Field Test Results of Space-Time Equalizers and Delayed Diversity Transmission in Central Tokyo Area

Transcription

1 Field Tet Reult of Space-Time Equalizer and ed Diverity Tranmiion in Central Tokyo Area Takehi Toda Yuukichi Aihara Jun-ichi Takada YRP Mobile Telecomm Key Tech. Lab Co., Ltd. Tokyo Intitute of Technology (At now, Fujitu Laboratorie Ltd., Matuhita Commun. Indutrial Co., Ltd.) 5-5 Hikari-no-oka Yokouka Japan, Tel/fax: /556 Abtract- Field tet of pace-time (ST) for combating inter-ymbol interference (ISI) at bae tation, wa conducted in micro- and macro-cell environment in central Tokyo area. Tet reult indicate that the ST provide ignificant better bit error rate (BER) than an array proceor alone doe, due to both pace and path diverity while uppreing long-delayed path. Furthermore, a delayed diverity tranmiion (DDT) in a mall delay pread environment provide ufficient delay-pread and improve BER of the ST. Firt-arrival-path -contrained array proceor T 3T (a) ST I Viterbi Etimated equence I. INTRODUCTION Space-time (ST) ha invetigated a a mean of improving capacity and tranmiion quality of high-datarate mobile communication [1]-[5]. It performance i highly dependent on real ST propagation cenario; thu it mut be evaluated in field. However, only a few field trial have been reported [4][5]. Thi i due to complexity in hardware ytem configuration and it development cot and time. We developed a tetbed that wa configuration-flexible and implementation-eay, and teted ST decribed by Fujii [3] in uburban [6][7]. For thi paper, we teted the ST for bae tation in micro- and macro-cell environment in central Tokyo area. A delayed diverity tranmiion (DDT) uing two antenna at a mobile wa tried in order to provide ufficient path diverity benefit to the ST in mall delay pread environment. How to ue of DDT here wa different from that of previou work [8][9] where DDT in a bae tation create frequency-elective fading at a mobile for flat fading channel. II. ST EQUALIZER AND DDT Firt-arrival-path -contrained array proceor 1T -delayed-path -contrained array proceor T 3T (b) ST II Fig. 1 ST for bae tation Data gen. Baeband Fig. 2 T Mod. Mod. 3T Branch-metric -combining Viterbi Amp. Amp. DDT for mobile tation Etimated equence Figure 1 (a) how a ST that i a combination of a firt-arrival-path-contrained array proceor and a Viterbi (ST I). Figure 1 (b) how another ST that i a combination of firt-arrivalpath- and 1T-delayed-path- contrained array proceor, and a branch-metric-combining (BMC) Viterbi (ST II). The firt-arrival-path-contrained array proceor pae 1T-delayed path component while contraining the firt-arrival path. On the other hand, a 1Tdelayed-path contrained array proceor pae the firtarrival path component while contraining the 1Tdelayed-path component. Longer delayed path component than 1T period are uppreed a interference, which are beyond the equalization range of the Viterbi. The array proceor can limit the equalization range that the Viterbi mut prepare, and thu conequently can decreae complexity of the equalization ytem. Figure 2 i a block diagram of the DDT at the mobile tation. The in-phae (I) and quadrature (Q) channel data i plit and the plit data i delayed in baeband. Here, for the ST, even when the DDT create long delay path beyond equalization range of the Viterbi ubytem, the antenna array preytem can uppre them and thu prevent diruptive degradation of the ST /2/$ IEEE PIMRC 22

