tma systems for gsm and dcs(20091214)

TMA Applicationfor GSM System

Jin Gang MeiJin Gang Mei

Project Manager

JG.Mei@comba-telecom.com0092-313-5136086

Comba Telecom Ltd

Topics

1. Tower-Mounted Amplifiers (TMA)2. TMA Components3. Benefits of TMA System4. Comba TMA Systems5. Link Balance with TMA6. Case Study - TMA SItes Selection7. TMA Installation

What is a TMA System?

What is a TMA?• A Low noise receiver

amplifier used to improve the up-link sensitivity of the BTS.

Why is it necessary?• To extend and maximise

coverage by providing network balance

• To improve the quality of service to the subscriber

• To reduce the infrastructure cost to the operator

PowerSupply

Antenna

TMA Installation

Service Antenna

Increasing Cell Radius

• A TMA located on the tower top can increase uplink range by 55% and bring the cell into balance.

• GSM,DCS & WCDMA systems virtually demand TMAs due to higher path loss and limited mobile transmit power.

• The risk of *not* using a TMA is lost calls near the cell boundary.

DownlinkDownlink

UplinkUplinkwithout TMAwithout TMA

UplinkUplinkwith TMAwith TMA

Sensitivity Improvement

BTS Receiver

BTSLNANF _

Feeder and Jumpers

dBLf 4=

-12010 dB

Thermal Noise Noise Figure in BTS

BTSLNAG _

Without TMAWithout TMA

dBNF BTSLNA 3_ =dBG BTSLNA 14_ =

BTS Receiver

Feeder and Jumpers

dBLf 4=

-12010 dB

Thermal Noise Noise Figure in Active Component

5.5 dB

LNALNA

TMANF TMAG

BBTSLNANF _

With TMAWith TMA

dBNFTMA 5.1=dBGTMA 11=

8.5 dB

dBNF BTSLNA 3_ =dBG BTSLNA 6_ =

8.5 dB

BTSLNAG _

Tower-Mounted Amplifiers (TMA)

Advantages of TMA• Extended network coverage

– Remove up-link limitation• Improved Network Quality

– Fewer dropped calls– Higher call throughput– Satisfied subscribers

• Reduces MS output power– Longer battery life and

less interference.• Reduced infrastructure cost

– Fewer sites

Disadvantages• Reduces the overall Mean

Time Between Failure (MTBF).

• Maintenance and supervision is more difficult.

• Lower intermodulation performance of site.

What comprises a TMA System?

It consists of 3 main components:

• Tower Mounted Amplifier– A low noise amplifier with bypass switch.

• Current Injector or Bias Tee – Facilitates injection of dc power onto the RF cable.

• Power Distribution & Management (PDM)– provides power and alarm handling up to 6 TMAs.

Tower Mounted Amplifier – Dual Duplex

ANT1 Port

BTS1 Port

Bias Tee

BTS PDM

+12VAlarm

To BTS

Bias Tee

Tx Fil

LNA LNA

Rx1 Fil

Rx2 Fil

Rx-Bypass

Bias Tee

Tx Fil

LNALNA

Rx1 Fil

Rx2 Fil

BypassLN

ANT0 Port

Bias Tee

BTS0 Port

To Antenna To Antenna

ANT1 Port

BTS1 Port

Bias Tee

BTS PDM

+12VAlarm

To BTS

Bias Tee

Tx Fil

LNA LNALNALNA LNALNA

Rx1 Fil

Rx2 Fil

Rx-Bypass

Bias Tee

Tx Fil

LNALNA LNALNALNALNA

Rx1 Fil

Rx2 Fil

Rx-Bypass

ANT0 Port

Bias Tee

BTS0 Port

To Antenna To Antenna

Tower Mounted Amplifier – Single Duplex

Bias Tee

Tx Fil

ANT Port

BTS Port

Bias Tee

BTS PDM

+12VAlarm

To BTS

LNALNA LNALNALNALNA

Rx1 Fil

Rx2 Fil

Rx-Bypass

To Antenna

TMA Naming Convention

• TA-G12FD– Twin GSM900 TMA with

fixed uplink gain of 12dB

• TA-C12FS03– Single CDMA850 TMA with

fixed uplink gain of 12dB– ’03’ denotes 3rd design

version

• TA – Tower Amplifier

• C – CDMA850• G – GSM900• E – EGSM900• D – DCS1800• P – PCS1900• W – WCDMA

• 12 – Uplink Gain 12dB• F – Fixed Gain• S – Singe TMA• D – Twin TMA

TMA Solutions

Type CDMA GSM EGSM DCS UMTS(AISG1.1)

