WO2000019674A1

WO2000019674A1 - Conversion of gfsk-modulated signals into qpsk-modulated signals

Info

Publication number: WO2000019674A1
Application number: PCT/DE1999/003057
Authority: WO
Inventors: Uwe Sydon; Jürgen KOCKMANN
Original assignee: Siemens Aktiengesellschaft
Priority date: 1998-09-25
Filing date: 1999-09-23
Publication date: 2000-04-06
Also published as: EP1116366A1

Abstract

According to the invention, a DECT controller is used for transmitting using a QPSK modulation method. An adapter module (23) is provided to this end, and converts the GFSK-modulated data that are output by the DECT controller (22) into QPSK-modulated data for sending. Said adapter module (23) can be e.g. an ASIC. The adapter module (23) can also control an HF-module (4, 5) of the DECT controller (22) in such a way that the data is modulated to a carrier frequency in the 2.4 GHz-ISM band. This makes it possible to produce a system for the 2.4 GHz-ISM band that is able to meet the standards for this band (FCC part 15) by using a QPSK modulation and by changing the carrier frequency after a set period of time (frequency hopping spread spectrum system). At the same time, it is possible to use a usual DECT controller, economically.

Description

description

TRANSMODULATION BETWEEN GFSK AND QPSK MODULATED SIGNALS

The present invention relates to a mobile radio device and a method for wireless transmission of QPSK-modulated data using a DECT baseband controller.

To replace the existing various analog and digital standards in Europe, the DECT standard was adopted in the early 1990s. It is the first common European standard for cordless telecommunications. A DECT network is a microcellular, digital mobile network for high subscriber densities. It is primarily designed for use in buildings. However, the DECT standard can also be used outdoors. The capacity of the DECT network of around 10,000 subscribers per square kilometer makes the cordless standard an ideal access technology for network operators. According to the DECT standard, both the transmission of voice and the transmission of data signals are possible. This means that cordless data networks can also be set up on a DECT basis.

The DECT standard will be explained in more detail below with reference to FIG. 2. Under the name DECT (Digital European Cordless Communication), a digital, cordless telecommunications system for ranges below 300 m has been standardized for Europe. This system is therefore suitable in connection with the switching function of a telecommunications system for mobile telephone and data traffic in an office building or on a company site. The DECT functions supplement a telecommunications system and thus make it the base station FS of the cordless telecommunications system. Digital radio connections can be made on up to 120 channels. conditions between the base station FS and the maximum of 120 mobile stations MS are established, monitored and controlled.

The frequency range is 1.88 GHz to 1.9 GHz on a maximum of ten different carrier frequencies (carriers). This frequency multiplex method is called FDMA (Frequency Division Multiple Access).

In the DECT standard, the data is modulated according to the GMSK (Gauss Minimum Shift Keying) method.

On each of the twelve carrier frequencies, twelve channels are successively transmitted using the time division multiplex method TDMA (Time Division Multiple Access). This results in a total of 120 channels for cordless telecommunications according to the DECT standard with ten carrier frequencies and twelve channels per carrier frequency. Because e.g. B. a channel is required for each voice connection, there are 120 connections to a maximum of 120 mobile stations MS. Alternating operation (duplex, TTD) is used on the carriers. After the twelve channels (channels 1-12) have been transmitted, the system switches to reception and the twelve channels (channels 13-24) are received in the opposite direction.

A time-division multiplex frame thus consists of 24 channels (see

Fig. 2). Channel 1 to channel 12 are transmitted from the base station FS to the mobile stations MS, while channel 13 to channel 24 are transmitted in the opposite direction from the mobile stations MS to the base station FS. The frame duration is 10 ms. The duration of a channel (time slot, slot) is 417 μs. During this time, 320 bit information (e.g. voice) and 100 bit control data (synchronization, signaling and error control) are transmitted. The useful bit rate for a participant (channel) results from the 320 bit information within 10 ms. It is thus 32 kilobits per second. In the DECT standard, each time slot contains, in addition to the 320 information bits mentioned above, a further 104 bits required for signal transmission and 56 bits of a guard field, so that each time slot contains a total of 480 bits.

For countries outside Europe, the DECT standard may have to be modified and adapted to local conditions. For example in the USA. the transmission cannot take place in the normal DECT range between 1.88 and 1.90 GHz, but rather the generally accessible one

2.4 GHz ISM band (Industrial, Scientific, Medical) available. Furthermore, changes would have to be made to adapt to national regulations, such as the American regulation FCC part 15. The American regulation mentioned describes the transmission methods permitted for the air interface, transmission powers and the available bandwidth. The use of DECT in this band is not permitted because the bandwidth of DECT (1.2 MHz) exceeds the permitted bandwidth of 1.0 MHz.

In addition, the FCC part 15 stipulates how much transmission power can be transmitted on a certain channel during a certain period of time. This requirement could also not be met by directly adopting the DECT standard.

One way of realizing an air interface that meets the above-mentioned regulations is to use a higher-quality modulation method, e.g. a QPSK-based system in which the carrier frequency is changed at predetermined time intervals (frequency hopping spread spectrum). The use of the higher-quality modulation method halves the bandwidth required, for example when using a QPSK system.

A problem arises if the existing DECT standard for the cost-effective implementation of the air interface dard designed controller ICs should be used, as is known, according to the DECT standard, the data is modulated according to a GFSK (Gauss Frequency Shift Keying) system on the carrier frequency.

The object of the present invention is therefore to provide a mobile radio device and a method which make it possible to create a QPSK air interface using an existing DECT controller.

This object is solved by the features of the independent claims. The dependent claims further develop the central idea of the invention in a particularly advantageous manner.

According to the invention, a mobile radio device for wireless transmission of QPSK data is therefore provided. The mobile radio device has a controller which is designed and developed for the transmission of GFSK-modulated data, for example in accordance with the DECT standard. According to the invention, a ballast module is provided which converts GFSK-modulated data output by the controller into QPSK-modulated data to be transmitted or converts the received QPSK-modulated data into GFSK-modulated data and sends it to the controller.

The ballast module must be designed so that after the conversion of the QPSK-modulated data into GFSK-modulated data according to the DECT standard, the QPSK-modulated data is synchronized, which can be done by a synchronization signal from the ballast module to the controller.

The ballast module can control an RF module in such a way that the data is modulated onto a carrier frequency FX that lies outside the DECT band. The carrier frequency can be, for example, in a 2.4 GHz band (ISM band). The ballast module can be implemented by an ASIC.

The ballast module can convert GFSK-modulated data into π / 4-QPSK-modulated data or convert received π / 4-QPSK-modulated data into GFSK-modulated data.

According to the invention, a method for wireless transmission of QPSK-modulated data by means of a controller is also provided, which is designed for the transmission of GFSK-modulated data, for example in accordance with the DECT standard. A ballast module converts GFSK-modulated data output by the controller into QPSK-modulated data to be transmitted or converts received QPSK-modulated data into GFSK-modulated data and transfers it to the controller.

According to the invention, the carrier frequency fx can be changed after a predetermined time period, the predetermined time period being a time slot or a frame (or a multiple thereof) of the DECT time frame.

The invention will now be explained in more detail using an exemplary embodiment and with reference to the accompanying drawings. Show it:

Fig. 1 shows an arrangement for digital

Radio transmission of data,

2 shows a schematic representation of the known DECT standard,

3 is a phase state diagram of the QPSK modulation and

4 shows a state transition diagram of the π / 4 DQPSK modulation, 5 shows a detailed illustration of a section of a mobile radio device according to the invention, and

FIG. 6 shows a further development of the device from FIG. 5, in which a ballast module sends a synchronization signal to the controller.

An arrangement for digital radio transmission of data is provided in FIG. 1. A base station 1 is connected to the fixed network by means of a terminal line 10. The

Base station 1 has an RF module 4, by means of which data can be transmitted or received by means of an antenna 6.

