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Communications (APCC), 2011 17th Asia-Pacific Conference on

Date 2-5 Oct. 2011

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Displaying Results 1 - 25 of 184
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • [Front inside cover]

    Page(s): 1
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  • [Front matter]

    Page(s): ii - xx
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  • Table of contents

    Page(s): xxi - xxxi
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  • On performance of bi-directional cognitive radio networks

    Page(s): 1 - 5
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    Future wireless Internet services require a broadband frequency spectrum with high data rates. Cognitive radio (CR) concept is a novel approach to improve the spectrum efficiency. The CR is based on the opportunistic usage of frequency spectrum, which is not occupied by the primary users. Conventional multi-user access in bi-directional CR network may be done by using either time division multiple access (TDMA), frequency division multiple access (FDMA) or code division multiple access (CDMA). Without adaptive or dynamic frequency reuse, TDMA and FDMA have lower spectrum efficiency in comparison with CDMA. However, the problem of CDMA in a multipath channel is a multi-user interference (MUI). In this paper, we present a bi-directional CR network with wireless network coding (WNC) in a multipath channel. Unlike the conventional multi-user bi-directional CR network, where the users access the spectrum holes in different time-slot or frequency, the proposed method allows secondary users (SUs) to access the spectrum holes simultaneously. The performance of bi-directional CR network with WNC is theoretically analyzed in terms of spectrum efficiency and the maximum number of SUs. The numerical results show that the spectrum efficiency and the maximum number of SUs of the proposed method increases in comparison with conventional CR network. View full abstract»

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  • Active secondary user selection algorithm of simo opportunistic spatial orthogonalization in fading cognitive radio networks

    Page(s): 6 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1203 KB) |  | HTML iconHTML  

    The opportunistic spatial orthogonalization (OSO) scheme, proposed by Cong Shen and Michael P. Fitz, allows the existence of secondary users during the period in which the primary user is occupying all licensed bands. This paper introduces an active secondary user selection algorithm which mitigates the interference from the primary user transmitter to the secondary user receiver. In order to select the active secondary user, we adopt a fusion center concept, which is utilized for the cooperative spectrum sensing. A proposed algorithm guarantees the minimum average throughput of the primary user and overcomes the average sum throughput of a conventional OSO. We have numerically analyzed the average throughput under various constraints. View full abstract»

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  • Dynamic bandwidth access to cognitive radio ad hoc networks through pricing modeling

    Page(s): 12 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1343 KB) |  | HTML iconHTML  

    Spectrum resources are becoming more and more congested as the number of wireless devices are increasing and becoming ubiquitous. Cognitive radios or secondary users (SUs) can provide the solution for better spectrum availability, bandwidth and economic aspects for both the primary service providers and the SUs. We propose a pricing model for spectrum sharing in a single level market where the primary service providers can trade spectrum with the secondary service providers. The proposed pricing model incorporates the reliability of the primary service providers and allowable coverage area, quality of the signal along with the pricing and spectrum bandwidth availability. An iterative distributed algorithm is used to reach the market equilibrium so that both the primary and the secondary service providers are satisfied with the allocated spectrum bandwidth and negotiated price. The performance of the proposed model is demonstrated using extensive numerical results with the stability analysis in reaching the market equilibrium. View full abstract»

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  • A novel operating and backup channel allocation scheme in IEEE 802.22 systems

    Page(s): 18 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB) |  | HTML iconHTML  

    In this paper, novel operating and backup channels allocation schemes for IEEE 802.22 system are introduced and their performances are investigated. Interference level and the probability of appearance for incumbent user are taken into account in order to optimally update the backup channels list. Additionally, the operating channel is allocated based on Carrier to Interference and Noise Ratio (CINR) so as to meet Quality of Service (QoS) requirement. Simulation results illustrate that performance is significantly enhanced by employing the proposed channel allocation schemes in the IEEE 802.22 system. View full abstract»

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  • Joint power allocation and beamforming in relay-assisted cognitive radio networks

