Open access peer-reviewed chapter - ONLINE FIRST

Lunar Science: Internet for Space Tourism

By Ayodele Abiola Periola

Submitted: September 30th 2018Reviewed: August 11th 2019Published: December 9th 2019

DOI: 10.5772/intechopen.89124

Downloaded: 53

Abstract

The increased interest in space exploration drives the development of novel technologies that are useful in other areas, such as aviation. The use of these technologies gives rise to new challenges and applications. Space tourism is an emerging application due to advances in space exploration technologies. This paper addresses two challenges aimed at ensuring continued internet access in space tourism. The first is designing network architecture to ensure continued internet access for space tourists aboard a space vehicle. The second is using aerial vehicle technology to enhance access to cloud content in areas with poor telecommunication infrastructure. The paper proposes the distributed handover algorithm ensuring that the space vehicle can execute handover from terrestrial wireless networks to aerial platforms and satellites as a last mile connection. It also proposes the concept of aerial diversity ensuring low cost access to cloud content. Performance simulation shows that the use of the distributed handover algorithm enhances channel capacity by 18.4% on average and reduces latency by 11.6% on average. The use of the cloud content access system incorporating aerial diversity enhances the channel capacity of terrestrial wireless networks by up to 85% on average.

Keywords

  • Space Tourism
  • Wireless Communications
  • Wireless Handover
  • aerial platforms
  • satellites
  • space tourist

1. Introduction

The internet comprises multiple converging technologies that interact together in a global network. Information access via the internet faces a significant number of challenges. These challenges influence the ease with which information can be accessed via the internet. The quality of service (QoS) associated with internet access is determined by metrics such as channel capacity, latency, throughput and packet loss rate.

Advances in networking have played a significant role in internet evolution. For example, the internet initially used wired technology as the communication media; however, the internet is now accessed via wireless radio [1, 2, 3]. This transition increases the mobility of subscribers seeking to access data [4, 5]. The emergence of smartphones has improved subscriber ability to access the internet. This increased access requires network algorithms to support the realization of enhanced QoS in fifth generation (5G) wireless networks and beyond 5G (B5G) networks.

Internet access via wireless technologies benefits from new technologies such as: (i) new variants of the internet protocol (IP) and the transmission control protocol (TCP) [6, 7, 8, 9, 10], (ii) improved packet switching [11, 12, 13], (iii) World Wide Web [14], (iv) IEEE 802.11 wireless network standard [15], and (v) artificial intelligence [16, 17].

Currently, there is increased interest in space exploration leading to the development of technologies such as small satellites [18, 19] and aerial vehicles such as stratospheric platforms [19] and drones [20]. The development of these technologies enables capital constrained organizations to engage in space exploration. This also enables the emergence of new applications requiring internet access such as space tourism. The emergence of space tourism [21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39] requires a solution to providing uninterrupted internet access to subscribers aboard a space vehicle, as well as improving accessibility to the cloud content internet.

This chapter addresses two challenges: it designs (i) a network infrastructure with associated mechanisms to ensure continued access for space tourist subscribers aboard a space vehicle and (ii) a solution to improve the cloud service accessibility in developing nations. The chapter makes the following contributions:

  1. Firstly, it proposes a network architecture that incorporates the space tourist subscriber in commercial space flights. The space tourist subscriber requires access to cloud-based content and the proposed network architecture ensures that there is a continuity of access to cloud content at every tier via the proposed handover mechanism.

  2. Secondly, it proposes a novel architecture that incorporates aerial diversity i.e. use of unmanned and manned aerial vehicles to achieve access to cloud content. This has the benefit of reducing congestion on in terrestrial wireless networks. The architecture uses manned and unmanned aerial and robotic entities for information delivery in the internet.

  3. Thirdly, it formulates the performance metrics and benefits for the proposed mechanisms. These metrics are examined considering networks that do and do not incorporate the proposed mechanism. The metric is the aggregate throughput for a network comprising multiple base station entities.

The rest of the paper is structured as follows. Section 2 formulates the problem being addressed in this chapter. Section 3 presents the proposed mechanisms. Section 4 formulates the performance model. Section 5 presents and discusses the simulation results and performance benefits. Section 6 is the conclusion.

The list of acronyms and the set of notations used in this paper are shown in Tables 1 and 2 respectively.

S/NAcronymMeaning
1APSHAerial Platform to Satellite Handover
2C-RANCloud Radio Access Network
3DHADistributed Handover Algorithm
4eNBEvolved Node B
5gNBNext generation Node B
6MAVManned aerial vehicle
7MIPv6Mobile internet protocol version 6
8P-GWPacket data gateway
9PMIPv6Proxy mobile internet protocol version 6
10QoSQuality of Service
11S-GWServing gateway
12SMIPv6Seamless mobile internet protocol version 6
13SISHSub –orbital Intersatellite Handover
14TCPTransmission Control Protocol
15TWAHTerrestrial Wireless Network to Aerial Network Handover
16TWNHTerrestrial Wireless Network Handover
17UAVUnmanned Aerial Vehicle

Table 1.

Acronyms used in this paper.

