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WO1999066653A1 - Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile - Google Patents

Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile Download PDF

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Publication number
WO1999066653A1
WO1999066653A1 PCT/DE1998/001685 DE9801685W WO9966653A1 WO 1999066653 A1 WO1999066653 A1 WO 1999066653A1 DE 9801685 W DE9801685 W DE 9801685W WO 9966653 A1 WO9966653 A1 WO 9966653A1
Authority
WO
WIPO (PCT)
Prior art keywords
bits
carrier frequencies
bit
register
value
Prior art date
Application number
PCT/DE1998/001685
Other languages
German (de)
English (en)
Inventor
Jürgen KOCKMANN
Olaf Dicker
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Priority to PCT/DE1998/001685 priority Critical patent/WO1999066653A1/fr
Priority to CA002335302A priority patent/CA2335302A1/fr
Priority to EP98936228A priority patent/EP1088404A1/fr
Publication of WO1999066653A1 publication Critical patent/WO1999066653A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H04B1/7143—Arrangements for generation of hop patterns

Definitions

  • the present invention relates to a method and a device for converting a random number sequence m carrier frequencies for a mobile radio transmission.
  • Frequency Hopper Spread Spectrum frequency hopping spread spectrum
  • a frequency spectrum spread spectrum system is understood to mean a system in which a large number of carrier frequencies are provided for the radio transmission of data and the carrier frequency currently used is changed periodically.
  • TDMA time division multiplex
  • the carrier frequency can be changed after each time slot or time frame of the time division multiplex transmission (or a multiple thereof).
  • Such a frequency hopping spread spectrum system has advantages in that the energy of the entire radio transmission is distributed over all carrier frequencies. This is particularly important when a generally detectable frequency band, such as the 2.4 GHz ISM (Industrial, Scientific, Medical) band, is used.
  • (FCC part 15) sets a limit on the maximum per carrier frequency occurring energy Festge ⁇ . Furthermore, the FCC part 15 stipulates that at least 75 different carrier frequencies must be provided.
  • time slots 12 each for upl k and for downlmk, are defined in a 10 ms frame.
  • the FCC part 15 only provides a bandwidth of less than 1 MHz for the ISM band.
  • the number of time slots was reduced to 12 time slots in a 10 ms time frame, ie 6 time slots each for uplink and for downlink.
  • each time slot would have a length of 833 ⁇ s.
  • the time slots in the DECT standard have a length of 417 ⁇ s.
  • an inactive DECT time slot of 417 ⁇ s between adjacent active time slots in which data is transmitted is required.
  • only 6 active time slots in each direction are used for data transmission. If such systems, which operate on the basis of slow frequency hopping, are also to meet the requirements of FCC part 15 in the ISM band, an inactive blind time slot of 417 ⁇ s must also be present between adjacent active time slots.
  • This blind time slot thus has half the length of a full time slot of 833 ⁇ s, which means that if a base time frame of 10 ms is maintained, four active time slots are available in each frame for uplink and downlink, between each of which blind time slots are sent.
  • the four active time slots each have a length of 833 ⁇ s, while the blind time slots each have a length of 417 ⁇ s.
  • frequency programming for frequency hopping in the next following active time slot can also be carried out at the end of the previous active time slot.
  • the programmed initial sequence can be set in the next active time slot.
  • An advantage of the frequency hopping spread spectrum system is that by providing a large number of carrier frequencies, the system becomes less sensitive to interference. In addition, the system's security against eavesdropping is increased, as the third party gel does not know which carrier frequency will be changed after a certain period of time.
  • the sequence of carrier frequencies that are used for transmission one after the other is determined by an algorithm.
  • Such an algorithm is implemented in an identical manner in the base station and in each mobile station of the mobile radio transmission. If a mobile part is thus synchronized with the associated base station, the handset and the base station will synchronously carry out the carrier frequency changes specified by the sequence of the (identical) algorithm.
  • the algorithm should ensure that each carrier frequency is used the same number of times and for the same length of time.
  • FCC part 15 stipulates that at least 75 different frequencies must be used within a period of 30 ms, whereby each frequency may be used for a maximum of 0.4 s. On average, all frequencies must be used equally frequently.
  • the base stations and the associated mobile stations each have identical random number generators, on the basis of which the algorithm for selecting or assigning the carrier frequencies works.
  • the different carrier frequencies and associated Tragerfrequenzagonist can, for example, m be stored in a table, wherein each Tra ⁇ associated gerfrequenz a specific position.
  • the polyvinyl sition will pay generator determined by the algorithm on the basis of chance ⁇ , the particular carrier frequency is read out from the table.
  • the present invention has for its object to provide a method and a device which enable simple implementation of a random number sequence m carrier frequencies for a mobile radio transmission. This task is solved by the features of the independent claims.
  • the dependent claims develop the invention in a particularly advantageous manner.
  • a method for implementing a random number sequence for carrier frequencies for a mobile radio transmission.
  • a shift register with a register content of n bits is provided.
  • the register content is shifted by 1 bit.
  • a decision is then made as to whether the value of a number of k bits in the register content is greater than a total number y of possible carrier frequencies, where k is less than n. If this decision is positive, the register content is shifted again by 1 bit and the decision is repeated. If the decision is negative, the value of the k bits is used to select a next carrier frequency.
  • the shift register comprises 16 bits, so that the shift register can easily be implemented in 8- and 16-bit processors.
