Recommendation ITU-R P (06/2017)

Transcription

1 Recommendation ITU-R P (06/2017) Propagation data and prediction methods or the planning o indoor radiocommunication systems and radio local area networks in the requency range 300 MHz to 100 GHz P Series Radiowave propagation

2 ii Rec. ITU-R P Foreword The role o the Radiocommunication Sector is to ensure the rational, equitable, eicient and economical use o the radio-requency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit o requency range on the basis o which Recommendations are adopted. The regulatory and policy unctions o the Radiocommunication Sector are perormed by World and Regional Radiocommunication Conerences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy or ITU-T/ITU-R/ISO/IEC reerenced in Annex 1 o Resolution ITU-R 1. Forms to be used or the submission o patent statements and licensing declarations by patent holders are available rom where the Guidelines or Implementation o the Common Patent Policy or ITU-T/ITU-R/ISO/IEC and the ITU-R patent inormation database can also be ound. Series o ITU-R Recommendations (Also available online at Series BO BR BS BT F M P RA RS S SA SF SM SNG TF V Title Satellite delivery Recording or production, archival and play-out; ilm or television Broadcasting service (sound) Broadcasting service (television) Fixed service Mobile, radiodetermination, amateur and related satellite services Radiowave propagation Radio astronomy Remote sensing systems Fixed-satellite service Space applications and meteorology Frequency sharing and coordination between ixed-satellite and ixed service systems Spectrum management Satellite news gathering Time signals and requency standards emissions Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2017 ITU 2017 All rights reserved. No part o this publication may be reproduced, by any means whatsoever, without written permission o ITU.

3 Rec. ITU-R P Scope RECOMMENDATION ITU-R P Propagation data and prediction methods or the planning o indoor radiocommunication systems and radio local area networks in the requency range 300 MHz to 100 GHz (Question ITU-R 211/3) ( ) This Recommendation provides guidance on indoor propagation over the requency range rom 300 MHz to 100 GHz. Inormation is given on: path loss models; delay spread models; eects o polarization and antenna radiation pattern; eects o transmitter and receiver siting; eects o building materials urnishing and urniture; eects o movement o objects in the room; statistical model in static usage. The ITU Radiocommunication Assembly, considering a) that many new short-range (operating range less than 1 km) personal communication applications are being developed which will operate indoors; b) that there is a high demand or radio local area networks (RLANs) and wireless private business exchanges (WPBXs) as demonstrated by existing products and intense research activities; c) that it is desirable to establish RLAN standards which are compatible with both wireless and wired communications; d) that short-range systems using very low power have many advantages or providing services in the mobile and personal environments such as RF sensor networks and wireless devices operated in TV white space bands; e) that knowledge o the propagation characteristics within buildings and the intererence arising rom multiple users in the same area is critical to the eicient design o systems; ) that there is a need both or general (i.e. site-independent) models and advice or initial system planning and intererence assessment, and or deterministic (or site-speciic) models or some detailed evaluations, noting a) that Recommendation ITU-R P.1411 provides guidance on outdoor short-range propagation over the requency range 300 MHz to 100 GHz, and should be consulted or those situations where both indoor and outdoor conditions exist; b) that Recommendation ITU-R P.2040 provides guidance on the eects o building material properties and structures on radiowave propagation,

4 2 Rec. ITU-R P recommends that the inormation and methods in Annex 1 be adopted or the assessment o the propagation characteristics o indoor radio systems between 300 MHz and 100 GHz. Annex 1 1 Introduction Propagation prediction or indoor radio systems diers in some respects rom that or outdoor systems. The ultimate purposes, as in outdoor systems, are to ensure eicient coverage o the required area (or to ensure a reliable path, in the case o point-to-point systems), and to avoid intererence, both within the system and to other systems. However, in the indoor case, the extent o coverage is well-deined by the geometry o the building, and the limits o the building itsel will aect the propagation. In addition to requency reuse on the same loor o a building, there is oten a desire or requency reuse between loors o the same building, which adds a third dimension to the intererence issues. Finally, the very short range, particularly where millimetre wave requencies are used, means that small changes in the immediate environment o the radio path may have substantial eects on the propagation characteristics. Because o the complex nature o these actors, i the speciic planning o an indoor radio system were to be undertaken, detailed knowledge o the particular site would be required, e.g. geometry, materials, urniture, expected usage patterns, etc. However, or initial system planning, it is necessary to estimate the number o base stations to provide coverage to distributed mobile stations within the area and to estimate potential intererence to other services or between systems. For these system planning cases, models that generally represent the propagation characteristics in the environment are needed. At the same time the model should not require a lot o input inormation by the user in order to carry out the calculations. This Annex presents mainly general site-independent models and qualitative advice on propagation impairments encountered in the indoor radio environment. Where possible, site-speciic models are also given. In many cases, the available data on which to base models was limited in either requency or test environments; it is hoped that the advice in this Annex will be expanded as more data are made available. Similarly, the accuracy o the models will be improved with experience in their application, but this Annex represents the best advice available at this time. 2 Propagation impairments and measures o quality in indoor radio systems Propagation impairments in an indoor radio channel are caused mainly by: relection rom, and diraction around, objects (including walls and loors) within the rooms; transmission loss through walls, loors and other obstacles; channelling o energy, especially in corridors at high requencies; motion o persons and objects in the room, including possibly one or both ends o the radio link, and give rise to impairments such as:

