Zhongding Lei

Zhongding Lei
Institute for Infocomm Research · Advanced Communications Technology

PhD

About

101
Publications
5,895
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2,334
Citations
Citations since 2016
2 Research Items
801 Citations
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150

Publications

Publications (101)
Conference Paper
In this paper, we present the baseband receiver design for the two mandatory physical-layer modes, i.e. the O-QPSK and BPSK modes, for ZigBee or IEEE802.15.4 operating in 2.4GHz and 868/915 MHz respectively. We propose new key receiver algorithms, including coarse frequency offset estimation, timing synchronization, fine frequency offset estimation...
Article
We consider a heterogeneous cellular network with densely underlaid small cell access points (SAPs). Wireless backhaul provides the data connection from the core network to SAPs. To serve as many SAPs and their corresponding users as possible with guaranteed data rates, admission control of SAPs needs to be performed in wireless backhaul. Such a pr...
Article
Trafc indication map (TIM) is one information element (IE) that is used to indicate the buffered frame status for the stations (STAs) and carried in the regularly transmitted beacons in the IEEE 802.11 based WLANs. To reduce the overhead of TIM signaling for the recent standardization of IEEE 802.11ah, which supports a large number of STAs and oper...
Conference Paper
Full-text available
Heterogeneous network (HetNet) is expected to be widely deployed in 4G cellular systems such as LTE- Advanced. One important requirement for LTE/LTE- Advanced networks is to support seamless and robust mobility so that a user can be handed over from one cell to another smoothly without service disruption. To ensure satisfactory user experience, 3GP...
Article
Full-text available
In vertical sectorization, multiple antenna elements form two beams to better serve users based on their locations in the cell. However, it is not known how to choose the radio network parameters to ensure good network performance and the amount of capacity gain achievable with vertical sectorization. In this paper, we propose an optimization appro...
Article
We consider the uplink transmission in multiuser wireless systems with multiple single-antenna transmitting users and a multiantenna receiver. We address two problems in this paper. The first problem is user admission, i.e., given a large number of users, how to admit the maximum number of users that can simultaneously satisfy quality of service (Q...
Conference Paper
In the new IEEE 802.11ah standard, a CRC code of 4 parity bits provides error detection for the SIG field of length 36 or 48 bits, giving rise to a significant performance penalty, which may be acceptable if there is an additional 32-bit Frame Check Sequence check on the payload in layer 2. However, in 802.11ah, there exist new Medium Access Contro...
Conference Paper
We address uplink user admission control problems in multiuser wireless systems with multiple single-antenna users and a multi-antenna receiver. Our aim is to select the maximum number of users that can simultaneously satisfy the given quality of service (QoS) and power constraints from a large number of candidates in the system. Both sum and per-u...
Article
When the joint processing technique is applied in the coordinated multipoint (CoMP) downlink transmission, the user data for each mobile station needs to be shared among multiple base stations (BSs) via backhaul. If the number of users is large, this data exchange can lead to a huge backhaul signaling overhead. In this paper, we consider a multi-ce...
Conference Paper
Full-text available
The IEEE 802.11ah task group has been formed to develop the specification for sub-1GHz WLAN. Due to the low operating frequency, it is expected that the 802.11ah can support coverage up to 1km. Such large coverage is well-suited for machine-to-machine (M2M) or machine-type communication (MTC) applications like smart grid and sensor networks. These...
Conference Paper
Joint transmission (JT) is an attractive coordinated multipoint (CoMP) downlink transmission technique in multi-cell networks. It offers high system throughput but needs to distribute each user data to multiple base stations (BSs), which can lead to huge backhaul signaling overhead when the number of users is large. In this paper, we address the pr...
Chapter
Cellular networks often assume homogeneous deployment, in which each base station has similar coverage, and overlaps with each other minimally due to careful planning by the operators. Conventional Inter-Cell Interference Coordination (ICIC) is designed based on this, relying on the backhaul for information exchange among these base stations for co...
Conference Paper
Coordinated multipoint (CoMP) transmission has been proposed as an important strategy to improve the signal quality for cell-edge users in future mobile cellular standards. However, when the joint transmission technique is applied in the CoMP downlink, the user data transferred from the data center to the base stations (BSs) can lead to a huge back...
Article
It is well recognized that the conventional cellular networks can no longer meet the user performance requirements in terms of throughput and coverage, which is due to the significant increase in the number of mobile users along with their traffic demands and the limited spectrum resource. This has stimulated the search for new approaches to allevi...
