System Structure of the BTS3900A

The BTS3900A consists of the following modules:*The BBU3900 is used for baseband processing and enables interaction between the BTSand the BSC.*The DRFU, the double-transceiver filter unit, performs modulation and demodulationbetween baseband signals and RF signals, processes data, and combines and divides signals.*The power distribution box and RF cabinet provides space for BBU3900 and DRFU andthe functions of power distribution, heat dissipation, and surge protection.

Structure of the BTS3900A Cabinet

The BTS3900A cabinet consists of the RF cabinet and the APM30 power cabinet. The RF cabinetis categorized into two types: 3RFU cabinet and 6RFU cabinet. For the BTS3900A, the APM30battery cabinet and APM30 transmission cabinet are optional. The battery cabinet provides longtimebackup power, and the transmission cabinet can accommodate the transmission equipmentof the user.The components of the BTS3900A include the DRFU, BBU, DCDU-02, FMUA, FAN unit, andGATM, among which the GATM is optional.Figure 2-1 shows the typical configuration of a BTS3900A cabinet that consists of a 6RFU cabinet and an APM30 power cabinet.

Logical Structure of the BTS3900ALogical Structure of the BTS3900AThis describes the logical structure of the BTS3900A. It mainly consists of the BBU and DRFUs.The logical structure of the BTS3900A consists of the RF subsystem, control subsystem, powersubsystem, and antenna subsystem.Figure 2-5 shows the logical structure of the BTS3900A.The logical subsystems of the BTS3900A are as follows:*RF subsystem whose functions are implemented by the DRFU*Control subsystem whose functions are implemented by the BBU*Power subsystem whose functions are implemented by the following modules:– PDU– Power Subrack (AC/DC)– DCDU-02– DCDU-03A– Battery*Antenna subsystem whose functions are implemented by the following modules:– GATM– TMA– Antennas

Software Structure of the BTS

The BTS software consists of the platform software, signaling protocol software, OM software,and data center. The latter three are application software, and the platform software providessupport for the application software.Figure 2-6 shows the software structure of the BTS.

Platform SoftwareThe platform software provides support for the signaling protocol software, OM software, anddata center. The functions of the platform software are as follows:*Timing management*Task management*Memory management*Module management*Managing the loading and running of the application software*Providing the message forwarding mechanism between modules*Tracing massages between modules to facilitate troubleshooting

Signaling Protocol SoftwareThe functions of the signaling protocol software are as follows:*Processing the radio network layer protocol*Processing the transport network layer protocol, which performs transport data configuration, ALCAP processing, and SAAL processing

*Managing the internal logical resources (such as cells and channels) of the BTS and themapping between physical resources and logical resourcesOM SoftwareThe OM software works together with the maintenance terminals such as the LMT to maintainthe BTS. The functions of the OM software are as follows:*Equipment management*Data configuration*Performance management*Commissioning management*Alarm management*Software management*Tracing management*Security management*Backup management*Log managementData CenterThe data center stores the configuration data of all the modules.

Power Distribution Modes of the BTS3900A

The BTS3900A allows the 220 V AC input.The description of the power distribution is as follows:*When the external 220 V AC is used, the PDU leads the 220 V AC into the PSU (AC/DC)in the power subrack (AC/DC). The PSU converts the 220 V AC to -48 V DC, and thentransmits the converted DC back to the PDU.*The PDU distributes the -48 V DC. Part of the -48 V DC is directly distributed to certainmodules. Part of the -48 V DC is distributed to the DCDU-02. The DCDU-02 thendistributes the -48 V DC to certain modules.*When the APM30 transmission cabinet is configured, the PDU leads the -48 V DC to theDCDU-03A in the transmission cabinet. The DCDU-03A then distributes the -48 V DC tocertain modules.*The power subrack (AC/DC) performs the charging and discharging of the batteries.

This describes the monitoring system of the BTS3900A. The monitoring system monitors thepower, fans, and environment. *The BBU can provides up to two RS485 bus ports and 16 Boolean inputs.*The modules on the RS485 bus 0 cannot substitute those on the RS485 bus 1.*If two MPUs with the same DIP switch setting are configured, they cannot be installed onthe same bus.

Components of the Monitoring System

Table 4-1 Monitoring signals of the BTS3900AUnit AddressFMUA (mandatory) bus0GATM2 (optional) bus0PMU (mandatory) bus1AFMU (mandatory) bus1GATM1 (optional) bus1FMUA (optional) bus1

Unit ControlFAN *Fan failure monitoring

*Adjust the fan speed*Temperature and fan speed monitoring

GATM Reports the RET control alarm signals.

