Page 4 - 20180911 Access Transformation white Paper Final

▪ P2P – FTTH (Point-to-Point, Fiber-To-The-Home): A point-to-point medium is, as the name suggests, a dedicated physical
connection to each subscriber. In P2P-FTTH, each subscriber connection is a dedicated fiber from the access-switch in the
distribution hub/Central Office (or from a cabinet in the outside plant) to the subscriber termination point. Most fiber access
P2P network use a version of the Ethernet protocol family.
▪ xDSL (Digital Subscriber Line): Mostly deployed by Telco operators, xDSL is adding data services onto the copper twisted pair
infrastructure that was initially deployed for traditional voice services. xDSL is a P2P technology where each subscriber
connection is a dedicated copper pair from the DSLAM (Digital Subscriber Line Access Multiplexer) in the Central Office (or
from a cabinet in the outside plant) to the subscriber termination point. There are multiple xDSL standards deployed in access
networks today.
▪ Fixed Wireless: This is more of a category than an individual technology. The category refers to using wireless technology to
connect to a fixed subscriber (as opposed to a mobile client). The signal travels over the air from a tower or a pole to a fixed, in
most cases outdoor antenna, at the subscriber location. Fixed wireless technologies are P2MP technologies. There are many
fixed wireless solutions being deployed going from closed proprietary systems (base station and client interact with
proprietary protocols) to system using open wireless mobile standards (3G, 4G LTE, pre–5G) with standard clients. Even
though no wire is used to connect the subscriber, the overall fixed wireless architecture is very similar to a wired access
network architecture.
If we want to understand how we can evolve the capacity of these different
access networks, we first must look at what technology or architecture

The “Triangle of Truth”– HFC Use components contribute to the amount of bandwidth available per end-point
Case (subscriber). There are only three levers that can be used to increase the
amount of bandwidth per subscriber: spectrum, spectral efficiency, and
spatial scope. Let’s start by looking at these levers in more detail.
Access capacity is based on three mechanisms – also 1. Spectrum: The important factor is the width of the spectral band not
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known as the “Triangle of Truth ” – increase the the frequency (a 20 MHz wide band at the 100 Mhz range can carry
available spectrum, effectively use the spectrum and the same amount of information as a 20 MHz band at the 1 GHz
reduce the spatial scope of the spectrum. range). No matter the medium the goal is to make more and wider
spectrum bands available, hence the push of 5G wireless to open the

higher frequency domains (20Ghz and above). The obvious benefits
of using higher frequency is the availability of more and broader
channels; the main downside is that higher frequency signals do not
propagate far, reducing the maximum distance between sender and
receiver and forcing placement of access nodes closer to the end-
user. On twisted pair copper every xDSL technology upgrade
introduces wider spectrum usage. In HFC networks total available
For example, let’s say you are using X GHz spectrum spectrum increased over time and more spectrum is being used by
on an HFC network. Then increasing the spectrum width of a channel and increasing the
number of channels that can be bonded together.
Total capacity of this HFC
2. Spectral Efficiency: How efficient is information encoded to be
Bandwidth per sub = -------------------------------------
transmitted on the available spectrum or in other words how many
Total Number of Subscribers
bits/s per Hz can the encoding mechanism provide? The benefits of a
Total downstream Capacity for a 32D DOCSIS HFC @ highly efficient encoding scheme are obvious and therefore it is being
256 QAM = Spectrum * Spectral efficiency = (32 * 6 introduced in any technology evolution path. The big downside is
MHz) * 8 bits/HZ = 1.536 Gbps that the higher the efficiency the “cleaner” (high Signal to Noise
ratio) the transmission media needs to be for the receiver to recover
If there are 200 active subscribers (spatial scope) on error free information.
this HFC network, then the average bandwidth per 3. Spatial Scope: This matter when the transmission medium from
subscriber = 1.536/200 = 768 Mbps sender to receivers is point to multi-point meaning multiple end-
points share the available bandwidth. Spatial scope simply put is the
amount of end-points on a single medium. The more end-points on a
shared medium, the less bandwidth per end-point

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