Conference Paper
In this paper, the problem of maximizing the sum rate of two interfering users, while limiting the received interference at each user, in an OFDMA-based system operating in downlink is considered. In a cooperative two cell scenario, for each particular user (located in the edge of cooperative cell and within area common with neighboring cell), it i...
Conference Paper
In this paper, precoding and receive filter matrices are designed such that minimum mean square error (MMSE) is achieved for interference alignment using 3-symbol extension in the multiple-input multiple-output (MIMO) X channels which comprise two transmitter-receiver pairs with M antennas at each transmitter/receiver. The performance of the propos...
Article
When the joint processing technique is applied in the coordinated multipoint (CoMP) transmission downlink, the user data for each mobile station (MS) needs to be distributed among multiple base stations (BSs), which incurs the exchange of user data via the backhaul. In order to alleviate the requirement on the backhaul capacity, we propose to minim...
Article
Coordinated multi-point processing at multiple base stations can improve coverage, system throughput, and cell-edge throughput for future cellular systems. In this paper, we study the coordinated reception of transmitted signals at multiple MIMO base stations to exploit cooperative diversity. In particular, we propose to employ cooperative multicel...
Article
In this paper, we consider a cooperative multiuser wireless cellular system under multipath fading channels. All base stations (BSs) and mobile stations (MSs) are equipped with multiple antennas. The multiuser interference in such a system is inherently asynchronous due to different path distance of BS to MSs. Theoretically we can at best synchroni...
Article
In this paper, a class of quasi-orthogonal space-time block codes (Q-STBC) is proposed for systems with two transmit antennas and three time slots, where the Alamouti code is not applicable due to the odd time slots. The proposed Q-STBC codes achieve rate one and full diversity with low complexity maximum likelihood decoding. The Q-STBC design also...
Conference Paper
Full-text available
In a distributed MIMO system (D-MIMO), multiple base stations work in cooperation manner to enhance system throughput by suppressing inter-cell and inter-user interference. In this paper, we propose two practical distributed algorithms that are based on block diagonalization technique. The proposed schemes eliminate the need of iterative computatio...
Article
In this paper, we consider the multiple base station cooperative transmission, a new technology being developed to lift the interference limits on wireless network. In practice, the biggest challenge facing multiple base station collaboration is the stringent requirement of the high-speed backbone to enable information exchange, especially for larg...
Article
In this paper, a beacon structure is proposed for the protection of incumbent wireless microphones in a cognitive radio system. The proposed beacon structure consists of two consecutive parts: synchronization bursts followed by payload bursts. Each part is transmitted on two orthogonal channels in parallel to shorten the required sensing windows fo...
Conference Paper
In this paper, a class of quasi-orthogonal space-time block codes (Q-STBC) is proposed for systems with 2 antennas and 3 time slots, where the orthogonal Alamouti code can not be applied due to the “odd symbol” problem inherited in the 3GPP frame structure. The proposed codes can achieve rate one and full diversity with lower complexity maximum lik...
Conference Paper
Coordinated multi-point processing at multiple base stations can improve coverage and throughput for future cellular systems. In this paper, we study the coordinated reception at multiple MIMO base stations by proposing cooperative multi-cell automatic repeat request (ARQ) protocols via wired backhaul links. In particular, we consider three protoco...
Article
In this paper, we consider the detection of orthogonal frequency-division multiplexing (OFDM) signals under frequency-selective fading channels for cognitive radio. First, we propose a new decision statistic for the signal detection based on the special feature-cyclic prefix embedded in OFDM signals. The probability distribution function (pdf) of t...
Conference Paper
Full-text available
Cognitive radio is widely expected to be the next Big Bang in wireless communications. Government spectrum regulatory committees in many countries have been taking steps to open the door to dynamic spectrum access using this technology and also laying down the rules for its implementation. International organizations have also been striving for sta...
Conference Paper
Full-text available
In this paper, a class of quasi-orthogonal space- time block codes (Q-STBC) is proposed for systems with 2 antennas and 3 time slots, where the orthogonal Alamouti code can not be applied due to the odd, also known as Orphan, symbol problem inherited in the 3GPP frame structure. The proposed codes can achieve rate one and full diversity with lower...
Conference Paper
Future cellular systems such as LTE-Advanced systems offer improved coverage, system throughput, and cell-edge throughput through the effective use of coordinated multi-point processing (CoMP). In this paper, we propose cooperative multicell automatic repeat request (ARQ), which exploits both the cooperation among base stations via backhaul links a...
Conference Paper
In this paper, we consider the multiple base station cooperative transmission, a new technology being developed to lift the interference limits on wireless network. In practice, the biggest challenge facing multiple base station collaboration is the stringent requirement of the high-speed backbone to enable information exchange, especially for larg...
