doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 1 60 GHz vs. 5 GHz Propagation Discussion Date: Authors:

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 2 LOS Path Loss at 60 GHz For LOS conditions path loss is mainly governed by the free-space propagation formula. Some papers have reported few dB less path loss and some papers few dB more than the free-space formula. For distances up to 10m, for LOS conditions, it seems like a reasonable assumption (Friis formula): At 1m distance path loss is 68 dB and at 10m distance the path loss is 88 dB. Standard deviation of approximately 5 dB was reported in the literature that accounts for shadowing. A margin due to shadowing has to be added if 90% coverage is to be determined, for example. The margin is a function of the path loss exponent and standard deviation.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 3 NLOS Path Loss at 60 GHz Very few NLOS measurements were made at 60 GHz. With increasing carrier frequency losses due to diffraction, reflection, and material penetration increase for NLOS conditions. When compared to 5 GHz, we estimate that these additional losses are in the 5-10 dB range [1,2]. Standard deviation of shadowing at 60 GHz NLOS propagation is larger than at 5 GHz.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 4 Total Expected NLOS Path Loss at 60 GHz Compared to 5 GHz Free space loss is additional 21 dB. Let’s assume that additional diffraction, penetration and reflection losses are 7 dB. The total additional path loss expected at 60 GHz when compared to the 5 GHz carrier frequency may be about 28 dB. Assuming NLOS distance path loss exponent of 4, this translates into communication range (distance) reduction by a multiplicative factor of 0.2, i.e: Range(60 GHz) = 0.2 Range(5 GHz). The calculation above does not include shadowing standard deviation, it includes only median path loss.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 5 60 GHz NLOS Range Reduction 10 dB Loss15 dB20 dB25 dB30 dB Range factor GHz compared to 5 GHz, path loss exponent = 4 (NLOS) Expected additional loss (includes path loss difference, antenna gain and PA transmit power estimates)

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 6 60 GHz NLOS Range Reduction: Cont’d 10 dB Loss15 dB20 dB25 dB30 dB Range factor GHz compared to 5 GHz, path loss exponent = 3 (NLOS) Expected additional loss (includes path loss difference, antenna gain and PA transmit power estimates)

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 7 60 GHz LOS Range Reduction 10 dB Loss15 dB20 dB25 dB30 dB Range factor GHz compared to 5 GHz, path loss exponent = 2 (LOS) Expected additional loss (includes path loss, antenna gain and PA transmit power estimates)

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 8 PA Power Given current PA technology developments, regulations, and safety reasons it may be expected that the consumer grade PAs at 60 GHz will have up to 10 dB less power that the ones for the 5 GHz WLAN applications, for example (10 mW vs. 100 mW). Some of the lower PA power can be compensated for by antenna gain.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 9 Antenna Gain at 60 GHz – Caution High directivity antennas in a scattering environment lose gain when compared to the omnidirectional antennas. In the literature this is regarded as antenna GRF (gain reduction factor). Directive antennas amplify only some propagation rays, others are attenuated and therefore multipath components are lost that results in a loss of power, loss of diversity, and reduced rank for MIMO systems that reduces spatial multiplexing gains. Omnidirectional antennas amplify all rays evenly, in most cases. Therefore, in path loss calculations, nominal (advertised) antenna gain determined in an anechoic chamber has to be reduced by GRF. It was shown that for outdoor environments the GRF is significant (5-7 dB for 20 o horizontal antenna beamwidth (-3dB beamwidth points)). Indoor environments experience more scattering than outdoor environments potentially resulting in larger GRF. Requires further investigation.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 10 LOS Delay Profiles for Different Antenna Beamwidths at 60 GHz With decreasing antenna beamwidth LOS component is amplified and reflected components are attenuated by the antenna pattern [3]. Tx Omni Antenna Rx Omni Antenna Tx Omni Antenna Rx 60 o Antenna Tx Omni Antenna Rx 10 o Antenna 10 dB 20 dB 30 dB

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 11 Blockage Effects If the LOS component is blocked by a person, for example, it was reported in the literature that up to 20 dB of signal power can be lost [4, 5]. This effect can be illustrated by removing LOS component from the delay profiles on the previous slide. The loss is more pronounced for narrow beamwidth antennas, where LOS component is more dominant. For the omnidirectional antennas there is some empirical evidence that the loss is considerably smaller, up to 6 dB [6]. This result seems too optimistic, should be verified by additional measurements (authors to emulate blockage have removed the strongest LOS path from the delay profile measurements, may not be accurate representation of blockage).

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 12 Blockage Effects: Cont’d To avoid large signal power loss in the case of the direct LOS path blockage, especially in the directional antenna case, adaptive beam antennas may be preferable. It is not clear how the adaptive beam antennas would perform when compared to the omnidirectional antennas in the case of a blockage. If the high reliability link is to be expected, the blockage scenario has to be carefully considered and solution found in order not to break the communication link. Closely spaced multiple transceivers may mitigate shadowing problem, but at the higher cost and complexity.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 13 Discussion To get better handle on 60 GHz propagation the following important measurements should be performed that are missing in the reported and published results: NLOS measurements (very few were reported). GRF - omni vs. directional antenna measurements. Diversity, MIMO measurements - as a next step.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 14 Discussion/Conclusion 60 GHz frequency band may be suitable for applications limited to short range communication, mesh, or distributed (densely deployed) networks. 60 GHz frequency band may not be suitable for applications that require similar range requirements and applications as a/b/g/n systems. To cover a regular house at 2.4 GHz or 5 GHz frequency bands one WLAN Access Point may be required, while for the same radio coverage at 60 GHz 9 units may be required (based on simple assumption that Range(60 GHz) = 1/3 Range(5 GHz)). Additional measurements and analysis should be done at 60 GHz frequency band.

doc.: IEEE /2793r0 Submission November 2007 Vinko Erceg, BroadcomSlide 15 References [1] P. F. M. Smulders and L. MI. Correia “Characterisation of Propagation in 60 GHz Radio Channels,” Electronics and Comm. Eng. Journal, April 1997, pp [2] H. Yang, P. F.M. Smulders and M. H.A.J. Herben “Indoor Channel Measurements and Analysis in the Frequency Bands 2 GHz and 60 GHz,” 2005 IEEE PIMRC, pp [3] Takeshi Manabe, Yuko Miura, and Toshio Iharw “Effects of Antenna Directivity on Indoor Multipath Propagation Characteristics at 60 GHz,” in Proceedings of IEEE PIMRC, Toronto, 1995, pp [4] K. Sato and T. Manabe “Estimation of Propagation-Path Visibility for Indoor Wireless LAN Systems under Shadowing Condition by Human Bodies,” Vehicular Technology Conference, Vol. 3, May 1998, pp – [5] S. Collonge, G. Zaharia, and G. El Zein “Influence of the Human Activity on Wide-Band Characteristics of the 60 GHz Indoor Radio Channel,” IEEE Trans. on Wireless Comm., Vol. 3, No. 6, Nov [6] T. Zwick, T. J. Beukema, and H. Nam “Wideband Channel Sounder With Measurements and Model for the 60 GHz Indoor Radio Channel,” IEEE Trans on Veh Technol, Vol. 54, No. 4, July 2005.