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In this paper, two novel approaches to filter-and-forward beamforming (FF-BF) in an underlay based relay-assisted cognitive network with frequency-selective channels are proposed. In our scheme, secondary users are allowed to transmit through multiple relays simultaneously with primary users over the same spectrum. Such a network suffers from both inter-symbol interference (ISI) and bidirectional...
This paper studies QoE (Quality of Experience) enhancement of audio-video IP transmission over the uplink channel, i.e., from subscriber stations (SSs) to the base station (BS), in the IEEE 802.16 BE service. We assume two types of capacity allocation schemes for uplink and downlink burst durations: static and adaptive. Furthermore, we introduce a piggyback request mechanism for uplink bandwidth requests...
In this paper, the queue dynamics of secondary users (SUs) in a multi-SU and multi-channel cognitive radio network is analyzed to obtain the expressions of quality of service (QoS) metrics. Specially, in the analysis, we take several lower-layer mechanisms and settings into account, including automatic repeat request (ARQ), finite-size buffer, adaptive modulation and coding (AMC) and non-ignorable...
In this paper, we consider a cognitive relaying network in which the secondary user accesses the channel with a certain access probability that depends on the feedback information sent by the primary destination. In addition, the secondary user is granted relaying capabilities by which it can relay primary traffic that was unsuccessfully transmitted by the primary user. We show that this proposed...
This study addresses the resource allocation problem for multi-user MIMO systems with consideration of real-time services. Specifically, we focused on the delay constraints modeling in this paper, since it is a fundamental QoS requirement for all real-time services. To simultaneously meet the delay constraints of all users, we first modeled this resource allocation problem with specific delay restrictions...
Long Term Evolution (LTE) has been proposed as a promising radio access technology to bring higher peak data rates and better spectral efficiency. However, scheduling and resource allocation in LTE still face huge design challenges due to their complexity. This paper divides the complex problem into three sub-problems: scheduling pattern, scheduling priority and quantity of scheduled data. Based on...
LTE standard defines strict requirements for service classes in order to provide end users with exceptional QoS characteristics including fast connectivity and high data rates. However there is no standard scheduling algorithm defined for LTE and the task of protecting end user satisfaction while maintaining service class restrictions is left upon the service provider and currently is an open issue...
We consider in this paper downlink scheduling at the Medium Access Layer (MAC) layer for delay sensitive traffic in wireless systems based on Orthogonal Frequency Division Multiple Access (OFDMA). We refer in particular to next generation wireless systems such as 3GPP-LTE. We propose an Opportunistic Packet Loss Fair (OPLF) scheduling algorithm based on calculating a simple dynamic priority function...
Orthogonal Frequency Division Multiple Access (OFDMA), Multiple Input Multiple Output (MIMO), and Adaptive Modulation and Coding (AMC) are advanced signal processing techniques introduced in the wireless 3GPP LTE standard. In MIMO-OFDMA system, by taking advantage of the spatial dimension and depending on the time-varying wireless channel condition, the most efficient modulation and coding with spatial...
In this paper, we investigate spectrum sharing and multiple access problems for the high-rate ultra-wideband (UWB) systems. Based on the use of the linear precoded orthogonal frequency division multiplexing (LP-OFDM) proposed as an evolution of the well known multi-band OFDM (MB-OFDM) solution supported by the WiMedia Alliance for future high-rate UWB systems, the objective of this paper is to study...
802.11e enhanced distributed channel access (EDCA) introduces different parameters to provide differentiated QoS support for various traffic classes. This brings additional difficulties and complexities to the traditional per-slot based Markov chain modeling techniques, where the transmission probability relies on generic time slots. Channel access cycle based modeling, which does not depend on per-slot...
A prototype of an enhanced QoS 802.11n circuit using a Tournament Contention Function (TCF) is presented in this article. First, the TCF developed is briefly explained. Then, a simple hardware implementation of this protocol in compliance with the 802.11n standard is proposed and evaluated.
Quality of Service (QoS) provided by the IEEE 802.11e amendment and by the proposed HCF Controlled Channel Access (HCCA) reference scheduler is tailored for Constant Bit Rate traffic streams. Moreover the numerous alternative scheduling algorithms are not suitable to serve Variable Bit Rate (VBR) traffic streams with the required QoS and real-time guarantees. This paper presents Immediate Dynamic...
As the technology of multimedia applications in Wireless Sensor Networks (WSNs) is highly desired nowadays, how to guarantee real-time service becomes one of the biggest research challenges in this area. Even though lots of related works have been conducted to meet this requirement in several ways, the specific traffic model for multimedia applications has not been taken yet. It makes these new approaches...
In high criticality crisis scenarios, such as disaster management, ad hoc wireless networks are quickly assembled in the field to support decision makers through situational awareness using messaging-, voice-, and video-based applications. These applications cannot afford the luxury of stalling or failing due to overwhelming bandwidth demand on these networks as this could contribute to overall mission...
In conventional cognitive radio networks it is usually assumed that the primary network remains unchanged. The onus is then placed on the secondary network users to make the best use of any residual radio capacity. In some situations however, the primary network operator may wish to accommodate secondary user access. This objective has motivated recent work which considers simple modifications at...
Multi-hop wireless communication is playing a key role in today's communication networks. Despite several advancements in communication protocols and technologies, QoS provisioning is still a challenging issue in multi-hop wireless communications. In this paper, we propose a novel scheduling mechanism based on resource reservation for guaranteeing the QoS performance of real-time sessions (RTSNs)...
Heterogeneous cellular networks which consist of macrocells and small cells can offer significant capacity gain by utilizing the resources of the small cells. However, to achieve this, the interference between the macrocells and the small cells must be carefully managed. In this work, we propose an uplink intercell interference control (ICIC) scheme which is a unified ICIC approach of handover based...
One of the today challenges for the mesh networks researches is reliable transmission of multimedia traffic. This traffic demands high quality of service (QoS), to provide which it is suitable to use Mesh Coordinated Channel Access (MCCA) — the novel medium access method described in IEEE 802.11s. According to MCCA, mesh stations (STAs) set up periodic reservations; if all STAs in the network support...
We present a new co-operative scheduling approach which provides not only more reliability but also higher effective capacity. Cooperation region is defined for active handoff users between two base stations (BSs) based on the user quality-of-service (QoS) requirements. A proper definition of co-operation or handoff region, where the user can be scheduled in a cooperative manner from more than one...
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