RF Fundamentals and the Radio Design of Wireless Networks

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2 RF Fundamentals and the Radio Design of Wireless Networks

3 What is Wi-Fi? Wi-Fi networks use radio technologies based on IEEE standards to provide secure, reliable, fast wireless connectivity, typically within a limited area such as a home or campus. A Wi-Fi network can connect electronic devices to each other, to the Internet, and to wired networks. Wi-Fi networks operate primarily in the unlicensed 2.4 and 5 GHz radio bands, and most of the times in both bands (dual-band) now. Unlicensed is good from the perspective that it is free spectrum and anyone can use it. It is not good from the perspective that, due to its common shared use, the spectrum tends to be crowded, sometimes causing interference among devices. 3

4 Enterprise Wireless LAN Solutions Allow companies to provide differentiated wireless access to: Employees Customers Students / Contractors Devices (M2M) Others, depending on the environment Provide the ability for users to move about untethered to wired hardware: ROAMING Serve numerous verticals, with very different requirements, including SECURITY Retail Manufacturing Finance Healthcare Energy Hospitality Education Transportation Sports 4

5 What is ? What is Wi-Fi? Wi-Fi products are designed to implement the IEEE standard and be certified for interoperability through the Wi-Fi Alliance to get the logo The technology has evolved over time, with new standard enhancements designated using a letter, e.g., a, b, etc. Lower case letter denotes the specific technology standards enhancements to the original standard Five main generations already, with the latest being ac, but still only halfduplex (like a hub was) Each generation defines performance enhancements for devices operating in one or both 2.4 GHz and 5 GHz bands Sixth generation will extend to other bands (3.5 GHz, 900 MHz, 60 Ghz etc.) IEEE Wireless Standard Frequency Band(s) Bandwidth or Maximum data rate b 2.4GHz 11 Mbps a 5GHz 54 Mbps g 2.4GHz 54 Mbps n 2.4GHz and 5GHz 450 Mbps ac 5 GHz 6900 Mbps 5

6 Who Gets the Higher Transmission Priority? 1. Access Point 2. Wireless Client 3. They all get equal access adopted CSMA/CA (Carrier Sense Multiple Access)/Collision Avoidance model where nodes (AP or clients) avoid collisions by transmitting only when the channel is sensed to be "idle. Other channel access models have been proposed. These models allow the AP to organize channel access in a structured way, but these have never been widely adopted 1. Legacy Point Coordination Function (PCF) e Hybrid Controlled Channel Access (HCCA) 6 6

7 Why is ac important today? ac comes in 2 waves: Wave-1 (now) et Wave-2 (mid-2015+) Many ac equipements exist on the market today (tablets and smartphones). There is a big ask for more density and more performance from the end-users already. Galaxy S5 Lumia 930 Samsung Note Toshiba Excite Pro ipad Air 2 iphone 6/6+ IDENTIFY AC EXISTING CLIENTS here: List_of_802.11ac_Hardware#Mobile_general_purpose_computers_. 28non-PC.29 7

8 At 11 mbps (802.11b)? At 54 mbps (802.11a or g)? At 300 mbps (802.11n5:2SS)? Smasung Galaxy S5 supports MIMO 2x2:2SS ac for the first time on a smartphone (866 mbps)! At 866 mbps (802.11ac:2SS)? How many packets can I transmit at that speed compared to the other speeds above? 8

9 BASICS OF RF

10 Channel reuse scheme in the Network Neighboring APs use different channels to reduce interference. On 2.4 GHz, the Reuse cluster size is equal to 3 On 5 GHz, the Reuse cluster size varies depending on channel width: Access Point

