Limiter-discriminator Detection Research Articles

PAM approach to weak CPM and its application to flight termination receivers

A method for computing the PAM representation for weak continuous phase modulation (CPM) is presented and applied to the modulation defined in the enhanced flight termination system (EFTS) standard. The pulse-amplitude modulation (PAM) representation was used to formulate a reduced-complexity detector whose performance is within 0.7 dB of maximum likelihood detection and 5.6 dB better than limiter-discriminator detection in the additive white Gaussian noise (AWGN) environment. The complexity of the reduced-complexity detector is less than 25% that of the maximum likelihood detector but, unlike the limiter-discriminator detector, requires a carrier phase PLL. In the presence of phase noise, the reduced-complexity detector outperforms limiter-discriminator detection when the RMS frequency deviation due to phase noise is less than 10% of the bit rate.

Performance Evaluation of Bluetooth Systems With LDI, Modified LDI, and NSD Receivers

Bluetooth is a popular short-range low-power radio standard for wireless personal area networks. Bluetooth transmitters employ Gaussian frequency shift keying (GFSK) and simple block codes for error correction. Recently, two new receiver designs for Bluetooth devices, which are the so-called modified limiter-discriminator detector with integrate-and-dump filtering (LDI) and noncoherent sequence detection (NSD), have been proposed in the literature. While the modified LDI receiver is a concatenation of a conventional LDI detector with an improved error-correction decoder, the NSD receiver fully takes into account the memory introduced by the GFSK. Both receivers have been shown to improve the Bluetooth system performance in terms of physical-layer metrics such as bit-error rate and packet-error rate. In this paper, we present a comprehensive performance evaluation considering practically more relevant metrics such as throughput, delay, and delay jitter at the medium-access control layer. To this end, we develop an evaluation framework, which includes the spatial distribution of Bluetooth devices, path loss, fading, realistic data traffic models, scheduling, automatic repeat request, and baseband packet selection. Our numerical and simulation results verify that the newly introduced Bluetooth receivers, especially NSD, offer a significant performance enhancement for Bluetooth systems in terms of practically relevant measures.

FSK With Limiter-Discriminator Detector in Nakagami Fading Channels With and Without Selection Combining

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, an equation for the error probability of M-ary frequency shift keying with limiter-discriminator detection in Nakagami fading channels for arbitrary <formula formulatype="inline"><tex>$m$</tex></formula> is derived. The authors do the same for selection combining with <formula formulatype="inline"><tex>$L$</tex></formula> diversity channels for integer <formula formulatype="inline"><tex>$m$</tex></formula> and for switch and stay combining with two diversity channels for <formula formulatype="inline"><tex>$m = 1$</tex></formula> (Rayleigh fading). The error probability for various values of <formula formulatype="inline"><tex>$m$</tex></formula>, <formula formulatype="inline"><tex>$L$</tex></formula>, frequency deviation, and filter bandwidth is computed. </para>

Improved Decoding for Bluetooth Systems

This letter presents an improved error-correction decoder for Bluetooth systems, employing the limiter-discriminator detector with integrate and dump filter (LDI detector) and the expurgated (15,10) binary Hamming code, which is used to protect the payload of data medium-rate packets. The proposed decoder exploits the error statistic of the LDI detector output and makes use of the single-error-correcting double-adjacent-error-correcting (SEC-DAEC) capability of the expurgated (15,10) code. As a result, notable improvements in data throughput and/or transmission range are achieved. Since the performance gains come at no additional cost in implementation, the proposed decoder is highly attractive for application in low-cost Bluetooth devices.

Envelope-Aided Viterbi Receivers for GMSK Signals With Limiter-Discriminator Detection

Continuous phase modulation schemes, such as Gaussian minimum-shift keying (GMSK), are frequently used with limiter-discriminator (LD) detectors. This paper studies how the side information derived from the signal envelope can enhance the performance of a Viterbi algorithm (VA)-based receiver operating on the LD output of a GMSK scheme. By considering the joint probability density function of envelope and frequency, different approximations yield different novel metrics for VA, using the three-variables envelope and its derivative, and frequency error in different combinations. Simulation results confirm that such envelope-aided VA gives significant performance gains, and that envelope information complements the frequency information output by the LD detector in frequency-selective fading channels.

Limiter discriminator detection of narrow‐band duobinary FSK in a land mobile channel

AbstractError rates (BER) for narrow‐band duobinary FM with discriminator detection and integrate and dump (LDI) post‐detection filtering in land mobile channel characterized by fading and Doppler frequency shift are obtained. The fading process is assumed to be much slower than data rate, allowing the fading process to be analysed in a quasistatic manner as it passes through the narrow‐band filter. A simulation model was constructed using the signal processing simulator, and the simulated error rate results are shown to agree well with the calculated error rate results. Copyright © 2004 John Wiley &amp; Sons, Ltd.

GMSK with limiter-discriminator detector in nakagami fading channel with and without selection combining

We derive an equation for the bit-error probability (BEP) of Gaussian minimum-shift keying with limiter discriminator detection in Nakagami-m fading channels including selection and switch-and-stay combining. We compute the BEP for various selections of system parameters.

Partial response CPM in satellite mobile systems

It is known that Gaussian minimum shift keying (GMSK) is an attractive signaling technique in mobile communications. In this study, it is demonstrated using partial response raised cosine (ZRC) modulation that other partial-response continuous phase modulation (PR-CPM) techniques can perform better than GMSK in a mobile system. ZRC signals are analyzed and compared with GMSK signals in a mobile channel. Differential phase detection (DPD) and limiter discriminator detection (LDD) receivers with decision feedback are separately considered for the detection of the two types of signals. In case of ZRC signals, the delay of the DPD receiver, and the sampling instant of the LDD receiver are selected to minimize the error probability. Numerical results are presented for land mobile, satellite mobile and Gaussian channels at different bandwidths and Doppler shifts. It is shown that ZRC signals can perform better than GMSK signals at the same bandwidth.

Worst case equalizer for noncoherent HIPERLAN receivers

Coherent detection of HIPERLAN Gaussian minimum-shift keying signals calls for complex and expensive receivers. However, when the channel delay spread is limited to at the most 50% of the symbol time and a reliable line-of-sight component of the radiated signal exists (Rician fading model), noncoherent detectors are capable of achieving a good performance. Based on the above motivations, we compare four different demodulation techniques, namely the following: (1) one-bit differential detector; (2) discriminator detector; (3) limiter discriminator detector; and (4) limiter discriminator integrator detector (LDID). The intersymbol interference introduced by these demodulators is nonlinear (with respect to the data symbols) and a decision-feedback equalizer (DFE) based on a mean square-error criterion may not be appropriate. Moreover, at this high speed, a DFE may be very complex to implement. Hence, we propose a new DFE design method that increases the eye-diagram aperture by removing the worst case interference. Performance of the above demodulators in the presence of a simple nonlinear DFE (with feedback part only) is computed in terms of the bit-error rate (BER) by means of the saddle-point approximation. This procedure, for static channels, turns out to be a very general tool with a simple and robust implementation. The same method can be applied, for multipath fading channels, to the BER evaluation as part of a semianalytic approach. The main conclusion from this work is that for LDID demodulators and in the presence of Rician fading channels with an average normalized root mean square delay spread of 0.3 and dual antenna diversity, the new equalizer lowers the outage probability from 60% to 10% at a BER of 10/sup -4/.

Comparison of duobinary and 4-level continuous phase frequency shift keying signals for narrowband land mobile radio applications

The bit error rate performance of partial-response duobinary continuous-phase frequency shift keying (CPFSK), and full-response 4-level CPFSK are compared under the condition of equal RF spectral occupancy and equal data rate, for both Gaussian and Rayleigh fading channels. Incoherent limiter-discriminator detection is assumed for all cases. The spectral efficiency requirements of the FCC, for the allocated 220-222 MHz band for land mobile communications, are used to establish the system specifications. It is shown that 4-level CPFSK system significantly outperforms the 3-level duobinary CPFSK. This is due to the fact that the receiver bandwidth may be lowered for 4FSK thereby higher frequency deviation can be achieved resulting in higher SNR at the receiver which outweighs the noise margin advantage of duobinary system. Simulation systems are designed to measure the performance for both static and Rayleigh-fading narrowband channels.

Limiter discriminator-detected GMSK with FM and GMSK interference in a land mobile channel

This paper addresses Gaussian minimum-shift keyed (GMSK) receiver performance analysis for limiter discriminator detection with cochannel interference resulting from a combined cellular voice and packet radio network. A specific example is cellular digital packet data (CDPD), which shares spectrum with cellular voice users; thus, the CDPD receiver will see both narrow-band frequency modulation (NBFM) voice and GMSK data interference. Previous studies investigated the performance of a GMSK receiver with a single GMSK interferer and multipath delay. In this paper, we extend earlier work to multiple Rayleigh fading (Doppler spread) interferers having NBFM (f/sub dm/=12 kHz) analog modulation and/or GMSK modulation. Probability of bit-error expressions are derived for the frequency modulation (FM) and GMSK interferer cases assuming medium-to-high signal-to-noise ratio regions. For scenarios of from one to six NBFM interferers, having the same total power, a corresponding Gaussian approximation is within 1.5 dB. Simulation results are also presented for various combinations of FM and GMSK interference. FM interference is only slightly worse than GMSK interference. Delay spread representing an urban scenario resulted in only a slight increase in the error floor.

Performance of phase-locked loop receiver in DECT system

The performance of the noncoherent phase-locked loop (PLL) receiver is compared to the performance of the limiter-discriminator detector and differential detector in the digital enhanced cordless telephone system. The results indicate that a well-designed PLL receiver based on the optimisation of PLL parameters and post-detection filtering has a performance advantage.

Noncoherent detection with Viterbi decoding for GMSK signals

Noncoherent detection with Viterbi decoding is proposed for the detection of GMSK signals in a Gaussian channel. Two detection techniques, limiter discriminator detection and differential phase detection, are considered with Viterbi decoding. The numerical results show that the proposed receivers with Viterbi decoding perform significantly better than the known receivers with feedback, and the improvement becomes more significant at narrower bandwidths.

Performance Evaluation of Optical FSK Heterodyne Receiver using Limiter Discriminator Detection

Article Performance Evaluation of Optical FSK Heterodyne Receiver using Limiter Discriminator Detection was published on August 1, 1995 in the journal Journal of Optical Communications (volume 16, issue 4).

Combined frequency and differential phase shift keying with non-coherent detection in a satellite mobile channel

We analyze the performance of combined binary frequency and M-ary differential phase shift keying (2FSK/MDPSK) in the satellite mobile channel (SMC). We use two detectors in which the frequency symbol is detected by a limiter discriminator detector (LDD) and the phase symbol by a differential phase detector (DPD). It is shown that this system is power and bandwidth efficient when compared with other systems with constant envelope (or nearly constant envelope) and noncoherent detection like L-ary DPSK (LDPSK), Gaussian minimum shift keying (GMSK) and MSK. >

Performance of sequence estimation scheme of narrowband digital FM signals with limiter-discriminator detection

A communication scheme using binary FM with noncoherent limiter-discriminator detection has been well known. Up to now, the improvement of bit error rate at the receiver side has been carried out through the bandwidth optimization of the IF filter, the decision feedback equalization (DFE), or simple two-state maximum likelihood sequence estimator (MLSE). This channel is inherently the intersymbol interference (ISI) channel due to the premodulation baseband filtering as well as the narrowband IF filtering. So the sequence estimation scheme using the Viterbi algorithm can be applied successfully, although the channel is not additive white Gaussian and maximum likelihood in the strict sense. In this paper, through computer simulations, we examine the actual BER improvement of the sequence estimation scheme with multiple-state trellis especially for MSK and GMSK signals. We mainly consider static AWGN and frequency nonselective Rician fading channels. Consequently, by adjusting the IF filter bandwidth, very large estimation gains are obtained compared to the conventional DFE or MLSE detector for AWGN and Rician fading channels. This scheme does not produce large demodulation delay and is implemented only by adding the signal processing part to the final stage of the receiver. This scheme seems to be very useful for any applications including satellite mobile channels. >

Improved post-detection processing for limiter-discriminator detection of CPM in a Rayleigh, fast fading channel

A simple, robust processing strategy, called the fading magnitude-integrate sample and dump (FM-ISD) processor, is proposed for use with limiter-discriminator detection of CPM signals in Rayleigh, fast fading channels. The FM-ISD processor is introduced as a simplification of an optimal estimator-correlator receiver. The performance is compared to a standard integrator processor and found to provide an improvement in performance for all values of signal-to-noise ratio. The FM-ISD processor is also shown to be robust to changes in modulation format, channel fading rate and pre-detection filter type. >

Relation between bit and symbol error probabilities for frequency shift keying with limiter - discriminator detection

In M-ary, Gray coded frequency shift keying with limiter discriminator detection the bit error probability is usually approximated by the symbol error probability divided by the number of bits in a symbol. This approximation is known to be excellent for phase shift keying with large energy-to-noise ratios and Gaussian channel. In other cases this may be questionable. The authors compute the exact values of bit error probability as a function of energy-to-noise-ratio per bit for Gaussian, Rayleigh and Rician channels. They also compute the relative error involved in this approximation.

Theoretical analysis of coherent optical FSK systems with limiter-discriminator detection

A detailed theoretical analysis, based upon Rice's (1963) theory of clicks, for evaluating the error performance of heterodyne optical FSK receivers with limiter-discriminator detection and pre- and integrate-and-dump (I&D) post-detection filtering is developed, accounting for laser phase noise, intersymbol interference (ISI) and intermediate-frequency (IF) filtered carrier envelope fluctuation effects. From the analysis it turns out that the envelope fluctuations induced by phase noise may produce, for operating IF bandwidths, a much smoother transition to the bit error rate floor than expected when considering IF infinite bandwidth, thereby generating performance degradation right in the operating signal-to-noise ratio (SNR) region. The contribution to this degradation due to a change in the click statistics generated by the envelope fluctuations is found to be negligible. From the analysis, it is also found that the floor gets lower and approached more rapidly as the modulation index and the bandwidth get larger, until the known floor for infinite IF bandwidth is reached. Finally, general curves are presented for system performance relating bit error probability to optimum IF bandwidth, optimum modulation index, laser linewidth and receiver sensitivity. These curves represent the ultimate limit to performance of a heterodyne optical FSK receiver with limiter-discriminator detection and pre- and I&D post-detection filtering. >

Limiter-discriminator detection of continuous phase modulation (CPM) Tomlinson filtering

Limiter-discriminator detection of continuous phase modulation (CPM) partial response signals is of special importance in systems in which phase coherence is very difficult to establish and/or maintain (e.g., mobile communications systems). The authors propose a Tomlinson-based approach which copes with the intersymbol interference (ISI) introduced by the baseband partial response frequency modulating pulses of the CPM schemes, (e.g., GTFM, GMSK, raised cosine (RC)). In this approach, the ISI equalization is divided between the transmitter and the receiver. The authors investigate, through simulation, the detectability performance and spectral properties of a number of CPM signals and receiver structures with special emphasis on the Tomlinson approach. It is shown that this novel application of the Tomlinson configuration allows the use of relatively simple receivers which exhibit almost the same performance as more complex Viterbi structured receivers. It is shown that a bandwidth-efficient narrow-band quaternary CPM-2RC modulation with either a Viterbi, a DFE or a Tomlinson receiver structure outperforms classical binary FSK (discriminator-integrate and dump detection) by approximately one db. It is pointed out in the paper that in general it is also possible to achieve detectability results similar to that of classical discriminator (integrate and dump) detection of binary CPFSK, for a number of bandwidth-efficient binary CPM schemes (e.g., GMSK) using the aforementioned receiver structures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>