# MAC Protocols for mmWave Communication: A Comparative Survey +
## 2 Existing Surveys  
In recent years, there have been several advancements in the MAC layer, matched by the progress in the available MAC protocols that operate at mmWave frequencies, as shown in Table 1. [PERSON] et al. [13] primarily studied WPAN related MAC protocols. In particular, they examined the IEEE 802.11 ad and IEEE 802.15.3c standards for the 60 GHz band focusing on carrier sense multiple access/collision avoidance (CSMA/CA), memory-guided directional MAC (MD-MAC), and time division multiple access (TDMA) protocols. These protocols consist of a contention access period (CAP), channel time allocation period, piconet controller (PNC), and beacon period. Moreover, a significant amount of their work involves device to device (D2D) communication, PHY layer techniques, and wireless backhaul.  
[PERSON] et al. presented a study of an interference management from a multi-input multi-output (MIMO) perspective, and described in general 5G network structures and partially described evolution of wireless technologies from a MAC perspective in [2]. [PERSON] et al. [10] conducted a supplementary study and addressed MAC layer issues in mmWave cellular networks, such as initial access, mobility management, resource block channelization, and different directional control mechanisms in the PHY layer of a mmWave band. In contrast, [PERSON] et al. [14] addressed various multiplexing techniques, and mmWave based PHY layer aspects, and reviewed the changes required in the MAC layer of a mmWave system to support its PHY layer adjustments. [PERSON] et al. [15] pointed out other common but important mmWave communication MAC design issues. Furthermore, they highlighted various IEEE standards used in the MAC layer of mmWave communication and addressed the collision and deafness problems of CSMA, TDMA, and ALOHA protocols.  
In [16], [PERSON] studied directional mmWave wireless systems for next-generation MAC approaches. In addition, [PERSON] et al. in [17] addressed MAC issues of various IEEE standards, channel access over multiple channels, interference mitigation, and reviewed the cross-layers between PHY and MAC layers. In [18], a compilation of the mmWave communications MAC protocols and scheduling systems for ad hoc networks, mesh networks, WPANs, and cellular networks from the literature were presented. They categorized their efforts into four areas; PHY layer, MAC layer, network layer, and cross-layer optimization. Furthermore, in [19], [PERSON] et al. conducted an in-depth study on MAC protocols for both mmWave and THz bands wireless networks. They also numerically analyzed the delay, network throughput, outage probability, and fairness index with varying node density.  
Similarly, [PERSON] et al. investigated existing communication protocols, strategies, and mechanisms, as well as 5G communication standard elements that help management of wireless technology with cohabitation [20]. They concentrate on access layer solutions for unlicensed frequency bands. Moreover, they also believe that resource sharing should be expanded to include not only spectrum management but also physical system management.  
[PERSON] et al. [21] mostly investigated the fundamentals of MIMO and mmWave, and subsequently analyzed some multiple access protocols for 5G wireless networks. Finally, in [22], we illustrated a simplified overview of mmWave protocols, focusing only on centralized MAC protocols as the primary part of this survey.