CN1110887A - A data transmission method and a cdma/fdma radio system - Google Patents

A data transmission method and a cdma/fdma radio system Download PDF

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Publication number
CN1110887A
CN1110887A CN94190368.0A CN94190368A CN1110887A CN 1110887 A CN1110887 A CN 1110887A CN 94190368 A CN94190368 A CN 94190368A CN 1110887 A CN1110887 A CN 1110887A
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frequency
cdma
code
transmission
spreading code
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伊尔卡·科斯基塔罗
阿托·基耶马
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Nokia Oyj
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Nokia Telecommunications Oy
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2628—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA]
    • H04B7/2634—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] for channel frequency control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention relates to a data transmission method utilizing combined CDMA/FDMA multiple access, and a corresponding radio system. Complementary codes are used as CDMA spreading codes in the system. Transmissions on frequency channels used are synchronized with each other. To increase frequency efficiency, at least some of the frequency channels are interlaced frequencies (f0, f1, f2, f3) having a mutual frequency difference selected from the zero points of auto- and cross-correlation functions calculated as a function of the frequency offset of the CDMA spreading codes used on the frequency channels.

Description

A data transmission method and a cdma/fdma radio system
The present invention relates to utilize the code division multiple access connection/frequency division multiple access of combination to connect the data transmission method of (CDMA/FDMA).
In design with implement in the mobile telephone system, subject matter is frequency utilization efficiently.Along with the radio traffic amount constantly increases, it is all the more important that this problem has become.System can utilize the frequency band of an appointment more efficiently, and the possible quantity of system user is just many more.When developing new mobile telephone system, radio channel multiple access method is the centre sphere of research.
The mobile telephone network of the first generation utilizes the FDMA method to implement.The design of the second generation mobile telephone network of employing digital data transfer is based on the FDMA/TDMA technology of combination.
Radio channel multiple access (CDMA) method of the third generation just just is applied to Cellular Networks recently.CDMA is based on a kind of multiple access method of spread spectrum technology, and it has several known advantages than the method for prior art, and for example, it does not need to make frequency planning, and the utilization ratio height of frequency band.
In FDMA, users are distinguished mutually by frequency, and each data-signal of user has the frequency band of a special use.In TDMA, frequency band is divided into time slot in succession, and each users'data signals is transmission in (recurrent) time slot that itself reappears.Under the situation of the FDMA/TDMA that makes up, several such frequency bands can use.
In CDMA, user's narrowband data signal is utilized the frequency band of a spreading code (having the frequency band wideer than this data-signal) modulation becoming broad.Utilized bandwidth such as 1.25MHZ, 10MHZ and 50MHZ in known test macro.This spreading code is made up of many bits.The bit rate of spreading code is more much higher than the bit rate of data-signal, and the bit of spreading code is called " segment " (chip), so that they and data bit and data symbol can be distinguished.Each user's data symbol be multiply by all segments of spreading code.So narrowband data signal expands to stand-by frequency band.Each user has an independent code.Several users can be transmitted on identical frequency band simultaneously, according to spreading code data-signal is distinguished mutually again in receiver.
The a plurality of correlators that are equipped with in receiver and a required signal synchronised, each correlator is discerned desired signal according to spreading code.Correlator recovers to become original narrow-band with this signal again.When signal arrives receiver, uncorrelated in ideal conditions in this receiver by the signal of another spreading code modulation, and keep their broadband.At the used spreading code of this system of selection, so that they are uncorrelated mutually, that is they are mutually orthogonals.
A kind of typical feature of a Cellular Networks environment is that the signal that transmits between a user and base station has more than along the straight line propagated from transmitted from transmitter to receiver, but can propagate along several paths with different length, this depends on the characteristic of environment.In following time, also can take place even this multipath propagation phenomenon is in direct face-to-face communication state between base station and mobile radio station.Reflection causes the main because signal of multipath propagation on the body surface around.Signal along different propagated has different transmission delays, so that their can the phase place difference when arriving receiver.
