802.11n wireless networking

802.11n is the latest standard for a local wireless network. You need the latest equipment to get full value from an 802.11n. Here are the secrets for success with 802.11n.

History of 802.11

802.11a and 802.11b were both released in 1999 with similar speeds on different bands. 802.11a used 5 GHz and almost no one adopted it. 802.11b used 2.4 GHz, a frequency readily available in many countries and similar to the frequency used for wireless telephones. 802.11b was easier to manufacture, cheaper, and handled the speed of dialup Internet connections. It was fast enough for email and the simple Web pages in use back then but not fast enough for the horrible Flash video advertising that now pollutes Web pages.

2003 gave us 802.11g, an update of 802.11b adding in the best of the 802.11a features. 802.11g made wireless connections to notebooks practical. Many people replaced their desktops with wireless notebooks and only occasionally complained about the lack of speed.

By 2007 802.11g was too slow for all the online video splattered all over the Web. Most of the video on the Internet is rubbish but it takes so long to download them, to find the few good morsels, that 801.11g had to be replaced. Some manufacturers and a lot of the buy-from-China-and-slap-a-brand-on-the-front companies announced 802.11n (draft). Some left of the bit about the new standard being an early draft. 802.11n (draft) devices failed to cooperate between brands and often failed to work within one brand. You might be able to use a Netgear wireless adapter with a D-Link wireless router but not a D-Link wireless adapter with a Netgear wireless router. In fact I found a D-Link 802.11n (draft) wireless adapter did not work with a D-Link 802.11n (draft) wireless router purchased at the same time. 802.11n (draft) was a mess you are better off missing completely.

Wind forward to October 2009. 802.11n is announced as a formal standard up to 150 Mbps (megabits per second) or about 15 MBps (megabytes per second), fast enough for full bandwidth video, fast enough to transmit from a Bluray player to your computer for active viewing.

802.11n specifications

802.11n specifies both the 2.4 GHz and the 5 GHz bands, a great leap forward given the saturation of the 2.4 GHz band by competing networks and devices. 802.11n includes a bandwidth jump 20 MHz from 40 MHz. 802.11 sends data in a stream and 802.11n allows 4 streams instead of 1, making 802.11n at least 4 times faster than 802.11g.

802.11n in practice

802.11n can work on both the 2.4 GHz and the 5 GHz bands. 2.4 GHz is saturated by cordless telephones and neighbouring networks. 5 GHz should provide more space. Some companies released equipment that will work on only one band or will not switch automatically between bands or defaults to 2.4 GHz without 5 GHz. Check the box before you buy. Make sure the specifications mention both frequencies. Check the default settings when you install the device.

The 40 MHz bandwidth is not compatible with the older 802.11g. Make sure you have automatic switching between bandwidths. On some D-Link routers I had to manually lock the router to 20 MHz bandwidth to make it compatible with an 802.11g notebook. I replaced one D-Link router with a TP-Link router and another with a Netgear router. Both the TP-Link and Netgear routers automatically switched between 20 MHz and 40 MHz bandwidth for the old notebook and some new 802.11n devices.

The fastest stream in 802.11n is 150 Mbps. 2 streams in parallel should give you 300 Mbps and 4 streams should give you 600 Mbps. A lot of manufacturers immediately announced 300 Mbps and 600 Mbps 802.11n devices. 300 Mbps appears to be easy because there is plenty of bandwidth in a single band, either 2.4 GHz or 5 GHz. The 4 stream 600 Mbps 802.11n appears to work only when using both the 2.4 GHz band and the 5 GHz band in parallel. All my tests were in areas with other 802.11 networks, mostly 802.11g networks, and cordless telephones on 2.4 GHz. Tests at very quiet times of the night still produced unreliable 600 Mbps.

Gory detail

This is the yucky internal bit where the CSI investigator applies the circular saw to the cranium. You can switch channels if you are squeamish.

The 2.4 GHz band is divided into 11, 12, 13, or 14 channels depending on your country. Each channel is 22 MHz wide giving you the old 20 MHz bandwidth of 802.11g. In theory you should have 14 times 20 MHz or 280 MHz to transmit data. The truth is the channels overlap and you can use only 4 channels in parallel. If one other person is transmitting on a network, you will have two channels each. If 4 networks transmit at the same time, they should all slow down to using only one channel each.

Streaming video from a DVD fills a 20 MHz channel about 30 percent of the time and three people could stream DVD video in parallel on one channel. Multiply 2 bands by 4 channels per band by 3 videos per channel and you get 24 videos streaming at the same time. Blu-ray floods a 20 MHz channel full time reducing the total video streaming to 8 videos when everyone uses Blu-ray.

When you switch to 40 MHz wide channels, you can use only two channels at the same time in one band. If there are two networks transmitting, you will have one each. When there are four networks transmitting, two networks will use a channel each and the other two networks will drop out for a while.

Using the two bands, 2.4 GHz and 5GHz, together gives you 4 channels in practice. One active cordless telephone conversation can knock out one channel, leaving only three for your use. If there are five networks actively transmitting, or four networks and a cordless telephone, something will drop out.

I find most areas have more than four networks available. 802.11n works because of the limited range of the old networks and cordless telephones. When everyone is using 802.11n networks, both bands will be busy. When everyone is trying to stream video, both bands will be choked.

Better antennas

Most of the wireless equipment suffers from second and third rate antennas. They are too small and too few. 802.11n lets you use MIMO, Multiple Input Multiple Output. Two antennas are better than one and three in a triangle is better again. External antennas give you better performance and range. You do not need the best in a small apartment. You do want the better antennas almost everywhere else.

