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88 Bell Labs Technical Journal ◆ Autumn 1996

IntroductionThe market for wireless telecommunications

infrastructure equipment is expected to continue to

grow at an astonishing pace. Lucent Technologies

Network Systems’ projections show the market for

infrastructure equipment and support services increas-

ing at a 20% compounded annual growth rate until

the year 2000. Factors that contribute to this growth

include:

• Deregulation in telecommunications markets

on a global scale,

• Rapidly growing economies and an insatiable

appetite for telecommunication services,

• Decreasing terminal costs,

• Migration of analog networks to digital net-

works, and

• Increased competition among service

providers and the resulting need for differenti-

ated services.

Rapid market growth, the emergence of new

applications and services, and general increases in

wireless use rates have changed our view of telecom-

munications services, the network infrastructure, and

end-user products we associate with mass-market

telecommunications. The network infrastructure must

support not only mobile communications, such as cel-

lular and personal communications services (PCS), but

also fixed wireless access for narrowband and broad-

band services, as well as data and network access to

people and computers. The advantages of tetherless

communications combined with a broader range of

services will continue to bring forth technology and

product innovations in this arena for the radio access

and integration of access systems with circuit-switched

narrowband terrestrial networks and packet-switched

broadband asynchronous transfer mode (ATM) net-

works. At the same time, end-user equipment will

evolve in terms of both the user interface and the

capabilities to handle speech, audio, data, image, and

video services.

The network infrastructure to support these ser-

vices must continue to evolve for base station and net-

work switching and control systems. This paper

♦ Next Generation Wireless NetworksGeorge E. Fry, Albert Jordan, David Y. Lee, Anil S. Sawkar, Nitin J. Shah, and William C. Wiberg

The market for wireless telecommunications infrastructure equipment is expected tocontinue to grow at an astonishing pace. Projections show the market for infrastruc-ture equipment and support services increasing at a 20% compounded annualgrowth rate until the year 2000. Factors that contribute to this growth include thederegulation in telecommunications markets on a global scale; rapidly growingeconomies and an insatiable appetite for telecommunication services; decreasingterminal costs; migration of analog networks to digital networks; and increasedcompetition among service providers and the resulting need for differentiated ser-vices. The network infrastructure to support new wireless services must continue toevolve for base station and network switching and control systems. This paper dis-cusses the next generation of wireless communications infrastructure productsdesigned and manufactured by Lucent Technologies that will provide end users witha wide range of wireless access and advanced services.

Bell Labs Technical Journal ◆ Autumn 1996 89

discusses the next generation of wireless communi-

cations infrastructure products designed and manu-

factured by Lucent Technologies to provide end

users with a wide range of wireless access and

advanced services.

Forces Driving ChangeNumerous forces drive the need for change in the

wireless infrastructure. Any one of these forces is suffi-

cient to cause wireless equipment vendors to adapt

their product offerings. In combination, they have a

multiplying effect resulting in an imperative for wire-

less network advances not seen before. This section

explores the various forces driving the need for next-

generation wireless infrastructure products.

Deregulation and the Competitive ClimateThe emergence of standards and persistent market

growth will continue to diminish the barriers to entry

and raise the level of competition among equipment

providers. We have already witnessed the emergence

of new entrants who have made great strides in estab-

lishing themselves in the market. Some have done so

by providing particular adjunct solutions consistent

with emerging standards (for example, stand-alone

home location register [HLR] databases, authentication

centers, intelligent antennas, and even cellular digital

packet data [CDPD] systems). Successive generations

of products, as well as competition facilitated by open

systems defined by both American National Standards

Institute (ANSI) and European Telecommunications

Standards Institute (ETSI) committees, have resulted

in the introduction of wireless solutions at extremely

competitive price points.

The net result is that today’s advanced base sta-

tions and switching equipment (hardware) will

become tomorrow’s commodity products, and manu-

facturers must innovate new products to maintain or

enhance market position. Success in the marketplace

will depend instead on the delivery of complete solu-

tions—especially software—that bring enhanced value

to carriers.

The Federal Communications Commission

recently completed the auction of A-, B-, and C-band

PCS frequencies in the United States. Total receipts—

$7.7 billion from the A and B bands and $10 billion

from the C band—are a clear signal of the intention of

the new entrants to compete aggressively in a mod-

ern emerging market. Internationally, governments

are quickening the pace of deregulation as they rec-

ognize the clear benefits of competitive forces driving

service costs down and enhancing local telecommuni-

cations infrastructures. Increased competition will

lead carriers to seek new ways to differentiate or

Panel 1. Abbreviations, Acronyms, and Terms

AMPS—Advanced Mobile Phone ServiceANSI—American National Standards InstituteAP—adjunct processorATM—asynchronous transfer modeCDMA—code division multiple accessCDPD—cellular digital packet dataDCS—digital cellular switchE-SMR—enhanced specialized mobile radioETSI—European Telecommunications Standards

InstituteGSM—Global System for Mobile

CommunicationsHLR—home location registerIN—intelligent networkIQ—in-phase and quadratureISDN—integrated services digital networkLAN—local area networkLEOS—low earth orbit satelliteMS—message serviceMSC—mobile switching centerMUX—multiplexerNNI—network-to-network interfaceOA&M—operation, administration, and mainte-

nancePCS—personal communications servicesPDA—personal digital assistantPDN—packet data networkPOTS—”plain old telephone service”PPC—packet processing complexPSTN—public switched telephone networkQOS—quality of serviceRF—radio frequencySMR—specialized mobile radioSMS—short message serviceSS7—Signaling System 7TCAP—Transaction Capabilities Application PartTDMA—time division multiple accessUNI—user-to-network interfaceWLL—wireless local loop


focus their service offerings and to reduce costs.

With competition increasing for basic voice ser-

vices and minute-of-use prices falling, carriers are

seeking to differentiate themselves in two notable

ways. First, they are attempting to develop branded

identities through the use of logos and signature

sounds/tones (for example, pre-call announcements

and voice mail notification tones) and focused market-

ing campaigns. Often, such attempts involve forging

marketing partnerships with other carriers in other

markets who may have deployed non-Lucent equip-

ment. In this situation, interoperability and feature

transparency are crucial to a campaign’s success.

Network-based features and services must be flexible

in the ways in which they are administered and pre-

sented to an end customer.

Second, carriers are trying to segment their sub-

scriber base and offer more targeted features and ser-

vices. Initially, these features and services have taken

the form of simple multirate and use-sensitive billing

plans. More recent approaches, however, have

become more complex, bundling wireless and wireline

services, adding geographic or time-of-day/day-of-

week restrictions, and supporting custom calling plans

or private networks. The trend is toward more sophis-

ticated horizontal (messaging, paging, and data) and

vertical (cellular dispatch, power company meter read-

ing) applications. Ideally, carriers would like to see a

continuous stream of new applications and features

becoming available to their subscribers. Such a strategy

is key to their differentiated and share growth in the

marketplace.

Additionally, to foster competition among equip-

ment vendors, carriers will demand solutions that are

based on industry standards with the ultimate goal of

achieving interoperability among network nodes.

Standards not only will allow carriers to secure solu-

tions at lower price points. Standards-based solutions

will also enable carriers to obtain a complete solution

by purchasing partial solutions from a multitude of

equipment providers. Such an environment will place

new pressure on equipment vendors to become com-

petitive in areas that were bundled with the total net-

work offering.

Increasing Customer Demand for TelecommunicationsServices

With the introduction of PCS, wireless local loop

(WLL), and data services, wireless networks will expe-

rience significant traffic increases. Projections indicate

that by the year 2000, nearly 50% of all traffic in the

network will be attributed to wireless traffic. This

increase will have a tremendous impact on the net-

work in terms of meeting quality-of-service (QOS)

parameters expected by customers for the services

requested. The anticipated increases in signaling and

capacity loads will require that current networks

evolve to continue to meet customer expectations.

Over the next three to five years, a multitude of differ-

ent access technologies will be introduced, and the

evolving network will need to support interoperation

among some subset of the growing set of all access

technologies.

Downward Pressure on CostsCarriers will be under increased pressure to lower

both capital outlays and annual expenses. Said

another way, carriers will seek to lower total network

life-cycle costs. Successful solutions, therefore, will

address network acquisition and deployment, network

operations, marketing and sales, distribution of termi-

nals, as well as service and general/administrative

functions.

Demand will increase for technological solutions

that reduce initial capital outlay, taking into account

equipment and site acquisition/preparation costs.

