Wireless Modem Design

Paradiddle Communications has extensive experience in the design and implementation of modems for wireless systems, including WPAN (Bluetooth, WiMedia Multiband OFDM), WLAN (IEEE 802.a/b/g), satellite (ORBCOMM GEN2, S-AIS) and cellular (GSM,IS-136). Over the years, we have developed modem solutions for
  • Custom (algorithm-specific) digital signal processing implemented in FPGA or ASIC.
  • Programmable (off-the-shelf) digital signal processor.
  • General-purpose processor.
In working with a client, our role is typically to develop modem algorithms for a specific target architecture and then to provide support to the project team during the implementation phase. Wireless modem algorithms are almost exclusively defined in integer arithmetic ("fixed-point"), due to the relatively high sample rates involved, as well as the requirement for power efficiency. When developing algorithms for programmable architectures, we now work almost exclusively with MATLAB. In this case, the first step is usually to define a set of integer vector operations that map well onto the target architecture. These operations are then implemented in both MATLAB and the target programming language (usually C or DSP assembly) in such a way, that the two implementations match each other EXACTLY. The modem algorithms are subsequently defined and modeled in MATLAB with the use of the pre-defined integer operations. We have found that this approach greatly simplifies the translation from MATLAB code to target code.
 
For custom DSP solutions, our involvement usually goes beyond the definition of integer algorithms to include a definition of the datapath architecture as well. This will eliminate many errors during the translation from high-level model to RTL model, and makes it much easier for us to support the design verification and system testing. Also, custom DSP solutions tend to be datapath-intensive with very little control flow, which means that the algorithm is often tailored towards a specific datapath architecture. See here for more information about our approach to custom DSP development.

Note: Although we specialize in algorithm and architecture design, we are also able to take on complete development projects. We do this in partnership with other software and hardware specialists in the San Diego area. Our Partners are among the best in the business, with many years of experience.