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This paper investigates open vs. closed access in the uplink of femtocell networks, for the particular case of orthogonal multiple access protocols like TDMA or OFDMA. Open access reduces near-far interference and provides an inexpensive way to expand the capacity of the operator's network. Additionally, with a cap on the amount of resources allocated to the cellular users, open access ensures the...
A queueing model is proposed for multiuser systems for increased spectrum efficiency and better QoS provisioning. Broadcast services are quickly finding their way in to the IP domain and service providers need to introduce different traffic servicing models to handle these bandwidth intensive multimedia services. In an Orthogonal- frequency-division-multiple-access system, using conventional subcarrier...
This paper considers a relay-assisted bidirectional cellular network where the base station (BS) communicates with each mobile station (MS) using orthogonal frequency-division multiple-access (OFDMA) for both uplink and downlink. We first introduce a novel three-time-slot time-division duplexing (TDD) transmission protocol. This protocol unifies the direct transmission, one-way relaying and network-coded...
Uplink scheduling in a multicell OFDMA system is considered. A non-collaborative intercell interference avoidance method is proposed, where base stations shut down certain subcarriers in a probabilistic manner based on the received interference level. Proportional fair scheduling is implemented in order to ensure fairness for cell edge users. A low complexity scheduling algorithm is proposed for this...
Energy efficiency is increasingly important for wireless cellular systems due to the limited battery resources of mobile clients. While modern cellular standards emphasize low client battery consumption, existing techniques do not explicitly focus on reducing power that is consumed when a client is actively communicating with the network. Based on high data rate demands of modern multimedia applications,...
In this paper we address the challenge of multiuser scheduling in the downlink of 3GPP UMTS/LTE. Long Term Evolution (LTE) imposes the constraint of using the same code rate, modulation order and transmit power for all resources a User Equipment (UE) is scheduled onto. This, in addition to the lack of channel knowledge, prohibits theoretical concepts such as capacity maximization to be applied for...
In this paper, a linearly coded (LC) relaying scheme is proposed for multiuser relay network in which a number of users communicate simultaneously with a common destination with the help of one relay node, by using orthogonal frequency division multiple access (OFDMA). The proposed linear coding at the relay node enables exploiting the frequency diversity in the relay-to-destination (R-to-D) link...
Subcarrier and power allocation plays an important part in optimizing the performance of OFDMA systems. However, inter-cellular interference is often neglected in resource allocation. In this paper, with the inter-cell interference taken into account, we propose a subcarrier and power allocation framework based on Game Theory in uplink OFDMA multi-cellular systems. In this algorithm, the subcarrier...
Fractional Frequency Reuse (FFR) is one of the key concepts for mitigating inter-cell interference and improving cell-edge performance in OFDMA networks. The standard FFR scheme is intuitive and optimal for the hexagon-shaped cell pattern. In contrast, real-life OFDMA systems have very irregular cell layout, thus the number of surrounding cells and their respective interference vary significantly...
The problem of competitive rate-maximization is an important signal-processing problem for power-constrained multi-user systems. It involves solving the power control problem for mutually interfering users operating across multiple frequencies. We introduced robust rate-maximization game for systems with bounded channel uncertainty. In this paper, we analyse the effect of uncertainty on the global...
This paper considered multiuser orthogonal frequency multiple access (OFDMA) scheme, which has been proposed as the transmission technique for 4th Generation (4G) cellular network. An optimum and dynamic radio resource (subcarrier and power) allocation scheme is proposed for OFDMA multiuser system. The proposed algorithm has considered a structured degree of flexibility among the services that can...
In this paper, we propose a new dynamic frequency assignment scheme for femtoCells in OFDMA networks. The femtoCell base stations are small cellular base stations specially designed to improve the poor indoor coverage and increase the system capacity for cellular and wireless broadband networks. However, these femto-base stations cause harmful interference to the macroCells. Therefore, the optimization...
Cognitive radio is an emerging research topic aiming to improve spectrum usage. This paper deals with resource allocation problem in OFDMA cognitive radio systems. Previous research that has dealt with this problem assume perfect knowledge of the channel state information (CSI) and few works consider the quality of the spectrum sensing in the resource allocation issue. The proposed approach combines...
The objective of the present paper is to propose a rapid and accurate method for the evaluation of the quality of service (QoS) perceived by the users in the uplink of wireless cellular networks. In doing so we aim to account for the dynamics induced by the arrivals and the departures of the users. In particular, the QoS is evaluated in terms of the blocking probability for streaming users and the...
In this paper, a new opportunistic feedback protocol for orthogonal frequency division multiple access (OFDMA) systems with mixed realtime (RT) and non-realtime (NRT) traffic is proposed and analysed. Based on the proposed feedback mechanism, a dedicated feedback channel is allocated for each RT user, while shared feedback channels are available for all NRT users. NRT users have to compete to send...
The emerging trend to provide users with ubiquitous seamless wireless access leads to the development of multi-mode terminals able to smartly switch between heterogeneous wireless networks. This switching process known as vertical handover requires the terminal to first measure various network metrics. A relevant metric is the allocation rate of network physical channels. In the context of OFDMA and...
In this paper, we propose a fuzzy logics based scheduling (FLBS) scheme for downlink orthogonal frequency division multiple access (OFDMA)/space division multiple access (SDMA) systems with multimedia traffic. The challenge in the scheduling problem of OFDMA/SDMA systems with multimedia traffic is how to effectively utilize the scarce radio resource as well as maximize the system throughput and guarantee...
In this paper, we present a new power allocation algorithm called distributed inter-cell power allocation (DIPA) that improves the throughput-fairness trade-off without inter-BS coordination for multi-cell OFDMA systems in fast time-varying environment. In order to preclude the affection of instantaneous channel variation, the DIPA is designed to operate in large time scale (or super-frame) based...
Broadband Wireless Access (BWA) is gaining interest due to the increasing demand of high-quality mobile wireless systems. In this context, the IEEE 802.16 standard, and particularly its OFDMA physical transmission mode, is one of the most promising and researched technologies. In OFDMA, data have to be mapped into a time-frequency matrix before the actual transmission. Efficiency, power consumption...
The problem of estimating multiple Carrier Frequency Offsets (CFOs) in the uplink of MIMO-OFDM systems with Co-Channel (CC) and OFDMA based carrier allocation is considered. The tri-linear data model for generalized, multiuser OFDM system is formulated. Novel blind subspace based estimation of multiple CFOs in the case of arbitrary carrier allocation scheme in OFDMA systems and CC users in OFDM systems...
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