tailieunhanh - Mobil Ad Hoc Networks Protocol Design Part 12

Tham khảo tài liệu 'mobil ad hoc networks protocol design part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 432 Mobile Ad-Hoc Networks Protocol Design The authors proposed a kind of clustering scheme to group nodes where each cluster employs a different spreading code under a CDMA scheme. Within clusters the channel was time-slotted to deterministically allocate channel access opportunities for each node. Hence the channel capacity could be measured in terms of time slots. Additionally time slots may be reserved as a way of promising channel capacity to individual data sessions. The ideas in 57 were taken further by Lin et al 30 wherein they devised a detailed algorithm for calculating a path s residual traffic capacity seemingly filling in the gaps in detail left by 57 . Similar to the aforementioned work they propose using a CDMA over TDMA network. The channel is time-slotted accordingly but several communicating pairs can share a time slot by employing different spreading codes. A path s capacity is expressed in terms of free time slots. Route discovery is based again on DSDV 58 . Routing updates are used to refresh the free slots information in routing tables. The proposed algorithm first calculates the best combination of free slots on the path for maximum throughput and then attempts to reserve them for a particular data session. In brief the algorithm deals with nodes in groups of three. Below each node we show the time slots that were free prior to a data session being admitted. In this case the same six slots were free at each node. At a first trivial glance it appears that the path capacity is six slots. This illustrates that nodes must have some common free slots to communicate but if all nodes have the same set of free slots the efficiency of utilisation is not very high. Then the effective path capacity usable by a new session is only two slots despite six being initially free at each node. Once the available time slots and path capacity have been determined reservation signaling takes place to reserve the necessary time slots for satisfying the requesting .