Unitary space-time modulation (USTM) is well-tailored for flat fading channels where neither the transmitter nor the receiver knows the fading coefficients. A systematic approach to designing USTM is proposed by Hochwald et al., which is not guaranteed full diversity and difficult to put into practice due to the large number of signal points in the two-dimensional constellation. Consequently, we modify the systematic method to search new unitary space-time coded 8PSK with full diversity. Simulation results indicate that the error performances of the searched codes are better than or at least the same as those of the USTM in [2].

Bit-interleaved coded modulation with iterative decoding (BICM-ID) is suitable for correlated Rayleigh fading channels. Additionally, BICM-ID using differential encoding can avoid the pilot overhead. In this paper, we consider BICM-ID using 16-DAPSK (differential amplitude and phase-shift keying). We first derive the probability of receiving signals conditioned on the transmission of input bits for general differential encoding; then we propose two new 16-DAPSK bit labeling methods. In addition, convolutional codes for the new bit labeling are developed. Both the minimum distance and the simulation results show that the proposed labeling has better error performance than that of the original differential encoding, and the searched new codes can further improve the error performance.

The complexity of maximum-likelihood (ML) decoding for unitary space-time modulation (USTM) is exponential in the code rate times symbol periods. In this letter, we propose a new USTM scheme which consists of USTMs with noncoherent multistage decoding. The decoding of the proposed scheme is less complex than ML decoding. We also find some good codes of the proposed scheme according to the design criterion. Simulation results indicate that our codes perform better than seamless USTMs over the quasistatic fading channels.

With the gradually increase of the application of new energy in microgrids, Electric Spring (ES), as a new type of distributed compensation power electronic device has been widely studied. The Generalized Electric Spring (G-ES) is an improved topology, and the space limitation problem in the traditional topology is solved. Because of the mode of G-ES use in the power grid, a reasonable solution to the voltage loss of the critical section feeder is needed. In this paper, the voltage balance equation based on the feedforward compensation coefficient is established, and a two cascade control strategy based on the equation is studied. The first stage of the two cascade control strategy is to use communication means to realize the allocation of feedforward compensation coefficients, and the second stage is to use the coefficients to realize feedforward fixed angle control. Simulation analysis shows that the proposed control strategy does not affect the control accuracy of the critical load (CL), and effectively improves the operational range of the G-ES.

Worms are a common phenomenon in today's Internet and cause tens of billions of dollars in damages to businesses around the world each year. This article first presents various concepts related to worms, and then classifies the existing worms into four types- Internet worms, P2P worms, email worms and IM (Instant Messaging) worms, based on the space in which a worm finds a victim target. The Internet worm is the focus of this article. We identify the characteristics of Internet worms in terms of their target finding strategy, propagation method and anti-detection capability. Then, we explore state-of-the-art worm detection and worm containment schemes. This article also briefly presents the characteristics, defense methods and related research work of P2P worms, email worms and IM worms. Nowadays, defense against worms remains largely an open problem. In the end of this article, we outline some future directions on the worm research.