what will 5g be? seminar report

What Will 5G Be? 2014-2015

CHAPTER 1

INTRODUCTION

5G is the next step in the evolution of mobile communication. It will be a key

component of the Networked Society and will help realize the vision of essentially

unlimited access to information and sharing of data anywhere and anytime for anyone

and anything. 5G will therefore not only be about mobile connectivity for people.

Rather, the aim of 5G is to provide ubiquitous connectivity for any kind of device and

any kind of application that may benefit from being connected.

Mobile broadband will continue to be important and will drive the need for

higher system capacity and higher data rates. But 5G will also provide wireless

connectivity for a wide range of new applications and use cases, including wearables,

smart homes, traffic safety/control, and critical infrastructure and industry

applications, as well as for very-high-speed media delivery. In contrast to earlier

generations, 5G wireless access should not be seen as a specific radio access

technology. Rather, it is an overall wireless-access solution addressing the demands

and requirements of mobile communication beyond 2020.

LTE will continue to develop in a backwards-compatible way and will be an

important part of the 5G wireless-access solution for frequency bands below 6GHz.

Around 2020, there will be massive deployments of LTE providing services to an

enormous number of devices in these bands. For operators with limited spectrum

resources, the possibility to introduce 5G capabilities in a backwards-compatible way,

thereby allowing legacy devices to continue to be served on the same carrier, is highly

beneficial and, in some cases, even vital.

In parallel, new radio-access technology (RAT) without backwards-

compatibility requirements will emerge, at least initially targeting new spectrum for

which backwards compatibility is not relevant. In the longer-term perspective, the

new non-backwards-compatible technology may also migrate into existing spectrum.

Although the overall 5G wireless-access solution will consist of different components,

including the evolution of LTE as well as new technology, the different components

should be highly integrated with the possibility for tight interworking between them.

This includes dual-connectivity between LTE operating on lower frequencies and new

technology on higher frequencies. It should also include the possibility for user-plane

aggregation, that is, joint delivery of data via both LTE and a new RAT.

Dept. of CS&E, Vemana Institute of Technology


CHAPTER 2

LITERATURE SURVEY

1. 5G technology of mobile communication: A survey: Gohil, A, Modi, H, Patel

S.K, Charotar Univ. of Sci. & Technol., Changa, India S,2013.

5G, researches are related to the development of World Wide Wireless Web

(WWWW), Dynamic Adhoc Wireless Networks (DAWN) and Real Wireless

Communication. The most important technologies for 5G technologies are 802.11

Wireless Local Area Networks (WLAN) and 802.16 Wireless Metropolitan Area

Networks (WMAN), Ad-hoc Wireless Personal Area Network (WPAN) and Wireless

networks for digital communication. 4G technology will include several standards

under a common umbrella, similar to 3G, but with IEEE 802.xx wireless mobile

networks integrated from the commencement. The major contribution of this paper is

the key provisions of 5G (Fifth Generation) technology of mobile communication,

which is seen as consumer oriented. In 5G technology, the mobile consumer has given

utmost priority compared to others. 5G Technology stands for 5th Generation Mobile

Technology. 5G technology is to make use of mobile phones within very high

bandwidth. The consumer never experienced the utmost valued technology as 5G.

The 5G technologies include all types of advanced features which make 5G

technology most dominant technology in near future.

2. Massive MIMO for Next Generation Wireless Systems,Erik G. Larsson, Ove

Edfors, Fredrik Tufvesson, Thomas L. Marzetta, IEEE Vol. 52, No. 2, pp.

186-195, Feb. 2014

Multi-user Multiple-Input Multiple-Output (MIMO) offers big advantages over

conventional point-to-point MIMO: it works with cheap single-antenna terminals, a

rich scattering environment is not required, and resource allocation is simplified

because every active terminal utilizes all of the time-frequency bins. However, multi-

user MIMO, as originally envisioned with roughly equal numbers of service-antennas

and terminals and frequency division duplex operation, Massive MIMO (also known

as "Large-Scale Antenna Systems", "Very Large MIMO") makes a clean break with

current practice through the use of a large excess of service-antennas over active

terminals and time division duplex operation. Extra antennas help by focusing energy

into ever-smaller regions of space to bring huge improvements in throughput and

radiated energy efficiency.



3. Millimeter Wave Mobile Communications for 5G Cellular, Rappaport T.S.,

Shu Sun ,Mayzus R., Hang Zhao, Azar Y., Wang K., Wong, G.N., Schulz

J.K., Samimi M., Gutierrez, F.IEEE, Page(s):335-349,2013.

The global bandwidth shortage facing wireless carriers has motivated the exploration

of the underutilized millimeter wave (mm-wave) frequency spectrum for future

broadband cellular communication networks. There is, however, little knowledge

about cellular mm-wave propagation in densely populated indoor and outdoor

environments. Obtaining this information is vital for the design and operation of

future fifth generation cellular networks that use the mm-wave spectrum. In this

paper, we present the motivation for new mm-wave cellular systems, methodology,

and hardware for measurements and offer a variety of measurement results that show

28 and 38 GHz frequencies can be used when employing steerable directional

antennas at base stations and mobile devices.

4. N. Lee, R. W. Heath Jr., D. Morales-Jimenez, and A. Lozano, “Base station

cooperation with dynamic clustering in super-dense cloudRAN,” in IEEE

GLOBECOM’13 Workshop on Cloud-Processing in Heterogeneous Mobile

Communication Networks, Dec. 2013.

The mobile Internet has seen tremendous progress due to the standardization efforts

around WiMAX, LTE and beyond. There are also early trends towards adoption of

software radio and a growing presence of general purpose platforms in wireless

networking. Such platforms are programmer-friendly and with recent advances on

multi-core and hybrid architectures, allow signal processing, network processor class

packet processing, wire-speed computation and server-class virtualization capabilities

for software radio realizations of 3G and 4G wireless stacks. Software radio over IT

platforms will enable the virtualization of base stations and consolidation of virtual

base stations into central pools (a local “cloud site”) with fiber connectivity to towers,

which we call a Wireless Network Cloud (WNC). A Virtual base station (BS) pool

supporting multiple BS software instances over a general OS and IT platform is an

important step towards the realization of the larger WNC concept. This paper

introduces the first TDD WiMAX SDR BS implemented on a commodity server, in

conjunction with a novel design of a remote radio head (RRH). We also present the

first working prototype of a virtual BS (VBS) pool, exploring the systems challenges

in supporting a VBS pool on multi-core IT platforms. The results from our VBS pool

prototype for WiMAX verify that these solutions can meet system requirements

including synchronization, latency and jitter.


http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Gutierrez,%20F..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Samimi,%20M..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Schulz,%20J.K..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Schulz,%20J.K..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Wong,%20G.N..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Wang,%20K..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Azar,%20Y..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Hang%20Zhao.QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Mayzus,%20R..QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Shu%20Sun.QT.&newsearch=true

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Rappaport,%20T.S..QT.&newsearch=true


CHAPTER 3

5G Requirements and Capabilities

In order to enable connectivity for a very wide range of applications with

vastly different characteristics and requirements, the capabilities of 5G wireless

access must extend far beyond those of previous generations of mobile

communication.

3.1 MASSIVE SYSTEM CAPACITY

Traffic demands for mobile-communication systems are predicted to increase

dramatically. To support such traffic in an affordable way, 5G networks must be able

to deliver data with much lower cost per bit compared with the networks of today.

Furthermore, in order to be able to operate with the same or preferably even lower

overall energy consumption compared with today, 5G must enable radically lower

energy consumption per delivered bit.

Another aspect of 5G system capacity is the capability to support a much

larger number of devices compared with today. The new use cases envisioned for 5G

include, for example, the deployment of billions of wirelessly connected sensors,

actuators and similar devices. Each device will typically be associated with very little

traffic, implying that, even jointly, they will have a limited impact on the overall

traffic volume. However, the sheer number of devices to be connected provides a

challenge, for example, in terms of efficient signaling protocols.


Fig. 1 5G Requirements and Capabilities


3.2 VERY HIGH DATA RATES EVERYWHERE

Every generation of mobile communication has been associated with higher data

rates compared with the previous generation. In the past, much focus has been on the

peak data rate that can be supported by a wireless-access technology under ideal

conditions. However, a much more important capability is the data rate that can

actually be provided under real-life conditions in different scenarios.

5G should be able to provide data rates exceeding 10Gbps in specific

scenarios such as indoor and dense outdoor environments.

Data rates of several 100Mbps should be generally achievable in urban and

suburban environments.

Data rates of at least 10Mbps should be achievable essentially everywhere,

including sparsely populated rural areas in both developed and developing

countries.

3.3 VERY LOW LATENCY

Lower latency has been a key target for both 4G and the evolution of 3G,

driven mainly by the continuous quest for higher achievable data rates. Due to

properties of the internet protocols, lower latency over the wireless interface is critical

to realize the higher data rates. 5G targets even higher data rates, and this in itself will

drive a need for even lower latency. However, lower latency will also be driven by the

support for new applications. Some of the envisioned 5G applications, such as traffic

safety and control of critical infrastructure and industry processes, may require much

lower latency compared with what is possible with the mobile communication

systems of today. To support such latency-critical applications, 5G should allow for

an application end-to-end latency of 1ms or less.

3.4 ULTRA-HIGH RELIABILITY AND AVAILABILITY

In addition to very low latency, 5G should also enable connectivity with ultra-

high reliability and ultra-high availability. For critical services, such as control of

critical infrastructure and traffic safety, connectivity with certain characteristics, such

as a specific maximum latency, should not only be ‘typically available.’ Rather,

connectivity with the required characteristics has to be always available with

essentially no deviation.



3.5 VERY LOW DEVICE COST AND ENERGY CONSUMPTION

The possibility for low cost and low energy consumption for mobile devices

has been a key requirement since the early days of mobile communication. However,

in order to enable the vision of billions of wirelessly connected sensors, actuators and

similar devices, a further step has to be taken in terms of device cost and energy

consumption. It should be possible for such 5G devices to be available at very low

cost and with a battery life of several years without recharging.

3.6 HIGH NETWORK ENERGY PERFORMANCE

While device energy consumption has always been prioritized, high energy

performance on the network side.

High network energy performance is an important component in reducing

operational cost, as well as a driver for better dimensioned nodes, leading to

lower total cost of ownership.

High network energy performance allows for off-grid network deployments

relying on decently sized solar panels as power supply, thereby enabling

wireless connectivity to even the most remote areas.

High network energy performance is part of a general operator aim of

providing wireless access in a sustainable and more resource-efficient way.

The importance of these factors will increase further in the 5G era, and the possibility

of very high network energy performance will therefore be an important requirement

in the design of 5G wireless access.



CHAPTER 4

KEY TECHNOLOGIES

4.1 Extreme Densification and Offloading

Ultra-dense networks will arise not only from an expanded user base and

shorter links, but also from an enriched topology, including different technologies and

operating in different spectral bands. Their purpose is to provide more capacity

through offloading where needed, such as in large sporting events (on an as-needed

basis, since there are of relatively short duration), in public places with a lot of users

such as airports, university campuses, or malls, or indoors, where the absorption loss

due to walls can considerably reduce link margin and, therefore, throughput. With the

advent of ultra-dense networks combined with the diminished role of the legacy

macrocell, handsets in close vicinity of each other can communicate directly through

device-to-device links. The many advantages extend from reduced power emission

and interference, to group broadcast and mesh networking, to enhanced security

provided from the absence of intermediate network routing. However, ultra-dense

networks pose their own set of challenges that must be addressed in order for them to

help achieve the 1000x increase in capacity required for 5G networks.

Fig. 2 Ultra dense Small Cells.

New propagation models are needed for ultra-dense networks. Driven by legacy

cellular systems, most models currently available are tower-to-ground with base

stations typically at 30 m and above. Device-to-device links, however, will be ground



to-ground: picocells on lightpoles and indoor femtocells placed on table tops or

mounted on walls or ceilings will be < 10 m above ground. The problem is that few

ground-to-ground channel models to date exist in the literature. In addition, most

channel models assume independent fading between links. In ultra-dense networks in

particular, it does not hold good because there will be significant correlation between

links, necessitating the study of joint links. NIST also has expertise in this area, but

much more work needs to be done for sufficient characterization. In addition, the

introduction of carrier aggregation to provide additional bandwidth will require

developing ground-to-ground and indoor channel models for new frequency bands. In

addition to channel propagation models, detailed system models are needed to

accurately characterize and develop signal processing algorithms at the physical

(PHY) layer, as well as Medium Access Control (MAC) layer and routing protocols.

A big issue that needs to be dealt with is interference mitigation:

Coordination algorithms for synchronizing cells, managing power, and

selecting carriers needs to be examined in terms of their inaccuracy (timing

offsets, etc.), and how these impact performance.

Determining the limits of densification (i.e. how much capacity reuse is

possible before interference or channel effects or overhead causes saturation)

is an important issue that needs to be addressed. This will require development

of additional models and simulation tools to answer.

Also, small cells in ultra-dense deployments that are not serving UEs (user

equipment) may go into sleep mode to conserve power, resulting in a network

populated by base stations that turn on and off in response to UE migration.

Additionally, future networks may include small cells that are deployed by

customers without direct setup by the service provider. This means that base

stations in ultra-dense deployments must be able to autonomously perform self-

organizing functions such as discovery, synchronization, authentication, and

power control, and selection of appropriate common carriers in networks that use

carrier aggregation.

5G and all networks beyond it will be extremely dense and heterogeneous,

which introduces many new challenges for network modeling, analysis, design

and optimization. It allows users in close proximity to establish direct

communication, replacing two long hops via the BS with a single shorter hop.



Provided there is sufficient spatial locality in the wireless traffic, reduced power

consumption and/or higher data rates, and a diminished latency.

4.2 Millimetre Wave

mmWave is a promising technology for future cellular systems. Since

limited spectrum is available for commercial cellular systems, most research has

focused on increasing spectral efficiency by using OFDM, MIMO, efficient

channel coding, and interference coordination. Network densification has also

been studied to increase area spectral efficiency, including the use of

heterogeneous infrastructure (macro, Pico, femto cells, relays, distributed

antennas) but increased spectral efficiency is not enough to guarantee high user

data rates. The alternative is more spectrum.

