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Mobile and Wireless Communications Summit, 2007. 16th IST

Date 1-5 July 2007

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Displaying Results 1 - 25 of 309
  • Enhancing Multiprotocol Service Discovery Framework in Pervasive Computing Networks

    Publication Year: 2007 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5667 KB) |  | HTML iconHTML  

    To obtain access to a specific service or peripheral we need a procedure that processes a query about service type, capabilities, location, and so on, and returns a services and peripherals list. Service discovery has two important components that people look on distinctly: first is a service discovery protocol which is used to communicate with services on the net; second is service description model which has to be sufficiently powerful so as to allow users to easily find a number of services with precise features but also largely compatible with existing systems. In this paper we propose a service discovery framework which is a previously result from our lab but has a fundamental capability that brings it one step ahead of its previous version: it is multiprotocol enhanced. It includes SLP (service location protocol) and universal plug 'n play protocol (UPnP) for services discovery, integrated with the powerful descriptive functionalities offered by OWL (ontology Web language), a language that permits creation of service ontologies for flexible description of services. This work describe the state of the art of discovery design activity which is being carried out within DAIDALOS (Designing Advanced network Interfaces for the Delivery and Administration of Location independent, Optimised personal Services), a project granted in the European 6' Framework Research Programme, within the IST (Information Society and Technology) thematic area. View full abstract»

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  • Interleaving Strategies for Concatenated Zigzag Codes

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (112 KB) |  | HTML iconHTML  

    Concatenated zigzag codes are attractive coding schemes since they offer excellent performance while having relatively low encoding and decoding complexity. Powerful codes are obtained by parallel concatenation of several constituent zigzag codes which encode interleaved versions of the data sequence. This implies a problem in interleaver design: Not only one interleaver which is optimized for iterative decoding is needed but several interleavers are needed. Each of those interleavers should provide good performance of iterative decoding while the interleavers should be mutually as independent as possible. We propose various interleaving strategies which take the specific properties of zigzag codes into consideration. We show the superiority of our proposals in terms of BER performance over straightforward interleaver design approaches such as congruential or s-random interleavers. View full abstract»

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  • A Low Complexity DDS IC for FM-UWB Applications

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (306 KB) |  | HTML iconHTML  

    This paper presents a low-complexity DDS IC for subcarrier processing in an FM-UWB transceiver. The IC implements data pre-filtering and FSK generation for the transmitter and quadrature LO signals generation for the receiver. The use of DDS techniques yields accurate signals whose parameters can be easily adjusted to accommodate a wide range of sub-carrier frequencies and bit rates. An interpolating DAC is used to directly generate the lowpass filtered analog output signals. The design will be fabricated in a standard 130 nm CMOS technology. View full abstract»

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  • Expectations and Actual Satisfaction about Mobile Communication Terminals before and after Purchase; Research on the Influence on Customer Loyalty

    Publication Year: 2007 , Page(s): 1 - 14
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3750 KB)  

    This thesis is intended to examine factors that affect customer satisfaction in the domestic mobile communication terminal market as to expectations before purchase and actual satisfaction after purchase. Also, how the factors that affect customer satisfaction about mobile phones influence the customer base was theoretically and positively examined. The mobile communication terminal industry, which has been the driving force behind the development of Korea as a great power in the information and communication industry, has a great influence on the global market as well as the domestic economy. Nevertheless. research efforts on the existing mobile communication market have been focused on the mobile communication service market rather than the mobile communication terminal market In addition, research on customer satisfaction about mobile communication terminals, which has been done by a few scholars in the related fields. has been limited to prices and brands. That is, the traditional research efforts on customer satisfaction about mobile communication terminal Products have been focused on the influences of prices and brands on the purchase of products rather than on the evaluation of the unique quality attribute of each product. Therefore, this thesis is intended to examine factors expected to enhance customer satisfaction about products and expand the customer base other than the external factors including the prices and brand images of mobile phones so that customer-oriented mobiles phones can be developed and manufactured. View full abstract»

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  • Blind SNR Estimation on WCDMA system with Unequal Power Signals and without any Prior Knowledge

