User's Guide

The Operational View SB300 Series
Page 54 Proprietary and Confidential 2110059 Rev 1.0
These errors result from various forms of electrical interference, noise generated by other cellular
subscribers (especially during peak usage periods), and the user being located in areas of poor
cellular coverage such as remote locations or inside buildings. The use of any cellular device
inside a building suffers from varying degrees of signal loss due to losses in the building walls and
office materials inside the building. Better signals can be achieved by locating the modem near a
window or other opening and by ensuring that the modem antenna is deployed in the vertical
position.
Within any cellular network, there will be regions of poor signal coverage. In these areas, noise
will affect communications. In addition, an effect known as co-channel interference can be heard
on the cellular channel. This is interference from a cellular phone in a different cell. These effects
will sporadically limit the communications link, leading to momentary loss of data, or a dropped
call.
6.1.3. Modem Pools
As discussed in Section 4.5.2 above, there are significant performance differences between
configuration profiles for cellular modems and landline modems. To help alleviate this, some
cellular carriers offer modem pools for cellular data calls.
Modem pools were developed to overcome the need to have a “cellularly aware” modem at the
landline side of a cellular data link. The end to end link actually consists of two back to back
modem connections. The cellular modem initiates a connection with the cell-side modem in a
pool, while at the same time the land-side modem in the pool initiates a connection with the
destination landline modem. The two modems within the modem pool pass data between
themselves using a buffered digital link. The cell-side modem typically supports the necessary
features to ensure a robust modem link.
To use a modem pool for a call, involves prefixing the called phone number with *DATA
(*3282).
Although benefits are generally gained by using modem pools, there are a few disadvantages to
this configuration:
• Call initiation time is long, and there can be long delays in end to end character echo.
• Calls to mobile modems cannot be made through a modem pool.
• Configuration is unique from base-station to base-station, it is not always optimized.
Section 6.5 below provides information for advanced users on optimizing the modem for
particular environments.
6.2. Configuring the Modem for CSC
You can configure the settings using either WirelessExpert or Watcher as described in Section 3.3
and 3.5.2. Alternatively you can enter the configuration using AT commands as described in the
following sub-sections.
6.2.1. Setting the NAM
See Section 2.2.2 for information on registering for CSC cellular service. Make sure your carrier
gives you a 10-digit NAM (area code plus phone number), Home System ID, and a side
preference (A or B).
1. +WS46=7 to ensure the modem is in CSC mode.
2. +WS178=n where n is the entry you wish to edit (1 or 2). This will make it the active NAM.
3. +WPNAM? to display the current entry and verify that it can be changed.
4. +WPNAM=num,sys,pref where num is the 10 digit phone number with area code and
without brackets, spaces, or dashes (i.e. 6042311100); sys is the Host System ID provided by
your cellular service provider; and pref is the numeric code for the side preference as shown
below: