Indoor Channel Measurements and Communications System Design at 60 GHz

Indoor Channel Measurements and Comm unications System Design at 60 GHz L. Rakotondrainibe 1 , G. Zaharia 1 , G. El Zein 1 , Y. Lostanlen 2 1 IETR-UMR CNRS 61 64, 20 Av. des Buttes de C oësmes, CS 14 315, 35043 Re nnes Cedex, Fra nce 2 SIRADEL, 3, Allée Adol phe Bobierre, CS 2434 3, 35043 Rennes Cedex -France lrakoton@insa-renne s.fr; gheor ghe.zaharia@i nsa-rennes.f r ; ghais.el-zein@insa-rennes.fr; yves.lostanlen@ieee.org Abstract This paper presents a brief overview of several studie s concern ing the indoor w ireless communications at 60 GHz perform ed by the IETR. The characteri zation and the modeli ng of the radio propagation c hannel are based on several measurement campaigns realized with the channe l sounder de veloped at IETR. Som e typi cal residenti al environm ents were also simul ated by ray tracin g and Ga ussian Beam Tracking. The ob tained results show a good agreement with the similar experimental results. Currently, the IETR is developing a high data rate w ireless communicat ion system opera ting at 60 GHz. The sin gle-carri er architecture of this system is also presented. 1. Introduction During the last decade, substantia l knowledge about the 60-GHz millim eter-wave (MMW) channel has been accumulated and different a rchitectures have been analyzed to de velop MMW communication system s for commercial appli cations [1-2]. The 60 GHz bandwidt h is suitable for high dat a-rate and short-di stance wireless communications. This in terest is particularly due to the large bandwi dth and the im portant power loss c aused by the free space and walls attenuation which permits to reuse the sa m e frequency bandwi dth even in the next floor of the same building. Concerning the 60 GHz fr ont-end techn ology, higher fre quencies lead t o smaller sizes of RF components i ncluding ve ry smal l antennas. The c ost is mainl y related t o the transceiv er RF front e nds. The developm ent of new wi reless comm unication syst ems requires a ccurate kn owledge of t he propag ation channel to efficiently sim ulate and design them , in cluding new m odulation schem es, coded and multiple access techniques. The rest of this paper is organized as follows: section 2 presents an overview of several st udies realized at IETR concerning t he measurements and characte rizatio n of the 60 GHz radi o propagati on chan nel. Section 3 reports recent work conce rning of a 60-GHz ra dio comm unication system . Some conclusio ns are drawn i n section 4. 2. Channel measurements and characterization During the last decade, several research activities were carried out at IETR in the 60 GHz bandwidth: the realization of the chann el sounder, the indoor radio chann el measurements, simulation and characterizatio n. 2.1 Channel sounder A 60-GHz wideban d channel sou nder was develope d at IETR (Fig. 1). Thi s channel soun der has 500 MHz bandwidth, 40 dB relative dynam ic and 2.3 ns effective ti me resolution, which means that two p aths separated from by 70 cm can be c orrectly discri minated. B ased on the s liding correlation technique, this sounder is optimized to perform long t erm measurement campaigns. Som e measurem ent results with D oppler analysis up t o 20 kHz are presented in [3]. Fig. 1 Cha nnel sounde r at 60 GHz realized by IETR 2.2 Channel measurements and characterization In [4-6], t he results o f several st udies concerni ng the radi o propagatio n at 60 GHz i n residentia l environ ments were publis hed. These stu dies are based on several m e asurement campaigns realized with the IETR channel sounder. The measurements have been pe rformed in residential furnishe d environm ents. The st udy of the a ngles-of- arrival (AOA) shows the i mportance of openin gs (such as do ors, staircas e, etc.) for the radio propagation bet ween adjacent room s (Fig. 2). From the database of impul se responses, several propagation characteristics are computed: attenuatio n, dela y spread, dela y window, c oherence ba ndwidth [5]. The wave propag ation depe nds on ante nnas (beam-width, gain and pol arization), phy sical environm ent (furni ture, mat erials) and hum an activity. A parti cular attention is paid to the influence of the human activity on radio propagation . In [6], it is shown that people moveme nts can make the propagation c hanne l unavailabl e during a bout one sec ond (Fig. 3).  However, the angular diversit y can be used : when a path is sha dowed, a nother one, comi ng from anot her direction, can maintain the radio link. From the char acterization of the indoor radio propaga tion, several recommendat ions conce rning t he deploym ent of t he very hi gh data rate 60 GHz wirele ss networks are derived i n [5].      