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Wireless communication typically use radio waves to communicate over short distances of a few feet to longer distances of many miles (or even up to millions of miles for deep space radio communication). However, techniques also include optical, sonic and electromagnetic induction.

Wireless communications involve numerous topologies. There are point-to-point devices using Bluetooth 3.0 and lower that only communicate directly with one other device (such as a smartphone and a Bluetooth earpiece). There are also point-to-multipoint, connecting a main device to multiple other devices (Wi-Fi and Bluetooth 4.0 and above).

Consider the following when choosing a wireless communication topology.

Compliance with local standards. Wireless compliance is much stricter than wired ones so are more difficult to pass. Radio compliance works on a few basic concepts. The device will only operate in the specific frequency allocated to that radio technology and may not interfere with other devices outside that frequency. It should not be interfered with by other devices operating in other frequency ranges. This is detailed in part 15 of the Federal Communications Commission (FCC) regulations. There are also rules regarding the maximum transmit power (EIRP), unique for each frequency range.

The FCC regulates product communications in the US. To sell a product, it must comply with standards and show the unique FCC ID on the product and packaging. In Europe, certification is approved through a self-certification CE marking that involves a number of harmonized standards. The specific European directive that deals with all products using the frequency spectrum is the Radio Equipment Directive (RED), previously R&TTE. Like FCC compliance, the CE mark must be shown on a product as proof of compliance for the European market.

FCC and CE are only two of the main certification standards. Canada, Australia, New Zealand, Hong Kong, Japan, South Korea, Asia-Pacific, Africa, and South America all have their own, which must be met in order to legally operate a product there.

Different regional standards, and achieving what’s called a “type approval” for each, is a significant design and test burden. Creating a discrete wireless transceiver design requires specialized radio design expertise together with an investment in radio test equipment, adding significant cost and time to new product development. Consequently, rather than dealing with the challenges of EMI generated from high-speed digital circuitry and meeting stringent EMC product regulations, many engineering teams opt for a simpler approach to incorporating wireless connectivity.

It is typically a good idea to select pre-certified wireless modules during early product development to improve a reasonable time-to-market, without significant delays in getting radio compliance. Available modules can either be programmable, or need an external microcontroller/microprocessor to properly function. Many off-the-shelf modules also include an embedded or onboard antenna, reducing the number of unknowns and certification issues.

It is possible at a later stage of development, closer to mass production, to consider developing a custom wireless solution. While it can be costly to develop and obtain the relevant certifications, the product cost can be reduced in larger volume situations. This may ensure initial production deadlines are met, and the product can be introduced and tested in the market before further investments are made.

There are a wide variety of wireless communication methods available in the marketplace. Each with it’s own advantages and disadvantages. Before choosing a possible module, clarify which of these technologies meets the demands of the target application.

  • Bandwidth
  • Distance
  • Security
  • Power
  • Frequency

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Bandwidth focuses on the volume of data, how, and how frequently, it’s sent. Wi-Fi offers an always-on connection, data rates from 11 Mbps (802.11b) to 1.3 Gbps (802.11ac). Bluetooth 3.0 and 4.0 offer up to 25 Mbps up to 60 meters at full power, but aren’t always connected. Sigfox and LoRa, can transmit 12 bytes every 10 minutes, thus reducing power consumption and maximizing battery life.

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Distance concerns the maximum distance between transmitter and receiver. Some technologies are better for short range like Bluetooth Smart (previously Bluetooth Low Energy). Other’s, like GPS, can receive signals from satellites orbiting the planet, thousands of kilometers away.

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Security, currently a hot topic for the Internet of Things (IoT) applications, and other wireless devices. Some wireless technologies solve this with strong encryption, negatively impacting battery life and often bandwidth. The important factors to consider include the sensitivity of the data, other devices on the same network, and the encryption provided by the wireless standard.

