Why is my VSAT Slow?

Understanding VSAT Speed!!

The Internet is no longer a luxury, but rather a necessity nowadays. Whether it is for a personal or a commercial use, one cannot afford not having access to the world wide web anymore. Many companies spend a good chunk of money acquiring equipment, software, databases, CRM, Oracle database…etc without securing the proper speed needed to integrate all these solutions to achieve business efficiency. Understanding VSAT speed is directly related to your business efficiency. KNOW WHAT YOU ARE SUBSCRIBING TO!!! That’s the trick.

VSAT bandwidth can be procured in two ways

Dedicated Bandwidth (SCPC – Single Carrier Per Channel):

This is straightforward. A dedicated line for you to conduct all sorts of commercial activities without worrying about sharing your bandwidth or peak congested time. So if you subscribe to 1 Mbps up/downlink, then this is what you will end up getting for your communications. This option is costly but it guarantees your speed for sure.

Shared Bandwidth (TDMA – Time Division Multiple Access)          

This is the less costly option, yet a tricky one. In this scenario, you are sharing the bandwidth with other clients around you in the same region. With TDMA, there are various variables that can make it a little complicated and very hard to compare rate structures between suppliers. For example, contention ratio (or subscription ratio) is determined by the VSAT Hub Operator and they may share this information with the clients or they may not since it can be changed by the operators without anyone’s consent. Contention ratio is the number of broadband users sharing the same data capacity. If you have a 10:1 contention ratio, it means that there are 10 users sharing the same channel. And if all of them are online at the same time, then your speed will definitely be affected. The lower the contention ration, the better the quality of speed. In addition, some VSAT Hubs use Frequency Hopping which works as a dynamic load balancer which might make the contention ratio sound less meaningful when it comes to understanding the level of service you are subscribing to. For example, a 2 Mbps down/512 Kbps uplink package with a contention ratio of 10:1 means that the MAXIMUM you will get for this subscription is 2 Mbps down and 512 up while you are using this channel. IT DOES NOT mean that this speed is guaranteed all the time. It only guarantees the maximum you can go for. But in case of net congestion, i.e. all 10 users are online at the same time, the provider can only guarantee 10% of usage dedicated to you in this case. So yes, you will not get what you thought you subscribed to. It is only a guarantee that you CAN reach this speed if none else is sharing the pipeline. Even though the customer doesn’t have any saying on the distribution of the bandwidth, the client can always request a CIR (Committed Information Rate) to be added to the TDMA which means that the provider will guarantee a minimum level of performance more than the 10% promised. Of course, this not a free service so expect a slight increase in your monthly bill to secure your CIR. CIR is essential if you are going to use VOIP telephony for example. A good quality VOIP phone requires about 30-40 kbps up/downlink. So it is very important to pay for CIR if you want to secure MINIMUM data to maintain a good quality of service. If you have systems deployed that require consistent speed, then CIR is a MUST otherwise, you won’t have reliable connectivity.

Please feel free to reach me if you need to discuss your maritime satellite projects. I will be more than happy to help.