Running HPNA 2.0 Over Existing
Cable/TV Coax
Abstract
As the home entertainment market moves towards high bandwidth digital media
delivery, reliable digital distribution of that media content within the home becomes
essential. With the broadband access point at the home entertainment Media
Center and the in-home network emanating from that point, it becomes possible to
provide high-quality digital streaming video, audio, voice over IP (VoIP) and Internet
access services to TVs, PCs and appliances throughout the home. This white paper
describes a simple way to transport digital media using the existing coaxial cable
and standard protocols. HPNA over Coax (HCNA) provides a robust, eight
prioritized Quality of Service 32 Mbit/s network that can also extend to clients on the
in-home telephone wiring. HCNA operates simultaneously with cable television and
cable modem services on the same coax.
Contents
Introduction............................................................................................................................................. 3
Background: Home Networking Alternatives ...................................................................................... 3
Using the existing Coax .......................................................................................................................... 4
HPNA Coax Tap (HCT) ..................................................................................................................... 4
Splitters and Attenuation ................................................................................................................... 5
Typical Installation Scenarios ................................................................................................................. 7
Digital Subscriber Line (DSL) and HCNA ........................................................................................... 7
Direct Broadcast Satellite (DBS) and HCNA ...................................................................................... 8
Cable Multi Service Operator (MSO) Systems and HCNA ................................................................. 9
HCNA Challenges and Mitigation.......................................................................................................... 10
HPNA Bandpass Splitter (HBS) ....................................................................................................... 10
IF TV Noise Filter ............................................................................................................................ 11
Spectrum Management ........................................................................................................................ 11
Summary .............................................................................................................................................. 13
Resources and Call to Action................................................................................................................ 13
Acronyms and Terms............................................................................................................................ 13
Appendix A – HCT-1 Frequency Response .......................................................................................... 14
Running HPNA 2.0 Over Existing Cable/TV Coax - 2
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Author's Disclaimer and Copyright:
Copyright © 2001,2003 Broadcom Corporation
All Rights Reserved
No part of this document may be reproduced or disclosed to any third party, in any form or by any
means, without permission in writing from Broadcom Corporation.
Some or all of the information contained in this document is the subject of a patent filing by Broadcom
Corporation. As such, this information is subject to strict non-disclosure rules.
Broadcom Corporation reserves the right to make changes to the products or information contained in
this document without notice. No liability is assumed as a result of their use or application. No rights
under any patent accompany the sale of any such products or information.
Epigram, InsideLine, iLine10, and iLine32 are trademarks of Broadcom Corporation.
Broadcom Corporation
16215 Alton Parkway
Irvine, California, 92618
www.broadcom.com
WinHEC Sponsors’ Disclaimer: The contents of this document have not been authored or confirmed by
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information contained in this document does not necessarily represent the views of the WinHEC
Sponsors and the WinHEC Sponsors cannot make any representation concerning its accuracy. THE
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be the trademarks of their respective owners.
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Running HPNA 2.0 Over Existing Cable/TV Coax - 3
Introduction
As the home entertainment market moves towards high bandwidth digital media
delivery, digital distribution of that media content within the home becomes
essential. With the broadband access point at the home entertainment center (via a
Media Center, a cable modem or a set-top box) and with an in-home network
emanating from that point, it becomes possible to provide high-quality digital
streaming video, Voice over IP (VoIP) and Internet access services throughout the
home. This document describes a simple way to transport digital media using
HPNA1 2.0 traffic over 75 Ω coaxial cable, in addition to phone cable, that may
already exist in a home. This HPNA over Coax technology is referred to as HCNA.
HPNA 2.0 coexists on the house’s existing coaxial cable and provides high quality
service to all nodes on most coaxial cable installations. Operating phone cable
based HPNA 2.0 adapters over the existing coaxial cable requires one filter/tap unit
per HPNA node to splice and match the HPNA signal into the coax. The filter/tap
unit may be integrated into the adapter. The HPNA signal will coexist on the coaxial
cable with most existing cable TV or off-air TV transmissions. In the limited cases
where there is spectrum conflict, dedicated coax can be run from the point of entry
to the DOCSIS cable modem or conditional access set-top box (STB). Broadcom
has designed and tested a simple, passive, three-port device called the HPNA Coax
Tap, (HCT-1) that allows the HPNA signals to coexist on the coaxial cable.
