Over-the-Air Performance Testing of a Real 4G LTEBase Station in a Reverberation Chamber

Massimo Barazzetta∗, Davide Micheli†, Franco Moglie‡ and Valter Mariani Primiani‡∗Nokia Solutions and Networks Italia, Via Roma 108, 20060 Cassina de’ Pecchi, Italy

Email: massimo.barazzetta@nsn.com†Telecom Italia, Via di Val Cannuta 250, 00166 Rome, Italy

Email: davide.micheli@telecomitalia.it‡DII, Universita Politecnica delle Marche, Via Brecce Bianche 12, 60131 Ancona, Italy

Emails: f.moglie@univpm.it, v.mariani@univpm.it

Abstract—Fourth generation (4G) cellular systems have beennowadays rolled out already in several countries in the world.With networks open to commercial use, one of the key issues ishow the quality perceived by the user is influenced by multipathpropagation, like it may happen in indoor locations or in any kindof places where electromagnetic waves are partially reflected bywalls and other objects. In order to verify this, the signal of areal 4G base station connected to the real radio access network ofTelecom Italia has been transmitted into a reverberation chamberwhere a client was running FTPs using a 4G capable USBdongle as a modem. This paper describe the tests that have beenperformed and focus on how changes in propagation conditionsaffected the performances perceived by the user.

I. INTRODUCTION

The use of reverberation chambers (RC) for testing wirelesssystems has been growing in recent years [1]. Reverberationchambers are able to replicate multipath propagation condi-tions [2], with the possibility to force the ratio between thediffuse and direct component of the electromagnetic field [3].General performance [4] and throughput of wireless commu-nication systems can be successfully measured inside an RC[5]. RCs are also used to check the performance of antennasfor wireless applications, such as those for MIMO systems [6],[7], including the measurement of the diversity gain [8] andthe total efficiency [9]. The possibility to range from a line-of-sight (LOS) to a complete no-line-of-sight (NLOS) condition,between receiving and transmitting antennas [10], allows tochange the ratio between the direct and the diffuse energy,typically quantified by the Rician K-factor [11]. The K-factorcan be further tuned varying the chamber loading amount [12],i.e. by the inserting a controllable quantity of absorbing ma-terials inside the chamber, or using two transmitting antennashaving different orientations [3].

The antenna received signal can be also manipulated to fit awanted statistical distribution, ranging from a pure Rayleigh todifferent degrees of Rician distribution, applying a proper sam-ple selection procedure [13]. Controlling the antenna reciprocalorientation, the chamber loading, and the stirrer rotating speedit is possible to give the wanted value to all the parametersof interest for wireless testing, such as the delay spread time[14], the coherence time [15], and the coherence bandwidth[16]. In that way, it is possible to replicate both dynamic andstatic propagation conditions [17] and to emulate both indoor[18] and outdoor [19] propagation conditions, including the

presence of high Doppler spreads [20]. The RC also allowsto combine both performance and immunity tests on completewireless systems, carried out in the same conditions [21].

These capabilities suggested to extend RC use for testingbase transceiver station (BTS) [22], also thinking to longterm evolution (LTE) radio access technology [23]. Testing aretypically carried out by means of BTS emulators [24] and otherlaboratory instrumentation to check channel performances. Inthe present work the function of a real, and commercially avail-able, LTE FDD [25] - BTS is analyzed, by measuring someparameters that characterize the quality of the transmission.

