Apunts d'Internet de les coses i IP UBIC

Eduard Garcia-Villegas Dept. of Network Engineering [email protected] Just some common sense rules put together in a nice set of colorful slides EFFICIENT Wi-Fi deployments The basics Where’s that fu*#}ng Wi-Fi ?!? Contents EFFICIENT Wi-Fi deployments oBig vs. small oAnalyze requirements o#STAs and #Needed radios oAvailable channels oReuse factor oDimensioning cells oOptimization Efficient Wi-Fi deployments 2 by Podere Casanova Wi-Fi deployments: intro Efficient Wi-Fi deployments 3 In the era of ubiquitous Internet… Wireless internet access can be a traumatic experience due to oMany concurrent users (dense scenarios) oCoexistence (older/slower devices, other technologies sharing the band, etc.) o… oPOOR DESIGN Wi-Fi deployments: big vs. small (1) Efficient Wi-Fi deployments 4 Coverage-driven design oIn the past: maximize cell size && minimize costs •Optimize AP location and increase cell sizeless APs needed (lower cost) •Problems: –more devices per AP (lower per STA throughput) » Reduced efficiency due to higher collision probability 5 STAs x AP <2 STAs x AP = STA VS. = AP Wi-Fi deployments: big vs. small (2) Efficient Wi-Fi deployments 5 = STA = AP LAME! Coverage-driven design oIn the past: maximize cell size && minimize costs •Optimize AP location and increase cell sizeless APs needed (lower cost) •Problems: –Longer distances AP  STA mean worse signal quality and, hence, more robust (slower) PHY rates are used » Capacity of the whole cell is reduced » Longer tx time more power consumed and more collisions Wi-Fi deployments: big vs. small (3) Efficient Wi-Fi deployments 6 = STA = AP HIDDEN NODES! CAN’T REACH ITS AP! Coverage-driven design oIn the past: maximize cell size && minimize costs •Optimize AP location and increase cell sizeless APs needed (lower cost) •Problems: –More hidden nodes more collisions –Power mismatch: AP (high tx power) and STA (low tx power) » STA can hear the AP, but the AP can't hear the STA » If you want a big cell, increase the antenna gain, not the tx power! Wi-Fi deployments: big vs. small (4) Efficient Wi-Fi deployments 7 Coverage-driven design oIn the past: maximize cell size && minimize costs •Optimize AP location and increase cell sizeless APs needed (lower cost) •It has problems in present (dense) deployments. Other key aspects oKPI requirements oClient and AP capabilities • Are modern ≥ 11n capable (how many antennas)? Coexistence with 11a/b/g? Dual band? oPropagation phenomena •Outdoor/indoor? APs mounted on ceiling, walls or floor? oUser density Efficient Wi-Fi deployments The basics Analyze requirements ANALYZE REQUIREMENTS Per user Total #STAs per RADIO #RADIOS NEEDED AVAILABLE CHANNELS REUSE FACTOR DIMENSION CELLS OPTIMIZE/ TROUBLESHOOT Wi-Fi deployments: requirements Efficient Wi-Fi deployments 9 The first thing is to identify key performance indicators (KPI) oMinimum bandwidth required to satisfy supported applications oMaximum latency tolerated oExpected Min-Avg-Max number of active devices Examples (per-user requirements): oSchool •BW: <3Mbps (video streaming; desktop/file sharing) •Delay tolerance: low (video streaming; intranet login) •Users: Min-Avg-Max = up to 30 per classroom oConvention center (1500 att.) •BW: <1 Mbps (web browsing; e-mail) •Delay tolerance: Medium •Users: “educated guess” –70% will connect Wi-Fi device –50% simultaneously –1500 x 0.70 x 0.5 = 525 ANALYZE REQUIREMENTS Per user Total #STAs per RADIO #RADIOS NEEDED AVAILABLE CHANNELS REUSE FACTOR DIMENSION CELLS OPTIMIZE/ TROUBLESHOOT Efficient Wi-Fi deployments The basics Dimension the cell Wi-Fi deployments: dimension cells (1) Efficient Wi-Fi deployments: the basics 17 What is the cell radius? oMax distance at which frames can be decoded •Ptis tx power –Decreases with MCS (to avoid distortion) •Sris receiver sensitivity –Increases with MCS –Rrreception range –dis the distance tx rx –αis the path loss exponent oDifferent radius depending on targeted MCS 𝑷𝒓≈𝑷𝒕 𝒅𝜶⟶ 𝑹𝒓≈𝑷𝒕 𝑺𝒓 𝟏𝜶 VERY FAST SLOW R1R2Rn Wi-Fi deployments: dimension cells (2) Efficient Wi-Fi deployments: the basics 18 How to set cell radius for Wi-Fi small cells? oReduce AP’s tx power •Reduces interference over other cells •Avoids AP/STA power mismatch •Reduces suitable rates NOT SO FAST SLOW Wi-Fi deployments: dimension cells (3) Efficient Wi-Fi deployments: the basics 19 How to set cell radius for Wi-Fi small cells? oReduce AP’s tx power •Reduces interference over other cells •Avoids AP/STA power mismatch •Reduces suitable rates oIncrease min tx rate of the cell •Reduces performance anomaly and allows higher average rate – Avoid “sticky” STAs •Possible unsupported devices –Accept, at least, 802.11b@11Mbps? OUT! NOT SO FAST Wi-Fi deployments: dimension cells (4) Efficient Wi-Fi deployments: the basics 20 BUT…interference goes beyond the cell edge oCarrier Sense Range (Rc) •Max distance at which frame preamble can be detected and, hence, prevent concurrent transmissions in the same channel. –Only 3dB SNR is enough! (>200m outdoors) –Behavior improved in IEEE 802.11ax oBeyond Carrier Sense Range •Transmitted frames are just noise LEAVE ME ALONE! Wi-Fi deployments: dimension cells (5) Efficient Wi-Fi deployments: the basics 21 Coverage strategy for maximal densification oReduce reuse distance •Low gain directional antennas •AP placement –Overhead: AP installed on the ceiling/lamp posts facing down –Side: AP installed on walls/pillars –Floor: under floor/under seat (stadiums or auditoriums) –Even consider mounting APs behind walls/obstacles and avoid LoS (enriches multipath diversity leveraged by MIMO) 120º vs. 60º coverage reuse Ch1 Ch1Ch1Ch1 reduced reuse distance ANALYZE REQUIREMENTS Per user Total #STAs per RADIO #RADIOS NEEDED AVAILABLE CHANNELS REUSE FACTOR DIMENSION CELLS OPTIMIZE/ TROUBLESHOOT Efficient Wi-Fi deployments The basics Finishing touches Wi-Fi deployments: channel plan (1) Efficient Wi-Fi deployments: the basics 23 Ch11 Ch11 Ch6 Ch1 Ch6 Ch11 Ch1 Ch6 Ch11 Ch1 In your dreams Reality(t) Dynamic and unpredictable spectrum utilization oLicense-free bands! Intelligent channel assignments are required Wi-Fi deployments: channel plan (2) Efficient Wi-Fi deployments: the basics 24 NO INTERFERENCE! Automatic and dynamic channel assignments aimed at reducing interference maximizing performance oAPs gather information of the environment •Number of APs detected •Power received from neighboring APs •Portion of time the channel was reported busy/idle by CCA Ch. X is free! Ch. X is free! Wi-Fi deployments: channel plan (3) Efficient Wi-Fi deployments: the basics 25 Automatic and dynamic channel assignments aimed at reducing interference maximizing performance oAPs gather information of the environment •Number of APs detected •Power