WiFi Will Never Be As Fast As Ethernet

With Ethernet, you expect (and generally get) 100Mbps performance from the network. With Gigabit Ethernet, you expect 1000Mbps. With 802.11g WiFi, you expect 54Mbps, but you seldom get that. Why is WiFi unreliable?

Ethernet is based on rigidly defined specifications. If you observe the limitations imposed on you by those specs, you get predictable results – those limitations should exceed your operating requirements. For instance, 100M Ethernet is provided for cable runs of up to 100 Metres (300 feet) between the computer, and the other network device (generally a hub / router / switch, or another computer).

Draw a 300 foot sphere around your home / computer room. With WiFi, you will probably find numerous factors within that sphere, that will interfere with your getting consistent 54M performance from a 802.11g network. With WiFi, there are things you just can’t control, and others that you can, but not easily.

  • Ethernet is a full duplex, dedicated medium. WiFi is half duplex, and shared – it has one media, the WiFi channel, which has to be shared for both sending and receiving the packets. And it’s shared with your neighbours.
  • Ethernet is a mature technology – it’s been around for much longer than WiFi. WiFi components have frequently upgraded firmware. Any time you ask the vendor for help, their first question will be “What version firmware are you running?”. This is not a delaying tactic, or needless protocol – it’s an attempt to ensure that your drivers are up to date, so they can help you effectively.

    Any time you get new hardware, you should always consider the possibility that the firmware was upgraded after your unit was packaged. Always get up to date firmware – and get it from the vendor.

  • Ethernet is a much more stable medium. With switched Ethernet, you have two hosts, for instance a router / switch, and a client computer. The two hosts are connected by a physical cable. The firmware and hardware on each host has to manage the conversation only with the other host.

    With WiFi, each host is managing / blocking conversations with dozens of other hosts (multiple channels, locations, and networks) constantly, and no two hosts are seeing the same complement of other hosts at any time or in any place. Managing relationships in the constantly changing WiFi population takes resources – and can make the WiFi device slower than it should be.

    Besides the constantly changing and differing population issue, there’s the security needs. WEP, WPA, WPA2, AES, CCMP, TKIP… The list of security protocols and standards is endless, and changes frequently. Managing security in any WiFi conversation takes resources – and can make the WiFi device slower than it should be.

  • Can you actually see a computer from the Access Point? With WiFi, if you don’t have a clear line of sight visibility between the network devices, you’ll not get a full strength signal. Distance is another factor. Signal strength falls off as distance increases. Put the computer in one room, and the AP in another (a normal use for WiFi), and see what signal strength you get. Walls and floors are a major signal problem. Signal loss will be higher if the signal has to travel diagonally thru the wall or floor, rather than at a right angle.
  • Look at the antennas on the AP and the computer, and see how much they are parallel – you will get maximum signal strength only when the 2 are perfectly parallel. Draw an imaginary line, extending at a right angle, from one antenna towards the other. Does it intersect the other? Try and make a line between the two intersect at a right angle. Signal loss will be higher if one network device is located directly above the other, and on another floor, if both antennas are pointed vertically.

    To make this simplest to understand, look at some examples.

    • If the AP and a computer are in the same room, locate both devices so both antennas are the same height off the floor. Point both antennas vertically.
    • If the AP and a computer are on different floors, locate both devices so the antennas are immediately above and below each other. Point both antennas horizontally.
    • If the AP and a computer are in different rooms, position both so a line from one to the other goes at a right angle thru the wall. Locate both devices so both antennas are the same height off the floor. Point both antennas vertically.
    • When you can’t be so precise in physical placement, point both antennas parallel to each other, per the above strategies.
  • An Ethernet cable is a media that YOU own, and physically control. With WiFi, you have to share the channel with all of your neighbours. And, with CSMA/CA, the sum of your bandwidth plus your neighbours bandwidth will never add up to 54M. Relying upon Collision Aviodance will always require wait time, where neither of you is transmitting. And the more neighbours that you have, the more wait time will be used by your equipment.
    • If your equipment is compatible, you may benefit from using NetStumbler, which is free. Find out how many of your neighbours are also using WiFi, and how close each is.
    • Try using a channel that isn’t being used by a neighbour close to you. With 802.11G 54M, only channels 1, 6, and 11 don’t overlap in frequency. If you have 2 neighbours – one on channel 1, and the other on channel 6, your best choice is channel 11.
    • Remember that wireless networks may come and go, so watch over a period of hours, if not days. NetStumbler is great for this – leave it running, and it will make a running list, showing each observed access point, and graphing its signal strength by time.
  • Your wireless neighbours are interference sources outside your home. You probably also have interference sources inside your home.
    • Baby monitors.
    • Computers.
    • Cordless phones.
    • Microwave ovens.
    • Wireless stereo speakers.

    If you install a WiFi device on your desktop computer, try and get one with an antenna that you can move above, and away from, the computer. Signal loss will be higher with a PCI WiFi card, with the antenna stuck at the back of the computer. This is particularly the case if your computer is a tower, sitting on the floor. The higher the antenna from the floor, the better the signal level.

  • You will only get maximum performance from similar equipment, and with no WiFi neighbours. You will have to share the channels with your neighbours. In any WiFi neighbourhood, no two WiFi devices will be within range of the same complement of other WiFi devices. The hidden node problem is a well known WiFi issue.
  • Maybe the router configuration has a setting that’s causing your problem. Start by checking your Transmission Rate setting.
    • If it’s on Auto, try setting it to a realistic rate. Start by setting it at the rate you think you’re getting, and see if your bandwidth improves even slightly. If there is any problem with your signal, auto may make the router spend more time recovering from problems, and less time actually sending and receiving.
    • If it’s on a low rate, try setting it at a higher rate. See if your bandwidth improves.
    • When tuning your Transmission Rate, using NetStumbler to analyse performance would be a very good idea.
  • For more thoughts on this subject, see BBR Forums How Can I Boost My Range? (#10944).

And however you set up your WiFi in the end, please secure your LAN. The performance hit you get, when your neighbours WiFi LAN comes on, pales in comparison to what happens if your computer is hacked, and joins a botnet.


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