How to solve the Problem with Creating CES service in Hybrid Network SDH&OTN

Introduction

As we still have some 3G Mobile sites and some customers have legacy telecom equipment, so we need E1 (TDM) in several sites.

The optimal solution from Huawei was through connecting POTN to SDH NEs through CQ1 boards, these boards are to be installed in the POTN NEs, their capacity is 4*STM1 SDH ports , the CQ1 converts them internally into Packet toward the back plane.

-The configuration is 2 steps, the 1st  is SDH in the SDH network and the 2nd is PW (CES) in the POTN (Packet) network 

-After installing the new CQ1 boards and connect them to the SDH OSN7500 SLT1 board, and then complete configuring the E1, I configured PW(CES) from the MD1 board in the POTN NE to CQ1, but an error message (( The Type of CES bearer is incorrect)) 

The Problem Reason

– After reviewing the whole configuration and the boards settings, I found that the CQ1 has a VC12 Format setting under the path Ne Explorer> CQ1> Interface Management> Path Configuration , the default setting is CRC-4 Multiframe and there are 2 other choices (Double Frame and Unframed)

E1 Frame Format

An E1 frame consists of 32 timeslots. E1 frames are available in different formats when classified based on the usage of timeslot 0 and timeslot 16.

In our case we focus on the frame formats based on the usage of timeslot 0.

E1 Frame

– The format of timeslot 0 in an odd-numbered frame is different from that in an even-numbered frame. The signal contained in timeslot 0 of an even-numbered frame is called frame alignment signal (FAS), the signal contained in timeslot 0 of an odd-numbered frame is called not frame alignment signal (NFAS), which contains the A-bit indicating remote alarms and spare bits Sa4 to Sa8. The FAS and NFAS each contain an X-bit. Based on the function of the X-bit, E1 frames are classified into generic dual-frames and cyclic redundancy check 4 (CRC-4) multiframes.

The Solution 

As SDH uses by default the Unframed E1 frame format, so I changed the format into Unframed then the service configuration succeeded and problem solved.