How does AMR increase capacity of system?

[reach2rsa]

I have few questions on AMR:
1.
Full rate says 8 channels.
Half rate says 16 channels....
Than how many channels in HR-AMR will be????

2.
How AMR increases capacity of system? This capacity enhancement is in terms of Erlangs or what?

3.
Any body have some document on AMR capacity? Please share

 

[WimaxforVideoPhone]

bsc amr

The AMR feature set provides improvements in system capacity and speech quality. The AMR
speech codec includes a set of xed rate speech codec modes for full rate (FR) and half rate (HR)
operations, with the ability to switch between the different channel coding modes as a function of
the propagation error conditions. An AMR HR for speech gives enhanced capacity over the air
interface and speech quality using codec mode adaptation. This requires selecting the optimum
channel (HR or FR) and codec mode (speech and channel bit rates) to deliver the best combination
of speech quality and system capacity.

An AMR HR call can occupy an 8 kbps timeslot (an Ater channel) on the terrestrial resource from
the BSC to the RXCDR, rather than the 16 kbps timeslot required for FR calls. If a percentage of
the active calls can be assumed to be HR, then efciency can be gained by reducing the number of
terrestrial resources between the BSC and RXCDR. This is possible only if the BSC can dynamically
allocate a timeslot to a CIC.

AMR half-rate channel mode
The AMR half-rate channel mode allows two AMR calls to be placed on a single air interface
timeslot. Use of the AMR half-rate channel mode increases cell capacity, without the need for extra
radio hardware. The cost of the increase in cell capacity with this release of the AMR half-rate
channel mode is the need for the provisioning of extra backhaul between the BSC and BTS and the
lower quality of service provided by AMR half-rate calls.
The BSS software allows the AMR half-rate channel mode to be enabled and disabled on a per
cell basis. Specic RTFs within a cell can be congured based on AMR half-rate channel mode
capability. Half-rate enabled RTFs are allocated an additional two E1 timeslots between the BSC and
BTS. Extra timeslot allocation is necessary if the BSC does not support 8 kbps switching, so AMR
half-rate call speech data must be carried in 16 kbps TRAU format between the BSC and BTS. If
DSW/DSWXs are used at the BSC 8 kbps switching is supported and 8 kbps backhaul can be used.
Given that, potentially, 16 AMR half-rate calls can be supported on an AMR half-rate carrier. An
AMR half-rate RTF must have four associated E1 timeslots provisioned between the BSC and BTS.
Due to reduced bandwidth, an AMR half-rate call has, in general, a lower perceived Quality of
Service (QoS) than a full-rate call. For this reason, a per cell database threshold is provided to allow
the operator to specify the level of congestion that must exceed in an AMR half-rate capable cell
before new calls can be assigned to half-rate trafc channels.

Added after 1 minutes:

And more ,,

When the received Bit Error Rate (BER) rxqual indicates that a half-rate channel is suffering
interference and that the speech quality of the call is therefore impaired, an intra-cell handovers
back to full-rate (or to another half-rate channel) is supported to maintain quality of service.
Alternatively, a database parameter is set in order to override any MSC channel rate preference, if
given, and the cell's congestion threshold, causing AMR calls to be assigned directly to half-rate
channels. This allows temporary forcing (from the OMC) of half-rate usage during busy periods.
Intra-cell handovers for quality reasons from half-rate are still permitted when the override ag is
set, but the target resource for the intra-cell handover is forced to half-rate.

 

[reach2rsa]

amr half rate + full rate

Thanks for valuable knowledge.