-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 1
CHAPTER 1
INTRODUCTION
The rapid increase of mobile data growth and the use of smart
phones are creating
unprecedented challenges for wireless service providers to
overcome a global bandwidth
shortage. As today's cellular providers attempt to deliver high
quality, low latency video
and multimedia applications for wireless devices, they are
limited to a carrier frequency
spectrum ranging between 700 MHz and 2.6 GHz.
The global spectrum bandwidth allocation for all cellular
technologies does not
exceed 780 MHz, where each major wireless provider has
approximately 200 MHz across
all of the different cellular bands of spectrum available to
them. Servicing legacy users
with older inefficient cell phones as well as customers with
newer smart phones requires
simultaneous management of multiple technologies in the same
band-limited spectrum.
Currently, allotted spectrum for operators is dissected into
disjoint frequency bands, each
of which possesses different radio networks with different
propagation characteristics and
building penetration losses. This means that base station
designs must service many
different bands with different cell sites, where each site has
multiple base stations (one
for each frequency or technology usage e.g. third generation
(3G), fourth generation (4G),
and Long Term Evolution - Advanced (LTE-A)).
To obtain new spectrum, it can take a decade of administration
through regulatory
bodies such as the International Telecommunication Union (ITU)
and the U.S. Federal
Communications Commission (FCC). When spectrum is finally
licensed, unavoidable
users must be moved off the spectrum, causing further delays and
increasing costs.
The need for high-speed connectivity is a common denominator as
we look ahead
to next generations of networks. Achieving 24x7 access to, and
sharing of, all our stuff
requires that we continue on our current path: going far beyond
simple voice and data
services, and moving to a future state of everything everywhere
and always connected.
Today, as the provisioning and take-up of data services, and the
types of connected
devices, on both fixed-line and mobile networks continues to
increase exponentially, the
rules of network provisioning need to be re-written. Data
services are by their nature
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 2
discontinuous. Moving to packet rather than circuit-based
service delivery allows more
users to share the same resource even though the overhead
associated with directing the
data becomes more complex. As fixed-line network infrastructures
have moved from
copper to the virtually-limitless capacity of fiber, this packet
delivery overhead has not
been an issue.
Successive advances in mobile network technology and system
specifications
have provided higher cell capacity and consequent improvements
in single user data rate.
The Increases in data rate have come courtesy of increased
computing power, and
increased modulation density made possible by better components,
particularly in the area
of digital receivers. In all this, there is one certainty that
must be considered wireless
spectrum is limited. In the long run, this must mean only those
connections which MUST
be mobile should be wireless. Were already seeing the rise of
television and radio
services delivered over the internet, todays Wi-Fi offload
becomes the starting point for
the norm of tomorrow, freeing up cellular system capacity to
give mobile users the best
possible service.
In the mobile world, capacity gains come essentially from three
variables: more
spectrum, better efficiency and better frequency re-use through
progressively smaller cell
size. Freeing up frequency bands currently used for other
systems will become a major
priority. Mobile broadband networks need to support ever-growing
consumer data rate
demands and will need to tackle the exponential increase in the
predicted traffic volumes.
An efficient radio access technology combined with more spectrum
availability is
essential to achieve the ongoing demands faced by wireless
carriers.
In this report, how millimeter wave beam forming can be used for
5G cellular is
presented & also the reasons why the wireless community
should start looking at the 3 -
300 GHz spectrum for mobile broadband applications. Discusses
propagation and device
technology challenges associated with this band as well as its
unique advantages for
mobile communication. And introduce a millimeter-wave mobile
broadband (MMB)
system as a candidate for next generation mobile communication
system. And show the
feasibility for MMB to achieve gigabit-per-second data rates at
a distance up to 1 km in
an urban mobile environment.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 3
CHAPTER 2
LITERATURE SURVEY
To date, four generations of cellular communication systems have
been adopted
worldwide with each new mobile generation emerging every 10
years or so since
around 1980: first generation analog FM cellular systems in
1981; second generation
digital technology in 1992, 3G in 2001, and 4G LTE-A in
2011.
Review of Previous Fourth Generations Systems:-
First-Generation Systems (1G):
The 1st generation was pioneered for voice service in early
1980s, where almost
all of them were analog systems using the frequency modulation
technique for radio
transmission using frequency division multiple access (FDMA)
with channel capacity of
30 KHz and frequency band was 824-894 MHz, which was based on a
technology known
as Advance Mobile Phone Service (AMPS).
Second Generation Systems (2G):
The 2nd generation was accomplished in later 1990s. The 2G
mobile
communication system is a digital system; this system is still
mostly used in different
parts of the world. This generation mainly used for voice
communication also offered
additional services such as SMS and e-mail. In this generation
two digital modulation
schemes are used; one is time division multiple access (TDMA)
and the 2nd is code
division multiple access (CDMA) and frequency band is 850-1900
MHzs. In 2G, GSM
technology uses eight channels per carrier with a gross data
rate of 22.8 kbps (a net rate
of 13 kbps) in the full rate channel and a frame of 4.6
milliseconds (ms) duration .The
family of this generation includes of 2G, 2.5G and 2.75G.
Third Generation Systems (3G):
Third generation (3G) services combine high speed mobile access
with Internet
Protocol (IP)-based services. The main features of 3G technology
include wireless web
base access, multimedia services, email, and video conferencing.
The 3G W-CDMA air
interface standard had been designed for always-on packet-based
wireless service, so that
computer, entertainment devices and telephones may all share the
same wireless network
and be connected internet anytime, anywhere.
3G systems offer high data rates up to 2 Mbps, over 5 MHz
channel carrier width,
depending on mobility/velocity, and high spectrum efficiency.
The data rate supported by
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 4
3G networks depends also on the environment the call is being
made in; 144 kbps in
satellite and rural outdoor, 384 kbps in urban outdoor and 2Mbps
in indoor and low range
outdoor. The frequency band is 1.8 - 2.5 GHz.
Fourth Generation Systems (4G):
4G usually refers to the successor of the 3G and 2G standards.
In fact, the 3GPP
is recently standardizing LTE Advanced as future 4G standard. A
4G system may
upgrade existing communication networks and is expected to
provide a comprehensive
and secure IP based solution where facilities such as voice,
streamed multimedia and data
will be provided to users on an "Anytime, Anywhere" basis and at
much higher data rates
compared to previous generations. Applications such as wireless
broadband access,
Multimedia Messaging Service (MMS), video chat, mobile TV, HDTV
content and
Digital Video Broadcasting (DVB) are being developed to use a 4G
network.
4G-LTE advanced:
LTE also referred to as LTE-Advanced, is claimed to be the true
4G evolution
step. LTE is an orthogonal frequency-division multiplexing
(OFDM)-based radio access
technology that supports a scalable transmission band width up
to 20 MHz and advanced
multi-antenna transmission. As a key technology in supporting
high data rates in 4G
systems, Multiple-Input Multiple-Output (MIMO) enables
multi-stream transmission for
high spectrum efficiency, improved link quality, and adaptation
of radiation patterns for
signal gain and interference mitigation via adaptive beam
forming using antenna arrays .
The coalescence of HSPA and LTE will increase the peak mobile
data rates of the two
systems, with data rates exceeding 100 Mbps, and will also allow
for optimal dynamic
load balancing between the two technologies.
Earlier releases of LTE are included as integrated parts of LTE
release 10,
providing a more straightforward backwards compatibility and
support of legacy
terminals, for example. The main requirement specification for
LTE advanced as
approved are:
Peak Downlink data rate: 1 Gbps, Peak Uplink data rate: 500
Mbps.
Transmission bandwidth: Wider than approximately 70 MHz in DL
and 40
MHz in UL.
User throughput at cell edge 2 times higher than that in
LTE.
Average user throughput is 3 times higher than that in LTE.
Spectrum efficiency 3 times higher than that in LTE; Peak
spectrum
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 5
Efficiency downlink: 30 bps/Hz, Uplink: 15 bps/Hz.
Mobility: Same as that in LTE.
Coverage should be optimized or deployment in local areas/micro
cell
Environments with Inter Site Distance (ISD) up to 1 km.
Fig.2.Evolution of wireless communication
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 6
CHAPTER 3
FIFTH GENERATION (5G) WIRELESS COMMUNICATION
As fifth generation (5G) is developed and implemented, we
believe the main differences
compared to 4G will be the use of much greater spectrum
allocations at untapped mm-
wave frequency bands, highly directional beam forming antennas
at both the mobile
device and base station, longer battery life, lower outage
probability, much higher bit
rates in larger portions of the coverage area, lower
infrastructure costs, and higher
aggregate capacity for many simultaneous users in both licensed
and unlicensed spectrum
(e.g. the convergence of Wi-Fi and cellular).
The backbone networks of 5G will move from copper and optic
fiber to mm-wave
wireless connections, allowing rapid deployment and mesh-like
connectivity with
cooperation between base stations.
5G technology has changed to use cell phones within very high
bandwidth. 5G is
a packet switched wireless system with wide area coverage and
high throughput. 5G
technologies use CDMA and millimeter wireless that enables speed
greater than 100Mbps
at full mobility and higher than1Gbps at low mobility. The 5G
technologies include all
types of advanced features which make 5G technology most
powerful and in huge
demand in the near future. It is not amazing, such a huge
collection of technology being
integrated into a small device. The 5G technology provides the
mobile phone users more
features and efficiency. A user of mobile phone can easily hook
their 5G technology
gadget with laptops or tablets to acquire broadband internet
connectivity. Up till now
following features of the 5G technology have come to surface-
High resolution is offered
by 5G for extreme mobile users, it also offers bidirectional
huge bandwidth , higher data
rates and the finest Quality of Service (QOS) .
Now a day, all wireless and mobile networks are forwarding to
all-IP principle,
that means all data and signaling will be transferred via IP
(Internet Protocol) on network
layer. The purpose of the All-IP Network (AIPN) is to completely
transform (to change
in composition or structure) the 100+ years of legacy network
infrastructure into a
simplified and standardized network with a single common
infrastructure for all services.
In order to implement 5G technology, Master Core technique is
needed to apply
All-IP Network (AIPN) properly. Hence, the Master core is
designed. The 5G Master
Core is a convergence of Parallel Multimode (PMM),
Nanotechnology, Cloud
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 7
Computing, and All IP Platform also 5G-IU technology. These
technologies have their
own impacts on existing wireless networks which make them into
5G.
5G wireless networks will support 1,000-fold gains in capacity,
connections for
at least 100 billion devices, and a 10 Gbps individual user
experience capable of
extremely low latency and response times. Deployment of these
networks will emerge
between 2020 and 2030. 5G radio access will be built upon both
new radio access
technologies (RAT) and evolved existing wireless technologies
(LTE, HSPA, GSM and
Wi-Fi). Breakthroughs in wireless network innovation will also
drive economic and
societal growth in entirely new ways. 5G will realize networks
capable of providing zero-
distance connectivity between people and connected machines.
5G requirements are:-
Immersive experience: at least 1 Gbps or more data rates to
support ultra-high
definition video and virtual reality applications.
Fiber-like user experience: 10 Gbps data rates to support mobile
cloud service.
Zero latency and response times: less than one millisecond
latency to support
real time mobile control and vehicle-to-vehicle applications and
communications.
Zero second switching: max 10 millisecond switching time between
different
radio access technologies to ensure a consistently seamless
delivery of services.
Massive capacity and always on: current mobile network systems
already
support 5 billion users; this will need to expand to also
support several billions of
applications and hundreds of billions of machines.
Energy consumption: energy-per-bit usage should be reduced by a
factor of
1,000 to improve upon connected device battery life.
Advantages of using 5G:-
5G technology will include spectral bandwidth more than 40 MHz
on frequency
channel which is a larger range than all other wireless
technology systems.
The artificial intelligence will be included in 5G technology
through advance
wearable computer technology.
Massive Distributed with Multiple-input and multiple-output
(MIMO) will be
provided by 5G which will help cut costs and make it
energy-effective.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 8
5G technologies may consume low battery power, provide a wide
range of
coverage, cheap rate of network services and many other
advantages.
4G technology provides speed up to 1 GBPS internet speed and so
it is possible
that 5G technology will provide more than 1 GBPS speed.
They are more efficient, highly reliable, highly secured
network.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 9
CHAPTER 4
MILLIMETER (mm) WAVE TECHNOLOGY
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 4. Millimeter wave frequency spectrum
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).
This 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
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 10
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, due to the natural evolution of computer and
communications technology. Our
work contemplates a 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
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 11
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.
4.1 HISTORY OF mmWAVE
Though relatively new in the world of wireless communication,
the history of millimeter
wave technology goes back to the 1890s when J.C. Bose was
experimenting with
millimeter wave signals at just about the time when his
contemporaries like Marconi were
Inventing radio communications.
Following Boses research, millimeter wave technology remained
within the
confines of university and government laboratories for almost
half a century. The
technology started so see its early applications in Radio
Astronomy in the 1960s,
followed by applications in the military in the 70s. In the 80s,
the development of
millimeter-wave integrated circuits created opportunities for
mass manufacturing of
millimeter wave products for commercial applications.
