The transfer method with the code modulation and transmission system operating according to this method of transmission

 

(57) Abstract:

The transfer method with the code modulation transmission system related to the field of radio communications between the base station and multiple subscriber stations in the transmission channels of the wideband signal. The transmission channel is represented by a high-frequency carrier oscillations, modulated with different codessC1, . . ., Cqwhile at least one of the transmission channels allocate as provided priority transmission channel relative to the other transmission channels due to the fact that the phase of the high-frequency carrier modulated by a code Csequipped with a priority channel transmission is shifted by a prescribed amount relative to the phase of high-frequency carrier modulated codes WITH1,...,qother transmission channels. Technical result achieved - increased reliability of detection on the receiving side of the established transmission channel with a specific code. 2 s and 5 C.p. f-crystals, 4 Il.

The invention relates to a method transmission code modulation and operating in this way is transferred to the transmission system according to the restrictive part of paragraph 1 of the claims or, with the coy tiled application DE 4333396 A1.

Working on the transfer method code modulation (CDMA) (CDMA = Code Division Multiple Access = multiple access code division multiplexing) transmission system is a communication system in which radio field is produced is shared by many subscribers. The communication system consists of a fixed or mobile subscriber stations that are in connection with the base station. Subscribers can communicate with each other through the base station. This includes the transmission channels, which in the case of CDMA method, as already described in the application DE 4333396 A1, may vary from each other due to individual channels encode useful information is exchanged in these communication channels. Individual channels of the encoding is done at the same time, for example, when transferring in the direction from base station to subscriber stations (in the following also denoted as passing down "Downlink") on the side of the transmission so that every bit of useful information is exchanged in a particular transmission channel, is divided into a certain number of labeled chips bits ("podutov"). Formed by this number of chips of the sequence of chips is a while, later the data transmission channels codes then modulate the high frequency carrier signal so this modulated carrier signal separate codes are superimposed on each other.

On the receiving side, that is, in the proposed example in a separate subscriber stations from a received high-frequency carrier signal through demodulation and filtering of the first selectrow suitable for the corresponding subscriber station transmission channel and thereby the code and hence, finally, restore the transmitted valuable information.

The bandwidth to be transmitted useful information in the case of CDMA method greatly expanded due to the above coding. You also talk about the transfer method with the range stretching". For the transmission of useful information using all available bandwidth.

In the modified CDMA method, namely TCDMA-way, which is a combination of the CDMA method and the well-known TDMA method (Time Division Multiple Access" = multiple access with time division multiplexing), for each code, and thereby the transmission channel set set the number of time channels so that the temporary sealing of channels, each code can be used by many subscribers.

In EP-A-430587 of estaline lots of modulated codes of high-frequency carrier and phase modulated codes of the high-frequency carrier oscillations are synchronous.

The present invention is to specify a way how you can transfer method code modulation or, respectively, transmission system according to the restrictive part of paragraph 1 of the claims or, respectively, of paragraph 7 of the claims, in order to detect the installed transmission channels with certain codes compared to other codes/transmission channels on the receiving side with a higher reliability.

According to the invention this task is to transfer method code modulation according to the restrictive part of paragraph 1 of the formula of the invention is solved by the features of the process specified in the claim.

The invention brings the advantage that the corresponding provided with a priority code, and thereby the transmission channel can be detected in the subscriber station with a relatively small additional running costs compared to conventional codes.

Suitable forms of further development of the method according to the present invention, as well as transmission system operating according to this method, follow from the dependent claims 2-7 claims.

In the following the present Amma for General explanations synchronous CDMA method,

Fig.2 is a diagram for explanation installed in TCDMA-way for a single code channel intervals,

Fig.3 in schematic form a possible design of a base station and

Fig.4 in schematic form a possible design of the subscriber station.

The present invention is illustrated in the following by the example of TCDMA-way. However, it should be noted that the present invention is not limited to such TCDMA-way, and is also applicable in the previously mentioned CDMA-way.

