Abstract:
A data transmission device is described which may use multiple data transmission technologies and/or multiple data transmission parameters of one or more data transmission technologies, having at least one transmitting device and one receiving device which can communicate with one another over at least one data transmission channel. A determination device for determining the transmission properties of the data transmission channel(s) for multiple data transmission technologies and/or multiple data transmission parameters of one or more data transmission technologies, and a selector device for selecting a certain data transmission technology having certain data transmission parameters according to the result of the determination, are additionally provided so as to be able to accommodate different transmission properties.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a data transmission device which may use multiple data transmission technologies and/or multiple data transmission parameters of one or more data transmission technologies, having at least one transmitting device and one receiving device which can communicate with one another over at least one data transmission channel. The present invention also relates to a corresponding data transmission method. 
   BACKGROUND INFORMATION 
   Although the present invention can be used with all desired data transmission technologies, it is explained here together with the problems on which it is based from the standpoint of mobile wireless technology. 
   There are various conventional technologies for multichannel wireless transmission, in particular TDMA (time division multiple access), e.g., GSM (global system for mobile telecommunications) or UMTS (universal mobile telecommunication system), FDMA (frequency division multiple access), e.g., DECT (digital enhanced telecommunication), GSM (global system for mobile telecommunications), DAB (digital audio broadcasting) and CDMA (code division multiple access) (IS95, UMTS). 
   Problematic interference which can occur with these different technologies is usually handled in different ways, if at all. In particular, conventional methods include elimination of intersymbol interference (ISI), elimination of multiple access interference (MAI), elimination of interference in the receiver, e.g., by equalizers or multiuser methods or joint detection methods, as well as elimination in the sender by pre-rake or joint preliminary equalization. See, for example, K. D. Kammeyer, “Nachrichtenübertragung [Transmission of Communications],” 2 nd  edition,  Information Technology Series , Teubner, Stuttgart, 1996, and A. Klein, G. K. Kaleh and P. W. Baier, “Zero Forcing and Minimum Mean-Square-Error Equalization for Multiuser Detection in Code-Division Multiple-Access Channels,”  IEEE Trans. Vehic. Tech ., vol. 45 (1996), 276–287 and R. Esmailzadeh and M. Nakagawa, “Pre-Rake Diversity Combination for Direct Sequence Spread Spectrum Mobile Communications Systems,”  IEICE Trans. Comm ., vol. E76-B (1993), 1008–1015. 
   In addition, different parameters are generally used under different transmission conditions, e.g., in the UMTS TDD mode, where different types of bursts are used, depending on the maximum channel delay. In this regard, see, the example, the UMTS-L1 expert group: “UTRA Physical Layer Description, TDD parts, V 0.2.0.” 
   One disadvantage of the conventional approaches is that a transmission technology having a given set of parameters is more advantageous than another transmission technology only under certain transmission conditions or with certain transmission properties of the data transmission channel. 
   Therefore, it may occur that an unnecessarily low transmission quality prevails under certain transmission conditions or there may be an unnecessarily great dependence of transmission quality on transmission conditions. 
   It would thus be desirable to create a data transmission system which can always guarantee optimum transmission quality, regardless of whether data transmission conditions are variable or constant. 
   SUMMARY 
   In accordance with an example embodiment of the present invention, a data transmission device is provided in which it is possible to accommodate different transmission properties. 
   In other words, it is possible to improve the data transmission under variable transmission conditions or to have data transmission quality be largely independent of transmission conditions. Assuming uniform transmission conditions, the resulting transmission quality will be either the same or better. 
   In accordance with the example embodiment, a determination device may be provided for determining the transmission properties of the data transmission channel(s) for multiple data transmission technologies and/or multiple data transmission parameters of one or more data transmission technologies and to provide a selector device for selecting a certain data transmission technology having certain data transmission parameters according to the result of the determination. 
   According to one example embodiment, a selector device may be provided in the transmitting device. 
   According to another example embodiment, the selector device may be provided in the receiving device. 
   According to another example embodiment, the data transmission channel is a wireless channel. 
