EP1088432A1

EP1088432A1 - Method and device for wireless data transmission according to an fsk method, especially a gfsk method

Info

Publication number: EP1088432A1
Application number: EP99938181A
Authority: EP
Inventors: Henrik Wagener
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1998-06-17
Filing date: 1999-06-11
Publication date: 2001-04-04
Also published as: WO1999066686A1; DE19827028C2; JP2002518939A; DE19827028A1; CN1315101A

Abstract

According to the invention, a mobile radio device is provided for wireless data transmission according to a GFSK method, as performed, for instance, with DECT devices. The device has a receiver (6), a first measuring device (6) for error rate of the received data, in addition to a second measuring device (3) for field intensity (8) during data reception. An evaluation unit (6) processes the measured error rate and the measured field intensity. Depending on the measured error rate and the measured field intensity, a control unit (13) regulates the frequency sweep of the GSFK method that is used for wireless data transmission (15) by a transmitter (5) in the mobile radio device (15) with the purpose of optimizing transmission performance. In order to optimize transmission performance, a first table (12) and a second table (14) are provided in the evaluation unit (6), which reproduce the range that may be obtained or the interference immunity that may be obtained of the transmission (15) depending on the selected frequency sweep.

Description

description

Method and device for the wireless transmission of data according to an FSK method, in particular a GFSK method

The present invention relates to a device and a method for the wireless transmission of data according to an FSK method, such as the GFSK method, as is used, inter alia, according to the DECT standard.

According to the DECT standard, data is modulated according to a GFSK (Gaussian Frequency Shift Keying) method. For details of the DECT standard, reference is made, for example, to David, Benkner, "Digital Mobile Radio Systems, Taubner Verlag, Stuttgart, 1996, ISBN 3-519-06181-3. According to the DECT standard, data in a frequency range from 1880 to 1900 MHz (in the extended case up to 1930 MHz) in 120 duplex channels. The channel spacing is 1728 kHz. The TDMA access method with frames of 10 ms is used. The duplex method is the TDD method.

However, the present invention applies to all FSK processes and their derivatives.

While in the amplitude shift keying, the amplitude of a Trä ^¬ gerschwingung by modulating the digital signals changed ^¬ is changed, the frequency remains, however, constant, it is returned exactly environmentally in the frequency shift keying (FSK, Frequency Shift Keying), the information that is, in the frequency contain. However, the abrupt switching from one frequency to another leads to relatively high spectral secondary sidebands, as a result of which a high bandwidth is occupied by the transmission signal. This behavior can be improved by baseband filtering. There is a frequency filter used g (t), the kei ^¬ but rather has NEN rectangular course, a smoothed curve. The smoothing function can be taken from a Gaussian low pass. GFSK modulation is thus obtained.

The impulse response h (t) of a Gaussian low pass is:

where B is the 3 dB cutoff frequency. The Gaussian low-pass filter can be switched directly before the modulation input of a VCO. Then there are pulses at the modulation input, which result from the folding of the original rectangular pulses with the impulse response of the Gaussian low pass:

Here erf (x) is the Gaussian error function:

1 ^x erf (x) = - j = e ^{~ u} du

The GFSK transmission filter can be uniquely identified by its Modula ^¬ tion index ( "BT ratio") mark. FIG. 6 shows the impulse response of the transmission filter for different modulation indices (BT). It can be seen here that as the modulation indices become smaller, the impulse response becomes wider and thus a "partial response" behavior occurs.

For use in the DECT devices Modulationsver ^¬ was driving GFSK with a nominal modulation index (BT) specified by 0.5, which ent a frequency deviation of 288 kHz ^¬ talks. When determining the modulation index of the frequency sweep, a range of 202 kHz to 403 kHz to ^¬ is bezüg ^¬ Lich permeable. According to the prior art, the frequency swing is set to a fixed value, so adaptation is not possible.

It is therefore the object of the present invention to create a possibility of creating the adaptation of a wireless transmission of data according to an FSK method to different environmental scenarios.

According to the concept of the invention, the frequency deviation of an FSK method, for example the GFSK method, is changed depending on various parameters.

The above object is more specifically achieved by the features of claims 1 and 9. The subclaims further develop the idea of the invention in a particularly advantageous manner.

According to the invention, a method for wireless transmission of data according to an FSK method is therefore provided. In this case, data is received and the error rate (BER, Bit He ^¬ ror rate) measured the received data. At the same time, the field strength (RSSI value) of the received data is measured. The error rate and the field strength are evaluated. Depending on the evaluation of the error rate and the field strength, the frequency swing of the FSK method is used, which is used for the wireless transmission of the data in order to optimize the transmission behavior.

The frequency swing can be changed within a preset range.

The optimization of the Ubertragungsverhaltens can be done using a table that reflects the achievable range of Übertra ^¬ supply depending on the set frequency deviation.