II. EXPERIMENTAL SET-UP

Fig. 1 reports a schematic block diagram of the adoptedmeasurement set-up. We employed the RC placed at EMCLaboratory of Universita Politecnica delle Marche. It hasdimensions 6×4×2.5 m3 and is equipped by a vertical z-foldedstirrer with variable rotating speed from 1 deg/s up to 80 deg/s.The chamber fundamental mode resonates at about 45 MHz,therefore the RC is well overmoded in correspondence ofthe BTS operating frequency (1800 MHz band, 10 MHzbandwidth). The RC is fed by the LTE BTS (Nokia Solutionsand Networks Flexi Multiradio) through a double polarizedtransmitting antenna. A 60 dB total attenuation is insertedalong each transmitter branch to achieve a realistic receivedpower level for the internal terminal (about -80 dBm). Theinternal terminal is made by a notebook equipped by a USBdata card category 3 [26]. In this paper, the terms “data card”and “user equipment” (UE) are used interchangeably. A laptop-based drive test tool (Nemo Outdoor V7.0), was running on thenotebook to record the main parameters of the air interface. Adirectional coupler is inserted along one branch, as indicatedin the figurename 1, in order to pick up the transmitted signaland send it to a LTE signal demodulator.

The LTE BTS provides also a set of statistical countersthat were collected during each test via a supervision system.The correlation between logs collected via the vector signalanalyzer, results of drive test tool and statistical counters hasbeen investigated. In order to be able to do this, it was crucialto synchronize the start time and the stop time of each testwith the measurement period and the clock of the BTS.

For the same reason, the clock of the client was also syn-chronized with BTS clock. During the tests also the RC loading

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Fig. 1. Schematic view of the measurement set-up. The notebook inside thechamber is equipped by a USB data card and a software test tools. The LTEsignal demodulator performs a vector signal analysis. The LTE base station isconnected by an optic fiber to the LTE network of Telecom Italia.

Fig. 2. Inner view of the RC. “A”: transmitting antenna, “B”: vertical stirrer,“C”: horizontal stirrer, “D”: notebook, “E”: USB LTE dongle, “F” absorbingpyramidal sheet, “G” absorbing plane sheet.

conditions were varied starting from the empty chamber byadding electromagnetic (EM) absorbing material. In particular,a medium load was obtained inserting two pyramidal absorberssheets, whereas the highest load was achieved adding other fiveabsorbing sheets, as shown in Fig. 2.

The insertion of the absorbing material determined theRC quality factor reduction. This action is important to makethe propagation conditions close to those occurring in realenvironments. As an example, let consider a typical roomhaving a volume V and a window with area A. Assuming idealreflecting walls around the window and neglecting the windowglasses, the theoretical Q factor value of such a reverberatingenvironment, excited by the large aperture A, can be achievedby [27]

Q =8πV

λA, (1)

where λ is the wavelength. Fig. 3 reports the measuredquality factor for the three chamber loading conditions andthe theoretical Q factor obtained by (1) for a room withdimensions 5 × 4 × 3 m3 having a 1.2 × 1.5 m2 window. Wecan note that the chosen loading conditions can emulate wellpractical situations. The Q factor reduction also determines thecoherence bandwidth enhancement and a variation in the power

Fig. 3. Measured quality factor for the empty chamber (green line), medium(red line) and high (black line) loading conditions. Dotted lines refer to theraw data, and continuous lines refer to the averaged date over a 100 MHzband. The theoretical quality factor of a practical room with a window is alsoreported (blue dashed line).

Fig. 4. Chamber coherence bandwidth as function of the absorbing materialamount. Dotted lines refer to the raw data, and continuous lines refer to theaveraged date over a 100 MHz band.

delay profile. Fig. 4 reports the coherence bandwidth, that inturn is the range of frequencies over which two frequencycomponents remain in strong amplitude correlation. Fig. 5reports the power delay profile, which gives the intensity of asignal received through a multipath channel as a function ofthe time delay. During the activity, also the rotating speed ofthe vertical stirrer has been varied between values of 1 deg/s,30 deg/s and 80 deg/s in order to replicate both almost-staticand more dynamic conditions in each load condition of thechamber.

