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It's been several years since the commencement LTE networks came online. Now, well-nigh all cellular-enabled devices sold today back up LTE for 4G service — sometimes even without 2G or 3G technologies supported. The offset LTE-compatible phones only had a few hours of practical battery life, but today's devices tin last an entire day or two on a unmarried accuse. That'due south still non enough, of course, but nosotros're getting at that place.

And so, what is LTE? To near, it is a faster network technology. To network operators around the globe, it is a mode 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 technology. In the cease, it is Long Term Development of the Universal Mobile Telecommunications System (UMTS).LTE-Logo

Merely that doesn't tell united states of america what LTE actually is. LTE is what the 3GPP (3rd Generation Partnership Project, the grouping responsible for standardizing and improving UMTS) designates as their next step. UMTS is the grouping of standards that define 3G for GSM networks across the globe, including AT&T and T-Mobile'southward 3G networks. The cdmaOne/CDMA2000 family unit of standards are not maintained by 3GPP, but past a different organization spearheaded by Qualcomm. For subscribers to operators with networks utilizing CDMA2000 engineering science, LTE is the replacement of mediocre CDMA2000 networks with a superior cellular telecommunication system offering flexibility and power to the network operator and the subscriber.

LTE is a very good, easily deployable network engineering, offering high speeds and depression latencies over long distances. For example, two of the four operators' LTE networks in New York Urban center were rated well for achieving this goal. Verizon's LTE service was rated with an average download speed of 31.1Mbps and an boilerplate upload speed of 17.1Mbps. T-Mobile'due south LTE service was rated with an boilerplate download speed of 20.5Mbps and an boilerplate upload speed of 13.5Mbps.

Of form, that doesn't hateful all networks are created equal. Some aren't quite able to achieve these goals. For example, Dart's LTE service was rated with an average download speed of four.0Mbps and an boilerplate upload speed of 2.5Mbps. AT&T'south LTE service was much ameliorate than Sprint's, but withal bad with an average download speed of 7.6Mbps and an average upload speed of ii.4Mbps.

In this article, we volition discuss what configurations LTE can exist deployed in, why LTE is easily deployable, how LTE works as a radio engineering science, what types of LTE be, how LTE affects battery life, what network operators want LTE to do, and the future of 4G as a whole. The most technical parts of the article are LTE can be deployed in, why LTE is hands deployable, how LTE works equally a radio applied science, and what types of LTE exist. For those who don't want that information, you lot tin skip to how LTE affects bombardment life and all the same become the gist of what we're saying. Merely to become the consummate motion 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 post-obit bandwidth blocks: 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, and 20MHz. Frequency bandwidth blocks are essentially the amount of infinite a network operator dedicates to a network. Depending on the blazon of LTE beingness deployed, these bandwidths accept slightly different pregnant in terms of capacity. That volition be covered afterward, though. An operator may cull to deploy LTE in a smaller bandwidth and grow it to a larger one equally it transitions subscribers off of its legacy networks (GSM, CDMA, etc.).

MetroPCS was an example of a network operator that has washed this. Before it was acquired by T-Mobile, a bulk of its spectrum is still defended to CDMA, with ane.4MHz or 3MHz dedicated for LTE depending on the market. There were a few markets with 5MHz deployed, but these were the exception, not the rule. Leap Wireless (who did business concern every bit Cricket Communications) had also done the same affair prior to being acquired past AT&T, except it used 3MHz or 5MHz instead of ane.4MHz or 3MHz. Neither of these operators could afford to cut CDMA capacity past a significant degree just nonetheless, 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 make larger bandwidths worth it either. Of form, these problems went away 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 wide channels for LTE all beyond the board for 750MHz, since it has the national allocation of spectrum available for it. In improver to that, the AWS spectrum it caused from the cablevision companies and other transactions have allowed it to roll out a second LTE pipeline with 15MHz or 20MHz channels in near places. Similar Verizon, T-Mobile is also rolling out wide channels for LTE on it'southward AWS spectrum. Combined with fantabulous backhaul, LTE service from those ii companies promise to be best in class. On AT&T'south side, LTE channel sizes vary depending on the market. In most markets, AT&T has 10MHz channels on 700MHz, but there are many where it only has 5MHz. It has resorted to cutting down GSM chapters to reuse the spectrum to support its customers, as singular 5MHz or fifty-fifty 10MHz channels aren't enough. Sprint has a similar problem, equally its main network is a singular 5MHz channel nationally. It is using the spectrum it has from acquiring Clearwire to supplement information technology with 20MHz channels for additional capacity.

