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Spectrum Efficiency - definition
I understand the need and desire
for rohc in cellular systems as this is where the majority of the
near-term use and revenue will come from. I am interested in seeing
the developments be useful for both aeronautic and space-based networks
if possible. That is, I believe we should attempt to ensure that
the compression techniques can be utilized other communications networks
as well as for cellular. I believe this is already stated in the
charter.
I would like the group to reconsider the definition of spectrum
efficiency in draft-ietf-rohc-rtp-01.txt and whatever other drafts may
use this definition. I believe this definition is overly cellular
specific and somewhat inaccurate.
“Spectrum efficiency
Radio resources are limited and
expensive. Therefore they must be
used efficiently to make the
system economically feasible. In
cellular systems this is achieved by maximizing the
number of users
served within each cell, while the quality of the
provided services
is kept at an acceptable level. A consequence of
efficient spectrum
use is a high rate of errors (frame loss and residual
bit errors),
even after channel coding with error
correction.”
I suggest the following:
Spectrum Utilization (Cellular)
Radio resources are limited and
expensive. Therefore they must be
used efficiently to make the
system economically feasible. In
cellular systems this is achieved by maximizing the
number of users
served within each cell, while the quality of the
provided services
is kept at an acceptable level.
I suggest removing the following statement, as I believe this is more a
statement of the way cellular system maximize the revenue producing
aspects of spectral utilization.
“A consequence of efficient spectrum
use is a high rate of errors (frame loss and residual
bit errors),
even after channel coding with error
correction.”
I believe this may be a better definition for spectrum efficiency:
Spectrum efficiency
The amount of useful information that can be transmitted over a given
spectrum (bandwidth) over a given period of time. For modem
designers, spectrum efficiency is defined as the amount of bits per
second per bandwidth. For packet communications systems, bandwidth
efficiency can be defined as the amount of useful user packet transmitted
per second per bandwidth excluding overhead. The difference
being that one can have a network with good spectral efficiency at layer
at two that results in a poor spectral efficiency when considering layer
three. For a given BER, burst errors are more desirable than a
binomial distribution of errors when considering packet
communications.
Will Ivancic
*********************************************
William D. Ivancic
NASA Glenn Research Center
21000 Brookpark Rd. MS 54-8
Cleveland, Ohio 44135
USA
Phone: 1 216 433 3494
FAX: 1 216 433 8705
Email: William.D.Ivancic@grc.nasa.gov
wivancic@grc.nasa.gov
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