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It's been several years since the first LTE networks came online. At present, nearly all cellular-enabled devices sold today support LTE for 4G service — sometimes fifty-fifty without 2G or 3G technologies supported. The first LTE-compatible phones only had a few hours of practical battery life, but today'south devices tin last an entire day or two on a single charge. That's still non plenty, of course, just nosotros're getting there.

And so, what is LTE? To virtually, it is a faster network technology. To network operators around the globe, information technology is a way to simplify their infrastructures to reduce costs while improving the quality of their offerings to subscribers. Advertisements by network operators declare it as the "nigh avant-garde" network applied science. In the terminate, it is Long Term Evolution of the Universal Mobile Telecommunications System (UMTS).LTE-Logo

Just that doesn't tell u.s. what LTE actually is. LTE is what the 3GPP (3rd Generation Partnership Project, the group responsible for standardizing and improving UMTS) designates as their side by side step. UMTS is the group of standards that define 3G for GSM networks across the globe, including AT&T and T-Mobile'south 3G networks. The cdmaOne/CDMA2000 family of standards are not maintained by 3GPP, only by a different organization spearheaded past Qualcomm. For subscribers to operators with networks utilizing CDMA2000 applied science, LTE is the replacement of mediocre CDMA2000 networks with a superior cellular telecommunications system offering flexibility and ability to the network operator and the subscriber.

LTE is a very good, easily deployable network applied science, offering high speeds and low latencies over long distances. For instance, two of the four operators' LTE networks in New York City were rated well for achieving this goal. Verizon'south LTE service was rated with an boilerplate download speed of 31.1Mbps and an average upload speed of 17.1Mbps. T-Mobile'due south LTE service was rated with an average download speed of 20.5Mbps and an boilerplate upload speed of xiii.5Mbps.

Of grade, that doesn't mean all networks are created equal. Some aren't quite able to achieve these goals. For instance, Sprint'due south LTE service was rated with an boilerplate download speed of four.0Mbps and an average upload speed of two.5Mbps. AT&T'southward LTE service was much better than Sprint'due south, but still bad with an boilerplate download speed of 7.6Mbps and an average upload speed of 2.4Mbps.

In this article, we volition discuss what configurations LTE can be deployed in, why LTE is easily deployable, how LTE works as a radio technology, what types of LTE exist, how LTE affects bombardment life, what network operators want LTE to do, and the future of 4G equally a whole. The nearly technical parts of the article are LTE can exist deployed in, why LTE is easily deployable, how LTE works as a radio applied science, and what types of LTE be. For those who don't want that information, you can skip to how LTE affects battery life and still get the gist of what we're saying. Merely to get the consummate moving picture, reading the whole article is advised.

How LTE is configured for deployment

LTE supports deployment on different frequency bandwidths. The current specification outlines the following bandwidth blocks: 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, and 20MHz. Frequency bandwidth blocks are essentially the corporeality of space a network operator dedicates to a network. Depending on the blazon of LTE beingness deployed, these bandwidths have slightly different pregnant in terms of capacity. That will be covered later, though. An operator may choose to deploy LTE in a smaller bandwidth and grow it to a larger ane as it transitions subscribers off of its legacy networks (GSM, CDMA, etc.).

MetroPCS was an instance of a network operator that has done this. Before information technology was caused by T-Mobile, a majority of its spectrum is nonetheless dedicated to CDMA, with 1.4MHz or 3MHz defended for LTE depending on the marketplace. There were a few markets with 5MHz deployed, merely these were the exception, not the rule. Jump Wireless (who did business organization as Cricket Communications) had also done the same thing prior to being acquired by AT&T, except information technology used 3MHz or 5MHz instead of ane.4MHz or 3MHz. Neither of these operators could afford to cut CDMA capacity by a significant degree just nevertheless, so LTE operated on tiny bandwidths. Additionally, neither operator had enough backhaul (the core network infrastructure and connections to the internet) dedicated to LTE to brand larger bandwidths worth it either. Of form, these issues went abroad when they were acquired. MetroPCS and Cricket transitioned service to the T-Mobile and AT&T networks, respectively. Their networks are being wound down and their spectrum is redeployed to support their new parent companies' GSM/UMTS/LTE networks.