2 P2 Rx 1 m Rx 6 m Tx P2 Tx Rx Tx P2 3 m Fig. 3 Tet environment,, and in central Tokyo area Table 1 Specification of exprimental ytem Radio frequency 3.35 GHz Modulation QPSK Tranmiion rate 4.96 Mb/ TDM frame format Tx. Antenna Rx. Antenna Array proceing algorithm Viterbi Training: 48/data: 28 ymbol (32 ymbol for correlation) - Colinear dipole (5.5 dbi) - 15λ antenna-pacing for DDT Four-dipole circular array (8λ pacing) - SMI for an array proceor alone - Contrained SMI Four tate, ten ymbol path memory III FIELD TEST Figure 3 how tet environment,, and in a central Tokyo area. Arrow, olid and dotted line indicate array antenna location, mobile coure driven in counterclock-wie ( P2 ), in the tet environment,, and, repectively. Table 1 and 2 decribe ytem pecification and antenna etup, repectively. A. Setup of Tet Environment,, and Tet environment : The array antenna wa lifted up at the almot ame height a telegraph pole (15 m) and wa lower than height of major building around (2 - m). Ditance between the Tx and Rx wa 2 1 m through the mobile coure. Tet environment : The array antenna wa placed on a rooftop of a even-toried building ( m), the almot ame height a that of major building around (2 - m), and wa about 3 m away from center of the mobile coure. Tet environment : The array antenna wa placed on Table 2 Antenna etup Tet environment Height of Tx antenna at 2 m mobile tation Height of Rx antenna for ST at bae tation Height of major building around Rx antenna Ditance between Tx and Rx antenna the rooftop of an outtanding tall building (7 m), twice higher than height of major building around (2 - m), and wa about 6 m away from center of the mobile tranmitter coure. The mobile peed wa 1 to 2 km/h. B. Meaured reult Figure 4 (a), (b), (c) and (d) how meaured received averaged over all branch, delay pread averaged over all branch, bit error for the array proceor alone, bit error for the ST, delay profile averaged over all branch, in firt burt (1 µec duration) in each frame (8 mec duration), for the tet environment, with the DDT,, and, repectively. Table 3 how delay-pread in the tet environment. Here, delay pread (σ) wa calculated a σ = max 15 m 35 m 7 m 2 - m 3-35 m 3-1 m 3 m 6 m Oberved delay pread Small Large 2 max ( ) p() d p() ave d, where i Nyquit ampling time, max i maximum delay

3 Received proceor Received proceor Received proceor (a) Tet environment (b) Tet environment with DDT (c) Tet environment Received proceor (d) Tet environment Fig. 4 Meaured, delay pread, bit error of array proceor and ST II, and delay profile.

4 time, p() i delay profile, and ave i average delay time calculated by max () d p() max ave = p d. Figure 5 how envelope correlation of the antenna branche in the tet environment, with DDT,, and, which are calculated by where e m, [( e m µ )( e µ ] ( σ σ ) ρ = E ), µ e m, and em σ e m n en em en are envelope, mean, and tandard deviation of received ignal repectively in m-th branch. Alo, E[ ] i enemble average. Thoe value were calculated every 2 frame (1 m mobile movement in 2 km/h). In the tet environment, 8 % and 9 % of the envelope correlation are le than.7 and.75 repectively. In the tet environment, 8 % and 9 % of the envelope cro-correlation are le than.76 and.79 repectively. Thu pace diverity effect i ufficiently obtained in.8-9 % of thoe tet environment. Figure 6 how envelope correlation between the firtarrival- and 1T-delayed path, in tet environment and with the 1T-DDT for 5λ- and 15λ- antenna pacing. A the 1T-DDT, the correlation i increaed, however, 95 % of the correlation for both 5λ- and 15λ- antenna pacing i le than.7, and thu path diverity in the Viterbi i ufficient in 95 % of thoe tet environment. IV. BER PERFORMANCES A. Effect of Path Diverity Combining Figure 7 how BER performance of the ST II compared with thoe of St I in the tet environment,, and, repectively. The ST II provided ignificant better BER than the ST I doe, due to the effect of path diverity combining. The ST II ue eparate array weight vector to contrain firt-arrival- and 1T-delayed- path, and thu obtain path diverity gain of both firt-arrival- and 1T-delayed- path, even when fading correlation between ignal on branche wa not low. Figure 7 alo how the BER performance of the ST II with the 1T-DDT in tet environment where delay pread i too mall to provide ufficient path diverity benefit to the Viterbi. The 1T-DDT create delayed path and increae the delay pread (hown in Fig 4 (b)), and then can improve BER of the ST II due to path diverity gain from thoe created delayed path. B. Effect of Space and Path Diverity Figure 8 how the BER performance of the ST II compared with thoe of the array proceor alone in the tet environment,, and, repectively. The ST II provide ignificant better BER than the array proceor alone doe, due to the effect of both pace and path diverity. ST proceing in each diverity branch doe not conume one degree of freedom with regard to the Table 3 pread characteritic in tet environment, with DDT,, and pread Environ. Environ. w/ DDT Environ. Environ. Ave Min..... Max St. dev CDF 1.8 Tet environment Correlation coefficient Fig. 5 Envelope correlation between branche in tet environment, with DDT,, and CDF W/o DDT 15λ w/ DDT Correlation coefficient Fig. 6 Envelope correlation between firt-arrival- and 1T-delayed path, in tet environment and with 1T-DDT for 5λ- and 15λ- antenna pacing uncontrained deired path. On the other hand, the array proceor alone exploit only firt-arrival path while conuming degree of freedom in uppreion of the delayed path; can not obtain pace and path diverity gain from the delayed path. 5λ W/ DDT

