OPTIONS TO INCREASE BLUETOOTH RANGE
In today’s challenging commercial, industrial, and residential environments, achieving long-range Bluetooth performance can be difficult due to various obstacles such as multiple networks present, long distances to achieve, and walls to penetrate. Therefore, many customers often seek advice on how to extend the range of their Bluetooth solutions. CEL recommends taking an in-depth systems approach to deal with extending Bluetooth range as each application, product, and network has different needs and requirements. While there is no one-size-fits-all solution, there are some main methods to improve Bluetooth communication, and CEL highlights them to its customers. These methods include optimizing the antenna, moving to a coded PHY, using a mesh network, and considering a range extender. By utilizing these methods, customers can increase their Bluetooth range, improve performance, and meet their specific application requirements.
1. ANTENNA
The antenna is a critical element for improving Bluetooth range performance, yet it is often overlooked or considered an afterthought in many designs. However, optimizing your antenna for efficiency and radiation pattern can have a significant impact on your range.
To achieve maximum range, the antenna’s efficiency and radiation pattern must be optimized. For instance, CEL strives to make its antennas more than 80% efficient and omnidirectional. Efficiency is confirmed by measuring and comparing conducted vs. radiated power. Radiation patterns are also measured and plotted to check for weak or no signal strength areas. A uniform radiation pattern in all directions is sought, as most customers cannot guarantee antenna installation and orientation in the field.
It is essential to consider both the Tx and Rx sides when looking at the antenna’s performance. It is not always possible to control both sides if one of two devices using them is a third-party device like a mobile phone, laptop or tablet. In this case, it is necessary to optimize the antenna for the best possible performance.
To calculate the achievable distance between two sets of antennas with different gain, the Friis equation is used. This equation helps to determine how far the signal can travel and the required antenna gain to achieve a specific range.
In conclusion, optimizing the antenna for efficiency and radiation pattern is critical for improving Bluetooth range performance. It is essential to consider both the Tx and Rx sides when looking at antenna performance, and the Friis equation can be used to determine the achievable distance between two sets of antennas. By optimizing the antenna, you can significantly improve the range of your Bluetooth devices, which can lead to better connectivity and a boost in overall performance.
Using the Friis equation, below is a range calculation showing the achievable distance between two sets of antennas, each with different gain.
2.TRANSMITTER AMPLIFICATION
Transmitter amplification is a method used to increase the output power of Bluetooth devices, thereby extending their range. This method involves adding an amplifier to the transmitter circuit to boost the signal strength. While this may result in increased power consumption, it has been found to have better power efficiencies than S2 and S8 CODED PHY options. In addition, using an amplifier may help avoid the need for a more expensive repeater, resulting in lower total installed costs.
One of the significant advantages of using a transmitter amplifier is that it can help achieve a point-to-point (Pt-Pt) connection, which offers better latency and throughput than a mesh network. A Pt-Pt connection also offers a less complex network to develop, install, and provision. This latter interface is particularly useful in industrial settings where there is a need for reliable and efficient communication between multiple devices together.
To understand how transmitter amplification can improve Bluetooth range, it’s essential to look at the calculations involved. The range of a Bluetooth device is dependent on its transmitter power, receiver sensitivity, and environmental factors such as obstructions and interference. As a rule of thumb, increasing the transmitter power by 3dB doubles the range of the device. Therefore, using a stronger Bluetooth transmitter can significantly improve the range of the device.
In conclusion, transmitter amplification is an effective way to extend Bluetooth range. It offers several advantages, including better power efficiencies, lower total installed costs, improved latency, and throughput. However, it’s essential to consider the potential impact on power consumption and to ensure that Pt-Pt connections are achievable in your application. Ultimately, understanding the calculations involved in transmitter amplification can help you make informed decisions on how to optimize your Bluetooth range performance. Below is a calculation on how your range improves with a stronger Bluetooth transmitter.
3.LEVERAGE A REPEATER
A repeater is a device used to extend the range of Bluetooth signals by receiving and retransmitting the signal. While it can be an effective way to increase Bluetooth connection range, it is generally considered less than ideal due to several factors.
Firstly, a repeater adds cost to the system. It requires additional hardware more power, and installation expenses, which can add up quickly. This can be a significant consideration, especially in large-scale deployments where multiple repeaters may be required to cover a wide area.
Secondly, repeaters add provisioning complexity to the system. They need to be configured and managed, which can be challenging, especially for large-scale deployments. Additionally, security factors need to be considered when using a repeater, as it can create new vulnerabilities in the network.
Despite these drawbacks, installing a repeater might be one of the quickest and easiest solutions to increase Bluetooth range when other options are limited. This is especially true when you have very few options to reach certain devices, or when you need to extend the range of a few devices in a specific location.
When considering using a repeater, it’s crucial to make strong considerations about location. You need to place the repeater in a position where it can receive the signal from the transmitter and transmit it to the receiver without obstruction. You also need to consider who’s installing it, as it requires expertise in installation and configuration. Finally, you need to consider if the physical network will change, as this can affect the performance of the repeater.
