Browsing by Author "Zhang, Q. T"

Now showing 1 - 5 of 5

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Interference analysis and outage performance of finite multi-antenna ad hoc networks
(IEEE, 2011-07-04) Chen, J; Zhang, Q. T; Ding, M
In this paper, the aggregate interference in a finite-area multi-antenna wireless ad hoc network is statistically characterized. While most of the existing studies model the spatial distribution of transmit nodes as a Poisson point process in an infinite plane, a binomial point process is adopted here to better characterize the node distribution in a finite area. In the test link, maximum-ratio combining (MRC) is employed at the receiver, whereas spatial multiplexing or transmit antenna selection is employed at the transmitter depending on the availability of limited feedback. Moments of aggregate interference as well as outage probability formulas are obtained. Interestingly, for a finite network, our analysis establishes the optimality of single-stream transmissions in spatial multiplexing with a MRC test receiver, and justifies the use of transmit antenna selection for further enhancing the outage performance with limited feedback. Simulations are provided to corroborate the analysis.
Embargo
Interference statistics and performance analysis of MIMO ad hoc networks in binomial fields
(IEEE, 2012-02-28) Chen, J; Zhang, Q. T; Ding, M
This paper investigates the interference statistics and system performance of a finite multiple-input-multiple-output (MIMO) ad hoc network. A finite network contains a finite number of nodes in a finite region. For such a network, the binomial point process, rather than the ubiquitously employed Poisson point process, is adopted to characterize the spatial node distribution. Reception techniques such as the maximal ratio combining (MRC) and zero forcing (ZF) are employed at the receiver, around which a guard zone is deployed. Either spatial multiplexing or antenna selection is employed at the transmitter side, depending on the availability of feedback. The moment generating functions of the aggregate interference power are first derived, based on which the moments of interference and the outage probability of a test link are obtained. It is shown that the full diversity provided by the channel can be achieved by single-stream transmission, including transmit antenna selection. A network performance measure, i.e., the average network throughput, is also analyzed. Simulations are provided to complement the analysis.
Embargo
Source optimization in MISO Relaying with channel mean feedback: A stochastic ordering approach
(IEEE, 2011-06-05) Ding, M; Zhang, Q. T
This paper investigates the optimum source transmission strategy to maximize the capacity of a multiple-input single-output (MISO) amplify-and-forward relay channel, assuming source-relay channel mean feedback at the source. The challenge here is that relaying introduces a nonconvex structure in the objective function, thereby excluding the possible use of previous methods dealing with mean feedback that generally rely on the concavity of the objective function. A novel method is employed, which divides the feasible set into two subsets and establishes the optimum from one of them by comparison. As such, the optimization is transformed into the comparison of two nonnegative random variables in the Laplace Transform order, which is one of the stochastic orders. It turns out that the optimum transmission strategy is to transmit along the known channel mean and its orthogonal eigenchannels. The condition for rank-one precoding (beamforming) to achieve capacity is also determined. Our results subsume those for traditional MISO precoding with mean feedback.
Embargo
Stochastic precoding for MISO interference channels with channel mean feedback
(IEEE, 2012-03-05) Ding, M; Zhang, Q. T
This work considers linear precoding strategies for multiple-input single-out (MISO) interference channels with channel mean feedback at transmitters, where the interference at each receiver is treated as additive noise. The challenge here is that previous precoder designs with perfect channel state information (CSI) at transmitters do not apply and new approaches are required. Based on the Laplace transform order, an altruistic non-equilibrium strategy, i.e., the stochastic zero forcing, is first proposed under practical assumptions, generalizing the traditional zero forcing which requires perfect CSI. Interestingly, the precoding matrices here are all rank-one beamformers as in the traditional zero forcing. The competitive use of the common physical media in MISO interference channels is also formulated as a strategic noncooperative game. In contrast to the perfect CSI case with a unique rank-one Nash equilibrium, with channel mean feedback, the Nash equilibria here are not necessarily rank-one in general. Nevertheless, when achieved by the rank-one beamforming, the equilibrium is unique and convenient for implementation. Accordingly, the condition for beamforming to achieve the equilibrium is derived. Comparisons of the above two strategies reveal no overall dominance of one over the other, thereby establishing stochastic zero forcing as an alternative to the Nash equilibrium designs.
Embargo
Transmit precoding in a noncoherent relay channel with channel mean feedback
(IEEE, 2012-01-05) Ding, M; Zhang, Q. T
This paper investigates the optimal source transmit precoding to maximize the ergodic mutual information between the input and the output of a noncoherent amplify-and-forward relay channel, with multiple antennas at the source and with a single antenna at both the relay and the destination. It is assumed that only the source-relay channel mean information is available at the source. The challenge here is that relaying introduces a nonconvex structure in the objective function. Therefore, previous methods dealing with channel mean feedback, which generally require the concavity of the objective function, cannot be applied. To circumvent the difficulty at hand, a different approach based on stochastic ordering is employed. The stochastic optimization problem here is ultimately transformed into the comparison of two nonnegative random variables in the Laplace transform order. It is shown that the optimal source transmit strategy is to transmit along the known channel mean and its orthogonal eigen-channels. Our result subsumes as an asymptotic case the optimal precoding for multiple-input single-output (MISO) channels without relaying under mean feedback. Furthermore, the analysis can be partially extended to the case with multiple antennas at the relay. Numerical examples are provided to complement and corroborate the analysis.