OME201101 GSM BTS312 Hardware Structure ISSUE3.0Wireless Training Department

ObjectivesKnow the functions and features of BTSMaster the BTS hardware structureMaster the signal processing of BTSUpon completion of this course, you will be able to:

ContentsPart 4: Antenna and Feeder SystemPart 1: OverviewPart 3: Signal ProcessingPart 2: System Components

General Introduction to BTS312Part1: Overview

Features and Functions

Features and FunctionsHigh integration and low power consumption15 radio carriers at the Abis sharing an E1 for transmission (15:1) Integrating optical transmission equipment, implementing optical fiber to BTSSupporting the configuration of up to S24/24/24 and facilitating expansion1-minute fast startup

Features and FunctionsSupporting GSM900,DCS1800,EGSM,RGSM Supporting short message cell broadcast and point to point short message GSM PHASE I/PHASE II and GPRSSupporting baseband hopping and RF hoppingSupporting the EFR and DTXSupporting A5/0, A5/1 and A5/2 encryptionSupporting half rate

BTS312 Cabinet and BoardsCommon equipmentTRXCDUair/fanBTS312 Cabinet and Boards:CDU: combiner & divider unit TRX: transceiver module PMU: power monitoring unit TMU: Timing/Transmission & Management Unit PSU: power supply unitTES: transmission extension power supply unitTEU: transmission extension unitTDU: time distribution unit

Power Supply

Power Supply System

PMUPMU (Power Monitoring Unit) structure

PSU ConfigurationThe configuration of PMU:

FMUProviding fan feedFan rotationspeed controlAlarm detection Interfaces24V power supply input interfaceFan box power supply input interfaceFan fault alarm detectionFan Monitoring Unit (FMU)

Key Components in the SystemPart2: System Components

Hardware Structure of BTS312DATA BUS/CONTROL_BUS/TIMING_BUSTMUPMUFH_BUSCDUPSUTRXTRXTRXTRX unitCommon unitCDUCDUTo antennaTo antennaTo antennaAntenna feeder unit

TMUBSCExternal synchronous clockMMI man-machine interfaceExternalAlarmingcontrolBIUOMUEACMCKStandby MCKExtended BIUDBUS Internal data busCBUS Internal control busTDUInternal clock busFunction: TimingTransmissionManagement

Panel of TMU

Indictors on TMU

TRX Module Structure

Functions of TRXBaseband speech processingUm and Abis interface signaling processingModulation and demodulationRF signal amplification

Functions of TRXPower amplifier unit (PAU) (output 46dBm/APC)Over standing wave alarm: Over-temperature alarm:

Panel of TRX

Indicators on TRX

TDUFunction:Time Distributing Unit

Position of TDU in the Rack

BUS Topology

Cabinet-top Connectors

Cabinet GroupEach BTS312 cabinet can accommodate 12 carriers. When the number of cell carriers is over 12, multiple cabinets need to be equipped, classified as basic cabinet and extension cabinet. They form a cabinet group (or equipment group). One group consists of 2 cabinets at mostOne set of BTS312 equipment group can contain two cabinets (24 TRXs).For the maximum capacity site, there are three groups with 72 TRXs.

Cabinet Extension CablingGreen colored sockets installed with matching connectors for resistance terminationExtension CabinetBasic CabinetBasic CabinetExtension CabinetBasic Cabinet GroupExtension Cabinet Group

System Operational PrinciplePart3: Signal Processing

Signal TypeSpeechSignalingLAPD SignalingOMLRSLLAPDm SignalingClock

Speech ProcessingBSC-TDU-TMU-DBUS-TRX-CDU-ANT-MSDBUSSCPCUIClock processTBPUDSPFH_BUSTDPPAURCURPUBSCExternal synchronous clockMMI man-machine interfaceExternalAlarmingcontrolBIUOMUEACMCKStandby MCKCBUSTBUSCDU

OML ProcessingBSC-TDU-TMU-CBUS-TRX (or PMU,CDU),

DBUSSCPCUIClock processTBPUDSPFH_BUSTDPPAURCURPUBSCExternal synchronous clockMMI man-machine interfaceExternalAlarmingcontrolBIUOMUEACMCKStandby MCKCBUSTBUS