Millimeter wave (mmWave) cellular systems, operating in the 30-300GHz

band, above which electromagnetic radiation is considered to be low (or far)

infrared light, also referred to as terahertz radiation.

Fig. 3 Millimeter wave frequency spectrum.

The main reason that mmWave spectrum lies idle, because of atmospheric and

rain absorption, strong path loss, low diffraction around obstacles and penetration

through objects.

Despite industrial research efforts to deploy the most efficient wireless

technologies possible, the wireless industry always eventually faces overwhelming

capacity demands for its currently deployed wireless technologies, brought on by the

continued advances and discoveries in computing and communications, and the

emergence of new customer handsets and use cases (such as the need to access the

internet).



mmWave trend will occur in the coming years for 4G LTE, implying that at

some point around 2020; wireless networks will face congestion, as well as the need

to implement new technologies and architectures to properly serve the continuing

demands of carriers and customers.

The life cycle of every new generation of cellular technology is generally a

decade or less (as shown earlier), due to the natural evolution of computer and

communications technology. Wireless future where mobile data rates expand to the

multi gigabit-per-second range, made possible by the use of steerable antennas and

mm-wave spectrum that could simultaneously support mobile communications and

backhaul, with the possible convergence of cellular and Wi-Fi services.

Recent studies suggest that mm-wave frequencies could be used to augment

the currently saturated 700 MHz to 2.6 GHz radio spectrum bands for wireless

communications. The combination of cost-effective CMOS technology that can now

operate well into the mm-wave frequency bands, and high-gain, steerable antennas at

the mobile and base station, strengthens the viability of mm-wave wireless

communications. Further mm-wave carrier frequencies allow for larger bandwidth

allocations, which translate directly to higher data transfer rates.

Mm-wave spectrum would allow service providers to significantly expand the

channel bandwidths far beyond the present 20 MHz channels used by 4G customers.

By increasing the RF channel bandwidth for mobile radio channels, the data capacity

is greatly increased, while the latency for digital traffic is greatly decreased, thus

supporting much better internet based access and applications that require minimal

latency. Mm-wave frequencies, due to the much smaller wavelength, may exploit

polarization and new spatial processing techniques, such as massive MIMO and

adaptive beam forming.

Given this significant jump in bandwidth and new capabilities offered by mm-

waves, the base station-to-device links, as well as backhaul links between base

stations, will be able to handle much greater capacity than today's 4G networks in

highly populated areas. Also, as operators continue to reduce cell coverage areas to

exploit spatial reuse, and implement new cooperative architectures such as

cooperative MIMO, relays, and interference mitigation between base stations, the cost

per base station will drop as they become more plentiful and more densely distributed

in urban areas, making wireless backhaul essential for flexibility, quick deployment,

and reduced ongoing operating costs. Finally, as opposed to the disjointed spectrum



employed by many cellular operators today, where the coverage distances of cell sites

vary widely over three octaves of frequency between 700 MHz and 2.6 GHz, the mm-

wave spectrum will have spectral allocations that are relatively much closer together,

making the propagation characteristics of different mm-wave bands much more

comparable and ``homogenous''. The 28 GHz and 38 GHz bands are currently

available with spectrum allocations of over 1 GHz of band-width. Originally intended

for Local Multipoint Distribution Service (LMDS) use in the late 1990's, these

licensees could be used for mobile cellular as well as backhaul.

A common myth in the wireless engineering community is that rain and

atmosphere make mm-wave spectrum useless for mobile communications. However,

when one considers the fact that today's cell sizes in urban environments are on the

order of 200 m, it becomes clear that mm-wave cellular can overcome these issues.

Fig. 3.1 and Fig. 3.2 show the rain attenuation and atmospheric absorption

characteristics of mm-wave propagation. It can be seen that for cell sizes on the order

of 200 m, atmospheric absorption does not create significant additional path loss for

mm-waves, particularly at 28 GHz and 38 GHz. Only 7 dB/km of attenuation is

expected due to heavy rainfall rates of 1 inch/hr for cellular propagation at 28 GHz,

which translates to only 1.4 dB of attenuation over 200 m distance. Work by many

researchers has confirmed that for small distances (less than 1 km), rain attenuation

will present a minimal effect on the propagation of mm-waves at 28 GHz to 38 GHz

for small cells.



Fig. 3.1 Rain attenuation in dB/km across frequency at various rainfall rates

Fig. 3.2 Atmospheric absorption across mm-wave frequencies in dB/km

Millimeter Wave Challenges:

1) Propagation Behavior

Millimeter wave transmission and reception is based on the principle of line of

sight (LOS) paths. Received signal strength is relatively stronger than other directions

in line of sight (LOS) path. Line of sight path correspond to the situations where the



main lobes of the transmitter and receiver pair are positioned in a way to capture the

line of sight.

Since the beam width is narrow and the distance covered by millimeter wave is small

(approx. 200 m). Even if there are obstacles usually large objects such as buildings

blocks these LOS paths we can still use mm-wave by the principle of Non-line of

sight propagation.

Non-line of sight path propagation takes place through paths that contains a single-

reflected signal and multiple reflected signal which will yield the best signal strength

for the receiver.

Except for connections between fixed devices, such as a PC and its peripherals, where

non-LOS may be encountered permanently, but most cases involves portable devices

that should be able to have LOS connections because these devices can be moved to

adjust aiming.

These reflections can establish non-LOS links, but these will be still tens of dB

weaker than LOS signal, hence the data rates provided by these non-LOS links are

quite less compared to rates provided by LOS signal.

So, how to improve the performance is

Incorporate directional beam forming.

Receiver and transmitter antenna should communicate via. Main beam to

achieve higher array gain.

Self-steerable smart antenna is required such that it adjust automatically to

achieve higher gain; hence the data rate is increased.

Smart antenna is required to distinguish between LOS and non LOS paths

2) Large Arrays, Narrow Beams

Fig. 3.3 millimeter wave beam width



Building a cellular system out of narrow and focused beams is highly

nontrivial and changes many traditional aspects of cellular system design. MmWave

beams are highly directional, almost like flashlights, which completely changes the

interference behavior as well as the sensitivity to misaligned beams. The interference

adopts an on/off behavior where most beams do not interfere, but strong interference

does occur intermittently. Overall, interference is de-emphasized and mmWave

cellular links may often be noise limited, which is a major reversal from 4G. Indeed,

even the notion of a “cell” is likely to be very different in a mmWave system since,

rather than distance, blocking is often the first order effect on the received signal

power.

Link acquisition. A key challenge for narrow beams is the difficulty in

establishing associations between users and BSs, both for initial access and for

handoff. To find each other, a user and a BS may need to scan lots of angular

positions where a narrow beam could possibly be found, or deploy extremely

large coding/spreading gains over a wider beam that is successively narrowed

in a multistage acquisition procedure. Developing solutions, particularly in the

context of high mobility, is an important research challenge.