In 1990s, the advent of automotive collision avoidance radar at
77 GHz marked
the first consumer oriented use of millimeter wave frequencies
above 40 GHz. In 1995,
the FCC (US Federal Communications Commission) opened the
spectrum between 59
and 64 GHz for unlicensed wireless communication, resulting in
the development of a
plethora of broadband communication and radar equipment for
commercial application.
In 2003, the FCC authorized the use of 71-76 GHz and 81-86 GHz
for licensed point-to-
point communication, creating a fertile ground for new of
industries developing products
and services in this band.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 12
Fig 4.1.0 J.C. Bose demonstrating millimeter wave in 1897
4.2 BENEFITS OF mm-WAVE SPECTRUM
Bandwidth: - The main benefit that millimeter Wave technology
has over RF
frequencies is the spectral bandwidth of 5GHz being available in
these ranges,
resulting in current speeds of 1.25Gbps Full Duplex with
potential throughput
speeds of up to 10Gbps Full Duplex being made possible. Service
providers can
significantly expand channel band width way beyond 20 MHz
Beam Width Interference Resistance: - Millimeter wave signals
transmit in
very narrow focused beams which allows for multiple deployments
in close range
using the same frequency ranges. This allows Millimeter wave
ideal for Point-to-
Point Mesh, Ring and dense Hub & Spoke network topologies
where lower
frequency signals would not be able to cope before cross signal
interference
would become a significant limiting factor. The beam width is
approx. 2 degree
this benefit from increased interference protection and spectrum
reuse. The
highly directional and narrow radiation pattern from millimeter
wave allows
many transmitters to be positioned near each other without
causing troublesome
interference even when they are using the same frequencies.
Using cross-
polarization techniques allows even more radios to be deployed
in an area, even
along the same path.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 13
Security: - Since millimeter waves have a narrow beam width and
are blocked
by many solid structures they also create an inherent level of
security. In order to
sniff millimeter wave radiation a receiver would have to be
setup very near, or in
the path of, the radio connection. The loss of data integrity
caused by a sniffing
antenna provides a detection mechanism for networks under
attack. Additional
measures, such as cryptographic algorithms can be used that
allow a network to
be fully protected against attack.
Fig 4.2. Millimeter wave beam width
4.3 ANTENNAS:- Due to the recent advancements in VLSI technology
it is possible to
develop circuits that work in millimeter wave frequency range.
The choice of integrated
circuit (IC) technology depends on the implementation aspects
and system requirements.
The former is related to the issues such as power consumption,
efficiency, dynamic range,
linearity requirements, integration level, and so forth, while
the later is related to the
transmission rate, cost and size, modulation scheme, transmit
power, bandwidth, and so
forth.
Narrow beam is the key feature of millimeter wave because of
this property we
can reduce fading, multipath and interference. The antenna
geometry is at chip size
because they have to operate in high frequency rage.
The physical size of the antennas are so small, this becomes
practical to build
complex smart antenna arrays that are steerable in nature.
Further integrating them on
chip or PCB becomes more feasible. These smart array antennas
are adaptive in nature.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 14
Fig 4.3 Antenna array for highly directional MIMO
transmission
4.4 PROPAGATION BEHAVIOUR
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.
Fig. 4.4.1.LOS and non-LOS links
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 15
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.
Fig. 4.4.2. Outdoor & indoor mesh
Path loss exponent for LOS path=2
Path loss exponent for non-LOS path =4
So, to improve the performance is
Incorporate directional beam forming.
Receiver and transmitter antenna should communicate via. Main
lobes to
achieve higher array gain.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 16
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
Fig 4.4.2 Performance improvements
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 17
CHAPTER 5
mm-WAVE CHANNEL PROPAGATION
5.1 THEORY AND MEASUREMENTS
There have been concerns about utilizing mm Wave frequency bands
for mobile cellular
communications. Some of these concerns regarding the propagation
characteristics at
higher frequencies such as higher penetration, precipitation,
and foliage losses are
reasonable even though the actual amounts of additional
propagation losses vary
depending on the material of the building, the strength of rain,
or the thickness of foliage.
The most common misunderstanding, however, of the propagation
characteristics at
higher frequencies is that they always incur a much higher
Propagation loss even in free
space compared to lower frequencies, and thus are not adequate
for long-range
communications. To clarify this misunderstanding, let us start
with the Friis transmission
equation, given by Eq. (5.1)
(5.1)
Where Pr is the receive power in unobstructed free space, Pt is
the transmit power,
Gt and Gr are the transmit and receive antenna gains, R is the
distance between the
transmitter and receiver in meters, f is the carrier frequency,
c is the speed of light.
