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with
George Georgevits
splitters used for the branching.
Logically, the MoCA network is a bus
topology, just like other types of Ethernet
network.
Connections to Ethernet devices
without a MoCA port (standard wireless
router, Ethernet switch, etc) are made by
connecting to the Ethernet port (typically
10/100Mbps) on a MoCA bridge, in much
the same way as is done with an HFC cable
modem or ADSL modem.
The bridge provides a gateway to other
networks and is simply a MoCA network
device, so a MoCA network can have a
number of bridges.
In the US, the cable service provider
usually provides the bridge to link the
MoCA enabled cable network to the
home owner’s MoCA network. Otherwise,
the cable network simply connects to
the home network via a splitter. This first
splitter is known as the root splitter.
Some minor remedial cabling work may
be required when establishing a MoCA
network. Splitters and sometimes one or
more amplifiers will be embedded in the
existing coax wiring.
These can sometimes cause problems.
Amplifiers and splitters are often only rated
to 1,000MHz (1GHz) or so, because this is
all that is needed for conventional pay TV
signals. MoCA on the other hand requires
bandwidth to 1,650MHz.
If the amplifier or splitter cannot perform
to this higher frequency, it will cause
significant performance degradation on
the MoCA network.
Sometimes there are un-terminated tap
points on splitters that will act as a source of
signal reflections and must be eliminated.
MOCA ADVANTAGES
The main advantage of a MoCA network
is that it uses existing cabling to provide
high-speed data communications to all
access points.
It also offers the reliability and security of
a cable-based network.
A MoCA network doesn’t have to be
connected to the internet. Its prime
function is to provide high-speed point-
to-point connectivity within the home. It
can work independently as a stand-alone
network and still provide this connectivity.
For file transfers within your home
that do not require internet involvement,
MoCA offers a very satisfactory high-
speed data service.
However, once you connect to a network
outside your home things can change.
One of the claimed advantages of MoCA
is that there are no delays associated
with transferring streaming content, as
can sometimes occur with internet TV or
internet-based HD video downloads (such
as movies).
This may be true if you are using MoCA
in the US, where a pay TV operator is
providing you with the content. However, it
is not the case in Australia when streaming
content accessed via the internet.
In Australia, pay TV companies do not
provide a MoCA compatible service, so the
only way to access streaming content is via
the internet.
When you watch internet TV, HD movies
or some other form of streaming HD
content in real time in Australia, you access
it via ADSL, HFC cable or whatever internet
access technology you have signed up for
with your ISP.
Regardless of the technology, it will
suffer from latency problems caused by
the limited bandwidth of your service and
the traffic-handling capabilities of your ISP’s
equipment. The internet infrastructure in
general can also be a problem, particularly
at times of peak traffic.
In short, you will sometimes experience
frame freeze and buffering delays,
regardless of whether your home network
is MoCA based.
Another of MoCA’s claims is that it
is reliable. This is probably true, if the
performance is compared with that of a
wireless network. However, it is certainly
no more reliable than the competing
technology, namely Gigabit Ethernet over
Category 5e twisted pair.
DISADVANTAGES IN AUSTRALIA
MoCA seems to be gaining acceptance
in the US, where a number of pay TV
operators are providing MoCA based
services.
The equipment is also available in the
UK, but support is said to be poor. The
technology is unheard of in Australia.
The reason (apart from incompatibility
with Australian HFC services) is that using
MoCA becomes cost effective only when
there already is a coax point in every room
of your home, or at least in every room
where you require network access.
Unlike US dwellings, Australian homes
are generally not wired throughout with
coax for access to cable TV. Most houses
have only one or two points, and MoCA
is not cost effective if the wiring needs to
be radically altered. Also, MoCA enabled
devices are not cheap, even in the US.
MoCA 2.0 is touted as being fast and
secure. Well, a Cat 5e cabled Gigabit
Ethernet network will support a 1Gbps
data rate to every port and is every bit as
secure as a MoCA network.
Furthermore, twisted-pair Ethernet is
not limited to 16 devices or to a maximum
span distance of 85m. Gigabit Ethernet
over Cat 5e cabling has a maximum link
length of 100m, so if the hub is centrally
located, it can reach ports up to 200m
apart. The distance limit can be pushed
even further if you use Cat 6 cabling.
Ethernet hardware is cheap and not
restricted to a few select suppliers. Most
entertainment devices these days are
equipped with at least one Ethernet port.
CONCLUSION
Although MoCA seems to be a
good idea at first glance, it is not suited
to the Australian environment for the
reasons outlined.