Networking – Can’t find router after channel-change

It might if there are other devices in the same frequency range (like cordless phones).

For comparison sake, I will use the (Qualcom) Atheros AR9485 (Poseidon) chip-set as an example. We will ignore the cost differences in favor of performance characteristics.

This answer is assuming that:

• both router and repeater have one physical radio (AR9485)
• both router and repeater have the exact same Dbi antennas
• both router and repeater are transmitting the same Dbm power levels
• both devices have the exact same TX/RX antenna chains (1x1 :1)
• both devices are setup in either repeater or WDS modes. (no wired uplink)

  ---

The one Radio problem

Repeaters with one radio, and routers in repeater-mode or WDS modes. Both devices must each divide the total amount of air-time by 50% (50% client to the original AP, and 50% acting as an AP to clients) The end result is usually Less than 50% of the original bandwidth. Devices operating in this mode can also exacerbate co-channel interference problems.

Dbi & Dbm

This translates to how well clients & original router can receive the repeater/router transmitted signals,(Dbm = TX power) and how well the repeater/router can hear the clients & original routers transmissions.(Dbi = relative RX power). both in the same environment, there should be ZERO difference in signal range.

Antenna chains

With wireless-N devices this directly correlates to performance, as wireless-n uses MIMO (multi in multi out) which leverages environmental structures and takes advantage of multi-path signal reflections to actually improve radio transmission performance, where in previous 802.11 specifications it was devastating to throughput. both having a 1x1 :1 antenna chain there would be absolutely no difference in performance in the same environment.

Repeater & WDS modes

Wireless (802.11-B/A/G/N) is half-duplex, in a basic scenario (1x1 :1; all stations close enough that each can hear each other), only one node can transmit at a time. [CSMA/CA] protocol is used to enforce this limitation, and every device on the same channel is technically speaking "in the same collision domain". This protocol is very susceptible to the "Hidden node problem", which absolutely will be present With a WiFi repeater. in a nutshell this means that data in a single burst is transmitted fast, but any switch-over of who's transmitting is going to be really slow, with collisions, pauses, etc.

There is still hope!

To overcome these limitations you have a couple options:

• Router/AP with a wired up-link. Still one radio, but on another channel (CSMA/CA collision domain) which can be set-up for seamless client roaming between the main and bridged Router/AP.
• A wireless Router that has multiple physical radio chip-sets. (2x 2.4ghz & 1 x 5.8ghz or vice versa) You would want one that supports third-party firmware, DD-wrt, Openwrt, Asus-wrt etc. This will allow you to put one radio in client-mode connected to the main router, and the second radio in access point mode on a non-conflicting channel. Either option totally overcomes the 50% bandwidth loss. If you do decide to go the wireless back-haul route, make sure you do a little research on the actual device you plan on purchasing.

I would recommend something with at the very least 256MB of ram, with a dual-core processor around 1-GHZ. Many devices on the market these days come with LNA's (low noise amplifiers) for the radio chip-sets on board.(This significantly increases range performance as it changes the received and transmitted signal strengths.) A good example is the ASUS RT-AC3200.