Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-04-27
2002-04-02
Olms, Douglas (Department: 2732)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C375S231000
Reexamination Certificate
active
06366569
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the telecommunications field. More specifically, the invention relates to a method and a configuration for transmitting data via a radio interface in a radio communications system, in particular in a mobile radio system.
In radio communications systems, messages (for example voice, image information, or other data) are transmitted using electromagnetic waves. The electromagnetic waves are thereby radiated at carrier frequencies which lie in the frequency band that is provided for the respective system. In the GSM (Global System for Mobile Communications), the carrier frequencies lie in the 900 MHz range. For future radio communications systems, for example the UMTS (Universal Mobile Telecommunication System) or other 3
rd
generation systems, frequencies in the approximately 2 GHz frequency band are provided.
The irradiated electromagnetic waves are attenuated owing to losses resulting from reflection, refraction and irradiation due to the curvature of the earth and the like. As a result, the reception power which is available at the receiving radio station drops. The attenuation is location-dependent and, in the case of moving radio stations, also time-dependent.
Between a transmitting and a receiving radio station there is a radio interface over which data is transmitted using the electromagnetic waves. In the GSM mobile radio system, subscriber separation is carried out using a time division multiplex method, the so-called TDMA (Time Division Multiple Access) method which is used in combination with a frequency division multiplex method FDMA (Frequency Division Multiple Access).
In the GSM mobile radio system as is known, inter alia, from J. Biala, “Mobilfunk und intelligente Netze” [Mobile Radio and Intelligent Networks], Vieweg Verlag [publishing house], 1995 in particular pages 80 and 269, and from P. Smolka “GSM-Funkschnittstelle—Elemente und Funktionen [GSM Radio Interface—Elements and Functions]” telekom praxis, No. 4/93, pp. 17-24, in particular
FIGS. 4 and 5
, a TDMA frame is divided into 8 timeslots. Data from communications links and/or signaling information is transmitted as radio blocks, so-called bursts, in the timeslots. Midambles with known symbols are transmitted within a radio block. These midambles can be used in the manner of training sequences for receive-end tuning of the radio station. The receiving radio station uses the midambles to estimate the channel pulse responses for various transmission channels. Because the transmission properties of the mobile radio channel are location-dependent and frequency-dependent, the receiving radio station can equalize the received signal using this training sequence.
The TDMA subscriber separation method used in the GSM mobile radio system has been developed and dimensioned for the transmission of information with a relatively low data rate. It also has a very restricted degree of flexibility when allocating data rates to a subscriber.
However, in future radio communications systems, and in particular third generation mobile radio systems, high data rates and individual, flexible allocation of transmitter capacities to communications links are desired. Furthermore, mixed operation of different services and data rates and asymmetry of the data rates and of the traffic volume such as, for example, the downlink and uplink (reverse and forward directions) in Internet applications are to be supported.
International PCT publication WO 97/08861 (see U.S. Pat. Nos. 5,768,269 and 5,793,759) discloses an configuration and a method for the bidirectional transmission of digital data over different transmission media. Here, data from a plurality of sources are subjected to a time division multiplex process in timeslots and to coding using orthogonal codes. The coded data are transmitted in frames between central and remote units, the frames being synchronized by means of a transmission interval without data.
European published patent application EP 0 767 557 A1 (see U.S. Pat. No. 5,838,672) discloses a time frame and timeslot structure based on a known TDMA subscriber separation method such as is used in the GSM mobile radio system described above. Here, a training sequence is embedded in a timeslot and surrounded by two data blocks.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method and a configuration for data transmission via a radio interface in a radio communications system which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind, and which enables a flexible and dynamically configurable time division multiplex structure for transmitting data in the downlink direction.
With the above and other objects in view there is provided, in accordance with the invention, a method of transmitting data over a radio interface in a mobile radio system, which comprises:
transmitting data of at least one communications link in a downlink direction from a base station to at least one radio station in radio blocks of a time division multiplex method organized in time frames;
periodically transmitting, within a time frame, training sequences and after a respective training sequence transmitting the radio block of at least one of the communications links, whereby the training sequences are transmitted with a constant transmission power higher than an average transmission power for the radio blocks.
In other words, the invention relates to a method and a base station for transmitting data in the downlink direction over a radio interface in a radio communications system. A base station transmits the data from at least one communications link in the downlink direction to a radio station in radio blocks in accordance with a time division multiplex method. Within a time frame, training sequences are transmitted in periodic fashion and after a respective training sequence the radio block of at least one of the communications links is transmitted. Here, the training sequences are transmitted with a constant transmission power which is higher than an average transmission power for the radio blocks.
This method according to the invention has the advantage that the times for the switching on and off of the transmitter and for the decay of the transmission channels are dispensed with, as a result of which the time component used for transmitting data can be increased. As a further advantage, this method permits the changes of the transmission properties on the radio link to be continuously detected by means of the radio station, and permits the radio station to carry out equalization of the received signals so that, for example, transmission of data is made possible even at higher speeds of the radio station which is embodied as a mobile station of a mobile radio system.
The fact that the training sequences at the transmitting base station end are transmitted with a constant transmission power which is greater than the average transmission power for the data enables the radio station to make precise channel estimations regarding the transmission properties independently of the location and of the power regulation for other radio stations whose data are transmitted in the same radio block or in other radio blocks between the training sequences. In addition, the higher transmission power results in an improvement of the average signal-to-noise ratio when the training sequences are received in the radio station.
In accordance with an added feature of the invention, the radio station interpolates and/or extrapolates the channel estimation from at least two training sequences. The interpolation and/or extrapolation is carried out here for all components of the multipath delay occurring during the transmission on the radio interface which can be resolved chronologically. This refinement has the advantage that the variation in the timing of the transmission properties over the radio blocks can be adjusted with the data intended for the radio station, in which case the e
Olms Douglas
Vanderpuye Ken
LandOfFree
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