Chapter 5 - The IEEE 802.16m Convergence Sub-Layer

Abstract

This chapter provides a description of the functional components and protocols associated with the IEEE 802.16m service-specific Convergence Sublayer (CS). The convergence sublayer is located on top of the IEEE 802.16 MAC sublayer and interfaces the MAC sublayer with the network layer protocols. The convergence sublayers of the IEEE 802.16m and IEEE 802.16-2009 standard have very similar behavior; the only differences are in the assignment and use of connection identifiers in the two standards, as well as exclusion of some unused legacy protocols. The Internet Protocol CS (IPCS) and Generic Packet CS (GPCS) are two types of the service-specific CS that are supported by IEEE 802.16m, which are used to transport packet data over the air interface. When using GPCS, the classification is performed in protocol layers above the CS, and the relevant information for performing classification is transparently provided during connection set-up or change. The Asynchronous Transfer Mode CS (ATM CS) and Ethernet CS variants that were specified in the IEEE 802.16-2009 standard are no longer supported in IEEE 802.16m due to a lack of industry interest. Other air interface standards such as 3GPP LTE also use such logical interfaces between their Layer 2 service access points and the network layer protocols. The Packet Data Convergence Protocol (PDCP) in 3GPP LTE performs ciphering and encryption of the MAC PDUs. This is an important difference between the MAC functions of IEEE 802.16 and 3GPP LTE.