CN1194511A - CDMA satillite communication system and its internal signal transfer method - Google Patents
CDMA satillite communication system and its internal signal transfer method Download PDFInfo
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- CN1194511A CN1194511A CN98105394A CN98105394A CN1194511A CN 1194511 A CN1194511 A CN 1194511A CN 98105394 A CN98105394 A CN 98105394A CN 98105394 A CN98105394 A CN 98105394A CN 1194511 A CN1194511 A CN 1194511A
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Abstract
A method relates to multi-user communication of CDMA satellite network. After a RF up-link signal containing encoding user information that undergoes the process of differential phase encoding and the bank spread of up-link Walsh function and pseudo random number sequence is received by a satellite receiver, the RF up-link signal undergo the process of incoherent quadrature demodulation and quadrature spread and then generates the differential phase signal with the encoding user information. And then the FR up-link signal undergoes the process of down-link Walsh function, the orthogonal component of PN sequential and differential phase encoding and the bank spread. With the completion of quadrature modulation, the RF up-link signal is sent to a ground receiver and undergoes the process of coherent quadrature demodulation and quadrature spread. And then down-link carrier phase is regained to detect and encode the encoding user information.
Description
The invention belongs to communication technical field.Specifically, the present invention is relevant with the method and system of CDMA satellite communication.
Compare with time division multiple access (TDMA) or frequency division multiple access (FDMA), code division multiple access (CDMA) is a kind of platform of multiple access more efficiently, thereby mainly is because CDMA can provide higher frequency reuse efficient with identical frequency in the more approaching geographically sub-district again.CDMA frequency reuse efficient is higher also to be an advantage for satellite communication.However, the satellite network of most conventional also is based on FDMA or TDMA, and the CDMA satellite network that proposes recently mostly has the straight-through character of folding pipe, that is to say and not carry out any Base-Band Processing or exchange on satellite.
If handle on satellite and exchange, no matter systematic function is can both improve qualitatively or on the capacity so.Yet, different with TDMA or FDMA method, on a regeneration satellite, adopt conventional CDMA method need separate different subscriber signals, so that on star, handle and exchange.Relevant up link demodulation can be used for Base-Band Processing and exchange on the star, but coherent demodulation need realize with complicated hardware, that is to say the phase place that must follow the tracks of carrier wave for each subscriber signal respectively, this is to be difficult to satisfy for the satellite that can only obtain limited power.
Therefore, be necessary to propose a kind of in satellite network on the line unit road receive the cdma communication scheme that does not need coherent demodulation, make on satellite, can carry out easily and handle and exchange.
The invention provides and carry out multi-multipoint CDMA transmission manner via satellite, can on satellite, carry out whole or necessary Base-Band Processing and exchange, and not need the uplink receiver on the satellite to carry out coherent demodulation.
These advantages of the present invention are owing to adopted method and system as follows.In ground transmitter, (coding) user message bit is divided into a series of bit groups in succession after, produce a differential phase by each message bit group being mapped to a predetermined psk signal space (constellation) for each message bit group.By the differential phase of each message bit group and the absolute phase of a last message bit group are added up to absolute phase of each message bit group generation.With the absolute phase signal RF carrier wave of up link is carried out phase keying, form a up link RF signal.This RF signal sends to the satellite as a part of satellite communication network behind Walsh (Walsh) function of uplink users and uplink beam code sequence spread spectrum.
After receiving the RF signal on the satellite, produce the baseband signal of two quadratures by incoherent quadrature demodulation.Then, with uplink beam code sequence and up user's walsh function digital orthogonal baseband signal is carried out despreading.By to phase bit comparison, extract the differential phase signal that is loaded with (coding) user message through each piece in succession of the baseband signal of despreading.Then, the differential phase signal is given to the transmitter of being responsible for corresponding down link purpose path.Two quadrature phase signals that produce according to the differential phase signal that transfers with downlink user walsh function and downlink beamforming code sequence spread spectrum after, be subjected to baseband frequency spectrum is carried out the low-pass filtering of shaping.Then, be added to respectively on the quadrature carrier components of down link, be sent to the ground based terminal that user message will be sent to through the quadrature base band component of spread spectrum.The RF signal through relevant quadrature demodulation, is transformed into quadrature phase component after ground receiver receives.By quadrature phase component being carried out despreading, extract the down link phase signal with downlink beamforming code sequence and downlink user walsh function.The phase signal that is extracted is exactly the differential phase signal of up link, but has been subjected to the noise in up link such as the down link and the pollution of interference.The phase signal that is extracted is used to recover user message.
The present invention is illustrated in (but being not limited to) following accompanying drawing, and identical label is represented identical unit in these accompanying drawings, wherein:
Fig. 1 illustrates ground proposed by the invention block diagram to satellite uplink transmitter basic function part;
Fig. 2 illustrates ground proposed by the invention block diagram to the receiver basic function part of satellite uplink;
Fig. 3 illustrates satellite proposed by the invention block diagram to ground downlink transmitter basic function part; And
Fig. 4 illustrates satellite proposed by the invention block diagram to ground descending link receiver basic function part.
The present invention mainly for CDMA satellite communication system and CDMA signal from the ground surface launching Stand and return via satellite the grounded receiving station and need to not carry out the relevant of uplink signal at satellite The transmission means of demodulation. The present invention since provide simply in up-link with identical Each signal that the CDMA carrier wave sends is separated the mechanism of separating that is in harmonious proportion, and therefore is conducive to locate on the star Reason and exchange. Because polluting the Noise and Interference of uplink signal is not put on satellite Greatly, be suppressed on the contrary, therefore improved expeditiously the cdma communication link. For further Reduce the BER (bit error rate) of up-link, can carry out channel-decoding and encode again at satellite. The differential phase of uplink signal through exchange, is sent to accordingly after being regenerated by DVB Face station receiver. In the relevant PSK technology for detection downlink transmission of earth station, because earth station The phase characteristic tracking that receiver can dispose easily according to the down link signal that receives connects The various devices of collection of letters carrier phase. In brief, the present invention to uplink signal transmit, Process on the star and down link signal transmits each one and carried out optimization.
The present invention is used for up-link with the difference PSK technology of CDMA net. Current (coding) The absolute phase of information code element according to the absolute phase of the differential phase of current code element and a upper code element it With definite. The conventional psk signal that is produced by the absolute phase signal is with sign up-link transmit leg Behind the walsh function spread spectrum, cover again the puppet of the particular satellite wave beam of up-link transmit leg with sign Random number (PN) sequence spread spectrum. Signal is uplink after power amplification. Up on satellite The link receiving step is basically with above these are opposite, to extract and regeneration is taken with the differential phase form The subscriber signal of band does not need to carry out channel-decoding. On satellite, do not need to be each transmit leg branch Do not estimate carrier phase, therefore can enjoy to all each subscriber signal collection of identical CDMA carrier wave Body carries out down coversion, is transformed into corresponding baseband signal component. The differential phase code element of regeneration is by being The system indication goes to a respective beam emitter, and downlink transfer is given predetermined purpose user. Connect on ground The receipts machine is easy to realize Phase Tracking, therefore finishes downlink transmission by relevant PSK demodulation. The channel decoding recovers the transmit leg message bit from up-link then.
Fig. 1 illustrates the ground of adopting the transmission of difference psk signal in direct sequence CDMA (DS-CDMA) net proposed by the invention block diagram to satellite uplink transmitter basic function part.Perhaps, transmitter shown in Figure 1 can be a part (remainder of system is shown in Fig. 2-4) of netting such terrestrial wireless network such as Cellular Networks or PCS.In Fig. 1, the information bit that forms user message carries out the PSK mapping again behind ground transmitter encoded (as grid coding).Can before or after symbol mapped, use bits/sym in a well-known manner and interweave, so that carry out hard or soft decoding.Encoded information bit is mapped as corresponding signal point in a predetermined psk signal space in a well-known manner by MPSK mapper 11.Regard a differential phase Δ φ as from the phase place that each coded information bits group (being code symbols) draws
u (i)(n).Differential phase coding device 12 will be by organizing the differential phase Δ φ of n
u (i)(n) with a last absolute phase φ who organizes n-1
u (i)(n-1) addition draws the absolute phase φ of coded information bits group n in a well-known manner
u (i)(n).Then, produce the homophase and the quadrature component of absolute phase signal.
