2 research outputs found
Adaptive thresholding based optimal rate and MIMO mode selection scheme for IEEE 802.11n WLAN
The emergence of multiple antenna technology in IEEE 802.11n WLAN has resulted in performance improvement in terms of throughput as well as transmission reliability as compared to legacy standards. Link adaptive transmission is critical to WLAN. Most of the existing algorithms for MIMO mode adaptation (between spatial multiplexing and diversity encoding) use ïŹxed SNR switching thresholds for rate selection. The use of a ïŹxed threshold in both MIMO modes, however, can only provide smaller throughput gain. The present studies on link adaptation do not consider the fundamental characteristic difference in the diversity encoding and spatial multiplexing encoding for MIMO. In this paper we propose a novel adaptive thresholding based optimal rate and MIMO mode (ORMM) algorithm for 802.11n wireless network. The proposed scheme adaptively switches between two SNR switching threshold vectors, separately determined for each MIMO mode analytically. Simulations over the Rayleigh fading channel shows that ORMM outperforms the existing approach of MIMO rate adaptation based on the use of ïŹxed switching thresholds for rate selection
Aspects of capacity enhancement techniques in cellular networks
Frequency spectrum is the scarce resource. From mobile operatorâs point of view, efficient utilization of the radio resources is needed while providing maximum coverage, and ensuring good quality of service with minimal infrastructure. In high capacity demanding areas, multilayer networks with multiband and multi radio access technologies are deployed, in order to meet the capacity requirements. In his doctoral thesis, Usman Sheikh has proposed a âSmart Traffic Handlingâ strategy, which is based on userâs required service type and location. Smart traffic handling scheme efficiently utilizes the different layers of the network, balances the load among them, and improves the system capacity. Power resources at base station are also limited. Usman Sheikhâs proposed âPower Control Scheme for High Speed Downlink Packet Access (HSDPA) networkâ improves the cell edge user experience, while maintaining the fairness among the other users in a cell. With the help of a proposed power control scheme, a user far from the base station can also enjoy the better quality of service.
Generally, mobile operators use macro cells with wide beam antennas for wider coverage in the cell, but future capacity demands cannot be achieved by using only them. âHigher Order Sectorizationâ is one possible way to increase the system capacity. Usman Sheikh proposed new network layouts called âSnowflakeâ and âFlowerâ tessellations, for 6-sector and 12-sector sites, respectively. These tessellations can be used as a basis for making a nominal network plan for sites with higher order sectorization. These tessellations would be helpful for simulation purposes. Through his work, he has also tried to highlight the importance of deploying âAdaptive MIMO Switchingâ in Long Term Evolution (LTE) system, the fourth generation of wireless networks.
In future, the fifth generation of wireless networks is expected to offer thousand times more capacity compared to LTE. The novel concept of âSingle Path Multiple Access (SPMA)â given by Usman Sheikh is a revolutionary idea, and gives a possibility to increase the system capacity by a giant margin. SPMA can be considered as a right step towards 5G technology.
Usman Sheikhâs work is of high importance not only from mobile operatorâs point of view; rather his contributions to the scientific community will also lead to better user (customer) experience. His work will definitely benefit the mankind in utilizing the limited resources in an optimum and efficient way