A15.2 EXAMPLE ON DL CDMA "OPTIMAL CAPACITY"

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Last updated: Jan 11, 2018
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Figure 448: Non interfered capacity finding – Downlink





{XE " CDMA:Algorithm"} {XE " CDMA: Non-interfered capacity"} 

  • Users (UEs) per cell = 20
  • Number of trial = 20
  • Delta number of users (UEs) per cell = 20
  • Tolerance of initial outage: 5%
  • Number of base stations = 19


  1. Run [number  of trials] with 20 UEs per cell
    1. Each “trial” consist of the following high-level steps:

                              i.                  Generate CDMA system as specified in scenario

                             ii.                  Add [UE per cell] x [number of base stations] = 380 UEs

                            iii.                  Run power balancing without adding any external interference

                           iv.                  After power balancing note if the percentage of dropped UEs is below 5%. [1]

                            v.                  Count the number of successful trials and see if it is still possible to reach the 80% target.

A. After 17 trials SEAMCAT concludes it is not possible to reach 80% and 20 UEs per cell is less than the specified systems optimal capacity[2]

B. Adjust [UE per cell] by adding [delta UE per cell] (20 + 20 = 40) and go to step 2.

2. Run [number of trials] with 40 UE per cell

    1. Same as step (a) above – but now the system is filled with 40 x 19 = 760 UE and allowed outage is 5% of 760 (38 UEs)

A. After running 5 trials of which none have been successful SEAMCAT determines that the system is filled with too many users

B. Adjust [delta UEs per cell] by dividing with 2 (20/2 = 10)

C. Adjust [UEs  per cell] by subtracting [delta UEs per cell]    (40 – 10 = 30) and go to step 3

3. Run [number of trials] with 30 UEs per cell

          1. System is filled with (30 x 19 = 570) and tolerance is 28 UEs

A. After running 5 trials of which none have been successful SEAMCAT determines that the system is filled with too many UEs

B. Adjust [delta UEs per cell] by dividing with 2 (10/2 = 5)

C: Adjust [UEs per cell] by subtracting [delta UEs per cell]    (30 – 5 = 25) and go to step 4

4. Run [number of trials] with 25 UEs per cell

    1. System is filled with (25 x 19 = 475) and tolerance is 23 UEs

A. After running 10 trials 5 of them have been unsuccessful so SEAMCAT determines that the system is filled with too many UEs

B. Adjust [delta UEs per cell] by dividing with 2 (5/2 ~ 3)

C: Adjust [UEs  per cell] by subtracting [delta UEs per cell]    (25 – 3 = 22) and go to step 5

5. Run of [number of trials] with 22 UEs per cell

    1. System is filled with (22 x 19 = 418) and tolerance is 20 UEs

A. After 17 trials SEAMCAT concludes it is not possible to reach 80% and 20 UEs per cell is less than the specified systems optimal capacity

B. Adjust [delta UEs per cell] by dividing with 2 (3/2 ~ 2)

C. Adjust [UEs per cell] by adding [delta UEs per cell] (22 + 2 = 24) and go to step 6

6.   Run of [number of trials] with 24 UEs per cell (let’s assume that it is the end of Figure 448)

    1. For the purpose of this example we assume that 24 UE per cell is the optimal capacity for the tested system.
    2. After 20 trials we assume that 16 trials were successful – so optimal capacity finding is terminated and SEAMCAT starts the actual simulation.



[1] With 380 UEs in the system and a tolerance of 5%– no more than 19 UEs can be dropped during power balancing if trial is to be considered successful

[2] As more than 80% is already successful there is no need to simulate more trials