Multiplex communications – Diagnostic testing – Determination of communication parameters
Reexamination Certificate
1999-10-27
2004-02-24
Ton, Dang (Department: 2661)
Multiplex communications
Diagnostic testing
Determination of communication parameters
C370S254000, C379S202010
Reexamination Certificate
active
06697336
ABSTRACT:
BACKGROUND OF THE INVENTION
TECHNICAL FIELD OF THE INVENTION
The invention relates to a method and a device for the optimized negotiation of communication parameters for the transmission of data on communication links.
A communication link is a coupling of at least two data terminals for the purpose of exchanging information. The line may be either generated for a specified time or is constantly available. The information is presented in form of a string of digital signals called bytes. The transmission of the bytes can take place in an analog or digital manner. An analog transmission, for instance, takes place in a conventional telephone network (so-called public switched telephone network (PSTN)). The analog transmission of data requires, however, a conversion of the digital signals into audio frequency signals, which are sent via the line. This is realized by means of a modulation method. The analog signals received by the receiver are demodulated and converted into digital signals. For this purpose modems are used between a data terminal equipment and the analog telephone network. Thus, the modems have the task of providing the digital signals sent by the data terminal equipment to the transmission link, which constitutes an analog transmission medium, and of adopting the received signals of the transmission link to the physical conditions of the data terminal equipment.
Another possibility of transmitting data consists in applying a digital switching technique. Said technique is, for instance, used in the widely spread ISDN (Integrated Services Digital Network) network. It is the aim of the network to obtain an integration of different telecommunication services in one universal telecommunication network. This particularly means that up to eight different or identical terminals, for example, telephone, fax, computer, videophone, can be connected to an ISDN access via a uniform interface. Another property of the network consists in the data transmission of 64 kbit/s for all services. Important standards for the data communication via ISDN are ETS 300 102-1, ITU-T I.411 and ITU-T V.110.
Another network forming part of the category of digital networks is the digital mobile communication network GSM (Global System for Mobile Communication). The usable data transmission rate is 9.6 kbit/sec per channel. When the GSM system was designed, it was particularly considered important to make services, that had previously been accessible via the conventional telephone network or ISDN, also accessible to GSM users. This refers to services such as facsimile, source data transmission or the access to data networks such as the internet. GSM offers the possibility to set up a connection to another ISDN and PSTN subscriber. In order to meet this requirement, networks of different types have to be coupled with each other. In this connection, i.e. the coupling of several networks, the term heterogeneous network is introduced and used therefor in the following.
As was already explained above, the networks differ from one another due to the transmission rate. Moreover, there is a plurality of additional parameters, which either have to be set or can be set optionally, the configuration of which, however, considerably influences the efficiency of the transmission.
For instance, in order to guarantee synchronization of data between a transmitter and a receiver, a choice has to be made between a synchronous or asynchronous transmission. In asynchronous transmission there is no common time pulse. The synchronization of the transmission is done by sending start and stop bits. Said bits enclose small amounts of data produced with the transmitter by means of fragmentation of complete messages, which are reassembled with the receiver so as to form complete messages. This, however, requires an agreement between the communicating units in view of the form of transmission. In this respect, the more efficient, i.e. the synchronous form of transmission can be applied. With the synchronous transmission an identical time pulse is required by both the transmitter and the receiver. The transmission of the pulse can take place in different ways, such as on a separate pulse line, or the clock pulse may be derived from the data stream by means of a PLL. Thus, it is however absolutely necessary to have both data terminal equipment adjusted identically. Said decision is to be made by the user, wherein it has to be taken into account that presently the synchronous type of transmission holds the status of a new service with the result that it is not already implemented by all network providers. This has, therefore, to be inquired by the user. Further important parameters, which are necessarily to be agreed upon if the GSM network is involved in the transmission, refer to the transmission mode, in particular to the so-called transparent or the so-called non-transparent mode. The essential distinguishing feature is that in addition to the standard error-correcting mechanisms an additional method for correcting faulty transmitted data as well as for the buffering of data is applied in the so-called non-transparent mode. This is of significance in case of a faulty transmission channel with which the GSM is characterized. The corresponding transmission mode is selected by the user and depends on the network. Thus, the user is also required to have knowledge in view of the configuration of connections.
The two above-discussed services—synchronous/asynchronous and transparent
on-transparent—only form one part out of a plurality of different services. Their number and kind varies in response to the underlying network.
For the adoption of the transmission parameters not only the underlying network, e.g. ISDN, GSM or analog: PSTN, but also the kind of the terminal used by the data terminal equipment is important. On one hand, the kind of the terminal depends on the underlying network, e.g. in analog networks a modem is applied and a terminal adapter (TA) in digital ones. On the other hand, there are differences in view of the parameters between the terminals of the same kind. The parameters may, for instance, vary on the basis of the transmission rate, e.g. 14.4 kbits/s, 28.8 kbits/s and 33.3 kbits/s.
When looking at a heterogeneous connection, at least one intermediate node is involved beside the terminals in data transmission, the task of which is to adopt the linked partial paths in view of the given network characteristics. For instance, a component called InterWorking Function (IWF) integrated in the GSM switching center (so-called mobile services switching center (MSC)) is responsible for adopting the transmission carriers between GSM and external networks. Said function converts the different modulation and signaling methods into one another. The conversion methods differ from one another due to the network connected between the InterWorking Function and the subsequent data terminal equipment. The cooperation between a mobile phone and an InterWorking Function is described in standard GSM 09.07.
It is, however, a problem that it is sometimes difficult for an InterWorking Function to make a difference as to whether the subsequent data terminal equipment is connected to a digital or an analog network. The InterWorking Function generally recognizes on the basis of the kind of switching center, to which the data terminal equipment is connected, which kind of data terminal equipment is concerned. This does not take place, however, if the subscriber is in another national network and the connection is set up via several networks, where intermediate nodes use a different kind of signaling, called National User Part Signaling. Said kind of switching node may support the transmission rate of 64 kbits/s, however, uses signaling protocols which deviate from the ISDN Standard. This can result in problems when selecting the transmission parameters through the InterWorking Function.
The data terminal equipment, which refers to both the terminals and the intermediate nodes, have the task to assure a parameter agreement such that a sa
Telefonaktiebolaget LM Ericsson (publ)
Wilson Robert W.
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