5441336876

3.2 Sectored antenna

Since we are unable to use omni directional antennas with N = 4 in the cities we must examine the possibility of using sectored antennas instead. In GSM a sectored antenna usually covers 120° and in a group of 3 sectored antennas they cover a total of 360°. To find the SIR for GMS type of sectored antennas we use

SIR = 10 log

[_ł_

|_<r⁷ + (g + 0.7)-T'

(4)

Using the previously discovered value of q and 7 together with (4) we find that the SIR for the cities is

SIRdty ~ 10 log q~'^r + {q + 0.7)-^

= 10 log

3.464^-3-⁶ + (3.464 + 0.7)~³-⁶

= 17.62 dB

which is above the reąuirement of 14 dB. This allows us to use sectored antennas in the city areas.

3.3 Voice channels

To find the number of voice channels m we use the following formula

Ib

BW

- 1 x

SpeechPerRF

(5)

Channels J N x Sectors

The —1 channel is the control channel which we have to make room for. We fili (5) with our numbers for the two cities and the highway and get

8.33 MHz

ITlcity " ^highway ^:

200 kHz 4.166 MHz

= 26 channels

200 kHz

4x1

- 38 channels

3.4 Traffic density

By assuming uniform distribution of the subscribers we can use this formula to determine the traffic density TD of each city

E x Pop x Pene x (1 + Growth)^ROT x Share Area

where E is the traffic per subscriber (cali intensity) in Erlangs, Pop is the population, Pene is the market penetration, Growth is the annual popu-lation growth, ROT is the roli out time in years and Share is the market

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