a wireless fabric company… · 2020. 10. 21. · to understand how to design a specific wi-fi...

A Wireless Fabric Company

Dave Moore

Sr. Director, Wi-Fi Business Acceleration

Step 1: Coverage vs Capacity

Copyright 2014 Cambium Networks, Ltd. All rights reserved.2

To understand how to design a specific Wi-Fi network, answering the question of whether coverage or capacity is the most important should be handled first.

Step 2: Identify the Client Device Types


The second step in designing a Wi-Fi network properly is to identify the device types that will be using the network. Understanding the capabilities and limits of those devices will help to determine AP

models to be used as well as how to model coverage and/or capacity.

Step 3: Identify the Applications

The third step in designing a Wi-Fi network is to identify and understand the applications

that will be run over the network.


• Email and Web Browsing traffic is light and sporadic.• Video surveillance creates significant and constant upstream traffic.• Client-Server networks create well-paced traffic patterns, controlled primarily

through the AP with heavy download and are well matched by Wi-Fi.• Peer-to-peer networks can create significant upstream and downstream

traffic that is not paced at the AP.• Video streaming from client devices, such as at public events, demands heavy

upstream loads, often at less than optimal MCS rates.• Multi-cast applications should be identified and understood well before

designing the network.• VoWiFi requires low latency and other special design considerations.

Backhaul and Core Network

The cause of many Wi-Fi complaints is not a fault in the Wi-Fi design.


• Insufficient backhaul • For individual APs• For access to resources (such as the connection to the Internet)

• Insufficient DHCP addresses• DNS issues• RADIUS misconfiguration or insufficient processing power• Broadcast domain too large• Insufficient MAC table size on switches• Bottlenecks

Regardless of fault, the Wi-Fi design and implementation is most often blamed. Therefore, it is important to verify the whole network is designed and operating well.

Choose the Best AP Models

• Mounting restrictions

• Cost vs Performance

• More streams means more performance and capacity

• Focused antennas for very high capacity

• Outdoor vs Indoor

• Aesthetics


Any one of these factors can be the most important in a design.

Roaming Considerations


• Design for at least 15% coverage between APs – specifically for the devices that are roaming.

• Encourage roaming by shrinking AP cell size.

• Lowering power is not a good method.

• Increasing Minimum Unicast Rate is a good method.

• Focused antennas are a good method in high density environments.

• Some clients roam poorly, or not at all. It may be necessary to force clients to disconnect when SNR is too low.

• Fast roaming devices (such as for VoWiFi) benefit from a smaller channel list.

Planning – Predictive Analysis


• Predictive Analysis tools offer a way to design a Wi-Fi network with confidence.

• Ekahau• iBwave• AirMagnet

• Great for indoors, but not so good for outdoor deployments.

• Use CAD files when possible.• Model obstructions, capacity requirements,

client and application requirements.• Verify AP model correctly modeled.• Reports can be used as a deliverable service.• Garbage in / Garbage out

Verification


• Post-install site surveys tools• Ekahau• iBwave• AirMagnet

• Initial benchmark after install.• Repeated benchmark to verify efficacy

at regular intervals.• Identification of interference sources

and coverage/capacity holes.• Trouble-shooting• Use as tool for meeting SLA.

Channel Considerations


• 2.4 GHz• Better propagation (good and bad)• Better penetration (good and bad)• Crowded by other systems

• 5 GHz• 4 bands with different regulations

possible• Less propagation (bad and good)• Less penetration (bad and good)• DFS channels – airports and naval

yards• UNII 3 used quite often for PtP and

PtMP .• Use all the spectrum that makes sense.

• Don’t eliminate 2.4 GHz or DFS channels out-of-hand.

Channel Width Considerations


• 2.4 GHz allows for 20 MHz or 40 MHz channels• 5 GHz allows for 20, 40, 80, and even dis-contiguous 160 MHz channels• 160 MHz and 80 MHz are rarely practical.• 20 MHz is generally the best option.

• Easier to find a clear channel• More focused power density means greater range• Less co-channel interference with more channel options• More capacity in deployments with multiple APs

Limit the number of WLANs


• Each SSID requires that the AP advertise its presence via a Beacon.

• By default, this beacon is sent every 100 ms.

• Beacons are sent at low data rates to better ensure that all clients hear it.

• Many beacons, mean many messages sent at low data rates.

• Each message sent at low data rates takes up valuable air time.

• 4 APs advertising 4 SSIDs that can all be heard in the same location will reduce air time usable for data by more than 50%.

• Fewer SSIDs means more capacity.

cnMaestro Settings – Wireless LAN


The Wireless LAN setting simplifies the menu bar layout.

Options that do not pertain to Enterprise Wi-Fi products are removed.

AP Groups and WLAN options are split out.

If you are only managing Enterprise Wi-Fi products, use this option.

cnMaestro Settings – Access and Backhaul


The Access and Backhaul option provides for management of all products.

All capabilities offered through the Wireless LAN option are present as well as others specific to PMP, ePMP, and cnReach.

AP Groups and WLAN options are combined under Configuration tab.

If you are managing multiple product types, use this option.

cnPilot Configuration - cnMaestro

“Wireless LAN” vs “Access and Backhaul” Views


AP Group Configuration

WLAN Configuration

Icon Name Expansion

cnPilot Recommended Base Radio Settings – 2.4 GHz


• Most default settings are fine.• Enable• Channel• Channel Width• Transmit Power• Antenna Gain• Beacon Interval• Multicast Data Rate• Mode• Candidate Channels

• Enable – May choose to disable in a high capacity deployment.

• Minimum Unicast Rate –Increase to shrink cell size or block 802.11b clients.

• Enable Airtime Fairness.

Airtime Fairness


• First developed after 802.11n was released.

• Airtime Fairness prevents slower clients from setting the pace for all clients.

• Provides significant performance increase for 802.11n clients when 802.11a, b, or g clients are present.

• 802.11ac aggregation techniques mitigate the problem significantly without the use of Airtime Fairness.

• Airtime Fairness is still relevant for 2.4 GHz, but can actually reduce performance of 802.11ac clients in 5 GHz.

cnPilot Recommended Base Radio Settings – 5 GHz


• Most default settings are fine• Enable• Channel• Channel Width• Transmit Power• Antenna Gain• Beacon Interval• Multicast Data Rate• Mode

• Minimum Unicast Rate –Increase to shrink cell size.

• Candidate Channel – adjust to fit your environment.

• Do not enable Airtime Fairness.

cnPilot Candidate Channel Options


• All – All 5 GHz bands are available.• Prefer Non-DFS – Only non-DFS channels are available.• Prefer DFS – Only DFS channels are available.• Specific – Create a white list of channels for use, with a space separating each one.• Choose based on RF environment, applications, and client devices.

cnPilot 2.4 GHz and 5 GHz Advanced Options


Advanced Settings are available to offer greater control of automatic channel selection, interference avoidance, and to aid with problematic client devices.

Although these settings can be configured differently for both 2.4 GHz and 5 GHz, in most cases, the same settings are best for both.

cnPilot – Automatic Channel Selection


• ACS options determine under what circumstances each AP will choose the best channel to use.• This option uses the lowest threshold in making a decision• 3 ACS options

• No Clients – Each AP will determine if another channel is a better choice and move to that channel when no clients are connected.

• On Startup – Each AP will determine the best channel on startup.• Schedule – Each AP will determine the best channel once a day at a specific time.

cnPilot – Enhanced Roaming


• Enhanced Roaming provides a method for forcing sticky clients to drop off of an AP when it should roam.• When a client’s connection drops below a threshold SNR trigger, the AP will send a Disconnect Message to

the client.• Well-behaved clients can be better “urged” to roam using the Minimum Unicast Rate option covered

earlier.• Extra care should be used when/if this option is enabled. It is very easy to create coverage holes.• In most cases, this option should not be enabled.

cnPilot – Off Channel Scanning


• Off Channel Scanning is a method for the AP to gather information about the RF status of all available channels.

• Recommendation - Enable this option, using the default values.

cnPilot – Auto RF


• Auto RF allows each AP to adjust their TX power based on surrounding APs.

• If other APs managed by the same cnMaestro account are heard on the same channel, the AP will reduce power to reduce co-channel interference.

• Power will increase if/when adjacent APs move off of the same channel.

• Autonomous – Each AP chooses independently.

• Centralized – cnMaestromakes choices.

• Recommendation – Enable, using default settings.

cnPilot – Interference Avoidance


• This option allows each AP to change channels if certain conditions occur, even if clients are connected.

• Works in conjunction with OCS. If Interference Avoidance is enabled, OCS should be as well.• AP will send out an 802.11h message prior to changing channels so that clients will know how

to follow the AP.• Recommendation – Enable, using the default options.

Thank You!

a wireless fabric company… · 2020. 10. 21. · to understand how to design a specific wi-fi...

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