Bi-Sector Array W-CDMA Deployment

Introduction Higher Order Sectorization has been used successfully on 3G (W-CDMA, UMTS, HSPDA) and 2G (CDMA) systems to increase capacity, i.e. using 3 to 6 sectors per site. Growing the number of sectors on a W-CDMA site is the most cost-effective way to increase the capacity of a network when compared with other options such as new site builds. However, current 6-sector techniques require significant site re-engineering, both to the site being upgraded and to the surrounding adjacent sites. The extensive site changes needed to introduce 6-sectors have often been found to be prohibitive. TenXc's Bi-Sector Array (BSA) is an innovative solution for operators to address capacity and quality challenges found in high-capacity macro cell site applications. TenXc's BSA uses an advanced phased array design to improve the efficiency of 6-sector sites and also to significantly reduce the need for optimization and network changes. A single BSA emits two unique asymmetric beams, each shaped so that, as a pair, they match the same coverage provided by an antenna of 65° horizontal beamwidth (which is most commonplace in 3-sector site deployments). Moreover, the beams are shaped such that the overlap between the two patterns is optimized, and the outsides of each beam quickly rolls off. This increases the capacity gains of W-CDMA systems by decreasing the interference generated between sites and minimizing the soft and softer handover losses.

The unique phased array design allows for a single ‘antenna’ to produce two asymmetric beams (each approximately 33o in

beamwidth), effectively reducing by half the number of antennas needed to expand from a 3-sector site to a 4, 5, or 6-sector site. This also reduces the lease and site impacts of upgrading current 3-sector sites since the total antenna count remains unchanged. Expanding the existing capacity of a system is much more effective, from both an initial CAPEX investment requirement and also for on-going OPEX, rather than building new sites or adding carriers.

Overview of Capacity Solutions for W-CDMA • Building new sites is costly, time-

consuming, and becoming harder due to zoning issues

• Traditional 6-sector solutions require increased antenna counts and require significant optimization effort

• Carrier additions require multi-site deployments to reduce inter-frequency handover issues

TenXc Approach • Optimum 6-sector solution: same

antenna count, minimal optimization • Reduced CAPEX and OPEX • Avoids costly carrier additions and

reduces inter-frequency handover issues

• Up to 54% site savings for Greenfield roll-outs

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The Bi-Sector Array Advantage

The Traditional 6-Sector Approach Expanding the capacity of a W-CDMA site by adding more sectors is well documented as an efficient method and has been used extensively in W-CDMA networks worldwide. Traditional approaches use narrow beamwidth (33° antennas) to build 6-sector deployments with an increase in capacity over a traditional 3-sector site by about 1.7 times. The doubling of the number of sectors has never led to a doubling of capacity due to the increased interference introduced by the new antennas and the increased soft and softer handover losses. In addition, upgrading a 3-sector site to 6-sector raises a large number of practical issues:

• Antennas are doubled on the site: a minimum of 6 antennas are needed

• Three additional antenna mounts and orientations are needed, increasing lease costs for the site and often requiring building or planning approval

• Orientations of sectors is needed to maximize coverage within a 6-sector area

• Orientations do not match or compliment 3-sector adjacent sites

• Coverage holes may be apparent despite the increased gains of the narrow beam antennas

• Full 6-sector conversions are needed to ensure coverage is maintained

Figure 1: Network Upgrade using Standard 6-Sector Design

Despite the engineering drawbacks of traditional 6-sector deployment, they have been used extensively in most W-CDMA networks as the most cost effective way of deploying additional capacity to high traffic areas.

The Bi-Sector Array 6-Sector Approach The Bi-Sector Array, by contrast, has been optimized to fit in to the existing coverage area of 3-sector sites and presents a unique upgrade strategy to 6-sectors. A typical pair of horizontal patterns of the BSA are shown in Figure 2. The asymmetrical beams preserve the composite coverage requirement of the original 65° area by virtue of slow roll off of the outer edges of each of the two beams. The inner contours of the beams, however, have been created to minimize interference, together with the low side lobes and high front-to-back ratio. The Bi-Sector Array uses advanced phased array technology to produce both the left and right beam from a single ‘antenna’ with ±45° polarizations producing a ‘two-in-one’ package. The unique shape of the BSA allows for a single sector to be upgraded without requiring any changes to surrounding sites: the BSA matches the existing coverage without changes to other sites. Expanding the BSA to all 6-sector sites results in a more efficient upgrade strategy for W-CDMA networks with the BSA offering the following advantages:

• No increase in the number of antennas required: a minimum of three BSAs are required for a 6-sector site

• No change in the antenna mounting requirements: the BSA directly replaces the existing antennas and reuses these mounts

• No change in the lease requirements of the site or the need for re-approval of the site

• No change to the surrounding sites reducing the optimization requirements and costs

• Ability to upgrade single sector or multiple sectors as traffic demands

Figure 3: Network Upgrade using Bi-Sector Array

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Figure 2: Left and Right Standard BSA Beam Patterns

Performance Advantages The Bi-Sector Array has been optimized to minimize interference in W-CDMA networks and also reduce the soft and softer handover loses. The BSA has been shown to offer significant capacity increase over standard 6-sector systems and to offer more than double the capacity of current 3-sector systems.

