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: A Survey of Mobile WiMAX IEEE 802.16m Standard 
Chapter Title:  INTRODUCTION 
1. Abstract of Cited Paper (BIB001):  This paper provides an overview of the emerging antenna features that are the technologies for inclusion in the initial release of Mobile WiMax, and examines the various application areas of these techniques as well as the advantages and limitations each are likely to possess. 
2. Abstract of Cited Paper (BIB002):  In order to meet the requirements of 4G mobile networks targeted by the cellular layer of IMT-advanced, next generation mobile WiMAX devices based on IEEE 802.16m will incorporate sophisticated signal processing, seamless handover functionalities between heterogeneous technologies and advanced mobility mechanisms. This survey provides a description of key projected features of the physical (PHY) and medium access control (MAC) layers of 802.16m, as a major candidate for providing aggregate rates at the range of Gbps to high-speed mobile users. Moreover, a new unified method for simulation modeling, namely the evaluation methodology (EVM), introduced in 802.16m, is also presented.

Literature Review:
IEEE 802. BIB003 , a solution to broadband wireless access (BWA) commonly known as Worldwide Interoperability for Microwave Access (WiMAX), is a recent wireless broadband standard that has promised high bandwidth over long-range transmission. The standard specifies the air interface, including the medium access control (MAC) and physical (PHY) layers, of BWA. The key development in the PHY layer includes orthogonal frequency-division multiplexing (OFDM), in which multiple access is achieved by assigning a subset of subcarriers to each individual user BIB001 . This resembles code-division multiple access (CDMA) spread spectrum in that it can provide different quality of service (QoS) for each user; users achieve different data rates by assigning different code spreading factors or different numbers of spreading codes. In an OFDM system, the data is divided into multiple parallel substreams at a reduced data rate, and each is modulated and transmitted on a separate orthogonal subcarrier. This increases symbol duration and improves system robustness. OFDM is achieved by providing multiplexing on user's data streams on both uplink and downlink transmissions. Lack of mobility support seems to be one of the major hindrances to its deployment compared to other standards such as IEEE 802.11 WLAN, since mobility support is widely considered as one of the key features in wireless networks. It is natural that the new IEEE 802.16e released earlier this year has added mobility support. This is generally referred to as mobile WiMAX BIB001 . Mobile WiMAX adds significant enhancements: • It improves NLOS coverage by utilizing advanced antenna diversity schemes and hybrid automatic repeat request (HARQ). • It adopts dense subchannelization, thus increasing system gain and improving indoor penetration. • It uses adaptive antenna system (AAS) and multiple input multiple output (MIMO) technologies to improve coverage BIB002 . • It introduces a downlink subchannelization scheme, enabling better coverage and capacity trade-off   . This paper provides an overview of Mobile WiMAX standards and highlights potential problems arising from applications. Our main focuses are on the PHY layer, MAC layer specifications of mobile WiMAX. We give an overview of the MAC specification in the IEEE 802.16j and IEEE802.16m standards, specifically focusing the discussion on scheduling mechanisms and QoS provisioning. We review the new features in mobile WiMAX, including mobility support, handoff, and multicast services. We discuss technical challenges in mobile WiMAX deployment. We then conclude the paper.