FDDsystemen

FDDsystemen, or frequency division duplex systems, are communication systems that separate uplink and downlink transmissions by using two distinct frequency bands. A fixed duplex spacing, or guard band, lies between the uplink and downlink bands to prevent interference. This requires paired spectrum, meaning two channels of equal bandwidth allocated specifically for opposite directions of transmission.

In operation, user equipment and base stations transmit and receive simultaneously on their respective bands. The separation of frequencies allows continuous bidirectional communication, at relatively stable latency and predictable interference characteristics. FDD is commonly used in cellular networks and other radio links that demand steady, always-on connectivity.

Applications and examples include traditional cellular technologies such as GSM and WCDMA, as well as LTE networks that deploy FDD bands. FDD is also used in some satellite links and microwave backhaul connections where licensing processes align with paired spectrum.

Advantages of FDDsystemen include the ability to support simultaneous uplink and downlink, consistent performance for steady traffic, and simpler uplink/downlink power control in some scenarios. They are well-suited for environments with relatively balanced or predictable traffic and where licensed, paired spectrum is available.

Limitations include dependence on paired spectrum, which can be expensive or scarce; the fixed duplex spacing can lead to inefficient use of spectrum if traffic is highly asymmetric; and the need for duplexers and related RF hardware adds cost and design complexity. Compared with TDD systems, FDD offers less flexibility in adapting to changing traffic patterns but often benefits from simpler synchronization and interference management in many deployments.