Seven Troubleshooting Tips for Wireless N Networks

By Eric Geier (NoWiresSecurity Founder & CEO) - originally published on InformIT.com

Were you all hyped about wireless N--its higher speeds and increased ranges--but are disappointed after hooking it up? If so, this article is for you. There are many things that can hold back the wireless N gear from delivering the great data rates and coverage everyone is talking about.

In this article, we'll review numerous things to consider, verify, and change to get past the fine print and on to a network that is as strong as possible.

Remember, what you see is not what you get. The box and marketing materials usually mention the maximum data rates and ranges for the wireless standards. The realistic values will be much less.

For example, you'll probably only get up to around 100Mbps of true throughput instead of the touted rates around 300Mbps. Windows also lies; it shows you the standardized data rates rather than the true values. You have to use other throughput testing programs to get a realistic value.

One more thing to consider before you start troubleshooting: The final 802.11n standard is not complete. The products released today are called Draft N 2.0 products. Thus the products and their behavior might change when the standard is actually done.

#1 Confirm that You're Using New Adapters

If you are seeing only a maximum data rate of 54Mbps (or lower), first check to see whether you're using a wireless N adapter instead of an old wireless G card.

Old adapters can connect to the new N gear, but the high speeds and performance are possible only on connections between a wireless N router or access point (AP) and a wireless N adapter. In short, you probably have to upgrade all the wireless gear.

#2 Verify that Hardware is from the Same Manufacturer

One reason why the Wi-Fi Alliance certifies wireless networking products is to ensure that manufacturers develop equipment that works together.

However, some features are proprietary and must be used with compatible gear to work. Additionally, there seem to be more interoperability issues with the wireless N gear.

One contributing factor might be that the official standard isn't complete; vendors are releasing Draft products. The point: You should use the same manufacturer for all your networking gear to prevent potential problems.

If you haven't already chosen a brand to stick with, think about any special wireless equipment you might have or want. For example, if you want to stream photos, videos, and music from your computers to your TV using a wireless media extender, you'd want to compare these devices between the different brands. Therefore you could get an idea of what brand would be the best for you.

When nailing down a company to go with, you should also search for product reviews online. Just typing the model number into Google might bring up some reviews.

Compare two or three reviews to get an idea of what other people like or dislike about the router's features, user-friendliness, and performance.

#3 Use WPA2 Encryption Only

The wireless N standard doesn't support WEP, so connections using this type of encryption will be limited to wireless G at 54Mbps, even when using N gear.

Plus, the first WPA version doesn't even provide maximum wireless performance on N networks. Therefore, you should use WPA2 (with AES) personal or enterprise encryption.

If you still have a very old adapter that supports only WEP encryption, check on the manufacturer's web site for any driver updates, and make sure that Windows is up-to-date.

If that doesn't help, you should trade it out for a new wireless card.

To change the encryption settings, log on to the router's configuration utility by typing its IP address into a browser.

The default IP and the password should be listed in the documentation, if needed. Then find the wireless settings and change the encryption type.

#4 Change Default Channel-width for High Speeds

If you find that speeds never exceed 130Mbps, you may just have to change default channel-width. To limit interference with older Wi-Fi gear, wireless N routers and APs are shipped with the 20-MHz-wide channel setting selected.

Part of the performance increase in wireless N is from moving up to a 40MHz-wide-channel, which is called channel bonding. Thus to achieve the maximum speeds, you have to change this default setting first.

To change the encryption settings, log on to the router's configuration utility by typing its IP address into a browser.

The default IP and the password should be listed in the documentation, if needed. Then find the wireless settings and change the encryption type.

To enable channel bonding, bring up a browser and type in the router's IP address to log onto the Web-based configuration utility. Then find the wireless settings and select 40MHz-wide channels.

Don't forget to save the changes.

#5 Disconnect Wireless G Clients for Best N Performance

Wireless N is backward compatible with wireless G, and even the ancient B standard. However, the traffic on the network is managed differently when older adapters are connected to an N network.

This has a negative effect on the speeds and performance. So if you aren't getting the data or throughput rates you desire, make sure that the network is only offering connections to other wireless N clients.

You can actually limit the types of clients who are allowed to connect, forcing the router to allow only wireless N connections.

If you want to do this, log on to the web-based configuration utility and change the setting in the wireless section.

If you still want to support wireless B/G clients, consider using any old wireless G routers or APs.

You could plug the wireless G router or AP into the back of the new router. Make sure that each is set on a different non-overlapping channel: 1, 6, or 11; or just 1 or 11 if using channel bonding on the N router.

Then make sure you allow only N connections on the new router and/or indicate the wireless type in the network name (SSID), so users know which they are connected to.

#6 Use Only 40MHz-wide Channels with Strong Signals

As mentioned, in order to pass the 130Mbps ceiling on wireless N connections, you must double the channel-width from 20 to 40MHz.

However, you might reconsider enabling channel bonding if all the users don't have a good signal.

This is because it might actually have a negative impact on clients with low signals, and you're better off leaving it alone.

#7 Check for interference

As with other wireless G networks, you should be concerned with the typical interference issues, such as neighboring APs being set with an interfering channel and interference from other radio or electronic devices.

However, wireless N throws another problem at you. Remember that if you change the default channel-width from 20 to 40MHz (to try for greater speeds), it doubles the frequency range of the transmissions.

If you do use channel bonding, you're limited to using two of the typical three nonoverlapping channels.

So you should make sure you're using only channels 1 or 11 on all your APs.

Plus check the air waves to see there are other networks in the area and select the channel accordingly.

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