cdma

CDMA networks are now at a crossroads in their competitive development and expansion activities. Current capacities are less than those provided by cellular AMPS and D-AMPS in combination, or by GSM. Clearly, a cost-effective path forward is needed to assure continued service viability toward realizing the true long-term capacity potential of these networks. The high stakes of PCS infrastructure capital investment allow few mistakes, requiring a process that minimizes the risks of putting cells in the wrong places and which assure future revenue growth and sustained high quality service under increasing traffic load.

Athena is a 2nd generation RF tool bringing new risk-minimizing capabilities to the planning, design, and operational optimization functions of CDMA network development. These new capabilities include:
* Pinpointing potential performance problem areas during the planning process; allowing optimum pre-launch configuration planning
* Streamlining implementation through minimized field testing and on-the-spot RF site qualification, eliminating tool calibration and focusing CW testing immediately to potential problem areas
* Enabling combined prediction and field-test optimization, coordinating design center and field-test activities with improved understanding of how the network is operating, and improved configuration control
* Enabling efficient prediction of performance under increasing traffic load, preserving the spatial resolution of reverse link noise rise, and allowing statistical calculation of noise rise beyond mere median estimates

The capabilities arise because of the enhanced spatial resolution, inherent prediction accuracy, and statistical interference engine embodied in the tool. Whether the RF engineering approach emphasizes minimizing forward link pilot pollution, or minimizing reverse link broadband noise rise, or both, these capabilities are needed for small imbedded cell design to maximize cell/sector capacity...hence, return on investment.

The detailed technical aspects of capacity planning require accurate definition of cell/sector overlaps, and the means to minimize these with varied geographic traffic distributions, thus building isolation into the network. Of particular importance is building the ability to handle high traffic gradients...accommodating adjacent high-traffic and low-traffic areas by containing the broadband noise migration from the high-traffic "hot-spots" into the low-traffic areas. Providing high "traffic load resolution" by the CDMA network is paramount in capacity optimization, and the design of this resolution cannot be accomplished using propagation predictions by empirical COST 231 Okumura/Hata models.

Athena is a versatile tool, integrating all the mapping capabilities of MapInfo with superior propagation prediction and statistical interference calculation engines. Both area and point-to-point "profile" modes are included. The profile mode includes a manual-input profile, allowing building heights to be added to terrain, and the point resolution to be interpolated to 10 meters, or less.

Virtually any kind of RF analysis can be performed using Athena.. At it's current state of development, Athena is more than just a propagation tool, however. Using the interference engine, Athena can perform complete multi-site system analyses including communications reliability in an interference-limited environment.

Athena offers new outputs that are particularly adaptable to CDMA. These outputs are in addition to the usual received power, field strength, and propagation loss displays for cells/sectors and composite coverage that most propagation tools employ. Also, the prediction accuracy of the CRC-PREDICT^TM model circumvents the need for a separate CDMA engine, with the advantage over COST 231-based CDMA tools that the spatial resolution and the statistical performance capabilities are preserved. The new Athena outputs include:

In the forward link, area mode:

1) The probability of achieving a given Ec/Io level without interference from any sector/PN, geographic probability contours displayed

Addressing the question, "Is the coverage adequate?" with more than just a deterministic answer.

2) The probability of achieving a given Ec/Io level in interference for a particular sector/PN, geographic probability contours displayed
Addressing the questions, "Which server is dominant?" "What are the relative strengths?"

3) The probability of achieving a given Ec/Io level in interference from any sector/PN , geographic probability contours displayed

Addressing the question, "Is there a dominant server?" Comparing 1) & 3) shows pilot pollution, if any

In the forward link, profile mode:

1) The high-resolution field strength vs distance (via linear interpolation of terrain) with added real clutter (building heights) along a radial from a base station, with visual terrain height display. And with clutter category selectable point-by-point

For trade studies in suspected problem areas (accurate roof-top to street-level signal prediction

2) The 30-meter resolution field strength vs distance for a give time availability, location variability & level of confidence along a radial from a base station, with visual terrain height display
For quick view into propagated signal variations, along with statistical rates of occurrence

In the reverse link, area mode:

1) The probability of achieving a given Eb/Nt from a realistically-sized and location-targeted group of mobiles (users) at each base station location (receiver), referenced to the level of a particular mobile, geographic probability contours displayed
Permits partitioning target-cell/sector and out-of-cell noise components by positioning and selecting groups of mobiles; mobile power control selected from forward coverage results
2) The probability of achieving a given Eb/Nt from a realistically-sized and location-targeted group of mobiles at each base station location (receiver), for any mobile within a group, geographic probability contours displayed

Permits assessment of reverse link coverage for groups of mobiles to investigate area effects In the reverse link, profile mode:

1) For the rapid point-to-point assessment and superposition of mobile-to-base links on a power basis
Athena is a predictive tool, meaning that it's engine computes performance in accordance with the laws of physics, rather than being a simple purely mathematical artifice requiring calibration with measured data. The question often arises about manual adjustments to converge computed and measured data. There are adjustments, and they each have physical significance. Before making permanent adjustments to merge particular data sets that affect absolute values, calibration of the drive test system is first recommended. Other than system-related link budget items and building or vehicle penetration losses, the adjustment handles include: * The height of the receiver....applicable to situations where roadways, bridges, and other man-made structures elevate the receiver above the terrain data base levels
* The vegetation description...valid whenever the clutter category shows vegetation, allowing both the tree height and number of mature trees per acre to be varied...the vegetation loss is computed by actual integration along the path...winter-to-summer variations can be accounted for
* The level of confidence...appropriate when probability is not being computed, recognizing that many measurement sets would be needed rather than just a single drive run to give the real statistical population of results
* A system gain adjustment, appropriate for use as a scaling factor for cases in which probability (reliability) is being computed
* Inclusion or omission of the Rayleigh statistical component; the lognormal distribution always being present
* The order of diversity, appropriate on the reverse link for accommodating the mode of handoff in interpreting probability in terms of predicted outages
* The mobile antenna gain...clearly affecting results in drive tests when driving both directions...the fact is, drive test equipment is not calibrated absolutely, so we have no way of knowing what the real receive power threshold is, for example.

The best way to apply Athena to a CDMA network depends very much on it's current performing character and the expansion goals of the operator. In any event, the starting points using Athena should be to baseline parts of the network either in which there are existing problems, or into which expansion cells, if any, are planned...so that the greater performance visibility and intuition available from using Athena can be factored into current operations and plans.
In a new network, or as a troubleshooting tool in an existing network, Athena will spatially identify potential trouble spots. Some of these will be real, and some will not, often due to saving elements of GIS which have not been modeled. Besides not requiring measured data for calibration, Athena will focus drive efforts toward these potential trouble spots. In this regard, the high spatial accuracy outweighs raw prediction accuracy...although, they are obviously related.
Wave Concepts was founded because there was no way to assess dense CDMA Infrastructure (small cells) accurately under increasing traffic load, so that a roadmap could be developed for an evolving network .Now, using Athena, such a roadmap is possible.