White Paper
Twin Beam technology adds immediate capacity without additional antennas Philip Sorrells, V.P. Strategic Marketing – Wireless May 15, 2013
Contents Contents Are snowballing capacity issues creating the perfect storm?
3
The quest for more capacity
3
Revisiting sectorization
4
Capacity performance makes six-sector attractive… in theory
5
The cost of better performance
6
Twin Beam technology makes six-sector implementation cost-effective and practical
6
Increasing capacity through pattern performance, signal strength and noise reduction 7 Reduced loading at the top of the tower
9
Success story: Twin Beam turns antenna competition into a solutions showcase
9
Improvements across the board
9
Making the complex simple
12
The bottom line is higher quality of service
12
References 13
2
Are snowballing capacity issues creating the perfect storm? “Even as they build the next generation of faster wireless networks… carriers are discouraging heavy data users by eliminating unlimited data plans and enforcing monthly caps.” Wireless carriers seek to ‘offload’ customers, Roger Yu, USA Today, 5/23/2012
Today’s mobile subscribers have a voracious appetite for data. In 2012, the volume of global mobile data traffic grew 70 percent, reaching 885 petabytes per month1. The growth is due to multiple factors. The number of smartphones continues to increase, as does the amount of data they consume. According to recent industry reports, 31 percent of all Internet users rely exclusively on their mobile device for Internet connectivity. The average amount of traffic per smartphone in 2012 was 342 MB per month, up from 189 MB per month in 2011 — an 81 percent rise1. The deployment of 4G networks is also on the rise. At the end of 2012, there were 144 4G networks worldwide. By the end of 2013, the number will swell to an estimated 230 2. In some cases, wireless service providers (WSPs) are bypassing 3G altogether, opting to layer 4G directly onto their current 2G systems. The rapid adoption of 4G is placing further strain on capacity-strapped networks. In 2012, a fourth-generation connection generated 19 times more traffic on average than a non-4G connection1. Although 4G connections represent only 0.9 percent of mobile connections today, they already account for 14 percent of mobile data traffic1. The capacity crunch has become so critical that, as USA Today reported, “Even as they build the next generation of faster wireless networks, carriers are discouraging heavy data users by eliminating unlimited data plans and enforcing monthly caps.”
The quest for more capacity In the quest for more capacity, WSPs are exploring a number of strategies — some old and some new. Among the more traditional are cell densification and the purchase of additional spectrum. Both strategies, however, present significant cost issues.
Increasing capacity
According to Shannon’s Law, increasing capacity in a given channel bandwidth requires WSPs to improve the signal-to-noise ratio and/or increase frequency reuse. Reducing noise
In 3G and 4G LTE networks, noise containment in the RF path is critical. External noise from a variety of sources — including multi-path reflection, environmental noise and interference from adjacent or nearby cells — can significantly decrease receiver sensitivity at the base station. As noise within the sector increases, mobiles increase their signal power levels, creating more uplink interference. Noise within the RF path is also problematic, with thermal noise and passive intermodulation (PIM) being the major culprits. Increasing frequency reuse
Another strategy for growing capacity is to increase opportunities for frequency reuse through higher order sectorization.
3
In the case of cell densification, adding new cells, the process of site acquisition and zoning approval can take up to two years, resulting in lost revenue for the WSP. Once approved, a new site can cost more than a quarter million dollars to build and commission. Adding more spectrum, assuming it is available, can easily run into the billions of dollars. In January 2013, AT&T announced a deal to pay Verizon Wireless $1.9 billion for spectrum in the 700 MHz band in 18 U.S. states3. More recently, WSPs have experimented with offloading traffic to ancillary networks such as localized Wi-Fi hot spots. This, too, is problematic. Creating a secure tunnel for the hand-off typically requires a connection manager client running Internet Protocol Security (IPSec) suite. The application must be downloaded and installed by the user and runs in the background where it can significantly affect the battery life of the device4. Small cell deployment is also being touted as an excellent way to add network capacity. According to Joe Madden, Principal Strategist with Mobile Experts LLC., more than five million carrier-grade small cells are expected to ship in 2017 5. But that does little to satisfy WSP’s immediate need for more capacity.
