Outdoor Lighting Networks:
Market, Technologies and Standards
Abstract: Providing the right amount of light where and when it is needed is an opportunity to transform
today’s cities into smart and livable urban spaces. New technologies are being introduced, such are
controls and outdoor lighting networks, which can deliver energy and cost savings through
adaptive lighting and streamlined maintenance. However, the full market potential for such
systems has not been achieved. This article provides an overview on the basic components,
architecture, technologies and standards relevant to adaptive controls and outdoor lighting
networks. A number of issues have been hampering the market, from lack of clarity in adaptive
lighting regulations, to system interoperability, cost and complexity issues. Standards and
recommended practices that drive regulation on adaptive lighting are paramount to clearing the
way to large scale deployment of intelligent and energy efficient lighting. Existing recommended
practices do not explicitly address adaptive lighting requirements. In the area of communication
technologies, the lighting industry has been trying to leverage existing technologies, such as
Internet protocols and connectivity standards (wireless and power line). However, the diversity
of approaches in applying them has resulted in incompatible solutions at multiple levels. On the
other hand, total solutions typically require customizations to address problems beyond what
standards and off-the-shelf platforms can guarantee. Therefore, there is a clear need for a
balanced approach where standards can be developed to bring immediate value to customers by
leveraging mature technologies, while leaving room for innovation.
Keywords: outdoor lighting networks, adaptive lighting, lighting controls.
1. INTRODUCTION
Lighting is key in providing safety and comfort in outdoor spaces such as roadways, parks,
parking lots, garages, tunnels, and bridges. Lighting also contributes to creating attractive urban
environments and enables cities to establish distinctive identities. Public outdoor lighting
accounts for a significant amount of a city’s energy and maintenance budgets. For instance, New
York City’s complex street lighting system with 262,000 lights on streets, bridges and
underpasses, accounts for approximately 6% of the 4.32 billion kWh municipal energy used
annually [1]. Another recent study estimated the US roadway lighting installed base (52.6
million lights) uses 52.8 TWh of energy annually [2]. Estimates in Europe point to a total energy
consumption for street and highway lighting of 59 TWh per year (80 million light points x 180
W lamp wattage x 4150 burning hours per year) [3]. In China, a recent report from Ministry of
Housing and Urban-Rural Development indicated that roadway lighting installed base was 17.74
million lights in 657 prefectural level cities by the end of 2010, and 5.67 million were new
installations during 2005-2010 [4]; the estimated energy consumption for city lighting was
around 4% of the total energy consumption annually in China (i.e. 4692.8 TWh x 0.04 = 187.7
TWh) [5].
As the numbers indicate, lighting is a pervasive infrastructure that directly impacts sustainability
and wellbeing in urban environments. Providing the right amount of light where and when it is
needed is an opportunity to transform today’s cities into smart and livable urban spaces.
As the industry transitions to LED lighting, new opportunities arise, so do new business and
technical challenges. New technologies are being introduced, such are adaptive controls and
networking, which are relatively new to traditional lighting customers. In particular, advanced
remote control and management systems, referred hereafter as outdoor lighting networks, can
deliver energy and cost savings through adaptive lighting and streamlined maintenance of
lighting and other city assets. However, the full market potential for such systems has not been
achieved, and mainstream deployment is still to be seen. A number of issues have been
hampering the market. Although there are differences per region, the main challenges include, in
no particular order of importance: lack of regulatory guidelines on implementing adaptive
lighting; lack of supporting energy metering structure; lack of interoperability and high cost.
Furthermore, the new technology is often perceived as complex by customers and the direct
benefits are not always clear. These issues have been receiving increasing attention from
governments, manufacturers, and the research community.
In this article, we focus on interoperability and standardization, which play a key role in
addressing customer and industry needs in the new outdoor lighting controls market. In the past,
lighting standards have addressed mainly mechanical and electrical aspects of luminaries and a
few control devices, such as ballasts/drivers and sensors. However, outdoor lighting networks
integrate a wider range of technologies, which is a relatively new concept to the outdoor lighting
industry. The interoperability between system components can drive down cost and address
customer’s call for availability of multiple suppliers, which are conditions for significant
investments in new technologies. While solutions based on industry standards are essential for
large scale deployments, customization and manufacturer’s ability to add value to whole
solutions will still play an essential role, especially in the nascent outdoor lighting network
market. Therefore, there is a need for a balanced approach where standards are developed to
bring immediate value to customers by leveraging mature technologies, while leaving room for
innovation.
The remainder of this article is organized as follow. First, we provide an overview of the controls
market with emphasis on the deployment challenges and interoperability needs. We also
introduce the main components, architecture and typical networking technologies used in
outdoor lighting networks as well as their capabilities and features available to customers. Then,
we give an introduction to the regulatory and standardization landscape. Finally, we conclude
with the opportunities for developing new standards to address current gaps and future
directions.
