A simultaneous packet transmission (SPT) technique is proposed to increase the throughput of a communication system. A SPT scheme employs multiple levels and employs multiple streams at each level above the first level. Every stream of the SPT has its assigned partition on the overall constellation. Symbols of an N ‐level SPT are formed by taking , bits from a selected stream of every level. The SPT scheme can employ higher code rates on streams at higher levels to increase the system throughput. Numerical results show that the SPT offers 15–30% throughput enhancement in turbo‐coded LTE systems.

Traditionally, concatenation of codes is used to increase the coding gain at the expense of the code rate and the throughput. In contrast, throughput enhancing concatenated codes (TECCs) are constructed here aiming to increase the throughput. In a TECC, the coded sequence of a code C transmitted through the channel is altered according to the coded bits of a second coded sequence of an implicit code . In this study, TECCs select one bit in every segment of n coded bits of C based on coded bits of , and flip that selected coded bit of C before transmission. Even though the coded bits of are not transmitted explicitly over the channel, the information of coded bits of is transferred to the destination through the altered bits which can be recovered by exploiting the extrinsic information of explicitly coded bits. Using iterative decoding between codes C and , the receiver can decode the coded bits of both the explicit code C and the implicit code jointly. TECCs that can increase the throughput of C by 25–37.5% without sacrificing the performance of C are reported, however, at the expense of increased complexity.

Here, non-coherent detectors for quadrature-multiplexed continuous phase modulation (QM-CPM) signals are developed (Fonseka et al., 2008). QM-CPM signals are more spectrally efficient than CPM signals, and multiamplitude QM-CPM signals can be constructed that outperform QAM. The non-coherent detectors view a QM-CPM signal as having composite states that represent the information modulated both onto the in-phase and quadrature-phase carriers. Viterbi decoding is used to jointly detect the quadrature-multiplexed signal components. Optimal sequence-based quadrature-matched filter (QMF) detectors are presented for use with QM-CPM detection and a QM-MSK detector is developed in detail. Differential phase and envelope (DPE) detectors are also presented which require less computation and are able to outperform the QMF-type detectors when the unknown carrier phase varies (phase jitter, phase hits etc.) within the sequence length used in the sequence-based QMF detectors. In the absence of these phase fluctuation effects, as the sequence length used in the QMF detectors increases, the performance of the QMF detectors approaches the performance of optimal non-coherent detection. The DPE-type detectors perform within about 2.5 dB of optimal coherent detection.

This paper introduces a family of bandwidth efficient modulation schemes called quadrature multiplexed continuous phase modulation (QM-CPM). QM-CPM can be thought of as an alternative to smooth pulse-shaped quadrature amplitude modulation (QAM). Like pulse-shaped QAM, QM-CPM modulates smooth continuous signals onto the in-phase (I) and the quadrature-phase (Q) channels, but these signals are derived from CPM signals instead of being filtered to attain their desired smoothness and spectral properties. QM-MSK (QMminimum shift keying) is developed and is shown to double the bits/Hz over MSK while maintaining MSK's normalized minimum distance of d2min= 2.0. Classes of M2-ary QMCPFSK (QM-continuous phase frequency shift keying) signals are derived from constant envelope M-ary CPFSK signals to construct bandwidth efficient modulation schemes which are comparable to and offer advantages over pulse-shaped QAM.

Closed-form expressions are derived for the channel capacity of dual-branch maximal ratio combining, equal gain combining, selection combining, and switch and stay combining (SSC) diversity systems over correlated Nakagami-m fading for the channel inversion with fixed rate transmission scheme. Since some of the final capacity expressions contain infinite series, the series are truncated and upper bounds on the truncation errors are presented. An expression is also derived that can be used to numerically determine the optimum adaptive switching threshold for the capacity of a dual-branch SSC system over correlated Nakagami-m fading channels. A closed-form expression for the optimum adaptive switching threshold is derived, however, for the case of independent branches. The corresponding expressions for Rayleigh fading are obtained as a special case of Nakagami-m fading. Finally, numerical results are presented, which are then compared to the capacity results that the authors previously obtained for the rate adaptation with constant power transmission scheme.