Revisiting sectorization In the last 50 years, wireless capacity has increased by a factor of about 1,000,000 6. This growth has come from better spectral efficiency, more spectrum and more cells/sectors. Since the 1990s, one of the most popular and effective strategies for increasing site and network capacity has been sectorization. Figure 1 illustrates that sectorization and cell densification have accounted for the majority of additional capacity over the last fifty years. The first sectorized systems replaced standard 360-degree omni-directional antennas with three separate directional antennas. The most commonly deployed configuration uses three antennas, each with a nominal azimuth beamwidth of 65-degrees. While the antennas within a sectorized cell share a common base transceiver station (BTS), each is managed and operated independently with its own power level, frequencies and channels. The use of three directional sector antennas versus one omni-directional antenna substantially reduces co-channel cell interference and triples the opportunity for frequency reuse. As a result, WSPs realize significant gains in capacity.
Figure 1 10,000 2,000 1,000
Growth Factor
“… more than five million carriergrade small cells are expected to ship in 2017 5. But that still leaves WSPs wondering how to resolve their immediate capacity issues now.”
100 20
25
10
1 Spectral Efficiency
Spectrum
Number of Cells/Sectors
Smart Cells and Wireless Capacity Growth, Agilent Technologies, LTE World Summit, May 26, 2010
4
Capacity performance makes six-sector attractive… in theory Several years ago, WSPs began to experiment with higher order sectorization, splitting traditional three-sector sites into six. The initial purpose was to generate additional capacity in hot spots and spectrum-limited markets. A six-sector site application splits each of the original 65-degree coverage areas into two sectors, each served by a separate narrowbeam antenna with a nominal azimuth beamwidth of 33 to 38 degrees. Properly done, higher order sectorization reduces the overlap interference, pilot pollution and soft hand-off areas — all of which contribute to more efficient spectrum reuse. In six-sector deployments, with rapid pattern roll-off and good sidelobe and backlobe suppression, WSPs typically increase capacity by 70–80 percent 7. Because each antenna is controlled separately, it provides tighter frequency and radiation control when it comes to customizing the footprint of the cell site. At the same time, six-sector antennas enable WSPs to take advantage of today’s more sophisticated modulation schemes. Crossover points between sectors typically occur at approximately –9dB, making them good candidates for use with 3G UMTS and CDMA networks, as well as 4G LTE systems. Higher order sectorization also enables WSPs to add capacity without adding sites. This is especially important in high-density areas such as urban and suburban locations where WSPs can respond quickly to changes in subscriber demographics by simply upgrading existing sites from three- to six-sectors. Figure 2 illustrates the significant reduction of inter-sector overlap in switching from a 65-degree to a 33-degree antenna. Reducing the overlap decreases the soft handoff area and provides additional capacity gains.
Figure 2 65° Sectors -30
-20
-10
0
10
33° Sectors 20
-40
According to a CDMA Development Group study, six-sector sites can improve voice capacity 70% to 100% and can increase data throughput 50% to 70% above current network baselines.
