arXiv subjects

Bin Xia

Publications and source records attributed to Bin Xia.

82 records · Page 5Linked to original sources

arXiv2016

Modeling and Analysis for Cache-enabled Cognitive D2D Communications in Cellular Networks

Exploiting cognition to the cache-enabled device-to-device (D2D) communication underlaying the multi-channel cellular network is the main focus of this paper. D2D pairs perform direct communications via sensing the available cellular channels, bypassing the base station (BS). Dynamic service is considered and the network performance is evaluated with the stochastic geometry. Node locations are first modeled as mutually independent Poisson Point Processes, and the service queueing process is formulated. Then the corresponding tier association and cognitive access protocol are developed. The delay and the length for the queue at the BS and D2D transmitter are further elaborated, with modeling the traffic dynamics of request arrivals and departures as the discrete-time multiserver queue with priorities. Moreover, impacts of the physical layer and content-centric features on the system performance are jointly investigated to provide a valuable insight.

cs.IT↗

arXiv2015

Optimal Caching Placement for D2D Assisted Wireless Caching Networks

In this paper, we devise the optimal caching placement to maximize the offloading probability for a two-tier wireless caching system, where the helpers and a part of users have caching ability. The offloading comes from the local caching, D2D sharing and the helper transmission. In particular, to maximize the offloading probability we reformulate the caching placement problem for users and helpers into a difference of convex (DC) problem which can be effectively solved by DC programming. Moreover, we analyze the two extreme cases where there is only help-tier caching network and only user-tier. Specifically, the placement problem for the helper-tier caching network is reduced to a convex problem, and can be effectively solved by the classical water-filling method. We notice that users and helpers prefer to cache popular contents under low node density and prefer to cache different contents evenly under high node density. Simulation results indicate a great performance gain of the proposed caching placement over existing approaches.

cs.IT↗

arXiv2015

When ICN Meets C-RAN for HetNets: An SDN Approach

In this paper, we contribute to novelly proposing and elaborating the integration of the ICN, C-RAN and SDN for the HetNet to achieve win-win situation. The vision of the proposed system is demonstrated, followed by the advantages and challenges. We further present the hybrid system with a large-scale wireless heterogeneous campus network.

cs.NI↗

arXiv2015

Analysis on Cache-enabled Wireless Heterogeneous Networks

Caching the popular multimedia content is a promising way to unleash the ultimate potential of wireless networks. In this paper, we contribute to proposing and analyzing the cache-based content delivery in a three-tier heterogeneous network (HetNet), where base stations (BSs), relays and device-to-device (D2D) pairs are included. We advocate to proactively cache the popular contents in the relays and parts of the users with caching ability when the network is off-peak. The cached contents can be reused for frequent access to offload the cellular network traffic. The node locations are first modeled as mutually independent Poisson Point Processes (PPPs) and the corresponding content access protocol is developed. The average ergodic rate and outage probability in the downlink are then analyzed theoretically. We further derive the throughput and the delay based on the \emph{multiclass processor-sharing queue} model and the continuous-time Markov process. According to the critical condition of the steady state in the HetNet, the maximum traffic load and the global throughput gain are investigated. Moreover, impacts of some key network characteristics, e.g., the heterogeneity of multimedia contents, node densities and the limited caching capacities, on the system performance are elaborated to provide a valuable insight.

cs.IT↗

arXiv2015

Simplified Multiuser Detection for SCMA with Sum-Product Algorithm

Sparse code multiple access (SCMA) is a novel non-orthogonal multiple access technique, which fully exploits the shaping gain of multi-dimensional codewords. However, the lack of simplified multiuser detection algorithm prevents further implementation due to the inherently high computation complexity. In this paper, general SCMA detector algorithms based on Sum-product algorithm are elaborated. Then two improved algorithms are proposed, which simplify the detection structure and curtail exponent operations quantitatively in logarithm domain. Furthermore, to analyze these detection algorithms fairly, we derive theoretical expression of the average mutual information (AMI) of SCMA (SCMA-AMI), and employ a statistical method to calculate SCMA-AMI based specific detection algorithm. Simulation results show that the performance is almost as well as the based message passing algorithm in terms of both BER and AMI while the complexity is significantly decreased, compared to the traditional Max-Log approximation method.

