ON THE OPTIMAL MULTI-RATE THROUGHPUT FOR MULTICAST WITH NETWORK CODING

This paper investigates the maximal achievable multi-rate throughput problem of a multicast ses-sion at the presence of network coding. Deviating from previous works which focus on single-rate network coding, our work takes the heterogeneity of sinks into account and provides multiple data layers to address the problem. Firstly formulated is the maximal achievable throughput problem with the assumption that the data layers are independent and layer rates are static. It is proved that the problem in this case is, unfortunately, Non-deterministic Polynomial-time (NP)-hard. In addition, our formulation is extended to the problems with dependent layers and dynamic layers. Furthermore, the approximation algorithm which satisfies certain fair-ness is proposed.

On Channel Assignment for Multicast in Multi-Radio Multi-Channel Wireless Mesh Networks:A Survey

The major challenge faced by wireless mesh networks is the capacity reduction caused by interference,and interference can be reduced or even eliminated through appropriate channel assignment.This article presents a comprehensive survey of channel assignment schemes for multicast in multi-radio multi-channel wireless mesh networks.We analyze the state-of-the-art channel assignment schemes for multicast and provide comprehensive taxonomy of the latest work.In general,we classify the channel assignment schemes for multicast into two types,that is,sequential multicast routing and channel assignment(SMRCA)and joint multicast routing and channel assignment(JMRCA).Detailed review of channel assignment schemes in each category is provided.Possible future research directions and corresponding solutions are also explored to motivate research interests in the field of channel assignment for multicast in wireless mesh networks.

Kernel Generalization of Multi-Rate Probabilistic Principal Component Analysis for Fault Detection in Nonlinear Process

In practical process industries,a variety of online and offline sensors and measuring instruments have been used for process control and monitoring purposes,which indicates that the measurements coming from different sources are collected at different sampling rates.To build a complete process monitoring strategy,all these multi-rate measurements should be considered for data-based modeling and monitoring.In this paper,a novel kernel multi-rate probabilistic principal component analysis(K-MPPCA)model is proposed to extract the nonlinear correlations among different sampling rates.In the proposed model,the model parameters are calibrated using the kernel trick and the expectation-maximum(EM)algorithm.Also,the corresponding fault detection methods based on the nonlinear features are developed.Finally,a simulated nonlinear case and an actual pre-decarburization unit in the ammonia synthesis process are tested to demonstrate the efficiency of the proposed method.

Performance Improvement of DCF Supporting Multi-Rate in IEEE 802.11b Wireless LAN

This paper proposes a new channel access algorithm based on channel occupancy time （COT） fairness to guarantee fairness and improve the aggregate throughput of 802.11b multi-rate WLANs. In the algorithm, the COT is used as fairness index to analyze the fairness of WLANs instead of the channel access probability （CAP） used in the distributed coordination function （DCF）. The standard COT is given by access point （AP） and broadcasted to all wireless stations. The AP and wireless stations in the WLAN can achieve COT-based fairness by adjusting their packet length, sending the multiple back-to-back packets at one time, or giving up an opportunity to access the channel. Analysis and simulations show that our algorithm can provide COT-fairness. Compared with the CAP-based algorithm, the proposed algorithm leads to improvements in aggregate throughput of IEEE 802. lib multi-rate WLANs.

Research of Multi-Rate LDPC Decoding in Optical Communication System

Low-density parity-check code (LDPC) not only has good performance approaching the Shannon limit, but also has low decoding complexity and flexible structure. It is a research hot-spot in the field of channel coding in recent years and has a wide range of application prospects in optical communication systems. In this paper, the decoding aspects and performance of LDPC codes are analyzed and compared according to the bit error rate (BER) of LDPC codes. The computer simulation was carried out under additive white Gaussian noise (AWGN) channel and binary phase shift keying (BPSK) modulation. Through theoretical analysis and simulation results, this paper explores the way of multi-rate LDPC decoding.

Study of multi-rate multi-user detection based on supervision decision

Multi-user detection (MUD) based on multirate transmission in code division multiple access (CDMA) system is discussed. Under the requirement of signal interference ratio (SIR) detection at base station and framework with parallel interference cancellation, a supervision decision algorithm based on pre-decision of probabilistic data association (PDA) and hard decision is proposed. The detection performance is analyzed and simulation is implemented to show that the supervision decision algorithm improves the detection performance effectively.

A SINGLE PROCESSOR MULTI-RATE VOCODER

This paper presents the design of a full-duplex multi-rate vocoder which implements an LPC-10, CELPC and VSELPC algorithms in real time. A single commercially available digital signal processor IC, the TMS320C25, is used to perform the digital processing. The channel interfaces are configured with the design of ASIC, and including timing and control logic circuits.

Multi-rate tracking controller analysis and design for target tracking systems

As the sampling rates of the inner loop and the outer loop of the target tracking control system are different,a typical digital multi-rate control system was formed.If the traditional single-rate design method was applied,the low sampling rate loop will seriously impact the dynamical characteristic of the system.After analyzing and calculating the impact law of the low sampling rate loop to the bandwidth and the stability of the tracking system,a kind of multi-rate control system design method was introduced.Corresponding to the different sampling rates of the inner loop and the outer loop,the multi-rate control strategy was constituted by a high sampling rate sub-controller and a low sampling rate sub-controller.The two sub-controllers were designed separately and connected by means of the sampling rate converter.The low sampling rate controller determined the response rapidity of the system,while the high sampling rate controller applied additionally effective control outputs to the system during a sampling interval of the low sampling rate controller.With the introduced high and low sampling rates sub-controllers,the tracking control system can achieve the same performance as a single-rate controller with high sampling rate,yet it works under a much lower sampling rate.The simulation and experimental results show the effectiveness of the introduced multi-rate control design method.It reduces the settling time by 5 times and the over shoot by 4 times compared with the PID control.

Multi-rate sensor fusion-based adaptive discrete finite-time synergetic control for flexible-joint mechanical systems

This paper proposes an adaptive discrete finite-time synergetic control （ADFTSC） scheme based on a multi-rate sensor fusion estimator for flexible-joint mechanical systems in the presence of unmeasured states and dynamic uncertainties. Multi-rate sensors are employed to observe the system states which cannot be directly obtained by encoders due to the existence of joint flexibilities. By using an extended Kalman filter （EKF）, the finite-time synergetic controller is designed based on a sensor fusion estimator which estimates states and parameters of the mechanical system with multi-rate measurements. The proposed controller can guarantee the finite-time convergence of tracking errors by the theoretical derivation. Simulation and experimental studies are included to validate the effectiveness of the proposed approach.

A NOVEL CROSS-LAYER STRATEGY OF VIDEO TRANSMISSION TO SOLVE PERFORMANCE ANOMALY IN MULTI-RATE IEEE 802.11 NETWORKS

When wireless hosts use different rates to transmit data in IEEE 802.11 networks, it will take on the state of performance anomaly which will severely decrease the throughputs of all the higher rate hosts. Hence, it is bad for video service transmission. Considering that video is very sensitive to packet delivery delay but can tolerate some packet losses, we propose a novel cross-layer scheme which takes these two characteristics into consideration. Firstly, the maximum number of retransmissions for a video Medium Access Control (MAC) frame is computed in MAC layer according to video frame rate requirement of application layer and current access delay of MAC layer. Secondly, within the margin of the tolerant Packet Loss Rate (PLR) of application layer, several video MAC frames are allowed to drop so that we can adaptively select the transmission rate as high as possible for the rest of video MAC frames in terms of current channel quality and the maximum number of retransmissions. Experiment results show that the proposed method can reduce the delay and jitter of video service and improve the throughputs of fast hosts. Therefore, it increases the quality of reconstructed video to a certain extent and relieves the performance anomaly of network effectively.

BLIND DETECTION FOR MULTI-RATE DS-CDMA SYSTEM WITH ANTENNA ARRAY AT THE BASE STATION

In this paper, we propose the blind space-time high rate multi-user detector for synchronous uplink multi-rate Direct Sequence Code Division Multiple Access （DS-CDMA） systems with antenna array at the base station. By employing antenna array at the base stations, the spatial dimension is used efficiently to suppress co-channel interference and increase the capacity for multi-rate CDMA system. After low rate physical users in the system are modeled as corresponding high rate virtual users, we construct the space-time signature vectors of virtual users. And subspace projection algorithm is employed to estimate space-time signature vectors blindly. Then a soft-decision high rate lnultiuser detector is proposed based on the estimated signature vectors, which avoids estimating the ambiguous complex factors which are necessary in traditional blind detector. Numerical simulation results evaluate the performance in terms of Bit Error Rate （BER） for the proposed scheme. Simultaneously, it demonstrates that the system capability increases two times when using twoelement antenna array.

