Bin Li

Beijing University of Posts and Telecommunications | BUPT · School of Information and Communication Engineering (SICE)

In this article, we suggest an efficient beam switching technique for the emerging 60GHz wireless personal area networks. Given the pre-specified beam codebooks, the beam switching process, aiming to identify the best beam-pair for data transmissions, is formulated as a global optimization problem in a two-dimension plane that is formed by the pote...

Despite the great potential of deep neural networks (DNNs), they require massive weights and huge computational resources, creating a vast gap when deploying artificial intelligence at low-cost edge devices. Current lightweight DNNs, achieved by high-dimensional space pre-training and post-compression, present challenges when covering the resources...

Massive multiple-input multiple-output (MIMO) radar, enabled by millimeter-wave virtual MIMO techniques, provides great promises to high-resolution automotive sensing and target detection in unmanned ground/aerial vehicles (UGA/UAV). As a long-established problem, however, existing subspace methods suffer from either high complexity or low accuracy...

Evolutionary computation, for example, particle swarm optimization, has impressive achievements in solving complex problems in science and industry; however, an important open problem in evolutionary computation is that there is no theoretical guarantee of reaching the global optimum and general reliability; this is due to the lack of a unified rep...

Cognitive radios may operate in practice under various adverse environments. For typical mobile and short-range scenarios, wireless links may tend to be time and frequency selective, i.e., the multipath propagations with time-varying fading coefficients will be inevitable. To cope with the encountered doubly-selective channels, in this paper we pre...

Radar-based gesture recognition combined machine learning methods can achieve excellent performance and has been utilized in a wide variety of applications. However, large-scale radar signal processing suffers from the risk of privacy leakage and the problem of limited computing resources. In this paper, we propose a federated learning framework ba...

To glean the benefits offered by massive multi-input multi-output (MIMO) systems, channel state information must be accurately acquired. Despite the high accuracy, the computational complexity of classical linear minimum mean squared error (MMSE) estimator becomes prohibitively high in the context of massive MIMO, while the other low-complexity met...

In 5G communications, the acquisition of accurate channel state information (CSI) is of great importance to the hybrid beamforming of millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) system. In classical mmWave MIMO channel estimation methods, the exploitation of inherent sparse or low-rank structures has demonstrated to impro...

Molecular networking has been identified as a key enabling technology for Internet-of-Nano-Things (IoNT): microscopic devices that can monitor, process information, and take action in a wide range of medical applications. As the research matures into prototypes, the cybersecurity challenges of molecular networking are now being researched on at bot...

Molecular communication (MC) is an emerging new communication paradigm where information is conveyed by chemical signals. It has been recognized as one of the most promising physical layer techniques for the future Internet of Bio-Nano Things (IoBNT), which enables revolutionary applications beyond our imagination. Compared with conventional commun...

Molecular communication is attractive to the emerging nano-scale communication systems. Traditionally, a detector recovers the information from only the concentration of single messenger molecule, while ignoring the variation of multiple participants in biochemical reaction. In this paper, we propose a non-coherent signal detector, by fully exploit...

Accurate channel state information (CSI) is extremely crucial to realize high‐accurate hybrid precoding, in millimeter wave communication systems. In order to improve the CSI estimation performance, several traditional channel estimators have been developed by exploiting the sparse or low‐rank property, whilst they bring huge channel training overh...

The development of reconfigurable intelligent surfaces (RIS) has recently advanced the research of physical layer security (PLS). Beneficial impacts of RIS include but are not limited to offering a new degree-of-freedom (DoF) for key-less PLS optimization, and increasing channel randomness for physical layer secret key generation (PL-SKG). However,...

Federated learning (FL) enables multiple local clients to collaboratively train a global model, which can reduce privacy leakage by sharing model parameters instead of private datasets. However, recent works have revealed that gradient-based data reconstruction attacks, e.g., deep leakage from gradients (DLG), improved DLG (iDLG), and inverting gra...

Compressed wideband spectrum sensing has attracted much interest in recent years, which enables flexible spectrum sharing to improve the efficiency of scarce frequency resource. Despite the great potential for sub-Nyquist-rate sampling, existing high-accurate compression sensing (CS) methods unfortunately incur the extremely high computational comp...

In 5G communications, the acquisition of accurate channel state information (CSI) is of great importance to the hybrid beamforming of millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) system. In classical mmWave MIMO channel estimation methods, the exploitation of inherent sparse or low-rank structures has demonstrated to impro...

Evolutionary computation, e.g., particle swarm optimization (PSO), has made impressive achievements in solving complex problems in science and industry. As an important open problem for more than 50 years, there is still no theoretical guarantee on the global optimum and the general reliability, due to lack of a unified representation of diverse pr...

Roadside units (RSUs) can help vehicles sense the traffic environment, so as to improve traffic safety. Since the sensing capability of single RSU is limited, we propose a multiple RSUs cooperative radar sensing network (RSU-CRSN) with signal-level fusion technique. Spatial registration is an essential prerequisite and foundation for RSU-CRSN with...

This letter considers downlink wideband channel estimation in an asymmetrical full-digital system where the number of uplink receive radio frequency chains is less than that of the downlink. This channel inconsistency will reduce downlink channel estimation accuracy. To deal with this problem, we adopt the coprime array topology in uplink receive a...

To support large-scale unmanned aerial vehicle (UAV) networks with both payload communication (PC) packets and control and non-payload communication (CNPC) packets, millimeter wave (mmWave) communication is convinced to be a promising solution. However, efficient user association and spectrum allocation are still challenging in mmWave-enabled UAV n...

The acquisitionof channel state information at transmitter (CSIT) is crucial to attain the potential benefits of the frequency division duplexing (FDD) massive multiple-input multiple-output (MIMO) system. Traditionally, CSI estimation at receiver and feedback to transmitter are separately designed, failing to maximize the estimation accuracy while...

Roadside units (RSUs) can help vehicles sense the traffic environment, so as to improve traffic safety. Since the sensing capability of single RSU is limited, we propose a multiple RSUs cooperative radar sensing network (RSU-CRSN) with signal-level fusion technique. Spatial registration is an essential prerequisite and foundation for RSU-CRSN with...

The development of reconfigurable intelligent surface (RIS) has recently advanced the research of physical layer security (PLS). Beneficial impact of RIS includes but is not limited to offering a new domain of freedom (DoF) for key-less PLS optimization, and increasing channel randomness for physical layer secret key generation (PL-SKG). However, t...

Machine learning has provided great potential in intelligent signal processing, e.g., channel estimation and signal detection. But still, it is difficult to deploy deep neural network (DNN) on low-cost and low-power edge devices, e.g., in both training and inference phases. For one thing, the training of massive network parameters incurs a huge com...

Reconfigurable intelligent surface (RIS) has been shown as a promising technique to increase the channel randomness for secret key generation (SKG) in low-entropy channels (e.g., static or line-of-sight (LoS)), without small-scale fading. In this letter, we show that even with the aid of RIS, collaborative eavesdroppers (Eves) can still estimate th...

The proliferation of low-cost Internet of Things (IoT) devices has led to a race between wireless security and channel attacks. Traditional cryptography requires high computational power and is not suitable for low-power IoT scenarios. Whilst recently developed physical layer security (PLS) can exploit common wireless channel state information (CSI...

The Unmanned Aerial Vehicle (UAV) is considered more and more often to assist the existing terrestrial communication systems. For UAV assisted cellular system, a critical challenge is the real time beam tracking for the UAV, introduced by the high mobility of it. The beam pointing deviation would result in the severe transmission performance reduct...

In this paper, we study the Physical Layer Security (PLS) problems in intelligent reflecting surface (IRS) multiple-input single-output (MISO) communication systems. A novel transmission scheme aimming to minimize the system energy consumption is proposed by jointly optimizing the phase shift matrix at the IRS and the beamforming vectors at the bas...

Millimeter-wave (mmWave) radar is critical to the emerging automatous driving. As one important step to estimate the range / velocity of unknown targets, constant false-alarm rate (CFAR) techniques should be firstly applied. Most CFAR methods focus on the point -based target model (i.e. each target is represented as one point), which may be inade...

Unmanned aerial vehicle (UAV) communications are vulnerable to smart attacks, where the attacker can change the attack mode (e.g., eavesdropping and jamming) via smart radio devices. To ensure secure transmissions against hybrid attacks, UAVs may transmit confidential information and misleading information alternately. In this paper, we consider a...