EMUA *Communicates with the central processing unit through the two RS485 ports*Input voltage monitoring*Provides independent 12 V DC/24 V DC temperature and humidity sensor ports.*Provides Boolean input signal monitoring ports, and connects to the Boolean monitoring signals in dry contact mode or OC mode.*Provides six external Boolean output control ports in relay node mode.

PMU *Communicates with the central processing unit through the RS232/RS422 serial port.*Manages the power system and charging and discharging of batteries.*It reports water alarms, smokes alarms, door control alarms, standby Boolean alarms, ambient humidity and temperature, battery temperature, and standby analog values.*Power distribution monitoring and alarm Reporting

DCDU-02 Provides the monitoring of surge protection failure

FMUA *Collecting environment alarm information in the cabinet. The environment alarm is classified into temperature alarm, humidity alarm, smoke alarm, water immersion alarm, and door status alarm.*Collects surge protection alarm information of the DC power distribution unit.*Monitors the operating status of fans. The fan speed can be adjusted based on the temperature or adjusted by the central processing unit.*Stops the rotation of the fans when the ambient temperature is low.*Temperature monitoring and reporting*RS485 port cascading and extension*The FMUAs can be cascaded.

Functions of the Monitoring System Table 4-2 Functions of the Monitoring System

Reference Clocks of the BTS3900/BTS3900AThe BTS3900/BTS3900A supports three types of reference clocks: line clock, BITS clock, andfree-run clock.Line ClockThe BBU3900 directly extracts clock signals from the E1/T1 interface. Then, the BBU exportsthe precise 2 MHz and 8 kHz clocks after frequency dividing, phase locking, and phase adjusting.The 2 MHz and 8 kHz clocks are used for frame synchronization and bit synchronization in theBTS3900/BTS3900A.BITS ClockThe BBU3900 supports the BITS clock mode by providing a port for the 2.048 MHz BITS clock.Free-Run ClockWhen the external reference clocks are unavailable, the oven controlled crystal oscillator(OCXO) on the GTMU of the BBU3900 provides the 13 MHz clock to ensure the normaloperation of the BTS.

Signal Flow of the BTS3900/BTS3900AThe signal flow of the BTS3900/BTS3900A consists of the traffic signal flow and the signalingflow of the BTS. The BTS3900/BTS3900A signal flow is classified into the DL traffic signalflow, UL traffic signal flow, and signaling flow.DL Traffic Signal FlowThe DL traffic signal flow is transmitted from the BSC to the MS through the BTS3900/BTS3900A. In the BTS3900/BTS3900A, the BBU and DRFUs work together to process the DLtraffic signals. Figure 6-1 shows the DL traffic signal flow of the BTS3900/BTS3900A.The DL traffic signal flow is as follows:1. The BSC sends E1 signals to the BBU through E1 or optical cables.2. After receiving the E1 signals, the BBU processes the E1 signals as follows:(1) Extracts clock signals from the E1 signals(2) Configures the BTS system based on the data configuration on the OML(3) Encapsulates the E1 data in the format of the CPRI frame, and then transmits the datato the DRFU through the CPRI signal cable3. After receiving the signals, the DRFU processes the signals as follows:

(1) Decapsulates the high-speed CPRI frames to obtain the baseband signals(2) Transmits the baseband signals to the relevant operation units for encapsulation andinterleaving(3) Converts the digital signals into the analog signals and modulates the analog signalsinto RF signals(4) Combines or divides the RF signals based on its own configuration(5) Transmits the combined or divided signals to the antenna subsystem

UL Traffic Signal FlowOpposite to the DL traffic signal flow, the UL traffic signal flow is transmitted from the MS tothe BSC through the BTS3900/BTS3900A. In the BTS3900/BTS3900A, the BBU and DRFUswork together to process the UL traffic signals. Figure 6-2 shows the UL traffic signal flow.The UL traffic signal flow is as follows:1. The antenna receives the signals sent from the MS. If the TMA is configured, the receivedsignals are amplified by the TMA and then transmitted to the DRFU through the feeder.2. After receiving the UL signals, the DRFU processes the signals as follows:(1) Divides the UL signals received from the antenna, Rx1 in, or Rx2 in(2) Converts the divided analog signals into the digital signals to obtain the baseband signals(3) Transmits the baseband signals to the relevant operation units for decryption and de-interleaving(4) Encapsulates the processed data in the format of the CPRI frame, and then transmitsthe data to the BBU through the CPRI signal cable3. After receiving the signals, the BBU processes the signals as follows:(1) Decapsulates the high-speed CPRI frames to obtain the baseband signals(2) Encapsulates the baseband signals in the format of the E1 frame, and then transmitsthe signals to the BSC through the E1 cable or the optical cable

