1. No category

5G Wireless and Millimeter Wave Technology Evolution: An Overview
Debabani Choudhury
Intel Labs, Intel Corporation, Hillsboro, OR 97124
Abstract — Current wireless communication networks and
technologies are being pushed to their limits by the massive
growth in demands for mobile wireless data services. We now
stand at a turning point in the wireless communication domain
where the technologies are being driven by applications and
expected use cases. This paper presents an overview on the drivers
behind the 5G evolution and presents the disruptive architectures
and technologies that are creating the backbone for the 5G
transition envisioned beyond 2020.
Index Terms —5G technologies and architectures, MM-waves for
5G, multi-antenna systems, beamforming, Massive MIMO.
I. INTRODUCTION
Next generation of wireless radio standard, 5G must deliver
radical improvement over current 4G in speed and other
functionalities so that it continues to satisfy ever-increasing
user expectations of Quality of Experience (QoE). With the
predicted 100-1000 fold increase in network capacity, 5G
promises to do much more than 4G in terms of denser network
coverage, faster download time, HD-video streaming and so on.
Fig.1 shows the landscape with some performance requirements envisioned for 5G. Proliferation of Internet of Things
(IoT) with 10s of billions of connected devices and entities will
also fuel the need for better Quality of Service (QoS) that
cannot be met just by the LTE evolution. 5G type wireless
network is expected to fill the gap with a revolutionary
enhancement in user experience (UX) [1-6].
to improve network and spectrum efficiency for 5G
transition.
II. KEY TECHNOLOGY DRIVERS FOR 5G
Emerging wide area wireless services and usage cases are
shaping the 5G vision and driving the 5G technology
requirements. Ultra high throughput, enhancement in network
capacity, ultra-low latency, ubiquitous connectivity, energy
efficiency, high reliability, low-cost devices and quality of
experience (QoE) are just some of the requirements that the
next generation wireless needs to achieve. The race is
currently on to find the wireless communication network,
system architectures, and technologies that will bring the big
data to the world beyond 2020.
A. Broadband Mobile with Higher Throughput
Endless enormous growth of data traffic volume is one of
the main drivers behind 5G and the annual 25-50% growth of
data rate is expected to continue till 2030 and beyond [7].
Fig.2 shows a wireless roadmap for market technologies
beyond 2020. Due to the ever-increasing needs for higher
capacity, mobile wireless communication with ultra wide
bandwidth will be the key motivation behind 5G evolution.
5G networks will transfer data much faster than today’s 4G
LTE-A and a major increase in speeds will help in
applications like ultra-fast HD-video streaming and instant
app update.
Fig.2 Wireless Roadmap, showing market entry of technologies [2].
B. Evolution of M2M and IoT
Fig.1 5G landscape and performance requirements.
This paper discusses the key use cases and applications
that are driving the 5G evolution. It also reviews the network
innovations for 5G and presents some enabling technologies
Internet of Things (IoT) proliferation calls for wireless
network densification and provides justification for transition to
5G. Prediction of tens of billions of IoT and machine to machine
(M2M) devices is presenting a unique set of demands from
wireless network service. Smart city/home, smart grid, smart
vehicle, e-health, emerging wearables, wireless industry and
logistics are some of the important drivers for 5G. In an IoT
978-1-4799-8275-2/15/$31.00 ©2015 IEEE
scenario, multifaceted wireless sensor networks will be
embedded in homes and cities for cost-effective, energy-efficient
maintenance with distributed intelligent sensors. In some cases,
both low- and high- cost sensors and video networks will
demand seamless management of the diversely connected
devices. Distributed sensor networks will be remotely controlled
to monitor decentralized distribution and consumption of energy.
Smart city and smart grid type of applications will work with
low- data rate and low-power sensors, but will need efficient,
reliable and low-cost environments [7, 8].
With many use cases of wireless and mobile communications, vehicular industry is becoming another important driver
for 5G. Connected vehicles, remotely controlled and self-driven
automobiles requires ultra-low latency and highly-reliable
wireless communications between infrastructures, human
entities and automobiles using dense networks and intelligent
sensing nodes.
Many industrial entities are also opting for reconfigurable
wireless links to reduce expenses of wired infrastructures. But
the industrial applications demand similar capacity and
reliability as wired setups with lower delay and low-error
probabilities. Logistic and tracking of goods are also use cases
influencing 5G evolution with reliable position and wide
coverage and low-data rate [9].
With the implementation of M2M and IoTs, wireless
communication is connecting an extensively large number of
devices in real time requiring highly-reliable communication
link with low latency and high efficiency.
