Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> TDMA Improvement Technology Based on 802.11 <s> We implement a new software-based multihop TDMA MAC protocol (Soft-TDMAC) with microsecond synchronization using a novel system interface for development of 802.11 overlay TDMA MAC protocols (SySI-MAC). SySI-MAC provides a kernel independent message-based interface for scheduling transmissions and sending and receiving 802.11 packets. The key feature of SySI-MAC is that it provides near deterministic timers and transmission times, which allows for implementation of highly synchronized TDMA MAC protocols. Building on SySI-MAC's predictable transmission times, we implement Soft-TDMAC, a software-based 802.11 overlay multihop TDMA MAC protocol. Soft-TDMAC has a synchronization mechanism, which synchronizes all pairs of network clocks to within microseconds of each other. Building on pairwise synchronization, Soft-TDMAC achieves tight network-wide synchronization. With network-wide synchronization independent of data transmissions, Soft-TDMAC can schedule arbitrary TDMA transmission patterns. For example, Soft-TDMAC allows schedules that decrease end-to-end delay and take end-to-end rate demands into account. We summarize hundreds of hours of testing Soft-TDMAC on a multihop testbed, showing the synchronization capabilities of the protocol and the benefits of flexible scheduling. <s> BIB001 </s> Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> TDMA Improvement Technology Based on 802.11 <s> Wireless mesh networks in general, and WiFi mesh networks in particular, offer a cost-effective option to provide broadband connectivity in sparse regions. Effective support for real-time as well as high throughput applications requires a TDMAbased approach. However, multihop TDMA implementations in wireless have been few and far-between, and for good reasons. These present significant issues in terms of time synchronization, TDMA schedule dissemination, multichannel support, routing integration, spatial reuse and so on. And achieving these efficiently, in the face of wireless channel losses presents a formidable challenge. In this work, we present an implementation of LiT MAC, a full-fledged multihop TDMA MAC, on commodity WiFi platforms. We undertake extensive evaluations using microbenchmarks as well as application level performance, using outdoor as well as indoor testbeds. We also present an integration of LiT MAC with various routing metrics, and a routing stability study of recently proposed routing metrics (ROMA, SLIQ). Our results show that we can achieve μs granularity time synchronization across several hops, and TDMA slot size as small as 2 ms. These imply low control overheads. Experiments over several days, on our nine-node outdoor testbed shows that LiT MAC's soft-state-based approach is effective in robust operation even in the presence of significant external interference. <s> BIB002 </s> Survey of Media Access Control (MAC) and Routing Technologies of WiFi-MESH wireless Network <s> TDMA Improvement Technology Based on 802.11 <s> Time Division Multiple Access (TDMA) MAC protocol in WiFi-based Long Distance (WiLD) networks has proved to be suitable solution in supporting long distance communications. Open source Atheros driver in Linux environment is found to be a flexible platform for implementing TDMA in WiLD networks. The earlier developments over this open source driver is limited to 802.11 a/b/g standards. But, ath9k device driver support is required for the latest 802.11n standard. In this paper, we build a TDMA-based MAC protocol using ath9k driver to achieve long distance communications. The various steps in implementing the protocol is discussed. Also, we examine the performance of the implemented protocol over point-to-point link. <s> BIB003
Moraes  proved the feasibility of introducing TDMA technology to 802.11 system firstly, and ROSALNet  , roadside Mesh network  , Driver level implementation of TDMA MAC in long distance WiFi BIB003 and other actual cases of application have further proved that, there are lower delay and jitter, and more robust characteristics in the WiFi-Mesh Wireless Network based on TDMA, and it is more suitable for longer distance and provides better support for mobility. The difficulty of implementation of TDMA lies on synchronization accuracy problem. Djukic BIB001 put forward a protocol named Soft-TDMAC, which realizes synchronization amid nodes via phase-locked loop. It realizes intense synchronization, downgrades errors and upgrades accuracy and allocation efficiency in the whole network through establishing synchronization tree with minimum hops in the whole network, but its reliability is low. Literature BIB002 discusses the theory of LiT-MAC and the procedure of implementation. This method raises the reliability of synchronization and take considerations of transmission with long distance and multichannel. However, the capacity of anti-interference is relatively low. Moreover, it needs united and concentrated supervisors for time scheduling. From a practical point of view, the current common practice to support the TDMA is based on modifying 802.11 protocol, namely these systems cannot communicate with other 802.11 systems seamlessly, and the system flexibility is reduced. The versatility of system will be significantly improved if the Soft-ware-Defined Networking (SDN) was adopted and a united layer was added for control to implement TDMA without changing the original structure. In addition, the timing accuracy will be raised if Precise Time Protocol (PTP) and some new technologies were utilized.