Wai Ho Mow

• PhD
• Hong Kong University of Science and Technology

Dementia is an overall decline in memory and cognitive skills severe enough to reduce an elders ability to perform everyday activities. There is an increasing need for accessible technologies for cognitive training to slow down the cognitive decline. With the ability to provide instant feedback and assistance, social robotic systems have been prove...

Real-world distributed storage systems (DSSs) are heterogeneous because storage nodes may have unequal per-symbol storage costs, and network links may have unequal per-symbol transmission costs. For some general classes of heterogeneous DSSs, the optimal tradeoff between storage and repair costs achievable by functional repair codes is known (at le...

We present a multi-group precoding scheme based on Björck sequences, achieving a tradeoff between complexity and BER performance. Experiments at ~200 Gb/s demonstrate that the proposed approach outperforms OCT while reducing complexity by 92%.

The quality and quantity of training data significantly affect deep learning model performance. In error correction, generating high-quality samples with minimal noise is crucial. This paper presents a method that combines a modified Importance Sampling (IS) distribution with active learning to generate high-quality samples. The suggested IS distri...

The quality and quantity of data used for training greatly influence the performance and effectiveness of deep learning models. In the context of error correction, it is essential to generate high-quality samples that are neither excessively noisy nor entirely correct but close to the decoding region's decision boundary. To accomplish this objectiv...

Compressed sensing is an alternative to Shannon/Nyquist sampling for acquiring sparse or compressible signals. Sparse coding represents a signal as a sparse linear combination of atoms, which are elementary signals derived from a predefined dictionary. Compressed sensing, sparse approximation, and dictionary learning are topics similar to sparse co...

Existing crowdsourced indoor positioning systems (CIPSs) usually require prior knowledge about the site and a tedious calibration process. Moreover, they may require a large number of landmarks while ignoring the topology information that may be contained in the crowdsourced data. In this paper, we present Leto, a system that uses le arned to p...

Index assignment (IA) is a low-complexity joint source-channel coding technique that has the potential for use in low-latency and low-power applications, such as wireless sensor networks (WSNs). Though binary IA has been extensively studied for assigning binary indices to quantized codewords (or symbols) under the assumption of binary symmetric cha...

Low-density lattice codes (LDLCs) achieve near-capacity performance on additive white Gaussian noise (AWGN) channels. The M-Gaussian decoder is the state-of-the-art message passing decoder for LDLCs in terms of the error performance. However, this decoder has complexity O(Md-1) with messages represented by Gaussian mixtures, where d is the degree o...

The single-layer perceptron, introduced by Rosenblatt in 1958, is one of the earliest and simplest neural network models. However, it is incapable of classifying linearly inseparable patterns. A new era of neural network research started in 1986, when the backpropagation (BP) algorithm was rediscovered for training the multilayer perceptron (MLP) m...

There are rising scenarios in communication systems, where the noises exhibit impulsive behavior and are not adequate to be modeled as the Gaussian distribution. The generalized Gaussian distribution instead is an effective model to describe real-world systems with impulsive noises. In this paper, the problem of efficiently evaluating the error per...

In this paper, we re-examine the classical problem of efficiently evaluating the block and bit error rate performance of linear block codes over binary symmetric channels (BSCs). In communication systems, the maximum likelihood decoding (MLD) bounds are powerful tools to predict the error performance of the coded systems, especially in the asymptot...

In recent years, digital copies of paper documents are used widely with the prevalence of various online services. As a result, it is critical to validate the authenticity of the uploaded document images to protect against attacks from malicious users. Out of various types of attacks, the recapture attack (by reprinting and recapturing) is effectiv...

In this paper, we analyze the symbol error rate (SER) performance of the simultaneous wireless information and power transfer (SWIPT) enabled three-node differential decode-and-forward (DDF) relay networks, which adopt the power splitting (PS) protocol at the relay. The use of non-coherent differential modulation eliminates the need for sending tra...

Envisioned as a promising component of the future wireless Internet-of-Things (IoT) networks, the non-orthogonal multiple access (NOMA) technique can support massive connectivity with a significantly increased spectral efficiency. Cooperative NOMA is able to further improve the communication reliability of users under poor channel conditions. Howev...

This paper investigates the rearrangement problem whose objective is to maximize the bilinear form $\boldsymbol x^T H\boldsymbol y$ associated with a certain matrix $H$ by explicitly characterizing the optimal permutations of the two vectors $\boldsymbol x$ and $\boldsymbol y$. We relate the problem to Hardy's discrete version of the famous Riesz r...

