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With the development of flash technology, multilevel per cell (MLC) NAND flash memory has mastered the key market because of its storage capacity superiority. However, excessive density increment leads to decay of reliability of MLC NAND flash memory, thus an appropriate error correction code (ECC) is required to address this issue. This paper presents an efficient multi-strategy ECC scheme called pre-check scheme which consists of hard, quantized-soft, and pure-soft decoders geared to MLC NAND flash memory based on polar code proposed by E. Arikan to overcome the aforementioned drawbacks with better performance and lower complexity. The hard decoder is designed to correct the majority of erroneous codewords in the initial phase of the flash memory, while the soft decoders aim to correct codewords which contain larger amount of errors. In addition, we clarify that the mapping scheme using Gray code can achieve best performance compared to other alternatives.

Secure communications become more, more important with the exponential growth of Internet data services. However, to massively deploy such services in current networks, we need to deal with different architectures, time-consuming encryption/decryption algorithms. Recently, numerous research efforts have been focused on parallel computing using high-end discrete GPGPU to achieve peak throughput, while the study on more cost-efficient integrated GPGPU is still open, which is included in almost all of the Intel CPUs currently, e.g. Celeron, Pentium, Core, even Xeon-E3 families. In this paper, we propose a generic heterogeneous computing approach for the decryption of RSA algorithm. Based on OpenCL, we are able to implement our idea on the off-the-shelf mini PC with low-cost integrated GPGPU. According to the experimental results, we show that the proposed scheme can fully utilize the capacity of integrated GPGPU,, a 2 times throughput improvement over the CPUonly solution can be expected.

The widespread application of multimedia wireless services and requirements of ubiquitous access have triggered rapidly booming energy consumption at both the base station side and the user equipment (UE) side. Hence, energy-efficient design in wireless networks is very important and is becoming an inevitable trend. In this paper, we study the energy-efficient resource allocation in both downlink and uplink cellular networks with orthogonal frequency division multiple access (OFDMA). For the downlink transmission, the generalized energy efficiency (EE) is maximized while for the uplink case the minimum individual EE is maximized, both under certain prescribed per-UE quality-of-service (QoS) requirements. For both transmission scenarios, we first provide the optimal solution and then develop a suboptimal but low-complexity approach by exploring the inherent structure and property of the energy-efficient design. For the downlink case, by modifying the original problem, we also find a computationally efficient and numerically tractable upper bound on the EE, which indicates the performance limit and is demonstrated to be quite tight if the number of subcarriers is larger than that of UEs and motivates us to find a near-optimal approach relying on the quasiconcave relation between the modified EE and transmit power. Simulation results show that the energy-efficient design greatly improves EE compared with the conventional spectral-efficient design and the low-complexity suboptimal approaches can achieve a promising tradeoff between performance and complexity.

In this paper, power allocation between pilots and data symbols is investigated to maximize energy efficiency (EE) for downlink orthogonal frequency division multiple access (OFDMA) networks. We first derive an EE function considering channel estimation error, which depends on large-scale channel gains of multiple users, allocated power to pilots and data symbols, and circuit power consumption. Then an optimization problem is formulated to maximize the EE under overall transmit power constraint. Exploiting the quasiconcavity property of the EE function, we propose an alternating optimization method in the low transmit power region and reformulate a joint quasiconcave problem in the high transmit power region. Analysis and simulation results show that the power ratio for pilots decreases with the circuit power. When the circuit power is small, the optimal overall transmit power increases with the circuit power. Otherwise, the optimal transmit power does not depend on it. Transmitting more data symbols to the users with higher channel gains improves the EE but at a cost of sacrificing the fairness among multiple users. Simulation results also demonstrate that compared with spectral efficiency (SE)-oriented design, the EE-oriented design can improve the EE performance significantly with a relatively small SE loss.

