Addressing the Challenges and Needs of the Wireless Network Installation and Maintenance Market

For today's Wireless Service Provider (WSP), deploying wireless networks is no easy task. At each step in the process (e.g., installation of site equipment, optimization/troubleshooting, network design, site construction, and base station configuration) problems can occur which threaten to hamper the WSPs ability to deliver continuous and stable service at a high level of Quality of Service (QoS). Problems can also occur during network maintenance. Fifty to sixty percent of cell site problems, for example, are caused by faulty cables, connectors and antennas. Interference is another major source of problems. Routinely testing a cell site's cables, filters, antennas, amplifiers, and troubleshooting any internal and external interference is therefore absolutely critical to ensuring an optimized base-station installation and maintaining optimized operation of wireless networks in the field.

Today's increasingly complex wireless networks and soaring operating frequencies, from sub-GHz levels up to 5.8 GHz, complicates this task, forcing the WSP to deploy and maintain more cell sites to cover the same size coverage area in the same amount of time

While traditional handheld installation and maintenance (I&M) test solutions can be used to address the required testing, they often consist of multiple boxes, meaning there are more things the engineer must learn how to use, keep track of, and in some cases, correlate results across. These solutions simply don't offer the speed, productivity and flexibility required to meet the increasingly demanding needs of today's RF field engineers and technicians. What's required is a fast, highly-integrated, multi-functional, and reliable tester that can effectively tackle today's increasingly complex wireless networks in less time.

The I&M market is today driven by consumer demand for wireless multimedia service which, in turn, is helping to define wireless broadband needs for third generation (3G) technology and beyond. To answer this demand, Network Equipment Manufacturers (NEMs) have introduced a range of sophisticated new 3G/3G+ wireless communication technologies (e.g., UMTS, HSDPA, HSUPA, WiMAX™, and 3GPP LTE) capable of handling the packet size (PS) data traffic required for high-speed data connections. The introduction of these technologies has brought about a number of key changes in the wireless service market, not the least of which is that voice call has become a commodity. Additionally, NEMs have been relegated to more of a consultant role, while WSPs now sit at the top of the food chain, driving technology adoption, service models, equipment costs, and testing requirements. WSPs want to grow data traffic in order to sell value-added services like video share to consumers, but at the same time are challenged to find properly-trained RF engineers to ensure cell sites are optimized to handle such services.

In the midst of these changes, the wireless communications industry is itself undergoing an evolution with the 3GPP, 3GPP2 and 802.x standards organizations each working to define new broadband standards for the next-generation communication platform (Figure 1). While WSPs much prefer technology evolution to an industry-wide revolution, it does not come without a price. Consider, for example, the evolved 3GPP network architecture. What began as GSM, a popular worldwide 2G standard for mobile phones, evolved to support higher data rates via GPRS. Support for increased data transmission rates and improved data transmission reliability was later added via EDGE. GSM then evolved into its 3G version, UMTS. HSPA was added to extend and improve the performance of existing UMTS protocols. LTE, a 4G version of UMTS, is currently in development and will further improve the UMTS standard to cope with future technology evolutions.

Due to these evolutionary changes, many networks today consist of three to four technologies on two to three different frequency bands. This complexity means that handovers between the networks are now more challenging than ever before and has resulted in interference becoming the main culprit of network failures. With fewer properly-trained RF engineers available, effectively dealing with problems like interference and others has become all the more challenging.

The growing demand for wireless multimedia service, coupled with the increased complexity caused by the digital wireless evolution, has placed increasing pressure on the WSP. Much of this pressure comes from the fact that operating frequencies are getting higher, while base stations are getting more complex, supporting multiple technologies and incorporating such new technologies as Multiple-Input Multiple Output (MIMO). At the same time, base stations are migrating to a smaller, faster, cheaper design--all of which means that more functional tests are required to ensure optimal network operation.

These trends further exacerbate an already complicated wireless network I&M process and add to the list of common culprits of failures in cell sites. At the top of the list are RF issues related to cable and antenna degradation, and antenna down tilt. Degraded feed lines cause poor coverage, unnecessary handovers, paging failures, and access failures on the uplink. Interference (e.g., from co-channel, adjacent channel, inter-modulation, external, and internal) is another common culprit. Downlink interference reduces coverage and results in dropped calls, while uplink interference causes access failure. Interference has a direct impact on the QoS of wireless communication services.

Other common causes of failures in cell sites stem from damage to filters and tower-mounted-amplifiers (TMAs), errors in radio settings and configurations, transmitter performance degradation, and receiver sensitivity degradation. Problems can also occur when the reference clock is out of sync, resulting in island cells and hand-over failures. Backhaul transmission is another source of faults, with T1/E1 breakdowns being the most common defect in a cell.