    Page(s): 22 - 27
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1280 KB) |  | HTML iconHTML  

    In cognitive radio (CR) networks, the secondary users (SUs) try to communicate opportunistically in the frequency band originally allocated to a primary network. This communication should be in a manner that the quality of service (QoS) is satisfied for both primary and secondary networks. In this paper, the considered system consists of a primary broadcasting network with one transmitter and M receivers, and a relay-assisted secondary network with one transmitter and one receiver. In this scheme, if the direct link between the cognitive transmitter and receiver is not maintained the target signal to interference plus noise ratio (SINR), the relaying process, begins where N relays assist the transmitter to transmit its data to the receiver. This relaying process continues until the target SINR is met at the cognitive receiver. This scheme employs joint power allocation and beamforming (BF) at the relay nodes and defines two optimization problems in a way that the objective in the first problem is minimization of the total transmission power of the relays. If there is not any feasible solution for the first problem, the second problem is proposed with the objective of maximizing the receive rate at the destination node. Genetic algorithm (GA) is applied to both defined problems to find optimum transmission power values and beamforming weight in the relay nodes. Simulation results show that applying beamforming scheme results in a considerable reduction in the total transmission power of the relay nodes, while satisfying the QoS in both primary and secondary networks. View full abstract»

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  • Self-optimization of single femto-cell coverage using handover events in LTE systems

    Page(s): 28 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1314 KB) |  | HTML iconHTML  

    In LTE systems, low-power required small-coverage-cell is additionally deployed on a macro-cell to enhance the system performance in the respects of coverage and capacity improvement. In this paper, we propose a self-optimization algorithm for a single femto-cell coverage. The objective function to be minimized for optimal coverage adjustment is the sum of camp on (CO) and unnecessary hand over (UHO) areas that is defined shortly. CO problem results in inefficient usage of base station with low received signal strength, and consequently, causes the low data rate. UHO incurs the wasteful usage of limited resources and overhead increase due to HO processes. We verify the validity of the proposed algorithm by comparing the performance with the result of theoretical analysis. Furthermore, we develop the proposed algorithm to increase the system throughput. View full abstract»

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  • Delay-aware packet scheduling algorithm for multiple traffic classes in 3GPP LTE system

    Page(s): 33 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1265 KB) |  | HTML iconHTML  

    In wireless mobile environments, large bandwidth and high quality of service (QoS) are recently required to support the increased demand for multimedia services. Long term evolution (LTE) is one of the promising solutions for the next generation broadband wireless access systems. In order to support high data rate with low latency, LTE simplifies network architecture and uses orthogonal frequency division multiple access (OFDMA) for downlink transmission technology. Packet scheduling algorithm is one of the important features to support QoS in LTE system. In this paper, we propose delay-aware packet scheduling (DAPS) algorithm considering QoS requirements of delays for various traffic classes, channel conditions, and fairness. To reflect delay experience at scheduling instance, DAPS algorithm observes how queue waiting time of head-of-line (HOL) packet is closed to allowed maximum packet delay. As a result, DAPS increases the number of transmitted packets with satisfying the required delay. Comprehensive simulation results show that DAPS algorithm yields better delay performance compared with two existing PF and M-LWDF algorithms. View full abstract»

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  • On resource block sharing in 3GPP-LTE system

    Page(s): 38 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (227 KB) |  | HTML iconHTML  

    In this paper, we deal with sharing of a resource block (RB) which is the basic resource allocation unit for scheduling in 3rd-generation partnership project long term evolution (3GPP-LTE) system. In 3GPP-LTE system, a scheduler of evolved node-B (eNB) allocates respectively one or more RBs to user-equipments (UEs) considered, considering their requests, their channel qualities, and the resource availability. In the case of constant-rate service (i.e., the real-time service), some of RBs may not be fully utilized, depending on the channel quality. Especially, in the case of multiple-input multiple-output (MIMO) multiplexing, the degree of resource wastage may become much severer since a much less amount of the resource may be required for the same data rate. In this paper, we introduce the concept of RB sharing where one RB can be shared by multiple UEs depending on their respective required rates and the corresponding channel qualities. Through computer simulations, we evaluate the average sum rates for both cases of RB sharing and non-sharing. From simulation results, we see that the RB sharing scheme can achieve much greater sum rate as compared to the non-sharing one. View full abstract»

