Abstract: Disclosed is a method for encrypted communications. A first IPsec endpoint selects a security association (SA) from a security association database (SAD) by using a selector and then extracts an indexing parameter from SA. The indexing parameter is used to determine an active key location from a key storage database (KSD). Data packets are then encrypted using a key from the active key location. The first IPsec endpoint also forms a security parameter index (SPI) in a header of the data packet by using a keyID from the active key location and transmits the encrypted data packet with the header indicating the SPI to a second IPsec endpoint.

Abstract: The present invention discloses, in a two-way radio frequency (RF) communications system having at least one repeater, a plurality of channels, and a plurality of subscriber units, a repeater receives a message that identifies a channel that is selected to serve as a rest channel for the system. The channel that is currently serving as the rest channel for the system is monitored by subscriber units that are idle in the system. If the repeater determines that the channel selected to serve as the rest channel is hosted by the repeater, the repeater periodically transmits an identity of the channel as the channel currently serving as the rest channel on at least the channel.

Abstract: A device detects a first signal on a channel that is one of a plurality of channels arranged in a first order on a list, with each channel being associated with a different site in a multi-site communication system. Upon detecting the first signal, the device attempts to measure and record signal strength of a signal at each channel on the list based on the first order beginning with the detected first signal, and selects as a home site the site associated with the channel having the signal with the highest recorded signal strength. The device rearranges the channels on the list into a second order based on the recorded signal strengths with the home site channel at the top. If necessary, the radio attempts to awaken its repeaters one after another based on the second order until a repeater is found to transmit a signal.

Abstract: A method for synchronizing the direct mode TDMA transmission of a set of radios by following a selected radio as the leader includes: receiving, by a radio, a communication from an other radio; identifying, by the radio, a leader according to a leadership election rule using the received communication from the other radio and a current leader information; setting, by the radio, the identified leader as its leader; and synchronizing, by the radio, a time slot boundary with a time slot boundary defined by the leader.

Abstract: A method for scanning a TDMA channel by a mobile station in a wireless communications landscape is disclosed. A mobile station detects RF energy on a TDMA channel to detect activity in the detected RF energy. The mobile station maintains knowledge of previous activity on the channel. If activity is present on the channel, the mobile station performs inspection of the activity to determine whether the activity is activity of interest, wherein the activity is activity of interest based on a comparison of the activity with the previous activity. The mobile station aborts the inspection of the activity, if activity is not present on the channel and the mobile station aborts the inspection of the activity, if the determined activity is not activity of interest.

Abstract: A wireless communication device accesses a scan list that includes a plurality of scan members sorted at least by receive frequency and attempts to detect whether a call of interest exists on a receive frequency by performing a group scan for a group of scan members that are marked scan undone and that have the same corresponding receive frequency, wherein the group includes a first scan member and at least one other scan member. The group scan includes inspecting the receive frequency to obtain inspection results; using the inspection results to determine that there is no signal on the receive frequency having signal attributes that match a set of attributes for the first scan member; and using the inspection results to evaluate at least one of the other scan members in the group to determine whether there is a corresponding signal of interest on the receive frequency.

Abstract: A method for facilitating transmission of data in a communication system is provided herein. In operation, a base radio of a plurality of base radios combines status information corresponding to a plurality of inbound frequencies and transmits the combined status information on a single outbound radio frequency. Further, each of the plurality of inbound radio frequencies corresponds to one of the plurality of base radios. Then, one or more radio terminals monitor the single outbound radio frequency to receive the combined status information, determine at least one available inbound radio frequency from the plurality of inbound radio frequencies based on the received combined status information, selects an inbound radio frequency of the at least one available inbound frequency, and transmitting the data using the selected inbound radio frequency to the corresponding base radio.

Abstract: A method for interrupting voice transmissions within a multi site communication system includes operating a repeater to engage in an interruptible voice communication; to identify an open burst location based on a repeat delay when the interruptible voice communication is sourced directly via a wireless network, and to identify the open burst location as irrelevant when the interruptible voice communication is indirectly sourced via a wireless network; and repeat the interruptible voice communication including the open burst location.

Abstract: Within a two way radio frequency communication system, a repeater transmits an identity of a rest channel when transmitting during an active communication call on a channel other than the rest channel. A subscriber unit communicating within the active communication, receives the identity of the rest channel, leaves the active communication; and initiates a new communication on the rest channel.

Abstract: A method for managing a packet in a communication system between two or more endpoints, a sender and one or more recipients, comprises receiving a first packet comprising a source identifier that uniquely identifies a sender of the first packet and a current source time assigned to the first packet by the sender, determining a received time for the first packet, retrieving a cached source time assigned by the sender to a second packet that was received prior to receiving the first packet, and determining whether to discard or process the first packet based on the current source time, the received time, and the cached source time. The current source time, the received time, and the cached time, in addition to predetermined parameters such as a maximum age and an anti-replay window allows a recipient to determine whether to process or discard a packet.

Abstract: A wireless communication device accesses a scan list that includes a plurality of scan members sorted at least by receive frequency and attempts to detect whether a call of interest exists on a receive frequency by performing a group scan for a group of scan members that are marked scan undone and that have the same corresponding receive frequency, wherein the group includes a first scan member and at least one other scan member. The group scan includes inspecting the receive frequency to obtain inspection results; using the inspection results to determine that there is no signal on the receive frequency having signal attributes that match a set of attributes for the first scan member; and using the inspection results to evaluate at least one of the other scan members in the group to determine whether there is a corresponding signal of interest on the receive frequency.

Abstract: To perform a channel inspection, a wireless communication device: monitors a common announcement channel (CACH) until detecting that a first set of identified parameters associated with a signal on a first channel matches a second set of known parameters for the first channel; performs an inspection on the first channel to determine whether the signal is of interest; and when the signal is not of interest, marks the first channel to prevent another inspection from being performed on the first channel until after the channel mark is removed. The communication device then leaves the first channel and continues to monitor the CACH for a change in the first set of identified parameters or an indication of an idle first channel, wherein the communication device removes the channel mark on the first channel.

Abstract: A device detects a first signal on a channel that is one of a plurality of channels arranged in a first order on a list, with each channel being associated with a different site in a multi-site communication system. Upon detecting the first signal, the device attempts to measure and record signal strength of a signal at each channel on the list based on the first order beginning with the detected first signal, and selects as a home site the site associated with the channel having the signal with the highest recorded signal strength. The device rearranges the channels on the list into a second order based on the recorded signal strengths with the home site channel at the top. If necessary, the radio attempts to awaken its repeaters one after another based on the second order until a repeater is found to transmit a signal.

Abstract: A repeater receives and repeats, on a multi-site channel, a sequence of control and media transmissions included in a session, wherein the session has a plurality of participants. While repeating these transmissions, the repeater further detects, from at least one of the transmissions, a start of the session and a type of the session. Based on the type of the session, the repeater determines whether to perform an arbitration during the session to control access to the multi-site channel, and restricts each performed arbitration to only transmissions received from the participants to the session. In addition, after repeating at least one of the control transmissions, the repeater sets a hang time having a duration that is determined based on a type of the transmission preceding the setting of the hang time.

Abstract: To perform channel inspection, a wireless communication device conducts a full inspection on a first channel carrying a first signal that includes: determining a location of a first synchronization message; and determining whether the first signal is of interest. Upon determining that the first signal is not of interest, the first channel is marked, wherein the marking includes remembering the location of the first synchronization message. The device leaves the first channel and determines an expected location of a second synchronization message on the first channel based on the location of the first synchronization message. Upon returning to the first channel which carries a second signal, the communication device conduct a partial inspection that includes: detecting whether the second synchronization message is present at the expected location, wherein the presence of the second synchronization message indicates that the second signal is not of interest.

Abstract: A transmitting device encrypts DMR voice superframes using encryption parameters and sends the encryption parameters in at least one of the voice superframes by: identifying a selected number of bits from a plurality of vocoder frames the voice superframe; replacing each of the identified bits with a corresponding bit of a first encryption parameter; placing at least one encryption parameter in an embedded signaling field of the voice superframe; and transmitting the voice superframe with the encryption parameters to a receiving device. The receiving device extracts the encryption parameters, which can be a key identifier, an algorithm identifier, and an initialization vector for use in decrypting messages from the transmitting device.

Abstract: In a two-way radio frequency (RF) communications system having at least one repeater, a plurality of channels, and a plurality of subscriber units, a repeater hosts a first channel that is currently serving as a rest channel. The channel that is currently serving as the rest channel is monitored by subscriber units that are idle in the system. When the repeater determines to select a second channel to serve as the rest channel, it determines whether there is at least one eligible channel to serve as the rest channel. If there is at least one eligible channel in the system, the repeater may select the second channel to serve as the rest channel from one of the eligible channels.

Abstract: A subscriber unit monitors a first channel currently serving as a rest channel for the system, wherein the channel currently serving as the rest channel for the system is monitored by subscribers that are idle in the system. The subscriber unit determines that a first call is being initiated on the first channel. If the first call is not of interest, the subscriber unit ceases to monitor the first channel, and monitors a second channel that will serve as the rest channel for the system when the first call starts on the first channel. If the first call is of interest, the subscriber unit participates in the first call on the first channel, and before or after the first call ends, participates in a second call on a third channel or monitors a channel currently serving as the rest channel for the system when the subscriber unit becomes idle.

Abstract: The present invention discloses, in a two-way radio frequency (RF) communications system having at least one repeater, a plurality of channels, and a plurality of subscriber units, a repeater receives a message that identifies a channel that is selected to serve as a rest channel for the system. The channel that is currently serving as the rest channel for the system is monitored by subscriber units that are idle in the system. If the repeater determines that the channel selected to serve as the rest channel is hosted by the repeater, the repeater periodically transmits an identity of the channel as the channel currently serving as the rest channel on at least the channel.

Abstract: A repeater receives an indication that a subscriber unit is initiating a call session on a channel, and indicates that the channel is busy. The repeater repeats a transmission from the subscriber unit and sets a timer for a first time upon determination that the transmission has ended. The timer is set for a second time if a new transmission is not received from a subscriber unit that is allowed to transmit on the channel prior to the expiration of the first time; otherwise, the repeater accepts a new transmission from a subscriber unit that is allowed to transmit on the channel if the new transmission is received prior to an expiration of the second time. Upon receipt of each new transmission received prior to the expiration of the second time, the repeater clears the timer, repeats the transmission on the channel, and resets the timer for the first time upon determination that the transmission has ended.