User's Manual

Designing an LGCell Solution
7-26 LGCell 4.0 Installation, Operation, and Reference Manual PN 8100-40
620004-0 Rev. B
7.2.4 Example Design Estimate
1. Design goals:
• Cellular (859 MHz = average of the lowest uplink and the highest downlink
frequency in 800 MHz Cellular band)
• TDMA provider
• 6 TDMA carriers in the system
• –85 dBm design goal (to 95% of the building) — the minimum received power
at the wireless device
• Base station with simplex RF connections
2. Power Per Carrier: The tables in Section 7.1, “Maximum Output Power per Car-
rier at RAU,” on page 7-3 provide maximum power per carrier information. The
800 MHz TDMA table (on page 7-5) indicates that the LGCell can support 6 car-
riers with a typical power per carrier of 4.5 dBm.
4.5 dBm per carrier would be the typical RF signal into the Main Hub’s
FOR-
WARD
(downlink) port. If the duplex port is used, you must take into account the
gain of the port (Table 7-25 on page 7-28) and adjust the input power accordingly.
For example, the duplex port on the 800 MHz LGCell provides 30 dB gain.
Therefore, the input power must be no greater than –25.5 dBm per carrier
(4.5 dBm – 30 dBm). Similarly, the PCS LGCell has a duplex port gain of 40 dB.
All other systems have 0 dB gain through all ports.
3. Building information:
• 8 floor building with 9,290 sq. meters (100,000 sq. ft.) per floor; total 74,322
sq. meters (800,000 sq. ft.)
• Walls are sheetrock construction; suspended ceiling tiles
• Antennas used will be omni-directional, ceiling mounted
• Standard office environment, 50% hard wall offices and 50% cubicles
4. Link Budget: In this example, a design goal of –85 dBm is used. Suppose 3 dBi
omni-directional antennas are used in the design. Then, the maximum RF propa-
gation loss should be no more than 92.5 dB (4.5 dBm + 3 dBi + 85 dBm) over
95% of the area being covered. It is important to note that a design goal such as
–85 dBm is usually derived taking into account multipath fading and log-normal
shadowing characteristics. Thus, this design goal will only be met “on average”
over 95% of the area being covered. At any given point, a fade may bring the sig-
nal level underneath the design goal.
Note that this method of calculating a link budget is only for the downlink path.
For information to calculate link budgets for both the downlink and uplink paths,
see Section 7.4 on page 7-31.
5. Path Loss Slope: For a rough estimate, Table 7-16, “Estimated Path Loss Slope for
Different In-Building Environments” on page 7-20, shows that a building with 50%
hard wall offices and 50% cubicles, at 859 MHz, has an approximate path loss slope
(PLS) of 37.6. Given the RF link budget of 92.3 dB, the distance of coverage from
each RAU will be 42 meters (138 ft). This corresponds to a coverage area of 5,641