Generally speaking, the higher the radio frequency employed, the shorter the transmission range that will be achieved for equivalent parameters (for example, transmitter power, antenna size and height, terrain, etc). Thus GSM cells operating at 900 MHz can cover greater areas than those operating at 1800 MHz.

More Site required in 1800 then 900 MHz network

Penetration inside buildings is generally regarded as more difficult at 1800 MHz than at 900 MHz

Differences between GSM 900 and GSM 1800

Range of cell coverage: The maximum range achievable in ideal conditions for a GSM 1800 cell is half that of a GSM 900 cell, though coverage is usually limited by terrain and interference rather than the theoretical limits of the system.

Transmitter power of handsets: GSM 1800 handsets have a maximum transmitter power that is half that of GSM 900 handsets, reducing further the level of coverage that can be achieved.

Frequency 900 MHzPower of MS 2 W, Rx sens -102Power of BS 20 W, Rx sens. -110Combiner loss 3 dB

Frequency 1800 MHzPower of MS 1 W, Rx sens -100Power of BS 8W, Rx sens. -110Combiner loss 3.5 dB

GSM 900:

Receive (uplink) 890-915 MHzTransmit (downlink) 935-960 MHz124 Absolute Radio Frequency Channels (ARFCN)

GSM 1800 (DCS1800):

Receive (uplink) 1710-1785 MHzTransmit (downlink) 1805-1880 MHz374 Absolute Radio Frequency Channels (ARFCN)

ARFCN:Bandwidth= 200 MHz8 TDMS timeslots

FREQUENCY BAND DIFFERENCE IN 900 Mhz AND 1800 Mhz

Formula:EiRP (dBi)=ERP (dB)+2.1ERP(dB)=Ant Gain (dBd)+POWER BTS (dBm)-Combiner loss-Cable loss-Fading margin

Calculation for EiRP 900 MhzOutput power : 43 dBmcoax-cable Loss : 4.0 dB PER 100 MtrsGain of antenna : 15 dBd (approx)Combiner loss : 3 dBFading margin : 2 dBRadiated power of antenna (ERP) : 49 dBMax. Radiated power of antenna (EiRP): 49 +2.1 =51.1 dBi

Calculation for EiRP 1800 MhzOutput power : 39 dBmcoax-cable Loss : 6.5 dB PER 100 MtrsGain of antenna : 15 dBd (approx)Combiner loss : 3 dBFading margin : 2 dBRadiated power of antenna (ERP) : 42.5 dBMax. Radiated power of antenna (EiRP): 49 +2.1 =44.7 dBi

Difference in power radiated (EiRP) calculation can also be observed

EiRP Calculation for 1800 and 900 Mhz

Free Space Path Loss for GSM 900

L0=32.4+20*log(f[MHz])+20*log (d[km])

L0=91.59+20 *log(1) for f=912MHz for d[km}= 1KM

L0= 91.59

Free Space Path Loss for GSM 1800

L0=32.4+20*log(f[MHz])+20*log (d[km])

L0=32.4+20*Log1873+20*log (1KM) for f=1873 MHz for d[km}= 1KM

L0=97.85

As we can see in free space also the 1800 MHz frequency have more losses then 900 MHz

FREE SPACE LOSS CALCULATION FOR 900 and 1800 MHz

Clutter Clutter loss 900

MhzClutter Loss 1800

Mhz

Suburban 17.6 dB 20.1 - 23.1 dB

Urban 22.6 dB 25.1 - 28.1 dB

Marsh 12.6 dB 13.8 dB

Open Land 3.0 dB 4.2 dB

Pine Forest 15.6 dB 20.9 dB

Semi Open 11.1 dB 16.6 dB

Forest 11.6 dB 16.9 dB

Water 0.1 dB 2.9 dB

Village 12.6 dB 15.2 dB

LOSSES IN SIGNAL STRENGHT FROM TRANMITTED SIGNAL IN BOTH THE BAND

Outer ZoneGSM900

Inner zone GSM1800

DUAL BAND NETWORK:

Consists of both the band in network as outer zones and inner zones

Advantages:•Increased network capacity•Can work as a feature that provides capacity, coverage, or both•Less expensive cost effective