The PSK modulator 13 of standard is with the absolute phase signal psi
u (i)(n) homophase and quadrature component are added on the component of two quadratures of a RF carrier wave with desired carrier frequency.Give user's walsh function W in the call establishment stage assignment in 14 usefulness systems through the RF signal of PSK modulation formation
u (i)(t) spread spectrum in addition in a well-known manner, 15 use again one with for example corresponding PN sequence of up link satellite beams b
u(t) further spread spectrum in addition in a well-known manner forms a signal S through spread spectrum
u (i)(t) deliver to RF transmission line 16 after.Can before with the signal mixing transmitting antenna, carry out RF earlier and amplify, to produce required transmitting power.
Fig. 2 illustrates the block diagram that adopts the up-link receiver basic function part of difference psk signal transmission in the DS-CDMA net proposed by the invention.In spaceborne up-link receiver for example, the RF signal r that is received
u(t) after incoherent quadrature down-conversion becomes a digital orthogonal baseband signal, be used in and be used for the PN sequence and the walsh function despreading in addition of spread spectrum in the transmitter, thereby required user message signal is separated with other subscriber signals of enjoying identical CDMA.Calculate two of the despreader phase differences between the output in succession with a phase comparator, so that on star, exchange.Two of the despreader that is calculated in succession the phase difference between the output be loaded with user message.
In Fig. 2, after suitable RF filtering and amplifying, the RF signal that is received is by being downconverted into baseband signal in the non-coherent demodulation of 21a and 21b with in the low-pass filtering of 22a and 22b.By at first at 23a and 23b wave beam code sequence b with the user
u(t) in a well-known manner despreading again at 24a and 24b walsh function S with the user
u (i)(t) despreading, and in integration and the quick-acting processing of 25a and 25b is from extracting the message signale that need issue the specific user through the homophase of demodulation and quadrature component.For up reception, all are received with identical CDMA carrier wave and the corresponding subscriber signal of same beam can collective's down conversion and despreading of wave beam code in addition.Then, utilize at code-element period T of 26 delays and carry out differential type bit comparison mutually at the positive blending output signal of 27 couples of integrator 25a and 25b in a well-known manner, draw the differential phase signal that is loaded with required information.Then, the differential phase signal of gained exchanges on satellite in a well-known manner, is transferred to the corresponding downstream link.
After carrying out corresponding exchange, the differential phase code element that satellite receiver is regenerated (supposing does not have channel-decoding) just need send to the destination, ground, so that caller information is decoded.Fig. 3 illustrates the block diagram of the interior satellite of CDMA net proposed by the invention to ground downlink transmitter basic function part.Two quadrature phase components of the differential phase code element that transfers are at 31a and the 31b walsh function W with the user of the down link of assignment through setting up this appealing
d (i)(t) behind the spread spectrum, added together with same signal component in a well-known manner at 32a and 32b from other callings that belong to this down link, again at 33a and 33b PN sequence b with downlink beamforming
d(t) spread spectrum in 34a and 34b filtering, carries out shaping to baseband frequency spectrum then.Be added to respectively through the quadrature phase signal of spread spectrum on the respective orthogonal components of a RF carrier wave with desired downlink carrier frequency.Resulting RF signal is sent to destination, corresponding ground.Though this processing can be carried out respectively each transmit leg signal, the present invention allows by needing in same downlink beamforming all signals with same carrier wave transmission to combine collective in addition the beam code spread spectrum and the quadrature modulation of downlink transmission.
Fig. 4 illustrates the block diagram of the satellite in the CDMA net proposed by the invention to ground descending link receiver basic function part.In descending link receiver, the RF signal that is received is after relevant quadrature down-conversion is orthogonal baseband signal, be used in and be used for the PN code sequence and the walsh function despreading in addition of spread spectrum on the star in the transmitter, thereby required user message signal is separated with other subscriber signals of enjoying identical CDMA Channel.With the carrier phase of a phase comparator calculating down link RF signal, carry out message detection.The carrier phase of down link is exactly the differential phase of up link, but has been subjected to the noise in up link and the down link and the pollution of interference.
In Fig. 4, after suitable RF filtering and amplifying, the RF signal r that is received
d (i)(t) be downconverted into baseband signal at 41a and 41b by relevant quadrature demodulation, be subjected to low-pass filtering at 42a and 42b again.By in a well-known manner at first at 43a and 43b wave beam code sequence b with the user
d(t) despreading is again at 44a and the 44b walsh function W with the user
d (i)(t) despreading is after put processing in integration and the speed of 45a and 45b, from extract the message signale that need issue the specific user through the quadrature phase component of demodulation.The positive blending output signal of integrator 45a and 45b obtains the carrier phase of down link after the well-known phase estimation 46, this is the differential phase that is subjected to noise and disturbs the up link of polluting that is loaded with required information.If used bits/sym to interweave, just dispose a deinterleaver in a well-known manner at ground receiver so according to the interleaver position at ground transmitter.Channel decoder 47 such as the Vito ratio decoder device that soft or hard decision are provided is used for recovering the user message bit.
Though the present invention is described in conjunction with illustrated embodiment, be appreciated that spirit of the present invention can carry out various modifications, all these should all belong to scope of patent protection of the present invention.
Claims (30)
1. method of communicating signals in the CDMA satellite communication network, described method comprises the following steps:
Receive a RF signal on a up link, this RF signal contains through differential phase coding and with the encoding user message of two code sequence spread spectrums relevant with this up link;
With the RF signal incoherent quadrature demodulation that the is received base band component that is orthogonal;
With two code sequences relevant the quadrature base band component is carried out despreading with up link;
To through the quadrature base band component of despreading certainly carry out the phase bit comparison in succession, regeneration is loaded with the differential phase signal of encoding user message;
The differential phase signal of regeneration is gone to selected downlink transmitter;
With two code sequences relevant the quadrature base band component of differential phase signal is carried out spread spectrum again with down link; And
To be added on the quadrature component of a downlink carrier through the quadrature base band component of the differential phase signal of spread spectrum again, form a down link RF signal.
2. by the described method of claim 1, described method also comprises this step of transmitting down link RF signal.
3. by the described method of claim 1, wherein on satellite, receive at the RF signal that receives on the up link, and the transmitter emission from the star of down link RF signal.
4. by the described method of claim 1, wherein two code sequences relevant with up link comprise a user's the walsh function and the pseudo-random number sequence of a uplink beam, and two code sequences relevant with down link comprise the pseudo-random number sequence of a user's a walsh function and a downlink beamforming.
5. by the described method of claim 1, described method also comprises the following steps:
In link transmitter, the encoding user message bit is divided into a series of bit groups in succession;
By each message bit group being mapped to a predetermined psk signal space, for each message bit group produces a differential phase;
By absolute phase addition, be that each message bit group produces an absolute phase with the last message bit group of the differential phase of current message bit group and current message bit group;
With the absolute phase signal uplink carrier is carried out phase modulated, form a RF signal;
With two code sequences relevant the RF signal is carried out spread spectrum with up link;
To send on the up link through the RF of spread spectrum signal.
6. by the described method of claim 5, wherein the RF signal of up link is launched at ground transmitter, and receiver receives on star.
7. by the described method of claim 5, wherein two code sequences relevant with up link comprise a user's the walsh function and the pseudo-random number sequence of a uplink beam.
8. by the described method of claim 1, described method also comprises the following steps:
Receive described down link RF signal, this down link RF signal contains this down link RF signal through regeneration, be added to user message on the quadrature component of down link RF signal behind the spread spectrum again;
With the down link RF signal coherence quadrature demodulation that the is received base band component that is orthogonal;
With two code sequences relevant the quadrature base band component is carried out despreading with down link;
According to quadrature base band component estimating down-ward link carrier phase through despreading; And
Recover user message.