RSL and LAPDm SignalingBSC-TDU-TMU-DBUS-TRX-CDU-ANT-MSDBUSSCPCUIClock processTBPUDSPFH_BUSTDPPAURCURPUBSCExternal synchronous clockMMI man-machine interfaceExternalAlarmingcontrolBIUOMUEACMCKStandby MCKCBUSTBUSCDU

Clock ProcessingBSC (or External Clock) -TDU-TMU-TDU-TBUS-TRXDBUSSCPCUIClock processTBPUDSPFH_BUSTDPPAURCURPUBSCExternal synchronous clockMMI man-machine interfaceExternalAlarmingcontrolBIUOMUEACMCKStandby MCKCBUSTBUS

TBUS ConnectionClock bus connection in a synchronous cell

Antenna and Feeder SystemPart4: Antenna and Feeder System

Antenna and Feeder System

CDU

Indicators on CDU

Alarm TestStanding wave testing function:When the tested standing wave exceeds the preset threshold (1.5:1 or 2.5:1), CDU will give corresponding alarms and indications. Testing the internal amplifier and the tower amplifier, CDU reports the alarms to TMU.

EDUEDU indicators are the same as those of CDU

SCUFour carriers are combined and output through 3dB bridges and the plug loss is 6.8dB.

FeederThere are several forms for the main feeder:7/8 inchCABLE LOSS=0.043dB/m5/4 inchCABLE LOSS=0.032dB/m1/2-inch super-flexible jumpersCABLE LOSS=0.11dB/mUsed between the antenna and the main feederBetween the antenna and the boosterBetween the cabinet and the lightning arrester

Antenna TechnologyAntenna gainAntenna PatternPolarizationDiversity technology

Antenna GainAntenna gain indicates the antenna feature of radiating electromagnetic waves in specific directions. Normally, the higher the gain, the stronger the far field strengthABGain A > Gain B

Antenna PatternThe antenna pattern describes the radiating abilities of antennas in all directions.Refers to the half-power angle in the horizontal plane.Omni AntennaDirectional antenna

PolarizationTwo main types of polarization: Vertical polarizationHorizontal polarizationThe types of antenna divided by polarization:Single polarization antennaVertical polarization for GSM One port for one feederBi-polarization antenna+45 degree and -45 degreeTwo ports for two feeders

Diversity TechnologyPolarization diversitySave antenna Space diversityd>10 x wavelengthFrequency diversityFrequency hoppingTypes of diversity:

Lightning ArresterLightning Arrester is used to prevent the equipment from being damaged by the lightening current inducted by the core line of the feeder.

TTA (Optional)The tower amplifier is installed next to the receiving antenna.It can be used to increase the receiving sensibility of the base station. consisting of:Triplex filterLow noise amplifier

When you finish this course, I wish you could get good knowledge of the hardware structure, the work principle , antenna feeder system and some assistant equipment such as the anti-lighting equipment of BTS312 system. This course may take you 2 hours.First of all , let me give you the general introduction of the BTS312.BTS is one of the most important parts in GSM system. It is the wireless part of the base station subsystem, and its position in the system is shown in this figure. BTS is a set of transceiving equipment that serves a certain cell and it is controlled by the BSC ( the base station controller). Connects with BSC through the Abis interface and connects MS through the Um interface. It helps BSC implement radio resources management, wireless parameter management and interface management. For HUAWEI BTS312, its characteristic is high integration and low consumption. On the Abis interface, we can provide 15 radio carriers using one PCM E1. We can use integration optical transmission equipment, implement optical fiber to BTS. To the maximum expansion, we can make a huge configuration as S24/24/24, and the BTS312 can restart within 1minute.BTS312 can support dual-band frequencies system, GSM Phase I /Phase II protocol, GPRS ,short message cell broadcast ,point to point short message ,base-band hopping and RF hopping without change hardware. Also BTS312 can support the EFR, DTX, A5 encryption and decryption.Here is the BTS cabinet. It is consists of common equipment frame, TRX frame, CDU frame, AIR box, fan box and switch box. In the common equipment frame there can be PSU, PMU, TMU, TES and TEU. In the CDU frame there can be CDU and SCU. For all of the abbreviations , there is the explanations on the right.Then the power supply system is also very important. BTS312 has the system AC and DC input 3 modes, which only one should be selected: they are 220VAC:Used for the AC power supply cabinet, with the AC/DC module and batteries attached; -48VDC:Used for the DC power supply cabinet with the DC/DC module and no battery; +24VDC:Used for the DC power supply cabinet, with no AC/DC module or DC/DC module, nor any battery.M900/M1800 BTS cabinet power distribution solution: no matter whether it is the 220VAC , the -48VDC or the +24VDC,their outputs are all collected to the output bus bar of the power supply motherboard. Then, the 26VDC is led out from the bus bar, along the cabinet wiring groove to the distribution copper bar of the distribution box at the top. The battery 26VDC input is connected to the diverter on the power supply backplane , and then is distributed through the distribution copper bar in the distribution box to the various power-consuming modules. The illustration of the whole power supply system is as shown in figure.PMU is located in the slot of the cabinet common frame near the power supply module group. The main difference between the DC/DC module monitoring board and the AC/DC module monitoring board lies in whether one has battery management functions. To reduce work load, both the AC/DC module and the DC/DC module use only one monitoring board. Take the AC/DC module monitoring board for instance.This table is the configuration of how many PSU and PMU needs when we set up a BTS . You see There always has a backup PSU for the safety.