5 VI. CONCLUSION We conducted field tet of pace-time (ST) for a bae tation in micro- and macro- cell environment in central Tokyo area. BER performance of the ST howed pace and path diverity effect againt multi-path fading environment. We alo tried a delayed diverity tranmiion (DDT) for the ST in mall delay pread environment. The tet reult howed that the DDT created delayed path and improved the BER of ther ST due to path diverity. ACKNOWLEDGMENT The author would like to thank Y. Ihikawa and Y. Kamio who were with YRP Mobile Telecommunication Key Technology Reearch Laboratorie Co. Ltd. and now are with Telecom Engineering Center and with Communication Reearch Laboratorie repectively, for their encouragement. REFERENCES [1] G. E. Bottomley, K. J. Molnar, and S. Chennakehu, Interference Cancellation with an Array Proceing MLSE Receiver, IEEE Tran. Vehicular Tech., vol. 48, no. 5, pp , [2] P. Pipon, P. Chevalier, P. Vila, and J.-J. Monot, Joint patial and temporal equalization for channel with ISI and CCI, Proc. IEEE Workhop on Signal Proceing Advance in Wirele Commun, pp , [3] M. Fujii, Path diverity reception employing teering vector array and equence etimation technique for ISI channel, IEEE Journal on Selected Area in Commun., Vol. 17, No. 1, pp , [4] J-F. Frigon and B. Danehrad, Field meaurement of high peed QAM wirele tranmiion uing equalization and realtime beamforming, Proc. IEEE Global Commun. Conf., pp , [5] T. Aai, S Tomiato, and T. Matumoto, Field tet reult for a beam and null imultaneou teering S/T- in broadband mobile communication environment, IEICE Tran. Commun., Vol. E84-B, No. 7, pp , 21. [6] M. Fujii and T. Toda, Implementation of pace-time uing multiple ingle-contrained SMI array proceor and MLSE, IEEE Tran. Wirele Commun., Vol. 1, No. 2, pp , 22. [7] T. Toda, Y. Aihara, and Y. Kamio, Field trial of pace-time uing multiple ingle-contrained array proceor and MLSE, Proc. IEEE Vehicular Tech. Conf. Fall, pp , 21. [8] J. H. Winter, The Diverity Gain of Tranmitter Diverity in Wirele Sytem with Rayleigh Fading, IEEE Tran. Vehicular Tech., vol. 47, no. 1, pp , [9] C. S. Bontu, D. D. Falconer and L. Strawczynki, Diverity Tranmiion and Adaptive MLSE for Digital Cellular Radio, IEEE Tran. Vehicular Tech., vol. 48, no. 5, pp , Average BER Tet environment ST I ST II ST II w/ddt Average E /N (db) b Fig. 7 Effect of path diverity combining in tet environ.,, and (ST I v.. II) Average BER Tet environment Fig. 8 Effect of pace and path diverity in tet environment,, and (array alone v.. ST II) Average E /N (db) b Array procor alone ST II ST II w/ddt