Radio Settings: Daten Raten und Antennen Optionen

Ausgangslage:

Es soll nur die Linke Antenne verwendet werden (1241 AP) auf dem 2.4GHz Band
Multicast soll auf dem 2.4 GHz Band mit (mindestens) 11 Mbit/s senden können. Alle OFDM Daterates sollen auf dem 2.4 GHz Band erlaubt sein
Broadcast Traffic auf dem 5 GHz Band soll mit 12 MBit/s senden können. Aktiviere zusätzlich sämtliche für VoWLAN empfohlenen Datenraten auf dem 5 GHz Band
Gewährleiste maximale Performance für 802.11g Clients

Sende und Empfangsantenne definieren:

Die Antenne definieren ist ziemlich staight forward, da nur das 2.4GHz Band verlang ist, macht man dies auf dem DotRadio 0 Interface. Man unterscheidet dabei zwischen Send und Transmit. Theoretisch wäre es also möglich auf der linken Antenne zu senden und auf der rechten Antenne zu empfangen.

AAP1(config)#int d0
AAP1(config-if)#antenna ?
 gain Configure Resultant Antenna Gain
 receive receive antenna usage setting
 transmit transmit antenna usage setting


AAP1(config-if)#antenna receive ?
 diversity use all antennas
 left use left antenna
 right use right right antenna
 <cr>

AAP1(config-if)#antenna receive left 
AAP1(config-if)#
*Mar 14 05:40:28.097: %LINK-5-CHANGED: Interface Dot11Radio0, changed state to reset
*Mar 14 05:40:28.127: %LINK-3-UPDOWN: Interface Dot11Radio0, changed state to up

AAP1(config-if)#antenna transmit left 

*Mar 14 05:40:44.161: %LINK-5-CHANGED: Interface Dot11Radio0, changed state to reset
AAP1(config-if)#
*Mar 14 05:40:44.191: %LINK-3-UPDOWN: Interface Dot11Radio0, changed state to up

Multicast soll mit 11 MBit/s versendet werden und alle OFDM Datenraten erlaubt:

Multicast wird jeweils mit der „highest mandatory“ Datarate versendet, diese muss also auf 11 Mbits/s definiert werden.

AAP1(config)#int d0
AAP1(config-if)#speed ?
 1.0 Allow 1.0 Mb/s rate
 2.0 Allow 2.0 Mb/s rate
 5.5 Allow 5.5 Mb/s rate 
 6.0 Allow 6.0 Mb/s rate
 9.0 Allow 9.0 Mb/s rate  
 11.0 Allow 11.0 Mb/s rate
 12.0 Allow 12.0 Mb/s rate
 18.0 Allow 18.0 Mb/s rate
 24.0 Allow 24.0 Mb/s rate
 36.0 Allow 36.0 Mb/s rate
 48.0 Allow 48.0 Mb/s rate
 54.0 Allow 54.0 Mb/s rate
 basic-1.0 Require 1.0 Mb/s rate
 basic-11.0 Require 11.0 Mb/s rate
 basic-12.0 Require 12.0 Mb/s rate
 basic-18.0 Require 18.0 Mb/s rate
 basic-2.0 Require 2.0 Mb/s rate
 basic-24.0 Require 24.0 Mb/s rate
 basic-36.0 Require 36.0 Mb/s rate
 basic-48.0 Require 48.0 Mb/s rate
 basic-5.5 Require 5.5 Mb/s rate
 basic-54.0 Require 54.0 Mb/s rate
 basic-6.0 Require 6.0 Mb/s rate
 basic-9.0 Require 9.0 Mb/s rate
 default Set default rates
 ofdm How to place OFDM rates in rates elements
 only-ofdm Set rates for best OFDM throughput (no ERP protection will be
 used)
 range Set rates for best range
 throughput Set rates for best throughput (includes non-OFDM rates and may
 cause ERP protection to be used)
 <cr>

AAP1(config-if)#speed 6 9 12 18 24 36 48 54 basic-11

Erklärung:

You use the data rate settings to choose the data rates the wireless device uses for data transmission. The rates are expressed in megabits per second. The wireless device always attempts to transmit at the highest data rate set toBasic, also called Require on the browser-based interface. If there are obstacles or interference, the wireless device steps down to the highest rate that allows data transmission. You can set each data rate to one of three states:
Basic (the GUI labels Basic rates as Required)—Allows transmission at this rate for all packets, both unicast and multicast. At least one of the wireless device’s data rates must be set to Basic.
Enabled—The wireless device transmits only unicast packets at this rate; multicast packets are sent at one of the data rates set to Basic.
Disabled—The wireless device does not transmit data at this rate.

Orthogonal Frequency Division Multiplexing (OFDM) data rate (6, 9, 12, 18, 24, 36, 48, 54)

Broadcast Traffic soll mit 12Mbit/s auf dem 5 GHz Band versendet werden. Zusätzlich sollen die Datenraten für VoWLAN optimiert werden.

AAP1(config)#int dot1Radio1
AAP1(config-if)#speed basic-12.0 18 24

Erklärung:

A minimum Signal to Noise Ratio (SNR) of 25 dB = -92 dBm noise level with -67 dBm signal should be maintained.
It is recommended to have at least two access points on non-overlapping channels with at least -67 dBm signal with the 25 dB SNR to provide redundancy.
To achieve maximum capacity and throughput, the wireless LAN should be designed to 24 Mbps. Higher data rates (36-54 Mbps) can optionally be enabled for other applications other than voice only that can take advantage of these higher data rates.
Recommended to set the minimum data rate to 11 Mbps or 12 Mbps for 2.4 GHz (dependent upon 802.11b client support policy) and 12 Mbps for 5 GHz, which should also be the only rate configured as a mandatory / basic rate. In some environments, 6 Mbps may need to be enabled as a mandatory / basic rate.

Gewährleiste maximale Performance für 802.11g Clients

AAP1(config-if)#short-slot-time 
AAP1(config-if)#preamble-short

Erklärung Slot Time:

You can increase throughput on the 802.11g, 2.4-GHz radio by enabling short slot time. Reducing the slot time from the standard 20 microseconds to the 9-microsecond short slot time decreases the overall backoff, which increases throughput. Backoff, which is a multiple of the slot time, is the random length of time that a station waits before sending a packet on the LAN.
Many 802.11g radios support short slot time, but some do not. When you enable short slot time, the wireless device uses the short slot time only when all clients associated to the 802.11g, 2.4-GHz radio support short slot time.
Short slot time is supported only on the 802.11g, 2.4-GHz radio. Short slot time is disabled by default.

Erklärung Preamble:

The radio preamble (sometimes called a header) is a section of data at the head of a packet that contains information that the wireless device and client devices need when sending and receiving packets. You can set the radio preamble to long or short:
Short—A short preamble improves throughput performance. Cisco Aironet Wireless LAN Client Adapters support short preambles. Early models of Cisco Aironet’s Wireless LAN Adapter (PC4800 and PC4800A) require long preambles.
Long—A long preamble ensures compatibility between the wireless device and all early models of Cisco Aironet Wireless LAN Adapters (PC4800 and PC4800A). If these client devices do not associate to the wireless devices, you should use short preambles.
You cannot configure short or long radio preambles on the 5-GHz radio.

Samuel Heinrich

Senior Network Engineer at Selution AG (Switzerland)

Arbeitet in Raum Basel (Switzerland) als Senior Network Engineer mit über 15 Jahren Erfahrung im Bereich Netzwerk