Abstract: In this talk, I will present results  from  two  recent
papers:

i)  TCP  Optimization  through  FEC,  ARQ and Transmission Power
Tradeoffs (WWIC 2004, by D. Barman, I. Matta, E. Altman,  and  R.
Azouzi);

ii)  TCP  Throughput Analysis under Transmission Error and
Congestion Losses (INFOCOM 2004 by F. Baccelli and Ki.  Kim);
                                                                                                                   
The first paper  proposes  a  TCP  optimization  through  proper
tuning of power management, FEC and ARQ in wireless environments.
The  results  show  that  increasing  power,  redundancy,  and/or
retransmission levels always improves TCP performance by reducing
link-layer  losses.  However,   such   improvements   are   often
associated   with  cost  and  arbitrary  improvements  cannot  be
realized without paying in return. It is therefore, important  to
consider  some  kind  of  net  utility  function  that  should be
optimized, thus maximizing throughput at least possible cost.
                                                                                                                   
In the second paper, the performance  of  a  large  population  of
long-lived TCP flows have been analyzed under a mix of congestion
and random losses. A joint throughput evolution under such mix of
losses  has  been proposed. The large population asymptotic model
shows that a) there exists a positive threshold on  the  wireless
error  rate  above which there are no congestion losses at all in
steady state; b) maximum mean value of the throughput is achieved
when wireless loss rate is equal to this threshold.