Browsing by Author "Liang, Jia-Ming"

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A Cross-Layer Framework for Overhead Reduction, Traffic Scheduling, and Burst Allocation in IEEE 802.16 OFDMA Networks
(2011-05-01)
Liang, Jia-Ming
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Chen, Jen-Jee
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Wang, You-Chiun
;
Tseng, Yu-Chee
;
資訊工程學系
IEEE 802.16 orthogonal frequency-division multiple access (OFDMA) downlink subframes have a special 2-D channel-time structure. Allocation resources from such a 2-D structure incur extra control overheads that hurt network performance. Existing solutions try to improve network performance by designing either the scheduler in the medium access control layer or the burst allocator in the physical layer, but the efficiency of overhead reduction is limited. In this paper, we point out the necessity of "codesigning" both the scheduler and the burst allocator to efficiently reduce overheads and improve network performance. Under the partial-usage-of-subcarriers model, we propose a cross-layer framework that covers overhead reduction, real-time and non-real-time traffic scheduling, and burst allocation. The framework includes a two-tier priority-based scheduler and a bucket-based burst allocator, which is more complete and efficient than prior studies. Both the scheduler and the burst allocator are tightly coupled together to solve the problem of arranging resources to data traffic. Given available space and bucket design from the burst allocator, the scheduler can well utilize the frame resource, reduce real-time traffic delays, and maintain fairness. On the other hand, with priority knowledge and resource assignment from the scheduler, the burst allocator can efficiently arrange downlink bursts to satisfy traffic requirements with low complexity. Through analysis, the cross-layer framework is validated to give an upper bound to overheads and achieve high network performance. Extensive simulation results verify that the cross-layer framework significantly increases network throughput, maintains long-term fairness, alleviates real-time traffic delays, and enhances frame utilization.
A Dynamic Reservation Scheme in Online Charging System for Family Shared Plan
(2015)
Huang, Huai-Sheng
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Su, Tzu-Chung
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Liang, Jia-Ming
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Tseng, Yu-Chee
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資訊工程學系
For simplifying billing and limiting data usage, Family Shared Plan (FSP) is now a popular plan provided by telecommunications operators. Based on the 3rd Generation Partnership Project (3GPP) specifications, Online Charging System (OCS) has to determine the Granted Unit (GU) and create reservations per session before a service is delivered by the serving network to a User Equipment (UE). However, fixed GUs cannot adapt to dynamic consumer behaviors, which usually require dynamic GUs. Clearly, giving small GUs will incur too many signaling messages for making reservations, but giving excessive GUs will cause unbalanced distribution of resources, especially in FSP cases. How to determine GUs is an open issue that can be self-defined by telecommunications operators. In this paper, we propose a new scheme for dynamically assigning GUs to UEs belonging to the same FSP, based on their historical data usage and total monthly data allowance. Simulation results show that our scheme can substantially save signalings by at least 22% compared to fixed scheme under unpredictable behaviors.
A Survey of Intelligent Video Surveillance Systems: History, Applications and Future
(2015-01-01)
Fan, Chung-Shuo
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Liang, Jia-Ming
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Lin, Yi-Ting
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Wu, Kun-Ru
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Li, Kuan-Yi
With advances in wireless network infrastructure providing powerful support for surveillance video communications, it is practical to meet the needs of intelligent surveillance systems in a wide range of applications. This survey offers a comprehensive overview of state-of-the-art technologies for intelligent video surveillance systems so as to provide researchers in this field with a summary of the progress achieved to date. The evolution of surveillance systems is outlined as well. In addition, the representative technologies for environment modeling, object classification, object tracking, behavioral analysis, and database implementation are summarized. Finally, we list several detailed discussions on possible future research directions.
