This paper describes a comprehensive system architecture that enables mobile-to-mobile communications for the purpose of enhancing the capacity of the cellular network.The architecture is developed using LTE Release-10 as the baseline. The impact on the protocol stack is discussed in detail. Neighbor discovery mechanisms are described to enable users to identify potential helper mobiles to enable a cooperative mobile relay. Resource partitioning for the mobile to-mobile link is detailed and changes to the design of the HARQ entity structure and timing are discussed.