Performance bounds for a UMTS RAKE receiver with imperfect timing synchronisation

Performance bounds for a UMTS RAKE receiver with imperfect timing synchronisation are presented. Firstly, an analytical expression for the bit error probability (P_e) performance of the RAKE receiver is derived. This analysis establishes that the bit error probability performance of the RAKE receiver is less sensitive to timing errors for higher spreading factors. However, significant performance degradations for all spreading factors confirm the need for timing synchronisation in the RAKE receiver. An extension of the analysis is presented for a multipath environment, allowing the derivation of an upper and a lower performance bound. The results indicate that a very simple interpolator providing 4 samples within a chip period results in a performance loss smaller than 0.15 dB