The Bluetooth wireless standard is coming into its own, and hundreds of millions of Bluetooth-enabled products will ship by the end of 2002. The Bluetooth technology will be self-contained within many products; for others, it will be an addition in the form of a PC Card that plugs into a mobile device or a dongle that plugs into a desktop system's RS-232 or parallel-printer port. As Bluetooth becomes ubiquitous, you'll find yourself having to test Bluetooth devices at the protocol-stack and RF levels.
A complete Bluetooth module comprises a radio transceiver, a base band-link controller, and a link manager (Figure 1). The base
A complete Bluetooth module comprises a radio transceiver, a base band-link controller, and a link manager (Figure 1). The baseband-link controller connects the radio hardware to the base band-processing and physical protocol layer. The link manager performs high-level protocol activities such as link setup, authentication, and configuration. Application-layer software sits above the link manager.
A Bluetooth implementation can operate as a single-chip (integrating radio and protocol stack) or multi-chip (separate radio and protocol ICs) design. Cellular-phone manufacturers may wish to combine the Bluetooth baseband function in the same device as the GSM (Global Standard for Mobile Communication) baseband function and, therefore, will want a separate Bluetooth radio. A digital camera manufacturer is more likely to select a single-chip design to simplify assembly.
RF, protocol, and profiles
Three aspects of a Bluetooth module need testing: RF, protocol, and profiles. You can perform many of the RF measurements with standard test instruments such as spectrum analyzers with vector demodulation, transmitter analyzers, power meters, digital-signal generators, and BERTs (bit-error-rate testers).
Some of the measurements, however, require the radio to form a standard Bluetooth radio-link connection with the test instrument and the test instrument to have some control over the equipment under test (Figure 2). For these tests, the test system must be able to support the Bluetooth protocol to make the link. Consequently, you can expect instrument vendors to develop new test instruments similar to the integrated radio test sets for digital cellular radio.
For protocol tests, you can use protocol sniffers that monitor and display data moving between Bluetooth devices. You can also use products such as the EBDK (Ericsson Bluetooth Development Kit). Ericsson will soon release a version of the EBDK, known as a Blue Unit, that will include software for use during early qualification testing. Eventually, some companies should develop complete reference test systems.
A profile is the application level protocol that makes a device perform its functions as the user expects. All Bluetooth devices that claim to offer a given functionality must use the appropriate profile from the Bluetooth specification. This requirement ensures interoperability between common devices from multiple vendors.
For example, the LAN access profile defines a data connection between a DT (data terminal) and a LAP (LAN access point). The profile defines the following services and connection states for the application layer: initialization of LAN access service, shutdown of LAN access service, establishment of LAN connection, loss of LAN connection, and disconnection of LAN connection.
Until a reference test system is available, early Bluetooth profile testing will require product-to-product interoperability testing. To facilitate this, a series of "Unplug fests" have been arranged by the Bluetooth Special Interest Group. At these meetings, companies with functional products can test product interoperability against products from other suppliers.
RF and single-chip measurements
The Bluetooth radio specification outlines the performance requirements for the radio and the test to confirm conformance. To measure the performance of a Bluetooth module, the test instrumentation must be able to establish a Bluetooth link with the EUT (equipment under test). It can then put the EUT into test mode. Test mode is a mandatory feature of a Bluetooth module in which the EUT can enter a loop back mode or can disable frequency hopping for making BER measurements, for example. A Bluetooth test system should also be able to disable hopping, set specific frequencies for tests, and control the transmit power level.
During design and development, you'll want to test the radio in isolation from the protocol stack that controls it. In these cases, you need to control the radio so you can set frequencies and levels to make raw transceiver measurements. You can then feed the radio output directly into a spectrum analyzer with vector signal analysis or into a transmitter analyzer and power meter to make the measurements (Figure 3). The measurements you can make will vary according to the control that the radio IC manufacturer provides over the IC connectors. The radio will have inputs controlling data in and out, Tx on, clocks, and supply voltage. Without a protocol stack, the radio may not function at all.
Many radio designs permit you to feed PRBS (pseudo-random bit sequences) into the transmitter modulator and use manufacturer-specific control lines to force the radio to transmit continuously at one frequency. Doing so enables you to make frequency, power, and modulation measurements as well as output spectrum measurements. As an alternative method to radio IC testing, you can build a test jig that holds the radio IC and has a protocol stack built onto it. This method allows for comprehensive testing and simulates the integrated module approach outlined below.
