DirectQAM)Module Technical Specification 7 January 2009 Version 1.0
)
x Eight DVB-C modulators with agileoutput using the DirectQAM principle
x Two independent groups of fouradjacent channels; Each group has
independent settings for base RF
frequency
x Gigabit-Ethernet interface for controland contribution of up to eight
Transport Streams
x RF-mute function for fail-over switchingx NIT-replacement for localising anetwork
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Str. Constantin Bosianu 16,040506 Bucuresti 4, Romania
tel: +40 745 076 696fax: +40 381 175 581
email: [email protected]
Technical Specifications
x Key component in next-generationHFC cable-TV IP networks.
x Cable-network emulator for
development labs, repair shops,
production testing, etc.
A schematic representation of an HFC
cable network with DirectQAM modules
is shown below.
The Headend receives TV programs from
contribution links, assembles Multi-Program
Transport Streams (MPTS), and multicasts
these on the HFC IP network. The
DirectQAM modules are located in the
Nodes that feed the final coax to the
homes. Each DirectQAM module
receives 8 multi casted MPTS streams and
trans modulates them to QAM.
A key advantage of the concept is that
the DirectQAM modules in each Node
can be configured to select a different
mix of streams.
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Technical Specifications
In order that the 67%V perceive aconsistent DVB network, the Headend
generates Network Information Tables
(NITs) and multicasts these in TS-over-IP
format to the Nodes. Each DirectQAM
module reads the appropriate
5HSODFHPHQW1,7DQG LQVHUWs it into theMPTS streams.
x RJ-45 Gigabit ruggedized Ethernet portx F-Type RF Outputx Power (connector type DB9)x 4x LED
x Power On (green)x Device Error (red flashing)x Ethernet link statusx Ethernet activity
Min Typ Max Unit
GIGABIT ETHERNET PORT
Standard
Data Rate
Connector
IEEE 802.3af
1000
RJ-45
Mbps
PROTOCOL
TS Encapsulation
Modes
Pro-MPEG CoP #3 release 2
UDP; no RTP, no FEC
Transport Packets / IP Packet
Latency (excluding jitter
tolerance)
1 7
10 ms
CONTROL
Multicast Support
Network Management
Time/Date Synchronisation
IGMP v2
SNMP v2c
(S)NTP For log timestamps
NIT REPLACEMENT
Size of NIT Buffer 10 kByte
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Technical Specifications
Min Typ Max Unit
DVB-C MODULATION
Standard
Constellations
EN 300 429
64 or 256 QAM
Symbol Rate
MER
Spectrum Flatness
Shoulder Attenuation
5.0569
40
55
43
5.3605
0,2
Ms/s fixed
dB
dB
dB
RF OUTPUT
Impedance
Return Loss
Connector Type
Level (per QAM Channel)
Step Size
Accuracy
RF-Off Attenuation
Spectral Purity
Wideband Noise
15
-23
-14
70
75
17
F female
0.5
-60
-3
+6
1
-135
:dB
dBmW in 75: 8ch ondBmW in 75: 1 ch ondB
dB
dB
dBc /-3dBm ref
dBmW/Hz @-
3dBm/QAM channel
level
RF FREQUENCY
Range
Step Size
Stability
Accuracy
Phase Noise @ 10 kHz
47
12.5
5
5
862*
-98
MHz
kHz
ppm
ppm
dBc/Hz
* 1000MHz is planned
RF level conversion table
dBmW//75 dBmV dBV+6 54.7 114.7
-3 45.7 105.7
-14 34.7 94.7
-23 25.7 85.7
Page 4 of 9 Specifications may change without prior notice!
Technical Specifications
OTHER SPECIFICATIONS
Min Typ Max Unit
POWER
Power Supply
Power Consumption
12
12
V +- 5%
W
ENVIRONMENTAL
Temperature Range 0 +45 C
REGULATIONS
EMC CE Industrial
MECHANICAL
Dimensions W x H x D 100x160x18 (PCB Only)
107x163x32 (Boxed version)
mm
The DirectQAM module features eight
complete DVB-C modulators, organised in
two groups of four. All eight modulators
are operated at the same symbol rate
and same input-to-output latency. Per
group of four an independent base
frequency and channel spacing can be
specified. Every channel can be switched
on or off individually.
