CA1046669A - Spread spectrum communication techniques for a code division message multiplexing system - Google Patents
Spread spectrum communication techniques for a code division message multiplexing systemInfo
- Publication number
- CA1046669A CA1046669A CA221,820A CA221820A CA1046669A CA 1046669 A CA1046669 A CA 1046669A CA 221820 A CA221820 A CA 221820A CA 1046669 A CA1046669 A CA 1046669A
- Authority
- CA
- Canada
- Prior art keywords
- carrier
- transmitter
- sub
- additional
- receiver
- 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.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/10—Code generation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/204—Multiple access
- H04B7/216—Code division or spread-spectrum multiple access [CDMA, SSMA]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
- H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
Abstract
ABSTRACT OF THE DISCLOSURE
A transmission system is described, suitable for transmitting multiple messages over a single carrier. At the transmitter, a message-modulated carrier is given an additional modulation by an identifiable signal. At the receiver, the carrier is identified by means of the additional modulation with messages being retrieved by demodulating the modulated carriers. The system is characterized in that, in the transmitter the carrier for each message is given an additional modulation causing a number of sub-carriers to be generated. The sub-carriers are synchronized in code and carrier frequency both mutually and jointly.
The carrier is solely modulated by an identifiable signal. The carrier and sub-carriers are then added to from the transmitted carrier.
A transmission system is described, suitable for transmitting multiple messages over a single carrier. At the transmitter, a message-modulated carrier is given an additional modulation by an identifiable signal. At the receiver, the carrier is identified by means of the additional modulation with messages being retrieved by demodulating the modulated carriers. The system is characterized in that, in the transmitter the carrier for each message is given an additional modulation causing a number of sub-carriers to be generated. The sub-carriers are synchronized in code and carrier frequency both mutually and jointly.
The carrier is solely modulated by an identifiable signal. The carrier and sub-carriers are then added to from the transmitted carrier.
Description
C~
- The invention re!.-Jtes to such a transmission sy~teln, suitable for the transmission of m~llti~le messages ~ver a sin~le cLIrriet wl~ereby an i additior.al modulaLion ~ cntifiablc by mcans of a sign~l - i9 given to the message-modulated carrier on transmission, and whereby the message-modulated carrier is recognized by the receiver through the additional modulation and me~sages are retrieved by democlulation Or ~lle ~odulated ~ carrier.
! In SS~ prcacl Spectru~ Multiple Access) individual message-modulated carriers arc given an aclditiclnal modul~tion by a wide-ban(l pseudo-random noise waveform (CDMA - ~ode Division Multiple Access), thus producing a different waveform for each carrier.
At the receiver the required carrier is selected by demodulation with the appropriate pseudo-random wave form.
The basic principle, i.e. a spectral spreading of the signal power over the available spectrum within the available cornmunicatlons bandwidth, can also be implemented in other ways such as frequency hopping, phase modulatlon and time hopping.
~ In conventional SSMA systems many different streams of analogue or i digital dat~ ~re multiplexed on the carrier altllough problems arise if the inormàtion streams are isochronous.
These problems may be solved in various ways which are both complex and costly. It iY well-known that spread-spectrum modulation with constant envelope or code-division techniques can be used to good advantage in communications systems whcre the processing gain provided by such techniques is necessary. For eYample, in satellite communication systems (using a soft or hard limiter) spread-spectrum multiple access (SSMA) i5 used to improve the quality of the receipt of the multiple-access carriers.
The present invention aims at providing a simplcr and cheaper solution in th~t an additional modulation is given in the transmitter to the carrier for each message, in such a way that sub-carriers are generated which are .: . ~
. ~ , - .
..
. , ~ .
synchronized in code ~n~l carr.er frequency bo~ll mutua]ly and jointly with a carrier, cxclusively mo~lulated by an iden-ifia~le signal, and the summation of the latter carricr ~nd Lhe sub-carriers form the trunsfer carrier of the transmitter, whereas in the receiver the sub-carricrs and the carrier itsclf are retrieved by derivaLion from the transfer carrier by means of the additionalmodulation, and the mcssages i~ the derived sub-carriers are retrieved from the carrier itself.
