Test-and-Measurement » Bluetooth Testing » Bluetooth Radio Conformance: Device Testing and Measurements

Bluetooth Radio Conformance: Device Testing and Measurements

bluetooth testing

radio conformance

rf measurements

device testing

bluetooth device

This page describes the Bluetooth device testing procedure to test Bluetooth PHY/RF (radio) layers. The testing of a Bluetooth device covers both transmitter/receiver parts as per Bluetooth radio (RF) conformance test specifications.

Introduction

Bluetooth RF test specifications were formalized by the Bluetooth SIG (Special Interest Group). IEEE initially standardized Bluetooth as IEEE 802.15.1 but no longer maintains the standard. Recently, the Bluetooth SIG published V5.1 as a successor to V5.0.

The 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.

The following figure depicts protocol stack layers in a typical Bluetooth device. The Bluetooth conformance testing requires validation of all these protocol layers. The major ones include the physical layer and radio frequency layers. The radio layer lies below the physical layer.

BLE Protocol Stack

Bluetooth devices operate in the 2.4 GHz ISM band, which ranges from 2400MHz to 2483.5 MHz.

Bluetooth Smart or BLE frequency channels

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.

The following table summarizes the Bluetooth measurements performed on the 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, a positive frequency deviation represents “binary-1” whereas a negative frequency deviation represents “binary-0.” | | | • In this test, the system verifies that the frequency deviations of the data bits transmitted in a GFSK packet are within limits. | | | • (Basic rate pass limit:) | | | • $140 \text{ KHz} \leq \Delta f_{1 \text{ avg}} \leq 175 \text{ KHz}$ | | | • $\Delta f_{2 \text{ max}} \geq 115 \text{ KHz}$ for at least 99.9 % of all $\Delta f_{2 \text{ max}}$ | | | • $\Delta f_{2 \text{ avg}} / \Delta f_{1 \text{ avg}} \geq 0.8$ | | | • (Low Energy pass limit:) | | | • $140 \text{ KHz} \leq \Delta f_{1 \text{ avg}} \leq 175 \text{ KHz}$ | | | • At least 99.9% of $\Delta f_{2 \text{ max}}$ values over 10 test packets $\geq 185 \text{ KHz}$ | | | • $\Delta f_{2 \text{ avg}} / \Delta f_{1 \text{ avg}} \geq 0.8$ | | Output power | Minimum output power : $0.01 \text{mWatt} (-20 \text{ dBm})$ | | | Maximum output power : $10 \text{mWatt} (+10 \text{ dBm})$ | | In-band spurious emission | • The purpose of this test is to verify that the level of unwanted signals from the transmitter within the operating band of the device does not exceed specified limits. | | | • (Pass limit for Bluetooth Basic rate/EDR:) | | | $P_{\text{Tx-26dB}}(f) \leq P_{\text{Txref}} - 26 \text{ dB}$ for $| M-N | = 1$ | | | $P_{\text{Tx}}(f) \leq -20 \text{ dBm}$ for $| M-N | = 2$ | | | $P_{\text{Tx}}(f) \leq -40 \text{ dBm}$ for $| M-N | \geq 3$ | | | • (Pass limit for Bluetooth Low Energy :) | | | $P_{\text{Tx}} \leq -20 \text{ dBm}$ for $F_{\text{Tx}} \pm 2 \text{ MHz}$ | | | $P_{\text{Tx}} \leq -30 \text{ dBm}$ for $\{F_{\text{Tx}} \pm [3+n] \text{ MHz}\}$ ; 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 receiver tests include the actual sensitivity level, interference performance, Out of Band Blocking, intermodulation characteristics, maximum usable level, reference signal definition, etc.

The following table summarizes the Bluetooth measurements performed on the 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 (C/I)	Both the interfering signal and wanted signal should be GFSK-modulated.
	Passing Limits for various C/I types are as follows.
	(C/I co-channel ) = 21 dB
	(C/I 1 MHz ) = 15 dB
	(C/I 2 MHz ) = -17 dB
	(C/I >=3 MHz ) = -27 dB
	(C/I Image frequency ) = -9 dB
	(C/I Image +/- 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 the 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%; a 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 the reference signal are as follows.
	Modulation = GFSK
	Modulation index = $0.5 \pm 1$ %
	BT = $0.5 \pm 1$ %
	Bit Rate = $1 \text{ Mbps} \pm 1 \text{ ppm}$
	Modulating Data for the wanted signal = PRBS9
	Modulating Data for the interfering signal = PRBS15
	Frequency accuracy better than $\pm 1 \text{ ppm}$

Bluetooth Device Testing and Measurements

The following figure mentions a generic test setup used for Bluetooth device testing and measurements.

As mentioned, a VSG (Vector Signal Generator) is used to generate Bluetooth-compliant signals which are fed to the receiver part of the Bluetooth device in order to test it. This test helps in receiver sensitivity and BER testing.

bluetooth test setup

A VSA (Vector Signal Analyzer) is used to test the transmitter part of the Bluetooth device. The common tests include power spectrum measurements, leakage tests, modulation quality, and so on.

The 3-port RF circulator at the 2.4 GHz band is used to direct the signal from the VSG to the Bluetooth device (Rx part) and from the Bluetooth device (Tx part) to the VSA.