A Study of Radio Resource Efficiency Management and Energy Saving in Next Generation Wireless Networks
Date Issued
2012
Date
2012
Author(s)
Chung, Yao-Liang
Abstract
For next generation wireless networks equipped with promising technologies such as 4th generation (4G) cellular network, their system capacities are supposed to be significantly improved. Nevertheless, because of fundamental physical characteristics of wireless channels, data packets often cannot be delivered to the destination successfully. As a result, the design focusing on the efficient and fast retransmission scheme especially for delay-sensitive flows to sufficiently utilize the radio resource in such a next generation wireless network plays a highly crucial role. Additionally, good objective-oriented radio resource allocation and management as well as energy-saving designs can help to efficiently improve in the aspects such like the system performance, the utility, the power consumption, and etc, respectively. In this dissertation, we will focus on five potential issues for improving the efficiency in various points of view in the next generation wireless network.
In the first topic, we present several multi-transceiver multi-channel fast packet retransmission schemes intended for transporting delay-sensitive flows in a multi-channel network environment. The proposed schemes are designed to allow the retransmission(s) for only one time using one or multiple channels simultaneously unlike other ones where the retransmission(s) of a link packet can only be in one channel and continue until it is successfully received. By using the application throughput as the objective, the optimal retransmission policy can be determined based on the estimated channel quality and the application-layer packet size. The optimized retransmission schemes are shown able to achieve better effective throughput (goodput) than those of other ones in various fading environments. The presented multi- transceiver multi-channel system model and fast retransmission schemes can be applied to the long term evolution-advanced network environment, in which the aggregation of multiple component carriers (CCs) or spectrum is considered an alternative to achieve significant throughput improvement.
The second topic addresses the design problem of a fast packet retransmission scheme intended for transporting delay-sensitive flows in a cooperative diversity (CD) network environment. This cooperative fast retransmission scheme exploits the advantages of the CD network environment, while allowing retransmission just one time via a cooperating user (i.e., partner) or via both the sender and the partner simultaneously. Complementary link packets are used for the retransmission whose policy can be adjusted on the basis of the qualities of channels among the sender, the partner and the receiver, as well as the application-layer packet size, using the application throughput as the objective. The CD-based optimized fast retransmission scheme is shown able to achieve better effective throughput than other CD-based or non-CD-based retransmission schemes in various fading environments. As a result, the proposed scheme should be an excellent fast retransmission mechanism for real-time multimedia transport in many CD environments.
In the study of the third topic, we aim to explore efficient packet scheduling schemes for users in multi-CC network environments. Two packet scheduling schemes are presented on the basis of the quantized water-filling criterion and the proportional fair criterion, respectively. The quantized water-filling packet scheduling scheme is designed to intentionally minimize the mean packet delay, where a close upper bound of the mean packet delay is derived, while maintaining the delay fairness among users, when the traffic load is unsaturated. The proportional fair based packet scheduling scheme is designed to improve the overall system performance, while maintaining fairness among all users. These two schemes are shown have much better performance than those of a network where CCs are not aggregated but used independently.
The forth topic presents a dynamic network selection scheme via a quota-based admission control design for accommodating access requests in a multiple heterogeneous and orthogonal network environment, which may become common for today’s 3G operators. The design philosophy of this scheme is to let the system utilization in the fastest networks be statistically balanced and sufficiently utilized. Performance metrics in terms of the overall system utility (i.e., the satisfaction index), the blocking probability, and the system utilization are investigated. From simulation results, it is shown that the proposed scheme has significant improvement in the aspect of the overall system performance than that of existing approaches.
Last, we study the topic of a power optimization model developed with respect to the radio resource allocation and the activation in a multi-CC network environment. We first formulate and solve the power-minimization problem of the base station (BS) transceivers for multiple-CC network environment, while maintaining the overall system and respective users’ utilities above minimum levels. The optimized power consumption based on this model can be viewed as a lower bound of that of other algorithms employed in practice. A suboptimal scheme with low computation complexity is proposed. Numerical results show that the power consumption of our scheme is much better than that of the conventional one in which all CCs are always active, if both schemes maintain the same required utilities. Next, we formulate a power-minimization problem of the BS transceivers for multiple-CC networks, while maintaining respective user types’ fairness indexes and respective users’ data rates. An efficient scheme is subsequently proposed to solve it. Numerical results demonstrate that the total power consumption of our proposed scheme is significantly much better than that of the case where all CCs are always active when the traffic load is relatively light.
Subjects
multi-channel transmissions
cooperative transmissions
multi-carrier networks
packet scheduling algorithms
queueing theory
dynamic network selection
green communications
energy-saving transmissions
optimization
SDGs
Type
thesis
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