Chapter 2Background and Related Works

2.1 Introduction to Smart Grid / Advanced Metering

Infrastructure

Growing the need for the Smart Grid (SG)

A smart grid [1, 2, 3] delivers electricity from suppliers to consumers using two-way

digital communication technology. Smart grid allows controlling appliances at

consumer’s homes to save energy, and reduce cost. The operation status of the smart

grids can be monitored in real time, so the smart grids are more reliable. Many

governments are promoting such a modernized electricity network as a way of addressing

energy independence, global warming and emergency resilience issues.

Figure 2. 1 Smart grid overview (source: U.S. Department of Energy)

Figure 2.1 shows an overview of the smart grid.

Utilities can archive energy efficiency and maintain the competitive of services by taking

advantages of the smart grid and its market benefits. The smart grid solutions that utilize

the information technology for data collection, monitoring and control, data analysis and

information communication infrastructure, will cost-effectively protect revenues today,

while laying the foundations for future services.

Figure 2.2 shows the conceptual framework of smart grid. The components includes

Service Provider, Operations, Markets, Bulk Generation, Transmission, Distribution, and

Customer.

Figure 2. 2 Smart Grid Conceptual Framework (source: The National Institute of Standards and Technology)

Advanced Metering Infrastructure (AMI)

Advanced Metering Infrastructure (AMI) [5] that is as part of larger Smart Grid

initiatives, is implemented by government agencies and utilities to meet the above

challenges. Extending from the current Automatic Meter Reading (AMR) technology,

AMI provides two way meter communications, and allows commands to be sent toward

the home for multi purposes, including Time-of-Use pricing information, demand-

response actions, or remote service disconnects.

Figure 2. 3 AMI overview (source: National Energy Technology Laboratory)

The Department of Energy estimates that over 280 Giga-watts of new generating capacity

will be needed by 2025. It results in new power plants would be built in the future. The

energy industry is facing the critical issues such as the need for new plants, maintaining

overburdened infrastructure, coping with an aging workforce, complying with

regulations, and environmental concerns. For a long time, the energy industry has

rightfully focused on the supply side of this challenge. But now, the demand side of the

equation can be significantly impacted by the existing of the wireless mesh networking

[13].

Figure 2. 4 AMI Enabled Integrated Utilities Operations (source: California Energy Commission Meter Scoping Study)

Wireless mesh networking can use as the backbone of the AMI solutions to enable two-

way intelligent networked communications with smart meters. With the AMI, the value

added services such as demand response and demand side management would be

enabled, besides meter reading. AMI solutions allows interoperable networks and

systems across the entire power structure aid in the management and control of energy

consumption, improve operations management, conserve the environment, and adhere to

evolving regulations [5].

2.2 Introduction to Wireless Mesh Network (WMN)

What is WMN?

A WMN [7, 10, 11] is a communications network made up of radio nodes organized in a

mesh topology. Wireless mesh networks often consist of mesh clients, mesh routers and

gateways. The mesh clients are often laptops, cell phones and other wireless devices

while the mesh routers forward traffic to and from the gateways which may but need not

connect to the Internet. A mesh network is reliable and offers redundancy. When one

node can no longer operate, the rest of the nodes can still communicate with each other,

directly or through one or more intermediate nodes. Wireless mesh networks can be

implemented with various wireless technology including IEEE 802.11, IEEE 802.15, and

IEEE 802.16 [7, 8, 9] , cellular technologies or combinations of more than one type.

Figure 2. 5 IEEE 802.11s terms: A Mesh Portal (MPP) connects to the wired Internet, a Mesh Point (MP) just forwards mesh traffic, and a Mesh Access Point (MAP) additionally allows stations (STA) to associate with it

WMN is as wireless infrastructure solution for AMI

When the WMN technology is applied in AMI solutions, it can bring new components to

the electrical grids, such as self-managing and self-healing mesh networking, intelligent

meters, and bridging to Home Area Networks (HAN) [5] for connectivity with energy

consuming appliances. The real time communication between the smart meters and the

utility’s data center provides detailed usage data while also receives and display Time-of-

Use (TOU) pricing information, and offers other on-demand abilities such as remote

connect or disconnect, unrestricted monitoring and control, etc. Customers are able to

access the usage data for tailoring consumption and minimizing energy expenses while

helping balance overall network demand.

When WMNs are used in the AMI, they can provide the following features [13, 18]:

Low cost of management and maintenance - WMNs are self-organizing and

require no manual address/route/channel assignments. It is simple to manage

thousands or millions of devices resulting in the lowest total cost of ownership.

Increased reliability – The WMN routing mechanisms provide the redundant paths

between the sender and receiver of the wireless connection. Communication

reliability is significantly increased because of the eliminations of single point

failures and potential bottleneck links. Network robustness against potential

problems, e.g., node failures and path failures due to RF interferences or obstacles,

can also be ensured by the existence of multiple possible alternative routes.