Verizon Cell Tower

On the other hand, Verizon Wireless has been using 10MHz broad channels for LTE all across the board for 750MHz, since it has the national resource allotment of spectrum available for it. In addition to that, the AWS spectrum information technology acquired from the cablevision companies and other transactions accept allowed it to gyre out a second LTE pipeline with 15MHz or 20MHz channels in most places. Similar Verizon, T-Mobile is also rolling out wide channels for LTE on it's AWS spectrum. Combined with excellent backhaul, LTE service from those two companies promise to exist best in class. On AT&T's side, LTE channel sizes vary depending on the market. In most markets, AT&T has 10MHz channels on 700MHz, just there are many where it only has 5MHz. It has resorted to cutting down GSM capacity to reuse the spectrum to support its customers, equally singular 5MHz or even 10MHz channels aren't enough. Dart has a similar trouble, as its primary network is a singular 5MHz channel nationally. Information technology is using the spectrum it has from acquiring Clearwire to supplement it with 20MHz channels for additional capacity.

Less spectrum means that fewer customers tin can obtain the same high speeds that Verizon's LTE customers get when connected to any particular cell. LTE can support upwardly to 200 active information clients (smartphones, tablets, USB modems, mobile hotspots, etc.) at full speed for every 5MHz of spectrum allocated per cell. That ways that if a particular tower has 20MHz of spectrum allocated to information technology, it tin can back up upwardly to 800 data clients at total speed. There are ways of supporting more than information clients per 5MHz, but doing so requires sacrificing speed and capacity, as the 200-per-5MHz ratio is the optimal configuration. However, spectrum isn't everything to LTE quality, as I volition discuss later.

How LTE actually works

LTE uses 2 different types of air interfaces (radio links), i for downlink (from tower to device), and i for uplink (from device to tower). By using different types of interfaces for the downlink and uplink, LTE utilizes the optimal style to exercise wireless connections both ways, which makes a ameliorate-optimized network and better battery life on LTE devices.

For the downlink, LTE uses an OFDMA (orthogonal frequency division multiple access) air interface every bit opposed to the CDMA (code division multiple access) and TDMA (time partitioning multiple access) air interfaces we've been using since 1990. What does this mean? OFDMA (unlike CDMA and TDMA) mandates that MIMO (multiple in, multiple out) is used. Having MIMO means that devices take multiple connections to a single cell, which increases the stability of the connection and reduces latency tremendously. Information technology also increases the total throughput of a connectedness. Nosotros're already seeing the real-globe benefits of MIMO on WiFi N routers and network adapters. MIMO is what lets 802.11n WiFi reach speeds of up to 600Mbps, though virtually advertise up to 300-400Mbps. There is a pregnant disadvantage though. MIMO works better the further autonomously the private carrier antennae are. On smaller phones, the noise caused past the antennae being and then close to each other will cause LTE functioning to driblet. WiMAX also mandates the usage of MIMO since it uses OFDMA besides. HSPA+, which uses W-CDMA (a reworked, improved wideband version of CDMA) for its air interface, can optionally use MIMO, too.

For the uplink (from device to tower), LTE uses the DFTS-OFDMA (discrete Fourier transform spread orthogonal frequency partition multiple access) scheme of generating a SC-FDMA (unmarried carrier frequency sectionalisation multiple access) bespeak. Every bit opposed to regular OFDMA, SC-FDMA is better for uplink because it has a better peak-to-boilerplate ability ratio over OFDMA for uplink. LTE-enabled devices, in order to conserve bombardment life, typically don't have a strong and powerful signal going back to the tower, so a lot of the benefits of normal OFDMA would be lost with a weak signal. Despite the name, SC-FDMA is nevertheless a MIMO system. LTE uses a SC-FDMA 1×2 configuration, which means that for every ane antenna on the transmitting device, there'southward two antennae on the base of operations station for receiving.

The major difference betwixt the OFDMA indicate for downlink and the SC-FDMA betoken for uplink is that information technology uses a detached Fourier transform role on the data to convert it into a form that tin can be used to transmit. Discrete Fourier transform functions are often used to convert digital information into analog waveforms for decoding sound and video, but it tin can exist used for outputting the proper radio frequencies too. However, LTE-Avant-garde uses higher order MIMO configurations for downlink and uplink.

