Apple iOS 4.3 - the latest operating system for Apple iPad, Apple iPhone and later version of the Apple iPod touch - extends the capabilities of such iOS devices in meaningful ways

You might describe iOS 4 as a long-term investment. While the initial version brought us the much-demanded multitasking, subsequent updates haven't been restricted to mere bug fixes. Instead, we've gotten a slew of noticeable, if not major, improvements: AirPlay, AirPrint, Game Center, and so on. The newly released iOS 4.3 is no exception, bringing not only a couple of significant enhancements in the form of the Personal Hotspot feature and Home Sharing, but also some smaller niceties as well.

As with Apple iOS 4, the 4.3 update plays well with only certain models - and on top of iOS 4.0's limitations, 4.3 narrows the field even further. You'll need an Apple iPhone 4 or Apple iPhone 3GS, an Apple iPad or Apple iPad 2, or a third- or fourth-generation Apple iPod touch to take advantage of the update.

Apple iOS 4.3: X marks the hotspot

We got our first taste of the Personal Hotspot capability with the release in the US of the Verizon iPhone 4 in February - now that feature has made its way to GSM-powered iPhone 4s as well. Personal Hotspot lets you share your iPhone's 3G data connection with other devices via your choice of Wi-Fi, USB, or Bluetooth. (Note that iPhone 3GS users can only share network connections via Bluetooth and USB, and not Wi-Fi - in essence the same limits placed on iPhone 3G owners with tethering.)

For iPhone 4 users, the feature replaces the tethering functionality that debuted in iOS 3.0, and nobody's shedding a tear over that. The tethering functionality was limited - it only worked over Bluetooth or USB and just supported a single connected device - and expensive - it cost £20 extra per month, required users to drop their unlimited data plans, and provided no extra data usage.

By contrast, the Personal Hotspot feature is more attractive. It may even be cheaper, depending on the data plan. The Personal Hotspot feature is also simple to set up: once you've changed your data plan over, you simply enable the hotspot feature under Settings -> General -> Network, and a new Personal Hotspot sub-menu appears in the top level of Settings. From there you can turn the feature on or off and set a Wi-Fi password. Clients can then connect via Wi-Fi or Bluetooth, or you can plug your iPhone into your PC via USB. A blue bar will appear at the top of the screen to let you know how many connections your iPhone currently has, even if you switch to other apps.

In terms of performance, USB actually appeared to provide the best throughput in my tests, which were conducted on a MacBook hooked up to an iPhone 4. The directed wired connection showed the highest download and upload speeds (Wi-Fi had lower latency, however). Bluetooth was by far the worst - no surprise, given that Bluetooth's transfer speed is in most cases slower than the phone's 3G connection. Wi-Fi held a firm middle ground in terms of speed, but it has the convenience factor of being wireless.

The GSM iPhone supports a maximum of five clients spread through the various connection methods. For example, you can only have a maximum of three devices connected via Wi-Fi, but to that you can add other clients via Bluetooth or USB. And, of course, the more clients you add, the slower the connection will get as the devices jockey for bandwidth.

Surprisingly enough, if you've got an iPad in addition to your iPhone, you can connect it to the hotspot via either Wi-Fi or Bluetooth. (USB is out of the question, however, even if you try using the iPad Camera Connection Kit.)

So, is the Personal Hotspot worth the cost? It depends on your data use and the data plans UK operators put in place. Your mileage may vary, of course, but it's worth looking into.

iOS 4.3

Apple iOS 4.3: Share and share alike

Introduced in iTunes 9, Home Sharing allows you to - among other things - play media from one computer on your local network on a different computer. In iOS 4.3, that feature gets extended to iOS devices as well. Once you've set up Home Sharing on your iPhone, iPad, or iPod touch, you'll be able to toggle back and forth between playing media from your local device and from Home Sharing-enabled computers on your network.

Setup is easy, if a bit obscure. First, you'll need to enter your Apple ID in Settings -> iPod; after that, you can access shared media via some combination of the iPod, Music, and Videos apps, depending on which iOS device you're using. Accessing your shared libraries isn't always obvious, though. On the iPhone, you tap the More button in the iPod app's toolbar and then select the new Shared option. You'll see all the shared iTunes libraries on your network (as well as your iPhone itself). Once you've tapped the shared library, all of the media you see in the iPod app refers to the shared library, illustrated by a titlebar at the top that bears the name of the computer to which you're connected.