5 Rec. ITU-R P path loss not only the ree-space loss but additional loss due to obstacles and transmission through building materials, and possible mitigation o ree-space loss by channelling; temporal and spatial variation o path loss; multipath eects rom relected and diracted components o the wave; polarization mismatch due to random alignment o mobile terminal. Indoor wireless communication services can be characterized by the ollowing eatures: high/medium/low data rate; coverage area o each base station (e.g. room, loor, building); mobile/portable/ixed; real time/non-real time/quasi-real time; network topology (e.g. point-to-point, point-to-multipoint, each-point-to-each-point). It is useul to deine which propagation characteristics o a channel are most appropriate to describe its quality or dierent applications, such as voice communications, data transer at dierent speeds, image transer and video services. Table 1 lists the most signiicant characteristics o typical services. TABLE 1 Typical services and propagation impairments Services Wireless local area network WPBX Indoor paging Indoor wireless video Characteristics High data rate, single or multiple rooms, portable, non-real time, point-to-multipoint or each-pointto-each-point Medium data rate, multiple rooms, single loor or multiple loors, real time, mobile, point-to-multipoint Low data rate, multiple loors, non-real time, mobile, point-tomultipoint High data rate, multiple rooms, real time, mobile or portable, point-topoint Propagation impairments o concern Path loss temporal and spatial distribution Multipath delay Ratio o desired-to-undesired mode strength Path loss temporal and spatial distribution Path loss temporal and spatial distribution Path loss temporal and spatial distribution Multipath delay 3 Path loss models The use o this indoor transmission loss model assumes that the base station and portable terminal are located inside the same building. The indoor base to mobile/portable radio path loss can be estimated with either site-general or site-speciic models. 3.1 Site-general models The models described in this section are considered to be site-general as they require little path or site inormation. The indoor radio path loss is characterized by both an average path loss and its associated shadow ading statistics. Several indoor path loss models account or the attenuation o the signal through multiple walls and/or multiple loors. The model described in this section

6 4 Rec. ITU-R P accounts or the loss through multiple loors to allow or such characteristics as requency reuse between loors. The distance power loss coeicients given below include an implicit allowance or transmission through walls and over and through obstacles, and or other loss mechanisms likely to be encountered within a single loor o a building. Site-speciic models would have the option o explicitly accounting or the loss due to each wall instead o including it in the distance model. The basic model has the ollowing orm: where: N : : d : do : L(do) : L : L total L(do) N log 10 d d o L (n) db (1) distance power loss coeicient requency (MHz) separation distance (m) between the base station and portable terminal (where d 1 m) reerence distance (m) path loss at do (db), or a reerence distance do at 1 m, and assuming ree-space propagation L(do) = 20 log where is in MHz loor penetration loss actor (db) n : number o loors between base station and portable terminal (n 0), L = 0 db or n = 0. Typical parameters, based on various measurement results, are given in Tables 2 and 3. Although these tables are or mainly up to 100 GHz corresponding to the scope o this Recommendation, the power loss coeicients at 300 GHz are also provided or possible uture extension o requency usage in indoor environments. Additional general guidelines are given at the end o the section. Frequency (GHz) TABLE 2 Power loss coeicients, N, or indoor transmission loss calculation Residential Oice Commercia l Factory Corridor (14) (4) (9) (14) (5) 33 (6) (14) (2) 28 (3) Data Centre 31

7 Rec. ITU-R P Frequency (GHz) Residential Oice TABLE 2 (end) Commercia l Factory Corridor (14) (12) 29.9 (12) 27.6 (8) (12, 13) 17.9 (12, 13) 24.8 Data Centre (14) (12) 29.6 (12) (12, 13) 18.6 (12, 13) (10) 13 (10) (4, 10) (1) 17 (1) 16 (1) (7)(9) (11) 16 (11) (4, 11) (1) (15) 19.5 (9, 15) 20.2 (15) (1) 60 GHz and 70 GHz values assume propagation within a single room or space, and do not include any allowance or transmission through walls. Gaseous absorption around 60 GHz is also signiicant or distances greater than about 100 m which may inluence requency reuse distances (see Recommendation ITU-R P.676). (2) Apartment: Single or double storey dwellings or several households. In general most walls separating rooms are concrete walls. (3) House: Single or double storey dwellings or a household. In general most walls separating rooms are wooden walls. (4) Computer room where there are many computers around the room. (5) Transmitter and receiver are on the same loor and both antennas are set at ceiling height o 2.7 m. (6) Path between transmitter and receiver is semi-shielded by metal materials and both antennas height is 1.5 m. (7) Transmit and receive antennas have 15.4 beam width. (8) Railway station (170 m 45 m 21 m(h)) and Airport terminal (650 m 82 m 20 m(h)): NLoS case, 60 hal-power beam width antenna or transmitter is set at the height o 8 m, and 10 beam width or receiver is set at 1.5 m on the loor. The value was obtained rom the maximum path gain among various Tx and Rx antenna orientations. (9) Transmitter and receiver are on LoS corridor. (10) Transmit antenna beamwidth 56.3º, synthesised 360º in azimuth at receiver with 19.7º beamwidth in elevation. (11) Transmit antenna beamwidth 40º, synthesised 360º in azimuth at receiver with 14.4º beamwidth in elevation. (12) The upper number is or LoS cases and the lower number is or NLoS cases. (13) The environments are same to (8) and a Tx antenna with 60 beamwidth is set at the height o 8 m and a Rx with an omni-directional antenna is set at the height o 1.5 m. (14) Open oice (50 m 16 m 2.7 m (H)): LoS case. Averaged results with Tx heights o 2.6 and 1.2 m. Rx height was 1.5 m height. Both Tx and Rx are omni-directional antennas. (15) Transmit and received antennas have 10 beamwidth.

