Deep dive: What is LTE?

Samsung Galaxy Note Edge

It’s been several years since the first LTE networks came online. Now, nearly all cellular-enabled devices sold today support LTE for 4G service — sometimes even without 2G or 3G technologies supported. The first LTE-compatible phones only had a few hours of practical battery life, but today’s devices can last an entire day or two on a single charge. That’s still not enough, of course, but we’re getting there.

So, what is LTE? To most, it is a faster network technology. To network operators around the world, it 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 “most advanced” network technology. In the end, it is Long Term Evolution of the Universal Mobile Telecommunications System (UMTS). LTE-Logo

But that doesn’t tell us what LTE actually is. LTE is what the 3GPP (3rd Generation Partnership Project, the group responsible for standardizing and improving UMTS) designates as their next step. UMTS is the group of standards that define 3G for GSM networks across the world, including AT&T and T-Mobile’s 3G networks. The cdmaOne/CDMA2000 family of standards are not maintained by 3GPP, but by a different organization spearheaded by Qualcomm. For subscribers to operators with networks utilizing CDMA2000 technology, LTE is the replacement of mediocre CDMA2000 networks with a superior cellular telecommunications system offering flexibility and power to the network operator and the subscriber.

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

Of course, that doesn’t mean all networks are created equal. Some aren’t quite able to achieve these goals. For example, Sprint’s LTE service was rated with an average download speed of 4.0Mbps and an average upload speed of 2.5Mbps. AT&T’s LTE service was much better than Sprint’s, but still bad with an average download speed of 7.6Mbps and an average upload speed of 2.4Mbps.

In this article, we will 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 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 easily deployable, how LTE works as a radio technology, and what types of LTE exist. 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. But to get the complete 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 amount of space a network operator dedicates to a network. Depending on the type of LTE being deployed, these bandwidths have slightly different meaning 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 one as it transitions subscribers off of its legacy networks (GSM, CDMA, etc.).

MetroPCS was an example of a network operator that has done this. Before it was acquired by T-Mobile, a majority of its spectrum is still dedicated to CDMA, with 1.4MHz 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 as Cricket Communications) had also done the same thing prior to being acquired by AT&T, except it used 3MHz or 5MHz instead of 1.4MHz or 3MHz. Neither of these operators could afford to cut CDMA capacity by a significant degree just yet, 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 course, these issues 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 across the board for 750MHz, since it has the national allocation of spectrum available for it. In addition to that, the AWS spectrum it acquired from the cable companies and other transactions have allowed it to roll out a second LTE pipeline with 15MHz or 20MHz channels in most places. Like 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 be 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, but there are many where it only has 5MHz. It has resorted to cutting down GSM capacity to reuse the spectrum to support its customers, as singular 5MHz or even 10MHz channels aren’t enough. Sprint has a similar problem, as its main network is a singular 5MHz channel nationally. It is using the spectrum it has from acquiring Clearwire to supplement it with 20MHz channels for additional capacity.

Less spectrum means that fewer customers can obtain the same high speeds that Verizon’s LTE customers get when connected to any particular cell. LTE can support up to 200 active data clients (smartphones, tablets, USB modems, mobile hotspots, etc.) at full speed for every 5MHz of spectrum allocated per cell. That means that if a particular tower has 20MHz of spectrum allocated to it, it can support up to 800 data clients at full speed. There are ways of supporting more data 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 will discuss 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). By using different types of interfaces for the downlink and uplink, LTE utilizes the optimal way to do wireless connections both ways, 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 division multiple access) and TDMA (time division 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 have multiple connections to a single cell, which increases the stability of the connection and reduces latency tremendously. It 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. There is a significant disadvantage though. MIMO works better the further apart the individual carrier antennae are. On smaller phones, the noise caused by the antennae being so close to each other will cause LTE performance to drop. WiMAX also mandates the usage of MIMO since it uses OFDMA as well. 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 division multiple access) scheme of generating a SC-FDMA (single carrier frequency division multiple access) signal. As opposed to regular OFDMA, SC-FDMA is better for uplink because it has a better peak-to-average power ratio over OFDMA for uplink. LTE-enabled devices, in order to conserve battery 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 system. LTE uses a SC-FDMA 1×2 configuration, which means that for every one antenna on the transmitting device, there’s two antennae on the base station for receiving.

Full Mobile Number Portability Rollout Likely to Miss May 3 Deadline


Telecom operators are likely to miss the deadline for the rollout of full mobile number portability across the country from May 3 due to some technical issues, an industry body has said.

“There is a possibility that it (Full MNP) will be delayed. Given our past experience, we have asked DoT to form a committee for coordinating rollout of full MNP. There are some network testing and routing issues that need to sorted out in time. The committee has not met yet,” industry body COAI Director General Rajan S Mathews told PTI.

The full MNP will allow subscribers to retain their mobile number in any part of the country even they change their operator or state.

At present MNP allows subscribers to change mobile network while retaining their number in same telecom circle.

The Department of Telecom had set the deadline of May 3 to start full MNP service and the Telecom Regulatory Authority of India (Trai) amended existing MNP regulation on February 25.