  • a device for converting a random number sequence m carrier frequencies is further provided for a mobile radio transmission.
  • This device comprises a shift register with a register content of n bits. Furthermore, a device for shifting the register content by 1 bit is provided.
  • the device additionally comprises a device for deciding whether the value of a number of k bits of the register content is greater than a total number y of possible carrier frequencies, where k ⁇ n. If the decision is positive, the register content is shifted by 1 bit and the decision is repeated. If the decision is negative, the value of the k bits is used to select a next carrier frequency.
  • the register content n of the shift register is 16. This allows the shift register to be easily implemented in 8-bit or 16-bit processors.
  • FIG. 1 shows a mobile radio transmission system with a base station according to the invention
  • Fig. 3 shows in detail the internal structure of a base station according to the invention.
  • FIG. 4a shows a shift register as used in the present invention.
  • Fig. 4b the content of the shift register for the different clocks of a period, and
  • Fig. 5 em flow chart to explain the method and the device for implementing the random sequence m carrier frequencies.
  • the arrangement for radio transmission of data has a base station 1 and a plurality of mobile parts (mobile stations), wireless telephones 2, 3 ....
  • the base station 1 is connected to the fixed network by a terminal line 10.
  • An interface device which is not shown, can be provided for communication between the base station 1 and the terminal line 10.
  • the base station 1 has an antenna 6, by means of which communication with the mobile part 3 takes place, for example, via a first radio transmission path 8 with the mobile part 2 or via a second radio transmission path 9.
  • the handsets 2, 3 ... each have an antenna 7 for receiving or transmitting data.
  • 1 schematically shows the state in which the base station 1 actively communicates with the mobile part 2 and thus exchanges data.
  • base station 1 The internal structure of base station 1 is shown schematically in FIG. 1.
  • the voice information data are fed to an RF module 4, which is carried out by a carrier frequency sequence unit is controlled.
  • RF module 4 which is carried out by a carrier frequency sequence unit is controlled.
  • the exact structure of a base station 1 according to the invention will be described later.
  • time slots Zx in a time division multiplex method TDMA (Time Division Multiple Access) are transmitted in succession on a plurality of carrier frequencies fx, ten of which are shown.
  • TDMA Time Division Multiple Access
  • work is carried out in alternating mode (duplex), i. that is, after the first twelve time slots Zx have been transmitted by base station 1, the system switches to reception and receives the second twelve time slots (Z13 to Z24) from one or more mobile stations in the opposite direction.
  • the time duration of a time frame is 10 ms, and 24 time slots Zx are provided, namely twelve time slots for the transmission from the base station to handsets and a further twelve time slots Zx for transmission from the handsets to the base station.
  • ten carrier frequencies fx between 1.88 GHz and 1.90 GHz are provided.
  • the present invention also finds particular application for transmissions in the so-called 2.4 GHz ISM (Industrial, Scientific, Medical) frequency band.
  • the generally accessible ISM frequency band has a bandwidth of 83.5 MHz.
  • FCC part 15 at least 75 carrier frequencies fx must be distributed over this 83.5 MHz.
  • a division of the bandwidth of 83.5 is particularly advantageous MHz on 96 carrier frequencies, ie a channel spacing of 864 kHz.
  • the frequency bands and standards mentioned above are given purely as an example.
  • the basic requirement for applicability in the present invention is that a so-called frequency hopping spread
  • the RF module 4 is supplied with information data if the base station 1 is to transmit to a handset 2, 3 Data can be received from handsets.
  • the RF module 4 modulates the digitally coded information data onto a carrier frequency fx.
  • the carrier frequency fx currently to be used is predetermined by a carrier frequency sequence unit, which is generally designated 20.
  • a detection device 24 is provided in the carrier frequency sequence unit 20, to which the demodulated signal is supplied by the RF module 4. Interference means that there is either a disturbance in the actual sense or an assignment by another transmitter.
  • a disturbance in the sense of the present description can thus be detected, for example, by demodulating a received signal on a carrier frequency and by determining whether a signal level is present on this carrier frequency or not.
  • a disturbed carrier frequency is a carrier frequency onto which a signal is modulated that exceeds a certain threshold value. Faults in the true sense can be detected by the occurrence of CRC errors or burst losses.
  • the detection device 24 uses the demodulated signal from the RF module 4 to determine how high the signal portion modulated onto a specific carrier frequency fx is. If the detected signal component lies above a predetermined limit value or one of the abovementioned errors has occurred, the detection device 24 emits the fault detection signal to a blocking / releasing device 21 21 shows a blocking / release format to a processor 23.
  • This blocking / release format indicates which of the carrier frequencies fx are blocked or released again due to the detection of a fault by the detection device 24, as will be explained later.
  • the processor 23 is supplied with a sequence from a random generator 22. Based on the implied random algorithm, the random generator 22 generates a randomly distributed sequence of carrier frequency values within the predetermined frequency band. The random generator 22 thus executes a procedure which is independent of the procedure for frequency blocking in the event of a fault. The processor 23 finally sends a control signal to the RF module 4, which specifies the carrier frequency value to be used for the RF module 4.
  • the processor 22 specifies how many different values it is to generate. This number of values to be generated corresponds to the number of values to be generated generating carrier frequencies, which must be at least 75, for example, according to the US regulation FCC part 15.