Conference Paper
Zero-IF architecture is a competitive alternative to the conventional super-heterodyne architecture for RF-to-baseband conversion in OFDM systems. Despite its advantages of low cost and high integratability, it suffers from the I/Q imbalance that contributes amplitude and phase mismatches between in-phase and quadrature branches, resulting in signa...
Conference Paper
In this paper, we propose a space-time block code (STBC) coding scheme with three decoding algorithms for the frequency-domain generation of single-carrier frequency division multiple access (SC-FDMA) which addresses the issue of orphan symbols. The proposed algorithms only require one time-slot to perform Alamouti coding as compared to the space-t...
Conference Paper
Network MIMO is a technology being developed towards lifting the interference limits on wireless network through collaborative transmissions from multiple base stations. However its great potential is shadowed by the stringent requirement of high speed/capacity backbones facilitating information exchange, including data, control signals, and channe...
Conference Paper
In multi-cell OFDMA systems, inter-cell interference can severely degrade the system throughput, particularly for cell-edge users. To mitigate the inter-cell interference problem, interference coordination is a promising approach that effectively restricts and allocates certain resources among users in different cells to minimize the effect of inte...
Article
This article presents a high-level overview of the IEEE 802.22 standard for cognitive wireless regional area networks (WRANs) that is under development in the IEEE 802 LAN/MAN Standards Committee.
Conference Paper
In this paper, we consider the detection of WiMax signals under noise uncertainty. Based on the special feature - cyclic prefix embedded in WiMax signals, we propose an optimal Neyman-Pearson likelihood test for the signal detection. We have derived rigorously the probability distribution function of the corresponding decision statistics under freq...
Article
This paper proposes and investigates a novel code-division multiple-access (CDMA) system. This two-layer spreading CDMA (TLS-CDMA) system can combat multiple-access interference (MAI) and multipath interference (MPI) simultaneously and effectively in a multiuser scenario over frequency-selective fading channels. Moreover, a two-layer cell-specific...
Conference Paper
In this paper, we consider the detection of OFDM signals used for Cognitive Radios. Based on the special feature - cyclic prefix embedded in OFDM signals, we propose an optimal Neyman-Pearson likelihood test for the signal detection. We have derived rigorously the probability distribution function of the corresponding decision statistics under freq...
Conference Paper
In this paper, an energy efficient structure for beacon signal transmission is proposed for incumbent wireless microphone protection in a cognitive radio system. The proposed structure consists of two consecutive parts: Synchronization with Index and Synchronization with Payload, transmitted as in-phase and quadrature components respectively. As op...
Conference Paper
Theoretical and experimental studies have shown the remarkable capacity and spectral efficiency of V-BLAST. In this paper, we study Fano detection algorithm for the V-BLAST system, which uses QR decomposition of the channel matrix and is based on depth-first tree search. Simulation results show that the performance is comparable to that of ML detec...
Conference Paper
IEEE 802.15.4b is an enhanced standard to the IEEE 802.15.4, addressing the needs for high-data rate transmission using 868 or 915MHz band in the wireless personal area networks. This paper details a modulation and code mapping scheme designed specifically for the standard's high rate transmission schemes operating in the 868MHz and 915MHz bands; w...
Conference Paper
In this paper, a block-spread interleaved frequency division multiple access (BS-IFDMA) scheme is proposed. It is capable of allocating users in block-level code-spreading process for multiple access on top of the IFDMA multiple access scheme for better user allocation. Orthogonality among users in block spreading is achieved when the block spreadi...
Article
In digital communications systems, receiver synchronization (in terms of timing and carrier frequency offset estimation) is fundamental before accurate channel estimation can follow. Timing errors can cause intersymbol interferences (ISI) that destroy OFDM subcarriers' orthogonality and degrade system performance [Athaudage, 2002; Speth et al., 199...
Conference Paper
In this paper, detection of digital TV signals is studied since there is strong motivation to better utilize the idle TV channels to improve spectral efficiency, as seen in the efforts of IEEE 802.22 Wireless Regional Area Networks (WRAN) international standard activities. Cyclostationary feature of DVB signals is explored so that the robust single...
Conference Paper
We detail a code mapping scheme designed especially for devices in the enhanced wireless personal area networks operating in both the 868 MHz and 915 MHz bands for the emerging IEEE 802.15.4b standard. This carefully designed coding scheme, called cyclic odd bit inversion length 16 (COBI-16), meets all the following three essential criteria: (a) no...
Article
An improved recursive algorithm for BLAST is proposed. The speedups of the improved recursive algorithm over the original recursive algorithm in the number of multiplications and additions are 1.47 and 1.2 respectively.
