Internet Wireless Controllers at TSP

Do not bring your own Wireless Router, Access Point, Range Extender, Wireless Print Server, Wireless Peer-to-Peer Network, Wireless Remote Control System or Bluetooth device!

We use 802.11A , B, G, N, and Mimo so all devices in these frequencies are subject to TSP rules.

Bluetooth devices operate in the same frequencies and may cause interference to users connecting with our network.

Banned telescope-related Internet and Bluetooth devices

If you bring one of these or similar devices during TSP, keep it powered off and do not mount it on or near your telescope. If we see this device on your telescope, you will be asked to remove it or leave.

Explanation of the Ban on wireless telescope-related devices

There are several reasons for our decision to ban certain wireless devices at TSP.

This is a question of other signals in the wifi band that interfere with basic service that our network provides. There are only 3 unique channels in the 2.4ghz spectrum. Those channels are 1, 6, 11. The same spectrum is shared by 802.11B, G, N, Mimo systems, Bluetooth, proprietary remote controls like doorbells, burglar alarms, baby monitors, some remote temperature/humidity sensors. These are joined by devices in the Industrial/Scientific/Medical (ISM) band such as microwave ovens.

Look at Unified Wireless Networking by Cisco (leading manufacturer of wireless infrastructure) describing use of 3 channels and the cellular style geographic re-use process employed at TSP.

There is nothing lacking in TSP’s equipment nor its methods. Both are industry best practices. There are identical “no other wireless network restrictions” at thousands of other companies all across the world. We are not alone when imposing this restriction: it is a common practice.

Peer-to-peer networks and other 2.4ghz transmission modes (handheld cordless home phones, microwaves, bluetooth, proprietary hand-held remote controls and a host of others) all compete for available spectrum, degrading signal to noise ratios. When this happens, clients can’t achieve the needed signal to noise ratio to communicate. This causes data loss, packets fail and are retransmitted, causing ever greater problems. This is why we limit all transmissions on our network to attaching to TSP networks as a client. Any other use competes and decreases network connections available for all users.

Putting up other access points, peer to peer networks and even excessive Bluetooth all degrade network response for normal wifi users. The TSP network uses all available channels so there are no spare frequencies. Looking through Cisco and other industry documents shows that any other conversations in the same band take away from the connection between wifi users and the access point to which they are attached. An access point will only watch for conversations sharing the same SSID. When users put up other Access Points, wireless routers, or start a peer to peer network, a different conversation is started. It doesn’t matter if it is on [1,6,11] or any middle channel. They transmit without regard to other networks in use and contend on the frequency. They also degrade signals such that none of the systems works to full potential. Transmission errors increase dramatically, due to degraded Signal-to-Noise Ratio. We already see massive retransmit counts on some tripods on the fields.

We have no problem if remote telescope controls can attach both the telescope unit and controller unit to the TSP network as a client. However, the banned models are implemented as an “ad-hoc” network, which is NOT as a client.They operate as separate or private networks, or wireless routers/access point, and these are not allowed on the ranch.

Smartphones, attached to the TSP network as a client are perfectly acceptable. In fact, they, along with all other computer and wifi devices that attach to our network are the reason for the network. Users should not employ apps on smartphones that implement bluetooth, peer to peer networks, or directly control other devices. Apps that connect to the TSP network as a client are fine.

Anything that attaches to our network as a client becomes “managed bandwidth” as opposed to unmanaged bandwidth such as bluetooth, rogue access points and private networks. A managed item is controlled by the network and works with rather than against other network users since transmit receive details are coordinated. Inter-channel and adjacent channel interference occurs with private networks and there is no way to avoid it.

A principle of radio frequency propagation is that a very low power device at a close range can easily overpower a much stronger device that is located at a distance. Here is a Cisco paper about 20 Myths of Wi-Fi Interference.

Pay particular attention to numbers 3, 7 and 11. Just because a user hasn’t been caught in the act doesn’t mean interference is not happening. This is mainstream industry practice and offered by Cisco in response to the biggest problems that IT departments currently have.

Apple sells both wifi and bluetooth equipment. Read Apple’s AirPort and Bluetooth: Potential sources of wireless interference about interference between these devices.

Texas Instruments talks about adjacent channel interference in The Effects of Adjacent Channel Rejection and Adjacent Channel Interference. Check figure 1 for a great graphic of what happens to the signal to noise (S/N) ratio when competing signals occur in band. S/N is everything. Communications come to a halt without adequate S/N. This is why other Access Point devices, wireless routers and and Peer-to-Peer networks can’t be allowed.

NIST studied the bluetooth issue in Interference of Bluetooth and IEEE 802.11: and found up to 65% packet loss on wifi networks when bluetooth “voice” exists. Scroll down to “Concluding Remarks” for their results. Bluetooth headphones with the user listening to music are a common example of this type of usage. Bluetooth …can be expected to dramatically impact wifi users that are near to the bluetooth device but more than a few feet away from the Access Point.

The Texas Star Party is EASILY the largest internet cafe in West Texas. It isn’t the same as a small office or even a Starbucks. We served well over 300 separate devices in 2010. Over 100 were online concurrently. Non-compliant devices have no legitimate right to the spectrum since they violate TSP terms of use. These rules are no different than those used in business and they exist for the same reasons.

[Our thanks to Rick Kirchhof for putting this together for us.]