c)  25% of area covered / 4 TRX per cell. The graph assumes constant 

allocation of TRX/cell with frequency. In an actual network higher 

efficiencies are possible.   

A re use of 1 may or may not be achievable.  But the likelihood of achieving a 

re use of 3 is much higher and is a close bound on the maximum utilisation.  

Furthermore the use of half rate encoding will open the prospect of 

considerable capacity increase. 

From the above analysis, it is apparent that for a particular spectrum, the 

Erlangs/MHz/Sq. Km is sensitive to reuse and deployment of microcells. A 

change in reuse from 9 to 3 increases the efficiency from 12 to 42 (for 10 MHz 

of spectrum), while the sensitivity of micro cell deployment is tabulated below.  

Spectrum = 10 

0% of macro 

15% of macro 

25% of macro 

50% of macro 

MHz 

are as micro 

are as micro 

are as micro 

are as micro 

Erlangs per MHz / 

11.6 15.8 20.6 30.3 

Sq Kms (reuse =9) 

These estimates are based on 2 TRXs per cell. But in practice, with the 

frequency increase more number of TRXs can be deployed in micro layer, 

which would further enhance erlang density. For example the Erlangs per 

MHz per Sq. Kms increases from 15.8 to 19.6 with 15% of macro areas 

covered by micros, if the no of TRX per cell in micro is increased from 2 to 3. 

It is clearly seen that it is possible to attain much higher efficiencies with 

greater number of micro cells and deployment of advanced techniques that 

improves the reuse factor. There exist GSM networks that have been able to 

achieve efficiencies in excess of 100 Erlangs per MHz per Sq Kms with about 

2 X 17.5 MHz of spectrum.  

This section primarily dealt with the theoretical efficiencies achievable and 

their sensitivities. The practical benchmarking vis a vis Indian networks is 

discussed later. 

3.2.2.1.2 

CDMA 2000 1x networks 

The theoretical efficiency of CDMA 2000 1x can be estimated as under: 

Traffic that can be carried per Frequency Assignment has been mentioned in 

TEC specification as 25 Erlang.  International data and discussion with 

experts suggest that the maximum packing density that can be arrived at in 

CDMA is about 5 sites per Sq. kms, while the international practices vary 

between 2 and 3.  

If we assume 4 carriers (in a bandwidth of 6 MHz) of CDMA 2000 1x, the 

spectral efficiency for a 3 sector comes out to 

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