- 

3) 

Trunking Gain Functionality   Directed Retry (DR) and Traffic 

Reason Handover (TRHO) techniques 

- 

4) 

Radio Link Enhancement Techniques   Uplink and Down Link 

antenna diversity, Mast Head amplifiers, Interference rejection  

- 

5) 

Half Rate and Adaptive Multirate speech coding 

- 

6) 

EDGE AMR enhancements 

The details of these techniques and their impact is provided in Annexure E. 

Minimum spectrum requirement to build hierarchical networks 

Some operators have raised concern that the present allocation levels are 

insufficient to build hierarchical networks. It is difficult to deterministically 

assess the minimum spectrum required for a hierarchical cell structure. It is 

theoretically feasible to provide coverage based on repeating clusters of four 

cells, each with three sectors.  If there is a single frequency per sector then 

the total spectrum required to provide continuous service would be 12 x 200 

KHz, i.e. 2.4 MHz.  This network would be very limited in terms of capacity 

and grade of service.  If instead each sector has four frequencies, the 

requirement of spectrum for voice services would be 2 x 9.6 MHz.  If we take 

take three carriers this would be 2 X 7.2 MHz.   

A micro layer then has to be added to provide additional capacity using 

repeated clusters of three cells, each with three sectors.  If each sector has 

three frequencies then the micro layer will require 5.4 MHz.  If each sector has 

two frequencies then the total requirement is 3.6 MHz.  

Hence a reasonable spectrum requirement for hierarchical cell structure could 

be assessed at about 2 X 10.8 MHz ~ 2X 15 MHz. 

3.2.2.4 International 

benchmarks 

London GSM networks 

Information on cellular radio cell sites is available on the UK's Ofcom website 

(

www.sitefinder.radio.gov.uk

).  This web site gives the location of all the base 

sites of all the UK operators, together with antenna height, transmitter power 

and frequency band. Figure 3.10 and Figure 3.11 give an analysis of the base 

station heights and powers in the West End of London and Figure 3.12 and 

Figure 3.13 gives power and heights for base stations in the City of London. 

In both cases, 80% of antennas are below 6 metres in height above ground 

level and 50% of transmitters are less than 9 dBW erp, indicating that most of 

the cells are micro cells. 

In both cases the cells are located within an area of 700 metres by 700 

metres (0.49 kmsq).  The numbers of base stations and packing density is 

given in Table 3.2. Clearly this represents a densely planned network utilising 

mainly micro cells in the areas of high traffic density.  The networks operate 

33