<bold>A Distributed Fairness Algorithm for Bus-Based Metropolitan Optical Network</bold>

In this paper, we focus in the performance of asynchronous Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol with variable packet sizes. We examine the fairness issue arising between ring nodes sharing a common data channel and show that the asynchronous CSMA/CA protocol suffers from bandwidth fragmentation and positional priority fairness problems. The paper provides the phenomenon of bandwidth fragmentation represents the most important issue in asynchronous CSMA/CA protocol because it leads to bandwith waste and, thus, increase unfairness for certain ring nodes. In this regard, we explore limitations of a previous proposed solution, the so-called Traffic Control Architecture using Remote Descriptors (TCARD). Afterwards, we present an algorithm, called Smart sPACEd tranSmission (SPACES), which deals with the aforementioned fairness problems. The devised scheme is based on a statistical and fully-distributed mechanism to great fair access to shared resources. As illustrated in this article, SPACES alleviates performance degradation and resources underutilization while achieving unfairness among ring nodes.