-30
30 -40
40
-50
-70
70
-80
-90
90
-90
100
-100
110 120
-130
130
-140
140 -150
-160
-170 180
170
160
150
20
-12
30 -130
40
-140
50
-150
60
-20 -2 20
70
-25 -2 25 --30 30
80
-110
10
0
-15 -1 15
-70
-80
-100
0
-10 -1 10
-60
60
-10
-5
-50
50
-60
-120
-20
--35 35 --4 40 4 0 -40
-110
-170
90
180
100
170
110
-120
-160
80
160 150
120
-130
140
130
-140
130
140 -150
-160
-170 180
170
160
12
150
(0) HBX-3319DS-VTM_00DT_1920 (1) HBX-3319DS-VTM_00DT_1920 (2) HBX-3319DS-VTM_00DT_1920 (3) HBX-3319DS-VTM_00DT_1920 (4) HBX-3319DS-VTM_00DT_1920 (5) HBX-3319DS-VTM_00DT_1920
5
The cost of better performance Traditionally, cell splitting into six sectors has been limited due to the requirement to change from one 65-degree antenna to two individual narrower beam antennas. The capacity and performance enhancements gained by implementing higher order sectorization are often undermined by the real cost of implementation. By definition, transitioning from a three- to a six-sector design doubles the number of antennas that must be purchased and increases many of the associated costs, including packaging, transportation and installation. While the number of antennas required doubles, the net structural impact on the tower is even higher. This is because, in order to generate a narrower beamwidth, a 33-degree antenna must be physically larger than a 65-degree antenna. In many cases, the surface area of the six-sector solution is more than double that of the three-sector solution. The larger surface area creates significantly more wind loading. If mount arms are used to move the antenna away from the tower, torque loads on the tower increase accordingly. Larger antennas also add more weight to the top of the tower, which is becoming increasingly crowded with other RF components such as filters, tower mounted amplifiers, multi-band combiners, and remote radio heads. Nowadays, many tower manufacturers are switching to lighter materials in order to save on manufacturing and customer shipping costs. As a result, the heavily loaded, lighter towers are far more susceptible to increased twist and sway, which can cause links to sporadically fail. In addition, tougher industry standards for tower loading, like ANSI/TIA-222 Rev G, impose additional limitations on the tower’s structural capacity. With six antennas instead of three, there is also increased potential for boresite alignment errors during installation. The industry has benefitted from recently introduced installation aides such as GPS assistance. Many installers, however, continue to align antennas using little more than a compass, visible landmarks or even hand-drawn lines on the pavement below. In a UMTS network, the antenna’s performance sensitivity to azimuth and tilt error increases as beamwidth is reduced8. When it comes to deploying a new site, zoning approval, especially in suburban neighborhoods, is more difficult to obtain with a six-sector site as well. In 2009, the FCC passed a regulation designed to shorten the time between the filing of the WSP zoning request and the decision by the municipality — 90 days for a co-located site or 150 days for all other applications. But the “shot clock”, as the law is known, has done little to speed the process. For WSPs looking to deploy larger, more visible six-sector solutions, obtaining the necessary approvals can take eight months or more. For these reasons, the six-sector site design, despite its ability to increase capacity and throughput, has not gained much traction in the market.
Twin Beam technology makes six-sector implementation cost-effective and practical Recently, however, CommScope engineers have perfected a “sectorsculpting” multi-beam design that alters the cost/benefit playing field for six-sector deployment.
Recently, however, CommScope engineers have perfected a “sector-sculpting” multi-beam antenna that alters the cost/benefit playing field for six-sector deployment. Introduced by CommScope in 2013, sector sculpting enables WSPs to create a six-sector solution — with all the expected capacity and pattern benefits — using just three Twin Beam antennas. By enabling WSPs to achieve higher-order sectorization without additional antennas, the technology effectively removes the major cost and time barriers associated with six-sector deployment and provides a capacity-generating solution that WSPs can deploy immediately.
6
Figure 3
The Twin Beam design provides a theoretical doubling of sector capacity. Each antenna produces two separate narrow azimuth beams whose positions are directed at +30-degrees and –30-degrees of the antenna’s boresite. In extended trials, WSPs are realizing an estimated 80-percent gain in capacity, while reducing their antenna count by half and significantly cutting CapEx and OpEx spending. The architecture of the sector-sculpting Twin Beam antenna, shown in Figure 3, uses a Butler matrix to split the input power and feed each of the four independently controlled column arrays. Dielectrically loaded elements on the phase shifters, created by CommScope during the development of the company’s patented remote electrical tilt (RET), enable WSPs to control phase shifting on the elevation as well as the azimuth plane. The circuit power dividers are standard off-the-shelf, solid-state 3 dB hybrid couplers. Applications for the Twin Beam include single and multi-band for GSM, 3G and LTE. High-band, low-band and dual-band models support all major mobile technologies in the 698–894 MHz, 824–960 MHz and 1710–2170 MHz bands, as well as 2 x 2 multiple-in multiple-out (MIMO) technology.
