specific CS resides on top of the MAC CPS and utilizes the services provided by the MAC CPS through the MAC SAP (service access point). It performs the following functions [2,3]: Accept higher-layer protocol data units (PDUs) and classify them. Deliver CS PDUs to the appropriate MAC SAP and receive CS PDUs from the peer entity. Next Generation Mobile Communications Ecosystem The standard has defined two CS specifications for mapping services to and from the MAC connections: the asynchronous transfer mode (ATM) CS and the packet CS. ATM CS: The ATM CS is the logical interface that links the different ATM services with the MAC CPS service access point. The ATM CS accepts ATM cells from the ATM layer and delivers the CS PDUs to the appropriate MAC SAP. It is specifically defined to support the convergence of PDUs generated by the ATM layer protocol of an ATM network. Since ATM cell streams are generated according to the ATM standards, no ATM CS service primitive is required. Packet CS: The packet CS is used for transport of packet-based protocols such as Internet Protocol (IP), Point-to-Point Protocol (PPP), and IEEE Std 802.3 (Ethernet). The packet CS performs the following key functions: Classification of the higher-layer protocol PDU into the appropriate connection. Delivery of the resulting CS PDU to the MAC SAP associated with the service flow for transport to the peer MAC SAP and receipt of the CS PDU from the peer MAC SAP. 4.2.1.2 MAC Common Part Sublayer (MAC CPS) The MAC CPS provides the core MAC functionality to support broadband applications. The functionality includes system access, bandwidth allocation, connection establishment, and connection maintenance. The MAC is connection-oriented which means that all services, even those that are inherently con- nectionless are mapped to a connection. This provides a mechanism for requesting the core functions, associated QoS, and transporting and routing data to the appropriate convergence sublayer. The connec- tions are referenced with 16-bit connection identif