Modulation type
List box {FSK, QAM}, default = "FSK"
FSK
Suitable for difficult conditions – longer radio hops, non-line of sight, noise / interferences on
Radio channel…
Note
FSK belongs to the continuous-phase frequency-shift keying family of non-linear mod-
ulations. Compared to QAM (linear modulations), FSK is characterized by narrower
bandwidth, a lower symbol rate and higher sensitivity. As a result, the system gain is
higher, power efficiency is higher, but spectral efficiency is lower.
QAM
Suitable for normal conditions offering higher data throughput.
Note
QAM belongs to the phase shift keying family of linear modulations. Compared to FSK
(non-linear modulations), QAM is characterized by wider bandwidth. The spectral effi-
ciency is higher, power efficiency is lower and system gain is typically lower.
Modulation
FSK modulations:
List box {2CPFSK; 4CPFSK}, default = "2CPFSK"
QAM modulations:
List box {DPSK; π/4DQPSK; D8PSK; 16DEQAM; 64QAM; 256QAM}, default = "DPSK"
FEC
List box {2/3; 3/4; 5/6; Off}, default = "Off"
FEC (Forward Error Correction) is a very effective method to minimize radio channel impairments.
Basically, the sender inserts some redundant data into its messages. This redundancy allows the
receiver to detect and correct errors; used is Trellis code with Viterbi soft-decoder. The improvement
comes at the expense of the bitrate. The lower the FEC ratio, the better the capability of error cor-
rection and the lower the bitrate. Bitrate = Modulation rate × FEC ratio.
Radio can receive not only radio frames with the very same setting, but also frames with different type
of modulation - the Auto-speed functionality.
Modulation types which can be combined (with the same radio frequencies, channel spacing and OBW
limit) are:
2CPFSK & 4CPFSK with or without FEC
or
DPSK & π/4DQPSK & D8PSK & 16DEQAM & 64QAM & 256QAM with or without FEC.
This functionality is used especially in the Individual link option (Flexible protocol) and the setting of
the Base - Remote communication settings (in Base Driven Protocol).
RipEX2 Radio modem & Router – © RACOM s.r.o.
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