Antenna performance is critical to the capacity and data throughput gains sought by the industry’s deployment of LTE Releases 10 and beyond, Ray Butler, vice president active wireless products engineering, Commscope, told AGL Bulletin at PCIA’s Wireless Infrastructure Show last month in Hollywood, Fla. He spoke on the “LTE Evolution” panel.
“We have done some analysis on antenna performance and what we are seeing is how well the pattern is shaped is very important for LTE in the macro-layer of the network and it is also true for the small cells,” he said.
Butler said there was a tendency in early deployments to use whip antennas in outdoor metro small cell sites, with a plan to place them on every street corner of the coverage area without performing the RF optimization. But this approach leads to system performance issues, because the radio issues that are present in the macro-cellular networks, – for example, carrier-to-interference ratio, containing the radio signal to the desired coverage area– also apply in small cells, according to his analysis.
“As operators get into the deployment, we are seeing a more practical approach being used, where a 2-foot to 4-foot antenna with electrical tilt capability is being specified instead of a whip antenna. You are better off using a high-performance antenna. It makes a huge difference in the network,” Butler said.
Small cells should be deployed with the same care and precision as a macrocell, according to Butler. “Many small cells will operate on the same frequencies as the umbrella macrocell, so you need to contain the radio signal and minimize the interference between the layers,” he said.
While the self-optimizing networks’ algorithms are powerful, Butler said that RF engineering is critical to unleashing maximum system throughput and capacity gains.
“You are never going to achieve full throughput and meet your capacity goals if there is too much overlap of coverage in each sector. If the signals overlap too much, you are going to have trouble with interference.”
In the area of high performance antennas, there are many considerations: MIMO versus beam forming and single-user MIMO versus multi-user MIMO for optimizing the antenna and the antenna configuration for the different LTE transmission modes.
“If you have a high mobility user, transmission diversity works the best. There is less dependence upon feedback,” Butler said. “If you have pedestrian traffic close to the site with a scattering environment where there are a lot of radio signal reflections, single- or multi-user MIMO is the best, because the traffic speed is slower and there is better signal-to-interference ratio.”
A user moving slowly close in to the antenna utilizes closed-loop feedback to maximize performance, so the antenna can be switched back and forth between beam forming and MIMO as needed to optimize the radio link, which creates the throughput gains.
The question arises, according to Butler, as to how antennas can be configured to maximize the throughput—either side by side or stacked vertically one on top of the other, for example. “The answer is rather intuitive: side by side, if users are spread horizontally and vertically for coverage down a corridor,” he said.
Butler discussed the various ways that high-performance antennas can increase the spectral efficiency of a wireless network.
“With single-user MIMO, the bit stream can be split into two paths for 2-way MIMO, which roughly doubles the spectral efficiency,” he said. “Multi-user MIMO sends multiple bit streams using the same spectrum to geographically separated users. Beam forming, on the other hand, sends a bit stream that focuses on or follows the user as he travels through the sector, which decreases interference and increases the signal-to-interference ratio.”
In the last quarter, Verizon Wireless announced that its LTE coverage build out was completed and its service now available to more than 303 million people in more than 500 markets, but it continues to improve upon the network and push LTE into the AWS Band, according to Fran Shammo, Verizon Wireless CFO.
“Throughout the rest of this year, we will continue to add capacity and optimize our 4G LTE network, ensuring that customers are receiving the quality and consistent reliability that they expect from our network and devices,” he said. Since June, the main emphasis at Verizon Wireless has been increasing capacity and densification.
This month, Verizon Wireless began deploying LTE in the Advanced Wireless Services band (1710 MHz to 1755 MHz for uplink, 2110 MHz to 2155 MHz downlink) to deal with capacity issues in major cities.
“Given the growth of this we have had some densification issues in major cities like New York, Chicago, San Francisco, what you see us doing is being very proactive in more in-building coverage, more densification cell sites,” Shammo said.
Wireless capital spending in the third quarter totaled $2.5 billion. Year-to-date, wireless capex was $6.7 billion, nearly 11 percent higher than last year.
“We are very focused on improving investment returns and capital efficiency and expect that our annual capex to revenue ratio will improve, even with the planned additional spending in 4G LTE,” Shammo said. “We are utilizing our AWS spectrum to further optimize the network and we are already spending some of the incremental capital we allocated to wireless capacity.
LTE is the fastest-growing mobile network technology worldwide, 2013 will be the peak year for deployments, TDD LTE is on the rise and Huawei and Ericson dominate infrastructure contract awards, according to several recent industry reports.
More than 184 LTE networks were in service as of the end of July, with another 159 planned or in deployment. Successful LTE deployments have been achieved by various by operators including Verizon Wireless, SK Telecom, NTT DoCoMo, Everything Everywhere and Vodafone D2 (Germany), according to a report from Informa Telecoms & Media.