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  • A low complexity scheduling scheme based on multi-user beamforming in TD-LTE downlink

    Page(s): 43 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1122 KB) |  | HTML iconHTML  

    Multi-user multi-input and multi-output based on block diagonalization algorithm can eliminate the multi-user interference, but in fact the existence of the non-ideal factors lead to the interference can not be cancelled completely. In this paper we study the performance of the 3GPP long term evolution system based on BD algorithm and propose a low complexity multi-user scheduling scheme to reduce the mismatch between the CQI and the PostSINR. To get the tradeoff between the cell average capacity and the cell edge user capacity, proportional fairness scheduling is applied. Finally, simulation results with 3GPP LTE are presented using system level simulator. View full abstract»

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  • On fractional and semi-soft handover in long term evolution (LTE) networks

    Page(s): 48 - 52
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    The fast pace of development of telecommunications technology and the challenges presented with the increasing number of users for any service, anywhere, anytime, access creates new problems with on the base stations capability and the handover/handoff (HO) techniques. To face these challenges much research have been made to come out with algorithms that can handle handover of user equipment (UE) while maintaining their respective quality of service (QoS). In this paper a hybrid HO algorithms called semi-soft handover (SSHO) and fractional soft handover (FSHO) in long term evolution (LTE) system are studied. The outage probability, the main metric to evaluate handover, is compared for different handover techniques. View full abstract»

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  • Modeling and simulation of packet scheduling in the downlink LTE-advanced

    Page(s): 53 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1193 KB) |  | HTML iconHTML  

    LTE-Advanced, the true 4G technology of 3GPP family, is a complex radio access technology with co-existence of many types of user equipments. As it is a new technology, there are few published research focusing on modeling and simulation of LTE-Advanced system. A simulation tool is indispensable for research relating to Radio Resource Management mechanisms such as packet scheduling. This paper presents detailed descriptions of a computer simulation tool that can effectively model packet scheduling, as well as describes some of its simulation results. View full abstract»

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  • Radio resource allocation scheme for device-to-device communication in cellular networks using fractional frequency reuse

    Page(s): 58 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1504 KB) |  | HTML iconHTML  

    Device-to-Device (D2D) communication is the technology enabling user equipments (UEs) to directly communicate with each other without help of evolved nodeB (eNB). Due to this characteristic, D2D communication can reduce end-to-end delay and traffic load offered to eNB. However, by applying D2D communication into cellular systems, interference between D2D and eNB relaying UEs can occur if D2D UEs reuse frequency band for eNB relaying UEs. In cellular systems, fractional frequency reuse (FFR) is used to reduce inter-cell interference of cell outer UEs. In this paper, we propose a radio resource allocation scheme for D2D communication underlaying cellular networks using FFR. In the proposed scheme, D2D and cellular UEs use the different frequency bands chosen as users' locations. The proposed radio resource allocation scheme can alleviate interference between D2D and cellular UEs if D2D device is located in cell inner region. If D2D UEs is located in cell outer region, D2D and cellular UEs experience tolerable interference. By simulations, we show that the proposed scheme improves the performance of D2D and cellular UEs by reducing interference between them. View full abstract»

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  • Power control for two-tier femtocell networks using pricing mechanism via emergency message

