EP0182843A1 - Appareil et procede de transmission de donnees - Google Patents

Appareil et procede de transmission de donnees

Info

Publication number
EP0182843A1
EP0182843A1 EP19850902597 EP85902597A EP0182843A1 EP 0182843 A1 EP0182843 A1 EP 0182843A1 EP 19850902597 EP19850902597 EP 19850902597 EP 85902597 A EP85902597 A EP 85902597A EP 0182843 A1 EP0182843 A1 EP 0182843A1
Authority
EP
European Patent Office
Prior art keywords
communication apparatus
cable
spread spectrum
data
computers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19850902597
Other languages
German (de)
English (en)
Inventor
Nigel John Mesh Data Limited SQUIBB
Paul Stuart Mesh Data Limited TAYLOR
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MESH DATA Ltd
Original Assignee
MESH DATA Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MESH DATA Ltd filed Critical MESH DATA Ltd
Publication of EP0182843A1 publication Critical patent/EP0182843A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/4013—Management of data rate on the bus
    • H04L12/40136—Nodes adapting their rate to the physical link properties
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/407—Bus networks with decentralised control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/16—Code allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/005—Optical Code Multiplex

Definitions

  • This invention relates to a method of data trans ⁇ mission and apparatus therefor.
  • the invention particularly, but not exclusively, relates to the transmission of data through cables such as existing cable TV systems, and to the transmission of data between two or more computers forming, for example, part of a local area computer network.
  • the invention may also be applied to related data transmission systems.
  • CATV Community Antenna TV Systems
  • the cable is often capable of transmitting up to 35 channels of TV signals.
  • this level of use tends to lead to a significant noise level in the cable and to a degree of cross-modulation.
  • cables of this sort are usually under utilized, and one object of the present invention is to provide means whereby this situation can be, at least to some extent alleviated, and/ or to provide means whereby the data transmission capacity of a cable can be increased.
  • spread spectrum as applied to communication apparatus , for example transmission and/or receiving apparatus , and otherwise in this application , there is meant the use of a radio frequency electro-magnetic wave modulated in any of three ways :
  • Modulation of the carrier by a digital code sequence of which the bit rate is much higher than the information signal bandwidth may be called a "direct sequence " modulated system.
  • a direct sequence modulation system typically occupies more than ten times the bandwidth of the originating signal.
  • Carrier frequency shifting in discrete increments in a pattern dictated by a code sequence Such a system may be referred to as a " frequency hopper ".
  • a frequency hopper system typically occupies more than ten times the bandwidth of the originating signal .
  • the transmitter jumps from frequency to frequency within some predetermined frequency set , the order of frequency usage being determined by a code sequence.
  • Pulsed-FM frequency modulation
  • chirp modulation in which a carrier is swept over a wide band during a given pulse interval.
  • the invention also provides apparatus for performing the method of increasing the data transmission capacity of a cable type communication system as defined in the accompanying claims.
  • a cable- connected computer network in which spread spectrum data transmission signals are employed which are readable and transmittable only by use of suitably- matched pairs of modulator/demodulator apparatus ( modems ) , whereby considerable security of information is provided .
  • Another embodiment of this aspect of the invention provides for CATV cables to be used for providing a telephone network carrying multiple voice channels in addition to the existing cable TV use of the network and without any significant interference with the latter .
  • Another aspect of the invention relates to data transmission by means of radiated signals as opposed to signals transmitted by cable or the like.
  • This aspect of the invention relates particularly, but not exclusively , to the provision of radiated signals linking computer terminals .
  • a method of linking two sets of data handling apparatus such as computers , by means of radiated signals .
  • the method comprises generating a radio frequency carrier wave , modulating the carrier wave to produce a spread spectrum wave , and using the spread spectrum wave to carry signals between said sets of apparatus.
  • This aspect of the invention also provides apparatus for performing the method of the invention.
  • Such apparatus may comprise a modulator/ demodulator unit associated with each set of data handling apparatus , the modem units being set to corresponding codes .
  • the invention also provides a method and apparatus comprising any novel step or feature disclosed herein or any novel combination of such steps or features.
  • Fig. 1 shows a block diagram of a direct sequence spread spectrum ( or pseudo-noise - PN ) transmitter j
  • Fig. 2 shows a spread spectrum or PN receiver in block diagram form
  • Fig. 4 shows a radiated ( broadcast ) data transmission system , using a cable to link transponder units ;
  • Fig. 5 shows , again in block diagram form , a cable system , using a headend unit to bridge forward and reverse channels ; and Fig. 6 shows a block diagram of a fibre- optic local area network .
  • Fig.s 1 and 3 show two alternative forms of spread spectrum or direct sequence transmitter .
  • information signals from the data source 12 are transformed into digital form by the data encoder 14 and employed by a digital modulator 16 for incorporation in the spread spectrum signal produced by a pseudo-noise (PN ) generator 18 by adding the digital information to the spectrum- spreading code produced by the PN generator before such code is used for modulating the carrier produced by carrier generator 20 .
  • PN pseudo-noise
  • Modulation of the carrier is effected in the transmitter proper 22 from which the output signal passes via power amplifier ( PA ) 24 to output connector 26 .
  • This technique is applicable to any spread spectrum apparatus that uses a code sequence to determine its radio frequency bandwidth , such as direct sequence systems or frequency hopping systems.
  • the information to be sent must be in a digital form for the purpose of addition to the code sequence .