This paper studies the detection and performance analysis problems for a relay network with $N$ parallel decode-and-forward (DF) relays. Due to the distributed nature of this network, it is practically very challenging to fulfill the requirement of instantaneous channel state information for coherent detection. To bypass this requirement, we consid...

Envisioned as a promising component of the future wireless Internet-of-Things (IoT) networks, the non-orthogonal multiple access (NOMA) technique can support massive connectivity with a significantly increased spectral efficiency. Cooperative NOMA is able to further improve the communication reliability of users under poor channel conditions. Howev...

In this paper, we analyze the symbol error rate (SER) performance of the simultaneous wireless information and power transfer (SWIPT) enabled three-node differential decode-and-forward (DDF) relay networks, which adopt the power splitting (PS) protocol at the relay. The use of non-coherent differential modulation eliminates the need for sending tra...

Emerging recently as a novel concept in communication system design, end-to-end learning introduces deep neural networks (NNs) to represent the transmitter and receiver functions. Consequently, the whole system can be interpreted as an autoencoder (AE), which can be optimized from a holistic approach through a data-driven training method. Until now...

In this paper, we analyze the symbol error rate (SER) performance of the simultaneous wireless information and power transfer (SWIPT) enabled three-node differential decode-and-forward (DDF) relay networks, which adopt the power splitting (PS) protocol at the relay. The use of non-coherent differential modulation eliminates the need for sending tra...

IP protocol is the core of TCP/IP network layer. However, since IP address and its Domain Name are allocated and managed by a single agency, there are risks of centralization. The semantic overload of IP address also reduces its scalability and mobility, which further hinders the security. This paper proposes a co-governing Multi-Identifier Network...

IP protocol is the core of TCP/IP network layer. However, since IP address and its Domain Name are allocated and managed by a single agency, there are risks of centralization. The semantic overload of IP address also reduces its scalability and mobility, which further hinders the security. This paper proposes a co-governing Multi-Identifier Network...

In many applications, including integer-forcing linear multiple-input and multiple-output (MIMO) receiver design, one needs to solve a successive minima problem (SMP) on an n-dimensional lattice to get an optimal integer coefficient matrix A* ∈ Z <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n×n</sup...

The conventional barcode is currently employed in some mobile payment applications. The barcode serves as a token which represents the identity of a user. However, attacks on the payment process can be initiated by intercepting the barcode images in various ways. In this work, we proposed a ideo-based Robust and Aesthetic 2D barCode (vRA Code) so t...

With the rapid advancement of sensing capability and computational power in consumer electronic devices, the use of mobile cameras for communications has attracted significant attention from both academia and industry. The design of a reliable communication system over the print-capture channel is a key challenge in some important applications, suc...

Owing to the rapid advancement in processing power and camera quality of mobile devices, research on the display-to-camera (D2C) communication channel has recently received increasing attention. Unlike the traditional QR Code, the unobtrusive D2C communication scheme normally serves both the human eyes and the mobile camera in commercial advertisem...

The full duplex (FD) two-way relay channel (TWRC) has recently been shown to be a feasible way to improve the network throughput in practical communications. In this correspondence, we consider the convolutionally coded physical-layer network coding (PNC) over the TWRC in which two sources work in the FD mode and there exists a direct link between...

Camera-based wireless video sensor networks present opportunities to use large numbers of low-cost, low-resolution wireless camera sensors for various applications such as outdoor remote surveillance and ubiquitous data transmission in line-of-sight systems. Owing to the continuously increasing popularity of displays and cameras, communication in s...

Recently, some picture-embedding schemes have been proposed to improve the aesthetic appearance of 2D barcodes. However, these aesthetic 2D barcodes are not robust to the distortions incurred by the print/display-and-capture channel under limited rendering space and resolution. In this paper, a picture-embedding 2D barcode named the Robust and Aest...

In this paper, we re-examine the decoding problem of a distributed Turbo code (DTC) over the three-node one-way relay channel based on the decode-and-forward protocol. In the traditional DTC scheme, the decoder at the destination assumes the error-free Viterbi decoding at the relay. However, the error propagation effect resulted from the unsuccessf...

A quasi-complementary sequence set (QCSS) refers to a set of two-dimensional matrices with low non-trivial aperiodic auto- and cross- correlation sums. For multicarrier code-division multiple-access applications, the availability of large QCSSs with low correlation sums is desirable. The generalized Levenshtein bound (GLB) is a lower bound on the m...