  • the processor 23 also provides the random number generator 22 with a starting value for its algorithm.
  • the mobile station receives this start value from the base station for synchronization, which is achieved by using the same start value and the same algorithm. With the same start value and the same algorithm, the same sequences are forcibly generated by the base station and the handset.
  • Base station 1 is the master in frequency allocation, i. H. at the start of a connection establishment, the random number generator is initialized in a mobile part with the state of the random number generator 22 of the base station 1.
  • the random number generators in the handset 2, 3 ... and in the base station 1 then generate the same carrier frequency values synchronously and independently of one another.
  • the procedure for frequency blocking which is carried out by the detection device 24 and the blocking / releasing unit 21, uses a unidirectional protocol on the air interface during the entire connection time between the base station 1 and a handset 2, 3. If the detection device 24 finds one of the possible frequencies fx as disturbed by the base station 1, the base station 1 thus informs all the mobile parts with which it operates connections that this disturbed frequency, if it is generated by the frequency of the random number generator, is to be replaced by another carrier frequency which is not detected as being disturbed.
  • the random number generator 22 is not influenced by the frequency blocking.
  • This frequency blocking is withdrawn by the blocking / release unit 21 when the blocked carrier frequency is again suitable for transmission or when it was blocked for longer than a previously defined time. 4a and 4b, it will now be explained how the random numbers can be generated by an algorithm that is simple to implement in a processor and at the same time the required computing time can be kept low.
  • the basis of the algorithm is a feedback shift register 25 with the length x, the length x being 4 in the example shown.
  • the shift register 25 is loaded with the value 0001 as shown. For each new value of the contents of the shift register are shifted by one bit to the right 25, wherein as shown in each case the left bit is re-calculation ⁇ net.
  • the type of feedback ie in the present example the modulo2 addition of the left bit with the rightmost bit of the shift register 25 can be changed.
  • the sequence length that is the periodicity according to which the ER sired sequence repeated periodically depending on feedbackers ⁇ lung maximum of 2 n -L, where the number of bits n of the shift register 25 is.
  • the sequence length is therefore 15 (and thus maximum for a four-bit register), ie after 15 generated values, the generated values are repeated periodically.
  • the value 0 is not generated with feedback shift registers.
  • 4b shows how the content of the slide Beregisters 25 for the example shown in Fig. 4a for the corresponding clocks of a period.
  • 4a is to be understood in particular as an example of the generation of random numbers by feedback shift register.
  • a 16-bit shift register can be used.
  • Such a shift register can be easily implemented with m 8 and 16 bit processors. Due to the different possibilities of feedback 27, different sequences can be generated with a 16 bit shift register 2048.
  • a carrier frequency corresponding to a value of the generated random sequence is maintained for the duration of a frame of, for example, 10 ms
  • the duration of the period is 65535 x 10 ms ⁇ 10.9 mm. This means that a maximum length sequence is repeated only every 10.9 mm for a 16 bit register.
  • the number of possible values of the sequence of the carrier frequencies is 65535 as explained.
  • the number of actually used carrier frequencies can be considerably smaller and moreover variable.
  • the carrier frequency cannot be obtained directly by converting the values of the random sequence.
  • the values of the random sequence are used by means of the method explained in the flowchart of FIG. 5 for selecting or setting the next carrier frequency in each case.
  • the various stages of the flowchart shown in FIG. 5 are randomized with appropriate devices. numbers generator 22 implemented.
  • the shift register 25 is initialized with an initialization step 28 with a corresponding initialization device.
  • the shift register can, for example, be set to the value "1".
  • the content of the shift register is shifted by 1 bit in a corresponding shifting device.
  • a decision step 30 m of a corresponding decision device is then used to decide whether the value of a number of k bits is greater than the total number y of the possible carrier frequencies fx.
  • the total number y of carrier frequencies can be 96, for example.
  • the value k 7, as explained above.
  • These 7 bits are advantageously the 7 lower (least significant) bits at the beginning of the shift register 25.
  • the 7 bits can represent a maximum of 127, while the total number of carrier frequencies is a maximum of 96.
  • the process would return to step 29, in which the shift register 25 is again shifted by 1 bit. Then it is checked again whether the value of the k bits is greater than the total number of carrier frequencies. If the decision in step 30 is negative, ie if the value of the k bits is less than the total number of carrier frequencies, the corresponding value of the k bits in step 31 is used to select or to determine the next carrier frequency fx.
  • the 96 possible different transmitter frequencies fx m ⁇ a table addresses from 1 to 96 conces- arranged. If the value of the k bits is 73, for example, then this value 73 is smaller than the total number 96 of the carrier frequencies. The value 73 is thus used in step 31 or m of a corresponding device for selecting the carrier frequency located at the address 73 in the table. Carrier frequency values can also be stored in the table, each of which is assigned to a specific carrier frequency. The present invention thus enables the conversion of a random number sequence into carrier frequencies in a simple manner, which is simple to implement in a processor. Furthermore, the method according to the invention and thus the device according to the invention are simple, reliable and, moreover, can be implemented without great expense, while at the same time keeping the computing time required low.

