The Performance Improvement of BASK System for Giga-Bit MODEM Using the Fuzzy System

Transcription

1 Int. J. Communcatons, Network and System Scences, 10, 3, 1-5 do:10.36/jcns Publshed Onlne May 10 ( The Performance Improvement of BASK System for Gga-Bt MODEM Usng the Fuzzy System Abstract K-Hwan Eom 1, Kyo-Hwan Hyun 1, Kyung-Kwon Jung 1 Department of Electronc Engneerng, Dongguk Unversty, Seoul, Korea Department of Electronc Engneerng, Hanlm Unversty, Chuncheun, Korea E-mal: khwanum@dongguk.edu Receved August 1, 09; revsed December 15, 09; accepted March 17, 10 In ths paper we propose an automatc bandwdth control method for the performance mprovement of Bnary Ampltude Shft Keyng (BASK) system for Gga-bt Modem n mllmeter band. To mprove the performance of the BASK system wth a fxed bandwdth, the proposed method s to adjust a bandwdth of low pass flter n recever usng the fuzzy system. The BASK system conssts of a hgh speed shutter of the transmtter and a counter and a repeater of recever. The repeater conssts of four stage converters, and a converter s constructed wth a low pass flter and a lmter. The nputs to the fuzzy system are the remnder and ntegral of remander of counter, and output s a bandwdth. We used a algorthm to fnd the optmum detecton from output of the counter. Smulaton results show that the proposed system mproves the performance compared to the fxed bandwdth. Keywords: BASK, Gga-Bt MODEM, Bandwdth, Low Pass Flter, Fuzzy System 1. Introducton The 60 GHz band stll beng free and unlcensed, a large bandwdth, for example of the order of 1 GHz, and easly be used. In dgtal modulaton of the 60 GHz band, a problem s ISI (Inter Symbol Interference) [1]. Dgtal base band sgnals often are rectangular pulse tran. When rectangular pulses are passed through a band lmted channel, the pulses wll spread n tme, and the pulse for each symbol wll smear nto the tme ntervals of succeedng symbols. Ths causes ISI and leads to an ncreased probablty of the recever makng an error n detectng a symbol. There are many methods to mnmze ISI as lkelhood sequence estmaton, whtened matched flters and decson-feedback equalzaton []. One approach to mnmzng ISI s to use pulse shapng technques. The most popular pulse shapng flter used n moble communcatons s the rased cosne flter. However, the maxmum value of the RF waveform and rased cosne fltered pulses do not always match [-]. Also, n Heterodyne method, IF process s gven gan of recever, but an ncrease n analog converson steps, the more the prce wll also ncrease. The BASK system conssts of a hgh speed shutter and a mxer of the transmtter, and a counter and a repeater of the recever for solves these problems. The hgh speed shutter of the transmtter s ntroduced for pulse shapng, whch can mnmze ISI. Usng repeater for mprove SNR and make rectangular pulse tran. The repeater conssts of few stage converters. A converter s constructed wth a low pass flter and a lmter. In ths paper propose an automatc bandwdth control method for performance mprovement of BASK system. Propose method s that adjust a bandwdth of low pass flter n recever usng the fuzzy logc system. The fuzzy logc system s normally used to formulate human knowledge, but here we create the membershp functons and the fuzzy rule base by means of the smulaton results. The nputs of the fuzzy logc system are the remnder and ntegral of remander of counter, and output s bandwdth. We use 8 bt counter and algorthm wth soft decson. Rule base nference was accomplshed usng the max-mn nference procedure. Defuzzfcaton of the bandwdth output was acheved the center of gravty computaton. In order to verfy the effectveness of the proposed method, smulatons were performed by fxed bandwdth and BER.. BASK System wth a Fxed Bandwdth In mllmeter wave band, BASK system wth a fxed

2 K.-H. EOM ET AL. bandwdth of Gga-bt MODEM wthout IF process usng hgh speed shutter for pulse shapng of nput sgnal and mnmze ISI n the transmtter, and usng repeater for mprove SNR and make rectangular pulse tran n recever. Fgure 1 shows the block dagram of BASK system wth a fxed bandwdth. In the transmtter, RCS s rased cosne sgnal generator. The transmtter uses a hgh speed shutter that can truncate the sde lobe of the rased cosne flter. A shutter performs swtchng wndow. The output of a shutter s gven by sn( t/ Ts ) () t, n 1 hs () t t (1) 0, n 0 Where () t s a gan for the symbol perod, s the roll off factor, t s the tme, T S s the symbol perod, and n s the state of the symbol. A shutter functon s to make a constant envelope. The recever uses a repeater wthout IF (Intermedate Frequency) that conssts of two stage converters. A converter s constructed wth the LPF and the lmter. Desgn parameters of converters are bandwdth of the LPF (BLPF) and stffness of the lmter (SL: Stffest Lmter). The theoretcal soluton s gven by y () t SL( G x ()) t () Where G x () t s the nput of the lmter, y () t s the output of the converter, SL s a transfer functon of the lmter. The block dagram of a converter s shown n Fgure. Pulse tran Encoder Shutter Mxer LPF Amp The repeater can mprove sgnal-to-nose rato (SNR), and make rectangular pulse tran. 3. Proposed Method The block dagram of proposed automatc bandwdth control s shown n Fgure 3. The proposed method s that adjust the bandwdth of low pass flter n recever usng a fuzzy logc system. The output of counter n recever depends on the pattern sequence deeply, so we need the controls for the ranges of bandwdth to mprove the performance of the system. The nputs to the fuzzy logc system are the remander and ntegral of remander of counter, and output s a bandwdth. In order to create the membershp functons and fuzzy rule base, we smulated on remnder and ntegral of remnder of counter. The smulaton results of the remnder and ntegral remnder of 8 bt counter s shown n Fgure. In Fgure, we can study that the sum of remnder jumps f a bg remnder happens n negatve or postve. Therefore we apply the bandwdth control usng the fuzzy logc system due to such stuatons. The nputs are fuzzfed accordng to the nput membershp functons and output membershp functons n Fgures 5 and 6. The fuzzy rule-base conssts of a total of 15 rules. The LPF x (t) Gan Gx (t) output σ 1 nput y (t) RCS A c cos( f t) Fgure. The block dagram of a converter. (a) The transmtter BDF Amp Rectfler LPF Amp DC cut flter BDF Amp Rectfler LPF Amp DC cut flter Pulse tran Decoder Counter nth 1th Pulse tran Decoder F y look Counter nth 1th (b) The recever U n U 1 Repeater U n U 1 Repeater Fgure 1. The block dagram of BASK system wth a fxed bandwdth. Fgure 3. The block dagram of proposed bandwdth control system.

