Radio

Radio settings directly control the behavior of the radio in the WAP device and its interaction with the physical medium; that is, how and what type of signal the WAP device emits.

Select Wireless > Radio in the navigation pane.

In the Global Settings area, configure the TSPEC Violation Interval, which is the time interval in seconds for the WAP device to report associated clients that do not adhere to mandatory admission control procedures. The reporting occurs through the system log and SNMP traps. Enter a time from 0 to 900 seconds. The default is 300 seconds.

Select the Radio interface to configure (Radio 1 or Radio 2).

In the Basic Settings area, configure these settings:

NOTE Local regulations may prohibit the use of certain radio modes. Not all modes are available in all countries.

Radio—Turns on or off the radio interface. By default, the radio is off.

NOTE If you enable the 5-GHz radio with 80-MHz bandwidth, and if the radio carries a high amount of traffic, then the WAP device will need more power than what the IEEE 802.3af PoE standard provides (12.95 W). It is highly recommended that when 80-MHz channel is in use, the WAP device should either be powered by a power adapter or an IEEE 802.3at Power Source Equipment (PSE). If the required power by the WAP device exceeds the maximum power delivered by the PSE, then the WAP device may reboot.

MAC Address—The Media Access Control (MAC) address for the interface. The MAC address is assigned by the manufacturer and cannot be changed.

Mode—The IEEE 802.11 standard and frequency the radio uses. The default value of Mode is 802.11a/n/ac for Radio 1 and 802.11b/g/n for Radio 2. For each radio, select one of the available modes.

Radio 1 supports the following radio modes:

802.11a—Only 802.11a clients can connect to the WAP device.

802.11a/n/ac — 802.11a clients, 802.11n, and 802.11ac clients operating in the 5-GHz frequency can connect to the WAP device.

802.11n/ac — 802.11n clients and 802.11ac clients operating in the 5-GHz frequency can connect to the WAP device

Radio 2 supports the following radio modes:

802.11b/g — 802.11b and 802.11g clients can connect to the WAP device.

802.11b/g/n (default) — 802.11b, 802.11g, and 802.11n clients operating in the 2.4-GHz frequency can connect to the WAP device.

802.11n 2.4 GHz — Only 802.11n clients operating in the 2.4-GHz frequency can connect to the WAP device.

Channel Bandwidth (802.11n and 802.11ac modes only)—The 802.11n specification allows a 40-MHz wide channel in addition to the legacy 20-MHz channel available with other modes. The 40-MHz channel enables higher data rates but leaves fewer channels available for use by other 2.4-GHz and 5-GHz devices.

The 802.11ac specification allows an 80-MHz-wide channel in addition to the 20-MHz and 40-MHz channels.

Set the field to 20-MHz to restrict the use of the channel bandwidth to a 20-MHz channel. For the 802.11ac mode, set the field to 40 MHz to prevent the radio from using the 80-MHz channel bandwidth.

Primary Channel (802.11n modes with 20 or 40-MHz bandwidth only)—A 40-MHz channel can be considered to consist of two 20-MHz channels that are contiguous in the frequency domain. These two 20-MHz channels are often referred to as the Primary and Secondary channels. The Primary Channel is used for 802.11n clients that support only a 20-MHz channel bandwidth and for legacy clients.

Select one of these options:

Upper—Sets the Primary Channel as the upper 20-MHz channel in the 40-MHz band.

Lower—Sets the Primary Channel as the lower 20-MHz channel in the 40-MHz band. Lower is the default selection.

Channel—The portion of the radio spectrum the radio uses for transmitting and receiving.

The range of available channels is determined by the mode of the radio interface and the country code setting. If you select Auto for the channel setting, the WAP device scans available channels and selects a channel where the least amount of traffic is detected.

Each mode offers a number of channels, depending on how the spectrum is licensed by national and transnational authorities such as the Federal Communications Commission (FCC) or the International Telecommunication Union (ITU-R).

In the Advanced Settings area, configure these settings:

DFS Support—This field is available only if the selected radio mode operates in the 5-GHz frequency.

For radios in the 5-GHz band, when DFS support is on and the regulatory domain requires radar detection on the channel, the Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) features of 802.11h are activated.

DFS is a feature that requires wireless devices to share spectrum and avoid co-channel operation with radar systems in the 5-GHz band. DFS requirements vary based on the regulatory domain, which is determined by the country code setting of the AP.

When using the 802.11h Wireless Mode, there are a number of key points about the IEEE 802.11h standard:

802.11h only works for the 5-GHz band. It is not required for the 2.4-GHz band.

If you are operating in an 802.11h enabled domain, the AP attempts to use the channel you assign. If the channel has been blocked by a previous radar detection, or if the AP detects a radar on the channel, then the AP automatically selects a different channel.