In this tutorial paper, a comprehensive survey is given on several major systematic approaches in dealing with delay-aware control problems, namely the equivalent rate constraint approach, the Lyapunov stability drift approach and the approximate Markov Decision Process (MDP) approach using stochastic learning. These approaches essentially embrace most of the existing literature regarding delay-aware resource control in wireless systems. They have their relative pros and cons in terms of performance, complexity and implementation issues. For each of the approaches, the problem setup, the general solution and the design methodology are discussed. Applications of these approaches to delay-aware resource allocation are illustrated with examples in single-hop wireless networks. Furthermore, recent results regarding delay-aware multi-hop routing designs in general multi-hop networks are elaborated. Finally, the delay performance of the various approaches are compared through simulations using an example of the uplink OFDMA systems., Comment: 58 pages, 8 figures; IEEE Transactions on Information Theory, 2011

With explosive growth of high-data-rate applications, more and more energy is consumed in wireless networks to guarantee quality of service. Therefore, energy-efficient communications have been paid increasing attention under the background of limited energy resource and environmental- friendly transmission behaviors. In this article, basic concepts of energy-efficient communications are first introduced and then existing fundamental works and advanced techniques for energy efficiency are summarized, including information-theoretic analysis, OFDMA networks, MIMO techniques, relay transmission, and resource allocation for signaling. Some valuable topics in energy-efficient design are also identified for future research.

LANGUAGE NOTE | Document text in Chinese; abstract also in English.本文從儒家倫理的天道基礎和現實基礎兩個角度分析儒家關於克隆人問題的立場與態度。本文認為，論證儒學關於現代生命倫理議題的看法，不應只局限於應用傳統儒學的某種觀點得出某種結論，或樂衷於表面的否定或肯定這樣的判斷。而應該對體現在儒家身上那種對人類生存與命運的強烈憂患意識和人文關懷有一種自覺的體認，這樣才能對儒學關於諸如克隆人這樣的現代生命倫理議題的立場與態度獲得較為全面和深刻的認識。從這樣的觀點出發，本文認為從儒家倫理的天道基礎而言，儒家不會對克隆人的正當性輕率地表示肯定和否定，而是根據具體的情境和目的決定自己的態度，但一般而言，儒家將不會主張克隆人。從儒家倫理的現實基礎來看，儒家對克隆人的態度是鮮明的，那就是認為克隆人缺乏倫理上的正當性，從而反對克隆人。This essay attempts to offer a Confucian view of human cloning. It analyzes the nature of human cloning from the perspective of Confucian ethics. It argues that we should not make simple “Confucian” conclusions about human cloning based on certainisolated Confucian views, but should take a personal view on the fundamental spirit of Confucianism. Evidently, the foundation of Confucian ethics is its view of the Dao of Heaven (tiendao). From the perspective of this essay, the Dao of Heaven offers twoprinciples with which people should comply. The first principle is that the Dao of humans must follow the Dao of Heaven. That is, people’s activities should not violate the will of Heaven. The second principle is the principle of continuous creation or generation (shengsheng buyi). Such continuous creation or generation is seen as the great virtue (dade) of Heaven. Accordingly, the Dao of Heaven is primarily the method of creation, which characterizes Confucian ethics.This Confucian view of the Dao of Heaven and its two basic principles should be brought to bear on the issue of human cloning in the full sense. By mechanically understanding and applying the principle of generation, it is possible to develop a view of human cloning that grants it legitimacy as a method of reproduction. However, the authentic Confucian sense of generation cannot be understood without the normal relationship between a man and a woman, or specifically, the relationship between husband and wife, which Confucians see as the ultimate starting point of any meaningful human generation. Without the union of husband and wife, human reproduction becomes an unnatural, abnormal event that goes beyond the scope of the Dao of Heaven. That is why Confucianism emphasizes the crucial function of marriage in the normal way of human life. Accordingly, Confucians think that both a father and a mother are necessarily (morally) required to create a normal human child. Techniques such as reproductive human cloning destroy the normal means of human generation and undermine the foundation of Confucian ethics. Confucians cannot accept such techniques.DOWNLOAD HISTORY | This article has been downloaded 185 times in Digital Commons before migrating into this platform.

In this paper, we quantify the benefits of employing relay station in large-coverage cognitive radio systems which opportunistically access the licensed spectrum of some small-coverage primary systems scattered inside. Through analytical study, we show that even a simple decode-and-forward (SDF) relay, which can hold only one packet, offers significant pathloss gain in terms of the spatial transmission opportunities and link reliability. However, such scheme fails to capture the spatial-temporal burstiness of the primary activities, that is, when either the source-relay (SR) link or relay-destination (RD) link is blocked by the primary activities, the cognitive spectrum access has to stop. To overcome this obstacle, we further propose buffered decode-and-forward (BDF) protocol. By exploiting the infinitely long buffer at the relay, the blockage time on either SR or RD link is saved for cognitive spectrum access. The buffer gain is shown analytically to improve the stability region and average end-to-end delay performance of the cognitive relay system.

