Friday 27 November 2015

What's the Difference? CDMA vs. GSM

https://www.youtube.com/watch?feature=player_embedded&v=P9UZhsmmC7g



CDMA vs. GSM: What's the Difference?

Two basic technologies in mobile phones, CDMA and GSM represent a gap you can't cross. They're the reason you can't use many AT&T phones on Verizon's network and vice versa. But what does CDMA vs. GSM really mean for you? 
CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for the two major radio systems used in cell phones. Both acronyms tend to group together a bunch of technologies run by the same entities. In this story, I'll try to explain who uses which technology and what the real differences are.
Which Carriers are CDMA? Which are GSM?
In the U.S., Sprint, Verizon and U.S. Cellular use CDMA. AT&T and T-Mobile use GSM.
Most of the rest of the world uses GSM. The global spread of GSM came about because in 1987, Europe mandated the technology by law, and because GSM comes from an industry consortium. What we call CDMA, by and large, is owned by chipmaker Qualcomm. This made it less expensive for third parties to build GSM equipment.
There are several variants and options carriers can choose, like toppings on their technological ice cream. In this story we'll focus on U.S. networks.
What CDMA vs. GSM Means to You
For call quality, the technology you use is much less important than the way your carrier has built its network. There are good and bad CDMA and GSM networks, but there are key differences between the technologies. Here's what you, as a consumer, need to know.
It's much easier to swap phones on GSM networks, because GSM carriers put customer information on a removable SIM card. Take the card out, put it in a different phone, and the new phone now has your number. What's more, to be considered GSM, a carrier must accept any GSM-compliant phone. So the GSM carriers don't have total control of the phone you're using.
That's not the case with CDMA. In the U.S., CDMA carriers use network-based white lists to verify their subscribers. That means you can only switch phones with your carrier's permission, and a carrier doesn't have to accept any particular phone onto its network. It could, but typically, U.S. carriers choose not to.
Many Sprint and Verizon phones now have SIM cards, but that isn't because of CDMA. The SIM cards are generally there for Sprint's and Verizon's 4G LTE networks, because the LTE standard also uses SIM cards. The phones may also have SIM slots to support foreign GSM networks as "world phones." But those carriers still use CDMA to authenticate their phones on their own home networks.
3G CDMA networks (known as "EV-DO" or "Evolution Data Optimized") also, generally, can't make voice calls and transmit data at the same time. Once more, that's an available option (known as "SV-DO" for "Simultaneous Voice and Data Optimization"), but one that U.S. carriers haven't adopted for their networks and phones.
On the other hand, all 3G GSM networks have simultaneous voice and data, because it's a required part of the spec. (3G GSM is also actually a type of CDMA. I'll explain that later.)
So why did so many U.S. carriers go with CDMA? Timing. When Verizon's predecessors and Sprint switched from analog to digital in 1995 and 1996, CDMA was the newest, hottest, fastest technology. It offered more capacity, better call quality and more potential than the GSM of the day. GSM caught up, but by then those carriers' paths were set.
It's possible to switch from CDMA to GSM. Bell and Telus in Canada have done it, to get access to the wider variety of off-the-shelf GSM phones. But Verizon and Sprint are big enough that they can get custom phones built for them, so they don't see the need to waste money switching 3G technologies when they could be building out their 4G networks.
The Technology Behind CDMA vs. GSM
CDMA and GSM are both multiple access technologies. They're ways for people to cram multiple phone calls or Internet connections into one radio channel.
GSM came first. It's a "time division" system. Calls take turns. Your voice is transformed into digital data, which is given a channel and a time slot, so three calls on one channel look like this: 123123123123. On the other end, the receiver listens only to the assigned time slot and pieces the call back together.
The pulsing of the time division signal created the notorious "GSM buzz," a buzzing sound whenever you put a GSM phone near a speaker. That's mostly gone now, because 3G GSM (as I explain later) isn't a time division technology.
CDMA required a bit more processing power. It's a "code division" system. Every call's data is encoded with a unique key, then the calls are all transmitted at once; if you have calls 1, 2, and 3 in a channel, the channel would just say 66666666. The receivers each have the unique key to "divide" the combined signal into its individual calls.
