Practical design and its evaluations for nested transmit diversity

Abstract

This paper provides the practical design of the transmit diversity technique with a nested coding technique and evaluates its performance via computer simulations. Similar to network coding techniques, the nested transmit diversity combines the transmit data with XOR operation. As a characteristic of the proposed transmit diversity, it can obtain diversity gain without some extra resources (e.g., transmit/receive antenna). In the proposed system, the transmitter simultaneously transmits two or more data sequences with a superposition technique, namely, nested coding technique. Suppose the case of two data superposing, the transmitting signal is composed of two data sequences, one is the data sequence to be currently transmitted, the other is the previously transmitted data sequence. In this case, the receiver has two types of decoding method corresponding to the previous decoding result. When successfully decoded at previous time slot, since the receiver knows the data-sequence transmitted at previous time slot which is referred to as superposition factor, it can completely remove the superposition factor with XOR manner. Different from a network coding, even if the receiver does not know the superposition factor (failed to decode the data), it can attempt to decode both data sequences. In this paper, we focus on the pragmatic design of nested transmit diversity. In order to achieve further improvement, we propose a reverse order decoding scheme. We reveal that the proposed nested transmit diversity can achieve diversity gain without extra resources.