Aggregated Allocation Bandwidth

Description

Aggregated Allocation Bandwidth is a physical-layer metric introduced in 3GPP Release 19 that quantifies the total frequency-domain resource occupied by a transmission. Rather than measuring the nominal channel bandwidth of a single carrier, it sums the bandwidths of every allocated resource block (RB) across all transmission occasions, including cases where two component carriers (CCs) are aggregated. Each RB comprises 12 subcarriers, so the bandwidth contribution of an allocation is computed as the number of allocated RBs (LCRB) multiplied by 12 and by the subcarrier spacing (SCS) in use. For two aggregated CCs the formula becomes LCRB,1 × 12 × SCS1 + LCRB,2 × 12 × SCS2, where the subscripts denote the respective carriers.

The concept is defined and tested in the RF specification series, notably TS 38.101 (NR User Equipment radio transmission and reception) and TS 38.521 (NR User Equipment conformance testing). These specifications govern how much spectrum a device may actually occupy and how that occupation is verified in test laboratories. Aggregated Allocation Bandwidth provides a single, well-defined quantity that test houses and chipset vendors can use when validating transmitter behavior such as occupied bandwidth, spectrum emission mask compliance, and maximum power reduction (MPR) calculations.

Architecturally, the metric sits at the intersection of scheduling and RF. The scheduler in the gNB decides how many RBs to grant on each carrier; the resulting LCRB values and the SCS configured per carrier determine the Aggregated Allocation Bandwidth. Because NR supports multiple numerologies (15, 30, 60, 120 kHz SCS), the same number of RBs can represent very different absolute bandwidths depending on the SCS. When carrier aggregation is used, the two carriers may even employ different numerologies, which is why the formula weights each carrier's RB count by its own SCS.

In operation, Aggregated Allocation Bandwidth influences several RF behaviors. A larger aggregated bandwidth generally requires higher linearity from the power amplifier and may trigger different MPR allowances to keep emissions within regulatory limits. It also affects the definition of the allocated channel bandwidth used in adjacent channel leakage ratio (ACLR) and spectrum flatness evaluations. For network planners, understanding this metric helps predict the instantaneous spectral load a UE places on the air interface, which is relevant for coexistence studies and for dimensioning guard bands between operators.

The term is closely related to other resource-allocation concepts such as the allocated resource block count, channel bandwidth, and transmission bandwidth configuration. While channel bandwidth describes the nominal width of a carrier, Aggregated Allocation Bandwidth describes what is actually used in a given transmission occasion, making it a more dynamic and scheduling-dependent quantity. This distinction is important for accurate conformance testing and for modeling real-world spectral efficiency.

Purpose & Motivation

Aggregated Allocation Bandwidth exists to give the 3GPP RF community a precise, testable definition of the spectrum a device actually occupies during a transmission, especially when multiple component carriers are aggregated. Before this term, engineers often relied on nominal channel bandwidth or per-carrier RB counts, which did not capture the combined spectral footprint of multi-carrier transmissions with potentially different numerologies. That gap made it difficult to write unambiguous conformance tests for occupied bandwidth and emission limits.

The metric solves a practical problem in carrier aggregation: when two CCs use different subcarrier spacings, simply adding RB counts is meaningless because each RB spans a different absolute bandwidth. By weighting each carrier's RB allocation by its own SCS, the formula produces a physically meaningful total. This enables consistent MPR determination, spectrum emission mask evaluation, and power spectral density compliance checks across diverse CA configurations.

Its introduction in Release 19 reflects the continued maturation of NR carrier aggregation, including scenarios with mixed numerologies and flexible scheduling. As networks push toward higher bandwidths and more complex aggregation, having a standardized way to express aggregated allocation bandwidth supports interoperability, regulatory approval, and predictable device behavior across vendors and test environments.