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4474 KB) |  | HTML iconHTML  

    In this paper we have estimated signal to noise ratio (SNR) of active users in uplink scenario of CDMA systems blindly. We have not any knowledge about PN (pseudo noise) code, frequency, and timing of received signals. In this way first we synchronized received signal of desired user and then we use subspace method for SNR estimation of synchronized user. This type of SNR estimation is classified as non data aided (NDA) methods. Our synchronization is based on maximizing of covariance matrix Frobenius norm. After that by estimating PN code of strongest signal we are able to estimate transmitted signal data, and by using estimated SNR, we can eliminate this signal from received signal by using SIC (serial interference canceller). By repetition this cycle for each user we can estimate SNR of active users in uplink scenario. Also, in this paper we use minimum description length (MDL) criteria for estimating signal subspace dimension. Standard divisions of estimated SNR show that good agreement with exact SNR for all users. View full abstract»

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  • Dynamic Scalable Software Downloads for Mobile Terminal Mass-upgrades

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (503 KB) |  | HTML iconHTML  

    This paper investigates various solutions to improve the scalability of software downloads for mobile terminal mass-upgrades. We look at procedures to improve transport- and network-layer performance by reacting on-the-fly to the dynamics of such downloads. Assisting the network layer, we present further work on dynamic adaptation of the one-to-many download method, particularly concentrating on the transport-layer implications of dynamic switching between many-unicast and reliable multicast. Specifically at the transport layer, we investigate the dynamic adaptation of reliable multicast characteristics for mass-upgrade downloads. Based on the unique heterogeneity in end-to-end performance characteristics of different source-receiver paths to mobile terminals, we argue the validity and usefulness of the solutions presented. View full abstract»

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  • Network and Service Discovery in Heterogeneous Broadcast Environment

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)  |  Patents (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3270 KB) |  | HTML iconHTML  

    This paper concerns network and service discovery problems in heterogeneous broadcast environment. Broadcasting has traditionally been limited to single network type. The future broadcasting landscape will be composed of different type of networks, especially the mobile broadcast networks like DVB-H, DMB, WLAN, WiMAX and 3G MBMS. Integration of these networks into a unified broadcast infrastructure requires extensions to the current network and service discovery methods. Existing methods are limited to a single network type which makes them cumbersome. There is a possibility to considerably improve this process by unifying the network and service discovery across different broadcast networks. The process can also be helped by utilizing location databases. In this paper, we propose a Universal Network and Service Discovery (UNSD) system and positioning information system which provides discovery support for many different network types and inclusion of positioning information. View full abstract»

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  • Cooperative Communications in Wireless Networks - A Requested Relaying Protocol

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (137 KB) |  | HTML iconHTML  

    In this paper we present a requested relaying protocol that helps mitigating multipath and shadowing effects in wireless networks. In our approach it is assumed that the destined mobile station has not been able to receive information from the base station and sends a request to surrounding terminals. Those terminals able to receive the request act as relays and help to transmit information from the base station to the destination. Performance analysis with respect to probability of decoding error and outage probability have been made with the results that both can be enormously improved by exploiting diversity. Additionally, order of diversity is defined and applied to our relaying approach as well. View full abstract»

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  • Joint Detection and Channel Estimation for OFDM Signals with Implicit Pilots

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (157 KB) |  | HTML iconHTML  

    Accurate channel estimation is mandatory for the performance of OFDM modulations (orthogonal frequency division multiplexing). For this purpose, pilot symbols and/or training sequences are usually multiplexed with data symbols. To avoid the spectral degradation associated to multiplexed pilots, the use of implicit pilots (i.e., pilots superimposed to data) was recently proposed. However, the interference levels between data and pilots might be very high, leading to performance degradation. In this paper we consider OFDM schemes where the channel estimation is based on implicit pilots. To overcome the difficulties inherent to the interference levels between pilots and data, we propose an iterative receiver with joint detection and channel estimation. Our performance results show that we can achieve performances close to the ones with perfect channel estimation, even when low-power pilots or sort frames are employed. View full abstract»