   According to another example embodiment, the determination device is designed to determine the rate of change of the data transmission channel. 
   According to another example embodiment, the selector device makes the selection in such a way that interference in the receiving device is eliminated when the rate of change of the data transmission channel exceeds a predetermined value, and interference in the transmitting device is eliminated when the rate of change of the data transmission channel drops below a predetermined value. 
   According to another example embodiment, the determination device is designed to determine the maximum delay of the data transmission channel. 
   According to another example embodiment, the selector device makes the selection in such a way that it selects a transmission technology having a certain burst structure as a function of the maximum delay determined for the data transmission channel. 
   According to another example embodiment, the selector device makes the selection in such a way that it selects a transmission technology having a certain reference signal as a function of the maximum delay determined for the data transmission channel and/or the rate of change determined. 
   According to another example embodiment, the data transmission device is a mobile wireless device, for example, a mobile telephone. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematic diagram of a data transmission device according to a first example embodiment of the present invention. 
       FIG. 2  shows a schematic diagram of a data transmission device according to a second example embodiment of the present invention. 
       FIG. 3  shows a schematic diagram of a data transmission device according to a third example embodiment of the present invention. 
       FIG. 4  shows burst structures for estimating short and long channels. 
       FIG. 5  shows burst structures for estimating slowly and rapidly variable channels. 
   

   DETAILED DESCRIPTION 
   In the figures, the same reference numbers denote the same components or those having the same function. 
     FIG. 1  shows a schematic diagram of a data transmission device according to a first embodiment of the present invention. 
     FIG. 1  shows a transmitter  10 , a receiver  20 , a determination device  101  for determining the transmission properties of the transmission channel, a selector device  102  for selecting a certain data transmission technology having certain data transmission parameters as well as data messages D 1  and D 2 . 
   As shown in the diagram of  FIG. 1 , transmitter  10  first sends an inquiry to receiver  20 , requesting it to respond with various transmission technologies and parameters. Receiver  20  then sends data message D 1  to transmitter  10 , indicating which technologies and respective parameters are supported. 
   Determination device  101  then determines the transmission properties of the data transmission channel(s), and selector device  102  selects a certain data transmission technology having certain data transmission parameters according to the result of the determination. 
   Transmitter  10  notifies receiver  20  of the technology selected and the respective parameters in data message D 2 . 
     FIG. 2  shows a schematic diagram of a data transmission device as a second example embodiment of the present invention. 
   In addition to the determination device already introduced,  FIG. 2  also shows a determination device  201  for determining the transmission properties of the data transmission channel, a selector device  202  for selecting a certain data transmission technology having certain data transmission parameters as well as data messages D 1 ′ and D 2 ′. 
   As shown in the diagram in  FIG. 2 , receiver  20  first sends an inquiry to transmitter  10 , requesting it to respond with various transmission technologies and parameters. Transmitter  10  then sends data message D 2 ′ to receiver  20 , indicating which technologies and respective parameters are supported. 
   Determination device  201  then determines the transmission properties of the data transmission channel(s), and selector device  202  selects a certain data transmission technology having certain data transmission parameters according to the result of the determination. 
   Receiver  20  notifies transmitter  10  of the technology selected and the respective parameters in data message D 1 ′. 
     FIG. 3  shows a schematic diagram of a data transmission device according to a third example embodiment of the present invention. 
   The data transmission device shown in  FIG. 3  is a cellular wireless transmission system in which there is a transmission from a base station BS to multiple mobile stations MS in the forward link and transmission from multiple mobile stations MS to base station BS in the reverse link. Data streams of various users (mobile stations MS) are separated by code division multiple access (CDMA), for example. 
   In the TDD wireless transmission system shown here, the forward and reverse links are in the same frequency band. The forward and reverse links are separated in time by alternating transmission of transmission bursts in the forward and reverse links. 
   Interference in the forward link is eliminated optionally either in the transmitter or in the receiver, e.g., by eliminating interference in the transmitter through joint preliminary equalization or by eliminating interference in the receiver through joint detection as described in the article by Klein et al. (discussed above). 
   An example of selecting the technology for eliminating interference in the forward link would be to determine the rate of change of the wireless channel by comparing successive channel estimates in the base station and to eliminate interference through joint preliminary equalization in the transmitter if the rate of change is below a certain threshold, and to eliminate interference through joint detection in the receiver if the rate of change is above the threshold. 
     FIG. 3  shows transmitted data SD, received data ED, duplexers  30  and  30 ′, a modulator M 1  without preliminary equalization, a modulator M 2  having preliminary equalization, a modulator M, detectors  40 ,  40 ′ and  40 ″, a channel estimator  50  and  50 ′, a determination device  60  and a decision-making device or selector device  70 . Switches S and S′ can be switched by decision-making device  70 . 
   Base station BS has a transmission part having modulators M 2  and M 1  with and without preliminary equalization, respectively, and a reception part having detector  40  and channel estimator  50  as well as a decision-making part for making a decision between preliminary equalization and joint detection, composed of determination device  60  and decision-making device  70 . Selector switch S is used to select modulator M 1  or M 2 . Selector switch S is controlled by decision-making device  70 . 
   Mobile station MS has a transmission part having modulator M and a reception part having channel estimator  50 ′, as well as detector  40 ′ for joint detection and detector  40 ″ for simple detection. 
   Decision-making device  70  in base station BS selects either no preliminary equalization in base station BS and joint detection in mobile station MS, or preliminary equalization in base station BS and simple detection in mobile station MS, depending on the result obtained by channel estimator  50  and determination device  60 . The decision made by decision-making device  70  of base station BS is relayed to mobile station MS over the wireless interface. 
     FIG. 4  shows burst structures for estimating short and long channels. 
   Another example of a cellular wireless transmission system as an embodiment of the data transmission device according to the present invention has block-wise data transmission in a data burst structure as illustrated in  FIG. 4 , where DB 1  denotes a first data block, DB 2  is a second data block, and MA is a midamble connected between them, with time t running from left to right. 
   The reverse link is optionally one of two possible burst structures, namely a burst structure having long data blocks and a short midamble, and a burst structure having short data blocks and a long midamble. The choice of data burst structure is made on the basis of a determination of the maximum channel delay by the mobile station in the forward link. 
   The choice of burst structure for the reverse link is made according to the maximum delay determined, namely a long midamble MA with long delays and a short midamble with short delays. 
   The type of burst that has been transmitted is determined in the receiver on the basis of the signal received. This embodiment can be used in particular in UMTS TDD mode. 
     FIG. 5  shows burst structures for estimating slowly and rapidly variable channels. 
   In this embodiment in the form of a cellular wireless transmission system, there is block-wise data transmission in a data burst structure. Reference signal R or R 1  or R 2  and data block DB or DB 1  or DB 2  are sent in chronological order. One of two possible burst structures is optionally used, namely a long reference signal R and a long data block DB or multiple short reference signals R 1 , R 2  which are separated from one another by reduced data blocks DB 1 , DB 2 . 
   The burst structure is selected by determining the rate of change in the wireless channel with the help of the reference signal by a comparison of successive channel estimates in base station BS or in mobile station MS. 
   The burst having a long reference signal R is selected if the rate of change of the channel is below a certain threshold, and the burst having multiple short reference signals R 1 , R 2  is selected if the rate of change is above the threshold. 
   The type of burst that has been transmitted is determined in the receiver on the basis of the received signal. This embodiment can also be used for the UMTS standard. 
   Although the present invention is described above on the basis of example embodiments, it is not limited to these embodiments, but instead can be modified in various ways. 
   Another example embodiment includes a wireless transmission system which supports various standards such as transmission according to the GSM standard and transmission according to the USTM standard. 
   A determination of the rate of change of the wireless channel and the maximum channel delay could be provided here. The choice of the transmission technology and the respective transmission parameters could be made by optimizing the data transmission quality at the measured rate of change and the measured delays. 
   Contrary to the description of the above example embodiments, the transmitter or receiver can also notify its remote station, without being explicitly required to do so, regarding which transmission technologies and parameters it supports, e.g., directly after establishing the connection.