1. In CDMA 1X system if we want to know the number of subscribers (customers)

supported by one BTS we need to know TRAFFIC MODEL (essential). This traffic

model can be supplied by Customer (if there is a formal tender/bidding) or we can

use our Default traffic Model. The traffic model describes the behavior of the

subscriber in the network according to the different environments.

For example, the Huawei default traffic model is:

GENERAL ASSUMPTIONS IN CDMA PROJECT

Voice Service Traffic Model

Grade of Service (GOS), Radio Channel 2%

Voice Activity Factor 0.4Mobile Customers

Proportion of mobiles in entire network 90%Busy hour traffic per customer 0.08Erl

FWT CustomersProportion of FWTs in entire network 10%Busy hour traffic per customer 0.08Erl

Cell Loading 50%Soft Handoff Ratio 30%

1x Data Service Traffic Model

Data service subscribers distributionHigh-end subscribers 15%Middle subscribers 25%Low-end subscribers 60%

Data service model parametersPPP Session Time(s) 350PPP Session Duty 10%

Access Rate Grade

Grade of Data Rate (kbps)

Data Rate (kbps) Statistics Proportion

Low-end Middle High-end9.6 9.6 100% 25% 5%9.6+9.6 19.2 0% 40% 5%9.6+19.2 28.8 0% 18% 20%9.6+38.4 48 0% 12% 25%9.6+76.8 86.4 0% 4% 30%9.6+153.6 163.2 0% 1% 15%9.6+307.2 316.8 0% 0% 0%Average (kbps)

9.6 26.11 69.60

Mixed Service Traffic Model

GENERAL ASSUMPTIONS IN CDMA PROJECT

Service Type Service ProportionVoice only 90%Voice and Data 10%

Assumptions on Terminal Types

The proportion between MS and FS in the entire network

MS (Mobile) 90%FS (Fixed Terminal) 10%

Types of FS's antennaIndoor 50%Outdoor Directional 50%

Assumptions on Subscriber Action

Subscriber Moving Speed 0Km/h 3Km/h 8Km/h

30Km/h

100Km/h

Voice 60% 20% 14% 5% 1%Data 90% 5% 2% 2% 1%

Assumptions on radio environment

Shadow Margin

Situation UrbanSuburban Rural

Area Coverage Probability 90% 90% 90%Marginal Coverage Probability 75% 75% 75%Shadow fading Margin (dB) 5.5 5.5 5.5Standard Deviation of Shadow Fading(dB) 8 8 8

Average BTS Antenna Height

Environment UrbanSuburban Rural

Antenna height (m) 30 40 50

Reverse Maximal Transmit Power for R-FCH and R-SCH at Different Service Rate.

R_FCH and R_SCH Maximal Transmit Powers when Convolution Coding is used.Max Terminal TX Power (mW)

200/250

Max Terminal TX Power (dBm)

23.01/24

R_FCH Data Rate (kbps) 9.6

R_SCH Data Rate (kbps) / 9.6 19.2 38.4 76.8153.

6Max R_SCH TX Power (dBm) /

19.17 20.5

21.29

21.91

22.35

GENERAL ASSUMPTIONS IN CDMA PROJECT

Max R_FCH TX Power (dBm)

21.55

19.17

17.87 16.17

14.03 11.1

Feeder Cable Loss for 450M Frequencies Band

Feeder Cable Loss (450MHz) dB/100m7/8 Feeder Cable 2.75/4 Feeder Cable 1.91/2 Jumper 7.6

NOTE: RED COLOR MEANS DEFAULT. All those parameter are suitable to be changed

by customer request. The coverage area is also important parameter for coverage

prediction.

2. After get the traffic model we do the Capacity planning based on that traffic

model. There are a lot of calculation, some made by our “CDMA2000 Radio

Netplan Estimate Tool” and other made by your self.

3. According to the calculation result you get the BTS Throughput and the Single

user Throughput. So the ratio between the BTS Throughput and the Single

user Throughput will give the number of subscribers supported by each BTS.

According to environment types the number of user is different from each type of

environment. Normally, dense urban environment can accommodate less users

compared with suburban, and suburban can accommodate less subscribers than

rural and so on.

After that we calculate the Erlang for each environment; what we do for that is:

(a) Voice channel element (Erl) = Total throughput for voice users of single cell / (Voice Rate*Voice activation factor)

or = Total voice users in a single cell * Erl value per voice user = A

(b) FCH channel element (Erl) = FCH data throughput of single cell / (Basic rate of FCH data) = B

(c) SCH channel element (Erl) = SCH data throughput of single sector / (Basic rate of SCH data* Utilization of data demodulation resource) = C

(d) Total channel element resource with soft handover taken into account = (Voice CE +PTT CE +FCH CE) / (1- Soft handover proportion) +SCH CE = (A + B) /(1-30%) +C= D

(Note: Huawei assume 30% soft handoff percentage.)

(e) Total channels resource (Erl) of each cell =Total CE resource with soft handover taken into account + common access channel resource (1 Erl per sector) = D + 3 = BHT

(f) Number of channels required for configuration =Erl_B (BTS basic CE, service blocking ratio) =Erl_B(BHT, 2%)=N.

NOTE: Erl(BHT,2%) is a table where we go on the column 0.02 until find the value

BHT, then we read the value of N. see the next figure.

Click here if you have access to the Internet and test the Erl_B table:

http://www.erlang.com/calculator/erlb/

Now, according to the above explanation I thing that you get the idea why I cannot

tell you the number of subscribers supported for each BTS. If you have more

information about traffic model I can help you. What you need is only to send me that

traffic model.

I CAN DO FOR YOU THE CALCULATION USING OUR DEFAULT VALUES, BUT YOU MUST

WAIT AT LEST TWO DAYS TO GET THE ANSWER, BECAUSE TOMORROW (13TH DEC) IF I

GET SEATE ON PLANE I’LL GO BACK TO MAPUTO, OTHERWISE I’LL TRY ON

WEDNESDAY. SORRY FOR THAT.

You can also give a look to our CRNP Estimation Tool. You can see the traffic model

sheet and the capacity sheets.

BHT

Service blocking ratio (QoS = 2%)

Number of CE

For any question feel free to ask me I’ll do my best to give you the right answer!