On the iPad, on the other hand, you'll need to tap the Library header in the top left of the iPod app to access the shared libraries. In the iPad's Videos app, a new Shared toolbar option appears at the top of the app which lets you browse shared libraries on your local network. The disparate interfaces unfortunately make accessing shared libraries very confusing.

Performance in streaming is very good: music and short videos start playing almost immediately. Longer videos (or HD ones) can take some time to buffer before they start playing back. Quality is very good in all cases, with music nearly indistinguishable in quality from that on the local device and the video clear and easily watchable. Playback was smooth, even with multiple devices streaming from the same library, and I was able to scrub around in HD videos without having to wait for lengthy rebuffering times. Among the few drawbacks, the Genius feature isn't available when you're accessing shared libraries and, since Home Sharing only supports content in your iTunes library, you can't stream photos stored on your computer.

One missing feature, however, is the ability to stream content from an iOS device to either another iOS device or a Mac or PC. At the moment, iOS devices are limited to being Home Sharing clients, not servers; adding that server functionality would be handy for cases where you want to share music or videos from your iPhone or iPad with friends.

That said, if you have an Apple TV or AirPort Express, there is another option: AirPlay.

iOS 4.3

Apple iOS 4.3: The AirPlay's the thing

AirPlay debuted in iOS 4.2 and iTunes 10 - like Home Sharing, it's a blanket term for several technologies, one of which is replacing the old AirTunes feature that let you stream music from your Mac or PC's iTunes library to Apple TVs and AirPort Express devices. AirPlay extended that, however, by letting you stream audio to those aforementioned devices directly from your iPhone, iPad, or iPod touch, and even in some cases adding video-streaming support.

In iOS 4.3, AirPlay gets further beefed up with the ability to stream video from compatible Websites, third-party applications, and the Photos app. So if you want to show off that HD movie you just shot on your iPhone 4, you can stream it to your Apple TV with the tap of a button. Plus you can take advantage of all the slideshow transitions on the Apple TV; in order to do that, you'll need to hit the AirPlay button while viewing a photo and then hit the Play button to choose your slideshow transition from the Apple TV's list.

However, it doesn't all work right out of the box. Third-party apps will need to add support for AirPlay video, so expect a slew of updates over the next few weeks and months. And for Websites, not only will the video need to be in a format that iOS devices can play (read: H.264-encoded MPEG4 videos), but the video providers will have to explicitly define their videos as AirPlay compatible.

There is a workaround, however, if you install this clever JavaScript bookmarklet, which lets you flip on AirPlay support for video on any page. (It worked in my limited testing, though the quality of the video was not always good.)

For those third-party apps that have implemented support (the only app I own that had updated as of this writing was Air Video), it works the same as with Apple's own built-in apps. When you start playing a video or a song, just tap the AirPlay control and select your Apple TV from the list. After a few seconds, the media should start playing there, but you'll be able to control it from your iOS device.

But because implementing AirPlay support is an opt-in choice, don't expect all of your video-based apps to flip the switch. Some, such as Netflix, have already said they don't plan to add that feature (the company cited redundancy, since the Apple TV already streams Netflix); others, such as Hulu, have shown in the past their reluctance to have their media available on a big screen.

I ran into a few glitches and inconsistencies while trying out AirPlay support. For example, while you can AirPlay videos from the Photos app, you cannot do so if you access your photos and videos via the Camera app; that's especially irritating, as the Camera app conveniently lets you filter just your photos or just your videos, a feature not available in the Photos app. Also, though Air Video's AirPlay support worked fine on my iPhone 4, it didn't work at all on my iPad (toggling between the iPad and Apple TV changed nothing); that may be a problem for the developer to fix, however. Finally, you can AirPlay content being played from a shared library via Home Sharing (see above), but it only appears to work with audio at present.

It's also worth noting that the CDMA iPhone (i.e. the Verizon iPhone in the US) is not currently compatible with AirPlay.

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