A system architecture, an empirical propagation model, and a software combined with a CAD tool, have been designed to offer mobile communication services to construction sites. Results have been validated by measurements.Peer ReviewedPostprint (published version

Agustí Comes, Ramon

Olmos Bonafé, Juan José

Pérez Romero, Jordi

Ruiz Boqué, Sílvia

Samper, Y

Electronics Letters

English

A system architecture, an empirical propagation model, and a software combined with a CAD tool, have been designed to offer mobile communication services to construction sites. Results have been validated by measurements.Peer Reviewe

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Software tool for optimising indoor/outdoor coverage in a construction site

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Aclcnodedgments: The authors would like to thank N.  Edagawa for fruitful discussions. They would also like to thank T. Mura- tani, K. Suzuki, S. Akiba and S. Yamainoto for their continued encouragement. 0 IEE 1998 Electronics Letters Online No: 19981498 H. Taga. M. Suzuki and Y. Namihira (KDD R&D Laboratories Inc., 2- 1-15, Ohara, Kamifiikuoka-slii, Saituma 356, JU~JUTZ)  E-mail: taga@sunb.eIb.lab.kdd.co.jp 7 September 1998 References POOL, c D., TKACH. R w., CHRAPLYVY. A K , and FISHMAN, D.A.: ‘Fading in lightwave systems due to polarization-mode dispersion’, IEEE Photonics Technol. Lett.,  1991, 3, pp. 68-70 BRCYERE. F , and AUDOUIN. 0.: ‘Assessment of system penalties induced by polarization mode dispersion in a 5 Gb/s optically amplified transoceanic link’, IEEE Photonics Ttclinol. Lett.,  1994, 6, pp. 443-445 ZHOIJ, J., and O’MAHONY, M J : ‘Optical transmission system penalties due to fiber polarization mode dispersion’, IEEE Photonics TechnoL Lett., 1994, 6, pp. 1265-1261 MORKEL. P R ,  SYNGAL, V., BUTLER, D.J., and NEWMAN, R.: ‘PMD- induced BER penalties in optically-amplified IM/DD lightwave systems’, Electron. Lett.,  1994, 30, pp. 806-807 OZEKI, T., and KUDO. T.: ‘Adaptive equalization of polarization- mode dispersion’. Tech. Dig. Conf. Optical Fiber Communication/ Int. Conf. Integrated Optics and Optical Fiber Communication (OFC/IOOC’93), 1993, San Jose, California, Paper W19 OSCAR VAN DEVENTER, M., NAGEL, H.G.J., VAN DEN AKKER, F M , and BRINKMAN, R J : ‘Improvement of polarisation mode dispersion tolerance in high bitrate systems’. Tech. Dig. 19th European Conf. Optical Communication (ECOC’93), 1993, Montreux, Switzerland, Paper We 16 BERGANO, N.S., KERFOOT. F.W., and DAVIDSON. C R : ‘Margin measurements in optical amplifier systems’, IEEE Photonics Teclznol. Lett. ,  1993, 5 ,  pp. 304-306 NAMIHIRA.  Y., NAKAJIMA, K , and KAWAZAWA, T.: ‘Fully automated interferometric PMD measurements for active EDFA, fibre optic components and optical fibres’, Electron. Lett.,  1993, 29, pp. 1649- 1651 Software tool for optimising indoor/outdoor coverage in a construction site S. Ruiz, Y. Samper,  J .  Perez, R.  Agusti and J. Olmos A system architecture, an empirical propagation model, and a software combined with a CAD tool, have been designed to offer mobile communication services to construction sites. Results have been validated by measurements. Intuoduction: Mobile communications technology is today robust and portable enough to be introduced into the construction sector as a way to improve the overall product quality and the work force safety. Base stations (BSs) linked by cable are typically used for indoor mobile systems, but in buildings under construction the installation of fixed cables should be avoided [ 11 and therefore other ways to offer coverage have to be employed. We propose the use of conventional BS installed outdoors, but in the building vicinity. In particular a DECT system is retained because of its suitability in such scenarios, so that the BSs and their controller can be in a communications container (hub). The increase in attenuation due to both a higher distance between terminals and external wall losses can be overridden by the use of directive antennas, the number of required antennas being dependent on building topology and distance to the hub. Instead of ray tracing or ray launching techniques, which are much more time consum- ing, we use a distance and partition dependent path loss empirical model [2, 31. A measurement campaign was carried out to obtain wall loss factors at DECT frequencies, and also to validate the propagation model. Propagation model: The model considers free