In Fig. 1 again presented in schematic form the principle of synchronous CDMA method. According to him radiocaster between the base station and subscriber stations in a temporary way of sealing channels are used alternately for transmission from the base station to the subscriber stations and for transmitting from the subscriber stations to the base station. Named first direction of transfer is indicated in Fig.1 as the down link direction ("Downlink"), and the last named direction of transfer is indicated as the direction of the link up ("Uplink"). In shown in Fig.1 time interval from 0 to TDthus, for example, partial interval 0 to Tr/2 redundant to the direction down. Ostasis is already mentioned above, the transmission of useful information is in the transmission channels, which are defined in the CDMA method codes. These codes, which are modulated useful informacjami to be transferred, is modulated high-frequency carrier signal which is radiated through the antenna. These codes are marked on Fig.1 as CSC1WITH2,...,q. When this code is CSrepresents the transmission channel, passed at least the synchronizing information in the form of fixed synchronization pattern. Other codes are used to transmit useful data. This should indicate that under the useful data you should understand any kind of digital signals. That applies, for example, signals, text, and data, voice signals in digital form, digital video, etc.

In Fig. 2 presents the case that according to the above-mentioned TCDMA-method for each schematically indicated in Fig.1 code defined a set number of time channels. These temporary channels in consecutive cycles of a temporary Association of the digital signals given in compliance with respectively one channel interval. This cycle of temporary integration of digital is but awarded in compliance with the time channel 1 - j. Temporal length TDsuch a channel interval corresponds, for example, the length to transfer the useful bits or, respectively, the clock bits.

In Fig.2 then the code sample1presents that the corresponding code is formed from characterizing its sequence of chips (sequence of bits) with a prescribed number of chips, the length of which is respectively TCand the logical level of which may be, for example, +1 or -1. The length of the sequence of chips, for example, 7 of the chip corresponds to the channel length of the interval TDand thus subject to the transfer of bits.

For the direction of the transmission up "Uplink" (TD/2 to TDalso rightly explained the separation channel spacing.

After the example of Fig.1 and 2 has been described TCDMA-way in General, in the following let us look more closely at possible design and principle of operation of the base station and are with her in the radio subscriber stations to the transmission direction down "Downlink".

First consider the example of Fig.3 base station, and it presents only essential to understanding this is th station BS must be continuously transmitted, on the one hand, the payload through many channels i (i=l, ..., q) code WITHi(i=1, ..., q) and, on the other hand, in particular the transmission channel S ID CS- synchronization information to all subscriber stations, such as mobile stations, namely TCDMA-way. Since this is TCDMA-way, as already mentioned earlier, for each code provides a set number of time channels (j), separate codes are used for transmission to multiple subscriber stations. For payload data and synchronization information, which, for example, can represent binary information with the logical levels "1" and "0", schematically identified individual data source, which supplies available bit payload or, respectively, the synchronization information. These data sources are indicated in Fig.3 in accordance with their coordination with the transmission channels 1 - q, S, and defined for them, time channels (j) as D11, ..., D1j; ...; Dq1, ..., Dqj; Ds1, ..., Dsj. After each of these data sources included a special branch of the modulation, which is given in accordance with one of the transmission channels 1 - q and S and one installed in them temporary channels. In the corresponding branch of the modulation Ave is ghadami for the corresponding channel transmission code (C1,...,qCS) modulate just provided a bit of useful data or, respectively, the sync bit. For this purpose apply the KLO-mode ("ON-OFF-Keying" = encoding-on-off) that is, for example, when you want to transfer the logic level "1" indicate the appropriate code, in contrast to this code when the logical level "0" to suppress.

Then, the corresponding modulated code fail to located in the corresponding branch of the modulation of the modulator (M1, ..., Mqor, respectively, MSto modulate this code high frequency oscillation of the carrier, the circular frequency of which isr= 2frand made available to the high-frequency generator GEN. For this purpose, the so-called binary phase modulation BPSK ("Binary Phase Shift Keying"). The modulators in the present exemplary embodiment is made so that the phase of at least one of the high-frequency carrier modulated by a code, in comparison with other phase high-frequency carrier modulated codes is shifted to the set value. The phase shift is, for example, 90ois equal. To do this, modulators include, for example, corresponding fotodigital or links of delay. In this example perform the modulated code WITHShigh-frequency oscillation of the carrier has a phase shift so that the presents of this code, the transmission channel in comparison with the rest of the transmission channels is selected or, respectively, provided with priority in order to facilitate synchronization, which is usually considered in CDMA systems as complex.

In addition, in the present exemplary embodiment is provided that is equipped with a priority code (here CScompared with other codes issued with higher energy, for example, with energy above 1 dB.

However, you can also alternative or additional manner to provide a priority of at least one other code, to increase the reliability of its detection in comparison with other codes. As an example, it is necessary to call the code that represents the transmission channel, which is used, for example, as a channel of transmission of the distress signal.