S/NParameterMeaning
1NSet of wireless networks
2CSet of cloud platforms
3SSet of subscribers
4nSSet of satellite networks
5nTSet of terrestrial wireless networks
6nSrThe rthsatellite network.
7nTuThe uthterrestrial wireless network
8CiThe ithcloud platform hosting content that subscriber szseeks to access
9szThe zthsubscriber desiring access to cloud based content
10αnTuThe coverage region of nTu
11αnSrThe coverage region of nSr
12βIs the network sub – indicator
13IβCitjCloud access indicator at epoch tj
14.Null set
15θSet of possible subscriber locations.
16θgSet of ground locations for subscribers
17θaeSet of aerial locations for subscribers
18θgcThe cthground location
19θaenThe nthaerial location
20NUpdated set of wireless networks
21ϕSUthe network designed to provide access to cloud content for θsu
22EsxMean latency for subscriber sx
23ThsxβtjThroughput associated with data accessed by sx;sxϵSvia network entity βat epoch tj
24DsxtjSize of data accessed by sxfrom network entity βat epoch tj
25PthγThreshold signal strength for terrestrial wireless network base station entity.
26lthThreshold Latency
27E1szThe mean latency computed for multiple subscribers.
28γSet of terrestrial wireless network base station entities
29ϷSet of stratospheric platforms
30ƿSet of satellites
31ϰϵγbϷlƿtEntity ϰdenotes transmitting nodes in terrestrial, stratosphere and outer space respectively.
32Pϰtj;The strength of the signal form entity ϰat epoch tj
33CterChannel capacity of space vehicle in terrestrial plane
34CaeChannel capacity of space vehicle in aerial plane
35CspChannel capacity of space vehicle in space plane.
36BzbBandwidth of channel zfor the bthterrestrial wireless network base station entity
37BzlBandwidth of channel zfor the lthstratospheric platform base station entity
38BzcBandwidth of channel zfor the cthin – orbit satellite.
39PtrγdzTransmit power between the space vehicle and terrestrial wireless network γdon channel z
40PtrϷlzData transmit power between the space vehicle and high altitude platform Ϸlon channel z
41PtrƿczData transmit power between the space vehicle and in – orbit satellite ƿcon channel z
42PintγdzInterference power between the space vehicle and terrestrial wireless network on channel z
43PintϷlzInterference power between the space vehicle and high altitude platform on channel z
44PintƿczInterference power between the space vehicle and in – orbit satellite on channel z
45h11γdzTransmit channel gain between space vehicle and terrestrial wireless network on channel z
46h11ϷlzTransmit channel gain between the space vehicle and high altitude platform on channel z
47h11ƿczTransmit channel gain between the space vehicle and in – orbit satellite on channel z
48h12γdzInterference channel gain between space vehicle and terrestrial wireless network on channel z
49h12ϷlzInterference channel gain between the space vehicle and high altitude platform on channel z
50h12ƿczInterference channel gain between the space vehicle and in – orbit satellite on channel z
51CaveAverage channel capacity for the space vehicle
52IγdϷlHandover indicator between γdand Ϸl
53IϷlƿcHandover indicator between Ϸland ƿc
54DAmount of transmitted data in bytes
55β1Latency associated with data transmission in absence of proposed handover mechanism
56β2Latency associated with data transmission after incorporating the handover mechanism
57PcoγbProbability of network congestion occurring on terrestrial wireless network γb
58ThγbChannel capacity of γbis denoted Thγb
59Th1clγbAggregate channel capacity of accessing cloud content without proposed cyber – physical system
60Th2clγbAggregate channel capacity of accessing cloud content with proposed cyber – physical system

Table 2.

Set of notations used in this paper.

2. Problem formulation

The discussion here is divided into three parts. The first part describes the system model. The second defines the problem and challenges being addressed in this chapter. The third focuses on the challenge being addressed as regards access to cloud based services.

2.1 System model

The network scenario comprises cloud radio access networks (C-RANs). Each C-RAN comprises a base station entity such as the evolved Node B (eNB) or next generation Node B (gNB). The eNB or gNB is connected to a cloud platform that provides resources in the network control plane. The base station entity is connected to cloud platforms that host content being demanded by subscribers. The system model assumes that subscribers can access the network i.e. cloud content at the desired epoch. The network comprises terrestrial wireless and satellite network segments. A scenario showing the network is shown in Figure 1.

Figure 1.

Network scenario showing the system model.

The scenario in Figure 1 shows the connection between two eNBs (i.e. eNB1 and eNB2) with overlapping coverage. The first eNB i.e. eNB 1 is connected to the cloud platform being the closer of the two eNBs. The packet data gateway (P-GW) of eNB 1 interacts with the gateway entity at the cloud platform hosting the content being accessed. The eNBs can execute handover to support the migration of subscriber SH. This is realized by the dynamics associated with serving gateway (S-GW) in seamless handover execution [46].

2.2 Problem definition: the ‘space tourist’ subscriber

The considered scenario comprises multiple networks enabling subscribers to access cloud-based content. Let N,Sand Cbe the set of wireless networks, subscribers and cloud platforms, respectively. Such as:

N=nSnTE1
S=s1s2sxE2
C=C1C2CyE3
nS=nS1nS2nSpE4
nT=nT1nT2nTqE5

Where:

nSand nTare the set of satellite and terrestrial wireless networks respectively.

sz,szϵSis the zthsubscriber desiring access to cloud-based content.

nSr,nSrϵnSis the rthsatellite network.

nTu,nTuϵnTis the uthterrestrial wireless network.

