- [Show abstract] [Hide abstract] ABSTRACT: In this paper, a new four-antenna based structure (FAS) is introduced for capacity improvement in future cellular networks with frequency reuse factor of 1. In FAS, each cell consists of one omni-directional antenna located at the cell center and three 120-degree directional antennas located at the cell edge. In order to achieve effective system bandwidth allocation among four antennas, novel spectrum planning schemes for both downlink (DL) and uplink (UL) are proposed. Theoretical analysis and simulation demonstrate that the proposed cellular structure can significantly improve the system capacity in both DL and UL, especially at the cell edge.
- [Show abstract] [Hide abstract] ABSTRACT: In this paper, throughput performance of the access links (i.e., base station to mobile station and relay station to mobile station) is analyzed for the two-hop IEEE 802.16j wireless relay networks with asymmetrical topology. In specific, three frequency reuse schemes are proposed to improve the spectrum efficiency of the access links: (1) an isolation band based frequency reuse scheme (IBFRS) which introduces an isolation band surrounding each relay station (RS) cluster (i.e, a separate RS or several adjacent RSs) so that the throughput of the access link can be improved by allowing frequency reuse between RSs and the base station (BS); (2) the dynamic frequency power partition (DFPP) scheme for reusing the frequency among RSs; (3) the selective reuse (SR) scheme for the RSs to further selectively reuse the frequency in the isolation band according to the interference measurement. Comprehensive simulation shows that by applying the proposed IBFRS+DFPP+SR, the throughput of the access link can be significantly improved.
- [Show abstract] [Hide abstract] ABSTRACT: In this paper, bandwidth allocation, in terms of distributing available data slots among different users, is studied for QoS provisioning in IEEE 802.16 networks. By considering the automatic repeat request with selective acknowledgement (ARQ-SA) scheme for erroneous wireless channels, a mathematical model is established to theoretically analyze the delay performance of transmitting service data unit (SDU) under a multiuser environment. The analytical results indicate that the delivery delay of the SDU is dominated by the time spent for the first transmission of all its protocol data units (PDUs). Based on this observation, a novel dynamic bandwidth allocation algorithm is proposed and a detailed performance analysis is provided. Simulation results show that the proposed bandwidth allocation algorithm can significantly improve the delay performance of SDUs and ensure the fairness among different users.
- [Show abstract] [Hide abstract] ABSTRACT: In a wireless LAN (WLAN) based on IEEE 802.11, supporting multiple classes of services with QoS constraints in MAC layer is very important. In this pa-per, we propose a class-based analytical model to support multiple traffic classes. Through investigating the relation-ship between access control parameters, such as contention window (CW) sizes and inter-frame space (IFS) under QoS constraints, we derive a mathematical model to character-ize the MAC behavior. In particular, we present an optimal solution which maximizes the throughput while satisfying the QoS requirements. Simulation results demonstrate the accuracy of our proposed model. Keywords— Medium access control (MAC), wireless LAN (WLAN), IEEE 802.11, quality of service (QoS).
- [Show abstract] [Hide abstract] ABSTRACT: In this paper, an adaptive resource reuse scheduling (ARRS) algorithm is presented with the goal of enhancing the system capacity for relay networks, which supports arbitrary topology and relay stations (RSs) mobility. Since one key step in ARRS is modeled as graph multicoloring, a fast [%p-]- approximation algorithm named dual sorting greedy (DSG) is provided for the problem. Simulation results show that ARRS achieves high system capacity and hence satisfies the multimedia service QoS requirements of relay networks efficiently.
- [Show abstract] [Hide abstract] ABSTRACT: In this paper, the throughput performance of the access links (i.e., base station to mobile station and relay station to mobile station) is analyzed for the wireless relay networks based on IEEE 802.16j. An isolation band based frequency reuse scheme (IBFRS) is proposed, which introduces an isolation band around each relay station cluster so that the throughput of the access link can be maximized by allowing frequency reuse between the relay stations and the base station. An analytic method is also proposed to determine the optimal isolation band. A comprehensive simulation shows that by applying the proposed IBFRS, the throughput of the access link can be significantly improved.
