What is the GPS L5 Band?

The GPS L5 band has a center frequency of 1176.45 MHz and a bandwidth of 12.5 MHz. It operates in the frequency range from 1170.2 to 1182.7 MHz. The broadcast of GPS signals in the L5 band has been reserved specifically for aviation safety services and mission-critical applications. Due to their critical nature, the signals transmitted in this band have relatively higher powers compared to signals in the GPS L1 and L2 bands. The lower frequency range of the L5 GPS band gives signals transmitted at these frequencies better propagation and penetrating properties over those sent in via L1/L2 bands, thereby enhancing the quality of reception.

Before December 2005, the basic GPS capability included the standard positioning service (SPS) on the L1 band and the precise positioning service (PPS) on both L1 and L2. Although these two bands offered good signal reception quality, the US government proposed a modernization plan to further improve the quality of service (QoS) with the introduction of the L5 band.

The GPS L5 signal consists of two different carrier frequencies which are in-phase and Quadrature, and these two signals are out of phase by 90˚. Each of them is modulated using the BPSK modulation scheme by a separate binary sequence. The in-phase signal consists of navigation, ranging, and synchronization data while the Quadrature signal contains only the synchronization data. Furthermore, the two signals use pseudo-random number (PRN) codes so that they are unique to each other and therefore, do not interfere when transmitted and received in the same L5 band. In general, every GPS system includes a PRN generator that generates different codes by selectively delaying one signal with respect to others in the time domain, which results in multiple unique satellite codes. These codes are then allocated to individual mobile users. 

The two carrier frequencies carry data using an in-phase signal and a pilot using Quadrature signal. A pilot signal is a signal that is used to provide reference (for timing synchronization, continuity, etc.) for other signals that are yet to be transmitted for primary communication purposes. Both the carrier signals have a time duration of 1 ms and deliver a chip rate of 10.23 Mbps during communication. 

The table below provides the important parameters used to generate GPS L5 signals in the bands. 

Click here to learn more about all GPS frequency bands.