Testing Bluetooth® Smart Products for the Internet of Things

Testing Bluetooth® Smart Products for the Internet of Things

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© 2015 LitePoint, A Teradyne Company. All rights reserved.

Bluetooth Smart- IoT 1

Table of ContentsIntroduction .................................................................................................................. 2 The Market Potential for Bluetooth Smart in the Internet of Things .......................... 2 Applications for Bluetooth Smart ................................................................................ 3 Key Performance Characteristics and Operational Features ...................................... 4 Technical Specifications: A Brief History...................................................................... 7 Key Technical Specifications for Bluetooth Smart ....................................................... 8 Testing Bluetooth Smart Devices ............................................................................... 11 Bluetooth Smart Testing and LitePoint’s Role ........................................................... 15


IntroductionBluetooth Smart, the low-energy version of Bluetooth, is playing an important role in the Internet of Things (IoT). The technology has low power consumption, the components are available at very low cost, and it is supported by all mobile platforms and operating systems.

Designed specifically to connect products that use minimal bandwidth and are battery powered, Bluetooth Smart is already employed in countless products to connect people, sensors, devices and systems. Companies are using the technology to bring connectivity to medical devices, wearables, household appliances, and even toys. Forthcoming advancements will bring IP communications and mesh networking capabilities to Bluetooth Smart, further expanding its use cases and market potential.

Companies of all types, from Fortune 500 firms to crowd-funded startups, are creating IoT products with Bluetooth Smart. But for any business to compete successfully in IoT, products must work “out of box” and function as promised. Fundamentally, before putting any product on the market, companies must test the product’s wireless connectivity to make sure only quality devices reach the customer base.

Why is wireless testing so important? For Bluetooth Smart and any standards-based wireless products, companies need to verify that the devices comply with wireless specifications, meet the basic performance levels guaranteed by the standard, and conform to regulatory limits. Testing also ensures interoperability with other devices and the ability to build scale in the market.

Wireless testing is the only way to ensure product quality during manufacturing. It can reveal faulty or marginal components, design drawbacks, and assembly issues that impede performance. Test findings can detect performance trend drifts early and minimize the time needed to troubleshoot problems and correct defects, enabling companies to get good products to market faster and with confidence. Testing can also prevent product failures that can adversely impact a company’s brand and revenues.

This paper describes the wireless testing required for IoT products built with Bluetooth Smart technologies. The paper characterizes the market and motivations for using Bluetooth Smart for IoT and describes leading applications. It summarizes the technology’s key performance characteristics and operational features and discusses test specifications that must be employed to ensure product compliance.

The Market Potential for Bluetooth Smart in the Internet of ThingsThe Bluetooth Smart market is already substantial and growing at an extremely rapid pace. The research firm IHS Technology estimates that 149.7 million Bluetooth Smart (single mode) chips were shipped in 2014. Shipments are expected to increase at a compounded annual growth rate of 56.9% through 2019. The firm expects that 1.425 billion chips will ship in 2019.i

The market potential reflects the technology’s role in IoT as well as the promise it offers to this ecosystem. Following are some of the key reasons Bluetooth Smart is a good technology for IoT products.

Wireless EverywhereBluetooth Smart was designed to help build the Internet of Things. It adds wireless connectivity to devices that previously required wired connections or were not connected at all. The protocol stack is designed to provide a simple communications link between devices that must operate with very low power consumption to transfer very small quantities of data over short ranges. It deliberately minimizes the cost of adding wireless connectivity to devices to help drive the expansion of wireless into more and more products.

Access to all Mobile Platforms All smartphones are built with Bluetooth connectivity and Bluetooth Smart enables low-power devices to connect natively to these devices and mobile applications. Bluetooth Smart is already available on all mobile operating systems. This gives Bluetooth Smart an advantage in the IoT market compared to other low-power wireless communications options, such as ZigBee and Z-Wave. This native capability makes product development convenient for developers and creates a vast potential market for smartphone-centric innovations, according to IHS.

Creating New Vertical MarketsBluetooth Smart is expanding wireless connectivity into new vertical markets, such as smart homes, and even prompting innovations that work across verticals, such as wearables. Bluetooth Smart also enables developers to develop custom profiles, and this is intended to yield new categories of products that the industry has not anticipated.


Developer Friendly and Low CostBluetooth Smart can lend itself to a wide range of solutions. It is convenient to work with and very inexpensive to use. Bluetooth Smart radios and system-on-chip components can be purchased at retail for as little as $1-2 each and for much less in bulk quantities. For those new to wireless product development, maker kits that can be used for experimentation and prototyping are widely available for just $20-30.ii Further, MEMs-based sensors, such as accelerometers, gyroscopes, microphones as well as proximity, light, pressure and other sensors, can be added to IoT products for very low cost—often for well under $1.iii The combination of affordable Bluetooth Smart and MEMS components is driving innovation of new products and industries in the Internet of Things.

Applications for Bluetooth Smart Bluetooth Smart enables companies to bring connectivity to devices that operate for years on tiny batteries. The following markets, and many others, will use Bluetooth Smart technology.

MobileThe native availability of Bluetooth Smart to connect to smartphones and other mobile devices creates a vast, available market for any device that uses Bluetooth Smart technology. In mobile applications, the smartphone acts as the central “hub” device that interacts with Bluetooth Smart peripherals, such as smart watches, fitness monitors, or home thermostats. A smartphone is typically built with Bluetooth Smart Ready (dual-mode) chipsets that enable the phone to connect with Bluetooth Smart as well classic Bluetooth devices.

PCs, Peripherals and Consumer ElectronicsBluetooth Smart is extending traditional Bluetooth use cases into new types of PC and consumer electronics applications. Devices in these categories include computer stylus and mouse devices, remote controls for home entertainment and gaming systems, camera shutters, and camera flash devices. Some of the more creative applications range from toothbrushes to toys.

Beacons Bluetooth Smart is opening up opportunities for beacons that send information to smartphones. The beacons can be battery operated, which makes them convenient to install for indoor or outdoor applications. The beacons automatically work with mobile devices customers already have and the services are easy to authenticate and manage.

Retailers are using Bluetooth Smart beacons to provide push marketing to in-store customers and to facilitate mobile coupons or payments. Other venues adopting Bluetooth Smart beacons include corporate offices, hospitals, sports and entertainment facilities, and connected homes. Personal asset tracking is expected to offer another popular use case.

WearablesWearables were the first “killer application” for Bluetooth Smart. Data gathered by the wearable device is typically communicated to a smartphone, where it is displayed, stored, used to trigger alerts, or transmitted to a cloud-based service for aggregation and further analysis.

Typical wearables include activity monitors, fitness trackers, smart wrist bands, smart watches, smart glasses, smart badges, child and pet monitoring products, medical aids, health monitoring devices, head- or hand-mounted terminals and cameras, smart clothing, and virtual reality headsets. Emerging use cases include hearing aids and ingestible products.

Smart HomeThe smart home market is currently served by a variety of proprietary and standardized wireless technologies, but Bluetooth Smart is gaining traction and increased attention in this sector. Current applications include remote control and monitoring of windows and door locks, lights, household appliances, heating and cooling equipment, ceiling fan remotes, energy management systems, entertainment center components, garage door controllers, security systems, and gardening systems.

Health and Wellness Bluetooth Smart is a very practical for health and wellness applications, whether used in clinical or home settings. The technology’s security features protect confidentiality of patient and medical information during transmission. Its frequency and modulation schemes avoid interference from other RF sources such as hospital electrosurgical devices and household appliances.

Bluetooth Smart medical devices on the market include blood glucose monitors, pulse dosimeters, heart rate monitors, blood pressure monitors, asthma inhalers, breathalyzers, posture sensors, thermometers, body scales, and stethoscopes. These devices can easily connect and send data to Bluetooth Smart compatible PCs, tablets, or smartphones that patients and doctors already own.


Sports and Fitness Sports and fitness products are some of the most popular use cases for Bluetooth Smart, due to its low-power consumption and ability to connect to smartphones that feed sensor data to applications and on to the cloud.

Many leading manufacturers are already producing well-known products in this category. The devices include cycling sensors, sport watches, smart bicycle handlebars, smart helmets, treadmills and treadmill remotes, spinning bikes, smart basketballs, and on-shoe and on-body sensors that track movements and physiological conditions.

AutomotiveCustomers already use classic Bluetooth for hands-free applications in cars. With Bluetooth Smart, companies can build key fobs or other keyless entry systems and wireless controls for windows, interior lights, and rear-seat entertainment systems. Bluetooth Smart can connect steering wheel controls to devices and systems while eliminating cables to help reduce car weight and improve fuel economy.

Key Performance Characteristics and Operational Features Bluetooth Smart has distinct performance characteristics and operational features that make its use in IoT applications practical and compelling. These attributes include its low-power requirements, its efficient architecture, deployment flexibility, interoperability, interface robustness and other attributes.

Low PowerBluetooth Smart devices operate with extremely low power consumption, enabling the radios to run on very small battery power sources for a year or more. Power consumption is extremely low in idle mode. Under all conditions, the power required for Bluetooth Smart is a fraction of that required for classic Bluetooth devices.

Table 1 presents general ranges of current consumption for typical Bluetooth Smart chipsets. Exact values depend on the chipset used and the characteristics of the communication link.

Table 1. Bluetooth Smart Current Consumption

Peak Current Idle Mode Current Average Current

tens of mA tens of nA ~ μA (assuming <1% duty cycle)

Bluetooth Smart’s low power consumption is enabled by its very simple link layer, which is designed to establish quick connections. The radio chips spend most of their time asleep, waking up only to send data. The data is transmitted in a few milliseconds (ms) compared to 100 ms that classic Bluetooth requires for data transmission.

Features enabling these capabilities include the following:

• Smart Host Control. Bluetooth Smart places a significant amount of intelligence in the controller. This allows the host to sleep for longer periods of time and wake only when the host needs to perform an action. This saves current because the host generally consumes more power than the controller.

• Adjustable, ultra-low duty cycle. Bluetooth Smart uses a synchronous protocol, like classic Bluetooth, but its duty cycle can be adjusted down to just 0.1% compared to Bluetooth’s 1% duty cycle.

