Re: [EFM] Minutes of P2MP Optics conference 22nd Aug 20002
Unfortunately the "required bandwidth" question is extremely complex and heavily
dependent on the service offering and usage models. We have installations with
>1000 subs served by a single gigabit link (with a mix of multicast and unicast
MPEG-2 - 4.5Mbps - video). The advantage of using EPON for this service is that
you could build slowly - start with high split ratios and increase the fiber
usage as service usage picks up.
Maybe some of the people on this reflector have experience in the CATV
distribution. I can remember some of the "rules of thumb" but I may be out of
date or inaccurate because it's a long time since I discussed any of this. If
the service is a mixture of multicast and unicast, then you can assume <20% take
rate for the unicast - this means that 160 channels will be used for 800
subscribers. Furthermore you can assume that 60% of subscribers will watch the
top 10 channels, the remaining 20% may be watching minority channels - say 50
channels between them. Thus the total channel requirement should be ~220 to
offer your 800 subscribers a top flight service package.
If you use MPEG-2, DVD quality then the b/w requirement would be 990Mbps - not
reasonable for 1 EPON (or even 1 pt-pt). If, instead you use MPEG-4 (or VHS
quality) then the b/w requirement is halved and should be reasonable for either
I hope this helps - I'm no expert on video distribution, I suggest that you find
somebody with MSO experience to get much better statistics.
"Mccammon, Kent G." wrote:
> You uncovered that I still have a copperhead mentality or should I say Bell
> Shaped Head. But, I am flying the fiber flag now. However, I sometimes can
> be observed attending copper subgroup meetings to participate in the latest
> vote in linecode battles.
> You answered my request with a GigE link between central office and a remote
> VDSL ONU. I was asking about the use of P2MP interfaces rather than P2P
> GigE for Hybrid Fiber/Copper architectures. With the expected efficiency of
> P2MP, could an operator feed 4 VDSL nodes with 200 subs each? Or would point
> to point GIgE be needed for each VDSL node? I like conserving my embedded
> feeder fiber if I can! I like single fiber P2P and PON for reducing fiber
> cost whether making the most use of what fiber is there or planning large
> deployments that scale.
> > -----Original Message-----
> > From: Hugh Barrass [mailto:hbarrass@xxxxxxxxx]
> > Sent: Friday, August 23, 2002 3:52 PM
> > To: Mccammon, Kent G.
> > Cc: 'gkramer@xxxxxxxxxxx'; Thomas.Murphy@xxxxxxxxxxxx;
> > firstname.lastname@example.org
> > Subject: Re: [EFM] Minutes of P2MP Optics conference 22nd Aug 20002
> > Kent,
> > It's great to see you're flying the "hybrid fiber/copper" flag!
> > Most video codecs are designed to spit out monotonic streams
> > of (nearly) equal sized frames. These frames will either be
> > at the MTU size or as long as the VSP dares to make them
> > (many will limit the frame size to 1024 bytes for
> > superstitious reasons). The data stream will consist of many
> > (i.e. >20) frames at the maximum size followed by one short frame.
> > Note that a gigabit link will be able to carry 200-400
> > streams of unicast or multicast video, so it will take a
> > large number of subscribers to fill the pipe (& therefore
> > stress the efficiency).
> > Hugh.
> > "Mccammon, Kent G." wrote:
> > > Glen,
> > > Referring to your comment about frame size distribution from actual
> > > traffic.
> > >
> > > > The size of unused slot remainder depends on frame size
> > > > distribution. This distribution for today's traffic is known and
> > > > there exist formula to calculate this unused remainder
> > (for the case
> > > > when assigned slot size has no correlation to the frame sizes).
> > >
> > > Does anyone in the group have a traffic sample from a network
> > > transporting digital video streams to give frame size distribution?
> > > For example, a traffic sample for digital video over fiber
> > to a VDSL
> > > ONU to serve several hundred VDSL lines to a residential gateway.
> > > That scenario may be a good one to look at for traffic on a
> > > residential GigaPON connected to multiple VDSL ONU
> > locations with data
> > > and switched digital video content.
> > >