Metrics and Techniques for Evaluation of FEC Systems
IEEE 802.16 Presentation Submission Template (Rev. 8)
Document Number: IEEE 802.16.1pp-00/25
Date Submitted: 2000-05-01
Source:
Eric Jacobsen
Voice:
(480)554-6078
Intel
Fax:
(480)552-0771
5000 W. Chandler Blvd. Ch7-410
E-mail:
eric.a.jacobsen@intel.com
Chandler, AZ 85226-3699
Venue:
IEEE 802.16 Session #7, Gaithersburg Maryland.
Base Document:
IEEE 802.16.1.pc-00/25 <http://ieee802.org/16/phy/contrib/802161pc-00_25.pdf>
Purpose:
Assist the IEEE 802.16 Working Group in assessing candidate FEC systems by providing recommendations on pertinent metrics and
techniques.
Notice:
This document has been prepared to assist IEEE 802.16. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s).
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Metrics and Techniques for
Evaluation of FEC Systems
A Presentation of IEEE 802.16.1pc-00/25
Eric Jacobsen
FEC Evaluation Metrics
• Error Performance
–
–
–
–
BER vs. Eb/No curves.
Block or Packet Error Rate
Coding Gain - Distance from Coded to Uncoded
Distance from Channel Capacity
• Latency
– 2x Interleaver or Block size.
– Processing delay, additional buffering.
• Complexity
– Gate count, Memory requirements.
– “Gates are cheap”, may not be driving concern.
FEC Error Performance Metrics
• BER vs Eb/No
– Best basis for Apples-Apples comparison.
• Avoid mixing SNR, CNR, Eb/No, BER, PER, etc.
– Deals only with Power ratios, not bandwidth.
– Focus is on payload information, not implementation.
• Coding Gain
– Deals only with Power Efficiency, not BW.
• Distance from Channel Capacity
– Measure of Channel Efficiency, rather than Power
Efficiency (accounts for both power and bandwidth).
FEC Effect on Signal Spectrum
Uncoded Signal
Power Spectral Density drops by 1/2
(3dB) due to BW spread caused by FEC.
Total signal power remains constant.
Signal Coded with
R = 1/2 FEC
Noise Floor (No)
Signal BW doubles with addition of FEC
overhead at R = 1/2.
Coding Gain and Distance to Channel Capacity Example
C, R = 3/4
C, R = 9/10
0.1
1.62
3.2
0.01
1 .10
e
P
3
=
R .
4
E1 10
B
1 .10
5
1 .10
6
d = ~1.4dB
Coding Gain = ~5.95dB
d = ~2.58dB
1 .10
Coding Gain = ~6.35dB
7
1
2
3
R = 3/4 w/RS
R = 9/10 w/RS
VitRs R = 3/4
Uncoded QPSK
4
5
6
Eb/No (dB)
7
8
PCCC Turbo Codes vs Intelsat Vit-RS
9
10
11
Bandwidth Efficiency Plane
(
l
o
b
m
y
s
/ 1.8
s
t
i
B
R = 7/8, 9/10, 13/14, 19/20
= 1.6
R = 7/8
R = 0.793
z
H
/
c
e 1.4
s
/
s
t
i
B 1.2
R = 3/4
R = 3/4
R = 0.495
1
R = 1/2
R = 1/2
0.8
0
1
2
3
4
5
6
7
Eb/No (dB)
Channel Capacity (CICO, QPSK)
Channel Capacity (BICO, QPSK) Indicated are the power requirements and BW
IDR/IBS Vit-RS
efficiencies for various codes using QPSK modulation
AHA TPC (+0.5db)
to achieve Pe = 10E-5.
PCCC Turbo Code w/RS
Tabular Comparison of Vit-RS and
PCCC Turbo Code
All Figures for Pe = 10E-6.
Code
Viterbi-RS
PCCC TC
Code Rate
_
9/10
Coding Gain
6.35dB
5.95dB
Distance to C
2.58dB
1.4dB
Eb/No at Pe = 10-6
4.2dB
4.6dB
Decoder
70k gates +
Complexity
10kbit memory
Latency (Tx + Rx) 20kbits
250k gates +
16kbit memory
22kbits