Bluetooth Low Energy Evolving: New BLE Modules Enable Long- Range Applications

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1 Bluetooth Low Energy Evolving: New BLE Modules Enable Long- Range Applications Utsav Ghosh Staff Product Marketing Engineer, Cypress Semiconductor Corporation Bluetooth has traditionally been associated with audio streaming and hands free applications like speakers and headsets. The introduction of Bluetooth Low Energy (BLE) took Bluetooth beyond audio and made it the de facto standard for applications that require the ability to send/receive data with a smartphone. Enhancements, such as the Bluetooth Mesh standard, promise to make Bluetooth the technology of choice for home/building automation and various industrial applications. Is BLE for Short-Range Applications Only? A common misconception about BLE is that it is only for short range applications that require communication distances of 10 meters or less. While the majority of BLE based devices do have this range limitation, it is not an intrinsic limitation of BLE technology. The range limitation is a design choice that is imposed by the product implementation, whether it be via IC or module form. Transmit Power and Receive Sensitivity 1

2 Transmit Power and Receive Sensitivity The key system parameters affecting the range of communication are: Transmit power (TXP): This is the strength of the transmitted signal and determines the distance to which the system can transmit data packets. A real world analogy for TXP is volume that a person speaks. The louder a person can talk indicates a higher output RF power. Receive sensitivity (RXS): This is the minimum signal strength that can be received by the system and determines the distance from which it can receive data packets. The converse analogy for RXS is how well a person listens or hears. The better a person s hearing corresponds to a lower equivalent receive sensitivity. Figure 1: Typical BLE Silicon Block Diagram Almost every BLE silicon or chip incorporates a power amplifier (PA) to boost the output power and a low noise amplifier (LNA) to improve the receive sensitivity as shown in Figure 1. Typical BLE silicon datasheets specify a maximum transmit power in the range of 0 dbm to +3 dbm,and several receive sensitivity specifications in the range of 87 dbm to 91 dbm. The receive sensitivity specification at the antenna when anon ideal or dirty transmitter is used, is the most critical specification. The Bluetooth Test Specification describes a dirty transmitter as a transmitter that changes RF parameters to simulate real world conditions. When measuring the wireless communication range that can be supported by solutions using typical BLE silicon, it is important to define whether the communication is two way or one way. Two-Way Communication A BLE connection involves two way communication and, therefore, requires each side of the BLE link to both transmit and receive. In the case of a BLE connection, the transmit power and receive sensitivities of each device contributes to the range of the solution. One-Way Communication 2

3 Conversely, one can design a BLE solution that merely advertises, or broadcasts, information in a connectionless state. In this scenario, a BLE device transmits information openly, and this information may be received by any other BLE device that is listening. This is an example of a one way communication. In this case, it is the transmit power of the broadcaster and the receive sensitivity of the receiver that contribute to the range of the solution. When measuring the wireless communication range that can be supported by solutions using typical BLE silicon, it is important to define whether the communication is two way or one way. Other Factors Range calculation will also involve additional factors: Antenna gain A number that describes how well the antenna converts input power into radio waves in a specific direction (transmission), and how well the antenna converts radios waves from a specific direction into electrical power (reception). Environment The environment that the RF waves travel through will impact the communication range of a solution. For example, water absorbs RF energy, therefore a rainy day may result in a lower communication range. Obstacles Elements in the path of the BLE communication can absorb RF energy or reflect the RF waves, which can result in constructive or destructive multi path interference. Typical BLE Range Solutions that use typical BLE silicon and typical antennas can generally maintain a BLE connection at a maximum distance of 100 meters, full line of sight range, in an open air environment. Full line of sight is defined as a connection where no obstacles exist in the path between the solutions involved in the BLE connection. When such solutions are evaluated in a home, office or factory environment, this range would be significantly lower, approximately 10 meters, due to the presence of obstacles and other environmental factors. Emerging Long- 3

4 Emerging Long- Range Solutions Applications like lighting and home/industrial automation typically require longer range. BLE solutions providers now offer long range modules to enable such applications. A BLE module typically integrates BLE silicon, crystals, an antenna and various passive components. Long range BLE modules additionally integrate a power amplifier that boosts the output power to approximately 10 dbm, and a low noise amplifier that improves the receive sensitivity of the BLE chip to ~ 95 dbm. These enhancements enable a BLE connection to be maintained between two long range BLE modules at a maximum distance of ~400 meters, full line of sight range in an open air environment. Regulatory Pitfalls One of the key system design aspects to consider when using power amplifiers to boost output RF power is how this affects regulatory approvals and certifications. Regulatory bodies (like FCC for USA) for most countries allow these power levels if the spurious emissions and other criteria are kept below their requirements. It is important to find out if the BLE module has already been fully certified for regulatory agencies before using the specific solution. This allows engineers to focus on their system design, and removes the burden of testing and debugging regulatory pitfalls. One of the key system design aspects to consider when using power amplifiers to boost output RF power is how this affects regulatory approvals and certifications. 4

5 Archived Feature Articles Long-Range For Battery Powered Applications Figure 3: Long Range BLE Module The obvious question in the mind of an engineer reading this article is whether these modules are still Bluetooth Low Energy, or will the current drawn increase prohibitively to support this extended range. The extended range does come with an increase in current consumption. The resultant current consumption is dependent on the current drawn by the BLE silicon, PA and LNA and also by the crystal accuracy. A good long range BLE module incorporates an accurate khz crystal. This crystal supplies the clock to maintain timing when the module is in a low power state and ensures that the module wakes up to transmit and receive at the same instant as the module on the other end of the BLE link. This reduces retransmissions and ultimately reduces the average current of the system, enabling long range communication for battery powered applications. Market Availability Cypress is one of the BLE solution providers that supplies a long range BLE module the EZ BLETMPSoC XT/XR Module (CYBLE ) ( blemodule). This module can maintain a BLE connection with a 1 second connection interval at 400 meters full, line ofsight in an open air environment while consuming 26.3 µa of current on average due to an accurate, on board khz crystal. Compared to ~17.5 µa average current consumption for Cypress s typical BLE solutions this is a 50% increase in average current for a 300% increase in range. The module can broadcast data over a full, line of sight range of 450 meters in an open air environment to a typical smartphone. Cypress s EZ BLE PSoC XT/XR Module also integrates an ARM Cortex M0 microcontroller and a wealth of mixed signal peripherals that enable significant bill of material (BOM) savings for any system design. Products like Cypress s EZ BLE PSoC XT/XR Module are expected to make BLE the technology of choice for applications like home automation, commercial lighting, smart cities, factory automation and others. With long range support and the simplicity of BLE, only your imagination limits your application! 5

6 Utsav Ghosh Utsav Ghosh is a Staff Product Marketing Engineer at Cypress Semiconductor Corporation, San Jose, California. He is currently a part of the Internet of Things business unit and handles marketing for Cypress s Wi Fi, Bluetooth and proprietary 2.4 GHz solutions. He has four years of experience in marketing wireless products across America, China, Taiwan, Korea and Japan. Before becoming a marketer, Mr. Ghosh spent three years developing firmware, software drivers and hardware for embedded systems at Wipro Technologies in India. Mr. Ghosh holds a Master s degree in Business Administration from the National Institute of Industrial Engineering, India and a Bachelor of Technology degree from the West Bengal University of Technology, India. He has also completed the Cypress Performance Academy Program for Business Administration and General Management, at the Santa Clara University Leavey School of Business in California, USA. 6