Heath and Reach
From ERA
Munday's Hill sand quarry, located in the South Bedfordshire village of Heath and Reach, approx 12 miles south of Milton Keynes and a mile north of Leighton Buzzard, was the location of the field trial held over two weekends in June 2007.
Location on Google Maps.
We added (significantly) to the mix the requirement to "beam back" material (still images, video and 2-way audio) to a group of students at an off-site location, in this instance at the Open University main campus in Milton Keynes. Such a requirement essentially meant that we needed a connection to the Internet.
There were basically two options for us to establish this connection: use the mobile phone network (via a 3G and/or GPRS data connection) or via ADSL.
1 3G/GPRS
A 3G connection can provide a link to the Internet at a speed of up to 384kbps. Given we had been asked to provide up to three audio/video streams plus the ability to send photos of reasonable resolution, we always knew the bandwidth would be insufficient. On top of this, we found that 3G reception, especially in certain areas of the pit, was very patchy and we felt such a connection would probably prove to be unreliable. We did some trials using a Vodafone PCMCIA data card in an HP laptop (Windows XP) but it was obvious that even obtaining a connection in the first place (even with a small external aerial) was difficult.
The "fallback" from 3G is GPRS, which has a maximum data rate of 114Kbps. A 3G connection will drop back to GPRS is the signal quality is not high enough, or will be used if 3G is simply not available (which it generally isn't outside populated areas).
HSDPA (sometimes referred to as 3.5G) where available currently offers data rates of up to 2.8Mbps with reduced latency, but such connections (at time of writing) are only available in and around London.
Another limitation of using the mobile phone network is that not all protocols are supported. Voice over IP (VoIP) for example is actually blocked by some of the network providers. Streaming video can also be problematic - you might be able to view a stream from a camera on a conventional Internet connection, but that wouldn't mean that you could create an outgoing stream via a 3G connection.
Latency is another factor since it can render a bi-directional AV connection unuseable.
In all cases, similar to ADSL (broadband), the bandwidth available via any single mobile phone network node is shared between users. In practical terms, this could mean that if another subscriber were to establish a connection, they would take some of the bandwidth our connection would already be using.
2 ADSL
We briefly considered peering a connection off an OU employee's existing ADSL link via a long chain of wireless hops, but this was dismissed as it would have required us to place aerials on land we did not know or have control over.
Instead, we found that the quarry company site offices had a number of conventional telephone lines and for our Internet connection, we used one of these lines for an ADSL connection. After permission was obtained from the company, an application was hastily put into BT for a basic ADSL account and we were lucky in that it was installed and made operational just days before the first of our two field trials.
