what is difference between SCPC AND DVB

Here's the difference, a little bit oversimplified:

SCPC is a single channel per carrier technology while DVB is multiple channels per carrier. Imagine a carrier as a slice of a satellite transponder bandwidth. With SCPC, only one customer can occupy the whole carrier. With DVB, many customers can be sharing a single carrier. There are particular advantages and disadvantages, if looking from the customer's perspective:

1) Price. DVB links tend to be less expensive because with DVB you don't need to secure each channel with a guard band - read wasted satellite space segment, that is extremely expensive. With SCPC, each channel has to have a guard band since 1 carrier = 1 channel, that means you need to buy more satellite space segment to provide the same amount of bandwidth with SCPC. The more the bandwidth you buy the less the effect of this course.

2) Possibility of sharing. DVB links can be shared. Some ISPs oversubscribe their DVB carriers a little to keep cheap prices, while saying they offer true CIR. You can't really check this so all you have is trust in your provider's integrity. This can be negliged for data but kills VoIP quality. SCPC links can't be shared at all with standard legacy SCPC platforms such as CDM-570L.

3) DVB adds some additional latency and possibly jitter, depending quality of service provided. This may be critical for VoIP traffic. There are DVB-based services on the market that are very good and can serve as a reliable transport for VoIP traffic. You can usually tell a good quality DVB service if the price is not really much different from SCPC. For example, if somebody offers a $4000/mo/meg SCPC uplink and at, the same time, $2000/mo/meg DVB downlink, you shall be alarmed. If price is more or less equal (I would anticipate something like 10-15% difference at maximum with DVB being cheaper) then it may mean that the quality of your DVB downlink may be as good as the SCPC uplink.

That's it.

Jitter means sporadic latency variations.

As for the DVB/DVB vs SCPC/SCPC service it depends on particular application, growth plans, pricing, configuration of DVB carriers, etc. Too many factors to answer in general.