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

Abstract

L'invention concerne un procédé et un dispositif permettant de convertir une séquence de nombres aléatoires en fréquences porteuses fx pour une radiocommunication mobile. Pour ce faire, un registre à décalage (25) présente un contenu de registre de n bits. On décale ce contenu de registre de 1 bit puis on détermine si la valeur d'un nombre de k bits du contenu du registre est supérieure au nombre total Y de fréquences porteuses fx possibles, sachant que k est inférieur ou égal à n. Dans l'affirmative, on décale à nouveau le contenu de registre de 1 bit et on procède à une nouvelle détermination. Dans le cas contraire, on utilise la valeur de k bits pour sélectionner la prochaine fréquence porteuse fx. On sélectionne la fréquence porteuse, par exemple, dans une table dans laquelle les fréquences porteuses possibles sont affectées à certains emplacements. Le procédé et le dispositif selon l'invention, sont simples, fiables et économiques à appliquer dans un émetteur-récepteur mobile.
PCT/DE1998/001685 1998-06-18 1998-06-18 Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile WO1999066653A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
PCT/DE1998/001685 WO1999066653A1 (fr) 1998-06-18 1998-06-18 Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile
CA002335302A CA2335302A1 (fr) 1998-06-18 1998-06-18 Procede et dispositif permettant de convertir une sequence de nombres aleatoires en une transmission de frequences porteuses pour une radiotransmission mobile
EP98936228A EP1088404A1 (fr) 1998-06-18 1998-06-18 Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DE1998/001685 WO1999066653A1 (fr) 1998-06-18 1998-06-18 Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile

Publications (1)

Publication Number Publication Date
WO1999066653A1 true WO1999066653A1 (fr) 1999-12-23

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PCT/DE1998/001685 WO1999066653A1 (fr) 1998-06-18 1998-06-18 Procede et dispositif permettant de convertir une sequence de nombres aleatoires en frequences porteuses pour une radiotransmission mobile

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EP (1) EP1088404A1 (fr)
CA (1) CA2335302A1 (fr)
WO (1) WO1999066653A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0084967A2 (fr) * 1982-01-27 1983-08-03 The Marconi Company Limited Système de communication par radio
US5235613A (en) * 1992-03-02 1993-08-10 The Boeing Company Frequency hopping method and apparatus
EP0767551A2 (fr) * 1995-10-02 1997-04-09 Telia Ab Méthode pour augmenter la capacité dans un système DECT
JPH09266455A (ja) * 1996-03-28 1997-10-07 Sanyo Electric Co Ltd 周波数ホッピング変調回路

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0084967A2 (fr) * 1982-01-27 1983-08-03 The Marconi Company Limited Système de communication par radio
US5235613A (en) * 1992-03-02 1993-08-10 The Boeing Company Frequency hopping method and apparatus
EP0767551A2 (fr) * 1995-10-02 1997-04-09 Telia Ab Méthode pour augmenter la capacité dans un système DECT
JPH09266455A (ja) * 1996-03-28 1997-10-07 Sanyo Electric Co Ltd 周波数ホッピング変調回路

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 098, no. 002 30 October 1998 (1998-10-30) *

Also Published As

Publication number Publication date
EP1088404A1 (fr) 2001-04-04
CA2335302A1 (fr) 1999-12-23

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