The received power can easily be seen as inversely proportional
to the frequency
squared when an ideal isotropic radiator (Gt = 1) and an ideal
isotropic receiver (Gr = 1)
are used at each end. In reality, however, antennas or an array
of antennas with antenna
gains of Gt and Gr greater than unity are typically employed at
both ends, and the antenna
gains are proportional to the frequency squared given a fixed
physical aperture size. Given
the same physical aperture size, therefore, transmit and receive
antennas at higher
frequencies, in fact, send and receive more energy through
narrower directed beams,
which is not commonly recognized . In order to verify this,
measurements have been
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 18
conducted in an anechoic chamber using two antennas supporting 3
and 30 GHz,
respectively, as shown in Fig. 5.1.
Fig.5.1 Results of verification measurements of propogation loss
predicted by
Friis equation
A patch antenna at 3 GHz and an array antenna at 30 GHz of the
same physical
size were designed for this measurement and placed within an
anechoic chamber at each
communication ends. The results in Fig. 5.1 show the same amount
of propagation loss
regardless of the operating frequency when an array antenna of
the same physical aperture
size is used at the 30 GHz receiving end. In addition, when
array antennas are used at
both transmitting and receiving ends at 30 GHz, the measured
receive power is 20 dB
higher than that of the 3GHz patch antenna case.
Along with the above-mentioned laboratory measurements , there
have been
recent studies regarding the outdoor channel propagation
characteristics that have shown
the potential for utilizing higher frequency bands for cellular
communications, outdoor
channel measurements were carried out at 38and 28 GHz,
respectively, on the campus of
the University of Texas at Austin. Another channel measurement
campaign was
conducted at 28GHz to produce measurement data for a suburban
environment at the
Samsung Electronics site in Suwon, Korea . In addition,
investigation of the channel
characteristics in a dense urban environment was done in
Manhattan, New York. All these
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 19
channel measurements were carried out at 38 and 28 GHz instead
of 60GHz and E-Band,
with many aspects considered including regional regulatory
status and availability of
significant amount of licensed spectrum. These study results
reveal that the key
parameters characterizing the propagation properties of the mm
Wave bands, such as the
path loss exponent, are comparable to those of typical cellular
frequency bands when
transmit and receive antennas are used to produce beam forming
gains. Transmission
links were established for a distance of up to 200300 m with
path loss exponents in the
range of 3.24.58 for NLoS and 1.682.3 for LoS environments,
which are similar to
those measured in the traditional cellular bands. Path loss
exponents below 2 are
frequently observed due to constructive addition of the
reflected and direct paths in street
corridors or tunnels in LoS environments.
While more extensive measurement campaigns are currently being
carried out in
Korea and in the United States to build a comprehensive
statistical mmWave channel
propagation model, it is evident that the mmWave bands have
strong potential as
candidate bands for next generation cellular services. After the
verification of the channel
feasibility, the next step is to develop underlying core
technologies to most efficiently
utilize the abundant spectrum in the mmWave bands and prove
commercial viability.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 20
CHAPTER 6
mm-WAVE BEAMFORMING ALGORITHM
An appropriate beam forming scheme focus the transmitted and/or
received signal in a
desired direction in order to overcome the unfavourable path
loss is one of the key
enablers for cellular communications at mm Wave frequency bands.
The small
wavelengths of mm Wave frequencies facilitate the use of a large
number of antenna
elements in a compact form factor to synthesize highly
directional beams corresponding
to large array gains.
Depending on the beamforming architecture, the beam forming
weights required
to form the directive beam could be applied in the digital or
analog domain. When
combined with an orthogonal frequency-division multiplexing
(OFDM) system, digital
beamforming is carried out on a subcarrier basis before the
inverse fast Fourier transform
(IFFT) operation at the transmitter and after the FFT operation
at the receiver, whereas
analog beamforming is performed in the time domain after the
IFFT operation at the
transmitter and before the FFT operation at the receiver
Digital Beamforming
Digital beamforming is done in the form of digital precoding
that multiplies a
particular coefficient to the modulated baseband signal per RF
chain.
Higher degree of freedom
Better performance
Highly flexible
Support for data multiplexing
increased complexity & cost
separate FFT/IFFT blocks , DACs, ADCs required / each RF
chain
Analog Beamforming
For analog beamforming, complex coefficients are applied to
manipulate the RF
signals by means of controlling phase shifters and/or variable
gain amplifiers (VGAs).
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 21
Simple
Beam forming with scalar complex weights
Effective method to generate high beamforming gains from large
number
of antennas
Reduce costs & complexity and power consumption
less flexible
It is this trade-off between flexibility/performance and
simplicity that drives the
need for hybrid beamforming architectures, especially when a
multitude of antennas is
required as in the mmWave bands.
Hybrid Beamforming Architecture
A hybrid beamforming architecture applied at both the
transmitter and receiver is
illustrated in fig. In this architecture, the sharp beams formed
with analog beamforming
(phase shifters) compensate for the large path loss at mm Wave
bands, and digital
beamforming provides the necessary flexibility to perform
advanced multi-antenna
techniques such as multi-beam MIMO.
Fig.6.Block diagram of Hybrid Beamforming Architecture
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 22
In hybrid analog-digital transceiver architecture, full spatial
processing at RF
frontend is to divide spatial processing on both RF-frontend and
baseband processing
units. The target of this hybrid multi-beam beamforming
architecture is provide support
for data multiplexing with reduced power consumptions and costs.
Similarly to analog
beamforming architecture, phase shifters in RF beamformers are
controlled digitally to
form narrow beams. The target of RF phase-shifters is to enable
adaptive analog beam
steering. The purpose of digital domain spatial processing is to
perform actual precoding
according to certain optimization criteria, e.g. zero-forcing,
minimum mean square error
(MMSE). The simulated performance of the hybrid beamforming
architecture in mm
Wave bands are presented in , where link- and system-level
simulation results are
provided with various numbers of transmit/receive antennas and
RF chains. Using a 500
MHz bandwidth at 28 GHz, presents some notable results for the
hybrid beamforming
system including an 8 dB gain over the conventional spatial
multiplexing scheme and 8
Gb/s average sector throughput with 16antennas with 4 RF chains
at the base station and
8 antennas with a single RF chain at the mobile station.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 23
CHAPTER 7
PROPOSED mm-WAVE BEAMFORMING
PROTOTYPE
The main purposes of the mm Wave prototype are to check the
feasibility of mm Wave
bands for sufficiently large geographical coverage for cellular
services and support for
mobility even in NLoS environments. The mm Wave beamforming
prototype developed
and tested at the DMC R&D Centre, Samsung Electronics,
Korea, including system
configuration, key parameters, and capabilities are described
here. This prototype
includes RF units, array antennas, baseband modems, and a
diagnostic monitor (DM), as
shown in Fig.7.1
Fig.7.1 Configuration of mmWave beamforming prototype
It is the worlds first mmwave mobile technology. Adaptive array
transceiver
technology operating in the millimeterwave frequency bands for
outdoor cellular
systems includes
RF units
array antennas
baseband modems
diagnostic monitor (DM)
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 24
Fig.7.2 Prototype setup model
Both transmit and receive array antennas have two channels.
Each comprises 32 antenna elements arranged in the form of a
uniform planar
array (UPA) with 8 horizontal and 4 vertical elements, confined
within an area of
60 mm 30 mm. This small footprint was made possible by the short
wavelength
of the carrier frequency at 27.925 GHz.
Two channels at the transmit and receive array antennas are
designed to support
various multi-antenna schemes such as MIMO and diversity.
The array antenna is connected to the RF unit, which contains a
set of phase
shifters, mixers, and related RF circuitry.
The set of phase shifters control the phases of the signals sent
to the antennas to
form a desired beam pattern. Therefore, by setting the phase
shifter values to a
particular set, transmit and receive array antennas are capable
of forming a sharp
beam pattern in the intended horizontal(azimuth) and vertical
(elevation) angles.
To reduce the hardware complexity, a sub-array architecture was
employed to
group8 antennas into a sub-array, thus requiring only4 RF units
per channel
instead of 32.
The reduction in the number of RF paths results in a reduction
of antenna gain at
the desired angle(except antenna bore sight), a reduction of
beam scanning ranges,
and an increase in side lobe levels, but still meets the overall
beamforming
requirements.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 25
The resulting full width at half maximum (FWHM) of the beam at
the antenna
bore sight is approximately 10 horizontally and20 vertically
with an overall
beamforming gain of 18 dBi.
In addition, a set of beam patterns is predefined to reduce the
feedback overhead
required for the adaptive beamforming operation between the
transmitter and the
receiver, where the overlapped beam patterns cover the intended
service area with
a unique beam identifier (ID) for each beam.
These beam IDs are used by the baseband modem to control the
phase shifter
weights and to feed back the preferred transmission beam
information to the
transmitter.
The baseband modem shown in Fig. 7.1 was designed and
implemented for real-
time operation with commercial off-the-shelf signal processing
units including
Xilinx Virtex-6 field programmable gate arrays (FPGAs), and an
ADC and a
DAC each with up to 1 Gs/s conversion rate.
The analog signal ports of the modem analog front-end (AFE) are
connected to
the RF/antenna input (output) port to transmit (receive) the
complex analog
baseband signal.
The baseband modem is linked to a DM program developed to
visualize the
operational status of the system and collect system statistics
including data
throughput, packet error rates, transmit/receive beam IDs,
received signal
constellations, and signal strengths.
Two sets of the mm Wave beamforming prototypes as specified
above were built,
playing the roles of a base station and a mobile station, and
various laboratory
and field tests in both indoor and outdoor environments were
performed.
For the downlink transmission, the base station periodically
transmits a sequence
of beam measurement signals in predefined beams so that the
mobile station can
carry out, also in predefined receive beams, channel quality
measurements of the
transmit-receive beam pairs and thus select the best beam pair
for data
transmissions.
The selected base station transmit beam ID is fed back to the
base station for the
subsequent downlink transmission until the next update
incident.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 26
In this fashion, the base and mobile stations quickly establish
the wireless
communications link and adaptively sustain the link even in high
mobility
conditions.
The communications link setup for the uplink is done in an
analogous way where
the roles of the base station and mobile stations are
interchanged.
The developed mm Wave beamforming prototype was designed to
complete the
search for the best transmit and receive beam pair within 45
ms.
Table 1 lists key system parameters of the implemented
prototype.
Fig.7.3.Key system parameters of the mmWave beamforming
prototype
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 27
CHAPTER 8
PROTOTYPE TEST RESULTS
Using the mmWave adaptive beamforming prototype, comprehensive
indoor and outdoor
field tests were carried out at the campus of Samsung
Electronics headquarters in Suwon,
Korea in early 2013.An aggregated peak data rate of 1.056 Gb/s
was achieved in the
laboratory with negligible packet error using two channels at
the base station supporting
two stationary mobile stations with 528 Mb/s each.
Outdoor coverage tests
- To demonstrate the service availability in a typical outdoor
environment for both
LoS and NLoS sites.
- The tests were performed at sites surrounded by tall buildings
where various
channel propagation effects such as reflection, diffraction, or
penetration are
expected to take place, as shown in Fig. 8.3.
Fig.8.1.Outdoor coverage test results of mmwave beamforming
prototype
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 28
Outdoor LineofSight (LoS) Range Test
- Error free communications possible at 1.7 Km LoS with >
10dB TX power
headroom
- Pencil BF both at TX and RX supporting long range
communications.
Fig.8.2 Outdoor LineofSight (LoS) Range Test
Outdoor NonLineofSight (NLoS) Mobility Tests
- Fast Joint Beamforming & Tracking Supports 8 km/h Mobility
in NLOS
- Mobility support up to 8 Km/h at outdoor NLoS environments
- 16QAM (528Mbps) : BLER 0~0.5%
- QPSK (264Mbps) : Error Free
Fig.8.3 Outdoor NonLineofSight (NLoS) Mobility Tests
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 29
As can be seen from the test results in Fig.8.3, satisfactory
communications links were
discovered even in NLoS sites more than 200 m away, mostly due
to reflections off
neighbouring buildings. On the other hand, there were a few
locations where a proper link
could not be established (i.e., coverage holes), which
necessitate solutions for coverage
improvement such as optimized cell deployment, intercell
coordination, relays, or
repeaters. Considering one of the important operation scenarios
in practical cellular
networks, communication between an outdoor base station and an
indoor mobile station
was also investigated. The above test results present link
qualities between an outdoor
base station to an indoor mobile station placed inside a typical
modern office building
with heavily tinted glass at more than 150 m separation. These
types of buildings are
representative of presenting highly unfavourable propagation
(penetration) conditions
even for current cellular frequency bands below 6 GHz.
