Feature #3682

Updated by laforge almost 4 years ago

3GPP TS 23.236 specifies the "Intra-domain connection of  
  Radio Access Network (RAN nodes to multiple Core Network (CN) nodes". 

 This introduces two concepts: 
 * a deviation from the strict hierarchy of classic GSM architecture where a BSC is always only served by one MSC 
 * the introduction of "MSC pools" where a pool of multiple MSCs cover one geographic service area. 

 This appears to be functioning by dividing the TMSI range between different MSCs, using the higher-order TMSI bits to identify the MSC and the lower-order TMSI bits for the actual TMSI within that MSC. 

 Section 5.3 describes the functions required to be implemented in the BSC. 
 * *NAS Node Selection Function* 
 ** investigate Initial L3 message at RR establishment 
 ** if TMSI is present, extract NRI and route requeest to MSC for that NRI 
 ** if only IMEI or IMSI is present, or no route for that NRI, send to 'ramdom' MSC (load distribution) 
 * when any MSC sends a PAGING REQUEST, store the IMSI <-> MSC relation as long as the paging is active 
 ** any incoming response to that paging gets routed to the MSC that has issued the paging 


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