ANALYSIS OF COMMUNICATION PROTOCOLS FOR NEIGHBORHOOD AREA NETWORK FOR SMART GRID Adithya Shreyas B.S., The Oxford College of Engineering, Bangalore, India, 2006

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ANALYSIS OF COMMUNICATION PROTOCOLS FOR NEIGHBORHOOD AREA
NETWORK FOR SMART GRID



Adithya Shreyas

B.S.
,
The Oxford College of Engineering, Bangalore, India
,
2006







PROJECT




Submitted in partial satisfaction of

the requirements for t
he degree of





MASTER OF
SCIENCE



in



COMPUTER ENGINEERING



at



CALIFORNIA STATE UNIVERSITY, SACRAMENTO



F
ALL

2010






ii



ANALYSIS OF COMMUNICATION PROTOCOLS FOR
NEIGHBORHOOD AREA
NETWORK FOR SMART GRID




A Project



by



Adithya Shreyas












Approved by:



__________________________________, Committee Chair

Isaac Ghansah
, Ph
.
D
.



__________________________________, Second Reader

Chung
-
E Wang
, Ph
.
D
.


____________________________

Date







iii




Student:
Adithya Shreyas



I certify that this student has met the requirements for format contained in the University
format manual, and that this project is suitable for shelving in the Library and credit is to
be

awarded for the Project.





__________________________, Graduate Coordinator ________________

Suresh Vadhv
a
, Ph
.
D.







Date


Department of Computer Engineering






iv


Abstract


of


ANALYSIS OF COMMUNICATION PROTOCOLS FOR NEIGHBORHOOD AREA
NETWORK FOR

SMART GRID


by


Adithya Shreyas


Smart Grid’s success heavily lies in the communication infrastructure underneath it.
In
Smart Grid,
Neighborhood Area Network

has a role to play in the HOME
-
to
-
HOME or
HOME
-
to
-
GRID communication.

There are quite a few tech
nologies in contention to be used to implement neighborhood
area network.
In this project the analysis for communication protocols for
Neighborhood
Area Network

for Smart Grid

is done by considering
few wireless protocols or standards
like IEEE 802.11, IEE
E 802.16, IEEE 802.15.4, 3G and few wired standards like Power
Line Communication and Optical Fiber Communication
.

The

requirements of
the
protocols/standards
considered for
Neighborhood Area Network

for Smart Grid
are
identified as

reliable, secure, power efficient, low latency, low cost, diverse path, scalable
technology, ability to support bursty, asynchronous upstream traffic.

The research a
lso

includes

analysis of
few routing and transport protocols which are used in wired and
w
ireless networks.

In Transport Protocols, UDP is a well suited protocol over all kinds of media which
enable time critical communication capabilities. For non time critical applications TCP or
SCTP could be considered. For Neighborhood Area

Networks, the p
rotocols/
standards


v


that
are

recommended
in this project
are IEEE 802.11 [Wi
-
Fi] and Cellular
technology

[GSM]
.



_______________________,
Committee Chair

Isaac Ghansah, Ph
.
D
.



_______________________

Date





vi



DEDICATION















To my parents,
teachers and friends





vii



ACKNOWLEDGEMENT


I am thankful to all the people who have helped and guided me through this journey of
completing my Masters Project.

My sincere thanks to Dr. Isaac Gha
n
sah
, for giving me the opportunity to work on my
masters project under him and for guiding me throughout the project. My heartfelt thanks
to Dr.Chung
-
E Wang for agreeing to be my second reader and providing me with his
invaluable inputs on revising my report.

My sincere thanks to Dr. Suresh Vadhva for his
invaluable support throughout my graduate program.

My special thanks to my friends Deepak Gujjar, Pooja Ramesh and Abhijith for helping
me with their ideas and by reviewing my project report. I would also lik
e to thank my
roommates and all my friends who have been there for me throughout this graduate
program at California State University Sacramento.

Last but not the least I would like to thank my parents Ramani M.S and Ramesh V, my
sister Shruthi Ramesh
, my uncles Shankar and Satish
,
my
friends

Vasuki, Subramani,
Pradeep and Karthik

for their unconditional love

and moral support
. They have always
motivated me and are the sole reasons for me to have come this far in life.








viii


TABLE OF CONTENTS

A
cknowledg
ement ………
……
...
……………………………………………………….
vii

List of Tables


…...
…………
...
………………………………………………………
.
..
xi

List of Figures …………………………………………………………………………...xii

List of Abbreviations ……….
...
………………………………………………
.
………..
xiv

Chapter

1. INTRODUCTION

………………………………………………
...
…………………
.
..
1

1.1.

Traditional Grid

……………………………………
...
…………………...
1

1.2.

Need for Smart Grid

…………………………………
..
………………….
3

1.3.

Smart Grid

……………………………………………
..
…………………
5

1.4.

Neighborhood Area Networks

…………………………
...
……………….
9

1.5.

Related Work

…………………………………………
...
……………….
11

1.6.

Scope of the Project

………………………………………
...
…………...
13

2.
REQUIREMENTS FOR NEIGHBORHOOD AREA NETWORK

……
..
…………..
15

3.
OVERVIEW OF CANDIDATE NETWORK PROTOCOLS AND STANDARDS

...
21

3.1.

IEEE 802.11

…………………………………………………………
...
...
22

3.2.

IEEE 802.16

…………………………………………………………..
...
.
3
4

3.3.

IEEE 802.15.4

………………………………………………………
...

41

3.4.

ANSI
C
12.22

..
…………………………………………………………..
44

3.5.

C
ellular Communication

…..……………………………………..
....
...
...
.
46

3.6.

Powerline Communication

……………………………………….
.
..
.....
..
51

3.7.

O
ptical Fiber Communication

…...………………………………..
..
......
.
53

3.8.

W
ireless Mesh Networks

……………………
...
……………

…..

….
54

4. ROUTING PROTOCOLS

…………………………………
...
……………………….
59



ix


4.1
.

Table
-
Driven Routing

Protocol ………………………………………….61

4.1.1.

D
estination
-
Sequenced Distance
-
Vector Routing
[DSDVR
] ……….......62

4.1.2.

C
lusterhead Gateway Switch Routing [CGSR] ..………………………..
63

4.1.3.

Wireless Routing Protocol ...…………………………………………….
64

4.2.

Source Intitiated On
-
Demand

…………………
………...
………………
65

4.2.1.

Ad HOC

On
-
Demand Vector Routing [AODV] ………………………..
66

4.2.2.

Dynamic Source Routing [DSR]
………………………………………..
68

4.2.3.

Temporally Ordered Routing Algorithm [TORA]
………………………
70

4.2.4.

Associativity
-
Based Routing [ABR]
…………………………………….
73

5.

TRANSPORT PROTOCOL
…………………………………………………….
75

5.1.

Transmission Control Protocol
………………………………………….
76

5.2.

User Datagram Protocol
…………………………………………………
78

5.3.

Split TCP
…………………………………………………………….......
79

5.4.

Stream Control Transmission Protocol
………………………………….
79

5.5.

Wireless
Datagram Protoc
o
l
…………………………………………….
81

6.
SECURITY ISSUES, VULNERABILITIES AND BEST PRACTICES

……………
82

6.1.

IEEE 802.11
……………………………………………………………..
82

6.1.1.

Vulnerabilities and Security Issues
……………………………………...
82

6.1.2.

Best Practices for 802.11
…………………………………
……………..
85

6.2.

IEEE 802.16
……………………………………………………………..
86

6.2.1.

Vulnerabilities and Security Issues
……………………………………...
86

6.2.2.

Best Practices for
802.16
………………………………………………..
87

6.3.

IEEE 802.15.4

…………………………………………………………....
88

6.3.1.

Vulnerabilities and Security Issues
……………………………………...
88



x


6.3.2.

Best Practices for
802.15.4
……………………………………………...
91

6.4.

GSM Security

………………………………………………………
…....92

7.
POTENTIAL RESEARC
H TOPICS ………………………………………………
...
.
93

7.1.

