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    Overview of 4G/LTE and Broadband Gateway Deployment

    It is one thing to look at network architectures with standardized interfaces and standardized functional components. It is another to consider a realistic deployment of network components that is realistic rather than theoretical.

    Figure 1 shows the major components and interfaces of a Long Term Evolution (LTE) mobile network from user equipment to network. Some of the major interfaces and components are labeled, but the emphasis here is on how these pieces are organized into a mobile network.

    Figure 1: LTE Network Deployment Scenario

    LTE Network Deployment Scenario

    The major parts of the figure are:

    • eUTRAN (E-UTRAN)—The Evolved Universal Terrestrial Radio Access Network (E-UTRAN) is the radio network portion of the LTE archteciture. The user equipment is part of the E-UTRAN, as is the radio tower, or evolved NodeB (eNodeB). The Uu interface connects the user equipment to the eNodeB, and the S1 interfaces connect to the Mobility Management Entity (MME) over the S1-MME interface (for the control plane) and the Serving Gateway (S-GW) over the S1-U (for user plane) interface.
    • The HSS, AuC, and PCRF—The Home Subscriber Server (HSS), authentication center (AuC), and policy and charging rules function (PCRF) act together to make sure that the user equipment is authorized to access a particular service or network and that the user is billed correctly for the service. The Sp interface connects the HSS to the PCRF, and the S6a interface connects the HSS to the MME. The Gx interfaces connect to the P-GWs because P-GWs enforce the policy and charging rules through the P-GW’s policy and charging enforcement function (PCEF).
    • P-GW and Internet—A grouping of P-GWs and Packet Data Network (PDN) such as the Internet form a public land mobile network (PLMN). The UE can attach to a local or HPLMN through a P-GW or through a remote PLMN when roaming (if permitted). The S5 interface connects the local P-GW to its S-GW through a packet-switched network (PSN). For roaming, the S8 interface connects the remote P-GW to its S-GW through a GPRS Roaming Exchange (GRX). Note that billing, handled by the billing gateway, is a local PLMN function (settlements are used for roaming). The Ga interface connects the P-GW and S-GW to the billing gateway.
    • S-GW, MME, EIR, and billing gateway—These components connect the radio network to the PLMN. The MME is a device that manages user equipment information. The equipment identification register (EIR), connected to the MME over the S13 interface, ensures that the user equipment has not been reported stolen. The MME communicates with the S-GW over the S11 interface. User authentication relates to the subscriber profile in the HSS (reached over the S6a interface). Charging information is coordinated with the billing gateway.

    Together, these components (and others) make up a complete mobile network.

    Published: 2011-11-16