C. Quality Of Experience (QoE)
In order to provide a high QoE for services, 5G systems will
need to be context-aware, utilizing context information in a realtime manner based on the network, devices, applications, and the
user and his environment. This context awareness will allow
improvements in the efficiency of existing services and help
provide more user-centric and personalized services. In the
5G Era, new ways to abstract and efficiently generate
context information are needed, as well as new ways to
share context information between the application, network
and devices.
To accommodate all the diverse use cases without increasing
the management complexities, 5G wireless communications
systems must be designed in such a way that the same
architectures are flexible enough and can be extended for new
and evolving unknown usage scenarios.
III. NETWORK INNOVATIONS
Heterogeneous networks (HetNet) refer to network
deployments with different types of network nodes, which are
equipped with different transmission powers, data processing
capabilities; different radio access technologies (RATs), and are
supported by different types of backhaul links [10]. 5G will have
new air interfaces to include cognitive designs to take advantage
of spectrum sharing, new modulation, full-duplex transmission
and so on. The network will be significantly impacted with
interop and integration with multiple radio access networks
(multi-RATs) including unlicensed frequencies like 60GHz band
[11].
Network densifications with small cells are being recognized
as one of the most promising technologies to deliver the 5G
wireless requirements. While small cells can greatly increase the
network capacity/coverage, extend the mobile device battery
life, and achieve wireless network energy efficiency, there are
still many challenges to overcome. One of the most significant
challenges is how to provide scalable, affordable, and flexible
mobile backhaul to connect high capacity small cells back into
the network [12,13,14]. Millimeter wave technologies are being
considered as one of the key enablers along with other
developing lower frequency spectrum sharing architectures to
realize dense networks targeted to enable 5G wireless
communication infrastructures.
IV. ENABLING 5G TECHNOLOGIES
Extremely higher aggregate data rates, large BW and ultra-low
latencies required by 5G wireless cannot be achieved by the
simple evolution of current wireless technologies [13]. This
section reviews some of the disrupting technologies that will be
useful in enabling the 5G transition.
A Extension to Higher Frequency/Millimeter Waves
All the frequency spectrums currently available to mobile
systems are concentrated in bands below 6 GHz due to the
favorable propagation conditions in those bands. These
frequencies are also in high demand by other wireless services,
including fixed, broadcasting and satellite communications. As a
result, these bands have become extremely crowded and
prospects for large chunks of new spectrum for mobile
telecommunications below 6 GHz are not very favorable for
transition to 5G architectures.
Recent advancements in mobile communication systems
and devices operating at higher microwave and mm-wave
frequencies, combined with advancements in antenna and RF
component technologies, have opened the doors to using nonconventional
bands
for
cellular
applications. Such
advancements will help enable dense small cell deployments
over a diverse set of higher spectrum. Such deployments will be
an important 5G usage scenario as there will be continued need
to meet exponential growth in traffic demand and to address
the requirement for gigabit data rates everywhere, including at
cell edge. It is expected that network architectures operating over
spectrum not traditionally used by cellular systems (e.g. 10-100+
GHz) will be deployed indoors and/or outdoors to meet 5G
network requirements.
With the potential for higher 10+GHz frequencies as well as
mm-wave deployment, the available spectrum might rise from a
typical 500MHz to several GHz. Many bands therein seem
promising, including 10-15 GHz, the local multipoint
distribution service at 28–30 GHz, 38-40GHz, the unlicensed
978-1-4799-8275-2/15/$31.00 ©2015 IEEE
band at 57-66 GHz, frequency-bands at 71–76 GHz, 81–86 GHz,
and 92–95 GHz [14]. But with the increase in carrier frequency,
signal penetration loss increases, diffracted signals become very
weak and thus the importance of line-of-sight (LOS) signal as
well as reflected signal component increases. Although
propagation at mm-wave bands covering 30-300GHz presents
some challenges, recent measurements indicated distance
dependent LOS communication channel characteristics similar
to microwave bands and non-LOS communication remains a
good option [15]. Extreme sensitivity to blockages, higher
atmospheric attenuation and need for accurate frequencydependent channels models call for further research to enable
mm-wave dense networks and relay infrastructures. Large
antenna arrays can be used to eliminate frequency dependent
propagation loss and to provide higher beamforming array gain
[13, 16]. Millimeter wave systems can operate in noise-limited
conditions rather than interference-limited situations by reducing
the impact of interference with narrow beam adaptive arrays.
When beams are blocked by obstacles, the use of adaptive array
processing algorithms can help to adapt quickly.
B. Millimeter-Wave Beamforming
Beamforming implementation with large number of mmwave front-end transceivers will be difficult due to high cost,
power consumption, and excessive demand for real time
signal processing needs with high beamforming gains [16, 17].