A design based on thc invention is charactcrize(l by Lhe transmitter having a codc gcnerator which produces Lhc iclcnLifiable signal and the lo additional modulation for the transmitter, and the receiver having a code generator which is synchronized by the identifiablc signll and which produces the additional modulations for the receivcr, additional modulations being sub-codes of the code generators.
The proposed method provides transparent channcls, i.e. for isochronous lnformation streams, by effectively earmarking for each channel a separate ; code-dlvision multiple-access carrier, such CDMA carriers being derivcd from the same timing 60urce.
. , I , This is achieved by combining the multiplexing o channels and the multiple acce66 feature of the separate carriers in one and the same equipment.
The resulting system is cheaper and simpler to operate; it has a high performance and provides transparent channels for a variety of different types of communications traffic.
The combining of multiplexing techniques and multiplc access features may ! be implemented using the apparatus described below, and as illustrated by way of example only in Fig 1 which 6hows diagramatically the transmitter; and ln Fig 2 which shows diagramatically the receiver.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the transmitter block diagram (Fig. 1) whicll illustrates a dèsign J ,_.. ",,.'' ., ; based on the invention, a clock pulse generator 1 feeds pulses to a code generator 2 which is, [or example, of the feedback sl.irt re~ister type.
X ~
' ~4~;~i69 By means of ~, c-)~1( sel~ctor 3 thc f~c~-1)ac1c Or gs11erator 2 can be set at the wanted cod~ zo~t).
A logic circuit shown scl1e1na~ically at 4 is couplet1 to a number of outputs of the code gc~r1erator 2, contains modulo-two ad~ers, and produces a number of sub-codes z1(t)~ z2(t), ~nd zn(t) of the ~o(t) code which is originating directly ~rom g~nerator 2.
A earrier generator 5 produces the cos~ t, sin~ot transmitter carrier wave.
In n plurality Or ~our-phase modulators 6l, 62, 6n carrier wave cos~Ot, sin~0t is modulated with codes Zl(t), Z2(t), Zn(t) and wit11 messages Bl, ~2 and Bn.
At theoutputs U , U2, U of modulators 6l, 62~ n~
SDl, SD2, SDn are equalized and fed to an adding network 7 through a plurality of regulators Nl, N2, Nn-In a multiplier 8 the eo8wot~ sin~ ot earrier i9 modulated by eode Zo(t).
Carrier SD modulated only by an identifiable signal obtained at output U
;`~ 18 al80 fed to the network 7 at the appropriate level via regulator N.
Aeeess of the output signal of network 7 to the eommunieations medium i9 aehleved through a band limiting filter 9.
In the reeeived bloek diagram (Fig. 2) whieh also illustrates a design ... .
based on the invention, a band pass filter lO at the input of a distribution amplifier ll reeeived the SSMA earrier wave originating from the transmitter.
The reeeiver has its own eode generator 12 with its built-in (and '~ thereiore not appearing on the sketeh) eode seleetor set in sueh a way that a further generator l2 delivers a eode Z (t) identieal to the Zo(t) eode produeed in the transmLtter by the generator 2.
8y multiplying the output signal of the distribution amplifier ll by eode Zo~t) ln a multiplier 13 the eoswOt~ sinwOt, earrier wave is retrieved.
8y means of a traeking deteetor 14, whieh eontains a voltage-stabilized erystal-oseillator, a timing signal M is generated to synchronize the two ~; , . .
generators 2 and 12.
.
. I , ,~ X
?~
A logic circ~ 15 -~ho~qc circuit design corres~lolltls to that of the logic circuit 4 at Lhc transmitLer and produces codes Zl(t), Z2(t) and Zn(l)~
whilst connected to some outputs of the code generator 12, which codes -tllrough a plurality o~.multipliers 171~ 172, 17 - may be used to derive sub-carriers S'D], S'D2~ SID from the output signals of the distrlbution amplifier 1 1 .
Dl' D2~ S Dn~ so derived, are uscd to restore messages Bl, B2, Bn ~Y means of a number of demodulators 201, 202, 20n.
In order to do this, demodulators 201, 202, 20 arc driven by a signal derived from carrier cosw0t, sin~Ot via a carrier tracking loop 21.
In the transmitter as given in the proposed design, all sub-codes were derived from the same code generator and they are used to modulate outputs from the same carrier oscillator.
}lowever, many different types of code and modula-ion techniques can be used for this purposc.
All sub-carriers on a particular link are thus q~ways synchronized ln code and carrier frequency.
In the receiver, the received carrier - after filtering - is di~trlbuted to the tracking receiver and to the individual channel receivers.
Since the timing carrier is basically umnodulated, it can be tracked ; by means of a receiver with a narrow bandwidth as determined by the frequency inaccuracy oi the communicaLions link.
The tracking receiver is equipped with a carrier tracking 100p which produces a reference for the coherent demodulation of the code-multiplexed channels.
1 , ' .
.
_4 X ' '~ . - ' .
`' ,'. ' : .. .. . ' ' ' , ' .. ', .., . . ', ' ' . '' : : ', ' ' . " ' ' ' , ' ' ' ' ~ - '' :
:: . ' ' ' , '' :, ' . '' .'' ', '. . ' ' ,.' , . ' ' ' ':" ', ' ' ' .. ,: .
- The invention re!.-Jtes to such a transmission sy~teln, suitable for the transmission of m~llti~le messages ~ver a sin~le cLIrriet wl~ereby an i additior.al modulaLion ~ cntifiablc by mcans of a sign~l - i9 given to the message-modulated carrier on transmission, and whereby the message-modulated carrier is recognized by the receiver through the additional modulation and me~sages are retrieved by democlulation Or ~lle ~odulated ~ carrier.
! In SS~ prcacl Spectru~ Multiple Access) individual message-modulated carriers arc given an aclditiclnal modul~tion by a wide-ban(l pseudo-random noise waveform (CDMA - ~ode Division Multiple Access), thus producing a different waveform for each carrier.
At the receiver the required carrier is selected by demodulation with the appropriate pseudo-random wave form.
The basic principle, i.e. a spectral spreading of the signal power over the available spectrum within the available cornmunicatlons bandwidth, can also be implemented in other ways such as frequency hopping, phase modulatlon and time hopping.
~ In conventional SSMA systems many different streams of analogue or i digital dat~ ~re multiplexed on the carrier altllough problems arise if the inormàtion streams are isochronous.
These problems may be solved in various ways which are both complex and costly. It iY well-known that spread-spectrum modulation with constant envelope or code-division techniques can be used to good advantage in communications systems whcre the processing gain provided by such techniques is necessary. For eYample, in satellite communication systems (using a soft or hard limiter) spread-spectrum multiple access (SSMA) i5 used to improve the quality of the receipt of the multiple-access carriers.
The present invention aims at providing a simplcr and cheaper solution in th~t an additional modulation is given in the transmitter to the carrier for each message, in such a way that sub-carriers are generated which are .: . ~
. ~ , - .
..
. , ~ .
synchronized in code ~n~l carr.er frequency bo~ll mutua]ly and jointly with a carrier, cxclusively mo~lulated by an iden-ifia~le signal, and the summation of the latter carricr ~nd Lhe sub-carriers form the trunsfer carrier of the transmitter, whereas in the receiver the sub-carricrs and the carrier itsclf are retrieved by derivaLion from the transfer carrier by means of the additionalmodulation, and the mcssages i~ the derived sub-carriers are retrieved from the carrier itself.
A design based on thc invention is charactcrize(l by Lhe transmitter having a codc gcnerator which produces Lhc iclcnLifiable signal and the lo additional modulation for the transmitter, and the receiver having a code generator which is synchronized by the identifiablc signll and which produces the additional modulations for the receivcr, additional modulations being sub-codes of the code generators.
The proposed method provides transparent channcls, i.e. for isochronous lnformation streams, by effectively earmarking for each channel a separate ; code-dlvision multiple-access carrier, such CDMA carriers being derivcd from the same timing 60urce.
. , I , This is achieved by combining the multiplexing o channels and the multiple acce66 feature of the separate carriers in one and the same equipment.
The resulting system is cheaper and simpler to operate; it has a high performance and provides transparent channels for a variety of different types of communications traffic.
The combining of multiplexing techniques and multiplc access features may ! be implemented using the apparatus described below, and as illustrated by way of example only in Fig 1 which 6hows diagramatically the transmitter; and ln Fig 2 which shows diagramatically the receiver.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the transmitter block diagram (Fig. 1) whicll illustrates a dèsign J ,_.. ",,.'' ., ; based on the invention, a clock pulse generator 1 feeds pulses to a code generator 2 which is, [or example, of the feedback sl.irt re~ister type.
X ~
' ~4~;~i69 By means of ~, c-)~1( sel~ctor 3 thc f~c~-1)ac1c Or gs11erator 2 can be set at the wanted cod~ zo~t).
A logic circuit shown scl1e1na~ically at 4 is couplet1 to a number of outputs of the code gc~r1erator 2, contains modulo-two ad~ers, and produces a number of sub-codes z1(t)~ z2(t), ~nd zn(t) of the ~o(t) code which is originating directly ~rom g~nerator 2.
A earrier generator 5 produces the cos~ t, sin~ot transmitter carrier wave.
In n plurality Or ~our-phase modulators 6l, 62, 6n carrier wave cos~Ot, sin~0t is modulated with codes Zl(t), Z2(t), Zn(t) and wit11 messages Bl, ~2 and Bn.
At theoutputs U , U2, U of modulators 6l, 62~ n~
SDl, SD2, SDn are equalized and fed to an adding network 7 through a plurality of regulators Nl, N2, Nn-In a multiplier 8 the eo8wot~ sin~ ot earrier i9 modulated by eode Zo(t).
Carrier SD modulated only by an identifiable signal obtained at output U
;`~ 18 al80 fed to the network 7 at the appropriate level via regulator N.
Aeeess of the output signal of network 7 to the eommunieations medium i9 aehleved through a band limiting filter 9.
In the reeeived bloek diagram (Fig. 2) whieh also illustrates a design ... .
based on the invention, a band pass filter lO at the input of a distribution amplifier ll reeeived the SSMA earrier wave originating from the transmitter.
The reeeiver has its own eode generator 12 with its built-in (and '~ thereiore not appearing on the sketeh) eode seleetor set in sueh a way that a further generator l2 delivers a eode Z (t) identieal to the Zo(t) eode produeed in the transmLtter by the generator 2.
8y multiplying the output signal of the distribution amplifier ll by eode Zo~t) ln a multiplier 13 the eoswOt~ sinwOt, earrier wave is retrieved.
8y means of a traeking deteetor 14, whieh eontains a voltage-stabilized erystal-oseillator, a timing signal M is generated to synchronize the two ~; , . .
generators 2 and 12.
.
. I , ,~ X
?~
A logic circ~ 15 -~ho~qc circuit design corres~lolltls to that of the logic circuit 4 at Lhc transmitLer and produces codes Zl(t), Z2(t) and Zn(l)~
whilst connected to some outputs of the code generator 12, which codes -tllrough a plurality o~.multipliers 171~ 172, 17 - may be used to derive sub-carriers S'D], S'D2~ SID from the output signals of the distrlbution amplifier 1 1 .
Dl' D2~ S Dn~ so derived, are uscd to restore messages Bl, B2, Bn ~Y means of a number of demodulators 201, 202, 20n.
In order to do this, demodulators 201, 202, 20 arc driven by a signal derived from carrier cosw0t, sin~Ot via a carrier tracking loop 21.
In the transmitter as given in the proposed design, all sub-codes were derived from the same code generator and they are used to modulate outputs from the same carrier oscillator.
}lowever, many different types of code and modula-ion techniques can be used for this purposc.
All sub-carriers on a particular link are thus q~ways synchronized ln code and carrier frequency.
In the receiver, the received carrier - after filtering - is di~trlbuted to the tracking receiver and to the individual channel receivers.
Since the timing carrier is basically umnodulated, it can be tracked ; by means of a receiver with a narrow bandwidth as determined by the frequency inaccuracy oi the communicaLions link.
