DE10053625A1 - Radio remote control method for moving objects e.g. model aircraft using narrow-band CDMA transmission system - Google Patents

Abstract

The radio remote control is performed using a narrow-band CDMA transmission system. To generate the transmission signal, a low-rate channel coding is used. At the receiver, different codes are used to discriminate signals transmitted in one frequency channel. Independent claims are included for a radio remote control method, and an apparatus for performing the method.

Description

The invention relates primarily to a method for radio remote control of movable objects (preamble of claim 1 and claim 4). Furthermore, the invention relates, according to claim 14, to a device for carrying out the method according to claim 1.

The creation of simple and inexpensive radio remote controls has been around for many Years in various areas of technology subject more intensely Development work. For example, from DE 93 19 508 U1 Radio remote control for the industrial sector, with a transmitter, the one Transmitter part with a transmitter, contains control electronics and a coder, known. An assigned receiving device contains a receiver part with a Receiver, a scan electronics and a scan-stop electronics and one Decoder. In particular, it is provided that the transmitting device is a device for automatic selection of a free frequency or a free channel for a Has data transmission.

For the radio remote control of moving objects, such as. B. model aircraft, -ships, or -cars, there are systems for unidirectional data transmission, where simple, communication technology transmission methods are used  be such. B. analog AM or FM, pulse duration modulation or pulse code modulation (PCM) with simple digital transmission methods. Since that too transmitting information is low, the systems come with low Transmission bandwidths.

For example, bandwidths of 10 kHz are used in model flying, whereby several adjacent frequency channels in the bands around 27, 35 and 40 MHz. The systems work with a constant transmission power that to the maximum desired range with the most unfavorable Propagation conditions is designed. In this way they also generate for others, relatively distant systems still have high levels of interference, their operation can interfere sensitively. Last but not least in model flying are disorders of the Communication anything but desirable as it can crash the expensive one Can fly objects. To make multiple use of frequency channels avoid, there are frequency plans in model flying clubs, into which one the desired frequency assignment must be entered in advance.

Furthermore contain both controlling element (transmitter) as well as controlled Element (receiver) of such systems usually have a lot of intelligence however, for the most part work separately from each other, since none is effective Exchanging information exists, apart from the real thing Control data.

There are also a few systems for the transmission of telemetry data (e.g. as a PC plug-in card), which the ISM tapes (Industrial, Scientific, Medical) use. However, there are only relatively low transmission powers in these bands allowed, so that a transmission only over short distances or with poor transmission quality is possible. Another disadvantage is that separate systems for remote control and telemetry data transmission are necessary, the joint use of mobility and ease of use strong limits.

For example, DE 43 12 676 C2 describes a circuit arrangement for telemetric transmission of physical status data from an object the model building technology known. By means of an HF Transmitters are such. B. engine speed, battery voltage, flight altitude or Temperature of a model airplane, a receiver station for optical and / or acoustic evaluation of the data supplied. For this purpose, the in Object provided transmission station, corresponding to the data to be transmitted Number of analog sensors operating over a multiplex Interrogator are connected to an A / D converter. In detail provided that the output of the A / D converter with an 8-bit micro Controller, which has a RAM, is connected in which the  Voltage values given to sensors can be saved as a telegram. On Data output of the micro controller is connected to an FFSK modem. The The output of the FFSK modem is connected to a control device (preferably) 433 MHz RF transmitter connected, each of which is a telegram measured voltage values, supplemented by a z. B. by means of a dip switch Specified device address that sends to the receiving station. The receiving station consists of a (preferably) 433 MHz RF receiver, the output of which is connected to an FFSK modem. Furthermore, the FFSK modem with one Data input of an 8-bit micro-controller with a RAM and an EPROM for storing device address, conversion factors, statistical Data, assignment of the transmitter sensor inputs connected. Finally, the Micro controller an audio output with amplifier for a headphone, one Output for an LC display and a serial V24 interface for connection of a computer.