III. DESCRIPTION OF THE BTS OPERATING CONDITIONSAND ANALYZED PARAMETERS

Some downlink tests were carried out varying the chamberquality factor, the stirrer rotating speed and the throughputnominal amount between the BTS and the receiving terminal.These conditions were obtained by setting properly the TCPreceiving window of the client in order to demand the through-put of 30 Mbps with a single file transfer, and then, runningtwo parallel FTP sessions to reach a condition of mediumbandwidth occupation (medium throughput, > 50 Mbps) andrunning three or more sessions to reach the highest throughput(> 70 Mbps) and fill completely the available bandwidth. Thelast condition (7−8 Mbps) was selected to replicate an almost

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Fig. 5. Chamber power delay profile as function of the absorbing materialamount.

typical case, where the LTE capable mobile (or data card) isused when running applications that use only a little portion ofthe radio resources available, like web browsing. In our tests,we manage to obtain a constant throughput of 7 − 8 Mbpsthroughout the test, just reducing the available bandwidth from10 MHz down to 1 MHz. Such value, is anyway always higherthan the coherence bandwidth at 1800 MHz (Fig. 4).

During the data transmissions the following statistical pa-rameters were measured and stored for the transmission qualityanalysis. Here a brief explanation of them is reported.

• Received signal strength indicator (RSSI): is the totalwideband power received by the UE. It includes allpossible contributes to the received signal, including noiseand interference [28].

• Reference signal received power (RSRP): is the averageof the power of resource elements that carry cell-specificreference signals [28].

• Reference signal received quality (RSRQ): is the ratio ofRSRP and RSSI [28].

• Signal to interference and noise ratio (SINR): is the ratiobetween the wanted part of the signal and the sum ofinterference and noise [29].

• Transport block (TB): is the information that is transmit-ted by the BTS in the LTE transmission time interval of1 ms.

• Block error rate (BLER): the rate of transport blocks(TB, [30]) received with errors, or never received, whichare negatively acknowledged by the UE in an automaticrequest for re-transmission process (HARQ).

• PDSCH net throughput: is the throughput measured atphysical layer at the client in the data downlink channel,removing the portion of the bit rate that was due to there-transmissions of negatively acknowledged TBs.

• Channel quality indications (CQIs): dimensionless mea-surement of air interface quality performed by UE andreported to BTS and used by the latter for link adaptationpurposes [28].

• Modulation and coding scheme (MCS). The LTE basestation decide how much a transport block transmissionshould be protected based on feedback received by theUE and BLER requirements. The higher is the protectionof one TB, the more robust is the transmission, but thelower is the amount of information that could be sent on

Fig. 6. Outer view of the RC (“A”) with the BTS rack (“B”) and the adoptedinstrumentation. “C”: attenuators, “D”: LTE signal demodulator, “E” portableLTE signal demodulator, “F” PC connected to the BTS and LTE demodulators,“G”: PC connected to the RC motor controller (“H”).

it. The protection level, together with the chosen modu-lation, identify the modulation and coding scheme [28]concept, which is defined for each transport block thatis transmitted. Thus, the LTE BTS has a link adaptationalgorithm that receives the feedback received by the UEand produce the MCS that best suite with the actual radioconditions and BLER requirements.

Also the error vector magnitude (EVM) was observed bythe LTE demodulator. It is a measurement of demodulatorperformance in the presence of impairments. The measuredsymbol location obtained after decimating the recovered wave-form at the demodulator output are compared against the idealsymbol locations [29]. Fig. 6 shows a photo of the outer ofthe RC with the BTS rack and the employed instrumentation.

IV. RESULTS

In this section we report some results referred to a LOScondition between the transmitting antenna and the receivingterminal. The radio link quality is quantified by SINR andRSRQ and it is affected by chamber radio propagation condi-tions. Degradation of quality affects in turn the channel qualityindication (CQI) reported by UE, that is used by the BTS inorder to choose the modulation and coding scheme (MCS)which best fits a desired working point in terms of target blockerror rate (BLER). Metal surfaces cause multiple reflectionswhich in turn increase the delay spread, as indicated in Fig. 5.The guard timer between the transmission of two contiguousLTE symbols on a given subcarrier is about few µs. Late arrivalcomponents signal which are caused by multiple reflections,may generate some intersymbol interference. Fig. 7, Fig. 8,and Fig. 9 report the RSRQ and the RSRP parameters forthe high, medium low throughput condition respectively. Asfar as the RSRP is concerned, it can be observed that in thehigh throughput case the RSRP level is higher when the RC isempty. This happens since the EM energy is maintained longerinside the RC due to the high quality factor value. It almosthalves in case of RC medium load, and it is further halved incase of RC high load. About the RSRQ, the higher the RC loadthe better the RSRQ. This effect can be observed in Fig. 7.

Fig. 10 reports the SINR behavior. Increasing the numberof absorbing sheets, it can be observed that there is an

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Fig. 7. Radio quality parameters for the high throughput condition. RSRQand RSRP parameters are reported. “Black squares” refer to the empty RC,“red circles” to the medium loaded RC, and “blue triangles” to the high loadedRC.

Fig. 8. Radio quality parameters for the medium throughput condition. RSRQand RSRP parameters are reported. “Black squares” refer to the empty RC,“red circles” to the medium loaded RC, and “blue triangles” to the high loadedRC.

improvement of SINR together with RSRQ, from 25 dB to29 dB. On the other way, when the RC is empty, the effectof stirrer rotation on SINR becomes relevant, whatever thedemanded throughput and the bandwidth occupation are. Thisis quite well visible in all SINR charts in Fig. 10, Fig. 11,and Fig. 12. The RC load affects the PDSCH net throughput.The remarkable improvement in the net throughput is dueto the strong reduction of the measured BLER. In mediumthroughput and low throughput cases, we can see similarbehaviors, even if the RSRQ and SINR improvements arescaled down due to the lower utilization rate of radio resources(4 dB to 2 dB improvements on SINR). In Fig. 10 andFig. 11, it can be observed that SINR is affected by both useractivity and chamber conditions in case of high and mediumthroughput. Whilst for low throughput case it is affected onlyby RC load conditions.

Fig. 13 shows the relationship between the PDSCH BLERreported by the drive test tool and statistical counters withthe RC conditions and different demanded throughput. Thethroughput is affected by the highest BLER when the RC isempty. The lowest BLER occurs with a medium RC load. Thevelocity of the RC stirrer affects the BLER too. In the lowthroughput case where band occupation is low and disruptiongenerated by the user on his own is negligible, the BLER ismaximum if chamber is empty and stirrer rotates fast.

Fig. 9. Radio quality parameters for the low throughput condition. RSRQand RSRP parameters are reported. “Black squares” refer to the empty RC,“red circles” to the medium loaded RC, and “blue triangles” to the high loadedRC.

Fig. 10. Radio quality parameters for the high throughput condition. TheSINR and the PDSCH net throughput are reported. “Black squares” refer tothe empty RC, “red circles” to the medium loaded RC, and “blue triangles”to the high loaded RC.

Fig. 11. Radio quality parameters for the medium throughput condition. TheSINR and the PDSCH net throughput are reported. “Black squares” refer tothe empty RC, “red circles” to the medium loaded RC, and “blue triangles”to the high loaded RC.

The purpose of this investigation is to understand if thetarget BLER set on the BTS is suitable for the propagationenvironment. Results are shown in Fig. 14 for the highthroughput condition, in Fig. 15 for the medium throughputcondition, and in Fig. 16 for the low throughput condition (forclarity, only the MCSs which were most frequently allocated

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Fig. 12. Radio quality parameters for the low throughput condition. TheSINR and the PDSCH net throughput are reported. “Black squares” refer tothe empty RC, “red circles” to the medium loaded RC, and “blue triangles”to the high loaded RC.

