Open Access: Hybrid Fiber Coax Management
Management of Hybrid-Fiber Coax (HFC) related to open access
By: Bruce Bahlmann - Contributing Author (your
is important to us!)
This article is
the fourth article in a 5 part series on open access. This series includes: Overview, Connectivity Management, Service Management, HFC Management, and Transparency.
Hybrid Fiber Coax (HFC) management is one of three key areas of
open access as described in the December 2000 Communications Technology (CT) article on
open access. The other key areas are Connectivity Management and Service Management that
were covered in the January 2001 and February 2001 issues of CT respectively.
HFC management concerns itself with the care and feeding of perhaps
the most critical component of the broadband transport the last mile (also called
the local loop). This portion of the transport (shown in Figure 1) permits the
Access for Content
Providers to reach broadband customers and broadband consumer devices.
Content Consumers to communicate with one another.
Access for Content
Consumers (e.g. TVs, Telephones, Computers, etc.) to reach an open market of Content
Figure 1: Broadbands
With so many providers and consumers crowded on either end of the
broadband transport several concerns have been raised regarding its management. This
article will take a closer look at what it means to manage broadbands transport with
particular focus on the management of HFC in an open access system.
Managing Broadband Transport Outages
Broadband transports that include twisted pair (copper), coaxial
cable, fiber optics, wireless transmitters/receivers, and satellite have one thing in
common. That is they all have one or more single point(s) of failure somewhere in their
delivery of services to their customers. Single points of failure are necessary to keep
costs down while delivering the best possible quality of service to customers. The fact
that all these technologies have at least one single point of failure can lower ones
expectations of the service and level the playing field on which they all compete against
one another for customers.
The broadband operator compensates for these one or more single
point(s) of failure with employees whose job is to oversee the health of their respective
broadband transport. In this case, an employee could represent someone working in the
network operation center that watches various monitoring systems, oversees events,
dispatches field employees to resolve the problem, and keeps all interested parties
informed about the status of events. Employees also represent service personnel whose job
is to repair/replace defective lines or equipment. An event could be anything from a
zero-outage service item (e.g. replacement of a redundant power supply gone bad) to a
reactionary correction of some outage on the broadband transport. Manual efforts can
actually benefit broadband operators, as it is cheaper and perhaps easier to train
employees on how events should be handled rather than teach these same things to a
computer. Primarily because employees can use common sense, experience, and if all else
fails they can ask for help if they dont know how to handle certain events. For
example, a computer cant determine that something is wrong when several calls come
in from customers residing in a particular area only an individual could relate
such events to a potential outage. Computers are not so fortunate to possess this
experience or common sense and as a result are left with the handling of more routine and
Unfortunately, the benefits of manual intervention in the management
of broadband can be detrimental as well. Humans, though exceptionally resourceful, are
prone to make mistakes. Stress as well as inexperience can result in expensive lessons
learned for both the broadband operator as well as their employees. As a result, broadband
operators have become increasingly cautious about making hasty changes to their complex
transports. This is not helped by the fact that these transports now carry multiple
services, each with its own operational criteria. Any change to these multi-service
transports to resolve one problem could in effect render the other services inoperable. No
more is this as important as in the case of open access.
Open access demands another level of management beyond that which
most broadband operators are equipped. Never before has the importance of knowing the
operational health of their transport been so important. Yet todays broadband
operator is ill equipped to manage their transport down to the End-of-Line (EOL). The EOL
is traditionally associated with copper based transport media and it defines a location
where the signal terminates. EOL could be a customer home or even a junction where some
number of customers could connect. Although some broadband operators have been able to
deploy some EOL monitoring devices that can provide them with complete transport
visibility, most have not (because of the expense). Instead, these broadband operators
only monitor major portions of the transport leaving the remaining portions (which
can represent anywhere from 30-50% of their customers) invisible. The invisible portions
must rely on the broadband operators existing (and even potential) customers to
alert them of potential outages.
Relying on subscribers to report outages will be further challenged
by open access. This is because many services that are created as a result of open access
may not all be owned or directly distributed by the broadband operator but rather by third
parties. Confusion is likely to result in these instances as if the service doesnt
work whom does the customer call (broadband operator, their Internet provider, or the
service provider). Once more, how can a broadband operator manually determine something is
wrong with invisible portions of their transport when customer calls go somewhere other
than their call center.
The answer to this may lie in technologies that provide further
visibility into a broadband operators transport. These technologies include
non-invasive network management, EOL devices, and possibly even intelligent use of
customer devices (such as CPEs, cable modems, set-top-boxes, etc.).
Managing Broadband Transport Capacity
When a telephone company designs a phone system that provides service
to a number of customers it rarely supports a case that allows every residence to use its
service at the same time. Although it is theoretically possible to provide such capacity,
phone systems typically dont dedicate the resources it would require to support this
case. Instead, they maintain support for a percentage (25-40%) of their customers to use
the service at the same time. This percentage typically covers peek usage but not much
more again so as to conserve resources and keep down costs.
This conservation of resources is a means of managing the capacity of
ones transport and everyone in the business of providing a service worries about capacity.
