User's Manual

3.3 Frequency Planning – Downstream
This Section describes some of the issues involved in planning a wireless network
deployment.
The ARCell wireless system uses different frequencies for Downstream (Access
Point to subscriber) and Upstream (subscriber to Access Point) communications,
which is referred to as a Frequency Division Duplex (FDD) system.
The Downstream uses a channel within the unlicensed 5 GHz “high” band, 5.725-
5.850 GHz. Upstream uses a channel within the “low” band, 5.250-5.350 GHz.
To cover a large metropolitan area, some pre-planning is needed for the use of the
right channels at each location.
6.4 <> 41.6
U/S IF
200 <> 860
D/S IF
ARCXtend
Subscriber
Transceiver
5729 <> 5843
D/S AIR
5258.4 <> 5341.6
U/S AIR
Modem
425<>550
D/S IF
6.4 <> 41.6
U/S IF
Laptop computer
LAN Data
All Frequencies are channel center in MHz
ARCXtend
Access Point
Transceiver
Upstream (Rx)
Downstream (Tx)
CMTS
Cable plant
tap
Figure 3-1: Frequency Plan.
Figure 3-1 illustrates the range of frequencies:
a) The Figure shows that Downstream be any frequency in the range 200
to 860 MHz. This is usually the frequency used by the wired modems.
b) The Access Point Transmitter modulates this channel to the 5.8 GHz
band..
c) The Subscriber Receiver Downconvert 5.8GHz signal to the 425-550
MHz IF, which is a standard CATV channel the modem can detect.
d) The modem hunts for this channel and the DOCSIS protocol. This IF
frequency is often different from the CMTS downstream frequency.
ARCXtend manual, August 2003 3-2