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Apple iPad 3 and Other Mobile Device Wi-Fi Output Power

Well, it’s here … Apple’s iPad 3 was announced today! If your organization is anything like mine, swept up in Bring Your Own Device (BYOD) and the consumerization of IT, you’ll be seeing those beautiful devices land on your Wi-Fi network faster than Devin can say “controller-less” :-) But with these shiny new mobile devices comes a reminder that supporting mobile devices on a Wi-Fi network is not easy.

Proper design of wireless LANs is dependent, in part, on the RF characteristics of both the access point and client devices. Smart mobile devices such as the Apple iPhone, iPad, Google Android devices, and others have presented WLAN design challenges for engineers. Due to their lower transmit power output and restricted antenna design, the WLAN infrastructure must be carefully designed to support these mobile devices. Lucky for us at Aerohive, we designed our recent Hive AP 330 and 350 models with “Ninja” hardware, including lower EVM, to support mobile devices! Heck, we’ve even got a whitepaper on The iEverything Enterprise and a FREE web-based Wi-Fi Planning Tool to help you get started. :-)

To properly determine how to design a wireless infrastructure to support these mobile devices engineers must understand their specifications and capabilities. However, very few original equipment manufacturers publish such information. So what do you do?

Answer - Ask the FCC, of course!

The FCC Office of Engineering and Technology (OET) tests and authorizes all equipment that uses radio frequency spectrum. They also maintain a handy public database of all equipment authorizations and details of testing.

In order to search the FCC OET Equipment Authorization database, you will need the FCC ID of the device you want to lookup. All devices that use radio frequency spectrum are required to print their unique FCC ID on a label on the device. It may also be printed on a separate document that accompanies the device. For instance, look at the FCC ID label for an iPhone 4S (pictured).

Similar information can be found on the Industry Canada Radio Equipment List (REL) Search (also see TRC-43 for interpreting the Emissions Designation). I haven’t found a good online source for researching European CE Mark products; if you know of one, please let me know!

Enter the FCC ID on the search page by splitting the ID into two parts. The first part contains the first 3 characters; the second part begins with the dash and includes the remainder of the FCC ID. Here’s a search on an iPhone 4S:

 

The results will appear, showing you a list of records for the device in question. The two far right columns will list which frequency band or range the record pertains to.

 

To find the Wi-Fi output power, you’ll want to look for the record that covers Wi-Fi frequency bands in the 2.4 or 5GHz bands. Once you’ve found the record(s) in question, click Detail in order to view the list of exhibits for that record. The list of exhibits includes documents submitted to the FCC from the manufacturer, as well as documents detailing the FCC test results.

 

Look for a document referring to the WLAN Test Report (or something similar). Open up the document and browse through it to find the maximum and average output power. Multiple usually exist because the FCC tests each mode of operation independently (802.11b, 802.11a, 802.11g, and 802.11n) because each mode results in different spectral emissions characteristics. This is due to different spread spectrum and modulation techniques, channel bandwidth, etc.

For the iPhone 4S, we see the following results for 802.11n operation:

 

Notice that power output is also different based on the frequency (channel) of operation. This is because the FCC requires minimal emissions in neighboring frequency bands, which typically requires lower power output at channels on the band edges.

Now you’re armed with the basic information you need to properly design a wireless network to support mobile Internet devices! Of course, much work lies ahead to determine proper coverage, capacity, and other variables that shape a wireless network infrastructure.

But Aerohive has your back since we deliver hi-quality Wi-Fi for Apple devices!


Cheers,
Andrew vonNagy



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