A Web-based Camera Dispatch System for Video Surveillance with Dynamic Requirements
(2015-01-01)
Li, Kuan-Yi
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Liang, Jia-Ming
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Fan, Chung-Shuo
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Tseng, Yu-Chee
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Lin, Yi-Ting
Video surveillance systems are commonly used to monitor environments, such as factories, shopping malls, offices, and schools, for safety and security. However, traditional closed-circuit television cameras can only capture static scenes. When unexpected events happen, such as fire accidents or stranger intrusion, the recorded video data cannot provide immediate and precise information. In this work, we design a camera dispatch system for video surveillance with pan-tilt-zoom (PTZ) cameras, which can monitor event-areas/targets real-timely and flexibly. Users can dynamically define the monitoring requirements, such as pixel-per-foot and viewing-angle of the event-areas/targets. Then, a dispatch algorithm will decide the most necessary cameras and corresponding settings to monitor the event-areas/targets immediately. The control panel is implemented as a web-based service. The demo shows that users can easily monitor potential event-areas/targets anywhere, anytime through a web browser.
A Web-based, Real-time Video Surveillance System by Leveraging PTZ Cameras
(2015)
Li, Kuan-Yi
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Liang, Jia-Ming
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Fan, Chung-Shuo
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Wu, Kun-Ru
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Lin, Yi-Ting
Video surveillance systems are commonly used for environmental monitoring. Nevertheless, existing systems such as [1, 2] can only monitor scenes statically. When an accident or a fire event happens, we cannot get the critical pictures and check those situations immediately. Therefore, we propose to leverage pan-tilt-zoom (PTZ) cameras and develop a real-time surveillance system, where the PTZ cameras can rotate in a horizontal plane by panning and in a vertical plane by tilting, and adjust the focal length by zooming, so we can control these cameras dynamically for the emergent area. Especially for the accessibility, we implement this system as a web service to help users easily define the emergent area and preview the video of cameras remotely. Specifically, our system is composed of multiple PTZ cameras and a web server, as shown in Fig. 1. The PTZ cameras are with fixed positions and can be controlled to pan, tilt, and zoom remotely by the web server. The web server maintains a website to provide the real-time surveillance service, consisting of two procedures: area setting and video displaying. The area setting is for users to define the monitored area, including the range and location of the monitored area. Then, all the cameras will be dispatched and face to the center of the monitored area. Finally, the video displaying procedure will show the monitoring results, including the video streams and the rotation parameters of the dispatched cameras. Fig. 2 shows the control panel of the implemented prototype, where there are two PTZ cameras deployed in the monitoring environment. On this panel, the left part is for video displaying and the right part is for the monitored area setting. More specifically, for the right part, the upper side is the floor plan of the monitoring environment which users can define the location of the emergent area by clicking on. On the lower left side, users can further specify the details of the area, such as its length and width. After setting, the monitored area will be marked as the red-dotted rectangle on the floor plan. Finally, the monitoring results, such as the coverage ratio of the monitored area and the rotation parameters of the cameras, will be shown on the lower central side. Note that the system also allows users to control the cameras manually on the lower right side.
Aggregating Small Packets in M2M Networks: An OM2M Implementation
(2016-01-01)
Lee, Sheng-Chieh
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Wu, Kun-Ru
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Hsu, Ching-Kuo
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Chang, Po-Yen
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Liang, Jia-Ming
IoT (Internet of Things) and M2M (machine to machine) have attracted a lot of attention since more and more devices are expected to connect to the Internet for special purposes such as environment monitoring, home automation, industrial surveillance, and e-Health care. Currently, the OM2M (Open source platform for M2M communication) is a promising project which implements oneM2M and SmartM2M standards as an open-source platform for integrating various M2M services, applications, and devices. However, the individual data generated from those IoT/M2M devices is usually quite small, which incurs a lot of control overhead and thus decreases network performance significantly. Therefore, in this work we design and implement an OM2M 'plugin' that can aggregate small IoT data effectively. We will show how the plugin works and verify the effectiveness on the network bandwidth in this demonstration.
