A random access micro-cellular system based on CSMA (RAMCS/CSMA) is proposed. On uplink in RAMCS/ CSMA, packets are transmitted by means of CSMA at the same carrier frequency in any cell. On downlink, packets are broadcast conforming to TDMA, also at the same carrier frequency in any cell. In RAMCS/CSMA, deployed microcells produce higher system capacity. Nevertheless, " handoff on a terminal " isn't required. In this paper, overview of the system, fundamental uplink performance, and two kinds of power control methods are presented. As for the control methods, one is control according to packet priority. The other is a way according to location of a mobile terminal. By means of CSMA, throughput performance on uplink becomes great and is saturated at 0. 39 per cell. And the performance strongly depends on the threshold level on carrier sense. Such a throughput performance is peculiar to RAMCS/CSMA and different from an ordinary CSMA system. The optimum threshold is also indicated here. Furthermore, it is clarified that both power control methods highly improve the throughput performance. As a result, it is found that RAMCS/CSMA is excellent for mobile communications.

In packet radio networks with TDMA, the throughput performance of network should be degraded due to the unequal traffic of each user. To overcome this problem, Mini-Slotted Alternating Priorities (MSAP) and TDMA with Parallel Transmission (TDMA/PT) were proposed. Especially, TDMA/PT can attain the thorughput performance more than one, even under unequal traffic. However, TDMA/PT cannot be used for mobile networks, because each terminal should know the location of every other terminal. In this paper, we propose an entirely new protocol named Slot Reservation TDMA with Parallel Transmissino: SR-TDMA/PT," which is suitable for mobile networks because a central station is able to locate every terminal easily. The central station also reserves time slots for each terminal so as to transmit packets in parallel as much as possible. Therefore, the throughput performance of SR-TDMA/PT is higher than TDMA/PT. We describe SR-TDMA/PT in detail and evaluate the performance of this protocol by simulation under various conditions.

In a radio network, while deploying microcells enhances spectral efficiency, it increases handoff in number and puts restriction on mobility of a terminal. As a solution of this contradictory matter, we propose a random access micro-cellular system (RAMCS). In the system deployed microcells produce higher system capacity, and "handoff on a terminal" isn't required. Therefore flexible mobility is given to terminals, and a terminal becomes simple. The aspect of the air interface is as follows. On uplink, packets are transmitted by means of random access (e.g., slotted ALOHA) at the same channel in any cell. On downlink, packets are broadcast at the same carrier in any cell and they are picked out conforming to TDMA. In this paper, a model of RAMCS is proposed. In addition, characters of RAMCS (e.g., throughput, system capacity, and delay) are clarified comparing it with a primary cellular system, where a spectrum can be reused repeatedly in different cells.