Aggregate BSS QoS Profile

Description

The Aggregate BSS QoS Profile (ABQP) is a functional construct within the GERAN architecture, specifically detailed in the BSS GPRS Protocol (BSSGP) specification (TS 48.018). It operates at the interface between the Serving GPRS Support Node (SGSN) and the Base Station System (BSS), which includes the Base Station Controller (BSC) and Base Transceiver Stations (BTS). The ABQP is not a standalone protocol but a logical profile used by the BSS to comprehend and manage the collective QoS requirements of all active Packet Flow Contexts (PFCs) for a given Mobile Station (MS). Each PFC corresponds to a specific data flow (e.g., for a PDP context) with its own QoS attributes like traffic class, priority, delay, and reliability.

Architecturally, the SGSN is responsible for establishing and managing individual PFCs for an MS based on its active Packet Data Protocol (PDP) contexts. However, from the BSS perspective, managing each PFC independently for radio resource allocation would be highly inefficient, especially when an MS has multiple simultaneous flows (e.g., web browsing and a voice call). The ABQP solves this by providing a consolidated view. The BSS calculates or derives the ABQP by aggregating the QoS parameters from all active PFCs for that MS. This aggregation process considers the most stringent requirements across flows to ensure the composite profile can satisfy all individual service commitments.

In operation, the BSS uses the ABQP to make critical radio resource management decisions. For instance, when scheduling uplink and downlink radio blocks on the Packet Data Traffic Channel (PDTCH), the BSS references the ABQP to determine the appropriate priority level, required throughput, and acceptable delay bounds for the aggregate traffic of that MS. This allows for efficient multiplexing of resources across multiple flows without needing to inspect each PFC separately for every scheduling event. The ABQP is dynamic; it changes as PFCs are created, modified, or released. The BSS must update its internal ABQP representation upon receiving BSSGP messages from the SGSN that modify the state of PFCs, such as RA-CONTROL or FLUSH-LL messages.

Key components involved with ABQP include the BSSGP layer, which transports PFC management messages, and the Radio Resource (RR) management functions within the BSC. The ABQP's role is pivotal in translating core network QoS policies (from the SGSN) into actionable radio interface parameters. It acts as a bridge between the granular, flow-specific QoS signaling from the core network and the resource-constrained, aggregate scheduling mechanisms necessary in the radio access network. This ensures that QoS commitments from the network core are upheld as effectively as possible over the air interface, balancing performance for multi-flow users with overall BSS capacity and stability.

Purpose & Motivation

ABQP was introduced to address the inherent complexity and signaling overhead of managing multiple, independent QoS flows for a single user within the resource-constrained GERAN environment. Prior to its conceptualization, the BSS would need to track and evaluate each Packet Flow Context individually for every radio resource allocation decision. This approach was inefficient and could lead to suboptimal scheduling, increased processing load on the BSC, and potential inconsistencies in QoS enforcement across different flows belonging to the same user.

The primary problem ABQP solves is the efficient translation of core network QoS parameters into practical radio interface actions. In GPRS and EDGE networks, radio resources (timeslots) are scarce and shared among many users. The creation of ABQP provided a mechanism for the BSS to synthesize a single, coherent QoS policy from potentially conflicting or diverse flow requirements. This synthesis allows the BSS's scheduler to treat the user's aggregate data traffic with a unified priority and resource allocation strategy, simplifying algorithms and improving real-time decision-making. It was motivated by the need to support more sophisticated services with differentiated QoS (beyond best-effort) in 2G/2.5G networks, such as streaming and interactive traffic, without overhauling the fundamental BSS architecture.

Historically, as GPRS evolved to support enhanced QoS features in later releases, the ABQP concept provided a stable foundation for QoS management in GERAN. It addressed the limitations of per-flow management by introducing an abstraction layer. This abstraction is crucial for scalability, enabling the BSS to support users with multiple concurrent applications (a common scenario with the rise of smartphones) while maintaining predictable performance and adhering to negotiated QoS profiles. It represents an important step in the evolution of QoS management from circuit-switched paradigms to the more flexible, flow-aware models needed for packet-switched mobile data.

Key Features

• Aggregates QoS parameters from multiple Packet Flow Contexts (PFCs) into a single profile
• Enables efficient BSS radio resource scheduling and prioritization for multi-flow users
• Dynamically updates as PFCs are established, modified, or released by the SGSN
• Simplifies QoS enforcement logic within the Base Station Controller (BSC)
• Translates core network QoS signaling into actionable radio interface parameters
• Provides a consolidated view for BSS management functions like congestion control

Evolution Across Releases

Defining Specifications