An Energy Efficient Sleep Scheduling Considering QoS Diversity for IEEE 802.16e Wireless Networks
(2010)
Chen, Jen-Jee
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Liang, Jia-Ming
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
Power management is one of the most important issues in IEEE 802.16e wireless networks. In the standard, it defines three types of power saving classes (PSCs) for flows with different QoS characteristics. It allows a mobile device to turn off its wireless radio when all its PSCs are in sleep states. In this paper, we consider the scheduling of power saving classes of type II in an IEEE 802.16e network with a BS and multiple MSSs (mobile subscriber stations). Previous work proposes to enforce all MSSs to have the same sleep cycle, thus leading to higher energy cost for those MSSs with less strict delay bounds. We observe that if the sleep cycles of MSSs can be assigned according to their delay bounds, MSSs can significantly reduce their duty cycles. We propose an efficient tank-filling algorithm, which is standard-compliant and can allocate resources to MSSs according to their QoS characteristics with the least number of active frames. Simulation results verify that our algorithm incurs less power consumption and leads to higher bandwidth utilization than the previous schemes.
An Energy-Efficient Sleep Scheduling With QoS Consideration in 3GPP LTE-Advanced Networks for Internet of Things
(2013-03-01)
Liang, Jia-Ming
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Chen, Jen-Jee
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Cheng, Hung-Hsin
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Tseng, Yu-Chee
;
資訊工程學系
With the design of data communications in mind, 3GPP LTE-advanced (LTE-A) is probably the most promising technology for Internet of Things (IoT). For IoT applications, continuous low-rate streaming data may be reported from devices over a long period of time, imposing stringent requirements on power saving. To manage power consumption, 3GPP LTE-A has defined the discontinuous reception/transmission (DRX/DTX) mechanism to allow devices to turn off their radio interfaces and go to sleep in various patterns. Existing literature has paid much attention to evaluate the performance of DRX/DTX; however, how to tune DRX/DTX parameters to optimize energy cost is still left open. This paper addresses the DRX/DTX optimization, by asking how to maximize the sleep periods of devices while guarantee their quality-of-service (QoS), especially on the aspects of traffic bit-rate, packet delay, and packet loss rate in IoT applications. Efficient schemes to optimize DRX/DTX parameters and schedule devices\' packets with the base station are proposed. The key idea of our schemes is to balance the impacts between QoS parameters and DRX/DTX configurations. Simulation results show that our schemes can guarantee traffic bit-rate, packet delay, and packet loss rate while save energy of user equipments.
Data Offloading for Dynamic Point Selection in Cloud Radio Access Networks (C-RAN)
(2018-01-01)
Hsu, Ching-Kuo
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Liang, Jia-Ming
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Chen, Jen-Jee
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Wu, Kun-Ru
;
Tseng, Yu-Chee
For next generation mobile communications. Cloud-RAN (C-RAN) is an emerging network architecture to provide broadband services. C-RAN separates computation entities, i.e., Baseband Units (BBUs), from base stations (BSs) and puts BBUs in a cloud located in a centralized network. With C-RAN, UEs can receive data from multiple collaborative cells and thus can leverage the dynamic point selection (DPS) technology to improve network efficiency. When user equipments (UEs) enter a hotspot and can not be served due to congestion, data offloading from the hotspot to its neighboring cells may take place to balance heterogeneous cells' loads. This work shows how to integrate such DPS offloading with the Discontinuous Reception (DRX) mechanism, which allows UEs to turn off their radio interfaces in a periodical manner. We address the resource allocation problem in heterogeneously-loaded C-RAN by optimizing UEs' energy consumption based on DRX while reserving sufficient bandwidths for UEs considering their quality-of-service (QoS) through DPS. We propose an offloading-based DPS scheduling scheme by exploiting not only maximal instantaneous throughputs but also minimal energy cost. Simulation results show that our scheme can improve throughput, resource utilization, and energy consumption as compared to existing schemes.