In general, spreading code not can with all possible delay value quadrature all, the signal with different delayed time will disturb the detection of other signal.In other words, interfere with each other between the user, this is called " multiple access interference ".CDMA is a kind of interference limiting system.The multiple access disturbing effect increases along with number of users and increases the signal to noise ratio deterioration during it makes and communicates to connect.For the user of some, signal to noise ratio is increased to the degree that is difficult to communicate by letter and increases number of users again can only sacrifice the quality that existing communication connects.Usually, having bandwidth for example connects for the radio channel of 1.25MHZ can have no more than 30 to 40 CDMA simultaneously.If for example will increase channel capacity, then must consider to use a new radio channel in the base station.With regard to spectrum utilization, though CDMA technology is more effective than prior art, wideband radio channel required in the CDMA/FDMA system still takies a large amount of frequency bands, especially in the zone of high power capacity demand.In view of the above, need more effectively utilize frequency spectrum now.
In the environment of a Cellular Networks, user's position with respect to base station and they each other for, be random.In the communicating to connect between mobile phone and base station, the multiple access disturbing effect is especially obvious.If the power of phone control inaccuracy, the then transmission of far standing near the phone meeting total blockage of this base station is even the strong signal of a low correlation may cause bigger interference to the detection of weak signal.This effect is called the problem of " closely to far away (near-far) ".The power of phone is controlled its purpose be,, guarantee all to equate from the power that each phone receives in this base station regardless of distance between this phone and the base station.Yet, for example because of the fast-changing characteristic of radio channel, so be difficult to realize accurate power controls.
If user's signal is completely orthogonal,, then disturb the problem that causes to eliminate by multiple access if also promptly they are incoherent.To this, code families has been created in the effort of being done, and makes cross correlation minimum between many codes.
The purpose of this invention is to provide a kind of data transmission method, wherein, multiple access is disturbed and can be utilized certain type code and reduced significantly by the problem that it causes, and they have such characteristic, that is can realize the higher capacity and the higher availability of frequency spectrum in this data transmission system.
Utilize method of the present invention to achieve this end, this method is characterized in that: use complement code as the CDMA spreading code; At least between adopting on some frequency band, put (interlaced) frequency, between put frequency difference on the frequency choose from the zero point of auto-correlation function and cross-correlation function, calculate above-mentioned auto-correlation function and cross-correlation function function as the frequency offset of employed CDMA spreading code on each channel; The transmission of carrying out on each used channel is the phase mutually synchronization.
The invention still further relates to CDMA/FDMA radio system with a plurality of channels.This kind system is characterised in that CDMA spreading code used in the system is a complement code; At least some channel is to put between frequency, their difference on the frequencies each other equal the difference on the frequency between auto-correlation function and the mutual zero of a function, calculate above-mentioned correlation function and be the function as the frequency offset of the employed CDMA spreading code of each channel, the transmission of carrying out on the channel of putting between each frequency is the phase mutually synchronization.
When some gauge condition satisfied, the present invention can utilize the spreading code family with desirable their cross correlation.This code families is called complement code.The characteristic of complement code is that they are made up of a plurality of isometric members (member) so that between these codes that form by combination cross-correlation with value all be zero for all delay values.In other words, the mutually complete quadrature of complement code.Yet, in order to being not mutually orthogonals like that all to all delay values as all members that constitute by complement code of spreading code.For this reason, the member of complement code must be transmitted in mutual incoherent channel, to avoid interference.In fact, this can realize with many diverse ways.A kind of alternative method is to come the transmission code member with different frequencies, and whereby, the interval between the frequency band should equal coherence bandwidth at least.Under the situation of CDMA, more feasible ground be that the code member is disconnected from each other opens with each in time domain.Enough guard times cover regularly inaccuracy, and time delay expansion and propagation delay effect are stayed between each code member.Other method that realizes uncorrelated channel comprises the carrier component of using different polarization level and using quadrature.
A major advantage of the present invention is, when adopting complement code, can transmit the signal of several users on identical frequency band and do not have the multiple access interference.If all users' transmitting synchronous is carried out, above-mentioned advantage is possible, and at this moment, the different members of complement code is not overlapping during the transmission but relevant.By checking the frequency that to seek out mutually transmission signals fully irrelevantly, not disturb mutually at the cross-correlation function of the code with less than the required frequency spectrum transmission frequency of code deviation the time.The radio channel of CDMA/FDMA system can be selected to such an extent that make that frequency-splitting equals two frequency-splittings between such zero point between the carrier wave of neighboring radio channel, be the bandwidth that they need less than employed spreading code, thereby the frequency band of neighboring radio channel is with overlapping.This " put technology " can make the utilance of frequency spectrum more much higher than the availability of frequency spectrum in the CDMA/FDMA system that has earlier.
