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We address the problem of downlink multiuser scheduling in practical wireless networks under a desired fairness constraint. Wireless networks such as LTE, WiMAX and WiFi provide partial channel knowledge at the base station/access point by means of quantized user equipment feedback. Specifically in 3GPP's LTE, the Channel Quality Indicator (CQI) feedback provides time-frequency selective information...
Multiuser (MU) - multiple input multiple output (MIMO) techniques are attractive to increase the downlink spectrum efficiency since they allow a small number of antennas at each user station (STA). In MU-MIMO systems, the transmission performance is affected by the STA combination that is spatially multiplexed in the same frequency and same time slot. Thus, the AP needs to determine the optimum STA...
Dynamic spectrum access (DSA) is an important design aspect for the cognitive radio networks. Most of the existing DSA schemes are to govern the unlicensed user (i.e., secondary user) traffic in a licensed spectrum without compromising the transmissions of the licensed users, in which all the unlicensed users are typically treated equally. In this paper, prioritized unlicensed user traffic is considered...
With the limited wireless spectrum and the ever-increasing demand for wireless services, how to enlarge wireless network throughput is a pressing issue. To exploit the wireless spatial capacity, concurrent transmissions, if controlled appropriately, can lead to overall higher spectrum utilization and network throughput. The optimal scheduling and power control for concurrent transmissions in rate-adaptive...
This paper shows a Self-organizing networks (SON) algorithm for interference coordination in downlink Orthogonal Frequency-Division Multiple Access (OFDMA) networks. A distributed algorithm is introduced with a proof of convergence for a static user population. The algorithm uses closed-form formulas for the transmit powers update, and is therefore computationally light. The proposed algorithm is...
The probability of instantaneous accepted packet error outage (IAPEO) is proposed as a performance measure for packet transmission with automatic-repeat-request (ARQ) schemes over wireless channels. It is defined as the probability that the instantaneous accepted packet error probability (IAPEP) exceeds an IAPEP threshold. We obtain a closed-form upper bound expression for IAPEO of a pure ARQ over...
In conventional WLANs, stations (STAs) select access points (APs) using the existing scheme based on the current quality of links. However, some novel improved architecture of WLANs is proposed with cognitive radio (CR) to negotiate spectrum usage, where the existing AP selection scheme might not be suitable for it. Thus in this paper, a new optimal AP Selection based on Restless Bandits (APSRB) scheme...
Carrier aggregation (CA) is one of the key features for LTE-Advanced. By means of CA, two or more component carriers (CCs) can be aggregated to form a much wider transmission bandwidth up to 100 MHz in order to meet the IMT-Advanced requirements. With CA, it is possible to schedule a user equipment (UE) on multiple component carriers simultaneously. From radio resource management (RRM) perspective,...
In recent years, the femtocell plays an important role in wireless networks not only for its spectrum reuse but also for its low power consumption. However, there exists several critical issues that need to be investigated, especially for the interferences between the macrocells and the femtocells. Two major access policies are considered in the femtocell network, including the closed access mode...
Femtocells are expected as the surest way to increase the system capacity with higher-quality links and more spatial reuse in future networks. In spite of their great potential, the system capacity is highly susceptible to network density because a large portion of users are exposed to inter-cell interference (ICI). In this work, we proposed a dynamic interference avoidance scheme in densely deployed...
A lot of access points (APs) in wireless mesh networks (WMNs) are battery powered. In order to minimize their energy consumption, the APs can adaptively adjust their transmission power and time based on various network conditions. In this paper, the problem of minimizing the AP energy consumption is formulated as an optimization problem with the constraint to satisfy the throughput requirements of...
The issue of distributed channel selection in opportunistic spectrum access is investigated in this paper. We consider a practical scenario where the channel availability statistics and the number of competing secondary users are unknown to the secondary users. Furthermore, there is no information exchange between secondary users. We formulate the problem of distributed channel selection as a static...
Prior work in implementing spectrum sharing scenarios for cognitive radio networks has relied on the unlikely assumption of full cross-channel knowledge made available to the cognitive transmitter (CT) and/or the target primary receiver (PR). However, estimation of this cross-channel knowledge is not only important from a practical stand-point, but also in limiting the real interference power felt...
Multi-Packet Reception (MPR) enables simultaneous receptions from different transmitters to a single receiver, which has been demonstrated to bring capacity improvement in wireless network. However, MPR does not improve the transmission capability of intermediate relay nodes in a multi-hop routing and thus these nodes may become the bottlenecks for increasing throughput despite of great reception...
Deploying energy harvesting nodes can significantly extend the lifetime of a battery powered wireless network. The nature of these systems calls for specific design principles to efficiently utilize the dynamic energy resources. In contrast to the conventional wireless networks, transmission policies for these systems should take into account the recharge process of the node as well as its battery...
It has been well recognized that channel state information (CSI) feedback is important for dowlink transmissions of closed-loop wireless networks. In this paper, we investigate the CSI feedback rate control problem in the analytical setting of a game theoretic framework, where a multiple-antenna base station (BS) communicates with a number of co-channel mobile stations (MS) through a minimum mean...
Cooperative sharing of spectrum among one primary user (PU) and multiple secondary users (SUs) helps to enhance the throughput of the whole system. In this paper, we propose a two-tier game in the sharing of spectrum in which SUs make their decisions on whether to cooperate under replicator dynamics and the PU adjusts its strategy to allocate time slots for the cooperative SUs' transmission. Furthermore,...
Scheduling schemes of wireless networks determine packet transmission opportunities for each network node by considering network parameters such as link quality, transmission rate, and delay. However, security has not been taken into account in these schemes, although it plays a critical role in network performance. In this paper a new scheduling scheme is proposed to determine packet transmissions...
In this paper we study the long-term throughput performance of repetition protocols coupled with power control for multiple access block-fading channels. We propose to use the feedback bits to inform the transmitter about the decoding status and the instantaneous channel quality. We determine the throughput of simple and practically inspired protocols; we show remarkable throughput improvements, especially...
Due to the massive use of parallel and distributed operations of inputs and outputs, iterative scheduling algorithms are attractive in finding a maximal size matching for an input-queued switch. For constructing a large high-speed switch, a distributed multi-chip implementation of an iterative scheduling algorithm should be followed. Since different chips may locate on different switch linecards and...
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