Subspace methods, e.g., multiple signal classification algorithm (MUSIC), show great promise to high-resolution environment sensing in the 6G-enabled mobile Internet of Things (IoT), e.g., the emerging unmanned systems. Existing schemes, aiming to simplify the computational 1-D search of the MUSIC pseudospectrum, unfortunately have still an unaffor...

Due to the public nature of wireless environments, legitimate communication systems are generally under the threat of Pilot Spoofing Attack (PSA). The malicious user may manipulate channel estimation by emitting the same pilot information, leading to the biased estimation of Channel State Information (CSI) and the degraded secrecy capacity. Althoug...

In this study, a spatial spectrum method is proposed to cope with the pilot spoofing attack (PSA) problem by exploiting the of uplink–downlink channel reciprocity in time-division-duplex multiple-input multiple-output systems. First, the spoofing attack in the uplink stage is detected by a threshold derived from the predefined false alarm based on...

Autoencoder, one of the most promising and successful architectures in deep learning (DL), has been widely used in wireless communications. However, fast-increasing size of neural networks (NNs) in autoencoder leads to high storage requirement and heavy computational overhead, which poses a challenge to practical deployment of autoencoders in real...

The advanced 6G Technology benefits the Internet of Things (IoT) in various applications. As one essential application scenario, smart grid (SG) incorporates communication and management techniques and promises an efficient and intelligent power system, whereby cognitive radio (CR) is believed to be an essential tool for better resource utilization...

Benefiting from the global deployment and fast commercialization of cellular systems, cellular-enabled vehicle-to-everything (V2X) opens up a significant prospect in the foreseeable future, for supporting proliferating vehicular services. Reliable and efficient resource allocation is a prerequisite for enjoying excellent quality of vehicular commun...

The 6th Generation (6G) of wireless systems are likely to operate in environments and scales that wireless services have not penetrated effectively into. Many of these environments are not suitable for efficient data-bearing wave propagation. Molecular signals have the potential to deliver information by exploiting both new modulation mechanisms vi...

Subspace methods are essential to high-resolution environment sensing in the emerging unmanned systems, if further combined with the millimeter-wave (mm-Wave) massive multi-input multi-output (MIMO) technique. The estimation of signal/noise subspace, as one critical step, is yet computationally complex and presents a particular challenge when devel...

In recent robotic applications, a critical need is to simultaneously detect communication (emission state) and estimate its trajectory. Whilst wireless sensor observations are useful, they are often uncertain due to the stochastic communication bursts and robot mobility. Over-sampling the information environment can incur excessive radio interferen...

Emerging cellular‐enabled unmanned aerial vehicles (UAVs) communication poses both opportunities and challenges to the current research of UAV applications. On the one hand, the advanced cellular technologies and authentication mechanisms make significant performance improvements of reliability, security, coverage, and throughput of UAVs possible....

Monitoring the networked dynamics via the subset of nodes is essential for a variety of scientific and operational purposes. When there is a lack of an explicit model and networked signal space, traditional observability analysis and non-convex methods are insufficient. Current data-driven Koopman linearization, although derives a linear evolution...

With significantly dynamic characteristics of the new aerial users, the emerging cellular-enabled unmanned aerial vehicle (UAV) communication paradigm raises great challenges to current research of UAV applications. As far as the robust channel allocation is concerned, the high mobility of UAV nodes and the unexpected disturbance of external enviro...

For millimeter-wave (mm-Wave) communications, signal detection in the presence of the power amplifier (PA) nonlinearity and unknown multipath channel has remained one challenging task in single-input single-output (SISO) communication system. Besides, the PA nonlinearity in multiple-input multiple-output (MIMO) communication system also has severe...

Recently, due to the deployment flexibility of unmanned aerial vehicles (UAVs), UAV-assisted mobile relay communication system has been widely used in the maritime communication. However, the performance of UAV-assisted mobile relay communication system is limited by the capacity of wireless backhaul link between base station and UAV In this paper,...

A closed‐form expression of the achievable secrecy rate is derived in this study, which is used as the objective function to find the optimal time allocation of channel estimation and transmission. Theory analysis and numerical results demonstrate that the maximum secrecy capacity depends on the total time budget as well as the power at the transmi...

Massive MIMO is considered as one key enabling technology in 5G communications. Although the high-quality channel state information (CSI) estimation is essential to improve the energy/spectrum efficiency of massive MIMO systems, the optimal MMSE estimator unfortunately creates one major challenge, due to its formidable computation complexity. In th...

The pilot spoofing attack (PSA) is one kind of active eavesdropping that happens in the channel training phase, in which an intelligent eavesdropper transmits identical pilot sequences synchronously with the legitimate user to spoof the transmitter. This attack leads to the estimated channel being a mix of a legitimate channel (the channel from the...

This study considers a downlink power consumption problem for unmanned aerial vehicles (UAVs)‐assisted wireless communications, in which UAVs are used as aerial base stations to provide service for the ground users and equipped with a directional antenna of fixed beamwidth. Moreover, the on‐board circuit power of UAV is taking into consideration. T...

Networked nonlinear dynamics underpin the complex functionality of many engineering, social, biological, and ecological systems. Monitoring the networked dynamics via the minimum subset of nodes is essential for a variety of scientific and operational purposes. When there is a lack of a explicit model and networked signal space, traditional evoluti...

With the gradual deployment of the fifth generation (5G) communication network, various challenging requirements are urgently expected to be met. One of the most important challenges is to ensure service quality under explosive traffic volume, which is putting pressure on the cellular network. In this paper, we aim to introduce the Unmanned Aerial...

Based on the cluster-fed reflector antenna, a low-coupling cluster-fed reflector antenna design scheme is proposed to solve the problem of feed occlusion and beam scanning of the forward-fed reflector antenna. The accuracy test and feed coupling test of the prototype are carried out, and the test results meet the design requirements. Then we optimi...

The cluster feed beamforming network uses a ground-based beamforming technique. In view of the complicated link transmission in ground-based beamforming networks, the channel calibration for forward/backward links of ground-based beamforming networks is given in the paper. Aiming at the problem of channel amplitude and phase inconsistency in beamfo...

In the process of Vehicular ad hoc network (VANET) infrastructure, Roadside Unit (RSU) can facilitate vehicle-to-vehicle (V2V) communications and enable communications between vehicles and the Internet. However, RSUs are expensive and immovable. Once installed on the side of the road, they cannot be moved. Therefore, as traffic flow changes, there...

As an emerging communication paradigm, molecular communication is suitable for exchanging information between nano-machines in a fluid medium (e.g., in vivo), utilizing molecules as a major carrier. Subject to the inherent long tail characteristic of channel response and the difficulties in obtaining Channel State Information (CSI), conventional co...

Nano-machines have the potential to achieve targeted drug delivery, improving efficacy and reducing side-effects and wastage. Coordinating multiple nano-machines require communication capability, and molecular communications (MC) is recognised as a key technology under the Internet-of-Nano Things (IoNT) ecosystem. Whilst secure communication is cri...

Many embedded networks are difficult to monitor, such as water distribution networks (WDNs). A key challenge is how to use minimum sparse sensors to measure contamination and transmit contamination data to a hub for system analysis. Existing approaches deploy sensors using multi-objective optimi-sation and transmit the data using ground penetrating...

Currently, most of the researches in molecular communication (MC) domain focus on the static MC scenarios. However, some envisioned important MC applications require mobile MC system. The investigation on mobile MC, especially the signal detection of mobile MC is limited. This work considers the problem of signal detection for mobile MC scenarios w...

Fingerprinting based localization is attracting increasing attention in recent years, yet the great majority of relative works focus on static multi-sensor circumstances. This letter, instead, considers a dynamical fingerprinting localization scenario for the device with intermittently emission status, whereby the fingerprints are obtained by the c...

In emerging Internet-of-Nano-Thing (IoNT), information will be embedded and conveyed in the form of molecules through complex and diffusive medias. One main challenge lies in the long-tail nature of the channel response causing inter-symbol-interference (ISI), which deteriorates the detection performance. If the channel is unknown, we cannot easily...

In emerging Internet-of-Nano-Thing (IoNT), information will be embedded and conveyed in the form of molecules through complex and diffusive medias. One main challenge lies in the long-tail nature of the channel response causing inter-symbolinterference (ISI), which deteriorates the detection performance. If the channel is unknown, existing coherent...

Molecular communications rely on diffusive propagation to transport information, which is attractive for a variety of nano-scale applications. Due to the long-tail channel response, spatial-temporal coding of information may lead to severe inter-symbol interference (ISI). Classical linear signal processing in wireless communications is usually oper...

Millimeter-wave radar, in marriage with virtual massive multiple-input multiple-output (MIMO) system, provides great promises to super-resolution environment sensing and target detection in unmanned ground/aerial vehicle (UGA/UAV). However, the existing target detection algorithms suffer from either low resolution/accuracy or high time complexity....

Nano-scale molecular communications encode digital information into discrete macro-molecules. In many nano-scale systems, due to limited molecular energy, each information symbol is encoded into a small number of molecules. As such, information may be lost in the process of diffusion–advection propagation through complex topologies and membranes. E...

We investigate the interference-aware spectrum reuse for heterogeneous small cell networks (SCNs), by specially considering dense-user deployment and stochastic-environment uncertainties. Most existing approaches, which are lack of evolving coordinations and rely on precise channel state information, tend to be inefficient in the context of dense S...

Many engineering, social, and biological complex systems consist of dynamical elements connected via a large-scale network. Monitoring the network’s dynamics is essential for a variety of maintenance and scientific purposes. Whilst we understand how to optimally sample and discretize a single continuous dynamic element or a non-dynamic graph, we do...

Extracting and detecting spike activities from the fluorescence observations is an important step in understanding how neuron systems work. The main challenge lies in the combined ambient noise with fluctuated baseline, which contaminates the observations, thereby deteriorating the reliability of spike detection. This may be even worse in the face...

The persistent increases of wireless terminals have brought about diverse shared networks, where robust and efficient spectrum reuse among heterogeneous users is of critical importance while still remains as a challenging task for practical application. In this paper, we study the problem of robust spectrum access (RSA) in a canonical wireless shar...

Ambient Backscattering Communication (AmBC) is regarded as a promising approach for green Internet-of-Things (IoT) networks. However, the noise nature of the ambient radio-frequency (RF) signal poses great difficulty for the signal processing at the receiver, resulting in an unsatisfied Bit Error Rate (BER) performance at a long communication dista...

As a promising approach to assist the fifth generation (5G) communication system, GEO satellite communication technology is expected to be utilized to provide an efficient and reliable coverage for the terrestrial cellular network. Most multi-beam GEO satellites work on the low-inclination geostationary orbit. Due to various unexpected factors, e.g...

In order to support a mass of current satellite applications, it becomes a trend to integrate satellite networks with terrestrial networks, called satellite-terrestrial networks. However, traditional network protocols cannot adapt to the dynamic and complex satellite-terrestrial network. Moreover, the computing and communication capabilities of som...

When the immune network is used in anomalistic electromagnetism signals detection, a critical issue emerged that lots of “detection holes (gaps of the detector coverage compare to the target area)” are caused by fixed-size detectors and invariable matching threshold. This paper improves the original model by increasing the detectors’ coverage and p...

Many engineering, social, and biological complex systems consist of dynamical elements connected via a large-scale network. Monitoring the network's dynamics is essential for a variety of maintenance and scientific purposes. Whilst we understand how to optimally sample a single dynamic element or a non-dynamic graph, we do not possess a theory on h...

The persistent awareness of dynamic links quality is of critical importance to shared access systems, e.g. promoting sensing accuracy or even enabling seamless sharing, which remains yet as a challenging task. In this work, we consider the shared access in heterogeneous small-cells, which are likely to be the main infrastructure components by utili...

Extracting and detecting spike activities from the fluorescence observations is an important step in understanding how neuron systems work. The main challenge lies in that the combination of the ambient noise with dynamic baseline fluctuation, often contaminates the observations, thereby deteriorating the reliability of spike detection. This may be...

This paper proposes a novel pilot spoofing attack detection scheme by introducing an auxiliary node as trusted user, which also participates in the uplink training process and assists to detect pilot spoofing in multiple-input single-output (MISO) systems. To do so, we design an efficient Three-phase Uplink Training (TPUT) method, with which a mali...

This paper investigates the problem of dynamic spectrum access with taking the uncertainty of the wireless environment into consideration. The existing previous works assumed that the wireless environment is static, i.e., the channel states remain unchanged during the transmission period. In this paper, we assume that the channel states vary from s...