A similar device for measured value transmission ("telemetry") radio-controlled models with sensors arranged in the model Determination of various measured values such as the state of charge of the rechargeable batteries or batteries, Height, speed of the model in all three axes, change in height ("Variometer") of the model or the like, with a radio telemetry transmitter on board of the model for transmitting the measured values (telemetry data) to one corresponding telemetry receiver for the pilot of the model is from the DE 195 02 713 A1 known. For this purpose, facilities for displaying the Telemetry data in, on or on the transmitter housing of the radio remote control of the Model provided.

Furthermore, DE 196 25 588 A1 describes a method and an apparatus for Radio remote control by means of coded electromagnetic pulses known which is the electromagnetic modulated on a high-frequency carrier Pulses are emitted by a corresponding transmitter. At the reception of a coded transmitter signal is from a receiver, which at least has saved a code, compared it with the stored code and if the stored code matches the code sent a function to be triggered via the radio remote control is activated. Still is provided that in addition to a first transmitter for coded electromagnetic Impulse at least one other transmitter is used. This station is receiving via a receiver integrated in the transmitter and an integrated one Signal processing unit one of the first transmitter in a sufficiently small Radiated, coded signal and stores in a corresponding adjustable operating state the received, coded signal as its own, coded transmission signal.  

DE 43 19 830 A1 also includes a CDMA transmission system at least one transmitter, in each of which a data sequence with a Code sequence is spread and with at least one receiver in which the data sequences are recovered using a detector. in the a frame structure is provided for each and each within a User information to be transmitted in the frame is in each case a signal burst summarized.

Finally, a receiver and a method for demodulating a CDMA signal are known from DE 44 41 543 A1. The recipient contains

• - A device for generating data samples from the received Signal;
• - A device for collecting data samples in the form of blocks complex data samples;
• A device for partially correlating the blocks of Data samples with shifts of at least one known one Signature sequence;
• - A device for selecting a predetermined number of Partial correlations;
• A device for estimating multipath channel tap coefficients;
• - A device for forming real parts of products of the selected Partial correlations with the reusable channel tap coefficients and

a device for combining the real parts of the products to at least one to determine transmitted information character sequence.

As the above assessment of the prior art shows, the Realization of an inexpensive transmission method with previous ones Devices and processes only possible to a very limited extent. Is particularly significant this is because a bandwidth and power efficient digital transmission method is of great use and the telecommunications industry as well as the Model making industry as extremely progressive, development-friendly industries can be seen, which quickly pick up improvements and simplifications and put it into practice.

The invention is compared to the known methods and devices The task is based on an inexpensive transmission method and a To design a device for implementing the method, the one interference-resistant, bidirectional, digital data transmission enabled.

This task is based on a method for radio remote control from movable objects, solved according to claim 1 in that the Radio remote control using a narrowband CDMA transmission system  takes place, a low rate to generate the transmission signal Channel coding and being used at the receiving end to distinguish between in one Frequency channel transmitted signals different codes are used.

The inventive method has the advantage that in a surprisingly simple manner by the use of a channel coding at a low rate (eg. B. convolutional coding with rate 1/8) a safe operation allows even at carrier to interference ratios of less than 1 becomes. This makes the system robust even against several equally strong transmission signals in the same frequency channel.

Furthermore, the object on which the invention is based, according to Claim 14, solved in that in the transmitter for generating a Low rate channel coding is either a channel encoder or a Convolutional encoder is arranged, the input of which supplies the binary data and its outputs each with a first input of a modulo-2 Adders are connected to the second input of each modulo-2 adder a signature generator is connected and that the output signal of Channel encoder or the modulo-2 adder a parallel-series converter is supplied, being in the decoder of the receiver even at equally strong A CDMA access is possible for transmission signals in the same frequency channel.

