In IEEE 802.16e wireless metropolitan area networks, users could take their broadband connections with them as they move from one location to another with different speeds. Providing QoS is more challenging for mobile...
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In IEEE 802.16e wireless metropolitan area networks, users could take their broadband connections with them as they move from one location to another with different speeds. Providing QoS is more challenging for mobile subscribers at vehicular speeds than for others. On the other hand, time variability and unpredictability of the wireless channel may cause QoS degradation for these users. Therefore, providing seamless handovers especially at vehicular speeds is necessary for maintaining QoS. This paper proposes a new downlink handover priority scheduling algorithm for different scheduling services which is providing lossless handovers and QoS. Taking the power degradation rates into consideration, this algorithm assigns higher priority to the users who have higher speeds. A priority based AMC (adaptive modulation and coding) is also performed for better performance. The analysis results show the efficiency of proposed scheme.
In this paper, we propose a low complexity cooperative communication systems with the amplify-and-forward protocol over a multiple distributed relay network where only one relay among relay candidates is selected acco...
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In this paper, we propose a low complexity cooperative communication systems with the amplify-and-forward protocol over a multiple distributed relay network where only one relay among relay candidates is selected according to a certain threshold. By setting different values of their threshold, we consider two different relay selection schemes: (i) achieving the maximum spectral efficiency and (ii) minimizing system complexity. From our provided statistics of the combined output signal-to-noise ratio and our analysis of the system complexity, we show that our proposed node selection schemes provide considerable spectral efficiency gain and outage performance while it has a relatively low complexity comparing to other schemes known in the literatures.
An innovative Optimization-based Space Vector modulation method (OSVM) for 3Phi-3Phi matrix converter was proposed in paper [1]. OSVM is a direct modulation method which maximizes the modulation capability for referen...
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ISBN:
(纸本)9781424442515
An innovative Optimization-based Space Vector modulation method (OSVM) for 3Phi-3Phi matrix converter was proposed in paper [1]. OSVM is a direct modulation method which maximizes the modulation capability for reference vectors by using available input voltages and output currents. The solution of OSVM immediately tells the modulability of reference vectors. The algorithm of OSVM proposed in [1] has been implemented in a matrix testbed. The experimental results will be presented in this paper. The experimental results will show the performance and validity of the OSVM method.
This paper presents a switched wireless video service which can swell the capacity by serving video channels through switched broadcast, switched multicast, or switched unicast instead of standard broadcast schemes. W...
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This paper presents a switched wireless video service which can swell the capacity by serving video channels through switched broadcast, switched multicast, or switched unicast instead of standard broadcast schemes. We extend the switched video service into wireless environment and then exploit WiMAX adaptive modulation and coding gain.
In this paper, we propose a PAPR reduction method for a 16-QAM OFDM system by combining the BCM scheme with PTS technique, called BCM-PTS. We use four binary Reed-Muller codes as the BCM component codes to construct a...
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In this paper, we propose a PAPR reduction method for a 16-QAM OFDM system by combining the BCM scheme with PTS technique, called BCM-PTS. We use four binary Reed-Muller codes as the BCM component codes to construct a 16-QAM BCM code and decompose this code as direct sum of a correction subcode for encoding information bits and a scrambling subcode for encoding PAPR bits. The PAPR bits are reserved in the fourth component code to generate a number of candidates for PAPR control. We consider the PAPR performance for Reed-Muller codes in natural and cyclic ordering, respectively. Numerical results show that our proposed method has better PAPR statistics than the original PTS technique in the 16-QAM OFDM systems.
In this paper we study the problem of finding capacity-maximizing constellations in BICM for asymptotically low signal-to-noise ratios (SNRs). We base our analysis on the so-called Hadamard transform and on a linear a...
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In this paper we study the problem of finding capacity-maximizing constellations in BICM for asymptotically low signal-to-noise ratios (SNRs). We base our analysis on the so-called Hadamard transform and on a linear approximation of the BICM capacity for asymptotically low SNRs. We fully characterize the set of constellations, input distributions, and binary labelings that achieve Shannon's limit E b /N 0 = -1.59 dB. For equiprobable input distributions, a constellation achieves this limit if and only if it is a linear projection of a hypercube.
