Selecting the Right Wireless Module

Abhishek A. Mutha is a senior technical correspondent at EFY

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There has been a significantly increased interest in the wireless and radio frequency (RF) modules in research as well as industry, feel industry experts. Alok Jain, co-founder, InkOcean.in, says, “It is primarily being driven by the hottest technology buzz of today—the Internet of Things (IoT). There are claims of many trillion dollars of economic output in the next few years in the realm of IoT devices.”

One of the most important elements that help make devices IoT-enabled is their being wirelessly connected to other devices or the device hub. Jain adds, “Over the past couple of years, many low-power wireless protocols have been jostling for this space. Noteworthy technologies among these are Wi-Fi, Bluetooth Low Energy (BLE), ZigBee and RF.”

Multiple wireless technologies such as Wi-Fi, ZigBee, near field communication (NFC), RF, BLE and IPv6 over low-power wireless personal area networks (6LoWPAN), to name a few, are integrated in modules today. Praveen Ganapathy, director applications-processors, sales and applications, Texas Instruments (TI) India, informs, “At a macro-level, considering all these technologies, today’s modules have low power, high bandwidth, high data throughput, high-level security and certifications. There is a trend towards integration of microcontrollers in modules as well.”

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He adds, “Traditionally, RF devices were separate components that needed separate processors or controllers, but integration of low-power microcontrollers with advanced sleep/power save modes enable wearable devices.”

Modules today also have the capability to handle RF in different bands. Ganapathy says, “Nowadays, there is higher transmission in 2.4GHz range, resulting in network congestion. There is a trend towards using sub 1Ghz and 5GHz bands to achieve a higher range.”

IoT-driven modules
IoT is driving the usage of wireless modules in a big way. Higher throughput and better performance are not the major factors looked at when buying a module, it is the high level of integration in these, informs Dhiraj Sogani, general manager and senior vice president, System BU, Redpine Signals Inc. Integration of multiple wireless standards is very critical for the IoT market. He says, “It is difficult to find a single wireless technology that will meet everyone’s requirements. Each has its own niche and application.”

Today’s RF modules for wireless applications include options for dual-band and quad-band and support key air interfaces including 2G, 3G, 4G (LTE), ZigBee, Wi-Fi and WiMax, which are favourable for IoT applications, informs Abhishek Rao, technical marketing manager, element14. He says, “The latest addition features an ultra-small core, which enables a much smaller footprint than the previous generation, delivering significant size reduction and greater platform flexibility across applications and end products.” He adds, “By incorporating the latest modules, IoT applications will have ultra-long ranges with minimal power requirement, boosting the overall system performance.”

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IoT is a horizontal market, and fields like industrial, medical, automotive, wearable or healthcare are some of the verticals where wireless modules are used. Sogani explains, “Modules manufactured today are more horizontal-specific rather than vertical-specific. Of course, there are some modules manufactured specifically for particular verticals but these are more expensive.”

Sogani adds, “There are very high-output power modules that can go up to 25dBm or modules catering to vehicle-to-vehicle communication; such modules are meant for niche applications.” Manufacturers are focusing on creating solutions with a high level of technology and software integration that can be used across multiple verticals.

New features for IoT
Redpine Signals recently announced a Wi-Fi, Bluetooth and ZigBee combination module, which is very unique in the market. Bluetooth includes Bluetooth Classic and BLE. Sogani says, “There is no other vendor who has this combination. With such a module, it is possible to create a system that is a perfect gateway for different wireless standards.”

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He adds, “Data can be collected on Bluetooth, ZigBee and Wi-Fi, and transferred to the cloud using Wi-Fi. We are seeing that Wi-Fi is becoming the hub for other wireless technologies to get onto the Internet.” With this unique combination of multiple wireless standards—Wi-Fi, Bluetooth and ZigBee—in one module, area, power and cost get reduced significantly, making it ideal for wearable devices.

With the advent of the IoT, everyone is jumping onto the IoT bandwagon with all they have, feels T. Anand, managing director, Knewron. Atmel launched WILC3000/WINC1500 series of Wi-Fi solutions in module format for developers. He says, “These modules are highly powerful and can be controlled via multiple types of serial interfaces.”

