The Spread Spectrum GFDM Schemes for Integrated Satellite-Terrestrial Communication System

Recently, integrated Satellite-Terrestrial(S-T) communication system, especially the integration of satellite communication with 5G/6G, is regarded as a research hotpot. Future integrated S-T communication systems are demanding a more compatible and robust physical layer waveform. Considering physical layer access waveform design, this paper proposed a novel Spread Spectrum Generalized Frequency Division Multiplexing(SS-GFDM) scheme for integrated S-T communication system. Traditional GFDM has many advantages such as excellent adaptability and low out-ofband(OOB) radiation. However, because of intrinsic inter carrier interference(ICI) and low signal-to-noise ratio(SNR), the multiple access performance is degraded. In this paper, we introduced CDMA technology into GFDM. Two different spread spectrum modes, Cyclic Code Shift Keying(CCSK) soft spread spectrum and Direct Sequence Spread Spectrum(DSSS), are considered and compared in this paper to illustrate the benefits of GFDM-CDMA in low SNR scenario. Moreover, this scheme integrates the slot-ALOHA protocol with GFDM-CDMA, which extends access freedom in frequency, time and code domain. The simulation and analysis results show that the proposed GFDM-CDMA scheme reduces the performance degradation caused by interference. It is effective in typical satellite channel with low complexity. Meanwhile, the peak-average-power-ratio(PAPR) and access performance has been enhanced significantly.

System Integration of Terrestrial Mobile Communication and Satellite Communication——The Trends, Challenges and Key Technologies in B5G and 6G

Mobile communication standards have been developed into a new era of B5G and 6G.In recent years,low earth orbit(LEO)satellites and space Internet have become hot topics.The integrated satellite and terrestrial systems have been widely discussed by industries and academics,and even are expected to be applied in those huge constellations in construction.This paper points out the trends of two stages towards system integration of the terrestrial mobile communication and the satellite communications:to be compatible with 5G,and to be integrated within 6G.Based on analysis of the challenges of both stages,key technologies are thereafter analyzed in detail,covering both air interface currently discussed in 3GPP for B5G and also novel network architecture and related transmission technologies toward future 6G.

Reflection on the Development of Satellite Communications and the Integration with Terrestrial Mobile Communications

With the further reduction in cost and the increase in bandwidth, as well as the increase in internet applications, satellite communications are gradually shifting from a complementary role to becoming a fully integrated component of terrestrial communications networks. This paper firstly introduces the development of satellite communications, mobile communications and the global space-terrestrial integrated network. We then propose the functional architecture and network architecture for the integration of satellite communications and terrestrial mobile communications based on 5 G core networks. Finally, in order to support the network of the future, four key technologies are presented, a space-terrestrial integrated air interface design, a multi-band space-terrestrial integrated transmission waveform design, space-terrestrial integrated switching and routing technology, along with spectrum sharing and interference coordination technology, all necessary for the development of space-terrestrial integrated networks.

Cooperative sensing,communication and computation resource allocation in mobile edge computing-enabled vehicular networks

The combination of integrated sensing and communication(ISAC)with mobile edge computing(MEC)enhances the overall safety and efficiency for vehicle to everything(V2X)system.However,existing works have not considered the potential impacts on base station(BS)sensing performance when users offload their computational tasks via uplink.This could leave insufficient resources allocated to the sensing tasks,resulting in low sensing performance.To address this issue,we propose a cooperative power,bandwidth and computation resource allocation(RA)scheme in this paper,maximizing the overall utility of Cramer-Rao bound(CRB)for sensing accuracy,computation latency for processing sensing information,and communication and computation latency for computational tasks.To solve the RA problem,a twin delayed deep deterministic policy gradient(TD3)algorithm is adopted to explore and obtain the effective solution of the RA problem.Furthermore,we investigate the performance tradeoff between sensing accuracy and summation of communication latency and computation latency for computational tasks,as well as the relationship between computation latency for processing sensing information and that of computational tasks by numerical simulations.Simulation demonstrates that compared to other benchmark methods,TD3 achieves an average utility improvement of 97.11%and 27.90%in terms of the maximum summation of communication latency and computation latency for computational tasks and improves 3.60 and 1.04 times regarding the maximum computation latency for processing sensing information.

LTE-Satellite: Chinese Proposal for Satellite Component of IMT-Advanced System

As a complementary to terrestrial mobile communication systems, mobile satellite communication system can fill the gaps that cannot be covered by terrestrial network, and provides an irreplaceable solution for emergency communication in disaster. To pave the road for future satellite/terrestrial integrated communication networks, ITU-R invited proposals for candidate Radio Interface Technology(RIT) for the satellite component of International Mobile Telecommunications(IMT)-Advanced. China proposed the RIT of Long Term Evolution(LTE)-satellite as a candidate to be considered as IMT-Advanced satellite technology. The submitted LTE-satellite candidate RIT is specified based on terrestrial LTEAdvanced FDD standards that are developed in 3GPP. Considering satellite requirements, a number of modifications to LTE-Advanced are made to adapt to satellite radio transmission environments. This paper provides a general introduction of the new characteristics of LTEsatellite.

Low power consumption high speed CMOS dual-modulus 15/16 prescaler for optical and wireless communications

Frequency synthesizer is an important part of optical and wireless communication system. Low power comsumption prescaler is one of the most critical unit of frequency synthesizer. For the frequency divider, it must be programmable for channel selection in multi-channel communication systems. A dual-modulus prescaler (DMP) is needed to provide variable division ratios. DMP is considered as a critical power dissipative block since it always operates at full speed. This paper introduces a high speed and low power complementary metal oxide semiconductor (CMOS) 15/16 DMP based on true single-phase-clock (TSPC) and transmission gates (TGs) cell. A conventional TSPC is optimized in terms of devices size, and it is resimulated. The TSPC is used in the synchronous and asynchronous counter. TGs are used in the control logic. The DMP circuit is implemented in 0.18 μm CMOS process. The simulation results are provided. The results show wide operating frequency range from 7.143 MHz to 4.76 GHz and it comsumes 3.625 mW under 1.8 V power supply voltage at 4.76 GHz.

Design and Implementation of End to End Encrypted Short Message Service (SMS) Using Hybrid Cipher Algorithm

The study on design and implementation of end to end encrypted Short Message Service (SMS) using hybrid cipher algorithm is motivated by high rate of insecurity of data observed during Short Message Service (SMS) on Mobile devices. SMS messages are one of the popular ways of communication. The aim therefore is to design a software for end to end encryption short message service (SMS) that can conceal message while on transit to another mobile device using Hybrid Cipher Algorithm on Android Operating System and implement it for security of mobile SMS. Hybrid encryption incorporates a combination of asymmetric and symmetric encryption to benefit from the strengths of each form of encryption. Various encryption algorithms have been discussed. Secondary sources were employed in gathering useful data. In this research work three methodologies are employed—Structured System Analysis Design Methodology (SSADM), Object Oriented Analysis Design Methodology (OOADM) and prototyping. With the help of the three cryptographic algorithms employed—Message digest 5 (MD5), Blowfish and Rivest-Shamir Adleman (RSA);integrity, confidentiality, authentication and security of messages were achieved. The messages encrypted by developed application are also resistant to brute force attack. The implementing programs were coded in Java.