8 6 Rec. ITU-R P TABLE 3 Floor penetration loss actors, L (db) with n being the number o loors penetrated, or indoor transmission loss calculation (n 1) Frequency (GHz) 0.9 Residential Oice Commercial 9 (1 loor) 19 (2 loors) 24 (3 loors) n (n 1) (n 1) (1) (apartment) 5 (house) (1) Per concrete wall. (2) Wooden mortar. 13 (1) (apartment) 7 (2) (house) (1 loor) 26 (2 loors) 16 (1 loor) 22 (1 loor) 28 (2 loors) For the various requency bands where the power loss coeicient is not stated or residential buildings, the value given or oice buildings could be used. It should be noted that there may be a limit on the isolation expected through multiple loors. The signal may ind other external paths to complete the link with less total loss than that due to the penetration loss through many loors. When the external paths are excluded, measurements at 5.2 GHz have shown that at normal incidence the mean additional loss due to a typical reinorced concrete loor with a suspended alse ceiling is 20 db, with a standard deviation o 1.5 db. Lighting ixtures increased the mean loss to 30 db, with a standard deviation o 3 db, and air ducts under the loor increased the mean loss to 36 db, with a standard deviation o 5 db. These values, instead o L, should be used in site-speciic models such as ray-tracing. The indoor shadow ading statistics are log-normal and standard deviation values (db) are given in Table 4. TABLE 4 Shadow ading statistics, standard deviation (db), or indoor transmission loss calculation Frequency (GHz) Residential Oice Commercial (4) (4) (4)

9 Rec. ITU-R P Frequency (GHz) TABLE 4 (end) Residential Oice Commercial (4) (2) 6.6 (2) 6.7 (1) (2, 3) 1.4 (2, 3) (4) (2) 6.8 (2) (2, 3) 1.6 (2, 3) (1) Railway station (170 m 45 m 21 m(h)) and Airport terminal (650 m 82 m 20 m(h)): NLoS case, 60 hal-power beam width antenna or transmitter is set at the height o 8 m, and 10 beam width or receiver is set at 1.5 m on the loor. The value was obtained rom the maximum path gain among various Tx and Rx antenna orientations. (2) The upper number is or LoS case and the lower number is or NLoS case. (3) The environments are same to (1) and a Tx antenna with 60 beamwidth is set at the height o 8 m and a Rx with an omni-directional antenna is set at the height o 1.5 m. (4) Open oice (50 m 16 m 2.7 m (H)): LoS case. Averaged results with Tx heights o 2.6 and 1.2 m. Rx height was 1.5 m height. Both Tx and Rx are omni-directional antennas. Although available measurements have been made under various conditions which make direct comparisons diicult and only select requency bands have been reported upon, a ew general conclusions can be drawn, especially or the MHz band. Paths with a line-o-sight (LoS) component are dominated by ree-space loss and have a distance power loss coeicient o around 20. Large open rooms also have a distance power loss coeicient o around 20; this may be due to a strong LoS component to most areas o the room. Examples include rooms located in large retail stores, sports arenas, open-plan actories, and open-plan oices. Corridors exhibit path loss less than that o ree-space, with a typical distance power coeicient o around 18. Grocery stores with their long, linear aisles exhibit the corridor loss characteristic. Propagation around obstacles and through walls adds considerably to the loss which can increase the power distance coeicient to about 40 or a typical environment. Examples include paths between rooms in closed-plan oice buildings. For long unobstructed paths, the irst Fresnel zone breakpoint may occur. At this distance, the distance power loss coeicient may change rom about 20 to about 40. The decrease in the path loss coeicient with increasing requency or an oice environment (Table 2) is not always observed or easily explained. On the one hand, with increasing requency, loss through obstacles (e.g. walls, urniture) increases, and diracted signals contribute less to the received power; on the other hand, the Fresnel zone is less obstructed at higher requencies, leading to lower loss. The actual path loss is dependent on these opposing mechanisms.

10 8 Rec. ITU-R P Site-speciic models For estimating the path-loss or ield strength, site-speciic models are also useul. Models or indoor ield strength prediction based on the uniorm theory o diraction (UTD) and ray-tracing techniques are available. Detailed inormation o the building structure is necessary or the calculation o the indoor ield strength. These models combine empirical elements with the theoretical electromagnetic approach o UTD. The method takes into account direct, single-diracted and single-relected rays, and can be extended to multiple diraction or multiple relection as well as to combinations o diracted and relected rays. By including relected and diracted rays, the path loss prediction accuracy is signiicantly improved. 4 Delay spread models 4.1 Multipath The mobile/portable radio propagation channel varies in time, requency, and with spatial displacement. Even in the static case, where the transmitter and receiver are ixed, the channel can be dynamic, since scatterers and relectors are likely to be in motion. The term multipath arises rom the act that, through relection, diraction, and scattering, radiowaves can travel rom a transmitter to a receiver by many paths. There is a time delay associated with each o these paths that is proportional to path length. (A very rough estimate o the maximum delay time to be expected in a given environment may be obtained simply rom the dimensions o the room and rom the act that the time (ns) or a radio pulse to travel distance d (m) is approximately 3.3 d.) These delayed signals, each with an associated amplitude, orm a linear ilter with time varying characteristics. 4.2 Impulse response The goal o channel modelling is to provide accurate mathematical representations o radio propagation to be used in radio link and system simulations or the system deployment modelling. Since the radio channel is linear, it is ully described by its impulse response. Once the impulse response is known one can determine the response o the radio channel to any input. This is the basis o link perormance simulation. The impulse response is usually represented as power density as a unction o excess delay, relative to the irst detectable signal. This unction is oten reerred to as a power delay proile. An example is shown in Fig. 1 o Recommendation ITU-R P.1407 except that the time-scale or indoor channels would be measured in nanoseconds rather than microseconds. This Recommendation also contains deinitions o several parameters that characterize impulse response proiles. The channel impulse response varies with the position o the receiver, and may also vary with time. Thereore it is usually measured and reported as an average o proiles measured over one wavelength to reduce noise eects, or over several wavelengths to determine a spatial average. It is important to deine clearly which average is meant, and how the averaging was perormed. The recommended averaging procedure is to orm a statistical model as ollows: For each impulse response estimate (power delay proile), locate the times beore and ater the average delay TD (see Recommendation ITU-R P.1407) beyond which the power density does not exceed speciic values ( 10, 15, 20, 25, 30 db) with respect to the peak power density. The median, and i desired the 90th percentile, o the distributions o these times orms the model.

11 Rec. ITU-R P r.m.s. delay spread Power delay proiles are oten characterized by one or more parameters, as mentioned above. These parameters should be computed rom proiles averaged over an area having the dimensions o several wavelengths. (The parameter r.m.s. delay spread is sometimes ound rom individual proiles, and the resulting values averaged, but in general the result is not the same as that ound rom an averaged proile.) A noise exclusion threshold, or acceptance criterion, e.g. 30 db below the peak o the proile, should be reported along with the resulting delay spread, which depends on this threshold. Although the r.m.s. delay spread is very widely used, it is not always a suicient characterization o the delay proile. In multipath environments where the delay spread exceeds the symbol duration, the bit error ratio or phase shit keying modulation depends, not on the r.m.s. delay spread, but rather on the received power ratio o the desired wave to the undesired wave. This is particularly pronounced or high symbol-rate systems, but is also true even at low symbol rates when there is a strong dominant signal among the multipath components (Rician ading). However, i an exponentially decaying proile can be assumed, it is suicient to express the r.m.s. delay spread instead o the power delay proile. In this case, the impulse response can be reconstructed approximately as: where: S : tmax : r.m.s. delay spread maximum delay tmax S. t / S e or 0 t tmax h ( t) (2) 0 otherwise The advantage in using the r.m.s. delay spread as the model output parameter is that the model can be expressed simply in the orm o a table. Typical delay spread parameters estimated rom averaged delay proiles or indoor environments are given in Table 5. In Table 5, column B represents median values that occur requently, columns A and C correspond to the 10% and 90% values o the cumulative distribution. The values given in the Table represent the largest room sizes likely to be encountered in each environment.

12 10 Rec. ITU-R P Freq. (GHz) 1.9 Polarization TABLE 5 r.m.s. delay spread parameters Time delay resolution (ns) Tx beam width (degrees) Rx beam width (degrees) A (ns) B (ns) C (ns) Note or A, B, C Residential VV 10 Omni Omni Oice VV 10 Omni Omni Commercial VV 10 Omni Omni TV studio VV 4.2 Omni Omni Oice (3) VV 1.8 Omni Omni (1) VV 1.8 Omni Omni (2) Corridor VV 1.8 Omni Omni Air cabin VV 1.8 Omni Omni Factory VV 1.8 Omni Omni Residential VV 10 Omni Omni Oice VV 10 Omni Omni Commercial VV 10 Omni Omni Residential VV 10 Omni Omni Oice VV 10 Omni Omni Commercial VV 10 Omni Omni Commercial VV 2 60 Omni Environment Computer 31.5 cluster Dual (4) 38 Commercial VV 2 40 Omni Computer cluster Oice/ classroom (5) (7) VV/HH VV/HH Corridor VV/HH Computer cluster Oice (6) Computer cluster (3, 5) (3, 5) (5) (5, 12) (5) (5, 12) (5) (5, 12) VV (8) VV (9) VV 0.22 Omni Omni (10) VV 0.22 Omni Omni (11) VV/HH (5) (5, 12)