The tracking receiver is equipped with a carrier tracking 100p which produces a reference for the coherent demodulation of the code-multiplexed channels.
1 , ' .
.
_4 X ' '~ . - ' .
`' ,'. ' : .. .. . ' ' ' , ' .. ', .., . . ', ' ' . '' : : ', ' ' . " ' ' ' , ' ' ' ' ~ - '' :
:: . ' ' ' , '' :, ' . '' .'' ', '. . ' ' ,.' , . ' ' ' ':" ', ' ' ' .. ,: .
Claims (7)
1. A transmission system suited for the transmission of multiple messages over a single carrier, where at a transmitter the message-modulated carrier is given an additional modulation by an identifiable signal, and where at a receiver the carrier is identified by means of the additional modulation, and messages are retrieved by demodulating the modulated carriers, the system being characterized in that in the transmitter the carrier for each message is given an additional modulation in such a way us to generate a number of sub-carriers which are synchronized in code and carrier frequency both mutually and jointly with a carrier solely modulated by an identifiable signal, the latter carrier and the sub-carriers being then added to form the transmitted carrier.
2. The transmission system defined in claim 1, further characterized in that in the receiver, derivations of the sub-carriers and of the carrier itself are retrieved from the transmitted carrier by means of the additional modulation, and messages in the derived sub-carriers are retrieved through the carrier itself.
3. A system as defined in claim 1, wherein the transmitter contains a code generator which produces the identifiable signal and the additional modulations for the transmitter.
4. A system as defined in claim 1, 2, or 3, wherein the receiver contains a code generator which is synchronized by means of the identifiable signal and which generates the additional modulations for the receiver.
5. A system as defined in claim 1, wherein the transmitter contains a code generator which produces the identifiable signal and the additional modulations for the transmitter, and the additional modulations are sub-codes of the code generator.
6. A system as defined in claim 1, wherein the receiver contains a code generator which is synchronized by means of the identifiable signal and which generates the additional modulating for the receiver, and the additional modulations are sub-codes of the code generator.
7. A system as defined in claim 1, wherein the transmitter contains a code generator which produces the identifiable signal and the additional modulations for the transmitter, and wherein the receiver contains a code generator which is synchronized by means of the identifiable signal and which generates the additional modulations for the receiver, said additional modulations being sub-codes of the code generators.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7403957A NL7403957A (en) | 1974-03-22 | 1974-03-22 | Spread spectrum communication using multiple transmission and access - imparts additional modulating signal to carrier at sender producing sub carrier and code |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1046669A true CA1046669A (en) | 1979-01-16 |
Family
ID=19821025
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA221,820A Expired CA1046669A (en) | 1974-03-22 | 1975-03-11 | Spread spectrum communication techniques for a code division message multiplexing system |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1046669A (en) |
| NL (1) | NL7403957A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2220824A (en) * | 1988-07-13 | 1990-01-17 | Philips Electronic Associated | Transmission system for sending two signals simultaneously on the same communications channel |
| US8195188B2 (en) | 1997-08-04 | 2012-06-05 | Enovsys Llc | Location reporting satellite paging system with optional blocking of location reporting |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4188610A (en) | 1977-08-29 | 1980-02-12 | Hydroacoustics, Inc. | Method of and apparatus for the generation and transmission of signals for echolocation and other signalling purposes, such as in geophysical exploration |
-
1974
- 1974-03-22 NL NL7403957A patent/NL7403957A/en not_active Application Discontinuation
-
1975
- 1975-03-11 CA CA221,820A patent/CA1046669A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2220824A (en) * | 1988-07-13 | 1990-01-17 | Philips Electronic Associated | Transmission system for sending two signals simultaneously on the same communications channel |
| US5073899A (en) * | 1988-07-13 | 1991-12-17 | U.S. Philips Corporation | Transmission system for sending two signals simultaneously on the same communications channel |
| US8195188B2 (en) | 1997-08-04 | 2012-06-05 | Enovsys Llc | Location reporting satellite paging system with optional blocking of location reporting |
Also Published As
| Publication number | Publication date |
|---|---|
| NL7403957A (en) | 1975-09-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |
Effective date: 19960116 |