The anti-collision mechanism is a very important part in Radio-frequency Identification (RFID) systems. Among all the algorithms, the Framed Aloha based (FA) ones are most widely used due to simplicity and robustness. Previous works mainly focused on the tag population estimation, but determined the reading strategy based on the classical results of Random Access (RA) systems. We show that a new theory is needed for the optimization of the RFID systems as they have characteristics very different from the RA systems. In this paper, We propose a new approach to minimize the total expected reading time by choosing the most suitable frame size based on the tag population distribution. We show that the optimal strategy can be used in different applications. The mathematical analysis and computer simulation show our approach outperforms the previous optimization works in the literature.

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The Random Access Channel (RACH) in Universal Terrestrial Radio Access -Frequency Division Duplex (UTRA-FDD) system is a contention-based channel mainly used to carry control information from mobile stations to base stations. The transmission of a random access request contains two steps: Preamble Transmission and Message Transmission. In preamble transmission, power ramping technique is used to favor the delayed preambles by stepping up the transmission power after each unsuccessful access. In doing so, the success of transmitting a long-delayed preamble is increased due to the power capture effect. In this paper, we analyze the blocking and throughput performance of preamble transmission under three power ramping schemes with fixed, linear and geometric step sizes. The interference caused by different power ramping schemes are also compared.

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It is well-known that TCP does not perform well in modern satellite-based communications due to the channel's very large bandwidth-delay product. The conventional solution is to make use of TCP's Large Window Scale (LWS) extension as defined in RFC1323 to increase TCP's windows size. However this can only be done if either the operating system or the application can be modified to explicitly make use of TCP's LWS extension during connection setup. This work proposes a novel TCP-SuperCharger (TCP-SC) to enable TCP to fully utilize the underlying network bandwidth without modification to the applications or the operating system. TCP-SC is implemented as a gateway along the path between the sender and the receiver. By estimating the receiver's processing capacity, TCP-SC allows the sender to transmit more data than the amount of receiver buffer available. As modern computers are very fast compared to network speed, this prevents the receiver's buffer limit from restricting the throughput achievable by TCP. Experimental results show that TCP-SC can enable existing TCP with default buffer size (64 KB) to achieve 98% link utilization over a satellite link such as the WINDS communications satellite with 1,000 ms RTT and 24 Mbps bandwidth.