Christiaan Roobol

Performance of a common channel packet access in WCDMA

This paper analyzes the uplink common channel packet transmission in WCDMA where different rates random access channels could be used for user packet transmission. A performance analysis is carried out to compare the performance of these channels under varying load conditions and two different back-off strategies.

On the packet delay in wireless local area networks with access port diversity and power control

Wireless local area networks have attracted considerable interest. To enhance the user capacity of such wireless packet communication systems, an architecture where terminals share a common radio channel and several access ports has been proposed in the literature. In this paper we will investigate the performance of such systems, considering several scenarios. Firstly access ports may only receive packets from nearby terminals. Secondly, all access ports may receive packets from any terminal. We distinguish between a highly mobile case, where terminals are assumed to be in a different position in every timeslot, and a stationary case, in which the terminals are at the same place all the time. Our results for slotted ALOHA packet access show that the delay performance of a mobile system is much better than a stationary system, due to the fact that in the mobile case all terminals get in a good position every now and then. Access port diversity slightly improves the performance of a stationary system. A clear difference between the mobile system and the stationary system is that the stationary system is unfair, in the sense that distant terminals have considerably worse performance than nearby terminals. We show that by using power control this problem can be solved. The delay performance of the mobile system can also be improved considerably, by using another power control algorithm.

Performance of Dual Mode Packet Access In DS-CDMA Systems

In this paper, a dual mode packet access scheme is analyzed where packet transmission can either take place on a common channel or on a dedicated channel. The common channel packet access is typically used for the transmission of short infrequent packets, where link setup and the necessary link maintenance for a dedicated channel would lead to unacceptable delays and overhead. Only open loop power control is used for common channel packet transmission. On the other hand, the dedicated channel transmission is mostly used for large packet transmissions. Unlike the common channels, the closed loop power control is in operation for all transmissions on the dedicated channels.