space propagation and the additional path loss, caused by the incidence angle and the physical obstacles that lie between transmitter and receiver, is added. The model should account for: the difference between the floor plan that is at the same height level than the BS and the rest of floors, and the effects of the angle of illumination (angle between the BS antenna and the surface of the external wall). Received power is calculated by P ~ [ d B m l  = P~[dBni] +GI, + GR - L d e s c  - t(p) ~ L (1) where P,, G,, G, and PR the transmitted and received power and antenna gain, respectively, L,,,, the lack of adaptation in the antenna (2.2dB is considered), t(9) the transmitter antenna radia- tion diagram and L the path loss. Total path loss is given by the following expression [3] (Fig. 1): L[dB] = Lo + 20 log(S + d )  + Le with where Lo is the l m  free space propagation loss, D and d are the perpendicular distances from the external wall to the BS and mobile, respectively, and S is the physical distance between the BS antenna and the external wall at the actual floor. The grazing angle 8 is calculated as sin0 = D/S and changes considerably with floor height at short distances D. Le is the attenuation of the external wall at perpendicular illumination and LGe is the addi- tional loss when 0 = 0” (20dB is considered). r l  is the attenuation due to internal walls, where Lwi is the attenuation due to a wall of type i and ki the number of walls of type i in the line between the transmitter and receiver. If there are no internal walls, the addi- tional loss is given by r 2  with a the extra attenuation in dB/m (-0.6dB/m is considered). Four different types of wall are consid- ered: light walls (non-supporting wall such as plasterboard, wood, L,,,: 1.5-3dB), medium walls (thin concrete or brick walls, L,,,,: 4- 6dB), heavy wall (concrete wall, L,,,: 7-10dB) and external walls (loss changes from 7 to 12dB). It is important to note that the loss factors are not physical losses but model coefficients which are optimised by multiple linear regression to the measured path loss. So the values include the effect of furniture, diffraction and scat- tering as well as the signal path guided through corridors. internal walls base station floor plan of building BS 4 D building elevation Fig. 1 Parameters used in propagation model m 2100 ELECTRONICS LETTERS 29th October 1998 Vol. 34 No. 22 Systeni urcliitecture: All the required BSs are placed outdoors and can be connected to the BS controller via cable inside the hub con- tainer. Moreover, this network layout allows the container to be moved from one construction site to another as needed, avcdding costly network deployment with indoor BS layout. Owing to the low transmitted power specified in the DECT system and to cope with building penetration losses, directive antennas will be used. This allows us to illuminate only the building to be covered reduc- ing interference with other systems. The antenna gain, the radia- tion beamwidth and the distance between the antenna a d  the building determine the number of floors to be covered by one sin- gle antenna and then if more antennas are required. Staircase Soffwure tool: An interactive software tool for assisting in BS placement, which is intended to be easy to use, has been designed. After the user has selected a possible BS location within a graphi- cal building plan, the system interprets the building plan and uses the proposed path loss model to estimate coverage regions. The software tool allows arbitrary antenna radiation patterns and ori- entations (and includes a database of commercial antennas). It can also deal with arbitrary building topology and construction mate- rials. The predicted signal level is represented in different colours and in 3D as the building is in progress, therefore offering the pos- sibility of designing the DECT network in an active way, choosing the best configuration at each construction stage the software is programmed in AutoLisp and in C language and runs combined with AutoCAD (at least the 13th version). A databasc is generated with information about different construction materials at the fre- quency band of the DECT system allowing the associatisn of building walls, windows, etc. to building materials from the data- base and therefore to attenuation. The software is structured by menus and submenus. Inteiactiv- ity is also possible as system parameters can be changed through the program. There are functions to help in choosing automati- cally the best antenna type and position accounting for the possi- bility of having more than one antenna. In this case, the coverage area is represcnted with an indication of which antenna is the best server at each floor plan and also giving the coverage percentage obtained with each antenna. The possibility that at the final con- struction stage perhaps it will be difficult to reach some locations of the building due to obstacle shadowing (walls and cdings already constructed can introduce considerable attenuation) has been also considered. In this case, there is the possibility of locat- ing a repeater (directive antenna pointing towards the B1S and omnidirectional antenna for the coverage of the floor(s) to obtain a global coverage of the building). Repeatcr coverage coul3 also be represented. As an example in Fig. 2 the received power for a given area inside the building is represented in different colc urs. 6.9 . . . . . . . . . . . . . . . . . .  " . . "  Fig. 2 Received signal level in area inside building hfmsuwment ~.rzi~~paign: A signal generator (HP8644A) wi.s uscd as the transmitter. Both a U4 monopole and a directive antenna were used as transniittcrs, the receiver being a U4 monopole con- nected to a spectrum analyser (HP8561A). The video output of the spectrum analyser was connected through an acquisition card to a personal computer. Fading due to movement was removed by averaging. Some of the wall loss factors obtained are given in Table 1. To validate the model more nieasureinents were made for different BS antennas and illumination angles, comparing pre- dicted and measured received power through the calculation of the RMS error. We found that the mean error is very low (0.7dB) wtth a deviation of - 6.4dB, which is of the same order as most mobile power prediction models. Table 1: Empirical wall loss factors I Type of wall I Attenuation I ~ ELECTRONICS LETTERS 29th October 1998 Vol. 34 No. 22 2101 Conclusions: Existing simulation tools do not take into account the fourth dimension on a construction site: time. They also sel- dom support specific systems such as DECT, devices such as directional antennas, and environments such as, for instance, those required to operate in a mixture of indoor and outdoor scenarios. Olur work enables construction companies to plan the DECT net- work in advance for the full duration of the construction project. Acknowledgments: This work has been performed in the frame- work of the ACTS project AC088 MICC 'Mobile integrated com- munications in constiuction'. The authors would like to acknowledge the contributions of their collegues from Bouygues Challenger, ETDE Reseaux et Communications, BICC PLC, Hochtief AG and Hochtieff Software, Fraunhofer Institut Arbe- itswirtschaft und Organisation, Dragados, Institut Cerda and Technical Research Centre of Finland. Also the authors wish to specially thank M. Deguine for his help in construction aspects and valuable discussions. 0 IEE 1998 Electronics Letters Onlinr No: I9981359 S. Ruiz, Y. Sampcr, J.  Pkrez, R.  Agusti and J.  Olmos (Univcrsitat F'oliticnica de Catulunja, D4-Curnp~is Nor& UPC, C/Jordi Girona 1-3, ON034 Rurcelon~i, S'min) 4 September 1998 E-mail: silvia@xaloc.upc.es References I Mobile Integrated Communications in Construction (MICC- AC088): Project managed by the European Coniission under the European Advanced Comm. Technologies and Services (ACTS) program General Information SEIDEL, s., and RAPPAPORT. T.: '914MHz path loss prediction models for indoor wireless communications in multifloored buildings', IEEE Trcms., 1992, AP-40, (2) ,  pp. 207-217 BERG, J E.: 'Building penetration'. Final report COST 231, Chap. 4, Section 4.6 2 3 Carry-select adder using single ripple-carry adder T.-Y. Chang and M.-J. Hsiao liistead of using dual carry-ripple adders. a carry select adder scheme using an add-one circuit to replace one carry-ripple adder requires 29.2% fewer transistors with a speed penalty of 5.9% for bit length 17 = 64. If speed is crucial for this 64bit adder, then two of the original carry-selcct adder blocks can be substituted by the proposed scheme with a 6.39'0 area saving and the same speed. ,rntr.oductiori: The carry-select adder (CSA) [l] provides a compro- inise between a small area but longer delay carry-ripple adder (CRA) and a larger area with shorter delay carry look-ahead 

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