Mobile operators are today facing the daunting challenge of providing cheap and valuable services to ever more demanding customers. As a matter of fact, mobile standards have not yet really addressed this expectation of open, cheap and flexible web oriented internet access. As an alternative, we introduced an IP-centric QoS model mainly inspired by IP policies commonly found in fixed networks. In the present paper we further describe a possible cross-layer design for this model. Some implementation challenges have been highlighted, together with possible solutions implying only minor modifications in evolved Node B, and none in terminals. Performances of this proposal compared to various implementations of the 3GPP QoS model have been evaluated using the ns-3 simulator in realistic scenarios. Some good properties of our IP-centric proposal compared to the standardized QoS model have been brought into evidence.