Sébastien Baey

Scheduling in OFDM Wireless Networks without Tradeoff between Fairness and Throughput

Providing multimedia services in wireless networks requires maximizing the system throughput without sacrificing fairness. Previous works focus on system capacity optimization but fail to jointly ensure adequate fairness. This paper proposes a new MAC scheduling scheme which dynamically takes in consideration the QoS experienced by the mobiles and the transmission conditions in an extended cross-layer design. Based on a weighted opportunistic algorithm, our resource allocation takes a maximum advantage of multiuser diversity optimizing fairness and system throughput. This provides an efficient support of multimedia services in OFDM wireless networks. Performance evaluation shows that the proposed scheduling widely outperforms the best existing wireless OFDM based scheduling schemes.

Compensated Proportional Fair Scheduling in Multiuser OFDM Wireless Networks

In wireless networks, providing a fair bandwidth allocation without too much reducing the system throughput is very challenging. Path loss attenuations induce unequal spectral efficiencies and in terms unequal throughtput for mobiles with different geographical positions. In the litterature, Proportional Fair (PF) is acknowledged as the reference scheduler in multiuser OFDM wireless networks. Opportunistically considering the channel state, PF is adapted to the wireless environment fighting the multipath fading negative effects. PF takes advantage of multiuser diversity and globally maximizes the throughput. Additionally, PF scheduling currently makes the best tradeoff between fairness and throughput maximization. However, severe fairness deficiencies appear when the mobiles experience unequal path loss. In this paper, we propose to solve this fairness issue with a modified PF scheme that introduces distance compensation factors. Simulation results show that this well-balanced resource allocation outperforms other existing scheduling schemes and jointly provides both high system throughput and high fairness.

An Efficient and Fair Scheduling Scheme for Multiuser OFDM Wireless Networks

This paper proposes a new MAC scheduling scheme for efficient support of multimedia services in multiuser OFDM wireless networks, both in the uplink and in the downlink. This scheme is based on a system of weights that dynamically accounts for the experienced QoS and the transmission conditions in an extended higher layers/MAC/PHY cross layer design. This approach solves the crucial issue of wireless multiple access schemes: ensuring fairness without sacrificing the throughput offered by the scarce bandwidth resource. Performance evaluation shows that the proposed scheduling outperforms existing wireless OFDM based scheduling schemes and demonstrates that choosing between high fairness and high system throughput is not required.

Comparison study of resource allocation strategies for OFDM multimedia networks

Advanced MAC scheduling schemes provide efficient support of multimedia services in multiuser OFDM wireless networks. Designed in a cross layer approach, they opportunistically consider the channel state and are well adapted to the wireless multipath fading environment. These schedulers take advantage of time, frequency, and multiuser diversity. Thereby they maximize the global system throughput while ensuring the highest possible level of fairness. However their performances heavily depend on the bandwidth granularity (i.e., the number of elementary resource units) that is used in the resource allocation process. This paper presents and compares the main OFDM scheduling techniques. In particular it studies the influence of bandwidth granularity on the resource allocation strategies performances. The paper reveals that though bandwidth granularity has never been considered in former studies, it is of major importance for determining the application range of advanced OFDM scheduling techniques.

Weighted fair opportunistic scheduling for multimedia QoS support in multiuser OFDM wireless networks

Efficient support of multimedia services in next generation wireless networks requires advanced scheduling schemes that achieve both system capacity maximization and full QoS differentiation. This paper proposes a new MAC scheduling scheme for multiuser OFDM wireless networks. Designed in an opportunistic cross-layer approach, this scheme uses a system of weights that dynamically adjusts the priority of the flows considering the transmission conditions and the QoS that they currently experience. This results in a very efficient management of the bandwidth. Performance evaluation shows that the proposed scheduling outperforms existing wireless OFDM based scheduling schemes providing full QoS differentiation, high fairness and system throughput maximization.