Examples include advanced antenna technology

(which increases per-site capital costs but lowers the

total capital expenditure required to service an area)

and microcell technology (which substantially lowers

site acquisition/preparation costs through small size

and innovative packaging). This is particularly impor-

tant for startup network operators who are under con-

siderable pressure from lenders to begin generating

revenue and hence, debt-servicing payments as soon

as possible.

Successful offers will also address growth and

maintenance costs, as well as back-end costs (for

example, network engineering, billing, fraud, and cus-

tomer administration/support activities), mainte-

nance/operations, and facilities charges.


Network enhancements need not strictly address

operations-oriented functions. For example, over-the-

air activation and fraud control features, which reduce

marketing and sales expenses, are two enhancements

currently being lauded heavily by carriers.

Carriers expect to buy a flexible platform that will

support incremental cost improvements as solutions

become available (that is, smaller cell sites, improved

voice quality, and enhanced fraud control). In addi-

tion, carriers expect the network to support incremen-

tal process improvements by the operations staff and

the sales and marketing teams.

The Pace of Technological AdvancesTechnology—particularly in the commercial hard-

ware and software industries—is advancing at an

unprecedented rate. The power of today’s computing

platforms continues to increase geometrically while

cost-to-performance ratios have placed these systems

in the commodity field. In fact, even the line between

the computing and telecommunications worlds has

begun to blur in favor of the computing model.

Advanced off-the-shelf software applications—

particularly in the area of middleware—have sup-

planted the ad hoc approaches to systems integration.

What once took a team of developers months to inte-

grate now takes a single user a few hours with the

help of these advanced packages.

The Internet is another technological advance

whose full impact is yet to be determined. While tele-

phony over the Internet is in its nascent stage, equip-

ment manufacturers would be wise to continue

exploring its potential in the coming years. The chal-

lenge for equipment vendors is to understand what

potential effects the Internet has for their products

and to take advantage of those opportunities.

Customers look to Lucent Technologies and its

world-class Bell Labs for leadership into revolution-

ary technologies and the products and services that

bring them to market.

The purpose of research and development is to

solve problems using existing techniques and scientific

knowledge to deliver technologies that can be sold as

products. Depending on whether the products and

markets are existing or new, the technology focus can

be redirected to address the needs of the particular

market segment. Figure 1 illustrates this concept.

To deliver total system solutions, technology plat-

forms are more important than one or two critical

Increasefunction

New

Current

Reducecost

Product

• E-SMR• Wireless FAX/image• Wireless data

• Cellular• SMR• Wireless LAN• Telepoint• Cordless• Paging

• PCS• Video distribution• Wireless multimedia• Mobile satellite• LEOS• PDAs

• Wireless local loop• Wireless PBX

Reducerisk

Increaseflexibility

Current New

Market

E-SMR – Enhanced specialized mobile radioLEOS – Low earth orbit satellitePCS – Personal communications servicesPDA – Personal digital assistantSMR – Specialized mobile radio

Figure 1.Market segmentation.


technologies. A platform spans multiple disciplines

and makes allowance for the following key opera-

tional factors:

• Technology insertions to extend product life,

• Multiple use to save development costs, and

• Reuse to save future development time.

For wireless, the trend is for technology to support

an application evolution from voice to multimedia; a

network evolution from fixed/homogenous to mobile

and heterogeneous; a system architecture from cen-

tralized host to distributed client server; transmission

and switching from a narrowband circuit to broadband

packet; radio-frequency (RF) coverage from outdoor

to seamless indoor/outdoor; RF distribution from

macrocell to micro/picocell; and equipment packaging

from indoor frame to miniaturized outdoor boxes.

Lucent Technologies Corporate NeedsIn addition to meeting customers’ needs, Lucent

Technologies’ product organizations must also meet

corporate requirements. These requirements are

mainly focused on reducing the development intervals

and total life-cycle costs of telecommunications prod-

ucts. For Lucent Technologies, the challenge becomes

defining a network infrastructure that will support

many different access technologies (such as code divi-

sion multiple access [CDMA], time division multiple

access [TDMA], and the Global System for Mobile

Communications [GSM]) across a wide range of hori-

zontal products (for example, wireless, wireline, and

data networks) while at the same time enabling the

reuse of advanced services and features across all offer-

ings. Meeting this challenge requires outlining a family

of products based on a common network infrastruc-

ture made up of the specific applications running on

well-defined hardware and software platforms. The

resulting purchasing volumes of these platforms will

translate into lower unit costs, thus benefiting the bot-

tom line across Lucent’s many businesses.

