Decision-feedback multiuser detection with feedforward orthogonal transformation

Our proposed orthogonal decision feedback detector (ODFD) contains an orthogonal feedforward filter and allows decision feedback. While the decorrelating decision feedback detector (DDFD) is motivated by the Cholesky factorization of the correlation matrix of signature sequences, our ODFD is motivated by the QR-factorization of the same correlation matrix. In the absence of additive noise, ODFD is robust to multiple access interference. We observe from simulations that ODFD outperforms the decorrelating detector, due to the decision feedback, but is out performed by the DDFD. While the flop counts and bit error rate analysis tends to exaggerate for Cholesky factorization based methods such as the DDFD, the QR approach such as the ODFD is comparable in efficiency if memory traffic and vectorization overheads are considered