Abstract: An AMPS system facilitates reception and processing of a DS CDMA signal transmitted by a mobile station (125). The AMPS system provides an alternate path for the signal to be received by a DS CDMA receiver (506) system. The DS CDMA receiver system generates a signal compatible with the AMPS system, adjusts the generated signal to be proportional to the DS CDMA signal, and inputs the adjusted signal (510) into the AMPS system. The AMPS system then processes the adjusted signal for purposes of handoff of the mobile station (125) from the DS CDMA system to the AMPS system.

Abstract: A communication system dynamically assigns channels to a subscriber unit so as to, inter alia, mitigate the effects of co-channel interference in the system. The communication system has a plurality of base-stations receiving the transmission of a subscriber unit desiring service. Upon receipt of the subscriber unit's transmission, each base-station determines a signal quality value, which it then reports to a system controller. The system controller determines the best signal quality value reported and assigns a channel to the base-station which reported the best signal quality value. The chosen base-station transmits to the subscriber unit on an assigned channel to establish communication. The assigned channel transmitted by the chosen base-station need not be associated with the channel the subscriber transmits on. In fact, either channel may be any one of the channels allocated for use by the communication system.

Abstract: A CM (105) receives requests for data transfer from a series of UMs (101-103) and from an EM (104). The requests contain the UM (101-103) or EM (104) address and the size of the data packet to be transferred. The CM (105) processes the requests on a FIFO basis, stores the requests in a queue and schedules either a small data channel (415) or a large data channel (420), depending on the packet size to be transferred, an acknowledgement channel (425) and also the corresponding number of required timeslots. The CM (105) picks the first request off the queue and sends a grant to the particular UM (101-103) or EM (104) which receive the grant and immediately access either the assigned small or large data channels (415, 420) in the required number of timeslots and the acknowledgement channel (425).

Abstract: Power control circuitry (100) uses two attenuators in the transmit path to achieve wide dynamic range. An intermediate frequency (IF) attenuator (200) is placed before a mixer (212) in the IF section of the transmit path and a radio frequency (RF) attenuator (221) is placed after the mixer (212) in the RF section of the transmit path. Power control circuitry (236) controls setting of the two attenuators in response to a magnitude control signal (102) related to a RF output signal at a desired power level. To conserve battery power of the subscriber unit, only the RF attenuator (221) is adjusted when the desired power level is to be within a given range below the maximum transmission level. For ranges below the given range, the RF attenuator (221) is set for maximum attenuation and the IF attenuator (200) is adjusted.

Abstract: There is provided a mechanism for Automatic Gain Control in a receiver. It comprises: determining, within a certain dynamic range, the difference in power between the desired signal and a signal received, and providing open loop gain control for the signal in response to the differential so determined, scaled by the receiver's gain characteristics, such that the signal is positioned within dynamic range so as to reduce saturation and noise.

Abstract: In a TDMA cellular network, there is provided a mechanism for shared-carrier frequency-hopping. It comprises: allocating on a frame basis within a reuse diameter to one coverage area during certain timeslot(s) at least one from a pool of TDM-frame-hopped carriers and allocating on a frame basis within that carrier reuse diameter to another coverage area during certain other, substantially non-overlapping timeslot(s) that frame-hopped carrier, all in substantially non-interfering time-synchronism with any proximal reuse of that carrier, whereby the advantages of frequency hopping are obtained. Stated differently, it comprises: at one instant in time, allocating within a reuse diameter to one coverage area at least one of a plurality of hopped carriers and at that same instant in time, allocating within that carrier reuse diameter to another coverage area another of that plurality of hopped carriers, all in time-synchronism with any proximal reuse of that carrier.

Abstract: A radiotelephone system verifies the carrier/interference (C/I) of a selected target channel before handoff. The subscriber (125), communicating to a source base-station (130) on a source channel, measures the received signal strength indication (RSSI) of a target channel at a target base-station (135) when the channel is keyed (transmitting) and dekeyed (not transmitting). The subscriber (125) transfers the measurements to a source base-station (130) which determines the ratio of the RSSI with the keyed channel (C) to the RSSI with the dekeyed channel (I). If the ratio is greater than a predetermined threshold, the source base-station (130) transfers the subscriber (125) from the source channel to the target channel at the target base-station (135).

Abstract: A receiver (100) has improved signal weighting parameter estimation. The receiver receives a signal (101) having encoded data. A decision circuit (106) is coupled to the received encoded data to generate a first signal weighting parameter which is used to modify the received encoded data. The modified data is then decoded to output the decoded data. The decoded data output is then re-encoded using a technique similar to that used by the transmitter. The re-encoded data is then used to calculate a second signal weighting parameter which, in turn, is used to modify a stored replica of signal (101). The modified version of the stored replica is then decoded to yield a more accurate estimate of the information contained within the signal (101) at a receiver (100).

Abstract: A digital radiotelephone system requiring a transfer of communication from a source base-site (200) in a source cell (100) to a selected one target base-site in a target cell. A source base-site (200) in the source cell (100) provides a first and a second threshold and measures the received signal strength of a mobile unit (225) communicating to the source base-site (200). When the measured signal strength at the source base-site (200) falls below the first threshold, the source base-site (200) initiates a handoff to target base-sites located by the mobile unit (225). The target base-sites measure the received signal strength of the mobile unit (225) and a target base-site is selected. The source base-site (200) is notified of the selected target base-site and hands off communication of the mobile unit (225) to the selected target base-site when the previously measured signal strength at the source base-site (200) falls below the second threshold.

Abstract: There is provided a method of digital Automatic Gain Control (AGC) in a receiver having limited dynamic range, particularly for discontinuous signals. The method comprises detecting the level of a received and AGC'd discontinuous signal, comparing the level of the AGC'd signal relative to the dynamic range of the receiver, and adjusting the AGC to establish a desired relationship between the AGC'd signal and the dynamic range limitation. There is also provided a method of handoff in a TDMA cellular-type transmission system utilizing this method of AGControl.

Abstract: A communication system provides data packet timing alignment to facilitate soft handoff. A vocoder (315) transmits compressed voice frames to base-stations (130,131) along links (110,112) of variable length, .DELTA..sub.L. The .DELTA..sub.L translates to a delay .DELTA..sub.t in the air-frames to be transmitted by the base-stations (130,131). To compensate for the time delay .DELTA..sub.t, the communication system advances both sets of air-frames to be transmitted by base-stations (130,131) by at least .DELTA..sub.t so that skipping of frames, relative to an air-frame reference (300), during transmission does not occur.

Abstract: A diversity receiver (300) has improved diversity weighting parameter estimation. The receiver receives different versions of a signal (101) having encoded data, combines the versions and decodes the data contained within the combination. The decoded data output is then re-encoded using a similar technique as that at a transmitter which transmitted the signal (101). The re-encoded data is then used to calculate a diversity weighting parameter which is used to modify a stored replica each version. The modified versions are then combined and decoded to yield a more accurate estimate of the information contained within the signal (101) at diversity receiver (300).

Abstract: A base-site (304) combines baseband frequency hopping and fast-synthesizer hopping to produce an economical frequency hopping communication system (300). The base-site (304) combines the fast-synthesizer frequency hopping capability of transmitters (307-309) with baseband frequency hopping to produce a frequency hopping communication system (300) which serves the same number of subscribers served by transmitters (208-213) in a purely baseband hopping communication system (200), but with fewer transmitters (307-309). The implementation of frequency-selective cavities (312-317) having very low loss eliminates the need for wideband hybrid combiners (112-114), which in turn eliminates transmitted-signal power loss experienced in a purely fast-synthesizer frequency hopping communication system (100).

Abstract: An equalization system for equalizing a corrupted signal is disclosed. The equalization system includes a complex matched filter (400) and a maximum likelihood sequence estimator (MLSE) (405) for removing the effects of phase shift, amplitude variations, intersymbol interference, etc. resulting from multi-pathing and noise contributed by the receiver front end. The system estimates a correlation signal C(t) (505) and synchronizes C(t) 505 to maximize its energy as seen on the taps of the complex matched filter (400). Taps having amplitude coefficients below a predetermined threshold are set to zero to produce a modified CIR estimate. The modified CIR estimate which has had the effects of noise virtually eliminated, is then used to construct the complex matched filter (400) and is also used as input to the MLSE (405) to produce a better equalized data signal.

Abstract: A central-site (100) has located within it a synchronization system for purposes of backing-up a GPS external synchronization system. The central-site (100) is coupled to a plurality of base-sites (102, 103) which are required to be synchronized to one another. When the GPS signal is lost, the synchronization system within the central-site (100) allows the plurality of base-sites (102, 103) to maintain synchronization to one another. In this manner, the necessity for a synchronization system within each of the plurality of base-sites (102,103) is eliminated.

Abstract: A radiotelephone system reduces noise interference during handoff by muting the audio path of a receiver employed in a target base-station (135). After receive a handoff request message, a target base-station (135) mutes the target audio path and determines if the target audio path had been enabled by an undesired interfering signal having a common SAT. If the target audio path had been enabled by a interfering signal having a common SAT, the target base-station (135) will use the SAT and the received signal strength indication (RSSI) of the desired transmission of the subscriber (125) to enable the target audio path. Once the SAT and RSSI are present and adequate, the target audio path is enabled, the source audio path is coupled to the target audio path, and the subscriber (125) is handed off from the source base-station (130) to the target base-station (135) without a third party experiencing an objectionable noise blast.

Abstract: A CM (105) receives requests for data transfer from a series of UMs (101-103) and from an EM (104). The requests contain the UM (101-103) or EM (104) address and the size of the data packet to be transferred. The CM (105) processes the requests on a FIFO basis, stores the requests in a queue and assigns either a small data channel or a large data channel, depending on the packet size to be transferred, and also the corresponding number of required timeslots. The CM (105) picks the first request off the queue and sends a grant to the particular UM (101-103) or EM (104) which receive the grant and immediately access either the assigned small or large data channels in the required number of timeslots.

Abstract: An apparatus scales binary samples representing a predetermined waveform (109) to achieve every possible transition in a multi-level transmission system. The predetermined waveform (109) is partitioned into M symbol intervals, each symbol interval having a corresponding waveform represented by a series of binary samples V stored in M separate ROM devices (311-316). Depending on the required amplitude and polarity of the transition, logic blocks (351-356) control scaling multipliers (321-326) and polarity multipliers (331-336) to perform the required scaling and inverting of the binary samples retrieved from ROM (311-316). The scaled and inverted samples are added together by an adder (345) and sent to a D/A converter (350) where the desired scaled and inverted waveform is converted/generated from the scaled and inverted binary samples.

Abstract: A cellular radiotelephone system transfers a call from a source base-site (200) to one target base-site (205,210). A source base-site (200) in the first RF coverage area (100) measures the signal strength (RSSI.sub.S) of a mobile (225), provides a forecasted signal strength (RSSI.sub.F) representing a would-be power increase of the mobile (225) and sets up two time windows. The source base-site (200) sends the measured and forecasted signal strengths to candidate target base-sites (205,210) found by the mobile (225) which measure the mobile (225) signal strength (RSSI.sub.T) and compare it once to RSSI.sub.S plus a hysteresis value. If RSSI.sub.T is greater than RSSI.sub.S, the call is transferred to the best responding cell. If RSSI.sub.T is below RSSI.sub.S, RSSI.sub.T is compared to RSSI.sub.F. During this time, the mobile 225 will increase power at the end of the first time window. If RSSI.sub.T is ever greater than RSSI.sub.

Abstract: A receiver module 140 controls the amplitude of a random burst signal 200 in a TDMA system. A random burst signal 200 presence detector 330 detects when the random burst signal 200 has arrived during a timeslot reserved for the random access burst 200. After detection, a control processor monitors the signal strength or amplitude of the random access burst 200 for a predetermined time period, determines the amount of AGC attenuation required, and inserts the required AGC attenuation to control the amplitude of the random access burst 200 for the duration of the timeslot.