Tomlinson-Harashima precoding (THP) with tilted constellation (THP-TC) is being noted for an efficient method to reduce the transmission power and enhance the performance of THP. However, THP-TC requires heavy feed-forward overhead to inform the receivers the rotation angles for each symbol. In this paper, for enhancing the performance and alleviating the heavy feed-forward of THPTC, we propose a class of Tomlinson-Harashima precoding schemes assisted with codebook (THP-CB) to help the processing of angle selection and signal rotation jointly for the transmit signals. The simulation results show that the proposed THP-CB schemes achieve significant performance improvement than the conventional counterparts. Furthermore, we show that the proposed THP-CB reduces more than 90% of the feed-forward overhead, while remaining identical transmission performance to conventional THPTC.

Spatial modulation (SM) and space shift keying (SSK) techniques have the unique advantages of their single-radio-frequency (RF) structures compared with conventional multiple-input-multiple-output (MIMO) techniques. However, the transmission rates of these techniques are decided by the maximal switching frequency or by the minimal switching time between the RF chain and transmit antennas, which has been a bottleneck for their applications in future broadband wireless communications. To alleviate this problem, we propose a class of novel offset SM (OSM) and offset SSK (OSSK) schemes, with the aid of channel state information (CSI) at the transmitter. Compared with conventional SM and SSK, the proposed OSM and OSSK schemes can reduce the switching frequency of the RF chain, by introducing an offset between the connected RF chain and the index of the spatial modulated antenna. In extreme conditions, the proposed OSM and OSSK can work without RF switching while maintaining the single-RF advantage of conventional SM and SSK schemes. Through theoretical analysis, we also develop the bit-error rate (BER) performance bounds for the proposed two schemes. Finally, our simulation results demonstrate that the proposed OSM and OSSK outperform their counterparts, including conventional SM, SSK, CSI-aided SM, and CSI-aided SSK, while having a simplified RF-switching structure.

Spatial Modulation (SM) has the unique advantage of its single-radio frequency (RF) structure compared to conventional multiple-input multiple-output (MIMO) techniques. However, the transmission rate of SM-MIMO is decided by the maximal switching frequency when it switches between the RF chain and transmit antennas, which has been a bottleneck for its applications in future broadband wireless communications. For alleviating this problem, in this paper, a class of novel offset spatial modulation (OSM) schemes are proposed with the aid of channel state information (CSI) at the transmitter. Compared to conventional SM, the proposed OSM scheme is capable of reducing the switching frequency of the RF chain, by introducing an offset between the connected RF chain and the index of the activated antenna. Furthermore, in some extreme conditions, OSM can even work without RF switching while maintaining the single-RF advantage of conventional SM-MIMO. Through theoretical analysis, we also develop a bit-error rate (BER) performance bound for the proposed OSM system. Finally, our simulation results demonstrate that OSM outperforms its counterparts including conventional SM and CSI-aided SM, while offering a simplified RF- switching structure.