13 Rec. ITU-R P Freq. (GHz) Environment Oice/ classroom Polarization Time delay resolution (ns) TABLE 5(end) Tx beam width (degrees) VV/HH Corridor VV/HH Rx beam width (degrees) (1) Tx and Rx antennas at ceiling height 2.6 m and (2) at desk level o 1.5 m. (3) Upper and lower values are LoS and NLoS cases, respectively. (4) Mean value o VV, VH, HV, and HH. (5) 20 db, (6) 25 db and (7) 30 db threshold. (8) 30 db threshold, receiver pointing towards transmitter. (9) 20 db threshold, receiver antenna rotated around 360 degrees. (10) Tx and Rx are on body to on body and (11) on body to o body. A (ns) B (ns) C (ns) Note or A, B, C (5) (5, 12) (5) (5, 12) (12) Receiver antenna was rotated in a step o 5 o around 360 degrees in measurements. The value represents a directional delay spread when the bore-sight o receiver antenna is not aligned to the direction o transmitter. Within a given building, the delay spread tends to increase as the distance between antennas increases, and hence to increase as path loss increases. With greater distances between antennas, it is more likely that the path will be obstructed, and that the received signal will consist entirely o scattered paths. The r.m.s. delay spread S is roughly in proportion to the area o the loor space, F s, and is given by equation (3). where the units o Fs and S are m 2 and ns, respectively. 10 log S = 2.3 log(f s ) (3) This equation is based on measurements in the 2 GHz band or several room types such as oice, lobby, corridor and gymnasium. The maximum loor space or the measurements was m 2. The median value o the estimation error is 1.6 ns and the standard deviation is 24.3 ns. When the delay spread S is represented in db, the standard deviation o S is in the range o about 0.7 to 1.2 db. 4.4 Frequency selectivity statistics Multipath propagation leads to requency selectivity. The extent o requency selectivity is characterized rom coherent bandwidth, average ade bandwidth, and level crossing requency as detailed in Recommendation ITU-R P Values o the average ade bandwidth that ell below the 6 db threshold rom measurements in indoor environments representative o laboratory and oice environment in the 2.38 GHz and in TV studios in the 2.25 GHz band are 27% and 21%, respectively. The corresponding level crossing requency values are: 0.12 per MHz and 0.24 per MHz.

14 12 Rec. ITU-R P Site-speciic models Whilst the statistical models are useul in the derivation o planning guidelines, deterministic (or site-speciic) models are o considerable value to those who design the systems. Several deterministic techniques or propagation modelling can be identiied. For indoor applications, especially, the inite dierence time domain (FDTD) technique and the geometrical optics technique have been studied. The geometrical optics technique is more computationally eicient than the FDTD. There are two basic approaches in the geometrical optics technique, the image and the ray-launching approach. The image approach makes use o the images o the receiver relative to all the relecting suraces o the environment. The coordinates o all the images are calculated and then rays are traced towards these images. The ray-launching approach involves a number o rays launched uniormly in space around the transmitter antenna. Each ray is traced until it reaches the receiver or its amplitude alls under a speciied limit. When compared to the image approach, the ray-launching approach is more lexible, because diracted and scattered rays can be handled along with the specular relections. Furthermore, by using the ray-splitting technique or the variation method, computing time can be saved while adequate resolution is maintained. The ray-launching approach is a suitable technique or area-wide prediction o the channel impulse response, while the image approach is suitable or a point-to-point prediction. Deterministic models generally make assumptions about the eects o building materials at the requency in question. (See 7 on building materials properties.) A site-speciic model should account or the geometry o the environment, relection, diraction, and transmission through walls. The impulse response at a given point can be expressed as: where: h(t) : N : Mrn : Mpn : nu: Pnv: rn : N M M rn pn h( t) 1 j n nu Pnv e ( t ) n n1 u1 v1 rn impulse response number o incident rays number o relections o ray n number o penetrations o ray n u-th wall relection coeicient o ray n v-th wall penetration coeicient o ray n path length o ray n n : delay o ray n. Rays, relected rom or penetrated through walls and other suraces, are calculated by using the Fresnel equations. Thereore, the complex permittivity o the building materials is required as input data. Measured permittivity values o some building materials are given in 7. In addition to the relected and penetrated rays, as described by equation (4), the diracted and scattered rays should also be included in order to adequately model the received signal. Especially, this is the case within corridors having corners and with other similar propagation situations. The uniorm theory o diraction (UTD) can be used to calculate the diracted rays. (4)

15 Rec. ITU-R P Eect o polarization and antenna radiation pattern In an indoor environment, there is not only a direct path but also relected and diracted paths between the transmitter and receiver. The relection characteristics o a building material depends on polarization, incidence angle, and the material s complex permittivity, as represented by Fresnel s relection ormula. The angles-o-arrival o multipath components are distributed, depending on the antenna beamwidths, building structures and siting o transmitter and receiver. Thereore, polarization and the eective antenna radiation pattern can signiicantly aect indoor propagation characteristics. 5.1 Line-o-sight case Eect o polarization Delay spread It is widely accepted that, in line-o-sight (LoS) channels, directional antennas reduce r.m.s. delay spread as compared to omnidirectional antennas and that circular polarization (CP) reduces it compared to linear polarization (LP). Thereore, in this case a directional CP antenna oers an eective means o reducing the delay spread. The prime mechanism o the polarization dependence can be attributed to the act that, when the CP signal is incident on a relecting surace at an incidence angle smaller than the Brewster angle, the handedness o the relected CP signal is reversed. The reversal o the CP signal at each relection means that multipath components arriving ater one relection are orthogonally polarized to the LoS component; this eliminates a signiicant proportion o the multipath intererence. This eect is independent o requency, as predicted theoretically and supported by indoor propagation experiments in the requency range 1.3 to 60 GHz, and applies equally indoors and outdoors. Since all existing building materials have Brewster angles greater than 45, multipath due to single relections (that is, the main source o multipath components) is eectively suppressed in most room environments irrespective o the interior structure and materials in the room. The possible exceptions are environments where very large incident angles dominate the multipath, such as in a long hallway. The variation in r.m.s. delay spread on a moving link is also reduced when CP antennas are used Cross-polarization discrimination ratio (XPR) Cross-polarized signal components are generated by relection and diraction. It is widely known that the ading correlation characteristic between orthogonally polarized antennas has a very low correlation coeicient. Polarization diversity techniques and MIMO (multiple-input, multiple-output) systems with orthogonally polarized antennas are developed that employ this ading characteristic. Employing the polarization diversity technique is one solution to improving the received power, and the eect o the technique is heavily dependent on the XPR characteristic. Moreover, the channel capacity can be improved by appropriately using the cross polarization components in MIMO systems. Thus, the communication quality can be improved by eectively using the inormation regarding the cross-polarized waves in a wireless system. The measurement results or the median and mean value o the XPR in each environment are shown in Table 6.

16 14 Rec. ITU-R P Frequency (GHz) Case 1: Case 2: Case 3: 5.2 Environment Oice Conerence room TABLE 6 Examples o XPR Values Antenna coniguration Case 1 Case 2 Case 3 Case 1 Case 2 Case 3 XPR (db) N/A 6.39 (median) 6.55 (mean) 4.74 (median) 4.38 (mean) 8.36 (median) 7.83 (mean) 6.68 (median) 6.33 (mean) N/A The transmitting and receiving antennas are set above the height o obstacles. Remarks Measurement The transmitting antenna is set above the height o obstacles, and the receiving antenna is set to a height similar to that o obstacles. Transmitting and receiving antennas are set to heights similar to that o obstacles Eect o antenna radiation pattern Since multipath propagation components have an angle-o-arrival distribution, those components outside the antenna beamwidth are spatially iltered out by the use o a directional antenna, so that the delay spread and angular spread can be reduced. Indoor propagation measurement andray-tracing simulations perormed at 60 GHz, with an omnidirectional transmitting antenna and our dierent types o receiving antennas (omnidirectional, wide-beam, standard horn, and narrowbeam antennas) directed towards the transmitting antenna, show that the suppression o the delayed components is more eective with narrower beamwidths. Table 7 shows an example o the antenna directivity dependence o a static r.m.s. delay spread not exceeded at the 90th percentile obtained rom ray-tracing simulations at 60 GHz or an empty oice. It may be noted that a reduction in the r.m.s. delay spread may not necessarily always be desirable, as it can mean increased dynamic ranges or ading o wideband signals as a result o missing inherent requency diversity. In addition, it may be noted that some transmission schemes take advantage o multipath eects.

17 Rec. ITU-R P TABLE 7 Example o antenna directivity dependence o static r.m.s. delay spread Frequency (GHz) Tx antenna 60 Omnidirectional Rx antenna beamwidth (degrees) Static r.m.s. delay spread (90 th percentile) (ns) Room size (m) Omnidirectional Omnidirectional Empty oice room Empty oice room Remarks Ray-tracing Ray-tracing NLoS Millimetre-wave radio systems are expected to use directional antennas and/or various beamorming techniques with multiple antenna arrays to overcome relatively high path loss and establish reliable communication links. It is necessary to study the inluence o antenna beamwidth on radio propagation characterization. The prediction methods o delay and angular spread with respect to antenna beamwidth have been developed based on measurements in a typical oice and commercial environments at 28 and 38 GHz, respectively. To derive the multipath distribution characteristics rom narrow to wide antenna beamwidths, channel impulse responses collected through a rotation o 10 o narrow-beam antenna were combined in the power, delay and angle domains. The r.m.s. delay spread DS depends on hal-power beamwidth o antenna (degree): DS ( ) log ns (5) 10 where is a coeicient o r.m.s. delay spread and the range o is deined as 10 o 120 o. Table 8 lists the typical values o the coeicients and a standard deviation based on each measurement conditions. The coeicients o delay spread represent cases when the boresights o antennas were aligned to have maximum receiving power in LoS and NLoS situations, respectively.

18 16 Rec. ITU-R P TABLE 8 Typical coeicients or r.m.s. delay spread Measurement conditions Coeicients o r.m.s. delay spread (GHz) Environment Scenario h 1 (m) h 2 (m) Range (m) Tx beamwidth (degree) Rx beamwidth (degree) (ns) Railway Station Airport Terminal Railway Station Airport Terminal Oice LoS NLoS LoS NLoS LoS NLoS LoS NLoS LoS omni 10 NLoS The r.m.s. angular spread AS depends on hal-power beamwidth o antenna (degree): AS () degree (6) where and are coeicients o r.m.s. angular spread and the range o is deined as 10 o 120 o. Table 9 lists the typical values o the coeicients and standard deviation based on each measurement conditions. The coeicients o angular spread represent cases when the boresights o antennas are aligned to have maximum receiving power in LoS and NLoS situations, respectively.

