We study the limits of cooperative coverage extension for multicast transmission in heterogeneous machine to machine networks. Terminals are equipped with both a long range interface, through which they connect to, e.g., a cellular network or satellite system, and a short range interface, which is used to create an ad-hoc capillary network among the terminals. Such a network is intended to enhance coverage by means of properly encoded cooperative transmissions. By applying the max-flow min-cut theorem we derive an analytical lower bound on the coverage as a function of both the information rate at physical layer and the rate of innovative packets per unit-time. Our results give the tradeoff between the coverage and the rate at which the information can be injected in the network, and at the same time quantify the gain derived from cooperation and give hints on how to tune important system parameters.
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