User's Guide Part 1

Wireless operation Chapter 1 Product description
phn-0896_009v003
1-22
UNDER DEVELOPMENT
Feb 2010
o When link mode optimization is set to TDM Traffic see Link mode
optimizati
on on page 1-20).
o When
TDD synchronization is enabled (see Time division duplex
s
ynchronization on page 1-25).
o In r
egions where radar avoidance is operational (see Radar avoidance on
pag
e 1-24).
OFDM and channel bandwidth
The PTP 600 series transmits using Orthogonal Frequency Division Multiplexing
(OFDM). This wideband signal consists of many equally spaced sub-carriers. Although
each sub carrier is modulated at a low rate using conventional modulation schemes,
the resultant data rate from all the sub-carriers is high. OFDM works exceptionally
over a Non-Line-of-Sight (NLoS) channel.
The channel bandwidth of the OFDM signal is configurable to one of five values: 5
MHz, 10 MHz, 15 MHz, 20 MHz and 30 MHz. Higher bandwidths provide greater link
capacity at the expense of using more spectrum. Systems configured for a narrower
channel bandwidth provide better receiver sensitivity and can also be an appropriate
choice in deployments where the amount of free spectrum is limited.
NOTE
The Channel Bandwidth must be configured to the same value at both ends
of the link.
Not all channel bandwidths are available in all regions or all frequency
variants.
Adaptive modulation
The PTP 600 series can transport data over the wireless link using a number of
different modulation modes ranging from 256QAM 0.81 to BPSK 0.63. For a given
channel bandwidth and TDD frame structure, each modulation mode transports data at
a fixed rate. Also, the receiver requires a given signal to noise ratio in order to
successfully demodulate a given modulation mode. Although the more complex
modulations such as 256QAM 0.81 will transport data at a much higher rate than the
less complex modulation modes, the receiver requires a much higher signal to noise
ratio.