9. in accordance with the method for claim 8, wherein said down link RF signal is the transmitter emission on star, and receive at ground receiver.
10. by the described method of claim 8, wherein two code sequences relevant with down link comprise the pseudo-random number sequence of a user's a walsh function and a downlink beamforming.
11. the method for communicating signals in the CDMA satellite communication network, described method comprises the following steps:
In upstream transmitter, the encoding user message bit is divided into a series of bit groups in succession;
By each message bit group being mapped to a predetermined psk signal space, for each message bit group produces a differential phase;
By absolute phase addition, be that each message bit group produces an absolute phase with the last message bit group of the differential phase of current message bit group and current message bit group;
With current absolute phase a uplink carrier is carried out phase modulated, form a RF signal;
With two code sequences relevant the RF signal is carried out spread spectrum with up link; And
To send on the up link through the RF of spread spectrum signal.
12. by the described method of claim 11, wherein up link RF signal is launched at ground transmitter, and receiver receives on star.
13. by the described method of claim 11, wherein two code sequences relevant with up link comprise a user's the walsh function and the pseudo-random number sequence of a uplink beam.
14. the method for communicating signals in the CDMA satellite network, described method comprises the following steps:
Receive a down link RF signal, this down link RF signal contains the user message on the quadrature component that is added to down link RF signal through regeneration, again behind the spread spectrum;
With the down link RF signal coherence quadrature demodulation that the is received base band component that is orthogonal;
With two code sequences relevant the quadrature base band component is carried out despreading with down link;
According to quadrature base band component estimating down-ward link carrier phase through despreading; And
Recover user message.
15. by the described method of claim 14, wherein down link RF signal transmitter emission on star, and receive at ground receiver.
16. by the described method of claim 14, wherein two code sequences relevant with down link comprise the pseudo-random number sequence of a user's a walsh function and a downlink beamforming.
17. a CDMA satellite communication system, described system comprises:
A RF receiver is used on up link receiving a RF signal, and this RF signal contains behind differential phase coding the encoding user message with two code sequence spread spectrums relevant with this up link;
An incoherent quadrature demodulator, the RF signal incoherent quadrature demodulation that is used for to be received base band component that is orthogonal;
A spread spectrum despreader is used for two code sequences relevant with up link the quadrature base band component being carried out despreading;
A phase comparator is used for the piece in succession through the quadrature base band component of despreading is carried out the phase bit comparison, the differential phase signal of regeneration encoding user message;
A switch is used for the differential phase signal of regeneration is gone to selected downlink transmitter;
A frequency multiplier is used for two code sequences relevant with down link the quadrature base band component of differential phase signal being carried out spread spectrum again; And
A quadrature modulator is used for through the quadrature base band component of the differential phase signal of spread spectrum again a downlink carrier being modulated, and forms a down link RF signal.
18. according to the described CDMA satellite communication system of claim 17, described system also comprises transmitter on the star, is used for receiver transmitting down link RF signal earthward.
19. by the described CDMA satellite communication system of claim 17, wherein cdma communication system is a receiver on the star.
20. by the described CDMA satellite communication system of claim 17, described system also comprises:
A PSK mapper, the encoding user message bit that is used for being divided into the message bit piece is mapped to differential phase;
A differential phase coding device is used for absolute phase addition with the last message bit piece of the differential phase of current message bit piece and current message bit piece, is that each message bit piece produces a current absolute phase;
A PSK modulator is used for current absolute phase a uplink carrier being carried out phase modulated, forms a RF signal;
A frequency multiplier is used for two code sequences relevant with up link the RF signal being carried out spread spectrum; And
A transmitter is used for and will sends on the up link through the RF of spread spectrum signal.
21. by the described CDMA satellite communication system of claim 20, wherein the RF signal of up link is launched by ground transmitter.