Huawei and Ericsson are dominating the market in terms of the allocation of infrastructure contracts. According to Informa’s calculations and data provided and validated by vendors, Huawei accounts for 40 percent of network contract awards, Ericsson has 34 percent and NSN follows with 17 percent. The other 9 percent is divided among Alcatel-Lucent, ZTE, Samsung and NEC.
“The top three vendors have illustrated significant technological expertise and support to mobile operators, with Huawei and Ericsson having attracted the largest share of contracts,” said Dimitris Mavrakis, co-author of the Informa report.
Unlike in the U.S. market, network sharing is popular in foreign countries to reduce opex and consolidate infrastructure platforms.
The Global Mobile Suppliers Association counts 200 LTE networks, a slightly higher number of commercially launched systems than Informa, including 182 networks deployed in FDD mode, nine TDD networks and nine FDD/TDD networks. In the longer term, several operators have expressed interest in converging TDD and FDD to increase network capacity, especially when existing unpaired spectrum holdings are available.
More than 50 mobile carriers worldwide have committed to TDD LTE technology, according to a report by Research and Markets, and more than 30 OEMs have commercially launched TD-LTE-compatible devices, the majority of which support both FDD and TDD.
“In October 2012, the TD-LTE ecosystem received a major boost when China’s Ministry of Industry and Information Technology announced that the entire 190 MHz of spectrum in the 2.5/2.6 GHz band will be allocated for TD-LTE deployments in China, which harmonizes its TDD spectrum with Japan and the U.S., two major LTE markets,” according to Research and Markets. “These developments could allow the TD-LTE ecosystem to reach significant economies of scale, boosting further infrastructure and device investments in TD-LTE technology.”
Although the market is going to move toward LTE-A, which includes several different updates on the existing LTE standard, most operators are just at the LTE stage, according to Darryl Schoolar, principal analyst, wireless infrastructure, Ovum.
“Some of these LTE-A announcements could be considered premature as they only are using one LTE-A feature, mainly carrier aggregation,” he said.
On Aug. 20, Ericsson announced that it has supported South Korea’s SK Telecom in expanding LTE-Advanced commercial service network to the downtown areas of 84 cities nationwide, including the entire Seoul metropolitan area and six other major cities.
On June 26, SK Telecom launched LTE-Advanced service with up to 150 Mbps speeds in the Seoul area, the downtowns of 42 cities and 103 campus towns, with a plan to deploy 32,000 LTE-Advanced base stations by the end of the year, including 300 college campuses.
NFL and college stadiums that sported only 2G or 3G technology have gotten a DAS makeover to upgrade them to LTE. Similar to wireless systems across country, stadium DAS, some of which had only 850 MHz and 1900 MHz frequencies, will now access the 700 MHz and AWS bands in addition to replacing SISO antennas with MIMO.
“So we are adding frequencies and MIMO capability, which gives you a defined advantage in capacity and throughput,” said John Spindler, TE Connectivity director, product management, in-building DAS.
TE Connectivity has been busy this summer outfitting 13 college and pro stadiums, including MetLife Stadium, home of the New York Jets and the New York Giants and site of the 2014 Super Bowl; FedExField, home of the Washington Redskins; Sports Authority Field, home of the Denver Broncos; Rose Bowl Stadium, home of the 2014 BCS National Championship game; and the University of Michigan stadium.
Of those DAS systems, about 75 percent are owned and deployed by wireless carriers. AT&T and Verizon Wireless are TE Connectivity’s biggest customers.
“A number of neutral host DAS providers have been very successful,” Spindler said. “It’s easy for carriers to make a business case to provide service for stadiums that seat 70,000 to 100,000 people.”
Spindler has seen as many as three separate DAS systems deployed in a stadium supporting three different carriers. Carriers’ ownership interest in DAS may be, in part, because high-profile venues bring them unwanted notoriety when a DAS fails to provide coverage.
“The sheer volume of users that fit into a stadium is why there is a high interest in ensuring there is coverage and capacity,” he said. “The carriers want to be in control of something as critical as the systems that are bringing their wireless service to the users in these venues.”
Each stadium is unique. For example, the DAS used at Boise State University and the Rose Bowl Stadium are carrier-owned, while the University of Phoenix Stadium DAS is a multi-operator neutral host system that hosts three carriers.
“At the end of the day, it is up to the carriers to go on a neutral host or to deploy their own DAS,” Spindler said.
Stadiums that had 12 sectors a few years ago now have as many as 32 sectors. Changing sector configurations can be a cost-effective way to increase capacity throughput. The big challenge is making sure the system is designed properly for the traffic patterns of the stadium when you have a capacity crowd, according to Spindler.
“They need to be properly sectorized so they deliver the necessary capacity,” he said. “Of course, when you heavily sectorize a stadium, you need to be very careful with your design so that sectors are carefully delineated. You don’t want a lot of soft handoff, because it reduces the network’s efficiency.”