583 Background: The incidence of squamous cell carcinoma of the anal canal (SCCA) has been rising in the last three decades. With changing patient demographics and behaviors, the trends in prevalence and incidence of the disease have changed in recent years. Methods: The Surveillance, Epidemiology, and End Results (SEER) data set from 2000 to 2014 was analyzed for trends in prevalence and incidence of SCCA and for associated demographic and tumor characteristics including stage (localized vs. regional vs. distant disease), age (20-34, 35-49, 50-64, > 65 years), and race/ethnicity (White, Black, American Indian/American Natives (AI/AN), American Pacific Islanders (API)). Results: 16,540 patients with SCCA were identified in the SEER database within the study period. The prevalence rate of SCCA was 0.01% (of 2000 standard U.S population), and the age-adjusted incidence rate of SCCA was 1.3/100,000. Prevalence and incidence was highest in patients age 50-64 and in the black population. Trend analysis of incidence demonstrated that while incidence rate continued to increase from 2000 to 2014, the average annual percentage change (APC) of incidence decreased from 4.80 before 2009 to 1.44 after. Patient population was divided into two groups: 2000-2008, with incidence of 1.6/100,000 and 2009-2014, with incidence of 2.1/100,000 (RR = 1.29, 95%CI = 1.25-1.33, p < 0.001). Incidence in the 2009-2014 group increased compared to the 2000-2008 group among all staged SCCA, patients 50 years of age and older (RR = 1.41, p < 0.001 and RR = 1.37, p < 0.001 for age groups 50-64 and > 65, respectively), and black (RR = 1.33, p < 0.001) and white (RR = 1.32, p < 0.001) race/ethnicity groups. APC in the 2009-2014 group decreased in all staged SCCA, increased in patients age 20-34, and decreased in all racial groups except AI/AN. Conclusions: There is a higher incidence and prevalence of SCCA in patients 50 years or older and in those of black ethnicity. Incidence of SCCA has increased in the US from 2000-2014, but the average APC in incidence has been decreasing except for in young patients and in those of AI/AN ethnicity. Awareness of disease prevalence and the pattern of change in incidence rate is important in the effort of disease prevention.

Cognitive radio and dynamic spectrum access represent a new paradigm shift in more effective use of limited radio spectrum. One core component behind dynamic spectrum access is the sensing of primary user activity in the shared spectrum. Conventional distributed sensing and centralized decision framework involving multiple sensor nodes is proposed to enhance the sensing performance. However, it is difficult to apply the conventional schemes in reality since the overhead in sensing measurement and sensing reporting as well as in sensing report combining limit the number of sensor nodes that can participate in distributive sensing. In this paper, we shall propose a novel, low overhead and low complexity energy detection based cooperative sensing framework for the cognitive radio systems which addresses the above two issues. The energy detection based cooperative sensing scheme greatly reduces the quiet period overhead (for sensing measurement) as well as sensing reporting overhead of the secondary systems and the power scheduling algorithm dynamically allocate the transmission power of the cooperative sensor nodes based on the channel statistics of the links to the BS as well as the quality of the sensing measurement. In order to obtain design insights, we also derive the asymptotic sensing performance of the proposed cooperative sensing framework based on the mobility model. We show that the false alarm and mis-detection performance of the proposed cooperative sensing framework improve as we increase the number of cooperative sensor nodes., 11 pages, 8 figures, journal. To appear in IEEE Transactions on Wireless Communications

In this paper, we shall focus on the design and asymptotic performance analysis of joint source channel coding (JSCC) for MIMO channels with limited Channel State Information (CSI) feedback. We consider rate adaptation, spatial power adaptation as well as precoder adaptation. We find that the optimal distortion exponent (achieved with perfect CSIT) can be realized using only spatial power adaptation and precoder adaptation with sufficiently large feedback rate. We also compare the average distortion of the limited feedback JSCC system using fixed bandwidth expansion scheme and dynamic bandwidth expansion scheme. We show that dynamic bandwidth expansion is more effective to reduce the limited feedback JSCC performance especially at large average bandwidth expansion.

