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A. Dejonghe,
J. Declerck,
F. Naessens,
M. Glassee,
A. Dusa,
E. Umans,
A. Ng,
B. Bougard, G. Lenoir,
J. Craninckx,
L. Van der Perre
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ABSTRACT: Wireless access schemes was implemented on software defined radios (SDRs) in the future. In mobile terminals, SDRs should couple a high functional flexibility to low power operation. A two-step approach is advocated in this context. First, energy-scalability is introduced in the SDR design. Secondly, intelligent run-time cross-layer control is introduced to enable low power operation, by exploiting this scalability as well as the dynamics in the system. As a result, SDRs can be realized achieving a power consumption which can be comparable with dedicated radios, both in standby/idle mode or when transmitting or receiving data. This concept is validated on a transaction-level model (TLM) of our SDR platform, showing architectural integration and paving the way towards chip instantiation.
Mobile and Wireless Communications Summit, 2007. 16th IST; 08/2007
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ABSTRACT: Achieving low energy consumption is one of the main challenges for wireless video transmission on battery limited devices. Moreover, the bandwidth is scarce and needs to be properly shared amongst different users. Congestion in the network can result in packet losses, with a significant impact on video quality. In this paper we propose the use of a channel-adaptive rate control mechanism in a multi-user WLAN up-link scenario. The benefit is twofold: the communication energy is reduced and congestion is strongly alleviated allowing an increase of the video quality or a network capacity increase for a similar quality
Acoustics, Speech and Signal Processing, 2007. ICASSP 2007. IEEE International Conference on; 05/2007 · 4.63 Impact Factor
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ABSTRACT: The efficient transmission of video content over wireless communication networks is a challenging goal, especially when considering multiple mobile users equipped with energy-constrained handheld devices and sharing the same channel resources. In the present work, considering the scenario of the real-time delivery of multiple MJPEG2000 video streams over a QoS-enabled 802.11e wireless LAN, we investigate the performance of multiple description coding and compare it with different video transmission techniques. We analyze if and when data redundancy of the information source can improve the end-to-end perceived quality in this realistic multi-user scenario
Multimedia Signal Processing, 2006 IEEE 8th Workshop on; 11/2006
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ABSTRACT: Multiple-antenna techniques (MIMO) have been proposed to improve wireless links spectrum efficiency and/or robustness. There exists a fundamental tradeoff between potential spectrum efficiency and robustness increase. But these multiple-antenna techniques come with an overhead in power consumption due to the duplication of part of the transmitter and receiver front-ends. From a system perspective, one has to focus on performance versus power consumption tradeoff. In this paper, we derive SmartMIMO: an adaptive energy-aware link adaptation approach which, next to the modulation and code rate, decides on using either space-division multiplexing (increasing spectrum efficiency) or space-time coding (increasing robustness) to transmit a given packet on a given MIMO channel. Energy-efficiency is shown to be improved by up to 30% when compared to non-adaptive techniques while the average rate is improved by up to 50% when compared to single-antenna transmission
Signal Processing Systems Design and Implementation, 2006. SIPS '06. IEEE Workshop on; 11/2006
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ABSTRACT: The need for higher data rates in wireless system has driven most of the recent wireless research arena. However, the increase of the system transmission rate implies higher system energy consumption. This creates a serious problem in the case of battery-powered devices such as wireless terminals. Therefore, a power management policy is necessary to dynamically trade off the system transmission rate and its energy consumption. In previous work, cross-layer energy-aware radio link control has been applied on OFDM-based WLAN transceivers. Such systems are designed for operating in indoor environment, where they can provide high throughput under low mobility conditions. Thus, the cross-layer energy-aware radio link control relies on a constant average path loss. However, in a wireless indoor environment, the average path loss can encounter significant random changes if, for instance, unpredictable object appears suddenly between the transmitter and the receiver, or simply if one or both terminal moves. The average path loss variation can reach up to 40 dB in some cases. Consequently, the power management stability can be dramatically affected. This paper aims at analyzing the sensitivity of the cross-layer energy radio link control due to such real-time average path loss variation. We also propose a more robust approach to ensure the stability of the considered radio link control strategy against random average path loss changes. From the simulation results, we have proven that the proposed radio link control approach can reduce the relative sub-optimal energy consumption per bit down to 5% compared with perfect calibration, which implies a factor 6 reduction in the sub-optimal energy consumed per bit regarding the existing radio link control.