Ci,CiϵCis the ithcloud platform hosting content that subscriber szseeks to access.

The coverage region of nTuand nSrare denoted as αnTuand αnSr, respectively. Let IβCitjϵ01,βϵnTunSr,tjϵt,t=t1t2twbe the cloud access indicator at epoch tj. The states Iβ=nTuCitj=0and Iβ=nTuCitj=1signify that the ithcloud platform Ciis inaccessible and accessible to base station entities of the uthterrestrial wireless network at epoch tjrespectively. The indicator Iβ=nSrCitj=0and Iβ=nSrCitj=1signify that the ithcloud platform Ciis inaccessible and accessible to base station entities of the rthsatellite network, respectively. The ground-based entity of the rthsatellite network is the terrestrial component of a satellite network.

A scenario described by the transition Iβ=nTuCitj=0,Iβ=nTuCitj+1=1,tj+1ϵtis one in which the cloud platform Ciis connected to network nTuat epoch tj+1and not connected at epoch tjrespectively. Another plausible scenario is β=nTuCitj=0,Iβ=nSrCitj+1=0,Iβ=nSrCitj+j=0,tj+jϵt, which describes a case where subscriber szmoves through the regions where access to cloud content via terrestrial network is infeasible at epochs tjand tj+1but feasible at epoch tj+j.

The variable IβCitjcan have a varying number of contexts described by transitions between different scenarios for different β,Ciand tj. A common factor across these scenarios is the implied assumption that NnSnT. However, this does not consider the requirement to provide internet access in outer–space. Hence, another scenario that is yet to be considered is one described as NnSnT=that considers the space tourist subscriber which has not been considered.

In the terrestrial plane, the subscriber szaccesses the cloud content from a terrestrial location. However, cloud content can be accessed from other locations such as the ocean, and near space regions. Let θdenote the set of possible subscriber locations, such as:

θ=θgθaeθsuE6
θg=θg1θg2θgvE7
θae=θae1θae2θaemE8
θsu=θsu1θsu2θsufE9

Where

θgand θaeare the set of ground and aerial locations respectively.

θgc,θgcϵθgis the cthground location.

θaen,θaenϵθaeis the nthaerial location.

θsuis the set of locations in space.

θsuv;θsuvϵθsuis the vsub – orbital location.

The definition of θexcludes the underwater and underground locations.

There is coverage for locations θgand θaegiven that Iβ=nTuCitj=1θg,θaehold true. The condition IβCitj=1θg,θaeindicates that there is no network coverage for locations θgand θae. Satellite and terrestrial wireless networks cannot deliver cloud access to space tourist subscribers when:

Iβ=nTuCitjIβ=nTuCitj+1Iβ=nTuCitj+jIβ=nTuCitw=0,θsuE10
Iβ=nSrCitjIβ=nSrCitj+1Iβ=nSrCitj+jIβ=nTuCitw=0,θsuE11

This is because terrestrial and satellite networks do not provide internet access for space tourist subscribers.

Let Ndenote the set of updated set of wireless networks such that:

N=NϕSUE12

Where ϕSUis the network designed to provide access to cloud content for θsu, then it is desired that:

{I((NN),Ci,tj),I((NN),Ci,tj+1),I((NN),Ci,tj+j),,I((NN),Ci,tw)}=0,θsuE13

This paper designs a network architecture which ensures that (13) holds true at all epochs.

The discussion so far assumes that data access from the cloud in the contexts considered above is accompanied with a high QoS. This assumes the availability of reliable network infrastructure. For instance, this assumption is not true where exists poor availability of high-performance terrestrial network infrastructure, or subscribers’ inability to access expensive satellite networks. This assumption is true for cloud service providers in nations with a high population demanding access to cloud content; described by the conditions:

Iβ=nTuCitjIβ=nTuCitj+1Iβ=nTuCitj+jIβ=nTuCitw=0,nT,θgE14
Iβ=nSrCitjIβ=nSrCitj+1Iβ=nSrCitj+jIβ=nTuCitw=0,nSE15

If we let Dsxtjand Thsxβtj,βϵnTunSrdenote, respectively, the size of data accessed by sxfrom network entity βand throughput associated with data accessed by sx;sxϵSvia network entity βat epoch tj, then the mean latency Esxcan be expressed as:

Esx=121wpj=1wr=1pIβ=nSrCitjDsxtjThsxβ=nSrtj+1wqj=1wu=1qIβ=nTqCitjDsxtjThsxβ=nTqtjE16

Given the threshold latency lth, the subscriber sxhas a significant delay if Esxlth. The delay Esxrefers to that of a single subscriber. In the case of multiple subscribers, the latency E1szis given as:

E1sz=121wpzj=1wr=1pz=1xIβ=nSrCitjDsztjThsxnsrtj+ϔ1E17
ϔ1=1wpzj=1wu=1qz=1xIβ=nSrCitjDsztjThsxnsrtjE18

There is a significant degradation associated with accessing cloud-based content when E1szlth,. Hence, a solution which ensures that the condition E1szlthholds true for a significantly long duration is required. Such a solution is proposed in this paper. This section presents the two challenges being addressed in this paper, namely:

  1. Ensuring that space tourist subscribers engaged in sub– orbital space tourism flight have continued access to internet and cloud-based content. For example, space tourist subscribers should be able to upload content observed at high altitudes and in outer space to the cloud with low latency.