The LTE technology itself also comes in two flavors: an FDD (frequency partition duplex) variant and a TDD (fourth dimension sectionalisation duplex) variant. The about mutual variant existence used is the FDD variant. The FDD variant uses separate frequencies for downlink and uplink in the form of a band pair. That means for every ring that a telephone supports, it actually uses ii frequency ranges. These are known equally paired frequency bands. For example, Verizon'southward 10MHz network is in FDD, so the bandwidth is allocated for uplink and downlink. This is normally noted as a 2x10MHz or 10+ten MHz configuration. Some also call it 10x10MHz, but this is mathematically incorrect, but they mean x+10MHz. Some will also call it a 20MHz network, merely this tin can be ambiguous. The TDD variant uses one unmarried range of frequencies in a frequency band, but that band is segmented to support transmit and receive signals in a single frequency range.

For example, an LTE TDD network deployed on 20MHz of spectrum uses the whole chunk as one large block for frequency allocation purposes. For network bandwidth purposes, a LTE TDD network'due south spectrum tin be further divided to optimize for the type of network traffic (half up and half downward, mostly down and a bit up, mostly up and a flake downward, so on).

In the United States, Sprint is the only network operator deploying LTE in the TDD variant. Everyone else is deploying in the FDD variant. The TDD variant becomes more important in Asia, equally China Mobile (the largest network operator in the world in terms of subscriber count) is using TDD frequencies for their LTE network. Sprint'south parent company, SoftBank, also uses LTE TDD in its dwelling house market place of Japan. Fortunately, LTE devices tin hands be fabricated to support both variants on a device without likewise much trouble.

Enough nearly specs – what nearly bombardment life?

Now nosotros pb to the part that most people care about: how it affects bombardment life. By itself, LTE devices should last roughly as long equally their HSPA+ equivalents considering of the optimized radios for both downlink and uplink operations. The reason why LTE devices right now eat batteries for breakfast is considering the network operators are forcing many of these devices into active dual-style operation.

For Verizon Wireless, this ways that most of their LTE devices connect to both CDMA2000 and LTE simultaneously and stay connected to both. This means that you are eating twice the amount of bombardment for every infinitesimal you are connected than yous would if you were connected just to CDMA2000 or LTE. Additionally, when you make calls on Verizon Wireless LTE phones, the CDMA2000 radio sucks downwards more power because yous are talking. Sending and receiving text letters causes pulses of CDMA2000 action, which cuts your battery life more than. Arguably, constantly changing radio states could be worse for battery life than a switch into one manner for a menstruum of time and switching dorsum, so text letters may actually kill the batteries faster.

Then at that place is handover. Handover is the operation in which a device switches from 1 network to another or from 1 tower to some other. Handover is the critical component that makes any cellular wireless network possible. Without handover, a user would have to manually select a new tower every fourth dimension the user leaves the range of a tower. (WiFi is an instance of a wireless network engineering science that doesn't inherently back up handover.) When the user travels outside the range of a WiFi network, the WiFi radio will just drop the connection. For cellular networks, this is even more critical considering the range of a tower is not very anticipated due to factors outside of anyone'southward control (similar the weather, etc.). LTE supports handover like all other cellular wireless networks, only information technology improves on information technology by doing it much faster when handing over to a supported type of network or prison cell.

However, Verizon and Sprint are doing handover from LTE to EV-DO and back past plugging in a connection to an enhanced version of the EV-Exercise data network core called eHRPD. This isn't a keen solution by any ways.

eHRPD

The fragile link-up between EV-DO and LTE make handover occur a lot more it is supposed to, which eats battery life fifty-fifty more. With AT&T and T-Mobile using an HSPA+ network aslope LTE instead of CDMA2000, handover performance is a lot smoother. As far as bombardment life goes, information technology should exist slightly better than Verizon and Sprint LTE phones considering LTE supports fast handover betwixt UMTS and LTE. AT&T LTE phones are normally not forced into agile dual-mode functioning because HSPA+ lets you lot employ data and talk at the same time. Equally a consequence, AT&T has no need to force the device into agile dual-way operation. However, battery life will still exist pretty bad considering LTE signals are withal very weak in most AT&T LTE zones, and AT&T LTE devices default to connecting to LTE signals whenever possible.

C Spire Wireless, U.S. Cellular, and other CDMA/LTE operators all take the same trouble every bit Verizon Wireless with LTE battery life because they do the aforementioned affair as Verizon Wireless and force active dual-mode operation with almost of their devices. As a result, turning off LTE will significantly improve battery life considering the phone switches back to unmarried-way operation. Or in the case of AT&T phones, passive dual-mode operation (for GSM/HSPA+ handover) since they are typically in passive tri-fashion operation for GSM/HSPA+/LTE handover. Passive multi-manner operation means that the device isn't constantly connected to multiple networks, only will establish a connection and hand over the connection if the bespeak on the electric current network is too weak or snaps. This is ideal for multi-mode operation, and Sprint switched to doing this terminal yr in order to command costs for new devices that support the tri-band LTE network it brands as "Sprint Spark". With the launch of Verizon VoLTE final year, Verizon has also increasingly started offering devices with passive multi-mode operation. This means that these new devices now take many of the same free energy conservation benefits that take ever been nowadays in GSM/UMTS/LTE devices.

