I- Hypothetical Reference Path/Connection
áៅá្áុá
27500km áៃ hypothetical reference path (ITU
G.282), áេá
ែá reference length 2500km áំáាá់
radio។ á្áុááោះ National portion (ITU-R) á
ែááា short
haul, medium haul áិá long haul។
II - Unavailability Objectives (designed
after 2005)
áិááá័á Unavailability: 10 áិáាáីáែáá្áាáSES(Sever
Error Second)
áេá្áើá˘áុáាáá៍ ITU-R F.1703 áំáាá់ designing
any fixed wireless link។
Unavailability áិáá្áុááីááឹáá្áុááំáĄុááេááួáá្áាំ។
áាá្áូááាáá
ាá់áុááាáា “out of service”” condition។
1. Availability ratio objective (AR):
áំáាá់áិááិáួááááá់ link áំáá់áោá:
á្áុááោះ:
-MO: Mean time between average,
OI: Outage Intensity, AR: Availability Ratio
-áំáៃ Bj ,Cj, Dj áិá Ej á˘ាá
áááាááៅá្áុááាáាááុááá្áាáៃá˘áុáាáá៍ ITU-R F.1703។
áá្áá្á j á˘ាá្á័ááើ:
á្áុááោះ:
Llink (min) = 50 km (áើá្áីáាá 50km,
á៏á
ាá់áុááា 50km áែá)
LR
= 2,500
km
Bj
áិá Cj á្áូááាáá្áá់á˘ោáá្áុááាáាá
3.1
The
ITU-R availability objectives
á˘ាá
á្áូááាáá
ែááៅáាáីá្áែá,
áាá˘ាá៌ access portion, short-haul portion, á្áááាំá long-haul portion។
2 - Equipment
Availability:
áូááá្ááááា The availability (A)
ááá់ terminal áួáá្áá់áោá A = (MTBF/(MTBF +
MTTR)) × 100% ។ áោះáីáាá§áááá៏áាá MTBF á៏á្á˘áិáេá á្áááាំá MTTRáីááឺáីá៉ោáá៉ាááាá៏
áោá,
á៏ availability ááុááិáá˘ាá
ááួááááាááĄើááំáាá់ Networks áែááំáាá់áំáុá
áុះá្áាáែ Route diversity áឺ
equipment protection á្áូááាáá្áើá្áាá់។
Unavailability
áៃ N
hops
=Unavailability
áៃáួá Hop áុááឹá N។
UP: Unavailability áោááាááាááាá
UP: Unavailability áោááាáá§áááá៏
Access Portion (50km<Llink)
áá្áá់áាá្áែá Access
portion á្áីáាá 50 km á ើá fixed
block objective
99.95% á្áូááាá allocated។
Short-Haul Portion (50km<=Llink<250km)
á˘ាá្á័ááឹáá្ááែáááាá 50 km áិá
250 km, áោáá្áើá៉ាá៉ាá៉ែá្á B6 áិá
C6
Long-Haul Portion (250km<=Llink<=2500km)
áាá˘ាá្á័ááឹáá្ááែáááាá 250 km áិá
2,500, áោáá្áើá៉ាá៉ាáែá្á B7 áិá
C7
III Performance Standards
·
System performance objectives á្áូááាááá៌áាáោá
ITU-R F.1668
·
Performance
objectives áូá
áា G.821, G.826, áិá G.828 áោáá
េááាáិááាá់áá្á
ូááូá
Long bursts áៃ
errors áេ។ Performance
Objective áិááែá្áុááិááួááេá ើááិá
áែáំáាá់ááះáេááួááែ
(Worst month)។
·
á្áូááាáá
ាá់áុááាáា
Minimum
system quality áំáĄុááេááៃ
“in
service” conditions។
1. ITU-T
G.821 Objectives
(á
េáá្áាááៅá្áាំ 1980)
·
áំáាá់áែ
Radio
circuit 64Kbps(áៅá្áោá
