In digital transmission systems for speech, audio, and video signals, the bitsgenerated by the source can be subdivided into groups with different bit errorsensitivities. If bits are inverted due to disturbed transmission, different intensitiesof distortion of the reconstructed signal occur. The transmission quality can beimproved if the bit classes are unequally protected by channel coding.The objective of this thesis is the realization and optimization of an alternativeconcept of unequal error protection without channel coding: modulation withunequal power allocation (MUPA). The available power is unequally distributedto the modulation symbols according to the individual bit error sensitivity and thechannel quality. The power allocation at the transmitter is optimized in the senseof the minimum mean square error (MMSE). MUPA requires only negligibleadditional complexity. In accordance with information theory, the quality of audio-visual signals is improved, although the average bit error rate is increased.The proposed technique of modulation with unequal power allocation can becombined with soft demodulation and is especially suited for systems such asBluetooth with weak or no channel coding. In comparison to conventionalmodulation schemes, significant improvements of the transmission quality andthe error robustness are achieved by MUPA.