  • Modulation of the carrier before spreading is effected by a suitable form of angle modulation so as to generate a constant-power radio frequency envelope.
  • the data encoders 14 and 32 put the " data from the data sources 12 and 30 into suitable digital form .
  • the output from the data encoder 14 is employed by the digital modulator 16 for insertion into the spectrum- spreading code produced by the spread spectrum or pseudo-noise ( PN ) generator 18 .
  • the data-containing pseudo-noise signal is added to the carrier from the carrier generator 20 in the transmitter proper 22 from which the output signal is passed via the power amplifier 24 to the cable system or an antenna , as described below.
  • the carrier itself is modulated by the data from the data encoder 32 prior to modulation in the transmitter proper 40 by the pseudo-noise from the PN generator 38.
  • the spread spectrum signal obtained by modulating the carrier with a pseudo ⁇ random sequence is a double sideband-suppressed carrier signal occupying a large frequency band , compared with the original modulation bandwidth of the data source.
  • Fig. 2 shows a spread spectrum or PN receiver 50 in which an input conductor 52 feeds the received signal to a preamplifier 54 from which the amplified signal is processed in primary and secondary circuits 56 , 58 and 60 , 62 with regard- to the PN code acquisition and code locking , and the carrier signal acquisition / tracking and locking .
  • a locally generated code sequence is compared with the received signal. When a " fit " occurs , recovery of the carrier takes place. Demodulation of the carrier in circuit 64 and recovery of the data stream by way of output circuit 66 can then occur. Extensive use of phase lock techniques is made to ensure tracking of the incoming signal. Synchronisation and locking circuits 68 and 70 are provided as shown.
  • the synchronisation clock information may be transmitted separately thus easing the problems of maintaining synchronism.
  • the transmitter and receiver apparatus of Figs. 1 to 3 to cable- type data transmission systems , it is to be noted that on a coaxial cable distribution system , a limited amount of bandwidth is available to carry TV signals from the headend to users. When the cable becomes fully occupied , further channels cannot be added by use of existing techniques.
  • the spread spectrum or pseudo-noise (PN ) signals produced by the apparatus of Figs. 1 and 3 can co-exist in the same frequency band as existing services on cable transmission systems without significant mutual interference.
  • Such existing or conventional data transmission systems employ narrow band modulation systems of the amplitude or frequency or phase modulation kind having high and localised spectral power transmission. These systems do not interfere with the wideband low energy content signal of the spread spectrum apparatus disclosed above, whereby additional signal transmission channels are readily provided in existing cable TV networks , regardless of frequency allocation and cable channel operating frequencies. Furthermore , the nature of the spread spectrum transmission gives a high level of security , thereby preventing unauthorised access to the data. Such access is only available with suitable apparatus programmed to recognise the coding sequence. Such security is important in relation not only to pay- as-you-use services , but also for data security.
  • a spread spectrum PN_data network employing transmission and reception apparatus as indicated in Figs. 1 to 3 may be installed on an existing cable network without modification to the installed and existing cable and signal transmission and reception and amplification hardware .
  • the new users of the system will each employ a modem unit set to a unique selected code , to allow reception and transmission of PN signals.
  • the spread spectrum apparatus is merely connected to the cable directly and the system functions with these additional channels just as if the channel capacity of the cable had been increased - which in reality it has.
  • code distribution may occur either from a central " key distribution " unit , or as a pre-loaded programme in the modem unit.
  • the two units are set to the same code sequence, and synchronism is achieved . Any number of units may be simultaneously in synchronism , permitting " broadcast " transmissions .
  • Access to the transmission medium may be governed by any one ' of the established data network protocols , for example CSMA - CD , token passing etc..
  • Figs. 4 and 5 indicate further applications of the spread spectrum technique.
  • a radiated or broadcast system employs a trunk cable 80 having transponder units 82 , 84 connected thereto at convenient local intervals.
  • the transponder units are ceiling mounted and individual data transmission units 86 , 88 , 90 and 92 , 94 (such as suitably equipped micro-computers ) transmit data thereto and hence to the trunk cable , and vice versa , by means of spread spectrum radiated signals 96 of the kind discussed above.
  • individual data transmission units 86 , 88 , 90 and 92 , 94 such as suitably equipped micro-computers
  • transmit data thereto and hence to the trunk cable and vice versa
  • a series of data sources can be conveniently connected to a central main computer , for example , in a very effective way.
  • a cable system 100 comprises a cable 102 having spaced taps 104 , 106 , 108 for local inputs directly connected thereby from local users with apparatus 110 , 112 , for example as described in the preceding embodiments.
  • a headend unit 114 is provided to bridge the forward and reverse channels of this pure cable connection system .
  • the transmitter and receiver techniques of the embodiment of Fig. 6 are very much on the lines of those of Figs. 1 , 2 and 3 but use light-emitting diodes/lasers to transmit , and photodiodes or similar to receive the optical signal.,
  • the figure shows a code division multiplex arrangement , with optical splitters allowing the insertion of a number of signals into the fibre.
  • the embodiments enable existing cable systems of data transmission to have their capacity increased without interfering with existing equipment or users.
  • This enables additional TV channels to be transmitted or other data services , including telephone channels , computer links, etc..
  • the embodiment provides a means for radio links between computers in a manner allowing transmission of data at rates hitherto contrary to the regulations , whereby non cable-linked computer networks become attractive and feasible.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Quality & Reliability (AREA)
  • Small-Scale Networks (AREA)