Increasing capacity through pattern performance, signal strength and noise reduction Figure 4 illustrates the radiation pattern of a traditional 65-degree antenna, and the two narrow beams generated by the Twin Beam antenna. Important characteristics to note include the difference in sector overlap between the beams and the consistent position of the null fill at approximately –9 dB. Figure 4
Three-Sector 65°
Twin Beam 38°
Figure 5 shows the pattern of a single 65-degree antenna, in red, overlaid on the patterns created by a Twin Beam antenna. As indicated by the patterns, the two narrow beams produced by the Twin Beam antenna exhibit wider coverage at the sector edges, more rapid pattern roll-off, and improved front-to-back ratio. This also enables providers of spectrum-limited GSM systems to employ a more aggressive back-to-back reuse of their broadcast control channel (BCCH).
7
Figure 5
Of particular note is the approximate 2–3 dB of increased gain at the boresite generated by the Twin Beam compared to the 65-degree antenna. For WSPs using advanced modulation schemes such as High-Speed Downlink Packet Access (HSDPA) and LTE, the increased gain extends 16 and 64 QAM capacity further toward the sector edge. The improved throughput yields higher quality of service for the customer. It also enables mobile devices to operate on less power, further reducing interference levels. The sector overlap, critical for increasing capacity, remains constant with the Twin Beam. Both beams are generated from the same radome and precisely engineered to maintain consistent overlap and null fill. In a traditional three-sector or six-sector site, each antenna must be accurately aligned in order to achieve overlap consistency. As previously noted, alignment issues due to human error are common in deploying any sectorized antenna solution. PIM is also of particular concern in 3G and 4G LTE networks where noise suppression is critical in order to reduce mobile power levels and associated uplink interference. It is important to remember that PIM is a systems issue; two or more passive components are required in order to create the disruptive intermodulation. Therefore, PIM must be controlled throughout the entire RF path. In the Twin Beam antenna system, CommScope achieves this through a rigorous and proactive manufacturing program that includes extensive PIM testing on every component, including the antenna. The program also provides PIM training and certification for customer and third-party installers. The ability of the Twin Beam sector-sculpting solution to effectively reduce PIM long term also speaks to the importance of viewing the antenna as an entire RF system, including cabling, connectors and any other passive components such as combiners and filters.
8
Reduced loading at the top of the tower A single Twin Beam antenna has the same approximate physical dimensions as a single 33-degree antenna, for a given frequency range. At the top of the tower, the weight and wind loading are essentially the same as well. For capacity-strained sites, WSPs can simply replace the three existing 65-degree antennas with three Twin Beam antennas and immediately realize dramatically improved capacity — on the order of 70 to 80-percent. Because the antenna count remains the same, no new lease requirements or lengthy zoning approvals are required.
Success story: Twin Beam turns antenna competition into a solutions showcase In late 2011, a major U.S. carrier was looking to add capacity within its core network in a key metro market. Coverage was being provided by a cluster of high-profile, three-sector urban sites operating in the 850 MHz and 1900 MHz bands. Nearly all of the sites were reaching their UMTS capacity limits. To generate added capacity at critical sites, the carrier was evaluating a variety of sectorsplitting solutions that would affect one sector at each site. The specific market represents a high-revenue opportunity for the carrier, so time to market was also a key concern. CommScope was one of three RF solutions providers asked to participate in the process. Working with its design simulation partner, Telecom Technology Services, Inc. (TTS), CommScope began by analyzing the carrier’s traffic patterns and capacity requirements. This involved simulating network loads and conducting pre-implementation drive testing, not just at the cell level, but at the cluster level as well. Based on their preliminary assessment, CommScope and TTS developed a robust strategy featuring the Twin Beam six-sector antenna solution. Beyond the advanced sector-splitting technology, CommScope was also able to provide the necessary RF path components, engineering design and project management for a turnkey solution. “The selection process started out as an antenna-only comparison, but the ability to deliver a turnkey capacity solution within the customer’s timeframe and budget soon became a key driver,” said Mike Wolfe, CommScope Regional Sales Manager.