Managing capacity allows the greatest distribution of service at the least amount of cost.
Not managing capacity requires huge expense with little (if any) regard to normal usage
patterns. To effectively manage capacity, one needs to continually keep tabs on the usage
of the transport. Because the transport is a finite medium, it must be closely monitored
to ensure that traffic does not reach capacity (even during peek times). It must also be
flexible enough to increase capacity where it is needed.
The advent of Quality of Service (QoS) presents some interesting
challenges for capacity management especially in the case of open access. QoS
provides dedicated capacity (or bandwidth) between a service provider and the customer.
For example, QoS provides dedicated capacity for the customer to place a phone call over
broadband so as to ensure that the quality of the service is not impacted by other
services that compete for finite capacity on the transport. While a phone call is small in
relative sense (representing only a fraction of the capacity available), the use of QoS to
increasingly reserve portions of a finite resource will represent a challenge for capacity
management. This is because it is unlikely that the whole broadband transport will be made
available for QoS. Again, like the telephone company phone systems, broadband must
maintain support for a percentage of their customers to use QoS services as well as
support other services that run on the broadband (e.g. best effort type services).
In open access, the broadband operator could quickly lose touch with
just what types of services are running over their broadband transport. Some services may
even use the same QoS capacity that is reserved for telephone or Video on Demand (VoD) so
as to ensure their service does not encounter any roadblocks during delivery. If the
broadband operator does not monitor their capacity they could even face legal problems
such as the blocking of 911 calls due to limited capacity. Open access could also
more quickly usher in new services that demand even more capacity. If these services push
maximum capacity other services could be impacted.
Managing capacity is also of concern outside the HFC where the
routing of packets can change quickly from one Internet Service Provider (ISP) to another
that could go against previous capacity planning. These swings in customer choice from one
ISP to another may be the result of unthinkable circumstances such as a merger or a severe
problem at an ISP that suddenly forces its customers to choose a new ISP. Since these
swings in choices cannot be foreseen, it is highly unlikely that the current capacity is
ready for this change.
The answer to managing capacity will lie in a broadband
operators ability to oversee their transports in terms of how much bandwidth is
being used and what types of services are being used. This requires bandwidth analysis
tools as well as keeping tabs on the services out there under development. Together these
will provide experienced staff with the information they need to stay ahead of future
changes in the need for capacity. It will also make the most optimum use of resources
(e.g. hardware) so as to keep the system sufficiently sized to handle the up coming need
for capacity while keeping down costs.
Managing Broadband Transport Spectrum
As more bandwidth is allocated to supporting open access (or perhaps
an array of digital services) broadband operators will find themselves in need of a way to
effectively manage spectrum. Today, they manage spectrum with paper and pencil
constantly conducting meetings with different business units to provide the best
combination of services to allocate to the available spectrum. Most broadband operators
allocate every bit of spectrum they have available to new services so as to maximize their
revenue opportunities. Since these services reside on specific (static) frequencies the
spectrum they consume is considered dedicated to that service.
In the digital domain several of these static things change. For
example, a single digital video channel only requires about 1/12th the
bandwidth of the same channel on analog. In addition, advanced technology allows up to 16
digital video channels within the space of a single analog video channel through the use
of what is called statistical multiplexing (or stat-muxing). As a result, the concept of
static frequencies reserved for specific services is becoming a thing of the past. In
fact, managing available spectrum could be the broadband operators ticket to
optimizing their transport in such a way as to provide them with the capability to deliver
additional services as they become available.
Figure 2: Spectrum
Figure 2 shows how stat-muxing could potentially allow services like
video, data, and voice to be combined in the most spectrum friendly way possible. In this
way, the needs for QoS with voice as well as some data services could be used with the
least amount of spectrum potentially only what they need rather than the minimum
defined by the QoS.
Open access will push todays manual spectrum management to its
limits as an increasing number of ISPs and service providers will have direct access to
broadband customers. Since each ISP and service provider will bring something unique to
the table these value added services will provide broadband customers with an
increasing number of service options (including a la carte services). As a result, the
spectrum required to run all these services will require flexibility beyond that which
manual static allocation of frequencies can support.
The answer to this growing need for spectrum is automation.
Essentially, open access will require dynamic spectrum allocation to provide bandwidth
on-demand for the growing number of services offered to customers.
The delivery component that broadband operators are least concerned
about regarding open access seems to be their HFC transport. However, their ability to
manage outages, capacity, as well as spectrum is far from poised to take on the challenge
of open access. If not addressed, solving these HFC problems post open access will be much
more difficult exercise and could leave their customers questioning their
Reducing the number of homes passed on a fiber node is a way that
broadband operators use to free up more bandwidth to customers. Interestingly, this
doesnt actually increase the amount of bandwidth available to customers rather it
merely reduces the number of customers competing for the same bandwidth. Increasing
available spectrum for services will become more attractive as the amount of bandwidth
required by any small number of homes is greater than what can be currently delivered via
conventional CMTSs. It very likely that costs to reduce homes passed per CMTS is a losing
battle what is needed is more spectrum not fewer homes passed.
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