1 deg/s 30 deg/s 80 deg/sStirrer Rotation Speed

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Fig. 13. Different throughput values of the BLER varying chamber loadand throughput condition: “HTP” stays for high throughput, “MTP” stays formedium throughput, and “LTP” stays for low throughput. Empty symbolsare the values reported by statistical counters, whereas filled symbols are thevalues reported by the drive test tool. “Black squares” refer to the empty RC,“red circles” to the medium loaded RC, and “blue triangles” to the high loadedRC.

are considered). Tests with high absorption load in chamberpresent slightly lower throughput than tests with medium loadin chamber. When the load is high (lower Q factor), BLER ishigher (up to 3%, if the stirrer rotates fast) and SINR is slightlylower. This could seem strange at first sight, since we expect areduction of multiple reflections when more absorbing sheetsare in the chamber, thus performances should be better. Indeed,when all absorbers are inside, UE sends better feedback (CQIs)on radio quality to the BTS. Based on these feedbacks, thelink adaptation triggers the selection of the highest MCS(MCS28) for the TB to be transmitted. Since the MCS28is less robust MCS27, in some TTI its transmission couldbe negatively acknowledged by the receiving end, especiallywhen fading conditions generate fast fluctuations that affect thetransmission. This turn into a higher BLER figure. It could beworth to explore the possibility to trigger MCS27 more often inorder to achieve better BLER figures overall, thus better end-user performances. The higher BLER measured in LQ (low Qfactor) compared to the MQ (medium Q factor) case (Fig. 13)indicate that, in the first environment, the system is slightlyunder-performing compared to the second. The link adaptationalgorithm selects among different MCSs, trying to reach an

Fig. 14. BLER in the case of high throughput condition: “HQ” stays forhigh Q factor RC, “MQ” stays for medium Q factor RC, and “LQ” stays forlow Q factor RC.

Fig. 15. BLER in the case of medium throughput condition: “HQ” stays forhigh Q factor RC, “MQ” stays for medium Q factor RC, and “LQ” stays forlow Q factor RC.

Fig. 16. BLER in the case of low throughput condition: “HQ” stays for highQ factor RC, “MQ” stays for medium Q factor RC, and “LQ” stays for lowQ factor RC.

overall BLER target that, in our tests, was set equal to 10%.Values lower than 10%, or approaching this target, could beconsidered good. Thus, MCS28 was frequently selected sinceits BLER was 3% only. Nevertheless, such value was higherthan the one measured in the MQ case (1%). On the other hand,when we move to the limit condition of empty chamber (HQ),the link adaptation is somehow deceived by the very difficultpropagation conditions, and BLER for MCS28 increase until49% in high throughput case with fast-rotating stirrer.

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V. CONCLUSION

Several tests have been carried out on the LTE BTSoperating inside a reverberation chamber. The chamber qualityfactor and the stirrer rotating speed were varied to analyze theireffects on the transmission quality. The results showed howthe link adaptation algorithm reacts in presence of the hostileconditions forced by the higher Q values and by the higherrotating speed. One point of interest highlighted by this studyis the understanding of the interworking between the adaptivemodulation and the channel quality. The BTS automaticallyswitched the modulation scheme from one to another to lookfor a BLER reduction, and this procedure could be furtherimproved on the basis of the observations of this work. Thus,one possible future item is how to tune the target BLER ofthe system, in order to fit the link adaptation behavior to thevarious channel conditions.

ACKNOWLEDGMENT

The authors would like to thank Telecom Italia for support-ing this research under the contract number ODA7010087992,and Anritsu for the support of measuring instruments.

REFERENCES

[1] A. Skarbratt, J. Asberg, and C. Orlenius, “Over-the-air performancetesting of wireless terminals by data throughput measurements inreverberation chamber,” in Proceedings of the 5th European Conferenceon Antennas and Propagation (EUCAP), 2011, pp. 615–619.

[2] E. Genender, C. L. Holloway, K. A. Remley, J. M. Ladbury, G. Koepke,and H. Garbe, “Simulating the multipath channel with a reverberationchamber: Application to bit error rate measurements,” IEEE Trans.Electromagn. Compat., vol. 52, no. 4, pp. 766–777, Nov. 2010.