  2. Designing a solution which ensures that the condition E1szlthholds true for subscribers desiring to access cloud-based content and for a significantly long duration.

3. Proposed solution(s) and associated mechanisms

This section presents the proposed solutions and is divided into two parts. The first part presents the solutions, mechanisms and associated network architecture to address the challenge involving space tourist subscribers. The second part discusses the solution that aims at ensuring the delivery of cloud-based content to subscribers at low latency when E1szlth.

3.1 Internet access continuity in space tourism

Space tourism subscribers are conveyed in a space vehicle that hosts communication subsystems which enables internet access. The space vehicle begins its journey from a terrestrial location with access to terrestrial wireless networks. The space tourists have access to the internet via the gateway of the terrestrial wireless network. In the context of the LTE-A utilizing the eNB, the P-GW and S-GW are the gateway entities. A handover is required to ensure the continuity of internet access as the space vehicle travels from the terrestrial location to outer space. Three handover levels are required in the proposed solution, these are:

  1. Terrestrial Wireless Network Handover (TWNH): The TWNH refers to the handover executed between base station entities i.e. eNB. It is executed using protocols such as the seamless mobile internet protocol version 6 (SMIPv6) [47], mobile internet protocol version 6 (MIPv6) and proxy mobile internet protocol version 6 (PMIPv6) [48, 49]. The handover context implied in TWNH has been sufficiently addressed in literature.

  2. Terrestrial Wireless Network to Aerial Network Handover (TWAH): The TWAH is necessary if the space vehicle connects to an aerial platform such as a high altitude platform as it sojourns to outer space. It involves the handover of a session from terrestrial wireless networks to aerial platforms. The aerial platforms in this context are connected using inter-platform links. Existing protocols such as that in [50] address the challenge of executing handover between terrestrial wireless networks and high altitude platforms.

  3. Aerial Platform to Satellite Handover (APSH): The APSH involves executing a handover to the satellite on the uplink when subscribers access data from the cloud. The execution of the APSH becomes necessary as the space vehicle’s altitude increases as it approaches low earth orbit. Existing approach consider that satellites should handover to stratospheric platforms in reaching the subscribers. The case here is different because the satellite network is in the last mile.

  4. Sub-orbital Intersatellite Handover (SISH): The execution of the SISH is required to ensure that the in-orbit space vehicle connects to the satellite enabling it to have the highest throughput and lowest latency. The SISH redefines the role of satellites in accessing cloud based information via the internet. This is because inter-satellite links have often been used with the aim of achieving global coverage using satellite networks; and not in the context of providing seamless high QoS internet connections to subscribers as a last mile technology.

The space tourist subscriber requires internet access for obtaining content from the internet or storing content for storage and later access. This should be realized without significant space segment acquisition costs. The contexts implied in the APSH and SISH require novel mechanisms and accompanying network architecture. This is because the APSH and SISH phases are peculiar to the space tourist subscriber. The relations between the TWNH, TWAH, APSH and SISH are shown in Figure 2.

Figure 2.

Relations between the TWNH, TWAH, APSH and SISH.

The scenario in Figure 2 shows a space vehicle sojourning from a terrestrial location to outer space. The space vehicle passes through the terrestrial plane, aerial plane and the space plane. The space vehicle(s) is connected to the terrestrial wireless network base stations and access the cloud based content via the internet through the gateways. In the aerial plane, the space vehicle is connected to the high altitude platform.

The high altitude platform receives contents from select ground based stations. These ground stations are those being used for radio astronomy. However, they are not engaged in receiving radio astronomy signals during epoch of use by high altitude platform. The use of such ground stations is feasible considering the emergence of multi-mode ground stations that can be used for radio astronomy and packet processing [51]. The multi-mode ground station is connected to the computing infrastructure of the astronomy organization. The computing infrastructure is linked to the cloud computing platform hosting the content to be accessed by the space tourist subscriber. Idle multi-mode ground stations relay cloud based content to the space vehicle in the space plane. The cloud platform sends the cloud content to be sent to select ground stations that communicate with stratospheric platforms in the aerial plane. The select ground stations are also used to enable communications between satellites and the space vehicle in the space plane.

Aerial platforms communicate with each other using inter-platform links that utilize free space optics to ensure low latency. This is done when the space vehicle moves from the coverage of a high altitude platform to the coverage of another high altitude platform. In moving from the aerial plane to the space plane i.e. executing the APSH, the space vehicle does not have line of sight and communicates with the satellite via the ground station. In the space plane, the space vehicle is able to move between satellites. This is enabled by satellite communications with selected ground stations.

The proposed handover mechanism requires that the space vehicle conveying space tourists pass overhead through radio astronomy observatories. This provides the added benefit of enhancing astro-tourism and enables space tourists to have an aerial view of astronomical observatories. The re-use of existing astronomy infrastructure [40] reduces the cost associated with launching an anchor satellite to maintain high QoS internet connectivity for the concerned space vehicle. The use of selected ground station infrastructure improves the revenue potential for astronomy organizations; and increases the utilization of the high performance infrastructure and ground stations. The space vehicle connects to a geostationary communications satellite [41, 42, 43, 44, 45]. The ground segment of the geostationary satellite is an idle multi-mode ground station.

The handover algorithm that enables the provision of seamless internet connectivity for the space vehicle comprises entities that function in the space vehicle, ground stations, high altitude platforms and satellites. The proposed distributed handover algorithm (DHA) functions are for the aerial and space modes. The DHA executes the TWAH and the SISH in the aerial mode and space mode, respectively.

The space vehicle host mechanisms that enable it to execute the TWAH, and the handover between aerial platforms. However, these mechanisms are not designed since they have received considerable research attention. Let γ,Ϸand ƿbe the set of terrestrial wireless network base station entities, stratospheric platforms and satellites, respectively.

γ=γ1γ2γdE19
Ϸ=Ϸ1Ϸ2ϷhE20
ƿ=ƿ1ƿ2ƿnE21

In addition, let Pϰtj,ϰϵγbϷlƿt,γbϵγ;ϷlϵϷ;ƿtϵƿdenote the strength of the signal form entity ϰat epoch tj. Given that Pthγis the threshold signal strength for terrestrial wireless network base station entity; the space vehicle measures the value of Pϰ=γbtjand Pϰ=Ϸltjand retains connectivity to the terrestrial wireless network if:

1dwb=1dj=1wPϰ=γbtj>PthγE22
1dwb=1dj=1wPϰ=γbtj>1hwl=1hj=1wPϰ=ϷltjE23

If (22) does not hold true, then (23) is also invalid. The APSH should be executed if:

1hwl=1dj=1wPϰ=Ϸltj>PthϷE24
1hwl=1hj=1wPϰ=Ϸltj>1hwb=1dj=1wPϰ=γbtjE25

The space vehicle is in the terrestrial plane if (22), (23) hold true and is in the aerial plane when (24), (25) holds true. The space vehicle moves from the aerial to the space plane if:

ϔ1<ϔ2<ϔ3E26
ϔ1=1h×j+jl=1hj=1j+jPϰ=ϷltjE27
ϔ2=1h×αl=1hj=j+j+1j+j+αPϰ=ϷltjE28
ϔ3=1h×wj+j+α+1l=1hj=j+j+α+1wPϰ=ϷltjE29

The transition in (26)(29) involves a movement of the space vehicle from the aerial plane to the space plane. This handover is executed in the APSH. A set of relations describing the handover and the associated transition involving movement from the terrestrial plane to the aerial plane has not been presented. This kind of handover has been sufficiently addressed in the literature focused on aerial–terrestrial communications [51, 52, 53]. However, the context being addressed here is that of ensuring connectivity with a manned aerial vehicle (MAV) i.e. the space vehicle intended for space tourism.

The handover and transition implied in the SISH becomes activated when Pϰ=Ϸltj<Pϰ=Ϸl+1tj;Ϸl+1ϵϷand the space vehicle selects satellite Ϸl+1. The flowchart in Figure 3 describes the relations executed in a handover procedure. The MAV searches for other networks of aerial platforms if the satellite signal is detected given that (26)(29) holds true. In Figure 3, it is assumed that the space vehicle is able to connect to the concerned entities; i.e., high-altitude platforms or satellites depending on the decision context. The space vehicle connects to the entity with the highest transmit power.

Figure 3.

Functional flowchart showing the execution of the proposed handover for the space vehicle i.e. MAV.

3.2 Cyber: physical system - enhancing cloud access

The discussion presents a solution that enables subscribers to access cloud content when E1szlth. This scenario i.e. E1szlthdescribes one in which terrestrial subscribers cannot access cloud content at low latency. In a terrestrial wireless network, a high latency arises when there is network congestion or network overloading. The occurrence of network congestion results in a low aggregate throughput in the network segment as well as a high latency. Existing research has considered the use of unmanned aerial vehicles to enhance the capacity of existing terrestrial wireless networks in several contexts [46, 47, 50]. Hence, unmanned aerial vehicles are suitable for addressing the challenge by providing an alternative path for accessing cloud content. Hence, unmanned aerial vehicles provide a cyber-physical extension (window) into the cloud platform. The proposed cyber-physical cloud comprises a central cloud platform or data center with several cloud extensions (windows). The use of the cyber-physical cloud also enhances the ability of space tourists to access cloud content. In this case, the space tourist is in the terrestrial plane when the condition E1szlthis observed to hold true. Hence, the proposed cyber-physical cloud access system also enhances the provision of cloud based content to the internet.

In the cyber-physical cloud, the central cloud platform connects to the terrestrial wireless network and the cyber-physical windows as shown in Figure 4. In Figure 4, the cloud connects to either the aerial vehicle or the terrestrial wireless network. The subscribers desiring access to cloud based content are connected to the base station or the aerial vehicle. In the event that E1szlth, the notification is sent to the cloud and aerial vehicles are deployed.

Figure 4.

Incorporation of MAV and UAV into enabling cloud access.

The condition E1szlthis verified at the cloud platform using information on the latency associated with data reception by each individual desiring access to cloud content. Each subscriber receiving content from the cloud via own terminals send information on the latency associated with content reception to the cloud platform. The usage of the term aerial vehicle implies both manned aerial vehicles (MAVs) and unmanned aerial vehicles (UAVs). The joint usage differs from the approach where only UAVs are used in the system [54].