The inventive method and the device for realizing the Procedures thus allow the use of asynchronous, uncoordinated Code Multiple Access (CDMA), where the use of one channel by several Transmission systems is possible, for example with a code rate of 1/8 through up to four transmission systems.

In a preferred embodiment of the invention, according to claim 2, a continuous phase modulation (CPM) to generate the transmission signal used, causing a transformation from baseband to another Frequency band is made.

This embodiment of the invention has the advantage that the Using CPM a bandwidth and performance efficient digital Transmission method with constant envelope. So that becomes a efficient and cost-effective RF amplification possible with only the slightest Linearity requirements have to be met. According to the invention, the continuous Phase modulation (CPM) combined with low-rate channel coding, the binary channel-coded signal by the (modulo-2) addition of a Signature sequence is modified, the is in a particularly simple manner simultaneous transmission of several systems in the same frequency channel made possible by code division multiple access (CDMA).  

In a further development of the invention, according to claim 3, for Generation of the transmission signal the addition of a (pseudo-random) Signature sequence, which is used on the receiving side to distinguish between in one Frequency channel of transmitted signals is used.

This development of the invention has the advantage that when the (modulo-2) addition of a pseudo-random, binary signature sequence is applied to the channel-coded bits, so-called subclass codes arise, as described, for example, in the specialist book by Friedrichs, Bernd: Kanalcodierung, Springer Verlag 1995 are. This results in a clear, reversible mapping of the codes, which still have the same information technology properties. However, the use of signature sequences enables several transmitter-receiver systems to transmit and receive simultaneously in the same frequency channel without having a decisive influence on one another. As a result, CDMA access is possible through the use of the signature sequences. The subclass codes in the transmitter created by the signatures can be directly taken into account in the decoder at the receiving end (e.g. in the case of a trellis decoder in the metric calculation), so that separate operations are no longer necessary to separate the different channels in the receiver.

Finally, the object underlying the invention, according to Claim 4, solved in that the radio remote control by means of a narrowband CDMA transmission system takes place, with simultaneous Determination of the interference powers in the individual frequency channels regular spectral measurement of the complete available Frequency band takes place during the receiving process.

This embodiment of the invention has the advantage that for the determination the assignment and thus the interference power of the individual channels in the Frequency band the signal of the complete frequency band spectrally analyzed what can take place during reception. A separate time slot in which the Device neither receives nor sends, can be provided, but is from Principle not necessary. Since the device receives regularly, this is done also the spectral analysis regularly.

According to claim 5, the spectral measurement is preferably carried out by Calculation of the FFT over a broadband signal section received spectral detection of multiple frequency channels.

Spectral analysis using a fast Fourier transform (Fast Fourier transform (FFT) from the broadband signal section received,  the spectral resolution takes up the channel spacing of the frequency channels. Becomes a high in spectral analysis in the frequency channel currently used Interference power is detected, so can be a channel with less Interference power can be changed. This can happen, for example by mixing from the HF band into the complex equivalent baseband. In In this case, the broadband signal window also shifts. Because the spectral Resolution is adapted to the channel spacing, only the assignment of the Results of the Fourier transform can be adjusted to the channels. The can be achieved, for example, that for the analyzed Signal window double the bandwidth of the frequency band to be analyzed is chosen.

A development of the invention is characterized according to claim 6 by using a carrier-sensitive frequency hopping method Specification of the measured interference powers in the available Frequency channels.

This development of the invention has the advantage that, based on the available information about the individual channels, a carrier-sensitive frequency hopping method can be used. So in previously used frequency channel determines an excessive interference power, so can automatically become a channel with appropriate or acceptable Interference power can be changed. Thus a self-organization of the Allocation of the dynamically changing frequency channels to many Remote control systems possible. This means that coordination of Radio channels as previously (e.g. on model airfields) are no longer required because multiple channels are automatically left. This is also a coexistence of corresponding systems with existing systems, who use the FM, AM method, etc. possible. The change of one Frequency channel usefully follows a pseudo-random delay in order to avoid frequency changes that are close to one another as far as possible and thus preventing multiple systems from being on the same frequency at the same time switch (see Aloha principle).