Code division turned out to be a more powerful and flexible technology, so "3G GSM" is actually a CDMA technology, called WCDMA (wideband CDMA) or UMTS (Universal Mobile Telephone System). WCDMA requires wider channels than older CDMA systems, as the name implies, but it has more data capacity.
Since its inception, GSM has evolved faster than CDMA. As I mentioned above, WCDMA is considered the 3G version of GSM technology. To further speed things up, the 3GPP (the GSM governing body) released extensions called HSPA, which have sped GSM networks up to as fast as 42Mbps, at least in theory.
Our CDMA networks, meanwhile, are stuck at 3.6Mbps. While faster CDMA technologies exist, U.S. carriers chose not to install them and have instead turned to 4G LTE to be more compatible with global standards.
The Future is LTE
The CDMA vs. GSM gap will close eventually as everyone moves to 4G LTE, but that doesn't mean everyone's phones will be compatible. LTE, or "Long Term Evolution," is the new globally accepted 4G wireless standard. All of the U.S. carriers are turning it on. For more, see 3G vs. 4G: What's the Difference?
The problem is, they're turning it on in different frequency bands, with different 3G backup systems, and even, in the case of the new Sprint Spark network, using an LTE variant (TD-LTE) that doesn't work with any other U.S. carrier's phones. There are very few phones that support all of the carriers' LTE bands.
Verizon has said it aims to start selling LTE-only phones in 2015, but for now, those will require special Verizon software to make voice calls, so that move won't make it any easier to switch carriers with your phone. Even without CDMA, the CDMA philosophy of carrier control of your phone will remain intact.
A growing number of phones support all of these standards, but it can be hard to tell which ones. The iPhone 6, the iPhone 6 Plus and the Google Nexus 6 are the most flexible. iPhone 6 and 6 Plus units from AT&T, T-Mobile, and Verizon can all be used on all three carriers, but they lack Sprint's special LTE bands. Sprint iPhones have all the bands, but Sprint has strict unlocking policies. Nexus 6 phones will technically work on all four carriers, but Sprint only allows phones purchased from Google or Sprint on its network.
HTC One (M8) and Samsung Galaxy S5 phones from Verizon will work somewhat on AT&T's and T-Mobile's networks, albeit with limited coverage because while they have CDMA, GSM and LTE, they don't have all the frequency bands AT&T and T-Mobile use. Variants of those same models sold by AT&T and T-Mobile won't work on Verizon at all, because they lack the CDMA radio needed for Verizon. It's a mess.
So what does all of this mean for you? If you want to switch phones often, use your phone in Europe, or use imported phones, just go with GSM. Otherwise, pick your carrier based on coverage and call quality in your area and assume you'll probably need a new phone if you switch carriers. Our Readers' Choice and Fastest Mobile Networks awards are a great place to start.

Friday 20 November 2015

Best budget smartphones of 2015



Best budget smartphones: buying advice
The first thing that you should know when buying a budget smartphone is that there's always a compromise compared to top-of-the-range phones out there. Don't expect performance to rival the latest iPhone or other high-end Android smartphones. Although budget smartphones will offer similar features to the most expensive phones, they're built to a price, so tend to have lower-quality, lower resolution screens, slower processors, less storage, poorer cameras and fewer features (such as no NFC or support for 4G).
There are two main operating systems that you will find on a budget smartphone: Google Android and Windows Phone 8. Both of these operating systems will let you download the major apps such Facebook, Twitter, Skype, Whatsapp and more. However, if you want Google apps including Gmail, YouTube, Maps and others, you should to opt for a smartphone running Android.
We like Windows Phone, but the choice of apps is much more limited, especially when it comes to UK-specific ones and those for physical gadgets such as smart home devices. Also, apps may not have the same set of features that you get on Android. You can't download TV shows from BBC iPlayer on Windows Phone, for example. And that will be a deal-breaker for some people.
Hardware
Processor
At the moment we have a strange situation where some cheap phones have the same processor - and performance - as much more expensive phones. For example, the new 4G version of the Motorola Moto E has the popular Snapdragon 410 CPU. Yet, there are lots of phones costing twice at much as the Moto E's £109 price with exactly the same chip.
