GSM Frequency Spectrum
■ DL: 935-960 MHz, UL: 890-915 MHz
■ 200 kHz channel spacing ( 124 channels
■ ARFCN 1 – 124
■ DL: 925-935 MHz, UL: 880-890 MHz
■ 200 kHz channel spacing ( Additional 50 channels
■ ARFCN 0, 975 - 1023
■ DL: 1805-1880 MHz, UL: 1710-1785 MHz
■ 200 kHz channel spacing ( 374 channels
■ ARFCN 512 – 885
UMTS Band I
1920-1980 and 2110-2170 MHz
Frequency Division Duplex (FDD, W-CDMA) Paired uplink and downlink,
Channel spacing is 5 MHz
Raster is 200 kHz.
Carrier frequencies are designated by a UTRA Absolute Radio Frequency Channel Number (UARFCN)
UARFCN = 5 * (carrier frequency in MHz)
e.g 1st carrier frequency is 1922.4 MHz (5 MHz – 200 kHz/2)
UL: 9612 to 9888
DL: 10562 to 10838
What is frequency reuse?
As the GSM spectrum is limited, frequencies have to be reused to provide enough capacity
Aim: Minimizing the frequency reuse for providing more capacity
But: More frequencies on air ( higher interference
Group of cells which do not reuse the same frequency (or frequency group) are said to belong to a ‘reuse cluster’
Reuse Cluster Size – RCS
Used if no of TRX per cell is the same.
Average Reuse Cluster Size – ARCS
Used by calculating average no of TRX per cell.
The lower the ARCS is:
■ the higher is capacity traffic (more TRX/cell)
■ The higher interference is
Traffic capacity/inference is always a trade-off.
BCCH reuse is always RCS, because we don’t need to use an average (always one BCCH per cell).
4 sites per reuse cluster
3 cells per site
REUSE Cluster Size:
Another example of BCCH RCS
3 sites per reuse...