Telephonic communications – Having light wave or ultrasonic link for speech or paging... – Including fiber optic link within telephone network
Patent
1994-04-11
1997-03-18
Cumming, William
Telephonic communications
Having light wave or ultrasonic link for speech or paging...
Including fiber optic link within telephone network
370467, 370524, 379 63, H04Q 730
Patent
active
056129904
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an apparatus for establishing communication between one or more digital radio channels and one or more digital wireline circuits.
DESCRIPTION OF THE PRIOR ART
Wireless telephones, such as cellular telephones, have been developed which employ digital modulation to communicate signaling, voice and synchronization. Such systems require a means of interfacing them to the public wireline network (Public Switch Telephone Network--PSTN). Prior art systems perform this function by converting the digital radio signals to standard analog signals, which are then transmitted to the PSTN.
By performing a digital-to-analog conversion each time data are transmitted between the wireline and wireless networks, many of the advantages of digital signaling are lost. It is accordingly an object of the present invention to alleviate this disadvantage.
PCT/EP90/02258 discloses an arrangement wherein cordless network termination units are connected by digital line to an exchange. However, each termination unit is only capable of handling one incoming line and the capacity of the termination units is therefore limited.
SUMMARY OF THE INVENTION
According to the present invention there is provided an apparatus for establishing communication between one or more digital radio channels and one or more digital wireline circuits, comprising an r.f. unit for transmitting and receiving signals over said digital radio channels, a digital interface unit connected to each wireline circuit, means for separating incoming signals into bearer channels and signaling information, and means for recombining the outgoing bearer channels and signaling information into the appropriate format for transmission over the outgoing medium. DECT, spread spectrum, or other systems can be used for the radio channels.
The invention provides a means of interfacing radio signals to the PSTN (Public Switched Telephone Network) or ISDN (Integrated Services Digital Network) either through a PBX (using a DNIC, for example) or directly, (using a Primary Rate Interface (PRI) or a Base Rate Interface (BRI), for example) while maintaining the advantages of digital encoding of voice and using message-based signaling.
By using a DNIC (Digital Network Interface Circuit) device, it is possible to locate the wireless base station remotely from the switching system in order to optimize the radio coverage of the base stations by allowing flexible location of the base stations.
In one embodiment the interface units, which are standard DNIC units, are connected to a standard ST serial bus. This in turn is connected to a multiplexer/demultiplexer unit, which separates the D (data) channels from the B (bearer) channels. The D channels are then interpreted to extract signaling information, which is passed through UART (Universal Asynchronous Receiver Transmitter) to the r.f. unit, where the signaling information is recombined with the bearer information for onward transmission over the radio channels. The system works in reverse for signals received over the digital radio channels.
The digital wireline circuits are preferably basic rate circuits operating at 192 kbps and offering two bearer (B) channels at 128 kbps and one data (D) channel 16 kbps. The remaining bits are used for control purposes. The r.f. section preferably uses a CT2 standard format.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a block diagram of an apparatus in accordance with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a DNIC interface 20, (and optionally additional DNIC interfaces 21) is connected to respective twisted pairs of copper wires 22, 23 carrying data at a rate of 80/160 kbps in full duplex mode for each pair of wires. The base rate channels provide a signaling "D" channel and one or more, usually two, "B" channels carrying voice or data.
The twisted pairs provide a 48 volt D
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Bligh Peter
Meier Rolf G.
Cumming William
Mitel Corporation
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