Qaysar Salih Mahdi1, Ismail Musa Murad2
1Tishk International University, Erbil, Kurdistan, Iraq
2Salahaddin University, Erbil, Kurdistan, Iraq
Corresponding Author: Qaysar Salih Mahdi, Tishk International University, Erbil, Kurdistan, Iraq
Abstract: The fifth generation of broadband wireless telecommunications will increase the speeds of upload and download with decreasing the access network latency and enable bandwidth in excess of 100s of Megabits per second (Mb/s) with latency of less than 1 millisecond (ms), as well as provide access network to billions of subscribers. The applications of mm-waves in 5G are modern developments but with challenges. In this paper the innovations and challenges of 5G are described such as mm-waves, small cells, Massive MIMO, Beamforming, Full Duplex FD, Non-Orthogonal Multiple Access NOMA, and Mobile Edge computing MEC. The 5G deployment has advantageous and disadvantageous. The results show that the millimeter waves development is the dominant innovation of 5G technology, which increases the data traffic 1000 times more data than 4G and offer manufacturing of industrial equipment communication systems with cheaper prices. It is concluded that 5G, represents a big step forward in increasing the flexibility of the network infrastructure, and improve scalability and service. Also 5G is not limited to telecommunication services but it represents the Beyond technology in research, automotive, energy, e-business, e-government, vertical industry, security, e-Health, improving human being’s life. 5G will be the future benchmark of smart city.
Keywords: Beamforming, Challenges, Cloud RAN, Full Duplex, Innovations, Massive- MIMO, MEC, mm-waves, NOMA, small cells.
1G First generation, started on 1980. 1G state-owned monopoly operators, very often obtaining the use of spectrum free of charge, to open-market starting with 3G, to 5G spectrum sharing. 2G Second generation global system for mobile communications (GSM) cellular networks started since 1990, initially provided digital voice service at bit rate 9.6 kbps. 3G Third Generation Universal Mobile Telecommunications System UMTS began on 2000 and offered up to 2 Mbps bit rate (often 364 kbps) initially, and then several tens of Mbps in downlink with High Speed Packet Access (HSPA). While since 2000, 4G Fourth-generation LTE features up to 300 Mbps in downlink, with a target of 1 Gbps, and up to 50 Mbps in uplink. Starting from the end of 2002, 5G Fifth generation cellular networks started as the first trail under research and it is expected to increase the bit rate significantly, up to 20 Gbps. Figure 1, shows the historical literature survey. Since, 2014, NOMA and Massive MIMO with MEC are new technologies obtained due to the 5G mm-wave deployments which offer softwarization and virtualization of wireless connectivity.
Figure 1: 5G literature survey
Millimeter waves (mm-waves) stand for radio waves with a carrier wave lengths between 1 mm and 1 cm, and they are planning to be applied in the fifth generation (5G) wireless communication. From last few years, wireless networks and mobile telecommunications assigned interesting development of 5G technology which will enable citizens of broadband calls, videos and data communication which they are never met before. 5G provides communication services not only for end users, but also for different vertical markets, such as automotive, energy, city management, government, healthcare, manufacturing, and intelligent transport systems. Such heterogeneity creates demand for a level of service agility typical of a software environment, rather than an “ossified” hardware one (Andrea Detti,2019).
2.1 5G Aim
5G aims as being new development than 4G, and to be the benchmark of the digital world, the fifth generation has ultra-high broadband infrastructure that will support the transformation of processes in all social and economic sectors and the growing consumer market demand. In fact, 5G is designed to create the conditions to launch new applications and provide new unique service capabilities not only to consumers, but also to new stakeholders (e.g. vertical industries, novel forms of service providers, infrastructure owners and providers) .This is reflected in ITU-R’s defined objective for IMT-2020: “Enabling a seamlessly connected society in the 2020 timeframe and beyond that brings together people along with things, data, applications, transport systems and cities in a smart networked communications environment” (ITU towards,2020).
2.2 What is 5G?
The 5G is the new fifth generation standard that allows obtaining superior performance both in terms of speed and latency compared to those obtainable today with 4G. However, 5G is not only faster and less latent as it is the key technology to enable many value-added services that are not accessible today through 4G networks (Khalid A. Fakieh,2015).
2.3 5G Concept
5G wireless networking contains software defined radios (SDR), network function virtualization NFV, NOMA, Massive-MIMO, MEC and digital modulation methods with virtual control. In the present days 3rd Generation (3G) mobile systems are in progress for endowing Internet Protocol (IP) service for instantaneous/synchronized and non-instantaneous services. In contrast, loads of wireless technologies have demonstrated and turned out to be significant and out of them one which is extremely vital is 802.11 “Wireless Local Area Networks” (WLAN) and 802.16 “Wireless Metropolitan Area Networks” (WMAN), with the possible addition of ad-hoc Wireless Personal Area Network (WPAN) and wireless networks for digital television and radio transmission (Khalid A. Fakieh,2015).
2.4 Why 5G?
The global society and the worldwide economy are becoming increasingly dependent on information and communication technologies (ICT), especially on wireless connectivity (Francisco Fontes, Ioannis Neokosmidis, Riccardo Trivisonno, Franco Davoli, Le Nguyen Binh, Spiros Mikroulis, Ioannis Tomkos, Valerio Frascolla, 2019). 5G will allow for new applications and unique service capabilities, not only for consumers but also for new industrial stakeholders, creating new business opportunities and allowing for novel Business to Business to Customers (B2B2C) business models.
3 The Evolution from 1G to 5G
We have witnessed a shift across the several generations, from 1G state-owned monopoly operators, very often obtaining the use of spectrum free of charge, to open-market auctions starting with 3G, to 5G spectrum sharing (Marco Chiani, Enrico Paolini, Franco Callegati, 2019). 1G advanced mobile phone system (AMPS). Second generation global system for mobile communications (GSM) cellular networks initially provided digital voice service at bit rate 9.6 kbps. Third generation UMTS offered up to 2 Mbps bit rate (often 364 kbps) initially, and then several tens of Mbps in downlink with High Speed Packet Access (HSPA). Fourth-generation LTE features up to 300 Mbps in downlink, with a target of 1 Gbps, and up to 50 Mbps in uplink. Fifth generation cellular networks are expected to increase the bit rate significantly, up to 20 Gbps. These bit rates, end to-end latencies down to 1 ms, ultra-reliability, and massive multiple access, will foster services such as enhanced mobile broadband, device-to-device (D2D) communication, ultra-reliable and low-latency Internet of Things (IoT) and machine-type communication (MTC), e-health, augmented reality and tactile Internet, industrial control for the Industry 4.0, automated driving and flying. Table 1, provides an overview of the main features of each cellular network generation.
Table 1 Evolution from 1G to 5G
4 Theoretical Principles
4.1 Frequency Bands for Cellular Generations
1G advanced mobile phone system (AMPS) and total access communication system (TACS) were operated in the 800 MHz and 900 MHz bands, respectively, while 2G GSM was initially operated in the 900 MHz band, and then also in the 1800 MHz and 1900 MHz (Marco Chiani, Enrico Paolini, Franco Callegati, 2019). Frequency bands around 2 GHz were for the first time used by UMTS networks, while a number of frequency bands are available worldwide for long term evolution (LTE), based on regulatory aspects in different geographical areas (e.g., 450/800/900 MHz, 1800/2100 MHz, 2600 MHz in Europe). From a spectrum allocation viewpoint, the main breakthrough introduced by 5G is the use of licensed, shared, and unlicensed frequency bands in the mm-waves band, above 24 GHz. The one around 60 GHz is of particular interest for indoor very-high data rate applications, wireless backhaul, and femtocell implementation.