Design and Implementation of Image Electronic Fence with 5G technology for Smart Farms
(2019-01-01)
Hsu, Ching-Kuo
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Chiu, Yen-Hao
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Wu, Kun-Ru
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Liang, Jia-Ming
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Chen, Jen-Jee
The 5G era brings the rapid development of the Internet of Things (IoT). New technologies, such as image recognition, have promoted the traditional agriculture to a new milestone. Through advanced research and development of image recognition, it can intelligently monitor the growth of crops and effectively reduce agricultural damages, while avoiding crops being stolen and reducing the manpower of farms. In this paper, we design and implement an image electronic fence based on the technology of image recognition and sensor fusion with 5G technology for smart farms. By applying cameras and beacon tags, our system can identify whether the incoming/leaving people are authorized or not at the entry and exit of farms. In addition, with the high speed and low latency of 5G technology, the video data of cameras can be transmitted in a flash and fused with the beacon detection. In this way, the incoming/leaving people can be identified efficiently so as to avoid the farms being damaged. Based on field trials, we validate that the identification accuracy of our system approaches 90% in average.
Dynamic Cooperating Set Planning for Coordinated Multi-Point (CaMP) in LTE/LTE-Advanced Systems
(2013)
Hsu, Po-Min
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Chen, Jen-Jee
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Liang, Jia-Ming
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資訊工程學系
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Department of Computer Science
Coordinated Multi-Point (CoMP) is considered as one of the most important technique in 3GPP LTE/LTE-Advanced. In CoMP, several base stations can be grouped together to form the cooperating set, where the cooperating set is used to improve the system throughput as well as the throughput of cell edge users. Most of the studies discuss static cooperating set, i.e., the size of the cooperating set is fixed, such as 3 or 7. However, when big activities occur with gathered crowds, such as gala parades and New Year\'s Eve, the amount of wireless communication demands in such areas is over the capacity of serving base stations. In this case, the static cooperating set can bring only limited help and fails to adapt to the actual conditions. Moreover, additional communication overhead among cells is introduced but futile. In this paper, we propose the dynamic cooperating set to solve the problem. The proposed method takes the actual traffic requirement and geographical area into consideration to form dynamic cooperating set to offload the wireless communication demand. Dynamic cooperating set can not only enhance the system and cell edge throughput but also utilize the radio resource in an efficient way. The latter avoids unlimited expansion of the cooperating set. Simulation results show that the throughput of our method is 1.23 and 1.36 times of the static CoMP scheme and no CoMP scheme, respectively.
Efficient and Consistent Flow Update for Software Defined Networks
(2018-03-01)
Wu, Kun-Ru
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Liang, Jia-Ming
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Lee, Sheng-Chieh
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Tseng, Yu-Chee
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資訊工程學系
Software defined network (SDN) provides flexible and scalable routing by separating control plane and data plane. With centralized control, SDN has been widely used in traffic engineering, link failure recovery, and load balancing. This work considers the flow update problem, where a set of flows need to be migrated or rearranged due to change of network status. During flow update, efficiency and consistency are two main challenges. Efficiency refers to how fast these updates are completed, while consistency refers to prevention of blackholes, loops, and network congestions during updates. This paper proposes a scheme that maintains all these properties. It works in four phases. The first phase partitions flows into shorter routing segments to increase update parallelism. The second phase generates a global dependency graph of these segments to be updated. The third phase conducts actual updates and then adjusts dependency graphs accordingly. The last phase deals with deadlocks, if any, and then loops back to phase three if necessary. Through simulations, we validate that our scheme not only ensures freedom of blackholes, loops, congestions, and deadlocks during flow updates, but is also faster than existing schemes.
