Receiving Mobile Station

Description

The Receiving MS (Mobile Station) is a term used in 3GPP specifications for short message service (SMS) to denote the mobile device to which a mobile-terminated (MT) short message is destined. It is defined in TS 23.040 (Technical realization of the Short Message Service) and TS 23.840 (Study on enhanced SMS). The Receiving MS is the final recipient in the SMS delivery chain, which typically includes the Short Message Service Centre (SMSC), the Gateway MSC (GMSC), the Home Location Register (HLR), the Visitor Location Register (VLR), the Mobile Switching Centre (MSC), and the Base Station Subsystem (BSS) or equivalent in later generations.

When a short message is submitted to the SMSC, it is routed towards the Receiving MS based on the destination MSISDN. The SMSC queries the HLR for the routing information, which may include the MSC/VLR where the MS is currently registered. The message is then forwarded to that MSC, which pages the MS and delivers the short message over the radio interface. The Receiving MS may be in idle or dedicated mode; if it is not reachable, the SMSC may store the message and attempt delivery later. The Receiving MS can acknowledge successful receipt of the short message, providing reliability.

The term 'Receiving MS' is used to distinguish the destination MS from the 'Sending MS' (the originator of a mobile-originated short message). In the context of MT short messages, the Receiving MS is the entity that ultimately receives the message. The definition has evolved slightly: in Rel-7 through Rel-11, it was defined as 'the mobile station to which an MT SM is destined.' In Rel-12, the wording was changed to 'the mobile station to which an MT short message is destined,' replacing the abbreviation 'SM' with the full term 'short message' for clarity. This change was purely editorial and did not alter the technical meaning.

The Receiving MS can be a wide range of devices: a basic feature phone, a smartphone, an IoT module, or a machine-type communication device. In all cases, it must support the SMS protocols and be capable of processing the received short message. The Receiving MS may also support enhanced features like concatenated SMS, where multiple short messages are reassembled into a longer message, or port addressing, where the message is directed to a specific application on the device.

In summary, the Receiving MS is the endpoint of SMS delivery. Its correct identification and reachability are essential for successful message delivery, and its capabilities determine how the message is presented or processed. The term has remained stable since Rel-7, with only a minor wording update in Rel-12.

Purpose & Motivation

The concept of the Receiving MS exists to clearly identify the destination of a mobile-terminated short message within the complex SMS architecture. Before the term was formalized, specifications often referred to the 'destination MS' or 'recipient MS' inconsistently, leading to ambiguity in protocol descriptions and implementation. By defining 'Receiving MS' in Rel-7, 3GPP provided a precise term that distinguishes the final recipient from intermediate entities like the SMSC or MSC.

This clarity is crucial for routing and delivery procedures. The SMSC and HLR must know exactly which MS is the intended recipient to query the correct VLR and route the message. The Receiving MS is also the entity that may return a delivery report, which is essential for services that require confirmation of delivery. Without a clear definition, interoperability between different vendors' equipment could suffer.

Furthermore, the Receiving MS concept supports advanced SMS features. For example, in concatenated SMS, the Receiving MS is responsible for reassembling segments. In port-addressed SMS, the Receiving MS must route the message to the correct application port. Thus, the term is foundational for both basic and enhanced SMS services. The minor wording change in Rel-12, replacing 'SM' with 'short message,' reflects a broader effort to improve readability and reduce jargon in 3GPP specifications, making them more accessible to a wider audience.