• Adjustable message length. Bluetooth Smart’s message length is adjustable to facilitate transmitting large quantities of data in a long packet. The approach is more energy efficient than sending multiple packets.

• Substantial packet capacity. With v4.2 enhancements to the Bluetooth Core Specification released in 2014, Bluetooth Smart provides 10 times the packet capacity of previous versions to deliver 2.5 times faster data throughput.

Two Modes: Single Mode (Bluetooth Smart) and Dual Mode (Bluetooth Smart Ready) Bluetooth Smart can be implemented with two types of radios: single mode and dual mode.

• The single-mode radio is the standalone implementation used for Bluetooth Smart. It is deployed in sensors and other low-power, battery operated peripheral devices that collect and transmit information to a hub device, such as a smartphone. Bluetooth Smart devices can connect to other Bluetooth Smart devices and to Bluetooth Smart Ready (dual mode) devices. The single-mode Bluetooth Smart devices will not work with classic Bluetooth.


• The dual-mode option is called Bluetooth Smart Ready. It supports both Bluetooth Smart and classic Bluetooth. It is used in hub devices, such as smartphones, tablets, personal computers, TVs, set-top boxes and game consoles, which receive data from sensors and other devices. The dual-mode chips execute a protocol that mediates between Bluetooth Smart and classic Bluetooth.

Hub and Peripheral Roles in a Single ChipWith v4.1 of the specification (released in 2013), the Bluetooth SIG added capability for a single chip to support both hub and peripheral roles. For example, a smart watch can act as the hub for a wearable device, such as a heart rate monitor, and it can also act as a peripheral to a smart phone, displaying messages from the phone. To give another example, a phone can continue to play its primary role as a hub, scanning for other devices and connecting to them, but it can also act as a peripheral to other devices, such as a set-top box or home security system. The Bluetooth SIG expects more and more devices to play dual roles, giving developers more flexibility in product development.

Interoperability Interoperability is essential to the successful performance and scalability of devices that use standards-based communications technologies. Because Bluetooth Smart operates worldwide in the open, license-free 2.4 GHz frequency band (along with classic Bluetooth), Bluetooth Smart technologies can interoperate in global markets.

To ensure interoperability of Bluetooth Smart devices, the Bluetooth SIG has defined the test structures and procedures companies must follow to verify that the RF physical layer used for Bluetooth Smart devices conforms to the specification to ensure interoperability. The test requirements are summarized on page 11 of this paper.

Interference RobustnessBluetooth Smart uses fast frequency hopping to secure robust transmissions even in the presence of other wireless technologies. It also uses a strong 24-bit cyclic redundancy check (CRC) technique on all packets to prevent errors caused by interference. These features are designed to bolster Bluetooth Smart’s performance in environments where multiple devices use different protocols, such as Wi-Fi, in the same 2.4 GHz spectrum. In addition, adaptive hopping and Wi-Fi/Bluetooth coexistence schemes enable Bluetooth Smart to be used in a compact device alongside a Wi-Fi radio.

Simplicity Bluetooth Smart uses a service-based architecture, depicted in Figure 1, to facilitate product and application development. All communications between a hub and peripheral (client and server) take place over the Generic Attribute Profile (GATT). With the GATT approach, developers can implement standards-based profiles in software and create applications that can be updated over-the-air. GATT profiles are listed on page 10.

Applications Apps

Generic Access Profile

Generic Attribute Profile

Logical Link Control and Adaptation Protocol

Attribute Protocol

Host Controller Interface

Link Layer

Physical Layer

Security Manager

Direct Test Mode

Host

Controller

Figure 1: Bluetooth Smart (single mode) architecture

Source: Bluetooth SIG


Host Control Bluetooth Smart places a significant amount of intelligence in the controller, which includes the physical layer, link layer and direct test mode. This approach allows the host device to sleep for longer periods of time and wake up only when the controller tells the host to perform an action. This minimizes power consumption.

Latency Bluetooth Smart is designed to send small amounts of information with minimal latency. The time to set up a connection and send data can be as fast as 3 ms (compared to 100 ms with classic Bluetooth).

Bit Rates Bluetooth Smart originally supported very short data packets (2-39 octets) that are transferred at 1 Mbps. With v4.2 of the specification, Bluetooth Smart allows a tenfold increase in packet size. It can transfer 2 to 257 octets in a packet, yielding throughput speeds that are 2.5 times faster than allowed with v4.0.

On the current PHY layer, the v4.2 “nominal data rate” is still 1 Mbps. However, the longer packets introduced with v.4.2 allow higher practical data rates at the application layer. Previously, the application layer nominal data rate was around 300 kbps (after overhead). With v4.2, this data rate is around 750 kbps (after overhead).

RangeBluetooth Smart has increased its modulation index to improve range compared to classic Bluetooth. According to the Bluetooth SIG, it offers a possible range of more than 100 meters but when inside a building that might have interference from other wireless technologies the normal range is currently around 20-30 meters. This can be changed by adjusting power to the radio, attenuation, and other parameters.

Security and PrivacyBluetooth Smart provides several security and privacy features. In general, Bluetooth Smart benefits from its pairing model because two devices must associate with one another to communicate. The pairing process is triggered each time a device receives a request to connect to a device it has not previously paired with. Once paired, the two devices can connect to each other without user intervention. The pairing relationship, once established, can also be removed by the user.

Bluetooth Smart supports full AES-128 encryption using CCM to encrypt and authenticate data packets. The technology also offers several features to protect privacy. A new feature added with v4.2 of the specification enables the device to frequently change its MAC address so the device can’t be tracked or associated with a user’s identity; this feature is expected to add value to Bluetooth Smart for beacon applications. The technology also employs mechanisms to prevent man-in-the-middle attacks and passive eavesdropping.

IPv6 SupportWith v4.1, Bluetooth Smart added core capability to use a dedicated channel for IPv6 communications. With this capability, Bluetooth Smart sensors and other devices can connect directly to the Internet and route Internet traffic without going through a smartphone or other hub device.

Forthcoming: Mesh NetworkingBluetooth Smart has been traditionally used as a peer-to-peer technology, but the Bluetooth SIG has begun working on a mesh networking capability. The organization expects to have a working version of the specification ready for prototype testing in late 2015; formal adoption of the specification is expected in 2016.


Technical Specifications: A Brief History Bluetooth Smart represents any version of the technology that uses v4.0 or later updates to the Bluetooth Core Specification. Version 4.0 was introduced in June 2010. It was initially referred to as “Bluetooth Low Energy.” The technology was branded “Bluetooth Smart” in 2011.

Table 2 presents the key enhancements to the Bluetooth Core Specification that led to the introduction of Bluetooth Smart (v4.0) as well as the technology’s most recent update, v.4.2. The Bluetooth SIG has not announced further updates but it continues to evaluate ways to improve low-energy, range, bandwidth, security, IPv6, features, mesh networking, as well as techniques that make devices easier to set up and provision.

Key milestones for Bluetooth Smart are presented on a timeline in Figure 2.

Table 2. Adopted Bluetooth Core Specifications

Specification Date Adopted Status

Core Version 4.2 02 December 2014 Active

Core Specification Supplement (CSS) v5 02 December 2014 Active

Core Version 4.1 03 December 2013 Active

Core Specification Addendum (CSA) 4 12 February 2013 Active

Core Specification Addendum (CSA) 3 24 July 2012 Active

Core Specification Addendum (CSA) 2 27 December 2011 Active

Core Version 4.0 30 June 2010 Active

Core Version 3.0 + HS 21 April 2009 Active

Core Specification Addendum (CSA) 1 26 June 2008 Active

Core Version 2.1 + EDR 26 July 2007 Active

Core Version 2.0 + EDR 05 November 2004 Deprecated Nov. 13, 2014

Volume 4: HCI Transports 01 January 2006 Active


Core Version 4.02010

Core Spec Addendum (CSA) 4 2013



Figure 2. Timeline of Bluetooth Smart specifications approved by the Bluetooth SIG


Key Technical Specifications for Bluetooth Smart In addition to the key performance and operating features described above, Bluetooth Smart has important technical specifications that differentiate the technology from classic Bluetooth. The key specifications are presented in Table 3 and discussed below.

Table 3: Comparison of Bluetooth Smart and Classic Bluetooth

Technical Specification Classic Bluetooth Bluetooth Smart

Frequency 2400 to 2482.5 MHz 2400 to 2482.5 MHz

Modulation Technique Frequency Hopping Frequency Hopping

Modulation Scheme GFSK GFSK

Modulation Index 0.35 0.5

Number of Channels 79 40

Channel Bandwidth 1 MHz 2 MHz

Nominal Data Rate 1 - 3 Mbps 1 Mbps

Application Throughput 0.7 - 2.1 Mbps 0.3-0.75 Mbps

Nodes / Active Slaves 7 Unlimited

Security 56 to 128 bit 128-bit AES

Robustness FHSS FHSS

Voice Capable Not capable

Frequency and Modulation Bluetooth Smart and classic Bluetooth both operate on frequencies in the 2.4 GHz band (2400-2482.5 MHz). They both use frequency hopping for the modulation technique and the Gaussian frequency-shift keying (GFSK) modulation scheme. The modulation index is their main difference. Bluetooth Smart uses a modulation index of 0.5, compared to 0.35 for classic Bluetooth. The difference enables Bluetooth Smart to lower power consumption and improve its range compared to classic Bluetooth.

ChannelsAn important difference between Bluetooth Smart and classic Bluetooth is the channel specification.

Bluetooth Smart uses 40 channels that are each 2 MHz wide and classic Bluetooth uses 79 channels that are each 1 MHz wide. Bluetooth Smart uses fewer, wider channels to simplify the radio chipsets and make them cheaper to produce.

The 40 Bluetooth Smart channels are shown in Figure 3. Three channels are used for device discovery and connection setup. These channels, also known as “advertising” channels, are used by the technology to search for other devices or promote its own presence to devices that might be looking for a connection. The advertising channels use the 2402, 2426 and 2480 MHz bands to avoid interference with Wi-Fi and other devices that use these channels. For comparison, classic Bluetooth uses 32 channels for these same tasks.