received from neighboring APs •Portion of time the channel was reported busy/idle by CCA oIdeally, client STAs too (and report via IEEE 802.11k) Ch. X is free! Ch. X is free! Wi-Fi deployments: The End Efficient Wi-Fi deployments: the basics 32 Don’t forget the wires! oData/power wires to APs • If not…multihop or mesh-based wireless distribution system oUplink pipe •Imagine all this headache for just a DSL WAN connection… Some references (1) Load balancing oGarcia-Villegas, E.; Vidal, R.; Paradells, J. (2006, June). “Load Balancing in WLANs through IEEE 802.11k Mechanisms,” in 11th IEEE Symposium on Computers and Communications, ISCC 2006. oGarcia-Villegas, E.; Vidal, R.; Paradells, J. (2008, July). “Cooperative Load Balancing in IEEE 802.11 Networks with Cell Breathing,” in 13th IEEE Symposium on Computers and Communications, ISCC 2008. oGarcia-Villegas, E.; Ferrer, JL.; Lopez-Aguilera, E; Vidal, R.; Paradells, J. (2009). “Clientdriven load balancing through association control in IEEE 802.11 WLANs”. European Transactions on Telecommunications, ETT vol. 20, no. 5, pp. 494-507. John Wiley & Sons. Sensitivity control oAfaqui, MS.; Garcia-Villegas, E.; Lopez-Aguilera, E.; Smith, G.; Camps-Mur, D. (2015) “Evaluation of Dynamic Sensitivity Control Algorithm for IEEE 802.11ax,” IEEE Wireless Communications and Networking Conference, WCNC 2015, pp. 1072-1077 oAfaqui, MS.; Garcia-Villegas, E.; Lopez-Aguilera, E.; Camps-Mur, D. (2016) “Dynamic Sensitivity Control Algorithm leveraging adaptive RTS/CTS for IEEE 802.11ax,” in IEEE Wireless Communications and Networking Conference, WCNC 2016 oAfaqui, MS.; Garcia-Villegas, E.; Lopez-Aguilera, E.; Camps-Mur, D. (2016) “Dynamic Sensitivity Control of Access Points for IEEE 802.11ax”, in IEEE International Conference on Communications, ICC’16 Efficient Wi-Fi deployments: the basics 33 Some references (2) Channel management oGarcia-Villegas, E.; Vidal, R.; Paradells, J. (2009). “Frequency assignments in IEEE 802.11 WLANs with efficient spectrum sharing”. Wireless Communications and Mobile Computing, WCMC vol. 9, no. 8, pp. 1125-1140. John Wiley & Sons oMengual, E.; Garcia-Villegas, E.; Vidal, R. (2013, September). “Channel management in a campus-wide WLAN with partially overlapping channels,” in The 24th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2013 oDeek, L.; Garcia-Villegas, E.; Belding, E.; Lee, S-J.; Almeroth, K. (2011, December). “The Impact of Channel Bonding on 802.11n Network Management,” in 7th International Conference on emerging Networking EXperiments and Technologies, CoNEXT’11 oDeek, L.; Garcia-Villegas, E.; Belding, E.; Lee, S-J.; Almeroth, K. (2014). “Intelligent Channel Bonding in 802.11n WLANs,” IEEE Transactions on Mobile Computing, vol. 13, no. 6, pp. 1242-1255 oDeek, L.; Garcia-Villegas, E.; Belding, E.; Lee, S-J.; Almeroth, K. (2013, June). “Joint Rate and Channel Width Adaptation for 802.11 MIMO Wireless Networks,” in IEEE Conf. on Sensing, Communication, and Networking, Secon’13, pp. 167-175 (Nominee for the Best Paper Award) oDeek, L.; Garcia-Villegas, E.; Belding, E.; Lee, S-J.; Almeroth, K. (2015). “A practical framework for 802.11 MIMO rate adaptation,” Computer Networks, vol. 83, pp. 332-348 Efficient Wi-Fi deployments: the basics 34 EETAC -UPC Master's degree in Applied Telecommunications and Engineering Management IoT & Ubiquitous IP Course offered at: