1. E1 Structure and Traffic Mapping

2. E1 Basics
T-1 and E-1 are digital telephony schemes provided by communication carriers that multiplex a number of digital voice channels onto a single, higher speed line.
T1 has 24 channels with data rate of Mbps.
E1 has 32 channels with data rate of Mbps.
The T-1 or E-1 transmission path is bidirectional and transmits and receives the digital information simultaneously.
E-1 is a multiplexing scheme used primarily in Europe and Asia that allows 30 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 speed digital line, 30 separate phone calls can be transmitted simultaneously over a single transmission path.

3. Basic TDM for E1
Here we use 32 voice channels for E1 and thus the output of the multiplexer will be the frames with the rate Mbps E1 line.

4. Continue…
In each scan cycle, the E-1 multiplexer sequentially takes a byte of information 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 is called a DS 0. For each scan cycle of the TDM, an 8-bit byte of information from each of the 30 channels is placed in that channel’s time slot.
The 30 voice channels (time slots 1-30) plus a time slot for channel signaling( 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 signaling includes such information as off hook, on hook, busy, and dial pulses.

5. E1 Data Stream
Following is the E1 data stream which is the output from the Time Division Multiplexer.
It contains the information in the form Frames after scanning the 30 individual PCM (Pulse Code Modulated) signal from 30 different voice channels .
First Frame will contain byte 1 from channel 0 to byte 1 from channel 31 and so on.

6. E1 STRUCTURE 32 time slots in one E1. Each one is 64 Kbps.
32 x 64 Kbps = 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 signaling Bits generally mapped at the end.
For normal case we put TRX from 1 to 20th slot, from 21 to 26th slot is used for giving Edge i.e. EDAP Pool and 27 to 31 timeslot is used for TRX and BTS signaling.
Last 31st slot is used for BTS signaling and management purpose

7. Framing in E1
Framing is necessary so any equipment receiving the E1 signal can synchronize identify, 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).

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

9. Traffic Mapping

10. Example of Traffic Mapping

11. DETAILS OF TRAFFIC MAPPING
From the traffic plan we can show how the time slot mapping of E1 channel is 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 the numbers 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.

12. Continue…
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.

13. Example of Traffic Mapping with EDAP

14. Example of traffic mapping in case of multi drop

15. THANK YOU
Bhairavi Dave