- [Show abstract] [Hide abstract] ABSTRACT: In this paper, in-sequence delivery delay of an acknowledged mode radio link control (AM-RLC) protocol in wideband code division multiple access (W-CDMA) networks is studied. Two special protocol phenomena, duplicated retransmission, and delayed acknowledgment, are reported. A two-step dependent Markov chain is adopted to model the AM-RLC protocol. The in-sequence delivery is evaluated by means of an analysis through tracking the transmission status of a specific packet data unit (PDU) and its blocking PDUs. Analysis results indicate that in-sequence delivery delay is approximately linear with frame error rate. Analysis results also exhibit that in-sequence delivery delay is highly related to status report interval. Based on this observation, a dynamic AM-RLC scheme is proposed. The proposed AM-RLC scheme dynamically changes status report interval according to channel status. Extensive simulations are carried out to verify the effectiveness of the proposed scheme. It is found that the proposed scheme can reduce status report without penalty to in-sequence delivery delay.
- [Show abstract] [Hide abstract] ABSTRACT: Reuse partitioning (RP), a promising technique for constructing high efficient multi-cell OFDM systems, has brought a lot of attentions from both industry and academia. In this paper, by considering the characteristics of various service flows, we first introduce a new performance metric, called flow-satisfaction-degree (FSD), and then formulate an optimization problem for maximizing the FSD over the whole system. We then propose a FSD-based scheduling (FSDS) algorithm for the static RP system. Simulation results demonstrate that the proposed algorithm greatly outperforms the traditional static allocation scheme in terms of FSD and system throughput for the fully loaded system.
- [Show abstract] [Hide abstract] ABSTRACT: Ultra wideband (UWB) network brings both chance and challenge to personal area wireless communications. Compared with other IEEE 802 small range wireless protocols (such as WLAN and Bluetooth), UWB has both extremely high bandwidth (up to 480 Mbps) and low radiation. Moreover, the structured MAC layer of UWB is the fundamental difference to WLAN. The top one is that only when two UWB devices belong to the same piconet can they communicate with each other directly, which means that we must jointly consider topology formation and routing when deploying UWB networks because the interaction between routing and topology formation makes separate optimization ineffective. This paper tries to optimize UWB network from a cross-layer point of view. Specifically, given device spatial distribution and traffic requirement, we want to form piconets and determine routing jointly, to maximize the overall throughput. We formulate the problem of joint optimization to mixed-integer programming and give a practical lower bound that is very close to the theoretical upper bound in our simulation. Furthermore, our lower bound is much better than an algorithm that only considers topology formation in UWB networks.
- [Show abstract] [Hide abstract] ABSTRACT: In this article we propose a unified radio network architecture, broadband wireless multimedia (BWM), which integrates broadcasting service and broadband wireless access service at both the application and physical layers. A simple, flexible, and comprehensive radio resource management framework is developed for the unified radio network. It is shown that the proposed radio network architecture has many advantages over existing ones. In addition, the new architecture is currently being considered in China for the system level design.
- [Show abstract] [Hide abstract] ABSTRACT: The IEEE 802.16e broadband wireless access (BWA) system is developed to cater for the rapidly growing requirement for multimedia wireless services. Since the heterogeneous services provided by the system are connection-oriented, admission control and associated resource reservation (RR) mechanisms are needed to achieve desired quality of service (QoS). In this paper, we develop a dynamic bandwidth reservation admission control scheme for the IEEE 802.16e system. In the proposed scheme, we set some overall reserved resource as admission guard bandwidth, which is dynamically adjusted according to the bandwidth request of on-going real-time variable-bit rate (VBR) services in addition to guaranteeing the resource requirement of potential handoff services. We also propose an analytical traffic model to evaluate the scheme. The results prove that our scheme can satisfy the bandwidth request of real-time VBR services and improve the system bandwidth utilization efficiently while guaranteeing the QoS requirements of all services at the same time.
