Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> MAC Layer Mechanism <s> The medium-access control (MAC) protocol is one of the key components in wireless local area networks (WLANs). The main features of a MAC protocol are high throughput, good fairness, energy efficiency, and support priority guarantees, especially under distributed contention-based environment. Based on the current standardized IEEE 802.11 distributed coordination function (DCF) protocol, this paper proposes a new efficient collision resolution mechanism, called GDCF. Our main motivation is based on the observation that 802.11 DCF decreases the contention window to the initial value after each success transmission, which essentially assumes that each successful transmission is an indication that the system is under low traffic loading. GDCF takes a more conservative measure by halving the contention window size after c consecutive successful transmissions. This "gentle" decrease can reduce the collision probability, especially when the number of competing nodes is large. We compute the optimal value for c and the numerical results from both analysis and simulation demonstrate that GDCF significantly improve the performance of 802.11 DCF, including throughput, fairness, and energy efficiency. In addition, GDCF is flexible for supporting priority access by selecting different values of c for different traffic types and is very easy to implement it, as it does not requires any changes in control message structure and access procedures in DCF. <s> BIB001 </s> Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> MAC Layer Mechanism <s> The performance of the distributed coordination function (DCF) of the IEEE 802.11 protocol has been shown to heavily depend on the number of terminals accessing the distributed medium. The DCF uses a carrier sense multiple access scheme with collision avoidance (CSMA/CA), where the backoff parameters are fixed and determined by the standard. While those parameters were chosen to provide a good protocol performance, they fail to provide an optimum utilization of the channel in many scenarios. In particular, under heavy load scenarios, the utilization of the medium can drop tenfold. Most of the optimization mechanisms proposed in the literature are based on adapting the DCF backoff parameters to the estimate of the number of competing terminals in the network. However, existing estimation algorithms are either inaccurate or too complex. In this paper, we propose an enhanced version of the IEEE 802.11 DCF that employs an adaptive estimator of the number of competing terminals based on sequential Monte Carlo methods. The algorithm uses a Bayesian approach, optimizing the backoff parameters of the DCF based on the predictive distribution of the number of competing terminals. We show that our algorithm is simple yet highly accurate even at small time scales. We implement our proposed new DCF in the ns-2 simulator and show that it outperforms existing methods. We also show that its accuracy can be used to improve the results of the protocol even when the terminals are not in saturation mode. Moreover, we show that there exists a Nash equilibrium strategy that prevents rogue terminals from changing their parameters for their own benefit, making the algorithm safely applicable in a complete distributed fashion <s> BIB002 </s> Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> MAC Layer Mechanism <s> CSMA with Enhanced Collision Avoidance (CSMA/ECA) uses a deterministic backoff after successful transmissions to significantly reduce the number of collisions. This paper assesses by means of simulations the throughput and conditional collision probability obtained from a single-hop ad-hoc network using CSMA/ECA. A comparison with the legacy CSMA/CA reveals that the proposed protocol outperforms the legacy one in all considered scenarios. Specifically, it is shown that CSMA/ECA presents advantages for both rigid and elastic flows. <s> BIB003 </s> Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> MAC Layer Mechanism <s> In this paper, we propose a Semi-Random Backoff (SRB) mechanism to combat network collisions for 802.11 DCF/EDCA in wireless LANs. SRB is fundamentally different from traditional random backoff methods because it provides a form of resource reservation at no extra cost. The key idea of SRB is to set the backoff counter to a deterministic value upon a successful transmission. This allows a station to reuse a time slot in consecutive backoff cycles without colliding with other stations, thus achieving resource reservations. In cases of failed transmissions due to network collisions or channel errors, SRB automatically reverts to the standard random backoff method. SRB can be readily applied to both 802.11 DCF and 802.11e EDCA networks with minimum modification to the existing DCF/EDCA implementations. Theoretical analysis and simulations are conducted to evaluate this new method and our results validate its good performance in small to middle-sized 802.11 wireless LANs. <s> BIB004 </s> Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> MAC Layer Mechanism <s> Distributed medium access control (MAC) protocols are proposed for wireless networks assuming that one-hop peers can exchange a small amount of state information periodically. Each station maintains a state and makes state transitions and transmission decisions based on its state and recent state information collected from its one-hop peers. A station can adapt its packet length and the size of its state space to the amount of traffic in its neighborhood. It is shown that these protocols converge to a steady state, where stations take turns to transmit in each neighborhood without collision. An important consequence of this work is that using such protocols, an efficient time-division multiple access (TDMA) like schedule can be formed in a distributed manner, as long as the topology of the network remains static or changes slowly with respect to the execution of the protocol. <s> BIB005
MAC Layer mechanism of 802.11 is based on CSMA/CA Mechanism conventionally. The CSMA/CA mechanism is simple and stable in the low loading network, while it may lead to node collision, unfairness, unpredictable and unstable problems in the high loading network. Scholars have provided a lot of approaches of improvement about CSMA/CA, but these approaches cannot solve the above problems in essence. From another opinion, some scholars introduce mechanisms of TDMA to Protocol 802.11, which could guarantee transmission of data without collision effects, to make systems adapt to outdoor environment and long-range multiple hop transmission. Improvement of the Fairness of CSMA/CA Mechanism 1) The Contention Window Adjustment Method BIB001 . The method can raise the capacity in long term by banning reset value of contention window reaching the least, but it fails to consider the short term fairness which makes some of the nodes suffer continuous collision and be forced to stay in the period of backoff for a long time. 2) Adjustment of Competitive Parameter BIB002 . This method can raise the capacity and gives consideration to fairness by the estimation of competitors (users) and adjustment of competition parameter. However, it complicate the communication, and would greatly downgrade the accuracy of estimation mentioned above especially when errors appear during such process. 3) Deterministic Backoff. This kind of methods turn the random mechanism of backoff into some definite mechanism mechod to almost reach non-collision transmission. Literature BIB003 and BIB004 put forward a method (CSMA/ECA) for deterministic backoff; Literature BIB005 considers fairness and the multi-hop character further, but the users in the system can not exceed the fixed quantity due to the deterministic backoff level; Literature  puts forward a method of sluggishly deterministic backoff. These methods mentioned can increase the capacity of the system through modification of CSMA/ECA, and assure further long-term fairness in the process of communication with the combination of fair-share strategy. At present, some methods have been implemented in software and hardware, and they are expected to be accepted by the 802.11 standards. However, it is worth considering that the methods mentioned above mainly consider backoff mechanisms of CSMA/CA and fairness issues, they cannot fundamentally solve the problem of data collision, and are limited to enhance throughput capacity in case of large capacity users.