Why Is Bluetooth® Low Energy Long-Range Connection So Important?
Nowadays, the number of Bluetooth devices and applications is continuously increasing. Applications such as warehouse asset tracking, smart home devices, livestock tracking, and remote control devices all require long-range connection capabilities in terms of functional needs and user experience. As Bluetooth devices proliferate, we need a solution that can maintain all devices in a connected state despite interference from other Wi-Fi and Bluetooth applications operating in the 2.4 GHz band.
Our CYW20829 chip features a high level of connection distance, with a maximum link budget of up to 116 dB and a powerful IP that incorporates multiple generations of development achievements, capable of addressing the issues of short Bluetooth connection distances and environmental noise.
A scenario I often encounter is misplacing my keys, sometimes taking hours to find them. I previously tried various Bluetooth trackers to locate my keys, but those products only covered my home. Recently, I used Infineon’s CYW20829 chip to solve this little annoyance. This chip achieves Bluetooth low energy long-range connection functionality through an encoded PHY layer, and its excellent RF performance can solve the problem of short connection distances while supporting stable connections under a larger link budget, addressing the issue I faced.
In this article, we will explore how to achieve connection distances of over 2300 meters using the AIROC™ CYW20829 Bluetooth® LE chip, leveraging Bluetooth low energy long-range encoded PHY layer technology.
Solution
Noise refers to any interfering RF energy in the RF environment, while the Signal-to-Noise Ratio (SNR) is the ratio of the desired signal to the interfering noise. A high SNR is ideal. Our CYW20829 chip has an SNR of Class S, with an output power of approximately 10 dBm signal strength and a low sensitivity of about -106 dBm. By reducing noise in real environments and considering the radiation pattern of the CYW920829M2EVK-02, we maximized the system’s SNR to achieve a connection distance of 2300 meters.
By using the CYW20829 chip with the S8 encoded PHY layer, I can track my keys over a larger range.
Noise Environment
In long-distance testing environments, noise and interference are the primary reasons for short connection distances. In real environments, increased noise means your Bluetooth devices may disconnect at ranges far shorter than advertised. To improve the SNR, we must reduce noise and interference during testing.
We conducted a test on a crowded beach where everyone carried multiple devices operating in the 2.4 GHz band, such as smartphones, smartwatches, and wireless earbuds. To minimize interference, we conducted the test in the morning to avoid crowds as much as possible. When we had to approach a crowd, we navigated around it to minimize the impact of noise.
In addition to avoiding crowds, we also ensured a Line of Sight (LoS) connection between peripheral devices and the central device. Just as walls inside buildings can limit Bluetooth connection distances, other structures (like beach umbrellas or lifeguard towers) can cause multipath propagation and may absorb RF energy. Multipath propagation occurs when radio signals travel between two antennas via multiple paths, which is undesirable as it can lead to interference and distortion of the desired signal. In real environments, LoS connections between devices may not always be reliable; however, even in noisy environments, our CYW20829 chip performs well.
We actively monitored the Received Signal Strength Indicator (RSSI) of the receiver and adjusted our walking position along the beach during testing to ensure the RSSI remained above the maximum sensitivity of the S8 encoded PHY layer.
The CYW20829 chip uses an internal power amplifier to achieve a maximum output power of 10 dBm, and the encoded PHY layer supports us in raising the maximum sensitivity of the CYW20829 chip to -106 dBm. The link budget refers to the absolute sum of all gains and losses in an RF system, measured in decibels. In ideal conditions, our maximum link budget is |10 dBm| output power + |-106 dBm| sensitivity = 116 dB.
Radiation Pattern
Antenna directivity is a measure of how much radiated energy is directed toward a specific direction, while antenna gain refers to the directivity and efficiency of the antenna. Antennas do not radiate the same power in all directions.
As shown in Figure 1, we measured the antenna gain of the CYW920829M2EVK-02 kit and determined the direction in which the kit radiates the strongest intensity. Different Bluetooth antennas have different optimal radiation directions, which affects our choice of orientation for evaluating the board during low power long-range performance tests. Since the directivity during transmission is the same as during reception, considering the maximum gain of the antenna, we placed the two evaluation boards facing each other.
Our kit can be regarded as a “directional” antenna because the radiation pattern is strongest in a specific angular direction.
We placed the evaluation boards facing each other, as shown in Figure 2.
Figure 1: CYW920829M2EVK-02 Radiation Pattern
Figure 2: CYW920829M2EVK-02 Evaluation Board Setup
Next, we will further upgrade this solution to achieve even longer Bluetooth connection distances. Stay tuned for the next article in this series.
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About Beinuo
Beinuo is a well-known IC product authorized distributor and application solution provider in China, offering services such as IC products, IC application solutions, and on-site technical support. Beinuo adheres to the principle of “continuously creating value for customers” and successfully went public in July 2017, collaborating with its parent company, Fujian Ruineng Technology Co., Ltd. (abbreviated as “Ruineng Technology” | Stock Code 603933) through a business model that develops and produces intelligent control systems for knitting equipment and value-added distribution of semiconductor chips.