2. OutdoorLightingControlsMarket
Figure 1 shows the outdoor lighting installed base worldwide, which is an aging infrastructure
including from old high-pressure mercury vapor, to low-pressure sodium (LPS), high-pressure
sodium (HPS) and metal halide lamps. Recent government regulations are phasing out mercury
vapor lamps in many countries, underscoring the renovation needs. Although HPS and metal
halide lamps have higher efficiency compared to older technologies, the rising LED technology
has the greatest energy and maintenance savings potential, especially when combined with
control systems. The market penetration of LED lighting in the outdoor segment is growing at a
fast rate, with luminaire prices dropping considerably year to year, as indicated in the recent DoE
SSL R&D Multi-Year Program Plan “the base price for LED-based outdoor fixtures providing
around 8,000-10,000 lm (i.e. typical replacements for 150W High Pressure Sodium or 175W
Metal Halide) has dropped from around 150 $/klm to around 80 $/klm and the efficacy has
increased from around 50 lm/W to around 80 lm/W” [6]. However, adoption of control systems
coupled with LED lighting has not been growing at similar pace, in fact it is much slower, which
has been raising concerns on the long-term impact of investing in an infrastructure that would
not be operating at its full potential due to the lack of control capabilities [7].
Outdoor Luminaire Installed Base (M units)
400
350
300
250
200
150
100
50
0
Europe
NA
China
Latam
RoW
World
Figure 1: Outdoor installed based and regional breakdown.
Typical outdoor lighting controls today are based on a simple photo-sensor used for on/off
operation at dusk/dawn. In spite of its simplicity and low cost, this approach leaves significant
room for improving energy efficiency. New control technologies offer adaptive lighting
capabilities that can save energy, reduce light pollution, and increase safety. For instance,
adaptive dimming during long periods of inactivity can provide considerable savings. Adaptive
control capabilities can provide additional 40 to 50% savings on top of simple LED luminaire
replacement [7], which highlights the great opportunity of combining LEDs and controls
technologies.
Advanced remote management capabilities can achieve additional savings by optimizing and
streamlining the maintenance of outdoor lighting and other city assets. Energy metering, also
enabled by remote managements systems, brings more transparency to energy
consumption/billing and enables customers to take full advantage of investments in energy
efficiency.
Advanced remote control systems have been introduced for a number of years. However, the full
commercial potential for such systems has not been achieved. For instance, a recently DoE
sponsored survey in the US shows that most deployments are pilot projects [2]. Deployments in
Europe have been increasing in the last few years, but market potential has not been fully
explored either [3]. In China, municipality began to deploy outdoor lighting control systems 20
years ago, starting from the mains power cabinet control system to the recent individual light
control system pilots, but all are proprietary solutions thus not interoperable and municipality has
to maintain several remote management systems at the same time.
A few road blocks to broader adoption of outdoor lighting controls include:
 Lack of standard guidelines on adaptive lighting practices to ensure safety;
 Metering/billing structure that enables customers to take full advantage of investments in
energy efficiency;
 Lack of interoperability between proprietary solutions;
 LEDs and advanced controls are still seen as complex technologies by customers and
their benefits are not always clearly demonstrated;
 Cost of advanced remote control systems.
Adaptive lighting is being considered by regulatory and industry guidelines as a fundamental
step to improve energy efficiency, meet dark sky ordinances and reduce light pollution. For
instance, the European Commission for Standards (CEN) has established the CEN/TC 169/226
JWG (Joint Working Group) with the task to revise EN 13201, which is widely adopted for
roadway lighting. The upcoming EN 13201 revision will consider the CIE 115:2010
recommendations for adaptive lighting, where the normal level of average luminance or
illuminance can be adapted to traffic volume and composition, weather conditions, and ambient
luminance. Interactive control systems linked to real-time data are also considered to enable the
normal lighting class to be activated in the case of road works, serious accidents, bad weather or
poor visibility. In NA, adaptive lighting is gaining a lot more attention recently. For instance,
discussions are ongoing within the IES roadway lighting energy management sub-committee, but
clear guidelines addressing safety concerns are still to be published. Similarly, metering/billing
standards are another aspect that needs a joint effort from stakeholders, regulatory bodies and the
industry.
Customers (e.g. municipalities, city managers, private companies, utilities, transportation
authorities, etc) have clearly imposed interoperability and standardization as conditions to deploy
emerging lighting technologies. However, most advanced outdoor lighting control systems in the
market do not interoperate, which is hampering adoption of the technology. Specific
interoperability and standardization needs for advanced outdoor lighting control systems are
discussed in Section 5.
