Cong Shen

Comparison of channel capacity for MIMO-DAS versus MIMO-CAS

This paper proposes a comparative study of MIMO channel capacity for both co-located antenna system (CAS) and distributed antenna system (DAS). In DAS we consider the channel model compassing the Rayleigh fading, log-normal shadowing fading and path loss. We find that different power allocation schemes and different locations of the mobile affect the channel capacity gain of MIMO-DAS significantly, and MIMO-DAS offers large capacity gain over the traditional MIMO-CAS, which is demonstrated in our simulations.

On the performance of V-BLAST with zero-forcing successive interference cancellation receiver

The performance analysis of the zero-forcing successive interference cancellation (ZF-SIC) detector in vertical Bell Labs layered space-time (V-BLAST) is generally considered difficult, mainly because of the nonlinear error propagation effect. In this paper, we first present the nearly exact bit error rate (BER) analysis of ZF-SIC V-BLAST with binary phase-shift keying (BPSK) modulation in the richly scattered Rayleigh-fading multiple-antenna channel. We derive the closed-form expressions of the error probability of each substream under a given number of transmit antennas. We further give a general recursive procedure to calculate the BER of each substream with arbitrary number of transmit and receive antennas. The procedure we give is easy to follow and is feasible in evaluating the BER performance of the V-BLAST with ZF-SIC receiver. It can be further utilized to develop an optimal transmission strategy for the open-loop V-BLAST. Our analytical results show excellent matches with the Monte Carlo simulation results.

Performance improvement of V-BLAST through an iterative approach

This paper proposes an iterative V-BLAST detection algorithm that improves the error performance over error propagation. Traditional detection algorithm cannot alleviate error propagation because the decision feedbacks from low-diversity substreams are used to decode high-diversity substreams. In our algorithm, we iteratively suppress the interference towards low-diversity substreams by using decisions from high-diversity substreams, and the system performance is highly improved over the traditional one, which is demonstrated via simulation results. Besides, existing algorithms combating error propagation operate in high complexity, while the complexity of our algorithm is proportional to the loop times, providing a tradeoff between performance and complexity.

Architecture of a software radio system based on cluster of workstations

Conventional software radio architectures cannot perform signal processing using application level software or have limited capability. To solve these problems, this paper proposes a new architecture that can perform signal processing using application level software on cluster of workstations. This paper introduces key technologies from RF to baseband. Especially, detail designs are given for core technologies of PCI card and parallel processing. Based on these principles, wireless voice communications for four standards are realized on the system. Theory and practice prove that this is a scalable, more ideal software radio and is a promising one with potential.

A novel spectral efficient transmit precoder scheme based on channel feedback

this paper we propose a novel spectral efficient transmit precoder scheme in which channel state information is fully utilized to maximize channel capacity. It is shown that this new scheme provides striking performance that is 3.5-5 dB from the outage capacity at 10% frame error rate even in the uncoded case. Compared with the open-loop scheme V-BLAST, this new scheme can not only maintain the same high bandwidth efficiency, but also achieve much better performance thanks to more effective transmission power allocation and diversity gain. Nearly 7dB gain can be provided by this new scheme over V-BLAST in a (2, 2) system.

A novel spectrally efficient transmit diversity scheme in MIMO-DAS

Regarding the distributed antenna system (DAS) as an extended MlMO system, we present a novel spectrally efficient downlink closed-loop transmit diversity scheme in MlMO-DAS by considering both small scale and large scale fading. We give the performance analysis of our scheme with both ML and MMSE-SlC detectors. We also improve our algorithm to solve some problems of MMSE-SlC detector. Simulation results show that better performance can be achieved with the improved algorithm, and at the same time it maintains the same high spectral efficiency.

A parallel ADC structure for software radio receiver

Nowadays the performance of ADCs still cannot fulfill the high requirement of the wideband receiver, in this paper we are motivated to solve this problem by proposing a parallel A/D scheme in the cellular base station with uniformly distributed channels. This scheme adopts multiple parallel ADCs with low sampling rate and high resolution degree to fulfill the requirement of both high sampling rate and high resolution degree. We believe that this scheme offers great practical value for the software radio system design under state-of-the-art technology.

A novel transmit optimization scheme for MIMO spatial multiplexing systems

In this paper, we propose a new kind of adaptive MIMO signaling scheme. Compared with other adaptive scheme, our approach utilize both the channel state information (CSI) and the constellation of the information streams. We also find that some precoders can be greatly enhanced by the constellation rotation, while others achieve nearly no improvement. We analyze this phenomenon and therefore develop some criteria to generalize the combination of them. Numerical simulations are presented and verify our results.

Adaptive V-BLAST with partial channel state information feedback

We are motivated to improve the performance of Vertical Bell Laboratories Layered Space-Time (V-BLAST) systems by applying link adaptation techniques based on partial channel state information (CSI) feedback. In our scheme, the partial channel state information is the second order statistics that are always available in practical applications. We derive the criteria that decide the optimal transmission policy based on minimum bit error probability. Simulations show that our scheme provides considerable performance gain over traditional V-BLAST transmission scheme. Since the second-order channel statistics varies much more slowly than instantaneous channel realization, the proposed technique would have practical applications in downlink multi-input multi-output (MIMO) systems that exhibit fading correlations between antennas.

Layered reconfiguration management in software radio systems based on general PCS and network

System reconfiguration and resource re-allocation are important issues in software radio systems. They are crucial in realizing multi-band and multi-mode. In this paper, a layered reconfiguration management strategy, which aims at reconfiguring the system more effectively, is proposed and implemented in the software radio systems based on general PCs and network. Relevant issues are discussed in this paper.System reconfiguration and resource re-allocation are important issues in software radio systems. They are crucial in realizing multi-band and multi-mode. In this paper, a layered reconfiguration management strategy, which aims at reconfiguring the system more effectively, is proposed and implemented in the software radio systems based on general PCs and network. Relevant issues are discussed in this paper.