Data density for Light Communications May 2015 doc.: IEEE 802.11-15/0496r1 November 2017 Data density for Light Communications Date: 2017-11-01 Author: Name Company Address Phone Email Cheng Chen University of Edinburgh cheng.chen@ed.ac.uk Prof. Harald Haas pureLiFi Ltd. harald.haas@purelifi.com Cheng Chen (University of Edinburgh) Edward Au (Marvell Semiconductor)

November 2017 Abstract This presentation discussed the data density capabilities relative to existing and emerging 802.11 technologies. Cheng Chen (University of Edinburgh)

802.11ax is going to address dense scenario: November 2017 802.11ax is going to address dense scenario: Dynamic sensitivity control Transmit power control Multiple network allocation vectors Cheng Chen (University of Edinburgh)

Pathloss exponent at 1-6 GHz in indoor environment: 2-3.5 November 2017 Pathloss exponent is a metric determines the decay rate of wireless signal power with propagation distance Pathloss exponent at 1-6 GHz in indoor environment: 2-3.5 Sparse AP deployment: too many users per cell Dense AP deployment: excessive interference causes low spatial reuse Cheng Chen (University of Edinburgh)

Electrical signal Path loss exponent of LC with IM/DD: 4 - 8 November 2017 Electrical signal Path loss exponent of LC with IM/DD: 4 - 8 Can be deployed densely without causing excessive interference Cheng Chen (University of Edinburgh)

Achievable single user data rate in a single cell deployment November 2017 Achievable single user data rate in a single cell deployment 802.11ax single user data rate: Coverage radius: 50m 160MHz modulation bandwidth MU-MIMO with 8 spatial streams OFDMA LiFi single user data rate: Coverage radius: 5.2m 180MHz, 625MHz modulation bandwidth OFDMA Blue filter A user is randomly located in the coverage area of an access point. The user achieves various data rate due to different path loss and fading. This figure shows the probability of a user achieving a certain level of data rate. Cheng Chen (University of Edinburgh)

Achievable cell data rate with multi-cell deployment November 2017 Achievable cell data rate with multi-cell deployment WiFi APs severely interfere with each other when separation between APs is less than 70m. Each LC AP is not able to cover a large area when separation between APs is greater than 10m. No severe interference between LC APs and each LC AP is able to cover a small when separation between APs is in the range of 6m to 10m. Cheng Chen (University of Edinburgh)

Data density comparison November 2017 Data density comparison WiFi: Large coverage, but wider interference spread LC: Smaller coverage, but very little interference spread Little interference spread means capability of dense spatial reuse of transmission resources, which leads to significantly higher data density. Cheng Chen (University of Edinburgh)

Transmission delay November 2017 WiFi: Massive number of stations (STAs) compete for time resource LC: a few number of STAs compete and less delay Cheng Chen (University of Edinburgh)

Simultaneous transmit and receive November 2017 Simultaneous transmit and receive WiFi: Only possible when back off count down of AP and a STA end simultaneously Requires synchronization and changes in the CSMA mechanism LC: Use different spectra for uplink (infrared) and downlink (visible light) No synchronization between uplink and downlink is required. Cheng Chen (University of Edinburgh)

November 2017 MU-MIMO 802.11ax: Requires massive amount of overhead for channel estimation. Channel sounding interval is from 10 ms to more than 100 ms [1] Synchronization between users are required when uplink MU-MIMO is required LC: Unidirectional source Fixed grid of ‘beam’ can be arranged with appropriate lenses ‘Beam forming’ becomes ‘beam selection’ [1] G. Redieteab, L. Cariou, P. Christin and J. F. Hélard, "PHY+MAC channel sounding interval analysis for IEEE 802.11ac MU-MIMO," 2012 International Symposium on Wireless Communication Systems (ISWCS). Cheng Chen (University of Edinburgh)