doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 1 Enterprise Simulation Scenario Date:

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 2 Improvements to the enterprise simulation scenario Situation The Enterprise Network simulation scenario (#4) is derived from n scenario with 1 AP with 30 clients The Enterprise Network simulation scenario (#4) assumes no fluorescent light effect because recent measurements have not replicated this effect. Complication 11ac has 5 or 6 channels at 5GHz whereas 11n had 12 channels. Overlapping APs are much more likely with 5 or 6 channels. We freshly present measurements of the fluorescent light effect showing that typically it is absent, yet is significant when present. Key Line We should make improvements to the Enterprise Network sim scenario (#4) in the functional requirements of 09/451 in order to account for overlapping APs and the fluorescent light effect. Summary

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 3 There are only five or six 80 MHz channels There are five 80MHz channels at 5 GHz −36-48, 52-64, , , −Plus a sixth, , with a regulatory change Typical channel plan with six channels is:

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 4 So we expect two overlapping BSSs APs co-channel with the (0,0) AP are at −(-20,-40), (20,40)m [44m range] −(-40,40), (40,40)m [57m range] −(0,60), (-60,0)m [60m range] Now range with -76dBm CCA (for 80MHz) is 50m: 17dBm + 3dBi - 47dB[1m] - 20log 10 (5m/1m) - 35log 10 (50m/5m) = -76dBm With multistorey deployments, 20dBm TX power, 6dBi antennas, cubes, realistic sensitivities, 10 or 20m breakpoint, the actual overlap is worse But let’s assume 2 overlapping BSSs for simplicity

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 5 Proposal: let’s add more realism into scenario #4 Uplink/downlink MU-MIMO / SDMA and OFDMA are valuable technologies that we should be exploring, yet they are more challenging in an OBSS world We should include OBSS as an “impairment” because otherwise there is a risk we will make suboptimal design choices based on false optimism The simplest proposal is to triplicate the APs and clients in scenario #4, keep the first copy at (0,0), translate the second copy by (20,40) and translate the third copy by (-20,-40)m −We can reduce the number of clients per BSS since 90 clients may be overkill (e.g clients per BSS) Note: multiple APs is more in harmony with Usage Model 2d in 09/161r2

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 6 A Fresh Look at Fluorescent Light Measurements 09/537r0 and 09/538r0 did not observe any Doppler spread from fluorescent tubes, and 09/537r0 reported a lack of literature on this topic. In the next few slides we present Cisco-sponsored measurements from the literature obtained in the timeframe on this topic We agree that 11n erred by making the fluorescent light effect a pervasive property of channels D and E. In our experience, there are locations where the fluorescent light effect is negligible −Yet when present it can be significant

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 7 Requirements for a fluorescent light effect From practical considerations, a significant fluorescent light effect requires: 1.Fluorescent lights (most typical of enterprise environment) 2.Preferably downward-pointed, uncovered(?) fluorescent light fixtures 3.Light fixtures which capture RF reflections and pass them through the fluorescent tube (akin to design goal of light dispersion) 4.A location with suitable multipath: e.g. a dominant fluorescent path, or two paths of similar strength with one affected by fluorescent tubes 1 is typical of enterprise, 2 is out of our control yet seems to happen in a proportion of customer sites (e.g. 1/3 sites with submissions), 3 is reasonably typical for downward-pointed fixtures due to coincident design, 4 is a statistical property (that is hard to capture, but see next slides)

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 8 Measurement Environment Three areas were tested; they were not cherry picked: they were simply chosen as a typical desktop location for a laptop Each area was tested in detail: the RX antennas were scanned over a local area of 4 x 4 wavelengths with a 0.05 wavelength increment (6400 locations). 2TX (2λ separation) x 2RX (0.5λ) antennas, all located in the same (cluttered) office room with clear LOS At each antenna position, 4 MIMO sub-channels (Tx1-Rx1, Tx1-Rx2, Tx2-Rx1, Tx2-Rx2) are measured 100 times with an interval of 1.3 ms while the antennas are stationary. Fluorescent lights ON using Australian (50Hz) electricity Measured during the night (2 hours per measurement) when no human activity was present As can be seen from the photo, the fluorescent tubes are surrounded by metal plates which might enhance the fluorescent light effect

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 9 Doppler variations only affect selected locations within the area Plot of power deviation between 1.3ms- separated samples of a single subcarrier −1.3ms due to HW Most locations for this subcarrier exhibit little power deviation About 10% of locations for this subcarrier show dB deviation Across the band (not shown), about 20% of locations are affected