By means of the antenna 6, radio transmission to a mobile station 2 can take place via a radio transmission link 8 or radio transmission to a mobile station (cordless telephone) 3 via a second radio transmission link 9. All of the mobile stations shown in FIG. 1 have the same structure, so that a more detailed explanation is only to be given on the basis of the mobile station 2 shown.

As can be seen in FIG. 1, this mobile station 2 has an antenna 7 for receiving or transmitting data from or to the base station 1. An RF module 5 is provided in the mobile station 2, which essentially corresponds to the RF module 4 used in the base station 1.

In base station 1, 20 denotes a modulator, the exact function of which is explained below. In the mobile station 2, 21 denotes a demodulator, which performs the inverse function of that of the modulator 20. It should also be pointed out that the base station 1 and each mobile station 2, 3 naturally have a modulator and a demodulator, as is known for radio transmission systems. As already mentioned at the beginning, the present invention is intended to provide an air interface possibility in order to adapt the known DECT standard to the regulations which apply to the American ISM band. The problem arises here that the base bandwidth of 1.2 MHz, which is required according to the DECT standard to provide the bit rate of 1.152 megabits per second, the maximum base bandwidth prescribed by the American regulation FCC part 15 of Exceeds 1 MHz. A higher quality modulation method is therefore used. For the purposes of the present description, a higher-value modulation method (in comparison to the GMSK modulation method of the DECT standard) is a modulation method in which there are more than two (ie 4, 8, ...) discrete carrier states and thus at least two bits combined into one symbol and transmitted together as one symbol in one step.

A higher-order modulation method in this sense is, for example, the quadrature phase shift keying QPSK (4 PSK), which is shown in FIG. 3. According to the QPSK modulation method, the input data are provided as bipolar pulses, i. H. the logical 1 is represented by + 1 and the logical 0 by -1. With serial / parallel conversion, the serial data stream is initially divided into bits of even and odd positions. After this conversion, two data signals are present, each with half the data rate of the original signal.

Another example of a higher-value modulation method is the π / 4-DQPSK modulation method shown in FIG. 4. The aim of this modulation method is to avoid phase jumps of 180 °, which lead to amplitude drops. For this purpose, two bits are combined to form a symbol and cause a phase jump compared to the last transmission phase by ± 45 ° or ± 135 °, as shown in the state transition diagram in FIG. 4. The 8 PSK or 16 PSK modulation methods, in which there are 8 or 16 discrete carrier states and thus 3 or 4 bits are combined and transmitted to form a symbol, should be mentioned as further examples of higher-value modulation methods.

All digital modulation methods have in common that with increasing m, d. H. with an increasing number of carrier states, and with a constant bit rate, the transmission bandwidth becomes smaller, since N = ld (m) bits are always combined to form a symbol and transmitted as a common symbol in a single step. In the present case, this means that the bit rate of the DECT standard can be maintained by the higher-value modulation method and at the same time the transmission base bandwidth becomes smaller than the maximum value prescribed by FCC part 15. By combining at least two bits, the base bandwidth can be halved, for example, while the bit rate remains the same.

Components developed and produced for the DECT standard, such as the DECT baseband controller, can continue to be used in a cost-effective manner since the time slot and frame structure of the transmission are not changed compared to the DECT standard.

In the following table, parameters of the air interface according to the invention are summarized once again, which have proven to be particularly advantageous.

The distribution of cordless telephones according to the DECT standard is currently essentially restricted to European countries, since the corresponding frequencies have been released here. For an introduction to other countries, such as the U.S.A., the above-mentioned air interface according to the 2.4 GHz ISM band is required. In this case, of course, some parameters have to be adjusted as explained above with regard to the rules applicable to this volume (fcc part 15). One way of doing this was described above. For a cost-effective implementation of such a system, the use of existing DECT controllers is advantageous, since the large number of items enables economic advantages to be achieved. Even if, as explained above, the time slot and frame structure of the transmission does not have to be changed compared to the DECT standard, it should be noted, however, that according to the DECT standard there is no need to change, but it should be noted that according to the DECT A GFSK modulation method is used as standard and there are no DECT systems that use QPSK-based modulation methods.