Leveraging the legacy 4G network. A concurrent utilization of microwave

and mmWave frequencies could go a long way towards overcoming some of

the above hurdles. An interesting proposal in that respect is the notion of

“phantom cells” (relabeled “soft cells” within 3GPP), where mmWave

frequencies would be employed for payload data transmission Signalling Data

from small-cell BSs while the control plane would operate at microwave

frequencies from macro BSs (Fig. 3.4). So it ensure stable and reliable control

connections, based on which blazing fast data transmissions could be arranged

over short range mmWave links. Sporadic interruptions of these mmWave

links would then be far less consequential, as control links would remain in

place and lost data could be recovered through retransmissions.

Fig. 3.4 mmWave-enabled network with phantom cells.



Novel transceiver architectures needed. Despite the progress made in WiFi

mmWave systems, nontrivial hardware issues remain and in some cases will

directly affect how the communication aspects are designed. Chief among

these is the still-exorbitant power consumption of particularly the analogto-

digital (A/D) but also the digital-to-analog (D/A) converters needed for large

bandwidths. A main consequence is that, although large antenna arrays and

high receiver sensitivities are needed to deal with the pathloss, having

customary fully digital beam formers for each antenna appears to be

unfeasible. More likely are structures based on old-fashioned analog phase

shifters or, perhaps, hybrid structures where groups of antennas share a single

A/D and D/A. On the flip side, offering some relief from these difficulties, the

channels are sparser and thus the acquisition of channel-state information is

facilitated; in particular, channel estimation and beamforming techniques

exploiting sparsity in the framework of compressed sensing are being

explored.

4.3 Massive MIMO

Multiple-antenna (MIMO) technology is becoming mature for wireless

communications and has been incorporated into wireless broadband standards like

LTE and Wi-Fi. Basically, the more antennas the transmitter/receiver is equipped

with, the more the possible signal paths and the better the performance in terms of

data rate and link reliability. The price to pay is increased complexity of the hardware

(number of RF amplifier frontends) and the complexity and energy consumption of

the signal processing at both ends.


Hundreds of Base Stations


Fig. 4: Massive MIMO

In single-user MIMO (SU-MIMO), the dimensions are limited by the number

of antennas that can be accommodated on a portable device. However, by having each

BS communicate with several users concurrently, the multiuser version of MIMO

(MU-MIMO) can effectively pull together the antennas at those users and overcome

this bottleneck. Then, the signaling dimensions are given by the smallest between the

aggregate number of antennas at those users and the number of antennas at the BS.

Furthermore, coordinated multipoint (CoMP) transmission/reception, multiple BSs

can cooperate and act as a single effective MIMO transceiver thereby turning some of

the interference in the system into useful signals.

Well-established by the time LTE was developed, MIMO was a native

ingredient thereof with two-to-four antennas per mobile unit and as many as eight per

base station sector, and it appeared that, because of form factors and other apparent

limitations, such was the extent to which MIMO could be leveraged. a number of

antennas much larger than the number of active users per time-frequency signaling

resource and given that under reasonable time-frequency selectivity accurate channel

estimation can be conducted for at most some tens of users per resource, puts the

number of antennas per base station into the hundreds. Initially it is termed as “large-

scale antenna systems” also known as “massive MIMO”.

Offers enticing benefits:

An enormous enhancement in spectral efficiency without the need for

increased BS densification, with the possibility as is always the case of trading

some of those enhancements off for power efficiency improvements.

Smoothed out channel responses because of the vast spatial diversity, which

brings about the favorable action of the law of large numbers. In essence, all

small-scale randomness abates as the number of channel observations grows.



Simple transmit/receive structures because of the quasiorthogonal nature of

the channels between each BS and the set of active users sharing the same

signaling resource. For a given number of active users, such orthogonality

sharpens as the number of BS antennas grows and simple linear transceivers,

even plain single user beamforming, perform close-to-optimally.

Massive MIMO Challenges:

1) Pilot Contamination and Overhead Reduction: Pilot transmissions can be made

orthogonal among same-cell users, to facilitate cleaner channel estimates but must be

reused across cell for otherwise all available resources would end up consumed by

pilots. It causes interference among pilots in different cells and hence puts a floor on

the quality of the channel estimates. So it’s called “pilot contamination,” does not

vanish as the number of BS antennas grows large, and so is the one impairment that

remains asymptotically. However, pilot contamination is a relatively secondary factor

for all but colossal numbers of antennas. Furthermore, various methods to reduce and

even eliminate pilot contamination via low-intensity coordination have already been

formulated. Still, a careful design of the pilot structures is required to avoid an

explosion in overhead. The ideas being considered to reign in pilot overheads include

exploiting spatial correlations, so as to share pilot symbols among antennas, and also

segregating the pilots into classes (e.g., channel strength gauging for link adaptation v.

data detection) such that each class can be transmitted at the necessary rate, and no

faster.

2) Architectural Challenges: A more serious challenge to the realization of the

massive MIMO vision has to do with its architecture. The vision requires radically

different BS structures where, instead of a few high-power amplifiers feeding a

handful of sector antennas, number of tiny antennas fed by correspondingly low-

power amplifiers; most likely each antenna would have to be integrated with its own

amplifier. Scalability, antenna correlations and mutual couplings, and cost, are some

of the issues that must be sorted out. At the same time, opportunities arise for

innovative topologies such as conformal arrays along rooftops or on building facades,

and we next dwell on a specific topological aspect in which innovation is taking

place.

3) Full-Dimension MIMO and Elevation Beamforming: Existing BSs mostly

feature linear horizontal arrays, which in tower structures can only accommodate a

limited number of antennas, due to form factors, and which only exploit the azimuth



angle dimension. By adopting planar 2D arrays and further exploiting the elevation

angle, so-called full-dimension MIMO (FD-MIMO) can house many more antennas

with the same form factor. As a side benefit, tailored vertical beams increase the

signal power and reduce interference to users in neighboring cells. Some preliminary

cell average and edge data rates obtained from Samsung’s network simulator are

listed in Table I where, with numbers of antennas still modest for what massive

MIMO is envisioned to be, multiple-fold improvements are observed.

TABLE I: FD-MIMO system-level downlink simulation results at 2.5 GHz. Half-

wavelength antenna spacing in both the horizontal and vertical dimensions at the BSs,

2 antennas per user, 30% overhead. The baseline is SU-MIMO with 4 antennas per

BS and the FD-MIMO results (average and edge data rates) are for MU-MIMO with

16 and 64 antennas, respectively corresponding to 4 × 4 and 8 × 8 planar arrays per

BS sector.

SU-MIMO FD-MIMO 16 FD-MIMO 64

Aggregate Data Rate (b/s/Hz/cell) 2.32 3.28 6.37

Edge Data Rate (b/s/Hz) 0.063 0.1 0.4

4) Channel Models: Parallel to the architectural issues run those related to channel

models, which to be sound require extensive field measurements. Antenna

correlations and couplings for massive arrays with relevant topologies must be

determined, and a proper modeling of their impact must be established; in particular,

the degree of actual channel orthogonalization in the face of such nonidealities must

be verified. And for FD-MIMO, besides azimuth, the modeling needs to incorporate

elevation, which is a dimension on which far less data exists concerning power

spectra and angle spreads. A 3D channel modeling study currently under way within

3GPP is expected to shed light on these various issues.

5) Coexistence with Small Cells: massive MIMO BSs would most likely have to

coexist with tiers of small cells, which would not be equipped with massive MIMO

due to their smaller form factor. Although the simplest alternative is to segregate the

corresponding transmissions in frequency, the large number of excess antennas at

massive MIMO BSs may offer the opportunity of spatial nulling and interference

avoidance with relative simplicity and little penalty. As networks become dense and

more traffic is offloaded to small cells, the number of active users per cell will



diminish and the need for massive MIMO may decrease. Aspects such as cost and

backhaul will ultimately determine the balance between these complementary ideas.

6) Coexistence with mmWave: mmWave communication requires many antennas

for beamsteering. The antennas are much smaller at these frequencies and thus very

large numbers thereof can conceivably fit into portable devices, and these antennas

can indeed provide beamforming power gain. Any application of massive MIMO at

mmWave frequencies would have to find the correct balance between power

gain/interference reduction and parallelization.

CHAPTER 5

DESIGN ISSUES FOR 5G

5.1 The Waveform: Signaling and Multiple Access



The signaling and multiple access formats, i.e., the waveform design, have

changed significantly at each cellular generation and to a large extent they have been

each generation’s defining technical feature. They have also often been the subject of

fierce intellectual and industrial disputes, which have played out in the wider media.

The 1G approach, based on analog frequency modulation with FDMA, transformed

into a digital format for 2G and, although it employed both FDMA and TDMA for

multiple access, was generally known as “TDMA” due to the novelty of time-

multiplexing. Meanwhile, a niche spread spectrum/CDMA standard that was

developed by Qualcomm to compete for 2G became the dominant approach to all

global 3G standards. Once the limitations of CDMA for high-speed data became

inescapable, there was a discreet but unmistakable retreat back towards TDMA, with

minimal spectrum spreading retained and with the important addition of channel-

aware scheduling. Due to the increasing signal bandwidths needed to support data

applications, orthogonal frequency-division multiplexing (OFDM) was unanimously

adopted for 4G in conjunction with scheduled FDMA/TDMA as the virtues of

orthogonality were viewed with renewed appreciation.5G could involve yet another

major change in the signaling and multiple access formats.

1) OFDM and OFDMA: OFDM has become the dominant signaling format for high-

speed wireless communication, forming the basis of all current WiFi standards and of

LTE, and further of wire line technologies such as digital subscriber lines, digital TV,

and commercial radio. Its qualities include:

A natural way to cope with frequency selectivity.

Computationally efficient implementation via FFT/IFFT blocks and simple

frequency-domain equalizers.

An excellent pairing for MIMO, since OFDM allows for the spatial

interference from multiantenna transmission to be dealt with at a subcarrier

level, without the added complication of intersymbol interference.

From a multiple access vantage point, OFDM invites dynamic fine-grained resource

allocation schemes in the digital domain, and the term OFDMA is employed to denote

orthogonal multiple access at a subcarrier level. In combination with TDMA, the

time-frequency grid into small units known as resource blocks that can be easily

discriminated through digital filtering. Being able to do frequency and time slot

allocation digitally also enables more adaptive and sophisticated interference

management techniques such as fractional frequency reuse or spectrum partitions



between small cells and macrocells. Finally, given its near-universal adoption,

industry has by now a great deal of experience with its implementation, and tricky

aspects of OFDM such as frequency offset correction and synchronization have been

essentially conquered.

2) Drawbacks of OFDM: OFDM is the unquestionable frontrunner for 5G. However,

some weak points do exist that could possibly become more pronounced in 5G

networks.

First, the peak-to-average-power ratio (PAPR) is higher in OFDM than in

other formats since the envelope samples are nearly Gaussian due to the summation of

uncorrelated inputs in the IFFT. Although a Gaussian signal distribution is capacity

achieving under an average power constraint, in the face of an actual power amplifier

a high PAPR sets up an unattractive tradeoff between the linearity of the transmitted

signal and the cost of the amplifier. This problem can be largely overcome by

precoding the OFDM signals at the cost of a more involved equalization process at the

receiver and a slight power penalty; indeed, this is already being done in the LTE

uplink.

Second, OFDM’s spectral efficiency is satisfactory, but could perhaps be

further improved upon if the requirements of strict orthogonality were relaxed and if

the cyclic prefixes (CPs) that prevent interblock interference were smaller or

discarded. The use of a novel OFDMA-based modulation scheme named frequency

and quadrature amplitude modulation (FQAM), which is shown to improve the

downlink throughput for cell-edge users. Perhaps the main source of concerns is the

applicability of OFDM to mmWave spectrum given the enormous bandwidths therein

and the difficulty of developing efficient power amplifiers at those frequencies. For

example, a single-carrier signaling with null cyclic prefix as an alternative to OFDM

at mmWave frequencies.

3) Potential Alternatives to OFDM: Some alternative approaches to incremental

departures from OFDM rather than the step-function changes that took place in

previous cellular generations.

Time-frequency packing: Time-frequency packing and faster-than-Nyquist

signaling have been recently proposed to circumvent the limitations of strict

orthogonality and CP. In contrast to OFDM, where the product of the symbol

interval and the subcarrier spacing equals 1, in faster-than-Nyquist signaling



products smaller than 1 can be accommodated and spectral efficiency

improvements on the order of 25% have been claimed.

Nonorthogonal signals: There is a growing interest in multicarrier formats,

such as filter bank multicarrier, that are natively nonorthogonal and thus do

not require prior synchronization of distributed transmitters. A new format

termed universal filtered multicarrier (UFMC) has been proposed whereby,

starting with an OFDM signal, filtering is performed on groups of adjacent

subcarriers with the aim of reducing side lobe levels and intercarrier

interference resulting from poor time/frequency synchronization.

Filter bank multicarrier: To address the drawbacks of rectangular time

windowing in OFDM, namely the need for large guard bands, the use of filter

bank multicarrier permits a robust estimation of very large propagation delays

and of arbitrarily high carrier frequency offsets, whereas OFDM would have

required a very long CP to attain the same performance levels.

Generalized frequency division multiplexing: GFDM is a multicarrier

technique that adopts a shortened CP through the tail biting technique and is

particularly well suited for noncontiguous frequency bands, which makes it

attractive for spectrum sharing where frequency-domain holes may have to be

adaptively filled.

Single carrier: Single-carrier transmission has also been attracting renewed

interest, chiefly due to the development of low-complexity nonlinear

equalizers implemented in the frequency domain.

Tunable OFDM: OFDM could be well adapted to different 5G requirements

by allowing some of its parameters to be tunable, rather than designed for

essentially the worst-case multipath delay spread. In particular, given the

increasingly software-defined nature of radios, the FFT block size, the

subcarrier spacing and the CP length could change with the channel

conditions: in scenarios with small delay spreads—notably dense urban/small

cells and mmWave channels—the subcarrier spacing could grow and the FFT

size and the CP could be significantly shortened to lower the latency, the

PAPR, the CP’s power and bandwidth penalty, and the computational

complexity; in channels with longer delay spreads, that could revert to

narrower subcarriers, longer FFT blocks, and a longer CP.



5.2 Cloud-Based Networking

Cloud networking is to provide network services in a manner similar to the

elastic compute and storage services provided in cloud computing so that it can be

accessed from anywhere and via a variety of platforms. And to use cloud computing

technologies within the network infrastructure as a more flexible, cost effective

approach to support both traditional network services and those delivered to

application tenants in a cloud computing environment. Network function

virtualization (NFV) and software defined networking (SDN) are the two technologies

to advance mobile communication networking. Although the move towards

virtualization is thus far taking place only within the core network, this trend might

eventually expand towards the edges. In fact, the term cloud-RAN is already being

utilized, but for now largely to refer to schemes whereby multiple BSs are allowed to

cooperate. If and when the BSs themselves become virtualized down to the MAC and

PHY.

1) Network Function Virtualization: NFV enables network functions that were

traditionally tied to hardware appliances to run on cloud computing infrastructure in a

data center. It should be noted that this does not imply that the NFV infrastructure will

be equivalent to commercial cloud or enterprise cloud. What is expected is that there

will be a high degree of reuse of what commercial cloud offers. It is natural to expect

that some requirements of mobile networks such as the separation of the data plane,

control plane and management plane, will not be feasible within the commercial

cloud. Nevertheless, the separation of the network functions from the hardware

infrastructure will be the cornerstone of future architectures.

Virtualizing Network Functions can potentially offer many benefits including, but not

limited to:

Reduced equipment diversity and reduced power consumption through

consolidating equipment and exploiting the economies of scale of the IT

industry.

Architecturally decoupling the network function, based in software, from the

support infrastructure, based in hardware. This can provide independent

scaling and innovation among both.

Increased speed of Time to Market by minimizing the typical network

operator cycle of innovation. Economies of scale required to cover



investments in hardware-based functionalities are strongly mitigated through

software-based deployment, making other modes of feature evolution feasible.

Availability of network appliance multi-version and multi-tenancy, which

allows use of a single platform for different applications, users and tenants.

This allows network operators to share resources across services and across

different customer bases.

Targeted service introduction based on geography or customer sets is possible.

Services can be rapidly scaled up/down as required.

Ability to deploy systems that elastically support various network functional

demands and which allow directing the capacity of a common resource pool

against a current mix of demands in a flexible manner.

Enable a wide variety of eco-systems and encourage openness. NFV opens the

virtual appliance market to pure software entrants, small players and

academia, thus encouraging more innovation to bringing more new services

and new revenue streams quickly at much lower risk.

Enable new types of network services. NFV can readily be applied to the

control and management plane in addition to the data plane. This allows

virtual networks to be created and managed by end users and third parties

using the tools and capabilities heretofore reserved only for native network

operators.

To leverage these benefits, there are a number of technical challenges which need to

be addressed:

Achieving high performance virtualized network appliances which are

portable between different hardware vendors, and with different hypervisors.

Achieving co-existence with custom hardware based network platforms while

enabling an efficient migration path to fully virtualized network platforms.

Similarly transitioning from existing BSS and OSS to more nimble DevOps

and Orchestration approaches.

Managing and orchestrating many virtual network appliances while ensuring

security from attack and misconfiguration.

Ensuring the appropriate level of resilience to hardware and software failures.

Integrating multiple virtual appliances from different vendors. AT&T would

like to “mix & match” hardware from different vendors, hypervisors from

different vendors and virtual appliances from different vendors without

incurring significant integration costs and avoiding lock-in.



SDN can act as an enabler for NFV, since the separation of control and data planes

enables the virtualization of the separated control plane software. NFV can also act as

an enabler for Software Defined Networks (SDN), since the separation between data

plane and control plane implementations is simplified when one or both of them are

implemented in software running on top of standard hardware.

2) Software Defined Networking: SDN is an architectural framework for creating

intelligent networks that are programmable, application aware, and more open. SDN

allows the network to transform into a more effective business enabler. SDN enables

applications to request and manipulate services provided by the network and allows

the network to expose network state back to the applications. A key aspect to the

architectural framework is the separation of forwarding from control plane, and

establishment of standard protocols and abstractions between the two. However, the

term SDN is also applied to a number of other approaches that espouse more open,

software-centric methods of developing new abstractions for both the control plane as

well as forwarding plane of networks.

Benefits of SDN include:

Creating multiple, virtual network control planes on common hardware. SDN

can help extend service virtualization and software control into many existing

network elements.

Enabling applications to request and manipulate services provided by the

network and allow the network to expose network state back to the

applications.

Exposing network capabilities through APIs

Making the control of network equipment remotely accessible and modifiable

via third-party software clients, using open protocols such as OpenFlow,

PCEP or even BGP-FlowSpec5.

Logically decoupling network intelligence into differentiated software-based

controllers, as opposed to integrated routers and switches. Often this flexibility

allows a more centralized layer of control with a more global network view,

and that has some benefits in terms of improving control plane algorithms.

5.3 Energy Efficiency

Classical designs for wireless communications, which tend to maximize rate,

capacity and coverage, potentially lead to solutions where energy efficiency drops.



Energy efficiency is understood from two viewpoints. On the one hand, the energy

spent by the infrastructure may increase, implying high operational costs for the

operator that will indirectly affect also the invoice of the finals users. On the other

hand, some communication strategies require high computational burden at the

terminal side having negative impact on battery lifetime. Hence, the intelligent use of

energy becomes a major new target in addition to the classical design criteria.

Currently two approaches to reduce energy consumption on the radio link exist. First,

small cells reduce the distance to the terminal. The main challenges of this approach

are related to providing an economic backhaul solution and to minimize the additional

deployment cost. The second approach is massive MIMO, where energy is more

focused towards the user by means of more directive beams. In this way, less energy

is wasted yielding interference for other users at the end. The challenges of massive

MIMO include the diffusion of energy due to scattering in NLOS scenarios, limiting

the achievable directivity, and the complexity of spatial multiplexing of users. Both in

the terminal and at the base station, the goal of minimizing the energy consumption

per bit will require a paradigm shift in wireless system design to dramatically improve

efficiency in terms of power and spectrum usage. Further research on implementation

technologies is necessary, focused on low power hardware architectures and energy

efficient signal processing. Some approaches have been proposed on multihop

cooperative networking, and wireless network coding. There are further potential

savings by operating the network with energy efficiency in mind. Nowadays base

stations consume a constant power, regardless of the traffic load. During off-peak

traffic hours, small cells are switched off while coverage is maintained by macrocells.

For active base stations serving a single user, following Shannon’s theorem, the most

energy efficient situation would be to use the full bandwidth and to reduce power so

that the throughput target is met. However, an interference limited multiuser scenario

is more typical in mobile networks. Serving multiple users having different signal to

interference ratios in a TDMA fashion such as round robin, changing the power

dynamically would result in unpredictable interference in adjacent cells. The same

holds for OFDMA, implying inhomogeneous interference on different frequency sub

bands. Hence, current PHY and MAC layers design needs technology advances,

including dynamic power control that is optimally coordinated among the users and

with surrounding cells so that there is proportionality between the traffic and the

energy consumption. Due to the rapidly increasing network density and the access



network consumes the largest share of the energy. Research has focused on the

following areas.

1) Resource allocation: The design of resource allocation strategies aimed at the

optimization of the system energy efficiency and by accepting a moderate

reduction in the data rates that could otherwise be achieved, large energy savings

can be attained.

2) Network Planning: Energy-efficient network planning strategies include

techniques for minimizing the number of BSs for a coverage target and the design

of adaptive BS sleep/wake algorithms for energy savings, since networks have

been designed to meet peak-hour traffic, energy can be saved by (partially)

switching off BSs when they have no active users or simply very low traffic. Of

course, there are different degrees of hibernation available for a BS2 and attention

must be paid in order to avoid unpleasant coverage holes.

3) Renewable energy: Another intriguing possibility is that of BSs powered by

renewable energy sources such as solar power. In developing countries lacking a

reliable and ubiquitous power grid, but it is also intriguing more broadly as it

allows “drop and play” small cell deployment (if wireless backhaul is available)

rather than “plug and play”. In a dense HetNet, plausible per-BS traffic loads can

actually be served solely by energy harvesting BSs, where the resource allocation

makes efficient use of both renewable and traditional energy sources.

4) Hardware solutions: Finally, much of the power consumption issues will be dealt

with by hardware engineers, low-loss antennas, antenna muting, and adaptive

sectorization according to traffic requirements.

Energy efficiency will be a major research theme for 5G, spanning many of the other

topics.

• True cloud-RAN could provide an additional opportunity for energy efficiency

since the centralization of the baseband processing might save energy,

especially if advances on green data centers are leveraged

• The tradeoff between having many small cells or fewer macrocells given their

very different power consumptions

• A complete characterization of the energy consumed by the circuitry needed

for massive MIMO is currently lacking.

• MmWave energy efficiency will be particularly crucial given the

unprecedented bandwidths.



CHAPTER 6

5G SPECTRUMS, REGULATION AND

STANDARDIZATION FOR 5G



5G technologies will encounter with public policy, industry standardization,

and economic considerations.

6.1 Spectrum Policy and Allocation

The beachfront microwave spectrum is already saturated in peak markets at

peak times while large amounts of idle spectrum do exist in the mmWave. Due to the

different propagation characteristics and phantom cells, future systems will need to

integrate a broad range of frequencies. Low frequencies for wide coverage, mobility

support and control, and high frequencies for small cells. This will require new

approaches to spectrum policy and allocation methods. Massive MIMO and small

cells, which address the efficient use of spectrum, must also be considered important

issues in spectrum policy. Spectrum allocation and policy is an essential topic for 5G.

1) Exclusive Licenses: The traditional approach to spectrum policy is for the

regulator to award an exclusive license to a particular band for a particular

purpose, subject to limitations (e.g., power levels or geographic coverage).

Exclusive access gives full interference management control to the licensee and

provides an incentive for investments in infrastructure, allowing for quality-of

service guarantees. Downsides include high entry barriers because of elevated

sunk costs, both in the spectrum itself and in infrastructure, and that such

allocations are inherently inefficient since they occur over very long time scales

typically decades and thus the spectrum is rarely allocated to the party able to

make the best economic use of it. To address these inefficiencies, market-based

approaches have been propounded. Attempting to implement this idea, spectrum

auctions have been conducted recently to reform spectrum, a process whereby

long-held commercial radio and TV allocations are moved to different (smaller)

bands releasing precious spectrum for wireless communications. A prime example

of this is the so-called “digital dividend” auctions arising from the digitization of

radio and TV. However, there are claims that spectrum markets have thus far not

been successful in providing efficient allocations because such markets are not

sufficiently fluid due to the high cost of the infrastructure. According to these

claims, spectrum and infrastructure cannot be easily decoupled.

2) Unlicensed Spectrum: At the other extreme, regulators can designate a band to

be “open access”, meaning that there is no spectrum license and thus users can



share the band provided their devices are certified (by class licenses). Examples

are the industrial, scientific and medical (ISM) bands, which are utilized by many

devices including microwave ovens, medical devices, sensor networks, cordless

phones and especially by WiFi. With open access, barriers to entry are much

lower and there is enhanced competition and innovation, as the incredible success

of WiFi and other ISM-band applications makes plain.

a. The downside of open access is potentially unmanageable interference, no

quality-of-service guarantees and possibly, the “tragedy of the commons,”

where no one achieves a desired outcome. Still, it is useful to consider the

possibility of open access for bands utilized in small cells as future

networks may involve multiple players and lower entry barriers may be

needed to secure the emergence of small-cell infrastructures.

b. Although interference is indeed a significant problem in current open

access networks, it is interesting to note that cellular operators nevertheless

rely heavily on WiFi offloading: currently about half of all cellular data

traffic is proactively offloaded through unlicensed spectrum. WiFi

hotspots are nothing but small cells that spatially reuse ISM frequencies.

At mmWave frequencies, the main issue is signal strength rather than

interference, and it is therefore plausible that mmWave bands be

unlicensed, or at a minimum several licensees will share a given band

under certain new regulations.

3) Spectrum Sharing: Options do exist halfway between exclusive licenses and

open access, such as the opportunistic use of TV white space. While the potential

of reusing is enticing, it is not crystal clear that reliable communication services

can be delivered that way. Alternatively, Authorized Shared Access and Licensed

Shared Access are regulatory frameworks that allow spectrum sharing by a limited

number of parties each having a license under carefully specified conditions.

Users agree on how the spectrum is to be shared, seeking interference protection

from each other, thereby increasing the predictability and reliability of their

services.

4) Market-Based Approaches to Spectrum Allocation: the advantages of

exclusive licenses for ensuring quality of service, it is likely that most beachfront

spectrum will continue to be allocated that way. Nevertheless, better utilization



could likely be obtained if spectrum markets could become more fluid. To that

end, liberal licenses do not, in principle, preclude trading and reallocation on a fast

time scale, rendering spectrum allocations much more dynamic. Close attention

must be paid to the definition of spectrum assets, which have a space as well as a

time scale, and the smaller the scales, the more fluid the market . In small cells,

traffic is much more volatile than in macrocells and operators may find it

beneficial to enter into sharing arrangements for both spectrum and infrastructure.

Dynamic spectrum markets may emerge, managed by brokers, allowing licenses

to spectrum assets to be bought and sold or leased on time scales of hours, minutes

or even ms. Along these lines, an interesting possibility is for a decoupling of

infrastructure, spectrum and services. In particular, there may be a separation

between spectrum owners and operators. Various entities may own and/or share a

network of BSs, and buy and sell spectrum assets from spectrum owners, via

brokers. These network owners may offer capacity to operators, which in turn

would serve the end customers with performance guarantees. However, would

require very adaptable and frequency agile radios. Offloading onto unlicensed

spectrum such as TV whitespace or mmWave bands could have unexpected

results. In particular, adding an unlicensed shared band to an environment where a

set of operators have exclusive bands can lead to an overall decrease in the total

welfare. because operators might have an incentive to offload traffic even when

this runs counter to the overall social welfare, defined as the total profit of the

operators and the utilities of the users, minus the costs. An operator might have an

incentive to increase prices so that some traffic is diverted to the unlicensed band,

where the cost of interference is shared with other operators, and this price

increase more than offsets the operator’s benefits. Further, while unlicensed

spectrum generally lowers barriers to entry and increases competition, the

opposite could occur and in some circumstances a single monopoly operator could

emerge within the unlicensed bands.

