Channel estimation plays a leading role in wireless communication systems such as GSM (Global System for Mobile communications). Putting the main emphasis on investigating the application of non-blind and blind channel estimation approaches to the identification of a full
I INTRODUCTIONOptimum receivers in digital communication systems require the knowledge of the transmission channel. In general, this knowledge is not available so that the channel's equivalent baseband impulse response has to be estimated. Hence, state-of-the-art mobile communication systems transmit training sequences to assist the receiver in estimating the channel impulse response. However, their repeated transmission leaves the communication system with a considerable overhead which could be used for the transmission of additional data sequences, if the channel estimation was solved blindly. In recent publications [2, 6], we have shown that some blind approaches yield promising results in estimating GSM channels although there is still a significant AE ¼ loss compared to non-blind channel estimation schemes. In order to reduce this loss, we have utilized an iterative channel estimation which employs the bits after channel decoding as a new "training" sequence. Furthermore, the separation of this sequence into different sections enables the use of GSM 1 £ This research is supported by the German NSF (DFG contr. #Ka 841/5-1) 1 By GSM, we understand GSM-900 as well as its derivatives DCS-1800or PCS-1900 for data or speech transmission at very high mobile unit speeds.Since high rate data transmission over mobile radio channels is playing a growing role, we have carried out our simulations for the TCH/F9.6 transmission mode for full rate data at ½¾ kbit/s.The paper is organized as follows: Section II gives an overview of the GSM communication system. Based on the so-called burst structure, we outline in section III the approaches of non-blind and blind channel estimation. In section IV, we describe the concept of iterative channel estimation in a GSM receiver. Finally, simulation results are presented in section V and the paper is concluded in section VI.