End to End xDSL Technology
Doğan ÖZMENOct, 2009
ISTANBUL
Introduction
ISTANBUL
3
POTS vs non-POTS modem communication
DSL technologies use other frequencies outside the voice band tomodulate information on your local telephone line.ADSL provides you a high speed connection on your local line.
Frequency (fHz)300Hz 3400Hz
Other frequencies used by DSL technologies:
ADSL > up to 1,1MHz
ADSL2+> up to 2.2 Mhz
Voice band
used by
POTS modems
(V.32, V.90, …)
Spectrum of local telephone line
4
Solutions offered by ADSL
PROBLEM
Bitrate of analogue modem limited to 64 kb/s
PSTN not suited for high speed data traffic
ADSL - modem
Redirection of data traffic to specific
network
SOLUTION
5
ADSL
Local exchange
Unshielded Twisted Pair (UTP)
up to 8,1 Mb/sDownstream
ADSL : Digital Subscriber Line
up to 800 kb/sUpstream
Asymmetric
0 - 5,4 km
Customer Premises
6
ADSL spectrum
Upstream DownstreamPOTS
300Hz
3400Hz
1,1 MHz30kHz 125 kHz 164 kHz
ADSL uses frequencies on the local line up to 1,1MHz.These frequencies do NOT overlap with the POTS band and is so allowing simultaneous voice communication.
ADSL
POTS
Copperwire
±8Mbps
±800kbps
138 kHz
7
POTS splitter (PS)
The lower frequencies used by ADSL can disturb the audible spectrum and need to be filtered out towards the telephone set.With on-hook and off-hook situations of your telephone the line impedance changes which will have an impact on the ADSL modem communication.
FILTER
SPLITTER
& UTP to LEX
8
Voice / Data over DSL ?
DataStandard ADSL
POTSTelephone Line
ADSLADSL CPE
PS
xDSL suitable for all types of communication (voice&data&video)
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E2E xDSL Technology
PSTN
BASMPLS
ISP/Internet
IPPOTS,ISDN
ANT
Residential
VOICE
ADSL modem to modem
PVC Connection
E2E data connection
DATA
LTNT
7302ISAM
10
E2E DSL
Internet Access Provider
PSTN
BASMPLS
ISP/Internet
POTS,ISDN
ANT
Residential
ADSL
TELECOM OPERATOR
Internet Service Provider
Mevcut a-b hattı
IP
7302ISAM
ATM
ADSL modem to modem
ATM connection
E2E data connection
MPLS connection
11
xDSL
� ADSL
� first approach to deliver high bandwidth over existing UTP
� killer technology for residential internet access
� SHDSL
� symmetrical high bandwidth service mostly for business users
� VDSL
� very high speed bandwidth for BB entertainment (video)
� can work both in symmetrical & asymmetrical mode
� FTTU
� fiber to the user = optical fiber all the way to the customer.
12
SHDSL
� Single-pair High speed DSL
� 192 kbps … 2.312 Mbps bidirectional (Single pair UTP)
� 384 kbps … 4.624 Mbps bidirectional (Double pair UTP)
� IMA support via SMLT board : combine 8 SHDSL lines links into one virtual link (8 x 2,312 Mbps)
� Limited in distance
� max 2,5 km loops
� No POTS/ISDN service
� SHDSL uses the entire frequency range
� no splitters required
Standards
14
ANSI standards
ANSI T1.413 Issue 1 1995First ADSL specification out in 1995 was STM based and not clearly build
ANSI T1.413 Issue 2 1998Second ADSL specification which was mostly driven by Alcatel and ATM based as is used today.
15
ITU-T standards
ITU-T G.dmt or G992.1Specification by ITU-T which is based on the ANSI T1.413 issue2 standard plus an extra handshaking protocol.Annex A: specifies operation above the POTS bandAnnex B: specifies operation above the ISDN band
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Spectrum
UP DOWN
PO
TS
UP DOWNISDN
1,1MHz
1,1MHz30kHz
138kHz
G.dmt Annex A
G.dmt Annex B
138kHz
17
Shannon-Hartley : Capacity vs. Distance
km
1 2 3 4 5 6UTP Cable length
CapacityMb/s
25
20
15
10
5
Shannon Hartley capacityADSL
8,1 Mb/s
2 Mb/s
6 Mb/s
Modulation
19
Quadrature Amplitude Modulation (QAM)
Transmitted data = Constellation
2
3
1
0
-1
-2
-3
0,5 1 1,5 2 2,5 3
1111 1001
0000
00110111 0101 0001
0110
1110
1101 1011
1100 1000 1010
0100 0010
1001 0000 1111
Symbol length (Ts)
Symbol is represented by a variation of amplitude & phase for a particular frequencyy = A . sin (2ππππ f.t + ϕϕϕϕ)
4 bits/symbol
>> QAM-16
t
A
ϕϕϕϕA
20
QAM vs. SNR
Bits/symbolQAM Signal/Noise ratio (dB) for
BER<10-7
4 QAM-16 21,8
6 QAM-64 27,8
8 QAM-256 33,8
9 QAM-512 36,8
10 QAM-1.024 39,9
12 QAM-4.096 45,9
14 QAM-16.384 51,9
table can be used in 2 ways : (a) what is minimum required SNR to modulate N bits on a carrier(b) how many bits can be modulated given a SNR of Y dB
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Discrete Multi Tone (DMT)
� For ADSL, multiple carrier frequencies are modulated on the 1 ADSL line using QAM.