4.2 Millimeter Waves
The Electromagnetic signals with carrier lengths between 1 mm and 1 cm are commonly denoted as mm-waves, and they are going to be used in the fifth generation (5G) of mobile communications (Stefano Tomasin, 2015). The portion of spectrum carrying signals with wavelength between 1 mm and 1 cm named mm-waves, is denoted by ITU and spans frequencies from 30 to 300 GHz. However, even frequencies below 30 GHz, the performance of the fifth generation (5G) of cellular communication systems is modified in order to fulfill broadband applications (e.g., remote control, monitoring, intelligent transport systems, and tactile interaction), with user experienced data rates up to 1 Gbps (500 Mbps) in downlink (uplink) and latency as low as 0.5 ms. IMT-2020 will be defined by third generation partnership project (3GPP) as a release, finally commercialized as 5G system to the end user. Conference (WRC) in 2015, has identified various spectrum portions between 24 to 86 GHz for mobile communications (Stefano Tomasin, 2015). Among opportunities, mm-waves are particularly favorable to the 5G scenario of small-cells envisioned by ITU, as their strong attenuation naturally reduces interference. Using of complementary metal-oxide semiconductor (CMOS) transistor production has allowed a cheaper implementation of the circuitry needed to handle millimeter wavelength signals. On the other hand, mm-waves also pose technical channels to overcome strong attenuations, provide a good channel estimate, and discover new users entering cells, as described in the following. Millimeter wave(mm-waves) signals provides large bandwidth and high throughput, which can be particularly in the following applications, V2V communications between very close vehicles and V2I communications for bulk data transfer. Figure 2, shows the mm-waves frequency spectrum.
Figure 2: mm-waves frequency spectrum.
4.3 Coverage issues
5G increases network capacity. Site densification necessarily poses economic issues that may slow down considerably spatial and temporal 5G deployment, unless a substantial Base Station BS cost reduction is achieved over the time (Marco Chiani, Enrico Paolini, Franco Callegati, 2019). It has been reported how SDN and network virtualization may contribute to cut costs, but there remains uncertainty about to what extent this will speed up 5G rollout. Recent studies have shown that, under a business-as-usual model, in UK 90% of the population will be covered with 5G not before 2027 and that 100% coverage will be extremely hard to reach due to prohibitively increasing deployment costs in less populated areas. Similar expectations have been reported for other countries during discussions at the 2018 IEEE 5G World Forum.
4.4 Full duplex FD
Compared to others like NB-IoT, LTE-M is optimized for higher bandwidth and mobile (in the sense of moving nodes) connections. As a consequence, it reaches up to 1 Mbps of data rate and well supports nodes mobility. One clue advantage of LTE-M included in the standard, is the possible choice for operation in either full duplex FDD, half duplex FDD or time division duplex (TDD). Its modulation is still OFDMA, following LTE numerology. One other peculiarity of LTE-M is the support of voice over LTE. See Figure (3).
Figure 3: Duplex with TDD than FDD.
4.5 5G Spectrum and Enabling Technologies
5G NR will operate in the frequency range from below 1 GHz to 100 GHz with different deployments (TR 38.913, 2017; RP-172101, 3GPP TSG RAN77,2017). There will typically be more coverage per base station (macro sites) at lower carrier frequencies, and a limited coverage area per base station (micro and pico sites) at higher carrier frequencies. Spectrum is fundamental for wireless communication and there is a never-ending quest for more spectrum to meet the demands of increased capacity and higher data rates. This is one of the major reasons why NR needs to exploit also frequencies in the mm-wave range, as well as aggregation of multiple wideband carriers (TR 38.913, 2017; RP-172101, 3GPP TSG RAN77,2017).
- 5G Challenges & Innovations
A new spectrum frontier: millimeter waves in 3GPP NR 5G cellular systems introduce unprecedented requirements in terms of data rate, latency, link resilience, and end-to-end reliability, which go beyond what existing mobile technologies can support. In this perspective, the mm-waves spectrum – roughly above 10 GHz has rapidly emerged as an enabler of the 5G performance demands in micro and pico cellular networks (T. S. Rappaport, S. Sun, R. Mayzus, H. Zhao, Y. Azar, K. Wang, G. N. Wong, J. K. Schulz, M. Samimi, and F. Gutierrez, 2013). Moreover, mm-wave systems operate through highly directional communications which tend to isolate the users and deliver reduced interference. Additionally, inherent security and privacy is also improved because of blockage and of the short-range transmissions which are typically established. Motivated by the above introduction, NR will boost the 5G performance by supporting, for the first time, frequencies up to 52.6 GHz in Release 15, including therefore mm-waves bands (3GPP, 2017). Nevertheless, communication at mm-waves introduces new challenges for the whole protocol stack, which may have a significant impact on the overall end-to-end system performance. First, signals propagating in the mm-waves spectrum suffer from severe path loss and susceptibility to shadowing, thereby preventing long-range omnidirectional transmissions. Second, mm-waves links are highly sensitive to blockage and have ever more stringent requirements on electronic components, size, and power consumption. Third, directionality requires precise beam alignment at the transmitter and the receiver and implies increased control overhead. In order to overcome these limitations, the NR specifications include new Physical (PHY) and Medium Access Control (MAC) layer operations to support directional communications, which are collectively referred to as beam management according to the 3GPP terminology [M. Giordani, M. Polese, A. Roy, D. Castor, and M. Zorzi, 2018; TS 38.300, 2018). In particular, NR networks must provide a mechanism by which User Equipment’s (UEs) and Next Generation Node Base Stations, see Figure (4).
Figure 4: Beam management structure in NR systems. SS blocks and CSI-RSs are used for beam measurements in idle and connected modes (M. Giordani, M. Polese, A. Roy, D. Castor, and M. Zorzi, 2018; TS 38.300, 2018).
5.1 Multipath Propagation of mm-waves signals
The most important characteristic of the mm-waves band for radio communication is its significant path loss attenuation due exclusively to the distance between the transmitter and the receiver. Indeed, the specific attenuation in free space due to the atmosphere raises from 5·10−3 dB/km at 2 GHz to about 2·10−1 dB/km at 24 GHz to dramatically increase to 20 dB/km at 60 GHz, due the peak of absorption of oxygen: these numbers translate into an attenuation of 10 dB at 200 km, 50 km, and 500 m, respectively. In order to incorporate other propagation phenomena, various channel models have been proposed for mm-waves (see (ITU-R M.2083-0, 2015) for an overview). Moreover, the mm-waves are subject to the blockage phenomenon, as their propagation is largely prevented by almost any physical object. This phenomenon is typically captured by either shadowing, modelling the presence of static objects, or fading, accounting for fast attenuations variations due to moving objects. Figure (4), shows one BS antenna is used and in this case the transmitting signals are blocked and attenuated due to the reflection from different buildings and the signal is attenuated due to the multipath reflection effect as shown in Figure (5), While Figure (6), shows the attenuation of mm-waves due to atmospheric attenuation which absorbs the radio signal.
Figure: 5 Millimeter waves Wave Reflections Building obstacles
Figure 6: Atmospheric attenuation produce wave absorption.
5.2 Small Cell Technology
Within the 3GPP 5G standard the channel model is described in the technical report series TR 38.901, which specifies various scenarios, including urban macro and micro cells, rural macro cells and indoor office (Stefan Parkvall, 2018). To avoid the problems mentioned before, many small cells are used instead of one large macro cell by distributing many small cell BS stations are used between buildings to fill in the coverage gaps and decreasing the transmitting distance between the BS transmitter and users, then decreasing the transmitting power per cell. Figure (7), shows example of using 4G large cells where the distance between different BS stations is too fare.
Figure 7: Macro cell for 4G technology.
With 5G mm-waves higher cell density could be achieved with small cells instead large cells then the cellular networks will have higher number of cells within certain area and increase the number of users within each small cell. By this principle the coverage area could be divided into cells and one access point per cell serves the users in the cell. Figures 8 (a) and (b), will offer denser deployment of access points with shorter distance and will reduce the power consumption. The challenge problem is the interference and signal attenuation therefore higher capacity will be maintained if bit/s/cell will be organized and planned very well. Figure (19), shows increasing data traffic [bit/s/km2] which handle 1000 times more traffic per area (e.g., 1 km2) which reflects the results of this research. The coverage area is divided into cells and one access point per cell serves the users in the cell and with denser deployment of access points shorter distances are achieved with reduce power, Figure (18), shows the results of using higher cell density which increases the performance of 5G network capacity.
Figure 8: (a) Higher cell density ( b ) Higher denser cell density
Figure (9), shows the introducing of small cells in the coverage gaps avoiding the obstacles from building and the reflection and multipath attenuation. The distance between the small cells depend on the population at each location.
Figure (9): The distance between the small cells depend on the population at each location.
Figure (10), shows the distance between difference small cells tower is decreased to 300m closer than the distance of 70km which is shown in Figure (7).
Figure (10): shows the distance between different small cells.
5.3 Integrated Circuits Advancements
The signals transmitted by smartphones and other consumer devices are generated and amplified by integrated circuits typically built with silicon-based technologies, like CMOS or bipolar CMOS (BiCMOS) (Ali A. Zaidi, Robert Baldemair, Mattias Andersson, Sebastian Faxér, Vicent MolésCases, Zhao Wang, 2018; Ericsson 5G Use Cases, 2018; 5G for Italy press release, 2016). Any active device has a maximum frequency of operation, called transit frequency, beyond which it does not provide any current gain. Practical amplifiers can actually be built only at a fraction of the transit frequency. As the transistor transit frequency is inversely proportional to its geometrical size, the continuous downscaling of the microelectronic technology favored systems operating at increasingly higher frequencies (Ali A. Zaidi, Robert Baldemair, Mattias Andersson, Sebastian Faxér, Vicent MolésCases, Zhao Wang, 2018). Only in ’10s of the third millennium the industry has been ready to mass-produce transistors with a minimum feature down to 28 nm and below, providing a reliable platform for applications operating above 10 GHz. Indeed, the advance of this technology has pushed the use of mm-waves in many fields, including communications (devices for HD transmission from digital set top boxes, Wi-Fi standards, satellite communications), sensors (road radars for cars, body scanners), and medical applications).
5.4 Signal Processing and Protocol
Due to the peculiarities of the mm-waves channel, special signal processing techniques and protocols must be adopted. Some surveys on mm-waves and their use for 5G communications have appeared in recent years and provide further insight into these and other topics, such as the use of multiple antennas; the estimation of the channel characteristics; and the discovery of new users entering a cell (Ali A. Zaidi, Robert Baldemair, Mattias Andersson, Sebastian Faxér, Vicent MolésCases, Zhao Wang, 2018; Ericsson 5G Use Cases, 2018; 5G for Italy press release, 2016).
- Massive MIMO and Beamforming
6.1 Massive MIMO
Massive MIMO is a core component of NR systems, while the combination of extreme cell densification, increased system bandwidth, and more flexible spectrum usage (e.g., by resource sharing) represents a feasible and sustainable solution to meet 5G performance requirements. MIMO techniques have also emerged in modern wireless networks to improve reliability and spectral efficiency. The main concept is to use multiple transmit and receive antennas to exploit multipath propagation. Massive MIMO technology is suggested to enhance the coverage and avoid multipath propagation and increasing spectral efficiency and capacity. The second advantageous of using mm-waves is the Massive MIMO antenna which produces massive beam forming critical for coverage at higher frequencies. Massive beam forming with reasonable antenna size enabled by higher frequencies i.e. mm-waves. Figure 11 (a) shows the MIMO antenna and Figure 11(b), shows 2 Massive MIMO and Figure 11(c), shows the 3 Massive MIMO with small cells technology, which enhance the coverage and avoid multipath propagation.
(a) MIMO Antenna (b) Massive MIMO (c) Massive MIMO with small cells
Figure 11: Massive MIMO Technology
Figure 12, shows example of the MIMO antenna with 128 antenna elements at 28GHz.
Figure 12: MIMO antenna with 128 antenna elements at 28GHz
For 5G technology, mm-waves with higher frequencies are introduced for multi-beams beamforming produce more focused signal with narrower beam width, which make the transmitting signal more focused in the desired direction and no spreading of power will happen, then offer higher power spectral efficiency. See Figure 13(a) with single focused beam and Figure 13(b) with two focused beam in mm-wave frequency range.
- One focused beam with mm-wave (b) Two focused beam with mm-wave
Figure (13): 5G Beamforming with mm-waves technology.
With MIMO array antenna multi-simultaneous narrow beams are used for different users. The transmitting beams in this case are visualized as laser beams between them as shown in figure (13). Figure (14), shows the comparison between the beam forming MIMO antenna and standard antenna which shows that in case of MIMO beamforming less interference and less energy consumption, if there are more than one user with more than different beams to cover their coverage the signals may interfere with each other if they are standing close, see Figure 14(a) while using the beamforming with mm-waves, the beams for different beams are not interfere, see figure 14(b). By this beamforming procedure at the same time, we simplify the implementation of the transmitter and the receiver and maximize the data rate of the transmission, i.e., we achieve the capacity of the MIMO channel. Note that the number of antennas at either side of the communication system limits the number of data that can be simultaneously transmitted. In practice, experimental results have provided reduction of the attenuation by 40 dB with the transmitter and the receiver equipped with uniform planar array antennas with 64 elements (R. Sabella, A. Thuelig, M. C. Carrozza , Massimo Ippolito, 2018).
(a) 4G Beamforming without mm-wave range (b) 5G Beamforming with mm-wave range
Figure 14: Comparison between 4G Beamforming without mm-wave range & 5G Beamforming with mm-waves.
6.2 Mobile Edge Computing MEC
5G will incorporate several state-of-the-art architectural and protocol approaches on top of his networking infrastructure to tackle the emerging needs for improved flexibility and performance . Such requirements lead to the design of two options for the 5G architecture: one, which represents an evolution of 4G LTE standard IP architecture, and the other where the core network functions interact with each other using a Service Based Architecture (SBA). This novel architecture allows the integration of the recent developments in the field of Cloud technology and Mobile Edge Computing. Indeed, besides a predictable increase in data transfer performance and spectral efficiency, 3GPP 5G requirements include very low latency (in the order of msec), high reliability, capability to offer access to distributed computation and storage facilities in addition to connectivity and bandwidth (Fabrizio Granelli, 2019). Those services can be classified as URLLC (Ultra-Reliable Low Latency Communication) services. Vehicular communications and remote control of robots or machinery belong to such class of services, and they are well-known 5G application scenarios . As a consequence of the above issues, it is necessary for the 5G architecture to incorporate additional functionalities, by exploiting the recent solutions existing on the Internet: The Cloud and virtualization. Cloud Computing represents the current paradigm for the delivery of services to a massive number of users, and it is based on the concentration of huge computation and storage resources in strategic locations (the datacenters) that can run services in an efficient and scalable manner by using advanced management and virtualization approaches. Indeed, by virtualizing key network functionalities, it is possible to detach software functions from dedicated hardware, with the advantage to be able to re-locate or modify their resources most efficiently and in real-time. This emerging paradigm is defined Network Function Virtualization (NFV). The above concepts can be introduced in the design of the next generation of mobile networks, leading to the definition of two emerging paradigms in the design of 5G: Cloud Radio Access Network (Cloud RAN) and Mobile Edge Computing or Mobile Edge Cloud (MEC) (Mai T. P. Le, Giuseppe Caso, Luca De Nardis, Maria-Gabriella Di Benedetto, 2018). It is foreseen that moving computing, storage, and networking resources to the edge of the radio access network (RAN) will be a key ingredient to alleviate backhaul and core network and to allow executing delay-sensitive and context-aware applications in the proximity of end users. Among them, the limited computing and storage resources per each MEC platform, the necessity for MEC platforms of different provider to collaborate, challenges in user mobility support in small cells, problematic applicability of centralized authentication protocols. A MEC platform follows the trend towards cloud-based architecture, but exploits the advantage of being located in close proximity to the end users, see Figure (15). In the case of 5G, this means in the RAN. MEC architectures take advantage of the existing NFV infrastructure but are further characterized by; low latency, proximity, location awareness, high bandwidth, and real-time insight into radio network information. The idea of a computing platform located at the network edge is not specific to the world of cellular networks.