In the event that the evaluation shows a low field strength and at the same time a low error rate, the fre- quenzhub can be optimized for maximum range using the table mentioned.

The transmission behavior can be optimized on the basis of a second table, which shows the achievable immunity to interference from the transmission depending on the frequency swing set.

In the event that the evaluation shows a high field strength and at the same time a high error rate, the frequency swing can be optimized for maximum immunity to interference using the second table mentioned.

The transmission can take place according to the DECT standard.

The optimum frequency swing can be chosen smaller for a maximum range than the frequency swing for maximum interference immunity.

According to the present invention, a device for wireless transmission of data according to an FSK method, such as is used according to the DECT standard, is further provided. The device has a receiver and a first measuring device for the error rate (BER, bit error rate) of the received data. Furthermore, a second measuring device for the field strength during the reception of the data is provided. An evaluation unit processes the measured error rate and the measured field strength. A control unit is also provided to control the frequency swing of the FSK process, which is used for the wireless transmission of the data by a

Transmitter is used, depending on the measured error rate and the measured field strength to optimize the transmission behavior.

Further features and advantages of the present invention will become ^apparent from the following exemplary explanation of an embodiment. example and with reference to the accompanying drawings, in which:

1 shows the structure of a device according to the invention for the wireless transmission of data in accordance with an FSK method,

2 shows the bit error rate as a function of the signal-to-noise ratio (SNR) according to a simulation,

3 shows the bit error rate of a wireless transmission as a function of the signal-to-interference ratio for a frequency swing of the interference signal of 340 kHz,

4 shows the bit error rate as a function of the signal

Interference ratio for a frequency swing of the interference signal of 288 kHz,

FIGS. 5a to 5d, the various spectra of GFSK signals for the measurement of changes shown in FIGS. 2 to 4 were ^¬ applies, and

Fig. 6 shows the impulse response g (t) of a GFSK filter.

The present invention is generally at FSK method application and is described, for example, using a GFSK procedural ^¬ proceedings.

According to the present invention, the phenomenon is excluded use is that depending on the set modulation index (BT) value FSK method, for example the GFSK method a different system behavior of drahtlo ^¬ sen transmission, for example with respect to the Grenzempfind ^¬ friendliness (range) or immunity. If the greatest possible range is sought for the transmission, the frequency deviation to be selected for this differs from the frequency deviation from one to the maximum Immunity optimized system. Therefore, according to the present invention, after evaluating the bit error rate (BER, bit error rate) and the corresponding RSSI (radio signal strength indicator, reception field strength) value, the system is adapted to different ones by appropriately setting the frequency swing (corresponding to a modulation index) Scenarios.

As can be seen in FIG. 1, digitally modulated signals can be received by an antenna 1 and sent to a receiver (receiver) 3. On the one hand, the receiver 3 transmits the received data (RX data) 7 and on the other hand the RSSI value 8 to an evaluation unit 6. More precisely, the receiver 3 transmits the received data 7 and the RSSI value 8 to a control unit 13 in the evaluation unit 6 .

In addition to the control unit 13, the evaluation unit 6 has a first table 12 and a second table 14, which are each connected to the control unit 13. The control inputs 13 integrated in the evaluation unit 6 controls the one hand, a local oscillator (synthesizer) 4 at which the Mobilfunkge ^¬ Raets 16 is connected to the receiver (receiver) 3, and a transmitter (transmitter). 5 On the other hand, the control unit 13 of the evaluation unit 6 controls the frequency deviation used by the transmitter 5. The evaluation unit 6 also transmits data 11 to be transmitted to the transmitter 5, which transmits this data (TX data) 11 with that specified by the control unit 13 10 duliert frequency deviation of the frequency of the local oscillator (synthesizer) 4 mo ^¬ and then passes to an antenna 2 for transmission over a wireless transmission 15th

The control unit 13 in the evaluation unit 6 thus receives the received data 7 and the RSSI value 8 from the receiver 3. The bit error rate of the received data 7 and the received field strength (RSSI value) measured by the receiver 3 are evaluated in the control unit 13, so that the following scenarios can be distinguished: Case a)

No or little influence by interference signals: the received data 7 have small bit error rates with a strong reception field at the same time.

In this case, the control unit 13 can control the frequency swing of the transmitter 5 for maximum range.

Case b)

Interference from other signals, such as DECT signals: In this case, relatively high bit error rates occur at relatively high reception field strengths. In this case, the control unit 13 of the evaluation unit 6 controls the frequency swing of the transmitter 5 for maximum immunity to interference.

To optimize the system for maximum range or maximum immunity to interference, the first table 12 and the second table 14 m of the evaluation unit 6 are provided. In the first table 12, the maximum achievable range of the wireless transmission 15 is specified as a function of the frequency swing that can be selected within a permitted range. The second table 14 shows the maximum immunity to interference as a function of the frequency swing.

