What is difference using 4.2 mhz and 5 mhz in 3G? Is there a difference in Throughput?
Only 3.84MHz is used for transmission, while the 116 kHz left acts as a built-in guard-band to adjacent UARFCN’s (580kHz + 3840kHz + 580kHz = 5MHz). If an operator owns the adjacent frequency bands, it is possible to reduce the size of the UMTS carrier from 5MHz to 4.4 or 4.2 MHZ, but this is not recommended.
please refer to he link for more details:
In Hw// refarming scenarios, UMTS performance is ordered as follows: 5 MHz > 4.6 MHz > 4.2 MHz > 3.8 MHz.
Average network-level uplink and downlink rates are 5% lower in UMTS 4.2 MHz than 5 MHz. UMTS 3.8 MHz
rates are 10 - 15% lower than UMTS 5 MHz. UMTS MOS is reduced by approximately 0.2.
GSM performance impact: EDGE rates are reduced by 15% and MOS falls by 0.1
Only 3.84MHz is used and the rest is a guard interval to neighboring channels. Also, operator has ability to move carrier frequency for up to 600kHz up or down in order to improve co-channel interference (inside those 5MHz). If you shorten it it is possible risk to raise co-channel interference.