Vasileios D. Papoutsis

User selection and resource allocation algorithm with fairness in MISO-OFDMA

Evaluating wireless mesh network performances has become a specific challenge since the emergence of ubiquitous computing. In this article, we consider the network capacity as the performance measure and study its behaviour under two different interference models: (i) usual IEEE 802.11 MAC layer with acknowledgments at each hop, and (ii) block acknowledgments reported at the transport layer that can be included in the IEEE 802.16 standard. We derive a linear program modeling crosslayer characteristics of the wireless mesh network that is solved using column generation. We quantify the capacity gain induced by the move of the MAC acknowledgments into the transport layer, and show that a better load distribution is also obtained.Evaluating wireless mesh network performances has become a specific challenge since the emergence of ubiquitous computing. In this article, we consider the network capacity as the performance measure and study its behaviour under two different interference models: (i) usual IEEE 802.11 MAC layer with acknowledgments at each hop, and (ii) block acknowledgments reported at the transport layer that can be included in the IEEE 802.16 standard. We derive a linear program modeling crosslayer characteristics of the wireless mesh network that is solved using column generation. We quantify the capacity gain induced by the move of the MAC acknowledgments into the transport layer, and show that a better load distribution is also obtained.

A Decentralized Subchannel Allocation Scheme with Inter-Cell Interference Coordination (ICIC) for Multi-Cell OFDMA Systems

Inter-cell interference (ICI) is responsible for user throughput degradation and especially for users found near cell border which additionally experience serious path-losses. Efficient methods for ICI mitigation are ICI coordination (ICIC) schemes which allocate certain resources among users in different cells. In this paper we propose a decentralized ICIC scheme in order to mitigate the ICI and enhance the capacity of the users found near the cell-edge area of a wireless multi-cell OFDMA system. Key features of the proposed scheme are the subchannel the allocation in a user selective manner considering instantaneous channel conditions and subchannel reuse minimization. The multi-cell subchannel allocation problem is decomposed into a distributed single-cell optimization problem with inter-cell coordination facilitaded by interfaces similar to X2 in 3GPP Long Term Evolution (LTE) networks. We prove through simulation that the proposed scheme yields better performance than existing conventional schemes.

Chunk-Based Resource Allocation in Distributed MISO-OFDMA Systems with Fairness Guarantee

The resource allocation problem for the downlink of Orthogonal Frequency Division Multiple Access (OFDMA) wireless systems is investigated. It is assumed that the Base Station (BS) consists of multiple antennas in a Distributed Antenna System (DAS), whereas a single antenna is available to each user. Also, the allocation unit is not the subcarrier, as in conventional OFDMA systems, but a set of contiguous subcarriers (chunk). The proposed suboptimal but efficient algorithm maximizes the system throughput subject to total available power and proportional data rate constraints among users. Simulation and complexity comparison are provided to show the benefits of chunk-based resource allocation to DASs.

Chunk-Based Resource Allocation in Multicast OFDMA Systems with Average BER Constraint

The resource allocation problem for the downlink of Orthogonal Frequency Division Multiple Access (OFDMA) wireless multicast systems is investigated. It is assumed that both the Base Station (BS) and each user are equipped with a single antenna and the allocation unit is not the subcarrier, as in conventional OFDMA systems, but a set of contiguous subcarriers (chunk). The aim of the proposed efficient algorithm is to maximize the total throughput subject to constraints on total available power and average Bit Error Rate (BER) over a chunk. Simulation and complexity analysis are provided to support the benefits of chunk-based resource allocation to multicast OFDMA systems.

A distributed radio resource allocation algorithm with interference coordination for multi-cell OFDMA systems

Inter-cell interference is a major problem in multi-cell OFDMA systems and can severely degrade the system throughput, particularly for cell-edge users. An efficient technique to mitigate inter-cell interference (ICI), is interference coordination that allocates certain resources among users in different cells. In this paper, we propose a novel and distributed algorithm in order to mitigate the inter-cell interference and enhance the capacity of the users near the cell-edge area of a multi-cellular network configuration. The main characteristics of the algorithm are the bandwidth allocation in a user selective manner and the collision avoidance with subchannels in use by users in neighboring cells. The algorithm requires coordination between base stations (BSs) in the sense that the cell-edge bands in adjacent cells should be orthogonal and channel occupancy state of each cell must be known to its neighboring cells. It is shown that the proposed algorithm has better performance than existing conventional schemes. Thus, our algorithm can be applied in next generation cellular systems 3GPP Long Term Evolution (LTE) and IEEE 802.16m.

Chunk-Based Resource Allocation in Multicast MISO-OFDMA with Average BER Constraint

The resource allocation problem for the downlink of Orthogonal Frequency Division Multiple Access (OFDMA) wireless multicast systems is investigated. It is assumed that the Base Station (BS) consists of multiple antennas in a Distributed Antenna System (DAS), whereas each user is equipped with a single antenna. The allocation unit is not the subcarrier, as in conventional OFDMA systems, but a set of contiguous subcarriers (chunk). The aim of the proposed efficient algorithm is to maximize the total throughput subject to constraints on total available power and average Bit Error Rate (BER) over a chunk. Simulation and complexity analysis are provided to support the benefits of chunk-based resource allocation to multicast Multiple Input Single Output (MISO)-OFDMA DAS systems.

Power efficient radio bearer selection for MBMS users in soft handover status

Multimedia Broadcast Multicast Services (MBMS) has been introduced in Third Generation Partnership Project (3GPP) Release 6 in order to address the need for efficient usage of the radio resources in multicast mode of UMTS. From the radio perspective, MBMS includes point-to-point (PTP) and point-to-multipoint (PTM) transmission modes. With PTP transmission mode one Dedicated channel (DCH) is established for each MBMS user within the cell. With PTM transmission mode one Forward Access Channel (FACH) is established covering a part of cells area and commonly shared by all the MBMS users within. In this paper we investigate the MBMS multicast mode under soft-handover condition in a cell and propose a mechanism that selects the transport radio bearer under soft-handover (SH) mode which reduces the Node Bs transmission power.

Efficient Resource Allocation Algorithm for Spatial Multiuser Access in MISO OFDMA Systems

The problem of user selection and resource allocation for the downlink of wireless systems operating over a frequency-selective channel is investigated. It is assumed that the Base Station (BS) uses many antennas, whereas a single antenna is available to each user and Orthogonal Frequency Division Multiple Access (OFDMA) is used as a multiple access scheme. The general mathematical formulation is provided but achieving the optimal solution has a high computational cost. For practical implementation, a suboptimal, but efficient algorithm is devised that is based both on Zero Forcing (ZF) beamforming and on spatial correlation and is less complex than other approaches. The algorithm maximizes the sum of the users’ data rates subject to constraints on total available power and proportional fairness among users’ data rates. Simulation results are provided to indicate that the algorithm can satisfy the fairness criterion. Thus, the algorithm can be applied to latest-generation wireless systems that provide Quality-of-Service (QoS) guarantees.