Uplink CP-CDMA System: Joint CFO and CIR Estimation without Pilots

Cyclic-prefix code division multiple access (CP-CDMA) has been shown to be effective in combating frequency selective fading channels. However, this effectiveness can be leveraged only with accurate channel impulse response (CIR) estimate and proper compensation for the carrier frequency offset (CFO). In this paper, we formulate a subspace-based joint CFO and CIR estimator without using any pilot symbols. The users´ spreading codes are selected following the steps in. We show that the selected users´ spreading codes must also satisfy an additional requirement in order to have the signal subspace dimension to be independent of users´ CFO and CIR. For high signal to noise ratio, we show that the proposed CFO estimator is unbiased and derive the theoretical mean square error for CFO estimate. Computer simulation results show that the proposed estimator´s performance is close to Cramer-Rao lower bound.