This paper presents a cross-layer design of adaptive modulation and coding (AMC) with truncated hybrid automatic repeat request (HARQ) for one-to-many multicast transmission, in order to increase the spectral efficien...
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This paper presents a cross-layer design of adaptive modulation and coding (AMC) with truncated hybrid automatic repeat request (HARQ) for one-to-many multicast transmission, in order to increase the spectral efficiency under the quality-of-service (QoS) constraints. For adaptive transmission over the channel common to the multicast group users, the AMC mode is chosen with the minimum SNR among the users to guarantee the target performance of all users. In the meanwhile, the minimum SNR required to support an AMC mode is aggressively designed by allowing retransmission with HARQ schemes. For the proposed design, we derive the average packet error rate, average number of transmission, and spectral efficiency and provide the performance numerically obtained. Numerical results show that the cross-layer design for multicast provides a significant performance gain at a small number of retransmissions as in unicast. In particular, it is observed that AMC design with HARQ is more beneficial in the low SNR region where multicast performs worse than unicast.
Increasingly wireless networks use multi-antenna nodes as in IEEE 802.11n and 802.16. The physical layer (PHY) in such systems may use the antennas to provide multiple streams of data (spatial multiplexing) or to incr...
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Increasingly wireless networks use multi-antenna nodes as in IEEE 802.11n and 802.16. The physical layer (PHY) in such systems may use the antennas to provide multiple streams of data (spatial multiplexing) or to increase the robustness of fewer streams. These physical layers also provide support for sending packets at different rates by changing the modulation and coding of transmissions. Rate adaptation is the problem of choosing the best transmission mode for the current channel and in these systems requires choosing both the level of spatial multiplexing and the modulation and coding. Hydra is an experimental wireless network node prototype in which both the MAC and PHY are highly programmable. Hydra's PHY is essentially the 802.11n PHY, and currently supports two antennas and the same modulations and codings as 802.11n. Because of limitations of our hardware platform, the actual rates are a factor of 10 smaller than 802.11n. The MAC is essentially the 802.11 MAC with extensions, including the ability to feedback channel state or rate information from the receiver. Hydra was designed to allow experimentation with real radios, PHYs, and network stacks over real-world channels and it is well suited to studying rate adaptation in multi-antenna systems. To allow controlled experimentation, we also have the ability to perform experiments over emulated channels using exactly the same MAC and PHY used for RF transmissions. We present rate control experiments based on transmission over both real and emulated channels. Our experiments include measurements for single antenna systems and two antenna systems using a single or multiple spatial streams. We study rate adaptation algorithms using both explicit and implicit feedback from the receiver. A novel aspect of our results is the first experimental study of adaptation between single and multiple spatial streams for 802.11n style systems.
A simple synchronization algorithm is proposed in IEEE 802.11b WLAN system. According to the auto correlative character of the frame header, the algorithm can get coarse synchronization through power summing and peak ...
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ISBN:
(纸本)9781424446995
A simple synchronization algorithm is proposed in IEEE 802.11b WLAN system. According to the auto correlative character of the frame header, the algorithm can get coarse synchronization through power summing and peak position comparing; then get accurate synchronization by finding the SFD field from the demodulated data of the frame header. Simulation results show that the algorithm can get accurate synchronization even if the channel is very bad. It is a simple and useful algorithm and can be easily realized through hardware.
It has been shown that, under belief-propagation (BP) decoding, random-coset GF(q) low-density parity-check (LDPC) codes and irregular repeat-accumulate (IRA) codes with q-ary nonuniform signal constellations approach...
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It has been shown that, under belief-propagation (BP) decoding, random-coset GF(q) low-density parity-check (LDPC) codes and irregular repeat-accumulate (IRA) codes with q-ary nonuniform signal constellations approach the unrestricted Shannon limit. Extrinsic information transfer (EXIT) charts are employed in the design of random-coset GF(q) LDPC and IRA modulation codes. However, in the EXIT charts of random-cost GF(q) LDPC and IRA modulation codes, there is no closed-form expression for check node decoder (CND) curves. The CND curves for random-coset GF(q) LDPC and IRA modulation codes rely on Monte Carlo simulations, resulting in high design complexity. This study presents new design methods for random-coset GF(q) LDPC and IRA modulation codes based on average zero-word probability. Average zero-word probability serves as a surrogate for LLR messages, just as mutual information acts as a surrogate for LLR messages in EXIT charts. Based on average zero-word probability, closed-form expressions of CND input-output relations are derived for random-coset GF(q) LDPC and IRA modulation codes. Simple convergent criteria for both random-coset LDPC and IRA modulation codes are proposed. Based on the proposed convergent criteria, six codes are designed with nonuniform signal constellations. Simulation results show that the proposed codes have near-capacity performance and are better than any codes employed by equiprobable uniformly-spaced signal constellations.
The Federal Aviation Administration (FAA) is considering the use of the 5091-5150 megahertz (MHz) band for the future potential implementation of wireless broadband networks for the airport surface, denoted as airport...
