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700 MHz Drive Tests
Decision Process for the Adoption of a 700 MHz Solution for the OWIN System
Report given to the Oregon Statewide Interoperability Executive Council
Don Pfohl
March 10, 2009

Federal Engineering Conceptual Design
In its instructions to Federal Engineering (FE), OWIN told FE to do a conceptual radio system design based on use of VHF (150 MHz frequency band) frequencies and to design a radio system that would be compliant with the Project 25 digital standards. Because of the limited time in which to do a complete inventory and needs analysis, FE was instructed to only consider existing State sites unless those State sites would not produce an estimated 95% mobile coverage by county. OWIN told FE to use the number of existing State transmitters at each site in order to design the needed system capacity.  The rationale was that through trunking, that same number of transmitters would greatly improve the number of talk paths available.

Original Conceptual Design
In compliance with OWIN’s instructions, FE delivered a conceptual design that increased the number of VHF transmitter sites from 164 to 183.  FE did a significant amount of work trying to make a frequency plan that would reach the OWIN capacity goals using the 183 sites. FE and OWIN agreed that the design goal for interference within the OWIN radio system should be kept below 5%.  In public safety radio engineering this is a prudent figure.  FE advised OWIN that given the capacity and the number of sites Oregon would need, there were not enough VHF frequencies period to build an OWIN, statewide VHF trunked radio system.

Federal Engineering Hybrid Design
FE asked OWIN if OWIN would consider a hybrid conceptual design that used both VHF and 700 MHz radio frequencies. OWIN and FE then worked out an approach that would use 700 MHz the length of Oregon’s Interstate 5 corridor and from the ridge of the Coast Mountain Range to the ridge of the Cascade Mountain Range. This would give a buffer between the VHF systems on the Coast and the VHF systems in eastern Oregon.  This design resulted in an additional 74 transmitter sites based upon projections of less coverage per site using the 700 MHz channels as opposed to the VHF channels. FE used the existing State sites and recommended use of additional sites where State sites would not provide the required coverage.

Value Engineering
OWIN had FE do a “Value Engineering” effort.  In essence, this was a look at lowering the total cost of the OWIN system through prioritization of State needs.  As part of this, the State agreed to reduce the original coverage requirement from 95% mobile coverage by county to “at least as good mobile coverage as the best State agency enjoys. In most cases, this was whatever the estimate coverage was for OSP in each county as OSP has the greatest number of transmitters located throughout the state.

Drive Test Documentation
"700 MHz Narrowband Coverage: Real World Results"
PDF Document, 49 pages
Presented by Don Pfohl, OWIN Technical Manager and Neil Horden, Federal Engineering Senior Consultant
 
 
"OWIN Drive Test Report and Data Analysis Findings Final Report"
PDF Document, 53 pages
The goal of the drive-testing was to simultaneously and comparatively measure radio signals in the VHF and 700 MHz frequency bands, transmitted from the same site, using commercially available Project 25 (P25) digital radio equipment similar to that OWIN could procure for its statewide public safety radio system.
 
This report presents the findings of the drive-tests and presents a detailed analysis of the data measured during the testing. Read the full report.
Created by Federal Engineering, July 24, 2008, Deliverable 1-A-1.2 
 
 
"OWIN Drive Tests Earn Industry Attention"
PDF Document, 1 page
A decision to test some anecdotal evidence from Colorado about public safety communications systems will mean cost savings for Oregon... Read More 
Release from the Oregon Wireless Interoperability Network, March 10, 2009