Testing Of the Digitel /4W G.SHDSL.bis Access CPE

A couple of weeks back I wrote a short “blog” about the end of life for Alcatel 2801 DTU and a migration path for this type of deployment.
This new migration path comes with a replacement card for the 28LC card; the new Alcatel GSLC line card. In summary this card works in two modes.

1. Again with a proprietary NTU ( Symmetricom Go-Wide2.3). This unfortunately is no longer in production and hard to source.
2. A 3rd party G.991.2 compliant NTU.

The second part is where the problem lies as many so-called compliant units wouldn’t work with the Alcatel GSLC card.

We at Xbridge have tested a few G.991.2 SHDSL modems, and so far only one modem has successfully passed all lab tests. This is the

Digitel 2/4W G.SHDSL.bis Access CPE.

The Digitel Modem comes in 2 flavors, 2 and 4 wire mode of operation and they can both work in stand alone mode (master-slave).
The choice of modem is the 2 wire since the GSLC line card only works in a 2-wire mode. One may deploy the 4-wire NTU, but would have to be configured to 2-wire operation.

From our initial set-up tests we found that unless the correct S/W code is preloaded on the Newbridge GSLC card as well as the modem’s firmware being of the correct release then the unit would not synchronize with the GSLC line card.

The Digitel modem has 2 data ports; V.35 and an E1 G.703. If the modem was used back to back i.e. one as a Master and one as a Slave then both ports could be used simultaneously, however when connecting just one modem directly to the Newbridge GSLC card then only one port could be used at any one time. The V.35 is more of interest because that compares to the data port of the 2801 DTU.

Whilst the E1 port could be used to replace the HDSL Lim (90-2380-01) when connecting Newbridge 2902 Mux (90-2904-01) via copper back to the central site, or for simply offering Full or fractional E1 services to the client.

"It is worth noting that this modem is backward compatible with the
older Newbridge DTUs namely the 2752s, 2753s etc, offering further flexibility "

Here are the test scenarios;
1. A TTC Bert Tester connected to the Digitel Modem and a loopback set within the Newbridge.
2. A TTC Bert Tester connected to an E1 card in the Newbridge and a loopback (both soft and hard) set on the G.SHDSL Modem.
3. A TTC Bert Tester connected to one Digitel Modem and a loopback set on another Digitel Modem/Newbridge 270x/ Newbridge 275x connected to the same line card. (normal deployment)
4. A TTC Bert Tester connected to one Digitel Modem and a loopback set on another Digitel Modem/ Newbridge 270x/ Newbridge 275x connected to a different line card in another Newbridge Mux.(normal deployment)

In summary here are the Pro & Cons of using this CPE.

Pro’s
Flexibility of using either V.35 or E1 Ports (75 Ohm / 120Ohm)
Front Panel buttons for providing local loop’s & remote loops for diagnostics
Far superior line/distance performances in comparison to the Newbridge HDSL line coding.

Con’s
No remote management of the modem as Newbridge uses propriety CPSS management protocol.
Unable to change signaling control leads and parameters remotely from the Newbridge 56020 network management platform. Unable to remotely downgrade or upgrade the circuit speed. This task would have the be done locally on the modem via the VT100 terminal interface.

Conclusion
The two main advantages are lower NTU cost and availability, whilst offering a migration path for customers struggling to source 2801 modems. The Digitel CPE is a carrier class modem and has a wide installed base amongst many PTT’s and carriers.

The main and only disadvantage is remote management. Since it’s not proprietary and doesn’t use CPSS (Alcatel Management Protocol), one has to locally configure the Modem (usually the data interface speed via the serial port before deployment).

Since this report we have now conducted trials in West Africa with a major PTT and have successfully demonstrated this modem in the field.

Xbridge Services will now seek distributorship from Digitel for further supply of this modem.

The datasheet for this modem can be found at

http://www.xbridgeservices.com/department/download_centre/

For pricing please contact us
http://www.xbridgeservices.com/action/contactus/

End of life for the Newbridge 2801 DTU

90-4925-01 Alcatel 2801 MainStreet DTU HDSL Data Termination Unit

For those not in the know the 2801 DTU manufactured by Alcatel / Newbridge is now end of life and becoming increasingly hard to source on the refurbished market.
The 2801 DTU is a client side desk top modem which comes with one universal serial Data port (V.35, V.36, TIA/EIA-449 (RS-449) or X.21) running speeds up to 1 Mb (2w Model 90-4925-01) or 2Mb (2W/4W Model 90-4926-01)

It seems that more and more Telecom manufacturers Alcatel, Siemens & Keymile to name a few are now removing desktop modems from their product portfolios leaving the consumer to resort to 3rd party alternatives. On this note if you have encountered similar issues with other Manufacturers I would like to hear your comments and how to ‘work around’ a solution.

However with the 2801 DTU, Newbridge deployed propriety coding from the line card ( 90-6396-01 - 27LC3-12 LINE CARD) to the 2801 Modem thus no 3rd party DTU’s are available.

At Xbridge we have looked at several migration options for customers including replacing the 27LC3-12 Line Card with the Alcatel GSLC Line Card 90-9553-01.

Over the next couple of postings I will run through the operability testing we have done with several desktop modem manufacturers and list the gains and pitfalls of running with a 3rd party solution.

On the next posting I will detail the testing carried out with the

Digitel 2/4W G.SHDSL Bis Acess CPE

If you want us to test operability with your CPE modem then please let us know.

One giant leap.... and a new beginning

Welcome to our new Xbridge blog ' Telecoms talk ', a blog that will offer technical advice, telecom debates and general industry news.
I usually have a lot to say, but when it comes to putting it down on paper its a much harder task to do.
So why create a blog and who will read it?
Well firstly let me introduce myself, My name is Phil Chappelle and I am the Managing Director of Xbridge Services Ltd. I have worked in a telecoms environment for the past 15 years so its fair to say that I have seen a lot of transitions over that period such as analogue voice to Voip and Telemetry data services to IP MPLS networks. I have worked with many PTT's, Carriers, Teleco, ISP's, WISP's and Satellite service providers through the UK, Europe Middle East and Africa.
My main technology focus has been predominantly with Newbridge Networks in voice and data WAN infrastructures but since starting my own business 9 years ago I have crossed the barrier into last mile copper and wireless access, IP convergence and other emerging technologies.
So why start a blog? Well quite simply I get asked a lot of questions and advice and I would like to share my responses to a wider audience. Similarly I would like to engage in other topics with new readers.
So who will read it, well who knows!! but I would imagine their are other like minded people out there like myself.