ժҪ Ϊ�������ϵͳ�������ӳٺ���������,��Ӧ�������ϵ�IEEE-1394b��������ϵͳ�����˴���Ԥ�����ƺ�ƽ����Ӧʱ��ȹؼ����Եķ���.����IEEE-1394bЭ��Ĵ���Ԥ������,����˵�ʱ���ݴ�����첽���ݴ���ķ�������(QoS,Quality of Service)���������(ӲQoS).��QoS��������Ƶĵ�ʱ���첽�����ϵ������,�����Ŷ��۽�����IEEE-1394b�첽�����QoS����(��QoS),�õ��˺�����Ӧ���ʱ��,IEEE-1394b�첽������е�ƽ����Ӧʱ��.���ͨ��IEEE-1394b��������ʵ��ϵͳ������IEEE-1394b��QoS��������,��֤�����۷������.��IEEE-1394b������QoS����ƾ���һ����ָ������.
In order to solve the problem of network delay and information obstacle in avionics system, the key characteristics which are bandwidth reservation mechanism and average response time of IEEE-1394b fiber optical bus system used in avionics system were analyzed. The equation which the QoS (quality of service)of isochronous data transfer and asynchronous data transfer must satisfy was derived (hard QoS) on the ground of bandwidth reservation mechanism in IEEE-1394b protocol. Considering the mixture of isochronous and asynchronous requests in admission control for QoS service, the QoS of asynchronous requests was analyzed based on queuing theory (soft QoS). For the case of ignoring reply interval, the average response time of IEEE-1394b asynchronous requests queues was got. The QoS service of IEEE-1394b was evaluated in IEEE-1394b fiber optical bus experimental system in the end. The theoretic derived results were verified. It has a directive meaning in QoS design of IEEE-1394b driver layer.