Using analog beamforming approach, number of transceivers
can be reduced, where each mm-wave transceiver is connected
with multiple active antennas and the signal phase of each
antenna element can be controlled by a network of analog
phase shifters. Designs with number of transceivers smaller
than number of antenna elements can be developed, but the
architecture might introduce severe inter-user interference for
inadequate spatial separation between users. To further
enhance the performance, digital beamforming can be utilized
over transceivers to achieve multiple data beam precoding on
top of analog beamforming. Fig.3 presents an example hybrid
beamforming architecture, where each of the N transceivers is
connected to M antennas [16]. Analog BF is performed over
only M RF paths in each transceiver, and digital BF is
performed over N transceivers. Large scale antenna systems
can be used with hybrid beamforming for mm-wave
applications.
links between the base station and the user interface rarely
have LOS and the use of high gain antennas is limited.
Multiple antenna technologies like Multiple-Input,
Multiple-Output (MIMO) and beamforming will thus play an
important role in defining 5G system architectures [18], in
particular for millimeter wave frequencies. Multi-User MIMO
(MU-MIMO) offers increased multiplexing gains and
improves spectral efficiency. Even though it has been included
in the 3GPP LTE-Advanced standard, its full potential is yet
to be realized.
Drastically higher capacity can be obtained by Very Large
MIMO (VLM) arrays employed at the base station, popularly
known as Massive MIMO. Increasing transmit array size in
multiple dimensions has desirable implications for coverage,
array gain, inter-symbol and intra-cell interference control,
and transmit power budget optimization. Fortunately, most of
the gains can be realized even at manageable antenna
dimensions. Massive MIMO technology can be deployed in
applications that do not require backward compatibility. Also,
a massive MIMO array can provide backhaul for base stations
that serve small cells in a densely populated service area [19].
New antenna technologies like steerable antennas for dynamic
beamforming patterns and massive MIMO with 100-1000
low-power antennas per BTs can be developed. Fig. 4 shows a
massive MIMO architecture with two-dimensional antenna
array beamforming that offer good coverage in azimuth as
well as in elevation.
Fig.4 Example Massive-MIMO Topology with 2D Array.
It is expected that massive-MIMO will be a core technology
to create significantly higher capacity either in the form of
distributed radio heads with centralized processing or in
deployment of hundreds of antenna elements in higher
frequency bands such as mm-wave, where antenna dimensions
become more practical [20-24].
Fig.3 Example hybrid beamforming architecture [16].
C. Multi Antenna Technologies
For millimeter wave point to point LOS communications
high gain antennas are used to make the connection. But the
D. Device-to-device D2D Communication
Device-to-device (D2D) communication leads to dense
spectrum reuse and the base station is no longer a traffic
bottleneck between source and destination. Local links are
established
between
nearby devices
using
D2D
978-1-4799-8275-2/15/$31.00 ©2015 IEEE
communication so that traffic goes from one device to another
without passing through base stations. D2D communication
can potentially improve user experience by reducing latency
and power consumption, increasing peak data rates, and
creating new proximity-based services such as proximate
multiplayer gaming. Multiple D2D links share the same
bandwidth, thereby increasing spectral reuse per cell beyond 1
[12, 13].
E. Simultaneous Transmission/Reception
Simultaneous Transmission and Reception (STR) at the
same time and frequency can provide higher spectral
efficiency. Doubling of spectral efficiency can be immediately
realized in point-to-point communication such as wireless
backhaul [12]. In addition, STR can improve network
efficiency in contention networks such as WiFi by mitigating
the hidden node problem. When a node receives a packet
designated to it and meanwhile has a packet to transmit, STR
or full-duplex (FD) capability enables it to transmit the packet
while receiving the designated packet. This not only doubles
the throughput, but also enables hidden nodes to better detect
active nodes in their neighborhood. STR makes device
discovery easier in D2D communication systems where a
device can discover neighboring devices easily by monitoring
uplink signals from proximate user equipment without
suspending transmission. It is expected that STR will play an
important role in 5G systems though evolution and integration
of WiFi networks, and in enhancements to D2D communications [1-3], [12, 13].
F. Network Co-operation and Interference Management
The aggressive spectral reuse envisioned with dense HetNet
architectures will not be realizable without advanced
interference management to control the resulting network
interference. 5G systems will need to manage such
interference through cooperation across densely deployed
small cells and end-user devices to provide a seamless
network experience to the mobile users [1-3].
