Optimal blind carrier recovery for MPSK burst transmissions

The paper introduces and analyzes the asymptotic (large sample) performance of a family of blind feedforward nonlinear least-squares (NLS) estimators for joint estimation of carrier phase, frequency offset, and Doppler rate for burst-mode phase-shift keying transmissions. An optimal or "matched" nonlinear estimator that exhibits the smallest asymptotic variance within the family of envisaged blind NLS estimators is developed. The asymptotic variance of these estimators is established in closed-form expression and shown to approach the Cramer-Rao lower bound of an unmodulated carrier at medium and high signal-to-noise ratios (SNR). Monomial nonlinear estimators that do not depend on the SNR are also introduced and shown to perform similarly to the SNR-dependent matched nonlinear estimator. Computer simulations are presented to corroborate the theoretical performance analysis.     

Performance evaluation of a reservation TDMA protocol for voice/data transmissions in a LEO satellite communication system

In this paper, the capability is investigated of a reservation TDMA‐based protocol to support constant bit rate and best‐effort traffics in Low Earth Orbit (LEO) satellite communication systems under typical propagation conditions. Differently from several previous papers on the same subject, we focus here on a communication channel affected by multipath fading and characterized by a high round trip delay. In our protocol, a higher priority is given to constant bit rate terminals with respect to best‐effort data terminals. The performance for constant bit rate and best‐effort terminals was derived by means of a suitable analytical approach and computer simulations. The results shown herein permits to evaluate the influence of the channel propagation conditions on the system performance. Moreover, they highlight that the reservation TDMA protocol exhibits a good behaviour for the communication channel under consideration and in comparison with a recent protocol based on the classical PRMA scheme. Copyright © 2003 John Wiley & Sons, Ltd.     

Coarse recovery of carrier frequency and symbol timing in multibeam satellite channels

A multibeam concept under full frequency reuse is a major prerequisite for high throughput satellite systems. The resulting interference problems might be tackled by appropriately designed precoding or multiuser detection schemes. However, before such powerful techniques are applicable, the most important transmission parameters have to be recovered successfully. In the context of this paper, a feedback structure for joint control of carrier frequency and symbol timing is investigated for a multibeam scenario, which has been developed in some previous work by the authors for a single user link. It is to be noticed that we describe a recovery method for a multibeam satellite network with suitably selected interference mitigation techniques; as a consequence, all cochannels are assumed to be aligned in frequency and time to the reference beam; other signal models are out of scope and not addressed in this contribution.     

Iterative symbol timing recovery for short burst transmission schemes

This paper presents a novel iterative symbol timing recovery (STR) scheme for short burst transmission formats, a paradigm commonly found in modern wireless systems, like, for instance, time division multiple access (TDMA) schemes and future wireless packet data networks. Both data-aided (DA) and decision-directed (DD) solutions are considered and performance is pursued by means of an iterative burst-by-burst scheme which exploits the Farrow structure for the polynomial interpolation filter. The convergence of the algorithm is discussed according to the expectation maximization (EM) framework. Performance is evaluated by simulating 4-QAM and 16-QAM transceivers and simulations results are compared under different modulation orders and channel conditions, for both the decision-directed and data-aided cases.     

Adaptive MAPSD algorithms for symbol and timing recovery of mobileradio TDMA signals

Dual-mode adaptive algorithms with rapid convergence properties are presented for the equalization of frequency selective fading channels and the recovery of time-division multiple access (TDMA) mobile radio signals. The dual-mode structure consists of an auxiliary adaptive filter that estimates the channel during the training cycle. The converged filter weights are used to initialize a parallel bank of filters that are adapted blindly during the data cycle. When the symbol timing is known, this filter bank generates error residuals that are used to perform approximate maximum a posteriori symbol detection (MAPSD) and provide reliable decisions of the transmitted signal. For channels with timing jitter, joint estimation of the channel parameters and the symbol timing using an extended Kalman filter algorithm is proposed. Various methods are described to reduce the computational complexity of the MAP detector, usually at the cost of some performance degradation. Also, a blind MAPSD algorithm for combining signals from spatially diverse receivers is derived. This diversity MAPSD (DMAPSD) algorithm, which can be easily modified for the dual-mode TDMA application, maintains a global set of MAP metrics even while blindly tracking the individual spatial channels using local error estimates. The performance of these single-channel and diversity MAPSD dual-mode algorithms are studied via computer simulations for various channel models, including a mobile radio channel simulator for the IS-54 digital cellular TDMA standard     

Performance evaluation of a finite buffer generalized selectiverepeat ARQ scheme for satellite communications

This article presents a new generalized selective repeat automatic repeat request (ARQ) scheme for error control in broadcast and point-to-point satellite communication systems. In the proposed scheme, each bit in a packet is repeated m times consecutively to increase the transmission reliability. Finite capacity buffers have been assumed at the earth stations. The throughput, theoretically derived for the proposed scheme, is optimized with respect to the number of copies transmitted per bit. A suitable algorithm to adaptively choose this number in relation to the transmission channel propagation conditions can also be used. In comparison with classical and modified versions of the selective repeat ARQ scheme as described in the literature, the proposed scheme provides enhanced throughput, especially with poor channel conditions and a high number of receiving earth stations     

