[e2e] Delivery Times .... was Re: Bandwidth, was: Re: Free Internet & IPv6

Detlef Bosau detlef.bosau at web.de
Fri Dec 28 05:01:51 PST 2012

I've just read a little bit on LTE.

Certainly, the bandwidth is increased: Depending on the spectrum in use, 
it may not be 5 MHz (as in UMTS) but 20 MHz.
As we all know Shannon-Hartley's theorem, data rate is only linearly 
increased by the bandwidth decrease, however, the is a logarithmic 
dependency on the noise. Hence, the more drastic increase of the net 
data rate will not be achieved by a bandwidth increase but by more 
aggressive line coding,
e.g. 64 QAM (or even 256 QAM in the future?) instead of 16 QAM or QPSK 
as it is used today. In addition. MIMO techniqures are used.

The good news is: Using LTE, "good" channels can be better utilized than 

The bad news is: The system dynamics will become more complex than now 
and TCP's congestion control, which does not work well with GPRS,
will likely work even worse.

May I ask a somewhat provoking question? Could it be that many of the 
buffer bloat problems, we frequently talk about, are not "buffer bloat" 
- but unhandled (or wrongly handled) congestion collapses? (And we can 
well say: "Corruption collaps", because both, congestion loss and 
corruption loss will require packets to be retransmitted and hence may 
cause network instability, when wrongly handled.)


Detlef Bosau
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The nonsense that passes for knowledge around wireless networking,
even taught by "professors of networking" is appalling.  It's the
blind leading the blind. (D.P. Reed, 2012/12/25)

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