General OTA information

The most important factor when optimizing content for OTA delivery is the size of the file, or application, in kilobytes. Smaller size means faster downloads. Airtime (data transfer and connection) also incurs costs, although a certain amount of airtime might be included in the end user's contract with the carrier.

Optimizing the application footprint (size of code and memory used by the application) is also important for both performance and making applications available for lower-end handsets, because Flash Lite applications require quite a lot of memory to run.

Factors affecting file size

The most obvious elements increasing the size of an application are bitmap graphics, video, and sampled sounds. Textual information, such as code and string data (possibly localized into many languages), also add up when the amount of text is large.

Using vector graphics is a good idea because they are lightweight. Just remember that vectors tax the device's CPU (central processing unit), so using vectors carelessly might make applications unusable because devices lack the CPU power to handle many complex vectors at one time.

Recommended maximum file size for OTA

In Western countries the maximum file size of mobile Java applications (.jad/.jar) used to be around 200KB. Currently the newest Java games distributed OTA are around 300KB. Low-end phones still have a limit of 64KB. As faster networks like 3G or even faster HSDPA become more common, more data can be transferred in less time, leading to increased file sizes.

For Flash Lite applications, as the distribution side is still picking up, there are no guidelines at this point. There seems to be no technical limit to the file size. However, in reality, there's always one—and it's either related to the carrier, network, file type (.jad/.jar, .sis), or device. Although it is possible to release an application in chunks (called episodic publishing), thus increasing the maximum size of the application, technically it's always more complex that releasing just one file.

On our OTA test bed, we used Flash Lite files that were a maximum of 400KB, and they posed no problems. We used a server configured to send data OTA with a shortcode/service number. Using this phone number, users order the application using their mobile device and receive the files on their phone. We tested on different carriers and their sims, and encountered no problems.

Although when there's no maximum allowed limit for OTA transfers, always test the application on all target devices to make sure the performance is adequate. There's no substitute for this testing, no emulator that you can rely on. It is this that makes mobile development challenging, as you have to secure access to all the target devices to which you intend to sell your content.

There are three ways to get access to your targeted devices:

• Buy all of the devices—and all of the new ones as they come to market
• Join device manufacturer developer programs so you can loan all the devices
• Use third-party work-for-hire companies that can port your application

All these options can be combined, and they all cost money—but this is a fact in any business.

If you plan to distribute content to Japan, the generally accepted maximum file size is 100KB, even though the oldest Flash Lite–enabled phones allow only 20–30KB applications.

Remember this: always check beforehand with your distribution channel (carrier or operator) about the possible limitations. We cannot give any specific guidelines in this article for a specific region or device. Some of the things you should take into account include the following:

• File size
• Supported handsets
• Billing system
• Technical screening process, including style compliance requirements, device and application testing, and restrictions placed on content (no violence etc.)
• Possible certification

Failure to comply with these rules will probably lead to a situation where the application will not be considered for OTA distribution.

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