Hybrid M-FSK/DQPSK Modulations for CubeSat Picosatellites

Transcription

1 RADOENGNEERNG VOL. NO. 1 APRL Hybrid M-FSK/D Modulation for CubeSat Pioatellite vo VEŘÁ Jan MRÁZ Dept. of Applied Eletroni and eleommuniation Univerity of Wet Bohemia in Pilen Univerzitni Pilen Czeh Republi ivertat@kae.zu.z janmraz@kae.zu.z Abtrat. Conventional CubeSat radio ytem typially ue one of everal bai modulation uh a AFSK GMSK BPSK and OOK or with between them on demand if poible. hee modulation repreent a balaned trade-off between good energy effiieny of high order M-FSK modulation and good petral effiieny of high order M-AM modulation. Utilization of modulation with the bet energy effiieny i not poible due to trit limit on oupied frequeny bandwidth. n thi paper the propoed group of hybrid modulation and propoed hybrid modulator and demodulator are preented. Novel olution offer intereting poibilitie of inreaing petral effiieny a well a energy effiieny of bai M-FSK modulation by embedding D ymbol between two M-FSK ymbol. Suh group of hybrid modulation offer uitable propertie for pioatellite e.g. imple realization onboard the pioatellite better energy and petral effiieny low PAPR wide range of adaptation by hanging the order of M-FSK uitable for eay non-oherent demodulation good immunity to Doppler effet with DM- FSK oding. Keyword CubeSat pioatellite ommuniation ytem adaptable modulation hybrid modulation. 1. ntrodution Sine 009 the PilenCUBE pioatellite i developed at the Univerity of Wet Bohemia in Pilen. One of our main goal i to enhane the uability of CubeSat pioatellite by inreaing the data throughput on downlink (data tranmiion toward ground tation). For thi purpoe it i neeary to ue adaptation of tranmiion to atual pae link hannel ondition and to ue a modulation with good energy effiieny and uffiient petral effiieny. For ommon modulation inreaing the energy effiieny dereae the modulation petral effiieny and vie vera [1]. Moreover the modulation with high petral effiieny (M-AM) are ompliated by need of amplifying in linear amplifier with low power effiieny []. hat i why ontant envelope modulation with a low peak to average power ratio (PAPR) are preferred in Cube- Sat projet [3]. Fig. 1. PilenCUBE pioatellite with deployable olar ell. herefore for an adaptable ommuniation ytem we are limited to a mall group of onvenient modulation with an eay implementation uing low power onuming pioatellite hardware. M-FSK modulation have a good energy effiieny and uitability for a non-oherent demodulation; however their petral effiieny i poor []. Better utilization of ignal pae dimenionality an inreae the petral and alo energy effiieny a it i preented in thi paper.. Hybrid Modulation Deign ntereting idea for inreaing energy and petral effiieny of modulation wa found in [] [5]. For thee purpoe hybrid modulation (two parameter of arrier modulated at the ame time) are ued. n [] the hybrid modulation M-FSK/ and diret bit demodulation (DBD) reeiver were deribed. n [5] hybrid M-FSK/ AM modulation were deribed. However both olution are not uitable for pioatellite ommuniation ytem due to hardware omplexity or ignal omplexity when the adaptation i required. he adaptation of ommuniation ytem with hybrid modulation i preented in [6] but in thi paper only withing between M-FSK and M-AM i onidered true hybrid modulation (two parameter of arrier modulated at the ame time) were not ued. n thi paper true hybrid modulation are deigned in relation to pioatellite ytem requirement and pae link harateriti.

