A year ago during my review of the LTE iPad 3 I decided to find out how long the iPad would last as a personal hotspot. With the display off and a single notebook tethered wirelessly to the iPad downloading at a constant 50KB/s, the LTE iPad 3 lasted 25.28 hours on a single charge.

The new iPad Air moves to a much smaller battery (32.4Wh vs. 42.5Wh), but at the same time it enjoys much lower platform power. The A7 SoC is built on Samsung's 28nm LP process, while the A5X used in the iPad 3 was a 45nm part. Qualcomm's MDM9600 in the iPad 3 was also built on a 45nm process, compared to the 28nm process used on the MDM9615M (the same modem used in the iPhone 5s). An improvement of two process nodes on both the SoC and modem should account for something. 

I also crudely measured idle platform power as being substantially lower on the iPad Air compared to the iPad 4. All indications seem to point to the iPad Air being just as capable of an LTE hotspot with insane battery life as previous generation models. To find out I crafted a slightly updated version of the old test.

I set the iPad Air up as a personal hotspot, wirelessly tethering it to a 13-inch MacBook Pro with Retina Display. I started a constant 100KB/s transfer on the MacBook Pro (2x the transfer rate of my iPad 3 test) and with the iPad Air's display off I measured battery life. Last time I chose 50KB/s as it was the average transfer rate across our old WiFi web browsing battery life test, I doubled the workload to be more reflective of more strenuous demands. In reality I'd expect to see a burstier usage profile, but that's something for me to test down the road.

A total of 24.08 hours and over 8GB of transfers later, the iPad Air finally died. Just like last time, you'll likely burn through your monthly data allotment before you run out of power.

I've always been a fan of tablets with cellular connectivity as it is really improves the usability of the device. Tethering to a smartphone is always an option, but there's something to be said about the convenience of having a single device that is immediately connected. The ability to turn a tablet into an LTE hotspot with incredible battery life is just an added bonus. 

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  • dokujaryu - Saturday, November 2, 2013 - link

    802.11ac hasn't finished group approval, and radios that satisfy the battery efficiency requirements of Apple probably don't exist yet. I think it's better not to go there yet. Innovation doesn't mean stupidly be first. Only a very extreme minority of customers would be able to benefit from it anyway.

    Having a new Nexus 7 2013, I can assure the the camera on the iPad is fine.

    IMO The most impressive thing about the iPad Air is the chip speed per core and the power efficiency, which is basically what this article is about.

    SD Cards are slow, even class 10 ones, even the SDXC ones. IMO they shouldn't be used outside of cameras and single-board computers IMO. There's no use explaining this to the average consumer who wants them, and no use explaining to the average consumer who has them that they are slow not to install things on them. Google and Apple agree, it's just easier not to give it to people.

    That being said, it would be cool on the phones at least if they would allow for an SD card to save camera images only, although that would make iPhoto and other I/O heavy apps slower. I know my Galaxy S4 photo gallery app speed went way down after storing things on micro SD instead of the internal memory.

    $100 price points for more NAND memory are getting tiresome. I think it could change on the 6.
  • eek2121 - Sunday, November 3, 2013 - link

    yeah...no offense dude, but sd cards are used for shit like cameras...including HD VIDEO cameras. You know the stuff that ACTUALLY stresses Input/Output...unlike the tiny little bit of flash inside your tablet. In short, SD cards (the well built, faster ones, not the budget versions) are FASTER, not SLOWER than the flash memory in your tablet. Oh and one other thing...a full blown SSD which blows away both that SD card as well as the eMMC in your tablet costs less than apple's storage upgrades. Disclaimer: not blaming apple since all tablet manufacturers do the same exact thing.
  • Impulses - Sunday, November 3, 2013 - link

    Actually, most HD video only requires about a class 4 card or so... Unless you're shooting high Mbit rates on a DSLR or something. Dunno what decided video cameras require, haven't kept up with that world, I'm guessing around 6-10MB/s sequential speeds if they're closer in bitrate to high end stills cameras (obviously talking about consumer stuff here, not a RED, which definitely don't use SD cards).

    Burst shooting is usually more demanding than video, since a DSLR can be firing up to 10 RAW + JPEG images in one second (so close to 300MB/s); that's usually done to a buffer of course but the quicker the card the quicker the buffer clears and you can start shooting again. These are all very sequential operations tho...

    Internal storage has an advantage in that it can be optimized for random I/O which is far more common on a mobile device, was removable media is usually poorly optimized for it. That hardly justifies some of the premiums on cheap flash hooked up to an even cheaper eMMC tho.
  • dokujaryu - Sunday, November 3, 2013 - link

    Sequential read and write is basically the easiest task you can ask of a storage device, which is all anyone tells consumers when they buy things.

    I wanted to be clear that I'm not saying you can't use SD cards as primary storage. I have a few Raspberry Pis, BeagleBones, and a Udoo, which all use SD or Micro SD as primary storage. I'm just saying the user experience is going to be poor unless the the speed bottleneck isn't the SD card or users / apps are smart enough to only use them only in appropriate tasks.

    Google tends not to mention any speed issues and instead describes complicated user edge cases that involve removing the card while an app is running, or while editing a photo, or other things.
  • zepi - Sunday, November 3, 2013 - link

    I don't really see external sd-card as a replacement or proper expansion of storage. From operating systems point of view it's logically different volume. And since none of the big Mobile OS platforms offer real file management as an integrated feature, i just feel that external storage is a hassle and hindrance to average user.

    I agree that 16->32 storage upgrade @ apple is expensive, but otoh it provides huge value for customer (expands usable space almost threefold). Similar value of storage space could never be achieved with a mere uSD, as it would mean that all software would need to be rewritten to handle multiple storages or OS would need to be able to move stuff between storages.

    Currently there are no elegant ways of handling multiple storage paths in mobile os'es an i think it's not going to change.

    Being a nerd i can find my way trough androids convoluted linux paths, but for average folks its a real horror.

    Anyone who wants to access and manage files should consider moving towards ubuntu...
  • mark3785 - Monday, November 4, 2013 - link

    If I recall correctly, and let me know if I’m just suffering from a faulty memory, I believe the lack of SD slots and USB ports goes back to Apple’s iPod days.

    Since they were the only company building music players and selling music (now DRM free), I believe part of the agreement with the music publishers was to make pirating music as difficult as possible and this precluded the addition of memory slots or USB ports to their devices.

    I’ve heard nothing more since pre-iPhone days, so I don't know if they're still bound by the same restrictions.
  • Lord 666 - Saturday, November 2, 2013 - link

    One element not discussed is by making it so thin, the iPad Air can now be bent. Played with on in the store and while not trying to break it, noticed by twisting it got the screen to flicker. This was not possible with even the iPad 2, 3, or 4. Time will tell if this will become a bigger issue in the future.
  • darwinosx - Saturday, November 2, 2013 - link

    Oh please..
  • Phynaz - Saturday, November 2, 2013 - link

  • NCM - Saturday, November 2, 2013 - link

    Cue the new 'You bend it, you buy it' store policy.

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