There is no standard for the interface between a protocol stack and a radio, typically known as the radio interface. You must use a test fixture to hold the radio IC and provide it with some base band control to give Bluetooth functionality. This arrangement lets you test radio ICs with a Bluetooth link and base band control.
The connection between the radio and the test instrument vary depending upon the Bluetooth device implementation. Some radios or integrated modules have printed antennas as part of the design. In this case, you may only be able to make a connection over the air to an antenna on the test instrument input. If you use this approach, then you must characterize the path loss for each of the 79 Bluetooth frequencies. If the radio IC has an RF output connector, a direct connection to the test instrument simplifies calibrated power and sensitivity measurements. Even if you use a direct connection, though, you should measure and correct for the path loss at each frequency.
Testing OEM Bluetooth products
OEMs buying commercial Bluetooth chip sets still need to test. Inevitably, packaging can influence the performance of a finished product because of the antenna's position as well as other internal electronics. In a mobile phone, the other electronics will, by definition, include an interfering radio transceiver. Similarly, PCs have high-speed clocks or noisy buses that can degrade module sensitivity.
In the OEM production environment, the tests have to validate performance in the shortest possible time. Production engineers need to select the subset of the conformance test specifications that are appropriate for their products' requirements.
To confirm that the device will operate over the Bluetooth specification's 10m range, engineers will still need to measure sensitivity and power levels. The conformance specification requires engineers to measure receiver sensitivity as a BER of more than 1,600,000 bits at three frequencies. This test alone would take at least 25 sec using standard single-slot DH1 packets and so, in practice, the test will measure fewer bits even at a reduced number of frequencies.
In addition to RF measurements, OEMs should perform a functional test. In the case of a Bluetooth-enabled digital camera, for example, functional testing can include sending an instruction over the Bluetooth interface to activate a shutter release with flash. Engineers would need to create this command at a high level in the protocol stack (typically the application level), and the test equipment would need to package the command into the Bluetooth format. Validating the camera's response to a high-level command would give the manufacturer confidence that the interface was functioning correctly, although it is not necessarily a guarantee of robust performance.
How to qualify products with Bluetooth interfaces
No product may be sold as "Bluetooth enabled" without first demonstrating compliance with the Bluetooth specification. You can refer to the rules laid out in the Bluetooth Qualification Program when you check compliance. Qualification is essential for ensuring that consumers have a good experience with Bluetooth-branded products. You must make sure that interoperability between products supplied by different manufacturers is guaranteed.
To obtain qualification, a manufacturer must first become a Bluetooth member by signing the adopters agreement. Two additional bodies help qualify a product: a BQTF (Bluetooth Qualification Test Facility) and a BQB (Bluetooth Qualification Body).
A BQTF is an accredited organization with the skills and equipment to test a product based on the Bluetooth specification. A BQTF may choose not to offer qualification for every aspect of the Bluetooth standard. For example, many profiles are limited to a few specific applications, and some aspects of the Bluetooth specification are optional. The BQTF performs measurements on behalf of the manufacturer on the appropriate radio, protocol, and profiles for the equipment under test. The BQTF prepares a test report that forms part of a compliance folder that is submitted to the BQB.
The role of the BQB is to review all submitted documentation and ensure that all the appropriate tests have been performed and passed satisfactorily. If all is well, the product is listed as Bluetooth qualified and may be sold as Bluetooth enabled.
Background to Bluetooth
As a standard for wireless communication between multiple devices, Bluetooth supports voice and data. In 1994, Ericsson began to develop the standard at its Lund site in Sweden. The project was initially called MC Link (multi-communicator link). In 1997, Ericsson approached other companies with a mutual interest in defining an open standard for a wireless link. In February 1998, five promoters—Ericsson, IBM, Intel, Nokia, and Toshiba—formed the SIG (Special Interest Group) to promote the standard, which they renamed Bluetooth.
The Bluetooth SIG announced the standard on May 20, 1998. Two years later, more than 1800 companies had joined the consortium as adopters of the technology. The consortium's objective is to create a de facto short-range wireless communication standard that all companies could use. In the autumn of 1999, the promoter group was expanded to nine companies, adding 3Com, Lucent Technologies, Microsoft, and Motorola. Although today the Bluetooth SIG standard is "owned" by the promoter group, it is expected that the standard will become an IEEE standard (802.15) this year and remain fundamentally the same.
