More Than A Day's Work
By Doug McGregor
Network engineering is no easy task. Among the challenges faced by companies are short lead times, constant shortages of staff and difficult environments. And with CDMA technology developing all the time, its more than a one-off assignment.
Build a wireless network and they will come. Build it incorrectly and they will leave. How well a network is constructed is often the difference between a satisfied subscriber and one who churns to the competition. Even the best marketing efforts are in vain if an operators wireless network performance is mediocre.
To this end, vendors often go to extremes when helping operators bring a network from the drawing board to reality. At Nortel weve gone as far as attaching cell site equipment to a helicopter to emulate coverage from a yet-to be constructed tower to braving 40 below zero temperatures all to get a network deployed on time.
WINNERS AND LOSERS
When building a wireless network, one of the first issues
to address is link budgets. This is of foremost importance when initially
rolling out a CDMA system or overlaying it on top of an existing analog
network. Without properly calculating RF link budgets, an operator will
not have the coverage or voice quality expected or promised. The RF link
budget defines the size, power and location of the cell sites, taking
into account in-building penetration, interference, traffic and other
To ensure that Sprint PCS could offer the coverage promised, Nortel resorted to some unorthodox methods during the network design phase of this operators roll-out. Cell site equipment was raised by helicopter to the height the equipment would eventually be installed on towers, and drive tests were done around the coverage area of these future cell sites. Similar tests were made by attaching cell site equipment to cranes, and by mounting equipment on water towers. By completing these simulations, a vendor can make sure the network is living up to expectations.
When integrating new cells into an existing system, Nortel has a set plan that defines how to achieve integration, complete related testing, confirm that new cells work well in this environment and actually bring the cells up as rapidly as possible.
For PCS operators, time to market is a major issue. In turn, many cellular operators need to make the transition from analog to digital quickly in order remain competitive and address capacity issues. These time to market requirements result in aggressive build-outs that require vendors such as Nortel to work 24 hours a day, seven days a week so as to meet operator needs.
Zoning issues, which are beyond the control of the operator,
sometimes delay build-outs, shorten lead times and require engineering
teams to work faster to keep an operators roll-out schedule on time.
Situations like these can present a logistical challenge and often mean
16-hour days for engineers.
Even with technical and weather-related problems, staffing issues sometimes present the most daunting challenge to network deployment. The shortage of engineers with installation, database, RF, optimization and technical support skills continues to be an industry-wide challenge. Vendors, many of whom compete with each other to obtain additional manpower, need a large, experienced work force in the field that can meet the deadlines set by operators hoping to get to market quickly.
On top of staffing issues, the fact that CDMA technology is still relatively new presents challenges. Sometimes it is necessary to provide on-the-job training to get staff up to speed on the issues and characteristics associated with CDMA.
Perhaps the area that is most challenging for engineers is network optimization. An AMPS or TDMA system begins with good coverage and capacity, but voice quality needs to be optimized. With CDMA, good voice quality is a given with a well-designed system, but coverage and capacity need to be optimized.
CDMA digital network deployment also requires clearing of additional channels to accommodate 1.25MHz channels, versus the 30KHz channels used for AMPS and TDMA. This can be challenging in the short term, but rewarding in the long run, given the performance and capacity advantages of CDMA.
One particularly interesting challenge Nortel encountered when deploying AirTouchs Great Lakes network in the Detroit, Mich. MSA was overlaying a CDMA system over another vendors AMPS network. Nortel was required to use existing AMPS sites, and to minimize the impact on the incumbent (Ericsson) analog infrastructure. This meant no adjustments to antennas or power levels at any of the existing cell sites. Interference from neighboring systems also had to be addressed.
AirTouch had to convince its cellular neighbors to change their frequency plans in order to accommodate the CDMA network. While CDMA tolerates interference from neighboring networks, such interference can reduce the capacity benefits of the technology if not properly managed.
OA&M is a crucial part of network deployment, providing a critically important set of tools to the vendor. These tools include a wide range of information such as whether an RF path is tuned and operating according to plan. Initially, diagnostics within the infrastructure equipment indicate whether it is operational as well as whether the T-1 connection between a cell site and the switch is working correctly. There are also end-to-end diagnostic tests that determine if a call is being completed. Tests can further reveal if the network is configured correctly.
Essentially, operational measures are used to show if
the network was deployed the way it was meant to be from RF and call completion
aspects. This data demonstrates if the systems performance is meeting
Once a system is in service, a vendors commitment to the operator is really just beginning. There is a need to continually analyze a systems performance. Automated data collection and data analysis tools are in place to constantly monitor the networks performance and provide data for preventative maintenance. If there are dropped or blocked calls, this data helps an engineer determine what to address before the operator needs to report a particular problem to the vendor. This is an ongoing process for the life of the system.
Challenges associated with deploying a CDMA network are continually addressed, enabling vendors and operators to build on the experience gained from previous network roll-outs. It was just a few short years ago that CDMA technology raised eyebrows and planted doubts in the minds of many operators, investors and even consumers. The successful roll-out of dozens of networks has erased those doubts.
The art of engineering a CDMA network has been a learning experience as it is with any new technology. Vendors and operators can be proud of their accomplishments, but cannot rest on their laurels. Network engineering is a job that continues long after cell site equipment has been installed on towers.