Frequency-time scheduling is an essential radio resource management (RRM) function in Orthogonal Frequency Division Multiple Access (OFDMA) wireless systems. In the literature, there are several OFDMA scheduling algor...
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Frequency-time scheduling is an essential radio resource management (RRM) function in Orthogonal Frequency Division Multiple Access (OFDMA) wireless systems. In the literature, there are several OFDMA scheduling algorithms such as the Hungarian and Max-Max algorithm. However, such algorithms do not consider the multiuser diversity into account. In this paper, we propose a scheduling algorithm that exploits the multiuser diversity in both time and frequency domains. Also, the proposed algorithm utilizes the Proportional Fairness (PF) criterion to achieve fairness among users in the system. In order to support multimedia bursty traffic, our algorithm allows more than one user to share a subband in each time frame. The proposed algorithm iteratively assigns the available subbands to be shared among different users concurrently. We compare the performance of the proposed algorithm with other OFDMA scheduling algorithms in the literature. Results show that the proposed algorithm outperforms other algorithms in terms of the throughput with comparable fairness performance.
Carrier frequency offset (CFO) may cause multiple access interference (MAI) among users in multi-carrier code division multiple access (MC-CDMA) system. In the paper the code sensitivity of spreading codes and its cor...
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ISBN:
(纸本)9781424447848
Carrier frequency offset (CFO) may cause multiple access interference (MAI) among users in multi-carrier code division multiple access (MC-CDMA) system. In the paper the code sensitivity of spreading codes and its correlative to the CFO is observed. An interesting property of orthogonality invariant for spreading codes under CFO has been presented. Based on the properties of code sensitivity, several algorithms of selecting the spread codes that will decrease the MAI caused by frequency offset are proposed. Using the presented code selection methods, the system capacity of MC-CDMA can be effectively increased without increasing the system complexity.
A cross-layer scheduling algorithm that streams pre-coded H.264 video over wireless networks to multiple users is presented. The algorithm can be used with the emerging wireless standards such as IEEE 802.16 and HSDPA...
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A cross-layer scheduling algorithm that streams pre-coded H.264 video over wireless networks to multiple users is presented. The algorithm can be used with the emerging wireless standards such as IEEE 802.16 and HSDPA. Our focus is maximizing the video perceptual quality after delivery with constraint of the limited wireless resources and the delay requirements from the practical point of view. At the application layer, the relative importance of each packet to the video perceptual quality is estimated by a packet relative importance index in a low complexity computation, which is evaluated directly in video compressed domain. At the physical layer, the channel state information is derived and an adaptive modulation coding design is introduced. Thus, the scheduling algorithm at the media access control layer for multiple mobile users is proposed depending on the information provided by the application and physical layer with the objective of maximizing the video quality. Simulations show that the proposed scheme performs significantly than the conventional scheduling schemes for video transmission.
This paper presents field experiments on open-loop precoding multiple input multiple output (MIMO) using a testbed targeting International Mobile Telecommunication - Advanced (IMT-Advanced) systems. Open-loop MIMO is ...
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This paper presents field experiments on open-loop precoding multiple input multiple output (MIMO) using a testbed targeting International Mobile Telecommunication - Advanced (IMT-Advanced) systems. Open-loop MIMO is realized by applying Rotational OFDM (R-OFDM) to MIMO transmission. MIMO R-OFDM is more robust with respect to correlated channels than conventional open-loop MIMO-OFDM as was shown by the authors in a previous study. MIMO R-OFDM is implemented in a testbed targeting IMT-Advanced systems and is evaluated in a mobile environment. The antenna spacings are changed, i.e. the correlation coefficients between two antennas are changed, then the validity of MIMO R-OFDM is evaluated. The results of the field experiment reveal that MIMO R-OFDM is effective when the transmitter antenna spacings are decreased. The maximum cumulative distribution function (CDF) gain of MIMO R-OFDM with respect to conventional MIMO-OFDM is 6 % when the antenna spacing of the transmitter is same as the wave length of the carrier. In addition, it was also found that the rotational angle should be determined based not only on modulation order and coding rate, but also on the correlation coefficients between transmitter and receiver antennas.
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