radiowaves

Multiple access techniques

FDM: – frequency division multiplexing – it is an analog multiplexing technique that combines low bandwidth analog channels into one large bandwidth analog channel TDM: – time division multiplexing – digital multiplexing technique for combining several low-rate digital channels into one high-rate digital channel Duplexing means sending and receiving simultaneously. FDD: – two bands of […] Read more»

radiowaves

Error Control codes for GSM

Uses: – Block codes to generate parity bits for error detection – Convolutional code for error correction – Interleaving for burst error correction —->   Block code    ———->    Convolutional code    ———–> Interleaving Read more»

radiowaves

CDMA technology

CDMA stands for Code Division Multiple Access. It uses code to convert between analog voice signals and digital signals. It also uses codes to separate voice and control data into data streams called channels. Steps of CDMA signal generation: 1. analog to digital conversion  – uses pulse code modulation 2. vocoding – voice compression uses […] Read more»