Nokia Bsc Types And Capacity 9651

Flexi Base Station Controller (Flexi BSC)

BSC nominal capacity and dimensioning Described here are the traffic handling capacities of the Nokia GSM/EDGE Base Station Controllers, BSC2i and BSC3i, with certain average call mixes. Additionally, the whole BSS (BSC) overload protection is described. The overload protection has been implemented to protect the equipment and the system in exceptionally high traffic cases. In the given network the BSC erlang (traffic handling) capacity must be checked so that the following nominal erlang capacity is not exceeded. This is the simplest case (that is, to check only erlang figures) in which the reference call mix can be used. In many cases the call mix in real networks differs from the nominal one. By a separate agreement Nokia can provide a separate statement of the BSC capacity for the call mix in question. The BSC traffic handling capacity in the case of GPRS should be noted separately. BSC2i and BSC3i traffic handling capacity with the following circuit-switched reference call mix is stated in documents: 

Product Description of Nokia Base Station Controller BSC2i, BSCi



Product Description of Nokia Base Station Controller BSC3i

In the example below, we assume that the BSC is defined to one location area. Example: BSC3i 2000 Traffic Handling Capactiy BSC3i is configured with 2000 full rate TRXs, circuit-switched: 

11880 erlangs total traffic handling capacity



25 mErl per subscriber, 475 200 subscribers



354 000 busy hour call attempts (BHCA)



120 seconds mean hold time



70% mobile-originated calls (MO)



30% mobile-terminated calls (MT)



1.5 handovers (HO) per call



2 location updates (LU) per call



0.1 IMSI detach per call



63% no paging response



1 SMS call rate subs/hour



(80% terminated SMS) In the circuit-switched (CS) case, for example, the nominal BSC paging load for BSC3i 2000 would be (note that both MT calls and MT SMSs create pages): 354 000 x 0.3 (MT) + 475 200 x 0.8 (SMS MT) = 486 360 + re-paging 0.63 x 486 360 = 792 767 pagings per hour. The nominal BSC3i 2000 RACH load (MO, MT, SMS, LUs) would be, for example: 354 000 (MO, MT) + 2 x 354 000 (LU) + 0.1 x 354 000 (IMSI detach) + 486 360 (SMS) = 1 583 760 RACHs per hour. Example: BSC3i 660 Traffic Handling Capacity BSC3i is configured with 660 full rate TRXs, circuit-switched:



3920 erlangs total traffic handling capacity



25 mErl per subscriber, 157 000 subscribers



117 000 busy hour call attempts (BHCA)



120 seconds mean hold time



70% mobile-originated calls (MO)



30% mobile-terminated calls (MT)



1.5 handovers (HO) per call



2 location updates (LU) per call



0.1 IMSI detach per call



63% no paging response



1 SMS call rate subs/hour



(80% terminated SMS) In the circuit-switched (CS) case, for example, the nominal BSC paging load for BSC3i would be (note that both MT calls and MT SMSs create pages): 117 000 x 0.3 (MT) + 157 000 x 0.8 (SMS MT) = 160 700 + re-paging 0.63 x 160 700 = 261 941 pagings per hour. The nominal BSC3i RACH load (MO, MT, SMS, LUs) would, be for example: 117 000 (MO, MT) + 2 x 117 000 (LU) + 0.1 x 117 000 (IMSI detach) + 160 700 (SMS) = 523 400 RACHs per hour. Example: BSC2i Traffic Handling Capacity BSC2i configured with 512 full rate TRXs, circuit-switched:



3040 erlangs total traffic handling capacity



25 mErl per subscriber, 120 000 subscribers



91 000 busy hour call attempts (BHCA)



120 seconds mean hold time



70% mobile-originated calls (MO)



30% mobile-terminated calls (MT)



1.5 handovers (HO) per call



2 location updates (LU) per call



0.1 IMSI detach per call



63% no paging response



1 SMS call rate subs/hour



(80% terminated SMS) In the circuit-switched (CS) case, for example, the nominal BSC paging load for BSC2i would be (note that both MT calls and MT SMSs create pages): 91 000 x 0.3 (MT) + 120 000 x 0.8 (SMS MT) = 123 300 + re-paging 0.63 x 123 300 = 200 979 pagings per hour, provided that all cells are paged in that BSC and there is only one LA defined per BSC. Here the load is on each Abis link of a broadcast control channel (BCCH) TRX on the same LA. The nominal BSC2i random access channel (RACH) load (MO, MT, SMS, LUs) would be, for example: 91 000 (MO, MT) + 2 x 91 000 (LU) + 0.1 x 91 000 (IMSI detach) + 123 300 (SMS) = 405 400 RACHs per hour. This is the total load per BSC which can be divided by the number of cells when calculating the number of RACHs per BCCH-TRX Abis. With this reference call mix the BSC processor load still remains in the safe area. The maximum 60% U load is the target for dimensioning. This gives enough margin for peak load situations as well as for new software releases. Some call mix is needed in order to get the main performance figures (erlangs, BHCAs) with maximum allowed processor load. With a different call mix, the BHCA value, for example, varies a lot because in a complex system such as GSM there are many other transactions, in addition to calls, which load the system. Roughly it can be said that the erlangs per air channel are the largest contribution to the BSC processor load; the next largest ones are the number of call procedures (call set-up, clearing), SMSs and location updates (LUR, IMSI Attach/Detach are similar) and, lastly, all different types of handovers. By saying that erlangs as such are significant we mean that there is a load in the system even though there is one call with indefinite length on each channel without having any HOs, LURs, and so on.

Packet-switched capacity 

BSC3i 2000: max. 100 PCU2 (50 physical PCU2 units per BSC, 2 logical PCUs in one PCU2 plug-in unit)



BSC3i 1000: max. 50 PCU2 (25 physical PCU units per BSC, 2 logical PCUs in one PCU2 plug-in unit)



BSC3i 660: max. 24 PCU1/PCU2 (12 physical PCU units per BSC, 2 logical PCUs in one PCU1/PCU2 plug-in unit)



BSC2i: max. 16 PCU1/PCU2 (16 physical PCU units per BSC, 1 logical PCU in one PCU1/PCU2 plug-in unit) Table: Connectivity of logical PCUs

Logical PCU2

16kbit/s Abis TSL

TRX

Cell/ Segments

BTS

256

256

64

128

256

128

64

64

(PCU2-D/PCU2-U) Logical PCU1 (PCU-B/PCU-T) Logical PCU1

256

(PCU/PCU-S)

(128 RTSL)