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Fractional frequency reuse (FFR) is an interference coordination technique well-suited to OFDMA based wireless networks wherein cells are partitioned into spatial regions with different frequency reuse factors. This work focuses on evaluating the two main types of FFR deployments: Strict FFR and Soft Frequency Reuse (SFR). Relevant metrics are discussed, including outage probability, network throughput,...
We investigate the maximum outage throughput for Orthogonal Frequency Division Multiple Access (OFDMA) systems in the presence of feedback channel capacity constraints. We attempt to establish an information-theoretic lower bound on the capacity of feedback channel and build the corresponding test channel that achieves this lower bound. Based on the derived test channel, we formulate the outage throughput...
The ability of adapting to the environment in the most efficient way is a crucial issue in Cognitive Radio (CR) networks. For this purpose, an accurate estimation of the characteristics and activity of the Primary Users (PUs) is required. A system that takes into account heterogeneous PUs with several features is developed. A new scheme is integrated in the system to exploit these motleys and to improve...
In this paper, we formulate a joint optimization problem for resource allocation and scheduling in multi-cell orthogonal frequency division multiple access (OFDMA) half-duplex decode-and-forward (DF) relay assisted networks. Our problem formulation takes into account multi-cell interference and heterogeneous data rate requirements. We transform the resulting non-convex and combinatorial optimization...
Machine learning algorithms have recently attracted much interest for effective link adaptation due to their flexibility and ability to capture more environmental effects implicitly than classical adaptation algorithms. However, past applications are limited to rather simple configurations such as identifying channel condition or link adaptation in fixed or slowly varying channels. Recently, more...
QoS provisioning is an important issue in the deployment of broadband wireless access networks. The scheduling scheme is essential to guarantee the QoS requirements of different service classes. WiMAX Orthogonal Frequency Division Multiple Access (OFDMA) system specifies the Orthogonal Frequency Division Multiplexing (OFDM) symbol mapping in a rectangular shape manner. In this paper, we propose a...
In this paper, we propose a distributed adaptive interference coordination algorithm for a practical orthogonal frequency division multiple access (OFDMA)-based mobile cellular systems. The designed algorithm can achieve an efficient frequency reuse for any user distribution and traffic load. Since no a priori frequency planning is required, the minimal coordination between base stations is also achieved...
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...
Communications over power line channels offer inexpensive and convenient solution for signal transmission; however power line channel suffers from multipath fading and frequency selectivity along with manmade burst impulsive noise. Data spread OFDM has been evolved as an efficient adaptive modulation that controls the power of each subcarrier according to its channel transfer function. This paper...
OFDMA (Orthogonal frequency division multiple access) based systems have been considered as a candidate for future wireless communication systems. In such a system, it is important to provide high data rate services for users with high mobility. For this purpose, decision-directed channel tracking (DDCT) techniques have been investigated for OFDM systems in high mobility environments. The performance...
This paper focuses on the coexistence problem of multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) systems and current radio systems such as IEEE802.11a. Aiming at improving the performance of MB-OFDM UWB, we attempt to avoid interferences from IEEE802.11a systems. The cognitive radio (CR) technology is introduced to detect the distribution of co-channel interferences...
This paper proposes a novel approach, based on game theory, for radio resource allocation in the downlink of cellular networks using Orthogonal Frequency Division Multiple Access. The reference technology is the Long Term Evolution of the 3GPP UTRAN. The main contribution is to identify a model for the allocation objectives, and how to approach them in a tunable manner. The resource management issue...
We focus on a new class of home networking applications that enable wireless communication between multimedia devices using the WiMedia MAC protocol. Applications like streaming video from DVD players to HDTVs, generate high data rates and can easily saturate the bandwidth even at the rates provided by UWB transmissions. Thus we need to enhance the MAC layer to improve bandwidth utilization and efficiently...
Efficient spectrum sensing ensures cognitive radio users opportunistically use the under-utilized frequency band without causing harmful interference to primary users. However, in practice, owing to the non-zero probability of the missed detection and false alarm of active primary transmission, a certain degree of performance degradation of the primary user is unavoidable. In this paper, we consider...
This paper presents system level downlink performance evaluation results for the TDD based LTE-Advanced networks utilizing some of the most recent technologies for mobile systems. The main enhanced technology components used in the systems include multi-user (MU)-MIMO, intra-site coordinated multipoint (CoMP) transmission and space-time-frequency proportional fair scheduling. Performance comparison...
This paper proposes a novel admission control (AC) algorithm for guaranteed quality of service (QoS) to all users. The proposed solution provides better utilization of system capacity using adaptive modulation (AM). A scheduler based on a per user priority function is also given in this paper. The AC is given by allocating the exact number of slots for each user that will meet its QoS. For every new...
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...
A novel coordinated scheduling algorithm for OFDM-based systems in multi-cell scenario is proposed in this paper. The studied algorithm based on the utility function is general for the downlink of networks. The algorithm coordinates the subcarrier assignment over the BS cluster. We first establish the framework for this inter-cell coordinated optimization problem through utility-based method. The...
When fast and accurate channel state information (CSI) at the transmitter is available, opportunistic power control (OPC) is an attractive alternative to signal-to-interference-and-noise ratio (SINR) target following approaches, because it maximizes throughput by taking advantage of fast channel variations. On the other hand, in multiple-input multiple-output (MIMO) systems, open loop schemes such...
Proportional Fair (PF) algorithm is known to achieve a good trade-off between efficiency and fairness by allocation opportunistically resources to users with good radio conditions, without sacrificing fairness considerations towards the other users of the system. On the other hand, Hierarchical Modulation (HM) is a means to increase the spectral efficiency of a given system by superposing an additional...
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