Radio Mode is an SCU Profile setting that indicates the use of 802.11a, 802.11b, 802.11g, and 802.11n frequencies and data rates when interacting with an access point, or the use of ad hoc mode to associate a station radio instead of an access point.
When SCU operates with a Summit 802.11g radio, an administrator can select from among the following radio mode values:
Note: The default is BG rates full.
Note: See "802.11a/g Radio Mode with 802.11g Radio" for additional information.
When SCU operates with a Summit 802.11a/g radio, an administrator can select from the following radio mode values:
Note: See "Preferred Band for 802.11a/g Radio" for more information.
Note: The default is ABG rates full.
When the radio mode value is ABG rates full, the 5 GHz (A) band is preferred over the 2.4 GHz (BG) band. When the radio mode value is BGA rates full, the 2.4 GHz (BG) band is preferred over the 5 GHz (A) band.
When trying to associate to an access point, the radio considers access points in the preferred band. If the radio is able to associate to one of these access points, the the radio will not try to associate to a access point in the other band. The only time that the radio attempts to associate to an access point in the non-preferred band is when the radio is not associated and connot associate in the preferred band.
When roaming, the radio considers only access points in the current band (the band in which the radio is currently associated). The radio will consider an access point in the other band only ifit loses association.
When an administrator tries to create or edit a profile, SCU determines which radio is operating in the device and populates the available radio mode values according to the radio type. Suppose a profile created for an 802.11a/g card is loaded on a device with an 802.11g card. If a radio mode value of A rates only, ABG rates full. If the administrator does not save any changes to the profile, then SCU leaves the profile, including the radio mode, unchanged. If the administrator saves any changes to the profile, then SCU saves the radio mode value as BG rates full.
A radio profile (configuration profile) is a set of parameters that are stored in the registry and that define the manner in which the radio (station) associates to a wireless LAN (WLAN) infrastructure.
A profile contains information including the System Set Identifier (SSID or the "name" of the WLAN infrastructure), the means of data encryption, authentication type, security credentials, etc. A station device that operates with more than one WLAN infrastructure (perhaps in different buildings) tends to have more than one profile set up on the device.
Note: If ThirdPartyConfig is selected (and after the device goes through a power cycle), WZC (Windows Zero Configuration) or another application is used to configure the SSID, Auth Type, EAP Type, and Encryption settings.
Note: When you use the drop-down to switch to a new active profile, a registry flush occurs of the entire Configs key and subkeys for the previous active profile.
Radio settings in SCU may be configured from the Profile tab. The following are SCU Radio Settings:
Note: If you select a specific bit rate, the radio connects to an AP only if that AP has the specified SSID configured with the selected bit rate as the only required rate.
Note: Summit highly recommends the use of Open which is also the SCU default. This setting can be edited from the Profile window of SCU.
Note: For a Cisco explanation of 802.11 authentication using Open and Network-EAP, see: Products Configuration Example.
Radio Type is an SCU parameter that indicates the type of radio installed in the device. It can be found on the Main tab of the SCU. See Radio Mode for more information.
Note: This is only applicable to SCU versions prior to v4.0.
RC4 is a widely-used software stream cipher that is used in protocols such as SSL (Secure Sockets Layer - to protect Internet traffic) and WEP (to secure wireless networks).
From the SCU Diags window, (Re)connect allows you to initiate a reconnect of the radio. A reconnect of the radio includes the following actions: Disable and enable the radio, apply (or reapply) the current profile, attempt to associate to the wireless LAN, and attempt to authenticate to the wireless LAN. SCU logs all activity in the output area at the bottom of the Diags window.
A regulatory domain is a set of countries that have adopted a common set of regulations that relate to the use of public airwaves. For 802.11 technology, the notion of regulatory domains applies to the 2.4 and 5 GHz frequency bands. A Summit radio's regulatory domain determines the radio's maximum transmit power and the operating channels available to the radio.
Summit radios are certified for operation in the following regulatory domains:
Note: Specific regulatory information is provided to device manufacturers in the Hardware Integration Guide (HIG) for the applicable radio. These HIGs can be accessed from the product pages of the Summit Wi-Fi Radio Modules page.