- [Show abstract] [Hide abstract] ABSTRACT: The IEEE 802.16e standard is a rapidly developing technology for broadband wireless access system. Its PHY OFDMA mode defines two subchannel building methods: diversity permutation and contiguous permutation (AMC subchannel). In this paper we propose a joint packet scheduling and subchannel allocation scheme applicable for the IEEE 802.16e OFDMA AMC subchannel. Since it is a multiuser, multi-service and multichannel packet-switched system, we define a distinct scheduling priority for each packet on each subchannel that integrates MAC QoS requirements, service type and PHY channel state information (CSI). Based on these scheduling priorities and specific scheduling mechanism, efficient QoS guaranteed resource allocation is achieved in our scheme. Intensive simulations show that our scheme outperforms throughput-oriented maximum C/I (MCI) and QoS-oriented priority schemes under various conditions.
- [Show abstract] [Hide abstract] ABSTRACT: Multimedia decoding is one of the key parts of many popular mobile multimedia applications, such as video telephony, streaming, and video playback. Since the multimedia decoding consumes a significant amount of energy on processors, it is crucial to lower the power consumption and prolong the battery life. In this paper, the statistical analysis of more than 600 processor load trace files is first presented. From the analysis, we found that it is feasible to predict the processor load of multimedia applications accurately using a low order linear time series model if the load is sampled using the feature period, which is obtained with fast Fourier transformation. Based on the analysis, we propose a novel interval-based DVS scheme to achieve penalty controllable energy reduction. The DVS scheme does not need any task profile or involvement of application program, and it is compatible with the service model of general purpose mobile operating systems. In addition, the proposed DVS scheme can handle the nonstationary behavior using an efficient online change detector, and important parameters, such as coefficients of the linear time series model, are estimated on the fly. More importantly, the proposed scheme can keep the overscaling rate (OSR) around a certain predefined value. Since the OSR has a simple and stable relationship with the deadline miss rate (DMR), the penalty incurred by DVS is effectively controlled. Experimental results show that the proposed DVS scheme achieves a much smaller prediction error than previous approaches and achieves a significant processor energy reduction with adjustable and controlled penalty
Conference Paper: Performance Analysis of ARQ Scheme in IEEE 802.16.[Show abstract] [Hide abstract] ABSTRACT: IEEE 802.16, also known as WiMax (worldwide interoperability for microwave access), introduces the automatic repeat request with selective acknowledgement (ARQ-SA) scheme to improve the reliability of the wireless link. For ARQ-SA, packets or protocol data units (PDUs), several of which compose one service data unit (SDU) from the upper layer, are transmitted orderly, but only those negatively acknowledged packets are retransmitted. We analyze the delay performance of SDU under ARQ-SA in a multiuser network environment. Our analysis shows that the SDU delay is mainly determined by the first transmission of all its PDUs. Further more, we propose a simple scheme to reduce the delivery delay of SDU. Simulation results are given to demonstrate the accuracy of the analytical one.
Conference Paper: Dynamic Bandwidth Allocation in IEEE 802.16[Show abstract] [Hide abstract] ABSTRACT: IEEE 802.16 has gained significant research attention because of its broadband wireless services over a large coverage area. Bandwidth allocation plays very important role at the link layer of IEEE 802.16. In this paper, by considering the Automatic Repeat reQuest (ARQ) scheme for an erroneous wireless channel, a dynamic bandwidth allocation algorithm for downlink traffic in a multiuser environment is proposed and a detailed analysis is performed. Simulation results show that the proposed algorithm significantly improves the delay performance of the Service Data Unit (SDU) which consists of multiple Protocol Data Units (PDUs), and ensures the fairness among different users.
Conference Paper: Dynamic radio link control protocol for UMTS/WCDMA[Show abstract] [Hide abstract] ABSTRACT: To provide a reliable transmission in 3GPP WCDMA systems, in the Radio Link Control (RLC) sublayer of the WCDMA, an Acknowledgement Mode (AM) is defined where an ACK frame is sent to indicate the data frame receiving status. In order to design a well-performed AM scheme, in this paper, we first investigate the AM protocol behavior and present the delay performance of the standard periodical AM-RLC scheme in the Bernoulli channel. Then, based on the observation from the performance above, we propose a dynamic AM scheme in RLC over a more general time-varying Markov channel. It is demonstrated that a much better delay performance can be achieved compared with the standard AM scheme with periodical acknowledgements.
