Dan J. Dechene

Energy-Aware Resource Allocation Strategies for LTE Uplink with Synchronous HARQ Constraints

In this paper, we propose a framework for energy efficient resource allocation in multiuser localized SC-FDMA with synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. The impact of retransmissions on the time-frequency problem segmentation is handled through the use of a novel block scheduling interval specifically designed for synchronous HARQ to ensure uplink users do not experience ARQ blocking. Using this framework, we formulate the optimal margin adaptive allocation problem, and based on its structure, we propose two suboptimal approaches to minimize average power allocation required for resource allocation while attempting to reduce complexity. Results are presented for computational complexity and average power allocation relative to system complexity and data rate, and comparisons are made between the proposed optimal and suboptimal approaches.

A Novel MIMO-Aware Distributed Media Access Control Scheme for IEEE 802.11 Wireless Local Area Networks

The current Internet architecture allows malicious nodes to disguise their origin during denial-of-service attacks with IP spoofing. A well-known solution to identify these nodes is IP traceback. In this paper, we introduce and analyze a lightweight single-packet IP traceback system that does not store any data in the network core. The proposed system relies on a novel data structure called Generalized Bloom Filter, which is tamper resistant. In addition, an efficient improved path reconstruction procedure is introduced and evaluated. Analytical and simulation results are presented to show the effectiveness of the proposed scheme. The simulations are performed in an Internet-based scenario and the results show that the proposed system locates the real attack path with high accuracy.This paper proposes a new distributed media access control (MAC) scheme to improve the network performance of Multiple-Input Multiple-Output (MIMO) wireless systems. In particular, this novel MAC scheme efficiently schedules two simultaneous transmissions between wireless stations (each equipped with three antennas) that are located in a single collision domain. Along with weighted nulling and intelligent packet fragmentation, this MAC scheme is capable of providing more efficient utilization of channel resources. The proposed MIMO-aware MAC scheme is compatible with the IEEE 802.11 standard. Detailed simulations are carried out to study the performance of the proposed scheme. The performance of the MIMO-aware MAC scheme is also compared with a recently proposed MIMO MAC scheme in the literature which is compatible with the IEEE 802.11 standard. Comparisons reveal that the proposed MIMO-aware MAC scheme achieves better throughput and delay performance under both saturated and unsaturated conditions.

Energy Efficient Resource Allocation in SC-FDMA Uplink with Synchronous HARQ Constraints

In this paper we propose framework for energy efficient (margin adaptive, MA) resource allocation in multiuser SC-FDMA under synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. To limit the impact of retransmissions on the time-frequency problem segmentation, we propose use of a block scheduling interval that ensures uplink users do not experience ARQ blocking. We formulate the optimal MA resource allocation problem under this framework and based on its structure, we propose a variable complexity sub-optimal approach to solving the resource allocation problem. The proposed methods performance is shown to minimize transmission energy for low complexity implementation.

Energy efficient QoS constrained scheduler for SC-FDMA uplink☆

Abstract In this paper we propose a framework for an energy efficient scheduler for multiuser SC-FDMA with queue state information (QSI) and quality of service (QoS) constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. The scheduling policy is obtained in two stages for the intra- and inter-user allocations respectively. A near optimal iterative allocation method is used for the inter-user allocation and the intra-user allocation policy is obtained using a constrained Markov decision process framework. Results are presented for the energy performance.

QoS, Channel and Energy-Aware Packet Scheduling over Multiple Channels

In this letter, we extend the study from our previous work in. First, we extend physical layer resource allocation problem to a packet based transmission scheme. The proposed packet assignment improves the implementation robustness as it allows for consideration of coded modulation schemes while still ensuring energy efficient transmission as with our previous work. Secondly, we study the impact of channel partition size selection on system performance and complexity.

Energy Efficient Quality of Service Traffic Scheduler for MIMO Downlink SVD Channels

In this paper we focus on minimizing the long-term average power consumption of a single transmitter providing Quality of Service (QoS) enabled traffic to a single receiver. Both the transmitting and receiving stations are equipped with multiple antennas. First, we present a general {Kx M} system model where K is the number of independently buffered QoS streams and M is the number of parallel channels available through MIMO SVD eigenmode transmission. Through application of the constrained Markov decision process (MDP) framework combined with a novel MAC layer rate assignment scheme, a randomized per-buffer scheduling policy is obtained. The designed policy exploits queue state information to schedule traffic while meeting throughput, delay and loss constraints. Packets scheduled for transmission during each frame are mapped across the set eigenmode channels subject to available channel resources and the set of channel eigenvalues. Simulation results are provided for several scenarios. System drawbacks, limitations and extensions are also discussed.

On the first and second order statistics of sparse MIMO channels

In this work sparse Multiple-Input, Multiple-Output (MIMO) channels are analyzed. Analytical expressions are derived for the first and second order statistics of the unordered channel eigenvalues and for capacity of a single cluster MIMO channel. We show that the capacity process is approximately Gaussian for even a small number of clusters and further derive an approximate LCR and AFD expression for the multiple cluster MIMO channel.

Full length article: Performance evaluation of MIMO-aware media access control protocol

Multiple-Input and Multiple-Output (MIMO) systems are recently being recognized for achieving simultaneous transmissions on wireless channels that overlap in time. As a result, new scheduling mechanisms are required that coordinate these multiple transmissions among wireless stations which share a single wireless channel. This paper proposes a new distributed MIMO-aware medium access control (MA-MAC) protocol which allows two simultaneous transmissions overlapped in time when stations are equipped with MIMO. The proposed MA-MAC protocol is compatible with the existing IEEE 802.11 standard for wireless local area networks (WLANs). It uses weighted nulling and intelligent packet fragmentation for its operation. Detailed performance analysis of MA-MAC protocol is carried out using the NS-2 network simulator. Firstly, this paper presents the concept of weighted nulling that is necessary for simultaneous transmissions on wireless channel, followed by a detailed description of the proposed MA-MAC scheme. Secondly, it presents the performance of MA-MAC scheme under various network scenarios that includes both saturated and unsaturated conditions. This paper presents the performance improvements shown by MA-MAC when compared with an existing medium access control scheme which is also proposed for scheduling simultaneous transmissions for MIMO.

Experimental Triple-Play Service Delivery Using Commodity Wireless LAN Hardware

In this paper we study the feasibility of utilizing wireless local area network (WLAN) technology to deliver the Triple-Play services (video, voice and data) over a specific system model. Existing protocols are shown to not efficiently manage the wireless channel therefore we propose a new Triple-Play time division multiple access (TP-TDMA) media access control (MAC) protocol to provide Quality of Service (QoS) for these Triple-Play services in a point-to-multipoint network over an existing 802.11a physical layer. Through extensive simulation analysis, the protocol is shown to offer better performance than the 802.11e Enhanced Distributed Coordination Function (EDCF). Moreover, this protocol is implemented in hardware using the MADWiFi driver to verify the real-world performance. Both results of the simulation study and hardware implementation are provided.

On energy efficiency of pilot assisted modulation schemes

In this paper we investigate energy efficiency of basic modulation techniques in systems with partial channel state information (CSI) at the receiver, obtained via channel estimation. Both in-band and superimposed pilot aided channel estimation schemes are considered. Efficiency is defined as amount of energy per bit of information delivered. The efficiency is optimized with respect to the number and/or power of pilots for a given modulation. It is shown that there is an optimal power allocation for every modulation scheme and channel estimation scheme.