Last but not least, cost remains as big road block for adoption of LEDs and advanced controls.
The market has seen considerable drops in the cost of LEDs in the last few years, and technology
maturity as well as standards are expected to contribute to maintain the downward trend in the
coming years.
3. OutdoorLightingNetworks
In recent years, the lighting industry has been introducing new technologies, such as solid state
lighting, adaptive controls and connectivity to offer comprehensive solutions for operation and
management of outdoor lighting. Advanced control systems, generally referred as Outdoor
Lighting Networks (OLNs), combine controls and connectivity to enable remote operation,
configuration and monitoring of outdoor lighting assets over large areas.
Figure 2 illustrates the typical system architecture and components of an OLN. A two-tier
architecture is generally used where the Light Points (LPs) in the field communicate with a
Central Management System (CMS) through a gateway. A LP is a uniquely identified unit within
an OLN, which includes the luminaire, light sources(s), control/communication modules and
may also include other assets (e.g. sensors). Connectivity between LPs and the gateway can be
implemented with different technologies including wireless and power line communications.
Figure 2 shows an example where LPs equipped with radios form a wireless mesh network. The
gateway provides remote communication with the CMS, typically leveraging available IP
networks or remote connectivity alternatives.
The CMS enables system operators (users) to remotely control and manage the OLNs. It
typically connects to one or more databases to store and retrieve data in order to make
information available to users. The CMS manages assets as well as alarms/status/reports received
from the OLNs, and supports discovery and configuration of devices within the OLNs. The
typical use cases and features offered by existing OLNs solutions in the market are summarized
in Table 1.
Figure 2: An
n Outdoor Ligh
hting Network A
Architecture Exxample.
Ta
able 1: Typical use
u cases and O
OLN features.
Fea
ature Configu
uration
•
•
Control
•
Descrription Users can
n identify, co
onfigure andd keep an up to date recoord of
attributess and capabillities associaated to LPs aand other asssets through
the CMS.
The CMS
S also allowss users to grooup light points in orderr to simplify
operation
n/managemen
nt. Configuuration of cerrtain propertties and
behaviou
urs (e.g. dimm
ming scheduule) can be ddone individuually or per
group. In
n fact, some systems
s
suppport only grooup based coontrol, for
instance, from a singlle controllerr in the poweer cabinet. O
Other OLNs
ndividual LP and group bbased controol and configguration.
enable in
Users can
n implementt adaptive ligghting by defining and ddeploying
scheduless (i.e. time in
ntervals and output levells) at which switching orr
dimming is used.
Monitoring
•
Users can override pre-defined control schedules or have special
schedules if necessary. For instance, during exceptional situations
different lighting conditions may be used at different areas of the city.
Another example is when the user wants to switch a LP or a group of
LPs to full power at an accident scene, during road work, or simply
for maintenance purposes.
•
OLNs can also support visualization of geographical location of Light
Points and other managed assets with clear indication of status
information, including light levels, alarms and failures.
Another useful feature is the ability to obtain energy consumption data
of LPs or groups of LPs, as well as historical data from the CMS.
Users (facility manager and maintenance crews) can also get
notifications when a LP malfunctions and associated information that
helps address the problem.
Users can also access a range of measurements reported by the LPs,
including electrical measurements, energy consumption, temperature,
operating hours, etc.
Increasingly OLNs are expected to include additional sensors, such as
light and motion sensors. Sensing information may be collected and
used for various purposes, including defining the adaptive lighting
strategies.
•
•
•
•
ReferenceProtocolStack
As in any computer network, the communications within OLNs as well as between the OLNs
and CMS follow a layered architecture, where each layer has a specific task. The OSI 7 layers is
used as guidelines in many systems, however, the Internet protocol stack (see Figure 3) is a
simpler and more practical reference that can be used to understand the communication
architecture with and within OLNs. The role of each of the five layers in the Internet protocol
stack is as follows:
 The application layer is responsible for establishing end to end communication between
applications (or processes), for example, HTTP is the protocol used to support the Web
and transfer hypermedia information between the application end point, i.e., browser
(client) and a Web site (server). Many other application protocols exist for different
purposes, such FTP (File Transfer Protocol), SNMP (Simple Network Management
Protocol), SMTP (Simple Mail Transfer Protocol), etc.
 The transport layer provides a data transport service for the application-layer messages
between client and server sides of an application. TCP (Transmission Control Protocol)
and UDP (User Datagram Protocol) are typical transport layer protocols in the Internet.
TCP provides a connection-oriented reliable service with flow/congestion control,
whereas UDP provides a simpler connectionless service with no delivery guarantees.
