Prof. Alex Haimovich, Project Leader
This group of ten researchers concentrates on studying high rate wireless data transmission for 3rd generation and beyond, modeling/simulations/performance evaluation, novel processing techniques and modulations.
During year 2001, the wireless industry continued preparations for the introduction of 3G services in the United States. Service was finally launched by one company in January 2002, with more companies expected to offer services later in the year. During the same year, researchers associated with the Transceiver Group at NJCWT continued work on a variety of topics related to 3G and beyond wireless networks. Major topics addressed included development of novel coding techniques such as space-time and turbo codes, robust methods for operation over channel with multipath impairments, research into advanced modulations for 4G such as multicarrier OFDM, multicarrier CDMA, ultra-wideband multiuser detection, and link layer techniques for improving performance of wireless networks.
The following topics are being addressed by the Transceiver Group in 2002:
Turbo Coding/Decoding for 3rd Generation Wireless Applications
Kobayashi, Princeton
We will continue to address some practical issues in turbo encoding/decoding for 3rd generation wireless communication applications and pursue some efficient approaches, such as scaling the extrinsic information and bi-directional SOVA to enhance the performances of existing suboptimum low-complexity turbo decoding algorithms. We will investigate the low-power implementation of turbo decoder, evaluate the performances of the above improved algorithms in the HSDPA (high-speed downlink packet access) environment, and develop the potential of space-time turbo coding for coding gain, spectral efficiency and diversity improvement in order to increase the quality and capacity of MIMO wireless systems.
Channel identification and Signal Recovery
Kobayashi, Princeton
We will work on the iterative receiver structure of OFDM systems, where the soft output of a convolutional decoder is used as the input to a channel equalizer, and the channel equalizer in return generates a soft output to be used by the convolutional decoder.
Channel Estimation and PAPR Reduction in OFDM
Kobayashi & Schwartz, Princeton
We will continue to investigate OFDM channel estimation via EM based algorithms and compare this algorithm with other channel estimation methods. This will include the following steps: 1) Apply these algorithms for OFDM systems with multiple antennas; 2) Estimate fast fading or time-varying wireless channels due to mobility since OFDM system performance is largely limited by ICI (Inter-Carrier Interference) caused by time variation of channels in one OFDM frame; 3) Investigate an OFDM system with channel coding to do iterative channel estimation in order to improve the overall system performance. We will also investigate new and effective methods to reduce peak-average power ratio (PAPR) in OFDM Systems. This will include studying complementary coding and other block coding. We will also investigate system performance of OFDM systems subject to nonlinear distortion and to investigate better methods to estimate channels in nonlinear distorted OFDM systems.
Adaptive Modulation in OFDM Systems
S. Schwartz, Princeton
We will continue our study of high data-rate systems such as OFDM and investigate the gains available with adaptive modulation. Errors in the channel model are critical to the processing gain attainable. The two major sources of error are: errors in the estimate, and the time delay involved when estimating the channel and then applying those estimates. We will investigate robust procedures robust for adaptive modulation, as well as the tradeoff between coding and modulation.
Iterative Decoding of Space-time codes in Multiuser Systems
V. Poor, Princeton
This study will combine three of the most promising capacity-increasing techniques in communication systems-namely, turbo processing. Multi-user detection and space-time coding-to produce efficient, iterative algorithms for near-optimal decoding of combined space-time and convolutional codes in multiuser systems will also be introduced into the iterative process.
Novel Receiver Processing Methods for Long Code CDMA Systems
V. Poor, Princeton
We will continue to exploit our new methodology for channel estimation and synchronization of long code CDMA systems. Building on our progress in 2001, the use of these methods for specific signal processing tasks, including synchronization, multi-user detection, and multi-path combining will be considered will be considered in the coming year.
Noncoherent Methods in High Speed Data Communications with Antenna Arrays
V. Poor, Princeton
We will study the spectral inefficiency caused by receiver noncoherence in fading channels with and without diversity and specular components.
Multi-user Transceiver Design for High Spectral Efficiency
S. Verdu, Princeton
We propose to develop new power control laws that require no information about interfering users fading conditions. We will analyze the impact of antenna diversity in the wideband low-power domain. We will also analyze the spectral efficiency potential of multi-user diversity, and design Low-Density Parity -Check code ensembles assuming a successive stripping decoder.
Multi-user Detection in Fading Channels
S. Verdu, Princeton
This study leads to fast adaptive algorithms for linear and nonlinear multi-user detection in the presence of fading. New scalable architectures based on iterative algorithmic structures and multi-user detection for orthogonal frequency division multi-access will be studied.
Adaptive Multi-user Technologies
Y. Bar-Ness, NJIT
The work will concentrate on the improvement of certain algorithms (triangulizer) and its implementation for multi-user separators.
Linear multi-user detection of Randomly spread CDMA
Y. Bar-Ness, NJIT
We intend to examine the performance of such systems using certain approximation tools.
Interference Avoidance in Multiple Base Station Systems
C. Rose, Rutgers
This project examines interference avoidance systems with multiple base station systems. Although the principles of interference avoidance are well understood in the context of a single base station receiver, the important case of multiple receivers has not yet been tackled. In this project, we frame the problem in an information theoretic context through the identification of achievable rate regions. We look to find performance measures analogous to the total squared correlation (TSC) in single base station systems.
CDMA Downlink Interference Suppression and Resource Allocation
R. Yates, Rutgers
The WCDMA (Wideband Code Division Multiple Access) air interface for 3G networks supports a wide variety of services such as speech, video, and high-speed data transmission. However, downlink interference, which usually has few sources (base stations) with relatively high interfering power, is an important limiting factor in system capacity. The purpose of this work is to characterize the downlink interference, such as the dimensionality of the interference subspace at different locations over a cell. This characterization will lead to techniques for interference suppression and resource allocation.
Turbo Space-Time Coded Modulation
A. Haimovich, NJIT
This project focuses on applying turbo space-time coded modulation (turbo-STCM) to wireless communications. We will continue work on layered space-time codes for large number of transmit-receive antennas, develop design principles and evaluate performance. We will study the application of the turbo space-time code to OFDM.
Ultra-Wideband Communications
A. Haimovich, NJIT
Channel measurements using UWB pulses. Study the application of UWB technology to 802.15 -W-PAN standards. Design of UWB transceiver. Extension of jam resistance analysis to M-ary PPM.
Low Power
D. Misra, NJIT
We will work on the Low Power Design of Sensor Array and its Interface Circuits, Controller and Transceivers for Wireless Ad-hoc Networks.
Network Chip
D. Misra, NJIT
We will work on the design of a network chip with a deadlock free routing algorithm for wireless.
Automatic Modulation Recognition
Y. Shi, NJIT
We will work on the automatic modulation recognition of communication signals. It includes carrier frequency estimation, feature extraction and modulation type recognition.
Successive Packing Interleaving for Turbo Codes
Y. Shi, NJIT
We will develop novel interleaving techniques using successive packing approach for Turbo Codes.