You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Hardware Decoders for Polar Codes: An Overview 
Chapter Title:  C. Memory-Efficient BP Decoders 
1. Abstract of Cited Paper (BIB001):  Polar codes have become increasingly popular recently because of their capacity achieving property. In this paper, a memory efficient stage-combined belief propagation (BP) decoder design for polar codes is presented. Firstly, we briefly reviewed the conventional BP decoding algorithm. Then a stage-combined BP decoding algorithm which combines two adjacent stages into one stage and the corresponding belief message updating rules are introduced. Based on this stage-combined decoding algorithm, a memory-efficient polar BP decoder is designed. The demonstrated decoder design achieves 50% memory and decoding latency reduction in the cost of some combinational logic complexity overhead. The proposed decoder is synthesized under TSMC 45nm Low Power CMOS technology. It achieves 0.96 Gb/s throughput with 14.2mm ::: 2 ::: area when code length N=2 ::: 16 ::: which reduces 51.5% decoder area compared with the conventional decoder design.

Literature Review:
It was observed in BIB001 that, if a single-column decoder follows a round-trip schedule, N messages instead of 2N need to be updated each time. Thus, the memory requirement is reduced in half. In BIB002 , two adjacent columns are combined into one so that intermediate messages need not to be stored. However, the corresponding message updating rules have to be modified accordingly. As a result, the overall memory usage is significantly reduced, at the cost of some combinational logic overhead.