A QoS-Aware Proportional Fairness Based Packet Scheduling Algorithms for Multi-Carrier OFDMA Systems
Date Issued
2010
Date
2010
Author(s)
Chang, Li-Chung
Abstract
In recent years, due to the fast development of the wireless technology, more and more people access a lot of applications via wireless networks. However, when people access wireless networks, it often leads to a short of frequency resources; thus, how to design an efficient packet scheduling algorithm to guarantee the QoS (throughput, delay, etc.)of the user’s real-time traffic and non-real time traffic and also to maintain the fairness among users have become important issues.
According to ITU’s requirements, in future cellular systems (IMT-Advanced systems), it must support data transmissions in multi-user environments with a target peak rate up to approximately 100 Mbps for high mobility (such as mobile access) and up to approximately 1 Gbps for low mobility (such as nomadic/local wireless access). To achieve such high speed data transmissions, it must use much larger frequency bands to transmit; however, the existing systems cannot provide such large consecutive frequency band. To overcome this problem, one must employ multiple carriers to fulfill the bandwidth requirement. Thus, both the 3GPP and IEEE 802.16 working groups have become candidates for IMT-Advanced standard, and both have adopted the concept “carrier aggregation,” which integrates multicarrier for transmissions to achieve the speed requirement of the IMT-Advanced. The proposed systems from respective working groups are LTE-Advanced and 802.16m. Moreover, in the recent studies of packet scheduling algorithms for a single carrier transmission, the OFDMA scheme is often assumed, since the OFDMA technology has many advantages, including high spectrum efficiency, resistance against multipath interference and etc. Therefore, the multicarrier systems discussed above are also expected to be designed with an underlying OFDMA technology.
In this thesis, we propose a QoS-aware proportional fairness based packet scheduling algorithm for multicarrier OFDMA systems considering the downlink environment. The proposed scheduling approach is different from most previous scheduler algorithms, which usually did not consider the supported applications; instead, they almost all focused on the physical layer. Thus, the main scheduling algorithm we proposed covers the packet layer, considering user’s QoS requirements (such as packets delay for real-time applications) and the fairness issue in multicarrier OFDMA system.
We use Matlab as the simulation tool to set up the simulation environment in which packets can be simulated according to different QoS requirements. We then examine and analyze the obtained simulation results. Based on the simulation results, the scheduling algorithm we proposed can be shown to provide improvement of the system transmission capacity, especially when the system load is high. We also show that the proposed algorithm does guarantee the packet delay for real-time service. Therefore the proposed algorithm can achieve all users’ QoS requirements as expected.
Subjects
Proportional Fairness
QoS
Scheduling
Multi-Carrier
OFDMA
Type
thesis
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