The sole use of UAVs in the absence of aerial diversity does not consider regional aviation safety concerns. The incorporation of MAVs with UAVs enables the use of aerial vehicles in a manner that meets aviation safety concerns. For example MAVs are human driven and can be used in areas with constraints on aviation safety. The MAV is an aerial vehicle with smaller dimensions than the conventional manned aircraft; it is equipped with a communication payload that enables data communication with the cloud platform.

In the cyber–physical cloud, the central cloud platform connects to the terrestrial wireless network and the cyber–physical windows as shown in Figure 4. In Figure 4, the cloud can connect to either the aerial vehicle or the terrestrial wireless network. The subscribers desiring access to cloud-based content are connected to the base station or the aerial vehicle. In the event that E1sz>lth, the notification is sent to the cloud and aerial vehicles are deployed.

The condition E1sz>lthis verified at the cloud platform using the information on the latency associated with data reception by each individual desiring access to cloud content. Each subscriber receiving content from the cloud via own terminals sends information on the latency associated with content reception to the cloud platform. The usage of the term aerial vehicle implies both MAVs and UAVs. The joint usage differs from the approach where only UAVs are used in the system [54]. The sole use of UAVs in the absence of aerial diversity does not consider stringent regional aviation safety concerns. The incorporation of MAVs with UAVs enables the use of aerial vehicles in a manner that meets stringent aviation safety concerns. For example, MAVs are human driven and can be used in areas with stringent constraints on aviation safety. The MAV is an aerial vehicle with smaller dimensions than conventional manned aircraft. It is equipped with a communication payload that enables data communication with the cloud platform.

4. Performance modeling and formulation

This section focuses on formulating the performance model of the proposed mechanisms. It is divided into two parts. The first part formulates the performance metrics of the mechanism enabling the internet access in space tourist applications. The second part formulates the performance analysis for the cyber-physical cloud system incorporating aerial diversity.

4.1 Performance model: pace tourist enabling mechanism

The formulated QoS metrics are the channel capacity and latency. The channel capacity for the space vehicle is formulated considering cases where the proposed handover mechanism is used and not used. The channel capacity achievable by the space vehicle in the terrestrial plane, aerial plane and space plane are denoted as Cter, Caeand Csprespectively and can be expressed as:

Cter=z=1zb=1dBzblog21+Ptrγbzh11γbz2Pintγbzh12γbz2+σ2E30
Cae=z=1zl=1hBzllog21+PtrϷlzh11Ϸlz2PintϷlzh12Ϸlz2+σ2E31
Csp=z=1zc=1nBzclog21+Ptrƿczh11ƿcz2Pintƿczh12ƿcz2+σ2;ƿcϵƿE32

Where:

zis the channel zwhich is distinct for each concerned communication entity.

Ptrγdz,PtrϷlzand Ptrƿczare the operational data transmit power between the space vehicle and (i) terrestrial wireless network on channel z, (ii) high altitude platform on channel zand (iii) communication satellite on channel zrespectively.

Pintγdz,PintϷlzand Pintƿczis the interference power between the space vehicle and (i) terrestrial wireless network on channel z, (ii) high altitude platform on channel zand (iii) communication satellite on channel zrespectively.

h11γdz,h11Ϸlzand h11ƿczare the transmit channel gain between the space vehicle and (i) terrestrial wireless network on channel z, (ii) high altitude platform on channel zand (iii) communication satellite on channel zrespectively.

h12γdz,h12Ϸlzand h12ƿczare the transmit channel gain between the space vehicle and (i) terrestrial wireless network on channel z, (ii) high altitude platform on channel zand (iii) communication satellite on channel zrespectively.

The average channel capacity of the space vehicle is denoted as Caveand given as:

Cave=13Cter+IγdϷlCae+I(Ϸlƿc)CspE33

Where:

IγdϷlϵ01is the handover indicator between γdand Ϸl. The cases IγdϷl=0and IγdϷl=1signify that a handover is not executed and is executed between γdand Ϸlrespectively.

IϷlƿcϵ01is the handover indicator between Ϸland ƿc. The cases IϷlƿc=0and IϷlƿc=1signify that a handover is not executed and is executed between Ϸland ƿcrespectively.

The latency associated with transmitting Dbytes of data without and with the incorporation of the proposed handover is denoted β1and β2respectively and given as:

β1=8×D×Cave1IγdϷl=0,IϷlƿc=0E34
β2=8×D×Cave1IγdϷl=1,IϷlƿc=1E35

The cases 8×D×Cave1IγdϷl=1,IϷlƿc=0and 8×D×Cave1IγdϷl=0,IϷlƿc=1have not been considered. This is because our discussion does not consider a partial handover as implied in the cases described by IγdϷl=1,IϷlƿc=0and IγdϷl=1,IϷlƿc=1. A partial handover results in a scenario where QoS of the space tourist subscribers suffer severe degradation due to frequent interruption.

