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Being in South East Queensland at the moment, with limited access to dial-up, I decided it would be the perfect opportunity to try out Vodafone’s data bundles, which are described here .

Now my standard provider I use for light GPRS usage, Optus, charges 0.55c/kB (decreasing to 0.33c/kB as usage increases) on GPRS Plan 2. Held up against the rest of the market offerings, this would be considered some of the cheaper pricing, as the average users are paying is the “standard” 2.2c/kB.

Unfortunately of course, this works out to around $5/meg, and with even some light email usage, instant messaging, and of course, the mobile bandwidth killer – web browsing, this can result in a very expensive bill.

I chose the $49.95/month “Power Use” package, which implies unlimited usage but the legal print suggests that 500M is considered excessive. I was able to easily apply at a Vodafone store, with no other fees (BYO handset) charged to me.

Test equipment: Dell Inspiron 8500 notebook with CSR Bluetooth chipset, Windows XP SP2, Sony Ericsson P800 (Phone: CXC162002 R2F, Bluetooth: CXC12529 R5A, Organiser: CXC162001 R2D02), Nokia 6230 (v4.43 24-08-04 RH-12 GSM P1.1)

Setting up

I was instantly able to use the service the moment I left the shop. My Sony Ericsson P800 was already configured for use with Vodafone GPRS, and I was able to immediately use all my internet-enabled Symbian applications with ease (and the piece of mind that it wasn’t costing a fortune!).

As for using with my Dell notebook, which was my primary purpose, I simply paired the phone using the XP SP2 Bluetooth settings (found on the system tray or in control panel), and created a dial-up connection in the normal manner, choosing the “Standard Modem over Bluetooth” modem. All that is required to be configured is the telephone number, which is a special number to inform the handset to open a GPRS data session (rather than an ordinary data call). For the Nokia phones, this is *99#, which activates the GPRS Modem profile (usually specified in the Connectivity menu). For the Sony Ericsson, it was of the form *99***X#, where ‘X’ is the number of the GPRS profile in the Control Panel > Connections > Internet Accounts.

Once this is done, the connection is opened in the usual manner, but is much quicker than a dialup modem - it takes a few seconds.

Using Bluetooth is quite convenient as the phone can be left in your pocket, or bag, or elsewhere in the room (i.e. connected to a charger).

Performance

The connection was tested via Bluetooth with a Nokia 6230 and a Sony Ericsson P800 handset, which are Class 10 devices (meaning, they can use up to 4 downlink timeslots and 2 uplink timeslots in either a 4+1 or 3+2 configuration).

The most obvious shortfall of GPRS is the high latency, which can be around half a second or more. This is somewhat higher than GSM data calls, and of course dialup, but this is the trade-off with low power usage and radio link efficiency.

Results from pinging some sites with an idle connection:


Pinging mirror.aarnet.edu.au [192.42.62.2] with 32 bytes of data:

Ping statistics for 144.135.18.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 596ms, Maximum = 1101ms, Average = 819ms


The transfer speed of GPRS is better than that of circuit switched data, but the actual speed depends on the multi-slot configuration in use (i.e. available network resources) and the signal strength and quality (as the coding scheme is switched between 4 different levels with varying degrees of error-correction).

Results from downloading some files off local FTP sites:

(mirror.aarnet.edu.au)

150 Opening BINARY mode data connection for openssh-3.8.tgz (405262 bytes)
226 Transfer complete.
ftp: 405262 bytes received in 86.45Seconds 4.69Kbytes/sec.

(ftp.planetmirror.com)

150 Opening BINARY mode data connection for rsync-2.6.3.tar.gz (583453 bytes)
226 Transfer complete.
ftp: 583453 bytes received in 115.73Seconds 5.04Kbytes/sec.

The transfer speed suggests comparable performance to 56k, but it is important to remember the latency is significantly higher. This means protocols which involve frequent but short bursts of data in each direction will suffer the most. Web browsing, in a sense, can be like that, as the web browser is constantly requesting objects such as images. Other applications, such as instant messaging (MSN), FTP and email are less sensitive.

Worth a mention is Vodafone’s transparent interception of HTTP and dynamic re-compression of images, to improve performance. I noticed this when writing this article, the screenshots when viewed via the Vodafone GPRS connection appeared significantly lower in quality than the JPEGs I had made on the local machine.

The reliability was reasonable, although the connection would randomly drop out at times, and furthermore, at differing points, both of the test handsets froze or crashed (rebooted) during the GPRS session. This is unacceptable behaviour; regardless of how the network behaves, the handset should NEVER respond in that manner. Both handsets were using recent firmware.

It’s important to note that with Vodafone GPRS, you are not provided with a unique global IP address. Instead, you are NAT’d (Network Address Translated) behind a private router, much the same as being on a LAN with a home gateway. This means there may be some problems with some services.

Finally, because continuous GPRS transfer involves use of the radio subsystem, battery power is consumed during data transfer. Still, with several hours of usage per day (15M or so), as well as regular use of the phone, I could generally get away with a daily recharge.

Conclusion

Is the price Vodafone are asking for this service on the scheme of things worth it? This depends on how desperately you need Internet access and the other forms of access available (i.e. net cafés, dialup, wireless), and their associated cost.

I found the $49.95 to be somewhat, but not excessively expensive for the quality of the service – obviously there are limitations to GPRS in terms of speed and latency, and issues of network usage affecting that performance, but the drop-outs were a nuisance.

For those traveling temporarily within Australia, like myself, paying the $50 fee might be an appealing option, because then you can switch the plan back to an ordinary Red SIM once you are done (as there are no lock in contracts) and switch it back to the data bundle when you need to use it again.

Here’s a brief summary of the pros and cons mentioned:

Pros:

• Network access in most places with Vodafone GSM coverage, great when continuously traveling as you don’t need to arrange different forms of net access at each destination
• Inexpensive compared to other GPRS offerings, particularly the $50 bundle
• Easy to setup (arguable to some)
• Transfer speeds similar to dialup

Cons:

• VERY High latency
• Dropouts
• Some handsets are unstable with heavy GPRS usage
• Behind NAT
• Can drain handset battery quickly