Knowledge Center: L
An alphabetical glossary of terms related to Laird's embedded wireless modules.
Logical Link Control and Adaption Layer Protocol. Used within the Bluetooth protocol stack, it provides a data link layer for Bluetooth; passes packets to either the HCL (Host Controller Interface) or, on a hostless system, directly to the Link Manager/ACL link.
The delay in communication between the sending and receiving of a signal. Latency is an inherent feature of electronic communications, and can be thought of as the sum of all factors (in serializing, queuing, and processing of the transmission) which cause the delayed receipt of a transmitted message. These factors include interference, crosstalk, attempts at re-sending, and more. Through proper configuration of radio hardware, latency can be reduced to a minimum for the best device performance.
LED is an SCU Global setting that indicates whether or not an LED is used. This setting applies only to select Laird radios.
In the 2.4 GHz frequency band used for 802.11b and 802.11g, there are between 11 and 14 available channels (depending upon regulatory domain). Of these channels, only 3 or 4 (depending upon regulatory domain) do not overlap with each other and are available for wireless LAN operation. When operating in the FCC regulatory domain (North and South America, parts of Asia, and the Middle East) most wireless LAN infrastructures are configured to operate on channels 1, 6, and 11. In the ETSI regulatory domain (Europe, Africa, and parts of Asia and the Middle East) most wireless LAN infrastructures are configured to operate on either channels 1, 6, and 11 or 1, 7, and 13.
By default, Laird's software is configured to scan all 2.4 GHz channels prior to initiating a roam. During a scan, a client device is unable to send or receive data; this means that the longer a scan period, the lower the client's performance.
Limiting the set of channels to be scanned (prior to a roam) to only the channels that are in use in the WLAN infrastructure is an effective means of decreasing scan time and improving performance. A Limited Channel Set may be enabled in two ways:
A Limited Modular Approval (LMA) may be granted if the device does not meet all modular requirements and if compliance can be demonstrated under the operating conditions in which the device will be used. An LMA is only issued in circumstances where the Grantee can demonstrate that it will retain control over the final installation of the device (to ensure compliance of the end product).
In a Bluetooth device, the logic layer that manages the connection between the host device and remote device(s) is called the Link Manager. Link Management Protocol is the standard for these communications. LMP messages are transmitted over an Asychronous Connection-Oriented Link (ACL) logical transport. This layer is distinct from the ACL layer that exchanges user data.
On Windows XP, SCU supports two sets of logon options:
To use logon options, follow these steps:
To activate SSO on the PreLogon dialog box, follow these steps:
When the active profile is configured to use LEAP, PEAP-MSCHAPv2, PEAP-GTC, or EAP-FAST, then for EAP authentication the software ignores the username and password saved as credentials in the profile and instead uses the username and password entered for the Windows logon.
Pre-logon connection is intended for situations where all of the following are true:
In other words, pre-logon connection enables EAP authentication to complete successfully before the user has completed the Windows login to satisfy SSO.
To activate pre-logon connection on the PreLogon dialog box, follow these steps:
The pre-logon connection method varies by EAP type. For LEAP, PEAP, or EAP-FAST, if the active profile includes credentials, then Laird Wi-Fi software uses those credentials; otherwise, the software must obtain the credentials from the Windows login or by prompting the user. If SSO is enabled, then the software uses the last valid Windows login credentials. If SSO is not enabled, then pre-logon authentication will fail, because the software cannot prompt the user; a WLAN connection will not be established until Windows login succeeds and the user can be prompted.
For PEAP, you can specify on the PreLogon Credentials dialog box the CA certificate to be used for pre-logon server validation. This certificate can differ from that used for post-logon server validation.
For EAP-TLS, you must specify on the PreLogon Credentials dialog box the user certificate to be used for pre-logon authentication.
If both SSO and pre-logon connection are active and EAP authentication is performed before Windows login, then after Windows login the software performs EAP authentication again using the credentials specified on Windows login.
In a Bluetooth Low Energy connection, the Link Manager Protocol (LMP) is replaced with the Low Energy Link Layer (LE LL). This performs similar tasks to the LMP but is simpler, and oversees all aspects of connection and security. This layer is organized close to the hardware, allowing for effective low-energy link management.
Microsoft Logo Test Kit. Provides a set of tests for specific Windows Mobile-based devices.
LSB, or least significant bit, is the lowest bit in a series of numbers and is located at the far right of the string. For example, in the following number, 4 is the LSB: 2014