Figure 15: MEC Architecture
6.3 Non-Orthogonal Multiple Access NOMA
Motivated by recent theoretical challenges for 5G and beyond 5G systems, this research aims to position relevant results in the literature on code-domain non-orthogonal multiple access (NOMA) from an information theoretic perspective, given that most of the recent intuition of NOMA relies on another domain, that is, the power domain . The comparative analysis shows that it is beneficial to adopt extreme low dense code-domain NOMA in the large system limit, where the number of resource elements and number of users grow unboundedly while their ratio, called load, is kept constant. Being acknowledged as an important enabler for 5G multiple access, non-orthogonal multiple access (NOMA) with its diverse dialects recently attracted a huge attention in the wireless community from both industry and academia (L. Dai, B. Wang, Y. Yuan, S. Han, C. l. I, and Z. Wang, 2015). In fact, NOMA has been currently proposed by the 3rd Generation Partnership Project (3GPP) for 5G New Radio (NR) (Z. Ding, X. Lei, G. K. Karagiannidis, R. Schober, J. Yuan, and V. K. Bhargava, 2017). Furthermore, NOMA is a strong candidate for beyond 5G systems, thanks to its capability of supporting massive communications. In traditional orthogonal multiple access (OMA) schemes (Z. Ding, X. Lei, G. K. Karagiannidis, R. Schober, J. Yuan, and V. K. Bhargava, 2017), users are allocated to orthogonal resource elements (REs) either in time, frequency, or code domains. A very different situation arises when the system is overloaded. Even under ideal conditions such as ideal propagation and ideal allocation strategy, the system is intrinsically affected by ‘collisions’ due to interference (J. G. Andrews, 2005). This scenario may be easily envisioned in 5G, for example in the internet-of-things (IoT), in which a huge number of terminals are required to transmit simultaneously. In order to enable detection at the receiver side, different users are detected based on the difference of power or spreading codes, leading to two main corresponding approaches: power-domain NOMA vs. code-domain NOMA (Z. Ding, X. Lei, G. K. Karagiannidis, R. Schober, J. Yuan, and V. K. Bhargava, 2017). To address interference provoked by the lack of a sufficient number of REs, controllable interference among REs may be introduced in the code domain with an acceptable complexity of receivers. This NOMA approach is currently known as code-domain NOMA (Martin L. Pall, 2018). However, with reference to NOMA, most of recent works in the literature focus on the power-domain case, which is based on the idea of serving multiple users at the same time/frequency/code with different power levels. This work, on the other hand, makes an effort to contribute to the understanding of code-domain approach, particularly from an information-theoretic perspective. In the context of massive connectivity, expected for 5G and beyond 5G systems, the number of users is supposed to be very large compared to the number of REs. In 4G, the orthogonal multiple access technique is used, see Figure (16).
Figure 16: OMA & NOMA techniques.
The key idea of NOMA, is to use the power level technique. In order to increase the data sum rate, different frequency bands are multiplexed with different power levels, each frequency band has its power level, and users can access the base station with different power levels and with higher number of users.
- 5G Advantageous & Disadvantageous
7.1 Advantageous of 5G
In the following paragraph, the advantageous of 5G are summarized briefly.
1) 5G will increase the speeds of upload and download with decreasing the access network latency and enable bandwidth in excess of 100s of Megabits per second (Mb/s) with latency of less than 1 millisecond (ms), in this case the time is more saved in addition to the cost will be cheaper for network access.
2) Indeed, the advance of this technology has pushed the use of 5G mm-waves in many fields, including communications (devices for HD transmission from digital set top boxes, Wi-Fi standards, satellite communications), sensors (road radars for cars, body scanners), and medical applications).
3) It will provide access network to billions of subscribers more than 4G LTE.
4) With 5G mm-waves higher cell density could be achieved with small cells instead large cells and increase the number of users within each small cell without interference and multipath propagation with high level of security.
5) Massive beam forming with reasonable antenna size enabled by higher frequencies i.e. mm-waves, decreases the cost of manufacturing.
6) Indeed, besides a predictable increase in data transfer performance and spectral efficiency, 3GPP 5G requirements include very low latency (in the order of msec), high reliability, capability to offer access to distributed computation and storage facilities in addition to connectivity and bandwidth.
7) In the case of 5G, MEC architectures take advantage of the existing NFV infrastructure but are further characterized by; low latency, proximity, location awareness, high bandwidth, and real-time insight into radio network information and offering softwarization and virtualization to the edge date centers and very closed to users offering time of transferring huge data and cost.
8) The scenario may be easily envisioned in 5G, for example in the internet-of-things (IoT), in which a huge number of terminals are required to transmit simultaneously.
9) 5G NOMA increases the data sum rate, with different frequency bands are multiplexed with different power levels, each frequency band has its power level, and users can access the base station with different power levels and with higher number of users which is saving of power cost.
7.2 5G Disadvangatous
- With 5G mm-waves, depending on the device communication range of frequency, the ever continuous source of communication can generate radiofrequency radiation that can damage DNA, can lead to uncontrolled cell growth. It can lead to pre-mature aging and other diseases.
