Svp Wp Final_jul09

Thinking in a New Dimension — Adding Vertical Sectors and Capacity in the UMTS Network

Quintel White Paper | July 2009

WHITE PAPER

Thinking in a New Dimension – Adding Vertical Sectors and Capacity in the UMTS Network

David Barker, Global CTO, Quintel and Keith Radousky, Americas CTO, Quintel

Table of ContentsExecutive Summary 3

The Capacity Challenge 4

Think in Another Dimension 5

SVP Benefits 7

SVP Economics 9

SVP Implementation 9

Quintel’s SVP Solution 10

About Quintel 11



Executive Summary

Global mobile data traffic is expected to double every year through 2013, a 66-

fold increase between 2008 and 2013. To keep up with the explosive growth,

wireless network operators are continuing to implement standard solutions

such as more sites, more spectrum and more sectors. The standard solutions

are not always possible because of zoning restrictions, tower loading and

spectrum limitations. While the challenges can be daunting, leveraging

Quintel’s antenna solutions to deploy Sectorization in the Vertical Plane (SVP)

is a proven and fast alternative, and provides significant benefits:

• Greater spectrum efficiencies giving increased capacity by up to 40%

• Significantly decreased/eliminated call blocking

• Increased data rates

• No additional antenna positions needed with Quintel’s SVP solution

• No additional spectrum required

• Lower capital and operating costs

• Efficient use of capital resources

• Increased revenue and reduced churn



There is an innovative and cost-effective approach to solve

capacity problems in UMTS wireless networks by adding sectors

in the vertical plane, or Sectorization in the Vertical Plane (SVP).

In dense urban areas, SVP also improves coverage and capacity

into tall buildings, while minimizing interference. The ability to

increase carriers’ capacity, quality and coverage leads to improved

customer satisfaction and lower churn.

The Capacity Challenge

Operators are aggressively migrating to new network air interfaces, such as UMTS, EVDO and soon LTE, to provide users with higher speed data, and higher quality of service. Increased network traffic and explosive growth in higher profit margin data usage are driving the investment. However, bandwidth availability, cumbersome regulatory processes, deployment delays, and the cost of adding new antennas (many towers are already loaded) are proving to be bottlenecks in the rollout process. For example, in some dense urban areas, it has become physically impossible to add more antennas. Consequently, operators have concluded that they need to look at more innovative ways to quickly and cost-effectively add multiple services using existing antenna real estate.

Sectorization in the Vertical Plane (SVP) implementation only involves swapping existing antennas for Quintel. SVP does not require any additional spectrum, azimuthal or horizontal antenna sector positions, or tower sites to add capacity in UMTS networks. With SVP, an operator can effectively squeeze more out of precious existing spectrum and leverage more out of existing sites by simply increasing the number of quality bits carried per hertz of spectrum per unit area. SVP can also be used to increase coverage into tall buildings where one vertical sector is directed upward toward the tall building(s), ensuring users in the building are in cell dominance, and another vertical sector is conventionally directed toward the street level.

By deploying SVP in congesting networks -- capacity is increased, network quality is improved, and coverage is enhanced -- and using Quintel solutions for SVP, this can then be deployed without adding additional antenna positions or other costly infrastructure.

“Operators have spent billions on 3G, and are reaping the benefits of increased data revenue. Operators are so worried about not having the fastest wireless network, that they will spend billions more on LTE and WiMAX.”

- Alan Nogee, In-Stat



Think in Another Dimension

SVP creates a cell-sector split in the vertical plane, producing an “overlayed” sector and an “underlayed” or smaller sector topology in the congested UMTS original sector. SVP can also be viewed as being similar to traditional overlayed/underlayed sectors, concentric cells, or frequency re-use partitioning techniques as used in GSM. Cell site selection criteria for SVP needs to consider the following:

• The efficiency of SVP increases when there is a significant proportion of traffic near the base station that can be absorbed by the newly created underlayed sector.