LTE — Mobile panacea?

The ultimate goal of the network operators deploying LTE is to supersede everything else they have with it. That means that it needs to get possible to handle voice calls, text letters, network alerts, etc. over the data network. Notwithstanding, no one developed the LTE specification with voice and text messaging in heed. It was designed as a data network only. So how practise they solve the trouble? By developing a VoIP solution that fits their needs. Two main standards came into being: VoLGA (Voice over LTE via Generic Access) and VoLTE-IMS (Voice over LTE via IMS). VoLGA was based on GAN (Generic Access Network), which is also known as UMA (Unlicensed Mobile Access). Deutsche Telekom was the only network operator that wanted to use this method, as the design for VoLGA was heavily derived from T-Mobile USA's implementation of UMA for its WiFi Calling characteristic. No i else wanting to deploy LTE wanted to use information technology equally a final or interim solution, as information technology would have meant keeping effectually the legacy GSM core network for this purpose.

Everyone else supported VoLTE-IMS (now referred to as VoLTE), which immune them to fully discard their older networks and simplify their network blueprint equally they decommissioned legacy networks. Withal, IMS is much more expensive and difficult to deploy than VoLGA, at least for GSM network operators. Simply IMS as well promised more flexibility. IMS could be used to make real-time video calling with all sorts of boosted features possible. And then, Deutsche Telekom dropped VoLGA and joined everyone else in supporting VoLTE.

VoLTE uses an extended variant of SIP (Session Initiation Protocol) to handle voice calls and text messages. For voice calls, VoLTE uses the AMR (Adaptive Multi-Charge per unit) codec, with the wideband version used if supported on the network and the device. The AMR codec has long since been used as the standard codec for GSM and UMTS phonation calls. The wideband version supports higher quality speech communication encoding, which would allow for clearer vox calls. Text messages are supported using SIP Message requests. Video calling uses H.264 CBP (constrained baseline profile) with AMR-WB sound codec over RTP (Real-time Transport Protocol) with VBR (variable flake rate). With this, video calls over IMS are supposed to be very high quality, no matter what the quality of the information connection. With VBR, the call tin adapt to the changing congestion levels of the data network to maintain a quality video call.

In a somewhat ironic twist, T-Mobile U.s. became the kickoff network in the earth to commercially deploy IMS-based voice calling and text messaging by using it for an improved WiFi calling solution. An update to the T-Mobile Samsung Milky way South II and an update to the T-Mobile HTC Amaze 4G both included the new WiFi Calling solution.

MetroPCS was one of the first carriers in the globe to deploy VoLTE, the other being SK Telecom in Republic of korea. While SK Telecom launched VoLTE nationally, MetroPCS only launched VoLTE in Dallas, TX. Initial implementations of VoLTE conspicuously showed much lower battery life, just that is largely resolved now. Later on acquiring MetroPCS, T-Mobile reconfigured its 2 networks for broadly rolling out LTE service and shutting down the CDMA service it inherited from MetroPCS. At the end of the summer of 2014, T-Mobile launched VoLTE and made information technology available nationwide shortly after the launch. Since it is based on their WiFi calling solution, information technology is able to support seamless handover from WiFi to LTE and back for voice calls, which no one else has done.

As for Verizon, AT&T, and Dart deploying VoLTE? Well, Verizon rolled out VoLTE in August 2014 nationally. AT&T launched VoLTE in select parts of the Midwest in May 2014 and has been gradually expanding it since. Sprint has non officially said anything about it all the same.

At this point, the major gotcha with VoLTE now is that it requires carrier customized firmware. Setting up a device to apply VoLTE requires a lot of configuration, more than what a SIM card can provide. Consequently, but operator branded devices will support VoLTE for now. Some unbranded devices may somewhen be preloaded with select operator VoLTE configuration information, but that volition remain the exception rather than the rule. Hopefully this item problem volition exist addressed presently, because information technology puts a crimp in whatsoever plan to move devices from 1 operator to some other.

