Dongming Bian

Constant envelope enhanced FQPSK and its performance analysis

Its a challenging task to design a high performance modulation for satellite and space communications due to the limited power and bandwidth resource. Constant envelope modulation is an attractive scheme to be used in such cases for their needlessness of input power back-off about 2~3 dB for avoidance of nonlinear distortion induced by high power amplifier. The envelope of Feher quadrature phase shift keying (FQPSK) has a least fluctuation of 0.18 dB (quasi constant envelope) and can be further improved. This paper improves FQPSK by defining a set of new waveform functions, which changes FQPSK to be a strictly constant envelope modulation. The performance of the FQPSK adopting new wave- form is justified by analysis and simulation. The study results show that the novel FQPSK is immune to the impact of HPA and outperforms conventional FQPSK on bit error rate (BER) performance. The BER performance of this novel modulation is better than that of FQPSK by more than 0.5 dB at least and 2 dB at most.

A novel space information network architecture based on autonomous system

Space Information Network (SIN) has recently become prevalent as a promising approach to solve the collaboration difficulty among current space programs. However, due to large scale, high component complexity and dynamic characteristics of the SIN, the task of proper SIN architecture design is challenging. We propose a novel architecture of SIN, which composed of Geostationary Earth Orbit (GEO) satellites as backbone network nodes, Low Earth Orbit (LEO) or Incline Geosynchronous Orbit (IGSO) satellites as enhanced coverage nodes, and high altitude platforms to meet the service requirements of emergency or hot-spot applications. Compared with most existing studies, the proposed architecture is autonomous system (AS) based. The complex and dynamic SIN is decoupled into semi-static subnetworks constituted by similar nodes which are easier to control.

A concatenated coded modulation scheme and its iterative receiving for deep space communications

Due to the long propagation distance between spacecraft and Earth station the high power efficiency is more important for deep space communication than others communication systems. One novel coded modulation scheme based on AR4JA code and FQPSK (Fehers QPSK) is proposed out in this paper, which can alleviate the challenge of huge loss in space communications. The novel approach utilizes the property that AR4JA code enables communication at very low signal noise rate and constant envelope property of FQPSK to overcome the nonlinear impact of high power amplifier. At receiver, large gain can be attained by iterative demodulation and decoding. The paper presents the system model of coded modulation and proposes out iterative receive algorithm. Finally, the bit error rate performance of new scheme is confirmed by computer simulation.

Efficient distributed storage strategy based on compressed sensing for space information network

This article investigates the distributed data storage problem with compressed sensing in the space information network. Since there exists a performance-energy trade-off, most existing strategies focus only on improving the compressed sensing construction performance or reducing the energy consumption, respectively. In order to achieve a better balance, a novel and efficient strategy, referred to as distributed storage strategy based on compressed sensing, is proposed in this article. Unlike other strategies which require source packets visiting the entire network, the proposed strategy is a “one-hop” method since information exchange is only performed between neighbors. Therefore, the compressed sensing measurement matrix depends heavily on the degree of each space node. We prove that the proposed strategy guarantees the compressed sensing reconstruction performance under both sparse orthonormal basis and dense orthonormal basis. Simulation results validate that, compared with the representative CStorage strategy and compressive data persistence strategy, the proposed strategy consumes the least energy and computational overheads, while almost without sacrificing the compressed sensing reconstruction performance.

Subset Optimization of Adaptive Coding and Modulation Modes According to DVB-S2X

With the increasing requirement in satellite communication, Digital Video Broadcasting-Satellite extension (DVB-S2X) standard is proposed to reach higher efficiency. DVB-S2X provides 112 adaptive coding and modulation modes to get high efficiency which approaches the Shannon limit. However, with the entire modes adopted in a system, the complexity will rapidly increase. To balance the efficiency and complexity, this paper puts forward an algorithm based on rainfall probability to optimize the mode subset. The simulation shows that with fewer modes optimized by the proposed algorithm, the spectral efficiency almost reaches that of the entire modes.

Study of interference localization using single satellite based on signal strength distribution in multi-beam antenna for satellite communications system

Large onboard antennas with multi-beams are used almost in all the Geostationary Earth Orbit satellite communications systems, which are always disturbed by jams and inferences. However, there are lots of factors restricting interference localization in satellite communications system because the system is not designed for location-oriented. This article makes use of the characteristic that each spot beam of multi-beams antenna has different gain at the position of interference, establishes the localization equations set by using the ground projection model of multi-beams antenna pattern, and gives two methods of solving equations. Thus, it proposes interference localization algorithm using single satellite, based on antenna gain and the distribution of signal strength in multi-beam space. Because of not depending on extra onboard equipments and other facilities, it has no effect on the construction and operation of satellite communications system. From the results of analyses and simulations, the localization precision can satisfy the general practical requirement. The algorithm could be used in checking the interference of the system, decision supporting of anti-jamming, and improving operation and management of the system.

A novel hybrid distributed storage strategy for Space Information Network

Hierarchical autonomous system (AS) network model makes the control of the entire Space Information Network (SIN) easier. In this paper, we investigate the distributed data storage problem in the SIN, a novel hybrid distributed storage (HDS) strategy is proposed to improve the data reliability based on the AS network model. After a data object is optimal encoded using maximum distance separable (MDS) codes, the storage process is divided into two phases: the inter-AS storage phase and intra-AS storage phase, respectively. The inter-AS storage is modeled as an optimal storage allocation problem for a heterogeneous network under multiple constraints, where different AS networks have different capacities and availabilities. Then, we deduce the distributed storage within each AS network to a data persistence problem. As a result, the data object is disseminated over the SIN and it can be recovered by collecting a few encoded packets. The proposed strategy utilizes the advantage of AS network model of SIN, while aiming to improve data reliability and energy efficiency.

Data persistence in planetary surface network using raptor codes and probabilistic broadcasting

This article investigates the data persistence problem in the planetary surface network of interplanetary Internet using the distributed raptor codes. In order to improve the lifetime of space information and space nodes’ energy efficiency in planetary surface network, we propose an efficient data persistence strategy based on raptor codes and probabilistic broadcasting. Unlike most existing data persistence strategies where the random walks are used to disseminate source packets, the probabilistic broadcasting mechanism is employed in the proposed strategy to reduce the data dissemination cost by exploiting the broadcast property of wireless networks. The decoding performance and data dissemination cost are analyzed. Simulation results validate that the proposed strategy consumes the least data dissemination cost while achieving a better decoding performance compared with other representative strategies.

Signal preprocessing based on gradient operators

There is a common belief that much of the licensed bands lies idle at any given time and location in wireless communications. In the case of high spectrum utilization, it is very vital to find out those spare bands for providing a better chance of opportunistic access in spectrum scarcity environment. In this paper, a novel algorithm based on gradient operators is proposed, which will be used to preprocess signals in wireless networks before detecting those spare bands quickly. After converting signal spectrum to two-dimension gray-scale image, it is time to apply the gradient operator to preprocess the wireless signals. Simulation results prove the practicality of the new algorithm as it can effectively reduce the impact of noise on the signal.