Requirement of integrated Network Planning for Dhaka Multi - Exchange Area.

Chowdhury Md. Ali.

At the end of April 2000, Dhaka has 31 switches in 15 Exchange/RSU sites and within 2 months it is going to be in 44 switches in 28 sites. By now Narayngonj, Tongi and Savar has become part of the Dhaka Multi-Exchange area and very soon Zinjira is destined to join. After completion of the Dhaka Telephone Project, all the existing Analog exchanges are destined to be closed and Dhaka Multi-Exchange Area (MEA) will become a fully Digital Network.

During the full analog era, logically, all the inter-exchange junctions were through Copper Cable Networks. Several attempts were made, all of them unsuccessful, for introduction of wire PCM for those junction routes. Optical Fibre Cable based PDH Junction Links of NEC were introduced through the Dhaka Telephone

Project, Phase-I, they had since been ser very well without any major mishaç Digital local switches, the second Tandem T3 in SBN and TAX2 in Mo (Alcatel E1OB) were introduced through DTI Project, ITX2 (NEAX61E of NE started through Satelite Project, Italted UT) exchange was installed in Narayng now new Ericsson (AXE 10) exchange RSUs (total 23 of them) are being ‘through Dhaka Telephone Project Phage-II (DTP-2). The 150 KL DTI Project has introduced a second network of Optical Fibre based PDH Junction Links of Alcatel now, through DTP-2, a third and further of Optical Fibre based SDH Junction (mixture of Fujitsu and NEC) are coming operation. The networks are shown in Fig 1 to 4

Fig 1. Optical Fibre based PDH (140 Mbps) Junction routes by DTP-l and Satelite Project (NEC Network)

Fig2. Optical Fibre based PDH ( 565 Mbps, 140 Mbps and 34 Mbps ) Junction routes by 150 KL DTIP and M/W Project ( Alcatel Network)

Fog3. Optical Fibre based SDH (STM-16,STM-4 and STM-1 ) Junction routes by DTP-2 (Fujitsu and NEC Networm.

Fig 4. Optical Fibre based STM-16 SDH Ring Junction Network (Fujitsu) by DTP-2 expansion

These separate, but in many cases overlapping networks will very soon become a problem, rather than being an asset for BTTB. Now is perhaps the best time to think and take quick but decisive steps for integration of these separate networks into a solid and unitary but safe and protected network for the Dhaka MEA environment. Without going into detailed finesse of network planning, I would like to humbly put forward some small suggestions for steps that may be taken in the direction of an "Integrated Network Planning for Dhaka Multi-Exchange Area."

Step 1: Conversion of the whole Network into SDH

Through the DTP-2, as shown in fig 3 & 4, all the network nodes of Dhaka are being connected through STM- 1 links. The equipment are being supplied by NEC and Fujitsu. Almost all the Digital Exchanges of Dhaka can be connected through these SDII links. Only some additional MUX equipment at different sites shall be required to augment these systems to take the additional loads. Since, reference prices are available, BTTB can directly order for necessary

equipment and service and procure such items in a short time-frame. The money involved shall be minimal compared to the huge benefits shall get through improved network performance and integrated maintenance. An immediate step may be taken, using GOB mone2 running time-frame of DTP -2 to start stream-lining process.

Step 2: Using the redundant PDH Systems for other purposes

If early steps are being taken to implement

step 1, the existing PDH systems, about 12 of them, shall become redundant. But all of them are still in a very good state of service. Step can be taken to use them elsewhere. Quite a lot of public and private sector organizati’ are requesting for wide-band digital access to BTTB network. The redundant links can be used to act as those feeder links. If such efforts are successful, that will recover a handsome portion of the investment put into step 1. Moreover, that step will also create new opportunities for BTTB to I introduce value-added wide-band service

Step: 3 Using redundant Optical Fibre Cable capacity

At present, in almost all the existing Optical Fibre Cables, for obvious reasons, there are quite a good number of spare fibre capacity. With the implementation of step 1, more of these fibres, and in some cases the whole cable itself shall become redundant. It shall be a unwise to keep this redundant capacity of these world-class optical fibres unutilized. The spare fibres and cables can be given on-lease to different public and private organizations for point-to-point or point-to-BTTB links. This shall create extra revenue earning for BTTB.

Step 4: Creating more geographical diversity

Though after completion of DTP-2, Dhaka MEA shall have four separate digital junction networks, the geographical diversity of the physical routes is not enough to ensure total protection of un-interrupted communication. The reason mainly is absence of geo-graphically diversified underground duct network. Steps must be taken, through the upcoming projects to create new UG Duct routes to ensure such diversities. Of course, this will involve huge amount of money and time, but it will be worth considering the safety of the network. When such routes are created, more integrated network can be developed to encompass the whole Dhaka MEA.

Step 5 Sketching of the comprehensive network plan for Dhaka MEA

Steps for sketching of a comprehensive network plan for Dhaka MFA can be taken immediately. This is essential for properly interfacing the present networks with new networks planned for the up-coming projects.

Step Immediate : Shifting of the Mohakhali -Narayangonj Digital Microwave Link

At present, a 140 Mbps 1 + 1 Digital PDH Microwave Link is working between Mohakhali and Narayangonj. This link is fed from Moghbazar by a 565 Mbps 1 + 1 Optical Fibre Link. With the introduction of the new STM-4 SDH I + I Optical Link between Central and Narayangonj and STM-16 MSP Ring SDH Link between Central and Moghbazar, thc Microwave link has become redundant. Immediate steps should be taken to shift all the traffic of the Microwave link to the Optical network. The redundant Microwave link can be used in any other emergency routes like Sylhet - Sunamgonj or Shahjibazar - Hobigonj. In conclusion, I would like request my esteemed senior colleagues to kindly note that, even if my humble suggestions are found to be not suitable or feasible, it is now very urgent to find out ways to make the network of Dhaka MEA into an integrated structure before the network webs itself into a complex jungle of co-axial and OF cables.