Mingchuan Yang

A Novel SLM Method for PAPR Reduction of OFDM System

Given that the conventional Selected Mapping (SLM) scheme needs to multiply pseudo-random phase sequences to the transmitted data meanwhile transmitting the whole side information, an exhaustive entropy and chaotic phase sequence based SLM method was proposed for reduction the peak-to-average power ratio (PAPR) of Orthogonal frequency division multiplexing (OFDM) in the paper. In the novel algorithm, exhaustive entropy was used to evaluate the randomness of phase sequence, chaotic sequences to reduce the large side information and improved Lorenz sequence digitalization method to enlarge sequence entropy, expanding the number of the candidate phase sequences vector space with the lower transmitted parameters of phase sequence. Simulation results show that different quantization methods of chaotic sequence have different exhaustive entropy and PAPR values. Furthermore, compared with the traditional SLM method, the new scheme proposed in the paper has better performance in reducing PAPR of OFDM system by about 0.1-0.5dB.

A Novel Multi-Beam Lens Antenna for High Altitude Platform Communications

Waveguide-form multi-beam lens antenna has several shortcomings, such like large size and weight of feed source. According to such situation, a lens antenna applied to high altitude platform is designed. The proposed antenna uses printed Yagi-Uda antenna as feed unit and applies CST MICROWAVE STUDIO® electromagnetic simulation software to analyze. The proposed antenna is manufactured and tested in microwave anechoic chamber. And the simulated and experimental results show that frequency range of the proposed antenna is from 1.77GHz to 2.44GHz with reflection coefficient less than -10dB, relative bandwidth is 31.8%. Antenna gain at 2.1GHz is 9.3dB, which basically accords with the simulated result. Finally, a multi-beam lens antenna fed independently with 6 printed Yagi-Uda antenna units is designed. The proposed antenna has characteristics of wide band, high gain, small volume and light weight. Thus it can be applied in the future high altitude platform communication system.

An exhaustive entropy based SLM method for PAPR reduction of OFDM systems

Orthogonal frequency division multiplexing (OFDM) is an attractive technology to provide immense improvements in wireless transmission capacity but high peak-to-average power ratio (PAPR) is a major drawback of OFDM system. Selected mapping (SLM) scheme has good performance for PAPR reduction. It requires the transmitting data to be multiplied by random phase sequences. However, the sequences are pseudo-random which will decrease the method effectiveness. Exhaustive entropy is introduced in this paper which can identify the strength of random phase sequences property. Then an exhaustive entropy based SLM method is proposed. The scheme improves the effectiveness of random phase sequences by selecting the larger exhaustive entropy of them. Simulation results show that the PAPR reduction performance is better than that of conventional SLM through this method.

Three-state semi-Markov channel model for HAP-high speed train communication link

Given that single-state model can only describe single channel environment, while multiple-state model brings more parameters and more complicated simulation work, a three-state semi-Markov channel model including LOS (light of sight) state, shadowed state and blocked state was proposed to solve this problem. A simulation model was established corresponding to the theoretical model, based on the analysis of simulation data, it matched well with the theoretical model. It is thus concluded that the proposed model is effective in analyzing the propagation characteristics, optimizing the modulation and coding schemes and simulating the performance of HAP (high altitude platform) communication systems. Some research aimed at providing broadband services for the passengers on board of a train via a HAP system has been resolved, such as CAPANINA project in Europe. However, there is no correlative research about HAP based the environment of high-speed train in China. Therefore, date elevation model (DEM) of the railway from Beijing to Tianjin was put into the simulation model, and correlative parameter aimed at the channel environment of China was obtained.

A Call Admission Control Algorithm Based on Utility Fairness for Low Earth Orbit Satellite Networks

A fair and adaptive call admission control algorithm for multimedia low Earth orbit (LEO) satellite networks was proposed. Based on current call dropping probability of destination cell, this algorithm reserves bandwidth for handoff calls using double threshold method. To avoid the discrimination of quality of service (QoS) caused by the allocation based on fair bandwidth, this algorithm adopts the bandwidth allocation rule based on fair QoS. Simulation results show that the proposed algorithm can accurately and adaptively reserve bandwidth, present satisfactory call blocking probability and greatly reduce handoff call dropping probability, while guarantees the high bandwidth utilization.

