###### Abstract
The issues that reside in MMAC protocols are as follows:  
* _The multi-channel hidden terminal_ occurs when two nodes are busy in the data transmission in one channel and are unaware of control packets sent by other nodes that want to communicate on a particular channel. When these nodes return to the control channel, they might want to communicate on that busy channel, causing a collision [18; 19]. * _The missing receiver_ occurs when the control packets sent to a receiver are not acknowledged due to it being busy in the data transmission with another node [20]. * _Deaftness_ occurs when the intended receiver is busy in the data transmission and ignores the control packets sent to it [21]. Generally, the radio antennas of the wireless nodes can operate in one of two modes, omnidirectional or directional. Nodes using omnidirectional antennas can listen to communications and transmit data in all directions. Using omnidirectional antennas is beneficial since the nodes do not need to direct their antennas in a specific direction for communication. This makes omnidirectional antennas easy to install and less expensive. However, the disadvantage of these antennas is that there is less signal strength, which reduces their range. The chances of collision are also higher in this case because the nodes listen to communications from all directions. On the other hand, nodes using directional antennas can only communicate in a specific direction. Using this antenna provides higher connectivity and a longer range. Moreover, it reduces interference and allows multiple communications in close vicinity without interference. Nevertheless, with directional antennas, nodes have a deafness problem. The overall cost and complexities of these antennas are higher than omnidirectional antennas [22; 23; 24]. The objective of this research is to improve the performance and efficiency of the MMAC protocol and compare it with other protocols with varying factors, namely, the number of stations and channels. The primary contributions of this work are as follows:  
* We propose an enhanced spectrally efficient asynchronous multi-channel MAC (E-SA-MMAC) protocol that utilizes the spectrum efficiently and increases the overall throughput in constrained environments. * The proposed protocol solves the issues of the multi-channel hidden terminal and deafness by using omnidirectionally broadcast control packets. * Further, a second protocol is proposed called Max-E-SA-MMAC, by modifying the backoff algorithm of the E-SA-MMAC, to improve fairness between the nodes. * An adaptive MMAC protocol is proposed; we took advantage of the performance characteristics of the evaluated protocols by opting for the more ideal transmission mechanism in the changing network environments. * An extensive performance evaluation of the proposed algorithms was carried out under three performance metrics--normalized throughput, Jain's fairness index (JFI), and channel access delay. * A full factorial design with analysis of variation (ANOVA) was also performed to analyze the impacts of the factors on the results. The rest of the paper is organized as follows. Section 2 comprises the literature review of different multi-channel MAC protocols that were studied for this research. The proposed solution of this paper is presented in Section 3 followed by the simulation, results, and performance evaluation discussion in Sections 4-6, respectively. Lastly, the conclusion and future work will be presented in Section 7.