• The cell site must be tall enough (above average terrain and clutter height) to produce a “clean” non-scattered radio propagation cell- split in the elevation plane.

SVP benefits from using independent antenna tilt for the two vertical beams. Intercell site interference into the overall network is reduced by enabling spatial filtering in the vertical dimension where a significant proportion of the radiated power to and from adjacent cell sites is reduced or removed. This also provides for additional capacity at neighboring cell sites through the WCDMA soft capacity mechanism (the cell breathing effect which transfers served traffic between cell sites).

SVP creates the underlayed sector by simply adding an RF transceiver (an additional radio), and hence similar to when adding extra spectrum, e.g., F2 or F3 channels for capacity. But, SVP for UMTS can use the same carrier frequency, although with a different scrambling code as the existing or original UMTS cell.

RF isolation and coverage separation between the overlayed and underlayed sectors is achieved by separately and independently tilting the sectors in the vertical plane.

UMTS Overlay Cells

UMTS Underlay Cells



The overlayed sector is designed to have similar RF coverage as the current sector. The underlayed sector is designed with more downtilt in order to serve traffic near the base station, and thus off-loading traffic from the overlayed sector to create traffic headroom.

RF parameters are also optimized to shift traffic from the overlayed sector to the underlayed sector. The more traffic is shifted, the higher the capacity gain. This solution addresses both power and OVSF code exhaustion conditions (i.e., soft and hard capacity limiting cases). Capacity gains of up to 40% are possible in qualified cell sites.

When splitting in the elevation plane, there naturally will be intercell interference and softer handover overhead between overlay and underlay cells. Softer handover overhead consumes OVSF channelization codes. It is important to note, however, that the total OVSF channelization codes have been doubled within the original sector footprint. Although softer handover overhead increases as a percentage for each of the split cells when compared to the softer handover overhead percentage for the original sector, we still have created significantly more OVSF codes to serve traffic, although this won’t be exactly double.

Intercell interference (Ec/Io quality for downlink and noise rise for uplink) will be re-distributed when compared to the original sector. As there will be a reduced number of users served per split cell, this will reduce the underlying uplink noise rise per cell. Users close to the cell will be in dominance of the underlay and will receive an improved Ec/Io; users at the cell edges will not “see” a downlink interference component associated with traffic transmission power to users served on the underlay cell. However, if a particularly significant traffic load is or can be generated within the softer handover boundary between overlay and underlay, then Ec/Io quality could be reduce in this region.

However, from a network optimization point of view, it is generally more desirable that users at the cell edges (who also see interference components from surrounding cell sites) have an adequate Ec/Io. Therefore, SVP can be viewed as re-distributing Ec/Io with the aim that cell edge quality can be improved, thereby making HSDPA throughput more “equitable” across the original sector footprint.



Cell splitting can be best optimized using variation and tuning of cell parameters such as: • Cell CPICH power for both overlay and underlay sectors.• Cell level softer handover offset variables or cell-preference variables to artificially

increase or change traffic served on the underlay. RAN variables normally exist for both idle and connected modes.

• Sector mechanical tilt. • Independent electrical tilt for overlay and underlay sectors.• The use of ACP tool or process, which can consider all interactions of variations

of antenna patterns, CPICH powers, traffic, softer handover overhead and intercell interference across a cluster of cell sites, can also be used as part of a cell site selection or network design.

In addition, SVP gains can be further optimized by taking advantage of any natural terrain undulations, or more specifically, the traffic distribution over terrain height and clutter variations, and variations in adjacent cell site antenna heights. For example, traffic close into the cell site which is also below-average terrain height should reveal additional gains for SVP (i.e., deployments where “null-fill” antennas would be normally deployed), and in the SVP case, could be considered as an enhanced, optimized or active “null-fill” application.