19 Rec. ITU-R P TABLE 9 Typical coeicients or r.m.s. angular spread Measurement conditions Coeicients o r.m.s. angular spread (GHz) Environment Scenario h 1 (m) h 2 (m) Range (m) Tx beamwidth (degree) Rx beamwidth (degree) (degree) Railway Station Airport Terminal Railway Station Airport Terminal Oice LoS NLoS LoS NLoS LoS NLoS LoS NLoS LoS omni 10 NLoS Obstructed path case When the direct path is obstructed, the polarization and antenna directivity dependence o the delay spread may be more complicated than those in the LoS path. There are ew experimental results relating to the obstructed case. However, an experimental result obtained at 2.4 GHz suggests that the polarization and antenna directivity dependence o the delay spread in the obstructed path is signiicantly dierent rom that in the LoS path. For instance, an omnidirectional horizontally polarized antenna at the transmitter and a directional CP receiving antenna gave the smallest r.m.s. delay spread and lowest maximum excess delay in the obstructed path. 5.3 Orientation o mobile terminal In the portable radio environment, propagation is generally dominated by relection and scattering o the signal. Energy is oten scattered rom the transmitted polarization into the orthogonal polarizations. Under these conditions, cross-polarization coupling increases the probability o adequate received levels o randomly oriented portable radios. Measurement o cross-polarization coupling carried out at 816 MHz showed a high degree o coupling. 6 Eect o transmitter and receiver siting There are ew experimental and theoretical investigations regarding the eect o transmitter and receiver site on indoor propagation characteristics. In general, however, it may be suggested that the base station should be placed as high as possible near the room ceiling to attain LoS paths as ar as possible. In the case o hand-held terminals, the user terminal position will o course be dependent on the user s motion rather than any system design constraints.

20 18 Rec. ITU-R P However, or non-hand-held terminals, it is suggested that the antenna height be suicient to ensure LoS to the base station whenever possible. The choice o station siting is also very relevant to system coniguration aspects such as spatial diversity arrangements, zone coniguration, etc. 7 Eect o building materials, urnishings and urniture Indoor propagation characteristics are aected by relection rom and transmission through the building materials. The relection and transmission characteristics o those materials depend on the complex permittivity o the materials. Site-speciic propagation prediction models may need inormation on the complex permittivity o building materials and on building structures as basic input data, and such inormation is given in Recommendation ITU-R P Specular relections rom loor materials such as loorboard and concrete plate are signiicantly reduced in millimetre-wave bands when materials are covered by carpet with rough suraces. Similar reductions may occur with window coverings such as draperies. Thereore, it is expected that the particular eects o materials would be more important as requency increases. In addition to the undamental building structures, urniture and other ixtures also signiicantly aect indoor propagation characteristics. These may be treated as obstructions and are covered in the path loss model in 3. 8 Eect o movement o objects in the room The movement o persons and objects within the room cause temporal variations o the indoor propagation characteristics. This variation, however, is very slow compared to the data rate likely to be used, and can thereore be treated as virtually a time-invariant random variable. Apart rom people in the vicinity o the antennas or in the direct path, the movement o persons in oices and other locations in and around the building has a negligible eect on the propagation characteristics. Measurements perormed when both o the link terminals are ixed indicate that ading is bursty (statistics are very non-stationary), and is caused either by the perturbation o multipath signals in areas surrounding a given link, or by shadowing due to people passing through the link. Measurements at 1.7 GHz indicate that a person moving into the path o a LoS signal causes a 6 to 8 db drop in received power level, and the K-value o the Nakagami-Rice distribution is considerably reduced. In the case o non-los conditions, people moving near the antennas did not have any signiicant eects on the channel. In the case o a hand-held terminal, the proximity o the user s head and body aect the received signal level. At 900 MHz with a dipole antenna, measurements show that received signal strength decreased by 4 to 7 db when the terminal was held at the waist, and 1 to 2 db when the terminal was held against the head o the user, in comparison to received signal strength when the antenna was several wavelengths away rom the body. When the antenna height is lower than about 1 m, or example, in the case o a typical desktop or laptop computer application, the LoS path may be shadowed by people moving in the vicinity o the user terminal. For such data applications, both the depth and the duration o ades are o interest. Measurements at 37 GHz in an indoor oice lobby environment have shown that ades o 10 to 15 db were oten observed. The duration o these ades due to body shadowing, with people moving continuously in a random manner through the LoS, ollows a log-normal distribution, with the mean and standard deviation dependent on ade depth. For these measurements, at a ade depth o 10 db, the mean duration was 0.11 s and the standard deviation was 0.47 s. At a ade depth o 15 db, the mean duration was 0.05 s and the standard deviation was 0.15 s.