cs.IT↗

arXiv2015

Iterative detection and decoding for SCMA systems with LDPC codes

Sparse code multiple access (SCMA) is a promising multiplexing approach to achieve high system capacity. In this paper, we develop a novel iterative detection and decoding scheme for SCMA systems combined with Low-density Parity-check (LDPC) decoding. In particular, we decompose the output of the message passing algorithm (MPA) based SCMA multiuser detection into intrinsic part and prior part. Then we design a joint detection and decoding scheme which iteratively exchanges the intrinsic information between the detector and the decoder, yielding a satisfied performance gain. Moreover, the proposed scheme has almost the same complexity compared to the traditional receiver for LDPC-coded SCMA systems. As numerical results demonstrate, the proposed scheme has a substantial gain over the traditional SCMA receiver on AWGN channels and Rayleigh fading channels.

cs.IT↗

arXiv2013

Wireless Information and Power Transfer in Two-Way Amplify-and-Forward Relaying Channels

The various wireless networks have made the ambient radio frequency signals around the world. Wireless information and power transfer enables the devices to recycle energy from these ambient radio frequency signals and process information simultaneously. In this paper, we develop a wireless information and power transfer protocol in two-way amplify-and-forward relaying channels, where two sources exchange information via an energy harvesting relay node. The relay node collects energy from the received signals and uses it to provide the transmission power to forward the received signals. We analytically derive the exact expressions of the outage probability, the ergodic capacity and the finite-SNR diversity-multiplexing trade-off (DMT). Furthermore, the tight closed-form upper and lower bounds of the outage probability and the ergodic capacity are then developed. Moreover, the impact of the power splitting ratio is also evaluated and analyzed. Finally, we show that compared to the non-cooperative relaying scheme, the proposed protocol is a green solution to offer higher transmission rate and more reliable communication without consuming additional resource.

cs.IT↗

arXiv2013

Surface dominated transport in single crystalline nanoflake devices of topological insulator Bi1.5Sb0.5Te1.8Se1.2

We report experimental evidence of surface dominated transport in single crystalline nanoflake devices of topological insulator Bi1.5Sb0.5Te1.8Se1.2. The resistivity measurements show dramatic difference between the nanoflake devices and bulk single crystal. The resistivity and Hall analysis based on a two-channel model indicates that ~99% surface transport contribution can be realized in 200 nm thick BSTS nanoflake devices. Using standard bottom gate with SiO2 as a dielectric layer, pronounced ambipolar electric field effect was observed in devices fabricated with flakes of 100 - 200 nm thick. Moreover, angle-dependent magneto-resistances of a nanoflake device with thickness of 596 nm are fitted to a universal curve for the perpendicular component of the applied magnetic field. The value of phase coherence length obtained from 2D weak antilocalization fitting further confirmed the surface dominated transport. Our results open a path for realization of novel electric and spintronic devices based on the topological helical surface states.

cond-mat.mes-hall↗

arXiv2013

Beta-Ag2Te: A topological insulator with strong anisotropy

We present evidence of topological surface states in beta-Ag2Te through first-principles calculations and periodic quantum interference effect in single crystalline nanoribbon. Our first-principles calculations show that beta-Ag2Te is a topological insulator with a gapless Dirac cone with strong anisotropy. To experimentally probe the topological surface state, we synthesized high quality beta-Ag2Te nanoribbons and performed electron transport measurements. The coexistence of pronounced Aharonov-Bohm oscillations and weak Altshuler-Aronov-Spivak oscillations clearly demonstrates coherent electron transport around the perimeter of beta-Ag2Te nanoribbon and therefore the existence of metallic surface states, which is further supported by the temperature dependence of resistivity for beta-Ag2Te nanoribbons with different cross section areas. Highly anisotropic topological surface state of beta-Ag2Te suggests that the material is a promising material for fundamental study and future spintronic devices.

cond-mat.mes-hall↗

arXiv2012

Temperature-dependent terahertz conductivity of topological insulator Bi$_{1.5}$Sb$_{0.5}$Te$_{1.8}$Se$_{1.2}$

Using Terahertz Time-Domain Spectroscopy, we study the temperature-dependent complex optical conductivity of the topological insulator, Bi$_{1.5}$Sb$_{0.5}$Te$_{1.8}$Se$_{1.2}$ single-crystal from 5 K to 150 K in the terahertz regime (0.4 -- 3.0 THz). We analyze our experimental results using the Drude-Lorentz model, with the Drude component representing the metallic surface state and the Lorentz term representing the bulk insulating state. We find the conductivity to be dominated by the Drude contribution, suggesting the presence of metallic surface states. The low-frequency real conductivity follows a thermally-activated behavior. Its origin is also discussed.

cond-mat.mes-hall↗