As time goes on, one of Lucent’s strategies to

increasing profitability while reducing capital invest-

ment is to add value to off-the-shelf hardware and

software platforms. This will require increased empha-

sis on gaining revenue from software sales. Advanced

architectures emphasizing hardware and software

reuse, such as the one discussed in this paper, can be

leveraged to increase reuse among product families

and thereby improve time-to-market and cost profiles

for those products.

Proposed Next Generation Wireless InfrastructureWhat might a wireless network that addresses all

the needs of end users, service providers, and equip-

ment vendors look like? To meet the demands placed

on future wireless communications by end users, ser-

vice providers, and equipment vendors, the next gen-

eration wireless network must:

• Support multiple access technologies on a sin-

gle network infrastructure;

• Separate wireless-specific and Lucent value-

added applications from commodity-based

hardware and software platforms;

• Leverage hardware and software platforms

from the commercial computing industry; and

• Support continuums of service, feature con-

tent, and reliability.

This section describes the basic network infrastruc-

ture and general approaches to service delivery.

Network TopologyThe network topology that results from combining

the various needs and approaches into a single net-

work is shown in Figure 2.

Several key characteristics distinguish this archi-

tecture. First is its division into three main areas: intel-

ligent network (IN) services, the core network, and the

access networks. Emphasis is placed on the functional

isolation between the networks and the interfaces

between them. Thus, each major area can evolve at its

own pace and the interoperability between them

remains intact.

Second is the architecture’s use of ATM features

throughout the network infrastructure. Using a single

network technology for all nodes greatly simplifies

network integration, as well as operation, administra-

tion, and maintenance (OA&M) functions. In addition,

broadband technology positions product offerings for

future growth.

Third is the emphasis on application and resource

servers in the IN and access networks. We propose

moving from the traditional, tightly integrated service-

control architecture to a more computer-centric dis-


tributed client/server model. Resource servers manage

the access network resources, such as radios and chan-

nels. Application servers—for example, call servers and

user agent servers, make requests of these resource

servers to carry out their functions. This model also

extends into the IN domain in which access network

application servers request services of IN servers. The

reverse may also be true. An IN server may make a

request of an access network server—for example, to

find and page a particular user.

The following subsections provide more detail on

each of the major infrastructure areas.

Intelligent Network ServicesThe term “IN services” applies to a broad category

of advanced capabilities provided by the network.

Examples of IN services include voice mail systems,

home location register (HLR) databases, short message

service (SMS) capabilities, and user agents that exist in

the IN network and act on behalf of a user. Typically,

IN services are implemented on adjunct processors

ATM – Asynchronous transfer modeCDMA – Code division multiple accessDCS – Digital cellular switchIN – Intelligent networkMS – Message serviceMUX – Multiplexer

PDN – Packet data networkPPC – Packet processing complexPSTN – Public switched telephone networkSS7 – Signaling System No. 7TDMA – Time division multiple access

Applicationservers

Resourceservers

Applicationservers

Applicationservers

Applicationservers

IN services

Corenetwork(s)

Backbone ATM switch(20 Gb/s and up)

Applicationservers

Resourceservers

Accessnetwork(s)

Edge ATM switch(2.4 Gb/s)

PPC5ESS®

DCS

PDN

PSTN

SS7 signaling network

CDMAMS

TDMAMS

OtherMS

Circuit switchedATM transport

ATMMUX

CDMAcell site

TDMAcell site

Othercell site

Figure 2.Next generation wireless network architecture.


(AP) and accessed through a common protocol stack.

Application messages are delivered to the IN server

through a Transaction Capabilities Application Part

(TCAP) and Signaling System 7 (SS7) protocol stack.

We propose providing access to IN servers directly

from the access network application servers, as well as

through the core network. By separating these

advanced services from the access network, we pro-

vide a means by which these services become available

on any access network—for example, TDMA and

CDMA. Further, by linking them with the core net-

work, we establish the basic infrastructure necessary to

achieve true wireless/wireline integration at the ser-

vice level. Thus, users will have access to these

advanced services regardless of whether they are

accessing them from a mobile or fixed terminal.