� These frequencies are equally spaced and for each carrier the SNR is measured to determine the maximum achievable QAM.
� The sum of all frequencies is put on the line
� This concept is called Discrete Multi Tone (DMT)
22
Discrete Multi Tone example
Ts (Symbol Time)
QAM-4 1
QAM-16 2
QAM-4 3
ΣΣΣΣ = DMT
1 DMT Symbol
23
ƒƒƒƒ1
ƒƒƒƒ2
ƒƒƒƒi
ƒƒƒƒ255
ƒƒƒƒj
10101100101111101010110010111110
1010001010110010100010101100
11111111
1010
010010
1011010110
1010
ΣΣΣΣ
Modem ADSLModem ADSL
ƒƒƒƒk
ƒƒƒƒm
ƒƒƒƒ...
ƒƒƒƒ...
QAM-4
QAM-16
QAM-8
QAM-4
QAM-32
RRÉÉCCCCEEPPTTIIOONN
EEMMIISSSSIIOONN
Symbol
(Discrete Multi Tone)
24
DMT and ADSL
� The spectrum used for ADSL is divided into 255 carriers.
� each carrier is situated at n x 4,3125 kHz
� For the upstream direction, carriers 7 to 29 are used
� For the downstream direction, carriers 38 to 255 are used
� On each carrier the SNR is measured and the QAM determined.
� minimum : QAM-4 2 bits/symbol
� maximum : QAM-16384 14 bits/symbol
� Symbol period for each carrier : 250 µs
25
Overview of the new standards
G.dmt = G.992.1 = current ADSL
G.dmt.bis = G.992.3 = second generation ADSL2
G.adslplus = ∆∆∆∆ on G.992.3 = ADSL2+
ITU-T
READSL= ∆∆∆∆ on G.992.3 = Reach Extended DSL
� G.dmt.bis = G992.3 = ADSL2
� performance : raising the bar
� loop diagnostics tools
� improved initialization & fast start-up
� power management improvements
� agreed Jan 2003
� G.adslplus = G992.5 = ADSL2+
� delta to ADSL2
� consent reached Jan 2003
� downstream bandwidth increase by doubling the frequency spectrum range up to 2,2 MHz
� at least 16Mbps should be supported
� READSL
� Reach Extended ADSL2
� target : 192 kbps DS - 96 kbps US on 6km 0,4mm loops
� consent targetted Sept 2003.
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ANTCPE
Central OfficePSTN
WWW Datanetwork
LEX
7300/7301/7302
MDF
3400Hz 1,1 MHz30kHz
Up Down
138 kHz
POTS
300Hz
Customer Premises
voicedata/voice
BB Access Server
Asymmetric Digital Subscriber Line (ADSL) access
data
data
voice “splitter”
“splitter”
27
MDF cabling UD - upstream traffic
PSTNPSTNPSTNPSTN
MDF
data
voice
Customer PremisesEquipment
Central Office
data +
voice
voice
data
data
www
28
www
PSTNPSTNPSTNPSTN
MDF
voice
voice
data
data
data +
voice
Customer PremisesEquipment
Central Office
data
MDF cabling UD - downstream traffic
29
ASAM Equipment practice evolution
Standard Density
High Density
Ultra Density
Extreme Density
4 lines/board144 lines/rack
12 lines/board384 lines/rack
24 lines/board768 lines/rack
48 lines/board2,304 lines/rack
Flexible Density
48 lines/board864 lines/rack
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ATM
WWW
IP/Eth
BTV
VoD
GigE
4 * E1E3
STM-1
STM-1STM-4
4 * E1E3
STM-1STM-4
ATM/SDH
7300 ASAM (R4)
7301 ASAM (R5)
BAS
ADSLSHDSLVDSL
ADSL2(+) …
7302 ISAM
7300/7301 ASAM
The 730x ASAM in the access network…
GigE