My wifi is weak at the top of the building. Is there a relay/sender thingy that can boost the signal to get the signal to go further?

If so, where can I get one, and does anyone know what it is called in Chinese?

This is a good question. Seems to me there are three basic specs, aside from security, speed, power and sensitivity. When I last shopped for a router I could figure out the speed part but the power and sensitivity seem to be expressed in distance. I bought a medium cost router as my base unit. I also have two portable wifi devices. one takes a WAN cat5 cable and the other is 3G to wifi. Both portables say something about 15 meters which is fine in a room (I am in a hotel room as I write this and am using the 3G device, the hotel wifi is unsecured).

I would like a wifi that is a is stronger but can't seem to translate the specs before the shop assistant yanks the box out of my hands. Most of the kids selling the stuff can't understand what I want or know less than I do.

Anyone have an answer?

you can get a wifi repeater.

don't know what they are called in chinese, sorry

wifi 放大器

s.taobao.com/[...]

You could get a router that supports the N standard (which theoretically should go for a long way too, depending on interference), but you will also need your receiver to support the standard. Most modern laptops will support but you should definitely check. Otherwise go the repeater route.

My friends were using an N standard router to give wifi to the whole street, about 500m long with line of sight a couple of years ago. One of them also modified a metal sieve to pick it up from about 3 km away! Electrical engineering students with too much time...

I'm using the N series router and have a laptop with N. Fine at close range but in either of the two back bedrooms the signal is crappy, even through only one concrete wall!

WiFi repeater is the way to go. Just put one where you still have sufficient signal and have it forward the signal to where you are.

1. Antenna - if your wifi router has an accessory antenna plug (N-Plug?) - you can add a "high gain" wifi antenna. This acts as a sort of passive repeater. You may optionally buy a long antenna cable and mount the repeater antenna closer (aka direct line of sight) to your weak signal location.

2. Frequency Settings. WIFI typically auto sets the frequency spectrum your router broadcasts/receives on within multiple bands (I forgot the N spectrum bands). You MAY be colliding with someone else's wifi router - hence the speed degradation. To test this - download a FREE wifi spectrum analyzer. It'll tell you how many people are sharing the different frequency spectrums/bandwidths - and you MAY be able to manually select the lowest used spectrum to artificially boost your throughput without spending more money. The software (if you get the right free stuff) will also estimate the signal strength in the various spectrums/bandwidths. The pervasive use of wifi with new adsl installations makes traffic collisions a high probability, so increasing the gain (signal to noise ratio etc etc) will make the wifi router's transmit signal stronger (good for downloads), but your uploads will still suck because you're contending with noise from other systems (and you haven't boosted your computer's send signal).

3. Location - you may want to wall-mount your wifi router in a somewhat higher location. Remembering that wifi doesn't penetrate concrete walls very well AND the low power (Q) nature of wifi routers were designed based on vague and arbitrary safety standards.

4. Hard Wire. Run network cables throughout the house and plug in another wifi router into your cable (100 mbps to 1gbps depending on your router's specs).

5. Encryption. If you've locked your wifi using WPA/WEP - this slows down the effective speed of traffic because your computer and the wifi router must encrypt/decrypt incoming and outgoing data - essentially causing a 2-3x+ delay. You can, at your own risk, turn off security and as long as nobody else is piggy-backing on your router (watching say internet TV) - you should notice an immediate improvement in speed and performance, to include extended range performance.

Changing frequency settings won't enhance the range. They can improve the transmission speed but if there's a weak signal, this won't change. Conflicting frequencies in buildings with many WiFi signals on the same band will lead to noise and therefore packetloss, which will cause the TCP/IP connection to throttle (it's designed to act that way in times where packetloss was still a very common thing - on phone lines).

Encryption, too, will not have any effect on your signal. Encryption does indeed cause some overhead and will make the transmission slower. Yet, and especially in a country like China and in a big city, encryption is a must-have. You may be able to block out piggybackers with MAC-filtering, but your data is still sent unencrypted over the ether. Which means that a password sent over simple HTTP can just be read by anyone near enough. That's not what you want.

Actually your right AlPage. I asked one of my mates who told me tye N standard is great for long range where you have LOS or thin wood impeding the signal, but worse than b\g in a concrete environment for range. The reason is because the n standard mostly uses a shorter wavelength, usually much shorter than the width of a concrete wall, which is blocked easily in concrete whereas the b\g standards use a longer wavelength. This is the same reason why FM radio is still fine behind concrete walls.