User's Manual

Designing a Fusion Wideband Solution
Page 90 InterReach Fusion Wideband Installation, Operation, and Reference Manual
© 2015 TE Connectivity D-620616-0-20 Rev K • TECP-77-044 Issue 9 • March 2015
LINK BUDGET ANALYSIS
A link budget is a methodical way to account for the gains and losses in an RF system so that the
quality of coverage can be predicted. The end result can often be stated as a “design goal” in which
the coverage is determined by the maximum distance from each RAU before the signal strength
falls beneath that goal.
One key feature of the link budget is the maximum Power Per Carrier explained in “Maximum
Output Power Per Carrier” on page 65.
CAUTION! While the maximum Power Per Carrier is important as far as emissions and signal quality
requirements are concerned, it is critical that the maximum signal into the Main Hub never
exceed 1W (+30 dBm). Composite power levels above this limit could cause permanent damage
to the Main Hub.
NOTE: To obtain the on-line Link Budget Tool, go the TE Customer Portal; se
e “A
ccessing the TE
Customer Portal” on page 230.
Elements of a Link Budget for Narrowband Standards
The link budget represents a typical calculation that might be used to determine how much path
loss can be afforded in a Fusion Wideband design. This link budget analyzes both the downlink
and uplink paths. For most configurations, the downlink requires lower path loss and is therefore
the limiting factor in the system design. It is for this reason that a predetermined “design goal” for
the downlink is sufficient to predict coverage distance.
The link budget is organized in a simple
manner: the transmitted power is calculated, the airlink
losses due to fading and body loss are summed, and the receiver sensitivity (minimum level a
signal can be received for acceptable call quality) is calculated. The maximum allowable path loss
(in dB) is the difference between the transmitted power, less the airlink losses, and the receiver
sensitivity. From the path loss, the maximum coverage distance can be estimated using the path
loss formula presented in “Equation 2—Path Loss Equation” on page 84.
Table 81 on page 91 provides link budget considerations for narrowband systems.