A clearer channel for SMS
C. Murray, Laura Cleary · Communications Engineer · 2004
Signaling System 7 (SS7) is a global standard that defines the signaling architecture and protocol used by public switched telephone networks (PSTN). Call setup, call forwarding, toll-free calling and customer billing are some of the common functions of SS7. Also called the "out-of-band" network, SS7 is separate from the voice channel. Its network architecture defines a set of nodes that provide the network entry points, switches for routing and databases for accessing call information. The proliferation in the use of mobile phones and, particularly, of short message service (SMS) technology has created a new form of network congestion, marked by sporadic bottlenecks directly caused by SMS which transmits data across the out-of-band SS7 data network. There are two ways to alleviate SMS congestion in SS7 networks. One method is to add more equipment but this is cost-prohibitive. A more economical and efficient approach is to increase the capacity of each signaling link. This can be done using clear channel SS7. Clear channel SS7 is defined by ITU specification Q.703 Annex A. Its link combines multiple channels to form a pipe, thus greatly increasing the capacity of the link. This expands network capacity for handling calls and SMS traffic without adding extra hardware.