Audio Note VINDICATOR Instrukcja Użytkownika

Acceptance Testing for DigitalLand Mobile Radio SystemsPresented by:Jay Jacobsmeyer, P.E.Pericle Communications [email protected] Rea

BER & MFD

RF Coverage Performance RF Fundamentals Still Apply to Digital– Mean C/(I+N) in fading must still achieve minimum level But Digital Introduces New E

Characteristics of the Signal Multipath Fading Dominates the Mobile Radio Channel– Fade rate is a function of the doppler frequency, V/λλλλ– E.g., fo

Rayleigh Fading(V = 30 mph, f = 850 MHz)-40-30-20-10010Amplitude normalized to mean, dB0.00 0.05 0.10 0.15 0.20 0.25 0.30Time in seconds

Multipath Delay Spread Simulcast Networks Aside, the Signal at the Antenna is ReallyMultiple Reflected Signals with Random Delays– Extent of problem

Coverage Test Prerequisites Complete All Radio Site Acceptance Tests– Including site noise, desense, and intermod tests Verify Backhaul Network Rout

What to Measure?RSS = Received signal strengthBER = Bit error rateFER = Frame error rate (= block error rate)DAQ = Digital audio qualityClosest to Use

•Method •Pros •Cons•Signal Level •+ Test can be automated•+ Specialized test equipment not req’d•+ Aligns well with coverage prediction•- Does not co

Signal Strength Signal Strength to be Measured in All Cases– Adequate C/N is necessary, but not sufficient condition– Measured simultaneously with ot

So What’s New with Digital?Many more systems, software, and technology between the user and their expectationsUsers who expect the “same performance …

Bit Error Rate Testing(Or Frame Error Rate Testing)Q Remove RF Channel from Service and Place in Test Mode– May be problematic for busy, operational s

Voice Quality Testing1. Select and Use an Exclusive Talkgroup2. Automated Voice Play and Recording Preferred– Duration consistent with a typical voice

DAQ & MOS DefinitionsExcellent.Impairmentsimperceptible.MOS 5Speech easily understood. Occasionalnoise/distortion.DAQ 4.0Good.Impairmentsperceptib

Scoring Methods Even With Training, Some Variance Occurs One Method that Works:– Decide on passing threshold (E.g., DAQ = 3.4)– Pick three scorers:»

PESQ Problem: Manual Scoring is Labor-Intensive– Training is required– Variability of scores is tough to eliminate Possible Solution = PESQ– Percep

Audio File Samples

Sample 1

Sample 2

“Radio Was Fun UntilThey Put Software In It”- Anonymous

Sample 3

Pass/Fail CriteriaAnd Use of Statistics

Estimate for SAR(Service Area Reliability)SARTTwhereT is the number of tiles passedT is the total number of tilesptpt(%) % = 100

Minimum Number of Samplesofnzp pd=−α/()2221Where p is the value of the SAR, zα/2 is the argument of theunit normal distribution for a confidence of 1-

Arguments of Unit Normal2.581.961.64Zαααα/21.6495%99%90%Confidence Level2.331.28Zαααα

Example(d = .02, p = 95%)ConfidenceWindow TestGreaterThan Test788456321n643321195n2.581.961.64Zαααα/21.6495%99%90%ConfidenceLevel2.331.28ZααααGreater

Some Purchasing Pitfalls Pitfall #1 - Failure to Specify Measurable Performance Standards Pitfall #2 - Failure to Specify Standards that Measure Dig

Summary An Acceptance Test Plan Must– Use measurable standards,– Specify precisely how each standard is to be measured,– Include the statistical test

Other Acceptance TestElements

Acceptance Test Elements RF Coverage System Capacity Reliability Resiliency /Fault Recovery Features and Functionality Management and Administra

System Capacity System Capacity Goes Beyond the Radio Link Capacity Often Difficult to Measure Directly– Sheer volume of messages– Unavailability of

System Capacity Specs.1. Define the Voice and Data Usage Models– Use busy hour traffic estimates– Consider fault / system recovery message loads– Watc

System Capacity Testing Distribute Between Factory and System Acceptance Tests Use Commercial Network Test Tools to Stress BackhaulComponents Use D

System Reliability/ Resiliency Consider Interaction Between All Systems– Momentary packet loss in one subsystem can cause lengthyreset in another– Id

Features and Functionality Centralized Conformance Testing for OpenStandards Assists With This Area However, Conformance Tests Still Not at StageWhe

Management & Administration Consider Information You Require to Support andManage the Network– Channel, site, link and system traffic, loading an

Final ThoughtThe view is nice but you really should only have to go out once.

Q&AEarly Land Mobile Radio - 1924Source: Bell Labs, http://www.bell-labs.com/history/75/gallery.html

References[1] W.C.Y. Lee, Mobile Communications Design Fundamentals, 2nd Ed.,Wiley, 1993.[2] W.C.Y. Lee, “Estimate of Local Average Power of a Mobil

Points of ContactJay M. Jacobsmeyer, P.E.Pericle Communications Company1910 Vindicator Drive, Suite 100Colorado Springs, CO 80919(719) 548-1040Fax: (

RF Coverage Testing

Vocoder IMBE™ by DVSI is the P25 Vocoder– Model-based like virtually all vocoders Optimized for Low Bit Rate Apps (< 4.8 kbps) Breakdown– 20 ms

ATP Implications Four Choices for Each Vocoder Frame– Accept frame (even if some errors detected)– Repeat frame– Adaptively smooth (interpolate) fram

Multi-Level Modulation C4FM is a Form of 4-ary FSK 2 Bits per Symbol, Four Possible Carriersfc11 10 00 011.2 kHz

ATP Implications Modulation Fidelity is an Option for Testing Can Be Alternative to BER– Is a measure of eye closure– Does not require taking a chan