Joint Wireless Information and Energy Transfer with Reduced Feedback in MIMO Interference Channels

To determine the transmission strategy for joint wireless information and energy transfer (JWIET) in the MIMO interference channel (IFC), the information access point (IAP) and energy access point (EAP) require the channel state information (CSI) of their associated links to both the information-decoding (ID) mobile stations (MSs) and energy-harvesting (EH) MSs (so-called local CSI). In this paper, to reduce th e feedback overhead of MSs for the JWIET in two-user MIMO IFC, we propose a Geodesic energy beamforming scheme that requires partial CSI at the EAP. Furthermore, in the two-user MIMO IFC, it is proved that the Geodesic energy beamforming is the optimal strategy. By adding a rank-one constraint on the transmit signal covariance of IAP, we can further reduce the feedback overhead to IAP by exploiting Geodesic information beamforming. Under the rank-one constraint of IAP's transmit signal, we prove that Geodesic information/energy beamforming approach is the optimal strategy for JWIET in the two-user MIMO IFC. We also discuss the extension of the proposed rank-one Geodesic information/energy beamforming strategies to general K-user MIMO IFC. Finally, by analyzing the achievable rate-energy performance statistically under imperfect partial CSIT, we propose an adaptive bit allocation strategy for both EH MS and ID MS.Comment: accepted to IEEE Journal of Selected Areas in Communications (IEEE JSAC), Special Issue on Wireless Communications Powered by Energy Harvesting and Wireless Energy Transfe

Multi-user Linear Precoding for Multi-polarized Massive MIMO System under Imperfect CSIT

The space limitation and the channel acquisition prevent Massive MIMO from being easily deployed in a practical setup. Motivated by current deployments of LTE-Advanced, the use of multi-polarized antennas can be an efficient solution to address the space constraint. Furthermore, the dual-structured precoding, in which a preprocessing based on the spatial correlation and a subsequent linear precoding based on the short-term channel state information at the transmitter (CSIT) are concatenated, can reduce the feedback overhead efficiently. By grouping and preprocessing spatially correlated mobile stations (MSs), the dimension of the precoding signal space is reduced and the corresponding short-term CSIT dimension is reduced. In this paper, to reduce the feedback overhead further, we propose a dual-structured multi-user linear precoding, in which the subgrouping method based on co-polarization is additionally applied to the spatially grouped MSs in the preprocessing stage. Furthermore, under imperfect CSIT, the proposed scheme is asymptotically analyzed based on random matrix theory. By investigating the behavior of the asymptotic performance, we also propose a new dual-structured precoding in which the precoding mode is switched between two dual-structured precoding strategies with 1) the preprocessing based only on the spatial correlation and 2) the preprocessing based on both the spatial correlation and polarization. Finally, we extend it to 3D dual-structured precoding.Comment: accepted to IEEE Transactions on Wireless Communication

Joint Wireless Information and Energy Transfer in a K-User MIMO Interference Channel

Recently, joint wireless information and energy transfer (JWIET) methods have been proposed to relieve the battery limitation of wireless devices. However, the JWIET in a general K-user MIMO interference channel (IFC) has been unexplored so far. In this paper, we investigate for the first time the JWIET in K-user MIMO IFC, in which receivers either decode the incoming information data (information decoding, ID) or harvest the RF energy (energy harvesting, EH). In the K-user IFC, we consider three different scenarios according to the receiver mode -- i) multiple EH receivers and a single ID receiver, ii) multiple IDs and a single EH, and iii) multiple IDs and multiple EHs. For all scenarios, we have found a common necessary condition of the optimal transmission strategy and, accordingly, developed the transmission strategy that satisfies the common necessary condition, in which all the transmitters transferring energy exploit a rank-one energy beamforming. Furthermore, we have also proposed an iterative algorithm to optimize the covariance matrices of the transmitters that transfer information and the powers of the energy beamforming transmitters simultaneously, and identified the corresponding achievable rate-energy tradeoff region. Finally, we have shown that by selecting EH receivers according to their signal-to-leakage-and-harvested energy-ratio (SLER), we can improve the achievable rate-energy region further.Comment: arXiv admin note: text overlap with arXiv:1303.169

Designer-User Interaction as the Core of the Design & IT Innovation Process: A Socio-Cultural Perspective

In this paper, a model of designer-user interaction as a socio-cultural phenomenon is proposed with the following question: how do the changes in the designer\u27s perspective on the user\u27s physical and social experiences lead to design refinement or design innovation sequences? Adopting Bourdieu’s theory of practice as a macro view, we interpret field as rules of action, habitus as modes of action, and practice as situated actions in the design process. Particularly, this research argues that the changes in the designer’s habitus, as a result of newly acquired knowledge from user research, entail innovation of practice and expansion of field. In addition, the concept of boundary object is considered how the designer’s research activities assist them in acquiring knowledge from various sources, and to translate / transform it across domain boundaries during the process. Four case studies are presented as empirical evidence

GENERATING DESIGNERS’ KNOWLEDGE ARTIFACTS AS ACTUAL PROTOCOLS IN THE DESIGN PROCESS

In this paper, we explore that designers can generate more effective interactions and decisions in the design process, when they use knowledge artifacts as design protocols with the following research question-- how designers could generate different types of knowledge artifacts with or without actual users in the design process? To address this, we adopt boundary objects as a theoretical foundation to argue the knowledge artifacts that designers produce. As an empirical approach, this study presents two case studies that represent the multiple knowledge artifacts between designers and users in a user-centered design projects. Based on this, it will provide feasible guidelines for designers to create effective knowledge artifacts with and without users as a design vocabulary in their actual design project settings