4RF Aprisa SR+ User Manual - page 95
Managing the Radio | 93
Aprisa SR User Manual
LISTEN BEFORE SEND
When the Access Mode is set for Listen Before Send, the Listen Before Send parameters can be set:
ACK
This parameter determines if unicast requests from the remote station are acknowledged by the base
station. Receiving acknowledgments increases reliability of transport but reduces available channel
capacity so if application has the capability to handle lost or duplicate messages, the ACK should be
disabled.
When enabled, the transmitter requests an ACK to ensure that the transmission has been successful. If the
transmitter does not receive an ACK, then random back-offs are used to reschedule the next transmission.
The default setting is enabled.
DATA COMPRESSION
IP Header Compression Ratio
The IP Header Compression implements TCP/IP ROHC v2 (Robust Header Compression v2. RFC4995,
RFC5225, RFC4996) to compress the IP header.
IP Header compression module comprises of two main components, Compressor and Decompressor. Both
these components maintain some state information for an IP flow to achieve header compression.
However, for reasons like packet drops or station reboots this state information can go out of sync
between compressor and decompressor resulting in compression and/or decompression failure resulting in
loss of packets.
The Compression Ratio controls the rate at which compressor and decompressor synchronize state
information with each other. Frequent synchronization results in reduced ratio.
IP Header
Compression Ratio
Function
Compression
Disabled
Disables IP Header Compression.
High
State information is synchronized less frequently thus achieving
the best compression ratio.
Medium
State information is synchronization less frequently than ‘High’
setting but more frequently than ‘Low’ setting.
Low
State information is synchronized frequently thus reducing the
compression ratio.
The default setting is High.