Cho
o
sing a standard for implementin
g Neighborhood Area Network
….
93

7.2.

Unpredictable latencies in
Wireless
Mesh Network

…………………

.
94

7.3.

PLC
for Home Automation
…………………………………………

...
95

7.4.

IP
based Networks

……………………………………………………
.
..
.
95

7.5.

Security for Routing protocols in Wireless Mesh
Networks

…………

96

7.6.

Limitation on Wireless Intrusion Detection

…………………………

.
.
97

7.7.

802.11
MAC Management Attacks

…………………………………
….
.
99

7.8.

Physical Security
……………………………………………………
...
..
.
99

7.9.

Denial of Service Attacks

……………………………………………

.
99

7.10.

Key Management in
IEEE 802.
15.4 …………………………………
...100

8.
CONCLUSION ……………………………………………………………………
.
.
102

B
ibliography

……………………………………
…….
………………………………
.
.104





xi


LIST OF TABLES


Table 1: Network Types, Coverage and
Bandwidth

................................
.........................

19

Table 2: IEEE 802.11 Standards and its Variations
................................
..........................

23

Table 3: Summary of GSM Specifications

................................
................................
.......

47

Table 4: Summary of Tech
nologies for NAN (continued)

................................
...............

57

Table 5: Summary of Technologies for NAN
................................
................................
...

58



xii


LIST OF FIGURES


Figure 1: Traditional Grid

................................
................................
................................
...

2

Figure 2: Smart Grid

................................
................................
................................
...........

7

Figure 3: Evolution of Utility Communication Requirements

................................
.........

15

Figure 4: Customer Domain: NAN, gatewa
y and HAN

................................
...................

16

Figure 5: Smart Grid Building Blocks

................................
................................
..............

17

Figure 6: Hierarchical Organization of Communication Networks
................................
..

20

Figure 7: IEEE

802 family and its relation to the OSI model
................................
...........

23

Figure 8: IEEE 802.11 Physical Layer Components

................................
........................

24

Figure 9: IEEE 802.11 Design Components

................................
................................
.....

25

Figure 10: Positive Acknowledgement

................................
................................
.............

26

Figure 11: RTS/CTS clearing

................................
................................
...........................

27

Figure 12: RTS/CTS clearing

................................
................................
...........................

27

Figure 13: Generic Data Frame
................................
................................
.........................

29

Figure 14: Frame Control field

................................
................................
.........................

29

Figure 15: 802.11 Generic Wireless Cards

................................
................................
.......

32

Figure 16: IP based WiMAX Network Architecture

................................
........................

36

Figure 17: IEEE 802.16 Protocol Layer

................................
................................
...........

38

Figure 18: Generic MAC PDU Format
................................
................................
.............

39

Figure 19: GSM User Authentication Process

................................
................................
..

49

Figure 2
0: Signal and Data Confidentiality in GSM

................................
........................

50



xiii


Figure 21: Ciphering in GSM

................................
................................
...........................

50

Figure 22: Wireless Mesh Network

................................
................................
..................

55

Figure 23: Infra
-
Structured and Infra
-
Structuredless Networks

................................
.......

60

Figure 24: Ad
-
Hoc Routing Protocols

................................
................................
..............

61

Figure 25: Cluster Head Gateway Switch Routing

................................
...........................

64

Figure 26: Propogation or RREQ packet

................................
................................
..........

67

Figure 27: Dynamic Source Routing

................................
................................
................

69

Figure 28: Temporally Ordered Routing Algorithm
................................
.........................

72






xiv


LIST OF ABBREVIATIONS


AES

Advanced Encryption Standard

AMI

Advanced Metering Infrastructure

AMR

Advanced Meter Reading

ANSI

American National Standards Institute

AP

Access Point

ASN

Access Service Network

ATM

Asynchronous Transfer Mode

BPL

Broadband over

Power Line

BPSK

Binary Phase Shift Keying

BS

Base Station

BWA

Broadband Wireless Access

CDMA

Code Division Multiple Access

CMAC

Cipher based Medium Access Control

CPE

Customer Premises Equipment

CRC

Cyclic Redundancy Check

CSN

Connectivity Service Network

CTS

Clear
-
to
-
Send

CUDP

Cyclic User Datagram Protocol

DC

Direct Current

DL

Downlink



xv


DoS

Denial of Service

DSSS

Direct Sequence Spread Spectrum

EAP

Extensible Authentication Protocol

ERP

Extended Rate Physical layer

FCS

Frame Check Sequence

FDD

Frequency Division Duplexing

FFD

Full Function Device

FHSS

Frequency Hopping Spread Spectrum

GSM

Global Satellite for Mobile communication

HAN

Home Area Network

HMAC

Hashed Medium Access Control

HSDPA

High Speed Downlink Packet Access

IEEE

Institute of Ele
ctrical and Elect
r
onics Engineers

IETF

International Engineering Task Force

IP

Internet Protocol

ITU

International Telecommunication Union

kWh

kilo Watt hour

LAN

Local Area Network

LLC

Link Layer Control

LoS

Line of Sight

MAC

Medium Access Control

MAN

Metropolitan Area Network



xvi


MIC

Message Integrity Code

MIMO

Multiple
-
input Multiple
-
output

MLME

Media Access Sublayer Management Entity

MPDU


MAC Protocol Data Unit

MS

Mobile Station

MSDU


MAC Service Data Unit

NAN

Neighborhood Area Network

NIST

National Ins
titute for Standards and Technology

NLoS

Non Line of Sight

NWG

Network Working Group

OFC

Optical Fiber Communication

OFDM

Orthogonal Frequency Division Multiplexing

OFDMA

Orthogonal Frequency Division Multiple Access

PAN

Personal Area Network

PCLP

Physical

Layer Convergence Procedure

PCMCIA

Personal Computer Memory Card International Association

PHY

Physical Layer

PKM

Privacy and Key Management

PLC

Power Line Communication

PMD

Physical Medium Dependent

QAM

Quadrature Amplitude Modulation

QoS

Quality of Serv
ice



xvii


QPSK

Quarternary Phase Shift Keying

RAN

Radio Access Network

RFD

Reduced Function Device

RTS

Request
-
to
-
Send

SAP

Service Access Point

SCTP

Stream Control Transmission Protocol

SIM

Subscriber Identity Module

TCP

Transmission Control Protocol

TDD

Time Di
vision Duplexing

TDM

Time Division Multiplexing

TKIP

Temporal Key Integrity Protocol

TMSI

Temporary Mobile Subscriber Identity

UDP

User Datagram Protocol

UL

Uplink

UMTS

Universal Mobile Telecommunication Systems

UWB

Ultra Wide Band

VLR

Visitor Location
Register

WAN

Wide Area Network

WDP

Wireless Datagram Protocol

WEP

Wired Equivalent Privacy

Wi
-
Fi

Wireless Fidelity

WiMAX

Wireless Interoperability for Microwave Access



xviii


WMN

Wireless Mesh Network

WNAN

Wireless Neighborhood Area Network

WPA

Wi
-
Fi Protected Ac
cess




1




Chapter 1

INTRODUCTION


1.1.
TRADITIONAL GRID

The traditional power grid designed in the
1950’s had

a primary and only objective of
providing electricity. The traditional grid could be divided into two subsystems namely,
transmission
system and distribution system.

The
Figure
1

[1]

shows the traditional power grid with the transmission system that
includes the power generation plan
ts, step up transformers, high voltage power lines and
substations. The distribution system consists of substations; step down transformers,
pole
-
top transformers, and medium voltage power lines. The power plants generate
electricity and step up the voltag
e for long distance transmissions using step
-
up
transformers. Further, electricity is transmitted across the high power transmission lines
over long distances to substations where the voltage is stepped down before transmitting
over the medium voltage powe
r lines to the customer premises. The pole
-
top
transformers further step down the voltage to suit the residential and commercial
specifications.






