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E SMLC (Evolved Serving Mobile Location Centre)

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The Evolved Serving Mobile Location Centre (E-SMLC) is a component of the Long-Term Evolution (LTE) network architecture that provides location-based services to mobile users. The E-SMLC receives location requests from user equipment (UE) and uses various methods to determine the user's location accurately. In this article, we will provide a detailed explanation of E-SMLC, its components, and its functions.

Background

With the increasing popularity of mobile devices, the demand for location-based services has grown significantly. Location-based services enable mobile users to access a wide range of location-based applications, such as navigation, geotagging, and location-based advertising. To support these services, the network must have the ability to accurately locate the mobile user. LTE is the latest wireless communication standard that provides high-speed data transmission, voice, and video services. LTE also supports location-based services through its Evolved Packet System (EPS) architecture, which includes the E-SMLC component.

E-SMLC Components

The E-SMLC consists of three main components: the Serving Mobile Location Centre (SMLC), the Gateway Mobile Location Centre (GMLC), and the Positioning Calculation Entity (PCE).

The SMLC is responsible for handling location requests from UE, processing them, and returning the location information to the requesting UE. The SMLC is located in the Serving Gateway (SGW) or the Packet Data Network Gateway (PDN GW). It communicates with the UE using the LTE Control Plane (C-Plane) protocol, which is used for signaling between the UE and the network. The SMLC also communicates with the GMLC using the LTE User Plane (U-Plane) protocol, which is used for user data transmission.

The GMLC is responsible for managing the location information database, which includes the location of all the UEs in the network. The GMLC is located in the Mobility Management Entity (MME) or the Serving GPRS Support Node (SGSN). It communicates with the SMLC using the U-Plane protocol, which is used for user data transmission. The GMLC also communicates with the PCE using the Diameter protocol, which is used for authentication, authorization, and accounting.

The PCE is responsible for calculating the UE's location using various methods, such as Global Navigation Satellite System (GNSS), Enhanced Observed Time Difference (E-OTD), and Observed Time Difference of Arrival (OTDOA). The PCE is located in the Location Services (LCS) server, which is connected to the GMLC. The PCE communicates with the UE using the U-Plane protocol, which is used for user data transmission. The PCE also communicates with the GMLC using the Diameter protocol.

E-SMLC Functions

The E-SMLC provides the following functions:

  1. Location-based Service Request Handling: The E-SMLC receives location requests from UE and processes them. It determines the type of location service requested and selects the appropriate positioning method to calculate the UE's location.
  2. Positioning Calculation: The PCE is responsible for calculating the UE's location using various methods. The PCE uses the location request received from the SMLC and determines the appropriate positioning method to calculate the UE's location accurately.
  3. Location Information Storage: The GMLC is responsible for managing the location information database, which includes the location of all the UEs in the network. The GMLC stores the UE's location information and retrieves it when required.
  4. Location Information Transmission: The SMLC is responsible for transmitting the UE's location information to the requesting UE. The SMLC sends the location information to the UE using the C-Plane protocol.
  5. Authentication, Authorization, and Accounting: The E-SMLC also performs authentication, authorization, and accounting functions to ensure secure and reliable location-based services. The PCE and GMLC use the Diameter protocol for these functions.
  6. Emergency Location Services: The E-SMLC also provides emergency location services, which enable emergency services to locate the mobile user accurately in case of an emergency. The E-SMLC supports emergency services such as the Emergency Call (eCall) service, which automatically contacts the emergency services when a serious accident occurs.
  7. Privacy Management: The E-SMLC also ensures that the privacy of mobile users is protected by implementing privacy policies and protocols. The E-SMLC provides the necessary privacy management functions to protect the user's location information from unauthorized access and use.

E-SMLC Positioning Methods

The E-SMLC uses various methods to determine the UE's location accurately. These methods include:

  1. Global Navigation Satellite System (GNSS): GNSS is a satellite-based positioning system that provides accurate location information by using signals from GPS, Galileo, and other satellite systems. The UE's GNSS receiver receives signals from the satellite and calculates the UE's location.
  2. Enhanced Observed Time Difference (E-OTD): E-OTD is a time-based positioning method that uses the time difference between signals received from multiple base stations to determine the UE's location.
  3. Observed Time Difference of Arrival (OTDOA): OTDOA is a positioning method that uses the time difference between signals received from multiple base stations to determine the UE's location. OTDOA is particularly useful in urban areas where the signal reflection and multipath propagation make other methods less accurate.

Conclusion

In conclusion, the E-SMLC is a critical component of the LTE network architecture that provides location-based services to mobile users. The E-SMLC consists of the SMLC, GMLC, and PCE components, which work together to process location requests, calculate the UE's location accurately, and transmit the location information to the requesting UE. The E-SMLC uses various positioning methods such as GNSS, E-OTD, and OTDOA to determine the UE's location accurately. The E-SMLC also provides emergency location services, privacy management functions, and authentication, authorization, and accounting services to ensure secure and reliable location-based services.