Potential Disadvantages of Satellite Data Systems - Shared bandwidth

From INVESaTWIKI

Shared bandwidth

Satellite systems are shared networks. Like unswitched Ethernet, every use of the system consumes bandwidth; the more users there are, the less bandwidth there is for any single user. Unlike cable systems, though, where the competition is generally limited to a single "drop" area or neighborhood, the competition for satellite bandwidth is nationwide. So, as more users begin using the satellite service and more high-bandwidth streams for audio and video are transmitted, overall per user capacity will drop. Some providers offer guaranteed bandwidth, and private networks can be built with guaranteed bandwidth allocations, however, these options will increase the cost of the system.
To an end user, this means that although the downlink bandwidth is configured for one Mbps (for example), the actual speed of data coming to the user from the satellite depends on the total amount of bandwidth the satellite is handling at that moment and how much it can dedicate to the user. The same is true of uplink bandwidth; how many other users are transmitting at the same time affects the upload speed. As in any shared system, the economies of sharing at some ratio (or oversubscribing) keep the costs down, as users are not paying for dedicated bandwidth; however, if the sharing arrangement is not carefully monitored and designed for peak demand (not average demand), end user performance will suffer for all users.
Satellites increasingly fall behind terrestrial networks in the amount of system capacity. Whereas most GEO spacecraft have less than 1Gbps of usable bandwidth, a single fiber optic cable can now carry over 1 Tbps (using multiple strands). Additionally, total satellite capacity is constrained by a finite number of orbital slots are available for GEO satellites operating in each frequency band. C and Ku band slots are essentially exhausted. [1],[2]

References

[1] more.net
"An Introduction to Satellite-based Data Services".

[2] Pioneer Consulting
"Abridged executive summary".