Relay-assisted communication has been shown to be an effective technique to improve the reliability and throughput of real-world wireless communication networks. It enables singleantenna users to form a virtual antenna array without installing multiple antennas at the transmitter or the receiver. This paper re-examines the decoding problem in the c...

A quasi-complementary sequence set (QCSS) refers to a set of two-dimensional matrices with low non-trivial aperiodic auto- and cross- correlation sums. For multicarrier code-division multiple-access applications, the availability of large QCSSs with low correlation sums is desirable. The generalized Levenshtein bound (GLB) is a lower bound on the m...

Packet recycling was recently introduced as an effective technique to counter the packet pollution attack to network coded systems. In this letter, some improved upper and lower bounds on the detection error probability, decoding error probability and the throughput of a finite-block-length network coded system with polluted packet recycling. By pr...

Although multiple-input and multiple-output (MIMO) wireless systems achieve significant data rates (e.g., multiplexing) and reliability (e.g., diversity) and are main enablers for high-rate 5G wireless systems, MIMO receivers require high implementation complexity. A solution is the use of integer-forcing (IF) linear receivers which first create an...

We consider the problem of finding the optimal coefficient vector that maximizes the computation rate at a relay in the compute-and-forward scheme. Based on the idea of sphere decoding, we propose a highly efficient algorithm that finds the optimal coefficient vector. First, we derive a novel algorithm to transform the original quadratic form optim...

Using physical layer network coding, compute-and-forward is a promising relaying scheme that effectively exploits the interference between users and thus achieves high rates. In this paper, we consider the problem of finding the optimal integer-valued coefficient vector for a relay in the compute-and-forward scheme to maximize the computation rate...

Presentation slides of the paper: Stephen Chiu Kwok LAM, Kai Lap WONG, Kwok On WONG, Wenxiu WONG, Wai Ho MOW, “A Smartphone-Centric PlaAorm for Personal Health monitoring Using Wireless Wearable Biosensors”, Proceedings of the Seventh InternaLonal Conference on InformaLon, CommunicaLons and Signal Processing, Macau, December 8-10, 2009.

Nowadays, 2D barcodes have been widely used as an interface to connect potential customers and advertisement contents. However, the appearance of a conventional 2D barcode pattern is often too obtrusive for integrating into an aesthetically designed advertisement. Besides, no human readable information is provided before the barcode is successfully...

A Z-complementary pair may be used as an alternative of a Golay complementary pair in many engineering applications. A new simple approach to generate more equal length Z-complementary pairs is proposed. It is proved that a new Z-complementary pair is composed of a linear combination of a complex Z-complementary pair and the same linear combination...

A two dimensional barcode containing encoded information can be embedded with an image with a high visual quality. The encoded information within the barcode is meaningful to machines, while the image is meaningful to humans. The two dimensional barcode embedded with the image is designed such that machines can decode the information encoded within...

This paper investigates linear precoding over nonsingular linear channels with additive white Gaussian noise, with lattice-type inputs. The aim is to maximize the minimum distance of the received lattice points, where the precoder is subject to an energy constraint. It is shown that the optimal precoder only produces a finite number of different la...

Display-camera communication has become a promising direction in both computer vision and wireless communication communities. However, the consistency of the channel measurement is an open issue since precise calibration of the experimental setting has not been fully studied in the literatures. This paper focuses on establishing a scheme for precis...

Binary sequences with low aperiodic autocorrelation levels, defined in terms of the peak sidelobe level (PSL) and/or merit factor, have many important engineering applications, such as radars, sonars, spread spectrum communications, system identification, and cryptography. Searching for low autocorrelation binary sequences (LABS) is a notorious com...

Motivated by applications such as battery-operated wireless sensor networks (WSN), we propose an easy-to-implement low-complexity two-way relaying scheme. In particular, we address the challenge of improving the standard two-way selective decode-and-forward protocol (TW-SDF) in terms of block-error-rate (BLER) with minor additional complexity and e...

The order of authors is incorrect in the following article.

We consider the compute-and-forward protocol design problem with the objective being maximizing the computation rate at a single relay, and propose an efficient method that computes the optimal solution based on the idea of sphere decoding. We first interpret the problem as a shortest vector problem (SVP) by the Cholesky factorization, which is der...

Favorable characteristics of wireless channels (including the inherent broadcast and superposition nature) provide a fertile ground for the extension of conventional network coding (NC) principles to wireless communication networks. However, the research of emerging wireless (physical layer) network coding (WNC) techniques have already revealed sev...

Two-dimensional barcodes are widely used in mobile advertisement business, while their decoding performance is not always satisfactory under uncontrolled environments. The corner detection accuracy has been identified as a critical factor affecting the overall system performance. The standard barcode detector performs a candidate search in the bina...

Systems and methods that recharge power supply units of portable electronic devices by leveraging energy harvesting or scavenging techniques. A recharge component accumulates energy from a plurality of sources, and supplies an electric current to the portable electronic device for a charge thereof. The sources of energy are based on routine user ac...

Network-on-chip (NoC) based multiprocessor system-on-chips (MPSoCs) have been proposed as promising architectures to meet modern applications' ever-increasing demands for computing capability under limited power budget. Understanding the behaviors of MPSoC applications is the key to design MPSoCs under tight power and performance constraints. In th...

In wireless networks, the compute-and-forward strategy is a promising physical layer network coding scheme that can achieve high rates by effectively exploiting the interference between users. However, the design of the optimal integer-valued equation coefficient vectors in a compute-and-forward scheme turns out to be a shortest vector problem, whi...

Levenshtein improved the famous Welch bound on aperiodic correlation for binary sequences by utilizing some properties of the weighted mean square aperiodic correlation. Following Levenshtein's idea, a new correlation lower bound for quasi-complementary sequence sets (QCSSs) over the complex roots of unity is proposed in this paper. The derived low...

As 2D barcodes become more and more popular, their new applications, like mobile marketing, give a strong motivation for embedding visual information in them. Information stored on a 2D barcode, being printed on paper or shown on a display device, can be delivered to people via a camera phone with suitable decoding software. The barcoding system ca...

The random linear network coding system can be modelled as a linear operator channel (LOC). Among all the LOC models, one of the most interesting models is the sparse LOC model, where the entries of the channel matrix take zero with high probability and any of the nonzero elements in the finite field with equal probabilities. It is well-known that...

Systems, methods, and computer-readable media for determining long binary sequences having low autocorrelation functions using evolutionary processes are disclosed. Biphase sequences are found with low peak sidelobe values meeting a predetermined criterion, e.g., threshold low auto-correlation function, including application of semidefinite program...

Consider the communication system model y = HFx + n, where H and F are the channel and precoder matrices, x is a vector of data symbols drawn from some lattice-type constellation, such as M-QAM, n is an additive white Gaussian noise vector and y is the received vector. It is assumed that both the transmitter and the receiver have perfect knowledge...

Although the 2-source wireless Butterfly Network (BN) represents a natural extension of the well-known 2-Way Relay Channel (2-WRC) scenario, a direct implementation of conventional Wireless Network Coding (WNC)/Physical Layer Network Coding (PLNC) principles in this network is not straightforward. While the information necessary for decoding of the...

The Lenstra-Lenstra-Lovász (LLL) algorithm is a popular lattice reduction algorithm in communications. In this paper, variants of the LLL algorithm with either reduced or fixed complexity are proposed and analyzed. Specifically, the use of effective LLL reduction for lattice decoding is presented, where size reduction is only performed for pairs of...

Spectrum sensing in wireless communications is provided to identify utilized and/or unutilized frequency bands reserved for primary users using a cyclostationary beamforming approach. An adaptive cross self-coherent restoral (ACS) algorithm can be utilized to extract signals of interest (SOI) at unique cycle frequencies related to primary and/or se...

The detriment arising from strong and frequently occurring impulses over an Orthogonal Frequency Division Multiplexing system is paramount because signals on sub-carriers appear to be corrupted simultaneously. To overcome this obstacle, clipping has been reported as an effective approach. Unlike previous works, this work derived the clipping thresh...

Inspired by the application scenarios such as battery-operated wireless sensor networks (WSN), we investigate the design of an easy-to-implement energy-efficient two-way relaying scheme in which two source nodes exchange their messages with the help of an intermediate relay node. Due to their efficient decoder hardware implementation, block codes,...

In the random linear network coding scenario with subspace codes applied, if the number of packets injected into the network is larger than the dimension of the subspace, the packets are not linearly independent. This paper addresses the problem of how to choose these packets to represent the subspaces so as to minimize the decoding failure probabi...

This work investigates linear precoding over non-singular linear channels with additive white Gaussian noise, with lattice-type inputs. The aim is to maximize the minimum distance of the received lattice points, where the precoder is subject to an energy constraint. It is shown that the optimal precoder only produces a finite number of different la...