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  • Effects of Spectral Shaping on OFDM Transmission Performance in Nonlinear Channels

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (442 KB) |  | HTML iconHTML  

    This paper proposes a spectral shaping method for OFDM signals that reduces nonlinear distortion. In this method, new subcarriers, which are produced from original subcarriers, are inserted into a conventional OFDM signal to smooth the spectral shape. The results of computer simulations in a nonlinear channel show that spectral-shaped OFDM signals have lower out-of-band spectrum properties and bit-error rate than conventional OFDM signals when an iterative clipping-and-filtering technique is used in the transmitter. View full abstract»

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  • Advice of Charge in Telecommunication Services

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (151 KB) |  | HTML iconHTML  

    The tariff packages in the mobile telecommunication industry have got more and more complex in the last few years. The telecommunication companies have introduced several different services among with different discounts and allowances, and the price calculation of the service, and the understand of prices became harder for the subscribers. Because of this, the advice of charge functionality is sorely needed. Sadly, the legacy charging systems do not have the appropriate mathematical model to aid this functionality. In this paper we present a novel model for price calculation, which is capable of the advice of charge functionality. Moreover we present three different AoC models, and we show their advantages with a simulation. View full abstract»

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  • Downlink beamforming and SINR balancing for the simultaneous provision of unicast/multicast services

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    The provision of multicast services is a relevant feature within the context of the further evolution of cellular communication systems. The scope of this paper lies on the application of adaptive antenna arrays in order to allow for space division multiple access (SDMA) in a scenario with both unicast and multicast users. A sub-optimum algorithmic solution is proposed for the problem of maximizing the minimum SINR perceived by the unicast/multicast users (SINR balancing), while satisfying the transmit power constraint. It is based on the unicast-only solution, which has been extended to the unicast/multicast case. It is shown that the proposed low-complexity algorithm provides a reasonable approximation to the optimal solution, outperforming diagonalization-based procedures such as block diagonalization. View full abstract»

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  • On the relation between atmospheric visibility and optical wave attenuation

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (6993 KB) |  | HTML iconHTML  

    The knowledge about the relationship between atmospheric visibility and optical wave attenuation in the atmosphere is essential in order to predict the performance of free space optical communication links. In this paper, a study of the available models of visibility -attenuation relation is presented. Visibility and attenuation are measured on an experimental free space optical link with a wavelength of 830 nm. New models are proposed based on the least square fitting of data from this measurement. View full abstract»

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  • Enhanced Methods for SIP based Session Mobility in a Converged Network

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    The worlds of fixed and mobile networks are merging towards fixed mobile converge (FMC). This process brings many challenges to networking technologies to support an optimal level of security, QoS and mobility across heterogeneous fixed and mobile access networks. Efficient mobility management mechanism able to provide desired level of mobility is one of the key issues in FMC development. This paper presents enhanced methods for SIP based session mobility that brings continuous mobility, privacy protection and interdomain mobility across access and core networks possibly managed by different providers. This paper is organized as follows. First an overview of the standard SIP mobility mechanisms is given with its advantages and drawbacks. Afterwards, the SIP controlled IP soft handover concept is proposed as the method to overcome standard SIP mobility shortcomings. Finally a conclusion is given. View full abstract»

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  • Techno-Economic Analysis of the Open Broadband Access Network Wholesale Business Case

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2466 KB) |  | HTML iconHTML  

    In this paper a business scenario is considered whereby a wholesaler deploys and manages needed residential equipment for public wireless cells. Connectivity is then sold to retailers of public wireless broadband services. This business model allows the costs of the residential wireless infrastructure serving the public environment to be shared among several parties. The relevant business model is specified and techno-economic results for a concrete business case are presented with a sensitivity analysis to identify the most critical business parameters. View full abstract»

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  • Bit Error Rate Calculation for OFDM Direct Conversion Receivers with Synchronization and Channel Estimation Imperfections

