The Maximum RSRP Achievable in a Design Polygon

I. BACKGROUND

The Reference Signal Received Power (RSRP) quantifies the signal level of the Reference

Signal in LTE. Under the AT&T LTE Design Guidelines, a minimum of 95% of the LTE

Design Polygon must meet the RSRP target of -113dBm (Indoor), weighted based on

clutter type.

Metric Green Target Yellow Target Red Target

RSRP ( - 113 dBm) Indoor

≥ 95% ≥ 92% < 92%

II. PROBLEM

There are cases where the LTE Design Polygon provided by AT&T either 1) includes

many coverage holes; and/or 2) the polygon is a bit too stretched along the edges,

making it impossible to achieve the 95% service area KPI target.

UMTS Baseline RSRP (-113dBm Indoor) Plot *

* The UMTS Baseline Project is the initial LTE Atoll Project with all transmitters configured to AT&T’s existing UMTS network.

edges too

stretched

coverage

holes

III. DESIGN PROCESS

The LTE Design Engineer optimizes the UMTS Baseline Project and selects the best

possible antenna types, tilts, heights and azimuths per transmitter to achieve the RSRP

target. The design process takes time both with manual optimization and using tools like

ACP and Capesso. Changes are made per transmitter and statistics are continuously

calculated to check the current status of the optimized design, until the RSRP target is

achieved.

IV. LESSON LEARNED

During the design process, the engineer should already have an idea whether the 95%

target is achievable or not. If the engineer is finding it difficult to achieve the RSRP

target, and before further design optimization is attempted, which takes time, a simple

procedure is suggested below to find out the maximum achievable RSRP in a design

polygon, without proposing New Site Builds, NSB’s.

Set the antenna types for all transmitters inside the focus zone to whatever the market-

preferred antenna is, then, run 3 scenarios with all the antenna tilts for all transmitters

set to 0, 1, and 2.

As an example, the following results are derived:

Metric Target UMTS

Baseline

Optimized Network

View

All Tilts Set to 0

All Tilts Set to 1

All Tilts Set to 2

RSRP ( - 113 dBm) Indoor

≥ 95% 86.79% 88.75% 89.72% 90.02% 89.70%

The maximum RSRP achieved in this case is only 90.02% with all the antennas set to 1-

degree electrical tilt, and this is still way below the “green target” of 95% or even the “yellow target” of 92%.

Present the results to the AT&T market as proof that there is nothing you can do using a

constrained design to meet the RSRP targets, then have the market decide whether they

want to go into an unconstrained design by proposing NSB’s.

V. CONCLUSION

A simple solution in finding out the maximum RSRP achievable in a design polygon was

presented. Doing this procedure before attempting further design changes and looping

into various statistics calculations will help save time and process.