2G vs 3G vs 4G: Which Technology is Best for Embedded Cellular Designs?
Monday, August 4, 2014
The project is over time, over budget and now your boss asks you to add cellular connectivity. You don’t have time to test all the different cellular technologies, so it is important that you select the correct one for your application. Which one do you use? Let’s see what makes each of these technologies a contender for your business.
2G and 2.5G
Unless you have a voice only application, data throughput is usually the first thing we think of when comparing cellular technologies. 2G GPRS offers data rates of up to 50kbps, and 2.5G, which includes EDGE, bumps up the data rate to 250kbps. This may not sound like much, but if your application is something like smart metering where you only collect a few bytes of measurements each day and send it to a server, then this is more than enough. If these data rates are sufficient for your application, then 2G cellular modules will likely be an attractive option due to their low price. Unfortunately, there’s a big down side: in a year or so there will no longer be 2G (or 2.5G) GSM networks available in the US. AT&T has already started turning off their 2G towers and are planning to completely do away with 2G by the end of 2016. The reason for this move is to free up frequencies for use in their high bandwidth 4G network. Even if you wanted to make a 2G product right now you may have difficulty since AT&T is no longer certifying any 2G products in anticipation of the shutdown. So now you’re probably wondering “why did this guy waste my time talking about 2G if it’s not available anymore?” Well, it may not be available in the US, but for many other countries it’s still a very good option because of the low cost of the modules. If you are planning to deploy your products in another country it is important to check that the network technology you plan to use is available and will be available in that country for a few years to come.
2G CDMA (1xRTT) offers the second lowest cost modules and supports data rates up to 153kbps which is sufficient for many M2M applications. Verizon is planning to have their 1xRTT and EVDO networks shut down by 2021. Sprint on the other hand is seeing this as an opportunity to win M2M customers and plans to maintain their 2G network well into the future. So for those who have modest throughput needs, a 2G Sprint module may be the way to go.
3G and 3.5G
To call a cellular service 3G, it has to comply with IMT-2000 technical standards. These standards require the system to provide peak data rates of at least 200kbps. This is just the minimum requirement, with many 3.5G HSPA+ modules offering peak upload rates of 5.7Mbps and download rates of 21Mbps. This speed comes at a price, as 3G modules can cost up to twice that of a 2G module. Some 3G modules, like Telit’s HE910-G, can use multiple frequency bands and also allow fall-back to 2G if there is no 3G reception available. The reason for supporting multiple frequencies is that it increases the number of countries in which a module can be used. If you are only planning to use 3G in North America, with no need for 2G fall-back, you can choose a cheaper module that only covers the 3G frequencies you need.
LTE smart phones have been offered by the major US carriers since 2010, so it’s not surprising that most cellular module providers are now offering LTE modules as well. Cat 3 LTE modules offer upload speeds of 50Mbps and download speeds of 100Mbps. LTE Advanced is another step up which allows the aggregation of multiple frequency bands to increase data rates. Cat 4 LTE combines two 10MHz bands, and has a maximum downlink speed of 150Mbps. With data rates like these cellular modules can be used for applications that were previously only possible through fixed line networks. Telit’s LN930 M.2 data card offers global LTE connectivity with coverage of 12 different LTE bands, as well as fall back to 3G. LTE modules are the most expensive option at the moment, but also offer the longest product life span. Having a module that works on both LTE and 3G networks is desirable since it offers a fall back option if one type of network is not available.
Unless your application requires very high data rates, LTE modules may still be too pricey for most applications. A good module provider can offer solutions that lessen the cost when transitioning from one cellular technology to another. Telit’s 910 family of modules tries to do this by offering all the cellular technologies in one form factor that is footprint compatible. This allows a customer to replace a 2G 910 module with an LTE 910 module without having to redesign the board. If you have a product that could benefit from LTE in future, this is a good strategy to consider.
Still wondering which technology to use? Or, ready to get started designing your chosen technology into your application? Call Symmetry at (310) 536-6190, or contact us online.
Why partner with Symmetry Electronics? Symmetry's technical staff is specially trained by our suppliers to provide a comprehensive level of technical support. Our in-house Applications Engineers provide free design services to help customers early in the design cycle, providing solutions to save them time, money and frustration. Contact Symmetry for more information.
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