To significantly enhance the spectral efficiency of the MBS service, UEP and MIMO are important core technologies to realize such challenging goal. Taking into account of the implementation constraints, 4 times 2 is widely accepted as a reasonable MIMO setup and is a mandatory configuration of the next generation wireless systems. Within the 4 times 2 MIMO configuration, D-STTD is an important transmission scheme which strikes a balance between spatial diversity and spatial multiplexing and it can achieve better performance than VBLAST. Traditional approaches focus on different ways to introduce UEP in single antenna systems. However, it is difficult to apply the conventional schemes in the D-STTD systems since the decoding error is mainly contributed by the spatial interference between different streams. In this paper, we shall propose a novel UEP scheme for MBS services using D-STTD in 4times2 MIMO systems and formulate a general design framework to determine various parameters of the proposed UEP scheme. For illustration, we give two examples on the determination of the UEP parameters for the uncoded UEP design and the coded UEP design. From the results, we found that the proposed UEP scheme can achieve significant MBS system performance gain compared to those baseline systems.

This paper considers the resource allocation problem in the wireless OFDMA system with a relay node. We consider orthogonal relay in which the relay node cannot transmit and receive simultaneously on the same frequency. As a result, the use of relay node may enhance or degrade the achievable transmission rate depending on the instantaneous channel states between the source and the relay, the relay and the destination as well as the source and the destination. Hence, it is very important to dynamically adjust the resources (subbands) allocated to the relay node so that the relay is used only at the right time according to the instantaneous channel states. Conventional approaches dynamically schedule the usage of the relay node in a centralized manner in which full knowledge of the channel states between any two nodes in the network is required. However, perfect knowledge of the channel states at various nodes is very difficult to obtain. In this paper, we shall propose a resource allocation algorithm, which iteratively allocates resource to the source and relay, and converge to the close-to-optimal allocation. Asymptotic achievable rate of the proposed algorithm is derived. We show that the system achieves significant improvement of the achievable rate compared to the point-to-point baseline system without relay as well as the baseline system with random subband allocation.

The articles in this special section focus on the Internet of things and the technologies and applications that will support the smart grid, its networking environments, and intelligent systems to be supported.

The articles in this special section address smart energy applications from the perspective of the Internet of Things (IoT). For smart grid applications, we need to predict the electrical load so that the underlying smart grid can effectively balance the power supply and demand. In general, predictions are made based on the data obtained using IoT and smart meter technologies. The (IoT) could accelerate establishment of such infrastructures. With IoT technologies, many more devices could be controlled and managed through the Internet; data pertaining to the grid, commercial buildings, and residential premises can readily be collected and utilized. To derive valuable information from the data, further information and data processing become essential.

With the aim of delivering any information in anytime and anywhere, the next generation (5G) wireless communication networks become a fashion topic in the wireless research areas and new waveform, as one of the key enabling technologies in 5G physical layer, attracts growing research attentions in recent years. However, the existing way of waveform research or analysis is based on the improvement of spectrum efficiency or utilization, while most of them fails to investigate the energy efficiency behavior, which is shown to be the key performance metric of 5G systems. In this paper, we mainly focus on surveying the waveforms from the energy efficiency point of view. Two categories of waveforms, namely filter-based waveform and spreading-based waveform, are analyzed and the related implementation issues are discussed. Moreover, we implement the above waveforms using software-defined radio based prototype platform and generate the measurement results for the energy efficiency comparison.

To explore the related ischemic stroke (IS) risk factors in youth and the importance of sleep quality in young ischemic stroke.A total of 219 patients aged 18 to 45 years (166 males, 53 females) with an initial onset of ischemic stroke from First Affiliated Hospital, Zhengzhou University and Puyang People's Hospital during June 2011 to February 2013, were recruited as the study cases. Meanwhile 231 patients aged 46 to 80 years (170 males, 61 females) from the same hospitals were selected as the elderly control group. And 149 young persons aged 18 to 45 years undergoing normal physical examinations from the same hospitals were taken as youth control group. For all cases, their ischemic stroke related risk factors and especially the importance of sleep quality were analyzed. Prospective analyses were conducted to re-considerate the related ischemic stroke risk factors in youth.Hypertension history, high cholesterol, diabetes, smoking and drinking, bad sleep quality, family history of stroke and hyperhomocysteinemia were associated with the onset of young ischemic stroke. The decreasing exposure rates were history of hypertension, smoking, poor sleep quality, hyperlipidemia, alcoholism, hyperhomocysteinemia and a family history of stroke and diabetes. In ischemic stroke young patients, bad sleep quality accounted for 55.7% and ranked third among all risk factors.The risk factors of young ischemic stroke ranks are different with other studies. As one of the most important factors for youth ischemic stroke, poor sleep quality should not be neglected.

