Our investigation shows a trend which we want everyone to know.
There is obviously a low probability that various factors affecting upstream and downstream throughput become equal.
Yes there is appreciable difference between TCP upstream and downstream throughput.
Throughput is a measure of the average rate that data (in bits) can be sent between one user and another and is typically measured in kilobits per second (Kbps) or megabits per second (Mbps). Throughput is what the user sees after overheads. For the same network connection, throughput can vary greatly depending on the protocol used for transmission, the type of data traffic being sent as well as the quality (SNR) and data bandwidth of a network connection.
An example of Upstream throughput is the speed of data sent from a client to a server through WLAN radio or system (e.g Uploading a file on the internet). An example of a downstream throughput is the speed of data sent from a server through a WLAN radio to a client system (e.g downloading a file on the internet).
Loss in performance of WLAN systems with respect to throughput obtained has been attributed to (i) the varying nature of the wireless channels resulting in incorrect reception of channel symbols at the physical layers, (ii) packet loss probability due to packet collisions and inefficiency of error correction schemes or mechanisms for the received channel symbols and (iii) queuing process and buffer overflows at the IP layer. Among these three causes of errors, both TCP downstream and upstream throughput are affected by (i) in approximately the same way. However the packet loss probability due to packet collisions and inefficiency of error correction schemes or mechanisms for the received channel symbols and the queuing process and buffer overflows at the IP layer varies considerably for upstream and downstream throughput hence the appreciable differences. What are the specific explanation for these appreciable difference in (ii) and (iii) for TCP upstream and downstream ?
TCP upstream is affected more by the buffer size of the client system and the bandwidth capacity. Also, at the client system,there is less possibilities of collision of packets with packets from other client systems. However TCP downstream throughput depends more on the buffer size of the WLAN radio. Also at the WLAN radio there is a high probability of packet collision due to several clients and servers connected to the radio which are sending their data through the radio. The WLAN radio serves as a bottle neck which constrains the packets to queue and possibly overflow the buffer leading to more losses. However the WLAN buffer has a larger bandwidth capacity than that of the client. What are the other reasons for the difference in TCP upstream and TCP downstream throughput
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