دانلود رایگان مقاله آنالیز عملکرد بلوک ACK بر اساس ALOHA شکاف دار برای شبکه بی سیم

Abstract

Recently, many variants of Slotted ALOHA (S-ALOHA) have been proposed to solve a problem of performance degradation in wireless networks with long propagation delay. However, they do not consider the effect of retransmission, which also largely degrades performance, and do not provide any analytical model that considers the effect. In this paper, we design a variant of S-ALOHA to support retransmission and derive analytical models that do consider its effect. The designed scheme has a framed structure that starts with a coordinators beacon. The beacon consists of a coordinators timestamp and Block ACKnowledgment (B-ACK). Using the timestamp, a node estimates propagation delay to the coordinator (PDC) in order to reduce guard time while transmitting a packet. Moreover, B-ACK is used to report the results of all transmissions attempted in the previous frame at once. As a result, the designed scheme can largely reduce the number of feedbacks and waste of guard time. Even if there is no analytical model that considers the long propagation delay and retransmission simultaneously, we choose the existing analytical models that consider a framed structure and B-ACK as reference models. However, they are not fully mathematical and partially use simulation results because of high computational complexity. Moreover, these models only analyze stability and throughput as performance metrics. On the other hand, our analytical models are fully mathematical models and can analyze all metrics, such as stability, throughput, and packet delay. We expect our analytical models to be a foundation for deriving fully mathematical models for variants of S-ALOHA using a framed structure and B-ACK.

5. Conclusions

In this paper, we simply designed BAS-ALOHA to support retransmission using B-ACK, and also derived analytical models for BAS-ALOHA for stability, throughput, and packet delay. Through time alignment with the estimated PDC and B-ACK, BAS-ALOHA can reduce guard time caused by large propagation delay, and can be used adequately for long propagation networks. All of our analytical models are fully mathematical, unlike existing models. Through numerical results, we showed the performance of BAS-ALOHA with various parameters: the number of slots in a frame, packet length, p0, and p1. We expect our analytical models to be a foundation for deriving fully mathematical models for variants of S-ALOHA using B-ACK