A NEW DESIGN METHOD OF CDMA SPREADING CODES BASED ON MULTI-RATE UNITARY FILTER BANK

It is well-known that the multi-valued CDMA spreading codes can be designed by means of a pair of mirror multi-rate filter banks based on some optimizing criterion. This paper indicates that there exists a theoretical bound in the performance of its circulating correlation property, which is given by an explicit expression. Based on this analysis, a criterion of maximizing entropy is proposed to design such codes. Computer simulation result suggests that the resulted codes outperform the conventional binary balanced Gold codes for an asynchronous CDMA system.

CHANNEL ESTIMATION OF MULTI-RATE DS-CDMA SIGNALS IN SLOW FADING MULTIPATH CHANNELS

In Direct-Sequence Code Division Multiple Access(DS-CDMA) mobile communi-cation systems, it is very important to obtain accurate estimation of the channel parameters,especially that of the propagation delay. But the near-far problem may make the estimationcomplicated and can degrade the estimation performance significantly. In this paper, an efficientMaximum Likelihood (ML) method is presented for channel parameter estimation of multi-rateDS-CDMA systems in slow fading multipath channels in a near-far scenario. The algorithmextended the ML approach to multi-rate DS-CDMA systems, and proposes decomposing a multi-dimensional optimization problem into a series of one-dimensional optimization and has improvedcomputational efficiency. Theoretical analysis and numerical examples show that the estimatorproposed is effective and near-far resistant.

On the Performance of Blind Chip Rate Estimation in Multi-Rate CDMA Transmissions Using Multi-Rate Sampling in Slow Flat Fading Channels

This paper considers blind chip rate estimation of DS-SS signals in multi-rate and multi-user DS-CDMA systems over channels having slow flat Rayleigh fading plus additive white Gaussian noise. Channel impulse response is estimated by a subspace method, and then the chip rate of each signal is estimated using zero crossing of estimated differential channel impulse response. For chip rate estimation of each user, an algorithm which uses weighted zero-crossing ratio is proposed. Maximum value of the weighted zero crossing ratio takes place in the Nyquist rate sampling frequency, which equals to the twice of the chip rate. Furthermore, bit time of each user is estimated using fluctuations of autocorrelation estimators. Since code length of each user can be obtained using bit time and chip time ratio. Fading channels reduce reliability factor of the proposed algo-rithm. To overcome this problem, a receiver with multiple antennas is proposed, and the reliability factor of the proposed algorithm is analyzed over both spatially correlated and independent fading channels.

Opportunistic Relaying Technique over Rayleigh Fading Channel to Improve Multicast Security

The performance of Rayleigh fading channels is substantially impacted by the impacts of relays, antennas, and the number of branches. Opportunistic relaying is a potent technique for enhancing the effects of the aforementioned factors while enhancing the performance of fading channels. Due to these issues, a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is taken into consideration in this study. So the investigation of a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is the focus of this paper. The primary goals of this study are to maximize security in wireless multicasting while minimizing security loss caused by the effects of relays, branches at destinations and wiretappers, as well as multicast users and wiretappers through opportunistic relaying. To comprehend the insight effects of prior parameters, the closed form analytical expressions are constructed for the probability of non-zero secrecy multicast capacity (PNSMC), ergodic secrecy multicast capacity (ESMC), and secure outage probability for multicasting (SOPM). The findings demonstrate that opportunistic relaying is a successful method for reducing the loss of security in multicasting.

Coded Multicasting for Content Delivery over Predictable Time-Varying Satellite Communication Networks

With the development of astronautic technology, communication satellites now have a tremendous gain in both quantity and quality, and have already shown their capability on multi-functional converged communication other than telecommunication. Under this circumstance, increasing the transmission efficiency of satellite communication network becomes a top priority. In this paper, we focus on content delivery service on satellite networks, where each ground station may have prefetched some file fragments. We cast this problem into a coded caching framework so as to exploit the coded multicast gain for minimizing the satellite communication load. We first propose an optimization-based coded multicast scheme by considering the special property that the satellite network topology is predictable and timevariant. Then, a greedy based fast algorithm is proposed, which can tremendously reduce the computation complexity with a small loss in optimality. Simulation experiments conducted on two Walker constellation satellite networks show that our proposed coded multicast method can efficiently reduce the communication load of satellite networks.

