latency


I’ve always wondered what the attraction of national satellites is. Especially geo-stationary satellites for telecom. Below is the explanation I finally came up with and my suggestion of what is appropriate in this day and age. The excerpt is from a piece published in Pakistan and Sri Lanka a few months back. In the 1960s, massive antenna connected to a geostationary satellite provided a qualitatively superior solution for international backhaul over the extant methods of copper cables wrapped in gutta-percha or radio waves that bounced off the ionosphere.
Bangladesh keeps talking about launching a satellite. Sri Lanka threw some money at it, but backed off. Myanmar is talking. Now India wants to gift SAARC member countries with a satellite to be launched using ISRO’s innovative, low-cost launch capabilities. Something Keynes wrote about economics gave me the answer to the puzzle of why our region’s decision makers are so enamored with telecom satellites.
All these years Sri Lanka was connected to its main international communication conduits (SEA-ME-WE 2, 3 and 4) from Colombo and Mount Lavinia (a suburb of Colombo) over branch cables. In the case of SEA-ME-WE 5, the new consortium cable that is expected to come online in 2016, the connection will be direct, in that the Alcatel built cable will terminate in Brown’s Hill in Matara (close to the southernmost point of Sri Lanka) and the eastern component to be built by NEC will commence from the same location. This will shave off several milliseconds from the delivered latency partly because of the use of superior regenerators and partly because of the reduced distance. This is what Wikipedia says: Latency is largely a function of the speed of light, which is 299,792,458 meters/second in vacuum. This would equate to a latency of 3.
LIRNEasia and its people have been intimately involved in the spurts and starts of the policy discussion on Bangladesh’s international connectivity. We were early in pointing to the need for an additional cable, pointing to the multiple vulnerabilities created by the single undersea cable controlled by the government-owned BTCL and the non-ring architecture of the dry link from Dhaka to Cox’s Bazar. Now, with 3-4 of the terrestrial cables coming online, we have a natural experiment running in what addressing redundancy means. Renesys has shown the results for those with backup and those without. Neat.
O3B is a new satellite company that is offering low latency (120-150 ms) satellite connectivity that should be of great interest to small countries without access to submarine cables; for those wanting redundancy for the existing cables, and even cruise lines. Simple physics does not allow geostationary satellites to give low latency. O3B is using medium orbit satellites. Worth a look.