In some non-typical cases, some of the existing radio frequency (RF) splitters may
need to be replaced with devices that provide an inexpensive HPNA bandpass
function, and some TVs may also need to have an inexpensive filter added between
the TV and the coax wall outlet. Broadcom has designed and tested simple, passive
devices that perform both these functions.
In addition to the physical installation consideration of installing taps and splitters, a
second consideration for designing home networks is spectral management. There
are several signals that may also be present on household coax and may interfere
with each other. The filter devices already discussed can also be used to manage
the spectrum on the coax network.
Background: Home Networking Alternatives
In most cases today, the home entertainment center is not networked in any way.
Typically, a phone jack is not present at or near most home entertainment centers,
and it is typically expensive or inconvenient to add the new wiring required for an
additional phone jack. Thus it is often impractical to use traditional telephone wire
HPNA to network the home entertainment center. Likewise, an Ethernet network
connection is too costly and troublesome to provision.
Recently, wireless networking products, such as IEEE 802.11b and more recently
IEEE 802.11a, are available, but these suffer from poor link reliability over even
fairly short transmission distances and cannot offer the low bit error rates that are
required to carry digital video without causing interruptions to the video stream. In
addition to the physical limitations, high-bandwidth wireless nodes are more
expensive than HPNA over coaxial cable solutions.
Broadcom’s HPNA products are referred to as iLine10TM, iLine32TM, and
iLine128TM
1
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Using the existing Coax
At or very near almost every home entertainment center there is pre-wired coaxial
cable that feeds the cable television or TV antenna signal to other rooms in the
house. Typically, coaxial cable is installed to all the other likely entertainment
locations in the house - the bedrooms, the study, or the family room - making coax
ideal for the delivery of high-speed digital content to wherever it is desired within the
home. HPNA 2.0 16/32 Mbit/s networking technology sharing a home’s existing
coaxial cable provides high-speed networking for the delivery of high quality digital
video, VoIP and shared broadband Internet access throughout the house without
adding any new wires. HPNA 2.0 can be added to the existing coaxial cable and be
fully compatible with the existing cable TV or off-air TV signals. HPNA 2.0 nodes are
also relatively inexpensive.
As more bandwidth is required, future HPNA standards delivering speeds up to 100
Mbps could be employed over the same network infrastructure, offering a simple
and convenient upgrade path for the provision of future services, such as high
definition television.
HPNA Coax Tap (HCT)
A HPNA Coax Tap (HCT) device is required, one per HPNA node on the coaxial
cable system, to splice and impedance match the HPNA signal onto the coax. The
HCT may be integrated into the HPNA node or may be an external unit to retrofit an
existing telephone wire based HPNA node. Broadcom has developed a simple
passive three-port diplexer/balun circuit with coax to coax DC bypass that has
proven very satisfactory in testing. The three ports are:
HPNA — RJ11 connector
Coax (to wall) — 'F' type RF connector
TV passthrough—'F' type RF connector
The electrical characteristics between the ports are as follows:
There is isolation between the TV and HPNA ports.
There is DC continuity between the Coax and TV ports.
There is a diplexer function between the Coax port, the HPNA and TV ports. This
directs energy between the Coax port and the HPNA or TV ports according to
the frequency band; energy in the 4 to 30 MHz band is directed to/from the
HPNA port, and energy above ~30 MHz is directed to/from the TV port.
The HPNA port has a transformer/balun to match the 75 of the coaxial cable to the
110 of the HPNA node.
Figure 1 shows the HCT block diagram. The specific frequency response of an
HCT-1 device is described in Appendix A. Commercially available devices, HCT-2
and HCT-3, are shown in Figure 2 and available from
www.CommunicationsEquip.com.
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Figure 1. HCT Block Diagram
Figure 2. HCT-2 and HCT-3
Splitters and Attenuation
A typical home coaxial cable installation is shown in Figure 3. This shows the two
levels of splitters that are typically used to feed coaxial cables to most rooms in the
house.
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Top of Tree
Television
Cable Head End
Splitter level 1
Television
Splitter level 2
Television
Figure 3. Typical splitter arrangement in a home.
Typically, a house will only use either cable TV or an off-air antenna but not both,
since that would require doubling up every coax run in the house. The “top of the
tree” is the point of entry where the cable TV or antenna is fed into the house’s
coaxial wiring plant. This is usually at the top of the splitter tree, as shown in Figure
3. Up to two or three levels of splitters may be used, and typically those levels are
integrated into a single enclosure.