2




The tra
ditional power grid infrastructure is
largely analog and electromechanical. It is
built on a producer
-
controlled model where the power flows only in one direction that is
from the grid to the consumers. Even with great advances in computer systems,
technologie
s like internet, and electronic

de
vices,
there still remains a vast disconnect
between
the traditional grid’s infrastructure and these advances in technologies. Most of
our day
-
to
-
day commodities directly rely on electricity whose infrastructure is aged out.

Whether or not there is a need
for the power supply to a particular region,
a
utility
supplies a scheduled amount of power to the regions under its jurisdictions. This lack of
communication informing the utilities, the demand for power and the utilities responding
back to the consumer w
ith an appropriate response is the
missing component in our
current grid
. As the demand for power is increasing day
-
by
-
day, it beco
mes very
Figure
1
: Traditional Grid



3




important that there be an

effective communication from

the consumer to the utilities
demanding
o
nly the required am
ount of power and the utilities in turn responding back
appropriately to the consumer based on the need.

1.2.
NEED FOR SMART GRID

[3
3
]

SUSTAINABILITY

Since 1982, the demand for electricity has exceeded the transmission growth by 25%
every year.
Increase in
demand
,

calls for increase in power generations which would
directly affect the carbon dioxide emissions from the power generation plants.
According
to a study

by U.S. Energy
I
nformation Administration [EIA]

department

[33]
, 40% of the
carbon dioxide emiss
ions are from electricity generation and 20% from transportation. A
5% improvement in electric efficiency is equivalent to carbon emissions from 53 million
cars.
Global warming of earth’s surface and lower atmosphere is a result of strengthening
the
greenh
ouse effect where the percentage contribution from carbon dioxide gas to
greenhouse effect is anywhere from 9


26%

[33]
. The human
-
produced gasses as a result
of electricity generation

and

transportation are the main cause for global warming.
Hence
,
a sma
rter grid is needed
, to support sustainability
.


RELIABILITY

In the current electricity grid
architecture
, the utilities are
informed of the blackouts or
outages
,

if and only if
,

a customer rings them up notifying an outage. This aging
infrastructure whi
ch lacks the outage management system is directly aff
ecting the
reliability of the g
r
i
d. To explain the effects of these blackouts, consider the northeast


4




blackout of 2003 in the US, which resulted in a $6 billion economic loss.
According to a
study

by U.S
. Energy Information Administration [EIA] department [33]
,

the US outages
costs

around $150 billion per year which is a $500 per person and
these outages are
getting worse. Also, from the first to the second half of the 1990’s,
there were

an added
41%
of

outages affecting more than 50,000 people and 15% increase in the average
customers getting affected

[33]
.
An intelligent grid with effective communications
infrastructure detects an outage
immediately
and notifies a utility office about the outage
;

also
they could be avoided
when

power is redirected to the place where the outage is
predicted.
To achieve an improved reliability, a smarter grid is the need of the hour.


RENEWABLE ENERGY

The main motivating factors for using renewable energy sources are to
reduce the carbon
emissions,
reduce the
dependency on oil and lower

the
cost

of electricity

over the

longer
run.
Power from renewable energy sources like solar, wind, geothermal and tidal
are low
power

and

intermittent
when compared to the one from tradit
io
nal power generation.
These
intermittent sources need a
distributed

generation to harness the power

and sell it
to the utility offices close by
. To handle both
the

distributed and intermittent power
sources, we need a smarter grid.


SECURITY

The current

centralized grid is vulnerable to terrorist attacks

because in case of attacks
there would be a complete outage and reconstruction of such huge centralized electricity


5




infrastructure
in a short time
would be impractical
.

In case of attacks, a significant
area is
affected with lack of power supply.

Having the power generation distributed would help
us
reduce the devastating effect of
terror attacks or any natural disasters.


Lastly, the average age of a skilled professional at the utilities is
a
round
48 yea
rs. This
would result in a 20% retirement of skilled labor
s

in a span of 7 years.
One
way we could
recover the loss of

these skilled labors in a significant way is by introducing a smar
ter
grid which could handle their

loss. Also, smart grid deployment wou
ld directly create
about

280,000 jobs in the US

[33]
.


1.3.
SMART GRID

Smart G
rid could be thought of as the I
nternet for energy. Smart Grid is an electricity
infrastructure co
nsisting of devices installed at

homes and businesses throughout the
electricity dis
tribution grid for the purpose of energy monitoring which utilizes the
computer, networking and communications technologies all the way from the generation,
transmission and distribution of electricity to consumer appliances and equipments. This
set up pro
vides consumers the ability to monitor and control energy consumption
comprehensively in real time across the
smart communication network
.
The consumers
that generate energy from sources such as: solar, wind or other systems, can also carry
out business wi
th the utilities by outsourcing the surplus energy that they generate.





6




The

actors of
a
Power

Grid
can

be categorized
in
to three main entities. They are

i.

Power Generators: Consisting of the centralized power plants, the small
generators and solar panels.

ii.

Power Distributors: These are the utilities who are responsible for deliviering
power to the customers.

iii.

Power Consumers: The end customers who utilize the services provided but t
he
distributors and consume energ
y.

The components of Smart Grid include: a

centralized power plant, generators

of
renewable energy
, demand management systems, processors, sensors and smart
appliances. An example of such a Smart Grid is shown in Figure 2[2].







7





Figure
2
: Smart Grid


In the
Figure
2
[2]
, the sensors detect the variations and fluctuation
s

in
the
electricity and
send information signals to the demand management systems. At the

demand

management system,
decision

signals are generated, so as to
increase or decrease the
electricity generation and
the
se

signals are sent
out
to the processors. The processors,
with
out

any

need for human intervention, would execute these instructions
and take
appropriate actions

instantaneously
.

To understand this process better, let us consider an example
of a peak time scenario
,

where in
,

at a certain time in a day
,
the
demand
for electricity would be at its peak and
the utilities might have to fire

up the peak generators

to meet the peak time demand. The
sensors would sense the
se

variations in the demand and would send out signals to
demand management system
s
. Also, demand management system
s

could be connected to


8




a database with
all
the data relatin
g to the peak times and other information, which
are

collected over a period of time.
Based on the signals sent over by the sensors, the demand
management system would send appropriate control signals to the processors and the
processors in
-
turn would take

appropriate actions like increasing the power generation,
triggering the system to send out the peak time prices to the consumers
. Also, based on
customized power p
rofiles registered by the consumers

with the utilities,
these processors

could
initiate
shu
t
t
ing
down
of
appliances or manage

the appliances

according to the
power profiles.

An analogy to the customized power profiles could be the different
profiles avai
lable on a mobile phone where
it would have different rin
g tone, message
alert, vibrate, back
light settings for each profile based on whether the user is at work,
home, meeting,
or
driving. Similarly, the power profiles could be a preset recommended
profile set by the utilities, or a customized profile from the consumer wherein, the
consumer speci
fies his requirements based on
his/her
need and the price information from
the utilities. For example, he would want to turn off the air
-
conditioner every fifteen
minutes for
a
ten minutes
interval
d
uring the peak times of the day,
maintain
ing

the
temperat
ure at 75 degree Fahrenheit.
Another example could be of t
urn
ing

on the
television at 8:30p
m
every

weekday and turn
ing

off the lights if no person is present in
the room for
a
duration

more than 20 minutes.

Smart grid is intelligent as it is capable of sen
sing the system overload and rerouting
power to prevent outages and give resolution to conditions or situations faster than a user
could respond. It is efficient as it meets the user’s increasing demand without adding
infrastructure. It is accommodating as

the user can do business with the utilities by


9




pumping energy back to the utilities with renewable
sources like wind, solar and other
sources. The consumer has the ease to choose the energy consumption
profile and
customize it according to his/her prefere
nces. For this reason along with the real
-
time
communication between the customer and the utilities makes it motivating. It is capable
of delivering power
,

free of sags, spikes, disturbances and interrupts which is the main
requirement for the data center
s
and this

could be termed as quality
-
focused. Since, the
Smart Grid’s deployment would be made distributed and not centralized; it becomes
secure and provides resistance to natural and terror attacks.

