The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Multiuser diversity combined with Orthogonal Frequency Division Multiple Access (OFDMA) are a promising technique for achieving high downlink capacities in new generation of cellular and wireless network systems. The total capacity of OFDMA based-system is maximized when each subchannel is assigned to the mobile station with the best channel to noise ratio for that subchannel with power is uniformly...
In this paper, the optimal number of pilot symbols for orthogonal frequency division multiplexing (OFDM) systems is determined based on the criterion of minimizing the loss in mean capacity, and the simulation results that verify the analysis are presented.
In this paper, a novel OFDM symbol timing recovery method, which is robust to doubly selective fading channels and carrier frequency offset, is proposed for the mobile terminals of CMMB system. The time slot timing synchronization is accomplished by using the inverse sliding correlation between the segmenting Sync sequences, which possess the inverse conjugate symmetry (ICS) characteristic. Furthermore,...
Spectrum awareness is one of the most challenging tasks in cognitive radio (CR). To adequately adapt to the changing radio environment, it is necessary for the CR to be able to perform joint detection and classification of low signal-to-noise ratio (SNR) signals without requiring much a priori information on the signal parameters. In this paper, we propose a joint detection and classification algorithm...
In this paper, we compare the performance attained by several scheduling policies when the resource allocation is performed in a per-user or in a per-frequency resource ordering. We test the capability of both approaches to deal with the quality of service (QoS) provisioning in a multi-service scenario in a mobile OFDMA network. We probe that the comparative performance of these two approaches depends...
An efficient feedback compression scheme is presented for signaling of explicit channel state information (CSI) to the transmitter side for MIMO OFDM systems in general and especially with coordinated multi-point transmission (COMP). Simulation results show that the required rates can be reduced by a factor of up to 17, compared to reporting of quantized frequency domain channel representations. This...
In this paper, the performance evaluation of the Mesh-based PHY of IEEE 802.16e standard (a.k.a Mobile WiMax) for above the sea propagation is presented. For a Mesh OFDM system, the independent bursts transmission among different communicating nodes compels the receiving nodes to perform frame locking using the preamble with size of only one OFDM symbol interval, short preamble length is used in favour...
In mobile reception of OFDM, the bit error rate characteristic is deteriorated, because the inter-carrier interference(ICI) is generated by the Doppler-spread of radio channel. The influence of ICI can be reduced by ICI canceller based on zero-forcing equalization. In this paper, Zero-forcing ICI canceller using the linear interpolation is studied in order to reduce the complexity of the circuits...
3GPP long term evolution is one of the major steps in mobile communication to enhance the user experience for next-generation mobile broadband networks. In LTE, orthogonal frequency-division multiple access is adopted in the downlink of its E-UTRA air interface. Although cross-layer techniques have been widely adopted in literature for dynamic resource allocation to maximize data rate in OFDMA wireless...
A growing number of mobile WiMAX deployments are in progress world-wide and the technology is anticipated to play a key role in next generation mobile broadband wireless networks. However, although the theoretical potential of WiMAX technologies is already well established, independent, publicly released, thorough evaluations of WiMAX network performance in the real world are yet to become available...
This paper presents the results of an experimental work where coherence bandwidth of an urban environment was measured in order to estimate the delay spread of this channel. An OFDM mobile communication system was assembled and the level of the pilot carriers was individually measured to produce the coherence bandwidth. The results have shown the expected difference between the delay spread on line-of-sight...
Link layer abstraction is crucial both the cross layer simulation and design and the interface to complete a system level simulator. The calibration takes an important role within this design. In this paper we have used several kinds of algorithms like EESM, CESM and LESM for the instantaneous channel, calibration and evaluation of the link level interface in WiMAX system 802.16e. In order to have...
This paper shows a delay probability of some traffics transmitted by each MT (Mobile Terminal) in a time slot in terms of VBR (Variable Bit Rate) traffic, analyzes that and proposes a generalization over new OFDM-based system to make up for the fault of existing WCDMA system. When a channel error exists, an average delay time processing in a time slot is analyzed and a generalization according to...
In a cellular system, efficient power saving techniques for a mobile station (MS) are necessary because of its inherently limited battery of MS. The paging indicator (PI) transmission scheme in CDMA cellular systems is known to be an effective power saving strategy. However, in OFDM-based cellular systems, the MS has to operate FFT for PI symbol detection, resulting in a significant power consumption...
MaxSNR scheduling is acknowledged as the reference resource allocation for multiuser OFDM wireless networks. Well adapted to the wireless environment, MaxSNR opportunistically considers the channel state and fights the multipath fading negative effects. Taking advantage of multiuser diversity, MaxSNR scheduling is well-known for maximizing the global cell throughput. However, throughput maximization...
This paper proposes multipath division turbo equalization with block inter-carrier interference cancellation (MD-BIC) for orthogonal frequency division multiplexing (OFDM). When the multipath delay difference exceeds the cyclic prefix (CP) length, the OFDM transmission performance suffers severely due to inter-symbol interference (ISI) and inter-carrier interference (ICI). Cellular systems with amplify-and-forward...
Spectrum splitting is the simplest approach to allocate the spectrum to femtocells overlaid with the existing cellular networks. In orthogonal frequency division multiple access (OFDMA) systems, this can be done by assigning a subset of orthogonal subcarriers to femtocells. To ensure subcarrier orthogonality and thus not interfere with existing macro Mobile Stations (MSs), the signals from the strongest...
In linear minimum mean-square error (LMMSE) channel estimation for multicarrier transmission, how to estimate the needed channel correlation function remains a problem for systems with small number of pilots operating in time varying channels. We consider approximating the channel power delay profile by a shape characterized fully by the mean delay and the root-mean-square (RMS) delay spread. We present...
This paper presents field experiment results for rotational orthogonal frequency division multiplexing (R-OFDM) transmission and demonstrates that R-OFDM is superior to conventional OFDM even in actual radio transmission. R-OFDM is a multi-carrier transmission scheme proposed by the authors. It is characterized by the use of rotational code division multiplexing that enables OFDM to obtain suitable...
Most of the existing scheduling algorithms in OFDMA and TDMA systems assume the availability of perfect channel quality indicator (CQI) at the transmitter. Unfortunately, this is unrealistic since the receiver (e.g. mobile users) estimates the CQI at time t - ?? and feed back this CQI estimate to the transmitter (e.g. base station). The scheduler uses then this outdated CQI at time t to make the allocation...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.