final TH-FH-PPM UWB

Frequency and Time Hopping PPM UWBMultiple Access Communication Scheme : 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme JOURNAL OF COMMUNICATIONS, VOL. 4, NO. 1, FEBRUARY 2009 Frequency and Time Hopping PPM UWBMultiple Access Communication Scheme Presented by ENG. AMGAD A.ELATY Under supervision of Prof.Dr.Eng.GAMAL A.ALFADEL © 2009 ACADEMY PUBLISHER جامعة حلوان كلية الهندسة جامعة حلوان قسم هندسة الإلكترونيات والاتصالات والحاسبات

CONTENTS : 

CONTENTS objective I. INTRODUCTION II. SIGNAL AND SYSTEM MODEL III. MULTIPLE ACCESS INTERFERENCE AND ERROR PROBABILITY ANALYSIS IV. SIMULATION RESULTS V. CONCLUSION Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme

Objective : 

Objective Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme 1- Model frequency and time hopping pulse position modulation (FTH-PPM) ultra wideband (UWB) for multiple access communications. 2- derived and analysis the bit error probability for the multi-user synchronous transmitter case in multipath channels with Additive White Gaussian Noise (AWGN). 3- Simulation results show that bit error probability performance and multiuser capacity of FTH-PPM UWB is much better than (TH-PPM) UWB system.

UWB Spectrum : 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme UWB Spectrum 1.6 1.9 2.4 Bluetooth, 802.11b Cordless Phones Microwave Ovens PCS 5 802.11a -41 dBm/Mhz “Part 15 Limit” UWB Spectrum Frequency (Ghz) 10.6 3.1 Spectrum allocation overlays existing users 1- power level is very low to minimize interference Suitable for battery-operated devices Low power is CMOS friendly 2- Large B.W (very high capacity) 6- High data rate for short distance Data rate scales with the shorter pulse widths made possible with ever faster CMOS circuits 3- Carrierless (no mixer) 4- Low sensitivity to fading 5- Material penetration capability I-INTRODUCTION

Slide 5: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme the presence of multiple signals being transmitted at the same time is a typical source of interference for wireless signals. There are several multiple access schemes proposed for UWB : Time Hopping (TH) , Frequency Hopping (FH) and Direct Sequence (DS) wherein orthogonal codes (OFDM) used to avoid (MAI) , by designing orthogonal hopping sequences . However, in practice, the received signal from different users are not orthogonal because of multipath and asynchronous transmission. Moreover, it is not possible to design orthogonal codes for all shifts. In TH, MAI can be reduced by increasing the number of time hops but at the cost of reduced data rate. Frequency Hopping OFDM shows that MAI can be completely removed under synchronized multiple access communication.

Slide 6: 

II. SIGNAL AND SYSTEM MODEL The frequency and time hopping M-ary PPM system model for Vth user is given by : --- (1) For M-ary PPM, signal amplitude so that (1) can be written as : --- (2) Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme

Slide 7: 

The frequency and time hopping M-ary PPM system model for V th user --- (1) Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme

Slide 8: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme Figure 1. Principle of frequency and time hopping UWB system The UWB pulse is transmitted in any one time slot occupying Tc seconds and Bf bandwidth.

Slide 9: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme The received signal from multipath channel for each user is: --- (3) is AWGN noise with power spectral density unknown multipath channel given by: --- (4) multipath gain co-efficient of user in path the multipath delay --- (5)

Slide 10: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme III. MAI AND ERROR PROBABILITY MAI is the factor limiting the performance and capacity of the system when more than one user is active. It can be modeled as a zero mean Gaussian random variable if number of users are large . Assuming M-ary PPM signal to be orthogonal (i.e ) the MAI and error probability analysis is carried out as follows. In order to evaluate MAI , we make the following assumptions: (a) is the number of active users, and the noise n(t) are assumed to be independent. (b) The time hopping sequence and multipath time delay are assumed to be independent and identically distributed (iid) over the time interval (c) The frequency hopping sequence is assumed to be (iid) over the frequency band B. (d) Perfect synchronization is assumed at the receiver, i.e is known at the receiver. Assume that and that the desired user corresponds to .

Slide 11: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme Figure 2. System model of FTH-MA M-ary PPM UWB system Note : No mixer (carrierless) M-ary correlator --- (6)

Slide 12: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme --- (7) Assuming PPM signal (Sm) is transmitted by user 1 --- (8) Where : Eg .. Average signal energy NMAI.. MAI component N .. AWGN component

Slide 13: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme --- (9) --- (10)

Slide 14: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme --- (11) --- (12)

Slide 15: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme The double differentiated Gaussian pulse is defined as : --- (13) The autocorrelation of double differentiated Gaussian pulse is then given by : --- (14) --- (15) (16)

Slide 16: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme (17) (18) (19) due to frequency hopping, (20) Increased with Ns , Eg , Nu decreased with Nth , Nfh the average probability of error for a single user under multiple access interference for binary PPM is given by : (21) Variance of AWGN

Slide 17: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme IV. SIMULATION RESULTS doubling the number of time hops Nth=2 and a repetition coding Ns=2 BER performance improves by an average of 3 db increase in number of time hops reduces the data rate. Fixed freq. hopping Nfh=1

Slide 18: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme Fixed time hopping Nth=256 doubling the frequency hops Nfh=2 gives improvement of 1 dB at BER of . This improved performance is due to a reduction in Multi-access and intersymbol interference. introduction of frequency hopping along with time hopping gives an improvement of 3 dB repetition coding Ns=2 gives improvement for BER

Slide 19: 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme BER vs. Number of users the probability of error decreases with the FH as a result of which more users is supported for a given BER. for a given BER, by Nfh=2 two more users can be accommodated.

V- CONCLUSION : 

Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme We have proposed and analyzed bit error probability performance of frequency and time hoping PPM UWB multiple access communication. We have derived an expression for the bit error probability for multi-user synchronous transmitter case. It is observed that introduction of frequency hopping along with time hopping improves BER performance by an average of 4 dB. Further, doubling the number of frequency hops improves BER performance by 1 dB. The proposed technique improves BER performance without reducing the data rate. V- CONCLUSION

THE END : 

THE END Frequency and Time Hopping PPM UWB Multiple Access Communication Scheme بسم الله الرحمن الرحيم ربنا لا تؤاخذنا إن نسينآ أو أخطأنا* ربنا ولا تحمل علينآ إصراً كما حملته على الذين من قبلنا* ربنا ولا تحملنا مالاطاقة لنا به *واعف عنا واغفر لنا وارحمنا* انت مولانا فانصرنا على القوم الكافرين* صدق الله العظيم