 The network layer is responsible for routing data packets between the source and
destination hosts on the network. The Internet Protocol (IP) is the only network layer


protocol in the Internet as it defines the basic addressing mechanism how data packets are
processed at each node between the source and destination. There are also other routing
protocols that are used together at the network layer to decide the routes the packets take
between nodes. The network (or IP) layer is known as the glue that binds the Internet
together. As the Internet expands into other systems and devices beyond computers
creating the Internet of Things (IoTs), IP integration should be considered while
designing and building connected systems, such as OLNs.
The link layer is responsible for delivering packets between two nodes in a route. The
network layer at each node passes the IP packet to the link layer to be delivered at the
next node in the route. As such, many different link layers maybe involved in transferring
a packet between source and destination. Examples of link layer protocols include
Ethernet, 802.11/WiFi, 802.15.4. The link layer also includes a Medium Access Control
(MAC) function to share the link between nodes.
The physical layer provides the interface between the link layer and the actual
communication medium and it is responsible for transferring the bits from one node to
the next. The physical and link layers are tightly coupled as the as data transfer and MAC
protocols are dependent on the type of medium used, for instance, twisted-pair, coaxial
cables, fiber, radio frequency, etc.
OSI Layers
Internet Protocol Stack
Application
Presentation
Application
HTTP, FTP, SNMP,…
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
TCP, UDP, RTP, …
IP (v4, v6)
Ethernet, 802.11, 802.15.4, 2G/3G …
Figure 3: OSI and Internet Protocol Stacks.
Figure 4 illustrates the mapping between the Internet protocol stack layers and typical protocols
used between different system components (LPs, gateways and CMS) in an OLN.
As can be seen, at the top layer (Application) vendor specific solutions are being used to address
lighting specific needs. Typically, different application layer protocols are used between
gatewayss and the CM
MS and betw
ween the gateeway and thee LPs, mainlyy due to the constrainedd
resourcess with the OL
LN in terms for both com
mputational power and bbandwidth.
Transporrt/network laayer standard
ds, such as TCP/UDP
T
annd IP are the typical choiices betweenn the
gateway and the CMS. Within th
he OLN, how
wever, transpport and netw
work layers aare often
integrated into propriietary protoccols. At the link
l
and phyysical layers,, existing tecchnologies annd
standardss are used att some extent. Since the gateway-CM
g
MS connectioon is typicallly IP-based, a
number of
o connectivity solutionss can be easily explored, from cellulaar modems ((2G/3G/4G) to
WiFi/802
2.11, to Etheernet and eveen fiber opticcs. The choiice will depeend mainly oon the scale oof
the project, location and
a availability of techn
nology (e.g. ccellular or W
WiFi coveragge). Vendorss are
taking ad
dvantage of radio
r
platforrms based on
n standards ssuch as 802.15.4 [11] annd power-linee
communications tech
hnologies [13
3] for conneectivity betw
ween LPs andd gateways. H
However, inn
many casses off-the-sh
helf platform
ms are custom
mized to impprove efficieency and reliiability. As a
result, co
ontrols and connectivity modules at the
t LP and ggateway leveel are not excchangeable,
especially
y when it co
omes to wireless-based OLNs.
O
Fig
gure 4: OLN an
nd protocol staccks examples.
4. Regulator
R
yandSta
andardsLa
andscape
e
This secttion providess an overview
w of regulations and stanndards that sshould be takken into acccount
on the deevelopment and
a deploym
ment of OLN
Ns.
Regulations defining quality of lighting are integral component of safety in outdoor spaces, and
thus must be considered in designing and deploying new technology.
The movement towards interoperable solutions has been a trend in many industries, from mobile
broadband to smart grid, and it is not different in the lighting industry. More and more customers
demand interoperability and availability of multiple suppliers when making significant
investments in new technologies, such as LEDs and OLNs.
LightingRegulationandStandards
Lighting regulations and standards have historically focused on quality of lighting in terms of
intensity, distribution aspects that are directly associated with safety in outdoor environments.
For instance, many customers use industry standards such as CIE and IES RP-8 as the basis for
specifying minimal requirements for proponents of lighting technologies. With the advent of
adaptive lighting enabling technologies, such as OLNs, there is increasing need to revisit
regulations and standards in order to promote efficiency while ensuring safety. This section
provides an overview of applicable regulation and standards, and analyzes the implications on
outdoor lighting control features enabled by OLNs.
IESRecommendedPractices
The Illuminating Engineering Society of North America (IES) publication most relevant to
outdoor lighting performance and controls are recommended practices/ANSI Standards
 RP-8-00 Roadway Lighting (Reaffirmed 2005);
 RP-33-99 Lighting for Exterior Environments.
