Challenges And Solutions Towards 5g Implemntation

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Recent Advances in 5G Technologies: New Radio Access and Networking

Challenges And Solutions Towards 5G Implementation

Ionel Petrut

Communications Department, Politehnica University, Lasting Software Timișoara, Romania

[anonimizat]

Georgeta Budura, Cornel Balint, Marius Otesteanu

Communications Department, Politehnica University, Timișoara, Romania

{georgeta.budura; cornel.balint; marius.otesteanu}@upt.ro

Abstract

The new 5G network is expected to enable connectivity anytime, to anyone and anywhere. Considering the details of 5G requirements and characteristics are still a subject of debate and research, this paper provides an analysis of the challenges 5G networks face and their essential requirements. As some aspects cannot be accommodated by the 4G networks, the main purpose of the 5G network is to be a better network, free from limitations, who is going to change the way most users access the network.

Introduction

It is not a secret anymore that we live in a widely connected world, which is becoming even more and more connected with every day that passes. In fact we are currently witnessing the impact of society`s development onto the way in which mobile and wireless communication systems are being used.

Essential services, such as e-banking, e-learning and e-health, will continue to proliferate and become more and more mobile. Thus, on-demand information and entertainment, such as augmented reality, will be delivered in the future over a big range of mobile and wireless communications systems. As a consequence, the users will be downloading an increasing number of mobile apps which each year that passes. Statistics predict that the number of mobile users worldwide will most likely be double until 2020, increasing to 9 billion people, considering the number of mobile devices in use at the moment.

Furthermore, mobile connections are not being made by just the people communicating, but are made more and more by machines. These machines, such as sensors and meters and Internet of Things (IoT) devices with embedded electronics, software and sensors can collect and transfer important data over a network. Some examples of IoT devices include implantable or wearable health and fitness devices, smart thermostats and lights, as well as manufacturing maintenance and repair sensors. The International Data Corporation (IDC) predicts that the Internet of Things installation base will continue to climb from 9.1 billion devices in 2013 to approximately 28.1 billion devices in 2020.

The coexistence of human-centred and machine-type mobile and wireless applications will result in a large diversity of communicational characteristics. The result of more smart devices and more device types is the existing of more connections, mobile applications and mobile data traffic with diverse requirements.

While examining the requirements and solutions for the 5G network, we can exercise and work on a plan for a network evolution that spans over several years. Past generations have been identified by a major new technology step, such as the definition of a new air interface, the expectation is that the 5G network will be approached from an end-to-end system perspective and will include major technology steps regarding radio access network and core-network.

Statistics predict that mobile data traffic will continue to increase from 2.5 exabytes per month in 2014 to 24.3 exabytes per month in the year 2019 [1]. A large variety of these mobile and wireless applications can be supported by the existing mobile broadband networks. However, new applications will demand for additional diverse requirements on mobile and wireless communication systems that the fifth generation wireless networks (also known as 5G technology) will have to support.

Materials and Methods

The purpose of this article is to make an overview over the status of the current advancement towards 5G`s development and what can be expected when 5G technologies will be implemented in the next years, whilst making a study of the challenges that 5G will bring and giving relevant solutions to those challenges. The wireless networks if the future should be able to offer wireless access to pretty much anyone and anything. Wireless access will continue to go beyond human beings and will expand in order to serve any device that may benefit from being connected to the internet. The free wireless connection vision is being known as the Internet of Things or as the Networked Society, but no matter the name, this vision benefits machine-to-machine communication (M2M) [2].

The work on 5G technologies is still in its early stages regarding the requirements and the component technologies. While defining the 5G requirements, without having any actual technology developed, cautious must be taken because some of the requirements may not be feasible in the specified timeframe.

Definitions for the 5G or for its requirements are not available. However, the complex requirements like the need to support a big number of devices that are always connected, energy efficiency and support of flexible interfaces can`t be achieved just by modifying the current systems. Some of the 5G requirements ask for the network to come up with new protocols or even new access technologies. One of the main challenges that appear is to satisfy the new requirements, while at the same time, address the costs that occur. Efficiency and scalability are the key design criteria, reflecting the need to respond to the traffic explosion and the high number of connected devices. The requirements for a 5G network are listed below.

