Subscribed to Licensed Shared Access

Description

Licensed Shared Access (LSA) is a regulatory framework that allows sharing of spectrum between an incumbent user (e.g., government, military) and one or more licensed operators. The 'Subscribed to LSA' concept refers to the set of LSA licenses that a user (i.e., a subscriber of a mobile operator) has subscribed to. In the context of 3GPP, this term is defined in TS 22.043 and 42.043, which specify the service requirements for LSA. The subscription data indicates which LSA bands and geographic areas the user is allowed to use, based on their operator's LSA license. When a user attempts to access an LSA cell, the network checks whether the user's subscription includes that LSA. If not, access may be denied.

Technically, the LSA framework involves an LSA Repository that holds information about the incumbent's usage and available spectrum, and an LSA Controller that manages the sharing arrangement. The mobile operator's network, specifically the LSA Client, interacts with the LSA Controller to obtain spectrum grants. The user's subscription to LSA is part of their overall subscription profile, stored in the HLR/HSS/UDM. This allows the network to enforce access control to LSA cells based on the user's subscription. For example, a user may have subscribed to LSA in a specific frequency band, but not in another, depending on their operator's agreements and the user's service plan.

The term was introduced in Release 4, but LSA itself became prominent later, around Release 14, with dedicated work on LSA in 3GPP. The definition 'Set of LSAs, which the user has subscribed to' has remained essentially unchanged across releases. However, the underlying architecture and procedures have evolved to support more dynamic sharing, including CBRS in the US and similar frameworks. The subscription data may include multiple LSAs, each identified by an LSA ID, which typically includes the geographic area and frequency range. The network uses this information to determine whether a user can access a particular LSA cell.

In practice, when a UE attempts to access a cell that operates under LSA, the network (e.g., MME/SMF) checks the user's subscription profile to see if the corresponding LSA ID is included in the subscribed LSA set. If yes, the UE is allowed to use the LSA spectrum, subject to dynamic availability from the LSA Controller. If not, the UE may be denied service on that cell or redirected to another cell. This ensures that only authorized users consume the shared spectrum, protecting the incumbent and other operators.

The 'Subscribed to LSA' concept is a key enabler for LSA-based spectrum sharing, allowing operators to offer differentiated services based on spectrum access. It also facilitates roaming, as the visited network can check the user's subscription to LSA before granting access. As spectrum sharing becomes more prevalent (e.g., in 5G and beyond), this concept remains relevant for managing access to shared bands.

Purpose & Motivation

The 'Subscribed to LSA' concept was created to manage access to shared spectrum under the Licensed Shared Access framework. It solves the problem of ensuring that only users who are authorized by their subscription can use LSA spectrum, protecting incumbent users and other operators from unauthorized access. Without this subscription control, any user could potentially access LSA cells, leading to congestion and violation of sharing agreements. The concept provides a standardized way to store and enforce LSA access rights in the subscription profile, enabling operators to offer LSA-based services and roamers to access LSA spectrum when permitted. It also supports the dynamic nature of LSA by allowing the network to check subscription in real-time during access attempts.