PowerPoint OME201101 GSM BTS312
Upon completion of this course, you will be able to:
Know the functions and features of BTS
Master the BTS hardware structure
Master the signal processing of BTS
Internal Use
Internal Use
HLR: Home Location Register
EIR: Equipment Identity Register
MSC: Mobile Switching Center
VLR: Visitor Location Register
SMC: Short Message Center
AUC: Authentication Center
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.
Internal Use
High integration and low power consumption
15 radio carriers at the Abis sharing an E1 for transmission (15:1)
Support various transmission modes and complex topologies,
e.g. SDH, E1, microwave, satellite etc.
Support the configuration of up to S24/24/24 and facilitating expansion
1-minute fast startup
Support GPRS and EDGE
Support A5/1 and A5/2 encryption/decryption
Internal Use
Hardware Structure
TES
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.
26890.unknown
P
S
U
P
S
U
P
S
U
P
S
U
P
S
U
P
S
U
P
M
U
T
M
U
T
E
S
T
E
U
T
M
U
T
E
U
T
R
X
T
R
X
T
R
X
T
R
X
C
D
U
C
D
U
T
R
X
T
R
X
T
R
X
T
R
X
C
D
U
C
D
U
T
R
X
T
R
X
T
R
X
T
R
X
C
D
U
C
D
U
TDU
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.
Internal Use
Internal Use
Internal Use
Provide Man-machine interface (MMI) and operation & maintenance link
Provide centralized BTS clock
Functions of TMU
EAC
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.
Internal Use
Flash
LI1,2,3,4
Green
Off
M/S
Green
Master Board: Slow flash Slave Board: Quick flash
PLL
Green
On: Free oscillation Quick flash(4Hz): Catching Slow flash(1Hz): Locked Off: Abnormal
Slow flash
Internal Use
Provide alarming channels
Provide bus-control interfaces
Functions of TDU
(2) External alarm interface (EAC1 and EAC2)
(3) 120Ω E1 interface (TME1)
(4) Built-in optical transmission E1 interface (TRA1, TRA2, TRB1, and TRB2)
(5) Storage battery management signal cable interface (PWRC)
(6) Clock interface (CKB1 and CKB2)
(7) Data bus interface (DCF2)
(8) 75Ω E1 interface (TX and RX)
(9) External synchronous clock interface (SYNC)
(10) Grounding cable interface for combined cabinet (SHELLGND)
(11) External power cable interface
(12) Feeder input interface (ANT)
(13) Cascading interface of CDU combined cabinet (CDU)
Internal Use
Power Supply
module is used.
When the supply input is -48VDC,the DC/DC module is used.
220VAC
-48VDC
+24VDC
EMI
filter
AC/DC
(DC/DC)
module
AC/DC
(DC/DC)
module
AC/DC
(DC/DC)
module
EMI
filter
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.
Internal Use
PSU Configuration
Fan
Fuse
Battery
Load
AC/DC
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.
Internal Use
Functions of FMU
Internal Use
Modulation and demodulation
RF signal amplification
Functions of TRX
RPU:RF signal Processing Unit
SCP: Signaling Processing Unit
CUI: Carrier Unit Interface
PAU: Power Amplifier Unit
FH_BUS: Frequency Hopping Bus
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.
23283.unknown
26705.unknown
Internal Use
Alarms of TRX
When the standing wave ratio at the power amplifier output port
exceeds 1.5, it reports standing wave alarm to the baseband unit
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
Over standing wave alarm
Flash
RDP
Green
Flash
FAIL
Red
Off
Filter ,amplify and distribute received signals
Provide power for the tower-top amplifier
Alarm detection
Combiner
Divider
Divider
Duplexer
TX1
TX2
TX-COMB
TX-DUP
RX1
RX2
RX3
RX4
HL-out
RX2
RX3
RX4
RX1
HL-in
RXD-ANT
TX/RX-ANT
RXD-out
LNA
LNA
Filter
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.
19798.unknown
19799.unknown
19800.unknown
19801.unknown
19802.unknown
19803.unknown
19804.unknown
19805.unknown
19806.unknown
19807.unknown
19808.unknown
19809.unknown
19810.unknown
19811.unknown
24663.unknown
19813.unknown
19814.unknown
19815.unknown
19816.unknown
19817.unknown
Standing wave ratio alarm
On: VSWR is greater than 1.5 and less than 2.5 Off: Normal
Off
VSWR2
Red
Off
TTA
Red
Off
LNA
Red
Off
MAIN: TTA power feeding selection knob of main receiving channel
DIVERSE: TTA power feeding selection knob of diversity receiving channel
FUSE :1.5A
Correspondence between knob setting and current strength of TTA
Note: MAIN is recommended to be set at 1(100mA),and DIVERSE to be set at 2(100mA).Other modes of setting are not recommended
Setting
MAIN
DIVERSE
Unit
0
off
off
1
100
65
mA
2
107
100
mA
3
205
205
mA
Internal Use
Alarm Detection
VSWR (Voltage Standing Wave Ratio) monitoring: CDU Monitors the status of antenna system. When the detected standing wave ratio exceeds the preset threshold (1.5 or 2.5), CDU will generate corresponding alarms
Low noise amplifier fault alarm: The signal is extracted from the power supply current of the low noise amplifier. When the current exceeds a certain level ,alarm signals are generated
Tower-top amplifier alarm: When there is a tower-top amplifier on service, the CDU monitors the status of tower-top amplifier by its working current. If the current exceeds a certain level , alarm signals are generated
Internal Use
Divider
Duplexer
TX1
RX1
RX2
TX/RX-ANT1
Divider
Duplexer
TX2
RX3
RX4
TX/RX-ANT2
LNA
LNA
SCU
Four carriers are combined and output through 3dB bridges and the insertion loss is 6.8dB
Tx_Comb
TX4
TX3
TX2
TX1
3dB
Bridge
3dB
Bridge
3dB
Bridge
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.
Internal Use
Internal Use
Speech Processing
DBUS
S
C
P
C
U
I
Clock bus connection in a synchronous cell
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.
24641.unknown
Blue colored sockets installed with matching connectors are for resistance termination
There are E1 cables between basic cabinet group and extension cabinet group
CKB1 CKB2
Internal Use
Internal Use
Lightning Arrester
Lightning Arrester is used to prevent the equipment from being damaged by the lightening current inducted by the core line of the feeder
feeder
jumper
Between the antenna and the tower-top amplifier
Between the cabinet and the lightning arrester
Internal Use
TTA (Optional)
The tower-top amplifier is installed close to the receiving antenna
It can be used to increase the receiving sensibility of the base station
Consisting of:
Simplex TTA
Duplex TTA
Triplex TTA
the receiving filter,
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.
Internal Use
TTA (Optional)
Low noise amplifier
RX filter
RX filter
Internal Use
Antenna Pattern
The antenna pattern describes the radiating abilities of antennas in all directions
Omni Antenna
Directional antenna
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 65°horizontal beam-width are available.
685.unknown
26722.unknown
677.unknown
8539.unknown
8542.unknown
8543.unknown
682.unknown
683.unknown
684.unknown
Vertical polarization
Horizontal polarization
Single polarized antenna
Dual polarized antenna
+45 degree and -45 degree
Two ports for two feeders
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.
691.unknown
24673.unknown
24675.unknown
BTS hardware structure
TX OUT