GB2251160A

GB2251160A - Method of transmitting data between transmission equipments in a branching repeater station and a repeater station applying the method

Info

Publication number: GB2251160A
Application number: GB9120857A
Authority: GB
Inventors: Jukka Tapio Ruosteoja; Harri Juhani Lahti; Erkki Matias Leskelae; Juha Teuvo Salmelin
Original assignee: Telenokia Oy
Current assignee: Nokia Oyj
Priority date: 1990-10-01
Filing date: 1991-10-01
Publication date: 1992-06-24
Anticipated expiration: 2011-10-01
Also published as: GB2251160B; FI904833A0; AU651382B2; AU8552491A; FI904833A; SE9102836L; SE517065C2; GB9120857D0; SE9102836D0; DE4132544A1; SE517065C3

Description

22-31 1,5J 1 Method of transmitting data between transmission equipments

in a branchinq repeater station and a repeater station applying the method The invention relates to a method of arranging data transmission between transmission equipments in a branching repeater station of a digital telecommunication network, and to a repeater station applying the method.

In a digital telecommunication network, such as a radio link or telephone network, the chain of transmission equipments comprises repeater stations at least some of which are usually able to branch the network e.g. into a two-dimensional cellular network.

In prior art arrangements for switching the traffic over branching repeater stations, digital signals multiplexed into transmission frames are opened by demultiplexing when received from the transmission path and converted by interface devices complying to the G. 703 standard, whereafter they are correspondingly multiplexed and framed again into a single signal required by the transmission path. In other words, the opened channels are transported in parallel form over the station from one transmission path to the other, which is necessary if one or more channels (which is on a lower hierarchic level than the transmission path) is to be branched from the repeater station in question.

In addition to this, all channels which have been demultiplexed have to be provided with their own interface circuits and wired over the repeater station by means of their own cables. If the transmission path has a high capacity and the number of branching channels is small, this arrangement is very 2 expensive.

The object of the present invention is to provide a method of arranging communication between digital transmission equipments, such as radio links, while avoiding the above-described drawbacks. The method according to the invention is thus characterIzed in that serial digital signals received by the transmission equipment of the repeater station from a transmission path are applied, while still in substantially serial form, to the repeating transmission equipment and therethrough to the following section of the transmission path, and that one or more branching channels are separated from the transmission path by demultiplexing and connected to the transmission path by multiplexing in a manner known per se.

The method according to the invention can be applied to any digital telecommunication system comprising branching or unbranching repeater stations and utilizing a transmission frame on the transmission path.

The primary object of the invention is to save the electric parts and especially the expensive interface components and cables required for the multiplexing/ demultiplexing of unbranching channels. The repeater bus needs only a simple cable over which data and timing can be transferred in both directions. Unbranching channels can be passed through the repeater station to the following section of the transmission path in the same form in which they were received from the preceding transmission path. The repeating transmission equipment utilizes the frame and the clock or timing it receives from the repeater bus and adds the channels branching at the station in question to the frame in the direction 3 of the transmission path in question. The channels from the repeater bus may be plesiochronous, that is, they have the same frequency, but a predetermined frequency deviation is allowed. The frequency dif- ferences between the channels can thereby be adjusted by positive justification, that is, a justification bit is provided for each channel in the frame. The justification bit is used either for the transmission of the signal of each channel or as "an empty bit".

The use of the justification bit is indicated by justification service bits. The transmission path is usually bidirectional.

The repeater station according to the invention, comprising transmission equipments receiving and transmitting signals from the transmission paths of a telecommunication network, is characterized in that unbranching channels in the repeater station are carried by a cable, e.g. twin cable, or the like extending from one transmission equipment of the station to the other, serial digital signals being arranged to be transmitted over said cable through the repeating transmission equipment to the following transmission path section, and that branching channels in the repeater station are separated from the transmission path by a demultiplexer and combined to the transmission path by a multiplexer in a manner known per se.

The technology used in the cables and interface circuits of the repeater bus depends on the bit rate.

Also in the case of an unbranching repeater station, the expensive interface parts for the main signal are saved when the cables between the transmission equipments are replaced with a repeater bus.

In the following the invention will be described by way of example with reference to the 4 attached drawings, in which Figure 1 shows a repeater station arrangement known from the prior art; and

Figure 2 shows a repeater station arrangement according to the invention.

The prior art repeater station shown in Figure 1 comprises two transmission paths A, B and therebetween transmission equipments 1, 2, multiplexers/ demultiplexers 3, 4, and Interconnecting cables 5.

