We introduce a minimum shift keying (MSK) waveform developed for use in radar applications. This waveform is characterized in terms of its spectrum, autocorrelation, and ambiguity function, and is compared with the conventionally used bi-phase coded (BPC) radar signal. It is shown that the MSK waveform has several advantages when compared with the BPC waveform, and is a better candidate for deep-space radar imaging systems such as NASA's Goldstone Solar System Radar.

The use of a noninteger symbol to sample time ratio, noncommensurate sampling, in pseudonoise (PN) code-tracking loops is investigated. A noncoherent PN code-tracking loop using noncommensurate sampling and single-bit quantization is presented. An analysis method is developed to characterize the system and determine the steady-state error variance of the timing estimate. The performance of an equivalent analog code-tracking loop is derived and compared with the digital loop to investigate the degradation incurred through sampling and quantization.

The use of a noninteger symbol to sample time ratio, noncommensurate sampling, in pseudonoise (PN) code-tracking loops is investigated. A noncoherent PN code-tracking loop using noncommensurate sampling and single-bit quantization is presented. An analysis method is developed to characterize the system and determine the steady-state error variance of the timing estimate. The performance of an equivalent analog code-tracking loop is derived and compared with the digital loop to investigate the degradation incurred through sampling and quantization

A sample-decision photon counting receiver architecture is proposed for use in optical communication systems operating in low-flux conditions such as proposed deep space optical links. The performance of this system using PPM signaling is analyzed and compared to the performance of an ideal photon counter and a slot-energy detection receiver architecture at representative operating points

Pseudonoise (PN) code tracking loops in direct-sequence spread-spectrum systems are often implemented using digital hardware. Performance degradation due to quantization and sampling effects is not adequately characterized by the traditional analog system feedback loop analysis. A low-complexity digital PN code tracking loop with one-bit non-commensurate sampling is analyzed, and the steady-state delay error variance is derived. The results are compared with that of an equivalent analog loop.

As larger diversity and coding gains are introduced into spread-spectrum systems to mitigate the effects of multipath fading and thermal noise, system performance is increasingly being limited by channel estimation error. To properly design these systems, performance measures incorporating the effects of estimation errors are needed. A lower bound on the probability of bit error for a RAKE receiver operating with imperfect phase estimates is presented along with a method to obtain a closed-form expression for its evaluation. Further, this lower bound is compared to an upper bound so that an accurate assessment of system performance can be obtained.

To extend the battery life of a Martian surface unit it is desired to minimize the energy consumed by the surface to orbit communications transceiver. The performance of three different transmission schemes are evaluated in terms of the energy-per-bit required by the transmit power amplifier to achieve a desired energy-per-bit at the receiver. A fixed-power variable-rate transmission scheme is shown to provide the largest savings in energy. Using this as the basis for selecting a multiple access system, a code division multiple access system is presented and its performance is analyzed.

Cooperative modulation techniques can reduce the energy requirements for the long haul transmission of data from localized sensor networks. This saving is vital in extending the battery life of power limited sensor nodes communicating over a time-limited channel. Several transmission methods, including a novel scheme that conveys information via node selection, are analyzed. The energy cost in local communications needed to support the cooperative long haul link is determined and used to make comparisons between the techniques.

In wideband code-division multiple-access (CDMA) systems, where large diversity gains are used to mitigate the effects of multipath fading, system performance is increasingly limited by channel estimation error. In a packet-based system, the estimation error can be reduced by increasing the header length; however this, for a fixed bandwidth, reduces the amount of transmit energy available to the data symbols and reduces the processing gain of the system. To determine the allocation of the transmit energy between the data and estimation symbols in order to minimize the probability of bit error, we use an approximate upper bound on the probability of bit error for a RAKE receiver operating with imperfect phase estimates.

The least-mean-square (LMS) estimator is a nonlinear estimator with information dependencies spanning the entire set of data fed into it. The traditional analysis techniques used to model this estimator obscure these dependencies; to simplify the analysis they restrict the estimator to the finite set of data sufficient to span the length of its filter. Thus the finite Wiener filter is often considered a bound on the performance of the LMS estimator. Several papers have reported the performance of the LMS filter exceeding that of the finite Wiener filter. We derive a bound on the LMS estimator which does not exclude the contributions from data outside its filter length. We give examples of this bound in cases where the LMS estimator outperforms the finite Wiener filter.

The least-mean-square (LMS) estimator is a nonlinear estimator with information dependencies spanning the entire set of data fed into it. The traditional analysis techniques which are used to model this estimator obscure this, restricting the estimator to the finite set of data sufficient to span the length of its filter. The finite Wiener filter is thus often considered a bound on the performance of the LMS estimator. Several papers have reported the performance of the LMS filter exceeding that of the finite Wiener filter. We demonstrate a bound on the LMS estimator, which does not exclude the contributions from data outside its filter length, and which demonstrates the ability of the LMS estimator to outperform the finite Wiener filter in certain cases.