Location Deferred Request

Description

Location Deferred Request (LDR) is a feature of the 3GPP Location Services (LCS) system. It operates within the standardized LCS architecture, which involves a LCS Client, a LCS Server (typically the Gateway Mobile Location Centre - GMLC), and the core network nodes (e.g., MSC, SGSN, MME) interacting with the radio access network and the UE. The LDR mechanism allows an authorized LCS Client to submit a location request with a deferred reporting condition. Instead of triggering an immediate location procedure, the network stores the request and activates it when the specified condition is met. The key components involved include the deferred location request parameters stored in the network (e.g., in the GMLC or a dedicated service node), timers, and event triggers. The request specifies criteria such as a single future absolute time, a periodic interval (e.g., every hour), or a change in area event (e.g., when the UE enters or leaves a defined geographical area). When the triggering condition occurs, the network executes the standard location determination procedure, which could be network-based (e.g., using timing advance or observed time difference of arrival), UE-based (using GNSS like GPS), or assisted/hybrid methods. Once the location is obtained, the network delivers the result (e.g., geographic coordinates) to the requesting LCS Client according to the deferred request's delivery instructions. This process decouples the request from the immediate network and UE resource usage for positioning, allowing for more efficient scheduling and battery-friendly operation for the UE, especially for non-urgent tracking applications. The feature relies on the network's ability to manage and correlate multiple deferred requests, handle their lifecycle (creation, activation, execution, cancellation), and ensure privacy and security as per subscriber consent.

Purpose & Motivation

Location Deferred Request was created to expand the utility of cellular location services beyond simple, immediate "where are you now" queries. Early LCS capabilities were primarily real-time, which limited applications to instant navigation, emergency services (E911), and similar time-critical uses. Many commercial and enterprise applications, however, require location information on a scheduled or event-driven basis without constant active polling. Examples include fleet management for periodic position logging, asset tracking for theft recovery (reporting location only upon movement), location-based advertising triggered by entering a shopping mall, or parental controls that alert when a child leaves a safe zone. Performing these with continuous real-time requests would be highly inefficient, consuming excessive network signaling resources, core network processing capacity, and UE battery life. LDR solves this by allowing a single request to define a future action plan. This reduces signaling overhead, optimizes network resource utilization, and is more considerate of UE power constraints. It enabled a new class of location-based services that are proactive, scheduled, or event-triggered, forming a foundational capability for the Internet of Things (IoT) and Machine-to-Machine (M2M) tracking use cases that emerged later. Its introduction in the R99 timeframe positioned GSM and UMTS networks to offer sophisticated value-added services.

Key Features

• Supports deferred triggering based on absolute time, periodic intervals, or change of area events
• Stores and manages location requests within the network (e.g., in GMLC) until activation
• Integrates with all standardized LCS positioning methods (Network-based, UE-based, Assisted)
• Reduces network signaling load compared to repeated immediate location requests
• Enables battery-efficient periodic or event-driven tracking for UEs
• Includes mechanisms for request cancellation, modification, and privacy authorization checks

Evolution Across Releases

Defining Specifications