Resulting in some branches of the modulation of the modulated high frequency carrier signals down the ZAT the shaft, that is driven by a control device ST in such a way that the modulated high frequency carrier signal down in accordance with the TCDMA-way channel respectively the interval associated with the outputs of the switches of channel intervals a summing device . Switches channel intervals indicated in Fig.3 according to their coordination to individual branches modulation as SS11, ..., SS1j; SSq1, ..., SSqj; SSS1, ..., SSSj.

With the help of the above summing device separate modulated high frequency carrier signals which are equal in frequency, superimposed on each other. Resultwise this overlay high-frequency carrier signal after amplification by the amplifier V1 is radiated through the antenna ANT1.

Otherwise, regarding the application of codes and temporary channels should be specified that they do not have any hard giving according to certain subscriber stations. Moreover, giving in compliance with codes and timeslots to individual subscriber stations through the base station BS. For example, you can keep the table from which follow already emali base station BS selects for connections to individual subscriber stations to be used codes and timeslots and informs the subscriber stations, for example, through information, transferable in the installed temporary channels channel synchronization (CS). For this choice is to first, for example, evenly as possible to take a temporary one code before select another code, and the selection of temporary channels and codes thus avoiding interference between the information to be transmitted in the same time channel. Select the code and temporary channels are not discussed in more detail below, as this is not the subject of the present invention.

Radiated via the antenna ANT1 modulated high frequency carrier oscillation is accepted individual connected with the base station BS subscriber stations. Admission procedures will be discussed subsequently in more detail. For this stem from the possible construction of subscriber stations, as shown in Fig.4. When this is specified, only the circuit elements that are necessary for understanding the present invention.

According Fig. 4 modulated high frequency carrier signal, adopted the designated subscriber device MS, enters via the antenna ANT2 to the amplifier V2, which is regulated to control a large, dynamic is selenia). The amplified carrier signal (rin the first mixing stage MIX1 mixed with the provided oscillator OSZ1 the oscillator signal with a frequency ofLso that there is a signal with an intermediate frequencyiwherei=rL. After amplification due also adjustable amplifier intermediate frequency signal V3 intermediate frequency sum, on the one hand, to switch timeslots ESSand, on the other hand, to switch timeslots ES1-ESq. These switches respectively form the input of the special branch of the filter for filtering the above-mentioned codes CSand Cl-Cqfor the clock information and the data payload. In the case of the present exemplary embodiment is based on the fact that the corresponding subscriber station MS is designed to receive all codes. An alternative to this, the corresponding subscriber station may be, however, designed to receive one of the codes or parts of codes WITH1-Cqand CS. In this case then would be provided by suitable switches and related branches of filtration.

Switch timeslots ESSduring the above cited is in each channel interval is closed. In contrast, switch timeslots ES1-ESqclosed only those that correspond to given in compliance with the subscriber station MS by the base station BS (Fig.3) code and timeslot.

After switch timeslots ESSand ES1-ESqincluded consistent with the signal filter, which is aligned with one of the codes CSand C1-Cq. These filters, which are indicated in Fig.4 in accordance with their giving in compliance with individual switches and thereby the branches of the filter MFCS, MFC1, . .., MFCqcan be performed, for example, as so-called "system agreed with signal filters", which, for example, described in the aforementioned German application laid DE 4333396 A1 or A SAW Matched Filter Based Spread Spectrum Technique Based for Indoor Multiple Access Systems", Z. Zhang, F. Seifert, R. Weigel, Proceedings 1995 IEEE MTT-S Symposium, Orlando, may 1995, pp. 899-902.

The output of the filter MFCSto which when closed switch timeslots ESSsummed signal of intermediate frequency, intermediate frequencyisupplies during the appearance of sychronizing bits and thus codeSthe output signal in the form of compressed output pulse. Atora OSZ2 oscillating signal intermediate frequencyi. Mixer MIX3 (Q-branch) receives in contrast, the oscillatory signal of the same intermediate frequency, the phase of which, however, is shifted by a /2. In this example running between the oscillator OSZ2 and mixer MIX3 included denoted by PS fotodigital. On the output side of both the mixer MIX2 and MH connected through the switch time gate (allocated time) to the comparator list. When given in compliance with the mixer MIX2 switch temporary gate marked ZS1, as given in compliance with the mixer MIX3 switch temporary gate marked ZS2. Both switches to the temporary gate when administered together. After the comparator OMRS then takes place coherent detection of the synchronizing signals.