Signaling FlowThis describes the BTS3900/BTS3900A signaling flow on the Abis interface. The BBU servesas the control unit and works with DRFU to process the signaling. Figure 6-3 shows the signaling flowThe signaling flow is as follows:1. The signaling data received from the BSC is transmitted to the BBU through the Abisinterface.2. The BBU encapsulates the signaling data in the format of the CPRI frame, and thentransmits the signaling data to the DRFU through the CPRI signal cable.3. The DRFU decapsulates the CPRI signals into the baseband signals, transmits the basebandsignals to the relevant operation units for processing.4. The BBU encapsulates the data of its own status in the format of the CPRI frame, and thentransmits the data to the DRFU through the CPRI signal cable.5. The BBU decapsulates the received CPRI signals to obtain the baseband signals.6. The BBU obtains the status of the BTS by analyzing the baseband signals. Then, the BBUtransmits the information on the BTS status to the BSC through the Abis interface.

Configuration Principles of the BTS3900/BTS3900A

The BTS3900/BTS3900A uses DRFU transceiver module and DRFU built-in duplexer. A singlecabinet provides up to 12 TRXs with the maximum cell configuration of S4/4/4 and supportsthe dual-band application. In the BTS3900/BTS3900A, the antenna subsystem, DRFUs, and BBU need to be configured.Basic Configuration Principles

• Smooth upgrade of configuration. If multiple types of hardware configurations meet therequirements for configuring the parameters in network planning, the configuration modethat implements the smooth upgrade is preferred.

• The BTS3900/BTS3900A solution is recommended in S4/4/4 cell configuration or lowerconfigurations. When multiple antennas are permitted, the BTS3900/BTS3900A solutioncan be applied in S8/8/8 and S4/4/4+S4/4/4 dual-band cell configurations.

• Wide coverage. The DRFU supports wide coverage. The DRFU can work in PBT, transmitdiversity, or 4-way receive diversity mode in configurations lower than S2.

Antenna Configuration Principles• One antenna can serve up to two DRFUs to support

the S4/4/4 configuration.• By default, the receive diversity is adopted in the

GSM. That is, two feeder (two single antennas or one dual-polarized antenna) must be

configured in a cell.• When one internal combination is allowed, the cell

configuration of S4 and lower configurations use a single antenna, the configurations of S5 to S8 use a double antenna, and the configurations of S8 to S12 use a triple antenna.

• Each sector of the BTS must be configured with the minimum number of antennas.

• For the 2-antenna receive diversity, each sector has two antenna channels; for the 4-antenna receive diversity, each sector has four antenna channels.

RF Configuration Principles

Table 8-1 RF configuration principles of the BTS3900/BTS3900A

Principle Configuration principles of the DRFU ports

Description ANT1 and ANT2 are the TX ports of the

duplexer. They are connected to jumpers. Rx1 in, Rx1 out, Rx2 in, and Rx2 out are used

for the interconnection between the DRFU modules. When the two TRXs provided by the DRFU belong to the same cell, both Rx1 in and Rx2 in can be the input ports for receive diversity of the two TRXs. When the two TRXs provided by the DRFU belong to different cells, Rx1 in is the input port for RX diversity of TRX 1; Rx2 in is the input port for receive diversity of TRX 2.

CPRI_0 and CPRI_1 are= the ports for high speed signal cables. They are connected to CPRI ports on the BBU.

ExampleIn the S3/3 configuration, three DRFUs need to be configured. The TRXs provided by the middleDRFU belong to different cells. Then, the Rx1 in port on the middle DRFU is the input port, which belongs to the first cell, for receive diversity of TRX 1. The input port for RX main diversity of TRX 2 is ANT1. The Rx2 in port is the input port, which belongs to the second cell, for receive diversity of TRX 2. The input port for RX main diversity of TRX 2 is ANT2.

Configuration principles of asingle cabinet

Star topology is adopted between the BBU and DRFUs. The DRFUs and the high-speed interfaces on the BBU have a one-to-one mapping relationship. That is, if DRFU slot 1 is idle, CPRI port 1 on the BBU is also idle.

A single cabinet supports the maximum cell configuration of S4/4/4.

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RF Configuration Principles

PrincipleConfiguration principles ofmultiple cabinets

Description *When star and ring topologies are adopted between the BBU and DRFUs, three levels ofDRFUs in a ring can be connected to one BBU.That is, one BBU supports 3 x 3 = 9 DRFUs.*When star and chain topologies are adoptedbetween the BBU and DRFUs, three levels ofDRFUs on a chain can be connected to one BBU. That is, one BBU supports 6 x 3 = 18 DRFUs.

ExampleNone

Non-combination in thetransmit channel

*The non-combination configuration is recommended for the DRFU to avoid the powerloss in combination and to reduce the powerconsumption of the BTS.*If combination is required, the cavity combiner must be configured outside the DRFU and one combination is recommended.

None

Configuring two TRXs inone sector

A single DRFU does not support the S1/1application; however, three DRFUs support theS3/3 application.*When the DRFU works in transmit PBT, transmit diversity, or 4-way receive diversity mode, a DRFU provides only one TRX. Therefore, the actual configuration does notinvolve the mode of configuring two TRXs inone sector.

For example, for a site in S5/4/7 cell configuration, nine DRFUs are installed meeting the requirements of S6/4/8 cell configuration but data is still configured inS5/4/7 cell configuration.

Principle Description Example

Number of DRFUs *When the number of TRXs of the site is less than 12, an odd number of TRXs can be configured for a cell. Number of DRFUs = round up [(Number of TRXs + Number of S1 cells) ÷ 2]*When the number of TRXs of the site is greater than 12, two TRXs should be configured for a cell. Number of DRFUs =round up (Number of TRXs after two TRXs are configured in one sector ÷ 2)

l S3/3/3: Number ofDRFUs = round up (9 ÷ 2)= 5; S1/2/3: Number ofDRFUs = round up [(6 + 1) ÷ 2] = 4.l After two TRXs areconfigured in one sector,the S5/5/5 configuration is S6/6/6. Number of DRFUs = (6 + 6 + 6) ÷ 2 = 9.

TRX allocation in doubleantenna mode

After TRX allocation, thecells with the odd number ofTRXs are adjacent cells.*S5 = S3 + S2 or S5 = S2 + S3*S6 = S4 + S2 or S6 = S3 + S3*S7 = S4 + S3 or S7 = S3 + S4*S8 = S4 + S4

*In S3/5/4, S5 can bedivided into S3 + S2.Then, the cellconfiguration is S3/(3/2)/ 4.*In S2/5/5, the first S5 isdivided into S2 + S3; thesecond S5 is divided intoS3 + S2. Then, the cellconfiguration is S2/(2/3)/ (3/2).

Principle Description Example

Configuring double TRXs in a site

*If the number of DRFUs is less than or equal to 6 in adouble-TRX site, the two TRXs are configured in the same cabinet. If the number of DRFUs of the two bands is less than 3, the 900 MHz DRFUs are installed in the 3 slots on the left, and the 1800 MHz DRFUs are installed in the 3 slots on the right.*When two RF cabinets are configured and the number of DRFUs of each band is less than 6, the 900MHz DRFUs are installed in the first cabinet and the 1800 MHz DRFUs are installed in the second cabinet. The DRFUs are installed in the slots according to the typical S4/4/4 configuration. When two RF cabinets are configured and the number of DRFUs of one band is greater than 6, the band with fewer DRFUs shares the cabinet with the other band. Mixed configuration of DRFUs are not allowed.

None

Board or Module

Description

BSBC 1 pcs must be configured.

UBFA 1 pcs must be configured.

UPEU *1 pcs must be configured.*1 pcs can be configured when the backup power is required. The UPEU, however, cannot be configured with the UEIU at the same time.

UEIU *1 pcs must be configured when three or more than three BTS3900 cabinets are configured.*In the outdoor application, 1 pcs must be configured when two or more than two APM30 power cabinets are configured.

GTMU *1 pcs must be configured.*The GTMU occupies slot 5 and slot 6.

UELP *Not required in the BTS3900*1 pcs must be configured in theBTS3900A. The UELP occupies slot 0.

Configuration Principles of the BBUOne BBU provides six CPRI ports. In the chain topology, a single BBU can support up to36 TRXs. Figure 8-1 shows the BBU slots.