Abstract: Encryption keys are transferred by obtaining a public and private key pair (42, 65) from a source device (21, 61). The public key is transmitted (42, 65) from the source device (43, 66) to a target device (23, 62). The target (23, 62) obtains a traffic key (44, 67) stored within the target device (23, 62). The traffic key is encrypted (45, 68) within the target device using the public key. The encrypted traffic key is transmitted to the source device (46, 69) where it is decrypted (47, 70) using the private key. The replacement encryption key(s) is(are) encrypted using the traffic key by the source device (48, 71) forming an encrypted replacement key message which contains a target slot identification for each of the replacement encryption keys. The encrypted replacement key message is transmitted to the target device (49, 72) where the replacement encryption key(s) is(are) recovered (50, 73). The replacement encryption key(s) is(are) then stored at the target device in an identified target slot (51).

Abstract: A method of performing a handover as shown in FIGS. 2-3 for a mobile station in a multicellular environment including the steps of determining to handover from one of the plurality of microcells to the macrocell, performing handover from the one of the plurality of microcells to the macrocell; and sending a false neighbor list to the mobile station.

Abstract: A method of spawning a communication service comprises the steps of detecting (201) a failed call attempt initiated by a first communication unit (101) and directed to a second communication unit (109), and determining (207) if a code associated with the first communication unit (101) is an authorized code associated with the second communication unit (109), wherein the first communication unit (101) is associated with a first user and the second communication unit (109) is associated with a second user. If the code is an authorized code, a communication service is spawned (209), resulting in a message directed at a user other than the second user, such as the first user or a third user, or a communication unit other than the second communication unit (109), such as the first communication unit (101) or a third communication unit (109), which may be associated with a third user other than the first user or the second user.

Abstract: A multi-channel digital transceiver (400) receives uplink radio frequency signals and converts these signals to digital intermediate frequency signals. Digital signal processing, including a digital converter module (426), is employed to select digital intermediate frequency signals received at a plurality of antennas (412) and to convert these signals to baseband signals. The baseband signals are processed to recover a communication channel therefrom. Downlink baseband signals are also processed and digital signal processing within the digital converter module (426) up converters and modulates the downlink baseband signals to digital intermediate frequency signals. The digital intermediate frequency signals are converted to analog radio frequency signals, amplified and radiated from transmit antennas (420).

Abstract: A user, after accessing (41) the communication system (10), selects (42) a paged email service option. In response, the communication system (10) dispatches (43) a service logic block to a service node proxy (110) of an email system (101-105). The service logic block is deposited (44) in a site-specific service logic block repository (112) of the email system (101-105). An email monitor is established (45) for the email system (101-105). Once established, the email system sends (46) an acknowledgment to the communication system (10). The user is then notified (47) of receipt of the acknowledgment.

Abstract: A base site (100) employs a method and apparatus for selecting two of a plurality of antennas (101-106) from which to receive a communication signal. A first signal quality metric is measured for a communication signal received from a first antenna (102) and a second signal quality metric is measured for the communication signal received from a second antenna (103). When the first signal quality metric differs from the second signal quality metric by a threshold, a signal receiver (113) is coupled to a third antenna (e.g., 101) and a third signal quality metric is measured for the communication signal received from the third antenna (101). Based on the three signal quality metrics, a primary antenna and a secondary antenna are selected from which to receive the communication signal.

Abstract: A method including the steps of performing a synchronization measurement of a received signal (102), and performing a handoff (110) between a first communication channel and a second communication channel in response to the synchronization measurement. An apparatus including a receiver (50) detecting a received signal over a first communication channel, a receive signal processor (44) responsive to the receiver (50), and a handover controller (40) responsive to the receive signal processor (44). The receive signal processor performs a synchronization measurement of the received signal. The handover controller (40) initiates a handoff between the first communication channel and a second communication channel in response to the synchronization measurement.

Abstract: Noise in an ADPCM signal is muted or suppressed by modifying the magnitude of the ADPCM information during noisy conditions. In one method, the ADPCM data is changed to a predetermined magnitude value. In another method, the magnitude is reduced by a predetermined amount.

Abstract: A remote power measuring device (1) is used to measure the power output of the transmission system (20). The measured power is then transmitted to a controller (5) and used by the controller (5), along with preset calibration data (41) for each power amplifier (3), to determine power output adjustment factors (22). The adjustment factors (22) are then communicated to the appropriate power amplifier (3) to adjust its output.

Abstract: A method and apparatus is provided for reducing interference in a radio communication link from a central site (230) to a mobile unit (228) in a cellular communication system. The central site (230) includes a first (202) and a second (216) antenna which serve the geographic region (214) in which the mobile unit (228) is located. The radio communication link may be provided by communicating a signal in a first radio communication channel between the first central site antenna (202) and the mobile unit (228). Similarly, the radio communication link may be provided by communicating a signal in a second radio communication channel between the second central site antenna (216) and the mobile unit (228). A measure of interference in the first radio communication channel providing the radio communication link is determined. The radio communication link is switched, in response to the measure of interference being above a predetermined threshold, from the first to the second radio communication channel.

Abstract: A method and apparatus for authenticating a roaming subscriber. In a preferred embodiment, a subscriber receives a challenge that is in a format of a local authentication protocol, and determines whether the local authentication protocol is the subseriber's home system authentication protocol. If it is not, the subscriber converts the challenge into a format (e.g., bit length) compatible with its home system authentication protocol, and processes the converted challenge with the subscriber's secret key and authentication algorithm into an authentication response. The authentication response is converted to be compatible with the local authentication protocol, and transmitted to a local system communication unit. The challenge and response is then forwarded to the subscriber's home system for similar conversion and processing, and subscriber's response is compared against a home system generated response.

Abstract: A digital radiotelephone system employs vocoders to convert between analog speech and a digital format suitable for transmission via radio. Under most circumstances, the highest data rate is selected for optimum audio quality. When the system occupancy exceeds a particular threshold, as detected at the fixed site of the system, some or all of the vocoders are instructed to switch to a lower data rate to provide for an increase in the number of communication channels. Further, a portable subscriber unit may autonomously change its vocoder data rate depending upon the charge state of its battery.

Abstract: In a cellular communication system (40) a handoff candidate list is generated for a source sector (51) by eliminating (12) from a list of potential handoff candidates (52-56) any sectors having an interference parameter exceeding a threshold value. The list is further reduced by determining (21) a handoff radius (60) and eliminating any candidate sectors (52-56) that fall outside the handoff radius (60). Candidate sectors (52-56) that do not have overlapping coverage areas are also eliminated (23). In addition, candidate sectors (52-56) having a relative angle of sight to the source sector (51) that exceeds a maximum angle are also eliminated (24). Finally, the list is reduced (15) to a preset number of candidates dependent upon the interference parameter.

Abstract: A transmitter transmits the desired signal using a continuous duty cycle at transmission rates of less than full rate (FIG. 6 ). The energy used in each power control group is related to the transmission rate. By repeating the power control groups, time division diversity (FIG. 6 ) is provided. In the receiver, the received power control groups are analyzed and compared to several levels of energy thresholds (73, 75, 77, 79). The results of the comparisons are converted into a power control signal (74, 76, 78, 80, 81) and returned to the mobile. The mobiles are capable of selecting the appropriate bit (93) and adjusting their power (94). Alternatively, an indicator of the transmission rate can be forwarded (155) in advance of the frame. The receiver compares a power estimate with the threshold for the transmission rate indicated (166).

Abstract: In a frequency hopping cellular communication system (40) having a number of base sites (41-48) and using mobile assisted handoff, a method is offered of providing base site identification signals. The method includes the steps of assigning each base site of the number of base sites to a slot of a intersite control frame; and, periodically transmitting, in the assigned slot of the intersite control frame, the identification signal of the base site.

Abstract: A method and apparatus for digital automatic frequency control includes circuitry for frequency controlling a first information portion of a digital input signal, correlating the output with a known characteristic of the first information portion, and outputting a timing signal and channel estimation signal. The digital input signal is also decimated using the timing signal and frequency controlled into a frequency controlled output signal. This signal is used, along with a signal quality estimate derived from the channel estimation signal and first information portion, to determine an estimated frequency correction signal. The estimated frequency correction signal is used to control the frequency correction steps.

Abstract: Each of a plurality of transmitters (31-37) transmits (62) one of a plurality of known signals. The known signals being known to a receiver (40). The receiver (40) then measures the known signals (63); and using those measurements, estimates the plurality of channel responses (64). The channel responses are then used to determine a power ratio parameter (65) and a phase correction parameter (66).

Abstract: In order to mitigate problems caused by total or partial failure of a number of sectorised radio channel unit transceivers (RCU) in a base station of a particular cell (16) of a radio communications system, base stations (26, 32) in adjacent cells (14, 20) increase the power transmitted from RCUs controlling sectors adjacent to that particular cell 16, thereby filling the gap in coverage left by the failure of that cell (16).

Abstract: An information gap in an ADPCM signal is detected in one or both of a transmitter or receiver. This detection can be accomplished using a voice activity detector. When an information gap is detected, a clock signal to the encoder and/or decoder is interrupted. Alternatively, null frames can be inserted into the encoder and/or decoder. When null frames are used, it is preferable to insert comfort noise into the signal output from the decoder.