8.7.4 System loading

The following procedures can be used for system loading during simulation and preparation of simulation outputs.

System loading

To determine the number of active mobile stations Act_MS in the network:

1. Set up:
   1.  Average traffic load in terms of a predefined number of users per cluster: N_UL
   2.  standard deviation of log-normal shadowing σ_shadowing
   3.  voice activity factor Act_Factor (fixed to 100%)
   4.  target maximum noise rise over the thermal noise in the network  η_target
   5.  target C/I (E_b/N₀_target) to fulfill service requirement depending on configuration and mobility (provided by link level simulations)
   6.  maximum transmit power of mobile station max_MS_Pw_Tx
   7.  power control range – MS_PC_Rang:
   8.  In the case that the CDMA uplink is the victim link, add the received power from the interfering system to the thermal noise power
2. For each event:
   1.  put down uniformly mobile stations at pseudo-random locations across the network and distribute speed among them
   2.  Add a new mobile station in the set of active users in the network

• • • compute average path-loss from the mobile station to the base station of each cell
    • generate a log-normal pseudo-random value to add to each of the path losses to model shadow fading
    • perform a pseudo-random weighted coin-toss to determine voice activity, where 1 occurs with probability Act_Factor  
    • compute required received power at the base station to meet E_b/N₀_target, given interference from pre-existing mobiles and other sources (  and )
    • compute required transmit power of the mobile station
    • adjust the required transmit powers of the all existing mobile stations perturbed by addition of the new mobile station
    • continue the adjustment until the convergence of power control loop is achieved. A convergence criterion could be that the variation of two consecutive transmit powers of each mobile station is within a predefined threshold. 
    • compare the number of active mobile stations, Act_MS, with N_UL
      • if  Act_MS ≥ N_UL terminate the addition of a new mobile station in the network
      • else measure the average noise rise over the thermal noise η and compare it with the target noise rise limit η_target
        • if η_target is reached, terminate the addition of a new mobile station in the network
        • else add a new mobile station and go to step 2b