primary rate 2.048 Mbps) áៃ
international
connection។
For
real microwave LOS link design ITU-T G.821 are using ITU-R F.594, F.634, F.696
and F.697។
á៉ាá៉ាá៉ែá្ááាá្á˘ែááើáá្áាá់ BER áិáááះáេáá˘á្áេá 1 áិáាáី។
áំáាá់ Out of service measurement áែááាáá្ááោáá៍á្áុááំáĄុááេá commissioning á៉ុá្áោះ។
áិááá័á:
- Errored second (ES): ááះáេááិáាáីáាáួááែáá៉ាáá ោá
áាá់áាá erroráួááើááĄើá
- Severely errored second (SES): ááះáេááួááិáាáីáួááែá BER áើá 10-3
Error
Performance Parameters
-ESR: á˘á្áាáៃ ES áៀááៅáឹááិáាáីááុááៅá្áុáááះáេááំáាááៃáá្áាá់áែááំáá់។
-SESR: á˘á្áាáៃ SES áៀááៅáឹááិáាáីááុááៅá្áុáááះáេááំáាááៃáá្áាá់áែááំáá់។
-BBER: á˘á្áាáៃ BBEs áៀááៅáឹá
blocks ááុááៅá្áុáááះáេááំáាááៃáá្áាá់áែá
áំáá់។
ááាá់áៃ Blocks ááុááិááិá blocks áាំáá˘á់áែááាá
SESs។
Objective
áៃ á៉ាá៉ាáែá្áBBER áឺáើá្áីá្áá់áូááá្áោáាááá៌áាáូá system performance reference áិááាá
ំáោះá្ááááៃáá្á ាáាáួááោះáេ។
High Grade (280 km ≤ L ≤2,500
km)
ITU
á៉ុáá៉áá្áá់áąáាááំáាá់ radio links áិá áោááំáá់
objectives áាá់á្áែááំáាá់ circuit áិá
áាáá្áែááៅáឹá Hypothetical
reference connections។
áំáាá់ real high-grade link áែááាá
á្ááែáá
á្áោះááាá 280 km áិá
2,500 km, áá្áá្á័ performance áាááូá
áាáá្áោá:
- BER ³ 10-3 (System threshold), áំáាá់áិááើá 0.054 × L/2,500% áៃ worst month
- BER ³ 10-6 (System threshold), áំáាá់áិááើá 0.4 × L/2500% áៃ worst month
- ES (64 kbps) áំáាá់áិááើá 0.32 × L/2,500% áៃ worst month
Medium Grade
Performance
objectives á្áូááាááំáá់áោá ITU-R á្áូááាáá្áើáំáាá់áិááិáួáááៃ
64-kbit/s channel។á្ááែá:
280 km áំáាá់ classes 1 áិá
2 á ើá 50 km áំáាá់ classes
3 áិá 4។
Medium and Local Grade áិáá˘ាá
á្á័ááើ circuit
length áេ។
Local Grade
Performance
objectives á្áូááាááំáá់áោá ITU-R
áំáាá់áិááិáួáááៃ 64-kbit/s:
- BER ³ 10-3
áំáាá់áិááើá 0.015%
áៃ worst month
- BER ³ 10-6
áំáាá់áិááើá 1.5%
áៃ worst month (áាá់á្áុá 1 áាáី)
- ES áំáាá់áិááើá 1.2%
áៃ worst month
áាááែáá
ែááំáាá់áោááៅ (Apportionment
of Objectives)
ITU-T objectives áំáá់áៅá្áុá standards áូá
áា G.821
áិá G.826 áំáាá់
international
Connections
áៅáើá
ំáាá 27,500-km reference circuit។
Three
overall objectives
áាáá្áោáá្áូááាááំáá់áោá
ITU-T áំáាá់ 27,500
km:
SES = 0.2%, SES=0.1% áំáាá់ equipment objectives
objective+0.1%áំáាá់ fading effect objective
DM = 10%
ES = 8%
-High-grade
portion (25, 00 km)ááួááាá 40% áៃ
the overall objective;
-Medium