By deploying SVP to congesting sectors, not only is capacity increased, but the network quality is improved due to less overall intercell site interference, particularly at cell edges and close into the site. Furthermore, SVP can be deployed in dense urban applications to ensure that upper floors of surrounding tall buildings are in cell dominance using one vertical sector, while at the same time ensuring existing street level and lower floor coverage is maintained. By deploying SVP, subscribers experience less blocking, fewer dropped calls, and higher data rates, thereby lowering churn.

SVP Benefits

1. SVP preserves overall cell and sector tessellation geometry of the network which other capacity enhancing techniques compromise such as adding sectors in horizontal plane (azimuthal cell splitting) or adding interstitial sites (classic cell splits). SVP permits much simpler neighbor list planning and neighbor re-optimization than with other techniques. With proper optimization of the SVP via CPICH and electrical tilt variations, no change in existing network “coverage” and original cell site boundaries can be readily achieved.

2. Unlike adding sectors in the horizontal plane, Quintel’s SVP solution requires no additional antennas, no increase in antenna width (required to create narrower, e.g., 33o azimuthal beamwidths), or additional horizontal plane antenna sector positions.

3. Quintel’s SVP is optimal for restricted or antenna limited sites with respect to wind loading, rentals, lease, rent or zoning costs and delays.



4. Since traffic demand across the UMTS network can be “lumpy,” SVP is ideal for “problem sites” which carry higher traffic than surrounding cell sites. SVP can solve capacity issues on a per sector (surgical) basis without disruption to neighbor sectors at the cell site or even for the entire cell site, creating up to six sectors (3 underlay and 3 overlay sectors). SVP in high traffic sectors creates a more equally loaded cluster of cells (load-balancing) which is a key UMTS network optimization technique. This load balancing is additionally enhanced due to the WCDMA soft capacity mechanism. Thus, SVP provides for better overall utilization of UMTS spectrum at a sector level, cell level, and over a cluster of cell sites.

5. SVP requires no additional spectrum and better utilizes existing spectrum within the same area.

6. SVP can be deployed in approximately two weeks (including design, installation and optimization) versus an additional RF carrier which takes much longer (several months) due to spectrum clearing in spectrum-liberalized markets where GSM spectrum needs to be re-farmed to make room for more UMTS spectrum (e.g., U.S. markets, and UMTS900 markets in Europe). With Quintel’s SVP, the limiting factor is not the antenna.

7. Quintel’s SVP is compatible with maintaining or re-enabling space diversity configurations (where there are two antenna positions per sector) on antenna-limited sites.

8. GSM/GPRS/EDGE network performance will not suffer by deploying SVP, in spectrum- liberalized markets. Re-farming to free up another 5MHz too early for an additional UMTS carrier will likely cause significant degradation of the GSM/GPRS/EDGE network which will increase churn.

9. SVP grows with the network. When the initial SVP configuration (F1 overlay/F1 underlay) exhausts, UMTS F2 can be deployed. The SVP configuration can then be leveraged to tilt the UMTS F2 independent of UMTS F1 to achieve better load balancing. This ability has been deemed desirable to better optimize the F1/F2 configuration.

10. The SVP underlay/overlay antenna system can also be applied to enhance GSM spectral efficiency by creating a GSM cell-sector split, thus ensuring GSM capacity and QoS are optimized. This may be useful in GSM only spectrum-limited markets (e.g., India), or alternatively in spectrum-liberalized markets when UMTS F2 is eventually re-farmed, thus the remaining GSM channels can then use the SVP configuration to ensure GSM spectral efficiency is maximized..

11. SVP can be deployed in dense urban areas to improve cell dominance coverage into surrounding tall buildings.

12. When an additional F2 UMTS carrier is ultimately required, all SVP radio equipment and antennas can be leveraged, thus decreasing the time-to-market for the additional UMTS carrier. When sectors with F1 & F2 begin to experience capacity blocking again in the future, SVP can be applied again to create F1+F2 overlay/F1+F2 underlay, thus delaying the need to re-farm for an F3 UMTS channel (if at all possible), and so on.



