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Broadband Speeds

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Eric Johnston
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Posts: 2108
Sep 17th, 2010 at 4:58pm  
Definitions of Satellite Broadband Speed

OFCOM has been contemplating the problem of how broadband services are described in adverts.

In the satellite context I have been aware of the problem for many years and have insisted that shared services are described as "Up to" bit rates and I've also tried to get service providers to show sharing ratios (e.g. 10:1, 20:1, 100:1). On this web site, shared services are never allowed to be described as 'unlimited'.

The idea of including sharing ratios is not satisfactory. An HX service, at say 15 Mbit/s, does in reality provide a variety of customer bit rates (e.g. up to 512k/s, up to 1 Mbit/s) all shared on the same 15 Mbit/s carrier. Actual individual packets arrive at the customer at 15 Mbit/s rate. Sharing ratios are meaningless when the fair access policy is based sharing out the traffic throughput based on tariff price.

My concern is how customer expectations may be kept realistic.

OFCOM's document is worth reading: http://stakeholders.ofcom.org.uk/binaries/telecoms/cop/bb/copbb.pdf

It still falls well short of inventing some comprehensible, and technically accurate, measure of what customers will get in terms of speed and traffic quantities.

Below I have made my own draft ideas for the meanings of certain speeds. The more you think about it the more difficult it becomes...
If anyone wants to comment please feel welcome.

a) Headline or advertised speed - This is the speed that the marketing and sales people use to describe the packages that they offer. In the case of shared VSAT services they must be described as "up to" speeds and the use of the word "unlimited" is banned.
This figure will be typically 512k, 1M or 2 Mbit/s and based either on traffic speed limiting (averaged over a whole second) applied at the hub router or by the actual data rate of the carrier.
A 10 Mbit/s carrier shared by VSAT sites may be used to provide a service advertised as "up to 2 Mbit/s". Actual individual data packets will be received at 10 Mbit/s rate but the average rate over a period of 1 second or more will be limited to 2 Mbit/s.
A 2 Mbit/s carrier shared by VSAT sites may be used to provide a service advertised as "up to 2 Mbit/s". The bit rate is limited to 2 Mbit/s by the carrier size.

b) Carrier speed - This refers to the actual carrier speed of the data connection
to the hub. This is the carrier information bit rate. Examples: 10 Mbit/s or 2 Mbit/s.

c) Actual customer throughput speed - This is the actual speed that a customer experiences over a particular second when they are connected to the internet. Measured at the customer PC screen. This figure is dependent on factors such as the ISP and customer network, traffic shaping and management, TDMA or SCPC, use of compression, acceleration and cache software/hardware, the number of subscribers sharing the network at the same time and the number of people accessing a particular website. This figure, measured over a period of 1 second, will vary from zero, up to the headline or advertised speed or much higher if caching/acceleration software or hardware is used. Speed measurements made over periods of less than 1 second may be much higher and measurements made over periods of more than one second, much lower. Actual measured customer throughput speed might also be expressed as averaged over longer periods, hour, day, week or month.

d) Average satellite throughput speed This is measured average throughput speed over the satellite for various period of time. Measured on the satellite link itself, either at the hub or at the customer modem.
Example, for a shared service with 2 Mbit/s headline rate:
Averaged over last 1 hour 118 kbits/
Averaged over last 4 hours 55.5 kbit/s
Averaged over last 1 day 27.8 kbit/s
Averaged over last 1 week 10.5 kbit/s
Averaged over last 4 weeks 6.4 kbit/s
ISPs may restrict average throughput speeds according to tariff options to achieve fair sharing.

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