How to Increase Range in Bluetooth Low Energy?

So Bluetooth is a Radio Technology in the form of Electromagnetic Radiation.

Electromagnetic Radiation can travel to a Certain Distance and that is a Range.

But wait!?

See the below Scenario -

In case of Wireless Communications, Range is maximum distance at which a Receiver can extract the Data from the Demodulated Wave

Range depends on generally two factors in case of Bluetooth:

• Increase the TX Power
• Encoding the Transmitted data with Forward Error Correction?
• Receiver sensitivity of the receiver radio

The receiver sensitivity is defined by how weak signals the receiver can receive compared to the level of interfering RF power received simultaneously.

In an operating RF link, the transmitter will transmit at a specified RF power level, and a (usually very tiny) fraction of that RF power will be picked up by the receiving antenna and fed to the receiver.

So as per the Bluetooth 5 Specification, there are Three different Phy Modes.

LE 1 M Phy

• Transferring data over the mandatory symbol rate of 1 mega symbol per second (Msym/s) where 1 symbol represents 1 bit. This results in a bit rate of 1 megabit per second (Mb/s), which is called as LE 1 M PHY

LE 2 M Phy

• BLE also supports an optional symbol rate of 2 Msym/s, with a bit rate of 2 Mb/s, which is called as LE 2M PHY

BLE have an additional Option called as LE Coded PHY

Since BLE is all about consuming low power, we cannot increase TX Power.

The LE Coded PHY allows range to be quadrupled (approximately), compared to Bluetooth 4 and this has been accomplished without increasing the transmission power required

If there is more Noise in Background. More the Noise in the received signal, the harder it becomes to decode.

At some point, there will be errors in the decoding process.

We can quantify the level of errors experienced and we call this the Bit Error Rate (BER). BER is essentially the probability that a transmitted bit will be incorrectly decoded by the receiver.

The LE Coded PHY uses Forward Error Correction (FEC), a particular approach to error correction. It works by adding additional, redundant bits to the transmitted packets. The sole purpose of those bits is to support the application of the FEC algorithm so that error correction can be performed.

LE Coded PHY have further 2 modes as mentioned below:

S2 : In LE Coded S=2 mode, each bit is represented by two symbols. Thus, the data rate is 500kbps. In this mode the range is roughly doubled compared to the LE 1M PHY

S8 : In LE Coded S=8, each bit is represented by eight symbols. This gives a data rate of 125kbps. In this mode the range is roughly quadrupled compared to the LE 1M PHY.

In general, all the Bluetooth Stacks have sort of API Methods that can be used to configure the PHY in either of the above modes.

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