SVP Economics

SVP cost-effectively increases UMTS capacity and quality in congested cell sites or individual sectors, thus deferring spectrum clearing engineering effort and cost in spectrum liberalized markets where, for example, GSM and UMTS share the same band. The longer additional UMTS carrier deployment is deferred, the more capital and operating expenses are reduced. SVP is a no-risk, high-reward endeavor that enables operators to lower cost, increase revenue, and improve network quality. Valuable UMTS spectrum is used more efficiently at all levels: per sector, per cell site, per cluster, over the network.

Deploying SVP has the same UMTS Node B equipment requirements as if adding another UMTS carrier or adding another sector through a conventional azimuthal sector cell-split. The advantage with SVP is that spectrum does not have to be cleared, and with a Quintel SVP solution, no more additional antenna positions have to be used. This will help maintain GSM/GPRS/EDGE quality and capacity, thus helping to control churn. Also, as time goes by, more GSM usage will offload to UMTS, thus easing spectrum clearing pain when it must be done. Accordingly, deploying SVP has no write-off of equipment.

SVP Implementation

SVP can be implemented quickly and easily by either:• Adding an extra conventional antenna in the blocking sector having a different tilt

angle to the existing sector antenna• Alternatively, Quintel antennas with dual tilt capability per array are the only practical

solution when the number of antenna positions is limited. In particular, if spatial diversity is required and/or needed to maintain the critical capability of separating tilts on GSM and UMTS (to maximize the flexibility to optimize each service) in spectrum- liberalized markets, then Quintel solutions are unique.



The figure below depicts one example of using a Quintel triple-array antenna to deliver existing GSM900 or 800 band service plus SVP for UMTS2100 and SVP for GSM1800, supporting the “on-air” combining of up to 8xTRX for GSM1800.

Because Quintel’s SVP requires no additional antenna positions, operators can implement new services quickly.

Quintel’s SVP Solution

Operators should include SVP to their rollout tool-kits as an option for adding sectors to increase UMTS capacity, increase quality and improve coverage in tall buildings, either with additional existing conventional antennas or with the Quintel Independent dual-Tilt Antenna System in antenna limited cases.

Quintel excels in overcoming the challenges of spectrum band liberalization, spectrum re-farming, and increasingly constrained (physical, legal/regulatory, or economic) sites.

Quintel solutions enable

global wireless operators to

increase QoS, rapidly deploy

new services, and realize

cost savings of up to 40%.

About Quintel

Quintel is a leading innovator in the design, development, and delivery of network-efficient antenna independent tilt solutions for wireless operators worldwide. Our products and services overcome prior limitations of network deployment to maximize your investment in wireless infrastructure.

In 2007, Quintel was spun-out by QinetiQ, a world-class research and development organization with hundreds of technical innovations. As a privately held company, Quintel and its investors share an unwavering commitment to commercialization of pioneering innovation. Quintel has enabled the development of next-generation wireless antenna solutions for an ever-expanding global wireless market. Quintel holds over 140 combined patents in 20 countries, and serves many leading global wireless operators across the Americas, Europe, and Asia. Quintel operates headquarters offices in Mountain View, California and Bicester, United Kingdom, with additional points of presence in the Americas, Europe, and Asia.

AmericasT: +1 (650) 353-4240F: +1 (650) [email protected]

Technical Support (Americas)T: +1 (602) [email protected]

EMEAT: +44 (0) 1869 362 960F: +44 (0) 1869 248 205 [email protected]

Technical Support (EMEA)T: +44 (0) 1869 362 [email protected]

For general company information, please email: [email protected]

© 2009 Quintel Technology Limited. All rights reserved. Quintel and the Quintel logo are registered trademarks and New Dimensions in Wireless and QTilt are trademarks of Quintel Technology Limited.

www.quintelsolutions.com

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