(3) The optimized cyclic shift selection achieves better performance than the random cyclic shift selection as expected.
(4) The optimized cyclic shift selection achieves better performance than the random cyclic shift selection due to its higher channel estimation accuracy.
Optimized cyclic shift selection at the relay can achieve better performance than random cyclic shift selection, but the gain is decreased for MU-MIMO.
(2) The proposed scheme with optimized cyclic shift selection and the method in [13] achieve the same performance.
As a conclusion, the proposed method can achieve the same performance for control information as the method in [13] with proper cyclic shift selection.
Two kinds of cyclic shift selection are considered for the proposed method: one is random selection without optimization and the other is optimized selection that maximizes the cyclic shift distance among UEs and the relay.
The algorithm, which is based on the previous work of Saad, may be succintly described as a multiple shift-and-invert, restarted Arnoldi procedure which uses reorthogonalization and automatic shift selection to provide stability and convergence, while minimizing the overall computational effort.
(3) The proposed scheme with optimized cyclic selection and the method in [13] achieve the same performance, which means that the maximum distance cyclic shift selection is very effective and enables very accurate channel estimation of H MB(k) from the superposed reference signals.