What's important is not the benchmark results (they're a way to compare phones to see if one is better or worse than another) but whether they feel responsive in real-world use. You'll need to read our reviews to find out whether a phone performs well or not.
Battery
Battery life is also a factor in performance. However, there's isn't a great difference between the best and worst budget phones in this respect. They generally have similar size batteries which typically last a day (and a bit) in 'normal' use.
Of course, if you use the phone for hours on end to browse the web, use it as a sat nav, play games or watch videos you'll find the battery might run out well before the day is out. Battery saver modes won't really help here, since the only modes which will significantly extend battery life will also prevent you from doing those things and limit use to phone calls and text messages.
Screen
When it comes to screens, arguably the other component you should care about, there are some things to look out for. One is resolution. With screen sizes gradually increasing, low resolutions mean text and icons can look blocky and jagged. On a 5in screen, 1280x720 is the minimum you want, but higher is always better. On smaller phones with, say, 4.5in screens, you can get away with 960x540, but again a higher resolution is better - all else equal.
Screen quality and brightness may not be so important to you, but it's worth checking our reviews to find out if a screen is particularly good or bad.
Cameras
People's phones are increasingly their main camera, so it pays to choose a phone with the best possible camera for photos and videos. Cameras are the first items to be cut down in budget phones, so it's common to find low-quality, low-resolution sensors and lenses. We always take test photos and videos and explain whether they're any good or not in our reviews.
What you can't do is to look at a camera's specifications and work out if it will take good shots or not: the numbers are largely meaningless.
Don't overlook the front camera. It's rare not to get one at all if you're spending over £60, but quality varies hugely. Avoid anything with a very low VGA (640x480) resolution and aim for at least 1.2 or 2Mp. Numbers do matter at this level, as manufacturers often really skimp on the front camera, so if selfies or Skype chats are order of the day, choose a budget phone with a good front camera.
Software
We've already mentioned the difference between Android and Windows Phone. Android is the best choice for most people, but be aware that manufacturers often add their own interfaces on top of Android. Google's own Nexus phones and Motorola's have 'plain' Android, but the rest are customised to greater or lesser degrees. Again, our reviews will give the specific details.
Some of these interfaces have extra features worth having, or a replacement camera app that's much better than the stock Android one. Others take it too far and can also be sluggish and unresponsive.
Going or a phone with plain Android generally means you'll get any updates faster, especially when a whole new version of Android comes out. It can be a wait of many months for other phones, or they may not get updates at all.
Customer service and warranty
We recommend buying phones from somewhere that offers good customer service and easy returns, should you be unlucky enough to have any problems with faulty hardware. Cheap deals might seem tempting, but they could turn out to be expensive if you can't get a faulty phone repaired. We've put together a guide on buying from the grey market which explains the advantages (and many disadvantages) of buying from the increasing number of Chinese retailers which offer shipping to the UK.
Best budget phones reviews:
UMI Fair
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 11 November 15
  • RRP: £95.19 from European warehouse
  •  
The UMI Fair has an excellent specification for not a lot of money. With a thin, metal frame it looks much more expensive than it is, and it includes all the features you're likely to need with a removable battery, microSD support, a fingerprint scanner and dual-SIM 4G LTE connectivity. Performance is adequate and the camera more than satisfactory, making this something of an all-rounder.
Read our UMI Fair review.
Microsoft Lumia 435
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 19 March 15
  • RRP: £49.99 with £10 EE top-up
  •  
The Microsoft Lumia 435 is the best phone you can buy under £50, even accepting the tired old Windows Phone apps argument. Bottom of Microsoft's line-up and just £49.99 on PAYG it's by no means a great phone, but for first-time or light users it wipes the floor with similarly priced Android phones (and iOS at this price point is just a pipe dream - or a nightmare, but whichever way you look at it, it's not going to happen). Unlike the more expensive Lumia 535, Microsoft has confirmed that the Lumia 435 will get Windows 10 when it is released later this year, which will make this the cheapest entry point for a Windows 10 computer, and that alone makes it well worth a look. 
UMI eMax Mini
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 17 November 15
  • RRP: £95.19 from China (plus import duty); £122.39 from Europe
  •  
The UMI eMax Mini is a very decent attempt at a budget Android phone with mid-range specs, and a strong rival to the Vodafone Smart Prime 6 that tops our budget phones chart. It's slower than the original UMI eMax in our benchmarks, but in real-world use it feels just as fast. The cameras have been improved and also the design, in our opinion, resulting in a cheap phone that offers strong value for money. 
Ulefone Paris
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 21 October 15
  • RRP: £88.39 (plus taxes - shipping from China)
  •  
The Ulefone Paris is a great budget buy at £88, but bear in mind that you may also need to factor in import duty. Even so, it's a great rival to the £125 Vodafone Smart Ultra 6, which sits at the top of our budget smartphone chart, with faster core hardware and 4G dual-SIM functionality, but a lower-resolution screen. The camera isn't as impressive as the rest of this budget phone's spec, but it's still acceptable for such a cheap device.
UMI Iron
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 20 October 15
  • RRP: £149.99 inc. VAT
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The UMI Iron is a good buy at £149.99, and the first we've seen to include eye-scanning security. This is a cool feature, if no more secure than the requirement for a four-digit PIN. Although the heart-rate scanner didn't work in our tests and the Micro-USB charging port seemed oddly misshaped, the UMI Iron nevertheless offers a good set of hardware and more than acceptable performance for the money.
Read our UMI Iron review.
UMI eMax
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 9 July 15
  • RRP: £115.59 (plus import duty)
  •  
UMI's eMax offers superb value for money. It's not as good-looking as other UMI phones we've reviewed, but the eMax has a big and bright full-HD screen for enjoying media and more, and showed very capable performance in the majority of our benchmarks. Photography is decent at this price, and enthusiasts will appreciate the Rootjoy support. At £115 you can't go far wrong with the UMI eMax.
Read our UMI eMax review.
Ulefone BeTouch
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 14 July 15
  • RRP: 147.06 (plus import duty)
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Ulefone's BeTouch is an unrivalled deal at £147. It's fast, it's dual-SIM with 4G connectivity, it has a working fingerprint scanner for security, the screen is large and with an HD resolution plenty crisp enough for the money, and there is absolutely no bloatware. A few minor quibbles aside, it's genuinely difficult to fault this phone at this price.
UMI Hammer S
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 20 October 15
  • RRP: £108.79 inc. VAT
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We really like the UMI Hammer S. It's not the fastest phone you'll find at this price, but it's fast enough for daily use. The design is nice, and genuinely useful technology - USB-C and the fingerprint scanner for example - comes at an attractive price. A strong rival to the excellent Vodafone Smart Ultra 6.
Microsoft Lumia 640
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 14 May 15
  • RRP: From £13.50 per month, £109.99 PAYG or £129.99 SIM-free
  •  
The Microsoft Lumia 640 is a worthy upgrade over the Lumia 630, and this Windows Phone now presents very good value for money. This is the Moto G of the Windows world, with a near-identical spec and a £20 lower price tag. Which phone you choose will come down to your software preferences - many users will be happy with Windows Phone, but if third-party apps feature heavily on your wishlist you may find that extra £20 for the Moto G money well spent. 
Motorola Moto G 4G 2015
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 9 April 15
  • RRP: £149 inc. VAT
  •  
If you're looking for a cheap 4G smartphone then the Moto E 4G is the best deal on the market right now. If you would rather have a cheap dual-SIM phone with 3G connectivity then the mark 3 Moto G is your best bet. But the new Moto G 4G for 2015 is not the best phone for either customer, and its larger, higher-resolution screen, marginally improved photography credentials and stereo sound are not enough for us to turn a blind eye to its £60 higher price, slower hardware and missing software features.
Moto G 4G
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 13 August 14
  • RRP: £135 inc VAT
  •  
Motorola's Moto G is the best budget smartphone around. At £135 it's got great build quality, an excellent screen, decent cameras and Android 4.3 Jelly Bean soon to be upgrade to 4.4 KitKat.
Read our Moto G 4G review.
EE Rook
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 22 July 15
  • RRP: £39 inc VAT (existing customers)
  •  
If you don't mind the basic design, the EE Rook isn't a bad little phone at all. We can hardly argue with the price of £39 for existing customers and the performance is better than we expected for a sub-£50 phone. It's mainly the miserable viewing angles of the screen which put us off so you are better off spending a little more if you can afford it.