The module gets Transport-Stream data by
real-time reception of up to eight UDP
streams. For each stream an independent
IP address and port address can be
specified. The joining of multicast groups is
supported.
The UDP packets are unpacked into
Transport Packets, which are stored
(conceptually) in a FIFO buffer.
The network will incur variable delay (jitter)
on the UDP packets. The DirectQAM
module measures the arrival time of the
UDP packets and applies a smoothing
algorithm to the timestamps by using a
linear regression algorithm. The result is an
estimate of what the arrival time would
have been without network jitter.
A secondary result from this process is an
estimate of the Transport Rate.
An intentional delay is added to the de-
jittered timestamps before releasing the
Transport Packets from the FIFO. The delay
corresponds to the maximum amount of
jitter that can be tolerated in the arrival of
the UDP packets.
The so-recovered Transport Stream is re
multiplexed to a fixed rate that matches
the symbol rate and modulation settings.
Re multiplexing in this context requires null
packet insertion and PCR correction.
The resulting TS is modulated in
accordance with the DVB-C standard by
applying PRBS, Reed-Solomon FEC,
Interleaving, QAM mapping and channel
filtering. Finally the signal is fed into a
direct digital I/Q modulator for generating
the modulated signal in the 47 .. 862* MHz
range.
The modulated signal is led through an RF
output amplifier with programmable gain
and regulation loop, resulting in a
cumulative output level between -23 and
-3 dBm at 75.
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Technical Specifications
Each DirectQAM module has a unique
MAC address sequentially assigned from a
MAC address range provided to STN.
Note: next to the unique MAC address
each DirectQAM module has an
independent unique serial number.
The IP address will be fixed, DHCP is not
supported. The fixed IP address can be
configured using a configuration tool. No
factory reset of the IP address is available;
the configuration tool will always be able
to reconfigure the IP address regardless of
the programmed value.
The IP-address configuration process works
with a laptop and the DirectQAM
module connected directly to each other
in a mini-network. A proprietary protocol is
used as follows. The configuration tool
broadcasts a UDP message. The
DirectQAM module reacts with an UDP
packet containing its current IP address
and MAC address. After that the
configuration tool sends a UDP packet to
the DirectQAM module to configure the
IP address, subnet mask and default
gateway. These settings are persisted in
flash memory.
Run-time network configuration includes
nine programmable multicast IP
address/port filters, eight for the QAM
channels and one to receive a NIT for the
NIT-replacement function.
The DirectQAM module joins multicast
groups using IGMP v2. Source-specific
multicasting (requiring IGMP v3) is
presently not supported but the MIB is
prepared for this as a future extension.
A special function supported by the
DirectQAM module to enhance
deployment options is NIT replacement.
The NIT in each Transport Stream can be
replaced by a NIT selected from an
independent NIT stream. The intention is to
DOORZ ORFDOL]DWLRQ of the NIT-actual. Asimilar function for the NIT-other is not
supported.
An IP address and PID can be
programmed to identify a multicasted
Transport Stream containing the
replacement NIT. The DirectQAM module
reads Transport Packets from the selected
PID and caches the NIT table internally.
Just a single NIT can be cached; The
same NIT will be used for all channels.
NIT replacement can be enabled
individually for each of the eight channels.
If NIT replacement is disabled, or if it is
enabled but no complete NIT has been
received yet, Transport Packets with PID
16 (NIT PID) are unaffected.
If NIT replacement is enabled and a
complete replacement NIT has been
received, then each packet with PID 16 is
replaced by a packet from the
replacement PID. The continuity counter
of the packets is automatically
incremented for each packet.
Please note that it is not required that PID
16 in the FKDQQHOV Transport Streamcontains a NIT. PID 16 may consist entirely
of null packets, too. Furthermore, if PID 16
does contain a NIT, the repetition rate of
the replacement NIT may be different
from that of the original NIT because of a
difference in number of packets.
While cycling the replacement NIT, the
DirectQAM module keeps monitoring the
NIT-replacement IP address to check
whether a NIT with a new version number
is available. If so, a new replacement NIT is
downloaded, but the old one is still being
scheduled.