    Page(s): 63 - 67
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    This paper proposes the power control method using a pricing mechanism via emergency message to mitigate the cross-channel interference for downlink transmission in two-tier femtocell networks, where macrocell and overlaid femtocells share the same frequency band (i.e., cochannel deployment). Macrocell users measure the channel gain from base station to user, and computes the achieved SINR. If the macrocell achieved SINR is not satisfied for a target SINR, a macrocell user broadcasts emergency message to close-by femtocell users. When femtocell users receive the emergency message, the femtocell pricing coefficient value is forced to increase, which in turn decreases their power, resulting in reduced cross-channel interference at the macrocell. Consequently, the macrocell user will then satisfy the target SINR faster, but with some modest loss in total throughput. View full abstract»

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  • A scheme for available bandwidth estimation in simultaneous multiple-pair communications

    Page(s): 68 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1058 KB) |  | HTML iconHTML  

    In grid networks, there are different communication pairs between senders and receivers, where they communicate simultaneously. These different simultaneous communications are called multiple-pair communications. In multiple-pair communications, an identical link that is shared on paths of different communications may exist. The link is called a common link. A controller of multiple-pair communications needs to know the link available bandwidth of the common link, which may limits the available bandwidth in simultaneous multiple-pair communications, for scheduled communications. An objective of scheduling is to complete all required communications as quickly as possible when each traffic demand is given. A conventional scheme is not able to estimate the link available bandwidth of a common link. This paper proposes a scheme for estimating an available bandwidth in simultaneous multiple-pair communications, which is called a simultaneous available bandwidth. To achieve this, the proposed scheme estimates the link available bandwidth of a common link by synchronizing packet streams at the common link if any common link exists and the bandwidth limits the simultaneous available bandwidth. The proposed scheme employs the metrics that are used to estimate the path available bandwidth of a single-pair communication in the conventional scheme, to synchronize packet streams. This paper formulates an optimal adjustment width of transmission time of a packet stream to synchronize packet streams when a target synchronization ratio is given. View full abstract»

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  • A consideration on contents management systems using quality transition mode in video contents utilization services by on-demand

    Page(s): 73 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1234 KB) |  | HTML iconHTML  

    Video contents service over a network is expanded by improvement in network speed and large capacity in recent years. Meanwhile, when users use a lot of contents, they are faced with the problem of the lack of memory capacity. Therefore, the contents management methods are important for the services. Then, we had proposed the management method using cache delivery and scalable contents. In this study, after a content utilization service model using mobile and home terminal is defined, we propose a management method using the data transition process of scalable structure. This is based on elapsed time and its content quality. We consider the efficiency in this model from a viewpoint of single quality and the quality of two. View full abstract»

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  • Efficient carrier selection schemes for dual-carrier HSDPA system

    Page(s): 79 - 83
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    Dual-carrier High Speed Packet Access (DC-HSPA) system has been developed as an alternative method to double data rate using more bandwidth, without use of MIMO. Since it utilizes two carriers at a time, scheduling is more important feature than a single-carrier HSPA (SC-HSPA) system. From the nature of the DC-HSPA, both carriers can be allocated to one user when the user has the highest priority on both carriers. However, if a single carrier is enough to empty the queue, one of carriers has to be selected to transmit own data, while the other carrier is assigned to the other user. Available resource on each carrier varies accordingly to the selected carrier, therefore, efficient carrier selection schemes for DC-HSPA system are proposed based on relative scheduling metric difference between users on each carrier. Simulation results show that proper carrier selection increases throughput as well as average user rate in DC-HSDPA system. View full abstract»

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  • A ring-based performance analysis for a call admission control in an LTE/WiFi heterogeneous network

    Page(s): 84 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1515 KB) |  | HTML iconHTML  

    Wireless Local Area Networks (WLANs) are generally deployed in indoor environments such as cafes, offices, and hotels, and therefore, once users enter the WLAN coverage, they tend to stay there in a longer time. That is, in the WLANs which we call double coverage areas, population density is higher and mobility is lower compared to the single coverage area. In this paper, we introduce a new parameter, representing the difference in mobilities (or populations) in and outside the WLAN coverages. Then, by extending the previous works in [2,3], we evaluate the impact of user's mobility in WLAN based on call blocking and handoff failure probabilities. Through simulations, we investigate proper preference settings by changing the WLAN load and the user's mobility parameter in a 3 ring-based sector with a WLAN hotspot. View full abstract»