During the second quarter earnings calls, LTE deployment was on the lips of several major carriers as they seek to catch up with Verizon Wireless.
T-Mobile US is pushing forward with its LTE upgrade and HSPA+ build out, and it has doubled its MetroPCS brand presence to 15 new markets. The carrier, which launched its LTE network in seven major metropolitan areas in March, lit up 116 Metro areas covering 157 million people with LTE by the end of July, exceeding its midyear goal of 100 million. The company is also still building out its HSPA+ network, which now covers 228 million people on AWS spectrum and 108 million in 1900 band.
“We have hugely accelerated the modernization and upgrading of our network to 4G LTE,” John Legere, president and CEO, told the second quarter earnings call. More than 200 million covered pops are projected to receive LTE by the end of 2013.
Also during the quarter, the carrier purchased of US Cellular’s spectrum covering 32 million POPs in cities such as St. Louis and Kansas City, Mo.; Nashville; Memphis, Tenn.; and New Orleans.
“Our coverage spectrum position is improving. The [US Cellular] spectrum is adjacent to our current holdings which provide key network efficiency benefit,” Legere said. “Further, due to the spectrum position and our network deployment program … we are on track to achieve 20×20 megahertz 4G LTE coverage in 90 percent of the top 25 market in 2014 and beyond.”
Additionally, T-Mobile is moving forward with the integration of MetroPCS, completing the planning and beginning the implementation of the network migration. So far, it has launched HSPA, HSPA+ and LTE in multiple MetroPCS markets and expects to complete the launch in all existing markets by the end of Q3. The implementation of multi-operator core network allows MetroPCS customers with LTE handsets to use T-Mobile 4G LTE network for data without a change in handset.
AT&T LTE Growth ‘On Track’
AT&T currently covers more than 225 million people with LTE and is on track to reach nearly 270 million pops by year end covering 400 markets.
“We continue to move fast with our 4G LTE deployment. We now expect to substantially complete our 4G LTE network by the next summer,” Ralph de la Vega, president and CEO for AT&T Mobility, told a second quarter earnings call.
AT&T bumped up its CapEx $900 million year over year to $5.5 billion in the second quarter.
“We spent that money at this time, because the network team could get more done and efficiently get it done and so we want to make sure we fund that and we will stick to that philosophy,” de la Vega said.
Network Vision Momentum Continues
While shutting down the Nextel platform, Sprint made progress on the Network Vision deployment in the quarter, completing 6,500 sites for a total of 20,000. LTE has been launched in 151 cities, including Los Angeles, Dallas, Atlanta, Miami and Boston. Sprint expects to provide 200 million people with LTE by the end of 2013.
“Momentum continued in the second quarter and expanding the Network Vision footprint we now have zoning complete on nearly 35,000 sites and leasing complete on close to 34,000. More than 30,000 sites are ready or have already begun construction. There are 600 cities under construction,” said Steve Elfman, Sprint president of network operations and wholesale.
Another significant milestone in the evolution of Network Vision is the closing of both the Midwest spectrum acquisition from U.S. Cellular and the acquisition of Clearwire. The U.S. Cellular transaction brought 20 megahertz of PCS spectrum in Chicago and its surrounding markets and 10 megahertz of PCS spectrum in the St. Louis market. Sprint has already begun to deploy LTE on the acquired spectrum and we’ll continue to do so through the third quarter of next year.
“With regard to Clearwire, we’ve been actively engaged with them to build both a network integration plan as well as the integration of all functions into Sprint,” Elfman said. “As it relates to expanding LTE on 2.5 gigahertz, Clearwire had roughly 2,000 TD-LTE sites commissioned at the time of closing and expect these and additional sites under construction to continue coming on air in the second half.
Future LTE Growth Looks Good Too — Moody’s
Tower companies will get a nice boost from Sprint’s purchase of its subsidiary Clearwire Corp. through upgrading existing cell sites and adding sites to achieve nationwide LTE coverage, according to Moody’s Investors Service in the report “Independent Towers Will Get an EBITDA Boost As Sprint Deploys Clearwire Spectrum.”
“We expect that Sprint will repurpose the Clearwire tower sites and add an estimated 15,000 to 18,000 cell tower sites, which will generate increased leasing revenue that the carrier pays to the tower companies,” says Moody’s Vice President — Senior Analyst Gregory Fraser, the author of the report. “These new tower sites will replace the 16,500 Clearwire sites scheduled to be decommissioned and will therefore eliminate the risk that lost rent from those towers would not be replaced with new rental revenue.”
Moody’s expects AT&T to further its 4G/LTE deployment on Leap’s underutilized spectrum on 15,000 to 20,000 sites (including the 9,700 leased sites acquired from Leap), which will also to the benefit of the independent tower firms.