e1 structure and traffic mapping

7/21/2019 E1 Structure and Traffic Mapping

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E1 Structure and Traffic Mapping


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E1 Basics

T-1 and E-1 are digital telephony schemes provided by communicationcarriers that multiplex a number of digital voice channels onto a single, higherspeed line.

T1 has 24 channels with data rate of 1.544 Mbps. E1 has 32 channels with data rate of 2.048 Mbps.

The T-1 or E-1 transmission path is bidirectional and transmits and receivesthe digital information simultaneously.

E-1 is a multiplexing scheme used primarily in Europe and Asia that allows30 individual voice channels to be carried on a common transmission

medium. By converting analog voice signals to digital signals using pulse coded

modulation (PCM) and the multiplexing these signals onto a high speeddigital line, 30 separate phone calls can be transmitted simultaneously over asingle transmission path.


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Basic TDM for E1

Here we use 32 voice channels

for E1 and thus the output of

the multiplexer will be theframes with the rate 2.048

Mbps E1 line.


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Continue

In each scan cycle, the E-1 multiplexer sequentially takes a byte ofinformation from each of the 30 channels and outputs this byte-interleaved information as a serial bit stream in the E-1 span.

In the bit stream, the eight bits of information from each channel iscalled a DS 0. For each scan cycle of the TDM, an 8-bit byte ofinformation from each of the 30 channels is placed in that channelstime slot.

The 30 voice channels (time slots 1-30) plus a time slot for channelsignaling( time slot 31) and a time slot for frame synchronization

(time slot 0) represent one frame of data on the E-1 line. In addition to carrying digital voice signals, the E-1 line must also

convey signaling information for each of the TRX. The signalingincludes such information as off hook, on hook, busy, and dial pulses.


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E1 Data Stream

Following is the E1 data stream which is the output from the Time DivisionMultiplexer.

It contains the information in the form Frames after scanning the 30individual PCM (Pulse Code Modulated) signal from 30 different voicechannels .

First Frame will contain byte 1 from channel 0 to byte 1 from channel 31 andso on.


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E1 STRUCTURE

32 time slots in one E1.

Each one is 64 Kbps.

32 x 64 Kbps = 2.048 Mbps.

0th slot is used for framing purpose. We divide each slot in four part (each

16 kbps).

So one TRX needs 2 time slot.

Each TRX and BTS needs its signalingBits generally mapped at the end.

For normal case we put TRX from 1 to

20th slot, from 21 to 26th slot is usedfor giving Edge i.e. EDAP Pool and 27to 31 timeslot is used for TRX and BTSsignaling.

Last 31st slot is used for BTS signalingand management purpose


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Framing in E1 Framing is necessary so any equipment receiving the E1 signal can synchronizeidentify, and extract the individual channels.

2M transmission utilizes two main types of framing:

Frame Alignment Signal (FAS)

MultiFrame Alignment Signal (MFAS)

Timeslot 16 is used for the multiframe alignment and Channel Associated Signaling

(CAS).


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Frame Alignment Signal (FAS)

For receiver to be able to identify each traffic channel in the E-1 frame, a framealignment signal (FAS) is transmitted in time slot 0 of every even frame using bits 2through 8.

Bit 1 is used for the international bit. The odd frames are used to carry national and international signaling as well as an

alarm indication for loss of frame alignment.

Bit 2 in the odd frame is set to a 1 to prevent the bit pattern in the odd frame fromduplicating the FAS in the even frames.


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Traffic Mapping


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Example of Traffic Mapping


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DETAILS OF TRAFFIC MAPPING

From the traffic plan we can show how the time slot mapping of E1 channelis done.

We can assign maximum 13 TRX to one E1 in normal mode.

In compress mode we can assign 15 TRX but lose 1 TCH in each TRX. Here the traffic channel is allocated in time slot 2 and time slot 1 is given for

link management i.e. frame synchronization.

Number of TRX used here are 6 in 222 configuration in 3 sectors so thenumbers given are 1,2,5,6,9 and 10 i.e. first 2 TRX of all the sectors.

Time slot 27 and 28 is used for signaling of TRX as each TRX requires its

own signaling. Time slot 31 used for BCF signaling, priority bits, MCB/LCB and Q1

management.

P1 indicates the priority for the site.


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MCB/LCB is used for loop protection. MCB is the Master Control Bit indicates

whether or not the clock timing is based on master . LCB is the Loop Control Bit

indicates the possibility of loop topology in the network.

MCB = 1 indicates signaling is based on the master clock.

MCB = 0 indicates signaling is based on some other clock (internal).

LCB = 0 indicates there is no possibility of timing loop and so slave is synchronized

with master.

LCB = 1 indicates slave is not synchronized with master and so there is possibility of

timing loop.

Q1 is the master slave management protocol used to manage applicants PDH network

elements.


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Example of Traffic Mapping with EDAP


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Example of traffic mapping in case of multi drop


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THANK YOU

Bhairavi Dave

e1 structure and traffic mapping

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