Dealing with this mounting list of potential problems, and the lack of skilled RF field engineers and technicians requires a test solution that is able to quickly, accurately and easily conduct a number of key measurements, including:

• Cable and antenna test (e.g., VSWR and return loss measurements)
• Distance to fault (DTF) measurements
• Filter and TMA measurements
• Transmit power measurements using a power meter
• Spectrum analyzer-based power measurements (e.g., channel power, adjacent channel power and occupied bandwidth (OBW))
• Interference analysis (e.g., spectragram and signal ID)
• Transmitting signal quality measurements

In addition to these measurement needs, today's RF field engineers and technicians also require a means of quickly calibrating their cable/antenna tester. As with any test instrument, adding a device to the test port (e.g., a jumper cable or adapter) requires the tester to be recalibrated using a calibration kit. Carrying the necessary kits into the field and recalibrating every time a device is added can be both cumbersome and time consuming. Utilizing an I&M test solution with the flexibility to handle this requirement, as well as the range of measurements previously mentioned, is key to avoiding service-quality problems and maintaining a high QoS.

Agilent Technologies' FieldFox RF Analyzer uniquely supports the key measurements required by today's WSP (Figure 2). As the most integrated handheld instrument for wireless network I&M available on the market today, it combines cable/antenna analysis, spectrum analysis (100 kHz to 4 or 6 GHz), power meter measurements and vector network analysis into one rugged, compact and lightweight package. This not only makes field operation simple and reliable, but enables the RF engineer or technician to carry just one tool into the field.

FieldFox's unmatched sweep speed reduces time-to-problem resolution with test times over 50 percent faster than other currently-available handheld I&M testers. This enables FieldFox to tackle increasingly complex wireless networks in less time, radically improving productivity. Fast fault location is further enabled by its 1001-point resolution and excellent dynamic range.

With FieldFox, RF field engineers and technicians performing base-station I&M can make a range of comprehensive measurements, including:

Cable and antenna test; and cable loss, insertion loss and transmission measurements

FieldFox can be used to test antennas, cables, filters, and amplifiers for the purpose of making return loss, VSWR, insertion loss/transmission, one-port cable loss and DTF measurements. Both return loss and DTF measurements can be made at the same time which helps correlate overall system degradation with specific faults in the cable and antenna system.

A key feature of FieldFox is QuickCal, the industry's first and only built-in calibration system which allows the user to calibrate the cable/antenna tester without having to carry a calibration kit into the field. Such functionality not only simplifies cable and antenna test and provides worry-free accuracy and repeatability with every measurement, but increases productivity as well. QuickCal also corrects drift error caused by temperature changes during instrument operation. FieldFox is also CalReady, which means that it is calibration ready at the cable and antenna test port immediately following power up. Users are then free to make return loss, one-port cable loss, insertion/gain, and DTF measurements without having to calibrate the analyzer in the field.

Spectrum analyzer

FieldFox features an optional built-in spectrum analyzer that covers frequency ranges from 100 kHz to 6 GHz. A fast spectrum scan detects interference and RF burst capture to measure intermittent signals. It displays four traces at the same time and allows the user to choose different detector modes.

Power meter with USB power sensor

FieldFox can connect with the Agilent U2000 Series USB power sensor to make RF/microwave power measurements up to 24 GHz. It provides true-average power measurements with high dynamic range from -60 dBm to +20 dBm (sensor dependent). The sensor has an internal zeroing function, with no external calibration needed.

Network analyzer

FieldFox has an optional network analyzer mode that provides standard vector network analyzer measurements such as S11 magnitude and phase, S21 magnitude, and a Smith chart display.

Testing a cell site's antennas, cables, filters, amplifiers, and troubleshooting interference is critical to ensuring good QoS in a network. Although traditional handheld I&M test solutions can address this task, they fail to offer the speed, productivity and flexibility required to meet the needs of today's RF field engineers and technicians. The FieldFox RF analyzer, with its high level of integration, calibration-ready measurements and fast test times not only provides the measurement functionality today's WSPs demand, but offers a dramatic productivity improvement as well. The result for the WSP is clear--the ability to more effectively deploy and maintain today's complex wireless networks in less time.

Agilent Technologies Inc. (NYSE: A) is the world's premier measurement company and a technology leader in communications, electronics, life sciences and chemical analysis. The company's 20,000 employees serve customers in more than 110 countries. Agilent had net revenues of $5.4 billion in fiscal 2007. Information about Agilent is available on the Web at www.agilent.com.

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