Throughput Scaling in Wideband Sensory Relay Networks: Cooperative Relaying, Power Allocation and Scaling Laws
Mathematics of Relaying and Cooperation in Communication Networks
April 10,2006 11:30 AM to 12:00 PM
Speakers:
Zhang, Junshan
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Abstract: |
A sensory relay network consists of one source node, one destination node and many relay nodes. We investigate the achievable rates and the scaling laws of power- constrained sensory relay networks in the wideband regime, assuming that relay nodes have no a priori knowledge of channel state information.
We first study narrowband relay networks in the low SNR regime. We examine the achievable rates in the joint asymptotic regime of the number of relay nodes n, the channel coherence interval and the SNR per link. We propose an information relaying scheme, namely amplify-and-forward (AF) with network training, in which each relay node carries out channel estimation and then uses AF relaying to relay data. We provide an equivalent source-to-destination channel model, and characterize the corresponding achievable rate. Our findings show that when 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. We then generalize the study to power-constrained wideband relay networks, where frequency-selective fading is accounted for. 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 applied 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 allocation policies result in achievable rates of the same scaling order, and the scaling law can be characterized under the condition that the energy per fading block per subband is bounded below and that the bandwidth W is sub-linear in n.
We will also talk about our ongoing work on the tradeoff between sensing and communications, and discuss cooperative routing in multi-hop relay networks. |
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