Conference Paper
Cognitive radio (CR) is seen as one of the revolutionary techniques for future spectrum utilization. The first and probably the most challenging task for CR is to detect/sense the white space of the spectrum for its usage. In this paper, detection of DVB-T signals is studied since TV band has been considered by Federal Communications Commission (FC...
Article
IEEE 802.15.4b is an enhanced standard to the IEEE 802.15.4, addressing the needs for high-data rate transmission using 868 or 915 MHz band in the wireless personal area networks. This paper details a modulation and code mapping scheme designed specifically for the standard's high rate transmission schemes operating in the 868 MHz and 915 MHz bands...
Conference Paper
IEEE 802.15.4b is an enhanced standard to the IEEE 802.15.4, addressing the need for high-data rate transmissions in the 868 and 915 MHz band in the wireless personal area networks. This paper details a code mapping scheme designed specifically for the standard's 915 MHz band that leads to efficient transmission and low implementation complexity. T...
Conference Paper
IEEE 802.15.4b is an enhanced standard to the IEEE 802.15.4, addressing the need for high-data rate transmissions in the 868 and 915 MHz band in the wireless personal area networks. This paper details a code mapping scheme designed specifically for the standard's 915 MHz band that leads to efficient transmission and low implementation complexity. T...
Conference Paper
Ultra-wideband (UWB) impulse radio systems based on non-coherent on-off keying (OOK) energy detection are relatively simpler to implement than their coherent counterparts, because the strict synchronization requirements are relaxed. However, the design challenge is to set a hard decision threshold value after energy detection because the detected e...
Conference Paper
We detail a cyclic odd bit inversion length 16 (COBI-16) code mapping scheme designed especially for devices in the enhanced wireless personal area networks operating in the 915 MHz for the emerging IEEE 802.15.4b standard. This carefully designed coding scheme meets all the following three essential criteria: (a) no spikes in the frequency spectru...
Conference Paper
In this paper, a pulse UWB system based on 16-ary ternary orthogonal keying (TOK) is proposed for low power low data rate wireless personal area networks (WPAN). The novel ternary sequence based common signaling in the UWB system is proposed to support efficient implementation for both simple energy detectors and complex coherent detectors. Three v...
Conference Paper
The maximum likelihood (ML) estimator and the Cramer Rao Bound (CRB) for frequency offset estimation are derived and compared against each other in a multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system. A total of 100 UWB channel realizations, as proposed by IEEE 802.15 channel modeling sub-committee, for eac...
Conference Paper
In this paper, a new pulse-based UWB system is proposed with low power ranging. The ternary sequence based common signaling is proposed to support power efficient energy detectors, differential detectors, and coherent detectors simultaneously. The preamble for ranging is designed to have good autocorrelation properties. The on-off keying based powe...
Conference Paper
We detail a cyclic odd bit inversion length 16 (COBI-16) code mapping and modulation scheme designed especially for devices in the enhanced wireless personal area networks (WPAN) operating in the 868 MHz for the emerging IEEE 802.15.4b standard. This COBI-16 scheme has been accepted and incorporated in the draft IEEE 802.15.4b standard. This carefu...
Conference Paper
We propose a pseudo-inverse minimum mean squared error (MMSE) based QR decomposition (QRD) M-algorithm (QRD-M) for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithm can effectively mitigate the detrimental effect of MIMO channel ill-conditions on the bit error rate (BER) performa...
Conference Paper
We present a comparative study of two tree search based detection algorithms, namely, the M-algorithm combined with QR decomposition (QRD-M) and the sphere decoding (SD) algorithms, for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. First, we show that nodes ordering before and during the tree searc...
Conference Paper
In this paper, we present a pre-transformed (PT) multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) system, in short PT-MIMO-OFDM system. We propose two receiver structures that combine the iterative subcarrier reconstruction and iterative interference cancellation to fully exploit both the spatial and the frequ...
Conference Paper
An algorithm based on distinguishing the first significant multipath (FTA) is proposed to address the critical issue of symbol timing synchronization and carrier frequency offset estimation in ultra wideband (UWB) multi-band OFDM (MB-OFDM) systems. FTA pinpoints the frame synchronization sequence and the start of its fast Fourier transform (FFT) wi...
Conference Paper
A list MIMO detection scheme is proposed to achieve near optimal maximum likelihood detection performance. The scheme is especially efficient in high data rate packet transmission systems, such as wireless LAN based hotspots, fixed broadband wireless access systems, 4G cellular based hotspots etc. The complexity of the optimal performance achieving...
