Robust ceramic color converters withstanding strong laser irradiations have recently drawn great attention for laser‐driven white lighting. However, the local emission within the incident laser spot usually expands to the whole surface area of the ceramics, which definitely makes it hard to achieve white light with high luminance and high directionality. Herein, a new strategy is proposed to solve the problem by elaborately introducing uniform spherical pores (diameter of ≈2 µm) into the phosphor ceramics with controlled contents from 8 to 24.6 vol%. The well‐distributed pores, acting as light scattering centers, enable reduction of the luminescent spot size greatly but without any losses in conversion efficiency. By using the high‐scattering ceramic color converters with 15% porosity, the light spot diameter is decreased by 46% and the central illuminance is increased by 156%. Moreover, laser‐driven white light with an enhanced beam directionality and uniformity is also achieved. A superhigh luminous flux of 7199 lm is realized by using this promising color converter in a rotary mode. The designed high‐scattering ceramics with controllable microstructures show great potential for use in extra‐high luminance laser‐driven lighting and projection.

Abstract-This paper investigates the compress-and-forward scheme for an uplink cloud radio access network (C-RAN) model, where multi-antenna base-stations (BSs) are connected to a cloudcomputing based central processor (CP) via capacity-limited fronthaul links. The BSs compress the received signals with Wyner-Ziv coding and send the representation bits to the CP; the CP performs the decoding of all the users' messages. Under this setup, this paper makes progress toward the optimal structure of the fronthaul compression and CP decoding strategies for the compress-and-forward scheme in C-RAN. On the CP decoding strategy design, this paper shows that under a sum fronthaul capacity constraint, a generalized successive decoding strategy of the quantization and user message codewords that allows arbitrary interleaved order at the CP achieves the same rate region as the optimal joint decoding. Further, it is shown that a practical strategy of successively decoding the quantization codewords first, then the user messages, achieves the same maximum sum rate as joint decoding under individual fronthaul constraints. On the joint optimization of user transmission and BS quantization strategies, this paper shows that if the input distributions are assumed to be Gaussian, then under joint decoding, the optimal quantization scheme for maximizing the achievable rate region is Gaussian. Moreover, Gaussian input and Gaussian quantization with joint decoding achieve to within a constant gap of the capacity region of the Gaussian multipleinput multiple-output (MIMO) uplink C-RAN model. Finally, this paper addresses the computational aspect of optimizing uplink MIMO C-RAN by showing that under fixed Gaussian input, the sum rate maximization problem over the Gaussian quantization noise covariance matrices can be formulated as convex optimization problems, thereby facilitating its efficient solution. Index Terms-Cloud radio access network, multiple-access relay channel, compress-and-forward, fronthaul compression, joint decoding, generalized successive decoding. (C-RAN) is an emerging mobile network architecture in which base-stations (BSs) in multiple cells are connected to a cloud-computing based central processor (CP) through wired/wireless fronthaul links. In the deployment of a C-RAN system, the BSs degenerate into remote antennas heads implementing only radio functionalities, such as frequency up/down conversion, sampling, filtering, and power amplification. The baseband operations at the BSs are migrated to the CP. The C-RAN model effectively virtualizes radio-access operations such as the encoding and decoding of user information and the optimization of radio resources [1]. Advanced joint multicell processing techniques, such as the coordinated multi-point (CoMP) and network multiple-input multiple-output (MIMO), can be efficiently supported by the C-RAN architecture, potentially enabling significantly higher data rates than conventional cellular networks [2]. This paper considers the uplink of a MIMO C-RAN system under finite...

Clarification of thermal saturation helps to guide the design of high-brightness yellow and green components for laser lighting and displays.

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