e1 and t1 Sdh and Pdh Dwdm Cdma Clocking

7/29/2019 e1 and t1 Sdh and Pdh Dwdm Cdma Clocking

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--- E1 and T1--- SDH and PDH

--- DWDM--- CDMA

--- Clocking


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T1/E1 Overview

Digital Telephony

Digital voice

Basic Time Division Multiplexing

T1 and E1 Applications


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Digital Telephony

Advantages of digital telephony are:

More efficient because multiple voice channels are multiplexed andtransmitted over a common transmission path.

More economical when compared to the number of equivalentanalog lines that would be required.

More reliable in that repeaters maintain the integrity of the digitalsignals over long distances.


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Digital Voice

Product of Analog to digital conversion.

Involves sampling, quantization and bitencoding.


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Basic Time Division Multiplexing


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PCM

Sampling

Quantization

Bit encoding

Adaptive Differential PCM


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T1/E1 Technology

T1/E1 Multiplexing

T1/E1 Framing

T1/E1 Signaling


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Industrial Standards For T1

AT&T Publication 43801



ANSI T1.403-1989

Bell core TR-TSY-000194


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Industrial Standards For E1

ITU-T Recommendation G.703




ITU-T Recommendation G.732 ITU-T Recommendation G.823

ITU-T Recommendation I.431


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Summary


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DWDM

Increase the bit rate

Nonlinear effects that can affect waveform quality.

Increase the number of wavelengths

Several wavelengths, or light colors, can simultaneously

multiplex signals of 2.5 to 40 Gbps each over a strand of

fiber.


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Sonet and TDM


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TDM interfaces


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WDM interfaces


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Process Of DWDM

OC-48c/STM-16c interface operating atthe 1310-nm wavelength.

Conversion of incoming optical signals intothe precise ITU-standard wavelengths tobe multiplexed, transponders are currentlya key determinant of the openness of

DWDM systems.


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Transponder converts the client optical signalfrom back to an electrical signal. This electricalsignal is then used to drive the WDM laser. Eachtransponder within the system converts itsclient's signal to a slightly different wavelength.The wavelengths from all of the transponders inthe system are then optically multiplexed. In thereceive direction of the DWDM system, thereverse process takes place. Individualwavelengths are filtered from the multiplexedfiber and fed to individual transponders, which

convert the signal to electrical and drive astandard interface to the client.


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Access Schemes:

FDMA:

Each pair of communicators is allocatedpart of the spectrum for all of the time.

TDMA:

Each pair of communicators is allocated all

(or at least a large part) of the spectrumfor part of the time.


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CDMA

Every communicator will be allocated the

entire spectrum all of the time.


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Coding

CDMA uses unique spreading codes to spreadthe baseband data before transmission.

The receiver then uses a correlator to despread

the wanted signal, which is passed through alowpass filter.

The rate of a spreading code is referred to aschip rate rather than bit rate.


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The Spreading Process

CDMA uses Direct Sequence spreading bycombining the baseband information tohigh chip rate binary code. The SpreadingFactor is the ratio of the chips(3.84Mchips/s) to baseband informationrate. Spreading factors vary from 4 to

512.


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Clocking

A reference source of timinginformation

Free run clocking occurs when local

oscillator is lost with externalsynchronization reference.


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Synchronization Techniques

Loop Clock Settings

Local Clock Settings


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Clocking Levels

Stratum 1

Completely autonomous timing source,

Stratum 1 timing is an atomic standard orreference oscillator

Example:

Primary Reference Source (PRS) asdefined in ANSI T1.101.


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Stratum 2:

Tracks an input and holds to the last bestestimate of the input reference frequency

The drift of a Stratum 2 with no inputreference is required to be less than 1.6 x10-8 per year.


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Stratum 3:

Stratum Level 3 is defined as a clocksystem that tracks an input as in

Stratum 2, but over a wider range.

A Stratum Level 3 clock system requires a

minimum adjustment range of 4.6 x 10-6.


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Stratum 4:

Stratum Level 4 is defined as a clocksystem that tracks an input, except that theadjustment and drift range is 3.2 x 10-5.

Stratum 4 clock has no holdover capabilityso in the absence of a reference it free

runs within the adjustment range limits.


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e1 and t1 Sdh and Pdh Dwdm Cdma Clocking