Adaptive and Generic Scheduling Scheme for LTE/LTE-A Mobile Networks

Abstract Schedulers for multi-carrier wireless networks are a central element of cellular systems and are subject to extensive research. However, state-of-the-art schedulers are hardly implementable in a real system such as long term evolution advanced (LTE-A), which imposes additional constraints on how resources are allocated. To address this problem, we first propose adaptive and generic scheduling scheme (AGSS) a generic resource allocation procedure that enables the implementation of state-of-the-art scheduling policies for building a LTE scheduler. In a second step, we propose our own scheduling policy called opportunistic PDOR aware (OPA) that both optimizes the use of the radio spectrum and provides the quality of service actually expected by applications. We show how to implement this policy using our generic scheduling scheme. We then compare the performance of AGSS to the classic scheme in a LTE environment when used with a given policy. We show that the proposed scheme outperforms the classic scheme whatever the policy. We also establish that OPA offers the best performances in terms of capacity and quality of service compared to state-of-the-art policies.

On the Link-Quality Aware Routing in Wireless Multi-Hop Networks: A Throughput-Stability Trade-Off Study

There are considerable researches focused on routing in wireless multi-hop networks dealing with random and unpredictable channel variations. As it is well-known that using the shortest path in terms of number of hops often leads to poor performance, most of the recent research efforts propose various link quality aware metrics. Yet, there is not many works addressing the stability issue of link quality aware routing which can be extremely important specially in providing quality of service for jitter sensitive applications. In this paper, we address the stability vs. throughput trade-off. We argue that a more reactive routing responds faster to link quality changes. This leads to detect the lossy channel faster and so converges to the higher quality path in a shorter time. Meanwhile, fast reacting to channel variations may produce higher path flapping and consequently higher jitter level.

Accurate 2-D localization of RFID tags using antenna transmission power control

Localization of tagged objects with sufficient precision is a main issue in many industrial applications. In this paper, a new approach is proposed for the localization of UHF passive tags simply using the environment learning approach. This method uses, for a given passive tag located in a 2-D space, an aggregate function of the Received Signal Strength Indicator (RSSI) for all the possible RFID readers transmission powers. Based on these measurements, we define a location signature, which is compared with those of other tags located at known positions in the neighborhood. We then implement a method based on the k-Nearest Neighbor (k-NN) algorithm to estimate the position of the target tag. Using a realistic test case involving seventy tags and four antennas, we show a very significant improvement of the localization accuracy in comparison with the results obtained using a single RSSI value.

Standard-Compliant LTE-A Uplink Scheduling Scheme With Quality of Service

In this paper, we focus on uplink scheduling with the practical constraints imposed by the Long-Term Evolution/Long-Term Evolution-Advanced (LTE/LTE-A) standard. We consider multimedia traffic generated by mobile users with heterogeneous quality-of-service (QoS) requirements. To tackle the resulting time and frequency problem, we then propose an adaptive and potential aware scheduling scheme (APASS), which is standard compliant and covers a wide range of scheduling objectives. This scheduling scheme is composed of three algorithms, which work jointly to provide an efficient solution. Our performance evaluation shows that the APASS outperforms other state-of-the-art scheduling schemes in terms of user satisfaction and delay.

Towards localization of RFID tags based on experimental analysis of RSSI

RFID has been developed for many applications such as object identification, object traceability, geometric localization, etc. In order to locate an object labeled by a tag, several characteristics of the tag responses have been studied. This yielded theoretical models whose accuracy is not sufficient in practice for targeted applications. In this paper, we investigate how to localize a tag based on the set of received signal strength indicator (RSSI) values measured for a large range of transmission powers. Using an extensive measurement campaign, we establish that the RSSI is a linear function of the transmission power of the RFID reader. Moreover, a minimum transmission power is necessary for activating the tag which also depends on its localization. As a result, the statistics of the RSSI for different transmission powers may be synthetized through a triple. We then show how this triple may be exploited for localizing a tag.