11 is the IEEE standard defining Wireless Access running in the Unlicensed Bands b/g (1997 / 1999 / 2003) 11 Mb / 54 Mbps and runs in the 2.4 GHz frequency band 3 non-overlapping 20 MHz channels (1, 6, 11) or 4? (1, 5, 9, 13)? Hint: it is an odd number a (1999) 54 Mbps and runs in the 5 GHz frequency band ( GHz) 16 non-overlapping 20 MHz channels in ETSI (864mbps) Shorter range than b/g n (2009) Backwards compatible to a/b/g but adding the powerful MIMO technology 215 Mbps max data rate in 2.4 GHz, 450Mbps in 5 GHz band Either 20 MHz or 40 MHz wide channels in 5 GHz, up or Gbps total with DFS Most useful running in the 5GHz band à Seven 40 MHz channels 11

12 Cisco BandSelect Technology Automatic band steering and selection for 5GHz capable devices BEFORE All clients crowd the 2.4GHz spectrum lowering performance AFTER 5GHz capable clients are automatically moved to cleaner 5GHz spectrum Wireless Client Performance 2.4GHz 2.4GHz 2.4GHz 5GHz 5GHz 2.4GHz Speed 5GHz Capable Speed 5GHz Capable Speed 2.4GHz Capable Speed 5GHz Capable Speed 5GHz Capable Speed 2.4GHz Capable Cisco BandSelect Improves Reliability and Performance 12

13 Know the zones of potential problems Metal cabinets Elevator Stairs Closed desks Labs Microwave oven (2450 MHZ) Meeting room Open desks Stairwells (reinforced building areas) President s office 13

14 What happens in the air? Path loss: attenuation due to distance Fading (frequency dependent) Shadowing Reflection at large obstacles Refraction depending on the density of a medium Scattering at small obstacles Diffraction at edges shadowing reflection refraction scattering diffraction 14

15 Common Sources of WLAN Interference Microwave ovens radar Bluetooth Other Wi-Fi Networks Older Microwave Links Game Controllers Wireless Headphones Wireless Video Mobile and Fixed Alarm Systems Motion Sensors Fluorescent Lights A Pinball Machine (really) FH 2.4/5 GHz cordless phones 15

16 Cisco CleanAir Technology Industry s First and only Chip Level Proactive and Automatic Interference Protection BEFORE Wireless interference decreases reliability and performance AFTER CleanAir mitigates RF interference improving reliability and performance Wireless Client Performance AIR QUALITY PERFORMANCE AIR QUALITY PERFORMANCE Cisco ClientLink Improves Predictability and Performance Fully available in 2600, 2700, 3500, 3600 and 3700 APs. CleanAir Express on 1600 and

17 CleanAir hardware visibility and resolution CleanAir Hardware based Solution 32 times Wi-Fi chip s visibility Accurate classification Multiple device recognition Spectrum intelligence solution designed to proactively manage the challenges of a shared spectrum Assess impact to Wi-Fi performance; proactively change channels when needed CleanAir Radio ASIC: Only ASIC based solution can reliably detect interference sources Best Practice: turn it on if supported by your APs (3500, 1600, 1700, 2600, 2700, 3600, 3700) For more info: CleanAir Express 17

18 RF Deployment Challenges Ensuring correct antenna installation Managing the RF spectrum Designing RF for capacity not only coverage Remembering that the wireless client devices dictate the cell size: 18

19 Does all of this work magically? Site Survey Site Survey Site Survey Site Survey! It is, most of the time, impossible to get a Bill of Material that is final in Wireless Experience is key, and a skilled partner is not optional for customers on voice and/ or location deployments 19

20 802.11N AND AC

21 Evolution to MIMO Technology Old Wi-Fi systems used Single Input Single Output (SISO) technology Single transmit stream Single transmit antenna Single receive antenna Severely impacted by multipath signals Performance improved by diversity Time Time Received Signals Combined Results Single-input Single-output (SISO) 21

22 Evolution to MIMO Technology (Cont.) MIMO requires at least 2 receivers or 2 transmitters per band Uses advanced signal processing to coordinate multiple simultaneous signals from multiple antennas Improved link reliability Received Signals Transmitter The Wireless Channel Receiver Time Time Combined Results 22

