Minimizing flow time in the wireless gathering problem

We address the problem of efficient data gathering in a wireless network through multihop communication. We focus on two objectives related to flow times, that is, the times spent by data packets in the system: minimization of the maximum flow time and minimization of the average flow time of the packets. For both problems we prove that, unless P=NP, no polynomial-time algorithm can approximate the optimal solution within a factor less than O(m^{1-e}) for any 0