Data transmission over these simple ASK RF TX/RX pairs is inherently unreliable, too much interference, characteristics of these TX/RX pairs, etc. So you need to implement an encoding scheme for error correction to achieve maximum performance. Manchester Encoding is one of the most popular for these types of TX/RX pairs.
Checkout this appnote concerning implementation:
**broken link removed**
It does a fair job of explain the necessity and implementation of Manchester Encoding.
The following is a good tutorial on actual implementation of RF TX/RX with PICs:
PIC Tutorial Twelve - RF remote control
You can uses the downloaded files from the above tutorial as a template for your project.
The above links deal with software implemenation of the encoding scheme. You can however use inexpensive encoder/decoder chipsets:
**broken link removed**
With encoding Baud rates of 19.2K can be regularly obtained as discussed in the above appnote PDF.
Without encoding your actual baud rate will be fairly limited, 1200 BAUD, as in the follow example projects:
Wireless Interface RF Modules
I want to welcome you to the Embedded Wireless Network Group, these links and many others are available in the group posting. I believe they should answer many of your questions and give you viable examples which to base your project.
If you have any other questions, feel free to ask me.
I'm constantly looking for reference material on this subject and others, if I come across anything related to your project I'll be sure and post it for you.
---------- Post added at 07:29 ---------- Previous post was at 07:14 ----------
I had forgot your project was Atmel based, so I've included the following Atmel appnote:
Manchester Coding Basics