This paper proposes a data transfer protocol called Logical Airlink Control Procedure for Packet Radio Systems (LAPPR) which offers a high throughput efficiency in fading channels. Two main ideas are presented in the flow control and retransmission control methods. A new flow control scheme called "P/F Sliding Flow" is proposed where a high channel utilization rate is provided by continuously transmitting the data frames. At that time, the acknowledgements for the data frames are reduced so as not to occupy both the forward and reverse channels and data exchange between different transmitter-receiver pairs is enabled. A retransmission control scheme called "Recovery Confirming Retransmission Control" is also proposed which makes conventional Automatic Repeat Request (ARQ) schemes significantly more effective in the fading environments by continuously sending the same frame. Computer simulations were carried out and the result showed that a throughput higher than conventional protocols can be achieved.

This paper proposes a new effective data transfer method for IEEE 802.11 wireless LANs by integrating priority control and multirate mechanism. The IEEE 802.11 PHY layer supports a multirate mechanism with dynamic rate switching and an appropriate data rate is selected in transmitting a frame. However, the multirate mechanism is used with the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol, low rate transmissions need much longer time than high rate transmissions to finish sending a frame. As a result, the system capacity is decreased. The proposed method assumes the same number of priority levels as the data rates, and a data rate is associated to a priority level. Priority of a transmission goes up with the used data rate. For this purpose, we have modified the CSMA/CA protocol to support prioritized transmission. By selecting the appropriate priority depending on the data rate and giving more transmission opportunities for high rate transmission, the system capacity is increased. The effect of the proposed mechanism is confirmed by computer simulations.

To improve the reliability and efficiency of multicast transmissions in wireless systems, a novel retransmission procedure is desired. In this paper, the representative acknowledgment scheme for reliable wireless multicast communications is proposed that offers quite a low packet loss rate. The proposed protocol carries out retransmissions in the datalink layer within the wireless region, and retransmissions do not affect the traffic in the wired region. The representative acknowledgment scheme employs both positive acknowledgment (ACK) and negative acknowledgment (NACK) to achieve reliable multicast transmissions and reduces the number of responses to be returned by forming groups of stations in the cell. One of the members in a group, called a representative station, returns a response for a received data frame while the others return a NACK if necessary. With this scheme, reliable multicast transmissions are enabled in wireless communications without spending much time as in conventional reliable multicast protocols. The performance of the proposed protocol is evaluated by numerical analyses and by computer simulation. The results show that 30% or more decrease in transmission time is achieved in a typical wireless environment.