Asymptotic Analysis on Spatial Coupling Coding for Two-Way Relay Channels

Compute-and-forward relaying is effective to increase bandwidth efficiency of wireless two-way relay channels. In a compute-and-forward scheme, a relay tries to decode a linear combination composed of transmitted messages from other terminals or relays. Design for error correcting codes and its decoding algorithms suitable for compute-and-forward relaying schemes are still important issue to be studied. In this paper, we will present an asymptotic performance analysis on LDPC codes over two-way relay channels based on density evolution (DE). Because of the asymmetric nature of the channel, we employ the population dynamics DE combined with DE formulas for asymmetric channels to obtain BP thresholds. In addition, we also evaluate the asymptotic performance of spatially coupled LDPC codes for two-way relay channels. The results indicate that the spatial coupling codes yield improvements in the BP threshold compared with corresponding uncoupled codes for two-way relay channels.Comment: 5 page

Sampled-data Control System Design Using Reverse Element

In this paper, the authors deal with one method for the control of sampled-data control systems. In contrast with ordinary sampled-data control systems, the polarity of the control signal is reversed at several instants in every sampling period. By deciding the instants properly, the finite settling time response can be obtained. Especially, for a step input, it is shown that the system error can be reduced to zero in one sampling period, irrespective of the order of the controlled element. Furthermore, the compensator is simpler than that for ordinary sampled-data control systems, because it consists only of a sampler, a hold element, and a reverse element which reverses the polarity of the control signal. Even for a controlled element with a symmetric saturation characteristic, the settling time has a finite value. Moreover, it is shown that the reverse element can be used along with an ordinary compensator containing delay elements, and that the settling time can be made shorter. The response for a random input is also analyzed for a typical sampled-data control system with a reverse element