Industry Collaborations

Over the years, I have had a number of exciting and fruitful collaborations with industry partners. Below is a listing of the general thrust of some of these projects:

• CCSDS Turbo Codes and LDPC Codes: CCSDS turbo codes and LDPC codes have excellent performance at low SNRs. There is recent interest in pairing these codes with the CPM-type modulations that are used in aeronautical telemetry (SOQPSK-TG in particular). Here are some reference BER curves for LDPC, SCCC, and CCSDS Turbo Codes paired with SOQPSK-TG. These FEC codes can also be used with amplitude phase shift keying (APSK), which is also under consideration for use in aeronautical telemetry.
• Demodulators for Space-Time Coding (STC) for Aeronautical Telemetry: Space-time codes (STC) have been adopted recently in the IRIG-106 telemetry standard. These codes have been shown to be an effective solution to the “two antenna problem” that arises in some testing scenarios. These codes are currently paired with SOQPSK modulation. One of the primary challenges in demodulating the STC signal is the fact that the signals from the two transmit antennas can arrive at the receiver with a delay relative to each other (i.e. a “differential delay”). This delay results in a significant increase in the complexity of the demodulation algorithms.
• Robust Soft-Decision Demodulators for CPM: Continuous phase modulation (CPM) is a bandwidth efficient modulation that can be generated at high transmission power (because it has a constant envelope). It is a natural choice for satellite and deep space communication, and any other application that requires a long-range link with size, weight, and power (SWaP) constraints. Common examples of CPM are GMSK, GFSK, SOQPSK, and PCM/FM. However, when paired with modern forward error correction (FEC) schemes, the received signal-to-noise ratios (SNRs) can be extremely small. Therefore, it is all the more challenging to build a demodulator for such applications that is robust in its synchronization and robust in its soft-output demodulation.
• Synchronization for Burst-Mode and/or Continuous Communications: In order for a communication link to be functional, synchronization between the transmitter and receiver is absolutely required. By synchronization we mean carrier frequency synchronization, carrier phase synchronization, and symbol timing synchronization. The challenge of synchronization is somewhat different depending on whether the link is continuous (i.e., on for a long duration) or bursty (i.e. on and off in brief packet bursts). This basic architectural difference results in some synchronization schemes that are feedback/PLL based and some that are feedforward/preamble based. I have had numerous industry collaborations on these topics for several different modulations (CPM, GMSK, SOQPSK, BPSK, QPSK, , OQPSK, QAM) and applications with and without FEC. [See my recent tech report on robust synchronization for CPM.]
• Reduced-Complexity Receiver Design: Implementation complexity is an important dimension in the design of communication systems. I have had numerous industry collaborations that have addressed reduced-complexity detection/demodulation/decoding methods (such as simplified trellis/Viterbi algorithm implementations), and reduced-complexity synchronization methods (including noncoherent and differential detection schemes).
• Modulation Design and Forward Error Correction (FEC) Design: Every communication scenario presents specific design requirements, which in turn motivate the use of specific modulation formats (QAM, CPM, etc) and specific FEC formats (LDPC, turbo codes, other modern iterative coding techniques). I have been involved in a number of different projects where we have designed modulation/demodulation and coding/decoding schemes for various applications.