CalAmp Viper 100, Руководство пользователя

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#9 Viper_SC_Manual_
001-5008-000_Rev12e.docx |
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5 NETWORK OPTIMIZATION
5.1 MAXIMIZING TCP/IP THROUGHPUT
After optimizing the Airlink, if there appears to be an unexplained speed loss, you can attempt to maximize TCP/IP
throughput.
TCP/IP throughput can be a challenge to measure as performance is related not only to the RF link, but how well flow-
control is implemented in the TCP/IP stack and each application’s design. Viper SC has been optimized with this in mind.
When the TX/RX led flashes green or red, this indicates data is moving across the network. It also indicates (by the LED OFF
periods) when data is not moving across the RF network at full rated speed. OFF periods indicate the application has not
presented data to the Viper SC radio modem.
Using different client/server combinations or applications may show improvements. For instance, one FTP server may work
30% faster than another; the buffer management is quicker to respond or has bigger message buffers – yet run at nearly
the same speed over a pure Ethernet (no RF) link.
Network Address Translation (NAT), payload data compression, and encryption have little effect other than adding a small
latency to the flow of traffic.
5.2 MAXIMIZING THROUGHPUT WITH A WEAK RF LINK
Further performance optimization can be done via the User Interface Setup web pages. Fundamental adjustments,
described in the following paragraphs, can be changed singularly or in conjunction with each other.
5.2.1 USE ROUTER MODE WITH RF ACKNOWLEDGEMENTS ENABLED
Selecting Router mode and enabling RF Acknowledgements is highly recommended when running over a weak RF link. This
mode ensures several levels of retry mechanisms are at work, each optimized to minimize TCP flow control delays or
prevent a dropped TCP/IP link. It requires some IP route planning to and from Viper units, but is well worth the increase in
link stability over the simple Bridge mode.
RF Acknowledgements can be enabled on Viper web pages under Setup (Advanced)

IP Optimization. RF
Acknowledgements must be enabled or disabled on all Vipers in the network.
Vipers are tested for BER at the factory with the optimizations described above. The units are configured for Router Mode,
RF Acknowledgements are enabled, MAC retries are set for 2, and OIP retries are set for 2.
5.2.2 REDUCE RF NETWORK BIT RATE
Viper has up to four speeds of operation available for each of the four channel bandwidths. The fastest speeds utilize 16-
level FSK (frequency shift keying.) The slower speeds in each bandwidth utilize 2-level FSK, yielding a higher Signal-to-Noise
level resulting in better sensitivity. When the received RF signal level is strong, the system is able to utilize the faster bit
rates. However, if the system has a low RF signal level or the RF signal levels are close to an elevated noise floor level, you
can run at a slower over-the-air speed for the system’s bandwidth. It may result in better overall performance.