oa Efficient Multiple Users Combining And Scheduling In Wireless Networks

Wireless networking plays a vital role in our daily life style and has tremendous applications in almost all fields of the economy. The wireless medium is a shared medium and, hence, user-scheduling is needed to allow multiple users access the channel jointly. Furthermore, the wireless channel is characterized by its time-based and location-based variations due to physical phenomena such as multi-path propagation and fading, etc. Therefore, unlike the traditional persistent round-robin scheduling schemes, the current standards of telecommunication systems support channel-aware opportunistic scheduling in order to exploit the varying channels of the users when they are at their peak conditions. The advantages of these schemes in enhancing the prospected throughput of the networks are evident and demonstrated. However, these schemes are basically based on selecting a single user to access a certain frequency sub-channel at a given time in order to avoid creating interference if more than one user access the same channel. Nevertheless, allowing multiple users to access the same channel can be feasible by using special coding techniques such as superposition coding with successive interference cancellation at the receivers. The main advantage of this is to improve the spectral efficiency of the precious wireless spectrum and to enhance the overall throughput of the network while maintaining the quality-of-service requirements of all users. Despite their advantages, multiple-users scheduling schemes require the use of proper resource allocation algorithms to process the channel conditions measurements in order to decide which users should be served in a given time slot and frequency sub-channel and the allocated data rate and power of each link in order to maximize the transmission efficiency. Failure to use a suitable resource allocation and scheduling scheme can degrade the performance significantly. We design and analyze the performance of efficient multiple-users scheduling schemes for wireless networks. One scheme is proven theoretically to be the most efficient one. However, the algorithm computation load is significant. The other scheme is a sub-optimal scheme that has low computation load to run the algorithm and it achieves very good performance which is comparable to the optimal scheme. Furthermore, we evaluate the performance gains of multiple-user scheduling over the conventional single-user scheduling under different constraints such as hard fairness and proportional fairness among the users and for fixed merit weights of the users based on their service class. In all of these cases, our proposed schemes can achieve a gain that may exceed 10% in terms of the data rate (bits/sec). This gain is significant taken into consideration that we use the same air-link and power resources of the conventional single-user scheduling schemes.