Improvements across the board “Once we were able to show how we could help improve performance across the entire system, the process became less of an antenna comparison and more about who could provide the best turnkey solution.”
TTS ran simulations for the targeted sites in order to quantify the expected gains when switching from the existing traditional three-sector configuration to the six-sector Twin Beam. Simulations modeled 3G UMTS and 4G LTE environments. Figures 6 and 7 illustrate the results of two UMTS simulations: Cell A, operating in the 1900 MHz frequency and Cell B, operating in the 850 MHz frequency. Figure 6 indicates the ability of the Twin-Beam antenna to reduce the soft hand-off areas within a given sector. Once the percentage of soft hand-off areas between the left and right beams are averaged, the total sector shows a 3.69% decrease in sector overlap.
9
Figure 6: Percentage of soft hand-off areas1 (within sector) Existing sector Cell A 1900 MHz Cell B 850 MHz 1
41.74
47.1
Split sector Twin Beam 40.29 (left beam) 35.81 (right beam) 38.41 (left beam) 43.73 (right beam)
Reduction in soft hand-off area –3.69
–6.03
The combined soft hand-off areas within a given sector, expressed as a percentage of the sector’s total coverage area.
Figure 7: Radio Resource Efficiency1 Existing sector Cell A 1900 MHz Cell B 850 MHz
1
53.4
65.32
Split sector Twin Beam 54.33 (left beam) 76.11 (right beam) 56.35 (left beam) 69.52 (right beam)
Aggregate change x2.44
x1.93
The percentage of a radio’s coverage area in which it is identified by mobile devices as the primary or serving radio.
Figure 7 illustrates the expected gain in radio resource efficiency. Radio resource efficiency is defined as the percentage of a radio’s coverage area in which it is identified, by mobile devices within the coverage area, as the primary or serving radio. When the existing sectors —Cell A and Cell B — are split, the radio resources available to handle traffic more than doubles in Cell A and nearly doubles in Cell B.
Figure 8
10
The 4G LTE simulations indicated significant advantages in deploying a Twin Beam six-sector solution in areas with high traffic loads. Figure 8 shows that, in a Twin Beam versus traditional three-sector deployment, the difference in peak user throughput increases as the sector load increases. This is primarily due to the Twin Beam’s ability to maintain a cleaner RF environment. TTS also simulated the effect of the Twin Beam on pilot pollution, a key contributor of interference. As shown in Figure 9, the results indicated a significant improvement in the ratio of pilot pollution removed (green) versus pilot pollution added (red). Another key benefit to note is that, as capacity and throughput increased at each individual site, performance across the entire cluster improved. This was due in part to the ability of the Twin Beam antennas to clean up inter-sector interference and reduce noise levels. As a result, the cell clusters showed improvements in the dropped call rate (DCR), received signal strength and system availability. “Once we were able to show how we could help improve performance across the entire system, the process became less of an antenna comparison and more about who could provide the best turnkey solution,” Wolfe added. Figure 9 Number of Bins Before
Number of Bins After
160
3.8
140 120
3.6
100
3.4
80 3.2
Percent
Number of Bins
Right Beam 4
60
3
40
2.8
20 Number of Pilot Polluters Number of Bins Before
Number of Bins After
160
3.8
140 120
3.6
100
3.4
80 3.2
Percent
Number of Bins
Left Beam 4
60
3
40
2.8
20 Number of Pilot Polluters
11
Making the complex simple Implementing a traditional six-sector solution involves greater complexity, such as additional RF connections and the need for more accurate antenna alignment. As an end-to-end provider who could design, engineer, install and support a turnkey solution, CommScope was able to simplify an otherwise complex process. In addition to demonstrating the capacity gains from the Twin Beam antennas, the CommScope team created a validation package that included key performance indicator (KPI) reports and post-installation drive testing in order to document the performance improvements. To further improve system performance, they also recommended modifications to cells outside the scope of the project and designed a construction plan with the assigned installation company. The project was backed by the company’s comprehensive RF Path Warranty. In the end, the implementation was successful, not only on the strength of the Twin Beam antenna, but also because of CommScope’s ability to effectively address the project’s entire ecosystem. “It really came down to close collaboration with the carrier to ensure their technical, budgetary and scheduling goals were achieved.,” Wolfe said.
