FI102935B - Method of connecting a mobile terminal to a TDMA barred network - Google Patents

Description

102935

A method for connecting a mobile station to a TDMA-based network ψ

The invention relates to a method for connecting a mobile station to a TDMA based network according to the preamble of claim 15. In this context, a mobile station refers to a telecommunications terminal generally intended for mobile communication and which can be used on the move or in a predetermined location.

The method according to the invention is intended to be used in particular for connecting a portable DECT terminal to a DECT system in connection with a DECT system, but it can in principle also be applied in any other TDMA based system.

15 A conventional fixed telephone network has e.g.

a disadvantage that when changing a subscriber device (e.g., a telephone) to a different location, it is necessary to specify a telephone number associated with the new location in the telephone exchange. Such change operations cause a lot of work for the operator 20 and for the subscriber they entail (additional) costs.

Known cellular or cellular networks, on the other hand, do not have the aforementioned disadvantage, but have the same phone number, regardless of where the telephone is located. 1 25 ti. In addition, the phones of such systems have subscriber-specific cards (e.g., SIM cards) which allow a single telephone to be switched to a subscriber's device of the desired subscriber.

In turn, fixed network terminals (e.g. telephones) 30 have at least the following advantages over cellular network terminals: - the terminals operate reliably, - the terminals receive power from the network, making them more reliable and user-friendly in this sense 35 - because the terminals are At 102935 locations, subscriber line related information (e.g., carrier and subscriber billing) is readily identifiable, * - speech quality is always very smooth, and 5 - radio is not causing blocking.

It is an object of the present invention to provide a method whereby the advantages described above can be combined with the same subscriber unit in the simplest and most efficient manner possible. This principal amount is achieved by the process of the invention, which is characterized in what is described in the characterizing part of the appended claim 1.

The idea of the invention is to branch off a fixed point-to-point connection using a digital full duplex transmission in a mobile station alongside the radio path and to implement the branching in an interface where the data packets (bursts) generated for the radio path occur substantially in the form in which they are transmitted. for processing required by the radio path (i.e., before any channel coding and / or interleaving required by the radio paths, etc.).

Thanks to the solution according to the invention, e.g. the following benefits: - no need for separate infrastructure for wireless and fixed subscriber connections,. - 25 - the same subscriber unit can be used in the most appropriate (most reliable) way, - the subscriber unit can be transferred from one fixed line to another fixed line without the need for the operator to perform modifications, 30 - the same telephone number can be used. , and the radio spectrum can be saved because subscribers can also connect to the network via a fixed connection.

In the following, the invention and its preferred embodiments will be described in more detail with reference to the examples of the accompanying drawings, in which: Fig. 1 illustrates a conventional DECT system, Fig. 2 illustrates a DECT system radio frame structure, Fig. 4 illustrates a frame structure for use with a pair cable of the system of Fig. 2, Fig. 5 illustrates parts of the portable DECT terminal relevant to the invention, and Fig. 6 illustrates the implementation of a wired interface according to the invention.

Figure 1 illustrates a reference model of a DECT system. In the figure (for the sake of clarity) similar designations are used (in English) as in international standards (cf. e.g. ETSI, ETR 015, March 1991: Radio Equipment and Systems, Digital European Cordless Telecommunications (DECT), Reference Document).

The DECT system can be connected to two types of network: - a local area network LN such as a subscriber exchange, and ·. * 25 - to a global network GN, which is typically a national or international network, such as a public telephone network.

The DECT reference model presented in the standards divides network elements into portable terminals PT and 30 into fixed systems FS. A fixed system is a collection of all * elements that represent fixed parts of a DECT network. These network elements (PT and FS) 5 communicate with one another via a radio path. The fixed system FS may contain multiple base stations (Radio Fixed 35 Part) but only one common control unit CCFP (Common «4 102935

Control Fixed Part).

The portable terminal PT is associated with an End System (ES), which is the system containing the application processes used (telecommunications services).

Conceptually, the DECT system comprises three components: the cells within which the subscribers move, each of which has a set of functions necessary to control and control that cell, - a Central System containing the necessary protocol and management functions for all DECTs. for maintaining connections in the system, and - Interworking unit (s) that perform protocol, format, and code conversions between the DECT system and the system connected thereto (eg, public switched telephone network, ISDN network, or GSM network).

As the DECT system is known per se, it will not be described further here. The DECT system is defined in ETSI standard ETS 300 175, which gives the reader a more detailed view of the system if he wishes.

Figure 2 illustrates how the principle of the invention changes the reference model shown in Figure 1. According to the invention, a carrying device is provided. · In addition to the radio path RP between the 25 terminals and the fixed system, another wired transmission line WL is implemented by means of a (copper) pair conductor, that is, on a transmission medium similar to that of a conventional fixed telephone network. Thus, the portable DECT terminal 30 may communicate with the fixed system either via a radio path or through a wired connection (subscriber loop). The portable terminal PT has a wireless connection part W1, which is implemented in a conventional manner for a DECT radio connection, and a wired connection 35 parallel part W2, which manages the connection to the paired cable.

• 5 The 102935 DECT system is assigned a 20 MHz frequency band between 1880 MHz and 1900 MHz. This band has a spacing of 1.728 MHz between RF channels (carriers). The average transmission power is only 10 mW, which allows for long operating times and on the other hand lowers the price of the phone.