Read our EE Rook review.
Samsung Galaxy Core Prime
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 21 October 15
  • RRP: £109 inc VAT
  •  
If you love Samsung Android phones then you'll like the Galaxy Core Prime. It does lack a few features, but the missing ambient light sensor is one cut corner too far. For only £79, we prefer Vodafone's Smart Prime 6. It has a 5in 1280x720 screen, better cameras and an ambient light sensor. Plus it runs an essentially plain version of Android.
Just5 Blaster 2
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 12 November 15
  • RRP: 149 Euro + 12 Euro shipping (approx £105 + £8.50 shipping)
  •  
Although you can't just walk into a shop and buy it in the UK, this Just5 Blaster 2 is certainly a better budget buy than the Samsung Galaxy Core Prime. At around £105 it's no surprise to find a plastic build, but we appreciate the inclusion in the box of interchangeable colour covers. The screen is good, if a little dull, and performance is spot-on at this price point. The cameras are acceptable, and the software free of bloat. A good all-round budget option. 
Motorola Moto G 2014 (second generation)
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 15 September 14
  • RRP: £145 inc VAT
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With a bigger screen, much better speakers and improved cameras, the new Moto G is a great budget smartphone. The lack of support for 4G will be a deal-breaker for some, though. It isn't without its rivals, but if you're specifically looking for a budget dual-SIM Android phone, it's a good choice.
EE Harrier Mini
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 7 July 15
  • RRP: £99 inc. VAT
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We're much keener on the Harrier Mini than we are its bigger brother. While both phones offer very good value, £99 sounds much more appealing than £199, and we prefer the Mini's more compact design. Performance is slower and the screen isn't as good, but you won't get top-end specs from either phone. But as much as we think the Harrier Mini is a great deal, the Vodafone Smart Prime 6 offers better value. It's £20 cheaper and has a larger, better screen, and it seems more adept in photography. Buy the Harrier Mini over the Smart Prime 6 only if you'll benefit from Wi-Fi Calling once it becomes available. 
Wileyfox Swift
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 24 September 15
  • RRP: £129 inc VAT
  •  
For a brand-new smartphone maker's first effort, we're impressed with the Wileyfox Swift. It's a stylish little handset which offers essentially the same specs as the Moto G for less money. We love the customisation available in Cyanogen OS but elements such as the cameras aren't as good as rivals. Vodafone's Smart Ultra 6 remains a better option for slightly less money - unless a 5.5in screen is too big in which case look at the Smart Prime 6 as an alternative.
Vodafone Smart Prime 6
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 25 June 15
  • RRP: £79
  •  
The Vodafone Smart Prime 6 is a great budget smartphone that we think is worth more than the £79 that Vodafone asks for it. Its processor may not be able to compete with grey-market phones like the Doogee F1 Turbo Mini, but it handles day-to-day use just fine with no noticeable lag. While the Moto E 4G performed slightly better during our benchmarks, the Smart Prime 6 has a bigger screen, better camera and is £30 cheaper, making it our choice out of the two handsets.
Motorola Moto E 4G
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 3 March 15
  • RRP: £109 inc. VAT
  •  
The new Moto E 4G is a worthy upgrade over the original Moto E, with upgrades in every area. For an extra £20 it adds 4G LTE connectivity and a front-facing camera, plus performance and storage improvements. It might not be as fast as the grey-market Doogee F1 Turbo Mini, but this Moto E 4G is a much better deal than the EE Kestrel, making it the best budget 4G phone intended for UK sale we've seen.
Vodafone Smart Ultra 6
  • Rating: ratingsratingsratingsratingsratings
  • Reviewed on: 4 August 15
  • RRP: £125
  •  
The Vodafone Smart Ultra 6 is worth its £125 price tag without a doubt. It's one of the best experiences we've had with a budget smartphone, and nothing about this phone suggests that it's budget apart from its price tag. Compared to the Smart Prime 6, this is definitely the better option to go for and we'd definitely pay the extra £50 for it – it's more powerful, has better cameras and a larger, higher quality display. It won't run the latest 3D mobile games but for every day use, it's a great phone and the fact that you can add up to 128GB of external storage means that there’s more storage than you can shake a stick at. Great work Vodafone.