Increasing advances in building reliable and efficient wireless sensor network (WSN) provide a promising prospect in the applications of monitoring and localization. However, due to the intensive measurement noise, observations from sensors can be severely deteriorated, rendering most existing localization schemes unattractive. In this paper, we pr...

In this paper, we consider a mesh-structured unmanned aerial vehicle (UAV) networks exploiting partially overlapping channels (POCs). For general data-collection tasks in UAV networks, we aim to optimize the network throughput with constraints on transmission power and quality of service (QoS). As far as the highly mobile and constantly changing UA...

Bayesian approaches have been used extensively in scientific and engineering research to quantify uncertainty and extract information. However, its model-dependent nature means that when the a priori model is incomplete or unavailable, there is a severe risk that Bayesian approaches will yield misleading results. Here, we propose a universal model-...

As a new paradigm that has advantages in the field of nanocommunication, molecular communication via diffusion (MCvD) achieves conveying information between nanomachines both in vitro and in vivo. In general, inter-symbol interference (ISI) is one of the dominant factors that restricts the quality of communication, incurred by the long tail nature...

Bio-receptor clustering is a common and yet not well understood phenomenon in cell biology. Cooperative signal detection can both enhance and weaken information decoding. This paper leverages on diversity combining knowledge in signal processing to show how inter-symbol-interference (ISI) and channel noise from diffusion can be reduced using cooper...

Dynamic spectrum sharing will facilitate the interference coordination in device-to-device (D2D) communications. In the absence of network level coordination, the synchronization among D2D users will be unavailable, leading to inaccurate channel state estimation and device detection, especially in time-varying fading environments. In this study, we...

One primary challenge in wireless ultraviolet communications (UVCs) is the inter-symbol-interference (ISI), which may block the detection of current informative signal, especially when channel-related characteristics are unknown. In this paper, we propose a UV channel-related Bayesian scheme that can simultaneously estimate the channel characterist...

Dynamic spectrum sharing is considered as one of the key features in the next-generation communications. In this correspondence, we investigate the dynamic tradeoff between the sensing performance and the achievable throughput, in the presence of time-varying fading (TVF) channels. We first establish a unified dynamic state-space model (DSM) to cha...

Molecular communications convey information via diffusion propagation, whereby the inter-symbol interference is inevitable due to the long-tail channel response. Thus, traditional linear processing framework, unfortunately, requires both high complexity and high signal-to-noise ratios. In this paper, we proposed a new processing paradigm inspired b...

The unknown noise variance and time-variant fading channels make the spectrum sensing design a challenging task for cognitive radios (CRs). Most existing sensing methods suffer from the information uncertainty and can hardly acquire promising performances in the adverse situations. To address this challenge, in this paper, we firstly formulate a dy...

In this paper, the throughput maximization of millimeter-wave (mm-Wave) ultra-dense networks (UDN) using dynamic spectrum sharing (DSS) is considered. Most of the existing works only allow temporal-domain access and admit at most one user at each time slot, resulting in significant under utilization of spectrum resource, which will be less attracti...

In multi-cellular organisms, molecular signaling spans multiple distance scales and is essential to tissue structure and functionality. Molecular communications is increasingly researched and developed as a key subsystem in the Internet-of-Nano-Things (IoNT) paradigm. Whilst short range microscopic diffusion communications is well understood, longe...

The energy efficiency of systems in general determines its operational sustainability. Harvesting energy is a crucial technology for a variety of wireless systems that have limited access to a reliable electricity supply or recharging sources. As such, these devices need to harvest electricity from alternative sources such as the natural environmen...

Deep neural network are one of the most powerful model for machine learning, which can learn the underlying patterns automatically from a large amount of data. So it can be extensively used in more and more Internet-of-Things applications. However, the training of deep models is difficult, suffering from overfitting and gradient vanishing problem....

Molecular Communications via Diffusion (MCvD) is sensitive to environmental changes such as the diffusion coefficient (mass diffusivity). The diffusivity is directly related to a number of parameters including the ambient temperature, which varies slowly over time. Whilst molecular noise models have received significant attention, channel fading ha...

This article addresses the inter-symbol interference (ISI) of Ultraviolet (UV) communications driven by scattering effect. We model UV channel-state-information (CSI) as Markov finite-state and design Viterbi scheme to estimate informative bits.