A
ll
these

features
make
Smart Grid
intelligent, effic
ient, accommodating, motivating, opportunistic, quality
-
focused,
and resilient

and lastly “green” as the carbon emissions are lowered with
increased efficiency.


1.4.
NEIGHBORHOOD AREA NETWORKS

The efficiency of Smart Grid greatly relies on communication. Communication
c
an

be
broadly
classified

into two types:


DATA COMMUNICATION

The utility offices collect the electricity usage information from consumers on a timely
basis to build a future dema
nd statistics. Example for this
would

be a smart device
which
is
part of an air conditioner sending the usage or power consumption information every
minute to the smart meter in kilo watt hour
[
kWh
]

units and the smart meters in turn send
the information

b
ack
to the utility office.



10




CONTROL COMMUNICATIO
N

These are real time communication signals to control the devices at the consumer or
business premises. Example for this could be turning off the air conditioners for a certain
period of time, on request from

the consumer during the peak hours when the price per
unit usage is high.

To explain this in
a better way
, consider
an example of
IEEE 802.15.4 standard where t
he
communication could between three main entities, reduced functional devices, fully
functiona
l devices and the utility offices. Reduced functional devices are those
devices
that carriers limited functionality to lower cost and complexity.
Fully functional devices
support

all IEEE 802.15.4 functions and features specified by the standard.
Further,
the
data communication could be between the reduced functional devices [RFD] (smart
devices installed in homes like heater, refrigerators, air conditioners etc.) and the fully
functional devices [FFD] (
say
smart meters), and, between the FFD’s to the utili
ty office.
Similarly, the control communication would be from the utility office to the FFD’s and
from FFD’s to the RFD’s.

The communication between the
RFD’s and the FFD’s installed at

home and business
premises is part of Home Area Network [HAN] and the
communication between the
FFD’s and the utility offices is part of Neighborhood Area Network. A set of FFD’s (say
smart meters from a group of houses) would communicate with a device on a pole and
this device would in turn communicate with the utility offi
ces over the neighborhood area
network. And each such device on the pole is interconnected thereby forming a mesh like
network constituting a neighborhood area network.



11




Neighborhood Area N
etworks

[NAN]

are a type of packet switched mobile data
networks. NA
Ns are flexible packet switched networks whose geographical coverage
area could be anywhere from the coverage of a LAN, to MAN, to WAN. In Smart Grid,
NAN has a role to play in the HOME
-
to
-
HOME or HOME
-
to
-
GRID communication.
The order of the day i
n network
ing is

to provide complete ubiquit
y, i.e., every device
location is
connected to millions of locations and across ten thousands of square miles.
The solution for complete ubiquity is wire
less neighborhood area network [
WNAN
]
.

The
ubiquitous network requirements for Smart Grid are identified as follows: reliable,
secure, power efficient, low latency, low cost, diverse path, scalable technology, ability to
support bursty, asynchronous upstream traffic to name a few.

In this repo
rt, we would mainly focus on the com
munication sector of Smart Grid, where
analysis of communication
, routing and transport

protocols for neighborhood area
network for Smart Grid in particular

are carried out
.


1.5.

RELATED WORK


In this section we will discu
ss the work done on communication infrastructure by other
organizations.


Electric Power Research Institute [EPRI] submitted a report on Smart Grid
Interoperability Standards Roadmap to
National Institutes of Standards and Technology
[NIST]
,

which lists the near
-
term actions that NIST proposes to take with regards to the
Interoperability framework. Few of the highest priority tasks related to communication
and cyber security are listed below

[5
]
:



12





Conducting an analysis to select Internet Pro
tocol Suite profiles for smart
grid applications
-

NIST should commission a group to perform a
comprehensive mapping of smart grid application requirements to the
capabilities of protocols and technologies in the Internet Protocol Suite to
identify Interne
t protocol Suite subsets as important for various
applications in the various smart grid domains.


Investigating Communications Interference in Unlicensed Radio
Spectrums
-

NIST should commission a group of experts to study the issue
of communications int
erference in unlicensed radio spectrums for smart
grid applications.


In the interim report, NIST suggests few standards
/
protocols to use in
communication
infrastructure to exchange meter data and control signals
. Few protocols that are
identified by NIST

for network interoperability are
TCP/IP,
UDP,
ANSI C12.22
,
IEC
-
61850,
Ethernet,
ZigBee,
LAN, WAN, WLAN,
Metropolitan Area Ne
twork (MAN),
IEEE 802.1
1
x MAC,
& IPv4, IPv6 Addressing, Distributed Network Protocol (DNP3)
[5
].


Number organizations

such as

Trilliant Inc. have come up with complete Smart Grid
communication solutions coupled with head
-
end software to provide utilities with a
solution to meet their Smart Grid networking demands. Few of the solutions that Trilliant


13




Inc. has implemented to the me
et the
d
emand
-
side management and smart metering
solutions are SecureMesh WAN, SecureMesh NAN, SecureMesh HAN and UnitySuite
HES

[Head
-
End Software]
. The SecureMesh solutions enable smart grid distribution,
metering

and home automation solutions and
UnityS
uite HES provides the scalable
network operations and management packages

[4
]
.

As of today, there is no widely deployed technology in North America to be used for the
implementation of neighborhood area network.
The aim of this project is to find suitable

standards/protocols that could be used for Neighborhood Area Network [NAN] for Smart
Grid.

Following chapters discuss the requirements for NAN and analyzes
standards/protocols for NAN in Smart Grid.



1.6.

SCOPE OF THE PROJECT


The aim of this project is to p
rovide a deep insight on

the communication protocols used
by the

neighborh
ood area network for Smart Grid. Also, to

analyze the protocols,
compare and recommend the best suitable protocol that could be implemente
d in
neighborhood area networks. And to

study the security issues with the
identified
protocols, and make few recommendations to solve any open issues and identify the
research ar
e
as based on this study.
Chapter 1 introduces

us to the traditional grid, need
for Smart Grid,
structure of
Smart Gr
id and lays the foundation for neighborhood
area
network. Chapter 2 emphasizes on neighborhood area network, its requirements for
Smart Grid and its significance in Smart Grid. Chapter 3
acquaints

us with the protocols
and standards that are in contention
for the implementation in neighborhood area


14




networks.
Chapter 4 discusses the different kinds of routing protocols that
find

their way
in
to

neighborhood area network. Following this would be the discussion on transport
protocols used in neighborhood area n
etwork

as part of Chapter 5
.
The next chapter will

discuss the security issues and vulnerabilities associated with the protocols and standards
discussed in Chapter 3.
Also Chapter 6

lists the best practices and recommendations for
the protocols or standar
ds discussed in Chapter 3.
Even w
ith all the best practices and
recommendations listed in Chapter
6
, there would sti
ll be few open issues that
need

to be
addressed;

Chapter 7

would

identify such research areas in neighborhood area network as
part of the cu
stomer domain for Smart Grid.





15




C
hapter

2

REQUIREMENTS FOR NEIGHBORHOOD AREA NETWORK


There has been a steady progress in the communication requirements for utility
applications, starting from the one
-
way communication for reading meter data or
Automated Meter Reading [AMR] to advanced two
-
way communication of Advanced
Metering Infrastructu
re [AMI], supporting the outage notification, demand response and
other applications [See
Figure
3
]

[3]
.


Figure
3
:
Evolution of Utility Communication Requirements




16




Smart Grid requirements that have extensions to these capabilities including distribution
automation and control, power quality monitoring and substation automation, need a
communication infrastructure that
allows utilities to interact with devices on the electric
grid as well as with the customers and distributed power generation and storage facilities
[
3
].

The customer domain consists of a Neighborhood Area network connecting the
utility to the smart meter
installed in the homes of the consumer, the gateway and finally
then home area network which connects all the appliances at home [See
Figure
4

[
34
]
].


