telephone calls can be made and received even when the computer is not operating Preferred embodiments of the invention will now be described in conjunction with the accompanying drawings, in which

Fig 1 is a block diagram of a connection device according to a first embodi- ment of the invention.

Fig. 2 is a block diagram of a telecommunication system employing connection devices according to the invention, and

Fig 3 is a block diagram of a connection device according to a modified embodiment of the invention

In the example shown in figure 1 , the connection device 10 comprises two real time ports 12 each of which is connected to a real time terminal which in this case is formed by an analogue telephone 14, two data ports 16 each of which is connected to a data processing unit represented here by a desk top computer 18, and a first network port 20 connected to a local area network LAN A second network port 22 is connected to the first network port of another connection device 10' which may have the same construction as the connection device 10

In case of an Ethernet LAN, the network ports 20 22 and as well the data ports 16 may conform the standard Ethernet 10/ 100 twisted paιr/RJ45 suitable for connection to a 100 Mbit/s data network or a 10 Mbit/s cable modem Thus the connection device may be used either in the 10 or the 100 M/bit modus The real time ports 12 mav be analogous RJ1 1 ports

Internally, the connection device 10 compπses a telephone adapter 24 for each of the ports 12 a coding/decoding unit (codec) 26 connected to the two adapters 24, a digital signal processing unit (DSP) 28 connected to the codec 26, a host processor 30 controlling the operation of the connection device, a memory 32 connected to the DSP 28 and the host processor 30 and including preferably a non-volatile memory part (flash), a network controller 34 and relay means 36 interconnecting the network controller 34 and the ports 16, 20 and 22

When a telephone call is made from one of the telephones 14, the call signalling data needed for establishing the connection and the voice data are coded in the codec 26 and are then processed in the DSP 28 under the control of the host processor The digital signal processing for the voice data may for example include data compression, echo cancellation and the like The processed voice data are buffered in the memory 32 and are compiled to form data packets that have a size in the order of 80 bytes and are to be sent through the LAN in intervals of. for example, 30 ms In a typical example, each packet comprises 24 byte of voice data and a 54 byte of header in accordance with the pertinent transmission protocols (e.g MAC, IP/UDP, RTP) Thus, a bandwidth of about 20 Kbit/s is required for transmitting the voice data in one direction through the LAN.

The network controller 34 controls the transmission of data through the relay means 36 Once a telephone connection has been established, there is a nsk of conflict between the voice data which are to be transmitted through the network port 20 every 30 ms and data packets from one of the computers 18 which are to be transmitted through the same port 20 but may be of a size that is consi- derably larger than that of the voice packets In order to assure a high quality of the telephone connection, it is therefore an important feature of the connection device 10 that the voice packets are handled with priority Thus, for example, when a voice packet is being compiled, the network controller 34 will reserve the port 20 for the transmission of this voice packet and will instruct the relay means 36 and/or the computers 18 to suspend the transmission of data packets

It would also be possible that data packets sent from one of the computers 18 are temporarily buffered within the connection device

When all components of the network are connected to the LAN through connection devices such as the connection device 10, it would also be possible to grant priority to the voice packets by reserving appropπate time slots in advance in the entire LAN, as long as a telephone connection exists

W en data packets are received through the network port 20 or 22. the headers of these packets are inspected, and if the packet is identified as a voice packet to be sent to one of the telephones 14, this packet is decompressed and decoded and forwarded to the pertinent port 12, and this handling of the packet is again performed with pπoπty, if necessary

Figure 2 shows an example of a LAN (Ethernet) with end-to-end architecture The network comprises a server 38 and a number of direct clients (four in this case) that are all connected to an Ethernet hub 40 through end-to-end connections. One of the direct clients is the connection device 10 that has been shown in figure 1 and to which the two telephones 14 and the two desk top computers 18 have been connected. The connection device 10' is again connected to the second network port of the device 10 and is thus indirectly connected to the Ethernet hub 40. Another connecuon device (not shown) may be connected to the device 10' in a similar manner, so that a cascade of connection devices is formed. Each of these connection devices may again connect up to two telephones and two computers

Figure 2 further shows another connection device 10" which has the same construction as the device 10 but which is used here only for connecting one telephone 14

The other two clients connected to the Ethernet hub 40 are a so-called gateway 42 serving as an interface to a public telephone network (e.g. ISDN) and a so- called gatekeeper 44 which administers all user IDs and internal and external addresses (including Internet addresses and telephone numbers)

Thus, the LAN shown in figure 2 can be used not only for telephone calls between one of the telephones 14 and the telephone 14' but also for telephone calls from any of the telephones 14. 14' to the outside

Every user of the LAN signs-on at the gatekeeper 44 where his address and/or telephone number is stored in a table When a telephone call is made from any of the telephones 14, 14', a request is sent to the gatekeeper 44 which looks up the telephone number or address of the receiving side and routes the call either to the pertinent connection device 10 or the gateway 42. Likewise, when a call for one of the users is received from outside, the gateway 42 will cause the gatekeeper 44 to look up the pertinent address, and the call will be routed to the user It will be understood that this system offers a high flexibility when a user moves within the LAN area from one location to another

The system may also be configured to allow telephone calls among the two telephones 14 connected to the same connection device 10, but this will not be ne- cessary in most practical cases

Figure 3 shows a modified example of a connection device 10a which is adapted to be connected to a broad band cable network and/or a hybnd fiber cable network (HFC) In this case, a built-in cable modem 46 is intervening between the relay means 36 and the network port 20 Optionally, a third network port 48 may be provided which is configured as a LAN port just as the port 22, so that a LAN can be established by cascading a plurality of connection devices

Claims

1 Connection device for a telecommunication system, comprising at least one real time port (12) connectable to a real time terminal (14) which is specificallv adapted for handling real time data, at least one network port (20, 22, 48) connectable to a data network for transmitting and receiving data packets which each include control information specifying at least the destination of the packet, and relay means (36) for feeding data from the real time port to the network port and vice versa, characterized in that it further comprises at least one data port (16) connectable to a data processing unit (18) capable of processing non-real time data, said relay means (36) is further adapted to feed data from the data port (16) to the network port (20, 22, 48) and to direct data from the network port either to the real time port (12) or to the data port (16), depending on the specified destination, and control means (30, 34) are provided for handling the real time data with a higher priority than non-real time data

2 Connection device according to claim 1 composing digital processing means (26) adapted for real time processing of voice data that are transmitted between the real time port (12) and the network port (20, 22, 48)

3 Connection device according to claim 1 or 2, comprising at least two network ports (20, 22, 48), one of which is arranged for connecting another connection device (10')

4 Connection device according to any of the claims 1 to 3, wherein a cable modem (46) is connected to one of the network ports (20)

5 Method for transmitting, through a data network, both real time data and non-real time data in the form of data packets which each include control information specifying at least the destination of the packet, comprising the steps of connecting at least one real time terminal (14) which is specifically adapted for handling real time data and at least one a data processing unit (18) capable of processing non-real time data to common relay means (36) and operating said relay means (36) to feed data from the real time terminal (14) and the data processing unit (18) to the network and to direct data from the network either to the real time terminal (14) or to the data processing unit (18), depending on the specified destination, with the real time data being handled with a higher priority than non-real time data

6 Method according to claim 5, wherein the real time data are voice data.