The bottom line is higher quality of service Obviously, creating increased capacity and keeping ahead of the data tsunami are both means to a greater end: increasing quality of service (QoS). In a July 2012 study by Comptel Corp.9, more than one in five respondents said they had experienced poor QoS, such as dropped calls, low bandwidth or slow loading of files at least once a week. Over two thirds said they felt “neglected” by their WSP. About 40 percent said they planned to switch WSPs within the next 24 months as a result. On the positive side, customers have consistently voiced a willingness to pay more for better QoS. A recent Comptel survey indicated that, worldwide, sixty percent of respondents would pay more for better and faster service. In the U.S., studies suggest that customers would be willing to pay as much as $10 a month more for more reliable connections, faster download speeds and a more seamless user experience. For WSPs, increasing the QoS means ramping up capacity — now. Increasing capacity using traditional methods of cell densification and the addition of antennas is expensive and time consuming. The Twin Beam sector-splitting solution is a fast and proven approach to quickly add capacity at their most critical sites. Twin Beam enables WSPs to significantly increase capacity without substantially increasing costs. At the same time, it can improve throughput, allowing customers to take advantage of faster data speeds throughout more of the network. The result is not only better, faster and more consistent QoS, but lower churn and greater potential for attracting new revenue from additional subscribers. Ultimately, WSPs will succeed by continuing to increase their average revenue per user (ARPU). Innovative strategies like CommScope’s sector-sculpting Twin Beam should be an important part of the solutions mix.
12
References Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2012–2017, Cisco, Feb. 2013
1
Global Mobile Broadband — The Fast Growth of LTE, Paul Budde Communication Pty Ltd, March 12, 2013
2
AT&T to Buy Spectrum From Verizon for $1.9 Billion, Scott Moritz and Todd Shields, Bloomberg, January 25, 2013
3
Managing Wireless Network Capacity, FierceWireless, May 2012
4
Madden: Small cells will carry more capacity than macros, Joe Madden, Fierce Broadband Wireless, March 27, 2013
5
Smart Cells and Wireless Capacity Growth, Agilent Technologies, Moray Rumney, May 26, 2010
6
CDMA Six Sector Cell Applications Handbook NBSS 7.0, Nortel, 1998
7
The Impacts of Antenna Azimuth and Tilt Installation Accuracy on UMTS Network Performance, Esmael Dinan, Ph.D., Aleksey A. Kurochkin, Bechtel Telecommunications Technical Journal, Vol. 4, No. 1 January 2006
8
Report: Want to Hold on to Subscribers? Show Them ‘More Love’, Andrew Burger, Telecompetitor.com, 2/22/12
9
www.commscope.com Visit our website or contact your local CommScope representative for more information. © 2013 CommScope, Inc. All rights reserved. All trademarks identified by ® or ™ are registered trademarks or trademarks, respectively, of CommScope, Inc. This document is for planning purposes only and is not intended to modify or supplement any specifications or warranties relating to CommScope products or services. WP-106683-EN (05/13)