6.2 Regulation and Standardization



Fig. 5 5G Timeline

1) 5G Standardization Status: Several regional forums and projects have been

established to shape the 5G vision and to study its key enabling technologies. For

example, the aforementioned EU project METIS has already released documents

on scenarios and requirements. Meanwhile, 5G has been increasingly referred to

as “IMT-2020” in many industry forums and international telecommunications

union (ITU) working groups [174] with the goal, as the name suggests, of

beginning commercial deployments around 2020. To explore 5G user

requirements and to elaborate a standards agenda to be driven by them, the ETSI

held a future mobile summit in Nov. 2013. The summit concluded, in line with the

thesis of this paper, that an evolution of LTE may not be sufficient to meet the

anticipated 5G requirements.

That conclusion notwithstanding, 5G standardization has not yet formally

started within 3GPP, which is currently finalizing LTE Rel-12 (the third release

for the LTE-Advanced family of 4G standards). The timing of 5G standardization

has not even been agreed upon, although it is not expected to start until later Rel-

14 or Rel-15, likely around 2016–2017. However, many on-going and proposed

study items for Rel-12 are already closely related to 5G candidate technologies

(e.g., massive MIMO) and thus, in that sense, the seeds of 5G are being planted in

3GPP. Whether an entirely new standards body will emerge for 5G which is

unclear; the ongoing success of 3GPP relative to its erstwhile competitors (3GPP2

and the WiMAX Forum) certainly gives it an advantage, although a name change

to 5GPP would seem to be a minimal step.

2) 5G Spectrum Standardization: Spectrum standardization and harmonization

efforts for 5G have begun within the ITU. Studies are under way on the feasibility



of bands above 6 GHz, including technical aspects such as channel modelling,

semiconductor readiness, coverage, mobility support, potential deployment

scenarios and coexistence with existing networks. To be available for 5G,

mmWave spectrum has to be repurposed by national regulators for mobile

applications and agreement must be reached in ITU world radio communication

conferences (WRC) on the global bands for mmWave communications. These

processes tend to be tedious and lengthy, and there are many hurdles to clear

before the spectrum can indeed be available. On the ITU side, WRC-18 is shaping

up as the time and venue to agree on mmWave spectrum allocations for 5G. In

addition to the ITU, many national regulators have also started their own studies

on mmWave spectrum for mobile communications. In the USA, the technological

advisory council of the federal communications committee (FCC) has carried out

extensive investigations on mmWave technology in the last few years and it is

possible that FCC will issue a notice of inquiry in 2014, which is always the first

step in FCC’s rulemaking process for allocation of any new frequency bands. As

discussed above, it is also unclear how such bands will be allocated or even how

they should be allocated, and the technical community should actively engage the

FCC to make sure they are allocated in a manner conducive to meeting 5G

requirements. Historically, other national regulators have tended to follow the

FCC’s lead on spectrum policy.

6.3 Economic Considerations

The economic costs involved in moving to 5G are substantial. Even if

spectrum costs can be greatly reduced through the approaches discussed above, it is

still a major challenge for carriers to densify their networks to the extent needed to

meet 5G requirements. Two major challenges are that BS sites are currently expensive

to rent, and so is the backhaul needed to connect them to the core network.

1) Infrastructure Sharing: One possible new business model could be based on

infrastructure sharing, where the owners of infrastructure and the operators are

different. There are several ways in which infrastructure could be shared.

Passive Sharing. The passive elements of a network include the sites

(physical space, rooftops, towers, masts and pylons), the backhaul connection,

power supplies, and air-conditioning. Operators could cover larger

geographical areas at a lower cost and with less power consumption if they



shared sites, and its might be of particular importance in dense 5G networks.

Regulation could be required to force major operators to share their sites and

improve competition.

Active Sharing. Active infrastructure sharing would involve antennas, BSs,

radio access networks and even core networks. BS and/or radio access

network sharing may be particularly attractive when rolling out small-cell

networks. This type of sharing could lead to collusion, with anticompetitive

agreements on prices and services. Regulations are required to prevent such

collusion, but on the positive side are the economies of scale.

Mobile virtual network operators. A small cell may be operated by a mobile

virtual network operator that does not own any spectrum but has entered into

an agreement with another operator to gain access to its spectrum within the

small cell. The small cell may provide coverage to an enterprise or business

such that, when a user leaves the enterprise, it roams onto the other operator’s

network.

Offloading. Roaming is traditionally used to increase coverage in scenarios

when service providers’ geographical reaches are limited. However, in 5G,

and as discussed above, traffic may be offloaded for a different reason: spatial

and temporal demand fluctuations. Such fluctuations will be greater in

smallcell networks. Recent papers consider the incentive for investment under

various revenue-sharing contracts that sharing increases investment, and the

incentive is greater if the owner of the infrastructure gets the larger fraction of

the revenue when overflow traffic is carried. A bargaining approach for data

offloading from a cellular network onto a collection of WiFi or femtocell

networks.

2) Backhaul: A major consideration that has been considered in several places

throughout the backhaul, which will be more challenging to provide for hyper-

dense ultra-fast networks. However, we find optimism in three directions.

Fiber deployments worldwide continue to mature and reach farther and farther

into urban corridors.

Wireless backhaul solutions are improving by leaps and bounds, with

considerable start-up activity driving innovation and competition. Further,

mmWave frequencies could be utilized for much of the small-cell backhauling

due to their ambivalence to interference. in fact be the first serious deployment



of non-LoS mmWave with massive beamforming gains given that the

backhaul connection is quite static and outdoors-to-outdoors, and thus more

amenable to precise beam alignment.

Backhaul optimization is becoming a pressing concern, given its new status as

a performance-limiting factor. The problem of jointly optimizing resources in

the radio network and across the backhaul. Compression techniques for uplink

cloud-RAN. Another approach is the proactive caching of high bandwidth

content like popular video.

CHAPTER 7



CONCLUSION

5G is the next step in the evolution of mobile communication and will be a

key component of the Networked Society. To enable connectivity for a wide range of

applications and use cases, the capabilities of 5G wireless access must extend far

beyond those of previous generations. These capabilities include very high achievable

data rates, very low latency and ultra-high reliability. Furthermore, 5G wireless access

needs to support a massive increase in traffic in an affordable and sustainable way,

implying a need for a dramatic reduction in the cost and energy consumption per

delivered bit.

5G wireless access will be realized by the evolution of LTE for existing

spectrum in combination with new RAT primarily targeting new spectrum. Key

technology components of 5G wireless access include extension to higher frequency

bands, advanced multi-antenna transmission, lean design, user/control separation,

flexible spectrum usage, device-to-device communication, and backhaul/access

integration.

CHAPTER 7



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