Pass Band

Description

In 3GPP terminology, a pass band refers to the frequency range in which a repeater operates under its operational configuration. A repeater is a device that receives, amplifies, and retransmits signals to extend coverage. The pass band defines the specific frequencies that the repeater is configured to amplify. This range can correspond to one or several consecutive nominal 5 MHz channels. If the channels are not consecutive, each subset of consecutive channels is considered an individual pass band. A repeater can have one or several pass bands, allowing it to support multiple non-contiguous frequency blocks.

The concept of pass band is crucial for repeater operation because it determines the frequencies that are amplified and passed through. Repeaters are used in cellular networks to fill coverage holes, extend cell range, or provide coverage in isolated areas. They are typically deployed in scenarios where a wired backhaul is not feasible or cost-effective. The pass band configuration ensures that the repeater only amplifies the intended frequencies, avoiding interference with other systems. It also allows the repeater to support multiple operators or multiple frequency bands simultaneously.

In 3GPP specifications, the pass band is defined in documents such as 21.905 (Vocabulary), 25.106 (UTRA repeater radio transmission and reception), 25.113 (Base station and repeater EMC), 36.106 (E-UTRA repeater radio transmission and reception), and others. These specifications detail the requirements for repeaters, including pass band characteristics, gain, output power, and spurious emissions. The pass band is a key parameter for testing and certification of repeaters, ensuring they meet regulatory and performance standards.

The operational configuration of a repeater includes the pass band settings, which can be static or dynamically adjusted. In some advanced repeaters, the pass band can be reconfigured remotely to adapt to changing network needs. The pass band must be carefully managed to avoid amplifying noise or interfering signals. For example, if a repeater is configured with a pass band that overlaps with another operator's frequencies, it could cause harmful interference. Therefore, coordination and filtering are essential.

Pass bands are also relevant in the context of carrier aggregation, where multiple component carriers are used. A repeater may need to support multiple pass bands to amplify different carriers. The 3GPP specifications ensure that repeaters can handle such scenarios by defining requirements for multi-band operation. Overall, the pass band is a fundamental concept for repeater design and deployment, ensuring that coverage extension is achieved without compromising network performance.

Purpose & Motivation

The concept of pass band exists to define the operational frequency range of a repeater, ensuring it amplifies only the intended signals. Repeaters are used to extend coverage in areas with weak signals, but without proper frequency management, they could amplify noise or interfere with other systems. The pass band provides a clear specification of which frequencies are amplified, allowing for coordinated deployment and avoiding interference. It also enables repeaters to support multiple non-contiguous frequency blocks by defining multiple pass bands. This concept was introduced in Release 5 and has been maintained to support evolving cellular technologies, including UMTS, LTE, and 5G. It is essential for regulatory compliance and efficient spectrum usage.