WIRELESS COMMUNICATION LAB MANUAL (SUBJECT CODE: )

Transcription

1 2012 WIRELESS COMMUNICATION LAB MANUAL (SUBJECT CODE: ) DEPARTMENT OF ELECTRONICS & COMMUNICATION ALPHA COLLEGE OF ENGGINEERING & TECHNOLOGY

2 1 Study of the Tx IQ/Rx IQ signals. Apparatus: 1. Mobile Phone Traine ST2132 kit 2. C.R.O 3. C.R.O Probes Procedure : 1. Insert the SIM and power On the trainer. 2. Make a Call to the trainer or from the trainer 3. Keep the Call On. Connect the probe of spectrum analyzer at TP (1) and observe the signal in the Tx band. Now connect the probe to TP (2) observe the signal in the Rx band. Connect two probe of CRO one at TP (3) & the other on TP (4) observe the Rx burst. A similar Tx burst can be observed by connecting probe TP (5) & (6) respectively. Signal figure shows an IQ Tx/Rx burst signal Conclusion: 1

3 2 Observe signal constellation of GMSK signal. Apparatus: 1. Mobile Phone Trainer ST2132 kit 2. C.R.O 3. C.R.O Probes Procedure: 1. Make a call to the trainer. 2. Receive the call and keep On. 3. Connect two probe of CRO one at TP (3) & the other on TP (4) observe the Rx burst signal. Conclusion: 2

4 3 Study the working of Audio IC and observe Audio Signal. Apparatus: 1. Mobile Phone Traine ST2132 kit 2. C.R.O 3. C.R.O Probes Theory : COBBA ASIC provides an interface between the base band and the RF-circuitry.COBBA performs digital to analog conversion of the received signal. For transmit path COBBA perform analog to digital conversion of the Transmit Amplifier Power Control Ramp and the In-phase and Quadrate signals. A slow speed digital to analog converter will provide automatic frequency control (AFC). COBBA is at any time connected to CPU (ASIC) with two interfaces, one for transferring Tx and Rx data between CPU and COBBA and one for transferring codec Rx/Tx samples. The audio control and processing are taken care by the COBBA-IC, which contains the audio codec and CPU. CPU contains MCU and DSP blocks, handling and processing the audio signals. The inputs can be taken from an internal microphone, a headset microphone or a hand free unit. The microphone signals from different sources are connected to separate inputs at the COBBA ASIC. Input for the microphone signals are differential type. Input and output selection and gain control is performed inside the COBBA ASIC according to control messages the CPU. DTMF and other audio tones are generated and encoded by the CPU and transmitted to COBBA IC for decoding. Audio Block 3

5 COBBA IC and CPU Communicate through a PCM Serial Interface. The interface consists of following signal: a PCM codec master clock (PCMDCLK), a frame synchronization signal to DSP (PCMSCLK), a codec transmit data line (PCMTX) and a codec receiver data line (PCMRX). The COBBA-IC generates the PCMDCLK clock, which is supplied to DSP. The COBBA-IC also generates the PCMSCLK signal to DSP by dividing the PCMDCLK. The PCMDCLK frequency is MHz and is generated by dividing the RFICIK 13 MHz by 13. The COBBA-IC further divides the PCMDCLK by 125 to get a PCMSCLK signal 8.2 KHz. AFC Function: AFC is used to lock the transceiver frequency to the frequency of the base station. AFC voltage is generated in COBBA with 11 bit DA converter. There is an RC-filter in AFC control line to reduce the noise from the converter. They are AFC tracks base station frequency continuously, so transceiver has got a stable frequency. Note : Before performing the observation, fully charge the battery and keep the charging On. Procedure: 1. Connect the probe of CRO to TP (8). 2. Make a Call to the trainer or from the trainer. 3. Ask the person on the line to speak and observe the audio frequency changes. Conclusion: 4

6 4 To study and verify the performance of SIM Detection. Apparatus: Procedure: 1. Mobile Phone Traine ST2132 kit 2. C.R.O 3. C.R.O Probes 1. Insert the SIM card 2. Switch ON the Trainer 3. Observe the LEDs all two LEDs will glow RST, VSIM stays ON. Since SIM card need power continuously & CLK goes with in 6-8 sec approximately, after switching on the trainer that s after registering to the network. A rise can be observed when there is a Tx/Rx of call or some function is accessed the clock of 3.2MHz (approximately). Sample Observation Table: Pin Name Measured parameter TP No. 1 SIM Supply Voltage 23 2 SIM RST Voltage 24 3 SIM CLK Frequency 25 4 SIM Supply Voltage 27 5 SIM Data Voltage 28 Observation Table: Pin Name Measured parameter TP No Conclusion: 5

7 5 Study and Measure the PWM signal of the Vibrator Apparatus: 1. Mobile Phone Traine ST2132 kit 2. C.R.O 3. C.R.O Probes Procedure: 1. Give a Call to mobile phone trainer and keep on ringing or press Menu and scroll with the help of up/down buttons until you find Tone select, then Ring Tone select and scroll a step up or down. 2. And wait until you observe the vibrator rotating. 3. Connect probe of the CRO to TP (39). PWM signal is observed. Since make/break phenomena rise/fall of the signal is obtained and vibrator will rotate. Fault Insertion: Make the pin (2) of switched faults 5 to OFF position. No Vibration (Even After Menu Activation) Fault Finding: Observe the signal TP (39) it will not be there and hence no vibration. Working principle: Since PWM signal is must for the Vibrator. It is due to problem in the CPU, UI IC or disconnection of path else faulty Vibrator. Conclusion: 6

8 6 Study and Analyze the Buzzer in a GSM Handset and measure the PWM signal of the Buzzer. Apparatus: 1. Mobile Phone Traine ST2132 kit 2. C.R.O 3. C.R.O Probes Theory: Alerting tones or melodies are generated by a buzzer, (Marketing Target 105dB.) Ringing driving circuit is mainly made by CPU, Driving IC N400 and Buzzer. Whenever there is an incoming call or message else ringing is software activated. Ringing Driving Control signal that s a PWM signal is obtained from pin no. D9 of Central Processing Unit (CPU) and given to pin number 3 of IC N400. After amplification in this IC this signal is made out from pin no.6 and reaches at one tapping of buzzer. Second tapping of buzzer is connected with VBATT ring sound is obtained from buzzer. In tables shows the relevant specifications Block Diagram Procedure: 1. Give a Call to trainer by making an incoming call and keep on ringing same as vibrator. 2. Connect probe of the CRO to TP (38). PWM signal is observed. Since make/break phenomena rise/fall of the signal is obtained and ring is heard. 7

9 Fault Insertion: Make the pin (1) of switched faults 5 to Off position. No Ring Sound Fault Finding: Observe the signal, it will not be there. Working principle: Since PWM signal is must for the Buzzer. It is due to problem in the CPU, UI IC or disconnection of path else faulty buzzer. Conclusion: 8

10 7 To study Global System for Mobile Communication (GSM) Data services & capability.. Apparatus: 1. GSM antenna and coaxial cable. 2. RS-232 Serial cable for interfacing to PC. 3. Hands free kit is all the time connected with serial cable. 4. Adaptor supplied is the only power source for trainer & must be connected when trainer is in use. 5. SIM is must for AT commands related to SIM & making calls. Theory: The Global System for Mobile Communications (GSM) is an international digital cellular telecommunications standard. The GSM standard was released by ETSI (European Standard and Technology Institute) back in First commercial services were launched in After its early introduction in Europe, the standard went global in 1992 when GSM services were introduced in Australia. Since then, GSM has become the most widely adopted and fastest-growing digital cellular standard, and it is positioned to become the world's dominant cellular standard. In fact, as of January 1999, GSM accounted for more than 120 million subscribers, according to the GSM memorandum of understanding (MoU) Association. With 324 GSM networks in operation in 129 countries, GSM provides almost complete coverage around the globe. Sample response on GSM trainer for various standards ETSI AT command as follows: AT OK AT+CIMI /* IDEA SIM IMSI */ OK AT+CGSN