Less spectrum means that fewer customers can obtain the same high speeds that Verizon'due south LTE customers get when continued to any particular cell. LTE tin back up up 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, information technology tin can back up up to 800 information clients at full speed. There are ways of supporting more data clients per 5MHz, only doing so requires sacrificing speed and capacity, every bit the 200-per-5MHz ratio is the optimal configuration. All the same, spectrum isn't everything to LTE quality, as I will hash out later.

How LTE actually works

LTE uses two different types of air interfaces (radio links), one for downlink (from tower to device), and one for uplink (from device to tower). Past using unlike types of interfaces for the downlink and uplink, LTE utilizes the optimal way to exercise wireless connections both means, which makes a better-optimized network and better battery life on LTE devices.

For the downlink, LTE uses an OFDMA (orthogonal frequency division multiple access) air interface as opposed to the CDMA (code partition multiple access) and TDMA (time partition multiple access) air interfaces we've been using since 1990. What does this hateful? OFDMA (unlike CDMA and TDMA) mandates that MIMO (multiple in, multiple out) is used. Having MIMO means that devices accept 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 connection. We're already seeing the real-world benefits of MIMO on WiFi N routers and network adapters. MIMO is what lets 802.11n WiFi reach speeds of up to 600Mbps, though most advertise up to 300-400Mbps. In that location is a pregnant disadvantage though. MIMO works better the further apart the individual carrier antennae are. On smaller phones, the noise acquired by the antennae being and so close to each other volition cause LTE performance to drop. WiMAX also mandates the usage of MIMO since it uses OFDMA equally well. HSPA+, which uses W-CDMA (a reworked, improved wideband version of CDMA) for its air interface, tin can optionally use MIMO, also.

For the uplink (from device to tower), LTE uses the DFTS-OFDMA (detached Fourier transform spread orthogonal frequency partitioning multiple admission) scheme of generating a SC-FDMA (single carrier frequency division multiple access) betoken. As opposed to regular OFDMA, SC-FDMA is better for uplink because information technology has a better pinnacle-to-average power 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 still a MIMO organisation. LTE uses a SC-FDMA ane×two configuration, which means that for every one antenna on the transmitting device, there'south two antennae on the base station for receiving.

The major divergence betwixt the OFDMA signal for downlink and the SC-FDMA signal for uplink is that it uses a detached Fourier transform function on the data to convert it into a course that tin exist used to transmit. Detached Fourier transform functions are often used to convert digital data into analog waveforms for decoding audio and video, but information technology can be 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 partitioning duplex) variant and a TDD (time division duplex) variant. The near common variant being 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 phone supports, it actually uses two frequency ranges. These are known as paired frequency bands. For example, Verizon's 10MHz network is in FDD, so the bandwidth is allocated for uplink and downlink. This is commonly noted as a 2x10MHz or ten+10 MHz configuration. Some also call it 10x10MHz, but this is mathematically incorrect, but they hateful 10+10MHz. Some volition too call it a 20MHz network, but this can be ambiguous. The TDD variant uses one single range of frequencies in a frequency band, but that band is segmented to support transmit and receive signals in a single frequency range.

For case, an LTE TDD network deployed on 20MHz of spectrum uses the whole clamper equally one big block for frequency allocation purposes. For network bandwidth purposes, a LTE TDD network's spectrum can be further divided to optimize for the blazon of network traffic (half up and half down, more often than not down and a bit up, more often than not up and a fleck downwards, and so on).

In the United States, Sprint is the merely network operator deploying LTE in the TDD variant. Everyone else is deploying in the FDD variant. The TDD variant becomes more important in Asia, as Communist china Mobile (the largest network operator in the world in terms of subscriber count) is using TDD frequencies for their LTE network. Sprint's parent visitor, SoftBank, also uses LTE TDD in its home market place of Nippon. Fortunately, LTE devices tin easily be made to support both variants on a device without too much trouble.

Enough well-nigh specs – what most bombardment life?

At present we pb to the role that most people care almost: how it affects battery life. By itself, LTE devices should terminal roughly as long every bit 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 because the network operators are forcing many of these devices into active dual-mode operation.