Page 6 of 9 Specifications may change without prior notice!
Technical Specifications
When the entire new replacement NIT has
been downloaded, the DirectQAMmodule starts scheduling the new NIT.
The product can be managed and
controlled with a web interface and
through SNMP (for a network
management system). Both interfaces
give access to all control settings, status
information, alarm status and the log.
The main purpose of the web interface is
product configuration and getting
diagnostics for troubleshooting. SNMP, the
industry-standard network-management
protocol, is intended for operational
control. The table below provides an
overview of the management and control
information available over the web and
SNMP interface. Further details can be
found in the detailed specifications.
IP Address / Port IPV4 address and port number; may be unicast or multicast
Channel enable Channel is used yes/no
Delay factor Maximum delay factor (indicator for IP jitter) in the last 10
seconds
TS rate TS rate as estimated by the DQAM module
Modulation
standard
DVB-C
Annex-B
)RUWKHPRPHQWMXVW'9%-&LVVXSSRUWHG7KH0,%VKRXOGEHprepared for supporting other modulation standards in later
models
Constellation 64, 256 Number of QAM constellation points: 64, 256
Base frequency 47 .. 862MHz Centre frequency of first channel in the group
Channel spacing 5 .. 8MHz Channel spacing between adjacent channels
Symbol rate 5.05 or 5.36 Symbol rate depending on constellation
Jitter tolerance 0 .. 100ms Amount of IP jitter that can be tolerated without corrupting the
outgoing TS (underflow/overflow of internal buffer). The jitter
tolerance (necessarily) will add up to the input-to-output delay
RF enable Enable output signal at RF output
RF level -23 .. -3 dBm Level at RF output with 0.5dB steps
NIT address / port IPV4 address and port number of replacement NIT
NIT PID 0 .. 8191 PID from which to get replacement NIT
NIT replace enable Enable NIT replacement
(S)NTP server Enable NIT replacement
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Technical Specifications
Time Current time recovered through (S)NTP
Log 256 entries Logs all settings, alarms and reboots
Output level -23 .. -3 dBm Output level actually measured
Temperature 0 .. 50C Ambient temperature
MIB II System, Interfaces, at, ip, icmp, tcp, udp, egp, snmp
RF level Unable to regulate RF level to the desired level
Temperature Device temperature exceeds a programmable threshold
Page 8 of 9 Specifications may change without prior notice!
Technical Specifications
Whenever a setting is applied that may
cause unwanted noise on the output (e.g.
because of DAC reconfiguration), the RF
output will be muted to avoid pollution of
the entire band. Settings that cause such
service interruptions will be clearly marked
in the configuration manual.
Any control setting applied through the
web or SNMP interface is persisted in flash
memory, so that when the device reboots
after a power cycle it starts with the last-
used settings.
The RF level and temperature alarms are
throttled to a maximum of one alarm per
5 minutes. If the alarm condition persists,
the corresponding trap is generated once
every 5 minutes.
A log is maintained in flash memory to
keep a persistent UHFRUG RI LQWHUHVWLQJevents. The main purpose of the log is to
facilitate post-mortem fault analysis.
Each log line will be time stamped with
the current date/time, which is
synchronised through NTP. When the
date/time has not been synchronised yet,
the number of seconds since last reboot is
used instead.
The log will keep track of the following
events:
o Device started
o NTP lock achieved
o Any control setting applied
o SNMP traps
When the DirectQAM module boots
some elementary consistency checks will
be applied, but no sophisticated self-test.
The DirectQAM module will employ a
watchdog to automatically restart the
device upon a software crash.
The productV ILUPZDUHDQGVRIWZDUHFDQbe uploaded via the web interface using
ftp. The first version of the DirectQAM
module will not implement a sophisticated
mechanism to authenticate the uploader.
$ GXDO-%,26 DUFKLWHFWXUH LV XVHG WRavoid disasters when a bad image would
be uploaded.
The DirectQAM firmware shall be
protected by a simple Intellectual-
Property copy protection mechanism.
Page 9 of 9 Specifications may change without prior notice!
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