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6 8
E L E CT R I C AL CONNE CT I ON
W I NT E R 2 01 5
CABLING
Coaxing Multimedia
A
n industry alliance of electronics
companies has developed a home
networking technology that runs
over existing coaxial cabling.
The stated aim of the Multimedia over
Coax Alliance (MoCA) is to provide a low-
cost and reliable technology for accessing
and distributing content throughout the
home, with little or no cabling remediation
work required.
Suitable content for a MoCA-compliant
network include HD TV, UltraHD TV,
gaming, large file transfers and general
local area network (LAN) traffic. MoCA
technology can also be used to provide
the copper link to a wireless router for
extending the reach of wireless networks.
The alliance has 53 member companies,
including some large entertainment
electronics manufacturers (Samsung, LG),
networking electronics manufacturers
(Cisco, D-Link, Huawei, Netgear, ZyXel),
cable TV operators (Verizon, Broadcom) and
some chip manufacturers and distributors.
Only members have access to the
technology, and MoCA-enabled devices
are certified to work on MoCA networks.
The alliance provides a list of certified
products on its website: www.mocalliance.
org/products/index.htm.
In essence, MoCA technology is another
form of coax-based Ethernet. Those with
long memories will recall the days of
10Base2 and 10Base5 coax-based Ethernet.
The last version of this type of network ran
at 10Mbps over 50W coax in a bus topology
using BNC connectors.
MoCA uses 75W coaxial cabling with the
familiar F-type screw connectors. This type
is installed in the home to provide access
to cable TV services (e.g. Foxtel in Australia)
or hybrid fibre coax (HFC) internet services
(also known as ‘cable internet’).
SPECIFICATIONS
The Alliance, established in 2004,
approved the first MoCA specification in
2006 and this is now the legacy 1.0 version.
Two approved versions of the MoCA
specification are available – 1.1 and 2.0.
Both were ratified in 2010 and both
support up to 16 networked devices on
a single network.
MoCA 1.1 provides 175Mbps net
throughput and operates in the 500-
1,500MHz frequency range.
MoCA 2.0 supports two performance
modes – basic and enhanced – offering
400Mbps and 800Mbps net throughput
respectively.
There is also a channel-bonded point-to-
point ‘turbo mode’ that can provide 1Gbps
net throughput.
The operating frequency range for
version 2.0 is 500-1,650MHz.
MoCA 2.0 also supports two low-power
modes: sleep and standby. It is backward
compatible with 1.1.
MoCA networking is intended to operate
on the same cabling as the pay TV service.
In the United States, pay TV frequencies
are outside the range of frequencies used
by MoCA, and the two services can operate
simultaneously on the same cable. A filter is
still fitted at the point of entry, to ensure the
MoCA network does not put any unwanted
signals back into the pay TV network.
MoCA is not suitable for use where
coaxial cabling is used for distributing a
satellite service. The output signal from
the low noise block on the dish occupies
a band generally in the region 950Mhz to
2,150MHz, depending on type, and this
overlaps most of the MoCA signal bands.
In Australia, HFC cable uses a band from
5MHz to 700MHz (Optus), or up to 750MHz
(Telstra), and the higher end conflicts with
MoCA frequencies.
This can be overcome by programming
the MoCA network to not use the
conflicting channels, but it may be one
reason why MoCA technology is not
offered by pay TV carriers.
NETWORK TOPOLOGY
The MoCA physical network topology is
determined by existing coax cabling and
is usually some form of tree topology, with
Network technology that uses
existing hybrid fibre coax cable
looks good at first glance,
but is it better than Ethernet?
George Georgevits
compares
the two.