Before you read this part in 3G Network Planning you should read the below Parts in first
capacity input analysis
it is one of the most important step in any dimensioning process is defining the input data and it is the second step after coverage dimensioning .
1-calculate traffic model
traffic model is a means of researching the capacity features of each service type and the QOS expected by the users who are using the service from perspective of data transmission.
1.1:Grade of service
The Grade of Service can be measured using different sections of a network. When a call is routed from one end to another, it will pass through several exchanges. If the Grade of Service is calculated based on the number of calls rejected by the final circuit group, then the Grade of Service is determined by the final circuit group blocking criteria. If the Grade of Service is calculated based on the number of rejected calls between exchanges, then the Grade of Service is determined by the exchange-to-exchange blocking criteria.
The Grade of Service should be calculated using both the access networks and the core networks as it is these networks that allow a user to complete an end-to-end connection.
Furthermore, the Grade of Service should be calculated from the average of the busy hour traffic intensities of the 30 busiest traffic days of the year. This will cater for most scenarios as the traffic intensity will seldom exceed the reference level.
The grade of service is a measure of the ability of a user to access a trunk system during the busiest hour.
The busy is based upon customer demand at the busiest hour during a week month or year.
Grade of service=(number of lost calls)/(number of requsted calls)
1.2 user profile
It is about avg call duration and number of requsted calls per day and srvice rate which will use.
It is different according to economical distribution for this city.
1.2.1 services rates
Service
rate Kbps
|
12.2
|
64
|
128
|
384
|
Circuit
switching
|
√
|
√
|
No
|
no
|
Packet
switching
|
No
|
√
|
√
|
√
|
For each service rate must identify number of users and user profile as traffic
Per user in Kb per hour or average number of calls and average call duration in minute.
Note : 12.2 Kbps circuit switching is voice calls so it have the most number of users .
Erlang=(bit transmitted)/(total capacity)
example: if we have 80 Kb per hour so
erlang = 80*1000*8/64000*60*60.
1.3 Speed of the user
Speed of the user is very important parameter which affect the signal to noise ratio for each service (Eb/N0)
Speed
|
Eb\No (circuit switching 12.2kbps)
|
Eb\No(circuit switching 64kbps)
|
Eb\No(packet switching 64kbps)
|
0
|
5.1
|
1.7
|
1.5
|
3
|
11.9
|
9.2
|
6.2
|
50
|
9.4
|
6.4
|
6.3
|
120
|
7.2
|
3.8
|
3.4
|
Speed
|
Eb\N0
(circuit switching 12.2kbps)
|
Eb\N0
(circuit switching 64kbps)
|
Eb\N0
(packet switching 64kbps)
|
Eb\N0
(packet switching 128kbps)
|
Eb\N0
(packet switching 384kbps)
|
0
|
5.1
|
5
|
4.7
|
7.9
|
11.4
|
3
|
13.4
|
7.78
|
3.9
|
7.2
|
10.8
|
50
|
10.8
|
15
|
11.4
|
9.7
|
11.3
|
120
|
7.8
|
10.4
|
9.7
|
8.8
|
12
|
1.4 area type
It is a parameter which effect on gama and ioc_ior values
Area type
|
Gama
|
Ioc_Ior
|
Dense urban
|
0.7
|
2.9
|
Sub urban
|
0.5
|
2.9
|
Urban
|
0.6
|
2.9
|
Rular
|
0.4
|
1.99
|
Dopen
|
0.3
|
1.9
|
1.5. Loading Factor (ETA)
The loading factor ETA take values between 0% to 100% .
for example if ETA = 50 % it mean that there are 150 % increase of interference above the introduced one by home user alone.
The inverse of the factor (1 +ETA) is sometimes known as the frequency reuse factor .
the frequency reuse factor is ideally equal to one in the single in the single cell case .In the multicell case as loading (ETA) increase the frequency reuse factor decrease.
2-Mpole & Npole
M pole is the uplink Pole capacity . which give a theoretical limit for the number of UEs that a cell can support . It is service (RAB) dependent . At this limit the interference level in the system is infinite and thus the coverage reduced to zero
N pole is similar to Mpole but in the downlink as it give a theoretical limit for the number of UEs that a cell can support .
We calculate Mpole and Npole for each service rate separately to calculate needed number of sites for each service rate.
3-spreading factor
The spreading factor is the concept of CDMA used in UMTS.As after spreading the user data the a single bit is called the chip.The spreading factor is the ratio of chip rate to bit rate
spreading factor=(chip rate)/(bit rate)
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4-activity factor
It is a definition for the time using to send data over a total holding time which I have a channel to send .This parameter has an impact on the air interface dimensioning as well as the hardware dimensioning . Low activity factor allows more users to share the same spectrum this however require more allocation of hardware resources.
Activity factor for packet switching = 1 as I send data all holding time but,
Activity factor for circuit switching=0.6 as there is time no data sent.
activity factor=(time used to send data)/(holding time)
5-alpha (interference factor)
It is the interference factor for uplink calculations .
6-Ior/Ioc
is the ratio of Cell Power to AWGN it is depend on the area type
7-Gama
It is the interference factor for downlink calculations