“Trai issued final guidelines with some delay. We need some time to work on those guidelines and make changes in network accordingly. We are thankful to DoT that it has reduced testing requirement to minimum level. We are working hard but there will be some delay. It looks very unlikely that it will happen from May 3,” Mathews said.

He said that there has to be certainty that networks of public sector companies BSNLand MTNL are ready with changes to facilitate full MNP.

“We have asked to form committee so that there can be coordination among telecom operators for various tests. It will take final call as and when its meet and thereafter we will need some time to make arrangements,” Mathews said.

Idea Cellular Launches 3G Services in Delhi

Aditya Birla Group company Idea Cellular on Tuesday launched its 3G services on 900MHz spectrum band in Delhi circle, a company statement said.

“With the 3G launch in Delhi, Idea has not only expanded its 3G footprint to 12 circles across the country, but has also become the only mobile operator to have seamless 3G network across the entire length and breadth of northern India,” said Ambrish Jain, deputy managing director of Idea Cellular.

“Innovation and efficiency in operations are the key drivers to Idea’s fast-paced growth in the Indian telephony market, and the launch of 3G on 900MHz spectrum band in Delhi is a testimony to this,” he added.

“Idea has nearly six million subscribers in Delhi with approximately 30 percent being data users. The existing 3G users will experience enhanced services and products and offerings while the new subscribers will benefit from our affordable 3G tariffs and superior network,” Sanjeev Govil, chief operating officer – Delhi, Idea Cellular said.

Idea’s network in Delhi region comprises of over 4,700 sites on 2G and over 5,000 hops on microwave. The network is being modernised along with the addition of 3G sites, to cater to the future demand of mobile data services in the metro circle, the statement said.

Idea is also in the process of setting up world-class service centres in the Delhi NCR region to service the evolving mobile consumers.

Airtel Launches 4G Internet Service in Moga, Punjab


Bharti Airtel announced the launch of its 4G network in Moga, Punjab, which has become the 11th town in the state to have this service.

The other cities in Punjab where 4G service are already available are Chandigarh, Mohali, Panchkula, Ludhiana, Jalandhar, Amritsar, Hoshiarpur, Phagwara, Kapurthala and Patiala.

Announcing the launch of the services, Airtel CEO for Punjab, Haryana and HP, Manu Sood, said customers can now experience an all new browsing experience with Airtel’s 4G home Wi-Fi.

Flush with an investment outlay of $3 billion (approximately Rs. 1.87 lakh crores) a year on networks, telecom major Bharti Airtel plans to double its 4G network by next fiscal as it gears up to take on competition, including the much-awaited foray of Mukesh Ambani-led Reliance Industries group.

(Also see: Videocon to Launch 4G Mobile Services in Bihar, Uttar Pradesh by December)

“We have decided to roll out (4G). We have 20,000 base stations now, in March, and we will be doing another 20,000 next year,” Bharti Airtel Chairman Sunil Bharti Mittal said during MWC in Barcelona earlier this month.

Mittal said funds would not be a constraint for the company’s expansion plans as it is spending $3 billion every year on networks alone, excluding spectrum, and its 2G and3G rollouts are among the most expensive in the country.

SIM Maker Gemalto Confirms Possible Spy Attacks, Denies 'Massive Theft'

European SIM maker Gemalto said Wednesday it had suffered hacking attacks that may have been conducted by US and British intelligence agencies but denied any “massive theft” of encryption keys that could be used to spy on conversations.Investigative website The Intercept last week said the US National Security Agencyand its British counterpart GCHQ hacked into the firm in 2010 and 2011 and stole the keys, with which they can secretly monitor communications over mobiles without using a warrant or wiretap.

The website made the allegations based on a document leaked by former NSA contractor Edward Snowden.

“In 2010 and 2011, we detected two particularly sophisticated intrusions which could be related to the operation,” Gemalto said in a statement.

“During the same period, we also detected several attempts to access the PCs ofGemalto employees who had regular contact with customers,” it added.

“At the time we were unable to identify the perpetrators but we now think that they could be related to the NSA and GCHQ operation.”

But the company denied that these attacks resulted in a large-scale theft of encryption keys.

“The attacks against Gemalto only breached its office networks and could not have resulted in a massive theft of SIM encryption keys,” it said.

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Pan-India Mobile Number Portability From May 3: Trai

Mobile subscribers from May 3 will be able to port their numbers anywhere in the country while changing service providers, as telecom regulator Trai has amended the regulation on it.Mobile Number Portability (MNP) currently allows consumers to change their service provider while retaining the same number only within a telecom circle, which in most cases, is limited to a state.

A person, for instance, while shifting from Delhi to Chennai will be able to retain the same mobile number while selecting a service provider.

In a statement Wednesday, Trai said it has “…issued sixth amendment to the Telecommunication Mobile Number Portability Regulation, 2009, which will facilitate full Mobile Number Portability (MNP) in the country, with effect from May 3, 2015.”

The Department of Telecom had on November 3 issued amendments to MNP licence agreement stating that MNP is to be implemented across the country within a period of six months from the date of amendment of the licences.

“Accordingly, the Authority has made the Sixth Amendment to the MNP Regulations effective from 3rd May 2015,” Trai said.

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