grade portion ááួááាá 30%
-Local-grade
grade portion ááួááាá
30%។
áូá
្áេះáំáាá់ High-grade portion, áៅáើá្ááែá2,500 km áោះááួááាá:
DM objective 4% (40%áៃ10%)
ES objective 3.2% (40%áៃ8%)
The ITU-R objectives áá្áá់á្áá់ radio route áាំáá˘á់áាáá្ááែááោá 2,500 km; áាáá័ááា
Objectives ááá់áាááួááាááួááាááá់áៃ ITU-T objective (27,500 km) áំáាá់ radio circuit។
áាáá្ááá DM objective áាá 0.4% áិá ES
objective áាá 0.32%។
(áែ
SES áែááាá overall objective 0.2% áៅáើ 27,500
km á្áូááាáá
ែááា: áួááំáាá់ equipment objectives 0.1% áិá áួááៀááំáាá់ fading effects objectives 0.1%។)
á៉្áាááៀá High-grade portion á្áូááាáá
ែáá˘ោá 40% áៃ
equipment objective
ááុá, áá្ááá
ááួááាááឺ 0.04% (40%×0.1%)áើá
ំáាá
2,500 km á ើááួááាááá់áៃ 0.04% áឺ 0.004%។ á ើá 0.1%
áៃ Objective ááុáá្áូááែááៅáá់áាáá
ែáá្áើááá្áា (0.05% each) áំáាá់ medium
áិá high-grade portions á
ំáោះ fading។
áូá
្áេះáំáាá់ High-grade
portion áៃ a radio circuit áើá្ááែá
2,500 km, SES objective áឺáាáááូáááាá 0.004% áិá 0.05%, áឺ 0.054%។
Practical Advice (áែáាំáំáាá់áាáá˘áុáá្áá៍)
áាáá្áេá, ITU-R
áំáាá់ 2,500-km radio circuit áែáá្á˘េááើ G.821 áឺ:
- SES = 0.054%
- DM = 0.4%
- ES = 0.32%
áើáá˘ាá
áំáាá់áាáាá្ááá្áាáាáួááឹá Real high-grade link objectives áែááាááើááĄើá
áាááើá។
áៅá្áុá Real
radio routes, SES objective áាáá្áាáំáាá់áាááេáá្á˘á់; áូá
áេះáើá្áី designing
a radio link á˘ោááាá G.821,
áាááែ SES objective áេះáេáួáá្áូááាááិáá្áុááាááំáá់áំá ំáៃ
á˘á់áែá។ áាáá្áេá, practical objective áá្áឹះáំáាá់ radio planner áឺ:
Outage
(10-3) <
0.054 × L (km)/2,500%
áៃ worst month
á្ááិááើ Link
áាááីá hop áែáá្áុááួá hop áាáá្ááែá 50 km:
Outage
< 0.054% × (50 + 50)/2,500= 0.00216% áៃ
worst month
áá្áá់áាáួááែáាá 2,678,400 áិáាáី
(31 á្áៃ×
24 á៉ × 60 á×60
áិ) áោះáាáá័ááា outage áៅá្áុá
worst month áួáá្áូááែáិá
áាá 2,678,400×0.00216/100=57.85 áិáាáី/áែ, áែááំáាáá˘ោá 29 áិáាáី
(57.85/2) á្áុááួááែá្áុááួá hop áែá outage
á˘áុá្áាáិ្áá˘ោááាá។
1. G.826
áំáាá់ International
digital paths áាáួááឹá PDH, SDH។ á្áុááááី SDH systems, ITU-T G.826 á្áើáំáាá់á§áááá៍áែá designed áុá March
2000 (á្áោá March
2000 SDH áឹáá្áើ G.828) ។
G.826
áិá G.828 á˘ាá
á្áូááាáá្áើáំáាá់ any digital reference connection, áោááិááិááី transmission technology áឺ
media are áាá˘្áីáោះáេ។
·
G.821
á្áូááាááើááាáិáá្áá់á្áាá់áំáាá់
high-capacity data services (áំáាá់áែ64kbps?)