The BSA has been deployed in many different CDMA networks and in different deployment scenarios as summarized in Table 1. Simulations confirm that W-CDMA systems will achieve the same performance gains. The performance in the field of the BSA has been verified to offer the following:

• Up to 2.3 times capacity improvement for 3-sector sites

• Up to 35% improvement in capacity for upgrades to 6-sector sites

• Improved Key Performance Indicators: Drop Call Rates, Call-set up

• Improved coverage

In addition, the Bi-Sector Array requires little or no optimization of the surrounding sites, and for 3-sector upgrades, does not require any changes to the site apart from the addition of the extra Tx equipment.

Pictures of typical BSA deployments are shown in Figure 4 and Figure 5.

City Country Upgrade Scenario Result

Montreal Canada 3-sector to BSA conversion Between 2.3 and 2.8 times capacity increase, improved Drop Call Rates.

Delhi India 6-sector to BSA conversion Improved capacity by 30%, improved Ec/Io, Softer handover improved from 32% to 14%

Dallas USA 3-sector to BSA conversion Capacity increased by 1.95 times, improved Drop Call Rates.

Detroit USA Two sectors of a 6-sector site upgraded 10% improvement in capacity

Miami USA Two sectors of a 6-sector site upgraded

15% improvement in capacity, 5% increase in coverage

San Jose USA 6-sector to BSA conversion Over 35% increase in capacity. 50% Improvement in drop call rates

Quebec Canada 3-sector to BSA conversion 2.1 times capacity improvement

Jaipur India 6-sector to BSA conversion 10% capacity improvement (prototype antennas)

Figure 5: 850/900 BSA on tower, India

Figure 4: 850/900 BSA (standard 33° antennas in foreground),

India

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Table 1: CDMA Deployment Summaries

Deployment Options

Existing Operators – Avoiding New Capacity Sites

The Bi-Sector Array can be used to boost capacity of existing sites that have reached maximum traffic carrying capability. For such sites the traditional approach is to build one or more new sites in the area and reduce the coverage area of the original site using increased antenna tilts or power reductions. Building new traffic sites is very expensive and time consuming and leads to an increase in the cost of running the networks (OPEX) with continuously increasing site rental and associated back-haul requirements. Expanding a site to 6-sectors using BSAs achieves the same traffic capacity as a new site and has a significantly lower effect on the OPEX of the network. Using figures from typical urban sites in India, the BSA has been shown to offer the lowest cost of providing capacity in an area both from a capital expenditure cost (CAPEX) and operating cost (OPEX). Using the BSA to expand capacity in an area is 20% more efficient for CAPEX and 40% more efficient for OPEX. These savings are for rooftop sites where towers and infrastructures are not needed. For towers, there is a savings increase to 35% for CAPEX.

Cost Comparisons

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rlang

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Figure 6: CAPEX and OPEX Comparisons

Deployment Scenario For an existing operator with high traffic areas the BSA would be used to build 6-sector high traffic sites in lieu of building new capacity sites. It is expected that between 20 and 25% of core traffic sites would be converted to BSA working in a mature network to provide maximum capacity benefits.

Existing Operators – Carrier Balancing W-CDMA systems need to perform a “hard handover” when different frequencies (carriers) exist in adjacent cells. In W-CDMA systems, a significant proportion of dropped calls are associated with the handover process (Huawei estimates that 90% of dropped calls occur during handover) and operators need to avoid large numbers of inter-frequency handovers. When deploying multiple carriers in a network, operators need to deploy the same number of carriers to more sites than is needed purely from traffic reasons, in order to reduce the number of inter-frequency hard handovers. For example, if two sectors in a network justify the addition of more carriers due to traffic reasons, the operator will need to deploy extra carriers to more sectors in the area in order to avoid performance issues from handover.

Figure 7: Multiple Carriers Additions in a Network

Figure 8: Using BSA to Upgrade Capacity

The BSA can be used to add capacity directly to the “hot-spot” area. The unique shape of the BSA, which matches the existing coverage footprint of a standard 65° antenna, allows single sectors to be upgraded as required. Adding a BSA to a site and doubling the number of sectors is equivalent to doubling the number of carriers on a site. Adding BSAs to the high traffic sites in preference to upgrading a large number of sites with additional carriers is highly cost effective. Deployment Scenario For an existing operator with high traffic areas the BSA would be used to build 4, 5 or 6-sector high traffic sites in lieu of adding carriers to a significant numbers of sites. When an area is fully 6-sector, additional carriers can still be added to sites in the area to add network capacity.

