rbs 3000

Overview of the WCDMAradio access network

Ericsson’s WCDMA radio access network(RAN) consists of radio network controllers(RNC), radio base stations (RBS), RAN op-eration support (RANOS) and tools for radioaccess management (TRAM). In Third-gen-eration Partnership Project (3GPP) specifi-cations, the RBS corresponds to Node B(Figure 1).

RNCThe main tasks of the RNC are • to manage radio-access bearers for trans-

porting user data;• to manage and optimize radio network re-

sources;

• to control mobility (the RBS provides theactual radio resources); and

• to maintain radio links. The RNC is connected to the core networkvia the Iu interface; user equipment (UE) isconnected to the RBS via the Uu interface(the air interface). RNCs are interconnectedwithin the radio access network via the Iurinterface; and the RBSs are connected to theRNC via the Iub interface.

RBSThe family of RBS 3000 products consistsof base stations for both indoor and outdoorinstallations, as well as single-sector andmultiple-sector configurations. The prod-uct architecture supports several configura-tions and establishes a basis for future de-velopment of RBSs that support macro-,micro- and picocell structures.

The range of RBS 3000 models gives oper-ators cost-effective solutions to capacity, cov-erage, power supply, space and environmen-tal requirements in network configurations.

TRAMThe tools for radio access management aidoperators in designing, testing, and opti-mizing the performance of radio and trans-port networks. Configuration data can bedownloaded from TRAM to the RNCs andRBSs via RANOS.

170 Ericsson Review No. 3, 2000

Family of RBS 3000 products for WCDMA systemsPierre Zune

Ericsson is the first company to take WCDMA technology out of the labo-ratory and test it in a real environment. At the end of 1999, Ericsson hadseventeen WCDMA test systems in operation in Asia, Europe and NorthAmerica.

The RBS 3000 product line is a comprehensive family of macro, miniand micro radio base stations (RBS) that were designed using input fromsecond-generation mobile systems.

In this article, the author gives an in-depth description of Ericsson’sfamily of RBS 3000 products.

Network management system

RANOS

CN and other management applications

TRAM

Tools for radio access management

Services

RAN customer services

User equipment

Radio base station

Radio network controller

Iu

Iur

Iub

Uu

Core network

Radio access network operation suport

Radio access network

Figure 1 Overview of the radio network, logicalinterfaces.

Ericsson Review No. 3, 2000 171

RANOSRANOS, which is the software for handling op-eration and maintenance tasks for the WCDMAradio-access network, gives operators a consolidat-ed view of information on alarms, configurations,and basic performance. It also provides interfacesfor easy integration into other management envi-ronments.

RBS 3000 familyThe design of Ericsson’s family of RBS3000 products is based on 3GPP require-ments. All RBS 3000 products are pre-test-ed and pre-configured before delivery tothe site. They also include a built-in self-test mechanism and an equipment config-uration wizard, which further reduce in-stallation time and speed up network roll-out.

A single RBS 3000 equipment configu-ration handles mixes of voice, circuit-switched and packet-data services withouthaving to be reconfigured for each differentkind of traffic.

Operators can easily increase coverage, the

number of simultaneous users, carriers, andsectors, by adding hardware boards or extracabinets.

RBS 3000 macro productsAll RBS 3000 macro products have been de-signed to handle a variety of services. TheRBS hardware and software feature a mod-ular design. The RBS hardware is flexible,meaning that the same equipment can han-dle most traffic situations. The architectureis scalable and thereby easy to expand. Op-erators can add extra carriers or more chan-nel capacity by installing additional boardsor another complete cabinet.

RBS 3202

The RBS 3202 (Figure 2) is an indoor macroradio base station. The basic configurationsupports up to three sectors and two carri-ers (3x2). The RBS can be extended to con-figurations of three sectors and four carriers(3x4) or six sectors and two carriers (6x2).The output power is 20/40 W radio fre-quency (RF) per carrier.

All units in the cabinet are easily accessi-

3GPP Third-generation Partnership Pro-ject

ATM Asynchronous transfer modeBP Board processorBSC Base station controllerBTS Base transceiver stationCBN Common bonding networkC/I Carrier-to-interference ratioCORBA Common object request broker

architectureCU Capacity unitdB DecibeldBm Decibel relative to 1 mWDDTMA Dual-duplex TMADL DownlinkDPX DuplexEACU External alarm connection unitEMC Electromagnetic compatibilityET Exchange terminalETB ET boardFDD Frequency division duplexHTTP Hypertext transfer protocolHW HardwareIDM Internal distribution moduleIP Internet protocolIPsec IP security protocolJava applet Distributed embedded Java pro-

gram that runs on a Web browserMCPA Multi-carrier power amplifierMMI Man-machine interfaceMTBF Mean time between failuresNMS Network management system

O&M Operation and maintenanceOMC Operation and maintenance centerPBC Power and battery cabinetRAN Radio access networkRANOS RAN operation supportRBS Radio base stationRET Remote electrical antenna tiltRF Radio frequencyRNC Radio network controller RRU Remote radio unitRTOS Real-time operating systemRX ReceiverSTM Synchronous transfer mode [syn-

chronous transport module]SW SoftwareTMA Tower-mounted amplifierTMS Test mobile station (terminal)TRAM Tools for radio access manage-

mentTRX TransceiverTU Timing unitTX TransmitterUE User equipmentUL UplinkUMTS Universal mobile telephony systemUTRAN UMTS terrestrial radio access net-

work VAC Volts, alternating currentVDC Volts, direct currentWCDMA Wideband code-division multiple

accesswTRU Wideband transceiver unit

BOX A, TERMS AND ABBREVIATIONS

Figure 2Description of the hardware structure inRBS 3000. Photograph of an RBS 3202.

ble from the front of the cabinet. All cableinterfaces are located at the top of the cabi-net. Thus, the cabinets can be mounted side-by-side or back-to-back.

RBS 3101

The RBS 3101 (Figure 3) is an outdoor macroradio base station. It supports the same rangeof configurations as the RBS 3202. The out-put power is 20/40 W RF per carrier.

The RBS 3101 features a weatherproofcabinet for outdoor sites with high capacityand high coverage. The cabinet contains in-tegrated power supply with backup batter-ies, space for transmission equipment, anda climate package. The RBS 3101 supports50 Hz and 60 Hz systems and can be pow-ered with single- or triple-phase AC.

RBS 3000 main-remote concept

Macrocell coverage in a microcell package

Site acquisition is an increasingly time con-suming and costly problem, especially inbusy urban environments. Ericsson’s solu-tion to this problem is the main-remote con-cept. At conventional site installations, allequipment, including digital parts, radioparts, and combiners are housed in one cab-inet. However, according to Ericsson’smain-remote concept, the RF and digitalbaseband parts are separated by an opticalinterface in a remote radio unit (RRU). The

RF parts have been moved closer to the an-tenna, which means that a smaller poweramplifier is used. Also, the radio parts aremade smaller, which further reduces powerconsumption. Less power consumptionmeans less heat, which means that the RBScan use convection cooling without anymoving fans—no noise. The main unit,which contains the transmission interface tothe RNC, • performs all system-level diagnostics;• provides system timing via the transmis-

sion interface source;• controls power and processes calls, en-

codes and decodes WCDMA; and• handles softer handovers.Some advantages of the main-remote con-cept are• easy and rapid installation—the main

unit and remote radio unit can be placedseveral kilometers apart, which meansthat the RBS can be installed practicallyanywhere;

• the main units and RRU can be hand-carried to a rooftop;

• macro coverage from wideband transceiv-er unit (wTRU) and mini RBS solutions;and

• greatly reduced power consumption(compared to the macro RBS).

RBS 3000 main-remote products includethe RBS 3401, RBS 3501, and the wTRUconcept.


Figure 3RBS 3101.

Main unit

Remote radio units

Figure 4Main-remote concept RBS 3401.


RBS 3401The RBS 3401 (Figure 4) is an indoor miniRBS. It weighs less than 30 kg and can bemounted on the wall or in a standard 19-inch rack. It can be delivered with an inte-grated power supply for single-phase AC,–48 VDC or +24 VDC. An optional exter-nal battery backup cabinet can be connect-ed to provide extended backup time. Whenused together with remote radio units andan optional external backup battery cabinet,the RBS 3401 constitutes a compact butcomplete macro base station solution.

RBS 3501

The RBS 3501 (Figure 5) is an outdoor miniRBS with a complete RBS system housed ina compact convection-cooled, weatherproofcabinet. The RBS 3501 offers macrocell cov-erage in a microcell package and can serveas either a traditional macrocell or microcellbase station.

The main unit can be mounted practical-ly anywhere—on a wall, pole, the side of abuilding, or rooftop. Its compact size andlow weight (with remote radio units) enableit to be hand-carried to the installation site.The RBS 3501 is powered by single-phaseAC, –48 VDC or +24 VDC.

wTRU concept

The wTRU concept (Figure 6) is a cost-effective solution for rapid roll-out of

WCDMA capacity in a GSM network. ThewTRU can be installed in any EricssonRBS 2000 macro cabinet. It occupies twoTRU slots and shares the GSM cabinet’spower and cooling resources with otherunits. The wTRU supports one carrier andone to three sectors.

Main unit

Remote radio units

Figure 5Main-remote concept RBS 3501.

Figure 6wTRU concept.

Remote radio unit The remote radio unit (Figure 7), which isa radio head with up to 10 W RF outputpower, is used together with the RBS 3401,RBS 3501 or wTRU. It can also be used withthe micro RBS 3301 to provide extendedcoverage. The remote radio unit houses anRF filter, power amplifier, RX low-noiseamplifier, and transceiver (TRX) for one sec-tor carrier. It also supports RX space diver-sity. The unit can be placed together withthe cabinet, on a rooftop, or on the towernear the antenna.

An optical digital interface connects themain unit and the remote radio unit. Thisensures high performance and enables oper-ators to place the remote radio unit up toseveral kilometers from the main unit. Sincevarious different main units support thesame optical digital interface, operators canreuse remote radio units when they upgradethe main unit, say, to increase capacity.

The weatherproof RRU is suitable for in-door and outdoor use. It generates no sig-nificant acoustic noise, because only con-ventional cooling is used. It is powered by–48 VDC, +24 VDC or single-phase AC.

Power can also be supplied via the optionalpower and battery cabinet (PBC).

RBS 3000 micro productsDesigners of the micro RBS drew heavily onexperiences gained in working with micro-and picobase stations for second-generationmobile phone systems. The exterior of themicro RBS is both weatherproof and dis-crete. This small, light-weight RBS can eas-ily be installed by one person.

RBS 3301

The RBS 3301 is suitable for indoor and out-door use (Figure 8). The cabinet houses onetransceiver and all necessary equipment forserving one cell. Convection cooling furthercontributes to a compact and weatherproofcabinet. The RBS 3301 has one carrier withomni-directional or sector-based coverage at1 W RF output power. Optional equipmentincludes an external antenna, an RRU (formacro coverage), and a power and batterycabinet.

The micro RBS has the same basic func-tionality as the macro RBS but with less ca-pacity and coverage. The transceiver andpower amplifier have been integrated into theRBS cabinet using ASIC technology. This de-sign yields high availability, small volume,low weight and low power consumption.

Backup power for short interruptions tothe AC power supply is built-in. An extrapower and battery cabinet can be connectedto extend backup power. Moreover, the re-mote radio unit can be used with the RBS3301 to increase coverage.

Operation and maintenance

Rapid implementation

One goal when designing the RBS 3000 wasto make installation and commissioningrapid and easy. The RBS 3000 is thus pre-tested and pre-configured before it is deliv-ered to the site—all hardware and softwareare configured at the factory. During in-stallation, field technicians need only entera few site-specific parameters (IP address,site name, and so on) via a Web browser ona standard laptop computer. Built-in com-missioning software gives field techniciansaccess to every function in the RBS 3000.

Live expansion

Without shutting down power or disturb-ing traffic, operators can increase capacityand coverage by adding boards to theRBS 3000.


RBS 3101 outdoor macroThe RBS 3101 is an outdoor RBS with one tofour carriers and one to six sectors at 20/40WRF output power per carrier. The power distri-bution system and battery backup have beenintegrated into the cabinet. External power is230/380 VAC.

RBS 3202 indoor macroThe RBS 3202 is an indoor RBS with one to fourcarriers and one to six sectors at 20/40 W RFoutput power per carrier.

RBS 3301 microThe RBS 3301 is a small, lightweight, weather-proof base station with no floor space require-ments. It has one carrier and one sector at 2 Wintegrated RF output power, and can be usedwith an optional remote radio unit for extendedcoverage.

RBS 3401 indoor miniThe RBS 3401 is a compact indoor mini RBSwith• three sectors and one to two carriers per sec-

tor; or • six sectors and one carrier per sector.Macro coverage is achieved using remote radiounits.

RBS 3501 outdoor miniThe RBS 3501 is a compact, convection-cooled, weatherproof, outdoor RBS with thesame specifications as the RBS 3401. Thanksto its compact design, it can be hand-carried tothe installation site.

Remote radio unitThe remote radio unit is a remote radio headwith a transceiver and power amplifier. It has upto 10 W RF output power and can be connect-ed via a digital interface to the RBS 3401/RBS3501, RBS 3301 and wTRU.

wTRU conceptThe wideband transceiver unit (wTRU) conceptgives operators a rapid and smooth way ofimplementing WCDMA coverage. The wTRUoccupies two TRU slots in a GSM RBS 2000cabinet. When used with remote radio units, thewTRU concept yields one carrier and one tothree sector coverage.

Pre-assembled site solutionsEvery RBS in the family of RBS 3000 productscan be delivered in pre-assembled outdoor con-tainers which include all the equipment that isneeded to build a complete site.

BOX B, THE RBS 3000 FAMILY OF PRODUCTS

Figure 7Remote radio unit.


Hot-repair hardware maintenanceWhen developing the RBS 3000, designersput special emphasis on minimum systemdowntime and low maintenance costs. Theyachieved these design objectives by meansof the hot-repair maintenance principle ofreplacing units that have been affected byfaults. By hot repair we mean that a faultyunit can be replaced with minimum impacton traffic handled by the RBS 3000.

The RBS 3000 products can be accessedfor the execution of management tasks fromany node in the network. The RBS 3000 canlocate the root cause of faults.

Power-saving mode

An optional function enables operators toorder RBS 3000 nodes into power-savingmode in order to lower overall power con-sumption.

Support for most transmission standards

The RBS 3000 supports most transmissionstandards. Cascading, star, and tree trans-mission configurations can be combined tosupport different network structures.

High availability thanks to manyredundancy concepts

The RBS 3000 includes several redundancyconcepts (such as n+1 redundancy, loadsharing, and processor cluster) for increasedavailability and reduced downtime.

Hardware architecture

PlatformEricsson’s WCDMA product portfolio isbased on a new platform, which is well suit-ed to building small-to-medium-scaletelecommunications products that requirelow-cost support for asynchronous transfermode (ATM) and IP transport.1 Both theRNC and RBS are based on this platform,which includes all the physical equipmentand associated software needed to create apacket-switching network node. The modu-lar design of the platform makes it easy foroperators to create nodes with different con-figurations, functionality, capacity and reli-ability. Transport can be concentrated in anynode, since every node has ATM switchingcapabilities.

Hardware structureThe family of RBS 3000 products featuresa modular design: several subsystems facil-itate easy expansion and evolution. The in-

terfaces between hardware units have beenclearly defined, and most will be maintainedthroughout product evolution. This flexibledesign means that new releases of hardwareunits and boards based on advanced ASICtechnology can easily replace or be added toolder units, enabling an increase in channelcapacity, for example.

RedundancyDepending on the operator’s needs, the RBScan be equipped for minimum hardwareconfiguration or high redundancy. Redun-dancy is based on the n+1 principle—thatis, if one unit fails, another unit takes over,thereby guaranteeing full capacity in theRBS. In terms of load sharing, if a unit fails,the functionality is maintained but capaci-ty abates.

Architecture of the hardware unitsThe RBS 3000 macro products are made upof a baseband subrack, radio subrack, multi-carrier power amplifier (MCPA) subrack,power-distribution equipment, tower-mounted amplifier (TMA), and a remoteelectrical antenna tilt (RET).

Baseband subrack

The baseband subrack is composed of ex-change terminal boards (ETB), a timing unitboard and an ATM switch board. The base-band subrack also contains boards for up-link/downlink functions for coding, inter-leaving, and modulation. The built-in ATMswitch board distributes incoming informa-tion from the transport link to radio-channel hardware.

Radio subrack

The radio subrack contains the main proces-sor of the RBS, an antenna interface unit(AIU), and boards with radio functionality.It also contains boards for handling digital-to-analog (D/A) signal conversion, modula-tion and demodulation, analog-to-digital(A/D) signal conversion and filtering for theRX path for each cell carrier. The AIU iscomposed of radio frequency (RF) parts,such as RF filters, a low-noise amplifier, andsplitters. Duplex filters minimize the num-ber of feeders and antennas by allowing re-ceiver and transmitter path connections tobe made to a common antenna.

MCPA subrack

The MCPA unit, which is a wideband lin-ear power amplifier, amplifies the carriers tobe transmitted in a cell.

Figure 8RBS 3301.

Power distribution equipment

The RBS is equipped with a capacitor unit(CU) that keeps the RBS in operation dur-ing short drops in –48V power. An externalalarm connection unit (EACU) can also beconnected to the RBS 3000. Operators candefine up to 32 external alarms and two out-put control ports. The alarms are galvani-cally separated from the RBS.

Tower-mounted amplifier

The low-noise amplifier, which is mountedon the antenna tower near the antenna, isused on receiving paths in order to lower theoverall receiver noise figure. It is a dual-duplex TMA (DDTMA), which means it in-cludes two duplex filters per branch. This

design uses the same feeder for receiving andtransmitting signals.

The TMA embodies two transmitter (TX)and receiver (RX) branches in one unit.Thus, only one TMA is needed per sector.Power is supplied via the RF feeder from theAIU in the RBS.

Remote electrical antenna tilt

The remote electrical antenna tilt controlsthe vertical tilt angle of the antenna lobe.The tilt angle ranges from 0 to X degreesdowntilt, where X is the verticalbeamwidth of the antenna. The maximumdowntilt angle approximately correspondsto the first upper null in the vertical radia-tion pattern. If a TMA is used, the RET ispowered by the AIU via the TMA; other-wise, the RET is powered directly from theAIU.

Software architecture

GeneralAll software can be downloaded to theRBS 3000 before it is shipped andinstalled. The software is stored in non-volatile program store in the main proces-sor. Besides simplifying and acceleratinginstallation, this design also speeds uprecovery after power failures, since iteliminates the need for reloading softwarefrom other nodes.

The RBS 3000 software is composed ofseveral subsystems in a layered architecture.The software platform, which provides basicsupport for application software, includes anexecution platform with operating system,ATM transport, and operation and mainte-nance (O&M) infrastructure. The RBS ap-plication software is built on the platformsoftware and handles the RBS hardware(Figure 9).

RBS application softwareThe application software is divided into sev-eral subsystems in a layered structure (Fig-ure 10).

Base station controller

The base station controller (BSC) subsystemis a service layer that interprets and executesthe application procedures initiated fromthe RNC.

Logical resource support

Logical resource support provides the ser-vice layer with control over RBS logical re-


Logical resource support

Equipment control

Hardware layer

FirmwareBoard processor

Main processor software

Operation and maintenance support

Base station controlFigure 10 RBS application software structure.

RBS application software

RBS platform software

Figure 9 RBS software structure.


sources, such as radio links, cell carriers,ATM connections, and so on.

Equipment control

The main purpose of the equipment controlsubsystem is to isolate the hardware imple-mentation from higher layers. It containsdevice board control functions, hardware resource-allocation algorithms and a control-signal transport-routing function.

Hardware layerThe hardware layer is divided into severaldevice-specific subsystems that containhardware and software. Each subsystem hasa software component in the board proces-sor of individual device boards. The associ-ated software is generally divided into threeparts (Figure 11):• a device-specific component, which is

unique to different types of hardware;• a board control component, which han-

dles O&M functionality (for instance,starting and loading) for the board—thiscomponent is common to all RBS deviceboards; and

• a low-level communication component—this component is also common to all RBSdevice boards.

RBS software platformThe RBS software platform provides services for the application software. These services are an ATM platform, a distrib-uted real-time system, basic O&M, man-agement interfaces, and transport services(Figure 12).

The RBS application software is distrib-uted over several processors using the inter-processor communication offered by theplatform. The main processors of theRBS 3000 cooperate to form a main proces-sor cluster (MPC) that executes most of thecontrol software. The processors that makeup the MPC are equal in terms of control—that is, there are no master-slave relation-ships between them. However, if one of theprocessors fails, the program execution ismoved to another main processor in theMPC. For control, most boards are equippedwith a board processor (BP). Those unitsthat do not contain a board processor aremonitored by other units.

ConclusionEricsson’s family of RBS 3000 products forWCDMA includes indoor and outdoor ver-sions of macro-, mini- and microbase stations.

The design is based on 3GPP requirements.The macro models consist of a weatherproof

outdoor model and an indoor model. Mini-and microbase stations can be mounted onwalls or poles, saving floor space. Remoteradio units can be located near the antennaapart from the rest of the base station equip-ment. This design reduces feeder losses andincreases the capacity of the base station.

For the migration from GSM toWCDMA, an individual WCDMA trans-ceiver (wTRU) can be plugged into emptyslots in existing GSM RBS 2000 macrobasestations to provide the fastest possible roll-out of WCDMA coverage and capacity.

The RBS 3000 products can be accessedfor the execution of management tasks fromany node in the network. The RBS 3000 hasbeen designed to accept software correctionsand upgrades while it is in service. Similar-ly, the RBS plug-in units can be replaced inaccordance with the hot-repair principle,and RBS hardware can be installed while theRBS 3000 is in operation.

MPC

BP BP

BP

BP

BP

MP MP

Figure12 Processor cluster.

Low-level communication support

Device function control

Board controlBoard processor

Device board

Hardware (DSP, ASIC, etc.)Figure 11Application structure of the device board.

1 Reinius, J.: Cello—An ATM transport andcontrol platform. Ericsson Review Vol.76(1999):2, pp. 48-55.

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