“Additionally, another new silicon vendor, Espressif, has also jumped in with their newly-launched ESP8266 systems on chip (SoC) as well as Wi-Fi modules around it. These modules are extremely cheap as compared to all other Wi-Fi modules in the global market,” Anand adds.
Shawn Hymel, creative engineer, SparkFun Electronics, informs that companies such as TI and Atmel are creating smaller, more integrated and lower-power Wi-Fi solutions. He says, “Atmel ATSAMW25, for example, contains an integrated ARM Cortex-M0+ processor along with a full 802.11 b/g/n stack. Other chips offer both Bluetooth and Wi-Fi on a single chip.”

He adds, “These modules are being used to create remote sensors the size of a fingernail that can post data to Web services like Xively, AT&T’s M2X, IBM’s Bluemix, data.sparkfun and so on.”

ESP8266 based modules are mainly universal asynchronous receiver/transmitter (UART) based modules and can act as access points by themselves, along with a standard Wi-Fi mode, informs Anand. He says, “Espressif has also released a software development kit (SDK) for the chip, so that one can actually fully unleash the potential of the chip and use all other general-purpose inputs/outputs (GPIOs) of the chip/module.”

He adds, “You probably would not need another microcontroller for your small IoT applications as the SoC would give you one analogue-to-digital converter (ADC) and eight to ten GPIOs—all being pulse-width modulation (PWM) and interrupt capable.”

Being in the market for over seven years, there have been significant advancements in Microchip’s module offerings too. Abhinay Venuturumilli, Wi-Fi product line manager, WPD Marketing, Microchip Technology Inc., says, “The new additions to our portfolio in the past year include BLE module RN4020 and Bluetooth dual-mode module BM77 that has very small footprint and supports Bluetooth 4.0.”

He adds, “Microchip has also released a sub-GHz module based on the new LoRaTM technology, enabling long-range coverage for low-power embedded applications.” This RN2483 433MHz/868MHz module is ideal for battery-operated sensors and low-power applications such as the IoT, machine-to-machine (M2M), smartcity, sensor networks and industrial automation.

CC3200, a Wi-Fi SoC with an integrated controller with video and audio interface, is a competitive solution from TI, and is apt for applications like home security. Ganapathy says, “We have launched C3200 as a module and chipset. It consumes very low power and can operate on batteries. There are very few modules in the market that can operate on batteries.”

Talking about a feature trend on the software side, Dhananjay Kulkarni, COO, Maven Systems Pvt Ltd, informs, “We now see mesh platforms being made available on more and more RF and Wi-Fi modules. Mesh algorithms allow a reach of several kilometres even if point-to-point range is only few tens or hundreds of metres.”

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He adds, “This is especially useful in case of applications such as street lighting, smartmeters, solar panels and windmill farms. The mesh-enabled RF and Wi-Fi modules convert many applications from wired to wireless and provide redundancy/high availability in the process.”

General selection criteria
Listed below are parameters that you could consider before locking down on a particular module for your next design.

Select the right wireless technology. It is important to choose the right kind of wireless standards that the end application would support. Ganapathy feels, the designer needs to figure out the right technology such as NFC, Bluetooth, BLE, ZigBee, 6LoWPAN, Wi-Fi or even proprietary RF for the end application. Each of these come with their own share of advantages.

He says, “NFC uses very low power, whereas BLE requires more power. ZigBee or 6LoWPAN provide designers with an option of meshing, which is not available with other technologies. With meshing, even if one node fails on the network, it is possible to get data via other active nodes.” He adds, “6LoWPAN and Internet protocol (IP) can help in easy connectivity to IP based networks, making connecting to the cloud or the Internet easy.”

“Bluetooth has been at the forefront of connecting sensors, boards, devices, accessories and peripherals to the Internet via various control devices like modems, mobile phones, dongles and PCs,” says Niraj Jha, CEO and MD, Fab.to.Lab.

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He adds, “In its latest avatar, the research on Smart Bluetooth (previously BLE/BT 4.0), as named by the pioneers in the industry in this field, is primarily focused on improving power consumption without significant compromises in range.” There are various other protocols like Zigbee, Z-wave and EnOcean, which are available readily in modules for prototyping and experimenting with wireless.

