A Study Of Dynamic_tdma_slot_assignment Base On Nodes In Frequecy Hopping

Multiple Access Protocol is called Media Access Control or MAC Protocol, it decides the way in which multiple users share limited channel resource. In a packet radio network, communication process generally is based on single packet, which lasts very short, wireless channel resource is essentially limited and lossy, MAC protocol's performance affects the utility efficiency of wireless channel and the composite capability of whole network, so up to date MAC protocol is still a key technology and hot topic in wireless communication networks.According to the manner of channel resource assignment, the MAC protocols of packet radio networks can be divided into three types:fixed (static), random access and dynamic (on-demand). Fixed type protocols, such as FDMA, TDMA etc, assign determined channel for every connection, are suitable for the networks whose services are average and stable, because of its assured quality of service (QoS) and higher channel efficiency, but this type of protocols are not fit for those networks whose services are bursty. Random access protocols, such as ALOHA, CSMA etc, are suitable for networks whose services are randomly distributed in a lot of users and those services are no-sensitive to time. On-demand protocols, such as pre-reserved, poll etc, can assign channel resources according to every terminal's real-time bandwidth requirement, compared to fixed protocols, this type of protocol has better adaptabilty to burst services. For example, when one node is idle, its bandwidth will be released to avoid channel resourse waste. Compared to random access protocols, on-demand protocols avoid time delay jitter caused by packet collision, back-off and time-out problem. Generally, it is required to design a dedicated control channel in on-demand protocols, by which all users can put forward a request for fixed or random access services.Aiming at the high reliability and mobility of military communication nodes, using cross-layer design for reference, this paper proposes a scheme that implements TDMA dynamic time-slot assignment based on the number of nodes in FH networks, this scheme not only ensues the QoS, but also improves the channel resource efficiency effectively.