Tables 12 and 14 are created, for example, before the actual transmission by analyzing the system behavior of the wireless transmission 15 by simulations with different frequency hubs. 2, the bit error rate was calculated as a function of the signal-to-noise ratio. The curves shown in FIG. 2 represent the following key data:

Frequency deviation of 202 kHz: lower limit of the allowed

Standards, Frequency swing of 288 kHz: nominal value,

Frequency sweep of 340 kHz: frequency sweep, as is fixed in some devices according to the prior art,

Frequency swing of 403 kHz: Upper permitted limit of the DECT standard.

By evaluating the diagram shown in FIG. 2, the conclusion is reached that in a system optimized for maximum range, a frequency deviation of 340 kHz has to be set, which corresponds to the above-mentioned case a).

Further simulations characterize the immunity to interference of a DECT connection (case b)). According to the results shown in Fig. 3 and 4, calculations can be seen that in this scenario continues the coexistence of different Syste ^¬ me must be considered. In the case of a disturbance signal with a frequency shift of 340 kHz (for example neighboring conventional DECT systems), the optimum frequency swing, as is to be used in the present invention, is also 340 kHz (see FIG. 3). According to the present invention, the nominal frequency deviation of 288 kHz is set in the case of co-channel interference in all systems (FIG. 4).

5a to 5d show the test signals used in the simulations.

According to the present invention, the system can be adapted to different scenarios by evaluating the bit error rate and the corresponding RSSI value by appropriately setting the frequency swing of an FSK transmission.

Claims

claims

1. A method for the wireless transmission of data according to an FSK method, comprising the following steps:

- reception (1, 3) of data,

Measurement (6) of the error rate of the received data,

- measurement (3) of the field strength (8) upon receipt of the data,

- Evaluation (6) of the error rate and the field strength, - Setting (5, 6, 10) of the frequency swing of the FSK method, which is used for wireless transmission (15) of the data, depending on the evaluation (12) of the error rate and Field strength to optimize the transmission behavior (13).

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the frequency deviation is changed within a preset range.

3. The method according to any one of the preceding claims, characterized in that the optimization of the transmission behavior will be based on a table (12), the transmission, the attainable range of the excess (15) dergibt depending on the set frequency deviation as ^¬.

4. The method according to claim 3, characterized in that large in the case that the evaluation (6) a small field strength and resulting in a low error rate at the same time, the frequency deviation on the basis of the table (12) to a maximum range ^¬ towards optimizing (13) .

5. The method according to any one of the preceding claims, that the transmission behavior is optimized on the basis of a second table (14) which shows the achievable immunity to interference of the transmission (15) depending on the frequency swing set.

6. The method of claim 5, d a d u r c h g e k e n n z e i c h n e t that in the event that the evaluation (6) results in a high field strength and a high error rate, the frequency swing is optimized (13) for maximum immunity to interference using the second table (14).

7. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the transmission (15) takes place according to the DECT standard.

8. The method according to any one of the preceding claims, characterized in that the optimum frequency swing for a maximum range is selected ge ^¬ ringer than the frequency swing for maximum noise immunity.

9. Device for the wireless transmission of data according to an FSK method, comprising:

- a receiver (3),

- a measuring device (6) for the error rate of received data,

a second measuring device (3) for the field strength (8) when receiving the data,

- an evaluation unit (6) for the measured error rate and the measured field strength, - A control unit (13) for setting the frequency swing of the FSK method, which is used for wireless transmission (15) of the data by a transmitter (5), depending on the measured error rate and the measured field strength, in order to optimize the transmission behavior.

10. Apparatus according to claim 9, d a d u r c h g e k e n n z e i c h n e t that the frequency deviation is variable within a preset range.

11. Device according to one of claims 9 or 10, so that a table (12) is provided in the evaluation unit (6) for optimizing the transmission behavior, which reproduces the achievable range of the transmission (15) depending on the set frequency deviation.

12. Apparatus according to claim 11, characterized in that optimized for the case where the evaluation unit (6) has a low field strength and at the same ermit a low error rate telt ^¬, the frequency deviation on the basis of the table (12) to a maxi ^¬ male reach out (13 ) becomes.

13. An apparatus according to any one of claims to 12, characterized 9, wherein a second table (14) is provided for the optimization of the transmission behavior in the Auswer ^¬ teeinheit (6), the pending set the achievable noise immunity of the transmission (15) from ^¬ from the Frequency deviation reproduces.

14. Apparatus according to claim 13, characterized in that in the event that the evaluation unit (6) determines a high field strength and at the same time a high error rate, the frequency deviation is optimized (13) for maximum immunity to interference on the basis of the second table (14).

15. Device according to one of claims 9 to 14, d a d u r c h g e k e n n z e i c h n e t that the optimal frequency deviation for a maximum range is chosen to be less than the frequency deviation for maximum interference immunity.

16. The device as claimed in one of claims 9 to 15, that it is designed for a transmission (15) in accordance with the DECT standard.