Quantifying Landed Unit Cost Penalties in Global Cellular Deployments
Landed cost penalties in cellular deployments compound through regional certification surcharges, carrier profile fees, tariff codes and roaming airtime multipliers.
Band 28 Duplex Spacing
Meaning
Frequency separations define the gap between the uplink and downlink channels within a specific radio spectrum allocation. In the context of the 700 MHz spectrum, band 28 duplex spacing provides a defined distance of 55 MHz between the transmission and reception frequencies. This gap allows a device to transmit and receive data simultaneously without the outgoing signal overwhelming the sensitive incoming signal.
Spectral Isolation
Maintaining a wide distance between the two directions of communication prevents the high-power uplink from blinding the receiver. Because band 28 duplex spacing is relatively narrow compared to other low-frequency bands, it requires high-performance duplexer components. These filters must have steep roll-off characteristics to effectively separate the signals.
Filter Performance
Physical constraints of small mobile devices make it difficult to house large filters that can handle the specific band 28 duplex spacing requirements. Surface acoustic wave technology is typically used to achieve the necessary rejection levels. If the filter fails to isolate the bands, the receiver sensitivity drops, leading to dropped calls or slow data rates.
Interference Management
Global regulatory bodies define these parameters to ensure that mobile networks can operate near other services like digital television without causing mutual disruption. The specific band 28 duplex spacing ensures that handsets remain compatible with infrastructure deployed across different regions. Engineers verify this isolation during the radio frequency front-end design to ensure the module meets the strict out-of-band emission limits required for certification.
This verification involves measuring the leakage of the transmit signal into the receive path under maximum power conditions.