User's Manual

302395 User’s Guide and Repeater Network Design Guide
4 February 2004
2.1.2 Data Rates and Range
The M/LC repeater hardware is based on the 802.11b specification and as such supports data rates of
1.0 Mbps, 2.0 Mbps, 5.5 Mbps, and 11.0 Mbps. As the data rate increases, the range deceases. At ½ watt
of output power, the expected ranges are as follows:
DATA RATE ANTENNAS EXPECTED RANGE
2.0 Mbps Two 6 dBi Omnis 8 miles
11.0 Mbps Two 6 dBi Omnis 3 miles
The M/LC Repeater network will always transmit at the highest data rate possible provided there is a
good RF link between the two access points. Therefore, in practically all instances, intra-access point
traffic will be at 11.0 Mbps. However, M/L hardware transmits at 2.0 Mbps, so communications between
clients and the M/LC access points will be at 2.0 Mbps.
2.1.3 M/LC Point-to-Point Links
In a M/LC infrastructure, any point-to-point links must also be Cisco-based. Point-to-point links generally
use the 24.0 dBi dish antennas at each end in order to provide a link for distances up to 24 miles.
Although they could use the same channel as the rest of the mine, it is best if they are on a separate
channel. However, it is even better if they operate completely out of the 2.4 GHz Frequency range in
order to keep the 2.4 GHz 802.11b channels as traffic free as possible. 5.8 GHz point-to-point links are
available from Modular Mining Systems. These Cisco 1400 Aironet links are compatible with a M/LC
repeater infrastructure. They are listed on the MMS intranet site.
2.1.4 Temperature Related Decisions
M/LC mobile repeaters do not ship with batteries because in many instances batteries are obtained locally.
However, if a mine site will be operating from 0 to –20 C for extended periods of time (several days),
then SLA (Sealed Lead Acid) AGM (Absorbed Glass Matte) batteries must be used. These are available
from Modular as part number 105900 and are 12V Size 27 108AH. Repeaters will ship with foam
insulated battery boxes, and the foam must be placed over the vent in cold weather.
If temperatures will be below –20 C for extended periods of time, then NiCad batteries are recommended
in order to avoid “blackout” periods. NiCads are relatively expensive and heavy. 20 NiCad cells provide
205AH at 1.2V each for a total of 448 lbs and 24V. With the battery box they weight over 600 lbs.
M/LC shovel and crusher systems are all LT (Low Temp) already since the mobile hubs used have the
larger Vicor power supplies. All cables are now Xtra-guard 4. Therefore, with respect to a M/LC
infrastructure, the battery configuration is the decision point. Also, see “Sizing a Solar Repeater” below.
2.1.5 Sizing a Solar Repeater
Modular provides a 150 W and a 300 W M/LC mobile solar repeater. The amount of sunlight during the
worst month of the year is what dictates which one should be purchased. A solar analysis may be obtained
by Emailing the city (or Lat / Long) mine location information to Modular. This analysis will estimate the
performance of each system during each of the 12 months of the year, and will include the optimum angle
of solar panel tilt. It is very important that the panels be tilted at this angle during installation and facing
perfectly South (if in Northern Hemisphere) or perfectly North (if in Southern Hemisphere).
In the rare case of excellent sunlight but constant colder temperatures (0 to –20 C), such as at very high
elevations, four SLA AGM batteries should be used in a 150 W mobile repeater. By design, usually only