Bluetooth offers wireless communication between one or more devices over a 10m range with a maximum gross data rate of 721 kbps in the unlicensed 2.4-GHz ISM band. The purpose of the technology is to offer a low-cost, simple-to-use alternative to wired connections. As such, the potential user base is large and varied.
The first adopters of Bluetooth are expected to be mobile-phone manufacturers with wireless headsets. Mobile phones could also interface with a Bluetooth-enabled PCs to exchange files or e-mail. A PC could have a wireless mouse and keyboard, and office printers could become Bluetooth enabled so that wireless printing is possible in any location. Other early adopters of the technology include PDAs (personal digital assistants), LAN access points, digital cameras, and security-access cards.
For protocol tests, you can use protocol sniffers that monitor and display data moving between Bluetooth devices. You can also use products such as the EBDK (Ericsson Bluetooth Development Kit). Ericsson will soon release a version of the EBDK, known as a Blue Unit, that will include software for use during early qualification testing. Eventually, some companies should develop complete reference test systems.
A profile is the application level protocol that makes a device perform its functions as the user expects. All Bluetooth devices that claim to offer a given functionality must use the appropriate profile from the Bluetooth specification. This requirement ensures interoperability between common devices from multiple vendors.
For example, the LAN access profile defines a data connection between a DT (data terminal) and a LAP (LAN access point). The profile defines the following services and connection states for the application layer: initialization of LAN access service, shutdown of LAN access service, establishment of LAN connection, loss of LAN connection, and disconnection of LAN connection.
Until a reference test system is available, early Bluetooth profile testing will require product-to-product interoperability testing. To facilitate this, a series of "Unplug fests" have been arranged by the Bluetooth Special Interest Group. At these meetings, companies with functional products can test product interoperability against products from other suppliers.
RF and single-chip measurements
The Bluetooth radio specification outlines the performance requirements for the radio and the test to confirm conformance. To measure the performance of a Bluetooth module, the test instrumentation must be able to establish a Bluetooth link with the EUT (equipment under test). It can then put the EUT into test mode. Test mode is a mandatory feature of a Bluetooth module in which the EUT can enter a loop back mode or can disable frequency hopping for making BER measurements, for example. A Bluetooth test system should also be able to disable hopping, set specific frequencies for tests, and control the transmit power level.
During design and development, you'll want to test the radio in isolation from the protocol stack that controls it. In these cases, you need to control the radio so you can set frequencies and levels to make raw transceiver measurements. You can then feed the radio output directly into a spectrum analyzer with vector signal analysis or into a transmitter analyzer and power meter to make the measurements (Figure 3). The measurements you can make will vary according to the control that the radio IC manufacturer provides over the IC connectors. The radio will have inputs controlling data in and out, Tx on, clocks, and supply voltage. Without a protocol stack, the radio may not function at all.
Many radio designs permit you to feed PRBS (pseudo-random bit sequences) into the transmitter modulator and use manufacturer-specific control lines to force the radio to transmit continuously at one frequency. Doing so enables you to make frequency, power, and modulation measurements as well as output spectrum measurements. As an alternative method to radio IC testing, you can build a test jig that holds the radio IC and has a protocol stack built onto it. This method allows for comprehensive testing and simulates the integrated module approach outlined below.
There is no standard for the interface between a protocol stack and a radio, typically known as the radio interface. You must use a test fixture to hold the radio IC and provide it with some base band control to give Bluetooth functionality. This arrangement lets you test radio ICs with a Bluetooth link and base band control.
The connection between the radio and the test instrument vary depending upon the Bluetooth device implementation. Some radios or integrated modules have printed antennas as part of the design. In this case, you may only be able to make a connection over the air to an antenna on the test instrument input. If you use this approach, then you must characterize the path loss for each of the 79 Bluetooth frequencies. If the radio IC has an RF output connector, a direct connection to the test instrument simplifies calibrated power and sensitivity measurements. Even if you use a direct connection, though, you should measure and correct for the path loss at each frequency.
Testing OEM Bluetooth products
OEMs buying commercial Bluetooth chip sets still need to test. Inevitably, packaging can influence the performance of a finished product because of the antenna's position as well as other internal electronics. In a mobile phone, the other electronics will, by definition, include an interfering radio transceiver. Similarly, PCs have high-speed clocks or noisy buses that can degrade module sensitivity.
In the OEM production environment, the tests have to validate performance in the shortest possible time. Production engineers need to select the subset of the conformance test specifications that are appropriate for their products' requirements.
