arXiv subjects

Xiaohui Lin

Publications and source records attributed to Xiaohui Lin.

25 records · Page 2Linked to original sources

arXiv2016

User Cooperation for Enhanced Throughput Fairness in Wireless Powered Communication Networks

This paper studies a novel user cooperation method in a wireless powered cooperative communication network (WPCN) in which a pair of distributed terminal users first harvest wireless energy broadcasted by one energy node (EN) and then use the harvested energy to transmit information to a destination node (DN). In particular, the two cooperating users exchange their independent information with each other so as to form a virtual antenna array and transmit jointly to the DN. By allowing the users to share their harvested energy to transmit each other's information, the proposed method can effectively mitigate the inherent user unfairness problem in WPCN, where one user may suffer from very low data rate due to poor energy harvesting performance and high data transmission consumptions. Depending on the availability of channel state information at the transmitters, we consider the two users cooperating using either coherent or non-coherent data transmissions. In both cases, we derive the maximum common throughput achieved by the cooperation schemes through optimizing the time allocation on wireless energy transfer, user message exchange, and joint information transmissions in a fixed-length time slot. We also perform numerical analysis to study the impact of channel conditions on the system performance. By comparing with some existing benchmark schemes, our results demonstrate the effectiveness of the proposed user cooperation in a WPCN under different application scenarios.

cs.IT↗

arXiv2016

User Cooperation for Enhanced Throughput Fairness in Wireless Powered Communication Networks

This paper studies a novel user cooperation method in a wireless powered communication network (WPCN), where a pair of distributed terminal users first harvest wireless energy broadcasted by one energy node (EN) and then use the harvested energy to transmit information cooperatively to a destination node (DN). In particular, the two cooperating users exchange their independent information with each other to form a virtual antenna array and transmit jointly to the DN. By allowing each user to allocate part of its harvested energy to transmit the other's information, the proposed cooperation can effectively mitigate the user unfairness problem in WPCNs, where a user may suffer from very low data rate due to the poor energy harvesting performance and high data transmission consumptions. We derive the maximum common throughput achieved by the cooperation scheme through optimizing the time allocation on wireless energy transfer, user message exchange, and joint information transmissions. Through comparing with some representative benchmark schemes, our results demonstrate the effectiveness of the proposed user cooperation in enhancing the throughput performance under different setups.

cs.IT↗

arXiv2014

Polymer-based Hybrid Integrated Photonic Devices for Silicon On-chip Modulation and Board-level Optical Interconnects

The accelerating increase in information traffic demands the expansion of optical access network systems that require cost reduction of optical and photonic components. Low cost, ease of fabrication, and integration capabilities of low optical-loss polymers make them attractive for photonic applications. In addition to passive wave-guiding components, electro-optic (EO) polymers consisting of a polymeric matrix doped with organic nonlinear chromophores have enabled wide-RF-bandwidth and low-power optical modulators. Beside board level passive and active optical components, compact on-chip modulators (a few 100 micronmeters to a few millimeters) have been made possible by hybrid integration of EO polymers onto the silicon platform. This paper summarizes some of the recent progress in polymer based optical modulators and interconnects. A highly linear, broadband directional coupler modulator for use in analog optical links and compact, and low-power silicon/polymer hybrid slot photonic crystal waveguide modulators for on chip applications are presented. Recently, cost-effective roll-to-roll fabrication of electronic and photonic systems on flexible substrates has been gaining interest. A low-cost imprinted/ink-jet-printed Mach-Zehnder modulator and board-to-board optical interconnects using microlens integrated 45-degree mirror couplers compatible with the roll-to-roll fabrication platforms are also presented.

physics.optics↗

arXiv2014

Improved performance of traveling wave directional coupler modulator based on electro-optic polymer

Polymer based electro-optic modulators have shown great potentials in high frequency analog optical links. Existing commercial LiNibO3 Mach-Zehnder modulators have intrinsic drawbacks in linearity to provide high fidelity communication. In this paper, we present the design, fabrication and characterization of a traveling wave directional coupler modulator based on electro-optic polymer, which is able to provide high linearity, high speed, and low optical insertion loss. A silver ground electrode is used to reduce waveguide sidewall roughness due to the scattering of UV light in photolithography process in addition to suppressing the RF loss. A 1-to-2 multi-mode interference 3dB-splitter, a photobleached refractive index taper and a quasi-vertical taper are used to reduce the optical insertion loss of the device. The symmetric waveguide structure of the MMI-fed directional coupler is intrinsically bias-free, and the modulation is obtained at the 3-dB point regardless of the ambient temperature. By achieving low RF loss, characteristic impedance matching with 50Ω load, and excellent velocity matching between the RF wave and the optical wave, a travelling wave electrode is designed to function up to 62.5GHz. Domain-inversion poling with push-pull configuration is applied using alternating pulses on a 2-section directional-coupler to achieve a spurious free dynamic range of 110dB/Hz2/3. The 3-dB electrical bandwidth of device is measured to be 10GHz.

physics.optics↗

arXiv2014

UV imprinting and aligned ink-jet printing for multi-layer patterning of electro-optic polymer modulators

The present work demonstrates an electro-optic polymer based Mach-Zehnder (MZ) modulator fabricated utilizing advanced ultraviolet (UV) imprinting and aligned ink-jet printing technologies for patterning and layer deposition. The bottom electrode layer is designed and directly ink-jet printed on the substrate to form the patterned layer. The waveguide structure is formed into a bottom cladding polymer using a transparent flexible mold based UV imprinting method. All other layers can be ink-jet printed. The top electrode is aligned and printed over the Mach-Zehnder arm. The modulator demonstrates a V-pi of 8V at 3kHz. This technology shows great potential in minimizing the fabrication complexity and roll-to-roll compatibility for manufacturing low cost, light-weight, and conformal modulators at high throughput.

physics.optics↗

arXiv2012

The crossing numbers of $K_m\times P_n$ and $K_m\times C_n$

The {\it crossing number} of a graph $G$ is the minimum number of pairwise intersections of edges in a drawing of $G$. In this paper, we study the crossing numbers of $K_{m}\times P_n$ and $K_{m}\times C_n$.

cs.DM↗

arXiv2012

The crossing numbers of $K_{n,n}-nK_2$, $K_{n}\times P_2$, $K_{n}\times P_3$ and $K_n\times C_4$

The crossing number of a graph $G$ is the minimum number of pairwise intersections of edges among all drawings of $G$. In this paper, we study the crossing number of $K_{n,n}-nK_2$, $K_n\times P_2$, $K_n\times P_3$ and $K_n\times C_4$.

cs.DM↗