Article

Achievable Rates and Scaling Laws of Power-Constrained Wireless Sensory Relay Networks

Dept. of Electr. Eng., Arizona State Univ., Tempe, AZ
IEEE Transactions on Information Theory (Impact Factor: 2.62). 10/2006; DOI: 10.1109/TIT.2006.880029
Source: DBLP

ABSTRACT A wireless sensory relay network consists of one source node, one destination node and multiple intermediate relay nodes. In this paper, we study the achievable rates and the scaling laws of power-constrained wireless relay networks in the wideband regime, assuming that relay nodes have no a priori knowledge of channel-state information (CSI) for both the backward channels and the forward channels. We examine the achievable rates in the joint asymptotic regime of the number of relay nodes n, the channel coherence interval L, and the bandwidth W (or the SNR per link rho). We first study narrowband relay networks in the low SNR regime. We investigate a relaying scheme, namely amplify-and-forward (AF) with network training, in which the source node and the destination node broadcast training symbols and each relay node carries out channel estimation and then applies AF relaying to relay information. We provide an equivalent source-to-destination channel model, and characterize the corresponding achievable rate. Our findings show that when rhoL, proportional to the transmission energy in each fading block, is bounded below, the achievable rate has the same scaling order as in coherent relaying, thus enabling us to characterize the scaling law of the relay networks in the low SNR regime. We then generalize the study to power-constrained wideband relay networks, where frequency-selective fading is taken into account. Again, the focus is on the achievable rates by using AF with network training for information relaying. In particular, we examine the scaling behavior of the achievable rates corresponding to two power allocation policies across the frequency subbands at relay nodes, namely, a simple equal power allocation policy and the optimal power allocation policy. We identify the conditions under which the scaling law of the wideband relay networks can be achieved by both power allocation policies. Somewhat surprising, our findings indicate that these two power allocati-
-
on policies result in achievable rates of the same scaling order, and the scaling law can be characterized under the condition that L/W, proportional to the energy per fading block per subband, is bounded below, and that W is sublinear in n

0 Bookmarks
 · 
109 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we investigate the effect of channel estimation errors on the capacity of amplify-and-forward cooperative relay systems. Since an exact capacity expression in the presence of channel estimation errors is difficult to be found, we turn to derive its lower bound instead. Accordingly, by maximizing the derived lower bound, we propose power allocation schemes for both single-relay and multi-relay systems. For single-relay systems, an analytical solution for inequality constrained problem is too complicated to be obtained. Thus, we propose a gradient descent algorithm with a log-barrier function to solve the inequality constrained problem. For multi-relay systems, in terms of the channel estimates and the corresponding mean-squared errors, we provide a water-filling solution for the optimal power allocation among the relays. Simulation results show that the proposed power allocation schemes yield capacity gain compared with equal power allocation at low to medium signal-to-noise ratios.
    Global Communications Conference (GLOBECOM), 2012 IEEE; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel representation for a two-hop decentralized wireless relay network (DWRN) is proposed, where the relays operate in a completely distributive fashion. The modeling paradigm applies an analogous approach to the description method for double-directional multipath propagation channels and takes into account finite system spatial resolution and extended relay listening/transmitting time. Specifically, the double- and single-directional information azimuth spectra (IAS) are formulated to provide a compact representation of information flows in the DWRN. The proposed analytical framework is then studied from a geometry-based statistical modeling perspective. Finally, we look into the problem of relay network tomography (RNT), which solves an inverse problem to infer the internal structure of an unknown relay network by using the double-directional IAS recorded at multiple measuring nodes exterior to the relay region. Numerical examples are presented to demonstrate the efficacy of the suggested channel description method and the RNT algorithm.
    IEEE Transactions on Vehicular Technology 01/2012; 61(2):455-465. · 2.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In wireless networks, the use of cooperation among nodes can significantly improve capacity and robustness to fading. However, many cooperation techniques have been developed for operation in narrowband systems for high signal-to-noise ratio (SNR) applications. It is important to study how relay networks perform in a wideband regime, where the available degrees of freedom is large and the resulting SNR per degree of freedom is small. In this paper, taking into account wideband transmissions with fixed power (W → ∞), we investigate the achievable rates and scaling laws of bursty amplify-and-forward relay networks in the wideband regime. Specifically, our results allow us to understand the effect of different system parameters on the achievable rates and scaling laws in the wideband regime, and highlight the role of bursty transmissions in this regime. We identify four scaling regimes that depend on the growth of the number of relay nodes and the increase of burstiness relative to the SNR. These results can serve as design guidelines to indicate when bursty transmissions are most useful.
    Proceedings of the 2009 IEEE conference on Wireless Communications & Networking Conference; 04/2009

Full-text

Download
0 Downloads
Available from