Journal of Communications and Information Networks, 2018, 3(1): 61-66 doi: 10.1007/s41650-018-0006-5

Research papers

Joint UE Location Energy-Efficient Resource Management in Integrated Satellite and Terrestrial Networks

Min Jia,, Ximu Zhang,, Xuemai Gu,, Xiaofeng Liu,, Qing Guo,

Corresponding authors: Xuemai Gu,guxuemai@hit.edu.cn

作者简介 About authors

Min Jia was born in 1982. She received her M. Sc. degree in information and communication engineering from Harbin Institute of Technology (HIT) in 2006, and her Ph. D. degree from SungKyungKwan University of Korea and HIT in 2010.She is currently an associate professor and Ph. D. supervisor at the Communication Research Center and School of Electronics and Information Engineering of HIT. Her research interests focus on advanced mobile communication technology and non-orthogonal transmission scheme for 5G, cognitive radio, digital signal processing, machine learning and broadband satellite communications. E-mail:jiamin@hit.edu.cn.

Ximu Zhang was born in 1993. She received her M. Sc. degree in Harbin Institute of Technology (HIT), in 2017. She is currently a Ph. D. candidate in Communication Research Center and School of Electronics and Information Engineering of HIT. Her research interests include broadband satellite communications and heterogeneous cloud radio access network. E-mail:17B905006@stu.hit.edu.cn.

Xuemai Gu was born in 1957. He received his M. Sc. and Ph. D. degrees from the Department of Information and Communication Engineering of HIT in 1985 and 1991, respectively. He is currently a professor and president of the Graduate School of HIT. His research interests focus on integrated and hybrid satellite and terrestrial communications and broadband multimedia communication technique. E-mail:guxuemai@hit.edu.cn.

Xiaofeng Liu was born in 1961. He is currently a professor in the School of Electronic and Information Engineering of HIT. His research interests focus on satellite communications and broadband multimedia communication technique. E-mail:liuxiaofeng@hit.edu.cn.

Qing Guo was born in 1964. He received his M. Sc. and Ph. D. from Beijing University of Posts and Telecommunications and HIT in 1985 and 1998, respectively. He is currently a professor and president at the School of Electronics and Information Engineering, HIT. His research interests focus on satellite communications and broadband multimedia communication techniques. E-mail:qguo@hit.edu.cn.

Abstract

Integrated satellite and terrestrial networks can be used to solve communication problems in natural disasters, forestry monitoring and control, and military communication. Unlike traditional communication methods, integrated networks are effective solutions because of their advantages in communication, remote sensing, monitoring, navigation, and all-weather seamless coverage. Monitoring, urban management, and other aspects will also have a wide range of applications. This study first builds an integrated network overlay model, and divides the satellite network into two categories: terrestrial network end users and satellite network end users. The energy efficiency, throughput, and signal-to-noise ratio (SINR) are deduced and analyzed. In this paper, we discuss the influence of various factors, such as transmit power, number of users, size of the protected area, and terminal position, on energy efficiency and SINR. A satellite-sharing scheme with a combination of the user location and an exclusion zone with high energy efficiency and anti-jamming capability is proposed to provide better communication quality for end users in integrated satellite and terrestrial networks.

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Cite this article

Min Jia. Joint UE Location Energy-Efficient Resource Management in Integrated Satellite and Terrestrial Networks. [J], 2018, 3(1): 61-66 doi:10.1007/s41650-018-0006-5