23 MIMO Uses Advanced Signal Techniques to improve link reliability and efficiency Maximal ratio combining (MRC) Performed by receiver Combines multiple received signals Increases receive sensitivity Works with MIMO and non-mimo clients message message message message Transmit beam forming (TBF) Performed by transmitter Ensures signal received in phase Increases receive sensitivity Works with MIMO and non-mimo clients message message message message Spatial multiplexing (SM) Transmitter and receiver participate Multiple antennas txmt concurrently on same channel Increases bandwidth Requires MIMO client message me ss age 23

24 Cisco s ClientLink Technologies Advanced Beam Forming Technologies Improve Wireless Client Performance Cisco ClientLink Improves Predictability and Performance 24

25 Advanced Techniques Improve Data Rates for All Clients 36 Mbps 54 Mbps 450 Mbps (The same applies exactly to ac) 25

26 Bonding Channels Improves Data Rates n supports 20- or 40-MHz wide channels, ac adds 80 and 160-MHz Primary and secondary channel 40 MHz = 2.2 aggregated 20-MHz channels Often referred to as an extension channel Can be above or below the primary channel Protection provided for 20 MHz / 40 MHz client use n can bond up to 40 MHz Now we are on an 8 lane Highway 26

27 What does ac bring? Even Higher Levels of Performance Larger channels (up to 160- MHz), more spasal streams (up to 8) Reduced number of unused opsons in n specificasons

28 Client cell sizes similar between.11n and.11ac There are so many data-rates in.11ac Using the internal.11n radio on the AP-3600i, we performed a quick cell size characterization with.11n rates using several.11n clients. When we switched to.11ac clients, and the.11ac radio module, it performed MHz with clients having a cell size similar to the.11n clients. Take-away.11n/11ac are similar rate/ range but of MHz and 256-QAM, you get a significant datarate boost 28

29 Any Rate over Range data? Comparing ac versus n using 3-SS clients 3 m 10 m 23 m 11ac client Dell E6430 with Broadcom 3-ss Vs. 11n client Apple 3-ss Macbook Pro (Take-away) ac 3-ss is able to get twice the speed than n 29

30 RF RELATED DEPLOYMEN T GUIDELINES

31 802.11n/ac Wireless Deployment Guidelines Capacity and Performance from Wireless Data Only Applications Data and Voice Casual wireless access (not primary access) Low bandwidth data applications ( , web, file access) Access Point installed every 25 meter Always use dual radio Access Points (2.4GHz and 5GHz) Location accuracy will be reduced High density wireless access (primary access) Simultaneous VoIP and data usage Access Point installed every 18 meter Always use dual radio Access Points (2.4GHz and 5GHz) Location accuracy will be increased depending on placement 31

32 Building example with few floors (capacity) 4 floors building 45m x 40m per floor 1800 m 2 per floor or a 7200 m 2 building 45m Assuming 1.6 wireless devices per user soon to be the norm (voice and data) in Enterprise and SMB Accepted metrics for employee density in an office building is 10 m² per employee (including all shared areas like lobby, restrooms, kitchen ) according to ILO estimates Calculations: For 7200m 2, we have 720 employees 720 employees means 1152 wireless devices 32

33 Enterprise WLAN Design Data Generic guidelines for only data application - Coverage 465 m 2 per AP (1 AP every 25 m) 7200 m 2 of carpeted area may require 16 APs 10% overlap of coverage cells for roaming support AP at 60% power for coverage redundancy In case of AP failure Average -75dBm at the edge of each cell Can only be confirmed by site survey Needs to be validated for capacity: 1152 devices on 16 APs = 72 devices per AP: too much! Max recommended value is around 50 devices per AP Coverage vs capacity 16 APs vs 24 APs (6 per floor) à evolution! 33

34 Enterprise WLAN Design Data and Voice Generic guidelines for voice and data applications - Coverage 270 m 2 per AP (1 AP every 18 m) 7200 m 2 of carpeted area may require 26 APs 15% overlap of coverage cells for roaming support AP at 60% power for coverage redundancy in case of single AP failure Average -67dBm at the edge of each cell Can only be confirmed by site survey Implement Cisco Centralized Key Management, r, OKC/PKC Reduces latency associated with roaming Do not implement Cisco Aggressive Load Balancing Needs to be validated for capacity: 1152 devices on 26 APs = 44 devices per AP: better! 34