Figure
4
: Customer Domain: NAN, gateway and HAN


The utilities
should

have the ability to support multiple communication networks like
Home Area Network [HAN], Neighborhood Area Network [NAN] and Wide Area


17




Network [WAN] for various applications like consumer energy efficiency, advanced
metering and distribution automation [See
Figure
5
]

[
4
]
.


Figure
5
: Smart Grid Building Blocks


Figure
5
[
4
]

shows

the building blocks of Smart Grid, which consists of Power System
Layer, Control Layer, Communications Layer, Security Layer, IT Infrastructure Layer
and the Application Layer. The Communications Layer is further divided into three sub
divisions. They are
:

Home Area Network [HAN], which as the name indicates is part of the customer
premises and involves the communication between the devices installed at the residential
or commercial premises to their respective Smart Meters.



18




Neighborhood Area Network [NAN
] is the communication network that aids the
communications between the utilities and the Smart Meters installed at the customer
premises.

Wide Area Network [WAN] is the communication network responsible for the backhaul
communications.

The Smart Grid com
munication requirements at high lev
el,
is

described below [2]:

SECURE

Privacy
, Integrity

and Confidentiality are the
three

main focus areas in communication
across the network. Hence, an end
-
to
-
end security must be employed to protect user
information and
protect the network from unauthorized access.


RELIABLE

The network has to provide maximum availability by incorporating fault tolerance
mechanisms and self
-
healing failover at each tier of the network. It must provide an
“always
-
on” communication as part

of the electric grid.


FLEXIBLE

The coverage has to be consistent over smaller rural regions to larger urban areas. The
communication network has to have the flexibility to cover the same disparate territories
as the grid itself.





19




SCALABLE

The network
needs to be scalable to meet the current and future requirements. It shoul
d
be capable of

support
ing

the changing requirements over time to accommodate the
current simple meter reading to the future multi
-
application that span from demand
-
side
management t
o distribution automation. Also, it should be upgradeable and interoperable
to ensure future
-
proof solution.


COST
-
EFFECTIVE

The capital and operational expenses of a communication network needs to be within the
potential savings.


The typical
characteri
stics of

different communication network layers could be
summarized as shown below in
Table
1
.


Scale of Coverage

Bandwidth
Required

Example for
Communication
Technologies

Home Area
Network

1000 of Sq.

Feet

1
-
10 Kbps

ZigBee

Neighborhoo
d Area
Network

1


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20




A
r
epresentation of the above table of information is shown in the
Figure
6
[2]
.



Figure
6
: Hierarchical Organization of Communication Networks

Limiting our scope of discussion to the requirements of Neighborhood Area Network, the
Neighborhood Area Network [NAN] requires higher bandwidths ranging anywhere fr
om
10 Kbps to 100Kbps to suffice the meter reading, demand response, remote disconnect
and other capabilities. One of the main requirements is to support mesh networking, as
the network needs to cover thousands of homes, essentially covering over a few squ
are
miles. These networks also have to provide low latencies, typically less than 10 seconds
as control signals are part of the two way communication.
They also have

to
support

excellent
signal
propagation in the challenging RF environment.





21




C
hapter

3

OVERVIEW OF CANDIDATE NETWORK

PROTOCOLS AND STANDARDS



Protocols
can

be categorized based on the type of connectivity namely wired and
wireless. Each has its own advantages and disadvantages. Reliability, quality of service,
security, cost effectiveness a
nd speed are the
advantages

to wired networks. While the
disadvantages

are difficult
y in installation
, addition of computers or systems may slow
down the network,

l
ooks disorganized and maintenance

of

cable are difficult. Wireless
networks are neat and cle
an
with

no untidy cables hanging around, also the set up is very
easy and does not need a great deal of networking experience. But the
downside to
wireless networks is

that they are not

as

reliab
l
e

and secur
e

as wired networks
. They also
have

potential rad
io interference due to obstacles, weather and other wireless devices.
Wireless networks have many
other
advantages over wired networks which are mainly
mobility, more flexible, easier to use and affordable to deploy and maintain. Every
network transmits da
ta over a medium and for wireless networks the medium is the
electromagnetic radiation. Wireless devices are constrained to operate in a certain
frequency band. Each band has an associated bandwidth, which is simply the amount of
frequency space in the ban
d. So, let us first consider the players in the wireless category
for communication protocols for Smart Grid.

For Smart Grid, a careful choice has to be made in selecting a protocol or a standard for
the data and c
ontrol information exchanges. This informa
tion exchange
involves highly
confidential consumer information
so customer

privacy

has to be protected. As far as the


22




control information is concerned, secu
rity is at the highest priority, if
misused, would
lead to financial

loss and sometimes could prove
to be fatal.

Keeping the above discussed points in mind, we could consider the following protocols
that could find a place in the communication arena of Smart Grid. They are IEEE 802.11,
802.15.4 and 802.16, ANSI C12.22, 3G,

Mesh Networks, optical fiber communication,
and power line communication.


3.1. IEEE 802.11


IEEE 802.11 is the set of standards defining the wireless local area network
communications operating in the 2.4GHz, 3.6GHz or 5GHz frequency bands. These are
def
ined and amended by the IEEE LAN/MAN standards committee. IEEE 802.11
includes the Wi
-
Fi [Wireless Fidelity] and its faster cousin IEEE 802.11g. The current
version is IEEE 802.11
-
2007 and other common and most implemented versions are
IEEE 802.11a, b, g a
nd n. IEEE 802.11 uses the radio wave physical layer. The bands of
operation of these protocols are set by ITU [International Telecommunication Union] for
radio communication. The ISM

[Industry, Scientific and Medical]

bands are usually
license
-
free provid
ed that the devices are low
-
po
wer. IEEE 802.11b/g operates at

2.4GHz, while IEEE 802.11a operates at 5GHz.

A short summary of the standard, speed associated and the frequency band is reported in

Table
2




23




IEEE Standard

Speed

Frequency Band

802.11

1Mbps , 2Mbps

2.4 GHz

802.11a

Up to 54Mbps

5 GHz

802.11b

5.5 Mbps, 11 Mbps

2.4 GHz

802.11g

Up to 54 Mbps

2.4GHz

802.11n

Up to 300 Mbps

2.4/5 GHz

Table
2
: IEEE 802.11 Standards and its Variations

IEEE 802.11 adds a number of management features to differentiate it from the wired
networks. They have a 48 bit MAC [Media Access Control] address and they look like
the Ethernet network
interface cards. These addresses are from the same address pool as
of the Ethernet, to maintain the uniqueness and compatibility when wireless
networks
are
deployed in
networks which contain

the wired network too.

Figure
7

[7]
describes the IEEE 802 family and its relation to the OSI model.


Figure
7
: IEEE 802 family and its relation to the OSI model




24




IEEE 802 focuses mainly on the lowest two layers of the OSI model because it involves
the physical and data link components. The MAC layer is responsible for setting the rules
for sending data and
specify
how to access the
,

whereas,

the physical layer is r
esponsible
for the transmission and reception of the data. 802.2 specify the link layer and logic link
control [LLC] which could be used by any LAN technology.

IEEE 802.11 is just another link layer that uses the 802.2/LLC encapsulation.
IEEE 802.11 has M
AC layer and two physical layer a FHSS [frequency hopping spread
spectrum] and DHSS [direct hopping spread
-
spectrum]. Later revisions of the 802.11
standards also include OFDM [orthogonal frequency division multiplexing] for higher
speed which is also back
ward compatible with IEEE 802.11b.

IEEE 802.11 physical layer has two physical medium components

[See
Figure
8
]

[7]
.
They are

i)

Physical Layer Convergen
ce Procedure [PCLP]: which maps the MAC frames

ii)

Physical Medium Dependent [PMD]: which transmits the MAC frames


Figure
8
: IEEE 802.11 Physical Layer Components


IEEE 802.11 Design consists of four major components

[See
Figure
9
]

[7]
. They are
Station, Access Point, Wireless Medium and Distribution system.



25






Figure
9
: IEEE 802.11 Design Compon
ents


i)

STATION
:
is a computing device

with wireless network interface cards.

Networks are built to transfer data between stations.

ii)

ACCESS POINT

[AP]
:

P
erforms the bridging function, which converts the
frames of 802.11 into another type (wireless
-
to
-
wired) of frame for delivery.

iii)

WIRELESS MEDIUM
: is used to transfer the frames between stations. The
architecture supports different physical layers to be dev
eloped to support 802.11 MAC.

iv)

DISTRIBUTION SYSTEM
:
Number of a
ccess
p
oints together form a larger
network. The distribution system is a
logical component which is responsible for
forwarding the frames to the destination.


CHALLENGES FOR THE MAC

There is
higher confidence of message reception at the destination with wired network
when
compared to wireless network, because

wireless medium is susceptible to
interception of radiations from other devices like microwave ovens, cordless phones etc.



26




IEEE 802.11

incorporates positive acknowledgement

[See
Figure
2
Figure
10
]

[7]
. Here
all frames must be acknowledged else the transaction is flagged as failure
and the frames
are considered lo
st.


Figure
10
: Positive Acknowledgement



Hidden node is another problem with wireless networks. The wireless medium spreads
across indefinite boundaries. In
Figure
11

[7]
, Node 1 is unreachabl
e to Node 3, but Node
2 is reachable to both Node 1 and 3. If Node 1 and Node 3 simultaneously
transmit

to
Node 2, it would not be able to make out any sense out of the transmission.



27





Figure
11
: RTS/CTS clearing

This results in collision.
Because wireless communication is half
-
duplex, which

is
transmitting and
receiving

does

not take place simultaneously, it is difficult to detect a
collision. To prevent collision, 802.11 implements RTS

[Request
-
to
-
Send] and CTS

[
Clear
-
to
-
Send] signals to clear the area

[See
Figure
12
] [7]
.


Figure
12
: RTS/CTS clearing




28




Nod
e 1 initially sends a RTS
frame. U
pon reception
of the RTS frame
by Node 2, it
then
sends
the
CTS frame indicating that it is clear to send
data. Node 1 sends the data frame
to Node 2 and in turn Node 2
returns

a positive acknowledgement.
The RTS
frames serve

two purpose
s
, firstly
reserves the radio link and secondly notifies other stations that it is
in information exchange with other stations.
RTS and CTS frames could be an overhead,
but the overhead could be
reduced by setting a threshold for RTS/CTS. Any frame
s

that
are
shorter
than the threshold are simply sent and RTS/CTS exchanges are performed if a
frame is larger than threshold. Thus it prevents collision with reduced overhead.

802.11 FRAMING

Framing in wireless cannot be as simple as in case of wired as it involves several

management features.
There are three types of frames namely:

DATA FRAMES

Data frames
could be of different type
depending on the network

and function
,
which
carries data from station to station
. One of the types could be data used for contention
-
based service or contention
-
free service. The other type could be one which
carries

frames that performs management functions. A generic data frame format is shown in
Figure
13

[7]
.



29





Figure
13
: Generic Data Frame

As show
n

in
Figure
13

[7]
, the data frame contains frame control, sequence control and
FCS [Frame
Check

Sequence]
fields
. The FCS
field

is

referred to as the cyclic
redundancy check because of the underlying mathematical operations.
The Sequence
Control field is a 16 bit field which is used for defragmentation and disregarding
duplicate frames. The Sequence Control field has two parts, A four bit field is the
Fragment number and the rest 12 bits is the sequence number [See
Figure
13
]

[7]
. The
Frame control field has many other components as show in
Figure
14
.

Figure
14
: Frame Control field

Protocol Version field indicates the version of 802.11 MAC contained in the frame. The
Type
and Sub Type

field
s

indicate

the
type

and subtype

of the frames
.

ToDS and F
romDS
indicate

whether the frame is destined for a distribution system.
Power Management field indicates whether the sender will be in a power saving mode or


30




not after the exchange of the current frame. The protected frame field indicates whether
protection is enabled by the link layer or not. Order bit indicates whether strict ordering
delivery is implemented or not.

CONTROL FRAMES
:
This performs area
-
clearin
g operations, channel acquisition,
positive acknowledgement and carrier sensing maintenance functions.

These use the
same fields as the frame control field [See
Figure
14
]

[7]
.

MANAGEMENT FRAMES
:
These perform
functions which take care of joining and
leaving the networks and to move association from a
ccess points to access points. This is
done by splitting the procedure into three parts. First, the mobi
le stations must locate a
compatible wireless network to use for access. Next, it must be authenticated with the
network to get itself identified and connect to the network. Finally a mobile station will
be associated with a network to gain access.

802.11

PHYSICAL LAYER

The physical layers are based on the radio technology
and different spread spectrum
techniques
used.



802.11a uses orthogonal frequency division multiplexing [OFDM] PHY



802.11b uses direct sequence spread spectrum [DSSS] PHY



802.11g uses
extended rate PHY[ERP]



31




Spread spectrum is a technique in which a signal in a particular bandwidth is spread in
the frequency domain

[8
]
.


This result

in a much greater

bandwidth

than the signal would
have if its frequency were not varied.

FREQUENCY HOPPING

SPREAD SPECTRUM

is a technique where
signals

are
transmitted by switching the carrier among many frequency channels in a pseudo
-
random
sequence which is known bo
th to receiver and transmitter
[9
]
.

DIRECT SEQUENCE SPRE
AD SPECTRUM

technique does not hop fro
m one
frequency to another, instead it is passed through a spread function and it is distribute
d
over the entire band at once
[
10
]
.

ORTHOGONAL FREQUENCY

DIVISION MULTIPLEXIN
G

is a technique where
large numbers of closely spaced orthogonal sub
-
carriers are

used to carry data. The data
is divided into number of parallel data streams for each such sub
-
carrier. Then,
conventional modulation techniques are used to modulate the sub
-
carrie
rs [
11
].









32




802.11 HARDWARE

Figure
15
: 802.11 Generic Wireless
Cards


Usually the wireless LAN cards

[See
Figure
15
]
[7]

have two antennas to improve the
reception and provide antenna dive
rsity. Transceivers are used to boost the outgoing
signal and process the incoming signal. It also
down
-
converts

the high frequency to a
more manageable
frequency by

extracting the data bits from the high frequency carrier.
Next comes the baseband processo
r which converts bits from the computer to
radio
waves

which is called modulation and the opposite process which is converting radio
waves to bits
is called demodulation.
H
eart of

the

device is the MAC controller which is
responsible for
taking the incomin
g frames from the host computer operating system’s
networking stack and decides when to send the data out the antenna into the air.





33




802.11 SECURITY ARCHITECTURE

One of the major features of wireless networks
is

the ease of connection.
This is because

802.11 networks announce th
eir existence
with the aid of beacon frames.
To protect
against unauthorized access to the network we have to apply access control. It could be
done
at various steps
as follows
:

STATION AUTHENTICATI
ON
: Before joining a

802.11 network station authentication
is performed using shared key authentication or sometimes using MAC address filtering
to filter out unauthorized client by MAC address.

LINK LAYER SECURITY
:
Link
-
layer authentication is transparent to network
protoco
ls, and will work for any network protocol
chosen
. Networks are increasingly
homogenous and
are based on IP.

Link
-
layer authentication can be used to secure both IP
and IPX.

Link Layer Security has a very small foot print and can be easily integrated with
the network interface cards
, access point devices and mobile devices.
WPA is an industry
standard for providing

strong link layer security to WLANs, and supports two
authenticated key management protocols using

the Exte
nsible Authentication Protocol
[EAP]
.

WPA also requires data frame encryption using TKIP

[Tempo
ral Key Integrity
Protocol]

and message integrity u
sing a Message Integrity Check [MIC].

