With MAP ATI, the Service Control Point (SCP) will send a MAP Any Time Interrogation (ATI) message to the HLR requesting location information. The HLR will in turn query the appropriate MSC (shown here as a SSP) to perform a VLR look-up.
The MAP ATI query comes from the Location Management Function (LMF), which may or may not be a traditional SCP. One of the key things to note about MAP ATI is that is does not always provide the most current Cell ID, but always provides the accurate Location Area.
While the MAP ATI is advantageous regarding no need for GPS on the hand-set and no need for other potentially expensive positioning solutions such as T-DOA, it is disadvantageous from a network management perspective. The HLR is the heart of the mobile operator network and is capacity sensitive. Therefore, most network planners do not allow access to the HLR or “pinging” it, on any scale, let alone for LBS applications that may scale to cause many queries per second.
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