LoRa Modulation Basics: CSS, Advantages, and Properties

This page describes LoRa modulation basics. It mentions LoRa modulation advantages or properties.

The LoRa modulation is also known as CSS modulation (Chirp Spread Spectrum modulation).

In this LoRa modulation technique, spreading of the spectrum is obtained by generating a chirp signal that varies continuously in frequency.

Due to this, the timing offset and frequency offset are equivalent between the LoRa transmitter and receiver parts. This simplifies the receiver design by avoiding complex algorithms.

Moreover, the frequency bandwidth of the chirp is equivalent to the spectral bandwidth of the LoRa modulated signal. It’s a robust modulation technique compared to other spread spectrum techniques such as DSSS.

It addresses all the issues encountered in DSSS and at the same time provides a low-cost and low-power-based solution. It’s also known as CSS modulation due to the Chirp Spread Spectrum technique employed.

The following equation/formula mentions the relation between bit rate, chip rate, and symbol rate of LoRa modulation:

Rb = SF * ( 1/[2^SF /BW] ) bits/sec

Where:

• SF = Spreading factor
• BW = Bandwidth of modulation

LoRa modulation incorporates error correction features in the physical layer, hence improving the error correction capabilities in the system at the cost of increased redundancy. The LoRa bit rate in bps can be defined by the following equation/formula for this system.

LoRa Modulation Advantages | LoRa Modulation Properties

Following are the properties or advantages of LoRa Modulation:

• Both bandwidth and frequency are scalable.
• It delivers a constant power envelope, and hence the power amplifier used for FSK can be reused, which saves cost.
• As it provides processing gain, less output power can deliver the same RF link budget.
• It is resistant against any in-band as well as out-of-band interference types due to its higher BT product. Moreover, the LoRa signal is immune against multipath fading due to its broad spectrum shape. Hence, it can be employed in both urban/suburban environments.
• LoRa modulation based signal is doppler resistant as doppler shift introduces very small frequency shift and also negligible time shift in the baseband signal.
• It delivers about four times more coverage range compared to FSK modulation due to its robust nature against interference and fading.
• It helps in achieving enhanced capacity due to the simultaneous transmission of multiple spread signals on the same RF channel with the help of different spreading factors.
• It discriminates between time and frequency errors linearly and hence it is considered to be an ideal modulation technique for radar as well as real-time localization applications.