Ⅰ. INTRODUCTION

The integrated satellite-terrestrial network is the signifi-cant information bridge of“The Belt and Road”. Satel lite and terrestrial networks coordinate with each other, serving for the end users. Companies such as 7-ELEVEN Inc. have been working on building a satellite-based integrated network based on ancillary terrestrial components (ATC)[1]. In 2009, Japanese scholars proposed building a satellite-terrestrial integrated mobile communication system (STICS)for emergency support[2]. The satellite air interface technology based on LTE was submitted to ITU in 2012[3], and the National High Technology Research and Development Program (“863”Program) of China proposed the integration of the information network of the space-air terrestrial integrated information network, which accelerated the process of satellite access to fifth-generation (5G) mobile communication[4,5]. As the satellite spectrum-sharing scheme has been proposed, the spectrum utilization rate has increased significantly, but the satellite and the terrestrial networks still have intensive co-frequency interference. Considering beam-edge users (BEUs) with severe interference, Vincent Deslandes divided user terminals into two main categories, satellite network terminals and terrestrial base station users, and then proposed a scheme of integrated satelliteterrestrial network spectrum-sharing based on an exclusion zone(EZ)in 2010[6]. Integrated satellite-terrestrial network spectrum-sharing based on EZs enhance the SINR; however, system throughput is reduced. Recently, the concept of integrated satellite-terrestrial soft frequency reuse has been investigated. Specifically, Refs. [7,8]verified that the throughput of the scheme had increased. Although some outstanding works have studied satellite spectrum-sharing schemes[9,10], the energy efficiency of the integrated satellite-terrestrial network system is relatively low. However, high energy efficiency conforms to the expectations of green communications for 5G mobile communications[11,12]. Ref. [10]optimized the energy efficiency, but ignored the inter-cell fairness and throughput. A consideration of the throughput, energy efficiency, SINR, and inter-cell fairness of the integrated satelliteterrestrial spectrum-sharing scheme has not been proposed yet, and this motivates our current work.

Ⅱ. THE PROPOSED METHOD

A. System Model

This paper considers satellite beams, macro base stations (MBSs), remote radio heads(RRHs), and a three-layers covered scene, as shown in Fig.1. For further consideration, it is assumed that for a terminal user located in a satellite beam, the received interference signal can be written as

Iu(i,k)=It,u(i,k)+Isat,u(i,k),(1)

where Isat, u(i, k) is the interference of the satellite to u(i, k), u(i, k)is the interference of MBS/RRH to RUE. In the integrated satellite-terrestrial network, the satellite beam, MBS, and RRH cause severe inter-layer interference. This will affect the system throughput, effective coverage, SNR, energy efficiency, and other properties; therefore, we reduced the intratier and inter-tier interference, respectively, through airspace multi-point cooperative transmission to reduce u(i, k), so as to eliminate intra-tier interference u(i, k). Assuming that there is a satellite cell, a High power node (HPN), and f RRHs. We can define the f th RRH as having f terminals, where f =0, 1, 2, …, F, the index f =0 refers to the MBS.

Figure 1

Figure 1   Three layers of an integrated satellite-terrestrial network


The signal received by terrestrial terminal UE k can be written as

Yi=(hif)HωifSif+(hif)HmiωmfSmf

+(hif)Hlfm=1NωmlSml+hisωisSis+nif,(2)

where the RRHs/MBS downlink channel matrix for the kth user is represented by hi f. Si f is the useful signal received by the terrestrial RRH/MBS. It is assumed that the scalar-valued data stream Si f is temporally white, with zero mean and unit variance. The satellite signal for the kth user is represented by Sis and the downlink channel matrix for the kth user is represented by his. As the inter-layer interference intensifies, the use of coordinated multiple-points transmission/reception (CoMP) is necessary. The inter-layer interference and the intra-layer interference are coordinated by CoMP, where efficient and effective zero-forcing(ZF)is used as an example for precoding. hi f and ωi f in the above formula meet

(hif)Hωml=0,miORlf.(3)

As a result, according to the Shannon capacity formula, the achievable transmission rate for terrestrial terminal UE k can be expressed as

Cif=Blb(1+(hif)Hωif(ωif)Hhifσ2+(his)Hωis(ωis)Hhis),(4)

where the energy efficiency can be expressed as

ηif=Cptot=fFi=1N1b(1+(hif)Hωif(ωif)Hhifσ2+(his)Hωis(ωis)Hhis)ξf=0Fi=1NPif+PC.(5)

The signal received by satellite terminal UE k can be written as

Yi=hisωisSis+(hif)HmiωmfSmf

+(hif)Hlfm=1NωmlSml+nif.(6)

The useful satellite signal for the kth user is represented by Sis, and the downlink channel matrix for the kth user is represented by his. Similarly, the inter-layer and intra-layer interference are coordinated by CoMP. Efficient and effective ZF is used to precode, and the above formula meets

(hif)Hωml=0,miORlf.(7)

According to the Shannon capacity formula, the achievable transmission rate for satellite terminal UE k can be expressed as

Cis=Blb(1+(his)Hωis(ωif)Hhisσ2),(8)

where energy efficiency for satellite terminal UE k can be expressed as

ηis=Cptot=f=0Fi=1N1b(1+(his)Hωis(ωis)Hσ2+(his)Hωis(ωis)Hhis)ξf=0Fi=1NPis+PC.(9)

