JVC Professional APRIL 2007 NAB-2007 The ProHD Report
Copyright 2007 JVC Professional Products Company All rights reserved Page 18 of 43
MODULATION
Max Bit
Rate
25MHz
Max Bit
Rate
12MHz
Max Bit
Rate
8MHz
Carrier-
to-Noise
Threshold
QPSK 32 Mbps 17 Mbps 10 Mbps 10dB
16-QAM 64 Mbps 30 Mbps 21 Mbps 17dB
64-QAM 65 Mbps 46 Mbps 31 Mbps 23dB
Fig. 5. Table shows approx. max bitrates for microwave channels
with 25, 12 and 8MHz bandwidth, using COFDM and QPSK/QAM
modulation schemes. 2GHz BAS relocation provides for new 12MHz
channel width, but recommends 8MHz “pedestal” digital modulation
bandwidth when using COFDM due to sideband re-growth adjacent
channel interference. Note the 21Mbps in the 8MHz column. ProHD’s
MPEG-2 TS (Transport Stream) over 1394 is 19.7Mbps, the only HD
camcorder able to supply a TS within the 21Mbps limit for reliable 16-
QAM link performance through the 8MHz pedestal 2GHz bandwidth.
The table above gives typical guideline numbers. There are several numbers of
modulation variables including Code Rate/FEC and Guard Interval, coupled with
maximum transmitter output power in various modes, to ultimately determine
reliable range under specific live remote conditions.
JVC’s ProHD GY-HD250U & HD200U are the only HD camcorders (bar none,
as of March 2007) capable of delivering a broadcast quality full bandwidth
1280x720p60 compressed TS out over 1394 at a bitrate of less than 21Mbps,
enabling robust 16-QAM microwave link performance over 8MHz bandwidth.
First-to-Air = Easy Microwave
In addition to the HD camcorder-to-ENG Van microwave link, the TV Station must
even more importantly consider how to cost effectively and easily accomplish the
HD microwave link back to the TV studio from the ENG Van, as this is an essential
service every day in the First-to-Air quest. Again, ProHD provides an easy solution
through the ability to interface and use many existing ENG Van-to-Studio links.
The key is the presence of an existing ASI input in the current digital microwave
transmitter in the ENG Van, accepting a compressed MPEG-2 digital video signal
within the ASI interface format. The Super Encoder in the ProHD camcorder
provides a very high quality compressed HD transport stream through a 1394-to-ASI
Bridge to the microwave transmitter/modulator, eliminating the need to purchase a
new HD encoder or to purchase a whole new microwave transmitter with a
(expensive) built-in encoder.