Scalability, flexibility and lower costs - WMNs are self-organizing and allow true

scalability. Nodes and Gateways are easily added at a very low cost with:

o No limitation on number of hops

o No network address configuration

o No managed hierarchical architecture

o No hard limitation on number of Nodes per Gateway

Robust security – WMNs have the security standards that allows all

communications in AMI are protected by mutual device authentication and derived

per-session keys using high bit rate AES encryption. This hardened security

approach allows for authentication as well as confidentiality and integrity

protection in each communication exchange between every pair of network

devices – Smart meters, Relays, or Wireless Gateways.

2.3 Related Works

2.3.1 Colorado Springs Utility AMI Network Infrastructure

A brief introduction

The AMI wireless network infrastructure used the Point-to-Multi Point topology. The

current meter data reading interval is five minutes for electric, fifteen minutes for gas and

water meters [6].

Figure 2. 6 AMI Wireless Infrastructure of the Colorado Springs Utilities

2.3.2 SkyPilot’s Synchronous Mesh Network Solution

A brief introduction

MetroFi has deployed a mesh network in the Silicon Valley – California [ref]. The

installed wireless mesh metropolitan area network can provide the Internet access service

to the resident user in a geographical area that covers about 250,000 households. The

SkyPilot’s Synchronous Mesh Network solution was employed to build this mesh

network. The SkyPilot’s mesh network solution combines standard-based WiFi access

with a high performance wireless mesh backhaul network using SkyGate nodes to

interface with the Internet, SkyExtender DualBand nodes that integrate WiFi access and

mesh backhaul [ref].

Figure 2. 8 SkyPilot Mesh Network Architecture (source: SkyPilot)

The mesh network MetroFi is a success deployment of the WMN onto the large

geographical area. However, in the AMI meter data collection application, there is a

different in the network traffic pattern compared to the regular Web applications. The

Web applications usually need the connection with low bandwidth uplink, and high

bandwidth downlink. In contrast, the AMI meter data reporting process requires the high

bandwidth uplink connections to send the data from smart meters to data center.

We can make an assumption that we intend to use the MetroFi network for the AMI

communication infrastructure solution. Then, there is a research opprtunity about the

MetroFi or WMN performance – Whether the WMN is suitable for the AMI network

infrastructure, especially for the real-time meter data reporting application?

Figure 2. 7 A SkyExtender was installed on the street light pole (source: SkyPilot)

2.3.3 EkaNet™ Smart Network - Wireless mesh network

solution for the Smart grid/AMI

A brief introduction

The wireless mesh infrastructure EkaNet [ref] includes the smart meter nodes, ranger

extension nodes, and gateway nodes. The smart meter nodes are networking together to

form the wireless mesh network. It means that, the communication between a smart meter

node and the gateway will replay on a number of other smart meters. The range extension

nodes are used to help connect the out of coverage nodes. The gateway nodes provide the

interface to the Internet network.

Figure 2. 9 EkaNet Smart Network Architecture for AMI

The EkaNet has been deployed in some world wide areas such as Guayaquil - Ecuador,

St. Petersburg – Russia. In Guayaquil – Ecuador, the utility has installed 3,614 wireless

meter nodes, 314 repeaters, and 47 gateways. Meter data collection interval period is

fifteen minutes.

Advantages

Wireless mesh network provides a low cost, easy deployment and management,

scalable, flexible

Disadvantages

The number of relay hops will increases with the increasing number of the the

smart meters. As a result, the network performance will go down fastly, especially

in the service place where the smart meter density is high, i.e. hundreds of smart

meters in the area 100 meters by 100 meters. In the high resident density area, the

mesh topology will not be a good choice for the network performance goal.

Instead, the point-to-multipoint topology such as WiFi infrastructure mode would

provide a better network performance.

2.4 Research Opportunities

This thesis discusses about the evaluation of performance of the WMN when it is

employed as the wireless infrastructure solution of the AMI real-time meter data

collection application.

The related works have proved that the WMN can be used in the networking solutions

that requires the deployment onto a large geographical area, such as the AMR/AMI meter

data collection application. However, the WMN infrastructure needs a high bandwidth

for transmitting the meter data from the smart meters to the data center in real-time. The

conducted researches has shown that the WMN network bandwidth is effected by the hop

number. The more hop number is the WMN routing path, the less performance is the

WMN [18, 19, 21].

2.5 Summary

In general, the wireless mesh network infrastructure can provides a cheap solution,

compared to the wire network, connectting the smart meters to the utility data center.

However, to answer the challenge question, whether the wireless mesh infrastructure is

suitable for the real-time meter data reporting process, this thesis will go into more detail

in the analysis of the performance property of the wireless network infrastructure

solution. We will develop new tools and techniques to assist the planning and design

phase. We will also use the network simulation method to evaluate the network

performance.