I am investigating the use of a wireless network for an application that would have all the wireless nodes working in a completely sealed metal enclosure. The enclosure is maybe a 10′ by 6′ room or smaller and filled with individual networked robotic mechanisms that move around the enclosure.
I am investigating the use of a wireless network for an application that would have all the wireless nodes working in a completely sealed metal enclosure. The enclosure is maybe a 10′ by 6′ room or smaller and filled with individual networked robotic mechanisms that move around the enclosure. Communications to the enclosure would be through a conventional network over wire. Probably Ethernet. However inside the enclosure the network would fan-out from a gateway to all the robotic mechanisms through a wireless network. It might be 802.11 WiFi but this is really part of the investigation. The unknowns are the performance issues that will arise from the changing positions of the individual robotic units with respect to each other and the access point and as well moving in and around metal obstacles that interfere with signal. We expect lots of multi-path transmission problems as a start. This alone maybe the big problem that make it all a bad way to go. I do not know what else to expect. It may be that wireless is not the best solution for an application such as this?
I need to come up with a way to evaluate this wireless application. I am hoping that you could give me an initial evaluation based on your expert knowledge of wireless networking applications as a first step. Also if this is at all feasible I need to come up with a way to build a wireless test bed to evaluate this approach. I think I am looking for some wireless nodes (WiFi cards??), a hub and some software that could load up the network and measure performance as the physical locations of the node move about and change traffic priorities. If you could help me with any information or direction I would appreciate it very much.
— Steven Oliver.
I think this is possible. There are a couple of things you might want to look into:
Consider Ethernet, specifically, Power over Ethernet (POE). This will let you send both power and a network connection over the same cable – one fewer set of wires that you will need to run to and inside the enclosure. Since you are trying to run a sealed enclosure, this will also reduce the chances of a power problem.
There are several things to consider for handling multiple devices inside the enclosure – and reducing the chances of signals being blocked inside it.
In a room with the dimensions you give, a single access point should be enough. I am thinking of access points like Cisco and others that run in the 100mw range. Even with regular “rubber duck” style antennas you should be able to cover the entire enclosure, although possibly with some blockages in the signal path. Depending on the availability of space in the enclosure, you might also consider a high-gain omni-directional antenna. This should saturate the signal throughout the enclosure. You should be able to drop the transmitter power within the enclosure with a higher gain antenna than the small black rubber antennas.
Since it sounds like you will have several enclosures to work with in this situation, you may want to consider a wireless-LAN controller. This can help keep the number of controllers manageable and centralize the configuration and operation of the wireless access points. Cisco has another wrinkle that might be worth considering – a wireless location appliance. By implementing multiple access points in the container, you build in fault tolerance – if one access point fails, you can continue until you can get it replaced. A side benefit is that the power level can be adjusted by this device and allow you to “see” the location of all the robots in the container on a map created by the location appliance. I am not sure how well this type of device would work in the size environment that you are describing but a test bed should give you a good indication of how well.
Depending on the brand of access point you decide on, your vendor may have additional software that can help you stress test the network. Quality of Service may be an option to help you prioritize the traffic to give the desired priorities to the traffic being handled by the access points. There are several application packages that can generate traffic but you may end up custom writing a package so that you can tailor the environment for a test that will duplicate your needs as much as possible.
