Smart antenna schemes in the WCDMA UTRA uplink with unknown channel model order

The impact of an unknown channel model order on the performance of smart antenna schemes for uplink transmission in the Universal Mobile Telecommunications System (UMTS) terrestrial radio access (UTRA) with wideband code-division multiple access (WCDMA) is investigated. Based on a common channel model, two different joint demodulation schemes with iterative interference cancellation are derived in the framework of the space-alternating generalized expectation-maximization (SAGE) algorithm, where the channel model order associated with a particular user is chosen as a small integer value. In the first scheme, the channel parameters to be estimated comprise the direction of arrival, the delay and the complex attenuation coefficient of the waves impinging at the receiver. In the second one, the channel impulse responses at the different sensors are modelled separately and only delays and the complex attenuation coefficients are estimated. Monte-Carlo simulations show that for environments with a large angular spread and a correspondingly large number of waves impinging at the receiver, the latter scheme being less complex is more robust in terms of the achievable bit-error rate (BER), while the BER floor of the conventional receiver is reduced considerably.