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Recent work has shown that distributed (or cooperative) beamforming can achieve cooperative gain, such as throughput gain and diversity gain, with no need for extra spectral holes in Cognitive Wireless Networks (CWNs). However, how to efficiently schedule cooperative beamforming to improve the quality of service of unlicensed secondary users has not been well addressed. In this paper, a simple opportunistic...
In this paper, we evaluate a multilevel coding (MLC) scheme with multi-stage decoding (MSD) designed for satellite broadcasting communications, where services with different quality of service (QoS) are desirable. A simple Land-Mobile-Satellite (LMS) channel model is presented, based on channel states and their transitions. The instantaneous channel capacity for suburban and forest scenarios is calculated...
In this paper, we propose an new admission control scheme jointly taking into account call-level QoS based on the dropping probability of handoff call and packet-level QoS based on the outage probability over threshold in IEEE 802.16e where user mobility is allowed and adaptive modulation and coding (AMC) is employed. The proposed admission control scheme is characterized by both a threshold for handoff...
In this paper, a new joint scheduling and hybrid resource allocation method is derived and investigated for a multi-user downlink Orthogonal Frequency Division Multiple Access (OFDMA) system that provides Time Delay-Sensitive services (TDS) and Time Delay-Insensitive services (TDI). A three sectored multi-cellular heterogeneous traffic environment is considered where users are randomly distributed...
Power control plays significant role in the cognitive network system where secondary users (SUs) co-exist with primary users (PUs), but the interference due to SUs may affect the performance of PUs. The approach of considering the outage probability of PU as quality of service (QoS) constraint, while using the maximization function of secondary user throughput is used in this paper. A generalized...
In this paper, the problem of joint subchannels and power allocation for a OFDM based downlink cognitive radio system is studied. The joint allocation problem is formulated as an optimization problem under multiple constraints. Different from recent researches, we consider a more practical scenario and choose the outage probability as the constraint guaranteeing QoS of primary users. Then the constraint...
Cooperative communications have been demonstrated to be effective in combating the multiple fading effects in wireless networks, and improving the network performance in terms of adaptivity, reliability and network throughput. In this paper, we investigate the use of cooperative communications with adaptive relay selection for resource-constrained wireless sensor networks, and propose QoS-RSCC, a...
We consider a broadcast channel (BC) in which the base station is equipped with multiple antennas and each user has a single antenna. We study the design of systems with linear precoders and probabilistically-constrained quality of service (QoS) requirements for each user, in scenarios with imperfect channel state information (CSI) at the transmitter. Each user's QoS is expressed as an upper bound...
We consider a broadcast channel with multiple antennas at the base station and single-antenna receivers, and we study transceiver design with quality of service (QoS) requirements in the presence of uncertain channel state information (CSI) at the transmitter. Each user's QoS requirement is formulated as an upper bound on the outage probability of the mean square error (MSE), and we demonstrate that...
The overall relay channel from the source to the destination via relays has temporal properties quite different from any cellular channel. This work presents a study for time-dependent performance of relay channels for both fast-fading and log-normal shadow fading in terms of average outage duration, frequency of outage and probability of outage. Results show that there is a good agreement between...
It is well recognized that power control is an important technique to combat the near far problem, the co-channel interference and the fading channel in the reverse link of direct sequence-code division multiple access (DS-CDMA). With tight power control algorithm, the system capacity and quality of service (QoS) can be enhanced. In this paper, we present the DS-CDMA model in Rayleigh fading channel...
Random beamforming has been considered as a practical scheme for MIMO BC system while achieving asymptotically optimal growth rate. However, this advantage is in terms of average sum rate performance, which is less meaningful when the quality of service is considered in system design. In this paper, we study the outage probability performance of random beamforming for both single receive antenna and...
In beyond 3G systems, one of the important factors is to address radio access technology (RAT) selection and load balancing between heterogeneous networks to ensure high spectral efficiency in an era where spectral resources are at a premium. This work aims to address the feasibility of utilizing WiFi as complementary service for HSDPA, to prevent quality of service deterioration in the event of network...
To efficiently utilize the limited spectrum of interference limited Wide-band Code-Division Multiple-Access (WCDMA) cellular networks, transmission rates allocation and base station association for mobile users need to be optimal. In this paper, Power-Controlled Rate and Coverage Adaptation (PCRCA) module is proposed to balance network load, maximize number of users admitted to the system while assuring...
Power consumption and Quality-of-Service are the critical factors when developing resource allocation strategies for wireless networks. In order to minimize total transmission power while meeting the end-to-end outage probability requirement in a distributed MIMO multi-hop network, we will formulate the power allocation task as a convex optimization problem. By using some approximations to the optimization...
IEEE 802.16, known as WiMAX, has received much attention for its capability to support multiple types of applications with diverse QoS requirements. Beyond what the standard has defined, radio resource management (RRM) still remains an open issue. In this paper, we propose a hierarchical downlink resource management framework for OFDMA based WiMAX systems. Our framework consists of a dynamic resource...
The operator of an UMTS radio access network has to define timeout thresholds for the radio resource control protocol. These timeouts have a strong influence on the quality of service of the user traffic. In general long timeouts favour the call setup time over the outage probability. For short timeouts it is the other way around. Furthermore the reached quality of service level depends on the load...
Assuring quality of service (QoS) is an extreme challenge in cellular multimedia delivery especially in single path transmission. One possible way to improve QoS is to provide multipath transmission. In this paper, we introduce a novel multi-path cellular network architecture through placement of additional base stations (BSs), i.e., antennae in the existing cellular architecture. This architecture...
Power control is one of the most efficient approaches to increase the capacity and quality of service (QoS) in cellular communication systems. Existing power control approaches are mostly suitable for environments with quasi-stationary channels, while in practice, the channel characteristics may vary very fast with time. Therefore these approaches do not accurately capture the the dynamics of a real...
A cell planning technique termed BRD (bandwidth and region division) is presented for overcoming interference, maintaining QoS (quality of service) and improving channel capacity over OFDM (orthogonal frequency division multiplexing)- based broadband cellular networks. Through an optimal combination of sectorization and zero padding, bandwidth and region division is achieved that minimizes the outage...
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