The Experts below are selected from a list of 18 Experts worldwide ranked by ideXlab platform

Ying Xu - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the code phase migration and doppler frequency migration effects in the coherent integration of direct sequence spread spectrum signals
    IEEE Access, 2019
    Co-Authors: Yuyao Shen, Ying Xu
    Abstract:

    Coherent integration of direct-sequence spread-spectrum (DSSS) signals is a commonly used technique to improve receiver performance. However, this approach is susceptible to the code phase migration (CPM) and Doppler frequency migration (DFM) effects resulting from the relative motion between transmitter and receiver. In this paper, the CPM and DFM effects are explored and characterized. To evaluate the CPM effect, a simple analytic expression for the coherent integration results under motions of arbitrary orders is developed. In addition, the theoretically derived integration loss and time synchronization error caused by CPM are quantitatively examined. The DFM effect is evaluated under the motions of arbitrary orders by Fresnel integration and numerical fitting. The obtained closed-form expressions are verified by simulation and are shown to be useful for the performance analysis and the DSSS receiver design. The theoretical and the numerical results show that when the amount of CPM is larger than about one code Chip Duration, the signal-to-noise ratio gain obtained by coherent integration no longer increases because of the integration loss caused by CPM. In addition, the integration loss (in decibel units) caused by DFM is approximately inversely proportional to the square of the time-bandwidth product when the time-bandwidth product is small, and it is inversely proportional to the logarithm of the time-bandwidth product when this product is large.

Yuyao Shen - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the code phase migration and doppler frequency migration effects in the coherent integration of direct sequence spread spectrum signals
    IEEE Access, 2019
    Co-Authors: Yuyao Shen, Ying Xu
    Abstract:

    Coherent integration of direct-sequence spread-spectrum (DSSS) signals is a commonly used technique to improve receiver performance. However, this approach is susceptible to the code phase migration (CPM) and Doppler frequency migration (DFM) effects resulting from the relative motion between transmitter and receiver. In this paper, the CPM and DFM effects are explored and characterized. To evaluate the CPM effect, a simple analytic expression for the coherent integration results under motions of arbitrary orders is developed. In addition, the theoretically derived integration loss and time synchronization error caused by CPM are quantitatively examined. The DFM effect is evaluated under the motions of arbitrary orders by Fresnel integration and numerical fitting. The obtained closed-form expressions are verified by simulation and are shown to be useful for the performance analysis and the DSSS receiver design. The theoretical and the numerical results show that when the amount of CPM is larger than about one code Chip Duration, the signal-to-noise ratio gain obtained by coherent integration no longer increases because of the integration loss caused by CPM. In addition, the integration loss (in decibel units) caused by DFM is approximately inversely proportional to the square of the time-bandwidth product when the time-bandwidth product is small, and it is inversely proportional to the logarithm of the time-bandwidth product when this product is large.

R Wyrwas - One of the best experts on this subject based on the ideXlab platform.

  • the effect of Chip waveform on the performance of cdma systems in multipath fading noisy channels
    Vehicular Technology Conference, 1992
    Co-Authors: R Anjaria, R Wyrwas
    Abstract:

    The effect of non-ideal Chip waveforms on the bit error rate (BER) performance of code division multiple access (CDMA) systems is analyzed. The waveforms considered include sine and raised cosine in addition to the ideal rectangular waveform. The waveforms are assumed to be time-limited to the Chip Duration and cause no interChip interference. The modulation type is differential phase shift keying (DPSK). The channel is modeled as a discrete set of Rayleigh faded paths, which makes the analysis appropriate for mobile cellular systems as well as indoor wireless communications. The receiver uses a matched filter (for despreading) and is followed by a RAKE type of receiver. >

R Anjaria - One of the best experts on this subject based on the ideXlab platform.

  • the effect of Chip waveform on the performance of cdma systems in multipath fading noisy channels
    Vehicular Technology Conference, 1992
    Co-Authors: R Anjaria, R Wyrwas
    Abstract:

    The effect of non-ideal Chip waveforms on the bit error rate (BER) performance of code division multiple access (CDMA) systems is analyzed. The waveforms considered include sine and raised cosine in addition to the ideal rectangular waveform. The waveforms are assumed to be time-limited to the Chip Duration and cause no interChip interference. The modulation type is differential phase shift keying (DPSK). The channel is modeled as a discrete set of Rayleigh faded paths, which makes the analysis appropriate for mobile cellular systems as well as indoor wireless communications. The receiver uses a matched filter (for despreading) and is followed by a RAKE type of receiver. >

Korkosz, Richard August - One of the best experts on this subject based on the ideXlab platform.

  • Serial acquisition of PN sequences in direct sequence spread spectrum communication systems
    1
    Co-Authors: Korkosz, Richard August
    Abstract:

    We consider serial search schemes for the acquisition of a pseudo-noise (PN) sequence in a direct-sequence spread-spectrum (DS/SS) communication system. Serial search acquisition schemes are by far the most commonly used class of acquisition schemes, due to the ease with which they are implemented. The main assumptions invoked in this thesis are that no data modulation is present during the acquisition process, and that the RF carrier has already been perfectly acquired, both in frequency and phase. Within this context, two basic models are considered, the Chip synchronous model and the Chip asynchronous model.In the Chip synchronous model it is assumed that the Chip boundaries of the received PN sequence are known to the receiver. Under this model, the unknown timing offset between the received PN sequence and the local PN sequence is an integer multiple of the Chip Duration. We extend the results of previous work for the Chip synchronous model, in which the PN sequence arising under the out-of-phase hypothesis is modeled either as a random sequence or a zero sequence. In particular, we show that the stopping times for the sequential probability ratio tests (SPRTs) used in the testing stage are exponentially bounded random variables when actual periodic spreading sequences are employed. Moreover, we study the mean acquisition time of the overall serial search scheme, and show that the scheme based on the random sequence model offers considerable savings in mean acquisition time for moderate to large values of signal to noise ratio (SNR).A more general model is the Chip asynchronous model, in which the Chip boundaries of the received PN sequence are not known to the receiver. Thus, measured in units of the Chip Duration, the unknown timing offset between the received PN sequence and the local PN sequence is modeled as a real number. We propose and study a novel serial search acquisition scheme for this model, in which the integer part and the fractional part of the offset are estimated separately. This is accomplished by splitting the available observations into two sets. One of these sets of observations is used to estimate the integer offset via serial search, and we show that the other set may be used to estimate the fractional offset simultaneously. We consider the design and performance of sequential probability ratio tests (SPRTs) for use in the testing stage which are based on both the random sequence and zero sequence models. In particular, we have obtained an SPRT based on the random sequence model which yields near optimal performance regardless of the (unknown) fractional offset. We prove that the stopping times of the SPRTs are exponentially bounded for any value of the fractional offset, provided the spreading sequence is periodic. A modified verification stage is presented such that the verification error probability satisfies any given specification. Moreover, as in the Chip synchronous case, we show that the acquisition scheme based on the random sequence model offers considerable savings in mean acquisition time for moderate to large SNR. (Abstract shortened by UMI.)U of I OnlyETDs are only available to UIUC Users without author permissio