Filter
Top Products
T226 White Paper
July 2003 (Rev C)
27
HR, and EFR) in that it offers multiple speech and
channel codec rates rather than a fixed ratio. Both half
and full rate channel types are defined for AMR. Eight
codec rates are defined for the full rate channel and 6
for the half rate.
AMR offers capacity advantages over the standard
GSM speech codecs in two ways. First, the half rate
mode exhibits significantly improved quality as
compared with the existing HR speech codec. Use of
the AMR half rate mode would double the number of
users that can use a given frequency and,
correspondingly, increase the network capacity without
the need for added infrastructure or bandwidth. A
secondary benefit of the half rate mode is that the talk
time of the mobile phone would be increased due to the
reduced duty cycle of the transmissions.
Second, the rate adaptability indirectly offers a
potential increased capacity with regards to the cell
repeat pattern of the system. Poor channel quality could
be made acceptable by changing the AMR rate to have
more channel coding. As a result, lower C/I ratios can
be tolerated in the system. By allowing for a lower C/I
ratio, a tighter re-use pattern may be used which
increases the system capacity.