V. SUMMARY
In this paper, an overview on 5G wireless use cases,
network innovation and disrupting technology evolution
needed for 5G- transition has been presented. Exponential
increase in the diversity of wireless applications, huge growth
in the demand for wireless data services along with the
increasing need for low-cost and energy efficient devices as
well as distinctive features of M2M and IoTs validate the need
for 5G. MM-wave architectures are viewed as key
technologies to achieve the 5G requirements. We expect that,
the combination of network innovations, new device
capabilities and support from key ecosystem participants will
help pave the road to 5G, and will progressively enrich our
mobile user experience with ubiquitous and ultra-fast
connectivity.
REFERENCES
[1] S. Talwar, D. Choudhury, et al., “Enabling Technologies and
Architectures for 5G Wireless”, 2014 IEEE MTT-S, June, 2014.
2) G. Fettweis, et al., "5G: Personal Mobile Internet beyond What
Cellular Did to Telephony”, IEEE Comm. Magazine, pp.140-145,
Feb. 2014
3) B. Bangerter, et al., "Networks and Devices for the 5G Era, IEEE
Communications Magazine, February 2014
4) G.Wunder et al., “5GNOW: Non-Orthogonal, Asynchronous
Waveforms for Future Mobile Applications”, IEEE Communications Magazine, pp.97-105, February, 2014.
5) J.Zander and P.Mähönen, “Riding the Data Tsunami in the Cloud:
Myths and Challenges in Future Wireless access,” IEEE
Communications Mag., vol. 51, no. 3, pp. 145–51, Mar. 2013.
6) G.Wunder et al., “5GNOW: Challenging the LTE Design
Paradigms of Orthogonality and Synchronicity”, 2013 IEEE 77th
Vehicular Technology Conference, pp.1-5, 2013.
7) Nokia White Paper, “5G Use Cases and Requirements”,
www.networks.nokia.com/file/31121/5g-requirements
8) Huawei White Paper, “5G: A Technology Vision”,
http://www.huawei.com/5gwhitepaper/
9] M. Weiser, “Computer for 21st Century”, Sci. Amer., Sept. 1991.
10] Q. Li et al., “5G Network Capacity: Key Elements and
Technologies”, IEEE Comm. Magazine, pp.71-78, March, 2014.
11] A. Savola, “5G Technologies: A Test and Measurement
Perspective”, Keysight Technologies Workshop, November, 2014.
12] N. Bhushan et al., “Network Densification: The Dominant
Theme for Wireless Evolution into 5G”, IEEE Communications
Magazine, pp.82-89, February, 2014.
13] F. Boccardi et al., “Five Disruptive Technology Directions for
5G”, IEEE Communications Magazine, pp.74-81, February, 2014.
14] L. Wei et al., “Key Elements to Enable Millimeter Wave
Communications for 5G Wireless Systems”, IEEE Communications Magazine, pp.137-143, December, 2014.
15] T. Rappaport et al., “Millimeter Wave Mobile Communications
for 5G Cellular: It Will Work”, IEEE Access, vol.1, pp. 335–349,
May 2013.
16] S. Han et al., “Large-Scale Antenna Systems with Hybrid Analog
and Digital Beamforming for Millimeter Wave 5G”, IEEE
Communications Magazine, pp.186-194, January, 2015.
17] X. Huang, Y. Guo, and J. Bunton,“A Hybrid Adaptive Antenna
Array”, IEEE Trans. Wireless Communications, vol. 9, no. 5,
pp.1770–79, May 2010.
18] F. Vook et al., “MIMO and Beamforming Solutions for 5G
Technology”, 2014 IEEE International Microwave Symposium,
pp.1-4, June 106, 2014.
19] E. Larsson et al., “Massive MIMO for Next Generation Wireless
Systems”, IEEE Comm. Magazine, pp.186-195, Feb., 2014.
[20] F. Rusek et al., “Scaling up MIMO: Opportunities and
Challenges with Very Large Arrays,” IEEE Signal Processing
Mag., Jan. 2013.
[21] D. Gesbert et al., “From Single User to Multiuser Communications: Shifting the MIMO Paradigm,” IEEE Signal Processing
Mag., vol. 24, no. 5, pp. 36-46, Oct. 2007.
[22] T. Marzetta, “Non-cooperative Cellular Wireless with Unlimited
Numbers of Base Station Antennas,” IEEE Trans. Wireless
Comm., vol. 9, no. 11, pp. 3590-3600, Nov. 2010.
[23] G. Xu et al., “Full Dimension MIMO: Status and Challenges in
Design and Implementation”, IEEE CTW, May 27, 2014
[24] J. Hoydis et al., “Massive MIMO: How Many Antennas Do We
Need,” Proc. IEEE Allerton Conference on Communication,
Control, and Computing, Urbana Champaign, IL, Sept. 2011.
978-1-4799-8275-2/15/$31.00 ©2015 IEEE