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New Operators – Reducing Sites Required for Deployment W-CDMA systems are initially Up-Link (reverse-link) limited, i.e. the coverage of the site is defined by the Up-Link power budget as shown in Figure 9. As the number of users increase the maximum available link budget decreases. For the Up-Link the main influence is the Noise Rise Associated with the users within the same cell. The effect of the Noise Rise in decreasing the link budget of the site, results in the coverage of the site decreasing as it accepts more traffic. For both CDMA and W-CDMA systems, an upper limit for Up-Link Noise Rise needs to be decided upon at the planning stage so that the cell does not shrink beyond an acceptable level. Normally the design level for W-CDMA systems is set between 50% or 75% of full capacity. With BSA 6-sector systems the carried traffic is split between the two sectors and hence the number of users in each sector is halved. This has a dramatic effect on the Noise Rise in the system. The Noise Rise of the Up-link is shown in Table 2. A system that is designed for an Up-Link loading maximum of 50% will have 1.8 dB higher link budget for a BSA sector than for a traditional 3-sector system. For a system designed for a 75% loading, the improvement in the link budget is 4 dB. Each Bi-Sector Array beam also has a higher gain than traditional 3-sector antennas (19.2 dB at 900 MHz, 19.3 dB at 1800 MHz), this being some 1.5 to 2 dB higher. The overall effect is to increase the link budget for CDMA and W-CDMA systems by between 2.8 dB and 6 dB. This significantly reduces the number of sites needed in a new build-out by up to 54%. Deployment Scenario For a new operator, the BSA would be used to build 6-sector sites in the core area where traffic growth is expected. The core of the networks would be built as fully BSA deployed 6-sector sites in order to reduce the number of sites needed. Expansion of the network would use new sites, as required, and use additional carriers, as available.

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160

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Figure 9: W-CDMA Link Budgets

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Loadings Normal NR BSA NR Link Budget Saving

5% 0.2 0.1 0.1 10% 0.5 0.2 0.2 15% 0.7 0.3 0.4 20% 1.0 0.5 0.5 25% 1.2 0.6 0.7 30% 1.5 0.7 0.8 35% 1.9 0.8 1.0 40% 2.2 1.0 1.2 45% 2.6 1.1 1.5 50% 3.0 1.2 1.8 55% 3.5 1.4 2.1 60% 4.0 1.5 2.4 65% 4.6 1.7 2.9 70% 5.2 1.9 3.4 75% 6.0 2.0 4.0 80% 7.0 2.2 4.8

Table 2: Up-Link Noise Rise

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Summary The TenXc Bi-Sector Array has been shown to be the most efficient antenna system for 3G and 2G based systems. The unique shape of the antenna array’ beams results in lowers interference in a system and focuses the radio energy exactly where it is needed and reduces the overlap and spill-over into other sectors. The array is a unique solution that allows for a direct one-for-one replacement for existing antennas in a standard cellular deployment, each array producing two beams. The coverage provided by the Bi-Sector Array matches the current footprint of a traditional sector and eliminates the need for adjacent site changes and optimization activities. The Bi-Sector Array increases the capacity of W-CDMA systems by over 2 times and has been shown to be more efficient than any other antenna system available. Further, significant cost and efficiency savings can be achieved by operators who implement the BSA and can lead to a minimum of 20% savings in capital expenditure when adding capacity and up to 40% savings in operational expenditures per site. Using the BSA can eliminate the need for deployment of multiple carriers in sites where the extra capacity is not needed. Deploying the Bi-Sector Array in lieu of additional carriers achieves higher capacity (more than doubles capacity) and avoids the issue of inter-frequency handovers increase where multiple carriers are deployed. The Bi-Sector Array can be used to directly reduce the number of sites needed in a new build. The BSA leads to up to 4 dB improvement in Up-Link Noise Rise and with the increased gains of the array can lead to an improvement in the available link budget of up to 6 dB. This can be used to reduce the number of sites that need to be built in an area up to 54%, significantly reducing costs and reducing the time taken to achieve a system launch.

About TenXc Wireless

Sculpting the Airwaves, Shaping the Future

TenXc Wireless is a leader in the development of performance-enhancing antenna products for mobile wireless networks . Leveraging unique beam-forming technologies and array design techniques, TenXc’s innovative solutions for improved spectral efficiency and signal quality enable service providers to profitably capture new service growth by addressing capacity, quality, and coverage constraints with reduced network costs and engineering time. TenXc’s products are based on over 30 years in the research and application of radio propagation, digital beam-forming, signal processing, and other radio frequency advancements for commercial satellite, mobile, and other wireless applications.

To learn more about how TenXc Wireless’ performance enhancing antenna products can improve your wireless network, please contact us today, or visit us at www.tenxc.com.

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