Table 3.1:  Assumptions used in assessing spectrum utilisation 

Assumptions 

Remarks 

Macro cell re use 

9 

Explained above 

Micro cell re use 

3 

Explained above 

Number of TRXs used 

2 

per micro cells 

300 metre radius for Macro 

Cell nominal radius 

cells, 80 metres radius for 

micro cells 

Synthesised Frequency 

Not included in theoretical 

Included by taking 

Hopping 

bench mark 

tighter reuse 

Not included in theoretical 

Included by taking 

Half rate codecs 

bench mark 

tighter reuse 

Hierarchical Cell 

Two layer   Macro and micro 

Structures  

Assumption 1)   No micro 

cells 

Area covered by Micro 

Assumption 2)   15% 

cell 

Assumption 3)   25% 

Assumption   separate 

Micro cell spectrum 

spectrum allocated to micro 

cell layer 

For the above case the total traffic capacity in the Macro cell area is 

calculated. The spectrum utilisation in Erlang/Km

2

/MHz is calculated using the 

traffic capacity, the area covered by the macro cells and the spectrum. 

A calculation of the spectrum utilisation of the area covered by the micro cells 

was also made to enable the peak spectrum utilisation to be gauged. The 

detailed model indicating a sample calculation is placed at Annexure D. 

Some results from the model are given in Fig 3.2 and Fig 3.3. These figures 

indicate Erlangs / MHz / Sq. Kms for a macro cell for different reuse factor vis 

a vis spectrum and the effect of adding micro cells. 

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