Cellular Wireless Local Area Network Research Articles

Maximizing signal strength for OFDM inside buildings

Propagation inside buildings suffer from large shadowing and high multipath effects. This is a serious problem for wireless local area network (WLAN) systems. This paper shows that shadowing and path loss can be minimized by exploiting the multipath tolerance of orthogonal frequency-division multiplexing (OFDM). This can be achieved by using multiple transmission antennas spread over the area of a WLAN cell. These antennas act as repeaters, transmitting and receiving the same signal at the same time. This decreases the average path loss, but increases the multipath delay spread. Using OFDM allows the advantage of reduced path loss to be utilized without detrimental effects of inter-symbol interference caused by the increased delay spread. The reduced path loss allows an increased system capacity, quality of service, or a decrease in intercellular interference in a cellular WLAN.

A cellular wireless local area network with QoS guarantees for heterogeneous traffic

A wireless local area network (WLAN) or a cell with quality-of-service (QoS) guarantees for various types of traffic is considered. A centralized (i.e., star) network is adopted as the topology of a cell which consists of a base station and a number of mobile clients. Dynamic Time Division Duplexed (TDD) transmission is used, and hence, the same frequency channel is time-shared for downlink and uplink transmissions under the dynamic control of the base station. We divide traffic into two classes: class I (real-time) and II (non-real-time). Whenever there is no eligible class-I traffic for transmission, class-II traffic which requires no delay-bound guarantees is transmitted, while uplink transmissions are controlled with a reservation scheme. Class-I traffic which requires a bounded delay and guaranteed throughput is handled with the framing strategy (Golestani, IEEE J. Selected Areas Commun. 9(7), 1991) which consists of a smoothness traffic model and the stop-and-go queueing scheme. We also establish the admission test for adding new class-I connections. We present a modified framing strategy for class-I voice uplink transmissions which utilizes the wireless link efficiently at the cost of some packet losses. Finally, we present the performance (average delay and throughput) evaluation of the reservation scheme for class-II traffic using both analytical calculations and simulations.