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→Myth Three: It's too bandwidth-inefficient for mobile.
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SATCOM links tend to run at around 9600 - that's the same speed as a GSM data call, which won't help you because you'll have never made one. The latency is around 30s. HF, on the other hand, runs considerably lower, and is half-duplex to boot - it'll run down to around 9 bits/s, and with radio turnaround times at the 2 minute mark every time you need to switch direction, that's almost glacial. | SATCOM links tend to run at around 9600 - that's the same speed as a GSM data call, which won't help you because you'll have never made one. The latency is around 30s. HF, on the other hand, runs considerably lower, and is half-duplex to boot - it'll run down to around 9 bits/s, and with radio turnaround times at the 2 minute mark every time you need to switch direction, that's almost glacial. | ||
Yet XMPP still works - at least as well as anything else. | Yet XMPP still works - at least as well as anything else. Isode have an excellent whitepaper on this: [http://www.isode.com/whitepapers/xmpp-constrained-bandwidth.html M-Link Support for XMPP over Constrained Networks], but the majority of XMPP running over SATCOM are ordinary open source servers such as Openfire. | ||
On mobile, the most concerning cost is the stream startup time - because it uses a sequence of round trips - but extensions such as XEP-0198 can help reduce this substantially. | On mobile, the most concerning cost is the stream startup time - because it uses a sequence of round trips - but extensions such as XEP-0198 can help reduce this substantially. | ||