The transmission paths A and B may be, independently of each other, a radio path, a coaxial telephone cable, an optical cable, etc.

In prior art repeater stations, e.g. Time Division Multiple Access (TDMA) multiplexed channels from the transmission path A, for instance, have to be disassembled from their data transmission frames by demultiplexing in the multiplexer/demultip-lexer 3, which may comprise several standardized hierarchic levels, e.g. 2,8,34 Mbit/s. Branching channels C pass through a conventional G.703 interface to a telecommunication network branch for which each particular channel is intended, e.g. to a telephone exchange, a mobile telephone base station, etc. Unbranching channels, that is, channels extending directly from the transmission path A to the transmission path B have to be passed in parallel form through G.703 interfaces 6 back to the multiplexer/demultiplexer 4, which may also comprise several standardized hierarchic levels, to be multiplexed therein. Each standard multiplexer always adds its own frame to each hierarchic level. Furthermore, each transmission equipment adds its own frame for the time of transmission, so that each multiplexing/demultiplexing of a signal received from the transmission paths requires plenty of logic operations.

As the transmission paths are generally bidirectional, it is essential that the repeater station is able to operate even when data is received from the branching channel C, whereby the data of the branching channel is multiplexed into the lowest hierarchic level.

As appears f rom. Figure 1, there are plenty of cables between the multiplexers/demultiplexers 3 and 4, e.g. 32 cables, when the capacity is 16 channels each 2 Mbit/s. The interface of each channel is realized by an expensive G.703 interface 6 obvious to one skilled in the art.

In Figure 2 showing the repeater station according to the invention, the transmission paths A, B are connected to the same transmission equipments 1, 2 (e.g. radio links) as in Figure 1. The multiplexers/demultiplexers and interconnecting cables shown in Figure 1 can now be replaced by a repeater bus 7 and simple multiplexer/demultiplexer components 9, 10, which may replace several hierarchic levels of standard multiplexers. All the other cables except the cables of the branching channels are replaced by the repeater bus arrangement according to the invention. The repeater bus consists e.g. of a twisted twin cable, and it is connected to the branching devices by relatively simple digital interface circuits 8, which are formed e.g. by fast ECL buffers. The traffic rate of the repeater bus may be e.g. 35 Mbit/s.

As the repeater bus 7 transmits data from one transmission equipment to the other substantially without opening the transmission frames, only the branching channels C are disassembled conventionally in the multiplexer/ demul tipl exer components 9 to the 6 G.703 interface 6. The disassembly of the data of the branching channels from the transmission f rames and its transfer to the transmission equipment for further transmission over the branch C are performed on well-known principles, and do not belong to the present invention.

In the arrangement according to the invention, the resynchronization (normalizing of timing) between the transmission frame and the branching channels after an interruption in the transmission path requires buffering. When a signal received from the transmission path and thus also from the repeater bus is interrupted, the branching channels can be synchronized with the local timing in such a manner that no errors occur in the signal. Af ter an inter ruption in the transmission path, the normal state is resumed without errors, and the signal received from the repeater bus and the branching channels are synchronized with each other by buffering.

It is obvious to one skilled in the art that the different embodiments of the invention are not restricted to the above examples, but may vary within the scope of the accompanying claims.

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Claims

Claims:

1. A method of transmitting data between transmission equipments in a branching repeater station of a telecommini cation network, c h a r a c t e r i z e d in that serial digital signals received by a transmission equipment of the repeater station from a transmission path are applied, while still in substantially serial form, to the repeating transmission equipment and therethrough. to the following section of the transmission path, and that one or more branching channels are separated from the transmission path by demultiplexing and combined to the trans mission path by multiplexing in a manner known per se.

2. A branching repeater station in a digital telecommunication network, comprising transmission equipments receiving and transmitting signals from transmission paths in the telecommunic tion network, characterized in that un branching channels in the repeater station are carried by a cable extending from one transmission equipment of the station to the other, serial digital signals being transmittable over said cable through the repeating transmission equipment to the following transmission path section, and that branching channels in the repeater station are separated from the transmission path by a demultiplexer and connected to the transmission path by a multiplexer in a manner known per se.

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3. A method of transmitting data between transmission equipments in a branching repeater station of a telecommunication network, substantially as hereinbefore described with reference to the accompanying drawings.

4. A branching repeater station substantially as hereinbefore described with reference to the accompanying drawings.