As said my Mark Tinka, if your ISP has good terrestrial infrastructure you can get an asymmetric uplink service from your ISP and have your downlink in DVB with another ISP by VSAT. Unfortunately in most of our countries we got bad terrestrial infrastructures so I recommend you to get your uplink and downlink by VSAT from reliable ISP. The DVB is a good service. The C band is more stable in our case as in Southern Africa it rains a lot.
Aboubacar KOUROUMA
AFRIPA Telecom Guinée
B.P: 6811 - Conakry
République de Guinée
Tél: +224 13 408885
Fax: +1 310 919 3038
-----Original
Message-----
From: owner-afnog at afnog.org
[mailto:owner-afnog at afnog.org] On Behalf Of Mark
Tinka
Sent: jeudi 20 mars 2003 14:26
To: Alamicha Chapuma;
pademmy at yahoo.com
Cc: afnog at afnog.org
Subject: RE: VSAT Access Providers
Ku is a cheaper transmission frequency, but is very prone to rain fade, heavy cloud cover and storms. Usually, the size of your satellite antenna will dictate the degree of signal loss you experience during bad weather.
C-band has been more native, and is much more stable than Ku band. However, satellite service providers have higher running costs on C-band, and as such, may, at times, pass these costs ont to the client. On a weather scale, only a very heavy, and I mean very heavy storm could take a signal out, albeit it's very unlikely. High level humidity can also present some signal deterioration, although not full blown loss of service.
DVB [Digital Video Broadcast] is the wave of the future on satellite transmisson techniques. DVB was meant to replace MPEG, as MPEG required more bandwidth to transmit video and audio. DVB can include several streams of media and protocols, independent of each other and using different mapping techniques to land at their destination. This is the same technology used by Pay-TV satellite companies such as Multichoice and DStv. It's purely a multicast service.
On the same technology, you can include IP, voice and audio. Each stream/session is encapsulated in the DVB stream, independently journeying it's way to the correct destination within the frequency.
Currently, DVB is being used as a downlink service only. A DVB receiver is required, running DVB-compliant protocol software to de-encapsulate the transmission. A normal 75ohm coaxial cable should suffice for that. Then, to your network, it connects via a 10/100Mbps fast ethernet interface. The DVB units can run either proprietory or general purpose software, such as Linux. Either way, they deliver.
What this means is you can have an uplink provided by another company, say your ISP, at 64Kbps or more, and a dedicated DVB satellite downlink with capacity of up to 45Mbps. The DVB receiver can already support this, as the DVB card supports up to 45Mbps and higher, and the LAN interface supports up to 100Mbps. So, you really have no problems when it comes to expansion and growth in terms of Internet downlink bandwidth.
Alternatively, you can have the DVB on the same satellite as your uplink. The uplink would still have to be a normal SCPC [Single Channel Per Carrier] link, although new technology is now even making that more efficient.
I'd recommend you take a normal SCPC link for the uplink, and a DVB for the downlink. You may have to check with your provider whether they support DVB. The satellite provider [like PanAmSat] may support, but the IP provider may not.
If initial cots outlay is a factor, then you can rent a leased-line or frame relay WAN connection to a local ISP, but setup a DVB downlink for you downlink capacity. That way, you only get to pay your ISP for a one-way, assymetric uplink service.
Regards,
Mark Tinka - CCNA
Network Engineer
Africa Online Uganda
5th Floor, Commercial Plaza
7 Kampala Rd,
Tel: +256-41-258143
Fax: +256-41-258144
E-mail: mtinka at africaonline.co.ug
Web: www.africaonline.co.ug
-----Original Message-----
From: owner-afnog at afnog.org [mailto:owner-afnog at afnog.org]On Behalf Of Alamicha Chapuma
Sent: Thursday, March 20, 2003 5:13 PM
To: pademmy at yahoo.com
Cc: afnog at afnog.org
Subject: Re: VSAT Access ProvidersI am new to VSATs - which system is best and why ? I gather the DVB can be with either KU-band or C-Band - correct?
Please clarify !
Alamicha Chapuma
----- Original Message -----
From: Paul Ademola Ajayi
To: Alamicha Chapuma
Sent: Wednesday, March 19, 2003 7:05 PM
Subject: Re: VSAT Access Providers
Hi,
What type of system do want? is it a KU-band, C-band or a DVB system which is very good and cost effective.
you can try verestar VSAT solution at verestar.com and emperion VSAT solution.
Paul Ademola Ajayi
Systems/Network Engineer
Orbit Wireless Internet Services
Plot 32, No. 6 Birabi Street, Off Presidential Hotel
G.R.A. Phase I Port Harcourt, Rivers State, Nigeria.
Tel.:234-84-573479Mobile:234-803-324-7220
E-mail: ajayi4u at hotmail.com OR pademmy at yahoo.com
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