RP-8 serves as the basis for design of fixed lighting for roadways, adjacent bikeways, and
pedestrian ways. This standard classifies areas and roadways according to road types, magnitude
of pedestrian flow, and road surfaces [8]. The standard includes three different criteria for use in
continuous roadway lighting design. These are illuminance, luminance, and STV (small target
visibility). The designer should use the one which best addresses the needs of the particular
project.
Furthermore, specific design criteria are defined for
 High mast lighting
 Pedestrian and bikeway
 Intersections
 Public right-of-way lighting
 Glare and sky-glow issues
 Transition lighting
The RP-33-99 Lighting for Exterior Environments provides guidance in dealing with design
considerations for electric lighting systems to solve multiple needs while being responsive to the
need for quality exterior lighting. There are a number of other Recommended Practices (RPs)
that provide design guidelines for specific outdoor lighting applications including RP-8-00
Roadway Lighting discussed above. The document links these RPs together, augmenting them in
subject areas not otherwise covered. It also aids in the establishment of community themes and
area classifications.
RP-33-99 describes basic considerations that should be incorporated into municipal lighting
ordinances, which include
 Illuminance levels and uniformity
 Addressing glare, light pollution, and light trespass
 Controls
 Luminaire maintenance
 Compliance monitoring
In the guidelines for controls, RP-33-99 recommends more appropriate control alternatives than
simple dusk-to-dawn controls, which include
 Automatically lowering lighting levels one hour after the close of business;
 Activating security lighting with motion sensors so that lights come on only when
someone is in the immediate area;
 Turning off lights with time clocks at (or before) midnight when there is no/minimal
activity;
 Turning off display, advertising, and specialty lights at (or) before midnight;
 Lowering light levels during all inactive periods.
CIE115:2010“Lightingofroadsformotorandpedestriantraffic”
The International Commission on Illumination (CIE) is the international authority on light,
illumination, color, and color spaces. Since its inception in 1913, the CIE has become a
professional organization and has been accepted as representing the best authority on the subject
and as such is recognized by ISO as an international standardization body.
The most relevant CIE document to outdoor lighting performance and control is CIE 115:2010
“Lighting of roads for motor and pedestrian traffic”. The document is based on experience
gained worldwide in the application of the luminance concept to the lighting of traffic routes. It
takes into account the needs of all road users and is based on maintained lighting levels and
lighting quality. This implies that performance must not fall below the prescribed limits, which
are minimum values, for the life of the installation.
The quality criteria for road lighting are based on the luminance concept to provide a bright road
surface against which objects are seen. It uses level and uniformity of road surface luminance, as
well as glare control, as quality criteria. The following lighting performance metrics are used in
[9]:
 Average luminance of the road surface [Lav]
 Overall uniformity of road luminance [U0]
 Longitudinal uniformity of road surface luminance [Ul]
 Threshold increment TI [fTI]


Surround Ratio SR [RS]
Discomfort glare
The standard defines requirements for both normal lighting and adaptive lighting. Normal
lighting class is the class which is appropriate if the same level is to be used throughout the hours
of darkness. In selecting the normal lighting class, the maximum value of the selected
parameters likely to occur at any period of operation should be considered, e.g. for traffic volume
consider peak hourly value.
In adaptive lighting, the normal level of average luminance or illuminance is adapted to traffic
volume and composition, weather conditions, and ambient luminance. The adapted lighting level
or levels should be the average luminance or illuminance from a class or classes which the
normal lighting class has selected.
In other situations an interactive control system linked to real-time data may be preferred. The
interactive control system will permit the normal lighting class to be activated in the case of road
works, serious accidents, bad weather or poor visibility.
Road lighting requirements have been defined for motorized traffic, conflict areas, and
pedestrians. For each of these categories, there are several lighting classes which are determined
by a weighting values (Vws) and Number of lighting class M = 6 - Vws.
The lighting classes for motorized traffic, i.e. the M lighting classes are intended for drivers of
motorized vehicles on traffic routes, and in some countries also on residential roads, allowing
medium to high driving speeds [9].
IDA
The International Dark-Sky Association (IDA) is a U.S.-based non-profit organization
incorporated in 1988. In 2008, the organization had about 5,000 members in 70 countries. The
mission of the IDA is "to preserve and protect the nighttime environment and our heritage of
dark skies through quality outdoor lighting". IDA's principal approach is to raise awareness
about the value of dark, star-filled night skies and encourage their protection and restoration
through education about the problems and solutions, including lighting practices that create less
light pollution.
The International Dark-Sky Association (IDA) and the Illuminating Engineering Society (IES)
Joint Task Force have defined the Model Lighting Ordinance (MLO) document to address the
need for strong, consistent outdoor lighting regulation [10].
The MLO defines lighting zones which reflect the base (or ambient) light levels desired by a
community. The Authority shall establish Lighting Zones within its boundaries of its jurisdiction.
