4648734
Selective channel feedback mechanisms for wireless multichannel scheduling
Opportunistic scheduling can significantly improve wireless network performance by exploiting the feedback information that conveys the underlying channel condition. In emerging multichannel systems, the perchannel feedback induces a substantial amount of feedback overhead and requires high computational complexity. To reduce the feedback overhead, we consider an opportunistic feedback strategy that activates the channel feedback opportunistically according to the channel condition. Then, we combine the opportunistic feedback with the best-n channel feedback scheme where a mobile user chooses the best n channels and transfers this information to the base station. We analyze the throughput and the amount of channel feedback information for proportionally fair opportunistic scheduling under Rayleigh fading i.i.d. channels. The numerical results confirm that our partial feedback schemes achieve a remarkable reduction in the amount of feedback information without a significant throughput degradation, thereby saving the scarce wireless bandwidth and limited battery power
4649924
WAF: wireless-adaptive fair scheduling for multimedia stream in time division multiplexed packet cellular systems
Cellular systems are designed to support voice service over the wireless channel but nowadays data-only networks such as cdma2000 1x EV-DO and high speed downlink packet access (HSDPA) are being deployed in the midst of evolution to the next generation wireless networks. Such systems become important because data services are essential in future wireless networks that are supposed to adopt the concept of all-IP to support integrated services. To increase the data transmission rate at downlink in cdma2000 1x EV-DO and HSDPA, the base station (BS) uses only a channel multiplexed by time division, not by code division. These systems use proportional fair scheduling to maximize throughput. While it is useful for non real time traffic, it does not provide appropriate QoS for real time services such as voice and video. Therefore we need to incorporate the multimedia QoS requirements into the design of a new scheduling algorithm. Our proposed wireless-adaptive fair scheduling (WAF) tries to allocate time slots with fair share according to the stream requirements considering the varying channel conditions to achieve good throughput. The simulation results show that our scheme can guarantee fair service and increase throughput by up to 41% compared to the purely fair (PF) scheduling scheme.
17089899
Delay-Sensitive Packet Scheduling for a Wireless Access Link
As the delay is a critical QoS factor, packet scheduling over a wireless access link that often becomes congested needs to have the objective of meeting each user's delay requirement. To incorporate the delay into the scheduler design, we consider the objective of maximizing the total utility (UT). However, since a utility-based scheduler that concerns delay requires high complexity, we introduce the concept of marginal utility. Representing the objective as minimizing the total marginal utility (mt), we develop some related properties for maximizing UT and minimizing MT. For the case with fixed service time, we show that the outcome of MT minimization becomes equivalent to that of UT maximization. For the more complicated case of varying service time, the MT minimization sheds light on the design of a simple scheduler. Overall, the marginal utility requires significantly low complexity for packet scheduling compared to the ordinary utility. Through simulations, we confirm that the marginal utility gives a way of flexible scheduling in meeting various delay requirements
253336
Parameter Optimization by a Genetic Algorithm for a Pitch Tracking System
The emergence of multimedia data in databases requires adequate methods for information retrieval. In a music data retrieval system by humming, the first stage is to extract exact pitch periods from a flow of signals. Due to the complexity of speech signals, it is difficult to make a robust and practical pitch tracking system. We adopt genetic algorithm in optimizing the control parameters for note segmentation and pitch determination. We applied the results to HumSearch, a commercialized product, as a pitch tracking engine. Experimental results showed that the proposed engine notably improved the performance of the existing engine in HumSearch.
1609683
Web-Based Energy Exploration Tool for Embedded Systems
We describe a Web-based energy estimation tool for embedded systems. An interesting feature of this tool is that it performs real-time cycle-accurate energy measurements on a hardware prototype of the processor. The authors describe the various steps involved in using the tool and present case studies to illustrate its utility.
29679621
Binding Algorithm for Power Optimization Based on Network Flow Method
We propose an efficient binding algorithm for power optimization in behavioral synthesis. In prior work, it has been shown that several binding problems for low-power can be formulated as multi-commodity flow problems (due to an iterative execution of data flow graph) and be solved optimally. However, since the multi-commodity flow problem is NP-hard, the application is limited to a class of small sized problems. To overcome the limitation, we address the problem of how we can effectively make use of the property of efficient flow computations in a network so that it is extensively applicable to practical designs while producing close-to-optimal results. To this end, we propose a two-step procedure, which (1) determines a feasible binding solution by partially utilizing the computation steps for finding a maximum flow of minimum cost in a network and then (2) refines it iteratively. Experiments with a set of benchmark examples show that the proposed algorithm saves the run time significantly while maintaining close-to-optimal bindings in most practical designs.
41031857
Address code optimization using code scheduling for digital signal processors
We propose an effective address code generation algorithm for digital signal processor (DSP) to minimize the number of addressing instructions. Unlike previous works in which code scheduling and offset (address) assignment are performed sequentially without any interaction between them, our work tightly couples code scheduling with offset assignment to exploit scheduling on optimizing addressing instructions more effectively. We accomplish this by proposing a new code scheduling algorithm that leads to an efficient sequence of variable accesses, minimizing addressing instructions. Experimental results with benchmark DSP programs show average improvements of 23.7% and 47.1% in the address code size and a naive storage assignment algorithm, respectively.
1627364
DC-DC converter-aware power management for battery-operated embedded systems
Most digital systems are equipped with DC-DC converters to supply various levels of voltages from batteries to logic devices. DC-DC converters maintain legal voltage ranges regardless of the load current variation as well as battery voltage drop. Although the efficiency of DC-DC converters is changed by the output voltage level and the load current, most existing power management techniques simply ignore the efficiency variation of DC-DC converters. However, without a careful consideration of the efficiency variation of DC-DC converters, finding a true optimal power management is impossible. In this work, we solve the problem of energy minimization with the consideration of the characteristics of power consumption of DC-DC converter. Specifically, the contributions of our work are: (1) We analyze the effects of the efficiency variation of DC-DC converters on a single task execution in DVS (dynamic voltage scaling) scheme, and propose a technique, called DC/spl I.bar/DVS, of DC-DC converter-aware energy-minimal DVS; (2) DC/spl I.bar/DVS is then extended to combine the effects of DC-DC converters with the procedures of general DVS techniques with multiple tasks; (3) Conversely, we propose a technique, called DC/spl I.bar/CONF, of generating a DC-DC converter that is best suited, in terms of total energy efficiency, to the intended application, and (4) finally, we complete our integrated framework DC-lp, which is based on DC/spl I.bar/DVS and DC/spl I.bar/CONF, that attempts to solve the DC-DC converter configuration selection problem and the DVS problem simultaneously. To show the effectiveness of the proposed techniques, a set of experimental results is provided. In summary, it is shown that DC-lp is able to save 16.0% /spl sim/ 22.1% of energy on the average, which otherwise was dissipated in the previous power management schemes with no consideration of DC-DC converter efficiency variation.