22. by the described CDMA satellite communication system of claim 20, wherein two code sequences relevant with up link comprise a user's the walsh function and the pseudo-random number sequence of a uplink beam, and two code sequences relevant with down link comprise a user's the walsh function and the pseudo-random number sequence of a uplink beam.
23. by the described CDMA satellite communication system of claim 17, described system also comprises:
A descending link receiver is used for receiving downlink RF signal;
A relevant quadrature demodulator, the down link RF signal coherence quadrature demodulation that is used for to be received base band component that is orthogonal;
A spread spectrum despreader is used for two code sequences relevant with down link the quadrature base band component being carried out despreading;
A phase comparator is used for according to the quadrature base band component estimating down-ward link carrier phase through despreading; And
A channel decoder is used for encoding user message is detected and decodes.
24. by the described CDMA satellite communication system of claim 23, wherein down link RF signal is received by ground receiver.
25. a CDMA satellite communication system, described system comprises:
A PSK mapper, the encoding user message bit that is used for being divided into the message bit piece is mapped to differential phase;
A differential phase coding device is used for absolute phase addition with the last message bit piece of the differential phase of current message bit piece and current message bit piece, is that each message bit piece produces a current absolute phase;
A PSK modulator is used for current absolute phase a uplink carrier being carried out phase modulated, forms a RF signal;
A frequency multiplier is used for two code sequences relevant with up link the RF signal being carried out spread spectrum; And
A transmitter is used for and will sends on the up link through the RF of spread spectrum signal.
26. by the described CDMA satellite communication system of claim 25, wherein the RF signal of up link is launched by ground transmitter.
27. by the described CDMA satellite communication system of claim 25, wherein two code sequences relevant with up link comprise a user's the walsh function and the pseudo-random number sequence of a uplink beam.
28. a CDMA satellite communication system, described system comprises:
A descending link receiver is used for receiving downlink RF signal;
A relevant quadrature demodulator, the down link RF signal coherence quadrature demodulation that is used for to be received base band component that is orthogonal;
A spread spectrum despreader is used for two code preface sign indicating numbers relevant with down link the quadrature base band component being carried out despreading;
A phase comparator is used for according to the quadrature base band component estimating down-ward link carrier phase through despreading; And
A channel decoder is used for encoding user message is detected and decodes.
29. by the described CDMA satellite communication system of claim 28, wherein down link RF signal is received by ground receiver.
30. by the described CDMA satellite communication system of claim 28, wherein two code sequences relevant with down link comprise the pseudo-random number sequence of a user's a walsh function and a downlink beamforming.
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| Application Number | Priority Date | Filing Date | Title |
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| CN98105394A CN1194511A (en) | 1997-03-04 | 1998-03-02 | CDMA satillite communication system and its internal signal transfer method |
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|---|---|---|---|
| US808,777 | 1997-03-04 | ||
| CN98105394A CN1194511A (en) | 1997-03-04 | 1998-03-02 | CDMA satillite communication system and its internal signal transfer method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100385886C (en) * | 2004-11-18 | 2008-04-30 | 中国人民解放军理工大学通信工程学院 | Differential bit soft value exporting method in orthogonal spectrum expansion differential phase modulation |
| CN100440731C (en) * | 2001-03-26 | 2008-12-03 | 科学技术振兴事业团 | Filter apparatus, reception apparatus, transmission apparatus, diffusion modulation apparatus, pseudo-random number sequence output apparatus, filter method, reception method, transmission method, dif |
-
1998
- 1998-03-02 CN CN98105394A patent/CN1194511A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100440731C (en) * | 2001-03-26 | 2008-12-03 | 科学技术振兴事业团 | Filter apparatus, reception apparatus, transmission apparatus, diffusion modulation apparatus, pseudo-random number sequence output apparatus, filter method, reception method, transmission method, dif |
| CN100385886C (en) * | 2004-11-18 | 2008-04-30 | 中国人民解放军理工大学通信工程学院 | Differential bit soft value exporting method in orthogonal spectrum expansion differential phase modulation |
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