Embedded multi-radio solutions for the IoT
While many of the benefits that radios combining multiple protocols offer may be obvious, many more may not. By Pelle Svensson, Product Marketing Manager, u-blox
During the last few years, integrated circuit vendors have released various multiradio devices that offer two or more wireless technologies in one physical package. This has led to the development of multiradio modules that typically include Classic Bluetooth, Bluetooth Low Energy, and Wi-Fi. Multiradio solutions enable product innovation for the Internet of Things (IoT) in many and varied applications including telematics, usage-based insurance, manufacturing, connected cities, healthcare, asset management, building and home automation, security systems and smart energy.
Multiradio devices reduce size, implementation cost and final product cost but, aside from these rather obvious benefits, there are many others. Pre-certified modules will reduce the time and effort involved in securing type approval from the various radio regulatory authorities for the finished product. The complexities of wireless co-location, where several antennas operate in close proximity within the same small device, are already taken care of too.
Also, multiradio devices permit a single physical implementation for a range of products. They can make use of external technology discovery and proximity detection, perhaps via Bluetooth Low Energy beacons, and they can be used as cost-effective and compact gateways for the IoT.
Why size matters
Smartphone manufacturers are particularly focused on reducing the size and cost of their products. Handsets need to integrate several wireless protocols (in addition to the cellular) to fulfil their goals of being multi-tasking units: Classic Bluetooth, Bluetooth Low Energy, Wi-Fi (2.4GHz and 5GHz), FM radio, satellite navigation and, in some recent models, NFC. Instead of embedding several discrete radios, possibly from different vendors, designers can dramatically reduce the wireless implementation size and cost by adopting a single multiradio solution instead. Printed circuit board size, complexity and cost are all reduced too.
Multiple discrete radios mean more components, more circuit board real estate and more testing. There are many fewer external components in a multiradio, and modules may also include LNAs (low-noise amplifiers), antenna matching components, oscillators, crystals and more components that would otherwise be external to the radio device.
Most multiradio solutions also implement a common antenna interface so fewer components are required, for example those for antenna matching. Some even have an integrated antenna, either as primary radiator or as a backup if an external antenna is damaged or becomes disconnected.
The more components that a printed circuit board has to carry, the more complex and expensive it becomes. Using a multiradio solution contributes to simplicity and will not only enable smaller boards to be used but may facilitate using boards with fewer layers, which can result in considerable cost savings.
The overall cost savings from using multiradio solutions make it economical to implement this design strategy across a product range, even when different products will eventually use only one of the available wireless protocols. For example, you may want to offer Bluetooth or Wi-Fi versions of a product, rather than one that’s designed for both.
The approach is particularly useful with a range of products that use a common architecture, and perhaps a common main printed circuit board for all the variants. Even if one of the products in the range only uses one of the wireless technologies, the implementation and maintenance is minimised for the entire product range.
There is often a requirement for two wireless-enabled devices to connect automatically when they come within range of each other. Sometimes one radio technology is used for device service discovery and another for data exchange.
One of the wireless technologies frequently implemented in multiradio solutions is Bluetooth Low Energy. With its unique radio service discovery, Bluetooth Low Energy becomes particularly useful in multiradio implementations. The protocol can be used to detect a user or device from the signal when close to another device, effectively acting as a proximity beacon. Once detected, a second radio technology can be used for the data exchange if higher bandwidth is required.
For example, in a retail point-of-sale environment, Bluetooth Low Energy signals may advertise the presence of the nearest receipt printer to a hand-held payment terminal. The connection set up and data transfer could then take place over Classic Bluetooth or Wi-Fi. In this use case only one of the radio technologies is being used at a time.
Some systems require wireless technologies to be operating concurrently. There is potential signal interference in these circumstances, resulting in higher latency because of the need to use packet traffic arbitration to avoid simultaneous data transmission and reception, or even data loss due to receiver input saturation.
These potential side effects are clearly unacceptable in mission-critical industrial and medical applications so it’s important to optimise coexistence of the various wireless technologies to ensure interference-free operation. Using multiple single-technology radios means that longer development time is needed to deal with the coexistence issue, adding to cost and extending time-to-market for the end product. In a stand-alone multiradio device, coexistence is handled within the multiradio chip, eliminating these challenges.
Implementing several single-radio solutions in a product requires extra regulatory testing. Even if a single wireless module has obtained modular regulatory approval, additional testing and reporting will be required when integrating additional radio modules into the device. This once again extends time-to-market, adds development cost, adds test facility cost, and increases technical risks. With a stand-alone multiradio module these problems are avoided.
A wireless gateway is a networking device that routes packets from a wireless device to the network. Gateways can combine the functions of a wireless access point and router, and often provide firewall security too. These converged devices save desk space and simplify wiring - one device replaces two. A gateway can also act as protocol converter for the installed base’s devices and transfer the converted data upstream using the new Internet data formats including RESTFul, XMPP and MQTT.
Multiradio solutions are particularly suitable when there is a need for different wireless technologies to connect devices in a gateway configuration. One technology is used to communicate downstream to sensors and actuators. A second radio communicates with existing networks upstream.
Consider the example of a medical device such as an infusion pump. Bluetooth low energy may be used with a handheld scanner to ensure that the pump is being connected to the right patient and that the correct medication is being administered. This connection carries very little data but within the same pump a Wi-Fi link may be used to provide a higher bandwidth connection for sending continuous monitoring data over a hospital network.
Using different technologies downstream and upstream is also ideal when a number of battery powered sensors require low power wireless communication and up-stream connectivity to an existing infrastructure, perhaps over Wi-Fi. One possible solution would be to use Bluetooth Low Energy to connect to sensors downstream and use Wi-Fi to transfer the sensor data upstream. The same technology can be used to extend geographical coverage using the Wi-Fi upstream link as a repeater. In this case, Wi-Fi is used to connect several Bluetooth Low Energy gateways in order to achieve greater coverage.
The u-blox ODIN-W262 is an example of a multiradio wireless module designed for the kinds of applications described above. The 14.8 x 22.3 x 4.5mm module supports multiple, concurrent Wi-Fi (2.4GHz and 5GHz), Classic Bluetooth and Bluetooth Low Energy links for product design flexibility and is configured easily for individual applications using AT-commands. Radio type approved in countries throughout the world, it even has a built-in antenna to make adding multi-protocol wireless connectivity to any product as quick and easy as possible.
When the Bluetooth Core Specification added a standard means of creating a dedicated data channel for IPv6 the groundwork was laid for future IP connectivity. With the rapid market adoption of Bluetooth Smart (Bluetooth Low Energy) and the addition of IP connectivity, everything points to Bluetooth as one of the fundamental wireless links in the Internet of Things. The recent additions to the standard make it possible for Bluetooth Smart sensors to use IPv6, giving developers and OEMs the flexibility they need to ensure connectivity and compatibility.