When 802.11h is enabled, the AP will not be operational in the 5-GHz band for at least 60 seconds due to radar scanning.

Setting up WDS links may be difficult when 802.11h is operational. This is because the operating channels of the two APs on the WDS link may keep changing depending on channel usage and radar interference. WDS will only work if both the APs operate on the same channel. For more information on WDS, see WDS Bridge.

Short Guard Interval Supported—This field is available only if the selected radio mode includes 802.11n.

The guard interval is the dead time, in nanoseconds, between OFDM symbols. The guard interval prevents Inter-Symbol and Inter-Carrier Interference (ISI, ICI). The 802.11n mode allows for a reduction in this guard interval from the a and g definition of 800 nanoseconds to 400 nanoseconds. Reducing the guard interval can yield a 10 percent improvement in data throughput.

The client with which the WAP device is communicating must also support the short guard interval.

Select one of these options:

Yes—The WAP device transmits data using a 400-nanosecond guard Interval when communicating with clients that also support the short guard interval. Yes is the default selection.

No—The WAP device transmits data using an 800-nanosecond guard interval.

Protection—The protection feature contains rules to guarantee that 802.11 transmissions do not cause interference with legacy stations or applications. By default, protection is enabled (Auto). With protection enabled, protection is invoked if legacy devices are within range of the WAP device.

You can disable protection (Off); however, legacy clients or WAP devices within range can be affected by 802.11n transmissions. Protection is also available when the mode is 802.11b/g. When protection is enabled in this mode, it protects 802.11b clients and WAP devices from 802.11g transmissions.

NOTE This setting does not affect the ability of the client to associate with the WAP device.

Beacon Interval—The interval between the transmission of beacon frames. The WAP device transmits these at regular intervals to announce the existence of the wireless network. The default behavior is to send a beacon frame once every 100 milliseconds (or 10 per second).

Enter an integer from 20 to 2000 milliseconds. The default is 100 milliseconds.

DTIM Period—The Delivery Traffic Information Map (DTIM) period. Enter an integer from 1 to 255 beacons. The default is 2 beacons.

The DTIM message is an element included in some Beacon frames. It indicates which client stations, currently sleeping in low-power mode, have data buffered on the WAP device awaiting pickup.

The DTIM period that you specify indicates how often the clients served by this WAP device should check for buffered data still on the WAP device awaiting pickup.

The measurement is in beacons. For example, if you set this field to 1, clients check for buffered data on the WAP device at every beacon. If you set this field to 10, clients check on every 10th beacon.

Fragmentation Threshold—The frame size threshold in bytes. The valid integer must be even and in the range of 256 to 2346. The default is 2346.

The fragmentation threshold is a way of limiting the size of packets (frames) transmitted over the network. If a packet exceeds the fragmentation threshold you set, the fragmentation function is activated and the packet is sent as multiple 802.11 frames.

If the packet being transmitted is equal to or less than the threshold, fragmentation is not used. Setting the threshold to the largest value (2,346 bytes, which is the default) effectively disables fragmentation.

Fragmentation involves more overhead both because of the extra work of dividing up and reassembling of frames it requires, and because it increases message traffic on the network. However, fragmentation can help improve network performance and reliability if properly configured.

Sending smaller frames (by using lower fragmentation threshold) might help with some interference problems; for example, with microwave ovens.

Aggregated 802.11n or 802.11ac frames (AMPDUs) cannot be fragmented. Fragmentation is applicable only for legacy radio modes, 802.11a or 802.11b/g.

By default, fragmentation is off. We recommend not using fragmentation unless you suspect radio interference. The additional headers applied to each fragment increase the overhead on the network and can greatly reduce throughput.

RTS Threshold—The Request to Send (RTS) Threshold value. The valid integer range must be from 0 to 2347. The default is 2347 octets.

The RTS threshold indicates the number of octets in an MPDU, below which an RTS/ CTS handshake is not performed.

Changing the RTS threshold can help control traffic flow through the WAP device, especially one with a lot of clients. If you specify a low threshold value, RTS packets are sent more frequently, which consumes more bandwidth and reduces the throughput of the packet. However, sending more RTS packets can help the network recover from interference or collisions that might occur on a busy network, or on a network experiencing electromagnetic interference.

RTS threshold is used only for legacy 802.11 data frames (that is, not for 802.11n or 802.11ac). In the case of 802.11n and 802.11ac, AMPDU transmissions are protected by an RTS/CTS exchange, regardless of the frame lengths.

Maximum Associated Clients—The maximum number of stations allowed to access each radio of this WAP device at any one time. You can enter an integer between 0 and 200. The default is 200 stations. The dual-radio WAP371 device can support up to 400 clients total.

Transmit Power—A percentage value for the transmit power level for this WAP device.

The default value of 100 percent can be more cost-efficient than a lower percentage because it gives the WAP device a maximum broadcast range and reduces the number of access points needed.