The comparator OMRS, in addition, connected to its output, on the one hand, to the control input of the oscillator OSZ2 to the frequency and phase regulation and, on the other hand, to the control input of the AGC to control the gain of these amplifiers V2 and V3.

Included after the filter MFCSthe just-described circuit elements MIX2, MIX3 and OMRS are so-called the scheme "the Costas loop". With its help the V) is converted into the base band and get a suitable synchronizing bits, namely, for example, (adaptive) decision thresholds. If the phase of the output signal appearing in the I-branch corresponds to the phase with which the base station BS (Fig.3) radiates the modulated code WITHSVysokochistye the carrier signal and is received at the subscriber station MS, the comparator OMRS scheme "loop Kostas" frequencyiand the phase generated by the oscillator OSZ2 oscillating signal is adjusted so (AFG = "automatic Frequency Control" = Automatic adjustment of the frequency = ARCH) that in the I-branch filter MFCSduring a temporary gate FSyou may receive a maximum of the previously mentioned output pulse of this filter (or, respectively, the maximum energy of the signal), while in the Q-branch filter MFCs receive a minimum output pulse. Time gate (window) FSwho has time closing switch temporary gate ZS1 and ZS2 is beginning to sync open so long as the subscriber station MS by monitoring signal peaks in the I branch or the Q-branch filter MFCSwill be found the clock cycle TPand the period of channel intervals (TDin Fig. 2). Only after synchronization pereklyuchatelei function. The value ofSset so that the interference noise due to different active moves in the same channel intervals are excluded.

The rest of the above-mentioned filters MFC1MFqconnected by their outputs together to the mixer MIX4. As related to these filters, switches timeslots ES1-ESqclosed only one appearing on the output connected with just closed switch timeslots filter output pulse supplied to the mixer MIX4. In addition, he served on offer for the above-mentioned Q-branch filter MFCSthe oscillatory signal of the oscillator OSZ2 with frequencyithat compared with oscillatory signal for the I-branch filter MFCs shifted in phase by 90othat is /2. Due to ongoing coherent detection codes C1-Cqwith Q-phase oscillating signal iin the frequency - and vasoregulation condition of the subscriber station MS with a closed switch timeslots (ES1-ESqthe output of the mixer MH occurs for a maximum of just received pulse data. In order to eliminate interference due to different active the Menen gate SZ3, the closed state is set to the time gate FXinside the corresponding channel interval. After this switch, the temporary gate is then given by (adaptive) threshold solutions suitable bits of data.

To determine the width of the temporary gate lW1and lW2that represent the initial value (lW1and the final value (1W2time gate FSand FX(FS=lW2-lW1FS=lW2-lW1) inside the channel interval Tdconsider the impulse response of the radio channel on the air interface between the base station BS and the subscriber stations MS to the corresponding filter MFCS, MFC1, ..., MFCq. The impulse response of the radio channel is given by the expression

< / BR>
where K indicates the number of paths for multipath propagation of the signal, i.e. the number of different transmission paths due to reflections (echo). The remaining parameters {k}, {tk} and {k} represent the attenuation of the amplitude, the relative time and the corresponding phase change. Due to this, the impulse response of the radio channel take into account the fact that due to individual reflections along with the main Maxim defined by the expression

< / BR>
and is the integer part of zdiffrepresents the difference between the time delays of the subscriber stations MS due to scattering of the provisions relative to the base station BS (Fig.3). To send down "Downlink" true lW1= 0, because the signals are sent to the corresponding subscriber station MS without differences of travel time. In the transmit direction up "Uplink" in the case of multiple active subscriber stations in the same channel spacing due to various provisions usually lW1not equal to "0".

Thermsis the so-called root-mean-square scattering random delay (random mean square delay spread") and is obtained as

< / BR>
Due to this not only delays the travel time, but also the components of the energy of the separate paths taken into account when determining the width of the time gate. So there is the right combination of signals for detection of the data and at the same time the maximum exclusion of outside interference of certain temporary gates FSand FX.

So you can take bits clock with a lower frequency of occurrence of errors, in addition to using a temporary gate on the output of the filter stretching have very good characteristics of cross-correlation to the synchronizing code CSso that caused data codes Ci(i=1, ..., q) of multiple access interference in the same channel spacing can be reduced to a minimum.

