Bidirectional decision feedback equalization for CDMA system with low spreading factor

In this paper, we propose a new approach to bidirectional decision feedback equalization (Bi-DFE) for CDMA systems with low spreading factor. Bidirectional DFE consists of a traditional DFE in parallel with another DFE operating on the time reversed sequence of the received signals. In order to further improve the performance of the proposed Bi-DFE, some modified techniques are applied as follows, a soft decision feedback equalization structure to eliminate the error propagation, optimized time delay parameter and unbiased estimator to be applied, symbol-level Bi-DFE and adaptive realization to lower the complexity. The results of simulation and analysis show that the performance of the proposed Bi-DFE is better than that of DFE, linear MMSE equalization and standard rake receiver.