Signal Processing Systems Design and Implementation, 2005. IEEE Workshop on; 12/2005
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ABSTRACT: Next generation wireless local area network (WLAN) terminals have to cope with increasing performance requirements while energy budgets are more and more constrained by portability. Next to low power circuit and architecture design, system-level power management is a key technology to fill this gap. Recently, radio link control techniques have been proposed, not only as a way to maximize performance but also to reach energy awareness. Transmit rate and power are adapted to meet exactly the user requirements while minimizing the average power consumption. However, schemes proposed so far do not exploit the characteristics of the specific modulation scheme considered in most recent WLAN standards: orthogonal frequency division multiplexing (OFDM). In this paper, we design a practical energy aware radio link control scheme, optimized for OFDM transceivers and compatible with current standards. Simulation results depict up to 80% transceiver power reduction when compared with throughput maximizing schemes.
Signal Processing Systems, 2004. SIPS 2004. IEEE Workshop on; 11/2004
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ABSTRACT: Low power consumption is imperative to enable the deployment of broadband wireless connectivity in portable devices such as PDA or smart telephones. Next to low power circuit and architecture design, system-level power management is revealed to be a key technology for low power consumption. Recently, "lazy scheduling" has been proposed for system level power reduction. It has been shown to be very effective and complementary to more traditional shutdown based approaches. So far, analysis has been carried out from the viewpoint of medium access control (MAC) and data link control (DLC) layers. Yet, effective power management in radio communication requires consideration of end-to-end cross-layer interactions. In this paper, we analyze the implication of "lazy scheduling" from the transport layer perspective. It is shown that a key trade-off between queuing delay and physical layer energy drives the global trade-off between user throughput and system power. Conditions under which "lazy scheduling" is efficient are established and important conclusions on effective system-level architecture and cross-layer power management are drawn.
Signal Processing Systems, 2004. SIPS 2004. IEEE Workshop on; 11/2004
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ABSTRACT: Next generation wireless local area networks (WLANs) have to cope with energy budgets severely constrained by portability, autonomy and high integration requirements. Practical power management approaches currently implemented aim at reducing the transceiver duty cycle. However, recently developed energy-aware link adaptation techniques, which trade off dynamically performance versus energy consumption, potentially bringing a factor-10 consumption reduction, promise to be more effective. Yet, to enable a meaningful trade-off, systems must present sufficient energy-scalability, i.e., energy consumption benefit when reducing the performance requirements or the environment constraints. This is not the case in current WLAN transceivers for which we show that duty cycle-based power management strategies are more effective. To make effective energy-aware link adaptation possible in future WLAN transceivers, we present techniques aiming at increasing their energy-scalability. Results show that a up to 7-fold energy consumption scalability can be achieved, providing significant margin to get energy consumption reduction by adapting to the user requirements.
Signal Processing Advances in Wireless Communications, 2004 IEEE 5th Workshop on; 08/2004
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ABSTRACT: The current demand in increasing data rate and quality of service in wireless communication has to cope with an energy budget severely constrained by autonomy and ubiquity requirements. Trading off performance and energy consumption deserves the highest attention to enable the "anything, anywhere, anytime" paradigm. However, wireless systems are traditionally dimensioned according to worst-case context scenarios, where the high dynamism of the propagation environment and the user requirements are not exploited. To exploit this dynamism, potentially enabling disruptive energy reduction, we propose a novel approach that trades off performance and energy by regularly reconfiguring the system in order to match the user requirements in given propagation conditions with the minimal total energy consumption. Simulations for a representative scenario show that the total energy consumption can be reduced by a factor 5 to 20 while considering system-level parameters only. Moreover, comparing the system dynamism with typical environment- and user-related time constants shows that implementing the configuration optimization at run-time with the proposed approach can be done with very limited overhead.
Signal Processing Systems, 2003. SIPS 2003. IEEE Workshop on; 09/2003