NETWORK OR TRANSPORT

LAYER SECURITY
:
Network layer security provides
end
-
to
-
end security across a routed netw
ork and can provide

authentication, data
integrity, and encryption services.
These

services are provided for IP

traffic only. IPSec is
a

standard network layer security protocol

which

provides a standard and extensible
method

to provide security to network

layer (IP) and upper layer protocols such as TCP


34




and UDP. It can also be used between routers or IPSec gateways.

Firewalls can be used to
isolate untrusted networks and authenticate users.

Also VPN termination devices can
supply encryption over untrusted

networks.

3.2. IEEE 802.16

[12][13]


WiMAX

[
Worldwide Interoperability for Microwave Access
]

is a trade name for IEEE
802.16 standard.
WiMAX

provides wireless transmission of data in variety of modes
from a point to multi
-
point links. It is also called as

the Last
Mile Connectivity of
Broadband Wireless
Access [
BWA]
with a range of around
30 miles

and

a data transfer
rate of up

to 280
Mbps with the ability to support data, voice and video.
Its operating
range is anywhere from 2GHz to 66GHz.
It does not requ
ire LOS
[
Line Of Sight
]
.

A
version of IEEE 802.16 which is IEEE 802.16e adds mobility features operating in the
range of 2
-
11 GHz license bands. Hence it allows fixed and mobile non Line of Sight
[NLOS] applications primarily to enhance OFDMA [Orthogonal F
requency Division
Multiple Access]
.

To summarize the salient
feature of
WiMAX

are:



It enhances orthogonal Freq
uency Division Multiple Access [
OFDMA
]

by

allowing fixe
d and mobile Non Line of Sight [
NLOS
]

applications.



QUALITY OF SERVICE

[QoS]



HIGH DATA
RATES
: Mult
iple Input and Multiple Output [MIMO]

along with

flexible sub
-
channelization schemes, coding and adaptive modulation helps

mobile
WiMAX

technology to support downlink [DL]

data rates up to 128 Mbps

per sector and
peak uplink [
UL
]

data rates up t
o 56Mbps per sector in 20MHz

bandwidth.



35






SCALABILITY
: The mobile
WiMAX

has the capability of operating in scalable

bandwidths from 1.25
to 20MHz by utilizing Scalable [
SOFDMA
]
.



SECURITY
: The most advanced security features includes Extensible
Authentication

Protocol
[
EAP
], advanced Encryption Standard [
AES
]
, Cipher Based
Message

Authentication Code [
CMAC
]

and Hashed Message Authentication Code

[
HMAC
]
.

WiMAX

system has two major
components
: They are:



BASE STATION
: consists of
high speed

electronics and tower like a cell
-
phone
tower. Base station provides coverage over an area called cell, which has a maximum
radius of upto 30 miles.



RECEIVER:
could be an antenna, stand
-
alone box or a PCMCIA [
Personal
Computer Memory Card International A
ssociation] card in a computer. This is also
referred to as Customer Premise Equipment [CPE].

IEEE 802.16e just provides an air interface, but the end
-
to
-
end
WiMAX

network
is
defined by
WiMAX

forums Network Working Group

[NWG]
, which is responsible for
de
veloping requirements, architecture and protocols for
WiMAX

using IEEE 802.16e
-
2005 as the air interface.


IP BASED
WIMAX

NETWORK ARCHITECTURE

The overall network

[See
Figure
16
]

[13]

could be divided into the following logical parts

for an IP based
WiMAX

Network Architecture:



36






MOBILE STATIONS [MS]:

used by end users to access the network.



BASE STATIONS [BS]:
is responsible for providing air interface to the mobile
stations. Also responsible for features like key management, session management and
dynamic host configuration protocol [DHCP] proxy.


Figure
16
: IP based
WiMAX

Network
Arc
hitecture




ACCESS SERVICE NETWORK [ASN]:

comprises
more than one base stations
and more than one

access service network gateway

to form the radio access network
[RAN].

Functions of Access Service Network gateway includes intra
-
ASN location
management and p
aging, radio resource management and admission control, caching of
subscriber profiles and encryption keys, establishment and management of mobility
tunnel with base stations,
Quality of Service [
QoS
]

and policy enforcement, and routing
to the selected
connectivity service network [
CSN
]
.



CONNECTIVITY SERVICE NETWORK [CSN]:

provides connectivity to
internet, public networks and corporate networks. Also, manages per user p
olicy
management and security a
nd IP address management.



37




WiMAX

network is based on t
he following principles [10]:



SPECTRUM: which allows
WiMAX

network to be deployed in both licensed and
unlicensed spectra



TOPOLOGY: Supports Radio Access Network [RAN] topologies



INTERNETWORKING: Enables internetworking with WiFi, 3GPP

[3
rd

Generation Partnership Project

which is responsible for the
specification
, maintenance
and development of global system for mobile communication [GSM]]
.



IP CONNECTIVITY: Supports IPv4 and IPv6 network interconnects in clients
and application servers.



MO
BILITY MANAGEMENT: Supports both fixed and mobile access and
broadband multimedia services delivery.

Figure
17

[12]
below shows
the IEEE 802.16 Protoc
ol Architecture that has 4 layers:
Convergence, MAC, Transmission and physical, which can be map
ped

to two OSI lowest
layers: physical and data link
.

WiMAX PHYSICAL LAYER

WiMAX uses Orthogonal Frequency Division Multiplexing [OFDM] which uses number
of su
b
-
carriers to carry data to overcome multiple signals hitting the receiver. There are
several standards associated to IEEE 802.16, one of them is IEEE 802.16
-
2004 which
uses 256 carriers and IEEE 802.16e uses scalable OFDMA. 802.16 use
s

many
modulation techniques like Binary Phase Shift Keying [BPSK], Quaternary Phase Shift
Keying [QPSK] and Quadrature Amplitude Modulation [QAM]. It also supports two


38




types of duplexing. They are Time Division Duplexing [TDD] and Frequency Division
Duplex
ing [FDD].


Figure
17
: IEEE 802.16 Protocol
Layer


IEEE 802.16 MAC LAYER

The primary task of the MAC layer is to provide interface between the higher transport
layer and the physical layer.
The MAC layer takes packets from the upp
er layer called
MAC service data units (MSDUs)

and organizes them into MAC protocol data units
(MPDUs) for transmission over the air

and
does
the reverse for the received transmission
.

The convergence service sublayer

can interface with a variety of
higher

protocols such as
ATM TDM Voice, Ethernet, IP and any other future protocols.

Figure
18

[12]
shows the generic form of the MAC PDU
. The MAC PDU is the data unit
exchanged between the MAC layers of the BS and its SSs. A MAC PDU consists of a
fixed
-
length MAC header, a variable
-
le
ngth payload, and an optional cyclic redundancy


39




check (CRC). Two header formats, distinguished by the HT field, are defined: the generic
header and the bandwidth request header. Except for bandwidth request MAC PDUs,
which contain no payload, MAC PDUs cont
ain either MAC management messages or
convergence sublayer data.

The encryption Control field indicates whether the data
payload in the header is encrypted or not.
The Type
field indicates the subheaders and
special payload types present in the message pay
load
.
Cyclic Redundancy Check [CRC]
Indicator [CI] field indicates if and how the CRC error check is used for the data.
Encryption Key S
equence

[EKS]

is an index value that is used to identify the location of
a data packet within a sequence of packets to e
nable the decryption of the packet.

A
connection identifier [CID]

is a unique number that is used to identify the logical path of
a communication system. Header Check Sequence [HCS] is a calculated code that is used
to check whether the header is received
correctly or not.



Figure
18
: Generic MAC PDU
Format



40





The MAC incorporates several features such as the following:



Privacy key management (PKM) for MAC layer security. PKM version 2
incorporates support for extensible
authentication protocol (EAP).



Broadcast and multicast support.



High
-
speed handover and mobility management primitives.



Three power management levels, normal operation, sleep and idle.



Header suppression, packing and fragmentation for efficient use of spec
trum.

WiMAX

SECURITY

Security is handled by the Privacy Sublayer of the WiMAX MAC. The primary features
of WiMAX security are as follows:

PRIVACY: Most advanced encryption standards like Advanced Encryption Standard
[AES] and 3DES [Triple Data Encryption S
tandard] are supported. In addition to the
above, 128 bit and 256 bit keys are used for deriving the cipher during the authentication
phase and also these are periodically refreshed.

AUTHENTICATION: To prevent unauthorized access, a flexible
means for
aut
henticating the subscriber stations and users is provided. This authentication is based
on the Internet Engineering Task Force [IETF] Extensible Authentication Protocol [EAP]


41




which
provides

different types of credentials such as username and password, digi
tal
certificates like
X.509 (
which has the username and MAC address) and smart cards.

KEY MANAGEMENT: The keys are transferred
securely
from the base stations to the
mobile stations
using the Privacy and Key Management Protocol version 2 [PKMv2]
w
hich inv
olves

periodical reauthorizing and refreshing of the keys.

INTEGRITY: The integrity of the control messages is protected using different message
digest schemes like AES
-
based CMAC [Cipher Based Message Authentication Code] or
MD5
-
based HMAC [Hashed Messag
e Authentication Code].


3.3. IEEE 802.15.4


IEEE 802.15.4 based wireless networking standard has emerged as a key to robust,
reliable and secure Home Area Network [HAN] deployments
. One of the major players
in HAN for Smart Grid is ZigBee which is based
on IEEE 802.15.4 standard. IEEE
802.15.4 defines the physical and medium access control layers for low data rate, short
range wireless communication. The operation is defined in both sub 1GHz and 2.4 GHz
frequency bands, supporting Direct Sequence Spread

Spectrum [DSSS] signaling with a
raw data throughput of 250Kbps and can transmit point to point, ranging anywhere from
tens to hundred of meters depending on the output power and receive sensitivity of the
transceiver.
Applications of IEEE 802.15.4

include light control systems, environmental
and agricultural monitoring, consumer electronics, energy management and comfort


42




functions, automatic meter reading systems, industrial applications, and alarm and
security systems.


IEEE 802.15.4
DEVICES

An IEE
E 802.15.4 network has only one
personal area network [
PAN
]

coordinator. There
are two types of devices described in the specification that communicate together to form
different network topologies:
full function device

[FFD] and
reduced function device

[R
FD]. An FFD is a device capable of operating as a coordinator and implementing the
complete protocol set. An RFD is a device operating with a minimal implementation of
the IEEE 802.15.4 protocol. An RFD can connect to only an FFD whereas an FFD can
connect

to both FFDs and RFDs.

A PAN co
ordinator is the main controller of the
network which can initiate or terminate a connection.


IEEE 802.15.4 PHYSICAL LAYER

The IEEE 802.15.4 has two PHY options based on direct sequence spread spectrum
[DSSS]. The PHY adopt
s the same basic frame structure for low
-
duty
-
cycle low
-
power
operation at both sub 1GHz bands (868/915 MHz) and at high band (2.4 GHz). The low
band
implements

binary phase shift key
[BPSK] modulation and operates in the 868MHz
band with a raw data rate o
f 20 kbps and in the 915MHz ISM band with a raw data rate of
40 kbps. The high band adopts
offset quadrature phase shift key

[O
-
QPSK]

modulation,
operates in 2
.
4GHz with a raw data rate of 250 kbps.




43




IEEE 802.15.4 MAC LAYER

The MAC sublayer

provides two services

namely

MAC data service and the MAC
management service interfacing to the
MAC sublayer management entity [
MLME
]

serv
ice access point [
SAP
] [MLMESAP]
. The MAC data service
is responsible for

the
transmission and reception of MAC protocol data units
[MPDU]

across the PHY data
service. The features of MAC sublayer are beacon management, channel access, GTS
management, frame validation, acknowledged frame delivery, association and
disassociation
.


IEEE 802.15.4
SECURITY

[19]

IEEE 802.15.4 supports both secure and non secure mode.
S
ecure mode

devices
use

AES

to implement the following services
:



ACCESS CONTROL
: This enables the device to accept frames from authentic
sources only.



DATA INTEGRITY
: T
he beacon, data, and command frames are encrypted using
AES encryption algorithm.
The AES algorithm is not only used to for encryption but also
to validate

data sent. This is achieved using Message Integrity Code [MIC] also called as
Message Authentication

Code [MAC]. The MAC can be of different sizes
:
32
, 64 and
128 bit
s
.
This MAC
is created encrypting parts of the MAC frame using the Key of the
network, so if we receive a message from a non trusted node
,

the MAC generated for the
sent message does not cor
respond to the one what would be generated using the message
with the current secret Key, so
the message is
discard
ed
.




44






FRAME INTEGRITY
: Ensures that the frames are received from the device that
has the key and the data is protected from modification witho
ut the key. Frame integrity
is provided to the beacon, data and command payload using a message integrity code
[MIC].



SEQUENTIAL FRESHNESS
: This is to prevent the replay attacks using a replay
counter which will reject a frame which has a value equal or le
ss than the previous
obtained counter value.


3.4. ANSI C12.22

[23]


Earlier

the data from the memory of
electronic

device
s
would be transported using a
proprietary protocol which was unique to a manufacturer. With the introduction of ANSI
C12.22,

an effort to standardize the data formats and transport protocols and desire for
interoperability
and support for multiple manufacturer
s

are

provided.
ANSI C12.22
defines the message services of Advanced Metering Infrastructure [AMI] for Smart Grid.
The co
ncept of ANSI C12.18, ANSI C12.19 and C12.21 are extended to come up with
ANSI C12.22.

ANSI C12.18 standard is a point
-
to
-
point protocol developed to transport the meter data
over an optical connection. ANSI
C
12.19 defines the table data format and ANSI C1
2.21
standard is developed to transfer the data over telephone modems.

An example
for

ANSI C12.22
could be described

as follows, a C12.22
-
compliant
message
could be sent on a
RF mesh network to reach an access point, and then use


45




GSM/CDMA 3G or WiMAX netw
ork backhaul and metro fiber networks WAN to move
data from end devices to utility control center/head ends.

The main advantage of the ANSI C12.22 open standards is that it enables interoperability
among smart meters, intelligent field devices and others d
evices so that smart meter data
can be collected, analyzed and C12.22 devices are controlled over any
NAN/AMI/Backhaul/WAN communication networks as long as the message conforms to
the ANSI protocol.

ANSI C12.22 can be transported over IP for Smart Grid L
ast Mile and other network
segments. If IP and
ANSI C12.22
are combined
,

C
12.22
-
compliant system avoids

utilities from the risk of single AMI/NAN network and smart meter technologies lock
-
in
.
It p
rovides adaptation to the rapid changes in
communicatio
ns te
chnologies that the

utilities choose to communicate with their end devices
.
If

the meter or the network
changes, the overall end
-
to
-
end communication system is not affected, as long as the new
solution provides interoperability at the C12.22/IP layer
.

The
reason
ANSI C12.22
is discussed is for the flexibility that it provides for the
interoperability to the Last Mile network for Smart Grid
.
ANSI C12.22
defines the
communication between
IP nodes and its communication devices and it’s

interface that
connects the
ANSI C12.22
Network (TCP or UDP).

In Smart Grid
,

ANSI C12. 22 find its application more appropriately in
Smart Grid
gateway devi
ces which defines the interface

to communicate the meter data to the utility
over the Smart Grid L
ast Mile network.




46




3.5.
CELLULAR

COMMUNICATION

One

way to meet the requirements for neighborhood area network is through cellular
communication. Cellular communication is ubiquitous, easy to install and incurs low
maintenance cost. The coverage is excelle
nt because it corresponds to the population
concentration and hence ubiquitous. Cellular communication is already established and
has
95
% coverage

extended to consumers and hence no additional efforts for installations
are required. Cellular technology is