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.

Optimal signal energies are derived for optimal binary digital communication systems with arbitrary signal probabilities and correlation with both coherent and noncoherent detection. The resulting bit-error probability (BEP) is computed and compared with the BEP of the same systems with equal signal energies. One of the conclusions is that for the coherent system with nonnegative correlation, and for the noncoherent system with arbitrary correlation, the optimal signals are on-off keying (OOK), i.e., the signal with probability p/spl les/0.5 has energy E/p, while the second signal has zero energy, where E is the average signal energy. The proposed system is also better than a system with source coding and equiprobable signals.

The effect of imperfect timing is analyzed in equal gain combining (EGC) and maximal ratio combining (MRC) techniques over Rayleigh and Nakagami-m fading channels with binary phase-shift keying modulation. In the case of EGC, the bit-error probability is derived, while in the case of MRC, error rate bounds are presented. Theoretical results are justified by computer simulation. Numerical results demonstrate that both EGC and MRC are fairly sensitive to timing errors, and comparatively, MRC is more sensitive.

It is known that continuous phase modulation (CPM) signals can be optimally detected by using coherent demodulation followed by Viterbi decoding. However, such a receiver is generally complicated, particularly at higher numbers of states, as it requires many correlators and many reference signals in the demodulator. In this study, a much simpler receiver, which employs a soft-decision phase detector followed by a Viterbi decoder, is proposed for the detection of CPM signals. The phase detector makes a decision in favor of one of the preselected phase subregions at the end of every interval, which is then used to calculate metrics for decoding. As in optimal detection, the Viterbi decoder decodes according to the trellis structure of CPM signals. The proposed receiver is analyzed in a narrow-band Gaussian channel with 2REC, 2-h, and trellis-coded continuous-phase frequency-shift keying signals. Numerical results show that the proposed receiver performs close to optimal detection with all types of signals considered in this study. The effect of the number of subregions in the phase detector is examined.

Two classes of constant envelope signals called, nonlinear PSK and combined nonlinear PSK/FSK are introduced. Nonlinear PSK signals select a constant phase angle during each interval depending on the state of the signal and the transmitted symbol. Combined nonlinear PSK/FSK signals select a linear phase variation during each interval and a discrete phase variation at the end of each interval depending on the current state and the transmitted symbol. Both classes of signals achieve the highest constraint length allowed by the number of states. The numerical results presented at preselected numbers of states show that these signals produce significantly high minimum distances. Distances higher than those found in the literature at the same number of states are reported. The spectra of nonlinear PSK signals are almost identical to the spectrum of BPSK signals, while those of combined nonlinear PSK/FSK signals are continuous but similar to that of BPSK signals.>

A nonlinear multipulse block coding technique is proposed to improve CPFSK signaling formats. The coding technique is developed to prevent merging events with lower distances by separating the respective paths in the time domain. Coded schemes are constructed with constant h, 2-h, and trellis coded CPFSK signals. The spectral variations and the performance/bandwidth tradeoffs of the proposed coded signals are found and compared to those without coding. It is concluded from the numerical results that the proposed coding technique can significantly improve the performance/bandwidth tradeoff of many CPFSK signaling formats, particularly, at lower bandwidths.>

A class of generalized nonlinear full-response CPM signals is constructed by extending the known ordinary nonlinear CPM signals. Numerical results presented at different numbers of states indicate that generalized nonlinear CPM signals achieve higher minimum Euclidean distances than ordinary nonlinear CPM signals.>

Two novel trellis-coding techniques, called nonlinear multi-h signaling and nonlinear asymmetrical multi-h signaling, which achieve higher constraint length than ordinary multi-h signals, are introduced with CPFSK signals. In contrast to ordinary multi-h signaling where the modulation index is changed at the end of every symbol interval, nonlinear multi-h signals are constructed by changing the modulation index based on the previous symbol, and the current symbol interval. A class of nonlinear asymmetrical multi-h signals, which change the modulation index based on the current symbol too, is then constructed by extending nonlinear multi-h signals and combining them with asymmetrical multi-h signals. Binary full-response nonlinear multi-h and nonlinear asymmetrical multi-h CPFSK signals are constructed and analyzed. Minimum Euclidean distances and spectral properties of these signals are calculated at different phase states and various selected modulation index patterns. Numerical results indicate that nonlinear multi-h and nonlinear asymmetrical multi-h signals achieve significantly higher distance than other existing multi-h formats reported in the literature.>

Traffic restoration in case of a failure in a circuit-switched telecommunications network involves finding alternate paths for all working paths that are severed by the failure, and rerouting affected traffic on these alternate paths. A new hierarchical self-healing ring (HSHR) architecture for circuit-switched networks is proposed and the design of HSHR networks is considered. A general cost model incorporating both the installation cost and the material cost is used. It is shown that the enumeration method, which finds the optimum configuration of HSHR, can only be used for small networks due to the complexity. Heuristic algorithms to find near-optimum HSHR configurations are presented. The routing and dimensioning of HSHR are also considered. Dimensioning of an HSHR is transformed into dimensioning of single self-healing rings inside the HSHR. Numerical results show that the performance of the heuristic is satisfactory.

Improved decision boundaries of narrowband Mary CPFSK with LDI, DC, and CDDD receivers are reported at modulation index 1/M. A simple method to determine each improved decision boundary by considering only the two closest symbols to that boundary is discussed. Numerical results presented for quaternary and octonary signals indicate that improved boundaries are almost identical to optimal boundaries and perform significantly better than the standard boundaries.

Block encoding is considered to increase the minimum distance of CPM signals. Codes are constructed to prevent merging events with low Euclidean distances. Numerical results presented with full response, partial response and trellis coded CPM signals indicate that block coding can significantly increase the minimum distance of the signals. Nonlinear block codes are also considered.>

A class of nonlinear CPM signals is introduced by extending nonlinear CPFSK signals to other forms of frequency pulses. The distance results and spectral properties of nonlinear CPM signals are reported. Bit error probabilities of nonlinear CPM signals are simulated in presence of adjacent channel interference.>

A correlatively encoded multi-h CPFSK signaling technique which performs significantly better than partial response multi-h signaling is introduced. Numerical results presented for binary 2-h signaling indicate that correlatively encoded 2-h signals can achieve significant gains over both constant h signals and partial response 2-h signals.>

A novel signal-space coded CPM (continuous phase modulated) signaling technique, called nonlinear CPFSK (continuous phase frequency shift keying) signaling, which guarantees the maximum constraint length allowed by the number of states is introduced. Nonlinear CPFSK signals use a suitably selected state transition matrix during all signaling intervals. The selected state transition matrix is realized by changing the modulation index of the signals, hence the modulation index used during any interval depends on the transmitted symbol as well as on the state of the system. Binary nonlinear CPFSK signaling schemes are constructed and analyzed. Numerical results indicate that nonlinear CPFSK signals can achieve attractive minimum distances compared with other existing CPM signaling formats.>

A continuous-phase frequency-shift-keying (CPFSK) signaling technique is suggested that combines convolutional encoding and multi-h signaling. In contrast to regular multi-h signaling, this technique changes the modulation index in a preselected pattern in order to maximize the minimum Euclidean distance. A rate-1/2 convolutional encoder along with a 2-h quaternary CPFSK modulator which uses two fixed modulation indexes is considered. Minimum Euclidean distances are calculated corresponding to the best encoder/mapper combinations for different modulation index patterns at attractive pairs of modulation indexes. Numerical results obtained for encoder memory lengths of one and two are used to illustrate that the minimum Euclidean distance of coded CPFSK signals can be significantly increased by combining with multi-h signaling. Modulation index patterns which perform significantly better than regular multi-h signals are determined. An error event analysis over the additive-white-Gaussian noise channel is carried out to investigate the actual error rate performance and to verify the theoretical results.>