According to the present invention, the functionality of a suitable module is therefore to be defined which enables signals from an existing DECT controller to be to transfer based systems (e.g. PWT). This module can be implemented, for example, in the form of an ASIC or in any other form. This module must implement the following functions:

- Implementation of GFSK modulation according to QPSK (e.g. π / 4-QPSK) - Modulation in the case of transmission,

- Implementation of QPSK (e.g. π / 4-QPSK) modulation after GFSK modulation in the case of reception, - Ensure synchronization in the "GFSK level" after the conversion from QPSK modulation to GFSK modulation,

Control of the RF module with a corresponding frequency information, d. H. - Implementation of the frequency control of a DECT controller to the requirements of the corresponding air interface and

Generation of the frequency information required by a DECT controller from the actual circumstances.

The invention will now be explained in detail with reference to FIG. 5. 5 shows a mobile radio device which can be a base station or a mobile station. As usual with a transmission according to the DECT standard, a DECT baseband controller 22 is provided. This baseband controller 22 has, among other things, a modulator / demodulator. According to the invention, however, an additional ballast module 23 is provided, which can be implemented, for example, by an ASIC.

As can be seen from FIG. 5, according to the invention the DECT baseband controller 22 transmits GFSK-modulated data to the ASIC 23 in the transmission state. The ASIC 23 converts the GFSK-modulated data into QPSK-modulated data and transmits it to the high-frequency module 4, 5. The high-frequency module 4, 5 then outputs this QPSK-modulated data to the antenna 6, 7. The base- band controller 22 is also connected to the ballast module 23 by means of a control line 24, which is used for setting the DECT carrier.

In the event that the transmission is to take place in a frequency band other than the DECT, the ASIC 23 continues to transmit carrier frequency information f _x by means of a control line 25 to the high-frequency module 4, 5 in order to control it to the corresponding carrier frequency. For example, transmission in the ISM-2.4 GHz band can thus take place.

When receiving QPSK-modulated data, which the high-frequency module 4, 5 transmits to the ASIC 23 and which can also contain a synchronization word in addition to the user data, the ASIC 23 continues to provide synchronization information together with the actual user data GFSK-modulated to the DECT base station. band controller 22.

As can be seen from FIG. 6, in the transmission state the GFSK modulator / demodulator 20, 21 of the DECT baseband controller 22 outputs GFSK-modulated data to the ASIC 23. The ASIC 23 converts the GFSK-modulated data into QPSK-modulated data and transmits it them to the high-frequency module 4, 5 of the DECT baseband controller. The high-frequency module 4, 5 then outputs this QPSK-modulated data to the antenna 6, 7.

In the event that the transmission is to take place in a frequency band other than the DECT, the ASIC 23 continues to transmit carrier frequency information f _x to the high-frequency module 4, 5 in order to drive it to the corresponding carrier frequency. For example, transmission in the ISM 2.4 GHz band can thus take place.

When QPSK-modulated data is received, which the high-frequency module 4, 5 transmits to the ASIC 23, the ASIC 23 continues to provide synchronization information to the QPSK modulator / demodulator 20, 21 of the DECT baseband controller 22. In the arrangement shown, the problem may arise that the synchronization method as used in the DECT baseband controller 22 must continue to function, ie the DECT controller must now synchronize itself with the data stream converted by the ballast module 23. Please note that the QPSK-modulated data is sent / received at half the data rate, since a QPSK symbol corresponds to exactly 2 DECT bits. This means that some DECT bits can be lost on reception that are generated by the

DECT baseband controllers 22 are required for synchronization.

According to the present invention, as shown in FIG. 6, the ballast module 23, which implements the conversion between the QPSK and the GFSK modulation method, transmits the DECT baseband controller 22 in its synchronized state permanently to a DECT synchronization signal (1, 0 - Episode). The DECT baseband controller 22 can thus synchronize with this sequence of the DECT synchronization signal from the ballast module 23.

