48
MDS iNET Series Reference Manual
05-2806A01, Rev. L
Additional Considerations for Mobile Operation
The following key points should be considered for all mobile installations:
•
Use middleware—The use of middleware in the mobile laptops is highly recommended for better oper-
ation of a mobile data system. GE MDS provides middleware from one of the vendors in this market.
Contact your factory representative for details.
•
Plan your network coverage—Deploy Access Points so that they provide overlapping coverage to each
other. Access Points must use the same network name to enable roaming.
•
Set the Remote radios to the lower speed (512 kbps for iNET-II, 256 kbps for iNET) to optimize cover-
age.
•
Set the RSSI Threshold to -85 dBm—This level is typically used for mobile systems with good perfor-
mance. Make sure there is overlapping coverage of more than one AP to provide a good user experi-
ence and continuous coverage.
•
For the fastest scan/association time, change the Remotes’
Beacon Learning
from
enabled
to
on assoc
and set the channels to
scan
in “Channel Configuration Menu”. This only applies to iNET-II Remotes
running firmware 3.0.0 or newer.
At Every Mobile (Remote) Radio
•
Fragmentation Threshold
[
256
]—Set to a small value. This parameter defines the size of the message
packets transmitted over the wireless media. These fragments are reconstructed into the original
packet before delivery to the external device at the remote end of the link. In a mobile environment
with rapidly changing conditions, setting this value to a minimum value improves the probability of
packets being sent complete on the first try.
At Every AP Radio
Parameter settings that should be reviewed for AP radios providing service to mobile remotes:
•
Compression
[
disabled
]—Disable radio compression. Data compression is best performed by the
middleware running on the mobile laptop PC. Gains in efficiency are made because middleware
compresses data at a higher stack level, and it aggregates multiple data frames and streams into a sin-
gle packet. Compression at the radio level, although highly efficient, works at the individual packet
level.
•
Dwell Time
[
Set to the minimum value
]—This setting controls the amount of time that the unit spends
on each frequency between hops. Although overall throughput appears to decrease by this setting the
effects of multipath fading are minimized through frequency diversity.
•
Beacon Period
[
Set to the fastest value
]—This parameter defines the interval at which the Access
Point transmits a synchronization beacon to all remotes. A faster setting minimizes resynchroniza-
tion times when remote radios roam between access points or in highly interrupted coverage areas
(dense buildings, for example).
•
RTS Threshold
[
0 -1600 bytes
]—Enable RTS flow at a small value. This setting is a wireless equiva-
lent to RTS/CTS flow control in a wired communications circuit. This mechanism prevents packet
collisions caused by the “Hidden Node” scenario, in which remotes can’t hear each other before
transmitting. When this value is set below 100 or above 1500, it is effectively disabled.
•
Spanning Tree Protocol [enabled/disabled]
—This setting controls the enabling and disabling of Span-
ning Tree Protocol (STP). STP is used to prevent loops from being created when connecting bridges
in parallel.
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