Performance evaluation of a satellite-switched variable-frame TDMA system

In satellite-switched time-division multiple access (SS/TDMA) systems, the demand assignment control is a suitable scheme for the bursty packets to enhance the capacity efficiency. In the system, by applying the demand assignment scheme, the minimum transmission time could be achieved by the efficient time slot assignment algorithm. According to a given traffic matrix, the minimum transmission time cannot exceed the fixed TDMA frame duration. The spare time may be left at the end of the TDMA frame as the growth space for the future needs. To increase the system efficiency, the spare time could be reduced. In this paper, a demand assignment protocol with a variable frame is proposed for the system. The Markov chain model is applied to analyze the system performance on throughput, balking probability and packet delay. Performance comparison with the previous presented protocol, the proposed protocol could show a simple control technique and the efficient performance results in the system. It is a suitable candidate to be employed in the satellite networks to provide communication between the satellite and earth stations.     

Performance analysis of integrated-services load-adaptive/TDMA satellite networks

A load-adaptive/TDMA multiple-access communications system which serves to interconnect broad-band multimedia packet streams is considered. In particular, the use of a satellite backbone communications link whose channels are dynamically assigned to network stations is investigated. Each station supports packetized voice and data message streams. Incoming streams to a station are statistically multiplexed by the station across the backbone channels currently allocated to this station. To enhance the multiplexing process, a variable bit-rate packet-voice encoding scheme is also employed. Stations periodically issue requests for backbone channel allocations, based upon their estimated loading status. We introduce two distinct multiple-access algorithms for allocating the shared backbone channels to the stations. We develop analytical methods for the analysis and design of such integrated multiplexing/multiple-access networks. Performance measures include voice and data packet delays and packet blocking probabilities. Voice stream performance is also characterized by the average number of bits per sample used by the voice encoding scheme. The effects of the propagation delay across the backbone link are especially demonstrated. Also illustrated are the performance improvements attained due to the use of the load-adaptive/TDMA scheme. Under the example of the ’all-voice’ traffic loading, an LA/TDMA scheme exhibits no obvious performance improvement over a fix-assigned scheme. However, as the burstiness of the traffic loading increases in the example of the ’data-voice’ traffic loading, a significant amount of improvement (36 per cent bandwidth savings) is realized by a LA/TDMA scheme.     

一种适合突发通信的位定时和载波相位捕获联合估计算法

在高速数字突发通信中,需要快速、高效地对接收信号的位定时和载波初始相位信息进行估计.本文提出一种能够同时进行位定时和载波初始相位同步的并行算法,与传统的先进行载波恢复,再进行位定时捕获的串行处理相比,该算法同步速度更快(8~12个符号),实现结构简单,适于数字化实现.     

Performance analysis of call assignment and carrier packing schemes for TDMA systems

In IS-136 and GSM time-division multiple-access (TDMA) systems that employ dynamic channel allocation, it is important to minimize the number of active carriers for a given load. This paper studies the carrier packing properties of both call assignment and carrier repacking schemes, where the average number of active carriers and the average number of intra-sector (repack induced) handoffs per call are the relevant metrics. We show that the simple to implement sequential trunk hunt (STH) call assignment scheme is almost as good as the optimal intelligent channel assignment (ICA) scheme and that the MaxPack repacking scheme is optimal for both of these TDMA standards among all call assignment and repacking schemes. The call assignment and repacking schemes considered are shown to have either closed-form or efficient numerical recursive solutions for the North American IS-136 standard, and in most cases we obtain the underlying state space distributions. A mixture of analytic and simulation results is also presented for the GSM standard. Numerical results show that most of the packing efficiency can be achieved simply by a good call assignment scheme such as ICA and that the additional gain from optimal repacking is generally in the 10-15% range for typical IS-136 and GSM configurations.     

Performance of a TDMA portable radio system using a cyclic blockcode for burst synchronization and error detection

A combined burst synchronization and error detection scheme is studied for a time-division multiple access (TDMA) portable radio system. Analysis, computer simulation, and experimental results of the false acceptance rate of the system using the combined scheme are presented. It is found that for a (161,147) code used in this study, which is capable of correcting ±6-b sync slippage, the error detection capability of the code is degraded by 3 b on a slow Rayleigh fading channel using coherent QPSK demodulation with differential decoding. However, lower implementation complexity and higher efficiency are obtained than with separate burst synchronization and error detection processes     

Performance of uplink random-access and downlink TDMA techniques for packet satellite networks

In this paper the integration of ALOHA random-access schemes and TDMA techniques in a multibeam packet satellite network are analyzed. The uplink channels operate according to a slotted-ALOHA protocol, while the downlink channels use a TDMA strategy. Two different models are described. In the first model, each transponder on-board the satellite is permanently connected to a preassigned spot beam. The second model uses a number of transponders lower than the number of spot beams. Some different strategies of transmission are proposed in the latter model, able to provide full interconnection among earth stations by channel-hopping capability of the transponders. The performance of the models is evaluated through queueing theory analysis and extensive computer simulations. The obtained results suggest the second model as an efficient candidate for the implementation of a multibeam packet satellite network. In that case, the system parameters must be carefully chosen in order to avoid possible instability conditions.     