1. User-Driven Requirements

1.1. Battery Life. Some of the IoT applications may involve battery operated sensor that are out there in the field and only occasionally transmit data. Wide-scale deployment of a 5G sensor based network would be possible only if the battery life of the devices will be increased or the energy consumption will be reduced.

1.2. Per-User Data Rate and Latency. The latency attributes define the typical data rate and the round-trip delay, the user’s experience. The values recorded for the latency attributes determine what applications are supported on a certain network.

1.3. Robustness and Resiliency. The 5G system will be used in the future as the primary source for communicating and as a replacement network for Public Switched Telephone Network. The 5G will also support emergency communications and public safety, as the key requirements is for the respective network to be robust, very reliable and also resilient.

The requirements would need to ensure the ability to defend the system against security attacks for mission-critical applications like public safety, smart grids, along with gas and drinking water distribution networks.

1.4. Mobility. The 5G systems are expected to support high-mobility scenarios, as well as low-mobility ones [3]. The machine-type communicating devices can require access to a network with the only purpose of sending a reduced amount of data. For these devices, reliability and resilience is the most important feature, even more important than mobility.

1.5. Seamless User Experience. The 5G systems will most likely contain layers, technologies and frequency bands that will work excellent when moving across networks, layers and frequencies. Interruption times of a few milliseconds for both inter-Radio Access Technology (inter-RAT) and intra- Radio Access Technology (intra-RAT) can be expected. Essential services like ultra-high definition video streaming or tactile devices will require end-to-end latencies of 1 millisecond at most.

1.6. Context-Aware Network. A context-aware network can be possible only if that network is context-aware and can dynamically adapt to meet those requirements. Full mobility doesn’t need to be provided to the Machine Type Communication (MTC) devices that are stationary.

Furthermore, the 3rd Generation Partnership Project (3GPP) mobility management and paging doesn’t need to provide full mobility for services that require device-initiated communication. Mobile operators will gain additional abilities, much needed in order to create customizable service plans for customers.

For example, the mobile operators will be requested to create one set of service plans for MTC customers, because they use a small amount of resources and a second set of service plans for smartphone users, because they use a large amount of network resources.

2. Network-Driven Requirements

In the last decades, the mobile communication systems have had a big significant contribution to the economic and social development of the world`s countries. The next figure summarizes the recent market trends, the high-level targets most relevant for 5G.

Fig. 1. Targets for 5G systems

2.1. Higher Data Rates. The 5G systems needs to provide higher data rates, especially when taking into account the rising trends of richer content and cloud service, it is a fact that 5G needs to provide higher data rate services along with a more uniform Quality of Service (QoS). The QoS can be achieved only through the improvement of the maximum data rate and equity in the user throughput.

2.2. Scalability. Providing support for the IoT devices is the key to 5G network`s success. An expected increase in the number of smart devices requires network elements that can scale up gracefully in order to handle the enormous growth. The 5G network should be able to scale well to handle traffic, such as the kind of traffic necessary for authorizing a large number of smart devices.

The 5G networks should be able to support both high-data-rate and low-latency conventional services alongside M2M applications that require lower bandwidth. Both frequent and interrupted data transmission will be needed in order for the transmission to be supported in an efficient manner. The devices in 5G networks will be stationary devices or nomadic devices that will not require mobility support or will require occasional support. The networks should not assume mobility support is necessary for all smart devices, but they will have to provide mobility support to those devices that need it.

2.3. Network and System Capacity. Due to the increase of mobile data traffic, the volume of data traffic is expected to be larger in 2020, compared to its values in 2010 [4]. That being said, 5G systems need to be able to manage the increasing traffic, an important challenge that for 5G. In order to handle this explosive traffic increase, an important requirement for 5G networks is to increase the traffic handling capacity of the while maintaining the Quality of Service.

2.4. Reduced Cost, Higher Energy Efficiency and Robustness against Emergencies. The 5G systems have to be able to provide an increased capacity per unit network cost and energy-efficiency while maintaining resilience to disasters. Even though cost reduction and energy-efficiency are not easily measurable, they should be taken into account as much as possible in the whole system designed.

