I have a wrt54gl G router in one room and am not getting very good speeds when connecting in another room. I'm planning on running a cable through the wall to the other room and installing an N access point. All devices I'd use have N capable adapters.
1) Is there any problem having G and N on the same network?
2) Most advice I see is to set the AP to the same SSID as the main router, although different channels, and to set the same security and password on both. Might it be better to use different SSIDs, so that I can make sure I'm connecting to the faster router?
First to ensure maximum speed lock your new AP/router to run N only disable the backward support for G. This will allow it to not send the extra overhead need to switch between n and g.
There is no issue at all running N and G on the same network. In fact the recommended design is to run separate AP for G and N like you are doing. Different channels is pretty much a given since they will interfere. If you make the SSID the same or not is a choice you have to make.
Some people are lazy and don't want to deal with selecting the network and such. They let the PC just connect to whatever is stronger. Problem is it will not switch until the signal degrades a lot. So you could connect to your G device walk into the other room and it will not switch. Now when it finally does switch it will only cause a minor outage.
Using different SSID you now control it all manually...and hopefully you are smarter than the PC and know when its a good time to change from AP to AP and which will give best performance. Of course the downside is its more complex and some people get confused easily with stuff like this.
Aha - the advice to use the same SSID on both is to make it easier for lazy users, rather than any technical reason. That's good to know.
I'm not sure I will be able to do N only on the new router. I was under the impression having G and N devices connected to the same AP was the problem, rather than having an AP that has G and N modes available for connection?
FWIW, separating me from the main router does much too good a job of attenuating the G wifi signal. I'm worried that it would do an even better job of blocking an N signal.
Ignoring dual band 5g which G can't run on. They signal levels and penetration are exactly the same. The limitation on transmit power are still the same. What changes is how the data is encoded into the radio. In theory at least since you get more data in the same amount of radio bandwidth N should always be faster. Mostly this is all smoke and mirrors because any lose either G or N causes retransmission it just that N can pack the retransmission into less radio bandwidth so it can do more of them.
It is much worse if you actually do connect a G and N to the same AP. But since it has to assume there is always a G device out there that may want to connect it still transmits out extra stuff even in the N transmissions so the G device can partially understand. I would have to look up how much overhead there is but the symptom you see is that many time the N is limited to 54m and does not use the 300m or 450m options. If you force it to only run N it will not fall back. They key thing is that it will fall back even if a unauthorized device even attempt to connect. Just the existence of a G device will many times mess up this compatibility stuff. Support is much easier if you force it to run N only when you have all N devices.
I was confusing G v. N with 2.4ghz v. 5ghz. It's 5ghz which has more trouble with walls.
Alas, the router I'm getting at the moment does not do N only (n is only available in b/g/n mode). It's mainly an inexpensive travel router, so I'll consider getting something better for home use. There is a lot of wifi traffic in the area (inSSIDer shows 22 APs at the moment, all on 2.4g and about 50/50 g/n), so the chance of interference is high.