Selective L5

What is Selective L5 band technology? 

Selective L5 is the u-blox feature that enables situational-aware GNSS. This technology combines ultra-low power operation with intelligent signal management. It dynamically makes best use of L1 and L5 GNSS frequencies based on real-time environmental conditions. When open-sky conditions provide sufficient positioning accuracy with L1 signals alone, the receiver conserves energy by operating in single-band mode. However, when signal challenges emerge, such as in urban canyons or dense foliage, the receiver automatically engages the L5 band to maintain positioning reliability. This situational awareness overcomes the traditional trade-off between positioning accuracy and battery life.
 

 

Position accuracy varies in different environments 

Standard precision GNSS (SPG) receivers deliver solid meter-level accuracy in open sky environments. However, in more complex settings, such as in cities or regions with dense tree foliage, satellite signals may be reflected or diffracted by buildings, infrastructure, or vegetation before reaching the GNSS receiver.  

These reflections, known as multipath effects, distort the receiver’s distance calculations and can cause positioning errors of 30 meters or more in dense urban areas. In applications where such positioning errors are unacceptable, L1/L5 dual-band GNSS receivers greatly improve accuracy. 

GNSS receivers operating only in the L1 band are more susceptible to multipath effects, as these distorted signals are not correctly identified by the GNSS receiver, and thus can significantly degrade positioning accuracy.  

In contrast, using L5 band signals improves the receiver’s ability to detect and mitigate multipath interference. The L5 signal is more resilient to these effects, allowing the GNSS receiver to place greater confidence in L5-based measurements in the presence of multipath conditions. This results in improved positioning accuracy in challenging environments. 

Smart L1/L5 dual-band operation to minimize power consumption  

Although L1/L5 dual-band GNSS delivers improved positioning accuracy in challenging environments, it also consumes more power compared to L1-only operation.  

Traditional dual-band GNSS receivers continuously operate in L1/L5 mode, even when environmental conditions do not require the L5 band to maintain an optimal position. Consequently, dual-band operation consumes significantly more power than L1 only operation. For many applications, such as wearables, asset trackers, or other battery-powered IoT devices, minimizing power consumption is a critical design requirement. Continuous L1/L5 dual-band operation can therefore shorten battery life and limit device runtime.
  
Ideally, the receiver would only activate the L5 band when environmental conditions require it, while maintaining energy-efficient L1-only operation wherever possible.

Smart use of L1/L5 dual-band only when beneficial to maintain the position accuracy 

u-blox GNSS products are configurable, allowing the host MCU to enable or disable L1/L5 operation when required. However, the challenge for the host MCU lies in accurately detecting environmental conditions to decide when to enable and disable the L5 band of the GNSS.

The Selective L5 algorithm, which is supported by the u-blox F11 platform, supervises various satellite signal parameters and automatically switches between using only the L1 band and using the L1/L5 dual-band. The GNSS receiver enables the L5 band only when beneficial, thus providing a similar position accuracy to that in rural areas while saving a lot of power. Selective L5 is an optional feature, and customers retain full control over enabling or disabling the L5 band as needed.

Balancing precision and power efficiency for smarter GNSS solutions 

Selective L5 technology represents a significant step forward in GNSS performance by intelligently balancing the need for meter-level positioning accuracy with the imperative of power efficiency. By dynamically adapting to real-time environmental conditions, it ensures reliable geo-location information in challenging environments without unnecessary energy consumption. This smart, situational-aware approach makes Selective L5 an ideal solution for a wide range of applications, especially battery-powered devices, where maintaining both accuracy and long battery life is essential.