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The Federal Aviation Administration (FAA) is considering the use of the 5091-5150 megahertz (MHz) band for the future potential implementation of wireless broadband networks for the airport surface, denoted as airport network and location equipment (ANLE). These wireless broadband networks could be used to address the increasing demand for data transmissions in the airport environment. The Orthogonal Frequency Division Multiple Access (OFDMA) implementation of the IEEE 802.16e-2005 standard is used in this paper to evaluate the spectral requirements of an ANLE network at a large airport. A methodology is developed to estimate approximate upper bounds on spectral requirements needed to support a set of potential applications that may participate in such networks. This methodology takes into account the physical layer characteristics of the OFDMA implementation of the IEEE 802.16e standard by evaluating physical layer data rates for the various modulation and coding schemes described in the standard. The upper bounds on spectral requirements described in this paper will provide a basis for estimating the total amount of radio spectrum that may be needed by an operational ANLE system.
We have developed a coded modulation system with continuous phase and a small controlled envelope variation called Constrained Envelope Continuous Phase modulation (ceCPM). For the spectrally efficient scenarios, with...
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We have developed a coded modulation system with continuous phase and a small controlled envelope variation called Constrained Envelope Continuous Phase modulation (ceCPM). For the spectrally efficient scenarios, within the ceCPM framework it is possible to find schemes with an SNR gain up to 2.5 dB over Continuous phase modulation (CPM) at symbol error probability 10 -3 , under the same requirement on spectral confinement and spectral efficiency as for the best CPM scheme. In this paper we discuss the design process for how to obtain such ceCPM schemes, and we elaborate on the properties of these ceCPM schemes.
Spectral efficiency, fairness and user satisfaction are crucial aspects for resource allocation in multi-user Orthogonal Frequency Division Multiplexing (OFDM)-based cellular networks. Classical Radio Resource Allocat...
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Spectral efficiency, fairness and user satisfaction are crucial aspects for resource allocation in multi-user Orthogonal Frequency Division Multiplexing (OFDM)-based cellular networks. Classical Radio Resource Allocation (RRA) strategies, such as Max-Rate (MR), Proportional Fairness (PF) and Max- Min Fairness (MMF), show different performances regarding the three aforementioned aspects. In this work, we present an adaptive RRA framework that joins the criteria of the three classical strategies in a unified manner and can be dynamically configured according to the cellular operator's objectives. We exemplify the flexible use of this general framework by proposing two adaptive RRA algorithms that provide strict fairness among users and maximizes the users' satisfaction, respectively. Simulation results show that the two proposed algorithms can efficiently achieve their respective objectives by means of the adaptation of the general RRA framework. I.
The transmission of multimedia signals, such as image over noisy wireless channels may cause inevitable errors that might severely degrade the visual message. Error concealment (EC) techniques by exploiting inherent r...
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ISBN:
(纸本)9781424448586;9781424448593
The transmission of multimedia signals, such as image over noisy wireless channels may cause inevitable errors that might severely degrade the visual message. Error concealment (EC) techniques by exploiting inherent redundancy reduce visual artifacts through post processing at the decoder. In this paper, we present a data hiding scheme for image error concealment in JPEG 2000 coding pipeline using integer wavelet, quantization index modulation (QIM) and region-of-interest (ROI) coding functionality. To restore the human interested portion of image, the information (image digest) of ROI is embedded into the region-of-background (ROB) using data hiding. Threshold based image segmentation together with morphological operations are used for finding ROI, while halftoning technique is used to obtain image digest from ROI. The simulation results show that the scheme results in efficient performance measure with various lost blocks in ROI.
Both cooperative diversity and adaptive modulation provide significant enabling techniques for future generations of wireless communication networks. In this paper, we consider an IRCC (incremental redundancy cooperat...
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Both cooperative diversity and adaptive modulation provide significant enabling techniques for future generations of wireless communication networks. In this paper, we consider an IRCC (incremental redundancy cooperative coding) based cooperative network, which uses adaptive node transmission. Two cases are considered: (i) adaptive transmission only at relay nodes; (ii) adaptive transmission at source and relay nodes. The performance of these two cases are evaluated in terms of the average bit error rate (ABER) and the average spectral efficiency (ASE) and compared with those of noncooperative scheme without adaptive transmission over Rayleigh fading channels. Simulation results show that the IRCC scheme without adaptive modulation (AM) provides 28% more spectral efficiency compared with that of noncooperative case without AM. However, using AM and selecting the best relay in the IRCC scheme, this improvement increases to 100% at SNR of 1 dB.
The purpose of this paper is to introduce a model intended to capture the behavior of the wireless channel at time scales which are related to packet transmission times. In this approach it is assumed that the prime f...
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The purpose of this paper is to introduce a model intended to capture the behavior of the wireless channel at time scales which are related to packet transmission times. In this approach it is assumed that the prime factor affecting data rate selection is the path attenuation. We model the wireless channel using a multistate stochastic process where each state corresponds to the nominal data rate achieved by the station when it uses a particular combination of modulation and coding (i.e., adaptive modulation). Differently from other proposals, in the proposed model state changes are created from mobility assumptions. We illustrate the use of this model with a case study.
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