Frequency Hopping

GSM and DCS both employ frequency hopping technique for two main advantages:

• To reduce Mulitpath Fading effect which is dependent in carrier frequency
• To randomize Co-Channel Interference (CCI)

The hopping algorithm is continuously broadcast on BCCH and MS/BTS transmits TDMA frames on different hopping carriers during a call on hopping TRX. Hopping is used on TCH, SDCCH and all Packet Data channels while BCCH and common control channels are not allowed to hop. Frequency hopping types are:

• Baseband Hopping (BBH)
• Synthesizer Hopping (SFH)
• Discrete Hopping

SMS Transfer during a Call

SACCH is also used for SMS delivery when a call is in progress.