Drew Lehman on 21 Sep 2009 06:39:08 -0700

[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]

[PLUG] WiMax Questions Answered

For those who attended the VM/WiMax presentation, I finally got some
answeres for the questions presented.  I am sorry it took so long to get
these questions answered, but the engineers are very busy right now.
Some questions I am still looking for.

Here are the questions asked about WiMax:

1. How does WiMax technically achieve the 3mi range vs 300 ft for WiFi
Greater power ( both Access Point and Client ),   directional antenna's
or better SNR due to modulation technology ( I think ODFM was
mentioned )

    Or is the 3 mi based on a constellation of repeaters, and not a
single Access Point ?

All of our WiMAX sites are high power macro sites (+55 - +56 dBm).
Typical site range is 1 to 1.5 mile radius (2-3 mile diameter).
Antennas are directional(3 sectors per site).

2.  If WiMax can use the unlicensed 2.4 GHz WiFi band,  does it scan and
not use this band if existing Wifi signals are detected ?

We do not use unlicensed frequency.  We are using the BRS spectrum 2.5
to 2.6 GHz.

3. On the client ( USB device ) what is the power consumption compared
to 802.11g    WiFi,     nominal  and/or peak    I've heard that WiMax
wasn't feasable for Mobile devices,  so is the Clear USB device
throttling back power when data isn't being sent to cut down this power
usage ?  ( But still has large peak power at high data rates ? )

Mobile power TX max = +23dBm.

4. For the home router  how is QoS enforced for VOIP ?   IE  for those
of us with our own  Asterisk PBX device connecting to existing wholesale
providers  ( using  SIP port 5060/5061  and RTP packets on ports 10000
thru 20000 ) will those packets be priortitized over other data.
Obviously this
applies both directions and so would involve both the software queuing
discipline in the home router and the queuing discipline at the ClearMax
downlink to the client.

This will have to be answered by the VOIP team.

5. For WiFi,  FCC ISM (point to multipoint) rules limit you to an
effective isotropic radiated power
( EIRP ) of 30dBm in to a 6dBi antenna.  What is the legal maximum EIRP
for WiMax at the antenna ?
 Ive heard it's 63dBm for licensed band or nearly 2000W compared to the
4W for WiFi.    Guess you
don't want to be close to that antenna.

Our power levels are +55 to +56 dBm.  Our RF antennas are 17.5dBi gain.
 I believe the max power is less than 2000W.

Philadelphia Linux Users Group         --        http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug