conservative rate algorithm provides the best case stability / robustness, but may

compromise maximum throughput. The optimistic rate algorithm always looks to

achieve highest throughput while sacrificing noise immunity and robustness. The

EWMA algorithm is a hybrid of the two.

Noise Immunity

: options define the robustness of the device to operate in the

presence of noise disturbance:

For Channel Hopping Signals configuration provides robustness against Channel

Hopping Signals.

For 802.11 Traffic Immunity provides robustness against external 802.11 traffic

sources that are from a foreign network.

Normal 802.11 Operation (default option) provides balanced immunity between

both types of interferers (Channel Hopping Signals and external 802.11 traffic).

RTS Threshold

: determines the packet size of a transmission and, through the use of

an access point, helps control traffic flow. The range is 0-2347bytes, or word “off”. The

default value is 2347 which means that RTS is disabled.

RTS/CTS (Request to Send / Clear to Send) is the mechanism used by the 802.11

wireless networking protocol to reduce frame collisions introduced by the hidden

terminal problem. RTS/CTS packet size threshold is 0-2347 octets. If the packet size

the node wants to transmit is larger than the threshold, the RTS/CTS handshake gets

triggered. If the packet size is equal to or less than threshold the data frame gets sent

immediately

Fragmentation Threshold

: specifies the maximum size for a packet before data is

fragmented into multiple packets. The range is 256-2346 bytes, or word “off”. Setting

the Fragmentation Threshold too low may result in poor network performance. Only

minor modifications of this value are recommended while default setting of 2346

should remain in most of the cases.

The use of fragmentation can increase the reliability of frame transmissions. Because

of sending smaller frames, collisions are much less likely to occur. The fragment size

value can typically be set between 256 and 2,048 bytes.

Multicast Rate

: This option allows Multicast packets to be sent in higher than usual

rates.

Client Isolation

: This option allows packets only to be sent from the router to the

CPE. In other words, CPE's on the same network as the AP will not be able to see each

other.

SuperG® /SuperAG® Features: select the checkboxes to enable the chosen SuperG®

(PowerStation2 and LiteStation2) or SuperAG® (LiteStation5) features:

Fast Frame – utilizes frame aggregation and timing modifications.

Bursting – more data frames per given time period are transmitted.

Compression – real-time hardware data compression is enabled.

Acknowledgement Timeout

AirOS has an auto-acknowledgement timeout algorithm which dynamically optimizes

the acknowledgement timeout value without user intervention. This is a critical feature

required for stabilizing long-distance outdoor links. The user also has the ability to

enter the value manually, but this is not recommended.

Distance: specify the distance value in miles using slider or enter the value manually.

The signal strength and throughput falls off with range. Changing the distance value

will change the ACK Timeout to the appropriate value of the distance.

ACK Timeout: specify the ACK Timeout. This is the amount of time the subscriber

station will wait to hear a acknowledgement response from the wireless device after

the data packet is transmitted. If the timeout is set too short or too long, it will result

poor connection and throughput performance.

Changing the ACK Timeout value will change the Distance to the appropriate distance

value for the ACK Timeout.

Auto Adjust control will enable the ACK Timeout Self-Configuration feature. If enabled,

ACK Timeout value will be derived dynamically using an algorithm similar to the

Conservative Rate Algorithm described above.

Antenna Settings

AirOS based devices have a possibility to switch the antenna polarities with a single

web management control. This is achieved by using Ubiquiti's patent-pending Adaptive

Antenna Polarity (AAP) technology.

AirOS devices often have multiple antenna options. In the case of the NanoStation,

there are 4 antenna modes:

1. Vertical Polarity

2. Horizontal Polairty

3. Adaptive: This mode chooses the best polarity dynamically. Adaptive – switches

adaptive antenna polarity mode which allows for the beam polarities to be switched

dynamically on the fly for improved performance in heavy noise environments.

4. External: This allows a connection to an external port / higher gain antenna

Antenna Alignment LED Thresholds

The LED's on the back of the AirOS Device can be made to light on when received

signal levels reach the values defined in the following fields. This allows a technician to

easily deploy an AirOS CPE without logging into the unit.

RSSI LED Thresholds specify the marginal value of RSSI which will switch on LEDs

indicating signal strength:

LED 1 (Red) will switch on if the RSSI reach the value set in an entry field next to it.

LED 2 (Yellow) will switch on if the RSSI reach the value set in an entry field next to it.

LED 3 (Green) will switch on if the RSSI reach the value set in an entry field next to it.

LED 4 (Green) will switch on if the RSSI reach the value set in an entry field next to it.

Wireless Traffic Shaping

Wireless Traffic shaping feature is dedicated for upstream and downstream bandwidth

control while looking from the client (connected on Ethernet interface) perspective.

Traffic Shaping

: The traffic can be limited at the AirOS based device in the upload

and download direction based on a user defined rate limit. This is layer 3 QoS.

Enable Traffic Shaping: control will enable bandwidth control on the device.

Incoming Traffic Limit: specify the maximum bandwidth value in kbps for traffic

passing from wireless interface to Ethernet interface.

Outgoing Traffic Limit: specify the maximum bandwidth value in kbps for traffic

passing from Ethernet interface to wireless interface.

QoS

Wi-Fi Multimedia (WMM) is a component of the IEEE 802.11e wireless LAN standard

for quality of service (QoS). The QoS assigns priority to the selected network traffic,

prevents packet collisions and delays thus improving VoIP calls and watching video

over WLANs.

802.11e / WMM

: This allows for improved latency performance for

Voice and Video applications. This is layer 2 QoS and happens at 802.11 frame level.

QoS (WMM) Level: choose the type of the network traffic to which the priority will be

set or disable the QoS feature. No QoS – disable QoS.

Video Priority – enable priority of the video traffic.

Voice Priority – enable priority of the voice traffic.

Services

This page covers the configuration of system management services SNMP and Ping

Watchdog.

Ping WatchDog

The ping watchdog sets the AirOS Device to continuously ping a user defined IP

address (it can be the internet gateway for example). If it is unable to ping under the

user defined constraints, the AirOS device will automatically reboot. This option creates

a kind of "fail-proof" mechanism.

Ping Watchdog is dedicated for continuous monitoring of the particular connection to

remote host using the Ping tool. The Ping works by sending ICMP “echo request”

packets to the target host and listening for ICMP “echo response” replies. If the

defined number of replies is not received, the tool reboots the device.

Enable Ping Watchdog: control will enable Ping Watchdog Tool.

IP Address To Ping: specify an IP address of the target host which will be monitored by

Ping Watchdog Tool.

Ping Interval: specify time interval (in seconds) between the ICMP “echo requests” are

sent by the Ping Watchdog Tool.

Startup Delay: specify initial time delay (in seconds) until first ICMP “echo requests”

are sent by the Ping Watchdog Tool. The value of Startup Delay should be at least 60

seconds as the network interface and wireless connection initialization takes

considerable amount of time if the device is rebooted.

Failure Count To Reboot: specify the number of ICMP “echo response” replies. If the

specified number of ICMP “echo response” packets is not received continuously, the

Ping Watchdog Tool will reboot the device.

SNMP Agent

Simple Network Monitor Protocol (SNMP) is used in network management systems to

monitor network-attached devices for conditions that warrant administrative attention.

AirOS contains an SNMP agent which allows it to communicate to SNMP manage

applications for network provisioning.

SNMP Agent provides an interface for device monitoring using the Simple Network

Management Protocol (an application layer protocol that facilitates the exchange of

management information between network devices). SNMP Agent allows network

administrators to monitor network performance, find and solve network problems. For

the purpose of equipment identification, it is always a good idea to configure SNMP

agents with contact and location information:

Enable SNMP Agent: control will enable SNMP Agent.

SNMP Community: specify SNMP community string. It is required to authenticate

access to MIB objects and functions as embedded password. The device supports a

Read-only community string that gives read access to authorized management stations

to all the objects in the MIB except the community strings, but does not allow write

access.

Contact: specify the identity or the contact who should be contacted in case a

emergency situation arise.

Location: specify the physical location of the device.

NTP Client, Web Server, Telnet Server

NTP Client

: The Network Time Protocol (NTP) is a protocol for synchronizing the

clocks of computer systems over packet-switched, variable-latency data networks. It

can be used to set the AirOS internal clock.

Web Server

: the following AirOS Device Web Server parameters can be set there:

Use Secure Connection (HTTPS): If checked Web server will use secure HTTPS mode.

HTTP mode is selected by default.

Secure Server Port: Web Server TCP/IP port setting while using HTTPS mode.

Server Port: Web Server TCP/IP port setting while using HTTP mode..

Telnet Server

: the following AirOs Device Telnet Server parameters can be set there: