What is LTE Advanced?

March 24, 2013
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Network-tower-lte-advanced-article

If you’re living in the U.S., and select other parts of the world, then there’s a good chance that you’re enjoying a fast LTE connection. Sadly for me living in the UK, our 4G network is lagging severely behind, and it looks like we could be left even further back in the dark ages once LTE Advanced goes online.

LTE Advanced is essentially a bandwidth expansion for existing LTE networks. If you read a technical document on it you’ll probably hear terms like higher spectral efficiency, improved performance at cell edges, and greater bandwidth efficiency, but for consumers we can simply say that LTE Advanced is going to be faster, potentially much faster.

4G_LTE_WEB_en

Source: Teliasonera

So here’s everything you need to know about how LTE Advanced works, and what this means for you.

How does it work?

The new functionalities introduced in LTE-Advanced are Carrier Aggregation (CA,) enhanced use of multi-antenna techniques, and support for Relay Nodes. All of these are designed to increase the stability, bandwidth, and speed of LTE connections.

Carrier Aggregation

Carrier Aggregation is something you may have heard about, especially if you’ve been following news regarding Qualcomm’s upcoming Snapdragon 800 chip. Essentially this technology is designed to multiply the bandwidth of LTE connections by allowing you to download data from multiple connections simultaneously. It’s not totally new though, carrier aggregation has been used in other wireless technologies for a while, and T-Mobile is already employing this technology to boost its HSPA+ speeds to 42Mbps on compatible handsets.

The problem with LTE is that eventually you reach a bandwidth limit, especially when you take into consideration that other services need the radio waves. In certain areas spectrum availability is already becoming a problem, with only small band areas free to use for LTE. This means that carriers have to chop up their LTE network into smaller bands. In order to overcome the speed limitations caused by this problem you need to be able read from multiple bands simultaneously, which is where Carrier Aggregation comes in handy.

Carrier Aggregation combines signals from different frequency bands, so rather than having to pick from the fastest connection in your area you can combine a signal from all of the carriers within range of your handset, even if they are operating all over the frequency spectrum.

intra-band carrier aggregation

LTE Advanced allows for multiple carriers operating in the same band (intra-band,) or inter-band in scenarios where frequency allocation is sporadic. Source: 3gpp

Here’s a more technical explanation of how this speeds things up: each aggregated carrier is referred to as a component carrier, these component carriers can then be combined to produce an aggregated carrier. The component carriers have a maximum bandwidth of 20MHz, and a maximum of five component carriers can be aggregated using LTE Advanced. Simple math tells you that five component carriers will allow for a maximum bandwidth of 100MHz with LTE Advanced. Although as the bandwidth of individual component carriers can and will vary, LTE Advanced might not always be five times faster.

In terms of data speeds this technique can provide extremely high peak data rates, theoretically up to 1Gbps when utilizing the maximum available bandwidth. However, in reality, carriers, hardware, and network coverage will fall short of this theoretical maximum, for example peaking at around 150Mbps download speeds with two 10MHz carriers enabled.

Another major benefit of Carrier Aggregation is that is allows for full backwards and forwards compatibility between existing LTE networks and LTE Advanced compatible devices. LTE Advanced connections will be provided through existing LTE bands, so standard LTE users will continue to use LTE as normal, whereas Advanced connections will make use of multiple LTE carriers.

MIMO

Multiple Input Multiple Output technology (MIMO) is another technology required for LTE Advanced to work as quickly as possible. MIMO increases the overall transfer bitrate by combining data-streams from two or more antennas.

MIMO

Source: Telecomhall

In other words, rather than sending a single piece of information from one sender to one receiver, you can send the same single piece of information from multiple senders to multiple receivers. It’s a parallel process, which substantially increases the amount of data you can send and receive each second (bits per hertz,) providing you have a receiver modem which can sort all the information out into the correct order. But that’s where the technology becomes a bit too complicated for this discussion.

Although MIMO is already used in current LTE networks, LTE Advanced requires that chips increase the number of inputs and outputs used simultaneously. LTE Advanced will support up to eight transmitters and receivers whilst downloading and four by four when uploading, although you couldn’t fit that many antennae into a smartphone. The increased MIMO arrangement will also improve the speed and connection quality of legacy connections such as CDMA, GSM, and WCDMA.

If you think about combining this sort of parallel data transfer with the ability to pick from a wider range of frequency bands and carrier signals, then you can appreciate why LTE Advanced can be so much faster and more stable than a standard LTE or older connection type.

Relay Nodes

The final piece of technology introduced with LTE Advanced is called relay nodes. Whilst relay nodes aren’t an integral part of improving your data speeds, they will improve the availability of LTE connections, and offer you more connections to choose from when sending a receiving data.

Simply put, a relay node is a low powered base station used to boost network coverage at the ends of and beyond the connection radius of the main station. These relay nodes connect wirelessly to the main station, and should help boost your signal when wondering close to the edge of your LTE network.

Of course access to improved connectivity will be entirely dependent on whether carriers bother to invest in building these nodes.

Smartphone Hardware

So we’ve seen discussed what it takes to produce a LTE Advanced network, but it also means that hardware manufacturers are going to need to invest in new technologies as well as network carriers.

Obviously the improved MIMO parallel networking will require different modems capable of organizing the received data. LTE Advanced modems will also have to be able to decode information sent from different frequency bands at the same, so current LTE smartphones aren’t going to be compatible.

Qualcomm demoed 4k streaming over a 150Mbps LTE Advanced connection at MWC 2013

Qualcomm demoed 4k video streaming over a 150Mbps LTE Advanced connection at MWC 2013

Broadcom has announced its LTE Advanced modem chip, called the BCM21892, which is expected to start rolling off the production belt in early 2014. Similarly Qualcomm has announced its own LTE Advanced modem which will be bundled in with the unreleased Snapdragon 800 SoC, which again isn’t expected to appear any time soon.

So far Broadcom has shown off its chip maxing out at 150Mbps peak download and 50Mbps upload, and Qualcomm’s own chip peaks at the same download speed. Technically the definition of true LTE Advanced speed is supposedly a minimum of 300Mbps download, but we won’t quibble about that as this is a good start.

When will I be able to use it?

There are no LTE Advanced networks or compliant handsets available as of yet, and the only manufacturers that I’ve heard of planning to put carrier aggregation technology into a chip are Qualcomm and Broadcom.

The Snapdragon 800 and Broadcom’s modem chips in all likelihood won’t be available until the end of this year, and we might not see them used in a handset until sometime in 2014.

Carriers across the U.S. and the rest of the world are also going to need to invest more resources into LTE networks before they are up to the speeds you can theoretically achieve with LTE Advanced. Of course that won’t stop carriers marketing new phones and deals offering pumped up potential max speeds, but in reality the introduction of the LTE Advanced marketing buzz words probably won’t see the massive jump in speeds that you’d hope for.

LTE Advanced networks are expected to start rolling out in the U.S. next year, around the same time as we expect to see the first compatible SoCs, but it will probably take another year or more after that until LTE network coverage is substantial enough to drastically improve your LTE speeds.

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