To increase the capacity of the network, place WAP devices closer together and reduce the value of the transmit power. This helps reduce overlap and interference among access points. A lower transmit power setting can also keep your network more secure because weaker wireless signals are less likely to propagate outside of the physical location of your network.

Some channel ranges and country code combinations have relatively low maximum transmit power. When attempting to set the transmit power to the lower ranges (for example, 25 percent or 12 percent), the expected drop in power may not occur, because certain power amplifiers have minimum transmit power requirements.

Frame-burst Support—Generally enabling Frame-burst support improves the radio performance in the downstream direction.

Fixed Multicast Rate—The transmission rate in Mbps for broadcast and multicast packets. This setting can be useful in an environment where wireless multicast video streaming occurs, provided the wireless clients are capable of handling the configured rate.

When Auto is selected, the WAP device chooses the best rate for the associated clients. The range of valid values is determined by the configured radio mode.

Legacy Rate Sets—Rates are expressed in megabits per second.

Supported Rate Sets indicate rates that the WAP device supports. You can check multiple rates (check a box to select or deselect a rate). The WAP device automatically chooses the most efficient rate based on factors such as error rates and the distance of client stations from the WAP device.

Basic Rate Sets indicate rates that the WAP device advertises to the network for the purposes of setting up communication with other access points and client stations on the network. It is generally more efficient to have a WAP device broadcast a subset of its supported rate sets.

Broadcast/Multicast Rate Limiting—Multicast and broadcast rate limiting can improve overall network performance by limiting the number of packets transmitted across the network.

By default, the Multicast/Broadcast Rate Limiting option is disabled. Until you enable Multicast/Broadcast Rate Limiting, these fields are disabled:

Rate Limit—The rate limit for multicast and broadcast traffic. The limit should be greater than 1, but less than 50 packets per second. Any traffic that falls below this rate limit will always conform and be transmitted to the appropriate destination. The default and maximum rate limit setting is 50 packets per second.

Rate Limit Burst—An amount of traffic, measured in bytes, which is allowed to pass as a temporary burst even if it is above the defined maximum rate. The default and maximum rate limit burst setting is 75 packets per second.

TSPEC Mode—Regulates the overall TSPEC mode on the WAP device. By default, TSPEC mode is off. The options are:

On—The WAP device handles TSPEC requests according to the TSPEC settings you configure on the Radio page. Use this setting if the WAP device handles traffic from QoS-capable devices, such as a Wi-Fi CERTIFIED phone.

Off—The WAP device ignores TSPEC requests from client stations. Use this setting if you do not want to use TSPEC to give QoS-capable devices priority for time-sensitive traffic.

TSPEC Voice ACM Mode—Regulates mandatory admission control (ACM) for the voice access category. By default, TSPEC Voice ACM mode is off. The options are:

On—A station is required to send a TSPEC request for bandwidth to the WAP device before sending or receiving a voice traffic stream. The WAP device responds with the result of the request, which includes the allotted medium time if the TSPEC was admitted.

Off—A station can send and receive voice priority traffic without requiring an admitted TSPEC; the WAP device ignores voice TSPEC requests from client stations.

TSPEC Voice ACM Limit—The upper limit on the amount of traffic the WAP device attempts to transmit on the wireless medium using a voice AC to gain access. The default limit is 20 percent of total traffic.

TSPEC Video ACM Mode —Regulates mandatory admission control for the video access category. By default, TSPEC Video ACM mode is off. The options are:

On — A station is required to send a TSPEC request for bandwidth to the WAP device before sending or receiving a video traffic stream. The WAP device responds with the result of the request, which includes the allotted medium time if the TSPEC was admitted.

Off — A station can send and receive video priority traffic without requiring an admitted TSPEC; the WAP device ignores video TSPEC requests from client stations.

TSPEC Video ACM Limit—The upper limit on the amount of traffic that the WAP device attempts to transmit on the wireless medium using a video AC to gain access. The default limit is 15 percent of total traffic.

TSPEC AP Inactivity Timeout—The amount of time for a WAP device to detect a downlink traffic specification as idle before deleting it. The valid integer range is from 0 to 120 seconds and the default is 30 seconds.

TSPEC Station Inactivity Timeout—The amount of time for a WAP device to detect an uplink traffic specification as idle before deleting it. The valid integer range is from 0 to 120 seconds and the default is 30 seconds.

TSPEC Legacy WMM Queue Map Mode—Enables or disables the intermixing of legacy traffic on queues operating as ACM. By default, this mode is off.

Click Save. The changes are saved to the Startup Configuration.

CAUTION

After new settings are saved, the corresponding processes may be stopped and restarted. When this happens, the WAP device may lose connectivity. We recommend that you change WAP device settings when a loss of connectivity will least affect your wireless clients.