Can Your WLAN Support the iPad?
When the iPad first came out two years ago, 300,000 were sold in the first three days. When the iPad 3 came out earlier in the year, over 3,000,000 were sold in the first three days. If that trend continues, we should expect that when the iPad 6 comes out it will be purchased by 100% of the world’s population during the first three days of release. Ok, that’s a long shot, but the point is a lot of iPads are being sold. And a lot of iPhones. And a lot of Androids. And the laptop market is still strong. What is the common theme here? They are all Wi-Fi devices and they all want a piece of your wireless network.
The MCPc anyplace workspace is a concept that says whatever your device, wherever you are, we’re going to make sure you have accessibility to your data. For an increasing number of enterprises, supporting mobile access has become synonymous with supporting the iPad. It's a refrain I am hearing again and again when I talk to our customers:
Can my WLAN support the iPad and other mobile devices?
To begin to determine if you are ready to support this influx of wireless clients, we need to look at the nature of the wireless devices requiring connectivity. Most wireless end clients manufactured in the last 24 months, including iPads, are shipped with an internal 802.11n radio. 802.11n works in both the 2.4 and the 5 GHz range. Remember that even smartphones will, if able, attach to your wireless network and run their data across it rather than the cellular carrier’s 3G or 4G networks. So what does that mean? That means that you are likely being forced to provide IP addresses to a whole lot of devices that were grabbing addresses from the cellular network just a couple years ago.
Most 802.11n clients including iPads and newer laptops will first try to connect in the 5 GHz range. The 5GHz spectrum tends to have less interference than 2.4 GHz because many devices, including cordless phones, microwave ovens and even Bluetooth devices, operate in 2.4GHz frequency.
Since there are very few standards surrounding the implementation of Wi-Fi radios in mobile devices, a common expectation is that the wireless experience on an iPad will be similar to that of a laptop. Unfortunately the power of the wireless radio in the iPad and laptops differ dramatically. Laptops typically have a transmit power of 30 mW to 50 mW (15 dBm to 17 dBm). iPads have an average transmit power of 10 milliwatts (mW, 10 decibels per mW [dBm]). Given the difference in transmit power, it is unrealistic to expect iPads and laptops to consistently connect to your WLAN at similar levels. Either the range or the performance expectations of the iPad are going to have to change.
iPads have roughly 60% of the transmit power of most newer laptops set at equal distance from an access point. A recent Gartner report noted that “if the IT organization is asked to provide the same performance as a typical laptop throughout the coverage area at 5GHz, the IT organization will need 300% more access points. Remember that there is a 6 dB difference between the transmit power of the iPad, which has an average transmit power of 10 dB, and the laptop, which has an average transmit power of 15 dB to 17 dB. Radio frequency (RF) basics tell us that the distance required to maintain the same throughput doubles for each 3 dB, but the coverage required grows exponentially, which will require 300% more access points.” In an office environment where typical WLAN designs called for designs of about 3000 sq. ft. for each cell, Gartner is suggesting that each cell will cover only 750 sq. ft. -- an area about 27’ by 27’. In a hospital where cell sizes often top out at 2000 sq. ft., that would translate to 500 sq. ft. per cell.
The 802.11ac Factor
When designing WLANs we now also need to be cognizant of the upcoming 802.11ac standard that is pending ratification. This standard is designed to operate only in the 5GHz range and to provide throughput upwards of 1 gigabit. Manufacturers like Cisco are already building access points with available draft 802.11ac modules. Cisco’s latest 802.11n access point, the 3600, features both a 4x4 MIMO antenna configuration as well as an expansion slot which will allow for the addition of an 802.11ac module. Devices like the 3600 allow for customers to embrace the 802.11n standard while also providing investment protection once the 802.11ac standard is ratified.
Knowing that iPads have always adhered to the latest IEEE wireless standards, it’s reasonable to assume that all iPads released after the formal ratification of 802.11ac will embrace this new standard. In the next generation iPad design it’s logical to assume that Apple will boost their radios to a higher transmit power to take advantage of the increased throughput.
Mobile Devices are Here to Stay and Will Grow in Numbers
While attending Cisco Live earlier this month I heard the resounding message from Cisco and third party software developers alike: The age of the wireless revolution is here!
By 2015 wireless devices are expected to outnumber wired by a staggering 5 to1! While many organizations have been planning for this migration for some time, in most cases there is still an awful lot of planning left to do. The smaller 802.11ac cell sizes will require an engineering redesign of legacy data/voice 802.11a/g environments. For organizations that want to bring the anyplace worskpace to its employees, this redesign will be critical to the successful deployment and maintenance of a WLAN capable of supporting it.
Kevin Cannon is an MCPc Solution Architect with a focus on Cisco advanced technologies, and has over 8 years of experience in developing and deploying WiFi, VoIP, video and RTLS solutions for mid-sized and enterprise-level organizations. Connect with Kevin on LinkedIn.
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