847 research outputs found
Decentralized Fair Scheduling in Two-Hop Relay-Assisted Cognitive OFDMA Systems
In this paper, we consider a two-hop relay-assisted cognitive downlink OFDMA
system (named as secondary system) dynamically accessing a spectrum licensed to
a primary network, thereby improving the efficiency of spectrum usage. A
cluster-based relay-assisted architecture is proposed for the secondary system,
where relay stations are employed for minimizing the interference to the users
in the primary network and achieving fairness for cell-edge users. Based on
this architecture, an asymptotically optimal solution is derived for jointly
controlling data rates, transmission power, and subchannel allocation to
optimize the average weighted sum goodput where the proportional fair
scheduling (PFS) is included as a special case. This solution supports
decentralized implementation, requires small communication overhead, and is
robust against imperfect channel state information at the transmitter (CSIT)
and sensing measurement. The proposed solution achieves significant throughput
gains and better user-fairness compared with the existing designs. Finally, we
derived a simple and asymptotically optimal scheduling solution as well as the
associated closed-form performance under the proportional fair scheduling for a
large number of users. The system throughput is shown to be
, where is the
number of users in one cluster, is the number of subchannels and is
the active probability of primary users.Comment: 29 pages, 9 figures, IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL
PROCESSIN
Dynamic Time-domain Duplexing for Self-backhauled Millimeter Wave Cellular Networks
Millimeter wave (mmW) bands between 30 and 300 GHz have attracted
considerable attention for next-generation cellular networks due to vast
quantities of available spectrum and the possibility of very high-dimensional
antenna ar-rays. However, a key issue in these systems is range: mmW signals
are extremely vulnerable to shadowing and poor high-frequency propagation.
Multi-hop relaying is therefore a natural technology for such systems to
improve cell range and cell edge rates without the addition of wired access
points. This paper studies the problem of scheduling for a simple
infrastructure cellular relay system where communication between wired base
stations and User Equipment follow a hierarchical tree structure through fixed
relay nodes. Such a systems builds naturally on existing cellular mmW backhaul
by adding mmW in the access links. A key feature of the proposed system is that
TDD duplexing selections can be made on a link-by-link basis due to directional
isolation from other links. We devise an efficient, greedy algorithm for
centralized scheduling that maximizes network utility by jointly optimizing the
duplexing schedule and resources allocation for dense, relay-enhanced OFDMA/TDD
mmW networks. The proposed algorithm can dynamically adapt to loading, channel
conditions and traffic demands. Significant throughput gains and improved
resource utilization offered by our algorithm over the static,
globally-synchronized TDD patterns are demonstrated through simulations based
on empirically-derived channel models at 28 GHz.Comment: IEEE Workshop on Next Generation Backhaul/Fronthaul Networks -
BackNets 201
Adaptive frame structure and OFDMA resource allocation in mobile multi-hop relay networks
The objective of this thesis research is to optimize network throughput and fairness, and enhance bandwidth utilization in wireless mobile multi-hop relay (MMR) networks. To enhance bandwidth utilization, we propose an adaptive OFDMA frame structure which is used by the base station and the non-transparent relay stations. To optimize throughput and fairness, we develop an adaptive OFDMA allocation algorithm by using the proposed adaptive OFDMA frame. The effectiveness of the proposed schemes has been verified by numeric simulations.
