Optimum bandwidth-distance performance in partial response CPMsystems

The problem of optimizing the baseband pulse shape in order to obtain the minimum effective bandwidth for a prescribed value of minimum Euclidean distance is treated for partial response CPM. Some comparisons with standard pulses are performed and the results are presented in the form of bandwidth-distance and spectral density plots     

Symbol synchronization in digital communication systems usingpartial response CPM signaling

The applicability of standard symbol synchronization schemes in digital communication systems using partial-response CPM (continuous phase modulation) signaling has been analyzed. Using the theory of maximum a posteriori estimation of the unknown parameter in Gaussian noise, a theoretical structure for the optimum symbol synchronizer in a system using partial-response CPM signaling is derived. As the first approximation, a closed-loop configuration, known as the early-late loop, is derived and discussed. Due to signal correlation in adjacent symbol time intervals, even this configuration is impractical for a hardware realization. For these reasons, different approximations of the general maximum-likelihood function, leading to the discrete bit timing loop realizations, are derived and discussed. The influence of the carrier phase synchronization error on these synchronizers is also discussed     

On the spectral efficiency of CPM systems over real channel in thepresence of adjacent channel and cochannel interference: a comparisonbetween partial and full response systems

In all the new radio systems to be designed-for example, local radio networks or portable communication systems-a crucial point is determination of the actual spectral efficiency obtainable. To this end, the fundamental role played by adjacent and cochannel interference must be considered. The computer program implemented allows general analysis of continuous phase modulation (CPM) systems with limiter-discriminator detection and symbol-by-symbol regeneration, the combined effects of intersymbol interference, noise, and adjacent channel or cochannel interference have been tested to give the design criteria of the transmission system. To emphasize the role played by interference, an ideal multipath-free channel has been considered: with reference to a binary case, Gaussian minimum-shift keying (GMSK) systems have been investigated and compared with full-response CPM systems to obtain a suitable tradeoff between spectral efficiency (connected to channel spacing at radio frequency) and signal-to-noise ratio with fixed bit-error probability. The numerical results presented emphasize the performance obtainable with full- and partial-response techniques for varying system parameters such as phase deviation index, receiver filter bandwidth, and spectral efficiency     

Autocorrelation function and power spectral density of complexphase modulated signals derived from full response CPM

A class of digital phase-modulated signals called DCPM (digital complex phase-modulated) signals is introduced. In this class, the imaginary part of the phase is obtained from the real part by a linear time-invariant transformation. A method for computing the autocorrelation function (ACF) of DCPM is presented. It is shown that the ACF does not always exist. The power spectral density of DCPM is computed for Hilbert, identity, and zero transforms. It is also shown that DCPM with the Hilbert transform has a suppressed sideband and can yield significant bandwidth savings over zero transform schemes     

Optimum and reduced complexity multiuser detectors for asynchronous CPM signaling

Maximum likelihood detector algorithms are developed for the matrix of transmitted symbols in a multiuser system in which the received signal is the sum of K cochannel continuous phase modulated (CPM) signals and additive white Gaussian noise. We illustrate that the maximum likelihood matrix detector, which provides optimum detector performance, consists of K sets of front-end matched filters followed by a Viterbi algorithm. We also derive two reduced complexity receivers, demonstrating through simulation that they perform within 1-2 dB of the optimal while substantially reducing complexity. The paper demonstrates how performance can be traded off against complexity, giving particular attention to cochannel Gaussian minimum shift keyed (GMSK) signals.     

A design technique for spectral shaping in CPM systems

We describe a technique of pulse shaping able to control the power spectral density of a full-response CPM signal in various frequency ranges, under the constraint of a prescribed minimum Euclidean distance. Some examples illustrating the potentialities of the method and some comparisons with standard pulses are presented     

A new performance bound for PAM-based CPM detectors

It is well understood that the pulse amplitude modulation (PAM) representation of continuous phase modulation (CPM) can lead to reduced-complexity detectors with near optimum performance. It has recently been shown that the PAM representation also extends to CPM schemes with multiple modulation indexes (multi-h CPM). In this paper, we present a detector for multi-h CPM which is based on the PAM representation. We also give an exact expression for the pairwise error probability for the entire class of PAM-based CPM detectors (single- and multi-h, optimal, and reduced-complexity) over the additive white Gaussian noise (AWGN) channel and show that this bound is tighter than the previously published bound for approximate PAM-based detectors. In arriving at this expression, we show that PAM-based detectors for CPM are a special case of the broad class of mismatched CPM detectors. We also show that the metrics for PAM-based detectors accumulate distance in a different manner than metrics for other CPM detectors. These distance properties are especially useful in applications with greatly reduced trellis sizes. We give thorough examples of the analysis for different single- and multi-h signaling schemes. We also apply the new bound in comparing the performance of PAM-based detectors with other reduced-complexity detectors for CPM.     

Optimum CPFSK systems with postdetection filtering and better than matched filter performance

A rigorous theoretical model for CPFSK receivers with post-detection filtering is presented. The sensitivity is within 0.3 dB of the best result (i.e. 36 received photons for a 10/sup -9/ error probability) for modulation index between 1.5 and 5. The sensitivity is better than the matched filter sensitivity in some cases. The phase noise tolerance is significantly improved.<>     

一种多天线接收的全响应CPM信号解调方法

由于需要使用匹配滤波器组和复杂的符号与载波同步算法,CPM优化接收机结构复杂。而其非相干解调接收机结构简单,但在低信噪比时,性能较差。针对CPM的这些局限,结合接收天线分集技术,提出了一种适用于全响应CPM信号的非相干解调方法。在该方法中对每路信号进行短时傅立叶变换后进行插值处理来获得谱线包络最大处的频率;然后将各个支路上的输出进行合并,从而直接估计出对应的基带波形;再在基带信号的基础上进行同步处理,恢复出传输的信息。仿真结果表明:该方法可以有效地将对全响应CPM信号进行解调,只要选择合适的接收天线数,可以使非相干解调的性能接近相干解调的性能。     

Noncoherently detected trellis-coded partial response CPM on mobileradio channels

A noncoherent receiver is proposed for partial response trellis-coded continuous phase modulation (TC-CPM) on interleaved flat Rician-fading channels. By using a multiple-symbol observation interval and a simple metric calculator, the power efficiency is improved over a receiver that uses a single-symbol observation interval. Performance bounds on the bit error probability are derived by defining a set of characteristic distances for CPM signals, and showing that TC-CPM is equivalent to a TCM scheme. Our results show that, with the same observation length, the proposed receiver is less than 0.5 dB inferior to a coherent receiver for which perfect channel information is needed. We also conclude that in terms of joint power-bandwidth complexity, 2RC is the best candidate for rate-1/2 TCM codes     

FFH OCDMA系统地址码的优化设计与性能分析

提出了一种修正单重合码(MOCS) ,它不仅具有单重合码(OCS)的码字持性,而且能降低OCS的色散效应和多用户干扰,从而能有效改善FFHOCDMA系统的误比特率性能。同时,MOCS减少了FFHOCDMA系统编解码器的光纤光栅个数,而且还可以减少FFHOCDMA系统所需要的波长数。     

Optimum fiber dispersion in high-speed TDM systems

Single-channel transmission at 40 Gb/s and above is investigated by numerical simulations with respect to optimal fiber dispersion. Since optimum dispersion depends on the bit rate nonzero dispersion shifted fiber is recommended for 40-Gb/s transmission and standard single-mode fiber for 160-Gb/s transmission     

Optimum frequency reuse in mobile telephony systems

The reason why cellular mobile telephony systems exist is that they allow frequency reuse. Dynamic allocation algorithms improve the network efficiency and the service quality. Dynamic allocation is closely related to the following instantaneous allocation problem: given a number of channels (frequencies), a cell structure and the number of calls to be accommodated in each cell, find the optimum allocation of channels to cells subject to restrictions concerning the distance of cells, where the same frequency can be reused. In this paper we formulate and solve this problem by showing that it can be reduced to a 0–1 programming problem. Finally we present results, and draw subsequent conclusions.     

Trellis termination in CPM

A technique is presented for terminating the encoder of continuous phase modulation (CPM) into a known trellis state. This is useful when block-wise a posteriori probability processing is employed, e.g. in iterative (“turbo”) receivers for serially concatenated CPM     

Analysis of secrecy outage performance for full duplex NOMA relay systems with appearance of multiple eavesdroppers

Full-duplex (FD) relay systems including a transmit antenna selection and a non-orthogonal multiple access (NOMA) methods are analyzed under presence of multiple eavesdroppers. A channel state information of both the considered system and eavesdroppers is assumed to be outdated and eavesdroppers eavesdrop information signals independently. A closed-form of secure outage probability (SOP), secrecy throughput of every user is derived to evaluate the secrecy performance, and the mathematical analysis approach is verified by the Monte-Carlo simulation. Furthermore, the Golden-Section Search algorithm is proposed to find the maximum of the secrecy throughput of the considered FD-NOMA system. Numerical results indicate that there exists the SOP floor in the considered system and it is constrained by the channel gain of near user. Moreover, there is the optimal signal to interference plus noise ratio value which minimizes the SOP of the system regardless of the number of eavesdroppers. In comparison with half-duplex NOMA model, the SOP of FD-NOMA model is better.

     

Optimum noise performance of optical amplifiers

The concept of noise figure F and noise measure M applicable to radio frequency and microwave amplifiers is reviewed and extended to cover optical amplifiers. Two noise figures are defined in the optical regime: one gives the ASE output, while the other gives the ratio of signal-to-noise ratios at the input and output. In the quantum regime, the lower limit on these optimum values is set by a generalization of Heisenberg's uncertainty relation. A Raman back-pumped fiber link with post-amplification with an erbium-doped fiber amplifier is used to illustrate the use of noise measure     

Performance of narrowband CPM systems withlimiter-discriminator-integrator detection and decision feedbackequalization in mobile radio channels

A completely analytical approach is presented to achieve error probability analysis of limiter-discriminator-integrator (LDI) detection of binary continuous-phase modulation in a land mobile radio channel characterized by Rayleigh fading and Doppler effects. Optimum choice of the postdetection integration time is carried out when varying both system parameters and propagation characteristics, namely the Doppler shift. The improvements obtainable by means of decision feedback equalization (DFE) are also considered, in the presence of error propagation. The algorithm allows a very general analysis, which can be applied both to a partial and a full response modulation pulse, with narrowband IF filter and multipath propagation. This leads to the optimization of various system parameters, such as filter bandwidth, the modulation index, and the postdetection integration time, whatever the choice of the modulation pulse     

Optimum wavelength for long-wavelength LED systems

The bandwidth limitations due to material and modal dispersion are calculated for long-wavelength LED systems using measured attenuation and group delay characteristics for fibres of two different types. The data presented allow the establishment of selection criteria for LEDs used in 140 Mbit/s systems.     

Optimum two-step dispersion management in WDM soliton systems

The first numerical simulations of a complete transoceanic wavelength-multiplexed soliton transmission system applying dispersion management are presented. Guidelines for management optimisation are given. The simple optimised two-level dispersion allocation scheme offers more than a doubling of the amplifier span without significant transmission degradation