Virtual multiple-input–multiple-output (MIMO) systems using multiple antennas at the transmitter and a single antenna at each of the receivers have recently emerged as an alternative to point-to-point MIMO systems. This paper investigates the relationship between energy efficiency (EE) and spectral efficiency (SE) for a virtual-MIMO system that has one destination and one relay using compress-and-forward (CF) cooperation. To capture the cost of cooperation, the power allocation (between the transmitter and the relay) and the bandwidth allocation (between the data and cooperation channels) are studied. This paper derives a tight upper bound for the overall system EE as a function of SE, which exhibits good accuracy for a wide range of SE values. The EE upper bound is used to formulate an EE optimization problem. Given a target SE, the optimal power and bandwidth allocation can be derived such that the overall EE is maximized. Results indicate that the EE performance of virtual-MIMO is sensitive to many factors, including resource-allocation schemes and channel characteristics. When an out-of-band cooperation channel is considered, the performance of virtual-MIMO is close to that of the MIMO case in terms of EE. Considering a shared-band cooperation channel, virtual-MIMO with optimal power and bandwidth allocation is more energy efficient than the noncooperation case under most SE values.

Objective. To study risk factors related to ischemic stroke (IS) in youth and the influence of sleep quality on youth ischemic stroke incidence.Methods. 223 patients aged 18 to 45 years who were admitted to Puyang People’s Hospital from June 2011 to February 2013 with a first-ever ischemic stroke were selected as the research cases. 158 young people with a normal physical examination were selected as the control group. The Pittsburgh Sleep Quality Index (PSQI) questionnaire was used to analyse the correlation between sleep quality and youth IS incidence. The US National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (MRS) scores were used to assess cases’ state of illness and prognosis three months after IS.Results. Univariate and multivariate logistic regression analysis showed that the association of these risk factors with youth IS incidence, from highest to lowest, was hypertension, hyperlipidaemia, smoking history, high homocysteine, the quality of sleep, family history of stroke, and alcoholism. Poor sleep quality ranked fifth among all risk factors and was positively correlated with poor prognosis for youth IS patients.Conclusion. The results of this study showed that sleep quality is an important factor in the pathogenesis and prognosis of youth IS.

In this paper, we consider energy efficient coverage planning in cellular networks. To save energy, each base station (BS) can work in sleep mode when there is no user in its coverage or the users can be served by neighbor base stations. With increasing coverage overlap, there is a tradeoff between the number of BSs per unit area and the proportion of active base stations. Analytical and numerical methods are presented to evaluate coverage planning schemes with different inter-BS distance. Evaluation results show that compared with the minimum coverage overlap scheme, the optimal planning scheme can reduce the network energy consumption by more than 20%, and the performance improvement depends on the user density, network topology, and the power consumption of sleep mode.

Bandwidth-power tradeoff, as one of the key relations in the green radio research framework, has attracted numerous research attentions in the recent years, due to the refreshed spectrum policies and the popularity of enabling techniques for bandwidth adjustment (such as software defined radio). Previous literatures show some preliminary results on the bandwidth-power tradeoff for heterogeneous networks, however, the practical issues such as site sleeping and inter-cell interference are still out of the research scope. In this paper, we formulate the network energy minimization problem and investigate the optimal bandwidth allocation strategy under the above two issues. Optimal bandwidth-power tradeoff is then derived to show the effects of key system parameters, including cell sizes and interference power levels, followed by some numerical examples to co-verify the analytical results.

To meet the global challenge of reducing greenhouse gas emissions and the exponentially growing data traffic, green design of cellular network is becoming a urgent issue for wireless network operators. In this paper, we first discuss the performance evaluation methodology for future wireless networks from the viewpoint of five basic metrics, i.e., throughput, power consumption, deployment cost, bandwidth, and latency. We then study the fundamental tradeoffs from Shannon's perspective based on the five metrics. Furthermore, we extend the tradeoff relation from point-to-point link to a heterogeneous network scenario taking into account realistic base station power model. Our study provides useful insights for the evaluation, modeling and deployment of future green wireless networks.