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 10 At this location, the channel across the whole band can change Here we look at the subcarrier power (y axis) over time at one location. The weakest subcarriers (2-6MHz) vary the most (from circa 0dB to -10 dB and back to 0dB) Even the strongest subcarriers (-8 to -6 MHz) jump in time: mostly +6dB, then a brief period down towards 4dB, then 8dB, back to 4dB, then back at the start to +6dB

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 11 Example impact of fluorescent light effect on channel estimation Assume the channel at a subcarrier is estimated initially during the LTFs then kept fixed for the packet duration. What impact does the fluorescent light effect have on the constellation after a ZF equalizer? Use an EVM-like measure: where E|x|y indicates the expectation of x over y. With fluorescent lights on, the channel is disturbed cyclostationarily, and the EVM degrades to about - 20dBm at 10ms intervals With fluorescent lights off, coherence is well maintained and EVM is a flat -25dB even after 60ms

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 12 What is the overall incidence of amplitude and phase variation? At 50% of locations and subcarriers, 1.5dB absolute maximum power variation across 1.3ms At 10% of locations and subcarriers, 3.5dB absolute maximum power variation At 1% of locations and subcarriers, 10dB absolute maximum power variation [3.2dB with lights off] At 50% of locations and subcarriers, 22deg absolute maximum subcarrier phase deviation across 1.3ms At 10% of locations and subcarriers, 32deg absolute maximum subcarrier phase deviation At 1% of locations and subcarriers, 80deg absolute maximum subcarrier phase deviation [32deg with lights off]

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 13 Yet, fluorescent light effect is most dramatic with faded subcarriers Plot of power deviation between 1.3ms samples of a single subcarrier versus median RSSI of that subcarrier (130ms) More faded subcarriers vary the most −E.g. when the main static paths superimpose destructively, a weaker dynamic fluorescent path has more influence Variations of dB are common Thus analysis of measurements should be extended to consider impact on the overall impact on capacity

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 14 Summary of the fluorescent light effect The fluorescent light effect is reasonably well-established: −There is peer reviewed literature: e.g. references [36-37] in 03/940r4; plus Hajime Suzuki, Mark Hedley, Graham Daniels, and Colin Jacka, "Spatial distribution of temporal variation caused by active fluorescent lights in office environment," In Proceedings of the URSI Commission F Triennium Open Symposium, pp , Cairns, Australia, June −There are previous positive IEEE submissions: e.g. [33-35] in 03/940r4 although the realism of these is not always clear-cut Of the measurements submitted to 11ac, 1 out of 3 buildings exhibit the effect. In the one building that showed the effect, 3 out of 3 typical laptop areas showed the effect. Within these typical laptop areas, the effect was present at about 20% of locations − Unlike the 11n model 1 out of 3 buildings is not very statistically significant; but it is high enough to be a concern: extrapolating, a non-negligible proportion of buildings are affected, and can degrade the benefits of TXBF & especially SDMA −Narrow nulls are more sensitive to time variation than broad beamforming peaks −The customer-facing vendor perspective is that this stuff should “just work”, whatever the customer’s building construction

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 15 Proposal for the fluorescent light effect Uplink/downlink MU-MIMO / SDMA are valuable technologies that we should be exploring, yet they are more challenging in a time-varying world We should include the fluorescent light effect as an impairment because otherwise there is a risk we will make suboptimal design choices based on false optimism As an initial proposal, we could assume some percentage of client locations are subject to the fluorescent light effect, and reinstate the 11n fluorescent Doppler model for these clients in the enterprise scenario −An initial proposal is 7% (1/3 buildings x 20% of locations at 1 building) Or take a data-driven approach: measurements of more buildings & multiple locations within these buildings, recording the level of the effect

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 16 Questions ?

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 17 Strawpoll 1 The Enterprise Scenario (Scenario #4) in 09/451 should incorporate overlapping BSSs, with additional APs at (20,40) and (-20,-40) and clients to match Y, N, A

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 18 Strawpoll 2 There is sufficient evidence of the fluorescent light effect that it should not be deleted from the 11ac channel model. Y, N, A

doc.: IEEE r0 Submission July 2009 Hart (Cisco Systems) Slide 19 Strawpoll 3 The Enterprise Scenario (Scenario #4) in 09/451 should include the 11n model of the fluorescent light effect for some small percentage of clients Y, N, A