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  • Stackable ROADM with optical amplifier for use in IP-over-CWDM networks

    Page(s): 90 - 95
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1943 KB) |  | HTML iconHTML  

    A stackable module with a bidirectional CWDM amplifier has been proposed to introduce the optical amplifier into an S-ROADM for use in an IP-over-CWDM ring network, and the performance was evaluated experimentally. Packet transfer changes were monitored during the lightpath reconfigurations, including 2 lightpaths which needed optical amplifications. The result clarified that the lightpaths were reconfigured successfully, including the remote activation of the amplifiers. As a result, the stackable feature of the amplifier module enables us to provide the cost-effective introduction into the network on an implement-it-when-necessary based service in a fully compatible way with the existing stackable ROADM modules, when constructing the S-ROADM with an amplifier. Therefore, the amplifier module can be used in the same way as the ROADM modules to construct the S-ROADM, providing manually adding capability of the amplifier to in-service networks. Thus, the amplifier module has a big advantage to use it flexibly and economically in the IP-over-CWDM networks. View full abstract»

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  • Novel multi-code pulse position modulation for performance improvement of 2-D OCDMA systems

    Page(s): 96 - 101
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    In OCDMA systems, pulse position modulation (PPM) and multi-code modulation (MCM) have been proven as efficient methods for respectively mitigating multiple access interference (MAI) and dispersion. In this paper, we propose to combine PPM and MCM to create a novel modulation scheme, multi-code pulse position modulation (MCPPM). We then theoretically analyze the performance of the 2-D OCDMA system using MCPPM over a linear dispersive channel, while taking into account the negative impact of MAI, optical-beating interference (OBI), and receiver noise. It is seen that the use of MCPPM can simultaneously relax the effects of MAI, OBI, and dispersion. As a result, in comparison to the conventional systems using PPM and MCM, the one using MCPPM can support a higher user bit rate and a larger number of users. Also, a lower transmitted power can be achieved. View full abstract»

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  • A simple and robust hybrid power transmit diversity in free-space optical communications

    Page(s): 102 - 106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1342 KB) |  | HTML iconHTML  

    Spatial diversity techniques are now widely adapted in most wireless radio-frequency communication systems to increase robustness against signal fading, and also attract a considerable amount of attention in free-space optical (FSO) communications. On downlink, user terminal cost and power consumption considerations indeed favor transmit diversity over receive diversity, and orthogonal space-time block code (OSTBC) appears to be most well-known transmit diversity scheme. However, OSTBC loses 3 dB in terms of total transmit power with respect to ideal hybrid power transmit diversity technique which requires perfect channel state information at the transmitter. In this paper, we present a simple scheme to recover the power loss using partial feedback for FSO links with intensity modulation and direct detection over log-normal atmospheric turbulence-induced fading channel. We also consider the deployment of other conventional transmit diversity techniques including equal power transmit diversity and switching transmit diversity as benchmarks. Simulation results show that most of the power loss is restored, and the proposed scheme performs very close to ideal performance outperforming other techniques. View full abstract»

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  • Monitored power pre-checking scheme for optical amplification management in lightpath reconfigurable IP-over-CWDM networks

    Page(s): 107 - 112
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1665 KB) |  | HTML iconHTML  

    A monitored power pre-checking scheme has been proposed and implemented for the effective amplification management during lightpath reconfigurations in IP-over-CWDM networks with ROADMs. The pre-checking performance was examined in an experimental IP-over-CWDM network by reconfiguring lightpaths. As a result, the pre-checking function worked properly, and the lightpaths were reconfigured successfully even for a longer lightpath than the allowable distance, including the amplification management performance. The pre-checking function provides an effective management performance to judge which lightpaths should be amplified, before the reconfiguration. View full abstract»

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