3 K.-H. EOM ET AL. 3 Integral of remander Integral of remander 0 (b) Broad bandwdth Fgure. Smulaton of counter for bandwdth control (a) Narrow bandwdth (a) Remander - Integral of remander (b) Integral of remander 0 Fgure 5. The membershp functon of fuzzy nput (b) Optmal bandwdth - Fgure 6. The membershp functon of fuzzy output. nput/output fuzzy relaton s chosen on the bass of the smulaton results as shown n Table 1. In Table 1, R and IR are remander and ntegral of remander. Lngustc Varables are NB (Negatve Bg), NM (Negatve Medum), NS (Negatve Small), N (Negatve), Z (Zero), P (Postve), PS (Postve Small), PM (Postve Medum) and PB (Postve Bg).

4 K.-H. EOM ET AL. Table 1. Fuzzy rules. IR R NB NS Z PS PB N PB PM PS Z NS Z PM PS Z NS NM P PS Z NS NM NB Average bt error rate BW control BW fx Rule base nference was accomplshed usng the maxmn nference procedure. Defuzzfcaton of the bandwdth output was acheved the center of gravty computaton [5].. Smulaton In order to verfy the effectveness of the proposed method, Smulatons were performed usng MATLAB. The carrer frequency was 60 GHz and message data rate was 1 Gbps. In order to mprove SNR, t s better to change angle of lmter as θ 1 < θ < θ 3 < θ, and these parameters are not requred exact value. algorthm parameters are constran length k = 7, codng rate = 1/, and generator polynomnals for octal codes are 171, 133 [6]. Fgure 7 shows the average BER for the sgnal pror to repeater and the sgnal posteror to repeater usng algorthm. In Fgure 7, SNR of non-shutter, the non-repeater, and the repeater s 31 db, 30 db, and db respectvely when the BER s Fgure 8 shows the average BER for the fxed bandwdth and automatcally controlled bandwdth by fuzzy logc system. In Fgure 8, the proposed automatc bandwdth control method by fuzzy logc system s mproved the SNR Average bt error rate BER performance repeater non-repeater non-shutter Carrer to nose rato E s /N 0 /db Fgure 7. BER performance for the repeater Carrer to nose rato E s /N 0 /db Fgure 8. Smulaton of BER performance. about 8 db at BER of 10-3 aganst the case of fxed bandwdth. 5. Conclusons In ths paper proposed a method for mprovng the performance of the BASK system for automatcally tunng the bandwdth of LPF. The BASK system was constructed a hgh speed shutter of transmtter and a repeater of recever. The shutter was ntroduced for pulse shapng to mprove the ntersymbol nterference and the repeater conssts of few stage converters, and a converter was constructed wth a low pass flter and a lmter. Proposed method was usng fuzzy logc system. Fuzzy nputs were remander and ntegral of remander of counter. Output was bandwdth. In order to verfy the effectveness of the proposed method, smulatons were performed by fxed bandwdth and BER. The smulaton results are summarzed as follows: Fuzzy System has nputs, 1 output, 15 the number of fuzzy rules. So that can be confgured smply. SNR of non-shutter, the non-repeater, and the repeater s 31 db, 30 db, db, respectvely at BER of The proposed method s mproved the SNR about 8 db at BER of 10-3 aganst the case of fxed bandwdth. 6. References [1] V. R. M. Thyagarajan, R. H. M. Hafez and D. D. Falconer, Broadband Indoor Wreless Communcaton n ( ~ 60) GHz Band: Sgnal Strength Consderatons, Unversal Personal Communcaton, Vol., October 1993, pp [] T. S. Rappaport, Wreless Communcatons, nd Ed-

5 K.-H. EOM ET AL. 5 ton, Prentce Hall, New Jersey, 0. [3] E. Lndskog and A. Paulraj, A Transmt Dversty Scheme for Channels wth Intersymbol Inference, Proceedngs of IEEE Internatonal Conference on Communcatons, New Orleans, Vol. 1, June 00, pp [] S. Haykn, Communcaton Systems, th Edton, John Wley Inc., Canada, 00. [5] R. Johnston, Fuzzy Logc Control, GEC Journal of Research, Vol. 11, No., 199, pp [6] M. Hosemann, R. Habendorf and G. P. Fettwes, Hardware-Software Codesgn of A 1. Mbt - 6 State - Decoder for An Applcaton-Specfc Dgtal Sgnal Processor, Proceedngs of IEEE Workshop on Sgnal Processng Systems 03, Seoul, 79 August 03, pp. 5-.