**1. Introduction**

A vehicular communication system is one of the key components of intelligent transportation and traffic management systems. Advanced traffic management systems are expected to improve traffic flow, reduce congestions and accidents, and optimize the energy consumption of vehicles. Vehicular communication systems should enable just in time data exchange mechanisms among different elements of traffic management. Early versions of the vehicular networks were developed primarily to support V2V communications which are now evolving to vehicle-toeverything (V2X) communications mode [1]. A V2V system enables vehicles to exchange messages within the close vicinity of a Host Vehicle (HV), whereas the V2X service enables the vehicle to exchange information among any data devices in

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*Moving Broadband Mobile Communications Forward - Intelligent Technologies for 5G…*

non-terrestrial networks (NTN)

[11] Boeing Seeks Permission to Launch Satellite Constellation in Same V-Band Spectrum as 5G Systems. Available from: https://www.fiercewireless.com/ tech/boeing-seeks-permission-tolaunch-satellite-constellation-same-vband-spectrum-as-5g-systems/

[12] Boeing Company. Application for Authority to Launch and Operate a Non-Geostationary Low Earth Orbit Satellite Systemin the Fixed Satellite Service. FCC, [Accessed: June 22, 2016]

[13] SaT5G Project Demonstrates 5G over Satellite and Holds Industry Briefing at University of Surrey. Available from: https://www.sat5g-project.eu/ sat5g-industry-day-27-november

(Release 16)

[1] The European Space Agency Will Promote Satellite 5G Internet. Available from: http://mediasat.info/2017/06/23/

[2] CEPT ECC Report "Satellite Solutions

for 5G". Approved: May 18, 2018

[3] 3GPP TR 22.822. 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on Using Satellite

Access in 5G; Stage 1 (Release 16)

[4] 3GPP TR 38.913. 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Study on Scenarios and Requirements for Next Generation Access Technologies; (Release 15)

[5] Recommendation ITU-R M.2083. IMT Vision-"Framework and overall objectives of the future development of IMT for 2020 and beyond". Accessed:

[6] 3GPP TR 22.737. 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on architecture aspects for using satellite access in 5G

[7] Khan F. Mobile Internet from the Heavens. Richardson, Texas, USA:

[8] Eneberg J. Satellite Role in 5G,

[9] 3GPP TR 38.104. 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Architecture

[10] 3GPP TR 38.821. 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Solutions for NR to support

Samsung Electronics; 2015

description (Release 15)

September 2015

(Release 16)

Inmarsat; 2017

esa-satellite-for-5g/

the vehicular network or in the infrastructure network. The enhanced features of vehicular networks are increasing the need for more flexible communication network architecture that can support diversified services, from time-critical safety services to high data rate entertainment services. The time-critical safety services are key features of the vehicular networks to reduce traffic accidents and offer better road safety services. Hence the role of the communication network will be crucial in a vehicular network.

The vehicular ad hoc network (VANET) architecture was initially developed using the dedicated short-range communication (DSRC) and the IEEE 802.11p networking standards [2]. The main objective of the VANET is to support V2V and vehicle-to-infrastructure (V2I) communication modes. The IEEE 802.11p network uses the random-access medium access control protocol carrier-sense multiple access with collision avoidance (CSMA/CA) to support V2V and V2I services. The advantages of the CSMA/CA protocol are in its simplicity, minimum control signaling, and the broadcast nature of transmission. These enable low packet transmission delay at lower teletraffic load. However, due to the lack of coordination among transmitters, packet collisions can occur which can increase the packet transmission delay as well as reduce the packet delivery ratio. Also, the performance of an IEEE 802.11p network is affected by the network node densities which could vary on roads depending on the road layout, congestions, and time of the day. Hence the main bottlenecks of an IEEE 802.11p vehicular network are the scalability and lack of adequate Quality of Service (QoS) support for a different class of services. However, the IEEE 802.11p standard-based vehicular network technology has matured, and many commercial products are now available [3, 4]. With the introduction of 5G technologies, the transportation and ICT industries have refocused their attention to developing new systems and products mainly relying on the Long Term Evolution (LTE)-based technologies [5].

support V2X services which encompass three modes of communications: V2V, V2I, and vehicle-to-pedestrian (V2P) in Release 14. To support vehicular networking requirements, the standard has developed a new channel architecture using the PC5 interface. The standard also supports the conventional Uu interface for different vehicular services. The PC5 interface includes the sidelink which has D2D communication abilities developed under Release 12 of the LTE standard. Release 12 was mainly developed for public safety applications. The V2X communication services are being enhanced in the LTE Release 15 and will be further enhanced in

*An LTE-Direct-Based Communication System for Safety Services in Vehicular Networks*

*DOI: http://dx.doi.org/10.5772/intechopen.91948*

In this chapter, we firstly review the vehicular networking and service requirements. Following the review of networking and service requirements, we briefly review the LTE-V/LTE-V2X standard. The discussion then focuses on our new algorithm referred to as Cluster-Based Cellular Vehicle-to-Vehicle (CBC-V2V) combined with a new peer discovery model referred to as Evolved Packet Core Level Sidelink Peer Discovery (ESPD). The chapter also presents the performance analysis of the CBC-V2V algorithm and compares the performance of the algorithm with other standard algorithms. In Section 2, we present the review on future vehicular network requirements. In Section 3, we briefly introduce the LTE-V/VX standard. In Section 4, our proposed LTE standard-based vehicular network resource allocation algorithm is presented. In Section 5, we present the simulation model developed to analyze the performance of the CBC-V2V algorithm. Conclu-

Traffic management systems are constantly evolving to improve road traffic services and the safety of road users. Recently, the 3GPP introduced a number of vehicular network use cases in the LTE-V2V Release 14 [7] for future vehicular networks. The study showed that the vehicular network requirements have evolved over time. In early days, vehicular networks were developed mainly to support safer vehicle movements and reduce traffic congestion. However, future vehicular networks are planning to support a range of basic and enhanced services. Some of the future suggested services are listed below. The following list shows that future vehicular network requirements have been extended to include several smart city services such as parking management services, pedestrian and vulnerable road user

safety. These services need to be supported by four different network

Release 16.

**101**

**Figure 1.**

*LTE network architecture.*

sions are drawn in Section 6.

**2. Future vehicular network requirements**

The LTE standard is commonly used as the 4G broadband wireless technology which is further evolving as one of the major components of the 5G technology [6]. The LTE is a wide-area wireless networking technology standard that uses the conventional cellular network architecture and uses direct radio communication between the user equipment (UE) and the base station commonly known as the eNodeB (eNB) as shown in **Figure 1**. The Enhanced UMTS Terrestrial Radio Access Network (E-UTRAN) represents the radio access network where the eNB and user equipment (UE) are located. The Evolved Packet Core Network (EPC) connects the radio access networks and the external network such as the Internet. The core network hosts various control entities, databases, and functional servers. Cellular networks have several benefits such as wide-area coverage, high data rate, and guaranteed QoS for multiple services. However, the conventional centralized cellular networks are not always suitable for vehicular networks to support some of the services particularly for distributing time-sensitive broadcast services such as the Cooperative Awareness Message (CAM). In a conventional cellular network, all data communication between devices must go through the eNB, irrespective of whether they are located next to each other or at a long distance. The CAMs are transmitted from each vehicle to its neighboring vehicles to distribute situational awareness information.

The CAMs are periodic messages that have a 10 Hz generation frequency with latency restrictions of 100 ms. In the 802.11p-based VANET, the CAM messages are broadcasted to the neighboring vehicles using the CSMA/CA protocol. Generally, conventional cellular networks can support unicast, broadcast, and multicast communications; however, these configurations are not suitable for the CAM message transmissions due to high signaling overhead. To accommodate the needs of vehicular networks, the 3GPP has started to standardize the LTE-V standard to

*An LTE-Direct-Based Communication System for Safety Services in Vehicular Networks DOI: http://dx.doi.org/10.5772/intechopen.91948*