Single 12, 18dB 12dB 12dB 12dB 12dB

Twin - 12dB 12dB 12dB 12dB

TA-G12FSGSM900 Single TMA

TA-D12FDDCS1800 Twin TMA

TA-W12FDAWCDMA TMA AISG1.1

Single TMA Dimension - TA-G12FS02

Dual TMA Dimension – TA-D12FD

Dual TMA Dimensions – TA-P12FD

250383.6

GSM1800 Dual Duplex TMA – TA-D12FD

Power Distribution Management Unit (PDM)

• Converts BTS voltage (-48VDC or +24VDC) to +12 VDC.• Power distribution to the TMA via a CIN.• Supervises TMA current consumption.

+12V +12V

BTS Sector

Tx/Rx Rx

Antenna

ANTANT

BTS BTS To BTS AlarmRelay Contacts

Power Distribution & Management

Unit A Unit B Unit C

-48V+24V GNDVIN

ALARM1Vout A Vout B POWER

ALARM2 ALARM1Vout A Vout B POWER

ALARM24515

Bias Tee (Current Injector)

• Injects dc power onto the feeder for the TMA.

• Acts as a surge protector.• N or 7/16 connectors in any

combination.• IP65, weather protected for

outdoor environment.

DCInput

TMA BTS

Spark gap

λ/4 λ/4

Current Injector – Outline Drawing

Current Injector – BT-Mx

Single Sector Cell with V-Pol Antennas

Single TMA

Bias tee

Single Sector Cell with X-Pol antenna

Tx/Rx Rx

Twin TMA

Bias Tee

3 Sectors Cell with V-Pol

3 Sectors Cell with X-Pol Antennas

Tx/Rx Rx

Twin TMA

Tx/Rx Rx

Twin TMA

Tx/Rx Rx

Twin TMA

Uplink Sensitivity Improvement with TMA

What is Noise?

• Noise comes from unavoidable thermal movements in all material. • This creates a “noise floor” that depends on:

– Boltzmann’s constant, k = 1.38 x 10-23 [K-1] – Temperature, T (normally 20 deg C = 293 K)– Bandwidth, B (normally calculated in one Hertz)

• This gives us the noise formula

• Noise power spectral density is the noise per Hz of bandwidth

• At room temperature,

• For 200kHz wide GSM channel, the thermal noise power is

( ) dBW log10 kTBPn =

( ) HzdBW log10 0 kTN =

HzdBm 1740 −=N

dBm 121−=nP

Amplifier Gain and Noise Figure

• The noise figure, NF, of a device is defined (in dB) as the difference in SNR between the i/p and o/p signals.

• In linear units, it is called noise factor, F.

( ) ( )( ) ⎥⎦

⎤⎢⎣

NSNSdBNF log10

Inputsignal Amplifier Output

signal

Gain = 5 dBNoise Figure = 2 dB

Thermal noisefloor

-110 dBm

Output signallevel-105 dBm

-121 dBm

-114 dBm

S/N = 9 dB

Thermal noisefloor

-121 dBm

-110 dBmInput signal

S/N = 11 dB

Calculation of Receiver Sensitivity

• Thermal noise floor is given by

• The noise at the input of a receiver is known as the receiver noise floor, and is given by

where NFr is the noise figure of the receiver

• The sensitivity of a receiver is given by

• For GMSK modulation, we need a detection SNR of 9 dB• If the receiver noise figure is 2 dB, then the sensitivity is

( )( ) dBm 30log10

dBW log10

kTBkTBPn

( ) dBW log10 rnr NFkTBP +=

SNRNFPSNRPP rnnrsens ++=+=

dBm 11092121 −=++−=sensP

NF in Cascade Amplifier Stages

InputAmp 1

Output

G1, NF1

Amp 2 Amp 3

G2, NF2 G3, NF3

• The overall noise figure, NFT, of a number of cascaded devices can be calculated from Friis' equation:

where gain and noise factor values are in linear units.