RF splitters can be two-, three- or four-way devices. They are simple, passive
devices that have approximately 4 dB split loss per two-way split, and approximately
10 dB of isolation between the output ports per two way split over a frequency range
from below5 MHz to above 500 MHz. Internally, three- and four-way splitters use
multiple cascaded two-way splitters to achieve the multi-way split. Two-, three-, and
four-way RF devices are characterized as follows:
Two-Way Splitters. Two-way splitters have the least split loss and isolation.
Three-Way Splitters. A three-way splitter consists of two internal two-way splitters,
with the second internal splitter cascaded off of the first internal splitter.
Four-Way Splitters. A four-way splitter consists of three internal two-way splitters,
with the second and third internal splitters cascaded off of each of the ports of
the first internal splitter. In the worst case, a four-way splitter has about 8 dB
loss per split and about 20~30 dB isolation between the extremities of the
splitter tree.
HPNA is a rate adaptive technology that depends on the characteristics of the
transmission medium. One of the dominant factors is the amount of attenuation
between two HPNA nodes. Broadcom’s 16 Mbit/s HPNA 2.0 product (iLine10TM)
works at full rate up to approximately 28 dB of attenuation and Broadcom’s
32 Mbit/s HPNA 2.0 product (iLine32TM) works at full rate up to approximately 20 dB
of attenuation. The rates progressively adapt down to 4 Mbit/s at approximately
42 dB of attenuation. The attenuation of the coaxial cable (RG-6 or RG-59) at HPNA
frequencies (4 to 10 MHz) over the typical distances found in a home is
insignificant. However, the attenuation through splitters bears further examination.
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In a typical home, such as that shown in Figure 3, if two-way splitters were used,
the worst-case coax path loss from the end of any one coax cable to another would
only be approximately 14 dB. (4 dB going up the tree from the second level splitter
plus 10 dB across the top-level splitter.)
If the same two-level system used four-way splitter devices instead of two-way
devices, the worst-case coax path loss from the end of any one coax cable to
another could be as much as 28 dB. (8 dB from the second level splitters plus
approximately 20 dB across the top-level splitter.) iLine10 would still be able to
provide full performance with this level of attenuation and only has minimal impact
on an iLine32 system.
For streaming video, VoIP or Internet access services from the broadband access
point at the top of the splitter tree down to any end node, the end-to-end path loss
will be 16 dB (comprising 8 + 8 dB based on a worst case scenario using four-way
splitters). As previously noted, this will not affect the performance of the iLine10 or
iLine32 systems.
In many HCNA systems, it is anticipated that digital high-speed video will stream
from the top of the splitter tree. End node to end node traffic is likely to have only
low bandwidth needs and so a path loss of even 42 dB should be considered
acceptable.
Services that require high bandwidth between the end nodes, or coaxial cable
installations with more than two levels of four-way splitters, may require some level
of mitigation to remove the isolation loss between output ports on the splitters in the
HPNA frequency band. Similarly, more levels of splitters will require mitigation of
isolation loss at more than one device.
Typical Installation Scenarios
Although there are many possible scenarios in homes, the following are
representative of typical scenarios. The diagram on the left side of each figure
shows the existing scenario. The diagram on the right side of each figure shows the
system after installation of the entertainment system, for example a Digital
Subscriber Line (DSL) system, a Direct Broadcast System (DBS) system, or a Multi
Service Operator (MSO) system, that uses HCNA.
Digital Subscriber Line (DSL) and HCNA
Figure 4 shows a typical topology for a home that receives content via a DSL
provider. The DSL access line is terminated in a DSL modem with a residential
gateway (router). The existing telephone wiring can be used to connect devices
such as computers. A HCT is added to bridge the telephone wiring to the coax
wiring in which digital video signals can be distributed to IP-STBs. IP-STB devices
receive and decode a full-bandwidth MPEG2 video stream from the Residential
Gateway using the HCNA digital network.
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DSL modem
/ Residential
Gateway
Phone wiring
Computer
DSL Head End
IP-STB
HCT
Television
Cable Head End
IP-STB
Television
→
Television
Figure 4. DSL provided content. The red “X” indicates where the exiting cable is cut.
Direct Broadcast Satellite (DBS) and HCNA
Figure 5 shows a typical topology for a home that receives content via a Direct
Broadcast Satellite (DBS) provider. The DBS antenna is terminated in a DBS-STB.
Additional televisions can be supported by using the existing coaxial cable to
connect the IP-STB with HCT and HPNA adapters. IP-STB devices receive and
decode a full-bandwidth MPEG2 video stream from the DBS-STB using the HCNA
digital network.