To confirm that the device will operate over the Bluetooth specification's 10m range, engineers will still need to measure sensitivity and power levels. The conformance specification requires engineers to measure receiver sensitivity as a BER of more than 1,600,000 bits at three frequencies. This test alone would take at least 25 sec using standard single-slot DH1 packets and so, in practice, the test will measure fewer bits even at a reduced number of frequencies.
In addition to RF measurements, OEMs should perform a functional test. In the case of a Bluetooth-enabled digital camera, for example, functional testing can include sending an instruction over the Bluetooth interface to activate a shutter release with flash. Engineers would need to create this command at a high level in the protocol stack (typically the application level), and the test equipment would need to package the command into the Bluetooth format. Validating the camera's response to a high-level command would give the manufacturer confidence that the interface was functioning correctly, although it is not necessarily a guarantee of robust performance.
How to qualify products with Bluetooth interfaces
No product may be sold as "Bluetooth enabled" without first demonstrating compliance with the Bluetooth specification. You can refer to the rules laid out in the Bluetooth Qualification Program when you check compliance. Qualification is essential for ensuring that consumers have a good experience with Bluetooth-branded products. You must make sure that interoperability between products supplied by different manufacturers is guaranteed.
To obtain qualification, a manufacturer must first become a Bluetooth member by signing the adopters agreement. Two additional bodies help qualify a product: a BQTF (Bluetooth Qualification Test Facility) and a BQB (Bluetooth Qualification Body).
A BQTF is an accredited organization with the skills and equipment to test a product based on the Bluetooth specification. A BQTF may choose not to offer qualification for every aspect of the Bluetooth standard. For example, many profiles are limited to a few specific applications, and some aspects of the Bluetooth specification are optional. The BQTF performs measurements on behalf of the manufacturer on the appropriate radio, protocol, and profiles for the equipment under test. The BQTF prepares a test report that forms part of a compliance folder that is submitted to the BQB.
The role of the BQB is to review all submitted documentation and ensure that all the appropriate tests have been performed and passed satisfactorily. If all is well, the product is listed as Bluetooth qualified and may be sold as Bluetooth enabled.
Background to Bluetooth
As a standard for wireless communication between multiple devices, Bluetooth supports voice and data. In 1994, Ericsson began to develop the standard at its Lund site in Sweden. The project was initially called MC Link (multi-communicator link). In 1997, Ericsson approached other companies with a mutual interest in defining an open standard for a wireless link. In February 1998, five promoters—Ericsson, IBM, Intel, Nokia, and Toshiba—formed the SIG (Special Interest Group) to promote the standard, which they renamed Bluetooth.
The Bluetooth SIG announced the standard on May 20, 1998. Two years later, more than 1800 companies had joined the consortium as adopters of the technology. The consortium's objective is to create a de facto short-range wireless communication standard that all companies could use. In the autumn of 1999, the promoter group was expanded to nine companies, adding 3Com, Lucent Technologies, Microsoft, and Motorola. Although today the Bluetooth SIG standard is "owned" by the promoter group, it is expected that the standard will become an IEEE standard (802.15) this year and remain fundamentally the same.
Bluetooth offers wireless communication between one or more devices over a 10m range with a maximum gross data rate of 721 kbps in the unlicensed 2.4-GHz ISM band. The purpose of the technology is to offer a low-cost, simple-to-use alternative to wired connections. As such, the potential user base is large and varied.
The first adopters of Bluetooth are expected to be mobile-phone manufacturers with wireless headsets. Mobile phones could also interface with a Bluetooth-enabled PCs to exchange files or e-mail. A PC could have a wireless mouse and keyboard, and office printers could become Bluetooth enabled so that wireless printing is possible in any location. Other early adopters of the technology include PDAs (personal digital assistants), LAN access points, digital cameras, and security-access cards.Tags: baseband, BERT, bit-error-rate testers, Bluetooth, Bluetooth Qualification Body, Bluetooth Qualification Test Facility, BQB, BQTF, data terminal, digital-signal generators, DT, EBDK, Ericsson, Ericsson Bluetooth Development Kit, EUT, GSM, IBM, IEEE, Intel, LAN, LAN access point, LAP, Nokia, parallel-printer port, PC Card, PDA, power meters, PRBS, pseudo-random bit sequences, RF, RS-232, Toshiba, transmitter analyzers, vector demodulation
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