Adding 3G Radio to Embedded Devices: Five Steps to Success

A 3G radio is rapidly becoming standard equipment on embedded devices. 3G technology offers much faster download and upload speeds compared to older cellular technologies and, for the first time, allows for simultaneous data and voice transmission. With these and other benefits, more OEMs are finding 3G radios make their devices much more capable and powerful.

Just as there are infinite applications for 3G technology, there are infinite ways to deploy it. Having so many options seems like it would make deployment easier, but it actually raises complexity. This article will walk you through key decisions to help you best integrate 3G technology with your existing hardware and software.

What is 3G?
The term 3G simply refers to the third generation of wireless telecommunications standards, including mobile voice and video calls and data transfer. There are several standards; however the most common are the CDMA standards known as CDMA2000 which includes CDMA2000 1xRTT, 1xEV-DO, 1xEV-DO Rev. A, 1xEV-DO Rev B, and the GSM standards known as WCDMA which includes UMTS, HSDPA, HSUPA, and HSPA+.

The most noticeable advance in the third-generation technology is speed. (See Figure 1 below . Comparison of data upload speed by network type.) Data throughput speeds are much improved. Download speeds of up to 14.4 Mbit/s are possible and capable of upload speeds up to 8 Mbit/s.

Figure 1. Comparison of data upload speed by network type.

Of course, performance varies substantially from device to device and even network-to-network. Generally 3G has come to indicate speeds of between 384kbits/s and 10Mbits/s.

To get a better understanding of how wireless technology has improved, let's look at its growth through a consumer application. With 2G wireless technology, it could take as much as 40 minutes to download one three-minute MP3 file. With 2.5G technology, the download time for that file may drop to just nine minutes. With 3G technology, the download time drops to as little as 11 seconds.

That's a dramatic increase in speed, though one of the biggest advances in 3G is that, it's possible to send voice and data simultaneously over the same wireless connection. This advance opens the door for many new potential applications.

Potential 3G applications
The uses for 3G technology are limitless, but here are a few common applications helped by its capabilities and capacity.

Handheld terminals . Handheld data collection and inventory devices are commonly used by factory, warehouse and field workers. These employees often also have to carry a two-way radio or cell phone to contact dispatch or other staff.

3G technology, which allows for simultaneous voice communication and data transfer, allows you to combine both of those devices. Doing so could potentially increase worker productivity and lower device and communications costs.

Device requirements vary by application, but include an audio codec supporting approximately 12.2 K/bps for voice. You also need to consider how much data the workers will need to send. Simple inventory tracking devices may require relatively little data capacity. Other field workers may need to transmit or download photos. Plan to provide appropriate bandwidth to meet their needs.

Kiosks . Video kiosks provide dynamic information and services and are increasingly in use in more public places. For example, a Kiosk can help generate interest in activities at tourist attractions. Adding video conferencing capabilities could help even more. Tourists who need help could get one-on-one assistance without the need for individual staffing at each kiosk location.

Adding a 3G radio to the kiosk could enable this assistance. Video conferencing requires 30 fps QVA high-quality video stream for download and 15+ fps VGA high-quality video stream for upload (limited by upload speed).

Surveillance systems . Surveillance systems can also receive a major upgrade using 3G wireless technology. Real-time video improves performance of video surveillance by providing a continuous monitor of activity.

Using 3G connectivity, the camera system will have sufficient band width for video and yet be protected from being disabled by severing a network cable. This application requires live streaming real-time video up to 15+ fps with QVGA or better resolution.Do you need 3G?
Is 3G worth the investment for your particular project? If you need simultaneous voice and data transmission ” earlier technology supports only one or the other at a time ” and relatively fast data speeds, the answer is “yes.”

There is no one particular “best way” to add 3G capabilities to a device. There are far too many options for there to be one recommended path. There are three different types of 3G radio form factors, all with unique benefits and design considerations.

Software integration isn't straightforward either. It's highly variable based on your radio selection and how you will use 3G in your application. And there are dozens of wireless service providers with two different network types. The choice among these is largely affected by where you will use the device.

