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Space Information Network (SIN) with backbone satellites relaying for vehicular network (VN) communications is regarded as an effective strategy to provide diverse vehicular services in a seamless, efficient, and cost-effective manner in rural areas and highways. In this paper, we investigate the performance of SIN return channel cooperative communications via an amplify-and-forward (AF) backbone satellite relaying for VN communications, where we assume that both of the source-destination and relay-destination links undergo Shadowed-Rician fading and the source-relay link follows Rician fading, respectively. In this SIN-assisted VN communication scenario, we first obtain the approximate statistical distributions of the equivalent end-to-end signal-to-noise ratio (SNR) of the system. Then, we derive the closed-form expressions to efficiently evaluate the average symbol error rate (ASER) of the system. Furthermore, the ASER expressions are taking into account the effect of satellite perturbation of the backbone relaying satellite, which reveal the accumulated error of the antenna pointing error. Finally, simulation results are provided to verify the accuracy of our theoretical analysis and show the impact of various parameters on the system performance.

Nowadays, the connected vehicles paradigm is to form a vehicular network (VN) to communicate with the surrounding environment and the VN plays a vital role in the next generation intelligent transportation system (ITS) [

Space Information Network (SIN) is regarded as an effective strategy to provide diverse vehicular services in a seamless, efficient, and cost-effective manner in rural areas and highways. For instance, satellites and high altitude platforms (HAPs) in SIN can help achieve ubiquitous coverage in rural areas. Further, they can provide road information and transport information to assist ITS, entertainment services dissemination as relays, and relieve the demands on terrestrial networks through data offloading [

The return channels of the low/medium Earth orbit (L/MEO) satellites are unstable and discontinuous intrinsically to the ground-based stations and vehicles, which limit the throughput as well as the delay sensitive services of SIN-assisted VN communications. Recently, high throughput backbone satellites (such as the Ka/Q/V-band geostationary Earth orbit (GEO) satellites) relaying for SIN communications are regarded as an effective strategy to improve the continuity of return channels as well as the throughput performance.

Theoretically, three GEO satellites which are

With the development of high throughput satellites (HTS), several GEO HTS can establish the backbone network of SIN, where the backbone HTS relaying for SIN-assisted VN is able to provide a global seamless broadband transmission by developing the intersatellite links. People believe that the SIN will enable a “terabit data rate capacity” broadband access, which was previously possible only with fiber-optic links, and offer the access availability of “anywhere and anytime” inherent to the satellites [

Therefore, considering the backbone HTS relaying communication undergoes the large-scale and complex SIN dual-hop channel properties, such as rain attenuation [

In our SIN communication scenario, space-based nodes (i.e., source nodes, like space mission explorers, orbiters and landers, space stations, spacecraft, manned and unmanned aircraft, etc.) can establish cooperative communications via an AF backbone HTS relaying.

Recently, SINs have attracted considerable research interest, and substantial effort has been devoted to investigating the performance of the research works of the hybrid satellite-terrestrial cooperative/relay networks (HSTC/RNs) by analyzing the complex multihop channel models. For that, by applying maximal ratio combining (MRC) at the destination, [

Moreover, to achieve higher system capacity and energy efficiency, multiantenna technique was investigated in [

Besides, the SINs backbone GEO satellites are subjected to various satellite perturbation forces (e.g., Earth oblateness perturbation, third-body gravitational perturbation, atmospheric perturbation, and solar perturbation), which leads to position drift and result in the beam center of the ground station antenna unfocused [

In this paper, we investigate the performance of SIN return channel cooperative communications via an AF backbone satellite relaying for VN, where both of the source-destination and relay-destination links undergo Shadowed-Rician fading, and the source-relay link follows Rician fading, respectively. By applying MRC at the destination, the equivalent end-to-end SNR of the system is first obtained, and then analytical expressions as well as the satellite perturbation effect are derived to evaluate the system performance. The detailed contributions of this paper are outlined as follows:

The system model of SIN return channel cooperative communications via an AF backbone satellite relaying for VN is first built, and we present a new analytical expression for the approximate statistical distributions of the equivalent end-to-end SNR of system (

To gain further insight, the effect of the satellite perturbation of the relaying GEO satellite is considered for the first time, which reveals the accumulated error of the antenna pointing error leads to the satellite elevation error. And the accumulated satellite elevation error is taking into account the derivation of the ASER expression.

