The combination of multi-radio and multi-protocol solutions can accommodate two or more radios running different multi-protocols on the same or different spectrum at the same time.
Today, the market is driven to design products with multiple radio frequency protocols in a box called a gateway. Wireless connection brings many different benefits, provides a better user experience, and different protocols provide complementary advantages. Each IoT device can communicate with the Internet through different protocols, whether it is Zigbee, Bluetooth, Z-Wave or Sub-1ghz, or some proprietary protocols. Multi-protocol (wireless) gateways play a vital role in IoT infrastructure because they collect data from sensor fields and push the data to the Internet via Wi-Fi, cellular, or other wired and wireless networks.
BHIOT-831 Gateway.jpg
The combination of multi-radio and multi-protocol solutions can accommodate two or more radios running different multi-protocols on the same or different spectrum at the same time. This method provides a more efficient and reliable data stream by using different protocols. Therefore, end users can take full advantage of this because they can connect multiple devices operating on different radio frequency bands and protocols through a single unit.
The key challenge of designing multi-protocol compact RF hardware
The emergence of multi-protocol hardware is a response to the recent popularity of multiple different communication protocols. Therefore, original equipment manufacturers face some key challenges when designing multi-radio hardware:
Multi-radio hardware requires a lot of time in antenna selection, layout, simulation, memory estimation, housing design, materials, and field testing
Control precise impedance to reduce interference, return loss, coexist between radios in the same location, so it can meet the requirements of FCC and CE regulatory agencies
If there are two or more radios operating at the same time and sharing the same spectrum, then there will be coexistence, which will cause mutual interference
Measure performance parameters such as communication delay, distance, efficiency and reliability of multi-radio hardware
Coexistence often affects the performance of the device, resulting in packet loss or data corruption, popping and popping noise in the audio, and reduced working range and coverage
Due to the applicability of different standards, when multi-radio hardware emerges, regulatory compliance in different geographic areas will also be a challenge
Things to consider when developing firmware for multi-radio hardware
Today's Internet of Things applications are becoming more and more complex, and the demand for storage capacity is also increasing. Let us understand the challenges of hardware engineering solutions brought by memory and firmware:
Developing user-friendly and flexible embedded applications requires complex state machines, powerful power optimization, memory density, and CPU performance. RF SoC or module needs more flash memory and RAM optimization for best performance
Providing the over-the-air (OTA) firmware update function requires enough flash memory to store the bootloader and twice the size of the application firmware to keep the old firmware while buffering the new firmware, so that the product can be used in today's booming IoT market Competitive
Without loss of performance, real-time management of multiple radios with various network architectures
In the absence of power, the flash memory can also retain user configuration and security key content for many years, because the information in the flash memory can be read and written thousands of times during the product life cycle. In this case, using RAM information can be quickly written to read, which allows the processor to work at such a high speed and can perform edge processing
Based on the above challenges, let us give a small example. A complex wearable/sensor/automation application may require 128 kB RAM and 512 kB flash memory provided by the RF module. A relatively simple beacon application may only need 24kbram and 192kbflash.
In order to solve the above-mentioned multi-radio hardware, memory and firmware challenges, let us understand how to use the hardware expertise of original equipment manufacturers to solve these problems and help improve the overall performance of the product.
The standard approach starts with a product understanding of all RF requirements and other peripherals, lists all RF interface protocol frequencies, and then performs a task such as module or SoC selection, relative antenna selection, material identification of the housing, module placement and antenna. 2D floor planning will be carried out in the early stage of PCB design, which helps to understand the actual location and parameters of all RF modules in detail:
Module or SoC selection: Selection criteria include RF protocol, modulation technology, manufacturer, MCU/processor requirements based on driver code availability, RAM, flash memory, OS, regulatory approval, maximum Tx output power, receiver sensitivity, power supply and data Rate to provide significant performance
Memory budget: For any radio frequency module, the memory budget is a very important parameter. Its definition or calculation is completely based on the radio frequency stack size, support for the number of devices, and application business logic. Before finalizing the module/SoC, the memory-related requirements should be well calculated and clarified
Antenna selection and placement: Antenna selection is the most important factor in multi-radio hardware, because the selection depends on frequency range, polarization, radiation pattern, gain, feed point impedance, standing wave ratio, and power handling capability use cases such as range coverage And space. For example, chip antenna vs PCB tracking antenna vs external antenna
In order to reduce the coexistence and interference between two modules with the same frequency, the antenna arrangement plays a vital role. In this case, the antennas should be placed perpendicular to each other. We are working hard to properly isolate the two radio frequencies in accordance with regulatory requirements. The isolation between the two antennas should be equal to or greater than 30 decibels. Sometimes, due to space constraints, it is impossible to achieve such isolation. Under this framework, it is necessary to consider the interference and radiation patterns of all radio frequency antennas. We also need to study the transmit power of the RF module or SoC according to the application requirements and performance.
RF simulation: In the early stages of product development, simulation is an effective strategy for predicting radio problems. There are many kinds of simulation software, such as HFSS, CST, ADS, etc., which should be used reasonably according to the type of problem.
Housing design and material: In order to achieve the best results, try to finalize a plastic housing with materials that can balance environmental, reliability, and RF performance requirements. Sometimes, COTS enclosures may cause placement challenges due to the pre-defined size and structure. In custom designs, we have the flexibility of PCB placement and can obtain better isolation and antenna placement options. The choice of the dielectric constant/dielectric constant of the housing material plays a crucial role in radio frequency performance. At 2.4GHz, good plastic materials include PC, ABS, PC+ABS, and PVC. Sometimes we also need to choose metal enclosures for outdoor and industrial applications. In this case, the choice of external antennas will be the key.
Design verification test: The design verification of the radio frequency interface is very important. It is necessary to define a set of verification test cases, such as antenna matching impedance and return loss, RF output power measurement, receiving sensitivity, indoor and outdoor distance testing, and worst-case RF environment in heavy traffic scenarios, and monitor them with an analyzer.