Wireless Communications & Voice over IP
Research comprising different aspects of packet based speech transmission aiming for a joint optimization of system parameters and adaptation to the given transmission channel.
- Speech Coding and Transmission Protocols: aspects of signal compression, error robustness, as well as protocols for IP based transmission
- Transmission Channel: modelling of the transmission channel, particularly WLAN and UMTS radio channels; utilization in system optimization and adaptation of parameters
- Packet Loss Concealment: methods for error protection and replacement of missing packets at the receiver; objective: robust speech transmission with best possible quality
- Simulation System: PC based system for testing developed algorithms with simulations and real-time transmissions of VoIP calls over different transmission channels
- An algorithm for the optimized, joint, Iterative Source-Channel Decoding which considers the residual source redundancy is presented. A transmission of speech and audio signals very close to the theoretical limit becomes possible if this algorithm is employed.
- Turbo DeCodulation is a combination of Bit-Interleaved Coded Modulation with Iterative Decoding and of Iterative Source-Channel Decoding, i.e., an iterative concatenation of demodulation, channel decoding and source decoding.
- MUPA: Modulation with unequal power allocation for unequal error protection without channel coding.
The research topic Quality, Capacity and Radio Resource Management is concerned with methods for the allocation of limited resources for speech and data transmission in mobile radio systems. These methods are analyzed both analytically and by simulation.