This is a series of three posts – all concerning the variation and consistency of various Apple iPad models with respect to Wi-Fi Performance.
In this first post, we’ll be focusing on just the output transmit power of the different devices. This is important because for accurate and consistent data flow, the client device must be able to talk back to the Access Point with enough power for the AP to accurately recreate the intended bit stream with as few as errors as possible.
You may be able to increase the power or provide better antennas on the Access Point side of the equation, but it is quite difficult to change the client transmit power. So the better it works directly out of the box, the better for your network.
The better the signal quality from any individual client device on your enterprise wireless network, the higher the usable Data Rate. The higher the data rate, the quicker each device gets on and off the precious RF media. Thus allowing for more throughput and higher densities.
In this experiment, I used a variety of Wi-Fi enabled iOS and non-iOS devices to compare their RSSI at a given point. In order to keep things as fair as possible, and to get consistent results, all devices were equidistant from the sensing device. We tested at five different locations, from 3 meters to 15 meters, through 1 to 4 walls made of wooden studs covered with sheetrock. Additionally the results from a Wi-Fi NIC sensing device were averaged with the results from a Spectrum Analyzer. So there were more than 350 data points used to come up with these per-device averages.
All of the locations, and sensing techniques were averaged together to get an aggregate view of the Received Signal from each of the devices.
If you are interested in the chip specifications, and other details, you can check out these two blog posts by Andrew VonNagy – Senior Wi-Fi Architect at Aerohive.
These results are all comparative – obviously with distances varying from 3 meters to 15 meters the actual RSSI’s were very different. But it is the consistent differences that are important here.
The following graph shows the results in the 2.4GHz frequency. The iPad 1 was used as the Baseline. I also added a couple of 2.4GHz compatible phones, two iPhones and an HTC G2 in for comparison. The two MacBooks were also added to show a comparison between the 1x1 in the hand-held devices from the 3x3 in the laptops.
Note the iPad 2 fares worse than the original iPad 1 by about -2dB. Remember, this is only the Tx power test – please hold your judgment till we get to the throughput testing on the next two posts to see what the actual results to a client look like.
Now lets look at the 5GHz frequency. The phones were excluded from this test since they are 2.4GHz capable only. Remember these are the aggregate averages between five different locations using two sensing technologies. Note the consistency between all the devices. These are much closer results.
In both the 2.4GHz and 5GHz frequencies, the new iPad – also known as the iPad 3 in the graphs – performed consistently better than the other older versions of the same device.
In fact, in the 5GHz range, it performed as well as the much larger MacBooks.
This was only raw Tx power testing. In the next posts we’ll look at both Tx and Rx throughput testing results.
Stay tuned for Keith's next two installments: