Abstract:
A system and method for determining the data rate of a frame of data at a receiver (50) of a variable rate communications system. A vocoder at a transmitter encodes a frame of data at one of the rates of a predetermined set of rates. The data rate is dependent on the speech activity during the time frame of the data. The data frame is also formatted with overhead bits, including bits for error detection and detection. At the receiver (50), the data rate for the frame is determined based on hypothesis testing. Because the data rate is based on speech activity, a hypothesis test may be designed based on the statistics of speech activity. The received data frame is first decoded by a decoder (34) into information bits at the most probable rate as provided by the hypothesis testing module (36). Data check element (42) generates error metrics for the decoded information bits. If the error metrics indicate that the information bits are of good quality, then the information bits are presented to a vocoder (44) at the receiver to be processed for interface with the user. If the error metrics indicate that the information bits have not been properly decoded, then decoder (34) decodes the received data frame at the other rates of the set of rates until the actual data rate is determined.
Abstract:
A support assembly for supporting a plurality of inclined plates (22) arranged in an array around a central axis includes a top support bracket (25) for supporting the upper edges (40) of the plates (22) and a plurality of base brackets (26) for supporting the lower edges (62) of the respective plates (22). The top support bracket (25) has a central axis aligned with the central axis of the array, and a plurality of side edges (28). Each side edge (28) has a downwardly inclined rim (32) at a predetermined angle corresponding to the desired plate orientation and a downwardly facing groove (42) for receiving the upper edge (40) of the respective plate (22). Each base bracket (26) has a base (46) for securing against a substantially flat support surface (16), a snap lock arm (52, 54) extending upwardly from the base (46) towards a respective side edge (28) of the top bracket (25) at a predetermined angle equal to the rim angle for snap engagement in an opening (60) spaced from the lower edge of the respective plate (22), and a groove (55) at the lower end of the snap lock arm (52, 54) for receiving the lower edge (62) of the respective inclined plate (22).
Abstract:
Apparatus and method employed in a communications system which has a transmitter (2) and a receiver (4), where the receiver determines at which of several rates individual frames in a signal have been transmitted by the transmitter. For example, if the transmitter (2) employs four transmission rates, the receiver (2) decodes each frame of the received signal based on the four rates to produce four cyclic redundancy check (CRC) bits, four symbol error rate (SER) values and one or more Yamamoto check values. If only two of the CRC bits check, then the receiver (2) compares to each other the SER values for those two rates to determine at which of the two rates a current frame was transmitted. If only one of the CRC bits check for a given rate, then the SER value for that rate is compared with a maximum SER threshold for that rate. Additionally, SER values for the other rates can be compared to minimum SER thresholds. Furthermore, the Yamamoto check values can be analyzed to determine whether looser or tighter minimum and maximum SER thresholds should be employed if the Yamamoto values check for the current rate, or do not check, respectively.
Abstract:
A base station (10) of the cellular telephone forward link power control system transmits frames initially at a high default transmit power level, then decreases the power level incrementally until either a frame erasure is detected, triggering an immediate sharp increase in transmission power, or until a predetermined period of time has elapsed, after which the base station (10) performs a fast downward move in the transmit power level. The fast downward move constitutes a sharp reduction in the transmit power level. In one example, the fast downward move is performed if one hundred consecutive frames are successively transmitted without a frame erasure. By providing the fast downward move in transmit power, the power transmitted is decreased on the average. In particular, the fast downward move allows the amount of transmit power to be reduced significantly in circumstances where slow incremental decreases in power would result in excess power being employed. Method and apparatus embodiments are disclosed.
Abstract:
The cellular telephone interface system has the capability to automatically choose between AMPS and CDMA cellular transmission protocols for data transmissions. The cellular telephone interface system includes a PC-modem card, such as a PCMCIA card (8), for interconnecting the cellular telephone (4) to a data source, such as a laptop computer, portable facsimile machine, or the like. The cellular telephone (4) is capable of transmission in accordance with either AMPS or CDMA transmission protocols. For AMPS, the PC-modem card (8) converts data signals received from the data source into PCM signals for forwarding to the cellular telephone (4). The cellular telephone converts the PCM signals into AMPS formatted signals for transmission to a local cellular base station. For CDMA transmission, the PC-modem card (8) converts the data signals received from the data source into RS-232E signals for transmission to the cellular telephone.
Abstract:
A system and method for passively determining the position of a user terminal (for example, a mobile wireless telephone) in a low-Earth orbit satellite communications system (100). The system includes a user terminal (106A, 106B, 106C), at least two satellites (104A, 104B) with known positions and known velocities, and a gateway (102) (that is, a terrestrial base station) for communicating with the user terminal (106A, 106B, 106C) through the satellites (104A, 104B). The method includes the steps of determining a range difference parameter (804) and a range-rate difference parameter (806). A range difference parameter represents the difference between (1) the distance between a first one of the satellites (104A, 104B) and the user terminal (106A, 106B, 106C) and (2) the distance between a second one of the satellites (104A, 104B) and the user terminal (106A, 106B, 106C). A range-rate difference parameter represents the difference between (a) a relative radial velocity between a first one of the satellites (104A, 104B) and the user terminal (106A, 106B, 106C) and (b) a relative radial velocity between a second one of the satellites (104A, 104B) and the user terminal (106A, 106B, 106C). The position of the user terminal (106A, 106B, 106C) on the Earth's surface is then determined (810) based on the known positions and known velocities of the satellites, the range difference parameter, and the range-rate difference parameter.
Abstract:
A dual-band coupled-segment helical antenna is provided operating in two frequency bands. The dual-band coupled-segment helical antenna (1200) includes a radiator portion (1202) having two sets of one or more helically wound radiators (1204, 1212) extending from one end (1234) of the radiator portion (1202) to the other end (1232) of the radiator portion (1202). Radiators of the firs set of radiators (1204) are comprised of two segments: a first radiator segment (1208) extends in a helical fashion from one end of the radiator portion (1202) toward the other end of the radiator portion (1202); and a second radiator segment (1210) is U-shaped and extends in a helical fashion from the first end of the radiator portion (1202) toward the second end of the radiator portion (1202). Radiators of the second set of radiators (1212) are comprised of a radiator (1212) disposed within said U-shaped segment (1210). The first set of radiators (1204) resonates at a first frequency and the second set of radiators (1212) resonates at a second frequency thereby providing dual-band operation, with minimal coupling between the frequency bands.
Abstract:
A method and apparatus to provide access to a dispatch system is disclosed. A communications manager (40) grants an exclusive system talker privilege to one remote unit (10) in the system at a time. After a remote unit (10) requests and is designated as the exclusive system talker, no other remote unit (20, 22) may transmit for a first pre-determined amount of time. After the first pre-determined time has elapsed, any other remote unit (20, 22) may request the exclusive system talker privilege and become the exclusive system talker. The exclusive system talker privilege is revoked by the communications manager (40) to any remote unit who retains the exclusive system talker privilege for more than a second pre-determined amount of time. The exclusive system talker privilege is also revoked upon the release of a push-to-talk button on a remote unit (10). Furthermore, a base station (44) in communication with a remote unit (10) designated as the exclusive system talker will generate a surrogate relinquishment request to the communications manager (40) if the exclusive system talker travels outside the coverage area of the system, loses power, or is destroyed.
Abstract:
Synchronization and bit count integrity of a synchronous data stream is preserved end to end even as it is transmitted via a medium which does not preserve the synchronous nature of the synchronous data stream. A terminal equipment unit (100) produces a constant rate bit stream which is provided to a communications unit (110). The communications unit (110) produces a first data frame comprising a first set of bits from the constant rate bit stream and a first length field value. A second data frame is produced which comprises a second set of bits from the constant rate bit stream and a second length field. A third data frame is produced which comprises a third set of bits from the constant rate bit stream and a third length field value. The first, second, and third data frames are transmitted to a base unit (118) which places the first set of bits from the first frame into a queue (150). A set of fill bits equal to the maximum number of bits contained in any frame is then placed into the queue (150). The base unit (118) then determines the number of bits in the second set of bits of the third data frame, based on the first length field value and the third length field value. The base unit (118) overwrites excess fill bits in the queue (150) with the third set of bits. The number of excess fill bits is equal to the difference between the maximum possible number of bits which may be contained in any frame and the number of bits in the second set of bits.
Abstract:
The present invention is a method and apparatus for transmitting high rate data packet in a CDMA communication system. The transmission system transmits a first channel assignment message indicating the at least one additional channel that will be used to support the high rate data packet. The first channel assignment message is sent in advance of the onset of high rate data communications. In addition the present invention provides within the first frame of high rate data a duplicate channel assignment message. A remote receiver uses the channel assignment messages to initialize its demodulation elements (114 and 120) to receive the additional information carried on the at least one additional channel.