Overload control for short message transfer in GPRS/UMTS networks

In the General Packet Radio Service (GPRS)/Universal Mobile Telecommunications System (UMTS) short message service (SMS) network, the serving GPRS support node (SGSN) stores the message in a queue until it is successfully transferred to the mobile device or its maximum waiting time expires. The queued message is forwarded to the new SGSN and is immediately removed from the waiting queue of the old SGSN, if the corresponding mobile device leaves the old SGSN area before the valid queueing time expires. Once the SGSN's buffer is full, all incoming messages must be discarded and retransmitted later. Under this situation, the messages, especially the forwarded messages, suffer from a longer delay before being successfully delivered. To prevent messages from being excessively delayed, this paper proposes an SGSN overload control scheme called the N-overload scheme. According to this scheme, a newly arriving message is discarded if the buffer is full upon its arrival. A forwarded message, however, is queued in an overload space of size N. Taking the forwarding and the expiration effects of queued messages into account, this paper also develops an analytical model to study the performance for the SGSN using the N-overload scheme. On the basis of the analysis, the optimal value of N is numerically determined so that the loss probability for the forwarded messages is minimized.