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (132 KB) |  | HTML iconHTML  

    In this paper we present an analytical approach to evaluate the M-QAM bit error rate (BER) of OFDM direct conversion receivers subject to carrier frequency offset (CFO), channel estimation error, outdated channel state information and flat receiver I/Q imbalance in Rayleigh time and frequency selective fading channels. Based on correct modeling of the correlation between channel estimates and received signals with carrier frequency offset and receiver I/Q imbalance, the bit error rate can be numerically evaluated by averaging bit error rates on different subcarriers using an analytical expression of triple integrals. The results illustrate that the analysis can approximate the simulative performance very accurately if the power delay profile of fading channels, the receiver I/Q imbalance parameters and carrier frequency offset are known. View full abstract»

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  • Echo Cancellation and Channel Estimation for On-Channel Repeaters in DVB-T/H Networks

    Publication Year: 2007 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5089 KB) |  | HTML iconHTML  

    This paper investigates the design and performance of an echo canceller for on-channel repeaters in DVB-T/H network within the framework of the PLUTO project. The possible approaches for echo cancellation are briefly reviewed and the main guidelines for the design of such systems are presented. The main system parameters are discussed. The performance of a FIR echo canceller based on an open loop approach for channel estimation is tested for different radio channel conditions and for different number of taps of the FIR filter. It is shown that a minimum number of taps is recommended to achieve a certain mean rejection ratio or isolation depending on the type of channel. Channel estimation based on training sequences is then investigated. The performance of maximum length sequences and constant amplitude zero autocorrelation (CAZAC) sequences is compared for different channels. Recommendations are given for training sequence type, length and level for DVB-T/H on-channel repeater deployment in single frequency networks. View full abstract»

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  • Performance Analysis of Orthogonal Transmit Diversity Over Intra-Cell Interference in WCDMA Downlinks

    Publication Year: 2007 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (274 KB) |  | HTML iconHTML  

    This paper extends the traditional orthogonal transmit diversity (OTD) analyses to the multipath intra-cell interference presented in a realistic wideband code-division multiple access (WCDMA) downlink channel. A generic OTD system model is proposed for analyses permitting maximizing the spatial and temporal diversity dimensions for multiple transmit antennas and space-time block code (STBC) respectively. Analytical expressions are derived to evaluate the Chernoff upper bounds on the bit-error rate (BER) for the OTD system under a variety of channel parameters. The expression shows that the BER upper bound can be simplified and determined using an attained signal-to-interference-plus-noise power ratio (SINK) obtained in terms of the number of transmit antennas, the phase difference between two transmit antennas, the channel orthogonality, and the relative cross-correlations of the desired signal to the intra-cell interferers power ratio when equal power allocation at each intra-cell user and perfect channel state information (CSI) are applied in the closed-loop TD system. View full abstract»

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  • Experimental Analysis of the MIMO Channel for In-door NLOS Multi-path Propagation

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (435 KB) |  | HTML iconHTML  

    Multiple-input and multiple-output (MIMO) channel measurement and analysis are presented based on multiple-input and single-output (MISO) antenna configurations associated with dynamic measurements. The measurement is considered in a time-stationary elliptical scattering in-door propagation scenario, where a special case of the "Kronecker" MIMO channel model is derived and the channel reciprocity for the uplink and downlink is assumed. The cumulative distribution functions (CDF's) of the delay spread and fading envelope, as well as the maximum-to-minimum eigenvalue ratio (MMEVR) are investigated and compared with respect to different antenna spacing and angular spread, respectively. For large angular spread, a wider arrival angle shows that it is not necessary to increase the un-correlated inter-subchannels. These analysis results meet most real MIMO channel statistical property scenarios. View full abstract»

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  • The Effect of a Rapidly Changing Urban Environment on Nomadic WiMAX Performance