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

Then there is handover. Handover is the operation in which a device switches from one network to another or from i tower to another. Handover is the disquisitional 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 example of a wireless network technology that doesn't inherently support handover.) When the user travels outside the range of a WiFi network, the WiFi radio will just drop the connexion. For cellular networks, this is even more than disquisitional considering the range of a belfry is non very anticipated due to factors outside of anyone's control (like the weather, etc.). LTE supports handover like all other cellular wireless networks, simply it improves on it by doing it much faster when handing over to a supported type of network or cell.

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

eHRPD

The fragile link-up between EV-Exercise and LTE brand handover occur a lot more than it is supposed to, which eats battery life fifty-fifty more. With AT&T and T-Mobile using an HSPA+ network alongside LTE instead of CDMA2000, handover functioning is a lot smoother. Equally far as battery life goes, it should exist slightly better than Verizon and Dart LTE phones considering LTE supports fast handover between UMTS and LTE. AT&T LTE phones are normally not forced into agile dual-mode operation because HSPA+ lets you use data and talk at the same fourth dimension. As a consequence, AT&T has no need to strength the device into active dual-style operation. However, battery life will notwithstanding be pretty bad because LTE signals are still 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 have the same problem equally Verizon Wireless with LTE bombardment life because they do the same thing as Verizon Wireless and force agile dual-mode operation with about of their devices. Every bit a upshot, turning off LTE will significantly amend bombardment life because the phone switches back to single-mode operation. Or in the case of AT&T phones, passive dual-fashion performance (for GSM/HSPA+ handover) since they are typically in passive tri-way operation for GSM/HSPA+/LTE handover. Passive multi-style functioning means that the device isn't constantly connected to multiple networks, merely will found a connexion and hand over the connection if the signal on the current network is too weak or snaps. This is ideal for multi-manner performance, and Sprint switched to doing this final twelvemonth in order to command costs for new devices that back up the tri-ring LTE network it brands every bit "Sprint Spark". With the launch of Verizon VoLTE last year, Verizon has also increasingly started offering devices with passive multi-way operation. This ways that these new devices at present have many of the same free energy conservation benefits that have always been present in GSM/UMTS/LTE devices.

LTE — Mobile panacea?

The ultimate goal of the network operators deploying LTE is to supercede everything else they have with it. That means that it needs to go possible to handle voice calls, text messages, network alerts, etc. over the data network. However, no one developed the LTE specification with voice and text messaging in listen. It was designed as a data network only. And then how do they solve the trouble? By developing a VoIP solution that fits their needs. 2 main standards came into existence: VoLGA (Phonation over LTE via Generic Admission) and VoLTE-IMS (Vocalization over LTE via IMS). VoLGA was based on GAN (Generic Access Network), which is also known every bit UMA (Unlicensed Mobile Access). Deutsche Telekom was the merely network operator that wanted to apply this method, as the pattern for VoLGA was heavily derived from T-Mobile USA's implementation of UMA for its WiFi Calling feature. No i else wanting to deploy LTE wanted to use it as a final or interim solution, equally it would have meant keeping around the legacy GSM core network for this purpose.

Everyone else supported VoLTE-IMS (now referred to equally VoLTE), which allowed them to fully discard their older networks and simplify their network design as they decommissioned legacy networks. However, IMS is much more expensive and hard to deploy than VoLGA, at least for GSM network operators. But IMS besides promised more flexibility. IMS could exist used to make real-time video calling with all sorts of additional 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 vocalization calls and text letters. For vox calls, VoLTE uses the AMR (Adaptive Multi-Rate) codec, with the wideband version used if supported on the network and the device. The AMR codec has long since been used every bit the standard codec for GSM and UMTS vocalization calls. The wideband version supports higher quality speech encoding, which would let for clearer voice calls. Text messages are supported using SIP MESSAGE requests. Video calling uses H.264 CBP (constrained baseline profile) with AMR-WB audio codec over RTP (Real-time Send Protocol) with VBR (variable bit charge per unit). With this, video calls over IMS are supposed to exist very high quality, no matter what the quality of the data connexion. 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 USA became the first network in the world to commercially deploy IMS-based voice calling and text messaging past using it for an improved WiFi calling solution. An update to the T-Mobile Samsung Galaxy S Ii and an update to the T-Mobile HTC Amaze 4G both included the new WiFi Calling solution.

