Point-to-multipoint radio transmission system

Details Point-to-multipoint radio transmission system Point-to-multipoint radio transmission system

1999-02-11

2001-02-06

Patel, Ajit (Department: 2738)

Multiplex communications

Communication over free space

Combining or distributing information via frequency channels

C370S281000, C370S344000

Reexamination Certificate

active

06185202

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a point-to-multipoint radio transmission system including a central station and multiple subscriber stations, the transmission channels being apportionable as necessary between the central station and the subscriber stations.
BACKGROUND INFORMATION
Radio transmission systems, whether terrestrial radio relay systems or satellite transmission systems, make it possible to install new radio connections, or expand existing ones, very quickly. In such radio transmission systems, the frequency spectrum available should be utilized as optimally as possible. This requirement can be met with point-to-multipoint radio transmission systems (radio relay, satellite radio).
A point-to-multipoint radio relay system is described in “Mikrowellenmagazin” Vol. 10, Number 6, 1984, pp. 629, 630. According to this, publication utilization of the frequency band of the available radio channel can be improved by assigning the necessary frequency band only as necessary. Communication between the central station and the individual subscriber stations takes place either by either frequency-divided multiple access (FDMA) or time-divided multiple access (TDMA), the frequency channels or time slots being apportioned to the subscribers as required.
In a point-to-multipoint radio relay system as described in German Patent Application No. 44 26 183, the transmission capacity is adapted flexibly to subscriber requirements in that the bandwidth of the individual transmission channels is adjusted to the data transmission rate requested in each case by the individual subscribers. Provision is also made for variable setting of the modulation type or modulation depth (for example, n-PSK with n=2 to 16, or M-QAM with M=4 to 256) on the individual transmission channels.
It is the object of the present invention to provide a point-to-multipoint radio transmission system with which transmission capacities can be flexibly allocated and adapted to the on-line subscriber stations without interfering with or interrupting existing radio connections.
SUMMARY OF THE INVENTION
The stated object is achieved by the features of claim
1
, by the fact that a control device is present which, in the event of a change in the transmission channels, adjusts one or more transmission parameters in modems with which both the central station and each subscriber station are equipped, in such a way that the bandwidth of the available radio channel is optimally utilized. In this context, each modem has two transmitting channels and two receiving channels, and signal transmission in the modem takes place via only one of the two transmitting or receiving channels. In the event of a change in the transmission channels, the adjustment to the new transmission parameters takes place in the transmitting or receiving channel which is not in operation at the time, while signal transmission continues on the other transmitting or receiving channel. Once acquisition of the new transmission parameters is complete, operation switches over to the transmitting or receiving channel which was not previously in operation. A first frequency splitter is provided which divides the entire frequency band available for the emission of signals into at least two subbands, the signals of the transmitting channels being selectably apportionable to the subbands. Also provided is a second frequency splitter which divides the entire frequency band available for received signals into at least two subbands, the signals of the subbands being selectably apportionable to the receiving channels.
The above-described features make it possible, in a point-to-multipoint radio transmission system, to adapt the available radio channel very flexibly to the necessary transmission channels of the individual subscribers, with no need to interfere with or interrupt radio connections. All transmission parameters can be controlled, with the goal of both efficiently utilizing the radio channel and optimizing signal transmission quality. Use of the digital frequency splitters, whose subbands can selectably be assigned to the transmitting or receiving channels, makes possible a very flexible distribution of the transmitting and receiving channels. In addition, the digital frequency splitter can reduce or increase (for example, halve or double) its input signal sampling frequency so that subsequent interpolators or decimators need to implement lower interpolation or decimation factors, thus decreasing the circuit outlay.


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