Efficient Resource Allocation for Energy Conservation in Uplink Transmissions of IEEE 802.16j Transparent Relay Networks
(2010)
Liang, Jia-Ming
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Wang, You-Chiun
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Chen, Jen-Jee
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Liu, Jui-Hsiang
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Tseng, Yu-Chee
By introducing the relay capability, the IEEE 802.16j standard is developed to improve the WiMAX performance. Under the transparent mode, existing studies aim at improving network throughput by increasing the transmission rates of mobile stations (MSs). However, we show that using higher rates will let MSs consume more energy. In the paper, we define an energy-conserved uplink resource allocation (EURA) problem in 802.16j networks under the transparent mode, which asks how to arrange the uplink resource to 1) satisfy MSs' requests and 2) minimize their energy consumption. Objective 1 is necessary while objective 2 should be achieved when objective 1 is met. The above bi-objective problem is especially important when the network is non-saturated. The EURA problem is NP-hard and we propose a heuristic with two key designs. First, we exploit relay stations to allow more concurrent uplink transmissions to fully use the frame space. Second, we reduce MSs' transmission powers by adjusting their rates and paths. Simulation results show that our heuristic can save up to 80% of MSs' energy as compared with existing work.
Energy-efficient DRX scheduling for D2D communication in 5G networks
(2018-08-15)
Liang, Jia-Ming
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Chang, Po-Yen
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Chen, Jen-Jee
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Huang, Chien-Feng
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Tseng, Yu-Chee
In recent years, intelligent devices such as smart phones and smart tablets are grown and developed rapidly. High-bandwidth media services such as live streaming, gaming and multi-user video conferencing are more and more popular. This results in spectrum resource depletion of the cellular network. To alleviate the problem, the 3rd Generation Partnership Project (3GPP) has proposed a new technology, called device-to-device (D2D) communications. However, D2D devices and direct link cellular users all share and access the same spectrum resource, thus degrading the network performance significantly due to the interference. In addition, due to the frequent communication nature of streaming and gaming services, the power consumption of devices is increasing dramatically. To mitigate above problems, this paper investigates how to improve the spectrum efficiency by well scheduling and allocating radio resource to more concurrent D2D and cellular users on the uplink direction and reduce unnecessary power consumption of devices via Discontinuous Reception (DRX) scheduling while guaranteeing users' Quality of Service (QoS). We propose an energy-efficient resource and sleep scheduling scheme. This scheme first establishes a conflict graph to maintain the transmission and interference relationship, and then tries to maximize concurrent D2D and mobile users by resource reuse. At the same time, the method also exploits DRX technology to further decrease possible interference and conserve devices' power consumption through optimizing their sleep operation. Simulation results show that our scheme can achieve better performance on system throughput, network capacity, and power saving compared to the existing schemes.
Energy-Efficient DRX Scheduling for Multicast Transmissions in 3GPP LTE-Advanced Wireless Networks
(2013)
Liang, Jia-Ming
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Hsieh, Po-Chun
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Chen, Jen-Jee
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Tseng, Yu-Chee
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資訊工程學系
The 3GPP LTE-A (Long Term Evolution-Advanced) is the most promising technology for next-generation wireless communications. It provides high transmission rate up to 1 Gbps and supports plentiful multimedia services, especially for those bandwidth required multicast type of services, such as IP TV and Voice/Video-over-IP services. However, when users activate more services at their user equipments (UEs), more energy is consumed. To save UEs' energy, the LTE-A standard defines the Discontinuous Reception Mechanism (DRX) to allow UEs turning off their radio interfaces and going to sleep to save energy when no data needs to be received. But, how to optimize DRX configurations for UEs is still left as an open issue. In this paper, we address the DRX optimization problem for multicast services, which asks how to guarantee the quality of service (QoS) of the multicast streams while minimize UEs' wake-up time. We propose an energy-efficient scheme to tackle this problem. T he scheme tries to arrange the best multicast data reception orders to reduces UEs' wake-up periods while consider the resource collision avoidance. Simulation results show that the performance of the proposed scheme is effective even if the network is under saturated condition.