The messy hereafter of 4G

We've only scratched the surface of what LTE is all virtually, only this commodity includes pretty much everything that LTE subscribers would care about. Some of the other aspects of LTE include SON (self-organizing network) capabilities, which allows information technology to flexibly classify capacity to parts of the cellular network equally it is needed by redistributing connections to an optimal configuration at any given fourth dimension. Handover to WiFi is another cool feature, also. Still, most of the features like the former are pretty much but seen from a network operator's side of things, and things like the latter may never really exist implemented.

LTE is a meaning jump in optimized cellular wireless applied science though. If you wish to get the highly-technical details of LTE and its ever-evolving specifications, bank check out the 3GPP'south specification series for LTE. Specifications for eHRPD and associated CDMA2000 specifications are bachelor on the 3GPP2's website. The VoLGA specifications are available on the VoLGA Forum'due south website. The 3GPP hosts the IMS specifications, with the GSM Association hosting IMS Profile for Voice and SMS specifications on their website. Nosotros've covered the major highlights in this article, as at that place is way likewise much to comprehend. Equally the specifications detail, at that place were many improvements at every level of a cellular network that result in a high-functioning, optimized network.

Whether LTE becomes the success story of the mobile manufacture remains to be seen. Network operators effectually the world are only at present deploying it, and already it is turning into a mess. The 3GPP has already approved nearly 45 frequency bands for LTE. Over thirty of them are for LTE FDD and the rest are for LTE TDD. Roaming is going to exist very difficult on LTE. For North America solitary, there are ten FDD bands and one TDD band for LTE. For Europe and Africa, there are 4 bands for FDD LTE and two bands for TDD LTE. For Asia and Oceania, there are the same iv FDD bands for Europe, 3 more frequency bands for FDD, and two more TDD bands. The remainder of the bands have yet to be used, only they are going to be used. Someone is going to accept to figure out how to fit more than bands on an LTE device without sacrificing portability. Fortunately, a number of bands are supersets/subsets of other bands, then some are easier to support than others.

htc-one-m8-windows-verizon-wide

So there'due south the 4G mess. Contrary to popular belief, LTE at the current stage was non always considered 4G. The International Telecommunications Union (or ITU) determines what can be considered 4G. Originally, the ITU declared that the collection of requirements known equally IMT-Avant-garde determined what would be considered 4G. LTE did not make the cut (though a futurity version of information technology called LTE-Advanced did). Neither did WiMAX or HSPA+. However, the American and Canadian network operators' commonage influence made the ITU revise their specification on what 4G is to include whatsoever wireless technology significantly evolved from 3G technologies. Virtually technophiles are of the stance that the IMT-Advanced specification determines what tin can be considered 4G, while most business people prefer the newer definition for 4G. For the purposes of this article, the revised standard is considered 4G. While this is out of the scope of this article (and likewise non really of import either), I'm laying it out now to foreclose any arguments. This means that LTE, HSPA+, and WiMAX are all considered 4G technologies, though WiMAX is yet officially on the listing of 3G technologies besides.

Since LTE-Avant-garde Release 10 has been codified and equipment is available, a number of operators effectually the globe have started using LTE-Advanced features. AT&T has deployed carrier assemblage in many of the aforementioned areas information technology has launched VoLTE, and Sprint intends to launch carrier aggregation in areas where the company has rolled out its tri-band "Spark" network. T-Mobile Us has been deploying and testing it since it started its rollout of LTE service and so that it can maximize the benefits of LTE-Avant-garde equipment in as many areas every bit possible. While T-Mobile isn't broadly using carrier aggregation all the same, information technology certainly has the option to practice so, in the hereafter.

I don't know what the hereafter holds for LTE, only information technology volition certainly exist very interesting. This is the most exciting time in the mobile manufacture since the switchover from analog to digital back in the early 1990s. LTE represents a paradigm shift from hybrid voice and information networks to information-only networks. Going frontwards, wireless network technology is likely to become more widely used because it volition get easier to obtain than wireline services (cablevision, DSL, etc.). It is doubtful that it would fully replace wireline data services though. Hopefully, the issues we face up with LTE now will go away over time.

As LTE continues to meliorate, we'll continue to see a steady migration of usage from older networks to LTE, especially operators using CDMA networks as a legacy technology. While nosotros may not have ubiquitous connectivity for a long time due to the sheer number of bands and configurations, new applied science geared to improve the situation is ever coming.