Considering the expected traffic increase and the need to remain competitive, the 5G networks should be able to provide a significant improvement cost benefit over the existing generation of networks. Rather than maximizing spectral efficiency, there is a concern regarding the energy consumption per bit, in terms of energy efficiency. Network functions should not transmit excessive energy, as energy consumption can be easily adapted to the current traffic conditions in order to achieve energy saving.

2.5. Automated System Management and Configuration. When deploying the 5G network, the density of the network will most likely increase significantly for reasons like higher data volume density and higher frequency spectrum usability. In order to better manage Capital Expenditure and Operating Expenses of running a network with a higher number nodes, an important requirement is that the networks are able to self-configure.

2.6 Network Flexibility and Support for Massive Connectivity. The 5G networks should allow the Radio Access Network and the core network to evolve and scale in an independent way. If we want to achieve this goal, the RAN and the core network should avoid mutual dependencies. Revisiting the current architecture can help minimize interdependency between them. One of the important 5G requirements is that the network needs to allow a big number of smart devices to be connected simultaneously, in order to support the connected cloud services even in a crowded situation.

2.7 Reduced RAN Latency. The 5G technologies have to provide higher data, but also a user-plane latency of less than 1ms over the Radio Access Network, a huge improvement from LTE’s 5ms thus eliminating future cloud services that necessitate zero latency and new services such as augmented reality and real-time dynamic control for Machine to Machine services. The low latency desiderate must be achieved while taking into account and satisfying the Quality of Experience for such service applications.

2.8 Coverage. Although coverage is limited by the band in use, 5G will need to improve coverage for all IoT-related applications in order to make 5G viable. While coverage depends on the frequency of operations conducted and the density of the deployment sites, it becomes clear that special actions need to be taken in order to ensure optimal coverage for specific services.

2.9 Security. The 5G technologies should address some security objectives like [5]:

Integrity: Ensuring that the information is not tampered with during transit. This also includes the ability to authenticate the source of the information and the recipient.

Confidentiality: Keeping sensitive information hidden from unauthorized users. This includes proper user authentication and data protection through encryption.

2.10 Diverse Spectrum Operation. The 5G networks are expected to operate in a diverse set of spectrum bands that include sub-6 GHz cellular bands (for coverage and low-power operations) and above-6 GHz bands (for ultra-high data rates). Because the propagation characteristics and the hardware implications are expected to be different, the 5G systems need deal with these requirements as soon as possible.

2.11 Unified System Framework. The 5G network should be as flexible and extensible as possible in order to support all requirements.

3. Improving the 4G Network Architecture through 5G

The basic functioning principles of the architecture for the 4G networks were conceived a few years ago [6], before the explosion of the mobile broadband usage, so they might be a little outdated. Some of the new requirements have been handled by modifications in the basic architecture of the network. Even if the 4G architecture is capable of satisfying these requirements, it does it by increasing the complexity of existing components and by adding some new components to the network.

3.1 Enhancement of Networking Flexibility. Along with the existence of smart devices in indoor environments, there is a need for some of the traffic to be routed locally, as other traffic needs to access Mobile Network Operators (MNO) or third-party services. For local offloading, the 4G networks require a Mobile Packet Gateway (PGW) deployed locally and that because mobile-network-specific tunneling is being retained for all of the traffic.

3.2 Additional Support for the Fundamental Attributes of Networking Layer. As a response to the development of use cases and the big network usage, the networking community has added new functions as overlays on the existing network. The 5G architecture needs to re-examine the network architecture in order to benefit from research in the future Internet Architecture and protocols that support mobility, security and content storage as components of the network.

3.3 Providing Flexible Mobility Solutions. Some of the network functions that handled device mobility in 4G are outdated to the specific requirements of the applications and the smart devices. The seamless mobility is provided, sustaining additional signal, processing and bandwidth overheads.

3.4 Multi-RAT Integration and Management. The 4G interactions are becoming widespread, thus resulting in a multitude of smart devices communicating over radio access technologies. These interactions have produced network topologies that support seamless access selection, authentication and seamless mobility. However, because the supporting network architectures were defined independently, today there is little cohesion in network functions and procedures, leading to an improper level of interworking, based mostly on redirecting the mobile usage to an alternative access technology, from where it can exercise a set of network procedures.