Optimized Power Allocation Scheme for Land Mobile Satellite Cooperative Diversity Communications

In this paper, an optimized transmitting power allocation scheme between the source and its cooperator is presented, minimizing the derived closed-form approximated outage probability expressions for the separately adopted maximum ratio combining (MRC) algorithm and selective diversity combining (SDC) algorithm at the satellite. The circumstance considered is the uplink of a dual-hop land mobile satellite cooperative diversity communication system with decode-and-forward (DF) protocol. Simulation results illustrate that the optimized power allocation scheme excellently outperforms the conventional uniform power allocation scheme on outage probability. The preferable choice of the combing algorithm between MRC and SDC in terms of the minimal outage probabilities changes with the variation of the maximum power allowed to consuming for transmitting a packet.

Performance evaluation and analysis of bundle protocol in cislunar communications

The bundle protocol (BP) is developed to solve the new problems in deep space exploration. To date, little work has been done in evaluating the performance of BP applied to an interplanetary Internet involving frequent link disruptions. This paper builds a PC-based Deep Space Communication Test-bed. It consists of three parts, the space link simulator, the high-speed Ethernet switch and the Linux-based personal computers. Compared with the simulation in OPNET, NS2 and other simulation software, the experimental results from the Test-bed will be closer to the real environment. The paper presents an experimental evaluation of BP over a typical three-node interplanetary structure involving frequent link disruptions. The performances were analyzed to compare the throughput of BP with custody transfer and BP without custody transfer under the various scenarios. The results show that BP without custody performs better than BP with custody in a cislunar environment.

Use of a hybrid of DTN convergence layer adapters (CLAs) in interplanetary Internet

Some work has been done with the DTN convergence layer adapters (CLAs) such as TCP-based CLA (i.e., TCPCL), Licklider transmission protocol CLA (i.e., LTPCL) and user datagram protocol (UDP)-based CLA (i.e., UDPCL) in space communication, running as an individual protocol. Because each DTN CLA is designed for a different type of communication link, using any single CLA under BP is generally inefficient over a heterogeneous end-to-end interplanetary infrastructure. In this paper, we propose to use a hybrid of DTN CLAs for efficient file transmission in interplanetary environment, i.e. using one CLA for one hop of the end-to-end path and a different CLA for another hop of the path. Based on experimental investigation of DTN protocols over a typical relay-type of interplanetary infrastructure, we found that a hybrid of TCPCL and LTPCL has significant goodput advantage over single-CL-protocol configurations at long link delays, especially with a high BER, and a transmission with LTPCL utilized over a long-delay hop is more tolerant of long channel delay and high channel error.

The effect of “window size” on throughput performance of DTN in lossy cislunar communications

Delay/disruption tolerant networking (DTN) offers a new solution to highly stressed communications in space environments. It is considered one of the most suitable technologies to be employed in space internetworking. To date, little work has been done in investigating how to achieve the best performance of DTN transmission over lossy, long-delay space channels. In this paper, we present an experimental investigation of how the throughput performance of Licklider transmission protocol (LTP)-based DTN is affected by the LTP flow control “window” size, established by the Number of Sessions (NOS) and Number of Bytes per Session (NBS) characterizing the LTP channel. The intent of the work is, in particular, to find a relationship between the window size and throughput performance of DTN in a typical lossy and long delay cislunar communications infrastructure. One major conclusion is that a bigger NOS generally results in higher throughput than a low NOS, and NBS does not affect the throughput significantly.

Two-step construction method of protograph-based AR4JA codes in deep space communication

This paper discusses the construction of the Accumulate-Repeat-4-Jagged-Accumulate(AR4JA) codes which is suitable for the deep-space communication based on the protograph. Two-step construction method of designing the AR4JA codes whose minimum distance grows linearly with block size, is proposed. Two-step expansion improves the traditional PEG with adding the ACE algorithm for placing edges in a protograph-based code, which brings down the error floor. Compared to the traditional random expansion and the one step expansion like Progressive Edge-Growth(PEG), the two-step construction algorithm aims at constructing the AR4JA codes with high performance and low complexity. Verified by the simulation, the BER performance of the two-step expansion method is similar to the ideal AR4JA codes in the deep space channel condition. With the same Eb/N0, the two-step construction method shows the lower BER than random construction method and one-step extension method through the simulation results.