One of the main tasks for future wireless systems is to reduce the environmental impacts of the wireless transmission under different network architectures, which motivates the research on the green radio. Traditional research focuses on study of the tradeoff relation in the homogeneous network architecture and the extension to the heterogeneous network is still open in the literature. In this paper, we shall investigate this open issue and derive the closed-form expression for the optimal bandwidth allocation scheme as well as the bandwidth-power tradeoff relation. The analytical result is then extended to the practical settings with the network layout of 19 hexagonal macro-cells. Both the analytical and numerical results show that the proposed bandwidth allocation scheme achieves the best bandwidth-power tradeoff in the heterogeneous network architecture, which is of great importance for the heterogeneous network deployment and the frequency planning. Moreover, we also show that the radius of the network and the power budget play an important role in the bandwidth-power tradeoff relation, which should be carefully considered in the heterogeneous network planning and optimization.

Optimizing energy efficiency (EE) for the MIMO broadcasting channels (BC) is considered in this paper, where a practical power model is taken into account. Although the EE of the MIMO BC is non-concave, we reformulate it as a quasiconcave function based on the uplink-downlink duality. After that, an energy efficient iterative waterfilling scheme is proposed based on the block-coordinate ascent algorithm to obtain the optimal transmission policy efficiently, and the solution is proved to be convergent. Through simulations, we validate the efficiency of the proposed scheme and discuss the system parameters' effect on the EE., Comment: 6 pages, 4 figures, accepted in IEEE proc. of WCNC 2012

In this paper, power allocation between pilots and data symbols is investigated aiming at maximizing energy efficiency(EE) for downlink orthogonal frequency division multiple access (OFDMA) networks. We first derive an EE function when the channel estimation error is considered, which depends on the large-scale channel gains of multiple users, the allocated power to pilots and data symbols, and the circuit power consumption. Then an optimization problem is formulated to maximize the EE under overall transmit power constraint. The relationship between the power for pilots and data symbols is analyzed based on Karush-Kuhn-Tucker (KKT) conditions and the impacts of channel gains on both power allocation and the EE are studied. Exploiting the quasiconcavity property of the EE function, a bisection searching algorithm is developed to find the optimal power allocation. Simulation results demonstrate the performance gain of the proposed optimal power allocation scheme in terms of the EE and the required overall transmit power.

In this paper, both configuration of active radio frequency (RF) chains and resource allocation are investigated for improving energy efficiency of downlink multiple-input-multiple-output (MIMO) orthogonal frequency division multiple access (OFDMA) systems. We first formulate an optimization problem to minimize the total power consumed at the base station with the maximum transmit power constraint and ergodic capacity constraints from multiple users. Then a two-step suboptimal algorithm is proposed. Specifically, the continuous variable optimization problem is first solved, and then a discretization algorithm is presented to obtain the number of active RF chains and the number of subcarriers allocated to each user. Simulation results demonstrate that the proposed algorithm can provide significant power-saving gain over the all-on RF chain scheme and the adaptive subcarrier allocation helps to save more power.

Conventional design of wireless networks mainly focuses on system capacity and spectral efficiency (SE). As green radio (GR) becomes an inevitable trend, energy-efficient design is becoming more and more important. In this paper, the fundamental tradeoff between energy efficiency (EE) and SE in downlink orthogonal frequency division multiple access (OFDMA) networks is addressed. We first set up a general EE-SE tradeoff framework, where the overall EE, SE and per-user quality-of-service (QoS) are all considered, and prove that under this framework, EE is strictly quasiconcave in SE. We then discuss some basic properties, such as the impact of channel power gain and circuit power on the EE-SE relation. We also find a tight upper bound and a tight lower bound on the EE-SE curve for general scenarios, which reflect the actual EE-SE relation. We then focus on a special case that priority and fairness are considered and suggest an alternative upper bound, which is proved to be achievable for flat fading channels. We also develop a low-complexity but near-optimal resource allocation algorithm for practical application of the EE-SE tradeoff. Numerical results confirm the theoretical findings and demonstrate the effectiveness of the proposed resource allocation scheme for achieving a flexible and desirable tradeoff between EE and SE.

