Millimeter-wave spectra combined with the goal of supporting high velocity communications such as high speed trains and low earth orbit non-terrestrial networks increase the need for a robust method to address severe Doppler effects. To date, most cellular applications require management of a link where the effective Doppler is less than a subcarrier spacing; however, with emerging applications we can expect to see far larger distortion. To address this, we present a Zadoff-Chu sequence-based approach to overcome the ambiguity associated with estimating very high levels of integer Doppler. This algorithm enables certain niche applications of 5G and affords flexibility when choosing waveform subcarrier spacing.

An error probability analysis is performed for an orthogonal noncoherent M-ary frequency-shift keying (MFSK) communication system employing fast frequency-hopped (FFH) spread spectrum with diversity. The signal is assumed to be transmitted through a frequency-nonselective slowly fading channel with partial-band noise interference. The partial-band interference is modeled as a Gaussian process. Both the information signal and the partial-band noise interference signal are assumed to be affected by channel fading; it is assumed that the two fading processes are independent and that channel fading need not necessarily affect the information signal and the interference signal in the same way. Each diversity reception is assumed to fade independently according to a Rician process. Adaptive gain control is employed to minimize partial-band interference effects, and the effect of inaccurate noise measurement on the ability of the adaptive gain control receiver to reject partial-band interference is examined. The effect of thermal noise is included in the analysis.

This paper investigates the performance degradation resulting from multitone interference of orthogonal, frequency-hopped, noncoherent M-ary frequency-shift keyed receivers (FH/MFSK) where the effect of thermal and other wideband noise is not neglected. The multiple, equal power jamming tones are assumed to correspond to some or all of the possible FH M-ary orthogonal signaling tones. Furthermore, the channel is modeled as a Ricean fading channel; and both the signaling tones and the multiple interference tones are assumed to be affected by channel fading. It is also assumed that channel fading need not necessarily affect the signaling tones and the interference tones in the same-way. When the information signal power exceeds the power of the individual interference tones, poorer overall system performance is obtained when the multiple interfering tones experience fading. This trend is accentuated as M increases. When the information signal experiences fading, the effect of fading multiple interference tones on overall system performance lessens, and for a Rayleigh-faded information signal, fading of the multiple interference tones has no effect on overall system performance regardless of M.

Error probability analysis is performed for a binary orthogonal frequency-shift-keying (FSK) receiver using fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a frequency-nonselective slowly fading channel with partial-band interference. Diversity is performed using multiple hops per data, bit. A nonlinear combination procedure referred to as self-normalization combining is used by the receiver to minimize partial-band interference effects. Diversity is found to completely negate degradation of the self-normalized receiver caused by partial-band interference and offers definite receiver performance improvement when the direct signal component is weak. The self-normalized receiver is sensitive to fading channels. For severe channel fading, the performance of a conventional noncoherent binary FSK receiver is generally either equivalent or superior to that of the self-normalized receiver.>

An error probability analysis is performed for both self-normalized and conventional M-ary orthogonal frequency-shift-keying (MFSK) noncoherent receivers using fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a Rician fading channel with partial-band interference. The self-normalization receiver uses a nonlinear combination procedure to minimize performance degradation due to partial-band interference. The performance of the conventional receiver is significantly degraded by worst-case partial-band interference regardless of the modulation order or number of hops per data symbol used, while the self-normalization receiver can provide a significant immunity to worst-case partial-band interference for many channel conditions when diversity is used, provided the signal-to-thermal-noise ratio is large enough to minimize degradation due to nonlinear combining losses. The improvement afforded by higher modulation orders is dependent on channel conditions.>

An error probability analysis performed for an M-ary orthogonal frequency-shift keying (MFSK) communication system employing fast frequency-hopped (FFH) spread-spectrum waveforms transmitted over a frequency-nonselective, slowly Rician fading channel with partial band interference is discussed. Diversity is obtained using multiple hops per data bit. Noise-normalization combining is employed by the system receiver to minimize partial-band interference effects. The partial-band interference is modeled as a Gaussian process. Thermal noise is also included in the analysis. Forward error correction coding is applied using convolutional codes and Reed-Solomon codes. Diversity is found to dramatically reduce the degradation of the noise-normalization receiver caused by partial-band interference regardless of the strength of the direct signal component. Diversity offers significant performance improvement when channel fading is strong, and performance improvement is obtained for high modulation orders (M>2). Receiver performance is improved when diversity, higher modulation orders, and coding are combined.>

The performance of a local/mobile radio communications system utilizing the slotted ALOHA multiple random access protocol is analyzed. The probability of correct packet capture is evaluated for a local/mobile packet radio system using ideal coherent binary phase-shift keying (BPSK) modulation. Both the near/far effect and the effect of Rayleigh fading on the probability of correct packet capture are taken into account, but the effect of thermal noise is neglected since the interference due to competing packets is dominant in practical systems. The probability of correct packet reception is evaluated for a system using spatial diversity. In addition, the effect on system performance of either convolutional coding with hard decision Viterbi decoding or binary linear block coding with hard decision decoding is evaluated. The pseudo-Bayesian algorithm that has been developed to stabilize a packet system based on the slotted ALOHA protocol at maximum channel throughput is found to be adaptable to the local mobile operating environment. For the system considered here, channel throughputs as high as 0.66 can be obtained.>