Core NetworkAlso referred to as the backbone network, the core

network provides the interconnect mechanism for the

various access networks. It provides the network-to-

network interface (NNI). Examples of NNI protocols

include TR303 for local loop networks and IS41 for

wireless networks.

The first aspect to note about the proposed core

network is its emphasis on ATM transport. High-speed

ATM connectivity affords flexibility in distributing

functions over multiple hardware platforms. Migration

of intelligence away from the endpoints of the net-

work allows ease of maintenance and administration

by the network service provider. Broadband technolo-

gies supporting voice, data, and video will drive the

telecommunications architectures of the future. With

an inherent packet-based transport mechanism, the

ability to support multiservice environments over a

common network, a more efficient signaling mecha-

nism, and built-in simplified OA&M procedures, ATM-

based networks promise to provide the ideal fixed

backbone to the multitude of access technologies—

both wireline and wireless—emerging for cellular and

PCS networks.

The second aspect to note in the core network is

the packet processing complex (PPC). To conserve

bandwidth on the air interface, wireless access proto-

cols transmit user information (for example, voice) at

compressed data rates in the range of 8 to 13 kb/s. The

public switched telephone network (PSTN) expects to

transmit user information at 64 kb/s. This conversion

is performed in the PPC. It is desirable to carry user

information at the compressed rate throughout as

much of the core network as possible for the same rea-

son—namely, conservation of bandwidth. This leads to

placement of the PPC within the core network, allow-

ing the compressed user information to travel as far as

possible through the core network before entering the

PSTN at the full 64-kb/s rate.

Access NetworkThis infrastructure area provides for termination

of the user-to-network interface (UNI). Examples of a

UNI for wired access include “plain old telephone ser-

vice” (POTS) and ISDN. For wireless access, CDMA,

wideband CDMA, TDMA, and GSM are the major

systems being deployed for cellular and PCS mobile

and wireless local loop (WLL) applications. In such a

network arrangement, one can see how users within

each of these technologies may access not only the

core network but IN services too.

The next generation wireless network divides the

access network into two major components. The net-

work complex consists of clustered processors inter-

connected via a traditional local area network (LAN)

or ATM switch. The cell sites are the remote end-

points of the network and provide termination of the

LAN

Clusteredcommercialprocessors

ATMedge switch

Server process

To cell sites

ATM – Asynchronous transfer modeLAN – Local area network

Figure 3.Next generation network complex.


air interface. The following two subsections provide

more detail about these areas.

Network complex. As Figure 3 illustrates, the

network complex consists of clustered processors

interconnected via a traditional LAN or ATM switch.

The network complex contains processes that perform

call and connection control, mobility management (for

mobile applications), and overall network manage-

ment. The key network elements are:

• Commercial computing platforms.

• An ATM edge switch that provides intercon-

nection to remote cell sites.

• Server processes that provide network man-

agement and call processing functions.

• A packet processing complex (PPC) providing

speech coders and protocol handlers that

process end-user traffic. Current and evolved

5ESS switches will support the functionality

based on the specific market segments.

• Interworking functions to gateway into other

networks—for example, packet data networks

and the PSTN.

• Interconnection technologies between the net-

work elements—for example, a LAN.

Cell sites. The access network component provid-

ing wireless connections to an end user is called a cell

site. It incorporates functionality to process over-the-air

information. The coverage capacity and reliability are

the key drivers for providing the QOS for a certain

geographic region. The ability to adapt a cell site to

network capacity and coverage demands by sectoriza-

tion, expansion of radio capacity, and migration to

spectrally efficient access technologies are some of the

major considerations in determining the architecture

for a cell site.

