Bluetooth radio conformance | Bluetooth Device testing and measurements
This page describes bluetooth device testing procedure to test bluetooth PHY/RF (radio) layers. The testing of bluetooth device covers both transmitter/receiver parts as per bluetooth radio (RF) conformance test specifications.
Introduction:
Bluetooth RF test specifications were formalized by Bluetooth SIG (Special Interest Group).
IEEE initially standardized bluetooth as IEEE 802.15.1 but no longer maintains the
standard. Recently bluetooth SIG has published V5.1 as successor to V5.0.
Following table mentions bluetooth standard versions, data rate, modulation and so on.
| Bluetooth Standard | Data rate | Modulation | Description |
|---|---|---|---|
| V1.0 | 1 Mbps | GFSK | Initial specification |
| V1.2 | 1 Mbps | GFSK | First FDA approved bluetooth medical system as per this standard has been developed. |
| V2.0 + EDR | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | EDR specification has been introduced for fast data transfer. |
| V2.1 + EDR | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | SSP (Secure Simple pairing) and EIR (Extended Inquiry Response) concepts have been introduced in bluetooth devices. |
| V3.0 + HS | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | |
| V4.0 (Smart) | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | BLE protocol stack and 128 bit AES have been introduced. |
| V4.1 | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | |
| V4.2 | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | Increased data throughput with data length extension, Increased privacy and so on. |
| V5.0 | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | 2 Mbps PHY for LE, LE Long Range |
| V5.1 | 1 Mbps, 2 Mbps, 3 Mbps | GFSK, π/4-DQPSK, 8-DPSK | Released recently in Jan, 2019, Refer Bluetooth v5.0 versus v5.1 >> |
Following figure depicts protocol stack layers in a typical bluetooth device. The bluetooth conformance testing requires to validate all of these protocol layers. The major among them include physical layer and radio frequency layers. Radio layer lies below physical layer.
Bluetooth devices operate in 2.4 GHz ISM band which ranges from 2400MHz to 2483.5 MHz.
The bluetooth uses 40 frequency channels out of which 3 are used as advertising channels and 37 are used as data channels.
Bluetooth Device testing for transmitter part
The common bluetooth transmitter tests include modulation spectrum tests, Spurious tests (in-band, out-of-band), radio frequency tolerance etc. Following table summarizes the bluetooth measurements performed on bluetooth transmitter part during bluetooth device testing.
| Bluetooth transmitter tests | Description with limits (if any) |
|---|---|
| Modulation characteristics | • Bluetooth packets use GFSK modulation scheme. In this modulation type,
positive frequency deviation represents "binary-1" where as
negative frequency deviation represents "binary-0". • In this test, system verifies frequency deviations of the data bits transmitted in a GFSK packet are within limits or not. • (Basic rate pass limit:) • 140 KHz <=Δf1avg <= 175 KHz • Δf2max >= 115 KHz for at least 99.9 % of all Δf2max • Δf2avg/Δf1avg >=0.8 • (Low Energy pass limit:) • 140 KHz <=Δf1avg <= 175 KHz • At least 99.9% of Δf2max values over 10 test packets >=185 KHz • Δf2avg/ Δf1avg >=0.8 |
| Output power | Minimum output power : 0.01mWatt (-20 dBm) Maximum output power : 10 mWatt (+10 dBm) |
| In band spurious emission | • The purpose of this test is to verify that the level of unwanted signals from the transmitter
within operating band of the device does not exceed specified limits. • (Pass limit for Bluetooth Basic rate/EDR:) PTx-26dB (f) <= PTxref - 26 dB for |M-N| = 1 PTx (f) <= -20 dBm for |M-N| = 2 PTx (f) <= -40 dBm for |M-N| >= 3 • (Pass limit for Bluetooth Low Energy :) PTx <= -20 dBm for FTx +/- 2 MHz PTx <= -30 dBm for {FTx +/- [3+n] MHz} ; where n =0,1,2,.. |
| Out-of-band spurious emission | The equipment manufacturer is responsible for the ISM out-of-band spurious emissions requirements in the intended countries of sale. |
| Radio Frequency tolerance | • The deviation of the center frequency during the packet shall not exceed
+/- 150 kHz, including both the initial frequency offset and drift. • The frequency drift during any packet shall be less than 50 kHz. • The maximum drift rate is 400 Hz/µs. |
Bluetooth Device testing for receiver part
The common bluetooth transmitter tests include actual sensitivity level, Interference performance, Out of Band Blocking, Intermodulation characteristics, Maximum usable level, Reference signal definition etc. Following table summarizes the bluetooth measurements performed on bluetooth receiver part during bluetooth device testing.