35 Disable Lower data rates Disabled not available to a client Supported available to an associated client Mandatory Client must support in order to associate Lowest mandatory rate is beacon rate Highest mandatory rate is default Mcast rate Every SSID counts: Each SSID requires a separate Beacon Each SSID will advertise at the minimum mandatory data rate 35

36 ANTENNAS AND AP PLACEMENT

37 A Radio Needs a Proper Antenna As the frequency goes up, the radiating element gets smaller Antennas are identified by color Blue indicates 5 GHz Black indicates 2.4 GHz Orange indicates Both Omni-Directional antennas like the one on the left, radiate much like a raw light bulb would everywhere in all directions Antennas are custom made for the frequency to be used. Some antennas have two elements to allow for both frequencies in one antenna enclosure. Cisco AP-3700/3600/2700/2600/1700/1600 use such antennas. Directional antennas like this Patch antenna radiate forward like placing tin foil behind the light bulb or tilting and directing the lamp shade Note: Same RF energy is used but results in greater range as it is focused towards one direction, at the cost of other coverage areas 37

38 Antenna placement Use the maximum number supported Use all same type of antennas on an AP Position all of them in the same orientation receivers transmitters Access points with internal antennas are designed to be mounted horizontally Antenna spacing is always a compromise on effects Target for positioning antennas around ½ to 1 wave length apart* *Results vary based on environment. Spacing on ½ wave length intervals has highest probability to provide best performance in multipath rich environment For 2.4 GHz ½ wave length ~ 6.35 cm For 5.2 GHz ½ wave length ~ 2.8 cm 38

39 Avoid Mounting AP Antennas Too High As a general rule, antenna heights of 3 meters or less are most conducive to good coverage and consistent positioning accuracy when doing location. As a general rule, antenna heights 2.4 GHz of over 6 meters should be avoided. If required, then tricks exist, but you need to consult a specialist It is important to understand the requirement for external antennas in cases like this, as the cost of a deployment will become significantly higher. 39

40 Antennas: use common sense Don t assume because MIMO is so great that you should deploy n AP s like this! 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 40

41 Wall mounting APs (1600, 2x00, 3x00) Orientation of the dipoles if wall mounting If using advanced features like location or voice, try to locate the AP on the ceiling, or when mounting the AP on a wall, orient the dipoles in this configuration. Because dipoles on a wall can easily get orientated wrong as people touch and move them. Better still might be to use a Patch antenna or use the Oberon wall bracket (see next). Be aware walls can add directional properties to the signal as they can have wiring, metal 2x4 construction and the wall attenuates the signal behind the AP limiting a nice 360 degree coverage. Note: The ceiling is usually higher and a better location for RF

42 Aironet n wall mount (style case) Third party wall mount option is available This optional wall mount best positions the Access Point dipoles for optimum performance Recommended for Voice applications, if you MUST mount the Access Point on a wall. Ceiling is a better location as the AP will not be disturbed or consider using patch antennas on wall installations 42

43 INSTALLATIONS THAT WENT WRONG

44 Installations that Went Wrong NEVER EVER MIX ANTENNA TYPES Antennas should always cover the same RF cell watch polarity 44

45 Other installations that went Wrong Ceiling mounted AP on the wall, above false ceiling, up against water pipe (?poor coverage?) Radio waves do not like metal cages 45

46 Installations that went Wrong Patch antenna shooting across a metal fence Multipath distortion causing severe retries 46

47 Installations that Went Wrong - Mesh GOOD INSTALL BAD INSTALL 47

48 Summary Cisco provides well engineered Access Points, Antennas, and Radio Resource Management features in the controllers. However, you need to understand the general concepts of Radio, otherwise it is very easy to end up implemen>ng a network in a sub- op>mal way. It is therefore undeniable that: RF MaZers

49 Thank you.