The Lighting Zone determines the limitations for lighting as specified in this ordinance, and
includes
 LZ0: No ambient lighting,
 LZ1: Low ambient lighting,



LZ2: Moderate ambient lighting,
LZ3: Moderately high ambient lighting,
LZ4: High ambient lighting.
MLO attempts to establish maximum lighting levels while IES Recommended Practices
establishes minimum lighting levels. Its intent is to
 Limit the amount of light that can be used
 Minimize glare by controlling the amount of light that tends to create glare
 Minimize sky glow by controlling the amount of uplight
 Minimize the amount of off-site impacts or light trespass
The maximum levels are determined by total site lumen limit and limits to off-site impacts. Two
methods are defined to determine compliance. The first one is prescriptive method which is
based on initial lamp lumens and the Backlight/Uplight/Glare (BUG) rating. The BUG rating is
used to limit both light trespass and glare. The second is performance method which is based on
software analysis of design.
MLO defines requirements for outdoor lighting control. It requires all outdoor lighting have
lighting controls that prohibit operation when sufficient daylight is available, and include the
capability, either through circuiting, dimming or alternating sources, to be able to reduce lighting
without necessarily turning all lighting off. Specific requirements are defined for Automatic
Switching and Automatic Lighting Reduction. Areas without street lights or with very low
ambient light levels should consider turning off all non-emergency lighting at curfew while
commercial areas or urban areas may prefer reduced lighting levels. A reduction of at least 30%
is recommended for most uses.
CommunicationStandards
As described earlier in Section 3, OLNs rely on communication protocols at different layers.
Standards are being used, although without uniformity across the industry. Many communication
standards have been leveraged, such as Internet Protocols (TCP, UDP, IP, etc), but the standards
described in this section deserve a closer look as they provide basic building blocks for OLNs,
from lower level connectivity to application layer messaging.
ZigBee/802.15.4
The ZigBee Alliance is an industry consortium that specifies and certifies solutions in many
application domains, from healthcare to building controls and lighting. In general, ZigBee
solutions are intended for control applications that require low data rate and low power
consumption, although the ZigBee Alliance has been taking a broader scope recently. A typical
ZigBee Specification [11] defines the Application (APL) and Network (NWK) layers which
operate on top of the IEEE 802.15.4 MAC/PHY standard [12]. Although ZigBee and 802.15.4
are different standards, sometimes this distinction is not very clear, as the term “ZigBee” is often
used in the loose sense without necessary relation to ZigBee certification.
The 802.15.4 radios operate in the ISM bands of 868 MHz in Europe, 915 MHz in US and also
2.4 GHz worldwide. Typical data rates are: 20 kb/s in 868 MHz, 40 kb/s in 915 MHz and 250
kb/s in the 2.4 GHz band. The typical communication range supported by most ZigBee/802.15.4
implementations (in 2.4 GHz) is about 50 m, but higher ranges can be achieved by increasing the
transmit power (up to 1600 m range can be achieved using 17 dBm transmit power). Actually,
the 802.15.4 standard does not specify a maximum transmit power. Instead, the standard leaves
this parameter open to the implementation, which is constrained only by government regulations.
The ZigBee NWK layer includes mesh routing capabilities. One of the main concern in larger
outdoor deployments (e.g. road/highway) is the number of hops needed to connect light poles to
gateways, given the limited range achieved with typical 802.15.4 chipsets designed for indoor
applications.
The ZigBee APL layer defines the framework for implementing basic initialization,
configuration, and network management functions, as well as manufacture specific application
objects. The ZigBee Alliance also specifies several stack profiles (e.g. Light Link, Home
Automation, Smart Energy, Commercial Building Automation …) that mandate a number of the
capabilities and expected behavior of devices within a certain application class in order to ensure
interoperability amongst multiple vendors.
Only indoor lighting applications are supported within the Light Link, Home Automation and
CBA profiles, and no outdoor lighting specific application profile has been introduced by the
ZigBee Alliance.
Although the ZigBee terminology is sometimes used, mainly 802.15.4 platform solutions have
been actually used by many lighting manufacturers with customized network and application
layers to deploy OLNs as shown in Figure 4.
ANSI/CEA‐709–ISO/IEC14908–PowerLine
Due to the ubiquitous availability of the power-line medium, it seems a good choice for
connecting LPs. The LonWorks® solution [13], uses the LonTalk protocol over power lines for
communication between the LPs and segment controllers, which also act as gateway for
connecting the OLN with the CMS. The LonTalk protocol is specified in the ANSI/CEA-709.1
standard. The LonWorks® solution has also been approved as an ISO/IEC standard (ISO/IEC
14908 series), which includes several specifications:
 ISO/IEC 14908-1: Communication protocol (LonTalk);
 ISO/IEC 14908-2: Twisted pair wire signaling technology;
 ISO/IEC 14908-3: Power line signaling technology;
 ISO/IEC 14908-4: IP compatibility (tunneling) technology.