[3] C. L. Holloway, D. A. Hill, J. M. Ladbury, P. F. Wilson, G. Koepke, andJ. Coder, “On the use of reverberation chambers to simulate a Ricianradio environment for the testing of wireless devices,” IEEE Trans.Antennas Propag., vol. 54, no. 11, pp. 3167–3177, Nov. 2006.

[4] C. Orlenius, N. Aijaz, and M. Franzen, “Active mimo performancemeasurements in connected reverberation chambers,” in 2010 Proceed-ings of the Fourth European Conference on Antennas and Propagation(EuCAP), Barcelona, Spain, Apr. 2010, pp. 1–3.

[5] N. Olano, C. Orlenius, K. Ishimiya, and Z. Ying, “WLAN MIMOthroughput test in reverberation chamber,” in Antennas and PropagationSociety International Symposium, 2008. AP-S 2008, San Diego, CA,USA, Jul. 2008, pp. 1–4.

[6] P.-S. Kildal, C. Orlenius, and J. Carlsson, “OTA testing in multipath ofantennas and wireless devices with MIMO and OFDM,” Proc. IEEE,no. 7, pp. 2145–2157, Jul. 2012.

[7] X. Chen, “Throughput multiplexing efficiency for MIMO antennacharacterization,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp.1208–1211, 2013.

[8] P.-S. Kildal and K. Rosengren, “Correlation and capacity of MIMOsystems and mutual coupling, radiation efficiency and diversity gain oftheir antennas: Simulations and measurements in reverberation cham-ber,” IEEE Commun. Mag., vol. 42, no. 12, pp. 102–112, Dec. 2004.

[9] C. Holloway, H. Shah, R. Pirkl, W. Young, D. Hill, and J. Ladbury,“Reverberation chamber techniques for determining the radiation andtotal efficiency of antennas,” IEEE Trans. Antennas Propag., vol. 60,no. 4, pp. 1758–1770, Apr. 2012.

[10] V. Mariani Primiani and F. Moglie, “Numerical simulation of LOSand NLOS conditions for an antenna inside a reverberation chamber,”Journal of Electromagnetic Waves and Applications, vol. 24, no. 17-18,pp. 2319–2331, 2010.

[11] X. Chen, P.-S. Kildal, and S.-H. Lai, “Estimation of average rician K-factor and average mode bandwidth in loaded reverberation chamber,”IEEE Antennas Wireless Propag. Lett., vol. 10, p. 14371440, 2011.

[12] C. L. Holloway, D. A. Hill, J. M. Ladbury, and G. Koepke, “Require-ments for an effective reverberation chamber: Unloaded or loaded,”IEEE Trans. Electromagn. Compat., vol. 48, no. 1, pp. 187–194, Feb.2006.

[13] A. Marin-Soler, M. Gruden, J. Sanchez-Heredia, P. Hallbjorner,A. Martinez-Gonzalez, A. Rydberg, and D. Sanchez-Hernandez, “Sam-ple selection algorithms for enhanced MIMO antenna measurementsusing mode-stirred reverberation chambers,” IEEE Trans. AntennasPropag., vol. 60, no. 8, pp. 3892–3900, Aug. 2012.

[14] C. L. Holloway, H. A. Shah, R. J. Pirkl, K. A. Remley, D. A. Hill,and J. Ladbury, “Early time behavior in reverberation chambers andits effect on the relationships between coherence bandwidth, chamberdecay time, RMS delay spread, and the chamber buildup time,” IEEETrans. Electromagn. Compat., vol. 54, no. 4, pp. 714–725, Aug. 2012.

[15] A. Sorrentino, G. Ferrara, and M. Migliaccio, “On the coherence timecontrol of a continuous mode stirred reverberating chamber,” IEEETrans. Antennas Propag., vol. 57, no. 10, pp. 3372–3374, 2009.

