What to look for in a router to be used as a wireless bridge?

[Zero1]

Hi guys.
I've just had a 100mbps connection installed, and it's time to update my gear to make the most of it. The current setup is as follows.

Modem (wired) Wireless router (wifi) Wireless router (wired) Computer

So the modem is downstairs and is connected to a wireless router by ethernet. That wireless router then connects to another wireless router upstairs thanks to DD-WRT, and devices to be connected to the network are connected to the upstairs router via ethernet. I know it would be easier to just get a wifi adaptor, but there are some things on my network such as DVD players and Laser printers that don't offer that choice.

I'm wondering which of the tests performed in the various reviews are most relevant to this kind of situation?

I'm currently using a Linksys WAG325N for the downstairs router, and a Linksys WRT54GL for upstairs, but it appears the most I can download is about 20mbps with this setup.

What should I be looking at? WAN to LAN, LAN to WAN or combined?


Finally if anyone has any suggestions on what to get, that would be appreciated. Preferably something with external antennas, but that doesn't matter too much as long as the power can be boosted in DD-WRT.

Thanks a lot

 

[stevech]

Suggestions

Replace the link from the main router to the secondary router (which is DD-WRT in WDS or bridge mode, I assume) -with a wired connection instead of wireless. This wired link is ideally cat5, but if that's impractical, you could use a pair of HPNA devices (see section in this forum by that title). This uses the home power wiring to bring LAN connectivity to the other area without the speed and interference issues of wireless. (Alternative to HPNA is MoCA, which uses existing TV coax).

The secondary device becomes an Access Point (AP). DD-WRT can do that. Or any router can do so. If your current DD-WRT-based router is not 11n, then you could purchase a decent 11n router and config. it to be an AP. This will improve the wireless speed for PC access in that second area.

The HPNA or MoCA should provide at least 70Mbps net yield of all overhead between the two devices in your home. Of course, it would be best to get the modem in the area of the home with most use - and eliminate the extra link.

The supposed 100Mbps Internet connection - you may want to check using SpeedTest.net - to see if any test servers on it can deliver more than 20 or so Mbps. It's uncommon to achieve 20 Mbps on the Internet, especially from busy web servers.

Be sure to not confuse a connection to an internet modem that is 100Mbps ethernet with the lesser speed of the modem and service. The "wire speed" may be 100Mbps but the modem speed may be 10 or 20Mbps (downstream; upstream is typically 1/8th that).

 

[thiggins]

I agree with Stevech's suggestion. Just look for HomePlug AV 200 Mbps or 500 Mbps adapters. HPNA is something different.

 

[Zero1]

Hi
Yeah, the connection is 100mbps (get 96 or so on speedtest, and 11.5MB/s downloading a Suse ISO).

I found with supplied wireless, I could only reach about 80mbps despite being sat next to the router (like 2m away). It's operating on the 5GHz band and apparently both are running at 300mbps.

Do you think this bottleneck is more likely the router itself or the wifi card iin the laptop?

Thanks

 

[thiggins]

It's Wi-Fi. 80 Mbps usable throughput is pretty typical for best-case N throughput.

 

[stevech]

Hi
I found with supplied wireless, I could only reach about 80mbps despite being sat next to the router (like 2m away). It's operating on the 5GHz band and apparently both are running at 300mbps.
Thanks

The 300Mbps is the burst rate on the air for one data frame. It's rare to get close to 100Mbps of real throughput with application/TCP and IP. In theory, you could get 60% of the air link rate (300Mbps) if both client and Access device (WiFi router) support 40MHz mode (300Mbps), both have ideal signal strength and no RF interference, excellent WiFi interfaces and fast CPUs, etc.

It's like a car's engine horsepower vs. what gets to the tires. Lots of losses in the system.
Or a better analogy: It's like my gross pay vs. my take-home!

 

[Zero1]

Or a better analogy: It's like my gross pay vs. my take-home!

This is something I can relate to!

Thanks for helping me understand the situation with wifi. I guess if I want faster speeds over the air, I need to go the way of three stream wireless N. I've already ordered a new wifi card and antenna for my laptop (Intel Ultimate N 6300), and I think I'll get a Linksys e4200.

Am I right in thinking that the rated speed of 300mbps for example is split between up and down? Eg if that is the case, a 300mbps setup would have 150mb download in theory, and this real world case of 60% would make the throughput around 90mbps which seems about right.

 

[stevech]

split between up/down - yes, essentially. WiFi cannot transmit and receive simultaneously. It's "half duplex" by nature. Like a push to talk radio, though far faster, of course. But take 60% of 300Mbps for a one-way transfer - as a theoretical max. You'll rarely see more than 100Mbps net yield at 300Mbps air link rate in WiFi due to many reasons, including the CPU speed in the router, air link issues (below), PC delays due to windows settings and CPU speed, etc. With 802.11a/b/g and 20MHz mode of 11n, the 60% number comes close.

Some of the overhead causes in WiFi are

- listen-before-transmitting; attempt to avoid transmissions from other devices colliding in time. Tech Term "CSMA/CA". This adds some delay. WiFi is in unlicensed RF bands so CSMA/CA is necessary for sharing.

- Retransmissions for error correction; If the receiving unit detects an uncorrectable error in the received data frame (packet), it will not reply with the expected "Acknowledgement" (ACK) message to the sender. The sender must time-out this expected ACK and re-send. Thus, this timeout adds delay and overhead. Errors happen due to signal too weak for the goal data rate, or interference. Higher the data rate, stronger the signal needed. WiFi reduces the data rate ("modulation order") if the signal strength is too low for the current goal rate, i.e., 300Mbps requires a superb signal strength and little interference.

- delays in the host PCs - TCP/IP stack and applications, and maybe disk I/O.

these are the principle overhead causes - beginning with the half-duplex nature of WiFi.