Table 8: Modulation Scheme Vs. Data Rate - Redline AN-30 System User Manual

Table 8: Modulation Scheme vs. Data Rate

Modulation
BPSK
BPSK
QPSK
QPSK
16 QAM
16 QAM
64 QAM
64 QAM
As indicated in the table above, higher order modulation schemes require greater S/N to
maintain the same BER performance. The noise in this case is defined as the noise floor
of the receiver, i.e., it assumes no interference from other sources (interference from
other sources are addressed below). The main path calculation for determining range
performance is given as:
Where:
Ptx is the transmit power level in dBm
Gtx is the transmit antenna gain in dB
FSL is the free space loss attenuation in dB, and
Grx is the receive antenna gain in dB
The FSL value is dependent on the range between the two terminals, the type of terrain
over which the link is deployed, and whether or not the link is operating line of sight
(LOS), optical line of sight (OLOS) or non-LOS (NLOS). The LOS FSL calculation is
well understood and easy to calculate, and relies on the fact there is absolutely no
obstacle near the direct path. The precise method for determining the amount of clearance
required for LOS involves making use of a factor known as the Fresnel zone. A Fresnel
zone is defined as a path difference of λ/2 away from the direct path, as shown in Figure
20. A "cleared LOS" link assumes there are no obstacles within 60% of the first Fresnel
zone of the direct path. The diagram below illustrates OLOS conditions, where a treetop
is within the first Fresnel zone, and a clear direct path exists between the antennas.
Redline Communications
Coding Over The
Rate Air Rate
(Mbps)
½ 12
¾ 12
½ 24
¾ 24
½ 48
¾ 48
⅔ 72
¾ 72
RSL = Ptx + Gtx – FSL + Grx
Page 67 of 80
AN-30 System User Manual
Uncoded Average
Burst Rate Ethernet Rate
(Mbps) (Mbps)
6
9
12 11.38
18
24 21.77
36 33.01
48
54
.....solving the first mile challenge
5.82
8.63
16.7
44.1
48.8