3.5 Enhanced Efficiency for Short-Burst and Small-Data Communication. The new smartphone applications frequently exchange short-bursts of data with their applications. When there are no other communicational needs, the smart devices have small amounts of data they need to send, but even so they have to go through the signaling procedure in order to transmit the data. To handle this more efficiently, the network needs to support a connectionless mode of operation, where devices can wake-up and send a short-burst of data.

3.6 Expanding Context Information. The 3G and 4G networks have limited knowledge of the smart device and less knowledge of the apps that request access. For the static devices subscription information is obtainable from the 3GPP Home Subscriber System data base. This includes information about device type and subscribed services. Standardized use of this information has been limited to determine the authorized PDN connections. This contrasts with the knowledge that can be obtained by apps and smart devices that produce big-data-based subscriber analytics. The 5G networks need an ampler and more flexible method if they need for the network to obtain relevant information in order to decide how the network resources will be allocated.

3.7 Further Enhancing Coverage and Services. The proximity service is a concept aiming at improving user experience and resource allocation by taking advantage of user proximity. Device to Device (D2D) communication is suitable for proximity services and has already been discussed in 3GPP. Since the cellular uplink resource is shared with the D2D link, the interface mitigation between cellular link and D2D link is essential. We should consider Device to Device communication as a tool that is well-integrated in the overall wireless-access solution. Besides what’s depicted in Figure 3.2, this also should include:

Using direct communication as a transmission mode, when nearby smart devices have end-user data to transfer between them.

The use of direct D2D communication in order to extend network coverage.

Cooperative smart devices where high-speed communication provides means for joint transmission and reception between multiple devices, opening up for more efficient communication.

Fig. 2. D2D Wireless Access Solution

Demand for the 5G technology is growing and commercial use will be available as soon as the initial stages of 5G are developed [7]. Furthermore, this technology is linked to the Machine to Machine (M2M) communication specific to the Internet of Things (IoT). Moreover, utilization of satellite communication is also being considered in 5G networks for deployment of services in isolated areas such as mountain regions or oceans. An additional benefit that can also be taken into account is that the terrestrial networks can be down due to natural disasters and then the need to rely on satellite communication becomes very important.

Results and Discussion

The 3G and 4G technologies were designed primarily for the superfast mobile internet. 5G continues on in this direction, but also wants to target what are known as vertical markets, which encompass several segments, including [8]:

Connected vehicles, not only to deliver entertainment and information to passengers, but also to guarantee safety via communications both between vehicles and between vehicles and infrastructure

Factories of the future

Smart cities with requirements in the areas of public transportation (similar to the needs of connected vehicles), the environment, managing buildings and energy consumption

Medicine, healthcare and robot-assisted surgery

Smart grid flow monitoring and management (electricity, gas, water, etc.).

Though the 4G network has not been around for many years, it is already proving to be insufficient when dealing with the need of denser networks and with the increased capacity that the use of smart devices and the emergence of the IoT are expected to bring in the future. But this is not just the technology`s fault, as the smart devices `revolution` was not yet taking place back when the 4G network requirements were disclosed.

Overcoming the limitations of the 4G network is the primary goal of the 5G network, as a concept that expresses an evolution of the wireless networks in order to meet future demands and also a revolution in network architecture in order to enable cost-conscious networks that can be scaled in an efficient manner [9]. The proposed technologies are trying to take a look into the future, because they want to be able to support the network`s demands when 5G networks will be deployed on a large scale.

Challenges are the inherent part of the new development; so, like all technologies, 5G has also big challenges to deal with. As we see past i.e. development of radio technology, we find very fast growth. Starting from 1G to 5G, the journey is merely of about 40 years old (Considering 1G in 1980s and 5G in 2020s). However, in this journey, the common challenges that we observed are lack of infrastructure, research methodology, and cost.

The IoT and the number of connections

The Internet of Things will definitely create an increase in the number of smart devices connected and the connections across the wireless networks. Some researchers predict that in the future billions of smart devices will be connected to the networks. Even though many devices will only be sending and receiving small data amounts, these smart devices will create some new demands in the total data volume. In the current 3GPP-based networks, there are limitations regarding the number of users connected simultaneously and limitations regarding the numbers of users transmitting or receiving data on specific network nodes. This limit will most likely be insufficient regarding the growth of IoT [10]. New access control mechanisms will appear as a mandatory requirement.