In conclusion, using a repeater can be an effective way to extend Bluetooth range when other options are limited. However, the cost, provisioning complexity, and security factors need to be considered before deciding to install a repeater. It’s crucial to place and install the repeater in the right location, have it installed by experts, and consider any physical network changes that may affect its performance. Ultimately, leveraging a repeater can be a quick and easy solution to extend Bluetooth range, but it should be considered in the context of the overall system requirements and limitations.
4.MOVING TO A CODED PHY
Bluetooth Low Energy (LE) Long Range or CODED PHY is a technique that was introduced with Bluetooth 5 to deliver a more robust coding scheme. This is achieved using Forward Error Correction (FEC) which gave us S2 and S8 coding schemes, at the expense of throughput and increased power consumption compared to other PHYs. The coded S2 and S8 provide data rates of 500kbps and 125kbps, respectively. In theory, range can be increased by 4X using this technique.
However, CEL’s internal testing on its Bluetooth modules at 1Mbps, and even comparing it to the Friis Equation (range calculator), show that only the S8/125kbps has much of a range advantage. This is because the S8 coding scheme compensates for its lower data transmission rate with increased robustness. In contrast, S2 coding scheme, which provides a data transmission rate of 500kbps, does not provide a significant range advantage.
It is essential to keep in mind that both communicating devices need to support CODED PHY technology. However, some smart devices may not support this feature, which means that the advantage of using CODED PHY technology may be lost.
CEL conducted a test scenario where they used their CBT250 module at 1Mbps PHY and a competitor module at 500kbps PHY (S=2 Coded PHY). The Tx power was kept the same for each calculation. CEL used a PCB trace antenna, while the competitor used a ceramic chip antenna. Despite the competitor increasing its Rx sensitivity, the range achieved by both modules was the same. This shows that CEL’s antenna performance compensated for its higher data rate, proving the importance of optimizing the antenna for efficiency and radiation pattern.
Test Scenario
- CEL's CBT250 module @1Mbps PHY
- Competitor module @500kbps PHY (S=2 Coded PHY)
- Tx power is the same for each calculation
- CEL-PCB trace antenna, Competitor-Ceramic chip antenna
Results/Takeaway
- Same range despite competitor increasing its Rx sensitivity (reducing it's data rate)
- CEL's antenna performance compensated for its higher data rate
5.MESH NETWORK
A Bluetooth Mesh Network is a group of Bluetooth devices that work together to communicate over a large area. This network is made up of nodes, which can either be a “relay node” (one that can pass on messages), “friend node” (one that can store and forward messages), “low-power node” (one that has limited power consumption), or “proxy node” (one that can connect the device to the internet). These nodes work together to extend the range of Bluetooth communication and ensure that the message is received by the final destination.
One of the advantages of a Bluetooth Mesh Network is its reliability and low latency. Since the message can take more than one path to reach its destination, it is less likely to get lost or interrupted. This makes it a good option for applications where communication is critical, such as in smart buildings or industrial automation.
However, setting up and managing a Bluetooth Mesh Network can be complex and challenging. There are multiple device types to connect and deal with, each with its own specific requirements and capabilities. Provisioning and managing the network can be complicated, especially if any of all the devices or nodes are battery-powered. Additionally, the cost of setting up and maintaining the network can be higher than other solutions to extend Bluetooth range.
In summary, a Bluetooth Mesh Network can be a reliable method to extend Bluetooth range, but it requires careful planning, technical expertise, and investment in infrastructure. If you can overcome the network complexities and fix the technical issues, as well as afford the higher costs, this is a reliable method to extend Bluetooth range.
6.PROPER DESIGN
Following implementation and integration guidelines is critical. It’s amazing the types of issues we have come across and resolved…from detuning the antenna with metallic paint on the housing, enclosing the radio in essentially a Faraday cage, placing a battery directly under the antenna, reducing/eliminating the impact of EMI generating devices, not accommodating any antenna keep-out or proper spacing, improper grounding, Etc. CEL provides specific guidance on the ground plane size and dimensions, as well as proper vias. The antenna keep-out, overhang, or spacing to your host and other boards is also critical to achieving long range performance. Finally, having maximum air gap distance to your housing is also essential. CEL is more than happy to provide front-end design support, make recommendations, do schematic reviews…to assist in optimizing the design. Also, CEL has invested heavily in simulation software, where we can run ‘what if’ tests to get an idea of what the Bluetooth range will look like in a given design and enclosure.
7.TEST IT, FIX IT, REPEAT
CEL has several tests that it likes to perform to verify companies are achieving maximum Bluetooth range. The first is Total Radiated Power testing; we compare the performance of the end-product to the TRP of the module. If we see deficiencies, we advise on implementation changes to the host board, module location/orientation, enclosure, or all. Next, we suggest that companies perform a PER test. Finally, we recommend and can assist with network or field testing.