Highlighting a problem of choosing Wi-Fi for an IoT application, Hymel shares, “Unlike Bluetooth, which allows devices to discover each other, Wi-Fi requires the client device to make a connection with Wi-Fi access points (AP) first. This works well from a computer or smartphone where you can enter Wi-Fi credentials, but most IoT devices do not contain an easy-to-use interface, such as a keyboard or touchscreen.”

Several companies have been employing novel approaches to solve this problem. He adds, “Electric Imp (electricimp.com), for example, has users send their service set identifiers (SSIDs) and AP passwords optically to the Imp device by holding the Imp to a screen (smartphone or monitor) that flashes white and black for 0s and 1s.”

Range. This is another important factor to consider. “Energy metering is a classic example of an application where a robust, long-range technology must be deployed,” says Ganapathy.

Sogani says, “It is important to look at the RF performance of the module carefully if an application needs a longer range of, say, 30 metres to 40 metres, in indoor environment or, say, over 200 metres, in outdoor line-of-sight environment with good data throughputs.”

Kulkarni informs, “Wi-Fi is restricted to 100 metres, while an RF can provide a range up to 700 metres line-of-sight. With a power amplifier, the RF range can be further extended to six kilometres.”

Certification. Another angle to look at is certification. Certified modules reduce a fair amount of effort, cost and development time for the designer. Venuturumilli feels, having certified wireless modules in various countries not only enables their customers to sell their end products in various geographies but also provides a time-to-market advantage while reducing risk in the design.

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With or without a microcontroller. The user also needs to decide on the microcontroller that needs to be used. Sogani notes, “If a designer opts for a large microcontroller, it is better to go for a module without an embedded microcontroller to make the product cost-effective. If a designer opts for a small microcontroller, it is apt to go for a module that runs bulk of the software such that there is minimal overhead on the microcontroller.”

He adds, “For a design without a microcontroller, it would be advisable to go for a module with an embedded microcontroller.” Depending on the type of microcontroller and operating system, the decision on the module needs to be made.

Pricing. The word module is being used by various companies for different levels of RF integration, notes Venuturumilli. He says, “Some modules are merely systems in package (SiP), while other modules have all RF components and antennae onboard, and are regulatory-certified.” “The challenge customers have with pricing is to make sure they are comparing modules with similar features,” he adds.

Power consumption. The amount of power consumed, which significantly depends on the range and purity of data exchange, has been a major focus for hardware designers to incorporate in their designs at the root-level, informs Jha. He says, “Power consumption is a different ball game altogether. Much of the improvements in this area are centred around developing hardware with greater range and higher frequencies and minimising data loss, without any increase in power consumption.”

He adds, “Much like in other fields, the wireless community is waiting with bated breath for major breakthroughs in battery technology to help their cause.”

Kulkarni feels power consumption of the module is especially important when you need battery-operated modules.

Miscellaneous. Mesh networks, redundancy and data transmission are some other important parameters to consider. “If you need high bandwidth data for transmitting audio/video data, Wi-Fi is apt,” says Ganapathy.

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Talking about mesh networks, Kulkarni says, “A mesh network would allow the reach to be increased hundred times that of point-to-point star network topology.”

Module form factor, functional capability and electrical characteristics are also necessary to consider. Venuturumilli informs, “A buyer must also check if the module is certified in the countries where customer wants to sell the product.”

He adds, “Availability of technical support while developing the application and risk of end-of-life by the supplier are two other important aspects.”

For future
With CC3000 (and future versions such as CC3100 and CC3200), Hymel informs that, TI created SmartConfig method that allows users to send their Wi-Fi credentials from their smartphones using a series of specially-constructed packets that only CC3x00 can interpret. He says, “As Wi-Fi chips get smaller with more features and solve the connection process problem, we can expect to see more IoT devices in the wild monitoring the air, our health, etc, as well as controlling physical objects from the Internet.”

Talking about Redpine Signals’ future products, Sogani says, “We are looking at incorporating wireless standards such as 802.11 ah for a longer range in an indoor environment. We are also looking at MIMO and 802.11ac products for higher throughput. For instance, 802.11ac 3X3 mode can give you 1Gbps or higher application throughputs.”

He adds, “We also have solutions coming up where microcontrollers will be integrated inside the modules.”


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