Figure 3 illustrates a frame structure for use on a DECT radio path RP. One frame is 10 ms long and consists of 24 consecutive time slots (0 ... 23), the first 12 of which are reserved for fixed-to-portable (F-P) and 12 for the mobile-to-fixed (P-F). The physical channels of the DECT system are thus formed using so-called. MC-TDMA / TDD (Multi Carrier Time Division 15 Multiple Access / Time Division Duplex). The length of one time slot is 416.7 με. The burst transmitted in a time slot is 364.6 με and has a total of 420 bits. This burst is a physical level packet (PHL Packet) of the DECT system, designated by the reference character PHL_P. The burst handles a 32 bit long synchronization field SYNC and a subsequent data field DATA 388 bits long. The data field consists of a Media Access Control (MAC) packet (MAC Packet) in the DECT system, designated by a reference character MAC_P. Figure 3 shows the data field ·. · 25 as it would be used eg during a normal call. The data field is divided into two parts, A and B. Field A transmits information about the signaling channel (C), the broadcast channel (Q), and the paging channel (P, Paging). These channels thus share the transmission capacity of 30 A (4.8 kbit / s) provided by Field A. The remaining CRC (16 bits) of field A is for error checking of the data. Field B transfers user information (I-channel) in a 320-bit burst. The remaining part X of the field B (4 bits) is determined by some bits of the I channel and used to detect interference.

t I

6, 102935

According to the invention, the twisted-pair cable uses a frame structure substantially similar to that of the radio path, but with transmission in both transmission directions simultaneously. (The solution is based on echo cancellation 5 technology, which will be described in more detail in connection with Figure 5.) Figure 4 shows the frame structure used in the twin cable. The frame length is 10 ms in each transmission direction, and the frame preferably comprises 12 consecutive time slots each transmitting (preferably) 10 physical plane packets PHL_P of the DECT system. In this way, each transmission direction has a speed of about 504 kbit / s. (Although the figure shows the guard time at the ends of each physical level packet PHL_P, such a guard time is not necessary for paired-cable transmission.) By using echo cancellation technology, full duplex transmission can narrow the spectrum of the paired cable.

Figure 5 shows those portions of a portable DECT terminal PT that are related to the present invention. The point of departure is that the portable terminal always has an interface through which DECT packets (preferably physical plane packets) are transmitted in both transmission directions. This interface is designated by the reference PI. The packet generation and unpacking takes place in unit 51, which unloads the incoming packets into bit streams corresponding to different channels (I, P, C and Q) and outputs these bit streams in the outgoing transmission direction. According to the invention, a selection unit 52 is fitted to the above interface to select the manner in which the terminal is connected to fixed parts of the network, i.e., whether it is connected via a radio path or via a pair cable. The "access mode" selection signal is designated by the reference CTRL. The selection unit couples the packet generation and decommissioning unit to either the RF subsystem W1 or the fixed 35 interface subsystem W2, which in turn is connected to one or more paired cables WL.

Figure 6 illustrates the structure of the subsystem W2 '. Outbound packets PHL_P are formed in unit 61 into frames according to Fig. 4, which are supplied to modulator / demodulator part 62. From the modulator, the transmission signal is supplied to both the adaptive echo cancellation unit 63 and the hybrid 64 10 to the pair cable WL. The hybrid performs a 2-wire / 4-wire conversion in a manner known per se.

The received signal Rx is coupled via a hybrid to the echo cancellation unit 63, which removes the component (echo) corresponding to the transmission signal from the received signal. The signal thus obtained is demodulated in unit 62 and frames are decompressed in unit 61. At the end of the fixed system is a subsystem W2 substantially similar to that of the portable terminal. The paired cable connection can be connected at the FS end of the fixed system to either the tu-20 radio station (Radio Fixed Part) or the common control unit CCFP.

The subsystem W1 is not described in more detail herein, since it is implemented in a manner known per se.

The above describes the way in which the paired cable time ·. 25 laws move the physical level packet of the DECT system. This is an advantageous embodiment in that it is as compatible as possible with the existing DECT system. It is also possible to transfer MAC-level packets in the time slots, whereby the synchronization pattern 30 can be placed e.g. in front of the frame. Such a solution requires larger changes to the existing technology, but it is a somewhat less expensive solution for transmission. in terms of passivity.

Although the invention has been described above with reference to the examples of the accompanying drawings, it is understood that the invention is not limited thereto but can be modified within the scope of the inventive idea set forth above and in the appended claims. Although the DECT system has been used as an example above, the method can be applied to any similar TDMA based system.

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Claims (4)

102935, 1. A method for connecting a mobile station to a TDMA-based transmission system, such as a DECT system, 5 wherein the mobile stations (PTs) are connected to fixed parts (FS) of the system via a radio path (RP) for transmitting successive TDMA frames spaced into successive time slots 10, characterized in that a parallel transmission from a pair cable (WL) is provided to the radio path such that: - the transmission in the pair cable takes place in both directions simultaneously in frames of substantially equal length 15 TDMA frame lengths, and - the time slots of the frames are formed from the data packets (PHL_P; MAC_P) that are formed in the mobile station for the radio path. Method according to claim 1, characterized in that the number of time slots in the frame corresponds to the number of time slots available in one transmission direction of the TDMA frame. 3. A method for connecting a portable DECT terminal to a DECT system according to claim 1, characterized in that frame slots are formed from physical level data packets created for the radio path. A method for connecting a portable DECT terminal to a DECT system according to claim 2, characterized in that the pair cable is connected from the portable terminal to a Common Control Fixed Part CCFP of the DECT system. 102935