Current cell site implementations have varying

degrees of functionality. The trend is to make cell sites

cheaper, smaller, and scaleable for pico, micro, and

macro environments. The number of access standards

will continue to proliferate beyond the current

Advanced Mobile Phone Service (AMPS), TDMA,

CDMA, and GSM standards. The service provider’s

expectation is to offer an access technology that meets

customers’ service needs in terms of bandwidth, bit

ATM – Asynchronous transfer modeIQ – In-phase and quadrature

MSC – Mobile switching centerRF – Radio frequency

3rd Generation• RF amp/filter• Spectrum digitizer• Intelligent radios• Base station controller• ATM backplane• MSC/wireless servers

Othernetworks ATM

4th Generation Activeantenna

2nd Generation

Othernetworks T1/E1

Digital bus

Analogcombiners/

splitters

Wirelessserver

Radioport

controller

Spectrumdata

processor

Spectrumdigitizer/

synthesizer

RFamp/filter

DigitalIQ bus

Wirelessadd-ons

MSCBase

stationcontroller

Intelligentradios

RFamp/filter

Figure 4.Cell site evolution.


error rates, voice quality, and coverage area. This

places a wide range of demands on cell site design. For

cost-effective implementation, cell sites will simply

work as protocol converters to terminate the physical

layer of the air interface and transport the raw infor-

mation processing in the network. This would allow

such hardware as speech coders to be taken out of cell

sites and centrally pooled in the network, providing

economies of scale and ease of maintenance and oper-

ation.

Given the foregoing discussion, one can envision

today’s rather complex base stations evolving to future

base stations that are much simpler and lower in cost

(see Figure 4).

Such technologies as fixed and adaptive beam anten-

nas will effectively address the coverage-versus-capacity

tradeoffs in the pico, micro, and macro environments.

SummaryWireless is expected to be a major driver for growth

in the telecommunications industry over the next

decade, becoming a cornerstone of the information soci-

ety. Future networks (both wireless and wireline) of the

type described in this paper will pave the way for an

environment in which the information revolution will

be made more portable, personal, and affordable.

(Manuscript approved October 1996)

GEORGE E. FRY is a member of technical staff in theWireless Systems Core TechnologyDepartment in the Wireless TechnologyLaboratory at Bell Labs in Whippany, NewJersey. He is conducting research and proto-typing efforts on next-generation wireless

networks. Mr. Fry holds a B.S. degree in mechanicalengineering from Clarkson University in Potsdam, NewYork. He also has an M.S. degree from the University ofNew Haven in Connecticut.

ALBERT JORDAN is manager of the PCS WirelessManagement Group at Bell Labs inWhippany, New Jersey. He is currently theproduct team leader for the next-generationCDMA in the AMPS PCS business leadershipgroup (BLG). Mr. Jordan, who holds two

patents, has B.S. and M.S. degrees in electrical engineer-ing, as well as an M.B.A., all from Stanford University inPalo Alto, California.

DAVID Y. LEE is a technical manager in the WirelessSystems Core Technology Department inthe Wireless Technology Laboratory at BellLabs in Whippany, New Jersey. He is respon-sible for wideband (5-MHz) CDMA proto-typing, base station technologies, as well as

management of intellectual property, technology plan-ning, and technical marketing. Mr. Lee holds aB.A. degree in chemistry and a B.S. in electrical engi-neering from the State University of New York(S.U.N.Y.) in Stony Brook. He also has an M.E. degreefrom Cornell University in Ithaca, New York.

ANIL S. SAWKAR is a technical manager in the NetworkSystems Wireless Technology Laboratory atBell Labs in Whippany, New Jersey. Hisgroup is responsible for wireless networkarchitecture, technology concept prototyp-ing, and for influencing wireless product

directions. Mr. Sawkar received a B.S. degree in elec-tronics engineering and an M.S. in electrical engineer-ing from Drexel University in Philadelphia,Pennsylvania.

NITIN J. SHAH is technology director of the WirelessSystems Core Technology Department inthe Network Wireless Systems Business Unitof Lucent Technologies. His department,which is part of the company’s networkinfrastructure manufacturing division, is

responsible for cellular, personal communications, andother wireless products. Areas of research he currentlyleads include technology planning, wireless networkarchitecture, radio multiple access methodologies, anddigital compression techniques for speech and visualcommunication. Mr. Shah received B.A., M.A., andPh.D. degrees in microelectronic engineering from theUniversity of Cambridge in England.

WILLIAM C. WIBERG is product management vice presi-dent at the Lucent Technologies NetworkWireless Systems Business Unit inWhippany, New Jersey. His organization isresponsible for researching, developing,and marketing products for Advanced

Mobile Phone Service (AMPS), as well as personal com-munications services (PCS). Mr. Wiberg has anM.S. degree in engineering systems from StanfordUniversity in Palo Alto, California, and an M.B.A. fromColumbia University in New York City. ◆