Figure 6 shows that DBS services can be used even though a Cable Modem is also
being used.
Satellite dish
DBS
Television
Television
IP-STB
Television
Television
Television
→
Figure 5. Replacing existing Ariel broadcast services with DBS.
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Television
Running HPNA 2.0 Over Existing Cable/TV Coax - 9
Satellite dish
Cable
Modem
Computer
DBS-STB
Television
Cable Head End
IP-STB
Television
→
Television
Figure 6. Using DBS services with a Cable Modem
Cable Multi Service Operator (MSO) Systems and HCNA
For households that wish to receive Cable or MSO services, HCNA can distribute
digital data over the same coax used to distribute the cable content. Architectures
with MSO services generally require one extra run of coax to the new main STB or
possible reorientation of some of the existing splitters. This allows the existing coax
to be reused with the main STB becoming the top of the distribution tree.
Figure 7 shows the connections when the main STB does not include a DOCSIS
cable modem. Content is transmitted from the cable head-end to the main STB
using a new coax run, and the existing coax tree is used to distribute digital data
from the main STB as well as relay the RF content through the main STB. Further
Digital MPEG2 content can be sent from the Main STB to IP-STB using the HCNA
digital network. If there are any DOCSIS cable modems, they use existing coax
cable separate from the HCNA network.
Cable
Modem
Computer
Main STB
Television
Cable Head End
IP-STB
Television
→
Television
Figure 7. MSO content with Cable Modem
Alternatively, if the main STB does contain DOCSIS cable modem functionality,
existing cable modems become redundant. In these types of scenarios, the existing
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coax is used to distribute digital data from the main STB using HPNA to IP-STB and
computers. An existing cable modem is replaced with an HCT and a HPNA adapter
as shown in Figure 8. Again, content is transmitted from the cable head-end to the
main STB using a new coax run and the existing coax tree is used to distribute
digital data from the main STB, as well as relay the RF content through the main
STB.
HCT &
HPNA
Computer
Main STB
Television
Cable Head End
IP-STB
Television
→
Television
Figure 8. MSO content and replacing existing Cable Modem with HCT and HPNA
Adapter (since cable Modem embedded in main STB)
HCNA Challenges and Mitigation
In order to maintain the highest HPNA throughput, coaxial cable installations with
splitters that have higher than average port to port isolation or more than two levels
of four-way splitters, will require some level of mitigation to remove the isolation loss
in the HPNA frequency band. This mitigation may be one of two forms. The existing
splitters (show in blue in the scenarios above) would be reoriented so that the main
path would be between an input and output port (4 dB of attenuation) instead of
between the output to output ports (greater then 10 dB attenuation). Alternatively,
the splitters may be replaced with HPNA friendly splitters (HBS) described below. If
there are more levels of splitters, mitigation is required at more than one device.
Additionally, there are some unintentional noise sources on the household coax.
Older built-in TV tuners can generate significant amounts of intermediate frequency
(IF) egress out of their antenna/cable TV F-connectors. TVs that are directly
connected to the coaxial cable may cause some interference to the HPNA signals
on the coax. A simple high-pass or notch filter that removes noise in the HPNA
band can be placed between the TV and the coax wall outlet. These can be loworder passive filter devices that are very inexpensive to produce.
HPNA Bandpass Splitter (HBS)
A HPNA Bandpass Splitter (HBS) is designed to replace conventional RF splitters
in wiring situations where there are multiple levels of RF splitters. Conventional RF
splitters, found in nearly all home coax wiring systems, may have significant
isolation (loss) between its output ports at frequencies around 5 MHz. Since HPNA
adapters use frequencies above 4 MHz, conventional RF splitters may need to have
an additional bandpass function. Essentially, a HBS is a conventional splitter design
with a few extra passive components added to provide a bypass for the HPNA
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frequencies between all ports on the splitter. Broadcom has built such devices and
tested them satisfactorily. These devices are also commercially available.
IF TV Noise Filter
An IF TV noise Filter (ITF) is designed to mitigate Intermediate Frequency TV
noise that may be coupled onto the coaxial cable from the input F-connector on a
television. IF noise typically is centered around 6 MHz, which falls directly in the 4 to
10 MHz HPNA band. The ITF is a 2-port device with two F-type 75  connectors on
it; one for the coax connection (wall) and the other for the TV. This may be
constructed by taking an HCT and terminating the HPNA port with a 110  resistor.