·
G.821
áាá់á្áុáááះáេá 1 áិáាáីáំáាá់áាááិáាá។
·
á៉ុá្áែá
្áាá់áាá់áាááះáេá 1 áិáាáីáាáែááាá់áំáាá់ SDH 155 áាá bits
á្áុááួá
áិáាáី។
·
áាááិáាá
G.826 á្á˘ែááើ
block áៃ bits áែáá˘ាá
áិá
áាá 1 áិáាáីáាáá្ááោáá៏áែáំáាá់ á ើááាáំáá់ objectives áំáាá់
system rate (áូá
áា E1,
E3, and STM-1) áាáាá circuit rate (E0=64Kbps)។
·
G.826
á្áូááាááំáá់áាáាáá្áាá់áៅáេááែá in-service áំáើááាá
G.826
Definitions
(áិááá័á)
Errored
block ratio (EBR): áួá block
áែááាá bit áួááឺá
្áើááាá errored; á ើááំá ំ block
á្áូááាááំáá់áុááá្áាáៅáាá system rate áួáá។
Errored second ratio (ESR): ááះáេááួá second áែááាá errored block áួááឺá ្áើá
- Severely errored second ratio (SESR): ááះáេááួá second áែááាáá ្áើááាá 30áៃ errored blocks áឺá៉ាáá ោá áាá់áាááួá severely disturbed period (SDP), á§áាá áá៍áៅ áេááែááាá loss of pointer áើááĄើá។
- Background block error (BBE): áួá errored block áែááិááើááĄើáá្áុáá្áែááួááៃ SES។
Errored second ratio (ESR): ááះáេááួá second áែááាá errored block áួááឺá ្áើá
- Severely errored second ratio (SESR): ááះáេááួá second áែááាáá ្áើááាá 30áៃ errored blocks áឺá៉ាáá ោá áាá់áាááួá severely disturbed period (SDP), á§áាá áá៍áៅ áេááែááាá loss of pointer áើááĄើá។
- Background block error (BBE): áួá errored block áែááិááើááĄើáá្áុáá្áែááួááៃ SES។
G.826
Specification
á˘ាá្á័ááើ System
rates áុááá្áា, objectives áំáាá់
27,500-km hypothetical reference path:
G.826
Apportionment
(áាááែáá
ែáobjective)
Overall
circuit á្áូááាááែáá
ែááៅáា á
ំáែááាáិ (national portion) áិáá˘á្áááាáិ
(international
portion)។
ITU-R
áាáá្áá់áូá apportionment objectives áំáាá់á
ំáែáá˘á្áááាáិáិááាáិ។
áាáាááាáá្áោá
áំáាá់á
ំáែáá˘á្áááាáិ:
áេáុááីááែáá្áិááៅá្áោááាáá្áá់á្ááááá់ Operator
áឺ block allowance ratio BL
áិááាá
áំáេá
á˘ំáីáាáើáាá្áើáាááា Terminal
country áឺ intermediate country áែááឹááំáá់áូá block
Allowance
factor BL ។ áេáុá distance allocation
factor FL = 0.01
× Lkm/500។ áេáុá block
allowance factor BL
á˘ាá្á័ááើáាáá្áើááើá connection áៃá្ááេááួá។
á្ááែááោá Lref áាááំáៃáá្áោះá˘ាáá្á 1,000 km។
National
portion
áំáាá់á
ំáែááាáិ, objectives á្áូááាááំáá់áំáាá់ long-haul, short-haul, á្áááាំá
access network។
áាáá្áោááឺáា SESR:
-áំáាá់ access, short haul, EPO áិáá˘ាá្á័ááើá្ááែá
link
áេ។
-EPO áៃ access á˘ាá្á័ááើ bit rate,
á៉ាá៉ាá៉ែá្á C (ááាááី 0.075 áá់ 0.085)
។
-EPO áៃ short haul á˘ាá្á័ááើ bit rate á˘ាá្á័ááើááៀááៃ G.826 áិá G.828, á៉ាá៉ាá៉ែá្á
B (ááាááី
0.075 áá់ 0.085)
។
-áំáាá់ long haul: áួááាáá
ំáែááីá។
á្áែááីáួá A (áួááាááេáុááែááំáូá A1
bááាááី 0.075 áá់ 0.085) áាáេáុááេáá˘ាá្á័ááើáែ
system technology (PDH or SDH)
