noncoherent detection

To meet the implementation constraint posed by ultra-wideband (UWB) delay lines, a new transmitted reference pulse cluster (TRPC) structure is proposed where a group of reference and data pulses with short, uniform spacing is used for transmission. This structure enables a simple, robust and practical auto-correlation detector to be implemented in the receiver. It overcomes the major hurdle to practical implementation of conventional transmitted reference systems, that is, the long wideband delay line requirement. TRPC is also compatible with the signal format proposed within the IEEE 802.15.4a Working Group for coherent and non-coherent systems. The performance of the proposed TRPC receiver and non-coherent pulse position modulation (NC-PPM) with energy detection are analyzed and compared. Simulation results show that TRPC outperforms the conventional TR, NC-PPM, the recently proposed dual pulse scheme and the frequency shifted reference system. In particular, it achieves power saving over NC-PPM by about 1.3-1.9 dB for IEEE 802.15.4a channel model 1 and 1.3-2.3 dB for channel model 8.

In this paper, a comprehensive study has been made on observing the performance of orthogonal multi-level chaos shift keying modulation scheme aided MIMO wireless communication system. The 4 4 multi antenna supported such simulated system incorporates various channel coding (1/2-rated Convolutional, (3, 2) SPC, LDPC and concatenated 1/2-rated Convolutional) and signal detection (MMSE, ZF and MMSE-SIC) techniques. Under scenario of audio signal transmission over AWGN and Rayleigh fading channels with utilization of Chaotic Walsh-Hadamard Transform codes, it is observable that the impact of channel coding concatenation under implementation of MMSE signal detection technique is very much significant in performance enhancement of the presently considered simulated system.

A non-coherent detection assisted Differential Phase Shift Keying aided large-scale MIMO system is designed in a wireless uplink where multiple single-antenna users are transmitting to the base station's receiver equipped with a very large number of receive antennas. We show that the signal to interference plus noise ratio (SINR) scales with the number of receive antennas, which confirms the same scaling law found in coherent systems. We propose a range of constellation designs that allow us to separate the users' signals at the receiver by relying only on the knowledge of the average received power per user. We analyse the error probability and provide insights into the beneficial selection of the constellation parameters. Finally, we provide some numerical results showing that our proposals require a lower number of receive antennas to achieve a given error probability than other non-coherent benchmark schemes available in the literature, while they are not far from an equivalent coherent system relying on realistic channel estimation settings.

with two-dimensional spreading for wireless transmission. We propose to allocate power among symbols of the active users transmitted from multiple transmit antennas based on a heuristic expression of the bit error rate (BER). Optimization principle consists of minimizing the average BER of all users in term of channel conditions, user multiplexing and number of transmit antennas. Due to the simplicity of the approximate BER expression, we can obtain a closed form expression of the optimum power to be allocated to each user on each transmit antenna. Simulation results show significant improvement of the BER performances compared to the equal power distribution for various modulations, several encoding gains and two antenna configurations.

-This paper presents a general frame work for computing the asymptotic error probability (i.e., at high average SNR's) of M-ary and binary signaling schemes over Rician and Rayleigh fading diversity channels. A general theorem (Theorem 1) relates the asymptotic error rate of multipath and multichannel receivers (over AWGN, IS1 free channels) to the multi-dimensional integral of the conditional error probability. Two other theorems are presented for the particular cases where the conditional error probability is a function of the sum of received SNR's (Theorem 2) or received amplitudes (Theorem 3). Theorems 2 and 3 are related for linear coherent systems, and closed form expressions are obtained for equal gain combining systems. Detection structures for typical diversity schemes (coherenffnoncoherent maximal ratio and equal gain combining, and quadratic noncoherent combining) are considered. We analyze the asymptotic error rates of some M-ary signaling schemes (MRSKMPAM with Kth order diversity and orthogonal signals with I< = 1 and with coherent and noncoherent detection). Binary signaling is also considered in our study. T tion systems over multipath or multichannel Rayleigh fading has been extensively studied in the literature [1]-[5], and Rician channels have also been considered [6], [7]. The complexity of the exact error rate expressions usually motivates a particularly important problem in practice, which is the asymptotical performance or asymptotic error rate evaluation at high average SNR's. This problem has been considered before by applying the limit theorems and/or some ad-hoc methods to the exact error rate expressions. Such methods resulted in some asymptotic error formulas for Rayleigh fading [4], [SI, while a similar analysis has not appeared for Rician Fading. However, a general approach for directly obtaining such asymptotic results for either channel type is not available.

In this paper, we propose a technique to reduce the number of trellis states in BCJR-type algorithms, i.e., algorithms with a structure similar to that of the well-known algorithm by Bahl, Cocke, Jelinek, and Raviv (BCJR). This work is inspired by reduced-state sequence detection (RSSD). The key idea is the construction, during one of the recursions in the reduced-state trellis, of a "survivor map" to be used in the other recursion. In a more general setting, two distinct survivor maps could be determined in the two recursions and used jointly to approximate the a posteriori probabilities. Three examples of application to iterative decoding are shown: 1) coherent detection for intersymbol interference (ISI) channels; 2) noncoherent detection based on an algorithm recently proposed by the authors; and 3) detection based on linear prediction for Rayleigh fading channels. As in classical RSSD, the proposed algorithm allows significant state-complexity reduction with limited performance degradation.

Recently, noncoherent sequence detection schemes for coded linear and continuous phase modulations have been proposed, which deliver hard decisions by means of a Viterbi algorithm. The current trend in digital transmission systems toward iterative decoding algorithms motivates an extension of these schemes. In this paper, we propose two noncoherent soft-output decoding algorithms. The first solution has a structure similar to that of the well-known algorithm by Bahl et al.(BCJR), whereas the second is based on noncoherent sequence detection and a reduced-state soft-output Viterbi algorithm. Applications to the combined detection and decoding of differential or convolutional codes are considered. Further applications to noncoherent iterative decoding of turbo codes and serially concatenated interleaved codes are also considered. The proposed noncoherent detection schemes exhibit moderate performance loss with respect to corresponding coherent schemes and are very robust to phase and frequency instabilities.

We show that several coding schemes, in particular turbo encoding, dramatically improve the performance of a noncoherently detected frequency shift-keying modulation with correlated signals.The proposed a posteriori probability (APP) decoder based on bit-by-bit decisions proves to be highly flexible and more efficient than a classical block decisions decoding scheme. Moreover, the choice of the FSK modulation tone spacing is important. Simulation results show that the turbo-coded FSK exhibits the lowest error probability when compared to TCM, convolutional and lattice encoding schemes. I. INTRODUCTION F REQUENCY shift-keying (FSK) modulation with orthog- onal signals is commonly used on noncoherent channels and exhibits an excellent robustness [1]. However, it suffers from its poor spectral efficiency. With a modulation tone spacing chosen smaller than , being the symbol period, the transmitted signals are correlated and the spectral efficiency increases. The price to pay for this bandwidth reduction is a degradation in the noncoherent detector performance.It can be shown that several coding schemes dramatically reduce this performance degradation. We describe two system models. The decoder of the first model makes classical block decisions from the signal correlations delivered by the matched filter bank. In the second model, the FSK noncoherent detector computes APP's for each coded bit, directly related to these correlation values. The decoder operates on these APP's, considered as channel observations, to make bit-by-bit decisions. Note that the second model is valid for all coding schemes: simple block or convolutional codes, parallel or serial concatenated (turbo) codes [2] and classical trellis-coded modulations (TCM) . Computer simulation results show that the turbo-coded scheme yields better results than either TCM, convolutional or lattice encoded schemes. As expected high latency coding schemes perform better than low latency schemes. Consider a -ary frequency shift-keying modulation with tone spacing and symbol period respectively denoted by and .

In this paper, we present a novel approach to analytically study and evaluate the error probability of frequencyhopping spread-spectrum (FHSS) systems with intentional or nonintentional interference over the additive white Gaussian noise and Rayleigh-fading channels. The new approach is based on the derivation of new formulas for the exact envelope characteristic function (EECF) of the general sum of n stochastic sinusoidal signals, with each of the n signals having different random amplitude and phase angle. The envelope probability density function (pdf) is obtained from the characteristic function (CF), which, in the important cases of interest, is shown to also give simpler formulas in terms of the Fourier transform (FT) of the Bessel functions. Previously, the Ricean envelope density had only been verified for the very special case where n = 1, and the phase is uniform and independent of amplitude. Here, a new formula for the exact density of the envelope of noisy stochastic sinusoids (EDENSS) is presented, which leads to the generalization of the Ricean envelope-density (GRED) formula under the most general conditions, namely, n ≥ 1 signals, dependent amplitudes, and phases having an arbitrary joint pdf. The EDENSS and GRED formulas are applied to compute the pdfs needed in noncoherent detection under noise. The derived formulas also lead to the exact formulas for the error probability of the FHSS networks using M-ary amplitude shift keying (MASK) without setting limits on the number of interferers or the symbol alphabet. The power of our EECF and FT methods is further demonstrated by their ability to give an alternative derivation of the exact general envelope-density (EGED) formula, which has previously been reported by Maghsoodi. The comparative numerical results also support the analytical findings.

This paper illustrates the enhancement of the performance of short-packet full-duplex (FD) transmission by taking the approach of non-binary low density parity check (NB-LDPC) codes over higher Galois field. For the purpose of reducing the impacts of self-interference (SI), high order of modulation, complexity, and latency decoder, a blind feedback process composed of channels estimation and decoding algorithm is implemented. In particular, this method uses an iterative process to simultaneously suppress SI component of FD transmission, estimate intended channel, and decode messages. The results indicate that the proposed technique provides a better solution than both the NB-LDPC without feedback and the binary LDPC feedback algorithms. Indeed, it can significantly improve the performance of overall system in two important factors, which are bit-error-rate (BER) and mean square error (MSE), especially in high order of modulation. The suggested algorithm also shows a robustness in reliability and power consumption for both short-packet FD transmissions and high order modulation communications.

In this work, we investigate differentially encoded blind transceiver design in low signal-to-noise ratio (SNR) regimes for orthogonal frequency-division multiplexing (OFDM) signaling. Owing to the fact that acquisition of channel state information is not viable for short coherence times or in low SNR regimes, we propose a time-spread frequency-encoded method under OFDM modulation. The repetition (spreading) of differentially encoded symbols allows us to achieve a target energy per bit to noise ratio and higher diversity. Based on the channel order, we optimize subcarrier assignment for spreading (along time) to achieve frequency diversity of an OFDM modulated signal. We present the performance of our proposed transceiver design and investigate the impact of Doppler frequency on the performance of the proposed differentially encoded transceiver design. To further improve reliability of the decoded data, we employ capacity-achieving low-density parity-check forward error correction encoding to the information bits.

Gaussian Frequency Shift Keying modulation has been chosen as the modulation technique for the physical layer of Bluetooth. Bluetooth is a standard for low cost and low power wireless communications between various mobile devices. The optimal demodulation of a GFSK signal involves an extremely complex Viterbi decoder. Therefore designers have opted for the noncoherent detection of GFSK which uses a frequency discriminator, followed by symbol by symbol detection. Here, we describe a decision feedback equalizer to be added after the discriminator. The DFE receiver gives gains in excess of 2 dBs. We also describe how to increase the current data rate of a Bluetooth system by increasing the symbol rate and not the alphabet size.

In this work, we investigate differentially encoded blind transceiver design in low signal-to-noise ratio (SNR) regimes for orthogonal frequency-division multiplexing (OFDM) signaling. Owing to the fact that acquisition of channel state information is not viable for short coherence times or in low SNR regimes, we propose a time-spread frequency-encoded method under OFDM modulation. The repetition (spreading) of differentially encoded symbols allows us to achieve a target energy per bit to noise ratio and higher diversity. Based on the channel order, we optimize subcarrier assignment for spreading (along time) to achieve frequency diversity of an OFDM modulated signal. We present the performance of our proposed transceiver design and investigate the impact of Doppler frequency on the performance of the proposed differentially encoded transceiver design. To further improve reliability of the decoded data, we employ capacity-achieving low-density parity-check forward error correction encoding to the information bits.

Hierarchical modulation has been considered for achieving higher data rates in Terrestrial-DMB (T-DMB) systems, which yields man-made noise caused by the shortened symbol distance. Such noise may produce a serious problem on a fast-fading channel for the proper operation of conventional T-DMB receivers using noncoherent differential detection because it can increase the required SNR larger than the securable SNR of the receivers. To overcome the weakness of being susceptible to fast fading of the noncoherent detection, we propose a novel decision-directed channel estimation method for the coherent detection of phase correction. In the proposed method, least-squares channel estimation is carried out with hard-decision symbols due to the absence of known pilots and then the estimated coefficients are exponentially averaged using a forgetting factor to compensate for the probable inaccuracy of the instantaneous estimation. Simulation results show that the proposed method secures higher data-rate transmission of advanced T-DMB systems by reducing the degradation caused by hierarchical modulation and fast fading. 1

Hierarchical modulation has been considered for achieving higher data rates in Terrestrial-DMB (T-DMB) systems, which yields man-made noise caused by the shortened symbol distance. Such noise may produce a serious problem on a fast-fading channel for the proper operation of conventional T-DMB receivers using noncoherent differential detection because it can increase the required SNR larger than the securable SNR of the receivers. To overcome the weakness of being susceptible to fast fading of the noncoherent detection, we propose a novel decision-directed channel estimation method for the coherent detection of phase correction. In the proposed method, least-squares channel estimation is carried out with hard-decision symbols due to the absence of known pilots and then the estimated coefficients are exponentially averaged using a forgetting factor to compensate for the probable inaccuracy of the instantaneous estimation. Simulation results show that the proposed method secures higher data-rate transmission of advanced T-DMB systems by reducing the degradation caused by hierarchical modulation and fast fading. 1

A non-coherent detection assisted Differential Phase Shift Keying aided large-scale MIMO system is designed in a wireless uplink where multiple single-antenna users are transmitting to the base station's receiver equipped with a very large number of receive antennas. We show that the signal to interference plus noise ratio (SINR) scales with the number of receive antennas, which confirms the same scaling law found in coherent systems. We propose a range of constellation designs that allow us to separate the users' signals at the receiver by relying only on the knowledge of the average received power per user. We analyse the error probability and provide insights into the beneficial selection of the constellation parameters. Finally, we provide some numerical results showing that our proposals require a lower number of receive antennas to achieve a given error probability than other non-coherent benchmark schemes available in the literature, while they are not far from an equivalent coherent system relying on realistic channel estimation settings.

Themulticarrier permutationmodulation technique proposed in this paper provides higher bit rates and spectrum efficiencies than that achieved in any state-of-the-art radio paging system. It can be used in simulcast networks with high power transmitters, where long symbol intervals and noncoherent detection are required. The technical feasibility of the proposed modulation technique is established through a set of laboratory and field experiments. Variations of the proposed modulation technique are discussed with regard to performance and complexity of receivers and transmitters.

Low-rate non-binary low-density parity-check (LDPC) codes for coherent and blockwise non-coherent additive white Gaussian noise (AWGN) channels are developed. The proposed construction is based on the concatenation of nonbinary outer LDPC codes with inner binary codes. In case the binary codes are chosen to be Hadamard or Reed-Muller (RM) codes, the complexity of the decoding scheme is considerably reduced. An asymptotic analysis of the concatenation with help of composite capacity considerations and density evolution (DE) is provided, from which guidelines on the choice of both inner and outer codes are devised. Finite length designs presented in this work confirm the excellent performance of the proposed codes. Index Terms-Blockwise non-coherent AWGN channel, code design, coherent AWGN channel, concatenated codes, low-rate non-binary LDPC/turbo codes.

Gaussian Frequency Shift Keying modulation has been chosen as the modulation technique for the physical layer of Bluetooth. Bluetooth is a standard for low cost and low power wireless communications between various mobile devices. The optimal demodulation of a GFSK signal involves an extremely complex Viterbi decoder. Therefore designers have opted for the noncoherent detection of GFSK which uses a frequency discriminator, followed by symbol by symbol detection. Here, we describe a decision feedback equalizer to be added after the discriminator. The DFE receiver gives gains in excess of 2 dBs. We also describe how to increase the current data rate of a Bluetooth system by increasing the symbol rate and not the alphabet size.

This paper focuses on maximum-likelihood sequence estimation of noncoherent-ary differential phase-shift keying (-DPSK) receivers for code division multiple-access (CDMA) systems, which make use of direct-sequence spread-spectrum modulations. A typical frequency-selective Rayleigh environment with multipath diversity at the receiver is considered. In this scenario, the optimum noncoherent decision metric, which requires an estimation of the channel tap weights envelope, is derived. Then, in order not to increase the receiver implementation complexity, a joint channel and data estimation strategy is proposed, which does not require the transmission of a known training sequence (blind estimation). In this case, the decision metric becomes a simple equal gain combining of multiple-symbol square-law detection decision metrics. For this suboptimum noncoherent detector, useful bounds on the bit error probability are provided through a theoretical analysis. Nonconstant and constant multipath intensity profiles are both considered for this purpose. Simulations are also carried out in order to verify the accuracy of the theoretical bounds.

The effect of time-domain and frequency-domain synchronization errors is quantified in the context of various coherently and noncoherently detected 1, 2, and 4 bits/symbol OFDM constellations, in order to demonstrate the wide applicability of the techniques proposed for mitigating the bit error rate (BER) performance degradations inflicted. A reference symbol is proposed and a range of correlation techniques are suggested for coarse and fine synchronization. Their performance is studied over time-dispersive Rayleigh fading channels, with the conclusion that the proposed synchronization techniques result in virtually unimpaired BERs over the range of wideband channels investigated in comparison to a perfectly synchronized system.