Hartmut Wilhelm

Whitened matched filter for attenuating frequency selectively faded interferers in GSM

For GSM/EDGE, the effect of a whitened matched filter (WMF) is analyzed in the frequency domain. It is illustrated how, by aliasing, the WMF improves the signal-to-interference-plus-noise ratio (SINR) compared with pure whitening. Simulation results show that, for independent frequency selective fading of wanted signal and interferers in particular, there is also an SINR improvement compared with ideal low-pass filtering. This improvement amounts to about 2 dB for a single cochannel interferer and is lower in more complex interference scenarios. The potential of the WMF, which is suitable for both GMSK and 8-PSK, is compared with that of dedicated interference suppression methods.

A GMSK compatible Modulation with improved spectral properties

For the controlled spectral shaping of modulation methods similar to Minimum Shift Keying (MSK), Gaussian filtered Minimum Shift Keying (GMSK) and Tamed Frequency Modulation (TFM), three optimization approaches with different degrees of intersymbol interference and envelope fluctuations are discussed. For a frequency division multiplex transmission with a bitwise correlating receiver, a weighting function for the transmitters power spectral density which is a good measure for the Bit Error Rate (BER) caused by Adjacent Channel Interference (ACI) is proposed. Its application to a separate or also joint optimization of the transmitter and the receiving filter reducing ACI power by roughly 20 dB is presented. For a given receiving filter, a compatible modulation that outperforms GMSK in both bandwidth and power efficiency can be designed.

Ein nachrichtentechnisches Märchen: Von der AM zur MSK

Vorwort Dieses Märchen wurde erdacht, um ausgewählte Aspekte von analoger und digitaler Frequenzmodulation unterhaltsam zu veranschaulichen. Es führt durch das Gedankenreich der Modulation und eignet sich insbesondere, um mit Studenten höherer Semester bereits behandelten Stoff aus einem anderen Blickwinkel zu betrachten. Grundkenntnisse von Amplitudenund Quadraturamplitudenmodulation, Phasenund Frequenzmodulation, dem Zeigerdiagramm im äquivalenten Basisband, ASK, FSK und PSK, Quellenund Kanalcodierung, signalangepaßtem Riter, Euklidischer Distanz sowie OFDM sind für das Verständnis recht hilfreich; ob sie unentbehrlich sind, mag der Leser entscheiden.