Additional features in Frequency Hopping

1. Frequency Hopping

Frequency Hopping improve s the C/I and Freq uency reuse factor and thus adds capacity into the radio network. The final capacity improvement of frequency hopping depends on the number of channels and the frequency bandwidth. The implementation of frequency hopping also has signification effect on the frequency planning which furturemore depends strongly on the frequency hoppin scheme. The baseband and Sythetized frequency schemes are typically utilized for example in the GSM mobile Network and frequency band limitation or sufficiency, as well as system limitations, have a signication effect on the selection of these frequency hopping schemes for different purposes.

Baseband Hopping

Baseband hopping is an elementary feature of the GSM system and its usage is not typically limited. Bandband hopping mean that the call ( radio connection between mobile station and base station) is switched between different transciever ( or frequencies) periodically or randomly during connection . This mean that the calls uses a different transciever from the pool of all the transcievers at each time slot. If there are three trainsciever ( frequencies, F1, F2 and F3) the call preceeds F1->F2->F3->F1-... on different time slot when cyclic hopping is used.

Synthetized Hopping

Synthetized Frequency hopping differs from base band hopping such in that there are both more system requirements and flexibility in synchronized hopping. First of all synthetized hopping mean that the frequency can be changed in each transceivers between time slots. Moreover, this meant that the whole frequency band can be reused in each transceiver which means the a wide band combiner is required to combine the frequency at the base station. This wide band combiner typically causes the first limitation for synthetized hopping namely that the maximum number of transceivers is restricted. Second, the BCCH frequency can not be included in syntetized hopping, because the BCCH time slot has to be sent at the same frequency all of the time; the BCCH transciever's frequency can not be changed.

Reference

Jukka, Matti Manninen "Radio Interface System Planning For GSM/GPRS/UMTS" 2001 Kluwer

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