Rolling out radio - Technology Tutorial - Tutorial

Communications News, June, 2000 by Mark McDiarmid

Accuracy is vital in radio network planning.

New and existing wireless operators are entering the global telecommunications market more aggressively than ever. The deployment of second- and third-generation services across radio-access technologies, such as global system for mobile communications, time division mulitple access, narrow and wideband code division multiple access, is now prevalent. To remain competitive, operators need to build out radio-access systems faster and cheaper without compromising coverage quality or footprint extent.

Operators and vendors need to understand the various means to achieve a cost-effective and timely network build-out. Accurate radio-network planning is vital to efficient deployment. Often, small procedural improvements produce significant cost reductions and improve deployment time, a matter of business success or failure. Remedial action to correct errors due to poor planning is highly expensive and time consuming.

ESTIMATING NETWORK ELEMENTS

Obtaining an accurate estimate of the size of the network is vital in the early planning stages. Fortunately, computing power has increased enormously over the past years, allowing many deployment strategies to be examined rapidly and analyzed for effectiveness. Calculated coverage footprint, quality and interference can all be predicted in a matter of days rather than months. The number of network elements required can then be efficiently and accurately estimated once the chosen rollout strategy is selected. This capability drives the business-planning process and provides a baseline radio-network plan.

Once operational, advanced database technologies allow for faster analysis of network configuration and performance. Accurate equipment configuration is a prerequisite to effective and timely network-growth planning. Central to this principle is database integration between the radio-planning tool, network configuration and performance-management systems. Integration requires that database systems support structured query language (SQL) standards.

Finally, engineering team organization has a significant impact on the efficiency, performance and ultimate quality of the work performed. One key decision faced by all engineering management is whether to centralize or regionalize engineering functions.

ACCURATE RADIO PLANNING

In numerous locations around the globe, probably one of the worst scenarios, after rollout, is when coverage quality is deemed inadequate due to low signal strength. If the problem is significant, remedies may call for the development of new cell sites. Ideal site locations are typically difficult to find between existing cell sites.

In the early design stages, only limited drive testing can be performed, since resources are usually scarce and time constraints tight. Consequently, reliance on predicted coverage is inevitable and its accuracy has a large impact on the quality of the initial design. To improve over-all prediction accuracy and reduce design error:

* Drive-test selected sites to evaluate predicted coverage;

* calibrate prediction models using drive-test data; and

* identify key sites and drive-test extensively.

The objective of any calibration routine is to derive a propagation model

that functions reliably over 90% of sites; a small number of sites are atypical and unpredictable at best. Atypical sites include:

* Tall sites with unusually good terrain clearance;

* sites covering strategic locations, such as highway intersections; and

* sites targeted at airports or sports stadiums.

Focusing drive-test data collection on model calibration and characterizing atypical sites provide maximum efficiencies while reducing initial drive-test costs.

Characteristics                   Regionalization

Communications                    Difficult

Required Engineering skills       Broad

Cost/Efficiency                   Average/High

Potential for Quality             Strong
  Design/Execution

Strengths                         Broader responsibility
                                  encourages focus on
                                  quality and pride of  work

Weaknesses                        Frequency planning must be
                                  coordinated between
                                  regional teams

Pitfalls                          Engineers can become
                                  isolated and rebel against
                                  headquarters intervention

Centralization

Easy

Vertical

Lower/average

Average to low

Vertically skilled engineers
become true `experts'

Problem solving experience
during optimization is
difficult to invest back into
the design processes.

Engineers become detached
from sites and local
geography

STANDARDS

Early in the process, design standards must be established and documented for engineering and operations to follow. Since, in any sizable rollout, many engineers will work simultaneously on the design, standards should include:

* Quality of service (QoS) objectives, including target-dropped call rates, blocking and speech quality;