The ISO/IEC 14908-2 and 3 specification define physical characteristics (twisted pair signaling)
and the power-line transport channel, respectively. The ISO/IEC 14908-1 defines the application
layer protocol (LonTalk), which specifies some basic addressing concepts.
The LonTalk application protocol is generally well accepted as an interoperable solution for
power-line based OLNs. However, communication over power lines has specific requirements
with respect to the electrical grid. It typically requires a dedicated grid for the LPs, which may
not be available everywhere. The data rate limitations of the power line medium (up to 5.4 kbps)
as well as the maximum number of nodes per power segment should also be taken into account.
Many vendors offer power line-based solutions, especially in Europe where dedicated electrical
grids are available. On the other hand, market penetration has been much slower in North
America, mainly due to the electrical grids, which are not always favorable to power line
communications. For this reason, wireless connectivity has been the technology of choice for
most OLNs solutions in the North America market. Furthermore, application layer
implementations are not interoperable across systems. This also underscores the importance of
unifying standards that can enable the operation and management of OLNs regardless of the
underlying infrastructure, be it wireless of power line.
NTCIP1213–ObjectDefinitionsforElectricalandLightingManagement
Systems(ELMS)
The NTCIP 1213 ELMS standard [14] has been developed as part of the broader USDOT’s ITS
(Intelligent Transportation Systems) Standards Program, which has been investing for many
years on collaborative development of standards for connected vehicles and connected
infrastructure within transportation environments. The National Transportation Communication
for ITS Protocol (NTCIP) defines the data transport framework between central management
systems (Center to Center – C2C) and between central management and field devices (Center to
Field - C2F). NTCIP includes application data definitions, also known as Data Dictionaries, as
well as data transport and networking protocols that can run on top of multiple connectivity
mediums. The NTCIP 1213 v02 is one of many data dictionaries, and it defines data elements in
ASN.1 using the SNMP Object Type Macro for field devices that monitor and control electrical
and lighting systems. An ELMS field device is a generic entity running an SNMP agent, to
receive the command from CMS, and translate the command to the specific luminaire/electrical
device operation. Supported features include configuration, control and monitoring of luminaires
and circuit branches.
Data reliability and efficient communication with field devices are some of the limitations of
NTCIP. Although there was an attempt to support asynchronous reporting via SNMP Trap
mechanism, the NTCIP 1213 specification only refers to NTCIP 1103v0, which was support to
describe the mechanism, but has never been defined as of the latest version from July 2010.
Therefore, in order to retrieve data, the CMS must continuously poll the ELMS devices, which
can become very inefficient, especially as in large deployments.
The NTCIP development started in 1992 and it has been built upon industry standard protocols
such as SNMP, which typically runs on top of an UDP and IP stack. UDP is a connectionless
transport protocol, which is efficient in delivering data packets when speed is more important
than sequencing and reliability. Back in 1992, SNMP may have been a logical choice given its
wide use in managing network equipment. Since then, connecting field devices to remote
management systems has become mainstream in many industries, and other technologies have
evolved, such as web services and cloud computing.
The NTCIP 1213 first version (v01) was never completed, and after a major content
reorganization, the NTCIP 1213 v02.19 was completed in 2005 and published by The Joint
AASHTO / ITE /NEMA Committee on the NTCIP. The latest release v02 was completed in
2010. As indicated in [15] the extent of market deployment of many NTCIP standards is not
clear. The NTCIP 1213 has not been widely adopted by the Lighting Industry, apart from a few
implementations and pilot projects.
5. StandardizationGapsandOpportunities
Standards and recommended practices that drive regulation on adaptive lighting are paramount to
clearing the way to large scale deployment of intelligent and energy efficient lighting solutions.
Existing recommended practices do not explicitly address adaptive lighting requirements. There
is uncertainty in the market mainly with respect to safety and liability concerns. Recently, this
gap has been recognized and several initiatives are considering guidelines for adaptive lighting,
such as upcoming design guideline by the IES roadway lighting and energy management subcommittee.
In the area of communication technologies, the lighting industry has been trying to leverage
existing standards, such as Internet protocols (TCP/UDP, IP) and connectivity standards
(wireless and power line). However, the diversity of approaches in applying them has resulted in
incompatible solutions at multiple levels. For instance, proprietary application layer messages
and data formats prevent or at least make it very hard to integrate multi-vendor systems within a
single CMS. As a result, customers are either tied to a single vendor or have to live with multiple
incompatible systems, which are expensive and complex to maintain.
