1. Diameter Signaling Router Mobile Number Portability User Guide
  2. vSTP G-Flex Feature
  3. Feature Overview

Feature Overview

In today’s mobile networks, subscribers are assigned to Home Location Registers (HLRs) and AuCs (Authentication Centers) in blocks or ranges of subscriber numbers. These ranges are used by MSCs (Mobile Switching Centers) to route many types of signalling messages to HLRs/AuCs. In this document, the term HLR is used to include AuC, as applicable.

G-Flex allows an operator to flexibly assign individual subscribers to HLRs and route signaling messages accordingly, based on subscriber numbering.

The G-Flex C7 Relay node is located in the operator's C7/SS7 network between the MSCs and HLRs. It can also serve as the direct interface to other networks.

There are several types of numbers that identify subscribers, which are assigned by MSCs to HLR/AuCs using this range mechanism:

  • MSISDN (Mobile Station International Integrated Services Digital Network) numbers, which use numbering plan E.164.

  • IMSI (International Mobile Subscriber Identity) numbers, which use numbering plan E.212.

  • MIN (Mobile Identification Number), which uses the E.164 numbering plan.

  • MDN (Mobile Directory Number), which uses the E.164 numbering plan.

G-Flex optimizes the use of subscriber numbers and number ranges by providing a logical link between any MSISDN number or IMSI, and an HLR.
  • Subscribers can be easily moved from one HLR to another.
  • Each HLR can be filled to 100% of its capacity by allowing subscriber number ranges to be split over different HLRs and individual subscriber numbers to be assigned to any HLR.
  • Subscriber number routing data is not required to be maintained in all MSCs in the network.
G-Flex is designed to alleviate problems in areas such as network load balancing and efficient use of HLR capacity. Today's rigid scheme for assigning subscribers to HLRs leads to several inefficiencies for network operators, as described in the following examples:

  • When IMSI numbers, which identify the SIM (Subscriber Identity Module), get lost or are otherwise out of service, “holes” sometimes open in the IMSI ranges. These holes result in HLR capacity that cannot be used because switches will not be routing messages using those lost numbers anymore.

  • In many cases, subscribers are “split” across multiple HLRs, as their IMSI range can point to a different HLR than their MSISDN range. Operators must take special steps to ensure that calls are not mishandled.

  • With the advent of MNP (Mobile Number Portability), the MSISDN no longer indicates the subscription network. This leads to holes in the MSISDN ranges that address HLRs. As in the case with IMSIs, these MSISDN holes result in HLR capacity that cannot be used by existing MSC routing schemes.

  • With the advent of MNP, operators need to handle message routing based on MSISDNs that are imported to the network from another operator and do not fit into the existing range mechanism.

  • Prepaid service may result in the allocation of a large block of IMSIs to an HLR, many of which may not be put in service immediately.

  • Corporate clients may reserve a large block of numbers that must be assigned to an HLR. Many of these may not be used immediately, or ever.