Xiyuan Peng

The Performance of Physical-Layer Network Coding in Asymmetric Rayleigh Fading Two-Way Relay Channels

Up to now, most of the researches about physical-layer network coding (PNC) are based on symmetric two-way relay channels. In this paper, we mainly study PNC in asymmetric two-way relay Rayleigh fading channels and classify the systems into five asymmetric cases. So as to describe the asymmetric cases, we introduce the asymmetric factors. We simulate the bit error rate (BER) performance of PNC in both symmetric and asymmetric cases with asymmetric factors fixed. After that we analyze the BER performance of PNC with one of the asymmetric factors is variable when two channels are relatively unreliable. Finally, we give the conditions that one kind of asymmetric scenario transforming to other kind. Also, in the matter of anti-noise performance, uplink asymmetry has worst performance and the phase asymmetry-downlink is the best case.

Physical-Layer Network Coding Scheme over Asymmetric Rayleigh Fading Two-Way Relay Channels

To improve the bit error rate (BER) performance of physical-layer network coding (PNC) in asymmetric two-way relay channels (TWRC), in this paper, we study a new PNC scheme named bi-quadrature physical-layer network coding (BQ-PNC) for Rayleigh flat fading TWRC. In BQ-PNC scheme, the two users employ quadrature carriers and the relay node use quadrature combining rather than XOR which is very common in other PNC schemes. We give the BER analysis of BQ-PNC and simulate the performance. Theoretical and simulation results show that the proposed scheme can significantly enhanced the BER performance, either in symmetric or asymmetric cases. Especially for uplink asymmetric TWRC, BQ-PNC can provide more than 4 dB gain compared with PNC scheme.

Modeling and Performance Analysis of Multi-layer Satellite Networks Based on STK

With the difference of satellite altitude, there are always some inherent defects in the traditional single-layer satellite networks. In this paper, in order to improve the performance of the single-layer networks, a multi-layer satellite network model composed of LEO/MEO/GEO and inter satellite link is proposed. In this model, the LEO and MEO layers are used as the access layer, and the data transmission is carried out to the ground. As the core layer, the GEO layer is responsible for the management of the whole network and the link assignment. Then modeling the network based on the STK satellite simulation platform and carrying out the simulation analysis of ground coverage, the performance of the inter satellite link and the link transmission. Theoretical analysis and simulation results show that the design of multi-layer satellite network is reasonable and effective, and also can be used in the construction of the integrated satellite-terrestrial networks.

Performance Analysis of Asymmetric Two-Way Relay Channels with Physical-Layer Network Coding

Up to now, most of the researches about physical-layer network coding (PNC) are based on symmetric two-way relay channels. In this paper, we mainly study PNC in asymmetric two-way relay channels with Rayleigh fading channels and classify the systems into five asymmetric cases. So as to describe the asymmetric cases, we will introduce the asymmetric factors. We simulate the BER performance of PNC for symmetric and asymmetric cases with asymmetric factors fixed. After that we analyze the BER performance of PNC with one of the asymmetric factors is variable when two channels are relatively unreliable. Finally, we give the conditions that one kind of asymmetric scenario transforming to other kind. Also, in the matter of anti-noise performance, uplink asymmetry is the worst case and the phase asymmetry-downlink is the best case.

A new joint channel equalization and estimation algorithm for underwater acoustic channels

Underwater acoustic channel (UAC) is one of the most challengeable communication channels in the world, owing to its complex multi-path and absorption as well as variable ambient noise. Although adaptive equalization could effectively eliminate the inter-symbol interference (ISI) with the help of training sequences, the convergence rate of equalization in sparse UAC decreased remarkably. Besides, channel estimation algorithms could roughly figure out channel impulse response and other channel parameters through several specific mathematical criterion. In this paper, a typical channel estimation method, Least-Square (LS) algorithm is applied in adaptive equalization to obtain the initial tap weights of least-mean-square (LMS) algorithm. Simulation results show that the proposed method significantly enhances the convergence rate of the LMS algorithm.