Energy-Efficient Dynamic Point Selection for Cloud Radio Access Networks (C-RAN)
(2017-01-01)
Hsu, Ching-Kuo
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Liang, Jia-Ming
;
Wu, Kun-Ru
;
Chen, Jen-Jee
;
Tseng, Yu-Chee
Cloud-RAN (C-RAN) is a promising network architecture for next-generation wireless communications. C-RAN separates computation entities, i. e., Baseband Units (BBUs) from base stations (BSs), and puts BBUs in a cloud located at a centralized network. With C-RAN, user equipments (UEs) can receive data from multiple collaborative cells and thus can leverage the dynamic point selection (DPS) technology to improve network efficiency. To save the energy of UEs, 3GPP LTE-A has defined the Discontinuous Reception (DRX) mechanism to allow UEs to turn off their radio interfaces and go to sleep in a periodical manner. However, how to cooperate DRX with DPS under the C-RAN architecture is still an open issue. Therefore, this paper addresses the resource allocation problem in C-RAN by asking how to optimize the energy conservation of UEs based on DRX while reserving sufficient bandwidths for UEs considering their quality-of-service (QoS) in C-RAN with DPS. To solve this problem, we propose an energy-efficient DPS scheduling scheme. The key idea of our scheme is to serve the UEs in the intersection of cells continuously and allocate resource tightly to avoid additional wake-up intervals. Extensive simulation results show that our scheme can serve more UEs while enhancing throughput and reducing their energy consumption as compared to the existing schemes.
Energy-efficient scheduling scheme with spatial and temporal aggregation for small and massive transmissions in LTE-M networks
(2019-01-01)
Liang, Jia-Ming
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Chang, Po-Yen
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Chen, Jen-Jee
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資訊工程學系
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Department of Computer Science
Machine-to-machine (M2M) communication is one of the key technologies to realize Internet of Things (IoT). Since IoT applications are mainly for smart sensing, such as metering, home surveillance, disaster detection, and e-health, their special sensing/uploading behaviors will result in periodic and/or event-driven small data transmissions, which may potentially decrease the radio resource efficiency. On the other hand, due to the frequent communication nature of sensing data for IoT applications, the power consumption is increasing dramatically. To reduce the power consumption of IoT devices, the 3rd Generation Partnership Project (3GPP) has defined the discontinuous reception/discontinuous transmission (DRX/DTX) mechanism to allow devices to turn off their radio interfaces and go to sleep in various patterns. However, how to optimize the DRX/DTX scheduling while improving the resource efficiency is still an open issue. In this paper, we investigate an uplink resource allocation problem over long-term evolution machine-to-machine (LTE-M) networks, which is standardized by 3GPP to improve performance on IoT. In this network, we consider the periodic, event-driven, and query-based IoT traffic while minimizing the devices' power consumption. We prove this problem to be NP-complete and propose an aggregation-efficient DRX/DTX scheduling (AEDS) scheme. This scheme takes advantage of both spatial and temporal data aggregation while applying DRX/DTX for energy saving. Specifically, the scheme consists of three phases. The first phase exploits long-term static scheduling for periodic data to ensure the latency and data rate while minimizing the devices' wake-up time. The second phase tries to decrease devices' power consumption through precisely determining their DRX/DTX configurations. Finally, the third phase employs short-term dynamic scheduling for event-driven and query-based data to improve transmission efficiency. Therefore, both small data and power consumption problems are relieved. Extensive simulation results show that the proposed scheme can improve resource efficiency, enlarge network capacity while reducing power consumption compared to the existing schemes. (C) 2018 Elsevier B.V. All rights reserved.