The reduced number of channels needed for Bluetooth Smart helps minimize time on air and power consumption. Bluetooth Smart switches on for just 0.6 to 1.2 ms to scan for other devices via the three advertising channels. Classic Bluetooth requires 22.5 ms to scan its 32 channels. Because of the approach it uses, Bluetooth Smart consumes 10-20 times less power than classic Bluetooth to locate other radios.


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LL 37 0 1 2 3 4 5 6 7 8 9 10 38 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 39

Figure 3. Bluetooth Smart channels. The 3 advertising channels are those using the 2402, 2426 and 2480 MHz bands.

ProtocolClassic Bluetooth uses 9 protocols to implement different device functionalities. Bluetooth Smart uses the Attribute Protocol (ATT), a simplified adaptation of the classic Service Discovery Protocol (SDP). ATT is sequential, performing one request at a time. As mentioned on page 5, above, Bluetooth Smart uses a client/server architecture, which allows a client to read/write certain attributes that are exposed by the server in a simple manner. The approach helps reduce power consumption compared to classic Bluetooth protocols.

PacketsA key feature of the Bluetooth Smart stack is a lightweight link layer (LL) that provides ultra-low-power idle mode operation, simple device discovery, and reliable point-to-multipoint data transfer with advanced power-save and encryption functionalities. Table 4 shows the link layer packet format. The protocol data unit (PDU) has increased with v4.2 of the standard.

Table 4. Bluetooth Smart Link Layer Packet Format

Preamble Access Address Protocol Data Unit (PDU) Cyclic Redundancy Code (CRC)

1 octet 4 octets 2 to 257 octets 3 octets

A Bluetooth Smart packet includes the following:

• Preamble for synchronization. Bluetooth Smart’s synchronization word is dynamically assigned during the link setup exchange.

• Access address. The packet uses a 4 octet (32 bit) access address for physical link identification on every packet for each slave. The long access address allows billions of devices to be connected.

• Protocol data unit (PDU). The PDU has increased with v4.2 of the standard. Previously, it was 2 to 39 octets. With 4.2, it is 2 to 257 octets. The implementation obtains significant power savings by omitting unnecessary information (such as information that is already known by the receiving device) whenever possible.

• Cyclic redundancy code (CRC). The CRC is 3 octets (24 bits). It ensures correction of the data in the PDU on all packets, helping increase robustness against interference.

ProfilesProfiles are specifications that define how two devices work together for a particular use case. Profiles are used to ensure optimum implementation of a use case on the wireless standard and to ensure interoperability between products developed by different manufacturers.

One of Bluetooth Smart’s key benefits is its use of generic attribute profiles (GATTs), which are described on page 10. The GATT profiles are part of the standard’s service-based architecture that implements profiles at the application layer, independent of the lower layers, to make innovation and product development easier and to facilitate OTA software updates.

The Bluetooth SIG has a developer tool, in beta as of June 2015, which companies can use to create custom profiles that are compatible with Bluetooth Smart. This is useful if the profile a company wants is not yet available from the Bluetooth SIG or if the company’s business model calls for a custom approach.


The Bluetooth SIG maintains a list of GATT profiles it has approved for use on Bluetooth Smart products. As of July 2015, with the latest Bluetooth Smart release (v4.2), the Bluetooth SIG had adopted 24 GATT profiles. Table 6 provides a list of these profiles. Please refer to the Bluetooth SIG site for a current list of GATT profiles that have been approved for Bluetooth Smart.

Table 6. GATT Profiles for Bluetooth Smart

Profile Use Case

Alert Notification Profile Enables a client device to receive different types of alerts and event information as well as information on the count of new alerts and unread items that exist in the server device.

Alert Notification Service Exposes different types of alerts.

Battery Service Exposes the state of a battery within a device.

Blood Pressure Profile Enables a device to connect and interact with a blood pressure sensor device for use in consumer and professional health care applications.

Blood Pressure Service Exposes blood pressure and other data from a blood pressure monitor for use in consumer and professional healthcare applications.

Current Time Service Defines how the current time can be exposed using the Generic Attribute Profile (GATT).

Device Information Service Exposes manufacturer information about a device.

Find Me Profile Enables a button pressed on one device to cause an alerting signal on a peer device.

Health Thermometer ProfileEnables a collector device to connect and interact with a thermometer sensor for use in healthcare applications.

Heart Rate Profile Enables a collector device to connect and interact with a heart rate sensor for use in fitness applications.

Heart Rate Service Exposes heart rate and other data from a heart rate sensor intended for fitness applications.

Human Interface Device (HID) Service Exposes human interface device reports and other HID data intended for HID hosts and HID devices

HID Over GATT ProfileDefines how a device with Bluetooth Smart wireless communications can support HID services over the Bluetooth Smart protocol stack using the Generic Attribute Profile.

Immediate Alert Service Exposes a control point so a peer device can cause the device to immediately alert

Link Loss Service Defines behavior when a link is lost between two devices.

Next Daylight Savings Time (DST) Change Service

Defines how information about an upcoming DST change can be exposed using the Generic Attribute Profile (GATT).