Physical-Layer Network Coding in Shallow Sea Underwater Acoustic Channels

To improve the limited-bandwidth in shallow underwater acoustic communication, we propose to apply the physical-layer network coding (PNC) to this communication system. This paper analyzes the model of shallow underwater acoustic channel – “Ray Model” and uses the adaptive equalization technique to eliminate the inter-symbol interference (ISI). Besides, we also study the principle of PNC and research the demodulation and mapping scheme in relay node. Finally, we combine the channel model and PNC technique in two-way relay communication (TWRC) system. The performance simulation of PNC is compared with the traditional multi-hop scheme and network coding (NC) scheme. The result shows that PNC scheme can improve the throughput of system but do not increase the bit error rate (BER) in the shallow underwater acoustic communication. It provides a new research direction for shallow underwater acoustic communication, and also expands a new field for PNC applications.

Combined Denoise-and-Forward and Superposition Coded Physical-Layer Network Coding in Data Length Asymmetric Two-Way Relay Channels

To improve the bit error rate (BER) performance of physical-layer network coding (PNC) in data length asymmetric two-way relay communication systems, a new PNC scheme named combined denoise-and-forward and superposition-based physical-layer network coding (DNF-SC-PNC) is proposed, and the decoding algorithm of the scheme is improved. In the scheme, the mixed information is denoised and superposed in the relay node, which will be broadcasted to destination node. The destination node will use SIC or LLR algorithm decoding. Theoretical analysis and simulation results show that DNF-SC-PNC can provide better BER performance and better throughput rate performance when the data length is asymmetric. Furthermore, we also proved the LLR algorithm can provide better BER performance and better throughput rate performance than SIC algorithm when the data length is asymmetric.

An Energy-Efficient Routing Algorithm in Three-Dimensional Underwater Sensor Networks Based on Compressed Sensing

Compressed sensing (CS) has become a powerful tool to process data that is correlated in underwater sensor networks (USNs). Based on CS, certain signals can be recovered from a relatively small number of random linear projections. Since the battery-driven sensor nodes work in adverse environments, energy-efficient routing well-matched with CS is needed to realize data gathering in USNs. In this paper, a clustering, uneven-layered, and multi-hop routing based on CS (CS-CULM) is proposed. The inter-cluster transmission and fusion are fulfilled by an improved LEACH protocol, then the uneven-layered, multi-hop routing is adopted to forward the packets fused to sink node for data reconstruction. Simulation results show that CS-CULM can achieve better performances in energy saving and data reconstruction.

A Research on Underwater Acoustic Channel Modeling and Simulation of Shallow Sea

In order to research the shallow underwater communication system further and conveniently, the paper study the characteristics of underwater acoustic propagation and choose “Ray Model” as the simulation. Then we describe this model from the point of geometry and analyze some parameters of shallow underwater acoustic communication. According to these factors, the received signal delay and loss can be calculated and the received signal can also be expressed. This paper uses the technique of adaptive equalization to solve the serious Inter symbol interference (ISI) from the multi-path signals by giving principles and formulas of the least mean square (LMS) error algorithm. Finally, the shallow underwater acoustic channel model can be simulated by MATLAB in 2ASK modulation. In the results of simulation, the severe ISI can be observed in the received signal and can be eliminated by equalization. We also get the bit error rate curve successfully. This simulation can provide the foundation for other underwater acoustic communication researches and works.

The CEEFQPSK Scheme for Two-Way Relay Communication Systems with Physical-Layer Network Coding

A physical-layer network coding (PNC) scheme based on CEEFQPSK (constant envelope enhanced FQPSK) is established for satellite communications. The scheme is implemented for uplink and downlink. In the uplink, the two signals to be sent are modulated into electromagnetic wave signal by CEEFQPSK in two channels (I, Q) and broadcasted to the relay node. At the same time, the electromagnetic wave signal is superimposed on the relay node and mapped into a binary bit, and then it will be modulated and broadcasted to the two terminals. In the downlink, soft information is received according to the maximum posterior probability criterion, and the required information is de-mapped with its own information. The bit-error rate (BER) and throughput of the entire system are analyzed by simulation. Theoretical analysis and simulation results show that the BER of the physical-layer network coding scheme using this method is close to that of the traditional scheme and network coding scheme, but the throughput is higher than the other two.