⎟⎟⎠

⎞⎜⎜⎝

⎛⋅⋅⋅+

−+= 11log10

GFFNFT

• The noise factor of the first stage contributes significantly to the overall noise figure.

TMA RF Impact

Gain + NF

Signal 1

Signal 2

TMA input Noise Thermal Noise floor

Signal at antennaterminal

Signal in to feeder

Signal afterfeeder losses

No TMA

Signal after TMA

Signal afterfeeder losses

With TMA

BTS without TMA

Example 1• Consider a GSM 1800 BTS

uplink arrangement as shown. • Assuming that a detection

SNR of 9 dB is needed, determine the minimum BTS receive power level needed (after the antenna).

Detection

DuplexerBTS

NF = 5 dBS/N = 9 dB

Loss = 1 dB

Loss = 3.3 dB

Jumper

Feeder cable7/8", 50 m

Loss = 0.5 dB

Antenna

Received power

RX sensitivity

BTS without TMA

Solution

• Thermal Noise Floor

• Receiver sensitivity

• Received power

dBmdBW

121 151

102002901038.1log10

log10323

−=−=

×⋅⋅×=

dBmPsens

07159121

−=++−=

01.715.03.35.01107

−=++++−=

Detection

DuplexerBTS

NF = 5 dBS/N = 9 dB

Loss = 1 dB

Loss = 3.3 dB

Jumper

Feeder cable7/8", 50 m

Loss = 0.5 dB

Antenna

Received power

RX sensitivitysensP

BTS with TMA

Example 2• Consider the BTS receive

system with TMA. • Determine the improvement in

the minimum BTS received power.

Detection

DuplexerBTS

S/N = 9 dB

Loss = 3.3 dB

Received power

RX sensitivity

NF = 1.4 dBGain = 12 dB

Loss = 0.3 dB Overall

Loss = 0.5 dB

NF = 5 dB

Loss = 1 dB

Loss = 0.5 dB

Loss = 0.5 dBNoise Figure

BTS with TMA

Solution

• Overall noise figure, NFT

• Received power

• Improvement in sensitivity

dB 12.305.2log10

5.017.038.1log101010

11010log10 106.51012

106.5104.1

⎥⎦

⎤⎢⎣

⎡ −+

08.415.012.39121

−=+++−=

( ) dB 70.64.1087.101 =−−−=

Detection

DuplexerBTS

S/N = 9 dB

Loss = 3.3 dB

Received power

RX sensitivity

NF = 1.4 dBGain = 12 dB

Loss = 0.3 dB Overall

Loss = 0.5 dB

NF = 5 dB

Loss = 1 dB

Loss = 0.5 dB

Loss = 0.5 dBNoise Figure

Sensitivity Improvement

Receiver Sensitivity. (TMA NF 1.5 dB, BTS NF 5 dB)

-111.00

-109.00

-107.00

-105.00

-103.00

-101.00

-99.00

-97.00

1 2 3 4 5Cable loss (dB)

No TMA

TMA Gain 6 dB

TMA Gain 12 dB

TMA Gain 15 dB

GSM1800 TMA Trial SiteCase Study

Performance Measurement

Handover Request Ratio due to• Uplink Signal (UL_RxLev)• Downlink Signal (DL_RxLev)• Uplink Quality (UL_RxQual)• Downlink Quality (DL_RxQual)• Power Budget (PB)

Drop Call Measurements• TCH Drop Call Rate (Drop #2)• Subscriber Perceived Drop Call Rate (Drop #3)• ErlangMin/Drop

Summary of Performance

• The uplink is stronger than the downlink (more HO due to DL).• Majority of the handovers are due to better servers (HO due to PB).• Generally, uplink quality has improved (lesser HO due to UQ).• Drop calls has reduced.• ErlangMin/Drop has increased to 85.81.• Neighbouring cells’ performance would also improve

– because calls that are handed over to them are due to better signal strength.

• Coverage or whether a subscriber can initiate a call is dependent on the downlink signals. In what used to be boundary coverage areas, the subscribers can now make AND expect to finish the calls.

Guidelines on Site Selection for TMA

• High TCH Drop Call Rate or High HO Failures,they are due to leak of uplink signal strength

• HO reason or Drop reason is due to poor uplink signal level and/or quality

• Handover due to Power Budget is low (~ 50% or less)• High feeder loss (> 2dB)• High BTS output power or low combining loss ，the downlink

coverage is big enough）• Link is “breaking” on uplink the uplink coverage is limited• No congestion in Both SDDCH and TCH

Case of Site Selection for TMA

• Analysing the following statistic of BSC 40, the duration is more than 1 week

• filter the site satisfied 1. DL_Lev-UL_Lev>02. Number of handover attempts due to uplink received strength (on

SDCCH)=03. %age of HO Attempts due to UL Lev>20%

{%HO_ATTEMPT_UL_LEV_LOW=HO_ATTEMPT_UL_LEV_LOW/( HO_ATTEMPT_UL_LEV_LOW+ HO_ATTEMPT_DL_QUAL_LOW+ HO_ATTEMPT_PBGT+ HO_ATTEMPT_DL_LEV_LOW+ HO_ATTEMPT_UL_QUAL_LOW )}

4. TCH in congestion rate(include handover)(%)=05. TCH in call drop rate(exclude handover)(%)>0;TCH in call drop

rate(include handover)(%)>06. Subscriber Perceived TCH Drop Call Rate >1%(Subscriber

Perceived TCH Drop Call Rate=TCH in call drop rate(include handover)(%))

Sites of Priority 1

Sites of Priority 2

Principle of Priority

• Priority 1 (P1): Sites with – HO Request due to weak UL Signal Strength > 20%, and Subscriber

Perceived TCH Drop Call Rate > 3%• Priority 2 (P2): Sites with

– HO Request due to weak UL Signal Strength > 20%, and Subscriber Perceived TCH Drop Call Rate 2% to 3%

• Priority 3 (P3): Sites with – HO Request due to weak UL Signal Strength > 20%, and Subscriber

Perceived TCH Drop Call Rate 1% to 2%

• If there is a “1” mark on the either one of the 3 columns, it means that one of the above criteria is satisfied, and a TMA is recommended based on the priority level.

• CMPak’s Drop Call target is < 3% for rural sites (low traffic) and <2%for urban sites (high traffic).

TMA System Installation

Connecting TMA to Antenna

• ANT port connects to Antenna port• BTS port connects to feeder cable

leading to BTS• TMA does not work in reverse

connection• Reverse connection will short DC

current supply short to groundANT0 ANT1

BTS0 BTS1

Tx/Rx Rx

Antenna

Mounting of TMA

• TMA is pre-fixed with mounting brackets• TMA can be mounted on wall using 4xM8 masonry bolts • For pole mounting, ring clamps are used to fasten the TMA onto the

Bias Tee Connection

• ANT port connects to feeder cable leading to antenna• BTS port connects to feeder cable leading to BTS• Two types of bias tee :

Model Connector Type

ANT 7/16 DIN-Female

BTS 7/16 DIN-Male

ANT 7/16 DIN-Male

BTS 7/16 DIN-FemaleBT-M2

Bias Tee Connection

• Bias tee must be position in front of lightning protection devices• Lightning protection devices placed in front of bias tee will caused

bias tee to malfunction

ANTENNA

BTSBTS

lightning protection devices

Connecting Bias Tee to PDM

• Bias tee is connected to PDM using RG174-KW3 cable

Power cable (RG174-KW3)

PDM Connection

• Connection at VIN port is polarity independent• Alarms are send via cable connected from Alarm 1 connector to

BTS installation

Main power supply: +24VDC or -48VDC BTS external

PDM Power Cable

Alarms

• Alarms are activated under the following circumstances– +12VDC power module failure– Broken connection between PDM and Bias tee– TMA LNA failure

• Alarm 1 pin configurations

• When alarm occurs, PIN 1-2 or 3-4 will become shorted/closed

PIN 1 2 3 4

Function Normally Open

Common Common Normally Open

LED Indicators on PDM

• Two LEDs for TMA alarms and one LED for power supply alarm• Green = Normal; Red = Alarm

Power supply alarmTMA alarms

TMA SYSTEM CONNECTION

THANK YOU

Jin Gang Mei

Project Manager

JG.Mei@comba-telecom.com00923135136086

tma systems for gsm and dcs(20091214)

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