Codes with absolute orthogonality in the whole area correlation, as, for example, Walsh codes are only available in very limited quantities and are therefore not particularly well suited for multiplex transmission code division of channels. Family code pseudo-random noise with a relatively small mutual correlations are codes Golda. Codes Golda available in large quantities, and, of course, only certain codes have good performance of mutual correlation. Codes gold can be obtained using the so-called preferred pairs of m-sequences (longest linear sequence).

Through the use of a temporary gate on the output of the filter MFCSneed codes strains, which have a possible small values of cross-correlation within a time gateS. Due to this, it turns out significantly less requirement of orthogonality in the whole area correlation. Therefore, it is possible to find numerous suitable codes stretching for TCDMA-skin the way:

< / BR>
< / BR>
where L is the code length stretching and lW1, lW2accordingly, the above-mentioned starting and ending index of the temporary gate to the output Gating on a consistent signal filter MFCS.

To stretch the clock bits can be used, for example, the already mentioned m-sequences due to their good characteristics of autocorrelation. Codes stretching for useful data can be selected from numerous codes goldi, i=l, ..., NSwith the same length L.

Due to the "On-Off-Keying modulation here for Elektrownia codes stretching take into account only the aperiodic correlation function. Aperiodic correlation of the two codes WITHsand C1(n)and C1(n)is cyclically shifted by n chip version1determined according to

< / BR>
< / BR>
The value of the time gate WITH1(n)retrieved from

.

For C1get maximum value of a time gate from

M1=max{F1(n)} for n=1, ..., L-1

with the corresponding index of n1for M1.

If the operation is repeated with eachifrom stock codesi, i=1, ..., N1then come..., L-1 and i=1, ..., Ns.

If the vector is sorted in the ascending order of

< / BR>
accordingly result in a new vector index

< / BR>
Finally, the desired codes are obtained as

< / BR>
Found according to the method codesi' have a relatively sychronizing codeSthe property that Ci' has the minimum cross-correlation with CSWITH2' after the second minimum cross-correlation with CSand so on, This method can be iteratively continued so that in equation (1) code WITHSreplace the amount of CSand Ci' and1replace WITH2and produce them these operations. Then get the second move, which has the minimum cross-correlation WITH respect to theSand Ci'.

At the third iteration in equation (1) code CSreplaced by the sum of the two already found codes + CSand C1replace WITH3so after performing the above operations of the method to determine the third code. This method accordingly continue with further iterations to determine all further codes.

You just described the way Elektrownia can also be used to determine the operation of the first code replaces the code CS.

1. The transfer method with the code modulation for information transmission between the base station and multiple subscriber stations in the transmission channels, which are represented by high frequency oscillations of the carrier being modulated with different codes CsC1, . . . Cq, characterized in that at least one of the transmission channels allocate as provided priority transmission channel relative to the other transmission channels due to the fact that the phase of the high-frequency carrier modulated by a code Csequipped with a priority channel transmission is shifted by a prescribed amount relative to the phase of high-frequency carrier modulated codes WITH1, . . . WITHqother transmission channels.

2. The method according to p. 1, characterized in that the phase shift is 90o.

3. The method according to p. 1 or 2, characterized in that the respective transmission channel, presents one of the codes CsC1, . . . Cqset many temporary channels for transmission with a temporary seal different information.

4. The method according to any of paragraphs. 1-3, characterized in that, as provided by the priority of the transmission channel in which any of paragraphs. 1-4, characterized in that the code Csrepresenting equipped priority transmission channel, transmit with higher energy compared with values1, . . . WITHqrepresenting the other transmission channels.

6. The method according to p. 5, characterized in that the difference in energy codesrepresenting equipped priority transmission channel, relative to the energy code1, . . . WITHqrepresenting the rest of the transmission channels is 1 dB.

7. Transmission system operating according to the method of transmission code modulation, for transmitting information between a base station and multiple subscriber stations in the transmission channels, which are represented by high frequency oscillations of the carrier being modulated with different codes CsC1, . . . Cq, characterized in that the base station is designed in such a way that it stands out at least one of the transmission channels as provided by the priority of the transmission channel relative to the other transmission channels due to the fact that the phase of the high-frequency carrier modulated by a code FROM thesequipped with a priority channel transmission is shifted by a prescribed amount relative to the phase of the high frequency knli contain, respectively, the means of detection, designed in such a way that through them first detected in accordance with the phase of at least part of the codes of the codes CsC1, . . . Cqand then from the corresponding code is recovering transmitted information.

 

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