Two antennas let your device pick up slightly different views of the signal if one antenna is blocked by a metal pole or another computer. Two external antennas on cables let you space the antennas out to see around big blockages including metal filing cabinets and fire doors.

Two antennas give you a better view in one direction, at a right angle to the line formed by the antennas. Three antennas let you place the antennas in a triangle to give your device a better view of the radio signals in all directions.

Three antennas in a line at the back of the router give you exactly the same single line as two antennas. You want three external antennas sitting in a triangle.

Four antennas lets you form a three dimensional triangle giving your device two views of the wireless signal in every direction including up and down. Use four antennas for a few floors of a multiple story building, perhaps a three story house.

The steel reinforcing in concrete floors can suck the power out of wireless transmissions and sometimes require a separate wireless router on each floor. The same happens with metal wall buildings. If you have a steel garage next to your house and set up your office in the steel garage, you might need a separate wireless transmitter in the garage. You can get extension cables for your antennas but they are useful only for a metre (three feet). For a longer distance, use a separate wireless router connected by an ethernet cable.

There are special waterproof outdoor antennas designed to project in one direction. If your office is at one end of a long block of land, you can use one of the long projection antennas to direct the radio waves right down to the back corner of the land. Unfortunately your notebook or netbook will not be able to focus a transmission back to the special antenna. You might need a special external antenna to send the signal back. Notebooks and netbooks do not have external antenna connections. The secret is to get an external USB network adaptor with an external antenna connector then to connect a directional antenna to the external adaptor.

Should you use repeating stations? Repeating stations are wireless routers that use one half of their bandwidth to connect to your exisitng router and the other half to connect to your notebook. You can double your range with a repeater half way along the path. The repeater could be solar powered so you do not have to connect power to the repeater. repeaters do use double the bandwidth for each transmission and, as a result, get twice as many dropouts. Repeaters are not good for streaming video. If you have to run a power cable to the repeater, you might as well run an Ethernet cable at the same time and use a separate router for better coverage with fewer dropouts.

The future of wireless

Now add to the complication. You have a digital television tuner broadcasting to your computer where you record your favourite show, Top Gear. Your wife or husband is watching Master Chef on their computer using a wireless connection from the same tuner. Your wireless media server is recording a movie from another channel on the same quad digital tuner. Your two children are also watching television. One is watching the fourth channel streamed from the quad tuner. The other is watching a movie streamed from your wireless media server. That adds up to 5 media streams fighting for 5 channels of 20 MHz. If your network uses both bands, there are only 8 channels of 20 MHz.

Your cordless telephone rings, you mute the sound on your computer, and answer the telephone. Now there is a cordless telephone interrupting one channel.

You live in an apartment. Each of the apartments near you, the one above, the one below, the one to the left, and the one to the right, have the same arrangement. Each is fighting for 5 out of the 8 available channels and all the networks are so close that they interfere with each other. no wonder wireless has a limited future.

Wired to the rescue

There are lots of wired options to reduce wireless usage. The important thing is to cut out the wireless network between the tuner and anything else because the dropouts spoil the show. After a show is recorded, the computer to computer file distribution can go at any speed. Wireless dropouts will result in retransmission and the file will be transferred without error.

US

USB connected digital television tuners are so cheap and effective that you can connect a tuner to every computer where you watch television, saving a wireless channel in the process and reducing the dropouts from wireless interference. In Sydney there are USB tuners selling for close to AU$50 complete with a remote control, an antenna, FM, and DAB radio. Buy one for home, one for your office, one for your wife, husband, plus each of your lovers and children. Go mad and buy one for your ex so he/she will spend more time watching television and less time harassing you on the telephone.

Set top box PVR

Lots of set top boxes include a disk or let you connect a disk to create a PVR. Some also have a wired LAN connection. If you record using a set top box onto disk, you cut out the bandwidth usage from the tuner to the recorder. You can then use the wired connection to distribute the file to other computers. If you do not have a wired network, you can transfer the file over the wireless network during a less busy time when you are only interrupting your neighbour's network transfers, not your own.

Televisions with multiple inputs and outputs

Televisions have multiple connections and some are USB. You can have the TV showing one picture and a set top box recording another show then switch the television to the set top box for playback. Your set top box or computer can record to a USB stick and you can plug the USB stick into the television for playback. Some televisions have a wired LAN connection. The combinations are almost endless. The low cost of devices means you can group the devices to remove all wireless connections for the live shows and reserve network traffic for file transfers.

Your office

You have an office at home in the form of a desk in a spare corner of the room used for storing unused toys, unironed clothes, and the furniture you cannot sell because it is from a period that has not yet been recycled by the fashionistas. The broadband connection enters here. You decide to add a wireless router in this room to service your whole house. For a few dollars more, you can get a wireless router with four wired connections. Everything in your office can then be wired and not chew up wireless channels or wait for slow wireless data transfers to fight through dropouts.

You have a notebook or netbook. You have to plug in the power to charge the battery. Plugging in a wired connection is very little extra work and reduces the wired traffic/delays/dropouts. If you have a decent brand of computer, you should be able to buy a low cost docking station (or port replicator) to connect power, wired network, USB, and video in one click. Docking stations are a superb idea made impractical only by some brands gouging masses of dollars from your pocket for a fancy sheet of plastic with a plug in the middle.

Docking stations solve the wireless congestion issue plus a good docking station includes a power supply. You can use a docking station at home, another at work, and not have to lug that heavy power brick back and forth.

Conclusion

Wireless networks will choke when everyone uses 802.11n and streams video. Look for wired options at every step to avoid the crunch next year. Hardware is so cheap, you can afford to duplicate the odd tuner and set top box.