Below, with reference to accompanying drawing the present invention will be described more fully.
Fig. 1 illustrates the example that a system has two users;
Fig. 2 a to Fig. 2 d illustrates and supposes the signal waveforms in receiver when radio channel is ideal communication channel;
Fig. 3 illustrates the example of a users'data signals expansion;
(inaccuracy) function situation when Fig. 4 a and Fig. 4 b illustrate the deviation of complement code;
Fig. 5 a is illustrated in the cdma system midband distribution condition of a routine;
Between illustrating, puts Fig. 5 b the bandwidth assignment example of frequency;
Fig. 6 illustrates the receiver example of enforcement according to method operation of the present invention;
Fig. 7 a and Fig. 7 b illustrate the transmitter example of enforcement according to the inventive method operation.
The present invention uses complement code as spreading code.To the more careful description of complement code, see also the thesis for the doctorate " Generalized Complementary Code Sets " (Los Angeles,U.S in 1971, University of California, the 87th page) of B.P.Schweitzer.
In data transmission system, each user must have an independent spreading code.If the capacity of this system is K user, then need K orthogonal code, they can realize that each complement code is by K member composition by complement code.Transmission for each code member needs K incoherent channel.
Fig. 1 illustrate a system have two users example.Each user has an independent code, and they have two member 14a, 14b and 15a, 15b respectively.The code member is transmitted in incoherent transmission channel 10 and 11, they can embodiment as adopting different frequencies or different time slots.Be respectively equipped with filter 16a, 16b and 17a, 17b at receiving terminal, with used code matches, and users'data signals S18 and S19 obtain by the output signal that makes up these filters.
The signal of two users' shown in Figure 1 system is hereinafter with the way of example explanation.Suppose that this system uses the BPSK(binary phase shift keying) modulation.The modulation condition that adopts is indicated by "+" and "-" symbol.Supposition again, the complement code of two mutually orthogonals is right below adopting in system: S 11=+++-, S 12=++-+and S 21=+-++, S 22=+---.Wherein, S 11And S 12User 1, S are given in assignment 21And S 22User 2 is given in assignment.At receiving terminal, the impulse response of matched filter is as follows: user 1 filter 16a:-+++, filter 16b:+-++; User 2 filter 17a:++-+, filter 17b:---+.If supposition, users'data signals is a binary system, d 1=1, d 2=0, then user 1 waveform is on the 14a output +++-, on the 14b output be ++-+.Correspondingly, on the 15a output user 2 waveform be+-++, on the 15b output be+---.
It is that ideal communication channel promptly not have to disturb and during the channel of noise generation yet that Fig. 2 a to Fig. 2 b illustrates the supposition radio channel, the signal waveform in receiver.Suppose that circuit gain is 1.Fig. 2 a illustrates signal and the summing signal S18 on matched filter 16a and 16b output when user's 1 transmission.Correspondingly, Fig. 2 b illustrates signal and the summing signal S19 on matched filter 17a and 17b output when user's 2 transmission.Each user has obtained responding similar waveform with an ideal pulse, can detect the data symbol that is transmitted from this waveform.Fig. 2 c illustrates signal and the summing signal S18 on matched filter 16a and 16b output when user's 2 transmission.Correspondingly, Fig. 2 d illustrates signal and the summing signal S19 on matched filter 17a and 17b output when user's 1 transmission.In which summing signal, all do not have waveforms detection to arrive, that is to say, do not have multiple access to disturb and take place.This is because spreading code has the cause of orthogonality.
In the preferred embodiment of the invention, users'data signals transmission a situation arises as shown in Figure 3 example.Suppose that this system adopts by K member S1, S2 ..., the complement code family that forms of SK.The length of each composition is the N segment, and the duration of each segment is T cSecond.In view of this, the code format of user i be Si1, Si2 ..., SiK, here, SiK(K=1,2 ..., K) be member S1, S2 ..., some among the SK, so each code is a quadrature with respect to other code.