- Too much UV radiation can cause skin burns, premature aging of the skin, eye damage, and skin cancer. The majority of skin cancers are caused by exposure to ultraviolet radiation.
- Non-ionizing radiation can heat substances. For example, the microwave radiation inside a microwave oven heats water and food rapidly.
- 5G will substantially increase exposure to radiofrequency electromagnetic fields (RF-EMF) on top of the 2G, 3G, 4G, WiFi etc. for telecommunications already in place. RF-EMF has been proven to be harmful for humans and the environment.” ( Lennart Hardell, 2017).
- Martin L. Pall summaries the following attacks due to 5G radio frequencies attack our nervous systems, this nervous system attack is of great concern (Martin L. Pall, 2018). Attack our endocrine (that is hormonal) systems and produce oxidative stress and free radical damage , and produce excessive intracellular calcium [Ca2+] i and excessive calcium signaling, Attack the cells of our bodies to cause cancer. Such attacks are thought to act via 15 different mechanisms during cancer causation.
Depending on the following formula the data traffic in cellular network is calculated in bits/s/km2,
8.1 Higher Cell density cells/km2
Figure (8), shows increasing data traffic [bit/s/km2] which handle 10 times more traffic per area (e.g., 1 km2). The coverage area is divided into cells and one access point per cell serves the users in the cell and with denser deployment of access points shorter distances are achieved with reduce power, Figure (8), shows the results of using higher cell density which increases the performance of 5G network capacity.
8.2 Higher Spectral efficiency bit/Hz/cell
The omni-directional antenna with higher beam width, distribute the power in 360 degrees which means decreasing the spectral power in certain direction per user. In order to increase the spectral efficiency, it is required higher power level and by using the beamforming and MIMO array antenna with mm-waves will offer many simultaneous transmissions and more directivity towards the users. Figure (17), shows the comparison between Omni-directional antenna and the multi-beams forming MIMO antenna. This result will provide 20X higher spectral efficiency compared with 4G LTE, because the signals are directed and focused towards the users as shown in Figure 16(b) with better directivity and better capacity.
Figure 17: (a) Omni-directional antenna (b) Multi- simultaneous Beams with MIMO antenna
8.3 Higher Frequency Spectrum
Figure (18), shows the results of introducing the mm-waves frequency spectrum which shows that the frequency spectrum is increased by 5X and more transmission per second and using much higher frequencies compared to 4G LTE. Now by applying formula (1), the total capacity is calculated and we will obtain 1000times more data as shown in figure (19) which shows increasing data traffic [bit/s/km2] which handle 1000 times more traffic per area (e.g., 1 km2).
Figure 18: Introducing higher data rate by 5G mm-waves technology.
Figure 19: 5G technology handle 1000 times more data.
Millimeter waves exploit a novel portion of the spectrum, to increase the throughput, a frame structure that can provide ultra-low latency, massive MIMO and several deployment architectures. The relationship between the wave frequency and antenna size is inversely proportional, and using the higher frequency wave, the smaller antenna size will be obtained. Thus, millimeter wave makes it possible to have a lot of transmitters and receivers installed on a small size cell or panel. Cloud RAN and MEC represent a big step forward in increasing the flexibility of the 5G network infrastructure, with the purpose to improve scalability and service support with virtualization and softwarization. NOMA motivated by the key challenge of finding and analyzing theoretical bounds for NOMA in massive communications. The 5G deployment has advantageous and disadvantageous but the advantageous will be more than the disadvantageous with concerns, therefore, the researchers are invited to go through deep and wide range of experimental works to minimize these disadvantages and the solution of most of these side effects will be minimized by the application of 6G and Beyond by using the 5G wireless satellites services in near future to avoid direct radiofrequency waves. It is concluded that that the millimeter waves development is the dominant innovation of 5G technology and 5G technology is not limited to telecommunication services but it represents the Beyond technology in research, automotive, energy, e-business, e-government, e-economy, vertical industry, security, experimentations, e-Health, sport, which improve human being’s life and facilitates the challenges of technology services and save money and space and offer faster speeds for uploading and downloading services. This will be the future benchmark of smart city.
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