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.