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1201 KB) |  | HTML iconHTML  

    This paper presents the results obtained during a three-month trial (February -April 2006) performed by COSMOTE towards the assessment of "fixed WiMAX" technology (IEEE 802.16-2004). The trial was conducted in the three largest cities of Greece, namely, Athens, Thessaloniki and Patra, in parallel, using "fixed WiMAX" equipment offered by three different vendors. The results presented here have been obtained at street-level during stationary measurements performed in the Athens centre, an urban NLOS environment, using a portable WiMAX CPE and a Laptop. The main characteristic of this environment is that it changes very rapidly and quite unpredictably, due to the existence of moving vehicles ranging from motorbikes, to buses and large trucks. These measurements simulate the system performance that an end-user perceives in such an environment, when he/she uses "fixed WiMAX", while enjoying a meal or drink in a restaurant, bar or cafeteria. Preliminary results indicate that in an urban street-level environment, with NLOS channel conditions, large throughput variations are observed, due to the existence of moving vehicles in the radio path. These variations may severely affect the quality of delay-sensitive real-time applications such as, video streaming and video-telephony. View full abstract»

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  • Digital Beamformer Antenna System

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB) |  | HTML iconHTML  

    Growing importance of smart antennas encouraged us to extend our research activity toward the development of a transmitting digital beamformer. In this paper we give an overview about our approach. View full abstract»

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  • Dynamic Fair Power Sharing Admission Control for HAP-UMTS communication system

    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (326 KB) |  | HTML iconHTML  

    Cellular communications using high altitude platform (HAPs) are studied for next generation broadband wireless network providing also third generation (3G) mobile services. The connection admission control (CAC) issue in a HAP-UMTS communication system represents a key problem in order to increase the capacity in terms of admitted users preserving the agreement quality of service. The main problem of a full centralized admission control approach consists in an excessive calls blocking for the traffic sources located in the middle of the aerial platform coverage area, due to the high additive interference level generated by all active users. With the aim of resolving this issue, we propose a novel strategy for the admission procedure, based on dynamic power sharing (DFPS), in order to guarantee a high fairness level to all users of the implemented cellular system, in term of calls blocked in each cell. Furthermore, we compare this approach with a previous one based on full centralized power sharing (FCPS). Simulation results show that the proposed CAC scheme can achieve better performances than the previous one, managing the active connections in a "fair" manner also under high load conditions. View full abstract»

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  • On-Board Link Layer Relay Mechanism to Enhance TCP in Satellite IP Networks

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3466 KB) |  | HTML iconHTML  

    Transmission control protocol (TCP) over satellite IP networks has attracted many researchers' interests for many years because the TCP performance degrades considerably due to the high propagation delay and high bit error rates in satellite links. Many proposals have been produced to enhance TCP performance in satellite IP networks, which are mostly involved of modifying system's architecture or TCP protocol stack. In this paper, we propose a novel on-board link layer relay mechanism. We use both analytical and simulation means to compare the traditional bent-pipe scenario and our on-board link layer relay mechanism. The numerical and simulation results indicate that the TCP performance can be enhanced substantially by employing our on-board link layer relay mechanism. View full abstract»

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  • Sampling Time Offset Estimation for IFDMA Uplink Systems

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (149 KB) |  | HTML iconHTML  

    This article investigates the influence of sampling time offset on the performance of an interleaved frequency-division multiple-access (IFDMA) uplink scheme for mobile radio transmission. It is shown that sampling time offset causes signal-to-noise ratio (SNR) degradation and leads to inter-symbol interference (ISI). In addition, an efficient algorithm is proposed which is capable to estimate sampling time offset by applying oversampling at the receiver. The proposed algorithm requires only three-times oversampling, does not use any pilot symbols, and is independent from the transmission channel and modulation alphabet. View full abstract»

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  • Suppression of ISI Caused by Sampling Time Offset in IFDMA Systems

    Publication Year: 2007 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (151 KB) |  | HTML iconHTML  

    In this article, we investigate the influence of sampling time offset on the bit error rate (BER) performance in interleaved frequency-division multiple-access (IFDMA) uplink systems. It is shown that even small sampling time offset results in inter-symbol interference (ISI) and in signal-to-noise ratio (SNR) degradation. To avoid this, a soft ISI suppression algorithm is proposed which allows to significantly improve the system performance. The proposed algorithm can be applied to both IFDMA uplink systems and to conventional orthogonal frequency-division multiple-access (OFDMA) uplink systems. View full abstract»

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