Phone Alert Status Profile Enables a personal user interface device (PUID) to alert its user about the alert status of a phone connected to the PUID device

Phone Alert Status Service Exposes the phone alert status when in a connection.

Proximity Profile Enables proximity monitoring between two devices.


Reference Time Update Service Defines how a client can request an update from a reference time source from a time server by using the Generic Attribute Profile (GATT).

Scan Parameters Profile Defines how a scan client device with Bluetooth Smart wireless communications can write its scanning behavior to a scan server, and how a scan server can request updates of a scan client’s scanning behavior.

Scan Parameters ServiceEnables a GATT client to store the Bluetooth Smart scan parameters it is using on a GATT server device so that the GATT server can use the information to adjust behavior to optimize power consumption and/or reconnection latency.

Time Profile Enables the device to get the date, time, time zone, and DST information and control the functions related the time.

Tx Power Service Exposes a device's current transmit power level when in a connection

Source: Bluetooth SIG July 2015

Testing Bluetooth Smart DevicesThe Bluetooth SIG has published specifications for testing the radio-frequency physical layer of Bluetooth Smart devices. By following the specifications when testing devices and ensuring that devices and sub-modules are compliant, companies can be confident that the devices they manufacture will interoperate at the air interface with products provided by other manufacturers.

This section discusses the following key test requirements for Bluetooth Smart:

• A predefined direct (non-link) test mode, which allows sending N packets from the device and counting the packets received by the device. It also sets the frequency.

- Non-link testing is mandatory for Bluetooth Smart

- In non-link test mode for Bluetooth Smart, test procedures assume full control over the host control interface or UART interface to test directly at the PHY level

• Simplified and optimized RF PHY test cases, including

- Dirty packets for sensitivity testing

- PER testing for receiver test cases

- Predefined test packet format

For complete documentation of all required tests, please refer to RF PHY: Bluetooth Test Specification, RF-PHY.TS.4.2.0, published Dec. 9, 2014 by the Bluetooth SIG.

Bluetooth Smart Direct (Non-Link) Test ModeNon-link testing is mandatory for Bluetooth Smart devices. It is performed quickly in the manufacturing environment to communicate with the DUT directly. It performs the physical layer evaluations manufacturers need to ensure all devices comply with the latest specification of the technology.

Non-link testing was pioneered by LitePoint to verify chipset functionality. It does not evaluate software. It is performed by interfacing directly with the PHY layer of the Bluetooth Smart protocol stack, bypassing the software stack. Companies do need to develop a non-link test program for Bluetooth Smart devices, but the expedited testing and cost benefits it provides in a high-volume manufacturing environment will typically offset program development efforts. The serial interface (e.g., UART) of the DUT must be available so the tester or controlling PC can send Direct Test Mode commands directly to the DUT and put the DUT in certain test conditions.

Link testing is an option for companies that want to test Bluetooth Smart software functionality. The link test mode requires the test software to interface with the Bluetooth Smart software stack to establish a link (as if the tester were a Bluetooth Smart device). The approach tests for software failures in addition to hardware failures and does not require any code development for the tester to communicate with the device. Sometimes link testing is the only choice, e.g., if the serial interface is not available for access and therefore non-link testing is not possible.


In a production line, however, software testing is not typically needed. Product failures are due to manufacturing differences that only affect hardware. For manufacturing testing one should assume that the software is working correctly and focus the testing process on looking for defects.

For testing classic Bluetooth devices, the Bluetooth SIG gives manufacturers the option to test their devices with either link or non-link mode. The differences between the two approaches are shown in Figure 4.

Link Based Test

HW

SW S

tack

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HCI: Host Control InterfaceLMP: Link Manager Protocol

HCI Interface

L2/CAP: Logical Link Control and Adaptation Layer ProtocolRF COMM: Serial Port Emulation

LMP

L2/CAP

RF COMM

PPP

TCP/UDP

IP

Baseband

Bluetooth Radio

HW

HCI Interface

LMP

Baseband

Bluetooth Radio

Figure 4. Link versus non-link testing

Bluetooth Smart PHY Test CasesTo ensure interoperability between all Bluetooth Smart devices in the marketplace, and to also verify that a basic level of system performance is guaranteed for all Bluetooth Smart products, the Bluetooth SIG defines the RF PHY test cases for the standard.

Bluetooth RF PHY test cases and test case implementations are derived from the Basic Rate Bluetooth RF test cases. However, introduction of the non-link (direct) test mode and the following factors have minimized Bluetooth RF PHY testing time considerably. The additional factors helping streamline Bluetooth RF PHY testing include

• Relaxed RF PHY spec (e.g., blocking resolution)

• Reduction of the number of RF PHY test cases (e.g., removal of regulatory tests)

• Optimized test case implementations

Tables 7 and 8 summarize the Bluetooth Smart RF PHY transmitter and receiver test cases, respectively. The test frequencies differ depending on the test case and on the particular device. Refer to the test specification document for a complete list of these frequencies and details of each test case.


Table 7. Bluetooth Smart Transmitter Tests

Test Description

TP/TRM-LE/CA/BV-01-C Output power at NOC1

Verifies the maximum peak and average power emitted from the BLE device at normal operating conditions.