Secure Wireless Multicasting through Nakagami-m Fading Channels with Multi-Hop Relaying

The additional diversity gain provided by the relays improves the secrecy capacity of communications system significantly. The multiple hops in the relaying system is an important technique to improve this diversity gain. The development of an analytical mathematical model of ensuring security in multicasting through fading channels incorporating this benefit of multi-hop relaying is still an open problem. Motivated by this issue, this paper considers a secure wireless multicasting scenario employing multi-hop relaying technique over frequency selective Nakagami-m fading channel and develops an analytical mathematical model to ensure the security against multiple eavesdroppers. This mathematical model has been developed based on the closed-form analytical expressions of the probability of non-zero secrecy multicast capacity (PNSMC) and the secure outage probability for multicasting (SOPM) to ensure the security in the presence of multiple eavesdroppers. Moreover, the effects of the fading parameter of multicast channel, the number of hops and eavesdropper are investigated. The results show that the security in multicasting through Nakagami-m fading channel with multi-hop relaying system is more sensitive to the number of hops and eavesdroppers. The fading of multicast channel helps to improve the secrecy multicast capacity and is not the enemy of security in multicasting.

Generation of Low-Delay and High-Stability Multicast Tree

Delay and stability are two key factors that affect the performance of multicast data transmission in a network.However,current algorithms of tree generation hardly meet the requirements of low delay and high sta-bility simultaneously.Given a general network,the generation algorithm of a multicast tree with minimum delay and maximum stability is an NP-hard problem,without a precise and efficient algorithm.To address these challenges,this paper studies the generation of low-delay and high-stability multicast trees under the model of spanning tree based on stability probability,degree-constrained,edge-weighted for multicast(T-SDE).A class of algorithms was proposed which creates the multicast tree greedy on the ratio of fan-out to delay(RFD)and probability of stability of terminal to obtain a high performance in multicast.The proposed algorithms greedily select terminals with a large RFD and a high probability of stability as forwarding nodes in the generation of the multicast tree,where the larger RFD and higher stability of upstream nodes are beneficial to achieve a low transmission delay and high stability in multicast.The proposed RFD can be compatible with the original model,which can take advantage of network connectivity during the generation of a multicast tree.This paper carries out simulation experiments on Matlab R2016b to measure the performance of the proposed algorithm.Experimental results show that the proposed algorithm can provide a smaller height,higher stability,and a lower transmission delay of the resulting multicast tree than other solutions.The spanning tree of the proposed algorithms can support low transmission delay and high stability in multicast transmission.

Max-Min Fair RIS-Aided Rate-Splitting Multiple Access for Multigroup Multicast Communications

Rate-splitting multiple access(RSMA)can cope with a wide range of propagation conditions in multigroup multicast communications through rate splitting optimization.To breakthrough the grouprate limited bottleneck,reconfigurable intelligent surface(RIS)technique can be introduced to assist wireless communications through enhancing the channel quality.In RIS-aided RSMA multigroup multicasting,how to provide fair and high-quality multiuser service under power and spectrum constraints is essential.In this paper,we propose a max-min fair RIS-aided rate-splitting multiple access(MMF-RISRSMA)scheme for multigroup multicast communications,where the rate fairness is obtained by maximizing the minimum group-rate.In doing so,we jointly optimize the beamformers,the rate splitting vector at the transmitter,as well as the phase shifts at RIS.To solve it,we divide the original optimization problem into two subproblems and alternately optimize the variables.The beamforming and rate splitting optimization subproblem is solved by using the successive convex approximation technique.The phase shift optimization subproblem is solved through the penalty function method to achieve a rank-one locally optimal solution.Simulations demonstrate that the proposed MMF-RIS-RSMA scheme can obtain significant performance gain in terms of the minimum group-rate.

Application Layer Multicast Model with Low Delay and High Stability

As an alternative of Internet protocol(IP)multicast,application layer multicast(ALM)is widely used with the advantage of simplicity and flexibility.However,the existing problems of large transmission delay and poor stability limit the application and development.In this article,to solve these problems,an ALM model based on node potential(NP)and topological index(TI)is proposed.The proposed model considers the factors of node capability and node distance in constructing and maintaining multicast tree to reduce transmission delay and increase stability,and thus it improves the application level in real-time multimedia multicast.The computer simulations prove that the proposed model reduces the ALM transmission delay,increases multicast tree stability effectively,and improves the ALM performance,and therefore it is suitable to apply in large-scale real-time multimedia environment.