21 Rec. ITU-R P Measurements at 70 GHz have shown that the mean ade duration due to body shadowing were 0.52 s, 0.25 s and 0.09 s or the ade depth o 10 db, 20 db and 30 db, respectively, in which the mean walking speed o persons was estimated at 0.74 m/s with random directions and human body thickness was assumed to be 0.3 m. Measurements indicate that the mean number occurrence o body shadowing in an hour caused by human movement in an oice environment is given by: N 260 D p (7) where Dp (0.05 < Dp < 0.08) is the number o persons per square metre in the room. Then the total ade duration per hour is given by: where T s is mean ade duration. T T N (8) The number o occurrences o body shadowing in an hour at the passage in an exhibition hall was 180 to 280, where Dp was 0.09 to The distance dependency o path loss in an underground mall is aected by human body shadowing. The path loss in an underground mall is estimated by the ollowing equation with the parameters given in Table 10. where: s 1.4 log ( ) log ( x x C L x) 10 ) ( 10 : requency (MHz) x: distance (m). 10 db (9) Parameters or the non-line-o-sight (NLoS) case are veriied in the 5 GHz band and those o the LoS case are applicable to the requency range o 2 GHz to 20 GHz. The range o distance x is 10 m to 200 m. The environment o the underground mall is a ladder type mall that consists o straight corridors with glass or concrete walls. The main corridor is 6 m wide, 3 m high, and 190 m long. The typical human body is considered to be 170 cm tall and 45 cm wide shoulders. The densities o passers-by are approximately persons/m 2 and 0.1 persons/m 2 or a quiet period (early morning, o-hour) and a crowded period (lunchtime or rush-hour), respectively. TABLE 10 Parameters or modelled path loss unction in Yaesu underground mall LoS δ (m 1 ) C (db) NLoS δ (m 1 ) O-hour C (db) Rush-hour

22 20 Rec. ITU-R P Angular spread models 9.1 Cluster model In a propagation model or broadband systems using array antennas, a cluster model combining both temporal and angular distributions is applicable. The cluster comprises scattered waves arriving at the receiver within a limited time and angle as shown in Fig. 1. Temporal delay characteristics are ound in 4 o this Recommendation. The distribution o cluster arrival angle i based on the reerence angle (which may be chosen arbitrarily) or an indoor environment is approximately expressed by a uniorm distribution on [0, 2. Cluster 2 Scattered waves FIGURE 1 Image o cluster model Cluster 3 Scattered waves Tx array Cluster 1 Scattered waves Reerence angle Rx array Arrival level (db) Arrival level (db) Cluster 1 Cluster 3 Cluster 2 Cluster 1 Cluster 2 Arrival time Cluster 3 0 Arrival angle i i : cluster arrival angle, i : standard deviation o angular spreadwithin a cluster, i P Angular distribution o arrival waves rom within i-th cluster The probability density unction o the angular distribution o arrival waves within a cluster is expressed by: 1 P 2 i i i exp 2 i i where is the angle o arrival o arriving waves within a cluster in degrees reerencing to the reerence angle and i is the standard deviation o the angular spread in degrees. The angular spread parameters in an indoor environment are given in Table 11. (10)

23 Rec. ITU-R P TABLE 11 Angular spread parameters in indoor environment LoS NLoS Mean (degrees) Range (degrees) Mean (degrees) Range (degrees) Hall Oice Home Corridor Double directional angular spread In a propagation model or broadband communication with multiple antenna arrays at the transmitter and receiver, the angular distribution at the transmitting and at the receiving stations is applicable. From measurements with 240 MHz bandwidth at 2.38 GHz, the mean RMS angular spread in an indoor corridor and oice environment or 20 db threshold level are given in Table 12. Station 1 height (m) TABLE 12 Double directional angular spread RMS angular spread at station 1 (degrees) Station 2 height (m) RMS angular spread at station 2 (degrees) Corridor and oice Statistical model in static usage When wireless terminals such as cellular phones and WLANs are used indoors, they are basically static. In static usage, the wireless terminal itsel does not move, but the environment around it changes due to the movement o blocking objects such as people. In order to accurately evaluate the communication quality in such an environment, we provide a channel model or static indoor conditions, which gives the statistical characteristics o both the probability density unction (PDF) and autocorrelation unction o received level variation at the same time. The channel models or indoor NLoS and LoS environments are discussed Deinition Nperson: number o moving people w: equivalent diameter o moving person (m) v: moving speed o people (m/s) Pm: S(x,y): T : rp: total multipath s power layout o moving area maximum requency shit or static mobile terminal received power at the mobile terminal : requency (Hz)

24 22 Rec. ITU-R P p(rp,k): R(t): RN(t): probability density unction (PDF) o received power deined as Nakagami- Rice distribution with K-actor K: K-actor deined in the Nakagami-Rice distribution P(): PN(): 10.2 System model autocorrelation unction o received level autocorrelation coeicient o received level power spectrum power spectrum normalized by power P(0). Figure 2 shows the system model. The moving objects considered are only people; the i th person is represented as a disk with a diameter o w (m) separated rom the mobile terminal (MT) by ri(m). Each moving person walks in an arbitrary direction between 0 and 2 at a constant speed o v (m/s) and moves within an arbitrary area S(x,y) around the MT. The number o moving people is Nperson and a moving person absorbs a part o the energy o the paths that cross his width, w. The multipaths arrive at the terminal uniormly rom all horizontal directions. Figures 3 and 4 show the typical rooms considered, rectangular and circular, respectively. Moving area: S( x, y) FIGURE 2 System model Moving person w Speed v r i Mobile terminal P FIGURE 3 Rectangular-shaped room layout L2 ( x1, y2) y 2 L ( x, y ) L2( x1, y2) y 2 L ( x, y ) Moving person BS Direct path Moving person x 1 MT x 2 x 1 MT x 2 L 1( x1, y1) y 1 L ( x, y ) L1( x1, y1) y 1 L ( x, y ) a) Without direct path (NLS) o b) With direct path (Lo S) P