MetroPCS was one of the start carriers in the globe to deploy VoLTE, the other existence SK Telecom in Southward Korea. While SK Telecom launched VoLTE nationally, MetroPCS only launched VoLTE in Dallas, TX. Initial implementations of VoLTE clearly showed much lower battery life, but that is largely resolved now. After 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 cease of the summertime of 2022, T-Mobile launched VoLTE and made it available nationwide presently afterward the launch. Since it is based on their WiFi calling solution, it 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 Sprint deploying VoLTE? Well, Verizon rolled out VoLTE in August 2022 nationally. AT&T launched VoLTE in select parts of the Midwest in May 2022 and has been gradually expanding it since. Sprint has not officially said annihilation nearly it nonetheless.

At this point, the major gotcha with VoLTE now is that it requires carrier customized firmware. Setting up a device to use VoLTE requires a lot of configuration, more than what a SIM menu can provide. Consequently, only operator branded devices will support VoLTE for now. Some unbranded devices may eventually be preloaded with select operator VoLTE configuration information, but that volition remain the exception rather than the rule. Hopefully this particular trouble will be addressed soon, because it puts a crimp in whatsoever plan to move devices from one operator to some other.

The messy time to come of 4G

We've just scratched the surface of what LTE is all about, simply this article includes pretty much everything that LTE subscribers would care near. Some of the other aspects of LTE include SON (self-organizing network) capabilities, which allows it to flexibly allocate capacity to parts of the cellular network every bit it is needed by redistributing connections to an optimal configuration at any given time. Handover to WiFi is another absurd feature, also. Still, well-nigh of the features like the former are pretty much simply seen from a network operator's side of things, and things similar the latter may never actually exist implemented.

LTE is a significant jump in optimized cellular wireless technology though. If you wish to become the highly-technical details of LTE and its always-evolving specifications, cheque out the 3GPP's specification series for LTE. Specifications for eHRPD and associated CDMA2000 specifications are available on the 3GPP2's website. The VoLGA specifications are bachelor on the VoLGA Forum'southward website. The 3GPP hosts the IMS specifications, with the GSM Clan hosting IMS Profile for Voice and SMS specifications on their website. We've covered the major highlights in this commodity, as there is way also much to embrace. As the specifications detail, there were many improvements at every level of a cellular network that upshot in a high-functioning, optimized network.

Whether LTE becomes the success story of the mobile manufacture remains to be seen. Network operators around the world are only at present deploying it, and already it is turning into a mess. The 3GPP has already canonical about 45 frequency bands for LTE. Over 30 of them are for LTE FDD and the residual are for LTE TDD. Roaming is going to be very difficult on LTE. For Due north America alone, there are ten FDD bands and ane TDD band for LTE. For Europe and Africa, in that location are 4 bands for FDD LTE and two bands for TDD LTE. For Asia and Oceania, in that location are the same four FDD bands for Europe, three more frequency bands for FDD, and two more TDD bands. The residuum of the bands take yet to exist used, merely they are going to be used. Someone is going to have 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

And so there's the 4G mess. Contrary to popular belief, LTE at the current stage was not e'er considered 4G. The International Telecommunications Union (or ITU) determines what can be considered 4G. Originally, the ITU declared that the drove of requirements known as IMT-Avant-garde determined what would be considered 4G. LTE did not make the cutting (though a future version of it called LTE-Advanced did). Neither did WiMAX or HSPA+. However, the American and Canadian network operators' collective influence fabricated the ITU revise their specification on what 4G is to include whatever wireless engineering science significantly evolved from 3G technologies. Nearly technophiles are of the opinion that the IMT-Avant-garde specification determines what tin can be considered 4G, while about business people adopt the newer definition for 4G. For the purposes of this commodity, the revised standard is considered 4G. While this is out of the scope of this article (and also not really important either), I'm laying it out now to forbid whatsoever arguments. This means that LTE, HSPA+, and WiMAX are all considered 4G technologies, though WiMAX is still officially on the listing of 3G technologies as well.

Since LTE-Avant-garde Release 10 has been codified and equipment is available, a number of operators around the world have started using LTE-Avant-garde features. AT&T has deployed carrier assemblage in many of the same areas it 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 USA has been deploying and testing it since it started its rollout of LTE service and then that it can maximize the benefits of LTE-Advanced equipment in equally many areas as possible. While T-Mobile isn't broadly using carrier aggregation yet, information technology certainly has the option to do so, in the future.

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

As LTE continues to ameliorate, we'll keep to see a steady migration of usage from older networks to LTE, especially operators using CDMA networks as a legacy technology. While we may not have ubiquitous connectivity for a long time due to the sheer number of bands and configurations, new technology geared to improve the state of affairs is always coming.