What are the requirements for a PC to accept a wireless card?

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An open PCI slot or USB port.

Either a PCI slot (for internal) or a USB port for external. Basically any relatively recent machine will go wireless. I have 2 new machines on my wireless network (Dell 5100's), a homebuilt machine (6 months old) and a pentium 3 machine(Dell optiplex). The new Dells connect with Dell USB branded dongles, my machine connects with a PCI card, as does the old optiplex.

Ummm... those are raw speeds. Real throughput is more like 5 Mbps for

802.11b, and more like 20 Mbps for 802.11g, and pretty much any broadband connection is within USB 1.1. Thus USB 1.1 won't slow Internet access (the most likely use), and probably won't even have all that much effect on computer-to-computer networking, particularly if there's more than one simultaneous wireless transaction.

Ummm... if your USB port is USB 1.1, then you'll be limited to 802.11b speeds (11Mbits/sec maximum). With USB 2.0, 802.11g speeds are possible (54Mbits/sec).

I beg to differ somewhat. You're correct on the thruput. A 5Mbit/sec thruput is not going to be a bottleneck for a 1.5 or 3.0Mbits/sec DSL line. However, it will be too slow for a 6Mbit/sec DSL or cable modem.

Also, the serial interface (USB) has to go faster than the raw wireless speed or the system will bottleneck. To the best of my limited experience, all 802.11g USB wireless devices have a feature where the driver sets the maximum speed to 11Mbits/sec if it's plugged into a USB 1.1 port. I just verified that with a Dlink DWL-G120.

11mbits/sec maximum association speed when connected to my WRT54G v1.1.

Incidentally, I try to refer to connection "speed" as the raw wireless data rate and use the term "thruput" for the actual transfer speeds.

As John says, either a spare PCI slot *inside* the PC, or a spare USB port on the *outside*.

My personal preference is the former; this just involves undoing a couple of screws on the side panel of the PC, removing the panel, taking out a blanking plate on the back of the PC so that the PCI card antenna can poke out, then just slotting the WiFI card in to a vacant slot. There's only one size slot the card will fit in. -ut the panel back. WIll take 5 mins tops.

With the PCI option however, you will have the WiFi antenna poking out the back of the PC, which if your PC is shoved under a desk in a corner of the room, will not help signal strengths. The advantage of the USB dongle is that it will be more readily positionable. For my PCI WiFi card, I bought a more 'powerful' antenna, and a 1m extension cable. Through a floor and doors, I still get maximum signal strength from the router.

Either way, make sure that you buy a WiF 802.11g capable card, not 802.11b.

You will also need access to a WiFi access point (AP) attached to your internet connection, this to transmit the data to/from your new WiFi desktop. E.g. I have broadband cable modem connected to a Linksys WRT54G router/AP. One of my PCs is connected to this router/AP by cable, and one by WiFi.

With all due respect, such speeds are very rare in practice -- that really isn't going to be an issue.

Crappy design, but I'll take your word for it.

I have 2 customers with 6000/512 DSL from SBC. They get about

4.3Mbits/sec sustained thruput. Both have been up for about year at this speed. Sometimes, usually in the middle of the night, the speed tests dribble up to about 5Mbits/sec.

Favorite speed test site:

other NDT test sites (see bottom of page).

Looking at the speed test results from DSLReports.com at:

see 4.4Mbits/sec is about typical for the higher speed cable and DSL connections. Ignore the reports that appear to be symmetrical speeds as those are probably directly from the ISP's. Hmmm.... Canada is getting faster speeds than the US.

In the past, I was proclaiming that I could get about 5Mbits/sec thruput on an 11Mbit/sec 802.11b connections. Well, that's true in the lab but not true in any reflection or interfence infested environment. More typically, I get about 3.5-4.0Mbits/sec max from

802.11b (WRT54G v1.1 and Orinoco Classic Silver). That would not be enough to keep up in speed with a higher speed cable or DSL connection.

A T1 is rate limited to 1.544Mbits/sec. You'll see a thruput of about

1.2Mbits/sec in both directions.

Only 256Kbits/sec upstream on a T1? You must be running servers through the T1.

I agree for a T1 at 1.5Mbits/sec. I also agree for a common DSL and slow cable connection at 1.5 or

3.0Mbits/sec. I don't agree for a high speed 6Mbit/sec DSL or similar cable modem speed.

Drivel: DSLReports.com speed test results that show broken routers with high packet loss but probably also shows lossy DSL, cable modem, and wireless connections.

I disagree. My broadband connection is to be upgraded to 10Mbps by the year end and there are a lot of ISP's in the UK that are offering 8Mbps and even 24Mbps for about $40 a month.

That's going to start to present issues for even 802.11g for people that aren't damn close to the AP.

David.

I tend to agree with John. How much throughput do you really get on a

6-10Mbps cable/DSL connection? I've variously seen the 'real' speed of the Internet calculated at 1-2Mbps. I can rarely get much more than that off my T1-LAN connected desktop machine. Right now, numion.com says it's 256Kbps and DSLreports.com says 738Kbps - but it's a busy period with 1000 or so computers on this LAN.