2 390. VEŘÁ J. MRÁZ HYBRD M-FSK/D MODULAONS FOR CUBESA PCOSAELLES Our olution an offer a imple hardware realization in pioatellite (baed on memory addreing) with adaptation mehanim robutne to the pae link behavior (Doppler frequeny hift phae traking diffiulty fading) and modern approah to the radio amateur reeiver ontrution baed on hardware frequeny down onverion in ommon reeiver followed by FF ignal proeing in peronal omputer. hi i important due to large number of radio amateur ground tation whih an o-operate around the world for pioatellite telemetry downloading. he FF ignal proeing in PC after frequeny down onverion i inpired by Dream open oure projet for oftware demodulation of Digital Radio Mondiale broadating (DRM) [7]..1 nreaing of Signal Spae Uage he bai M-FSK modulation (with a et of M orthogonal frequenie) reate an M-dimenional ignal pae. With inreae of M the ditane between ymbol tay the ame due to dimenion ortogonality in omparion to the onventional M-AM or M-PSK modulation where the ditane between ymbol dereae a M inreae beaue we tay in two dimenion. hi lead to intereting behavior of M-FSK in omparion to M-AM and M-PSK. With the ame ignal quality (E b /N 0 ) inreae of M dereae bit error rate for M-AM and M-PSK thi ha a revere dependene. n other word inreaing the order of M ha an inreae in energy effiieny a onequene for M-FSK. However a M inreae the petral effiieny of M-FSK dereae. M-FSK modulation an alo be imagined a a et of ASK modulation with on-off ignaling at ubarrier orthogonal frequenie. More detail for bai M-FSK M-AM and M-PSK modulation propertie omparion an be found in [1] with a imple dedution f f f f Fig.. Signal pae of hybrid -FSK/ modulation. A better ignal pae utilization an be realized by antipodal or bi-orthogonal ignaling on ubarrier. n the firt ae (antipodal ignaling) a BPSK ymbol i embedded between two ymbol of M-FSK modulation. n the eond ae (bi-orthogonal ignaling) a ymbol i embedded between two neighboring ymbol of M-FSK modulation. n [] thi i alled hybrid M-FSK/ modulation. With the ame ignal power and frequeny bandwidth more bit an be tranmitted o the petral effiieny and energy effiieny i inreaing in omparion with onventional M-FSK. For example the hybrid -FSK/ modulation ha a ignal pae a preented in Fig.. During the ymbol period one of 16 different ymbol an be tranmitted. oding an be realized on M-FSK ide a well a on ide of hybrid modulation to obtain poibilitie of non-oherent demodulation.. Bai Hybrid M-FSK/D Modulation he hybrid M-FSK/D modulation offer good poibilitie of a imple realization of modulator onboard the pioatellite with a limited omputing power. Our propoed modulator i baed on memory addreing. n the memory ample of a harmoni funtion are tored. Frequeny hange are realized by inreaing or dereaing the inrement of memory addreing. Phae hange are realized by tep in memory addreing. he following modulator an realize a ignal et of M ignal m0 m1 m m3 t o f m 1f t 0 t o f m 1f t 1 t o f m 1f t (1) t o f m 1f t 3 1 for m 1... M and 0 t and f. hi ignal et ontain all ombination of M orthogonal arrier of the FSK etion of hybrid modulation and four direte phae hift of the embedded D etion of hybrid modulation. Direte phae hift are differentially oded between two adjaent ymbol. n the deigned memory baed modulator arbitrary M-FSK modulation arbitrary M-PSK modulation arbitrary DM-PSK modulation and arbitrary hybrid M-FSK/D modulation an be eaily implemented. Our propoed demodulator i baed on the FF analyi of reeived (and in frequeny down onverted) ignal. he M-FSK part of hybrid modulation i demodulated by earhing for the maximum amplitude in the FF reult the D part of hybrid modulation i demodulated by omparing the phae in two adjaent ymbol at frequenie given by the M-FSK demodulator..3 Advaned Hybrid DM-FSK/D Modulation At advaned hybrid DM-FSK/D modulation differential oding of the M-FSK etion i applied. hi ould be ueful in hannel with Doppler effet e.g. underwater aouti ommuniation [8] or in atellite RF