Abstract

Un procédé pour améliorer la capacité de transmission de données d'un système de communication de type à câble prévoit l'utilisation d'un appareil à spectre large (pseudo-bruit) connecté ou couplé au câble pour une communication simultanée à travers celui-ci avec l'équipement de communication existant sans provoquer d'interférence avec ce dernier. Est également décrit un système informatique de réseau local utilisant des signaux de spectre large rayonné recourant à une séquence de codes commune.
EP19850902597 1984-05-29 1985-05-29 Appareil et procede de transmission de donnees Withdrawn EP0182843A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8413579 1984-05-29
GB8413579 1984-05-29

Publications (1)

Publication Number Publication Date
EP0182843A1 true EP0182843A1 (fr) 1986-06-04

Family

ID=10561584

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19850902597 Withdrawn EP0182843A1 (fr) 1984-05-29 1985-05-29 Appareil et procede de transmission de donnees

Country Status (3)

Country Link
EP (1) EP0182843A1 (fr)
AU (1) AU4402185A (fr)
WO (1) WO1985005745A1 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2607339B1 (fr) * 1986-11-21 1989-03-31 Thomson Csf Systeme de transmission numerique a demodulation coherente, amenage pour la transmission simultanee de deux messages binaires
US4943973A (en) * 1989-03-31 1990-07-24 At&T Company Spread-spectrum identification signal for communications system
US5588022A (en) * 1994-03-07 1996-12-24 Xetron Corp. Method and apparatus for AM compatible digital broadcasting
US5404377A (en) * 1994-04-08 1995-04-04 Moses; Donald W. Simultaneous transmission of data and audio signals by means of perceptual coding
US7346070B2 (en) * 2004-02-05 2008-03-18 Lucent Technologies Inc. Shared wireline code division multiple access
GB0614542D0 (en) * 2006-07-21 2006-08-30 Vodafone Plc RF Distribution Spreading
GB0614543D0 (en) 2006-07-21 2006-08-30 Vodafone Plc RF Distribution

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4392220A (en) * 1980-05-30 1983-07-05 Nippon Electric Co., Ltd. Modem to be coupled to a directional transmission line of an SS multiplex communication network
US4425642A (en) * 1982-01-08 1984-01-10 Applied Spectrum Technologies, Inc. Simultaneous transmission of two information signals within a band-limited communications channel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8505745A1 *

Also Published As

Publication number Publication date
AU4402185A (en) 1985-12-31
WO1985005745A1 (fr) 1985-12-19

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Inventor name: TAYLOR, PAUL, STUARTMESH DATA LIMITED

Inventor name: SQUIBB, NIGEL, JOHNMESH DATA LIMITED