Fig. 2 Received power in the horizontal pla ne  (NLOS, with a receiving horn antenna)               ─ Measurement --- 5 dB threshol d ─ Attenuatio n (channel static) + Shadowing beginnin g Attenuation (dB) 0 Shadowing c luster be ginning Time (min)   Fig. 3 Huma n activity m easurem ent at 60 GHz (Receiver antenna: horn, ch annel activity: 4 persons) 2.3 Deterministic simulation of the 60 GHz radio channel Two deterministic simulation to ols have been used to co mplement the experimental ch aracterization: a ray-tracing tool [6] and a 3 D Ga ussian Beam Tracking (GBT) technique [7]. Both t ools provided comparable coverage sim ulations i n a resident ial indo or environm ent (a house) at 60 GHz an d 500 MHz ba ndwidth. I n Fig. 4, simulated coverage res ults based on GBT algorit hm are shown. This m ethod based on Ga bor frame approach is particularly well suited to high frequencies and permits a collective treatment of rays wh ich offers significant computation t ime efficiency. The advance d determi nistic predict ion tool X-Siradif ba sed on ray-t racing has furt her shown a good agreement with th e power-de lay measurement results (see Fig. 5), which is important for suc h a wide bandwidth. Besides the ray-tracing t echnique can easily and accurately take into account any measured antenna patterns. In [ 6], other com parison results conce rning the chan nel impul se response and the angles- of-arrival are given. Besides, the ray-tracing techni que ca n easily and accurately take into account any measure d antenna patterns. However at 6 0 GHz static si mulations a re not suffi cient to hel p for the desig n of comm unication sy stems. SIRADEL is still pursuing its investigation on indoo r propagation by setting up dynamic scenarios to simulate the presence of people in the room (mobilit y models, direct path and obstru ction). 3. Design of a 60 GHz wireless communication system Studies for di fferent ty pes of single carrie r (SC) modul ation and ort hogonal f requency divisio n multiplexi ng (OFDM) were proposed in t he IEEE 802.15.3 Task Group 3c for the fu ture wirel ess communication systems operating at 60 GHz. The choice of m odulation sc hemes for 60 GHz radio i s highly depe ndent on t he characteristic s of the propagati on channel, the use of hi gh gain antenna/ antenna array and t he limitations im posed by the RF technology. Some SC modulation s as BPSK and QPSK ar e considered. The SC has two m ain advantages over OFDM: lower complexity and low er PAPR (peak-to average power ratio). IETR, one of the pa rtners of the Techim@ges project, is currently involved in the design and th e realization of a low-cost, hi gh data rate (abo ut 1 Gbps) and sm all-distance (d < 10 m) wireless com munication s ystem. Fig. 6 shows the single carrier system arch itecture proposed by IETR whi ch uses a BPSK m odulation. The 3.5 G Hz and 58.5 GHz phase locked oscilla tors use a 70 MHz frequency synthesizer. At the receiver, the in termediate frequency and the clock are obtained from the received signal. Th e frequency-domain equalizer (FDE) and som e error correcting codes are un der study. In o rder to improve the link budget, es pecially for poi nt-to-point ap plications, it i s preferable to use high-gai n directive antennas.  Fig. 6 Singl e-carrier wirel ess comm unication syst em at 60 GHz 4. Conclusion In this paper, a brief overvi ew of several studies perform ed at IETR on 60 GHz i ndoor wireless communicat ions is presented. T he characterizat ion of the radi o propagation c hannel is base d on several measurement campaigns realized w ith the channel sounder of IETR. Some typical residential environ ments were also simulated by ray tracing and Gaussian Beam Tracking. The obtained resu lts show a good agreement w ith the experime ntal results. C urrently, the IETR is developi ng a SC wirel ess comm unication syst em operatin g at 60 GHz. 5. Acknowledgments The study on t he 60 GHz i ndoor radio c hannel was supp orted by t he French Natio nal Research Net work in Telecommunications RNRT COMMINDOR. The realization of the 60 GHz wireless communications system is part of the research project Tec him@ges supported by t he French “Media & Network Cluster” and the COMMIDOM project of the “Région Bretagne”. 6. References 1. H. Yang, P. F. M. Smulders, and M. H. A. J. He rben, “Ch annel Characteri stics and Tra nsmission Perform ance for Various Channel Co nfigurati ons at 60 GHz”, EURASI P Journal on Wirel ess Communicatio ns and Networki ng , Volume 2007, ID 19613, 15 p ages, March 20 07. 2. N. Guo, R. C. Qiu, S. S. Mo, and K. Takah ashi, “60-GHz Millim eter-Wave Radio: Pri nciple, Techno logy, and New Results”, EURASIP Journal on Wireless Communications and Networki ng , ID 68253, 8 pa ges, Sept. 2006. 3. S. Guillouard, G. El Zein, and J. Ci terne, “Wide ban d Propagation Measurements an d Doppler Analysis for the 60 GHz Indoor Chan nel”, IEEE M TT-S Dig est , 1999. 4. S. Collonge, G. Zahari a, and G. El Zein, “ Wideband and Dy namic Characteri zation of the 60 GHz Indoor Radio Propagation-future Home WLAN Arch itectures”, Ann als of Telecommun ications , special issu e on WLAN, March- April 2003, Vol. 58, N° 3-4, pp. 417-447. 5. S. Collonge, G. Zaharia, G. El Zein, “Influe nce of th e huma n activity on wide-ba nd ch aracteristics of the 60 GHz indoor radio c hannel”, IEEE Trans. on Wireless Communications , Vol. 3, Issue 6, Nov . 2004, pp . 2396-2406 . 6. Y. Lostanlen, Y. Corre, Y. Louët, Y. Le Hel loco, S. Collonge, G. Zaharia, and G. El Zein, “Com parison of Measurements and Simulations in Indoor Env ironments for Wireless Local Networks at 60 GHz”, IEEE Vehicular Technology Conference 2002 , Birmingham, USA, May 2002 . 7. R. Tahri, D. Fournier, S . Collonge, G. Zaharia, a nd G. El Zein, “E fficient and Fast Gaussian Beam-Tracki ng Approach for Indoor-Pro pagation Mode lling”, Microwave and Optical Technology Let ters , Vol. 45, N° 5, June 2005, pp. 378-3 81.  60 GHz Ref. 70 MHz Data output CAG FI 3. 5 GHz Clock recovery   PLO 56.5 GHz Sample r LN A  Data input Amp PLO 56.5 GHz PLO 3.5 GHz  Ref. 70 MHz 