3 RADOENGNEERNG VOL. NO. 1 APRL ommuniation [9]. f the differene of Doppler frequeny hift between two ymbol i muh maller than the M- FSK frequeny paing then thi differentially oded modulation i robut with repet to the Doppler hift ompenation error [10]. Conept of our propoed modulator and demodulator for hybrid modulation are in Fig. 3 and Fig.. Data input PCM/NRZ bit mapping Bit log(m) log(m) log(m) oding oding log(m) Choie of jump in memory addre Choie of memory addre inrementation Memory addre ounter Memory (ampled harmoni funtion) Digital to analog onverter Analog output of hybrid DM-FSK / D for RF onverion are poible for two limit of frequeny bandwidth (0 khz bandwidth related to reeiver audio output the ignal proeed in PC via ound ard 1.5 MHz bandwidth related to PilenCUBE experimental radio) in dependene on the reeived ignal quality C/N 0. hi i enumerated for onventional a well a for propoed hybrid modulation. FSK FSK 8FSK 16FSK 3FSK 6FSK 18FSK 56FSK Analog input of demodulator Fig. 3. Hybrid DM-FSK/D memory baed modulator. ADC SPC Data output PCM/NRZ Sample of DM-FSK / D Bit log(m)-1 Sample 1 Deteted frequeny deoding of DM-FSK and FF D part of Deteted phae hybrid Sample M modulation PSC 56FSK 10FSK Fig. 5. Evaluation of onventional M-FSK modulation on the propoed hybrid M-FSK/D oftware modulator and demodulator. D Fig.. Hybrid DM-FSK/D FF baed demodulator. Hybrid modulator a well a hybrid non-oherent demodulator were realized in Matlab oftware and their performane in AWGN model of hannel wa teted. 3. Reult for Hybrid Modulation he propoed hybrid modulator and demodulator were realized in Matlab and evaluated by BER meaurement in dependene on E b /N 0 parameter for the AWGN hannel model. n the propoed oftware modulator there were onventional modulation -FSK up to 10-FSK and D modulation (a a referene to hybrid modulation) realized. From the hybrid modulation group there were -FSK/D up to 10-FSK/D modulation and D-FSK/D up to D10-FSK/D modulation realized. Software defined FF baed nonoherent demodulator were alo realized in Matlab. BER performane of onventional modulation are in Fig. 5 and Fig. 6. Performane of the hybrid modulation are hown in Fig. 7 and Fig. 8. he required E b /N 0 for BER equal to 10-5 and BER equal to in the AWGN hannel together with petral effiieny of all teted modulation are ummarized in ab. 1. he petral effiieny i alulated for the null to null frequeny bandwidth for the orthogonal arrier with paing for nonoherent demodulation. For meaured reult of energy effiieny and reult of petral effiieny it wa alulated how high data rate Fig. 6. Evaluation of onventional D modulation on the propoed hybrid M-FSK/D oftware modulator and demodulator. FSK/D FSK/D 8FSK/D 16FSK/D 3FSK/D 6FSK/D 18FSK/D 56FSK/D 51FSK/D 10FSK/D Fig. 7. Evaluation of hybrid M-FSK/D modulation on the propoed oftware modulator and demodulator. he reult how that the propoed hybrid modulation have better energy effiieny in omparion with the M-FSK modulation with orreponding petral effiieny. Signifiant enhanement i notieable for low order FSK modulation. For example the -FSK modulation an be

4 39. VEŘÁ J. MRÁZ HYBRD M-FSK/D MODULAONS FOR CUBESA PCOSAELLES replaed by the 16-FSK/D modulation in the almot ame bandwidth at more than 6.6 db better energy effiieny (ee ab. 1). no hannel bandwidth limit hannel bandwidth limit 1.5 MHz hannel bandwidth limit 0 khz DFSK/D DFSK/D D8FSK/D D16FSK/D D3FSK/D D6FSK/D D18FSK/D ranmiion data rate [bit/] D56FSK/D D51FSK/D D10FSK/D Fig. 8. Evaluation of hybrid DM-FSK/D modulation on the propoed oftware modulator and demodulator. E b /N 0 [db] E b /N 0 [db] Spetral effiieny (BER=10-5 ) (BER= ) [bit//hz] D FSK FSK / D D-FSK / D FSK FSK / D D-FSK / D FSK FSK / D D8-FSK / D FSK FSK / D D16-FSK / D FSK FSK / D D3-FSK / D FSK FSK / D D6-FSK / D FSK FSK / D D18-FSK / D FSK FSK / D D56-FSK / D FSK FSK / D D51-FSK / D FSK FSK / D D10-FSK/D ab. 1. Reult for all teted modulation on the propoed oftware defined modulator and demodulator. Before reahing the hannel frequeny bandwidth limit the propoed hybrid modulation offer a greater than 50% inreae of data rate in omparion with M-FSK modulation (under the ondition of the ame reeived ignal quality). After reahing the bandwidth limit the propoed hybrid modulation offer a greater than 150% inreae of the data rate. hi i notieable by omparing the reult in Fig. 9 and Fig. 10 at the ame C/N 0 (reeived ignal quality) Fig. 9. Obtainable data rate at bandwidth limitation in dependene on C/N 0 for a ommuniation ytem implementing a onventional modulation 10-FSK up to -FSK and D adaptation. ranmiion data rate [bit/] no hannel bandwidth limit hannel bandwidth limit 1.5 MHz hannel bandwidth limit 0 khz Fig. 10. Obtainable data rate at bandwidth limitation in dependene on C/N 0 for a ommuniation ytem implementing the propoed hybrid modulation 10- FSK/D up to -FSK/D adaptation. Channel bandwidth [Hz] no hannel bandwidth limit hannel bandwidth limit 1.5 MHz hannel bandwidth limit 0 khz modulation with better petral effiieny mut be applied due to bandwidth limit modulation with maximal energy effiieny i ued Fig. 11. Oupied frequeny bandwidth related to data rate in Fig. 10 for a ommuniation ytem implementing the propoed hybrid modulation 10-FSK/D up to -FSK/D adaptation.