Energy-Efficient Sleep Scheduling with QoS Considerations in 3GPP LTE-Advanced Networks
(2013)
Liang, Jia-Ming
;
Chen, Jen-Jee
;
Cheng, Hung-Hsin
;
Tseng, Yu-Chee
;
資訊工程學系
With the design of data communications in mind, 3GPP LTE-Advanced is probably the most promising technology for next generation mobile communications. For mobile applications, continuous communications at the user equipments (UEs) over a long period of time, imposing stringent requirements on power saving. To manage power consumption, 3GPP LTE-Advanced has defined the Discontinuous Reception (DRX) mechanism to allow UEs to turn off their radio interfaces and go to sleep in various patterns. Existing literature has paid much attention to evaluate the performance of DRX; however, how to tune DRX parameters to optimize energy cost is still left open. This paper addresses the optimization problem of the DRX mechanism, by asking how to minimize the wake-up periods of the UEs while guarantee their QoS, especially on the aspects of traffic bit-rate, packet delay, and packet loss rate in mobile applications. Efficient schemes to optimize DRX parameters and schedule UEs' packets at the evolved Node B (eNB) are proposed. The key idea of these schemes is to analyze and balance the impacts between QoS parameters and DRX configurations. Simulation results show that our scheme can fully satisfy QoS requirements of the UEs while save considerable energy, compared to the existing schemes.
Energy-Efficient Uplink Radio Resource Management in LTE-Advanced Relay Networks for Internet of Things
(2014-01-01)
Chen, Jen-Jee
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Liang, Jia-Ming
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Chen, Zeng-Yu
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資訊工程學系
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Department of Computer Science
For M2M (Machine-to-Machine) machines in cellular networks, employing high transmission rates or transmitting in large power actually cost them much energy. This is harmful to the machines, especially they are operated by batteries. The Relay Node (RN) in Long-Term Evolution-Advanced (LTE-A) networks is used to enhance the coverage of high data rate and solve the coverage hole problem. Considering the limited energy nature of machines, connecting to the RN instead of the BS is a better choice for cell-edge machines. In this paper, we consider an uplink resource and power allocation problem for energy conservation in LTE-A relay networks. The objective is to minimize the total energy consumption of machines while guarantee their quality of service (QoS). We prove this uplink resource and power allocation problem to be NP-complete and develop an energy-conserved resource and power allocation method to solve the problem. Simulation results show that our algorithm can effectively reduce the energy consumption of machines and guarantee their required service qualities.
Energy-efficient uplink resource allocation for IEEE 802.16j transparent-relay networks
(2011-11-10)
Liang, Jia-Ming
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Wang, You-Chiun
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Chen, Jen-Jee
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Liu, Jui-Hsiang
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Tseng, Yu-Chee
The IEEE 802.16j standard is defined to enhance WiMAX networks with relay capacity. Under the transparent mode, existing studies only target improving network throughput by increasing the transmission rates of mobile stations (MSs) and maximizing concurrent transmissions. However, using a higher transmission rate or allowing more concurrent transmissions could harm MSs in terms of their energy consumption, especially when they are battery-powered. In this paper, we consider the energy-conserved resource allocation problem in the uplink direction of an IEEE 802.16j network under the transparent mode. This problem asks how to arrange the frame usage with satisfying MSs' demands as the constraint and minimizing their total energy consumption as the objective. We prove this problem to be NP-complete and develop two energy-efficient heuristics, called demand-first allocation (DFA) and energy-first allocation (EFA) schemes. These heuristics employ a gradient-like search method to approximate the optimal solution. Specifically, DFA tries to satisfy MSs' demands first by using as less frame space as possible. Then, with the remaining frame space. DFA tries to save MSs' energy by lowering their transmission rates or adjusting their transmission paths. Viewed from a different perspective. EFA first allocates the frame space to MSs to consume the least energy. Since the total allocation may exceed the frame space. EFA then exploits spatial reuse and rate adjustment to pack all demands into one frame. simulation results show that our heuristics can approximate the ideal performance bounds and save up to 90% of MSs' energy as compared to existing results. (C) 2011 Elsevier B.V. All rights reserved.