Fig. 3 illustrates the transmission of a signal bursts, wherein, transmits n data bit or data symbol b nIn the beginning of pulse train, each data symbol b nThe first member Si1 to spreading code modulates.The duration of this transmission is nNTc second.The back with a transmission intermittently.Transmission purpose intermittently is in time domain code member in succession to be kept apart mutually.Though all complement codes are mutually orthogonals, many code members are not incoherent like that for all delay values.For this reason, transmitting time span intermittently must be enough, so that for multipath propagation that takes place between transmission period and timing inaccuracy, the cross correlation between the code member can not occur in receiver.Transmission time span intermittently be may be prescribed as T M+ T R+ T △Second, wherein, T MBe the multipath expansion time, T RBe the difference between the signal propagation delay, T △It is the timing offset value.After this transmission intermittently, each data symbol b/-n modulates the Si2 of member subsequently of spreading code, after this follows one again and similarly transmits intermittently.Like this, data symbol is modulated one by one to all spreading code members.
In view of the above, the present invention has adopted a kind of combined CDMA/FDMA method.It uses a plurality of frequency bands, distinguishes each user each other based on spreading code, on each frequency band.It is previously known that CDMA and FCMA are combined in this wise.But according to this way that solution of the present invention is selected the frequency band that adopts, it is novel comparing with previous method, and more much effective with regard to frequency efficiency.The selection of channel is based on the zero point of the complement code cross-correlation function that calculates when transmission frequency is setovered.
Fig. 4 a illustrate to complement code calculate from deviation and mutual deviation function example.This departure function is described out autocorrelation and the cross correlation when many codes have mutual frequency offset.In this concrete example, each code has four members.Each code member is made up of four segments.Like this, ratio is 16.Among Fig. 4 a, article one curve representative code of drawing by solid line from departure function.The scale of transverse axis is as follows: 1.0 mean since frequency error and during a segment phase change 2 π, thereby the maximum point on the transverse axis 0.25 means the phase shift pi/2, also promptly 90 °.In Fig. 4 a, corresponding mutual deviation function is drawn by dotted line.Can see, under this concrete occasion, can find three common zero points for these curves.Can that is to say as the channel spacing in this system corresponding to the frequency offset at these zero points, can be used as channel carrier wave frequency in this system, put frequency between these frequencies are called by the frequency of pointing out those zero points.
Fig. 4 b illustrates Fig. 4 a identical curve like that, but the maximum of transverse axis increases to 1.0 now.Can see that the component of offset from zero is arranged on the pi/2 spacing, under this concrete condition, its adjacent of stop using more than four puts frequency.Putting frequency subsequently can not adopt, and after the transmission filter of transmitter is separated from each other out all multibands, also promptly after 2 π, just can adopt again.This is corresponding to normal difference between the FDMA frequency band.
In this example, bit transmits with four segments of expansion, and as shown in Fig. 4 a, has to put frequency between four and can use.The channel spacing just difference between the frequency is this bit frequency.Yet the frequency band of each channel is more much bigger than this bit frequency, so the frequency spectrum major part of all multichannels is overlapping fully.If increase ratio (ratio is 4 in the above-mentioned example), the number of putting channel between then spendable frequency correspondingly increases, but channel spacing remains unchanged.
Fig. 5 a is illustrated in a kind of usual way that distributes different channels in the cdma system.In example shown in Fig. 5 a, used three frequency ranges 50,51 and 52, centre frequency is respectively f a, f bAnd f cAccording to the FDMA principle, do not disturb each other for making the transmission on the different frequency, the frequency spectrum on different center frequency must be not overlapping.
But Fig. 5 b illustrate allocated channel of the present invention method and with the proportional frequency of utilization of spectrum width.This figure is for the purpose of illustration only this method of explanation, and it is not the real frequency spectrum figure that is produced by a spectrum analyzer.Occur in frequency f 0Transmission frequency spectra has the width in zone 53.According to method of the present invention, put frequency f between also can using 1, f 2And f 3Distinguishing the corresponding frequency spectrum of having drawn respectively on 54,55 and 56.Can see, almost completely overlapping at the frequency spectrum of putting signal on the frequency between difference, yet, when carrier frequency was selected according to the zero point of spreading code departure function, do not disturb between all multi-frequencies are mutual.Putting carrier frequency between a group subsequently is in frequency f 4, f 5, f 6And f 7On, corresponding frequency spectrum is 57,58,59 and 60.Compare with Fig. 5 a, it may be noted that according to method of the present invention and can accomplish the more efficient use frequency.