Article
Full-text available
In this paper, an iterative detection method for an uncoded pretransformed (PT) orthogonal frequency division multiplexing (OFDM) system where the channel is not known at the transmitter is proposed. The iterative detection starts with linear detection. The noiseless received signal at the weakest subcarrier (corresponding to the smallest channel a...
Article
A downlink transmission scheme in a switched-beam antenna system for providing diversity and beamforming simultaneously based on the space-time block coding technique is proposed. The scheme involves selecting multiple beams based on the uplink reception of the switched-beam antenna system, and determining multiple orthogonal beams from the selecte...
Conference Paper
Full-text available
This paper proposes a space-time coding architecture for single-carrier block spread CDMA systems. The proposed scheme employs a novel block spreading and despreading operation, which lead to significant reduction in the receiver complexity. The performance of the system is enhanced through space-time coding transmission. Extensive simulation studi...
Conference Paper
With the proliferation of new data-incentive applications in mobile networks, how to efficiently disseminating data among mobile devices has attracted more and more research attention. Different techniques have been put forward to increase the dissemination efficiency. In this paper, we propose a new class of scheduling strategies for data dissemin...
Conference Paper
We introduce a power control scheme for wireless data in a direct sequence code-division multiple-access radio mobile system under multipath environments. The motivation for this study is twofold: limiting inter-user interference to increase the system throughput; reducing power consumption to prolong battery life. We utilize the delay insensitive...
Conference Paper
The multiple-input-multiple-output (MIMO) multicarrier-code division multiple access (MC-CDMA) system is a potential scheme for future mobile packet transmission. The consideration of performance and computational complexity of different MIMO system configurations leads to various applications. In this paper, the performance of V-BLAST scheme for c...
Conference Paper
A performance comparison between convolutional coded vertical Bell-lab layered space time (V-BLAST) and groupwise space time trellis coded (GSTTC) multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is presented in this paper. Both systems have the same data rate and employ receivers with comparable complex...
Conference Paper
Recently, an iterative detection method is proposed for a pre-transformed OFDM system, where significant performance gain is shown to be achieved through linear processing (Z.Lei et al., Apr. 2003). An analytical treatment of the subject is given. The optimum transform design and reconstruction criteria are given to maximize the minimum SNR. In the...
Conference Paper
Next generation wireless networks are mainly designed to support intermittent packetized data traffic. This situation raises the question of how to do power control for information sources other than voice. To explore this issue, we utilize the delay insensitive property of the data traffic to transmit packets when the channel condition is good and...
Article
In this letter, an improved square-root algorithm for Bell Labs Layered Space-Time (BLAST) system is proposed. It speeds up the original square-root algorithm by 36% in terms of the number of multiplications and additions. Compared with the recursive algorithm, it requires only a 13.6% higher number of multiplications and a 38.9% higher number of a...
Article
The zero-forcing interference suppression and cancellation scheme proposed by Tarokh et al., in 1999, for grouped space time coded system suffers performance loss due to limited diversity gains for the first detected antenna groups, and power allocation was suggested to overcome this problem. In this letter, we propose an ordered detection algorith...
Article
Full-text available
A low complexity detection algorithm for VBLAST OFDM system is presented. Using the fact that the correlation among neighboring subcarriers is high for wireless LAN channels, this algorithm significantly reduces the complexity of VBLAST OFDM detection. The performance degradation of the proposed algorithm is small compared to conventional detection...
Conference Paper
We propose a low complexity VBLAST OFDM detection algorithm. In this method, we partition the subcarriers into a number of groups. The group size is determined by the frequency correlation between different subcarriers. Within each group, we use conventional VBLAST detection on the centre subcarrier and record the detection order. For the rest of t...
Conference Paper
In this paper, both post-FFT and pre-FFT beamforming in an OFDM system are studied. A maximum signal-to-noise ratio (max-SNR) post-FFT beamformer and a switched-beam pre-FFT beamformer are proposed. For each subcarrier, the max-SNR post-FFT beamformer combines multiple-antenna outputs and maximizes the beamformer output SNR based on estimated one-t...
Conference Paper
We study the performance of a Walsh-Hadamard transformed (WHT) space-time block coded (STBC) OFDM system, which we refer as the WHT-STBC-OFDM system. We show that, with the WHT transform, the error performance of the STBC coded OFDM system can be improved in terms of both bit error rate (BER) and packet error rate (PER) through simple linear detect...
Conference Paper
A list sphere decoder (LSD) based turbo receiver is introduced for groupwise space time trellis coded (GSTTC) systems. It can approach the single-user bound by iteratively exchanging soft information between the LSD and the soft-input soft-output (SISO) maximum a posteriori (MAP) space time trellis (STT) decoder. The LSD approximates the SISO maxim...