**Figure 1.** *LTE network architecture.*

the vehicular network or in the infrastructure network. The enhanced features of vehicular networks are increasing the need for more flexible communication network architecture that can support diversified services, from time-critical safety services to high data rate entertainment services. The time-critical safety services are key features of the vehicular networks to reduce traffic accidents and offer better road safety services. Hence the role of the communication network will be

*Moving Broadband Mobile Communications Forward - Intelligent Technologies for 5G…*

The vehicular ad hoc network (VANET) architecture was initially developed using the dedicated short-range communication (DSRC) and the IEEE 802.11p networking standards [2]. The main objective of the VANET is to support V2V and vehicle-to-infrastructure (V2I) communication modes. The IEEE 802.11p network uses the random-access medium access control protocol carrier-sense multiple access with collision avoidance (CSMA/CA) to support V2V and V2I services. The advantages of the CSMA/CA protocol are in its simplicity, minimum control signaling, and the broadcast nature of transmission. These enable low packet transmission delay at lower teletraffic load. However, due to the lack of coordination among transmitters, packet collisions can occur which can increase the packet transmission delay as well as reduce the packet delivery ratio. Also, the performance of an IEEE 802.11p network is affected by the network node densities which could vary on roads depending on the road layout, congestions, and time of the day. Hence the main bottlenecks of an IEEE 802.11p vehicular network are the scalability and lack of adequate Quality of Service (QoS) support for a different class of services. However, the IEEE 802.11p standard-based vehicular network technology has matured, and many commercial products are now available [3, 4]. With the introduction of 5G technologies, the transportation and ICT industries have

refocused their attention to developing new systems and products mainly relying on

The LTE standard is commonly used as the 4G broadband wireless technology which is further evolving as one of the major components of the 5G technology [6]. The LTE is a wide-area wireless networking technology standard that uses the conventional cellular network architecture and uses direct radio communication between the user equipment (UE) and the base station commonly known as the eNodeB (eNB) as shown in **Figure 1**. The Enhanced UMTS Terrestrial Radio Access Network (E-UTRAN) represents the radio access network where the eNB and user equipment (UE) are located. The Evolved Packet Core Network (EPC) connects the radio access networks and the external network such as the Internet. The core network hosts various control entities, databases, and functional servers. Cellular networks have several benefits such as wide-area coverage, high data rate, and guaranteed QoS for multiple services. However, the conventional centralized cellular networks are not always suitable for vehicular networks to support some of the services particularly for distributing time-sensitive broadcast services such as the Cooperative Awareness Message (CAM). In a conventional cellular network, all data communication between devices must go through the eNB, irrespective of whether they are located next to each other or at a long distance. The CAMs are transmitted from each vehicle to its neighboring vehicles

The CAMs are periodic messages that have a 10 Hz generation frequency with latency restrictions of 100 ms. In the 802.11p-based VANET, the CAM messages are broadcasted to the neighboring vehicles using the CSMA/CA protocol. Generally, conventional cellular networks can support unicast, broadcast, and multicast communications; however, these configurations are not suitable for the CAM message transmissions due to high signaling overhead. To accommodate the needs of vehicular networks, the 3GPP has started to standardize the LTE-V standard to

the Long Term Evolution (LTE)-based technologies [5].

to distribute situational awareness information.

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crucial in a vehicular network.

support V2X services which encompass three modes of communications: V2V, V2I, and vehicle-to-pedestrian (V2P) in Release 14. To support vehicular networking requirements, the standard has developed a new channel architecture using the PC5 interface. The standard also supports the conventional Uu interface for different vehicular services. The PC5 interface includes the sidelink which has D2D communication abilities developed under Release 12 of the LTE standard. Release 12 was mainly developed for public safety applications. The V2X communication services are being enhanced in the LTE Release 15 and will be further enhanced in Release 16.

In this chapter, we firstly review the vehicular networking and service requirements. Following the review of networking and service requirements, we briefly review the LTE-V/LTE-V2X standard. The discussion then focuses on our new algorithm referred to as Cluster-Based Cellular Vehicle-to-Vehicle (CBC-V2V) combined with a new peer discovery model referred to as Evolved Packet Core Level Sidelink Peer Discovery (ESPD). The chapter also presents the performance analysis of the CBC-V2V algorithm and compares the performance of the algorithm with other standard algorithms. In Section 2, we present the review on future vehicular network requirements. In Section 3, we briefly introduce the LTE-V/VX standard. In Section 4, our proposed LTE standard-based vehicular network resource allocation algorithm is presented. In Section 5, we present the simulation model developed to analyze the performance of the CBC-V2V algorithm. Conclusions are drawn in Section 6.

### **2. Future vehicular network requirements**

Traffic management systems are constantly evolving to improve road traffic services and the safety of road users. Recently, the 3GPP introduced a number of vehicular network use cases in the LTE-V2V Release 14 [7] for future vehicular networks. The study showed that the vehicular network requirements have evolved over time. In early days, vehicular networks were developed mainly to support safer vehicle movements and reduce traffic congestion. However, future vehicular networks are planning to support a range of basic and enhanced services. Some of the future suggested services are listed below. The following list shows that future vehicular network requirements have been extended to include several smart city services such as parking management services, pedestrian and vulnerable road user safety. These services need to be supported by four different network

configurations, i.e., V2V, V2I, V2P, and Vehicle-to-Network (V2N). Some of the service characteristics are briefly summarized in **Table 1**.

**Service Main purpose Communication mode Service requirements**

*An LTE-Direct-Based Communication System for Safety Services in Vehicular Networks*

mode

HV and RV

services

LTE-D2D

V2V and V2I

HV and RV communicate using V2V transmission

communication using V2V

V2V communication using

Mainly V2V services, but V2X communication can also be used to obtain forward traffic flow information

communication services

RSU-based I2V and V2I

services

Periodic broadcast CAM message, support high mobility, early warning

Communicate messages over a distance to generate warning message with ample time to respond. Event-based broadcast

Event-based CAM message broadcast to cars within 300–500 meters

The service can support a maximum latency of 1 sec and a maximum frequency of one message per second

Able to transmit and receive V2I messages with a maximum relative velocity of 160 km/h. Support an appropriate communication range necessary for early

delivered within 100 ms via an RSU with low delivery loss. An RSU should be able to transmit V2X messages at a maximum frequency of

I2V message transmission with a maximum latency of 1 sec and maximum frequency of one message

warning

10 Hz

per second

V2X and V2I services A V2X message should be

message

message

The FCW service has been proposed to warn the driver of a host vehicle (HV) about an impending rear end collision with a remote vehicle (RV) or vehicles. The FCW service can help reduce collisions

*DOI: http://dx.doi.org/10.5772/intechopen.91948*

The CLW service enables an HV to broadcast selfgenerated loss of control message to RVs. Upon receiving the message, RVs warn drivers for appropriate

This service enables all vehicles to acquire location, speed, and direction information of surrounding emergency vehicle(s) to assist smooth movement of emergency vehicles

The CACC service provides convenience and safety benefits to group of vehicles in close vicinity. Can be used for platooning structure

This service allows vehicles to receive forward road queue warning messages. Road user safety can be significantly increased by using this service

Using this service, V2X messages are delivered from an UE to other UEs via an installed Road Side Unit.

This application sends alert messages to the driver to manage possible blind spot or the curve at an appropriate speed. An RSU is placed before a curve to transmit information such as curve location, recommended speed, curvature, and road surface

conditions

action(s)

Forward collision warning

Control loss warning

Emergency vehicle warning

Cooperative Adaptive Cruise Control (CACC)

Queue warning

Road safety services

Curve speed warning

**Table 1.**

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*Service characteristics.*


**Table 1** shows that communication needs and service requirements of future vehicular networks are quite diverse with variable QoS requirements. It is expected that over time, the service categories will grow, and their requirements will evolve. To support the above multiservice requirements, the current IEEE 802.11p networks will not be adequate due to higher traffic volume and inadequate QoS support for multiservice networks. Also, some of the services such as emergency vehicle warning or curve speed warning may need longer transmission ranges and may also increase the collision probability in CSMA/CA-based IEEE 802.11p networks. Another important consideration for the future vehicular network is the support of autonomous vehicles that require low delay and low loss reliable communication networks. Hence, the main objective of the LTE-V/LTE-V2X standard is developing an advanced cellular-based vehicular network. In the following section, we review the LTE-V2X standard based on Release 14.


*An LTE-Direct-Based Communication System for Safety Services in Vehicular Networks DOI: http://dx.doi.org/10.5772/intechopen.91948*

**Table 1.** *Service characteristics.*

configurations, i.e., V2V, V2I, V2P, and Vehicle-to-Network (V2N). Some of the

*Moving Broadband Mobile Communications Forward - Intelligent Technologies for 5G…*

service characteristics are briefly summarized in **Table 1**.

• Cooperative Adaptive Cruise Control (CACC)

• Forward collision warning (FCW)

• Control loss warning (CLW)

• Emergency vehicle warning

• V2V emergency stop

• V2I emergency stop case

• Automated parking system (APS)

• Wrong-way driving warning (WDW)

• V2X services in areas outside network coverage

we review the LTE-V2X standard based on Release 14.

**Table 1** shows that communication needs and service requirements of future vehicular networks are quite diverse with variable QoS requirements. It is expected that over time, the service categories will grow, and their requirements will evolve. To support the above multiservice requirements, the current IEEE 802.11p networks will not be adequate due to higher traffic volume and inadequate QoS support for multiservice networks. Also, some of the services such as emergency vehicle warning or curve speed warning may need longer transmission ranges and may also increase the collision probability in CSMA/CA-based IEEE 802.11p networks. Another important consideration for the future vehicular network is the support of autonomous vehicles that require low delay and low loss reliable communication networks. Hence, the main objective of the LTE-V/LTE-V2X standard is developing an advanced cellular-based vehicular network. In the following section,

• V2X road safety services via infrastructure

• Queue warning

• Road safety services

• V2X message transfer

• Pre-crash sensing warning

• V2N traffic flow optimization

• Warning to pedestrian messaging

• Vulnerable road user (VRU) safety

• Curve speed warning

**102**

communication services. The ProSe function allows users to directly communicate and exchange data with neighboring devices by sending a registration message to the eNB with a ProSe application ID. The eNB organizes the communication between the devices using the control channels. Once the communicating devices are matched by the eNB, then they can directly communicate using the PC5 interface as shown in **Figure 3**. The PC interface functions are summarized in **Table 2**.

*An LTE-Direct-Based Communication System for Safety Services in Vehicular Networks*

The channels in the Uu and PC5 interfaces are organized as logical, transport, and physical channels. **Figure 4** shows the mapping structure of these channels used for the sidelink communication in the LTE standard. There are two logical channels introduced for sidelink communication: first is the SL Traffic Channel (STCH), and second is SL Broadcast Control Channel (SBCCH). The STCH is an interface to the Physical SL shared Channel (PSSCH), which transports the data carrying user information over the air. The SBCCH is used to broadcast control data, for synchronization in the out of coverage or partial coverage, or for the synchronization between UEs which are located in different cells. There is also a Transport and Physical Sidelink Control Channel carrying the SL control information (SCI). There is a new transport and physical channel for direct discovery: sidelink discovery channel (SL-DCH) and the physical sidelink discovery channel

Details of these interfaces can be found in [10].

*DOI: http://dx.doi.org/10.5772/intechopen.91948*

(PSDCH).

**Figure 3.**

**Table 2.** *PC interfaces.*

**105**

*LTE release 12 D2D reference network architecture [9].*

through the interface

PC1 The ProSe application server can communicate towards a ProSe application in the UE

PC2 The ProSe application server can communicate with the ProSe function through this

PC4 The ProSe function connects with Evolved Packet Core in the network through PC4

PC3 The ProSe function can connect to the UE through the PC3 interface

PC5 A PC5 interface enables direct communication between two UEs

**Interface Main functions**

interface

interface