Preferably, according to claim 7, a source coding for Reduction of the data to be transferred used.

This configuration has the advantage that despite the low data flow nevertheless sufficient information can be transmitted by the amount of the data to be transferred is reduced.

Furthermore, according to claim 8, the source coding DPCM, ADPCM or AQDPCM used.  

For example, AQDPCM (Adaptive Quantization Differential Pulse Code Modulation) used to compress the control information, so let For example, controller deflections differ depending on the amplitude quantize finely. Looking at z. B. the remote control of a model airplane, this would be the case for the individual control sticks (for elevator, rudder,...) small control movements around the current controller position a high one Resolution (= finer quantization) desirable for stronger ones Control movements, on the other hand, would result in a lower resolution (= coarser Quantization) are sufficient, since the accuracy in the movement of the human hand is lower. This fact can be explained by the Use of AQDPCM can be exploited in the rough and Fine quantization can be adapted to the current conditions. It can but also with advantage the other source codes, such as B. DPCM or ADPCM can be used.

In a preferred embodiment of the invention, according to claim 10, as duplex method time division duplex (TDD) or code division Duplex (CDD) used.

This embodiment of the invention has the advantage that Use Time Division Duplex (TDD) or Code Division Duplex (CDD) a data transmission in the same frequency channel in both directions possible. When using TDD, there is a time slot in the protocol for the Provide back channel. So it is possible from the controlled unit Sending data back to the control unit, creating numerous new ones Open up applications. So now, for example, is the transmission of telemetry data (altitude, speed, etc.) within the Remote control band possible without additional radio components. Continue to leave data for condition monitoring (tank filling, power supply, etc.) from the controlled unit to the control unit. So that can Remote control modules can be expanded into small cockpits, on which the view and monitor all information. In addition, the Monitoring of data security for transmission is conceivable, whereby Warning functions could indicate unreliable data traffic through the use of protective mechanisms in the protocol, for example Cyclic Redundancy Check (CRC), can be recognized. Could continue Mechanisms are provided that allow fallback settings of the controlled unit could flexibly define, d. H. it could be more easily set what settings the controlled unit in the event of tearing off the Radio connection should accept (e.g. manually making the desired Setting on the controlled unit and transmission of information to the Apply as fallback setting).  

Preferably, according to claim 11, an exchange of Performance control data between controlling and controlled unit made and according to this data there is a minimization of Transmission power through both units.

By using the duplex connection for mutual exchange of Power control data for minimizing the transmission power are shared controlling as well as controlled unit regularly with each other, how strong the Signals are received mutually. This allows both units to do their own Minimize transmission power and depending on the distance and propagation conditions adapt between the two units to the current requirements. This has the Advantage that battery life maximizes interference generation for others Systems is minimized and thereby also a higher spatial density of Systems in the same frequency channel is possible. This allows several Systems operating in the same frequency channel in a smaller spatial area Be operated at a distance from each other. One transmits at a given Channel bandwidth (e.g. 10 kHz for radio remote control systems) with low code rate, This means that only a small data flow is possible, which means that only a relatively low one Signal powers are incurred. This has the advantage of being much longer Battery life results and that the interference on other systems turn out to be significantly lower than with conventional processes.

In a preferred embodiment of the invention is, according to claim 15, for transformation into the desired HF band on the transmission side of the parallel Series converter is connected to a modulator and the receive signal to Mixing into the equivalent complex baseband and sampling becomes a mixer or fed to a complex digital mixer.

This embodiment of the invention has the advantage that cost-effective way to a channel with less Interference power can be changed by using the mixer from the RF Band in the complex equivalent baseband and also the broadband Signal window is moved. Alternatively, the HF- Band in the complex equivalent baseband only selected the frequency band and the frequency channel used for the transmission is marked with a second, then fully complex mixer after branching off the broadband Signal window, selected.

In a further development of the invention, according to claim 19, the receiver for spectral analysis means for preprocessing the data with a filter and / or windows, which are used to carry out a fast Fourier Transformation associated with an FFT processor and for reduction  the influence of short-term effects in those at the output of the FFT processor Measurable values that can be tapped are sent to one before evaluation Mean value generator (MIT) supplied.

This allows the quality and the influence to be increased in a simple manner be reduced by short-term effects.

Further advantages and details can be found in the description below of preferred embodiments of the invention with reference to the Take the drawing. The drawing shows:

Fig. 1 shows a preferred embodiment of a transmitter of the overall system according to the invention and

Fig. 2 shows a preferred embodiment of a receiver of the overall system according to the invention.

Fig. 1 shows an example of the method described corresponding transmitter S. The binary data is transferred thereby in a convolutional encoder FE rate 1 / n and subsequently modified by a plant characteristic signature sequence by signature generator SG. The data, which in turn is serialized in a parallel-series converter (PS), is then transformed into the desired HF band by means of a modulator M, for example by using continuous phase modulation (CPM). The outputs 0, 1,. , ., n-1 of the convolutional encoder FE each with a first input of a modulo-2 adder A0, A1,. , ., An-1 connected and the second input of each modulo-2 adder A0, A1,. , ., An-1 is connected to the signature generator SG.

FIG. 2 shows an example of an embodiment of a receiver E according to the described method, the received signal for mixing into the equivalent complex baseband and sampling being fed to a mixer DEM or a complex digital mixer MI. The output of the mixer DEM or MI is connected to a decoder D via means for filtering, delaying and subsampling, namely FIR, FII, V, MFR, MFI. A Viterbi decoder is preferably used as the decoder D. In an embodiment not shown in the drawing, the decided data obtained during the decoding are fed to a carrier phase synchronization, which estimates the current carrier phase therefrom and these are in turn fed back into the decoder D so that they can be used for the determination of subsequent bits. This results in a new carrier phase synchronization that can be integrated into the decoding process on the receiver side. Carrier phase synchronization in itself is described, for example, in the diploma thesis by Enzner, Gerald at the Chair for Telecommunications II, University of Erlangen-Nuremberg, August 2000 "Noncoherent sequence estimation for coded M (D) PSK and CPM transmission" or in the journal IEEE Transactions on Communications, COM- 47 : 1303-1308, September 1999 "Noncoherent sequence detection of Continous Phase Modulations" by Colavolpe, C; Raheli, R. or in the dissertation by Schober, Robert at the Chair of Telecommunications II, University of Erlangen-Nuremberg, Shaker Verlag 2000 "Noncoherent detection and equalization for MDPSK and MDAPSK signals" described and explained in detail.

Furthermore, the receiver E assigns means VVR, VVI for spectral analysis Pre-processing the data with a filter and / or window, which for Perform a fast Fourier transform with an FFT processor FFT are connected. To reduce the influence of short-term effects in the measured values that can be tapped at the output of the FFT processor these are fed to an averager MIT before evaluation A. In particular, the averager MIT submits the measured values for the Services in the individual frequency channels of averaging or filtering.

In comparison to the known prior art, one according to the invention cost-effective method and a device for realizing the Procedure specified in which a noise-resistant, digital Radio remote control with power control, a self-organizing Channel allocation and return channel provision using duplex methods Telemetry data transmission is made possible.

All shown and described execution options, as well as all in the description and / or the drawing disclosed new individual features and their combination with one another are essential to the invention.

Claims (20)

1. A method for radio remote control of moving objects, characterized in that the radio remote control is carried out by means of a narrow-band CDMA transmission system, a low-rate channel coding being used to generate the transmission signal and different codes being used on the receiving side to distinguish signals transmitted in a frequency channel. 2. The method according to claim 1, characterized in that for generation a continuous phase modulation (CPM) is used for the transmission signal, thereby transforming from baseband to another frequency band is made. 3. The method according to claim 1, characterized in that for generation of the transmission signal the addition of a (pseudo-random) signature sequence takes place, which on the receiving side to distinguish between in one Frequency channel of transmitted signals is used. 4. Method for radio remote control of moving objects, thereby characterized in that the radio remote control by means of a narrowband CDMA transmission system takes place, with the simultaneous determination of the Interference services in the individual frequency channels a regular spectral measurement of the complete available Frequency band takes place during the receiving process.   5. The method according to claim 4, characterized in that the spectral Measurement by calculating the FFT over a broadband received Signal section for spectral detection of several frequency channels takes place. 6. The method according to any one of claims 1 to 5, characterized by the Use of a carrier-sensitive frequency hopping method according to the requirements the measured interference powers in the available Frequency channels. 7. The method according to any one of claims 1 to 6, characterized in that Source coding is used to reduce the data to be transmitted becomes. 8. The method according to claim 7, characterized in that for Source coding DPCM, ADPCM or AQDPCM is used. 9. The method according to any one of claims 1 to 8, characterized in that Duplex methods for bidirectional data transmission in the same Frequency channel can be applied. 10. The method according to claim 9, characterized in that as a duplex Time division duplex (TDD) or code division duplex (CDD) method is used. 11. The method according to claim 9 or 10, characterized in that a Exchange of performance control data between controlling and controlled Unit is made and that according to this data a The transmission power is minimized by both units. 12. The method according to any one of the preceding claims, characterized by the transmission of telemetry data and / or data for Condition monitoring from the controlled to the controlling unit. 13. The method according to any one of the preceding claims, characterized characterized in that when evaluating the received signal one in the Decoding process integrable carrier phase synchronization takes place. 14. Device for performing the method according to claim 1, characterized characterized in that in the transmitter (S) for generating a channel coding with low rate either a channel encoder or a convolutional encoder (FE) is arranged, the input of which the binary data are supplied and  whose outputs (0, 1,..., n-1) each with a first input of a Modulo-2 adders (A0, A1,..., An-1) are connected that the second Input of each modulo-2 adder (A0, A1,..., An-1) with one Signature generator (SG) is connected and that the output signal of the Channel encoder or the modulo-2 adder (A0, A1,..., An-1) a parallel Series converter (PS) is supplied, being in the decoder (D) of the receiver (E) even with transmit signals of the same strength in the same frequency channel CDMA access is possible. 15. The apparatus according to claim 14, characterized in that for Transformation into the desired HF band on the transmission side of the parallel series Converter (PS) is connected to a modulator (M) and that that Receive signal for mixing into the equivalent complex baseband and Sampling a mixer (DEM) or a complex digital mixer (MI) is fed. 16. The apparatus according to claim 15, characterized in that the Modulator (M) generates a continuous phase modulation. 17. The apparatus according to claim 14 and 15, characterized in that the Output of the mixer (DEM, MI) via filtering means, delay and subsampling (FIR, FII, V, MFR, MFI) with the decoder (D) in Connection is established. 18. The apparatus according to claim 14, characterized in that as a decoder (D) a Viterbi decoder that is used in decoding received determined data a carrier phase synchronization that estimates the current carrier phase and that this in turn be fed back into the decoder (D) to use them for the To be able to use the determination of subsequent bits. 19. The apparatus according to claim 14, characterized in that the Receiver (E) for spectral analysis means (VVR, VVI) for preprocessing of the data with a filter and / or window, which for Perform a fast Fourier transform with an FFT Processor (FFT) are connected and that to reduce the influence of short-term effects in the output of the FFT processor (FFT) measurable values, these before the evaluation (A) one Averaging devices (MIT) are supplied. 20. The apparatus according to claim 19, characterized in that the Averaging (MIT) the measured values for the performance in each Frequency channels averaged or filtered.