| Bluetooth receiver tests | Description with limits (if any) |
|---|---|
| Actual sensitivity level | The actual sensitivity level is defined as the receiver input level for which a
BER of 0.1% is achieved. The actual sensitivity level of the receiver shall be less than or equal to -70 dBm. |
| Interference performance (Carrier to Interference ratio) | Both the interfering signal and wanted signal should be GFSK-modulated.
Passing Limits for various C/I types are as follows. (C/Ico-channel) = 21 dB (C/I1 MHz) = 15 dB (C/I2 MHz) = -17 dB (C/I>=3 MHz) = -27 dB (C/IImage frequency) = -9 dB (C/IImage +/- 1 MHz) = -15 dB |
| Out of band blocking | • The out-of-band blocking test is performed by generating the signal of interest and
then combining it with the interfering signal that is out-of-band. • The BER of <= 0.1% (or PER better than 30.8% for a minimum of 1500 packets) is still the same passing limit. • The power of level of the interfering signal varies with frequency. |
| Intermodulation characteristics | The purpose of the receiver intermodulation test is to verify that the receiver can demodulate a Bluetooth signal among unwanted signals nearby in frequency.
Passing limits for BR and LE are as follows. For Basic Rate BER <= 0.1% For LE PER < 30.8%; minimum of 1500 packets are used during the bluetooth device testing. |
| Maximum usable level | The maximum usable input level the receiver can operate at shall be >= -10 dBm. BER shall be <= 0.1% at -10 dBm input power. |
| Reference signal definition | The parameters of reference signal are as follows. Modulation = GFSK Modulation index = 0.5 ± 1% BT = 0.5 ± 1% Bit Rate = 1 Mbps ±1 ppm Modulating Data for wanted signal = PRBS9 Modulating Data for interfering signal = PRBS15 Frequency accuracy better than ±1 ppm |
Bluetooth device testing and measurements
➤Following figure mentions generic test setup used for bluetooth device
testing and measurements.
➤As mentioned VSG (Vector Signal Generator) is used to generate bluetooth
compliant signals which is fed to receiver part of the bluetooth device in order to test it.
This test helps in receiver sensitivity and BER testing.
➤VSA (Vector Signal Analyzer) is used to test transmitter part of bluetooth device.
The common tests include power spectrum measurements, leakage test, modulation quality and so on.
➤The 3-port RF circulator at 2.4 GHz band is used to direct signal from VSG to bluetooth device (Rx part) and
from bluetooth device(Tx part) to VSA. Refer working of RF Circulator >> for more information.
References:
• www.bluetooth.com
Bluetooth and BLE Related Links
Also refer bluetooth tutorial covering following sub topics:
Bluetooth tutorial
BLE tutorial
Frequency
PHY Layer
MAC layer
Stack
Power classes
Security
products
versions
Bluetooth Vs BLE
BLE (Bluetooth Low Energy) Links
➤Bluetooth v4.2 versus v5.0 >>
➤Bluetooth v5.0 versus v5.1 >>
➤BLE states and state diagram >>
➤BLE advertising and data channels >>
➤BLE protocol stack architecture >>
➤BLE connection process >>
➤BLE advertising and data packet formats >>
RF and Baseband Measurement Links
IoT Wireless Technologies
RF Wireless Test and Measurement Solutions
BER Testing equipments
Agilent T & M Solutions
Anritsu T & M Solutions
Rohde & Schwarz T & M solutions
wireless channel emulator
Vector signal generator
Vector signal analyzer
Power Analyzer Equipments
Protocol Analyzer