Sameh Najeh

A Simple Superposition Coding Scheme for Optimizing Resource Allocation in Downlink OFDMA Systems

In this paper, we propose to apply a simple superposition coding strategy for downlink of OFDMA systems. The novelty of this paper consists on allowing at most two users to share the same subchannel. The main idea is to consider the subchannels allocated to the users with the weakest link, and allow these subchannels to be shared by some potential users who can transmit some number of bits with only a small amount of power. To decrease the overhead of the proposed OFDMA system, we restrict to use a predetermined superposition encoding|decoding scheme. We address the problem of resource allocation, which consists on finding the optimal subchannel assignment in the OFDMA system. A low complexity algorithm, denoted Share Specific Subcarrier Allocation (SSSA) is then proposed. It offers a fairness allocation among users. This can be done by taking into account all user’s buffer states information. Simulation results confirm that the proposed technique outperforms the classical algorithms in terms of total throughput and dropping probability.

Radio resource allocation scheme for intra-inter-cell D2D communications in LTE-A

Device-to-Device (D2D) communications provide the means to users of cellular networks for reusing licensed spectrum by creating a direct link between two devices. However, enabling D2D communications in a cellular network presents a challenge in resource allocation because of the potential severe interference it may cause to the cellular network due to the reuse of the spectrum with the cellular users. Such interference can be prevented otherwise diminish if radio resource assigned intelligently with the coordination from the eNodeB (eNB). In this paper, we analyze the resource allocation problem in a multi cell environment and we propose a new scheme for Intra-Inter-Cell D2D communication when both Intra Cell D2D (Intra-cell-D2D) and Inter Cell D2D communication(Inter-cell-D2D) are present in the system.

Resource allocation in OFDMA networks with femto and macro-cells coexistence using Fractional Frequency Reuse (FFR)

Femto-cell is a recent solution that offers improved indoor coverage and enhances the system capacity. However, deploying femto-cells with macro-cells coexistence may introduce a phenomenon of interference. To remedy this problem, we propose in this paper a frequency allocation scheme for the downlink based on the Fractional Frequency Reuse (FFR). Unlike previous works in which a macro-cell is divided into two regions ( the inner and the outer regions ), our solution consists of dividing a cell into three regions, i.e, adding an intermediate region to exploit users diversity in the cell. We evaluate then the total throughput in a two-tier LTE femto-cells OFDMA network when varying the femto-cells number. The aim is to reduce interferences between both macro and femto cells and to maximize the total throughput. Simulation results show that by introducing a third region, the total throughput is considerably enhanced since the reuse factor is increased and a higher spectrum efficiency is achieved.

Subcarrier and bit allocation scheme for D2D communication based on OFDMA cellular networks

On future cellular networks, the study of subcarrier and bit allocation over D2D communications has become an important issue. Especially, the minimizing of the total transmit power consumption under a given requirement has become the topic of many researches. A pratical and efficient subcarrier and bit allocation scheme is proposed for D2D communications underlaid on wireless cellular networks to minimize the total transmit power consumption and maximize the resource utilization efficiency. System simulations demonstrate that substantial gains can be obtained using the proposed scheme. This not only gives significant overall power consumption of BSs, but makes a low run time, compared with existing schemes.

Resource allocation of OFDMA based cognitive radio systems under partial channel state information and raw sensing information

1 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 both partial CSI and raw sensing information (RSI), in order to offer a better compromise between the throughput and the quality of service (QoS) of the secondary system. The proposed algorithm is a sub-optimal low complex algorithm based on two steps. Simulations were drawn to evaluate the performance of this algorithm in terms of achievable data rate, power consumption, generated interference and QoS of the secondary users.

Predictive approach for OFDMA resource allocation over fixed wireless channels

WiMAX is a broadband wireless technology that supports fixed, nomadic, portable and mobile access. For the fixed or portable applications, the channel can be considered as a static. In this paper, we propose to use channel prediction in order to improve the performances of resource allocation algorithms, in term of outage probability and average throughput. Moreover, for a dynamic OFDMA system, when different traffics are offered at each time slot, a good scheduling of the available resources among the users is necessarily. We propose an algorithm of resource allocation based on both the prediction of the channel and the traffic in order to overcome the buffer overflow. For a Constant Bit Rate (CBR), we show that the channel prediction yields a significant average throughput.

Tractable framework for modeling and analyzing Joint CoMP Transmission and eICIC technology in two-tier heterogeneous cellular networks

Motivated by the advantages offered by the Coordinated MultiPoint (CoMP) technique in wireless cellular network, we propose in this paper a cell association scheme based on Joint Transmission (JT) CoMP, where a set of randomly located base stations, possibly belonging to different network tiers, cooperate to jointly transmit data to CRE users so as to mitigate co-tier and cross-tier interference and to attain an improved network performance. Furthermore, enhanced Inter-cell Interference Coordination (eICIC) technology is also incorporated in the proposed policy in which the Macro tier is muted on a fraction of total subframes, which are allocated exclusively to Pico users. Using tools from stochastic geometry, an exact integral expression for the outage probability and ergodic rate are derived. Simulation results show the advantages carried by our proposed scheme in enhancing the network spectral efficiency.

Resource allocation algorithm in downlink of OFDMA systems based on users' classification and superposition coding

In this paper, we propose a simple proportional fairness resource allocation technique for downlink OFDMA system, by re-arranging the set of users into four classes and setting different priority order. The classes are obtained according to buffers states and channels conditions. We offer priority to users having a delay sensitive traffic by considering those who have the fullest buffer and good channel conditions. Moreover, we propose to use the superposition coding technique to increase the system capacity. In fact, we will allow a degraded user (having bad channel condition) and a potential user (having good channel condition) to share the same subcarrier. At the degraded user side, the receiver will proceed as usual and will consider the information sent to the potential user as an additive noise. At the potential user side, a successive decoding process will be adopted. To avoid error propagation, which can occur in this case, the amount of transmitted power to each user will be optimized accordingly. A suboptimal resource allocation algorithm, based on the mentioned superposition scheme and users classification, is derived. Simulation results confirm that the proposed technique offers a proportional fairness allocation and outperforms the classical algorithms in terms of total throughput.

Joint proportional fairness admission control and superposition coding for OFDMA networks

In this paper, we aim to design an OFDMA frame-based resource allocation scheme allowing the power consumption minimization, the throughput enhancement and the queues stability. We have proposed a novel proportional fairness admission control strategy in order to guarantee the desired QoS for each user. To increase the number of admitted users, we investigate a joint superposition coding and admission control process permitting to further exploit the multiuser diversity. Furthermore, we have suggested a power and bandwidth allocation scheme permitting to minimize power consumption while ensuring buffers stability and satisfying the QoS requirements of users in a heavy load context. Numerical studies are conducted to evaluate the performance of the proposed algorithms in terms of served user and power consumption.

Interference management scheme for network-assisted multi-hop D2D communications

In a cellular network its very difficult to make spectrum resource more efficiently. Device-to-Device (D2D) technology enables new service opportunities, provides high throughput and reliable communication while reducing the base station load. For better total performance, short-range D2D links and cellular links share the same radio resource and the management of interference becomes a crucial task. We propose a radio resource allocation for multi-hop D 2D routes based on interference avoidance approach. Our analysis and numerical results indicate that even with Channel State Information (CSI) knowledge, we are able to improve the system performance in terms of throughput by allowing coexisting D2D communications while satisfying the cellular users constraints.