4.2 Performance model: cyber-physical aided cloud access system

The deployment of either the UAV or MAV in the proposed cyber–physical cloud access system enables the delivery of cloud content when it could otherwise be challenging. This is due to the incidence of network congestion or any other event that could lead to high delay in the terrestrial wireless network segment. In the formulation, the cloud content traverses multiple cells in an infrastructure-based network. The occurrence of congestion on any of the forwarding network nodes increase the latency associated with accessing cloud content by remote subscribers. The probability of congestion on terrestrial wireless network γbwith own base station and associated gateway entity is denoted Pcoγb;γbϵγ. The probability of deploying either MAVs or UAVs that spans the coverage of γterrestrial wireless networks is denoted as Pcyγ. Given that the channel capacity of γbis denoted as Thγb; the aggregate channel capacity associated with cloud content without and with the cyber–physical system is denoted as Th1clγband Th2clγb, respectively.

Th1clγb=b=1fPcoγb×b=f+1dPcoγb×ThγbγbE36
Th2clγb=b=1fPcoγb×b=f+1dPcoγb+b=1fPcyγb×b=f+1dPcyγb×ThγbγbE37

5. Simulation and discussion of results

This section presents and discusses the simulation results and performance benefits of the proposed mechanisms. It is divided into three parts. The first part presents the simulation parameters for the proposed mechanisms. The second part presents results indicating the performance of the space tourist subscriber. The third part presents results on the proposed cyber-physical aided cloud system.

5.1 Simulation parameters

The simulation parameters used to investigate the performance benefit of the handover mechanism for the space tourist subscriber are shown in Table 3. The parameters used to investigate the performance of the cyber – physical cloud access system are shown in Table 4.

S/NParameterValue
1Mean of transmit power Ptrγdzfor the space vehicle.202.9 mW
2Mean of interference power for space vehicle in terrestrial plane, Pintγdz10.3 mW
3Channel bandwidth in terrestrial plane, Bzb1.5 MHz
4Number of channels that are simultaneously accessed in terrestrial plane4
5Mean of transmit power of space vehicle in aerial plane, PtrϷlz313 mW
6Mean of interference power of space vehicle in aerial plane, PintϷlz38.9 mW
7Channel bandwidth in aerial plane2.25 MHz
8Number of channels that are simultaneously accessed in aerial plane4
9Mean of space vehicle transmit power Ptrƿczin space plane.227.6 mW
10Average space vehicle interferer power in space plane,PintϷcz32.6 mW
11Channel bandwidth in space plane5 MHz
12Number of channels that are simultaneously accessed in space plane4

Table 3.

Parameters used to investigate the performance of the handover mechanism.

Epoch 1Epoch 2
Base station indexMean congestion probabilityMean MAV, UAV deployment probabilityMean backhaul throughput (Gbps)Mean congestion probabilityMean MAV, UAV deployment probabilityMean backhaul throughput (Gbps)
10.38880.568535.32790.36640.441129.3312
20.76270.617529.55020.50610.460034.6044
30.59620.426719.50830.53520.551029.7344
40.77230.549521.45680.72740.570942.5083
50.61860.571222.36930.53340.534228.5267
60.64300.417635.39910.52300.631922.5061
70.39110.592730.03740.31450.614134.6840
80.31090.492831.49550.49690.548627.6927
90.49910.441121.97820.22910.441325.4814
100.59530.433649.27610.27470.407241.4290
110.44210.579128.44920.55750.651333.4003
120.60490.498641.89640.17300.599641.9393
130.35880.465413.72610.15030.261712.4052
140.52730.381128.55710.45340.342525.8474
150.55280.643745.37980.50480.506138.7138
160.63400.328211.05720.32330.59008.7650
170.37550.486925.04080.39630.530029.4266
180.58430.482034.97770.60280.455629.6869
190.38430.579230.55580.53040.517737.5723
200.57940.463229.20890.56550.556235.5610
210.67850.460031.29130.54640.588125.5595
220.26950.436937.43730.68590.604738.6078
230.59350.455040.73900.55820.403429.8772
240.34680.587535.41070.44120.486238.5071
250.44910.457239.02790.36550.482733.7495
260.42120.588127.45720.27940.567934.3914
270.49290.559830.89140.57230.508025.5206
280.53010.399634.46660.52080.606533.9866
290.51380.548221.82940.30150.517729.1524
300.46200.501842.41020.47370.494851.8990
310.54260.505018.77300.65040.393115.3598
320.60050.421535.48990.50520.553728.0000
330.18180.606138.95590.19640.578739.6352
340.53600.620210.58870.51370.62826.8601
350.58480.416235.92820.44190.507629/9443
360.21030.509922.94080.49890.624738.3689
370.22270.674221.72250.57900.560044.0250
380.70690.608637.31770.65960.442127.1582
390.42960.683239.03510.44960.670934.6300
400.45390.436834.18600.47930.644236.4133

Table 4.

Simulation parameters – cyber – physical aided cloud access mechanism.

5.2 Discussion of results – space tourist

The results of performance simulation are presented in this subsection. The performance benefit of the proposed handover mechanism is investigated using the channel capacity and latency as metrics. In addition, the performance benefit of incorporating aerial diversity is investigated using the aggregate channel capacity. The proposed aerial diversity mechanism is used to improve access to cloud content in terrestrial wireless networks.

