Multiplex communications – Wide area network – Packet switching
Patent
1992-09-15
1995-06-27
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
375202, H04B 169
Patent
active
054286026
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the realization of frequency-hopping in radio transmitter systems, radio receiver systems and radio transceiver systems.
2. Description of the Related Art
The specifications of the European mobile radio system GSM (General Systeme Mobile) define a so-called frequency-hopping function in which the transmitting frequency during signal transmission and correspondingly the receiving frequency at the receiving end is varied continuously by using a suitable number of frequencies, e.g. four predetermined frequencies. Frequency-hopping has two advantageous effects, viz. frequency diversity and interference diversity.
Frequency diversity improves the quality of a radio link mainly in cases where the radio transmitter and the radio receiver move slowly with respect to each other. When the frequency of a radio link in a digital mobile radio system is varied sufficiently from one channel time slot to another, fading situations imposed on different channel time slots do not correlate with each other consequently the time slot interleaving utilized in the system also helps to improve the quality of transmission at the reception when fading occurs.
The interference diversity effect is based on the fact that the frequency-hopping sequences of base stations using the same or adjacent frequencies are different or at least at different phases with respect to each other, whereby the frequencies interfering with each other also vary from one time slot to another, and the effect of severe sources of interference is divided between several radio links, and so the effect of the interference on an individual link is reduced.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a radio system realizing such a frequency-hopping function.
This is achieved by a radio transmitter system according to the invention, which system comprises means for transmitting at least one signal in least at two transmitting frequencies, the frequencies varying in accordance with a predetermined frequency-hopping sequence. The system comprises a fixed-frequency radio transmitter for each transmitting frequency, and means for switching the at least one signal as a baseband signal from baseband signal processing stages to fixed-frequency radio transmitters in accordance with the frequency-hopping sequence.
The invention is also concerned with a radio receiver system which comprises a radio receiver for receiving at least one signal in at least two receiving frequencies, which frequencies vary in accordance with a predetermined frequency-hopping sequence. The system comprises a fixed-frequency radio receiver for each receiving frequency, and means for switching the at least one received signal as a baseband signal from the fixed-frequency radio receivers to baseband signal processing stages in accordance with the frequency-hopping sequence.
The invention is further concerned with a radio transceiver system which includes a radio transceiver for transmitting at least one outbound signal in at least two transmitting frequencies, which frequencies vary in accordance with a predetermined frequency-hopping sequence. The radio transceiver also receives at least one inbound signal in at least two receiving frequencies, which frequencies also vary in accordance with the frequency-hopping sequence. The system comprises a fixed-frequency radio transceiver for each pair of transmitting and receiving frequencies, and means for switching the at least one outbound signal as a baseband signal from baseband signal processing stages to the fixed-frequency transceivers and for switching the at least one received inbound signal as a baseband signal from the fixed-frequency transceivers to the baseband signal processing stages in accordance with the frequency-hopping sequence.
The basic idea of the invention is that a separate dedicated fixed-frequency transmitter or receiver is provided for each transmitting or receiving frequency, and the frequency hopping is carried out
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Nguyen Chau T.
Olms Douglas W.
Telenokia OY
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