A Summit radio can be programmed for any one of these four domains. By default, Summit radios are set to a "Worldwide" regulatory domain which is a "lowest common denominator" (a set of channels operating at a transmit power that is allowable within all regulatory domains).
From the SCU Diags window, Release / Renew allows you to obtain a new IP address through DHCP release / renew. SCU logs all activity in the output area at the bottom of the Diags window.
In networks where one radio is out of range, a repeater or "daisy chain" can be established to carry traffic to the out-of-range radio. A repeater is a bridge between two areas of the network. For example, if two networks exist on opposite ends of the wireless environment and are out of range from each other, a repeater radio can be placed between the two to carry traffic from one end to the other. A repeater functions like a signal booster, and may be composed of multiple radios depending on the distance that the range must be extended.
A Revision Control System (RCS) is a software utility or collection of utilities that can track, store, restore, and merge revisions of files. This is very useful for documents (most commonly code) that undergo frequent and heavy revisions. A Revision Control System simplifies the process of keeping track of separate iterations of a document (with aid of another utility, like the Linux diff function) and logs these iterations with version numbers, which increase incrementally with each saved revision. This is especially helpful with revisions of computer software, where changes made in consecutive revisions have the potential to break the code or create unexpected and unwanted behavior.
Radio Frequency. Electromagnetic energy with wavelengths between the audio range and the light range.
A Bluetooth protocol that emulates the serial cable line settings and status of an RS-232 serial port; used to provide serial data transfers.
As a station device moves throughout a facility, it will tend to move in and out of the range of the access points that make up the network infrastructure. In order to maintain constant connectivity and stable performance, a moving station device will disassociate from one access point and then reassociate to another access point that provides for better connectivity. Roaming is the term applied to this action. The "decision" to initiate a roam is based on a number of conditions and parameters. With Summit software release 1.02.20 and later, Summit provides two complementary sets of roaming algorithms to provide for more reliable connectivity. Those sets of algorithms are:
The standard roaming algorithm is employed when Summit-enabled station devices are operating in areas of relatively strong RF coverage. This roaming algorithm is based on the signal strength, or Received Signal Strength Indication (RSSI, which is measured in dBm) of the current AP (the access point to which the station is currently associated) and any other APs that are within range of the station. The Summit radio calculates a moving-average RSSI for the current AP and treats it as the "current RSSI". This value is displayed on the Status tab of the Summit Client Utility (SCU).
The administrator can configure three parameters for the standard roaming algorithm:
A Standard Roam scenario would be as follows: A station that is associated to an AP sees the RSSI go below the -75 dB Roam Trigger value, e.g. it goes to -80 dB. This prompts it to initiate a roam scan looking for a better AP ("better" in terms of signal strength). If it finds one, it will roam to it if the RSSI on the target AP is greater than the current AP by the Roam Delta value and it has been associated to the current AP for at least the Roam Period value.
Changing these parameters allows users to customize the roaming behavior of the station for environments that might be somewhere on a continuum between two extremes: if an environment has under-coverage (i.e., relatively few APs for the size of the facility) then the user can set the Roam Trigger to look for a new AP sooner and set the Roam Delta and Roam Period to smaller values so that the station will roam more quickly when it finds an alternative to the current AP. On the other hand, if an environment has over-coverage (i.e., a relatively large number of APs for the size of the facility) the user can set the Roam Trigger to a high value so that the station will only start looking for a new AP if the current AP signal gets very low, the new AP has a much stronger signal (Roam Delta), and the station has been associated to the current AP for some larger amount of time (30 seconds perhaps). How a given customer will configure these settings will depend on their RF environment, but also on the types of devices they use (laptop vs. data terminal for example), how those devices are used (truck-mounted going 25 MPH (40 KPH) or carried on a belt and being walked around), and what types of data they handle (voice/video vs. low data rate/latency insensitive bar-code scanning).
Aggressive Roaming is employed when Summit-enabled station devices are operating in areas of relatively weak RF coverage such as the edge of a coverage area. Aggressive roaming uses settings that are not configurable but have been determined in real customer environments to be optimal for reliable connectivity in areas of relatively weak coverage. Aggressive Roaming can, however, be disabled as is explained in this section. Aggressive roaming is triggered when the radio misses too many of the beacons expected from the current AP during a defined interval. The number of expected beacons is determined from the AP's beacon rate and DTIM interval.