Finding the “best” approach for your device involves understanding your needs and goals and carefully evaluating your choices at each major decision point in the design process. Here are five steps you can follow to maximize your success integrating 3G into your device:

Step 1: Ask the right questions in the requirements phase
There are a few key questions you'll need to consider during the requirements phase.

1. What cellular networks will be available for your device? . Different radio technologies are supported in different areas of the world. About 85% of the cellular systems in North America use CDMA.

GSM is the international standard used in much of Europe, Australia, Asia and Africa. Different parts of the world may also use different frequencies for their radio bands. Your answer to this question will help you define which radio standard your device needs to support and what radio you will choose.

2. What are the projected annual shipments of your device? . Your projected shipments will influence how embedded your radio will be in your device. The three common cellular design implementations are air cards, embedded chipsets, and embedded radio modules. The choice is a trade-off consideration between development cost, unit cost, time to market and risks.

An embedded radio chipset will be designed into your circuit-board and typically licensed from a company like Qualcomm. An embedded mini-module is an off-the-shelf wireless module with pre-integrated, pre-tested system software. An air card or dongle is a free-standing radio that plugs into your device externally through a USB interface.

If your device is expected to ship in high-volume over 100,000 units, you should consider an embedded on-board radio chipset. The R&D investment, as well as radio certification costs required to embed a radio are high, but these radios require the least space and have the lowest unit cost.

For low-volume projects of less than 1000 units, an air card or dongle radio is often a good choice. R&D and certification costs are minimal ” in some cases, it's practically plug-and-play ” but individually these radios need the most space and cost the most.

For production rates of up to 20,000 to perhaps 100,000 units, embedded radio modules are ideal. The embedded module is an enclosed device with the radio chip set sans antenna. The radio modules are certified and interface over USB using a PCI Express interface forma factor.

The modules can be easily integrated into a device while allowing flexibility in antenna placement. The benefits of the radio module include allows for small form factor designs, certification at the module level reduces certification costs and risks, and moderate design efforts for software and hardware.

The modules I/O can include data, audio, and GPS support making the modules ideal for feature rich devices. Do keep in mind that if you need to use the 3G radio for voice calls, an external radio is not a good choice ” even for low-volume projects. A large amount of custom work is needed in order to route the voice paths onto external radios.

3. What is the lifespan of your device? .Be aware that just because you don't need the high-speed capability of 3G now, you may need it in the future. Consider the data plan cost over the entire life of the device.

Older technology (2G, 2.5G) may not maintain its cost advantage over the lifespan of the device if network operators offer incentives to move traffic onto the newer 3G infrastructure. Additionally, network operators may phase out older technologies.Step 2: Understand certification testing up-front
To operate on a commercial network, a 3G radio must be certified by several organizations including the network operator. If you have chosen a pre-certified embedded mini-module or external radio for your device, then you will work with the network carriers in the geography you are deploying your device to get certified on their network.

If you have chosen an embedded radio, then you'll be responsible for government certification (i.e. FCC in the United States), 3G standards organization and, finally, wireless carriers.

Here are some tips for streamlining certification:

* Get your wireless carrier's requirements as early as possible and design to those specifications.
* Thoroughly test your device before applying for certification.
* Work with a certification house to do advanced testing before you apply for certification

Keep in mind that there are often long lines for certification. To minimize delay, it's in your best interest to do everything possible to ensure you will pass on the first attempt. And, if the return on investment works out, consider using a pre-certified radio to significantly cut the amount of certification work you will have to do yourself.

Step 3: Plan hardware changes
The size of your radio has huge implications on your hardware design. If you're using a large radio, understand that you may need to make housing and electrical changes to incorporate it into your design. Whatever radio you select, make sure that you have the necessary hardware interfaces available.

Choosing an antenna also requires careful consideration. A bad antenna choice can void the capabilities of a high-performance radio. The antenna is often the cause of certification problems.

There are two basic options: an external antenna and an internal antenna. An external antenna offers the best performance but will also cost the most and be the most susceptible to physical damage. An internal antenna will typically be 1 dB less effective than an external antenna. But an internal antenna will be lower cost and work within a protected environment.

Also, understand that if you will be using Wi-Fi in addition to 3G communications in your device, you will need two antennas.

Testing is critical. During development, test the performance of your radio early and often. You will want to test interference and throughput. Radio placement, antenna selection and other factors dramatically impact throughput. By testing early, you can make appropriate changes early in the development process when the modifications are easier and less costly to make.

Step 4: Integrate software
Part of adding the 3G radio is developing software that integrates the hardware into your system. If using a commercial operating system such as Windows Embedded CE, this typically involves modifying a radio software stack, integrating radio drivers and modifying the power management architecture to support the radio module.

Integrating the radio is not an isolated code addition. Numerous hooks are required. For example, to add a radio to a Windows Embedded CE device, you need to integrate the Windows Embedded CE Radio Interface Layer (RIL) driver with the Windows Embedded CE Cell Core module that includes the RIL proxy.

A USB 2.0 driver will need to be integrated with the USB controller on the embedded radio or mini-module. Voice and data pathways must be carefully programmed.

An option for streamlining software integration is to choose an embedded radio with pre-integrated, pre-tested software. (See Figure 2 below ) Development time and cost can be dramatically reduced.

Figure 2. System software block diagram of Windows Embedded CE embedded mini-module

Power management . Depending on how your device will be used, power management may be another critical area. If your device will need to run on battery power, you will likely want to invest significant development resources to maximize battery life.

It's an investment that can pay sizeable returns. In a typical device, for every 0.1 mA optimization in average idle current, the device gains approximate 3 hours of battery standby time.

To optimize power management, you will need to design a framework that can take advantage of the power states defined by the radio and turn off pathways when they are not in use. (See Figure 3 below .)

You may want to tweak power settings throughout the development process. Every project is unique and repeated testing and experimentation is the best way to find the magic combination of settings that works best for your device.

Figure 3. Audio routing and power management framework.

Audio management. In vertical applications, audio integration has limited capabilities and does not include handset-like functionality making audio implementations less complicated.

If using an embedded radio module, digital audio signals are made available on the connector and these can be routed directly to the code for D/A and A/D conversion. The audio management system will provide audio routing configuration.

Again the RIL driver must be developed to appropriately route the control signals over the USB bus or more complex connections.

Consider the user . During development, be sure to consider every possible way the device will be used. Is it possible the user will receive a call while uploading inventory data? At a tourism kiosk, will a user try to initiate a video conference while an overview video is streaming?

Understanding all user scenarios early in the development process will help you design the device to eliminate conflicts. It will also help you focus testing efforts. Use your list of user scenarios as a checklist during testing.

Step 5: Provisioning
To use your device on a 3G network, you will need to work with the network operator to provision the phone. You can either activate the device during production, installation, or the first time that it is used. The best activation method depends on the device.

A vending machine is a good example of a device that can be activated during installation. These machines are typically installed by technicians who deliver them to the location, verify that they are set up properly and ensure that the machine is receiving a good wireless signal. The technician could provision the machine during the installation process.

A device like a handheld data terminal is better provisioned as part of the manufacturing process. In general, any device that is resold through a sales channel should already be provisioned.

If you are responsible for provision, plan for the appropriate IT resources. If you're producing sizable quantities, work with your network operator to develop an automated activation script.

If your device supports a WCDMA (aka GSM) radio with a SIM card and the SIM card already has a plan and pre-arranged billing, then it just needs to be placed into your device.

Conclusion
Whether it's allowing simultaneous voice and data transmission or high-performance wireless data capabilities even in remote locations, adding a 3G radio can open your device to advanced new features and capabilities.

By carefully considering your needs now and in the future, exercising careful attention to detail throughout the development process, and using pre-built components and software when appropriate, you can take advantage of its potential while minimizing development time, design complexity and expense.

Mike Cannon is a Solution Architect with Bsquare. He assists customers developing Windows Embedded devices. Prior to Bsquare, Mike worked at Texas Instruments as a Project Manager supporting wireless phone OEMs developing OMAP-based devices, and, before that, as a Systems Engineer developing GSM solutions. Mike holds degrees in electrical and computer engineering from Louisiana State University

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