áិá bit rate។ ESR áិá BBER á˘ាá្á័ááើ bit rate, á
ំáែáᯠSESR áូá
á្áាá
ំáោះá្áá់ rate។
Llink á˘ាá
áែááាááឺá្áីáាá 100 km។
Practical
Advice (áែáាំáំáាá់áាáá˘áុáá្áá៍)
Planning
engineers áែááែáំáឹááិáá្áុááាá design networks á˘ោáá្áááាá G.821 áឺ G.826
Objectives,
áែáាááá្áá់áូááាááែáá
ែááឺáំá ំáៃá៉ាá៉ាáែá្ááៅá្áុá apportionment Rules áាំááោះ
áិááូááាááំáá់áេ។
áូá
្áេះáាááá្áá់ááá្ááá
ំាáាá
់á្áូáá្áើáĄើá។ áá្áá្á័áាá់á្áែááៅá្áុá Hypothetical
path áឹááំáááááá្áើáៅá្áុá real networks áាá់á្áែááើááែááែáាáplanning network áំáាá់ large PTT។ radio
planner á
ាំáាá
់á្áូááិááá់á្ááេááៃ service áែááំáុáá្áូá
áាáá្áá់។
áេះáឺáាáិá្ááាááá្áឹះáែáá្áូááិá
ាááាáៅáេáá្áូáá្áើááូá
Standard áាáួáááááá្áើ។
á្ááិááា Backbone
radio system áែáá្áូááá្áូá traffic
áែáá˘ាá
áá្áូááើ Fiber áááែá,
Quality
standard á្áá់áំáុááួáá្áូááាáá្áើááើá។ á្ááិááើá្áាá transmission medium
á្áេááៀááេá ើá service áិááំáាá់áូá
áា voice service áៅáាá់áំáá់áááá quality standard áាááំáុáá˘ាá
á្áូááាáááááá្áើ។
1. G.828
ITU-R
F.1668-1 áឺáា á˘áុáាáá៏áៃáិá្áុáែáá្á˘ែááើ ITU-T G.828 áែááំáá់ error-performance objectives áំáាá់á្áá់ real digital fixed wireless
links។ áាáំáួáá˘ោáá˘áុáាáá៍áុá ITU-R
F.1092
áិá F.1189។ Error
performance objectives (EPOs) áំáាá់ wireless link áែááាáá្ááែá
L
á˘ាá
áááាááីá្ááែá link áុááá្áា:
EPO = Bj ×
Llink /LR + Cj
á្áុáោះ Bj áិá Cj á្áូááាááំáá់áៅá្áុááាáាááុááá្áាáៃ F.1668-1 á ើá LR = 2,500 km។
á˘á្áាáិ្ááួáá
ំáួááួááá្á
ូá:
Long haul, short haul, áឺ
access network
§ Intermediate country áឺ
terminating country
§ Link length áិá
áាá áឺ áំáាំá 1,000
km;
§ Capacity (bit rate áិááា
kilobits per second)
§ Equipment designed áំáាá់
G.826 áឺ G.828
á§áាá áá៍áាáá្áោáá្áើáូááá្á EPOáាááើ។
áá្áá់
150 Mbps (VC-4, TC-4)) áោááាáá
ំáួá hops áែááាáá្ááែáááុá 105 km:
SESR = B1 × Llink /2,500
km + C1
á្áុááោះ
B1
= 1 × 10-4
(1 + Br
)
C1
= 0
Llink = 105 km
0 < Br
(block allowance ratio) <
1 (áá្áá់ Br = 1)
SESR = 84 × 10-7 (22 SES/áែ)
Practical
Advice (áែáាំáំáាá់áាáá˘áុáá្áá៍)
§ á្áូááា áាáា Short outages (less than 10 consecutive seconds)
áិááិááើá 22 áិáាáីáៅá្áុá worst fading month។
§ Very short outage on the radio
equipment á˘ាá
á្áើá˘ោááាá longer outages áោááាá
network equipment loses។
§ á
ំáួá hops áឹááá្áែááៅáេááាááុá
§ Mix
of different services áូá
áា TDM,
Ethernet áោááាá quality
of service áុááá្áា
§ Adaptive
Code Modulation
1. Real-World Conclusions
Microwave radio hops áៃ transmission
links á្áូááំáេááៅáាá reliability and quality objectives áំáាá់
end-to-end circuits
áែáá្áូááាááá្áូááើáា។
áី ITU-T, áំáá់ objective of the radio route (or link) á ើá
individual hops can á˘ាá
á្áូááាá designed áា subset
áៃ link requirements áាំááោះ។
áែá
ំáួá Link áាá់áែáើááĄើá objectives áិáá្áែá្áួááុááីáើááំáូá, á៉្áាááៀá
Operator á á់áាá hop áួáááើá្áីá˘ោááំáេááាá áá្áាá់ performanceáាááុáá្áាáៅáេá
Operator á á់áាá hop áួáááើá្áីá˘ោááំáេááាá áá្áាá់ performanceáាááុáá្áាáៅáេá
áែááាá្áូááាááá្á
ូááៅá្áុá Network ááá់áេ។
The worst month, unidirectional performance
objectives
á˘ាá
á្áូááាááំáែááៅáា Bidirectional
annual figure។
Annual performance figure áេះáá្áាá់ááá្áូááាááូááá្á
ូááៅá្áុá annual availability figure áើá្áីáá្áើááាááា hop reliability objective។ áាáួá៉ាááួááេáááាá 99.99% áិá 99.999%
á្áូááាáá្áើááááោá operator។
Hop reliability outage á្áូááួááá្á
ូááូá equipment outage, propagation
outages
áោááាá
á្áៀááិá Multipath
fading, á្áááាំá adjustments áួáá
ំáួááំáាá់ interference áិá diffraction fading (áៅáេááែááាáាááá្ááាááៅá្áោááá្áá្á័á˘ាáាá់áាáុáá្ááា) ។
áៅá្áុááាáá˘áុáá្áá៍áេáាááិá្áាáាááá្á
ូá Performance áិá availability áៅá្áុá reliability
Objective áែáួá។ áេះáិááែááា ITU
definition
áេá ើááាáាááាáះáំáាá់áឹááឹááាáៅáេá
áែááេáិáាááា Reliability
figures 99.99% áឺ 99.999% áាáá័ááាáាáិááាá់áááៅáឹá ITU standards áេ។
Availability áឺáា annual figure
áើá្áីáំáá់ end-to-end circuit, áោááួááá្á
ូááូá equipment
Outages,
maintenance outages (planned and unplanned), áោááá្á
ូááូá improvements áាáááះ
redundancy áៅá្áុá equipment áិá system
architecture។
áៅá្áុá
ITU, availability áិá performance
á្áូááាáá˘áុáá្áá៍áាá
់áោááĄែááីá្áា, áាáួááឹááាáá្áុáá្áាááែááá្áើááĄើááោá ACM radio systems, áាá្áូááាáá្áá់á˘áុáាáá៍
áŽáាáាááុáá្áាáេះá្áូááាááá្áាáុá។
Radio links áួáá្áូááាá designed áាáួááឹá network availability goal in mind, áិááá់
any equipment or link redundancy á ើááá្áាá់áá link performance goal
áំáាá់ the critical traffic carried over the
network។
áោáá្áើ
Adaptive modulation, hop
reliability á
ាំáាá
់á្áូááាááááាáំáាá់áំáá់
modulation áិáួáá។ traffic
áំáាá់á្áូáááួááាááូááំáិá reliabilityá្áá់áាá traffic áá្áែááែááាá˘ាá
áៅá្áុááá្áá្á័á˘áាááាáុá្ááĄះá៉ុá្áោះ (á្áាáá្áៀááឺáá្ááាá multipath) ។
I. ITU-R F.1668: Error Performance
Objective Calculations, BJ and CJ
ITU-T G.828
Intermediate Country
Terminating Country
ITU-T G.828: SDH
National Portion
Long
Haul
Access
Section
ITU-T G.826
Intermediate Country
Terminating Country
ITU-T G.826 SDH
National Portion
Long
Haul
Access
Section
II. ITU-R F.1703: Availability
Objective Calculations, BJ and CJ
National
AR:
Access, Short, Long Haul Portion
OI:
Access, Short, Long Haul Portion
International
AR
OI