Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Slotted Aloha with multi-AP diversity and APS transmit beamforming | Zheng and Yao EURASIP Journal on Wireless Communications and Networking 2011 2011 119 EURASIP Journal on . http content 2011 1 119 Wireless Communications and Networking a SpringerOpen Journal RESEARCH Open Access Slotted Aloha with multi-AP diversity and APS transmit beamforming Di Zheng and Yu-Dong Yao Abstract Slotted Aloha is an effective random access protocol and can also be an important element of more advanced media access protocols. This paper investigates slotted Aloha in a radio environment with multiple access points. Specifically we examine the impact of multi-access-point multi-AP diversity on the performance of slotted Aloha. The paper considers both omni-directional OM and beamforming BF antennas at transmission nodes. This leads to the investigation and comparison of four different network scenarios . OM with multi-AP diversity OM without multi-AP diversity BF with multi-AP diversity and BF without multi-AP diversity. Performance evaluations and comparisons are presented in terms of throughput and average packet delay. Keywords Slotted Aloha Multi-access-point diversity Beamforming Capture effect Rayleigh fading Throughput Average packet delay I. Introduction Slotted Aloha has been extensively used in wireless environments 1-4 in which the power levels of received packets can be different due to independent fading. It is possible that the strongest packet captures the receiver even when there is a packet collision 5 which could increase throughput. This phenomenon is referred to as the capture effect. A lot of research have been conducted for the investigations of the capture effect under various fading channels including Rayleigh Rician and Nakagami 6-8 . Besides the capture effect beamforming BF techniques can also potentially increase throughput since they are able to reduce collisions in slotted Aloha as compared to omni-directional OM antennas. The applications of BF at both receiving and transmitting sides have .