- [Show abstract] [Hide abstract] ABSTRACT: This paper addresses the throughput optimization problem in multihop ultra-wideband (UWB) networks by jointly considering network topology formation and routing. Given a spatial distribution of UWB devices and traffic requirement, we want to form piconets and select paths to maximize the network throughput. Although there have been several works considering the problem of selecting paths to achieve the optimal throughput in multihop wireless networks, to the best of our knowledge, none of them takes the topology formation into the consideration. In this paper, we use Boolean matrices to model role assignment in UWB networks and formulate the throughput optimization problem as a nonlinear programming (NLP) problem. Since the throughput optimization problem is NP-hard, we give an upper bound of the optimal throughput by relaxing some constraints and using pseudo-Boolean optimization to linearize the NLP. We prove that the solution of the upper bound is at most three times of the optimal throughput. Based on the topology formed by solving the upper bound, we formulate a lower bound of the optimal throughput as a linear programming problem and use column generation to solve the lower bound. Numerical results show that the lower bound is very close to the upper bound. Simulation results demonstrate the effectiveness of the scheme.
- [Show abstract] [Hide abstract] ABSTRACT: The wireless personal area network (WPAN) is designed for short-range connectivity among fixed or portable moving devices. The ultra-wideband (UWB) technology is being defined as the physical-layer (PHY) support for the high-rate WPAN. At medium access control (MAC) layer of the WPAN, a delayed acknowledgment (Dly-ACK) or burst-ACK (B-ACK) scheme is introduced to improve the channel utilization by reducing the overhead of ACK. In this paper, the authors first study the delay performance of the Dly-ACK scheme. An analytical model is developed for the Dly-ACK mechanism, and the delay is decomposed into queuing delay and delivery delay. These delay metrics are derived, and some important observations are obtained. In particular, there exists an optimal burst size, which is determined by the input traffic load and is very insensitive to the channel error rate within a normal error-rate range. It is also demonstrated that Dly-ACK cannot work properly if the burst size is fixed. The authors then propose a dynamical Dly-ACK scheme that can adaptively change its burst size according to the queue buffer size. Simulation results show that the dynamical scheme can improve the delay performance significantly.
- [Show abstract] [Hide abstract] ABSTRACT: Beacon period (BP) is an overhead in UWB MBOA MAC, since no data frame is allowed during a BP. In this letter, we model the current BP contraction scheme in MBOA spec as a greedy distance-2 graph coloring algorithm, and formulate the BP contraction problem as a 0-1 programming problem. The theoretical numerical results show that the current BP contraction algorithm has good performance. Furthermore, we study the impact of device joining/leaving order on the performance of the algorithm. Simulation results demonstrate that the impact is not significant and the performance of the algorithm is stable with varied device ordering. Therefore, we conclude that there is no much room for any further significant improvement over the current BP contraction algorithm in MBOA spec.
- [Show abstract] [Hide abstract] ABSTRACT: Dly-ACK scheme in IEEE 802.15.3 MAC is designed to reduce the overhead of the ACK frame in MAC layer and improve the channel utilization. However, how to using the Dly-ACK is open for implementation. In this paper, we propose an adaptive Dly-ACK scheme for both TCP and UDP traffic. We first point out the problems of applying fixed Dly-ACK scheme to these two traffic scenarios and show that the system performance is rather poor and the causes of these problems are presented. Based on our observations, two enhancement mechanisms for fixed Dly-ACK are then proposed. The first one is to request the Dly-ACK frame adaptively or change the burst size of Dly-ACK according to the transmitter queue status. The second is a retransmission counter to enable the destination DEV to deliver the MAC data frames to upper layer timely and orderly. Simulation results show that, with our enhancements, the system performance can be improved significantly compared with the conventional Imm-ACK and fixed Dly-ACK. We also investigate the impacts of some important parameters such as the buffer size on the system performance. Some important guidelines for the Dly-ACK design are given. Finally, it is worth to point out that our Dly-ACK enhancements are compatible with the standard and it is transparent to the upper layer protocols, i.e., either UDP or TCP.
The Hong Kong University of Science and Technology
Chiu-lung, Kowloon City, Hong Kong
- Department of Electronic and Computer Engineering