Each is put frequency and can use in single mesh, or they can be assigned on the different mesh.When network is in synchronous regime, if between the member of spreading code the coefficient T in the transmission of defined intermittently RCover the difference of the propagation delay between the mesh, then disturb putting between the carrier frequency between impossible mesh multiple access.In fact, because transmission is worthless for indefinite length intermittently, so this is limited in a way the scale of system's mesh.
If those mesh are enough far away apart from one another by getting, on same frequency, just can not disturb, identical frequency also can re-use in different mesh.In FDMA, rely on common frequency planning to accomplish this point, thereby the frequency number is corresponding to trooping of re-using.On the principle, derive from the outside interference meeting of trooping and take place to a certain extent, promptly because long propagation delay makes quadrature bar body no longer satisfied, its interference is rendered as usual CDMA multiple access and disturbs, and just is bordering on white noise.
Adopting gain process to tackle multiple access among the common CDMA disturbs.According to method of the present invention, multiple access is disturbed just to occur in to derive from and is re-used in the outside interference of trooping.In theory, why gain process needs, and only is to be used for tackling thermal noise and above-mentioned interference.On the other hand for example because high-quality gain process and if power system capacity is enough big, then propagation delay expansion requires (also being the restriction of mesh scale) to be eased.
Fig. 6 illustrates the simplified block diagram of the base station receiver of method operation of the present invention.For brevity, two receiver unit 61a and 61b only are shown among Fig. 6.In fact, the number of base station receiver is much more.This receiver comprises usually: filter 62a, 62b, the first multiplier 63a, 63b; The second multiplier 64a, 64b; High-frequency generator 0Sc1, OSc2; Demodulator 66a, 66b; And the circuit 65a, the 65b that produce spreading code.For brevity, receiver shown in Fig. 6 only comprises a spreading code demodulator unit 64-66.In fact, communicate to connect (CDMA Channel) for each, cdma receiver generally comprises a plurality of these type of spreading code demodulator unit, can receive the signal component of a plurality of multipath propagations, and presses the typical C dma mode with they additions.In addition, a plurality of CDMA Channel are transmitted on identical carrier wave usually, and each channel has the spreading code demodulator unit group of a special use, are added on this demodulator unit group by an output signal to the shared multiplier 63 of all demodulators.
Fig. 7 a and Fig. 7 b illustrate the simplification circuit block diagram according to two transmitters of method operation of the present invention.This transmitter generally includes: filter 72a, 72b; The first multiplier 73a, 73b; The second multiplier 74a, 74b; High-frequency generator osc1 ', osc2 '; And the circuit 75a, the 75b that produce spreading code.This transmitter also comprises the multiplier 74 and the spreading code unit 75 of a special use, uses for each CDMA Channel that will transmit on same carrier wave.Be added on the public multiplier 73 from the output signal of multiplier 74 and spreading code unit 75.
Suppose that receiver 61a receives the signal that mobile radio station transmitter 71a comes, receiver 61b receives the signal that mobile radio station transmitter 71b comes. Users'data signals 76a, 76b arrive transmitter 71a, 71b, and the spreading code with the user in multiplier 74a, 74b multiplies each other.The output signal of multiplier 74a, 74b is modulated a high-frequency signal that obtains from oscillator osc1 ', osc2 ' in multiplier 73a, 74b.This modulated signal is subjected to the filtering of band pass filter 72a, 72b, is added to then on antenna 70a, the 70b.The frequency of oscillation of high-frequency generator osc1 ', osc2 ' is selected like this, and promptly they are consistent with the mutual deviation zero of a function of use spreading code, and this is characteristics of the present invention.For instance, above-mentioned each that communicates to connect of imagination is on different frequencies.Under a kind of actual conditions, several users are given in a frequency assignment easily.The transmission frequency f of osc1 ' 0Expression, the transmission frequency f of osc1 ' 1Show.According to the present invention, osc1 ' departs from out a bit frequency each other with the frequency of osc2 ', and as shown in Fig. 5 b, their frequency spectrum almost is fully overlapping.
