Power System Maha Butt Department of Computer Science,

Power Optimization in 5th
Generation of Wireless Communication System

Maha Butt

Department of Computer Science, Bahria
University
Islamabad Campus, Pakistan

[email protected]

 

Abstract— In the past few decades mobile wireless technology
has experience of various generation of technology revolution & evolution,
namely from 0G to 4G. An advance implementation of 5G technology which are
being made on the development of World Wide Wireless Web (WWW). The main
purpose of this paper is to highlight and compare the 3G, 4G and 5G networks in
terms of energy efficiency. In current era, energy efficiency has become a
matter of key importance for 5G wireless network. So there is a need to use
energy-efficient architecture to meet the demands of increased capacity, an
improved data rate and the better quality of service of the next-generations
networks.

 

Keywords— 3G,
4G, 5G, Energy Efficiency

I.      Introduction

A wireless communication or simply wireless system is the exchange of
information between different nodes that are not connected by physical cables.
Most common wireless systems use radio waves for information transfer. This is
alternative of physical medium such as, fiber-optic and coaxial cables, which
are more expensive. Today mobile networks are primary need of everyone. People
within a city, country, inter-continental or even across the world connected
through wireless networks, which leads to congestion of network, low
connectivity speed and low bandwidth. Without wireless network easy personal
communication is not possible 1.

The successor of 1G, 2G is 3G. The third
generation (3G) came into practice in 2000, which provided transmission
rate up to 2Mbps along with improvement in QoS. 3G technology offered users a
wide range of advanced services including web based applications, audio and
video files. To support multimedia applications 3G had to deliver
packet-switched data with better spectral efficiency, at far greater speed. The
main disadvantage of 3G mobile phones was that they require more power than
most 2G models 2.

Fourth generation (4G) is the successor of 3G with
the extension of bandwidth and services offer in 3G. 4G offers a speed of 100Mbps
with premium quality and high security. The main discriminate factors between
3G and 4G are data rates, way of transmission, access technology to the
internet, QoS and security. But the problem is that energy consumption is
growing even more with the development of 4G system worldwide 1, 3.

Next to 4G is 5G (5th generation),
which leads to excellence of wireless communication in mobile technology. 5G
will provide all previous features with better response like bandwidth,
spectral efficiency, energy efficiency etc 4.

With the development of 4G network
worldwide, energy consumption is growing even more which is very dangerous for
user health. High power emitted by handsets while in use tends to harm the user
in close proximity. So there is need to adopt energy efficient architecture
which will also satisfy the user’s demand of battery life. Energy efficiency is
traditionally defined as the computation of number of bits transmitted per joule
of energy consumed 3.

 

Fig 1. Evolution of 1G
to 5G technology

    Remaining
part of the research paper is organized as, Section II presents Literature
Review, Section III presents discussion and comparison of different approaches,
Finally paper is concluded in the last section IV.

 

II.LITERATURE REVIEW

     The Following table shows different power
optimization method which are used in different generations with their pros and
cons. Like sleep mode of BS and use of relays method is used in 3G for power
optimization. “Base Stations(BSs) consume 60-70% of the total network
energy”5. Thus, reducing power consumption rate of BSs plays vital role
in green communication.

Enabling sleep mode in BS as shown in fig. 2,
usually different BSs need to cooperate to each other. A BS controller (BSC) is
used to exchange traffic between these BSs If some BS are at sleep, they
release their channel resources to active neighbour BSs, while these active BSs
use such resources to provide wide range of coverage to the mobile users located
nearby to sleeping BSs 6.

Table 1: Power Optimization method in
3G, 4G & 5G

 

 

 

 
Sr.No

 
Technology

 
Power Optimization Method

 
Pros

 
Cons

1

 
3G

 
Sleep mode of BS & use
of Relays

·         
Low implementation cost.
·         
No need to modify current structure of cellular network.

·         
Blocking events might occur due to insufficient available
capacity in active BS.
·         
Implementing RSs in the network introduces other costs.

 
2

 
4G

 
BS energy saving, use of
relays and small cells.

·         
By using Small Cells, no need to deploy additional expensive macro
base stations usually hard to install in dense urban areas.
·         
Deployment of Small cells requires minimum changes in the current
standard and can save a lot of user’s battery consumption.
 

 
 
 
 
————

 
3

 
5G

 
Use of Small cells, Relays with SCA and D2D
communication, SWIPT, C-RAN.

 
·         
By using these technologies energy will be saved up to 35%

 
 
————

 

 

 

Fig 2. Cell zooming Technique (a) Always ON configuration (b) Analyzing
phase (Possibility of BS sleep mode) (c) Final configuration

with cell zooming and sleep mode

 

Without changing the current structures of cellular
network, another way of improving energy efficiency of BSs is the use of low
power relay stations (RSs). By adding RSs in the

 

 

network, broadcast power can be saved
due to diminished distances between transmitter receiver pairs 5. A Cellular
network using Relay stations is shown in fig. 3.

 

Fig 3. Relay aided Cellular network

 

Another
method is Use of small cell as shown in fig. 4, which is used in 4G for
power optimization. Small cells are basically small base stations that divide a
cell site into abundant smaller pieces, and it is a term that includes picocells, micro cells, femtocells and can cover indoor/outdoor systems.

 

 

The
main purpose of small cells is to enhance the macro cell’s data capacity, overall
network efficiency and speed. Small cells are usually used in very inhabited areas,
such as train stations, shopping malls, sports places and airports – in short,
any place where a lot of people using data at a time from the same given point.

 

Fig 4. Macro-Femto Cell Deployment

 

In 5G, some modern
technologies are added with previous like use of Relays with Small Cell Access
Point (SCA) and D2D Communication.

Relay in the
company of small cell is Crucial. Base station firstly connects with relay node,
which then communicates with specific SCA of the building, where Mobile Station
(MS) is placed inside of that building.

Device-to-Device
(D2D) communication plays a vital role in enhancing the EE of the cellular
network. It maintains the reliability of the connection among the users, by
establishing direct connection and latency reduction. Traffic divesting on
the direct connection minimizes the load on the BS, and helps the BS to convert
in sleep mode. 7

To meet the high
demand of EE, the most emerging technology is Wireless Power transfer (WPT). By
using this technology nodes charge their batteries from electromagnetic

 

 

radiations. The
component used for this reason is Rectenna which transforms the microwave force
to direct current 3.

Another
component of 5G energy efficient architecture is cloud RAN (C-RAN). The main
purpose of C-RAN is reducing the BS sites by using the centralized processing.
Base station and small cell will be connected to the C-RAN which will diminish
transmission distance and it will lead to lower power consumption. It can also be
turned off easily in no traffic hours to save power. Hence C-RAN plays a vital
role in Energy Efficiency 3.

III.DISCUSSION AND COMPARISON

     OF VARIOS APPROACHES

    As we have discussed above, Base Stations
consumes a huge amount of energy in cellular network. This energy consumption
depends upon the mobile traffic in cell area (BS

area), which
changes from time to time, peak to low. By considering this situation, a
technique named as Cell Area revision method (CAR) is used which changes the
transmission area of a cell according to real time network traffic. CAR is categorized
into three methods: 8

       
I.           
Cell Zooming Technique

     
II.           
Macro-femto Cell deployment

  
III.           
Relay deployment

1)   
Cell Zooming Technique

This technique is used in 3G and explained
well in Fig. 2. It zoom-in or zoom-out cell area according to the mobile
traffic and the level of transmission power increases or decreases accordingly.
Power consumption model introducing sleep modes and cell zooming, reduces the
power consumption by up to 14.4% 8.

Every technique has its pros and cons too, so
here are some advantages of Sleep mode technique. This technique is easier and
less costly for tasting and implementation. It requires no modification in current
structure of cellular network. Some disadvantages are blocking events might
occur due to insufficient available capacity in active BS. Trade-off between
performance and saving, current modelling not accurate enough. 

2)   
Macro-femto Cell deployment

This technique is used in 4G with the
combination of previous techniques and explained well in Fig.4. Femto cells are
used to manage the mobile traffic when a BS is in sleep or power saving mode. They
also reduce the distance and transmit power between the user and BS especially
in the indoor activities 8, 3.

By using Small Cells, no need to install other
expensive macro base stations which are usually hard to install in crowded
urban areas. Use of Small cells requires least changes in the current structure
and can save a lot of user’s battery consumption.

3)   
Relay Deployment

Relays are primarily introduced to enhance
the coverage area of BS but later it was realized that relaying can be applied
to increase the throughput of the network as well as reduce the transmission
power. The basic principle used in a relay assisted network is that mobile
station (MS) receive signals from both relay node (RN) as well as base station
(BS) depending on which provides strong signals which generally depend on the
distance between them 5. Relays are used in 3G, 4G and 5G as well. A relay
aided network in explained well in Fig. 3.

Plus point of use of Relays is RN splits the
longer path into shorter once by giving LOS communication and thus reducing the
resulting total path loss. This accordingly reduces the power needed for
transmission. One of the important points is that direct communication consumes
less energy than using relays for shorter distance. Optimal placement of the
relays plays an important role to optimize the power consumption of the
network.

 

Energy efficient
techniques in 5G

    5G is the
combination of energy harvesting technologies. 
Names of these technologies have been shown in table 1. Some of these
have been discussed above. Now the most upcoming technology is Simultaneous
wireless information and power transfer (SWIPT), where nodes charge their
batteries from electromagnetic radiation. As shown is Fig 5

  

Fig 5. Simultaneous wireless information and power transfer 

 

In 5G network, a
variation of MIMO is planned in which a very large number of antennas are
employed at the base station called Massive MIMO. Using this technology, the
base station can communicate with multiple users concurrently in the same
frequency band hence providing high multiplexing as well as array gain at the
same time. Massive MIMO technology is not only spectrum efficient but energy efficient
as well 3.

 

Energy
Efficient architecture in 5G

    The architecture includes the concepts of
SWIPT, massive MIMO and cloud RAN for improving EE in the next generation
network. The proposed architecture is shown in Fig 6. To represent the various
scenarios considered, we have taken different user equipment represented as
clients in our architecture. C7, C8 and SCA2 directly communicate with the base
station due to line of sight path and good channel conditions between them. C4,
C5 and C6 are located indoors and hence send signal to SCA2 and not directly to
the base station. SCA2 as located in line of sight path of base station doesn’t
require a relay. But C9, C10 and C11 along with SCA1 are not in line of sight
path of the base station so require a relay for good reception as well as power
optimization. The relay used can be mobile, fixed or UE relay. C1, C2 and C3 as
shown communicate with SCA1 as they are located indoors. The SCA1 then communicates with the relay which in
turn communicates with the base station. The relay node is chosen according to
relay selection policy for power optimization.

In our
architecture, we have considered different channel conditions including both
line of sight and non-line of sight paths as both have different path loss and
hence will require different power from the base station to maintain the
required SNR for a particular application. There can be four channel conditions
which are without relay and without penetration

 

 

that is simple
line of sight path, without relay and with   penetration that is due to various obstacles
present in the channel. Thirdly, there is with relay without penetration and
last is with relay with penetration which includes the path with relay as well
as includes effect of refection, refraction and diffraction through various
obstacles present in the atmosphere. Also, in the indoor communication as well
there are expected to be two paths, i.e., both line of sight and non-line of
sight paths exist indoors as well. This is due to presence of obstacles inside
the building as shown in our architecture.

 

 

Fig 6. Proposed architecture for power optimization in 5G network.

 

 

Table 2: Energy saving by different techniques

S.No.

Techniques

Energy Efficient

1

SWIPT

30%

2

Small Cells

11.1%

3

C-RAN

21.2%

4

Massive MIMO

30.3 Mbit/J

5

Relays

9.7 dB power reduction

 

 

IV.CONCLUSION

In this paper,
we have discussed the growing demand for energy efficiency in the next
generation networks. We have analysed the trends in the field of wireless
communications in the last decade which indicated a shift towards pursuing green
communication for the next generation network. We
have gone through the various techniques which can be used in the future for
optimizing the power of the network and the presented a summary of the work
that has already been done to improve energy efficiency of network using these
techniques. A system model for EE improvement with the use of relay selection
has also been described along with a comparison of various algorithms used for
EE in relay based environments.

 

 

REFRENCES

1 Olumuyiwa Oludare Fagbohun, “Comparative
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2 Haard Mehta, Darpit Patel, Bhaumik Joshi, Hardik
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October-2014, pp. 56-60

3 AKSHITA ABROL, RAKESH KUMAR JHA, “Power Optimization
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January 2017

5 Sheng Zhou,
Andrea J. Goldsmith, Zhisheng Niu, “On Optimal Relay Placement and Sleep
Control to Improve Energy Efficiency in Cellular Networks”, IEEE 2011

6 Jingjin Wu, Yujing Zhang,
 Moshe Zukerman,
“Energy-Efficient Base-Stations Sleep-Mode Techniques in Green Cellular
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February 2015

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8 Ratheesh, Vetrivelan,
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