Efficient design and implementation of LTE UE link-layer protocol stack

3GPP Long Term Evolution (LTE) and its enhancement has become the main candidate of 4G standards. Due to the requirements on high data rate and low latency for broadband wireless communication systems, LTE air-interface protocol stack must be designed and implemented with high data processing efficiency. Following a general description of the LTE user equipment (UE), this paper analyzes the main challenges in the link-layer protocol stack design and implementation, including the data processing efficiency, synchronization, flexibility and portability. A reference design of LTE UE link-layer protocol stack software is then presented with several design methodologies. A memory access optimization and light-weighted thread model are proposed to improve the data processing efficiency, while a hardware triggered synchronization mechanism is exploited to maintain synchronous between the link-layer protocol stack and the physical layer. Finally, the platform flexibility and portability is achieved by employing interface abstraction and adapters. Extensive system level testing shows that the proposed LTE UE protocol stack software achieves high data rate and low data processing latency in a hardware resource restricted platform, which can be further extended to commercial LTE UE products.