The total throughput of the integrated satellite-terrestrial network system can be expressed as

C=BTf=0Fi=1N1b(1+(hif)Hωif(ωif)Hhifσ2+(his)Hωis(ωis)Hhis)

×(1+1+(his)Hωis(ωif)Hhisσ2).(10)

The energy efficiency of the integrated satellite-terrestrial network system can be expressed as

ηEE=Cptot=Bf=0Fi=1N1b(1+(hif)Hωif(ωif)Hhifσ2+(his)Hωis(ωis)Hhis)ξf=0Fi=1NPis+ξf=0Fi=1NPif+PC

×Bf=0Fi=1N1b(1+(his)Hωis(ωis)Hhisσ2)ξf=0Fi=1NPis+ξf=0Fi=1NPif+PC(11)

B. Interference Analysis

Integrated satellite-terrestrial network users can be divided into two categories: satellite network terminals and terrestrial network terminals. The terrestrial base station signalpropagation model[13]in the macro cell can be expressed as

PL=128.1+37.61g(R)+1g(F),(12)

where R denotes the distance from the terminal to the base station and lg(F)denotes the shadow fading distributed normally. The link loss of the satellite signals only considers the fading of free space, regardless of the influence of rain or other weather conditions, and can be expressed as

PL=92.45+20lgf+201gd.(13)

It is calculated that the interference of the terrestrial terminal downlink to the satellite network terminal downlink is negligible for the satellite network terminal. In contrast, the ratio of the terrestrial network terminal uplink signal to the satellite network terminal uplink interference is severe, because the terrestrial network terminal and satellite network terminal transmission powers are almost the same. In terms of free space loss, the satellite is particularly far from the terrestrial terminal, and the free space loss of terrestrial and satellite network terminals is very small. The environment in which the terminal is located will affect the degree of interference.

Ⅲ. FRAMEWORK FOR THE MODEL

A. Traditional Integrated Satellite-Terrestrial Spectrum Sharing Scheme

The whole spectrum of the satellite integrated network is divided into seven parts. Seven bands create a cluster, and the frequency reuse factor is 7. The satellite-terrestrial spectrum 7-color multiplex diagram is shown in Fig.2.

Figure 2

Figure 2   Satellite-terrestrial spectrum 7-color multiplex diagram


In Fig.2, the terrestrial cell can reuse all of the frequency band with only the satellite beam frequency band, except in the traditional satellite spectrum-sharing scheme. This allows the limited tight spectrum resources to effectively improve the overall system throughput. However, this scheme can cause a certain degree of co-frequency interference between the satellite and the terrestrial user. The distance from the center of the beam can lower the received satellite interference intensity. Therefore, the EZ is established around each satellite beam, and each user or base station in the EZ cannot reuse the frequency band used in the beam; only other frequency bands can be selected. The establishment of the EZ can increase the angle to the beam center, effectively reducing the antenna gain. Therefore, both the signal transmitted by the satellite and the interference signal can be effectively reduced, and the satellite or terrestrial network user terminals SINR and energy efficiency can be effectively improved.

B. Integrated Satellite-Terrestrial Spectrum Sharing Scheme Based on EZ

First, the whole band in the integrated satellite-terrestrial network is divided into seven parts, where seven bands are a cluster and the frequency reuse factor is 7. The base station in the peripheral area of the beam has severe interference to the satellite, and the satellite has severe interference to the terrestrial cell-edge user(CEU). Therefore, the establishment of EZ in the vicinity of the beam area requires users or base stations in the EZ to select a different frequency band. Based on the above principle, seven-color multiplexing of integrated satellite-terrestrial network are shown in Fig.3.

Fig.4 shows the integrated satellite-terrestrial network frequency band isolation. In the case of seven-color multiplexing, the higher isolation frequency is set to a higher level of protection. The isolation degree id designated from high to low in order to set the first-class protection, second-class protection, third-class protection, and forbidden frequency band. The base station/UE prior uses higher levels of the protected frequency band to achieve lower co-frequency interference.

Figure 3

Figure 3   Integrated satellite-terrestrial spectrum sharing scheme based on EZ


Figure 4

Figure 4   Integrated satellite-terrestrial network frequency band isolation


Fig.5 shows the change in energy efficiency with terrestrial user transmitting power under different numbers of terrestrial satellite terminals. For example, to define the width of EZ by 3 dB(providing 3-dB isolation for the user or base station), we take the interference from the satellite to the terrestrial network terminal. The interference size calculation formula is given by

PUE_rec=PSAT+Gr+PL+Pshadowloss,(14)

where the satellite antenna gain is represented by Gr and the satellite-terrestrial link loss is represented by PL, where PSAT and PL+Pshadowloss basically remain the same. Therefore, reducing Gr can reduce the co-frequency interference.