TP/TRM-LE/CA/BV-02-C Output power at EOC1

Verifies the maximum peak and average power emitted from the equipment under test (EUT) at extreme operating conditions.

TP/TRM-LE/CA/BV-03-C In-band emissions at NOC1

Verifies that the in-band spectral emissions are within limits at normal operating conditions.

TP/TRM-LE/CA/BV-04-C In-band emissions at EOC1

Verifies that the in-band spectral emissions are within limits at extreme operating conditions.

TP/TRM-LE/CA/BV-05-C Modulation characteristics

Verifies that the modulation characteristics of the transmitted signal are correct (i.e., the frequency deviation is measured with different payload sequences).

TRM-LE/CA/06/C Carrier frequency offset and drift at NOC1

Verifies that the carrier frequency offset and carrier drift of the transmitted signal are within specified limits at normal operating conditions.

TP/TRM-LE/CA/BV-07-C Carrier frequency offset and drift at EOC1

Verifies that the carrier frequency offset and carrier drift of the transmitted signal are within specified limits at extreme operating conditions.


Table 8. Bluetooth Smart Receiver Tests

Test Description

TP/TRM-LE/CA/BV-01-C Receiver sensitivity at NOC1

Verifies that the receiver sensitivity is within limits for nonideal signals at normal operating conditions. The nonideal signals (dirty packets) used in this test are within the specification limits but deviate from the ideal case. All Bluetooth Smart devices must meet PER better than 30.8% for a minimum of 1500 packets transmitted by the tester at -70 dBm input power.

TP/TRM-LE/CA/BV-02-C Receiver sensitivity at EOC1

Verifies that the receiver sensitivity is within limits for nonideal signals at extreme operating conditions. The nonideal signals (dirty packets) used in this test are within the specification limits but deviate from the ideal case. All Bluetooth Smart devices must meet PER better than 30.8% for a minimum of 1500 packets transmitted by the tester at -70 dBm input power.

TP/TRM-LE/CA/BV-03-C C/I and receiver selectivity performance2

Verifies the receiver’s performance in presence of co- and adjacent-channel interference. The receiver mirror image rejection performance is also verified in this test.

TP/TRM-LE/CA/BV-04-C Blocking performance2

This test verifies that the receiver performs satisfactorily in the presence of interference sources operating outside the 2400MHz - 2483.5MHz band.

TP/TRM-LE/CA/BV-05-C Intermodulation performance2

Verifies that the receiver intermodulation performance is satisfactory (PER better than 30.8% for a minimum of 1500 packets transmitted by the tester).

TRM-LE/CA/06/C Maximum input signal level

Verifies that the receiver is able to demodulate a wanted signal at high signal input levels (-10 dBm or higher).

TP/TRM-LE/CA/BV-07-C PER Report Integrity

Verifies that the device report mechanism reports the correct number of received packets to the tester.


1 NOC and EOC tests are the same except for the operating conditions (extreme temperature, air humidity, supply voltage), which do not impact the test equipment requirements.

1 NOC and EOC tests are the same except for the operating conditions, which do not impact the test equipment requirements. 2 Testing selectivity, blocking and intermodulation performance require two signal sources.


Testing with Dirty Packets Nonideal signals, also known as dirty packets, can affect receiver sensitivity. Therefore the Bluetooth Smart RF PHY test specification document requires the use of dirty packets for receiver sensitivity test cases. The purpose of the test is to ensure that the receiver sensitivity is within limits for nonideal signals at normal operating conditions.

Every 50 packets, the carrier frequency offset, modulation index and symbol timing error are changed to specific value combinations described in the test specification. These are presented below in Table 9.

Table 9. Bluetooth Smart Transmitter Parameters for Dirty Packets

Test run Carrier frequency offset Modulation index Symbol timing error

1 100 kHz 0.45 - 50 ppm

2 19 kHz 0.48 - 50 ppm

3 - 3 kHz 0.46 + 50 ppm

4 1 kHz 0.52 + 50 ppm

5 52 kHz 0.53 + 50 ppm

6 0 kHz 0.54 - 50 ppm

7 - 56 kHz 0.47 - 50 ppm

8 97 kHz 0.5 - 50 ppm

9 - 25 kHz 0.45 - 50 ppm

10 - 100 kHz 0.55 + 50 ppm

As part of the carrier frequency offset, a defined frequency drift is added to the signal characteristics. This is implemented by adding a sinusoidal low frequency modulation to the signal, with deviation of 50 kHz and a modulation frequency of 625 Hz (90° should be equivalent to the duration of a packet). The modulating signal is synchronized with the packets so that each alternating packet starts at 0° and 180° of the modulating signal. Figure 5 illustrates the frequency drift emulation principle.

50 kHz frequencydrift @ end of

packet

reference packet

Start of packet

Positive frequency drift

f

t

Negative frequency drift

90˚45˚T/4 = 400μs(fmod=625Hz)

Figure 5. Frequency drift in Bluetooth Smart sensitivity testing


How Significant are Dirty Packets?When receiver sensitivity is tested in the same Bluetooth Smart device with and without dirty packets, the difference is a deviation of about 1 to 2 dB in the receiver input power as the device meets the sensitivity threshold of 30.8%. This is shown in Figure 6.