[16] X. Chen, P.-S. Kildal, C. Orlenius, and J. Carlsson, “Channel soundingof loaded reverberation chamber for over-the-air testing of wirelessdevices: Coherence bandwidth versus average mode bandwidth anddelay spread,” IEEE Antennas Wireless Propag. Lett., vol. 8, pp. 678–681, 2009.

[17] K. A. Remley, S. J. Floris, H. A. Shah, and C. L. Holloway, “Static anddynamic propagation-channel impairments in reverberation chambers,”IEEE Trans. Electromagn. Compat., vol. 53, no. 3, pp. 589–599, Aug.2011.

[18] H. Fielitz, K. Remley, C. Holloway, Q. Zhang, Q. Wu, and D. Matolak,“Reverberation-chamber test environment for outdoor urban wirelesspropagation studies,” IEEE Antennas Wireless Propag. Lett., vol. 9, pp.52–56, 2010.

[19] J. Kunthong and C. Bunting, “Statistical characterization of the 900MHz and 1800 MHz indoor propagation using reverberation sourcestirring technique,” in IEEE Antennas and Propagation Society Inter-national Symposium, 2009. APSURSI ’09, 2009, pp. 1–4.

[20] K. Karlsson, X. Chen, J. Carlsson, and A. Skarbratt, “On OTA testin the presence of doppler spreads in a reverberation chamber,” IEEEAntennas Wireless Propag. Lett., vol. 12, pp. 886–889, 2013.

[21] R. Recanatini, F. Moglie, and V. Mariani Primiani, “Performance andimmunity evaluation of complete WLAN systems in a large reverbera-tion chamber,” IEEE Trans. Electromagn. Compat., vol. 55, no. 5, pp.806–815, 2013.

[22] G. Ferrara, M. Migliaccio, and A. Sorrentino, “Characterization of GSMnon-line-of-sight propagation channels generated in a reverberatingchamber by using bit error rates,” IEEE Trans. Electromagn. Compat.,vol. 49, no. 3, pp. 467–473, Aug. 2007.

[23] M. Andersson, A. Wolfgang, C. Orlenius, and J. Carlsson, MeasuringPerformance of 3GPP LTE Terminals and Small Base Stations inReverberation Chambers. Boca Raton, FL: CRC Press, Taylor &Francis Group, 2009, ch. 12, pp. 413–458.

[24] P.-S. Kildal, A. Hussain, G. Durisi, C. Orlenius, and A. Skarbratt, “LTEMIMO multiplexing performance measured in reverberation chamberand accurate simple theory,” in 2012 6th European Conference onAntennas and Propagation (EUCAP), 2012, pp. 2299–2302.

[25] “LTE; evolved universal terrestrial radio access (E-UTRA); FDD re-peater radio transmission and reception,” ETSI, Sophia Antipolis Cedex,France, 3GPP Technical Specification TS 36.106 V8.7.0, Jul. 2012.

[26] “LTE; evolved universal terrestrial radio access (E-UTRA); user equip-ment (UE) radio access capabilities,” ETSI, Sophia Antipolis Cedex,France, 3GPP Technical Specification TS 36.306 V8.9.0, Apr. 2013.

[27] D. A. Hill, Electromagnetic Fields in Cavities: Deterministic andStatistical Theories. Hoboken, NJ: Wiley-IEEE Press, 2009, p. 206.

[28] “LTE; evolved universal terrestrial radio access (E-UTRA); physicallayer procedures,” ETSI, Sophia Antipolis Cedex, France, 3GPP Tech-nical Specification TS 36.213 V8.8.0, Oct. 2009.

[29] H. Holma and A. Toskala, LTE for UMTS: OFDMA and SC-FDMABased Radio Access. John Wiley & Sons, Ltd, 2009, pp. 83–135.

[30] “LTE; evolved universal terrestrial radio access (E-UTRA); physicallayer, measurements,” ETSI, Sophia Antipolis Cedex, France, 3GPPTechnical Specification TS 36.214 V8.7.0, Jun. 2010.

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