Figure 5

Figure 5   Change in energy efficiency with terrestrial user transmitting power under different numbers of terrestrial satellite terminals


C. Joint UE Location Energy-Efficient Resource Management in Integrated Satellite and Terrestrial Networks

In addition, with the increase of protected areas, both the downlink energy efficiency and SINR of terrestrial network terminals gradually increase because the size of the protected area directly reduces the amount of interference, and the distance between the terrestrial terminal user and the satellite increases. The attenuation of the satellite signal link slightly increases, further reducing the interference caused by the satellite downlink. This is from the perspective of reducing interference to improve the system’s SINR and energy efficiency. Based on the above simulation results, we propose a resource allocation scheme with higher energy efficiency. In the process of frequency allocation, we first consider establishing an EZ around the satellite, and then consider whether the user of the ground network is located at the center or edge of the terrestrial cell. At the edge of the cell, We allocate higher protection frequency bands so as to ensure that the SINR is not too low. If the ground terminal is in the center of the terrestrial cell, the received useful signal will be strong. Therefore, we can assign it to a lower level of protection. The simulation results show that adopting a frequency allocation strategy based on user location and EZs is a solution with high energy efficiency and improved SINR.

Ⅳ. EXPERIMENTAL EVALUATION

This section provides simulation results to validate the proposed scheme in comparison to other schemes. The result in Fig.6 shows that when the user density is low, the SINR of the cluster cell in the new scheme is much better than that of others.

The simulation results show that when the local surfacenetwork terminal number increases from 2 000 to 8 000, the energy efficiency of system presents a downward trend. The number of local surface network terminals, which act as interference sources, is large. The higher this number is, the stronger the interference from the terminal to the satellite uplink, and the lower the energy efficiency is. In addition, as the launch power of the ground network terminal increases, the satellite receives a greater interference signal from the ground network terminal. Therefore, the energy efficiency of the satellite terminal uplink decreases. The transmitted power of interference sources affects the satellite link SINR, which influences the energy efficiency. Therefore, the greater the number of ground terminals and the greater the terminal launch power is, the lower the energy efficiency of the satellite link will be.

Figure 6

Figure 6   The energy efficiency varies with the size of EZ


The simulation results show that a larger reserve satellite link is beneficial to energy efficiency, because as the reserve increases, the satellite receiver gain is reduced, and the interference sources from the satellite distance also increase, as does the anti-interference performance of the system.

Fig.7 shows that the closer the ground network terminal is to the base station and the stronger is the received useful signal. The closer the ground network terminal is to the base station, the stronger is the received useful signal. Thus, the SINR and energy efficiency of the downlink of the terrestrial network terminal is higher, which is considered to be the increase of the received signal strength. In addition, with the increase in protected areas, both the downlink energy efficiency and SINR of the terrestrial network terminals gradually increase, which is because the size of the protected area directly reduces the strength of the interference, and the distance between the terrestrial terminal user and the satellite increases. The attenuation of the satellite signal link slightly increases, further reducing the interference caused by the satellite downlink. This is from the perspective of reducing interference to improve the system’s SINR and energy efficiency.

Figure 7

Figure 7   Energy efficiency of terrestrial network terrestrial station at different positions from ground base station with the change of EZ


Ⅴ. CONCLUSION AND FUTURE WORK

In this paper, we have proposed a satellite-terrestrial energy-efficient spectrum-sharing scheme based on UE location. We first classify the users in the satellite-earth integrated network into two categories(satellite network terminal users and terrestrial network users)and establish the satellite-earth integrated network architecture. Second, the terrestrial terminal located in the center of the terrestrial cell receives an intense useful signal, and we can obtain a high SINR by using a full frequency-reuse scheme. Third, the satellite beam is isolated by ranking the different frequency bands corresponding to the base station and user location. This paper proposes a spectrum-sharing scheme combining the user location and protected area, which is a resource allocation scheme with high energy efficiency. The simulation results show that the proposed scheme is a spectrum sharing scheme with high energy efficiency, and conforms to green communication well.

The authors have declared that no competing interests exist.
作者已声明无竞争性利益关系。

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