In a data communication system capable of variable rate transmission, high rate packet data transmission improves utilization of the forward link and decreases the transmission delay. Data transmission on the forward link is time multiplexed and the base station transmits at the highest data rate supported by the forward link at each time slot to one mobile station. The data rate is determined by the largest C/I measurement of the forward link signals as measured at the mobile station. Upon determination of a data packet received in error, the mobile station transmits a NACK message back to the base station. The NACK message results in retransmission of the data packet received in error. The data packets can be transmitted out of sequence by the use of sequence number to identify each data unit within the data packets.

Method and apparatus for high-rate packet data transmission

The continuous phase modulation (CPM) signaling scheme has gained interest in recent years because of its attractive spectral properties. Data symbol pulse shaping has previously been studied with regard to spectra, for binary data and modulation index 0.5. In this paper these results have been extended to the M -ary case, where the pulse shaping is over a one symbol interval, the so-called full response systems. Results are given for modulation indexes of practical interest, concerning both performance and spectrum. Comparisons are made with minimum shift keying (MSK) and systems have been found which are significantly better in E_{b}/N_{0} for a large signal-to-noise ratio (SNR) without expanded bandwidth. Schemes with the same bit error probability as MSK but with considerably smaller bandwidth have also been found. Significant improvement in both power and bandwidth are obtained by increasing the number of levels M from 2 to 4.

Continuous Phase Modulation--Part I: Full Response Signaling

An apparatus (101, 110) and method for adaptive forward error correction in a data communication system (100) provides for dynamically changing forward error correction parameters based upon communication channel conditions. Data having a current degree of forward error correction is received (305), and a channel parameter is monitored (310). A threshold level for the channel parameter is determined (315), and the monitored channel parameter is compared to the threshold level (320). When the channel parameter is not within a predetermined or adaptive variance of the threshold level, a revised forward error correction parameter having a greater or lesser degree of forward error correction capability is selected (330, 340, 350, 360), and the revised forward error correction parameter is transmitted (370). The device receiving the revised forward error correction parameter, such as a secondary station (110), then transmits data encoded utilizing the revised error correction parameter (425).

Apparatus and method for adaptive forward error correction in data communications

A serial flash integrated circuit is provided with an integrated error correction coding (“ECC”) system that is used with an integrated volatile page memory for fast automatic data correction. The ECC code has the capability of correcting any one or two bit errors that might occur on a page of the flash memory array. One bit corrections are done automatically in hardware during reads or transfer to the page memory, while two-bit corrections are handled in external software, firmware or hardware. The ECC system uses a syndrome generator for generating both write and read syndromes, and an error trapper to identify the location of single bit errors using very little additional chip space. The flash memory array may be refreshed from the page memory to correct any detected errors. Data status is made available to the application prior to the data. The use of the ECC is optional.

Serial flash integrated circuit having error detection and correction

A new modulation technique, cross-correlated phase-shift keying ( XPSK ), is introduced. XPSK is a band-limited offset QPSK modulation technique which has an almost constant envelope. In XPSK modulators, a controlled amount of cross correlation between the in-phase ( I ) and quadrature ( Q ) channels is introduced. I and Q cross correlation reduce the envelope fluctuation Of the intersymbol-interference and jitter-free OQPSK (IJF-OQPSK) modulation scheme, introduced by Feher et al. [1], [2], from 3 dB to approximately 0 dB, thus further improving the performance of IJF-OQPSK systems in nonlinear radio systems [7], [14]. It is shown that the baseband signal of the modulator, the P_{e} = f(E_{b}/N_{0}) performance, and the spectral characteristics of nonlinearly amplified (hard-limited or saturated) radio systems of XPSK and tamed frequency modems (TFM) are practically the same. The XPSK demodulator is a conventional OQPSK demodulator, the TFM demodulator requires a somewhat more complex signal processor. For this reason, the XPSK approach may lead to significant demodulator hardware cost savings, particularly in point-to-multipoint distribution systems such as broadcast systems. Simulation results for linear and nonlinear (saturated amplifier) systems operated in an adjacent-channel interference environment (in addition to thermal noise) are presented. Measurement results performed on a 128 kbit/s rate hardware-prototype modem are also reported. Experimental eye diagram and power spectrum density measurement results are in close agreement with the computer simulation results.

XPSK: A New Cross-Correlated Phase-Shift Keying Modulation Technique

A method for effecting error protecting coding in digitally modulated analog information as a function of the quality of transmission characteristics in the communication channel is provided in which the error code is embodied in the source code word, such as by reducing the number of significant bits and substituting error protecting code bits. This results in the maintenance of transmission capacity while providing the space needed for the redundant signals required to preclude error.

Adaptive error correcting transmission system

An analysis of constant envelope digital partial response continuous phase modulation (CPM) systems is reported. Coherent detection is assumed and .the channel is Gaussian. TPe receiver observes the, received signal over more than one symbol interval to make use of the correlative, properties of the transmitted signal. The systems are M-ary, and baseband pulse shaping over several symbol intervals is considered. An optimum receiver based on the Viterbi algorithm is presented. Constant envelope digital modulation schemes with excellent spectral tail properties are given. The spectra have extremely low sidelobes. .It is concluded that partial response CPM systems have spectrum compaction properties. Furthermore, at equal or even smaller bandwidth than minimum shift keying (MSK), a considerable gain in transmitter power can be obtained. This gain increases with M. Receiver and transmitter configurations are presented.

Carl-Erik Wilhelm Sundberg

Papers

Adaptive error correcting transmission system

Continuous Phase Modulation-Part 11: Partial Response Signaling