WLAN vendors, when they're willing to comment, say they're not seeing any surge of problems.
"We have upgraded dozens if iOS devcies internally and have not seen any performance degradation," according to Bruce Miller, vice president of product marketing, networks, at Xirrus, a WLAN vendor. "We have not received any communications from our customers with issues related to iOS upgrades either, either directly into [Tech] Support or via social channels."
A teacher, identified as bravescoach, started a thread on Apple's site describing problems at at Indianapolis-area school with 750 students and a mix of personally-owned mobile devices, though "hundreds" have iPhones and iPads. The school's Wi-Fi network is based on Cisco Aironet WLAN gear.
"There is definitely an issue where iPhone 4S and iPad 3rd generation devices are "unable to join network" after updating to iOS 6," he writes. "Needless to say it is wholly impractical to revert firmware on any of these machines just to deal with two [types of] devices. Each of these devices were fully capable of connecting while on iOS 5.1.1."
Other iDevices, including iPhone 3GS, iPhone 4, iPod touch 4th gen, and iPad 2 "all work fine." According to this poster "several schools" in the area have run into problems. His own iPad 3 works, updated to iOS 6, works on his home network, with a Linksys router, but not on the school's WLAN.
A variety of suggestions have been put forward including resetting or changing the authentication/encryption being used by the client devices and the network. But that's not an option for many enterprise WLANs.
Users with working iPhone 5 Wi-Fi are seeing some startling increases in throughput, as some of the comments above show. This is due almost entirely to the fact that it now supports Wi-Fi connections over the 5-GHz band instead of just 2.4 GHz. [see "FAQ: iPhone 5 and 5GHz Wi-Fi"]
Xirrus this week has run a series of tests with the new iPhone 5, connecting to its Wireless Array access point. One set of tests compared Wi-Fi performance of iPhone 5 on 2.4GHz with 20 MHz-wide channels and on 5GHz with 40 MHz-wide channels. The second set of tests Wi-Fi performance of the iPhone 4S on 2.4 GHz with 20 MHz-wide channels. Each test measured the throughput and time to send and receive a 100MB file.
For iPhone 5 on 2.4 GHz: throughput was 42.24Mbps and 19 seconds uploading, and 38.31Mbps and 21 seconds downloading the file.
The iPhone 4S had comparable numbers in 2.4 GHz: 32.18Mbps and 20 seconds uploading; and 40.23Mbps and 25 seconds downloading.
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