The volume of data

The data volume is a key driver when developing new 5G technologies. The amounts of data that are being carried on mobile networks is growing every year with values between 25 and 50% and is expected to rise even more until 2030, mainly because of the apps that require higher data rates and because of the increases in resolution and the developments regarding 3D video [11]. Long-Term Evolution established that voice is not a dedicated circuit switched service, but also an application using data connectivity. The challenge of data capacity in the end-to-end network needs to be expanded, and this is not only the air interface but the entire access network. As this new technology develops, the overcrowded in the system change, and new data jams will have to be overcome.

Increasing network capacity without increasing the costs for users

As the number of users grows every day, they are consuming more data, but they are unwilling to pay more in order to cover the increase in data usage. For the mobile service companies the greatest challenge if them all is to increase the data capacity of their networks without increasing the service cost for the end users. A technology developed in 3GPP for Long-Term Evolution networks is to separate the distribution of control and user data planes in order to align to the new data requirements [12].

An example is to provide the control plane signaling to a wide area only using a macro cell and then user plane data through small cells, all within the coverage of the macro cell mentioned previously. This aspect enables a bigger capacity of user plane data within the area without adding any complexity to the network. These methods are more efficiently when they are using existing sites and technologies in order to increase data capacity without adding extra cost to the user`s bills.

Fast and flexible deployment architecture

When implementing the 3G and 4G networks the speed was restricted at the speed at which suitable backhaul network capacity could be provided. The capacity and flexibility of the backhaul were also considered [13]. The 5G network technologies face the challenge to develop The Comprehensive R Archive Network as an evolution of network design, meanwhile complementing the user and control plane separation in the direction towards a more flexible cloud based network [14].

Some functions of the Radio Access Network are being moved from the cell site back into a secured baseband cloud service. This aspect provides an efficient solution for supporting scaling, leading to easier reconfiguration, because the network core signaling is being held within the cloud and the only physical elements are the RF transceivers that provide internet connection.

Offering real-time information

When dealing with critical information, offering it in real time is essential. The emergency services and other type of critical services will always require real-time information and high reliability. In hospitals, wireless networks can be used for providing remote patient monitoring and care. Police officers, firefighters and ambulance workers also need high-reliability connections without having to worry about call dropping or busy networks. Today, some of the critical services are being provided by using dedicated networks, with limited data capacity and high investment required for providing network coverage.

The future requirements will be related to offering high data rates and real-time interaction in order to allow these critical services to respond even faster [15]. It becomes clearer that new network technologies are required for critical scenarios, because it is there where the ability to connect and operate in degraded infrastructure must be assured. This can only be achieved by using device to device communicational means and flexible reconfiguration for the networks.

Augmented reality

As augmented reality becomes more and more used even on personal devices, the demand regarding the network performances is being highly increased. The key aspect regarding augmented reality is that the network delay must be very small in order to enable true interaction between the real and the virtual environments. Because the human brain is sensitive to delays when processing visual data, if the delay is not small enough virtual reality services can`t be delivered properly.

The link between the smart device and the server has to be perfectly optimized for it to provide low latency. New routing architectures face the requirement that the overall delays required can`t be achieved by using traditional server architectures. Critical low latency services will need a special network infrastructure and architecture in order to locate the server closer to the user, thus ensuring that delays and latency between the user and the augmented reality service is reduced as much as possible [16].

M2M communication and automotive

There are a lot of automotive wireless connectivity apps already under development or in early trials. The intelligent transport system is creating demand for a different type of communications: vehicle-to-vehicle communication and vehicle-to-infrastructure communications, as well as linking the vehicles with other smart devices.

An ultimate goal regarding M2M communication is fully autonomous driving, but this aspect requires very secure and very reliable communications for a widespread public deployment. The 5G networks should be able to support this desiderate, if the network can deliver the capacity, the coverage and the latency combination that is required by the use of heterogeneous network technologies [17]. The big challenge to the network architecture is being able to provide the flexibility needed, but also with the high reliability and high availability demands required by autonomous driving.

