directqam specifications v1.0b

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

Protected by worldwide patents Page 1 of 9 Specifications may change without prior notice!

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.

Page 2 of 9 Specifications may change without prior notice!


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



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



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.



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.



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



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



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.


directqam specifications v1.0b

Documents