Similarly, filtered in band pass filter 62a, 62b from the signal that receives on receiver 61a, the 61b, among multiplier 63a, 63b, carried out multiplying each other the first time by the high-frequency signal that obtains from oscillator osc1, osc2 then, spreading code circuit 65a, 65b by the user comes signal to carry out multiplying each other the second time in multiplier 64a, 64b again, after this can demodulate data.The frequency of high-frequency generator osc1, osc2 departs from out a bit frequency as described abovely mutually.
Appended each figure and all be to say the present invention in order to example about their narration.On the details with regard to them, within the appending claims scope, can make change to method of the present invention.

Claims (7)

1, a kind of data transmission method that utilizes combined CDMA/FDMA multiple access is characterized in that:
Use complement code as the CDMA spreading code;
At least putting frequency between adopting on some frequency band, all the difference on the frequency of putting between the frequency selected correlation function from the zero point of auto-correlation and cross-correlation function, is the function of the frequency offset of the CDMA spreading code that uses in as each channel in calculating;
Transmission on employed all multichannels is synchronous mutually.
2, according to the method for claim 1, it is characterized in that, in transmission, a transmission burst with predetermined number data bit or data symbol is transferred out, this arteries and veins string carries out the spreading code modulation to the code member (Si1) in the CDMA complement code, thereafter follow a transmission intermittently, transmit pulse train subsequently again, this pulse train is modulated second member of CDMA complement code, after this then be one again and transmit intermittently that the rest may be inferred.
According to the method for claim 2, it is characterized in that 3, transmission time span intermittently is T M+ T R+ T △, wherein, T MBe the multipath expansion time, T RBe the difference between the intra-network signal propagation delay, T △It is user's time synchronized deviation.
4, according to the method for claim 1, it is characterized in that, put frequency between having used several.
5, according to the method for claim 1, it is characterized in that, put the bandwidth that difference on the frequency between the frequency pool equals a transmitter filter at least between used.
6, a kind of CDMA/FDMA radio system that includes several channels, it is characterized in that: the CDMA spreading code that uses in system is a complement code; At least some channel is put frequency between adopting, they have a mutual difference on the frequency, equaling the difference on the frequency between zero point of auto-correlation and cross-correlation function, is a function of the frequency offset of the CDMA spreading code that uses in as each channel on function is calculating; All transmission of putting on the frequency channels is synchronous mutually.
According to the radio system of claim 6, it is characterized in that 7, this system includes between several groups puts frequency.
CN94190368.0A 1993-06-10 1994-06-06 A data transmission method and a cdma/fdma radio system Pending CN1110887A (en)

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US5953327A (en) * 1996-10-29 1999-09-14 Stanford Telecommunications, Inc. Class of low cross correlation non-palindromic synchronization sequences for code tracking in synchronous multiple access communication systems
JP3301724B2 (en) * 1998-03-13 2002-07-15 直樹 末広 Toothed Spectrum Communication System with Complementary Sequence Repetitive Modulation Comb
EP0993702A2 (en) * 1998-04-30 2000-04-19 Cellon France SAS Code division multiple access transmitter and receiver
US6567482B1 (en) * 1999-03-05 2003-05-20 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for efficient synchronization in spread spectrum communications
FR2806158B1 (en) * 2000-03-07 2002-05-17 Commissariat Energie Atomique METHOD FOR DETERMINING THE POSITION OR ORIENTATION OF AN OBJECT USING A MAGNETIC FIELD AND CORRESPONDING DEVICE
WO2002007338A1 (en) * 2000-07-04 2002-01-24 Linkair Communications, Inc. Method of converting spread spectrum multiple address code in a code division multiple access system
KR100922000B1 (en) * 2009-08-18 2009-10-14 세영정보통신(주) Simultaneous interpretation system for bidirectional audio data communication based on binary cdma
CN102427375A (en) * 2011-12-28 2012-04-25 哈尔滨工业大学 Code hopping multiple access method based on complementary code

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EP0489794A4 (en) * 1987-01-27 1993-06-09 Advanced Systems Research Pty. Ltd. Improvements in a spread-spectrum multiplexed transmission system
US5319634A (en) * 1991-10-07 1994-06-07 Phoenix Corporation Multiple access telephone extension systems and methods
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