If you're just using the connection for Internet access, USB 1.1 isn't going to make much difference. If you have local file sharing, it's going to be significant - not least because aiui a single USB 1.1 connection is going to force your whole WLAN to use 802.11b.

Try the diagnostics output under more details. Lots of numbers in there. Sometimes, I get a suprise.

I have no clue what they mean by having 3001-3003 open. It seems to use those for OUTGOING connections, not incoming. I guess if the firewall were a proxy server, that would be a problem. However, for conventional wireless routers, that permit outgoing connections on literally any port number, it should not be an issue.

Interesting speed test site you listed as your favorite. I noted it says: "Systems behind firewalls must permit TCP ports 3001, 3002, and

3003." Are these normally open? I have a Linksys BEFW11s4 which functions as a firewall and Zone Alarm. The test seemed to work just fine.

Bob

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Even your connection isn't going to be running at more than USB 1.1 speeds except in rare circumstances.

Hi, Bear in mind the line is 10 or 24Mbps capable. It's not going to run at that speed all the time every time. So I won't worry about it. Tony

I'll let you know but USB1.1 isn't the bottleneck here, it will be the radios. 802.11b will be inadequate and even g will drop back quickly to a speed that will be too low for these higher speeds once the signal drops.

Flat out at 54Mbps, throughput can only be half that at best and then the lower rates will again be potentially too low.

David.

No but when a download is trundling down from a well hosted site (or several downloads at once, we don't all just view web pages), things will start to struggle.

David.

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It doesn't actually "struggle" -- TCP/IP throttles back gracefully to whatever the link can handle.

May I humbly suggest you reconsider your opinion. Dialup external modems so the same thing. If you set the serial port data rate to

19.2Kbits/sec, it will set the maximum connect speed to 14.4Kbits/sec. To get 56K speeds, you need 57Kbits/sec or faster SIO speeds. Admittedly, you can force the modem to connect at a higher speed, but that will just eventually overflow the modem buffer.

The same thing applies to USB which is just a fancy name for a serial port with a weird connector. Max data rate for USB 1.1 is

12Mbits/sec. It makes no sense for the wireless to go any faster as the driver buffer will overflow. So, they limit the speed to 11Mbits/sec.

I would call this "defensive design" as I really would not want to explain to customers why their USB wireless is eating packets due to an inability for the USB/SIO interface to keep up with the wireless data rate.

Almost all that I've ever played with. Multitech, Supra, Hayes, USR, etc. I used LOTS of these modems on Unix boxes for modem pools and got to know their idiocyncracies and bad habits intimiately. Very old photo of Cruzio with various Portmasters, USR modems, and lots of cables:

only ones that would run with a faster SIO rate than connect rate out of the box were the early Telebit T2000 modems and that was later fixed with a firmware update.

True. You could set it up to run that way if you wanted. If the initial connect was at 33.6 and the line conditions sucked, the modem would slow down. However, if you setup the SIO for 9600 baud, you could never go faster than V.32 at 9600 unless you forced the connect speed to some specific rate. It was also specifically warned against in the manuals to always keep the SIO rate faster than the connect speeds. It could be done, but that was NOT normal or desireable operation.

The same applies to USB 1.1 versus 2.0 for wireless. You can run an

802.11g wireless devices with a USB 1.1 port, but that is NOT normal or desireable operation.

Running it that way assumes that:

1. There's a hardware flow control mechanism that works. It can't be in the PC's driver code because the flow problem is between the wireless bridge side and the USB interface. That puts it inside the USB device. Got RAM? Got money? How many seconds of bursty traffic do you want to buffer?
2. CTS/RTS flow control is functional to prevent excessive repetitious packets when the PC drops incoming packets because the USB

1.1 interface can't handle them. This will drop thruput somewhat.

1. The TCP layer can handle it. A basic wireless rule-of-thumb is to NEVER transmit a packet if you know it will be dropped. Resends are very bad for thruput. The 802.11g MAC layer will also reduce the connection speed or the TCP layer will delay sending packets to deal with the excessive NACK's. Anything to eliminate retransmissions.

The high speed bursty traffic does have one advantage. It clears the air faster than a slower connection speed. This gives other devices on the system more air time to transmit. However, it won't take too many retransmissions to ruin any benifits offered by this improvement.

In my never humble opinion, it's much easier to just back off the wireless connect speed and let the sending wireless device control the traffic. Given the requirements for running at faster wireless speeds versus just rate limiting the wireless connection, methinks this was an acceptable compromise.

Sure, I use this for bandwidth management all the time. So, what's the difference in design? Letting the wireless run as fast as possible and dropping packets at the USB interface will eventually result in the TCP layer noticing and slowing down sending packets. The result would be something like 54Mbit/sec connection speeds, but the thruput controlled by the slowest device (USB 1.1 or 12Mbits/sec). You get all the problems of running at higher speeds (short range, low noise immunity, interference potential), with no benifit in thruput over 802.11b (11Mbits/sec). Same issue as the modem analogy. You could run it this way, but there's no real benifit.