11 OK AT+CMGR=1 /* Checking SMS & received it in text format */ +CMGR: "REC READ","Airtel", 06/05/24,10:51: 10+22" Dear Customer Register, View and Pay your Airtel Bills online at and you could be the lucky one to get waiver in your Airtel bill.t&c apply. OK AT+CMGR=3 +CMGR: "REC READ","ETISALA",,"06/03/11,20:30:43+16" Etisalat, UAE national telecom provider welcomes you. Subscribe to AHLAN Visitor service & make first call home for FREE plus 9 free SMS. For info call 10 OK RING RING /* Incoming call */ +CLIP: " ",145 ATA /* Incoming call accepted */ +WIND: 9 OK ATH /* Call disconnected /* OK ATDL /* Command to redial last number */ ; +WIND: 14 /* SIM Removed & its indication */ AT+CGMI /* Manufacturer command */ WAVECOM MODEM OK AT+COPS=? /* Network list */ Note: AIRTEL (Service provider) SIM used. +COPS: (2,"AirTel","AirTel","40493"),(3,"","","40467"),(3,"IDEA","IDEA","40478"),(3,"CellOne","CellOne","40458") OK Conclusion: 10

12 8 Theory: To study amplitude modulation in MATLAB Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent. The amplitude modulated signal is defined as: AM = E (1 + m.cosμt) cosωt = A (1 + m.cosμt). B cosωt = [low frequency term a(t)] x [high frequency term c(t)] Here m is the modulation index, u is the modulating frequency and w is the carrier frequency. PROGRAM: clear all close all m=0.5 n=3 fc=30000 fm=2000 t=1:0.001:10 g=cos(2*3.14*fm*t) %modulating signal u=cos(2*3.14*fc*t) %carrier signal k=m*g o=n*g w=1+o e=1+k l=ec*u p=l.*e %modulated signal for m<1 q=l.*w %modulated signal for m>1 c=1+g a=l.*c %modulated signal for m=1 subplot(5,1,1) plot(t,g) xlabel('time') ylabel('amplitude') title('modulating signal') subplot(5,1,2) plot(t,u) xlabel('time') ylabel('amplitude') title('carrier signal') subplot(5,1,3) plot(t,p) 11

13 amplitude amplitude amplitude amplitude amplitude xlabel('time') ylabel('amplitude') title('modulation for m<1') subplot(5,1,4) plot(t,q) xlabel('time') ylabel('amplitude') title('modulation for m>1') subplot(5,1,5) plot(t,a) xlabel('time') ylabel('amplitude') title('modulation for m=1') OUT PUT: 1 modulating signal time carrier signal time modulation for m< time modulation for m> time modulation for m=1 2 0 Conclusion: time 12

14 9 To study BER performance of BPSK system in AWGN channel Theory: Additive white Gaussian noise (AWGN) is a channel model in which the only impairment to communication is a linear addition of wideband or white noise with a constant spectral density(expressed as watts per hertz of bandwidth) and a Gaussian distribution of amplitude. PROGRAM: clc; clear all; format long; N=50000; f=sqrt(0.5); index=1; for k=1:2:10 x=10^(k/10); % SNR in db p=sqrt(1/x); bera(index)=0.5*erfc(sqrt(x)); data=randint(1,n); x=2*data-1; Output n=f*(randn(1,n)+j*randn(1,n)); y=x+p*n; d=real(y); for kk=1:n if(d(kk)>=0) data_detect(kk)=1; else data_detect(kk)=0; end end error=xor(data,data_detect); bers(index)=sum(error)/n; snr(index)=k; [snr(index) bera(index) bers(index)] N=N+10000; index=index+1; end semilogy(snr,bera,'-bd',snr,bers,'- -ro'); grid on; legend('analytical','simulation') xlabel('snr db'); ylabel('ber'); Conclusion: 13

15 10 To study and perform modulation and demodulation QPSK signal through AWGN channel. BLOCK DIAGRAM: OUTPUT: 14

16 CONCLUSION: 15

17 11 To study and perform modulation and demodulation 8 - PSK signal through AWGN channel. BLOCK DIAGRAM: OUTPUT 16

18 CONCLUSION 17