I just got a bluetooth mouse to go with my work laptop. The work laptop is a Compaq 6910p and the mouse is a Microsoft Wireless Notebook Presenter Mouse 8000.

I got the Microsoft one specifically because it was the only one on the shelf at Staples that actually used Bluetooth. Thus allowing me to use the built-in bluetooth radio on the laptop, instead of having to use one of those USB dongles to connect the mouse. It's good, it works.

Anyway, I have noticed that when I am downloading a large file from the intertubes, or doing a big netbios file copy across the network, the mouse movement is jerky. When it's done with the copy or download, all is fine.

My guess is that the following is happening: The 6910p has some sort of limitation where its bluetooth radio and its built-in wireless radio share an IRQ or a DMA or some other magical hardware TLA that I don't entirely understand how they work under windows. So the OS has to swap back and forth between the two items (bluetooth and wireless) to get its job done.

Does that sound like a likely scenario?

I can't verify this because I can't seem to find any "Resources" tab for the bluetooth radio in the device manager.

What other ways can I look this up? Anyone have any ideas?

Your internal BT, is it one of those combo wi-fi bluetooth mini cards.

I'd like to speculate that the BT and Wi-Fi are competing for use of the same transmitter.

Another speculation is that the priority of the BT driver is not high enough.

Isn't BT run as a service?

I don't know. How would I tell?

I can't speculate as to the problem in your case, but I've never used a BT mouse nor have I ever heard of one that didn't have some intermittent drop-out of response problems on any platform, Mac or Windows.

IMO, BT is great for syncing data, pretty good for a keyboard, but terrible for a mouse.

My next mouse will likely be a Logitech VX Nano (or something similar but not yet released if I don't get it soonish). I have found in the past MS mice more responsive, but recent models have not lived up well physically to regular use.

It's more likely that the BT and wifi don't have specific co-existence support, and BT is trampling over wifi or vice-versa. BT hops all over the 2.4GHz band, including all over the frequencies that wifi uses...

It is possible to implement coexistence, allowing either one to give way to the other depending on how important the data is, but there's little in the way of standards to determine how this is done (each chipset manufacturer seems to have their own idea), and unless the wifi and bluetooth are actually on the same bit of PCB then it's really unlikely to have been wired up. Given that a lot of PCs have wifi as a mini-PCI card and BT as a USB device, my guess is that this is what you're seeing.

eg:
http://www.wi-fiplanet.com/tutorials/article.php/1379911

Of course, if you're tightly integrating these things on a mobile device, you can do it right

Hugo

Bruno reminded me about my own experiences with wireless mice. I've tried a couple. One I purchased, and one that came with my HP Media Center. Both exhibited the intermittent performance he mentioned. Notably, as a power saver, they both tended to get into a sleep mode, and had to be shaken and clicked till they reconnected. They are also susceptible to being very screwy when the batteries are low.

I use a BT mouse on a Mac Mini connected via WiFi all the time and it works just fine.

If it's a mini-pci card there will most likely be a way to easily pull it. Look for a hatch cover on the bottom of the lappy. My Sony has a hatch that's large enough to access both the memory and wi-fi cards.

If it's a combo card it may say so on the fcc label.

Microsoft Bluetooth mouse on a VAIO laptop and also works fine. I used to play games on that laptop over WiFi and I've never noticed any problems.

I don't have any problems while playing games, either. I played a bunch of TF2/CS:S and it was fine. And most web surfing is fine. It's only when it's downloading a huge single file from the web, or copying huge single files across the local network.


Yes, it's one of those. I seem to recall looking at it before. I think it had either three or two outrigger plugs on it for antennas or such.


Me too.


Understood. That's not what's happening to me, though, it's specifically a jerkiness to the mouse movement rather than a complete dropout, and it's something that I can induce and correct by simply stopping and starting a large file download.


Very very interesting. Do you think that perhaps it's this very coexistence support that's making the two devices swap frequencies back and forth?

Wouldn't there also be glitches with the download if they were trampling on each other. Does the download loose speed at the same time as the mouse acts up?

Is BT a polled service like s-bus? Maybe the mouse is being swamped by other signals? What it can't hear it can't respond to.

It was my main PC for nearly a year and I never noticed anything when downloading or uploading large files *shrug*

I have a BT Mogo mouse for my Latitude D620 and no problems. I LOVE the mouse BTW. The BT in this laptop is definitely a separate board from the wifi.

I do have similar trouble as you when my BT/GSM cellphone is too close to the mouse. When the phone is in my pocket under the desk everything works ok, but it makes me wonder what its doing to my human bits.

Happy new year!

This doesn't appear to be a proximity problem as far as I can tell.

Also, an additional data point: This only seems to be an issue when the large file download is coming very fast, i.e., it's saturating the bandwidth.

For example, right now I'm downloading a huge file from a web site, but everything is working fine because the download is trickling in at only 87k per second. It's only when I have something that's coming down the wireless pipe very very fast that there seems to be an issue.

Might that be a clue? Is there something that a wireless connection does at high bandwidth that it doesn't do at low bandwidth? Something that kicks in and out instantly when the demand changes?

*shrug* just sounds like interference between the same usage of the 2.4GHz band from the WiFi and the Bluetooth.

But then why only during large bandwidth-intensive downloads, and not during light (but constant) bandwidth usage like web surfing and online gameplay?

Its transmitting less when you're only doing light usage. It splits everything up into frames so if you're not doing much then it won't be sending as much.

Possibly because when it's heavy traffic, the retries keep getting squished by the interference too - when it's light, even when there's a collision, the retry usually gets through?

Hugo

Are there *that* many retries and collisions during a large high-bandwidth file download?

You'd think that downloading a single large file in a constant stream would be the thing that was simplest and which resulted in the fewest problems.

You download a large file over your WiFi connection. It saturates the 2.4GHz spectrum. Then you use your BT mouse. It can't communicate because the spectrum that it wants to use is already saturated. Wireless retries result as a consequence of the two devices talking over each other. This probably always happens, but when it's being used constantly, the retries are much more likely to also fail. Domino effect.

A bandwidth saturating download is not "simple" in network terms. TCP based networking is packet based with an acknowledgment, and every usually ~1500 bytes of data is an individual packet. Every single individual packet over wireless has to be sent and confirmed received before the next one can be sent, so if you are talking about a 600kbps download (easy even for pokey broadband speeds in the US), thats ~400 packets a second that have to be sent with ~400 confirmations that have to be received. If any one of those packets gets blasted by interference, thats another round of transmit and acknowledgment, holding up the entire "stream". Mix in other TCP based traffic on the machine, along with wireless beaconing and other overhead, and you have a lot of individual transactions going on over WiFi. Then there is your bluetooth mouse, that based on the spec, can change frequency 1600 times a second, requiring 3200 exchanges in one second between the bluetooth radio and the mouse.

Dig out a 10mbit hub, and see how often the collision light blinks just based on casual web browsing with 2 machines. Toss in a file download on one, and the collision light will be on quite a bit. WiFi is like a hub, but with more overhead when multiple devices are connected due to all the wireless negotiation and tracking.