On the other hand, it should be recognized that the total solution typically requires
customizations to address problems beyond what is defined in existing connectivity standards.
For instance, wireless-based OLNs require efficient mesh routing protocols to deliver data across
a network of potentially thousands of LPs. Customization can be very useful in this case to offer
reliability and scalability that are crucial in large scale deployments and necessary to guarantee
quality to the end users.
It has been recognized that solutions based on industry standards are essential for long-term
success and large scale deployment of OLNs. It is also important to note the role and potential
added value of customized solutions, especially in a nascent market where technology is
evolving. As technology matures, industry standards can bring cost and scale advantages to
customers. Therefore, there is a clear need for a balanced approach where standards can be
developed to bring immediate value to customers by leveraging mature technologies, while
leaving room for innovation. Furthermore, in an industry where typical lifetime of solutions is
more than 10 years, special attention should be given to defining scalable architectures that
enable evolution and integration of new standards as technology matures.
There have been attempts to address interoperability and standardization of outdoor lighting
networks, most notably, the power-line technology standards (ANSI/CEA 709, ISO/IEC 14908)
and the NTCIP 1213 Object Definitions for Electrical and Lighting Management Systems
(ELMS). However, these standards have not been able to achieve mass market deployment. In
addition to technical limitations, no existing standard is established as the industry’s choice for
unifying the operation and management OLNs based on heterogeneous communication
technologies.
Interoperability at the application layer is a first natural step for standardization and
interoperability. This would enable lighting systems that behave in a consistent way across
vendors, which brings immediate benefits to customers. Secondly, technologies used at this level
are relatively mature, such Internet based protocols, web services, etc., and can leverage
heterogeneous networking infrastructures, regardless of the underlying technologies to connect
the light poles.
New standards should focus on the minimal levels of interoperability required to meet
customers’ needs, while allowing the industry to differentiate on deployment, operation, and
management of OLNs. For instance, at the OLN implementation level (connectivity between LPs
and gateways), solutions combining standard and customized enhancement may still provide
today the best performance in terms of reliability, scalability and quality of service, which
ultimately benefits the customers. As technologies at this level mature, industry standardization
would become a natural step.
6. ConclusionsandFuturedirections
The combination of energy efficient LED technology with outdoor lighting networks has the
potential to deliver not only energy and cost savings, but also contribute to the creation of more
attractive, intelligent and sustainable outdoor environments. However, several challenges are
hampering the market penetration of these technologies. In this article, we provide an overview
on the basic components, architecture and technologies used in OLNs. Furthermore, we identify
specific interoperability issues and standard gaps in both regulatory aspects as well as
communication technologies. There is clear need for industry based standardization that
addresses immediate customer needs while leaving room for innovation and future evolution of
OLNs.
References
[1] NYCDOT, “Green Light - Sustainable Street Lighting for NYC”,
http://www.nyc.gov/html/dot/downloads/pdf/sustainablestreetlighting.pdf.
[2] NEEA Study: Technology and Market Assessment of Networked Outdoor Lighting Controls, June 2011.
[3] E-street Initiative - Market Assessment and Review of Energy Savings, 2006.
[4] MoHURD of P.R.China, “Green City Lighting Development Plan in the 12th-five year” (in Chinese),
http://www.mohurd.gov.cn/zcfg/jsbwj_0/jsbwjcsjs/201111/t20111114_207381.html.
[5] NEA of P.R.China, “Annual Total Electricty Consumption of China in 2011” (in Chinese),
http://www.nea.gov.cn/2012-01/14/c_131360365.htm.
[6] DoE, “Solid-State Lighting R&D Multi-Year Program Plan”,
http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_mypp2012_web.pdf, April 2012.
[7] Prof. Siminovitch , CLTC, at “Taking the Long View on LED Street Lighting” July 2010 issue of LD+A.
[8] ANSI/IES, “IES RP-8: American National Standard Practice for Roadway Lighting”.
[9] CIE, “CIE 115:2010 Lighting of roads for motor and pedestrian traffic”.
[10] IDA/IES, “Model Lighting Ordinance”, June 2011.
[11] ZigBee Alliance, “ZigBee specification”, ZigBee document number 053474r16 (ZigBee-2007 draft), May 2007.
[12] IEEE 802.15.4 Standard: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications
for Low-Rates Wireless Personal Area Networks (LR-WPANs), IEEE Press, New-York 2003.
[13] ANSI/CEA, “ANSI/CEA-709.1: Control Network Protocol Specification”
[14] NTCIP, “NTCIP 1213 v02: Object Definitions for Electrical and Lighting Management Systems”.
[15] Intelligent Transportation Systems (ITS) Standards Program Strategic Plan for 2011—2014, Final Report,
FHWA-JPO-11-052, Version 1.01, April 2011.