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Power is one of the most important aspects in selecting the correct module for a product. The difference between a battery operated device and an always-connected wall socket can significantly change how the device operates. A device that is always powered from a wall socket is much easier to design. Wireless products that run from batteries need to consider recharging, replacement or designing long-life power supplies. Initially, replacing a battery might appear a trivial task, but when a customer has many thousands of devices, such as an IoT sensor deployed in remote locations, the resources and subsequent cost required become significant.

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While the frequency is important, it is not necessarily the main criterion when selecting a wireless module. However, there may be some situations where there is saturation in a specific frequency band, or it may not be legal in certain circumstances for a product to operate in a specific frequency band.

There are many different names and technologies used in digital cellular networks for use with mobile devices like cell phones. It’s useful to know they are all just evolutions of each other. General packet radio service (GPRS) and enhanced data GSM evolution (EDGE) are second-generation technologies, also known as 2G. Their download speeds are 114 Kbps and 384 Kbps, respectively. 3G is the third generation of mobile telecommunications, and high speed down-link packet access (HSDPA) is an enhancement of this with download rates of 3.1 Mbps for 3G and 14 Mbps for HSDPA. Evolved high speed packet access (HSPA+) is a fourth-generation technology that allows up to 168 Mbps. 4G long term evolution (LTE) supports HD streaming and download speeds up to 299.6 Mbps.

One of the key things to note in choosing any GSM module is the ability to future proof a product. This means the developer only needs to design one PCB and swap the desired module into place, easily integrating voice and data connectivity to be deployed in any region or wireless network. As the network operators move to upgrade their infrastructure, they will eventually decide to stop supporting older technologies like 2G and 3G in favor of easier to maintain networks like 4G and upcoming 5G.

When looking to integrate any wireless module into a product, it’s important to review how communications with the host is established. UART and I2C are popular methods of interfacing, but often the availability of extra IO ports, such as GPIO and USB, aid the addition of other sensors and devices. Other features that should be considered include whether the desired communications protocol (FTP, HTTP, etc.) is supported, and increasingly important for IoT designs, the capability to update the module’s firmware over the air (FOTA). Security features such as crypto-authentication and encryption techniques are key to provisioning a secure communications link.

Wi-Fi and Bluetooth are two of the most popular wireless technologies in use. Wi-Fi is used by nearly every home and business as a method of connecting users to a local network and/or internet access. Bluetooth is used in a wide range of low-power devices from hands-free headsets to wireless speakers, mice, keyboards, printers, and many more. Whereas Wi-Fi is intended for high-speed communication on a local area network, Bluetooth is intended for portable equipment. They are often complementary technologies, and many modules come with both Wi-Fi and Bluetooth features.

LoRa and Sigfox are two similar wireless technologies that both work over the 868 MHz (EU) and 902 - 928 MHz (US) frequency bands. They operate in a similar fashion over the same frequency. They are used for low-power wide area networks (LPWAN) for wide range networks with very low data rates, making them ideal for the IoT applications. Sigfox is designed as an ultra-narrowband technology which can transmit up to 12 bytes every ten minutes at a distance of 30 - 50 km, and can receive up to four messages per day. LoRa, on the other hand, is designed more for a command and control scenario. The data packet size is still low, but can be defined by the user. There’s no limit on receiving data, and it has a reduced range of 15 - 20 km.

LoRa and Sigfox both operate in the industrial, scientific and medical (ISM) radio bands, which are normally reserved for use other than for telecommunications. That said, there are still modules that are developed for use in the ISM band. These modules usually use their own proprietary protocols for communication. The most common frequencies for these bands are 433 MHz, 863 MHz to 870 MHz (EU), 902 to 928 MHz (US) and 2.4 GHz to 2.5 GHz.

Some wireless networks don’t work on a point-to-point or point-to-multipoint system. Some wireless technologies like ZigBee, WiMAX and Bluetooth Mesh, operate on a many-to-many network. This means a device doesn’t need to be in range of the device it needs to talk to, as it can pass the signal through a network of similar devices to get to the end device.

A pre-compliant module can save significant costs for development and compliance testing. However, further testing of the new product before release into the market is still required. A module is pre-compliant in and of itself, but once it is added to another system or product, its behavior could be affected

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