User's Manual

ROAMEO System System Overview 27
Bosch Security Systems, Inc.
Technical Manual
F.01U.306.750
Rev. 01
Roaming
The ROAMEO system allows beltpacks to move between the radio coverage area of one AP-1800 to the radio coverage area
of another AP-1800. This is called roaming. Roaming is monitored and maintained by the system of access points, making it
transparent to the user. Handoff from one coverage area to another is done in such a way to make it nearly seamless. Roaming
does not involve any processing on the OMI, allowing the OMNEO bit stream to be completely uninterrupted.
In order for seamless hand-off to occur, the AP-1800 RF coverage area must overlap. This allows the beltpack handoff
commands to be sent to both the current access point and the new access point in the coverage area which ensures a seamless
hand-off.
The 80 RSSI (Received Signal Strength Indicator) contour line shown in Figure 6 is a number related to the access point’s RF
signal strength as received at the beltpack. This can be measured using the beltpack’s site survey screen when testing an access
point location. For more information, see “Site Survey” on page 39.
IMPORTANT: When there is little or no coverage overlap, a beltpack can experience undesirable audio break-up before
the hand-off to a new access point occurs.
When access points boot, they scan the area and pick an RF carrier and time slot based upon the other beacons detected in the
area. The access points also avoid using carriers and time slots already in use by using AP IDs (access point identification).
Each access point in a system has to be set to a unique AP ID using the IPedit application. An algorithm based upon the AP ID
of the access point forces access points to never select the same carrier and slots.
In high density beltpack areas where more than six wideband access points may be required, some access points may not
detect an RF carrier already in use, that can result in roaming issues. The system works best if these scenarios are avoided by
designing high density areas with good access point overlap. Figure 7 shows how all seven access points can detect and
coordinate carriers and time slots with each other, even when there are more than six devices present. The 112 RSSI contour
line can be measured by a beltpack using the site survey screen when testing an access point location. See “Perform a Site
Survey” on page 46.
FIGURE 6. SimpleFigure 6 Roaming Diagram