The closed-form expression for the end-to-end ASER (

Our system model of the SIN return channel cooperative communications via an AF GEO HTS relaying for VN is considered as shown in Figure

The proposed system model of SIN return channel cooperative communications via an AF GEO HTS relaying for VN, where each node is equipped with a single antenna, the relay point

The space node

As illustrated in Figure

During the second time phase,

Assuming that perfect channel state information (CSI) is available at

In this paper, the GEO HTS satellite is considered as backbone relaying node for SIN-assisted VN communications to enhance the continuity as well as the throughput of the return channel. This is the first work to analyze the performance of cooperative communication for SIN dual-hop channel properties. To gain further insight, the effect of the satellite perturbation of the GEO HTS is analyzed, which reveals that the accumulated error of the antenna pointing error leads to the satellite elevation error.

The satellite is always subjected to a variety of perturbation forces, especially to the GEO satellites, which will lead to perturbation drift and accumulate the antenna pointing error. The satellite perturbation forces include the Earth oblateness perturbation [

The Earth oblateness perturbation is caused by the facts that the Earth is not an ideal sphere and it has uneven internal density distribution. It affects the long-term change of the right ascension of ascending node (RAAN)

The diagram of antenna pointing error is shown in Figure

The diagram of antenna pointing error caused by satellite perturbation,

In general,

Therefore, from (

As the

Then, the cumulative distribution function (CDF) of

Moreover, the relationship between the Rician factor

The

Let

Recall the definition of

For the analytical tractability, we retain our focus in the case when the channel severity parameters take integer values in the rest of this paper; that is,

To solve the three parameters

In order to exactly measure the effect of satellite perturbation on the SIN return channel cooperative communications via an AF GEO HTS relaying, the important quality-of-service (QoS) metric, that is, average symbol error probability (ASER), is analytically studied and evaluated in our proposed SIN-assisted VN systems.

Since MRC is applied at the destination, we derive the close-form expression by using MGF according to [

Considering

In the following, we derive the expressions for

By using the definition of MGF and substituting (

By using [

By substituting

Based on the definition of ASER of an MPSK modulated system (i.e., (

Alternatively, the following approximation of (

As shown in (

This section gives the numerical results to demonstrate the validity of the theoretical analysis and the effect of satellite perturbation on the SIN return channel cooperative communications via a GEO HTS relaying.

We assume the node

Initial position and velocity vector of GEO HTS and other system parameters.

Parameters | Description |
---|---|

Earth gravity model | WGS84_EGM96.grv |

Satellite mass | 1000 kg |

Mass-area ratio of satellite | 0.1 m^{2}/kg |

Reflection coefficient of spacecraft | 1.2 |

Solar radiation pressure model | Spherical |

Third-body gravity | Sun, Moon |

The elevation error affected by the satellite perturbation is shown in Figure

Elevation error caused by GEO satellite perturbation.

As shown in Figure

We assume

ASER with satellite perturbation versus various

ASER with satellite perturbation versus various

ASER performance versus various

Figures

Moreover, three subfigures in Figures

In this paper, we investigate the ASER performance of SIN return channel cooperative communications via an AF GEO HTS relaying for VN, where both of the

By the definition of MGF, from (

Considering

By using [

Thus, (

In order to make the derivation more clear, we define

After some algebra manipulations, we can rewrite (

Now, we can rewrite

Let

By substituting (

Then, by using the Binomial expansion for

The integral part of (

The authors declare no conflicts of interest regarding the publication of this paper.

Jian Jiao, Houlian Gao, and Qinyu Zhang contributed equally to this work.

This work was supported in part by the National Natural Sciences Foundation of China (NSFC) under Grants 61771158, 61701136, 61525103, and 61371102, the National High Technology Research & Development Program no. 2014AA01A704, the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology under Grant HIT.NSRIF.2017051, and the Shenzhen Fundamental Research Project under Grants JCYJ20160328163327348 and JCYJ20150930150304185.