Simulation result for the space vehicle average channel capacity is presented in Figure 5. Figure 5 shows two sub-figures, i.e. a and b. The average channel capacity before and after the incorporation of the proposed handover mechanism is presented in Figure 5a and b, respectively. Analysis of the result shows that the incorporation of the proposed mechanism enhances channel capacity. This is because of the continuity in data transmission during space vehicle sojourn. It is observed from the results that the channel capacity is enhanced on average by 18.4%.

Figure 5.

Average channel capacity of the space vehicle before and after introducing the proposed scheme. (a) Average channel capacity achieved by space vehicle in Mbps in the absence of the proposed handover mechanism. (b) Average channel capacity achieved by space vehicle in Mbps after introducing the proposed handover mechanism.

The result for the latency of the space vehicle is presented in Figure 6a and b. Figure 6a and b shows the latency without and with the proposed mechanism, respectively. Results show that the proposed mechanism reduces the latency associated with accessing cloud content by the space vehicle. Analysis shows that the proposed handover mechanism reduces latency on average by 12%.

Figure 6.

Average latency of the space vehicle before and after introducing the proposed scheme. (a) Average latency achieved by space vehicle without the proposed handover mechanism. (b) Average latency achieved by space vehicle after the incorporation of the proposed handover mechanism.

The investigation also examines how aerial diversity enhances cloud content access. The use of aerial diversity ensures that network congestion does not affect the ability of the space vehicle subscriber to access cloud content. The metric used to investigate the performance benefit of incorporating aerial diversity is the aggregate channel capacity. This is the achieved channel capacity when the access of cloud content requires communications between multiple base stations. This is investigated using the parameters in Table 4. The aggregate channel throughput obtained via simulations for two epochs (i.e. epoch 1 and epoch 2) is shown in Table 5.

Aggregate channel capacity (bits per second)
Epoch 1Epoch 2
Number of base stationsWithout aerial diversityWith aerial diversityWithout aerial diversityWith aerial diversity
26.76 × 1043.85 × 1041.88 × 1053.94 × 105
41.61 × 10111.56 × 10128.78 × 10121.72 × 1013
61.73 × 10194.10 × 10191.73 × 10203.54 × 1020
83.33 × 10267.87 × 10261.89 × 10275.75 × 1027
104.45 × 10331.23 × 10341.10 × 10345.44 × 1034
121.01 × 10411.92 × 10412.05 × 10411.15 × 1042
145.74 × 10471.10 × 10483.82 × 10473.45 × 1048
166.40 × 10541.66 × 10557.47 × 10546.75 × 1055
189.49 × 10612.62 × 10628.71 × 10611.02 × 1063
201.18 × 10693.34 × 10691.74 × 10691.99 × 1070
221.16 × 10763.02 × 10762.42 × 10762.98 × 1077
241.94 × 10834.54 × 10834.04 × 10833.71 × 1084
263.17 × 10906.85 × 10908.46 × 10907.67 × 1091
289.40 × 10891.53 × 10901.26 × 10901.42 × 1091
309.40 × 10891.18 × 10971.26 × 10902.07 × 1098
327.64 × 10969.06 × 101031.11 × 10971.29 × 10105
345.85 × 101039.87 × 101101.11 × 101042.80 × 10112
365.74 × 101102.17 × 101258.62 × 101106.46 × 10126
381.31 × 101255.59 × 101321.74 × 101251.59 × 10134
403.69 × 101327.34 × 101394.43 × 101323.67 × 10141
Mean improvement in aggregate channel capacity70.3634%Mean improvement in aggregate channel capacity85.1583%

Table 5.

Aggregate Channel capacity before and after incorporating aerial diversity.

The simulation results in Table 5 show that incorporating aerial diversity enhances the aggregate channel capacity. The incorporation of aerial diversity enables the delivery of cloud content when the terrestrial wireless network experiences congestion. The aggregate channel capacity is increased as aerial diversity influences data transmission for an increasing number of base stations. This is because the MAV and UAV are deployed in a manner that enables the delivery of cloud content for a larger terrestrial wireless network coverage area. Therefore, aerial diversity enhances the aggregate channel capacity associated with accessing cloud content by the space vehicle subscribers as seen in epochs 1 and 2. Aerial diversity enhances the aggregate channel capacity by 70.4 and 85.2% on average at epoch 1 and epoch 2, respectively.

6. Conclusion

This paper has proposed a distributed handover algorithm (DHA) for a network comprising terrestrial, aerial and space-based segments. DHA enables aerial platform to satellite handover and suborbital intersatellite handover in a space vehicle. The network uses ground stations deployed for radio astronomy. Simulation shows that DHA enhances channel capacity and reduces latency by 18.4 and 11.6% on average, respectively. The paper also proposed the joint use of manned and unmanned aerial vehicles for improving accessibility to cloud content while minimizing aviation safety concerns. The aerial vehicles are deployed when cloud access via terrestrial wireless networks is subject to significant latency due to network congestion. Simulations show that using aerial diversity reduces the effect of network congestion on terrestrial wireless networks. The aggregate throughput achieved on the terrestrial wireless network increases by up to 85% on average.

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Ayodele Abiola Periola (December 9th 2019). Lunar Science: Internet for Space Tourism [Online First], IntechOpen, DOI: 10.5772/intechopen.89124. Available from:

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