The ITF would direct all energy from the TV below 30 MHz into the terminated port,
thus, no interfering energy in the HPNA band would appear on the coax port. Figure
9 shows a typical installation with HPNA running over the existing coaxial cable in a
home.
Satellite dish
Cable
Modem
Computer
DBS-STB
HCT
Television
Cable Head End
IP-STB
HBS
HCT
Television
ITF
Television
Figure 9. Placement of HBS and ITF mitigation devices
Spectrum Management
The coaxial cabling within a typical home is subject to several sources of ingress. In
addition to the expected terrestrial broadcast and cable broadcast television signals,
other intentional signals such as cable modems or STB conditional access signals
may be present. Some example signals and the signal spectrum are shown in Table
1. Fortunately, HPNA signals do not conflict with most of the existing signals. In
cases of overlap, the topologies described above obviate the need for further
mitigation.
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Table 1 Signals on household coax
Service
Downstream Cable Broadcast
Downstream Aerial Broadcast
Downstream Cable Modem
North American Upstream Cable Modem
European Upstream Cable Modem
Upstream Conditional Access
IF Local Oscillator Leakage
Bi-Directional Remodulators
(typically on Channel 3 or 4)
ILine10 (HPNA 2.0)
iLine32 (HPNA 2.0)
iLine128 (HPNA 3.0)
IEEE 802.11b/g
IEEE 802.11a
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Frequence (MHz)
55 ~ 1000
54 ~ 84 , 174 ~ 216, 470 ~ 806
50-54 ~ 300-864
5 ~ 42
5 ~ 65
8 ~ 12 (192 kHz wide pulses)
6 (approx.)
Channel 3: 60~66
Channel 4: 66~72
4 ~ 10
4 ~ 10
4 ~ 21
2400 ~ 2483
5150 ~ 5350, 5470 ~ 5725
Running HPNA 2.0 Over Existing Cable/TV Coax - 13
Summary
In conclusion, Broadcom has shown and can demonstrate that it is entirely feasible
and relatively inexpensive to run HPNA 2.0 over a home’s existing coaxial cable,
maintaining compatibility with existing cable TV/off-air TV services, and that this can
be achieved without changing the infrastructure and, in the great majority of cases,
without further mitigation. Such a system enables the easy delivery of multiple highspeed, high-bandwidth, high-quality digital entertainment and data services to easily
be extended to every room in the home.
Call to Action and Resources
Call to Action:
For system manufacturers: Consider using HCNA in Media Center PCs to create an
entertainment network using the existing coaxial wiring in the home.
For device manufacturers: Consider using HCNA in IP Set Top Boxes (IP-STB) to
connect to an entertainment network using the existing coaxial wiring in the
home.
For questions about HPNA over Coax (HCNA), please send e-mail to Stephen Palm
[email protected].
Acronyms and Terms
DOCSIS
DBS
DSL
HBS
HCNA
HPNA
IEEE
ITF
HCT
MSO
RF
STB
VoIP
Data Over Cable Service Interface Specification
Direct Broadcast Satellite
Digital Subscriber Loop
HPNA Bandpass Splitter
HPNA Coax Network Adapter
Home Phoneline Networking Alliance or Home Phoneline Networking
Adapter http://www.hompna.org
Institute of Electrical and Electronics Engineers, Inc. http://www.ieee.org
IF TV noise Filter
HPNA Coax Tap
Multi Service Operator
Radio Frequency
Set Top Box
Voice over IP
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Appendix A – HCT-1 Frequency Response
Figure 10, Figure 11, and Figure 12 show the frequency response of an HCT-1
device.
Figure 10 shows very low loss between the coax and HPNA ports in the HPNA
band (about 1.2dB maximum at 10MHz) and excellent isolation between these two
ports at frequencies above 30MHz.
Figure 11 shows very low loss (less than 1dB) above 50MHz between the coax and
TV ports of the HCT-1. Also note there is good isolation between these two ports in
the HPNA band: this will prevent stray IF interference from the TV from affecting the
HPNA on the coax.
Figure 12 shows excellent isolation between the TV and HPNA ports at all
frequencies. The worst case (at the diplexer crossover frequency of 30MHz) is still
better than 6dB.
(a) (b)
Figure 10. Coax to HPNA Port – HCT-1 Frequency Response (a) 0 – 10 MHz (b) 0 – 500
MHz
Figure 11. Coax to TV Port – HCT-1 Frequency Response
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(a) (b)
Figure 12. TV to HPNA Port – HCT-1 Frequency Response (a) 0 – 10 MHz (b) 0 – 500
MHz
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