Throughput of inhibit sense multiple access with propagation delays

Abstract

Abstrut-A large number of terminals transmitting data packets over a common radio channel to a central base station is studied. In inhibit sense multiple access (ISMA), the base station broadcasts a busy signal when an incoming packet is being received, to inhibit other terminals from colliding transmissions. This busy signal arrives at each terminal with a propagation delay, proportional to the distance between the base station and the terminal. This leads to unfairness in the probability of successfully transmitting a data packet, since nearby terminals have more up-to-date information on the actual channel status than remote terminals. This unfairness is additional to the advantage that nearby terminals have because of the capture effect, which is also considered here. The paper applies nonstationary Poisson precesses to describe the random arrivals of data packets at the central receiver. It is shown that the probability of a successful attempt to transmit a packet decreases, approximately linearly with the distance between the transmitter and the central receiver. The total throughput is also assessed, and is found that the assumption of a fixed propagation delay adopted in CSMA studies by others gives too optimistic results for ISMA. Moreover, our analysis suggests a subtle change of the fixed delay approximation that enhances its accuracy, without adding complexity. The effect of propagation delays in random access radio networks are of increasing importance, since newly developed systems are designed to transmit with increasingly high bit rates.

Performance analysis of inhibit sense multiple access with mixed priority classes

“…The differences between the analysis results and the simulation exhibit the same tendency as for the conventional model [4]. The reason seems to be similar.…”

“…System [4] In the ISMA system all terminals send packets to the base station using a single channel. The base station broadcasts an idle signal or a busy signal according to the state of the channel.…”

“…In the ISMA system the throughput of a terminal at distance r from the base station is given as follows [4].…”

“…The tendency, however, is that the bit rate gradually increases and the delay is expected to increase in future compared to the packet length, which cannot be ignored. Thus, performance should be analyzed by taking this situation into account [4]. From that viewpoint, this paper presents a performance analysis that considers situations where delay is considerable.…”

“…The inhibit sense multiple access (ISMA) system was proposed in order to remedy the hidden terminal problem [4]. In the ISMA system, the base station sends a signal to notify about the state of the channel.…”