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Faster, Stronger 802.11b

Posted by timothy on from the sharing-with-more-neighbors dept.

stoney27 writes: "Looks like U.S. Robotics has doubled the speed of 802.11b plus increased the range. See link on MacCentral." You'll need upgraded equipment at both the base-station and computer ends to get a boost in speed, but they claim compatibility with standard 802.11b.

4 of 111 comments (clear)

  1. We Poor Europeans ... by frankske · · Score: 3, Insightful

    So we poor .EU people (where 802.11a is not allowed as the 5.4 GHz band is not free) can get a speed bump as well? I only wonder at what range the 22Mbps will work? 50m? 25m?

    1. Re:We Poor Europeans ... by HappyWithKilts · · Score: 2, Insightful

      There has been no official indications on 802.11a. in the UK, though the lobbying is hoping to cover both varieties - as well as any variants.

      802.11b is currently open for non-commercial use but there is no licence available at any cost for commercial use. The word is that in June 802.11b becomes free-for-all with no licence needed.

      Will be interesting to see how the EU handle this don't you think? Bit unfair if we in the UK can get a licence for nothing and you in Belgium have to pay.

      Let's stir it up! :-)

  2. 11a,b,g factoids by sshore · · Score: 3, Insightful

    11g is really 11a-style OFDM at 2.4 Ghz rather than the 5 Ghz band. There would be two (at least) 11g modes: a compatibility mode whereby OFDM packets and legacy 11b CCK packets coexist, and one which is "pure" OFDM at 2.4 Ghz.

    The compatibility mode adds a huge overhead to each transmitted packet. An 11g transmitter in this mode must first complete a legacy 11b RTS/CTS operation on the air which, if successful, is followed by the actual packet. Even if the actual packet were transmitted at nearly infinite bandwidth, the effective bandwidth you'd see on a connection would be quite low - think 10 Mb/s on average. That's not exactly chopped liver and its way better than legacy 11b, but it's definitely not 54 Mb/s.

    There are suprisingly large differences between 11a products, even those using the exact same vlsi chips. There are two primary reasons: differences in choice of output power amplifier (or lack thereof) and differences in choice of antenna. You can deduce some of what's going on by looking at power and sensitivity ratings in manufacturers product specs. By the way, this also a great way to distinguish between 11b products as well.

    Second generation 11a products have much better receiver sensitivity and output power than the first generation versions. And they do transmit through walls... although not concrete or metal or mirrors or some ceramics.

    The main reason why 11b can reach farther than 11a in some situations is that 11b can ratchet down to 1 Mb/s whereas 11a is defined for rates from 54 down to 6 Mb/s (11g is identical to 11a in this regard). The difference in SNR and sensitivity needed at a receiver to pick out the 11a or 11g signal accounts for nearly all of the differences in range ... and these differences are quite small if you have a good 11a radio with a good antenna.

    Thus, 11g will have the same power, SNR, and receiver sensitivity challenges as 11a in the 5 Ghz band, but will also have a small boost in signal propagation efficiency in the lower band.
    Don't get bamboozled by the hype about compatibility with 11b. Compatibility for sharing the channel does not imply that the radio properties of 11g are the same as 11b.

    Most vendors are busy bringing out 11a+b base stations and NIC cards. 11g in compatibility mode looks like a nightmare, whereas 11g in "pure" mode looks like 3 more channels of high performance OFDM if you have an 11a radio that can tune to both the 5Ghz and 2.4 Ghz bands. Aside from the higher-power outdoor channels at 5.8, this provides 11 channels for OFDM (8 at 5 Ghz plus 3). And this means that a group of base stations in an AP-dense environment will certainly be able to find a clear channel.

    I didn't say much about the PBCC-based 22 Mb/s products. PBCC is actually a clever design but is likely going to be overshadowed by OFDM at 5 Ghz (11a) and OFDM at 2.4 Ghz (11g variants).

  3. TI Isn't giving up.... by chriso11 · · Score: 2, Insightful

    TI has been pushing the PBCC modulation scheme for years. Recently, PBCC was dumped from the 802.11g spec, so now TI is trying to do an end run around the spec, and making it a done deal.
    The OFDM method used in 802.11g and 802.11a is more elegant, and provides a higher data rate than the PBCC. Of course, in fairness, Intersil is pushing for OFDM.

    Bottom line: if 802.11g isn't out soon, TI will be in a good position to put PBCC back into 802.11g by market pressure. The catch - 802.11g will be slightly (maybe $20) to support this lower performance mode.

    --
    No, I don't trust in god. He'll have to pay up front, like everybody else.