There is another board related to the power system , it is the FMU. It runs from system power supply to processing of the working power supply needed by fans and provides fan revolution speed control so that the fan can maintain a constant revolution speed within the fluctuation of system power supply, meeting the system heat design requirements. Also the FMU detect alarms such as blocking and short-circuiting. First of all , let me give you the general introduction of the BTS312.TEU .

In addition, this is the hardware structure of BTS. From the figure you can find out that our BTS system is consists of three parts, common unit, TRX unit and antenna feeder unit. This figure is the most important part of our course. Therefore, we will give you more detail explanation when you study the system function and work principle.

TMU 41. .BIU 1.OMU ( -).EAC , Alarm box. Alarm box . : (-)/ .

TMU is the abbreviation of the timing/transmission and management unit. It is the basic transmission and control function entity of M900/M1800 BTS. Functionally, it can be divided into the interface unit (BIU), the clock unit (MCK), the operation and maintenance unit (OMU), and the local man machine terminal interface (MMI). BIU handles the conversion between E1 signals of Abis interface and in-board digital signals, and provides link multiplexing and de-multiplexing, E1 clock extraction, cross connection, synchronization and timing functions. Each board contains four E1 interfaces. On BTS312 are installed two TMU boards, which can extend the E1 port into eight lines.MCK provides the BTS system with reference clock and system clock functions. On BTS312 are installed two TMU boards, which enables the MCK unit on the two boards work in the clock active/standby status.OMU is the core of maintenance and operation of BTS. OMU connects BSC maintenance and operation links, handles collection and reporting of BTS alarming, software loading, parameter configuration functions .Also OMU can do board running control, testing, external alarm collection and control functions. MMI is connected via the RS232 interface or the network interface to OMU for the terminal operation and maintenance of the base station. MMI can simulate most of the BSC base station maintenance (BTSM) functions. Via OMU. It can extract alarm information, issue configuration data, load software, handle testing, and control board running status. It is an important tool for office deployment, system commissioning and base station repair.Ok from the figure you can see that the signaling comes from BSC enter BTS through BIU then goes to the DBUS. Moreover, you will easy to know there are six other interfaces just like DBUS, so they are like next page shows. :MMI

This is the panel of TMU. The most important indicate light are LI1. LI1 Always on means communication in first E1 lines is breakdown; and LI1 Flash means remote alarm of the first pair E1 lines .when the light is Off then means communication of the first pairs E1 lines is normal. The other important light is PLL. This shows the phase discrimination indication of the clock. When it is always On means clock in the free oscillating state, when it Flash quickly at 4 Hz means Clock in the capturing state( capturing the clock of BSC); when it Flash slowly at 1 Hz means the clock is Locked;Moreover, it is off means something wrong.

The salient feature of BTS 312 is its modularized structure. That is, it integrates all software and hardware entities (including base band processing, RF unit, power amplifier and power supply) that perform all the processing functions of one carrier into one plug-in module TRX. TRX can be subdivided into two parts: base band signal processing unit (TBPU) and radio frequency signal processing unit (RPU).TBPU is consists of Signaling processing unit (SCP),Digital signal processing unit (DSP),Carrier unit interface (CUI) and Clock processing units, It chiefly handles the functions such as the Um interface rate readjustment, channel coding , interleaving and encrypting. And also it perform BURST generation, GMSK modulation, hopping control functons. It transmits transparent signaling to BTS, and processing part of signaling about wireless resources management, which is non-transparent to the BTS.RPU consists of the transmitting activation and frequency combination unit (TDP), the power amplifier unit (PAU), and the reception unit (RCU). It chiefly handles the reception and sending of radio frequency signals, up and down frequency conversion, power amplification, power control, and radio hopping.

There are two special function of BTS312 that is the Over-temperature and over standing-wave alarms. That means when the temperature of the power amplifier exceeds 85, the power amplifier unit reports the over-temperature alarm via the baseband unit, and automatically turns off the power amplifier. When the standing wave at the power amplifier output end exceeds 1.5, it reports standing wave alarm to the baseband unit.This is the panel of TRX the most important indicate light is RCP and RDP . the common status is both flashes at one time per second.The previously mentioned TMU is the basic BTS transmission and timing control function entity at one BTS. One of TMU functions is the centralized provision and management of BTS clocks. BTS clocks SREF, OBCLK, FCLK, and FN are provided by the TMU board in the master cabinet. These four types of clocks are sent to the top of each cabinet to be distributed by TDU to each TRX in this cabinet. TDU can also perform the functions of transferring other signals such as alarming signals. And TDU is the transferring center for all cabinet buses in the synchronous cell.

TES provides TEU with various types of working power supply and handles communication transfer. TES provides the base station transmission extension unit TEU with power supply, which includes +5V, -5V and ringing current, so that TEU board can work normally to perform transmission network functions, thus realizing base station built-in transmission.

First of all , let me give you the general introduction of the BTS312.In the simplex RS485 bus structure, it distributes the clocks which generated by the master TMU in the master cabinet to the various slave cabinets . It is shown in Figure . The TDU of each cabinet is hung on the bus. After receiving clock signals, it transfers them to the TRX in the local cabinet. The TDU of the terminal cabinet is connected to the matching head. First of all , let me give you the general introduction of the BTS312.The antenna feeder system consists of combine & divider unit (CDU), lighting arrester booster, low consumption transmission cables and antenna. It performs functions of radio frequency signal sending and reception, as well as antenna feed alarm detection.CDU performs transmitted signals combining and filtering, as well as received signal filtering, amplifying and distribution. it also can provide booster of DC power through a bias-T circuit. Two kinds of CDU are available in BTS312: one with 3dB-hybrid bridge combine CDU, and one with cavity filter combine (CCDU). One 2-way hybrid combiner and two 4-way splitters are integrated in hybrid CDU. CDU's functional diagram is shown in the Figure. The combining part combines two carriers and sends them to the antenna interface. Frequency hopping function is supported. The distribution part is made up of Main receiving part and Diversity receiving part, It amplifies the received signals and sends them to several receiving channels. When the number of channels is more than four, the distributor can be cascaded into a 1-8 distributor, that is, HL-out is connected with HL-in.LNA , .

The CDU has the Standing wave testing function, When the tested standing wave exceeds the preset threshold (1.51 and 2.51.5), CDU will give corresponding alarms and indications ON VSWR1&VSWR2 two indicate lights. Testing the internal amplifier and the booster , CDU reports the alarms to OMU.Here we have another equipment to used in antenna system, it is SCU. With the SCU , Four carriers are combined and output through 3dB bridges and the plug loss is 6.8dB. 900 1800 25 207/8 75 605/4 90 80

To reduce system transmission losses, the base station uses low loss radio frequency cables. The feeders have several options, including 7/8-inch and 5/4-inch. 1/2-inch jumpers are used between antenna and main feeder, and between the cabinet and the lightning arrester.Applied for the connections from the antenna to the main feeder, the antenna to the tower amplifier, and the cabinet to the antenna feeder arrester.When we finish talking about the CDU&SCU, maybe it is necessary to talk about the antenna and feeder . that is Antenna gain ,Antenna Pattern ,Polarization and Diversity technology.Antenna gain indicates the antenna feature of radiating electromagnetic waves in specific directions. Normally, the higher the gain, the stronger the far field strength, and the greater the effective coverage, but nearby dead zone might occur. For single polarization antenna, it is 9/11 dBd and For BI-polarization antenna, it is 11/13/15 dBd.

The antenna pattern describes the radiating abilities of antennas in all directions. In the field of communication, this normally refers to the horizontal pattern. Usually, there are two kinds of base station antennas: 360 Omni antennas and directional antennas. Directional antennas with 120, 90, and 65horizontal beam-width are available.Polarization is used to describe electric field direction. Mobile communication antennas include single polarized antennas and dual polarized antennas. With the dual polarized antennas, the two antenna polarization directions are mutually vertical. Therefore, the use of dual polarized antennas can reduce the number of antennas needed.The electronic broadcasting in the cities has the following features:(1) The average value of the electronic field strength varies slowly with different places and times. The rule of its variation follows the logarithm of normal distribution, which is called slow attenuation.(2) The electronic field strength instantaneous value, due to the multi-route transmission, undergoes the selective attenuation along with the transmitting route. The rule of its attenuation follows the Rayleigh distribution, which is called fast attenuationEither the fast or slow attenuation will ruin the communication quality, even worse, it will bring about communication interruption. You know there are two kinds of fading in radio transmission .Either fast fading or slow fading will affect the quality of mobile communication, or even lead to communication interruption in some cases. The diversity reception technology is one of the most effective ways to deal with fast fading. In case two fading signals are correlativeless, the use of suitable diversity reception and combination technologies will effectively annul the fading effect. Diversity includes polarization diversity and space diversity. In mobile communication application systems, either the space diversity or polarization diversity technologies can be used. Theoretical inferences show that in case of space diversity, when the distance between two antennas is greater than 10 wavelengths, the diversity gain is desirable .On the other hand, polarization diversity enjoys the advantage of convenient antenna installation and space saving and is widely used. By the way, frequency hopping is another diversity called frequency diversity.Besides the E1 transmission mode, M900/M1800 BTS also has the built-in transmission system. It supports not only the 155M SDH optical interfaces and PON optical interfaces through optical transmission, but also the built-in xDSL interfaces. All the above transmission modes are built in BTS ( all the boards that realize other transmission modes than basic E1 are called transmission extension unit TEU). The SDH transmission mode uses the ASU board of the Huawei SDH 155C, while the PON transmission mode uses the PAT board of the Huawei access network products.

The tower amplifier consists of three parts: the receiving filter, lower noise amplifier and feeder, and alarming. The signals from the antenna is first filtered by the band pass receiving filter, eliminating the outside band interference, then the weak signals will be amplified by the low noise amplifier, finally, the amplified signals will be transmitted to the indoors units through the low consumption cable. The ASU SDH optical synchronous transmission system is standard STM1 transmission equipment. ,With the existing mature technologies of Huawei standard SBS155/622 products, it is completely compatible with the existing SBS155/622 products. And it can form hybrid network with them in optical channels, 2M tributaries, clocks, main control, order-wire and other functions. It can be used to form ring-, chain-, and point to point network topological structures. It can also be combined with SBS155/622H and SBS155/622B products into complex network structures . The ASU SDH optical synchronous transmission equipment has inherited merits of powerful network management capacity and convenient operations of Huawei's standard transmission equipment. It uses the same set of network management system as all the Huawei SBS series of SDH optical transmission equipment.The lightning arrester is used to prevent damage of lightning current inductive to the center conductor of feeder. Usually, there are two kinds of lightning arresters. The first type uses the microwave principle to conduct the low frequency lightning current to the ground so as to arrest the lightning. The second one is a discharging tube lightning arrester. When the voltages at both ends of the discharging tube reach a certain value, the tube conducts to arrest the lightning. Our system use the second one, the discharging tube lightning arrester. And the feeder should be connected to ground on the top of the tower ,on the bottom of the tower and near the feeder window. And the ground ports of BTS cabinet should be connected to the ground too.