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stds-802-16: SUB11 COMMENT

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[Detailed Description of Proposed Insertion, Deletion, Change]
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5.3 Spectral efficiency
The spectral efficiency is an important performance parameter of
 a wireless access system. The 802.16.3 system introduces specific 
aspects that shall be taken into consideration.

5.3.1 Cell size
The large cell radius, up to 50km, will produce a large propagation
delay difference between near and far CPE units. This difference 
can be as large as 150us. The PHY and MAC protocol SHOULD provide
for far CPEs propagation delay compensation.

5.3.2 Multirate support
In order to preserve the same link budget, the wireless systems may
use different modulation schemes for far and near CPEs. In this way
the data rate to/from relatively near CPE can be higher, increasing
the overall system capacity. The PHY and MAC protocols SHALL provide 
for multirate support.

5.3.4 Interference minimization
The inter-cell and intra-cell interference have a negative effect on
system capacity. The burst transmission in the down-link minimizes the
interference effects, as the necessity to lower the rates or to
retransmit data packets. The PHY and MAC protocols SHALL support
bursty transmission and SHALL NOT use the spectrum if there is no
information to transmit.

5.3.5 Packetized voice traffic
The SoHo, Small business and multi-tenant units will support a number
of simultaneously voice call. The voice and associated signaling are
transmitted in small packets, that have an intrinsic overhead due to
the associated MAC and PHY headers. In order to improve the spectral
efficiency, the MAC and PHY protocol SHALL permit the concatenation
of the short packets, going to the same destination, into a single larger

5.3.6 Support for VAD and IP header compression
The voice activity detection and silence suppression are widely used
to reduce the number of the transmitted packets. The MAC protocols 
SHOULD permit to take advantage of the VAD benefits, while still 
providing for the same level of QoS.
The IP header, with IP v.4, is as large as 40bytes and will be much more
with IP v.6. The IP header compression standard permits to reduce this 
overhead to 5 bytes. The 802.16.3 MAC protocols SHOULD permit to take
advantage of the IP header compression benefits, while still providing
for the same level of QoS.

5.3.7 Requests for bandwidth and retransmissions
To minimize the overhead associated with the ARQ process and the requests
for fast bandwidth allocation, the PHY and MAC protocol SHOULD permit to
concatenate the data, management and/or  ACK messages."

[Reason for Edit]
Introduce requirements to improve spectral efficiency.