5 RADOENGNEERNG VOL. NO. 1 APRL n an adaptable ommuniation ytem the modulation type i hanged in dependene on the reeived ignal quality. During a bad reeived ignal quality period a modulation with bet energy effiieny i ued (from implemented group of modulation). A the ignal quality i inreaing the data rate i alo inreaing a well a the oupied frequeny bandwidth. When the allowed frequeny bandwidth i reahed then the ommuniation ytem ha to with to a more petrally effetive modulation for an inreaing data rate and for keeping to the bandwidth limit (ee Fig. 11).. Conluion he propoed novel modulator and demodulator with hybrid M-FSK/D and DM-FSK/D offer better energy effiieny a well a a better petral effiieny in omparion with onventional M-FSK modulation. Hybrid modulation an be ued for a CubeSat ommuniation ytem with adaptation implementation epeially under the wort atellite link ondition (pioatellite elevation angle bellow 10 ). At thee elevation the pioatellite on low Earth orbit tay for a high perentage time period neverthele the radio ontat i poible [11]. he propoed hybrid modulation an enure a better data rate than ommonly ued pioatellite CW beaon [1] [13] under thee bad ondition. When the bandwidth limit i not reahed (due to low order of realized M-FSK part of modulation) then the propoed hybrid modulation offer a 50% inreae of data rate in omparion with the onventional M-FSK modulation due to a better energy effiieny. When the bandwidth limit i fully ued then the hybrid modulation offer a 150% inreae of date rate due to utilization of better energy effiieny a well a better petral effiieny. he propoed hybrid modulation an alo replae the very often ued AFSK modulation. n thi ae the 16-FSK/D modulation ha a imilar petral effiieny with differene of energy effiieny approximately 6.6 db for BER equal to 10-5 and 7.1 db differene for BER equal to. Aknowledgement hi projet wa funded by the Czeh Siene Foundation and regitered a a projet number 10/09/055 Power effiient pae probe for experimental reearh baed on pioatellite. hi work wa alo upported by the intitutional upport at the Univerity of Wet Bohemia in Pilen part POSDOC-01. Referene [1] AO M. Priniple of Communiation Chapter 8 - Digital modulation tehnique [online]. Shanghai Jiao ong Univerity 01 p [] WE L. KORN. Combined frequeny and differential phae hift keying with non-oherent detetion in atellite mobile hannel. EEE ran. Veh. eh vol. p [3] POKORNÝ M. S-band onventional radio onnetion of the PilenCUBE pioatellite. n th European CubeSat Sympoium. Bruel (Belgium) 01. [] RUDY L. Diploma hei. he performane of onventional and DBD reeiver for / modulation when operating in the preene of noie and Rayleigh fading. Monterey Naval Potgraduate Shool 1988 p [5] LAF A. Dotoral hei. Hybrid AM - FSK (HFM) OFDM traneiver with low PAPR. Ghulam haq Khan ntitute of Engineering Siene and ehnology 009 p [6] DGHAM F. ALOUN M. Spetrally effiient hybrid FSK/AM with optimum bit and power loading. n Pro. EEE nternational Conferene on Communiation (CC 06). 006 vol. 11 p [7] Dream DRM Reeiver A oftware Digital Radio Mondiale (DRM) reeiver [online]. Available at http//oureforge.net/projet/drm/ [8] EGNOR D. et al. frequeny hopping (DFH) modulation for underwater mobile ad-ho network. U.S. Navy Journal of Underwater Aouti 011. [9] KOVÁŘ J. KASAL M. Automati ompenation of Doppler hift in ommuniation with atellite on non-geotationary Earth orbit. Elektrorevue 008 p (n Czeh). [10] VEŘÁ. Dotoral hei. Effetive Communiation Sytem for Pioatellite. Univerity of Wet Bohemia in Pilen Faulty of Eletrial Engineering p. (n Gzeh). [11] VEŘÁ. LNHAR R. POKORNÝ M. KAVALÍR. Signal quality evaluation for pioatellite ommuniation ytem. n nternational Conferene on Applied Eletroni 01. Pilen (Czeh Rep.) 01. SBN [1] KAVALÍR. PilenCUBE ground tation. n th European CubeSat Sympoium. Bruel (Belgium) 01. [13] KLOFAS B. ANDERSON J. A urvey of CubeSat ommuniation ubytem. n 5th Annual CubeSat Workhop. California Polytehni Univerity 008 p About Author... vo VEŘÁ wa born in 1980 Czeh Republi. n 01 he reeived Ph.D. degree at the Faulty of Eletrial Engineering Univerity of Wet Bohemia in Pilen. he dotoral thei topi dealt with the area of effetive ommuniation ytem for pioatellite. Reearh interet over wirele ommuniation and pae hardware deign. Sine 009 he i a member of the PilenCUBE group whih deal with advaned CubeSat pioatellite development. Jan MRÁZ wa born in 198 Czeh Republi. n 01 he reeived hi Ph.D. degree at the Faulty of Eletrial Engineering Univerity of Wet Bohemia. he dotoral thei topi dealt with the area of antenna integration into the V reeiver hai. Reearh interet inlude antenna ytem and wirele ommuniation ytem. Sine 009 he i alo member of the PilenCUBE group.