Cellular Network Infrastructure » Distributed GSM

h1. Roaming

Roaming occurs if a subscriber from autonomous network A travels to autonomous network B.  It's outbound roaming from network A, and inbound roaming from network B.

{{mscgen_link()

msc {

  hscale = 2;

  ms [label="MS (village A)"], vlr [label="VMSC/VLR (village A)"], hlr [label="HLR (village B)"];

  ms => vlr [label="MM LOC UPD REQ (IMSI=334-42-001-0123456)"];

  vlr => vlr [label="Determine HLR IP address from 334-42-001 prefix"];

  vlr => hlr [label="SendAuthInfo REQ"];

  vlr <= hlr [label="SendAuthInfo RESP"];

  ms <= vlr [label="MM AUTH REQ"];

  ms => vlr [label="MM AUTH RESP"];

  vlr => hlr [label="UpdateLocation REQ"];

  vlr <= hlr [label="InsertSubscriberData REQ"];

  vlr => hlr [label="InsertSubscriberData RESP"];

  vlr <= hlr [label="UpdateLocation RESP"];

  ms <= vlr [label="RR CIPHER MODE COMMAND"];

  ms => vlr [label="RR CIPHER MODE COMPLETE"];

  ms <= vlr [label="MM LOC UPD ACK"];

  ...;

  ...;

  ...;

}

}}