Because this deviation can influence the number of devices that pass or fail receiver sensitivity tests on the manufacturing line, LitePoint recommends using dirty packets in sensitivity testing of Bluetooth Smart devices. Alternatively, manufacturers can choose to test with standard packets and tighten the pass/fail threshold (limit setting) accordingly during sensitivity testing.

Figure 6. Packet error rate (PER) measurement of Bluetooth Smart device, with and without dirty packets, at -90 dBm to -100 dBm receiver input power.

-90

60.00

50.00

40.00

30.00

20.00

10.00

0.00

(%) P

ER

-92 -94 -96Power (dBm)

-98 -100

Bluetooth LE PER measurement

Perfect PacketDirty PacketLimit @30.8%

Packet Error Rate (PER) TestingPacket error rate (PER) testing is used for Bluetooth Smart receiver testing as opposed to the bit error rate test (BER) used for classic Bluetooth devices. The PER requirement is expressed as PER < 30.8% after at least 1,500 packets.

This PER requirement equates to a BER of 0.1% under a series of assumptions specified in the Bluetooth Test Specifications document. The assumptions are used to describe a hypothetical (yet unrealistic) situation in which the number of significant bits in a Bluetooth Smart packet is 368 bits (out of a total of 376 bits), and the probability of the sequence containing no bit errors is 0.999368 = .692. Hence, the resulting PER requirement is (1 – 0.692) • 100% = 30.8%.

Bluetooth Smart Testing and LitePoint’s Role Unquestionably, Bluetooth Smart is helping open up new markets for wirelessly connected devices that interconnect sensors, people and systems in the new era known as the Internet of Things. The technology’s low cost and low-power characteristics position it well for IoT and it is developer-friendly, which also encourages its use by product manufacturers.

Given the competition in IoT, companies need to bring their products to market quickly and with complete confidence that the products are viable and scalable in the market. Fundamentally, the wireless technology must work as intended or a company will risk shipping a marginal product. Tests measuring key RF physical layer characteristics must be performed to ensure products conform to the Bluetooth Smart specification, are free of defects, function at optimal levels, and interoperate with other compliant products on the market.

LitePoint Corporation is at the forefront of wireless testing and offers convenient test solutions to help companies perform Bluetooth Smart tests quickly and cost effectively. The company looks forward to helping companies test their Bluetooth Smart products. For more information about LitePoint’s Bluetooth Smart test solutions, please visit www.litepoint.com.


Bluetooth Curiosities

Why is it called Bluetooth?The companies that developed Bluetooth in the late 1990s used the name “Bluetooth” as a code name for the technology while it was being developed. The name refers to a Danish King, Harald Bluetooth, who was influential in uniting parts of Scandinavia that were fractured by feuding clans and wars during the tenth century.

The founders of the Bluetooth SIG thought the name was particularly fitting because the technology united a variety of competing concepts and strategies, in the global communications and computing industries, for providing wireless connectivity between devices. The SIG retained the name when introducing the formal standard and it is a well-known brand today.

What is the significance of the Bluetooth logo?The Bluetooth logo is a graphic illustration of the initials for Harald Bluetooth’s name. The graphic design combines symbols for H and B that were drawn from the rune alphabet used by ancient Danes.

References

Specification of the Bluetooth System, Covered Core Package version 4.2, published Dec. 2, 2014 by the Bluetooth SIG. Go to: https://www.bluetooth.org/en-us/specification/adopted-specifications

RF PHY: Bluetooth Test Specification, RF-PHY.TS.4.2.0, published Dec. 9, 2014 by the Bluetooth SIG. Go to: https://www.bluetooth.org/en-us/specification/adopted-specifications

i Lee Ratliff, principal analyst for connectivity and IoT at IHS Technology, provided market projections and market context that helped inform this paper. Telephone interview June 25, 2015. ii Steve Hegenderfer, director of development programs at the Bluetooth SIG, provided context on component costs, Bluetooth Smart’s role in the market, and technical features. He also provided updates on various forthcoming Bluetooth Smart capabilities mentioned in this paper that are now in development at the Bluetooth SIG. Telephone interview June 11, 2015. iii Guillaume Girardin, technology and market analyst for MEMS and sensors at Yole Développement, provided context on MEMS prices. Email interview Aug. 6, 2015.


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DISCLAIMERLitePoint Corporation makes norepresentations or warranties withrespect to the contents of this manual or of the associated LitePoint Corporation products, and specifically disclaims any implied warranties of merchantability or fitness for any particular purpose. LitePoint Corporation shall under nocircumstances be liable for incidentalor consequential damages or relatedexpenses resulting from the use of thisproduct, even if it has been notified ofthe possibility of such damages.

If you find errors or problems with thisdocumentation, please notify LitePointCorporation at the address listedbelow. LitePoint Corporation does notguarantee that this document is error-free. LitePoint Corporation reserves theright to make changes in specificationsand other information contained in thisdocument without prior notice.

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Testing Bluetooth® Smart Products for the Internet of Things

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