Providing ubiquitous coverage with wireless metropolitan area networks (WMANs) can be costly, especially in sparsely populated areas. In this scenario, cheaper relay stations (RSs) can be used to provide coverage instead of expensive base stations (BSs). The RS extends the coverage area of traditional BSs. This sort of network is known as a wireless MMR network. This thesis focuses on MMR networks that use orthogonal frequency division multiple access (OFDMA) and time division duplex (TDD) as a multiple access scheme and a duplex communication technique (e.g., WiMAX). The use of OFDMA resources (e.g., OFDMA symbols and subcarriers) and how they are shared in current schemes can reduce system capacity and network throughput in certain scenarios. To increase the capacity of the MMR network, we propose a new protocol that uses an adaptive OFDMA frame structure for BSs and RSs. We also propose adaptive OFDMA resource allocation for subscriber stations (SSs) within a BS or RS. We derive the maximum OFDMA resources that RSs can be assigned and synchronize access zones and relay zones between a superior station and its subordinate RSs. This is bounded by three properties defined in this thesis: a data relay property, a maximum balance property, and a relay zone limitation property. Finally, we propose max-min and proportional fairness schemes that use the proposed adaptive frame structure. The proposed scheme is the first approach that incorporates the adaptive technique for wireless MMR networks. We evaluate our scheme using simulations and numerical analysis. Results show that our technique improves resource allocation in wireless MMR networks. Further, in asymmetric distributions of SSs between access zones and relay zones, the proposed OFDMA allocation scheme performs two times better than the non-adaptive allocation scheme in terms of average max-min fairness and 70% better in terms of average throughput.Ph.D.Committee Chair: Dr. John A. Copeland; Committee Member: Dr. George F. Riley; Committee Member: Dr. Henry L. Owen; Committee Member: Dr. Mary Ann Ingram; Committee Member: Dr. Patrick Trayno
Recent advances in radio resource management for heterogeneous LTE/LTE-A networks
As heterogeneous networks (HetNets) emerge as one of the most promising developments toward realizing the target specifications of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, radio resource management (RRM) research for such networks has, in recent times, been intensively pursued. Clearly, recent research mainly concentrates on the aspect of interference mitigation. Other RRM aspects, such as radio resource utilization, fairness, complexity, and QoS, have not been given much attention. In this paper, we aim to provide an overview of the key challenges arising from HetNets and highlight their importance. Subsequently, we present a comprehensive survey of the RRM schemes that have been studied in recent years for LTE/LTE-A HetNets, with a particular focus on those for femtocells and relay nodes. Furthermore, we classify these RRM schemes according to their underlying approaches. In addition, these RRM schemes are qualitatively analyzed and compared to each other. We also identify a number of potential research directions for future RRM development. Finally, we discuss the lack of current RRM research and the importance of multi-objective RRM studies
Review on Radio Resource Allocation Optimization in LTE/LTE-Advanced using Game Theory
Recently, there has been a growing trend toward ap-plying game theory (GT) to various engineering fields in order to solve optimization problems with different competing entities/con-tributors/players. Researches in the fourth generation (4G) wireless network field also exploited this advanced theory to overcome long term evolution (LTE) challenges such as resource allocation, which is one of the most important research topics. In fact, an efficient de-sign of resource allocation schemes is the key to higher performance. However, the standard does not specify the optimization approach to execute the radio resource management and therefore it was left open for studies. This paper presents a survey of the existing game theory based solution for 4G-LTE radio resource allocation problem and its optimization
Radio resource allocation in relay based OFDMA cellular networks
PhDAdding relay stations (RS) between the base station (BS) and the mobile stations (MS) in a cellular system can extend network coverage, overcome multi-path fading and increase the capacity of the system.
This thesis considers the radio resource allocation scheme in relay based cellular networks to ensure high-speed and reliable communication. The goal of this research is to investigate user fairness, system throughput and power consumption in wireless relay networks through considering how best to manage the radio resource.
This thesis proposes a two-hop proportional fairness (THPF) scheduling scheme fair allocation, which is considered both in the first time subslot between direct link users and relay stations, and the second time subslot among relay link users.
A load based relay selection algorithm is also proposed for a fair resource allocation. The transmission mode (direct transmission mode or relay transmission mode) of each user will be adjusted based on the load of the transmission node.
Power allocation is very important for resource efficiency and system performance improvement and this thesis proposes a two-hop power allocation algorithm for energy efficiency, which adjusts the transmission power of the BS and RSs to make the data rate on the two hop links of one RS match each other.
The power allocation problem of multiple cells with inter-cell interference is studied. A new multi-cell power allocation scheme is proposed from non-cooperative game theory; this coordinates the inter-cell interference and operates in a distributed manner. The utility function can be designed for throughput improvement and user fairness respectively.
Finally, the proposed algorithms in this thesis are combined, and the system performance is evaluated. The joint radio resource allocation algorithm can achieve a very good tradeoff between throughput and user fairness, and also can significantly improve energy efficiency
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