Approximate symbol error probability evaluation of M-ary pulse amplitude modulation with imperfect carrier recovery

In this letter, we propose an approximate symbol error probability (SEP) of M-ary pulse amplitude modulation (PAM) under a noisy carrier phase in a closed form when the carrier phase is governed by Tikhonov probability density function. The approximate results are desirable to evaluate the behavior of the system. The accuracy of the approximation is verified with respect to the numerical integration.     

Performance of fully variable demand assignment SS/TDMA satellite systems

Fully variable demand assignment in a SS/TDMA satellite system requires frequent burst time plan changes with reconfiguration of the on-board switch matrix state sequence. The burst managment presented in this paper assumes that bursts are not reconfigurated into new bursts during such burst time plan changes but merely shifted in time. The performance of this burst management procedure as obtained from simulations over three different networks is reported in terms of throughput gains, required signalling capacity and time required to change burst time plan.     

Phase recovery of the coherent carrier frequency in synchronous detection

This paper considers a method of phase recovery in synchronous detectors that ensure the synchronous detection of signals with amplitude modulation, amplitude-phase modulation, angle modulation or with appropriate manipulations. In addition a transfer function was obtained for the phase-locked loop of direct control and the simulation results of modeling were also presented.     

Performances of synchronous multiuser detectors for grey-type image transmissions

This article presents the results obtained by three multiuser detectors, namely the conventional, the minimum mean square error and the optimal maximum a posteriori one, when grey images are transmitted, as well as the inter-correlation between users and the amplitude imbalance effects on their performances. Three metrics are used to measure and compare the quality of the received images: the bit error rate, the peak signal-to-noise ratio and the mean structural similarity index. Based on the results obtained, we compared the performances achieved by the three detectors and their sensitivity to system imperfections. Several interesting conclusions are highlighted in the final section.     

Performance evaluation of HDAF relaying systems for pilot and data symbol burst transmission over quasi‐static Rayleigh fading channels

This paper analyzes averaged symbol error probabilities of burst transmission consisting of pilot and data symbols for hybrid adaptive decode‐or‐amplify‐forward (HDAF) relaying systems. Under the assumption of quasi‐static Rayleigh fading channels with independent and non‐identically distribution, we consider a channel estimation scheme based on pilot symbols and show how channel estimation error affects received signal‐to‐noise ratio (SNR) and symbol error probability (SEP). Firstly, all the possible detection error‐events are presented for all the relay nodes, and their probabilities are derived as forms related with data symbol burst transmission. For the given error event, we analyze the conditional SEP as an exact form and then, the averaged SEP (ASEP) is approximately derived as a closed‐form. The simulation results verify that our derived ASEP expression is accurate over all the regions of SNR. Utilizing the proposed expressions, we can evaluate ASEP performance of HDAF relay systems easily and fast. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance analysis of blind carrier frequency offset estimatorsfor noncircular transmissions through frequency-selective channels

This paper deals with the problem of blind estimation of the carrier frequency offset of a linearly modulated noncircular transmission through an unknown frequency-selective channel. A frequency estimator is developed based on the unique conjugate cyclic frequency of the received signal, which is equal to twice the frequency offset. Consistency and asymptotic normality of the frequency estimator together with a closed-form expression for its asymptotic variance are also established. The closed-form expression of the asymptotic variance enables analysis of the performance of the proposed frequency offset estimator as a function of the number of estimated cyclic correlation coefficients used. It is shown that optimum is obtained if the number of correlation coefficients taken into account coincides with the degree of the channel. Numerical simulations are provided and confirm the conclusion of the theoretical asymptotic analysis     

Performance evaluation of uplink power control algorithm over TDMA systems

Future PCS (personal communication system) cellular networks will mainly be driven by high link quality, high bandwidth utilization, low power consumption and efficient network management. Power control is one of the several major techniques which could help to achieve these goals. By exploiting power control techniques, co-channel interference could be reduced and as many links as possible could be obtained with satisfactory link quality. SIR-based (signal-to-interference ratio-based) power control was proposed as a technique for managing co-channel interference in cellular radio systems. Furthermore, new distributed autonomous feedback power control methods were introduced to achieve excellent performance without the difficult centralized control used in SIR-based methods. Unfortunately, the implementation of those power control algorithms is still challenging owing to the precision of SIR. The main aim of this paper is to investigate an uplink power control algorithm which depends indirectly on the signal-to-noise ratio in the TDMA (time division multiple access) cellular system. Simulation of the prototype hardware implementation of the receiver baseband signal processing based on the PACS (personal access communications system) specification is used as the main approach to explore the performance evaluation of this power control technique. According to simulation results, suitable values of those parameters used in this power control algorithm are derived, and the minimum frequency reuse factor under different propagation environments is also obtained for PACS under power control. © 1998 John Wiley & Sons, Ltd.