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Cooperative detection involving neighboring base stations is a promising means to increase spectral efficiency in the uplink of cellular systems. To fully utilize the new degrees of freedom that come with base station cooperation, it is essential that a joint scheduler is aware of the interference conditions in all participating cells in order to perform efficient resource and rate allocation. However,...
Multiuser diversity combined with Orthogonal Frequency Division Multiple Access (OFDMA) are a promising technique for achieving high downlink capacities in new generation of cellular and wireless network systems. The total capacity of OFDMA based-system is maximized when each subchannel is assigned to the mobile station with the best channel to noise ratio for that subchannel with power is uniformly...
In this paper, we propose a channel and queue aware cross-layer algorithm for allocating power and sub-carriers to users in Orthogonal Frequency Division Multiple Access (OFDMA) networks. Our algorithm uses utility to build a bridge between the physical layer and upper layers and also to balance the efficiency and fairness of the radio resource allocation. The objective is to develop a method based...
Modern wireless networks, such as WiMAX or LTE are using OFDM/OFDMA as the enabling technologies for broadband transmission in cellular environments with QoS capabilities. In these networks, such schema as radio resource management, admission control, scheduling are essential. In this article we firstly introduce a Time-Frequency Burst Mapping algorithm for radio resource management that improves...
Cross-layer algorithms that jointly allocate resources at different layers are known to foster the communication performance in wireless networks. Recent works have shown that fading and queue information are among the most critical parameters to consider in cross-layer designs. Motivated by those findings, this work develops optimal algorithms that use instantaneous fading and queue length information...
In this paper, we analyze the performance gain achieved when a channel-aware deferring (CaD) strategy is applied to defer the allocation of users with transitory bad channel state in a mobile OFDMA system. Users with good channel conditions receive more resources and the radio resource utilization improves. To reduce the impact of the CaD strategy on the quality of service (QoS) provisioning for the...
In this paper, we study resource allocation and relay selection in a decode-and-forward downlink OFDMA cooperative network assuming imperfect channel state information (CSI) at the base station (BS). We assume that due to feedback delay, the BS has only outdated CSI of BS to users and inter-user links. We propose a centralized optimization framework in which the BS takes decisions on the basis of...
This paper presents a comparison between CDMA and SC-FDMA for reverse link (RL) cellular voice and data communications. The comparison is based on CDMA2000 1x (circuit-switched voice), CDMA2000 1xEV-DO (packet data) and 3GPP LTE Release 8 (SC-FDMA based packet voice and data). We illustrate various modes of LTE system operation and associated trade-offs. For the comparison of data communications we...
Deploying femtocell networks embedded in the Macrocell coverage greatly benefits communication quality in variety manners. However, the lack of schemes to effectively mitigate detractive interference, fully utilize radio resources and provide quality-of-service (QoS) guarantee (in terms of delay) creates challenges to practically facilitate the concept of femtocell. To tackle these challenges to achieve...
Long Term Evolution represents an emerging and promising technology for providing a broadband ubiquitous Internet access. But several aspects have to be considered in order to provide an effective service to users. In particular, in this work, we consider the problem of optimizing the performance of real time downlink communications using a novel two-level scheduling algorithm. The upper level exploits...
WiMAX cellular packet networks have become an attractive solution for many applications these days. One of the main reasons for that, is the QoS support that WiMAX provides. An important part of the WiMAX QoS framework is the scheduling services defined for different types of traffic and the uplink BW allocation mechanism associated with these scheduling services. These 5 uplink scheduling mechanisms...
In order to improve the efficiency of paging management, various paging strategies have been proposed for tracking single mobile user in the wireless cellular network. However, most of the schemes have ignored the important problem of efficient search for multiple mobile users under delay and bandwidth constraints. Given the condition that the search is over only after all the users in the group are...
In this paper, we propose two modified proportional fair scheduling algorithms for multiuser multicarrier systems. Compared to the existing proportional fair scheduling algorithms, our proposed algorithms are devised to support the delay constraint for the real-time applications as well as to guarantee a certain level of fairness. The simulation results show that the proposed scheduling algorithms...
In this paper, we present a method to optimally manage the access slots for the initial ranging contention process in IEEE802.16e air interface. In conventional method, the number of the initial access slot is fixed to a large number in common circumstance. The reason using the static large slot is to reduce the initial access collisions by slot contentions of the mobile terminals. Therefore the usage...
In this paper, the waiting time analysis for an OFDMA wireless cellular system with finite buffering and Adaptive Modulation and Coding (AMC) is addressed. When AMC is considered, several concentric regions within cells serving users with different data rates are differentiated. Phase type (PHT) distribution functions are used to model the conditional cumulative distribution function of the waiting...
Multi-hop relays will be deployed as one of the promising technologies for future cellular networks to enhance the performance of cell boundary users and to reduce deployment and operating cost. However, they have many challenges which include signaling overhead and latency in order to be practically deployed due to a hierarchical multi-hop structure, and the situation is much severer in uplink case...
The interaction between wireless optimized scheduling algorithms and TCP congestion control mechanisms can have adverse effects on the performance of the system. We focus on the queue based max-weight (QBMW) scheduler, a scheduling strategy which is known to be throughput-optimal under unregulated traffic sources. We use fluid modeling to describe the time evolution of the congestion window size and...
This paper proposes a novel cross-layer scheduling scheme for a single-cell orthogonal frequency division multiple access (OFDMA) wireless system with partial channel state information (CSI) at transmitter (CSIT) and heterogeneous user delay requirements. Previous research efforts on OFDMA resource allocation are typically based on the availability of perfect CSI or imperfect CSI but with small error...
Packet scheduling algorithms are viewed as one of the key mechanisms for increasing the diversity order, robustness and effectiveness of a wireless multi-user communication system. Traditional packet scheduling are mainly designed for homogeneous single traffic scenarios. In this paper we present a novel scheduling algorithm that support real-time (RT) and non real-time (NRT) traffics at the same...
This paper presents a cross-layer concept with respect to a joint design of beamforming and scheduling in a cellular MIMO-OFDM-based network. Conventionally, the beamforming and scheduling processes are designed more or less independently of each other. In contrast, this paper describes a combined approach of the scheduling and beamforming procedure, with the aim to maximize the capacity and fulfill...
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