i-rant

It took me several days to figure this out, but there’s a system setting called net.inet.tcp.slowlink_wsize that controls download speeds for “slow link” connections (i.e., PPP). The default value for this variable is 8192 bytes, but this needs to be significantly increased in order to maximize EDGE download performance.

1. First, use RMAC or some other method to create a startup script in your /Library/StartupItems folder.
2. Next, use TextEdit to modify the startup script to make it look like the example script that I listed under item 6 in my first post. Save and restart.
3. Figuring out the ideal value for net.inet.tcp.slowlink_wsize involves doing some tweak testing. Initiate an EDGE phone connection and run the tweak test, and then follow the instructions at Broadband Reports.com to calculate the optimum RWIN value.
4. Edit the startup script again to set net.inet.tcp.slowlink_wsize to your new optimum RWIN value. In my sample script, I highlighted my own optimum RWIN value in red. You may find that another value works better for you. Save and restart.

From my experimentation, I deduced that,

* net.inet.tcp.slowlink_wsize = RWIN for PPP connections
* net.inet.tcp.recvspace = RWIN for broadband connections

Adding this startup script increased my EDGE download speeds almost three-fold.
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As you can see, I’m getting close to maximum theoretical EDGE speeds for a Class 4 device. 119 kbps is FAST! While wading through Howardsforum, I noticed that a lot of Mac users were complaining about slow EDGE download speeds. It’s clear to me that none of them realized they had to adjust their system settings. Who can blame them? It took me hours of Googling and experimentation to figure out the solution to the problem. It’d be nice if somebody would post a man page for the each sysctl writable variable.

I tested out a theory of mine by successfully streaming a 96 kbps iTunes broadcast using my EDGE phone. Satellite radio and the iPod are both screwed.

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1. Newark, DE (6/18/05):

Upload: 38 kbps
Download: 139 kbps

2. Alexandria, VA (6/16/05):

Upload: 38 kbps
Download: 115 kbps

Download: 145.6 kbps

3. Washington, DC, U.S. Capitol Building (6/15/05):

Upload: 38 kbps
Download: 96 kbps

4. Baltimore, MD, Inner Harbor (6/20/05):

Upload: 36 kbps
Download: 57 kbps

Specifications

Phone: Motorola V551 (Class 4 EDGE)
Computer: 12″ PowerBook G4 (1 GHz Rev B)
OS X Version: 10.3.9
Tethering Method: Bluetooth®
Signal Strength: Maximum
Modem Script: Motorola 3G CID1

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http://www.internetfrog.com/mypc/speedtest/

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Using a Cingular Nokia 6230 as a Bluetooth Modem with OS X.

In my constant search for fast, low-cost wireless data access, I recently abandoned T-Mobile’s T-Zones inexpensive 5-dollar-per-month GPRS data service (they started blocking every port except for 25, which only allows email access) and now I “tether” my Mac to Cingular Nokia 6230 for bluetooth internet access, which I use quite often as I am out in the field and need to get email on my Powerbook or need to download a file for a client who only has dialup. The nice thing about the Nokia 6230 is that it is capable of EDGE speed data which is typically 2-3 times faster than GPRS. I can usually establish a connection of around 180Kbps which will let me download at around 22KBps. Granted there is tons of latency and the battery on the cellphone won’t last forever, however in certain situations it is very convenient. You must make sure you can get EDGE speeds for this to work Contact Cingular to see if it’s available in your area.

Now onto the fun part.

First requirement is Cingular’s MediaWork Unlimited package for $24.99/month. It used to be $19.99/month, however they recently raised the price. Next, download the 3G Nokia modem scripts from www.taniwha.org.uk and install them in your /Library/Modem Scripts folder. Do not download the GPRS scripts, as you will not achieve EDGE speeds with them.

On the phone go to:

Menu->Settings->Connectivity->Bluetooth->Bluetooth On

and

Menu->Settings->Connectivity->Bluetooth->Bluetooth Settings->My phone’s visibility->Shown to all.

This will allow the Mac to find your phone via bluetooth.

Once the scripts are downloaded and installed, go up to the bluetooth menu and pair the phone with your Mac. Pair the phone to use as a modem for GPRS data. On the next screen in the setup assistant enter the following data in.

Username: WAP@CINGULARGPRS.COM

Password: CINGULAR1

GPRS CID String: wap.cingular

Modem Script: Nokia 3G CID1

I personally have the modem accessible from the menu bar so I just click on it and connect that way. This is an inexpensive way to get fairly highspeed data from your Nokia 6230 via the Cingular network for a lot less than the cost of the $80/month full EDGE data service.

Ryan Grimes — R. T. Grimes Consulting (Serving the Indianapolis Metropolitan Area) /
– ACDT, ACPT, ACTC (10.1), ACHDS.
Ryan can be contacted at ryan[at]rtgrimesconsulting.com or (317)534-0562

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Here is a little gift for those that are Cingular GSM customers with a unlimited data plan. After an hour or so of playing around with my Sony T637, I figured out how you can use this phone as a Bluetooth modem.

Before we begin the setup process, you must download the scripts needed for your phone from Ross Barkman’s page. I haven’t tested any other scripts, but the Sony Ericsson 3G scripts are those that are needed for the T637. Once your download has finished, you can then place the scripts in top-level Library/Modem Scripts folder.

Instructions:

1. Set up a new Bluetooth device using the setup assistant (Mobile Phone).
2. Once your Bluetooth phone is found, you will have to initiate a pairing of the device with your Bluetooth-enabled Mac.
3. The next step asks how you will be using your phone; set up iSync to transfer contacts and events, use Address Book, and access the internet using your phone’s data connection. There are two options underneath all this:
* Dial a specific number access number for your ISP.
* Use a direct, higher speed connection to reach your internet service provider (GPRS, 1xRTT)
Select the second option.
4. This is going to take you to the last part of this setup, which is going to ask you for all the information it needs to connect to the Cingular network. All CAPS is a must!:
* Username name: ISP@CINGULARGPRS.COM
* Password: CINGULAR1
* GPRS CID String: ISP.CINGULAR
* Modem script: Sony Ericsson 3G CID1

Now that this part is complete, it’s on to the Internet Connect window.

1. Open Internet Connect, and you should see the following under the Bluetooth section (again, all CAPS):
* Telephone Number: ISP.CINGULAR
* Account Name: ISP@CINGULARGPRS.COM
* Password: ********* (CINGULAR1)
2. Hit the Connect button, and you should connect without any issues. If you get an error saying No Response from the other end, give it a few minutes and try again.