Once aggressive roaming is triggered, the radio scans for a "better" AP every second. If Aggressive Roaming is triggered Aggressive Roaming will stop only when the station finds an AP with an RSSI that is stronger than that of the current AP and the station then roams to that AP. Aggressive Roaming will stop after a successful roam or if the number of received beacons returns to the expected number. If the station moves completely out of the coverage area for all APs, it will miss all beacons, determine that it no longer is associated to an AP, and will change its status to "Not Associated". The station will then revert to Standard Roaming.
In some environments such as environments with more than enough RF coverage (and significant co-channel interference) it may be desirable to disable Aggressive Roaming. This may be done through the "Aggressive Scan" menu item on the Global Settings tab in the Summit Client Utility (SCU). Changing the Aggressive Scan value from "On" to "Off" will disable this feature.
Aggressive Scanning may also be disabled by adding the below DWord to the registry and setting it to all zeroes as per the below:
Roam delta indicates the signal strength (RSSI) level (in dBm) that the radio looks for in a different access point (after the roam trigger is met) before it attempts to roam to the new access point.
Note: For an example of how Roam Delta works, refer to Standard Roaming.
Roam period indicates the amount of time a radio collects RSSI scan data (after association or a roam scan) before it considers roaming to a different access point.
Note: For an example of how Roam Period works, refer to Standard Roaming.
Roam trigger indicates the signal strength (RSSI) (in dBm) at which the radio scans for an access point with a better signal strength. When scanning for a different access point, the radio looks for one with an RSSI at the indicated roam delta dBm level or stronger.
Note: For an example of how Roam Trigger works, refer to Standard Roaming.
RSSI (Received Signal Strength Indication) refers to the strength of a transmitted signal as measured by a receiving device and typically is expressed as a negative number of decibels (dB). As a received signal weakens, the RSSI value decreases (becomes a larger negative number); as the received signal strengthens, the RSSI value increases. Typical Wi-Fi RSSI values in real-world environments range from a high of -50 dBm to a low of -95 dBm.
RSSI is a key value used by rate shifting algorithms. As RSSI decreases, these algorithms employ increasingly robust modulation schemes to maintain connectivity while decreasing data rate and throughput.
The Summit Client Utility (SCU) displays the RSSI value and also a graphical representation of the signal on the Status tab:
The Roam Trigger global setting is the RSSI value at which a Summit radio begins to scan for an AP to which to roam.
Note: For Summit 10, 15, and 20 Series radios, SCU handles RSSI as an absolute value. For Summit 30 Series radios, SCU handles RSSI as a relative value of received signal strength less ambient noise. Therefore, the RSSI reported in SCU and compared to the Roam Trigger will be lower with the 30 Series than with the 10, 15, and 20 series. Other parameters related to scanning and roaming, such as Roam Delta, behave similarly for different radios under like conditions.
Real-time locating systems (RTLS) identify, locate, and track objects or people within a confined area in real time. Wireless RTLS tags are attached to objects or worn by people and generally use wireless signals to report to fixed reference points, which read their location. Examples of RTLS include tracking automobiles in an assembly line, locating pallets of merchandise in a warehouse, or finding medical equipment in a hospital.
RTS Thresh (Request To Send threshold) is an SCU Global setting that indicates the packet size (in bytes) at which a Request To Send (RTS) or Clear To Send (CTS) is required on the link.
For SCU, the RTS Thresh integer range is 0 to 2347 (bytes) with a default setting of 2347 bytes.
Note: For 30AG (MSD30AG and SSD30AG) radio modules, this parameter is disabled.
Antenna diversity refers to the use of multiple antennas to increase the odds that a functional signal is received.
Rx (Receive) Diversity is an SCU Global setting that indicates how to handle antenna diversity when receiving data from an access point. Rx Diversity setting options include:
Note: The 'Start on' setting indicates the first antenna that is used upon startup if there is no history or failed history. After the initial start, SCU first samples the antenna that was last successfully used.
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