Wireless LAN Access Points Uplink and Downlink Delays : Packet Service-Time Comparison
Iyad Al Khatib, Rassul Ayani, Gerald Q. Maguire · 2002
Wireless LAN access points are very important connecting nodes transferring traffic between two media in opposite directions. Hence the performance of the wireless LAN access point should be looked upon from two different reference points: uplink (from WLAN to Ethernet) and Downlink (from Ethernet to WLAN). This paper builds on our previous modeling of the wireless access point as a single server, FIFO, queuing system to analyze the service times in both directions. The previous analysis showed that the average service time is a function of payload. Measurements have revealed that the uplink service time is much smaller than the downlink service time for the same payload. In this paper, we investigate the absolute value of the difference between the uplink and downlink service-times. We refer to the absolute value of the difference in time between uplink and downlink as the UDC, or theUplink-Downlink Contrast. Results show that as the packet size increases, the UDC either decreases or increases monotonically depending on the brand of the access point. For a decreasing UDC, the absolute value of the difference between the uplink and downlinkservice-times decreases, hence the UDC is convergent. Similarly, the UDC is divergent if it increases with increasing packet size. These results can be used to select a WLAN accesspoint given the size of packets transmitted by an application or multiple applications over a Local Area Network.