Device-to-Device communication

Device-to-Device communication was placed outside of the realm of mobile networks, because these communications use direct links that don`t rely on information over the network. Let`s take for example the walkie-talkie devices, which have existed for a long time but they have a limited capacity of transmitting data. The previous existing networks have developed push-to-talk technology while trying to deliver similar user experience but some apps are not guaranteed to have sufficient coverage. D2D allows a direct communication, which is developed in LTE Advanced, the challenge being the fact that you have to have a more robust implementation in 5G networks, where they are designed to handle exactly these types of communications [18].

Air interface

In order to implement the new 5G network, a new air interface will be necessary. Existing research suggests that more than one type of air interfaces will need to coexist in the network. From a theoretical point of view, this will be ideal, but from an operational and economical perspective, significant development costs and deployment effort will occur. Some new air access schemes will need to be developed as to meet the new requirements and to improve the existing access schemes.

Orthogonal frequency-division multiplexing has a limited use in LTE because interferences, therefore low interference evolutions will be required in order to support much denser frequency deployments [19]. For wider bandwidth deployments optimized waveforms suitable for 1GHz of transmission bandwidth are needed. As multiple-input and multiple-output technology has been successfully implemented into 4G networks, it becomes clear that 5G networks will continue to support and expand this technology. The static time/frequency resource allocation blocks need to be revised, seeing as more and more flexible methods of allocating and managing resources are being required [20].

Network densification

The 3G and 4G networks became congested very quickly and mobile operators needed to add more cells and sectors to the network system in order to increase capacity. This has evolved to include many small cells that offer various connectivity options. With the new technologies, the 5G networks will most likely consist of several layers of connectivity from macro-layers for lower data speed connectivity, through complex layers for high data speeds [21].

Network deployment and coordination are important challenges faced by the 5G networks. These challenges need to be promptly addressed, knowing that they continue to increase with the growing of number of network layers. This aspect creates new challenges regarding coverage optimization, for the access network algorithm optimization and also for device mobility measurement capabilities.

Concluding, the 5G networks will be designed for managing a large amount of data services. Network densification is very appropriate for increasing its capacity in order to meet all future demands. The costs implications when developing a new network will be significant, thus making the industry to develop more and more technologies that can be used for expanding the existing technologies and infrastructure in an efficient way. In order to support all of these requirements, researchers investigate for specific technologies usable with the 5G networks, with solely the aim of proposing new efficient solutions that will then be included into the 5G network specifications.

Conclusions

While the future of technology is becoming very difficult to predict, we should be expecting an accelerating pace of technological change. The 5G network is not a term officially used for any particular specification or in any official document yet made public by telecommunication companies or standardization bodies, but will surely be a reality in the next years.

The 5G networks will need to meet some very challenging requirements and will need to cover a large range of actual services and possible scenarios. The system concept regarding the 5G`s radio access is very important in order for a successful migration from Long Term-Evolution Advanced networks to the 5G network, also the effective integration of key radio access technologies should be considered.

In the proposed evolution concept toward the 5G network it was emphasized the importance of the efficient integration of lower and higher frequency bands in order to meet the future challenges. Also, there were described several views on RAT and its relationship with 5G radio access. Furthermore, the discussion touched themes like the new radio access technologies that will be used, identified as being the most promising technologies that can be used for improving system performance.

Regarding the ongoing proof-of-concept activities, the existing network architecture used in 3G and 4G should support the evolution to the 5G. More specifically, the built-in scalability and flexibility of the network are being required in order to support a large range of QoS and a big number of network nodes and smart devices.

Right now, there are some 5G related discussions. Studies on 5G have gained interest worldwide as we can see by the acceleration of efforts by governmental entities and research bodies from both academia and industry like the METIS project for Europe, the ARIB 2020 Strategy from Beyond Ad Hoc group and the 5G Mobile Communications Promotion Forum for Japan. In 3rd Generation Partnership Project, the standardization and conceptualization of the 5G network is expected to take-off starting with the LTE Releases 14 and 15.

In particular, in order to commercialize 5G by 2020, 5G discussions have been started at end of 2015. After finishing the discussing, it is expected that the specification of 5G network and initial functionalities will be announced by the end of 2018.

Data Availability

The paper presented, being a synthesis work, has all of the sources of information used available in the attached reference list. The authors can confirm that all relevant data was included in the reference list.

Conflicts of Interest

The authors declare that there is no known conflict of interest regarding the publication of this paper.

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