Fig. 2
Density overestimation in MHCP model. Nodes around red circle would be retained. The nodes x3 and x4 are retained for they have the lowest mark in their contention domain, and nodes x1, x2, and x5, x6 are retained for they have the second lowest mark in their contention domains, while the corresponding nodes with the lowest mark (x2, x5, x6, x7) are not the one with the lowest mark in their contention domains. A reasonable scheme would retain x3, x4, x1, and x5 or x3, x4, x2, and x6