Surprisingly amicable indoor
coverage results were obtained with only the totally obstructed,
farthest side of the
building resulting in lost connections. While the spots showing
BLERs around 10~20
percent can be improved with conventional error correction
schemes such as hybrid
automatic repeat request (HARQ) and modulation/coding adaptation
schemes, remaining
coverage holes would need to be covered with other alternative
schemes, such as repeaters
and indoor femto cells, as in traditional cellular systems.
Building Penetration Test
- Outdoortoindoor penetration made through tinted glasses and
doors
- Most Signals Successfully Received at Indoor MS from Outdoor
BS
Fig.8.4 Building Penetration Test
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 30
The test results were extremely encouraging and resulted in
error-free transmission at
264 Mb/s and less than 1 percent BLER at 528 Mb/s transmissions
due to the fast adaptive
beamforming algorithm running at both communications ends. The
design capability of
the adaptive joint beam searching and switching algorithms
implemented in our prototype
could easily support mobility higher than 8 km/h. The ensuing
results will provide a firm
ground for the development of mm Wave-beam forming-based 5G
cellular networks.
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 31
CHAPTER 9
CONCLUSION
An overview of using Millimeter wave Mobile Communication for 5G
Cellular is
presented in this paper, and how 5G Cellular systems can
overcome the issues related to
the previous generations of Communication systems and evolved to
be the most
promising System.
As the additional availability of spectrum for cellular usage in
the lower
frequencies becomes scarce, the significant amount of
underutilized spectrum in the
mmWave bands could potentially provide the answer to the very
large bandwidth
requirements for 5G.The large bandwidth available at millimeter
wave frequencies results
in very high data transmission rate; also helps to minimize the
amount of time that a node
needs to stay in transmission mode; and therefore, minimizes the
possibility of its
transmission being detected. This article shows how these high
frequencies exhibit them-
selves as strong candidates for cellular bands with recent
channel measurement,
simulation, and prototype results.
The advanced hybrid beamforming algorithm described exploits
both analog and
digital domain beamforming, which not only offers sharp
beamforming to cope with the
propagation loss but also allows advanced digital domain
processing such as multi-beam
MIMO with manageable complexity. The main portion of the article
is dedicated to
presenting the results of recent mmWave prototype, which
features a large system
bandwidth in excess of 500 MHz at 28 GHz and supports tens of
antennas placed in planar
arrays at both ends of the communications. The prototype
incorporates a real-time
baseband modem, full mmWave RF circuitry, and relevant software.
The advanced
adaptive beamforming system successfully demonstrates that the
mmWave frequency
band is capable of supporting a few-hundred-meter radius of
outdoor and indoor coverage
with more than 500 Mb/s data rate with support for mobility as
high as 8 km/h even in
NLoS environments. The security and reliability provided is
quite huge. Hence
considering all the factors given above these millimeter wave
frequencies is going to serve
the future generations of wireless communications enabling the
ALL IP features and
providing good quality of service (QOS).
-
MILLIMETER-WAVE BEAMFORMING FOR 5G CELLULAR COMMUNICATIONS
FEDERAL INSTITUTE OF SCIENCE AND TECHNOLOGY, M.TECH
COMMUNICATION ENGINEERING 32
REFERENCES
[1]. Wonil Roh, Ji-Yun Seol, JeongHo Park, Byunghwan Lee, Jaekon
Lee,
Yungsoo Kim, Jaeweon Cho, Kyungwhoon Cheun, Millimeter-Wave
Beamforming as an Enabling Technology for 5G Cellular
Communications , IEEE Commun. Mag., Feb. 2014, pp.106-13.
[2]. T. Rappaport et al., Millimeter Wave Mobile Communications
for 5G
Cellular: It Will Work! IEEE Access, vol.1, May 2013, pp.
33549.
[3]. Z. Pi and F. Khan, `An introduction to millimeter-wave
mobile broadband
systems,'' IEEE Commun. Mag., vol. 49, no. 6, pp. 101_107, Jun.
2011.
[4]. S. Rangan, T. S. Rappaport, and E. Erkip, Millimeter-Wave
Cellular
Wireless Networks: Potentials and Challenges,Proc. IEEE,
vol.
102, no. 3, Mar. 2014, pp. 36686
[5]. T. Rappaport et al., Broadband Millimeter-Wave
Propagation
Measurements and Models Using Adaptive-Beam Antennas for
Outdoor
Urban Cellular Communications, IEEE Trans. Antennas and
Propagation, vol. 61, no. 4, Apr. 2013, pp. 185059.