GE MDS iNET 900, Справочное руководство

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05-2806A01, Rev. J iNET Series Reference Manual 143
4.4.3 Data Latency—TCP versus UDP Mode
The latency of data passing through a network will depend on user data
message length, the overall level of traffic on the network, and the
quality of the radio path.
Under ideal conditions—low traffic and good RF signal path—the
latency for units operating in the TCP mode, will typically be around 5
ms in each direction. However, when UDP multicast traffic is trans-
ported, the outbound packet latency (from AP to remote) is dependent
on the beacon period.
UDP multicast packet latency can be minimized by setting the
Beacon
Period
to
Fast
(52 ms). Changing beacon rate to
Fast
will result in an
average latency of 31 ms, assuming outbound packets wait for a beacon
transmission 50% of the time (26ms) plus the normal packet latency
(5 ms).
4.4.4 Data Compression
Enabling this option uses an LZO compression algorithm for
over-the-air data. Varying levels of data reduction are achieved
depending on the nature of the data. Text files are typically the most
compressible, whereas binary files are the least compressible. On
average, a 30% increase in throughput can be achieved with compres-
sion enabled.
Compression is used on data packets of 100 bytes or more, including
Ethernet, IP, and TCP/UDP headers.
4.4.5 Packets-per-Second (PPS)
The iNET-II radio has a limit of approximately 140 PPS (70 PPS in
iNET). Consider this restriction when planning your network, especially
when smaller packets are expected to make up the majority of the traffic
as is the case with VoIP (Voice over IP).
4.4.6 Station-to-Station Traffic
When sending frames from an endpoint connected to one transceiver to
another endpoint with a different transceiver, the throughput will be
halved at best. This is because all frames must go through the AP and
thus are transmitted twice over the same radio system. Therefore, in the
previous 100-byte UDP example, the number of over-the-air bytes will
be 380 bytes (190 bytes x 2) if the frame has to go station-to-station.
4.4.7 Interference has a Direct Correlation to
Throughput
Interference could be caused by other radios at the same site, in nearby
locations, or by high power transmitters such as paging systems.