The prerequisite for this is that the ballast module 23 can synchronize with the received QPSK signal (symbol synchronization). If the timing of the synchronization changes, as detected by the ballast module 23 on the basis of the received QPSK signal, the timing of the DECT synchronization signal which the ballast module 23 outputs to the DECT baseband controller 22 is adjusted accordingly. So there is only the synchronization word

(DECT synchronization signal) has to be shifted slightly in time, rapid synchronization can take place in the "DECT level".

According to the present invention, an inexpensive module can thus be created using a DECT baseband controller in accordance with a QPSK modulation method. Reference list

1 base station

2 mobile station (cordless telephone) 3 mobile station

RF module base station

Antenna base station

Antenna mobile station 8 first radio transmission link

9 second radio transmission link

10 terminal line

20 modulator

21 demodulator

22 baseband controllers

23 ASIC module

24 control line

25 control line

Zx: time slots f _x : carrier frequency

Claims

claims

1. Mobile radio device for wireless transmission of QPSK-modulated data, comprising - a controller (22) which is designed for a transmission of GFSK-modulated data, and

- A ballast module (23) which converts GFSK-modulated data output by the controller (22) into QPSK-modulated data to be transmitted or converts the received, QPSK-modulated data into GFSK-modulated data and gives it to the controller (23) .

2. Mobile radio device according to 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 ballast module (23) in the synchronized state outputs a synchronization signal to the controller (22).

3. Mobile radio device according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n t that the controller is a DECT controller (22).

4. Mobile device according to one of claims 1, 2 or 3, characterized in that the ballast module (23) synchronizes to a received, QPSK-modulated signal.

5. Mobile device according to claim 4, so that the ballast module (23) shifts the synchronization signal for the controller (22) depending on its synchronization with the QPSK-modulated signal.

6. Mobile radio device according to one of the preceding claims, characterized in that the ballast module (23) controls an RF module (4, 5) in such a way that the data are modulated onto a carrier frequency fx which lies outside the DECT band.

7. Mobile radio device according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the carrier frequency fx is in a 2.4 GHz band.

8. Mobile radio device according to one of the preceding claims, that the control module is an ASIC (23).

9. Mobile radio device according to one of the preceding claims, that the control module (23) converts GFSK-modulated data into Pi / 4-QPSK-modulated data or converts received Pi / 4-QPSK-modulated data into GFSK-modulated data.

10. A method for the wireless transmission of QPSK-modulated data by means of a controller (22) which is designed for the transmission of GFSK-modulated data, a ballast module (23) output by the controller (22) to send out GFSK-modulated data Converts QPSK-modulated data or converts received, QPSK-modulated data into GFSK-modulated data and sends them to the controller (23).

11. The method for wireless transmission of QPSK-modulated data according to claim 10, d a d u r c h g e k e n n z e i c h n e t that the ballast module (23) in the synchronized state

Outputs synchronization signal to the controller (22).

12. The method of claim 11, d a d u r c h g e k e n n z e i c h n e t that the controller is a DECT controller (22).

13. The method according to any one of claims 11 or 12, characterized in that the ballast module (23) from a received, QPSK- modulated signal synchronizes.

14. The method according to claim 13, so that the ballast module (23) shifts the synchronization signal for the controller (22) in time depending on its synchronization with the QPSK-modulated signal.

15. The method according to any one of claims 10 to 14, so that the ballast module (23) controls an RF module (4, 5) in such a way that the data are modulated onto a carrier frequency fx that lies outside the DECT band.

16. The method according to claim 15, so that the carrier frequency fx is in a 2.4 GHz band.

17. The method according to any one of claims 10 to 16, characterized in that the ballast module (23) converts GFSK-modulated data into Pi / 4-QPSK-modulated data or received Pi / 4-QPSK-modulated data into GFSK-modulated data .

18. The method according to any one of claims 10 to 17, so that the carrier frequency fx is changed after a predetermined period of time.

19. The method according to claim 18, so that the carrier frequency fx is changed after a time slot (Zx) or a frame of the transmission.