In this paper, we consider the problem of multi-relay selection for multi-stream cooperative MIMO systems with $M$ relay nodes. Traditionally, relay selection approaches are primarily focused on selecting one relay node to improve the transmission reliability given a single-antenna destination node. As such, in the cooperative phase whereby both the source and the selected relay nodes transmit to the destination node, it is only feasible to exploit cooperative spatial diversity (for example by means of distributed space time coding). For wireless systems with a multi-antenna destination node, in the cooperative phase it is possible to opportunistically transmit multiple data streams to the destination node by utilizing multiple relay nodes. Therefore, we propose a low overhead multi-relay selection protocol to support multi-stream cooperative communications. In addition, we derive the asymptotic performance results at high SNR for the proposed scheme and discuss the diversity-multiplexing tradeoff as well as the throughput-reliability tradeoff. From these results, we show that the proposed multi-stream cooperative communication scheme achieves lower outage probability compared to existing baseline schemes.

The pressure of the energy bill from operators and the request of the environmental protection from the governments and public results in more urgent requirement on the energy consumption and CO 2 emission. Traditionally, the bandwidth and the transmit power are jointly considered to maximize the throughput of the wireless networks, while the energy efficiency of the wireless transmission is ignored. In this paper, we shall introduce a circuit-level power modeling to analyze the above effects and propose the joint bandwidth-power scheduling algorithms for energy efficiency in the wireless communication systems. We show that bandwidth and power shall be considered jointly for different channel statistic to maximize the energy efficiency. In addition, we characterize the bandwidth-power-energy efficiency relationship to obtain the design insights for future energy efficient communication networks.

The pressure of the energy bill from operators and the request of the environmental protection from the governments and publics results in more urgent requirement on the energy consumption and CO$_2$ emission. Traditionally, adaptive modulation has been proven to be an efficient solution to improve the system performance over the radio fading channels. To obtain the design insights for energy efficient adaptive modulation scheme, we shall introduce a circuit-level power modeling to analyze the effects and characterize the bandwidth-power-energy efficiency tradeoff relations for wireless communication systems. We show that different bandwidth, power and modulation schemes shall be used under different channel conditions to maximize the energy efficiency and the adaptive modulation scheme can greatly help to improve the tradeoff curves.

Global warming and climate changing is among the major challenges in the 21st century. In wireless communications, green architecture design is an urgent demand for operators, not only because of the social responsibilities but also their willingness to reduce the network construction and operating cost. Previous literatures tried to tackle deployment cost and energy efficiency in a separated manner. However, these two aspects are interacting with each other and the design of green architecture needs a holistic consideration of both. In this paper, we try to shed some light on the green architecture design by analytically characterizing the open relations between energy efficiency and deployment efficiency, which is found somehow different from our intuition and there might not be a simple tradeoff between the two. This study has positive impact on the future network planning and optimization.

This paper considers the multi-user MIMO collaborative spatial multiplexing uplink scheduling scheme in multi-cell time-division duplexing system. An transmitter centric (TC) beamforming and scheduling scheme has been proposed to reduce the inter-cell interference opportunistically. Most previous works in the area of mimo beamforming and scheduling are aiming at improve the signal to interference plus noise power ratio at receiver directly. These receiver centric (RC) schemes requires interference covariance at receiver. However, in multi-user system, the uplink interference at base station (BS) is fluctuant and can't be acquired for scheduling due to the dynamics of the scheduled user set in other cells. It makes the uplink scheduling problem challenging. Our proposed TC scheme considers the pollution which is defined as the sum power of user signal arriving at other BSs. User selects the transmit beamforming vector with highest signal to pollution plus noise ratio (SPR) and informs its home BS. To enhance the signal and suppress the pollution, a scheduling criterion is derived based on SPR metric with awareness of intra-cell interference. The proposed scheduling scheme is compared with conventional RC and single-user TC spatial multiplexing in the scenarios with various antenna configurations, BS and user numbers. The simulation result shows that our proposed TC scheme can better reduce the pollution and significantly improve the system capacity.

Network MIMO is considered to be a key solution for the next generation wireless systems in breaking the interference bottleneck in cellular systems. In the network MIMO systems, open-loop transmission scheme is used to support mobiles with high mobilities because the BSs do not need to track the fast varying channel fading. In this paper, we consider an open-loop network MIMO system with L BSs serving L+1 mobiles based on partial cooperation where all the L BSs cooperatively serve a cell-edge MS. Exploiting the heterogeneous path loss between cellcenter MS and cell-edge MS, each of the L BS also serves a cellcenter MS non-cooperatively. We first propose a flexible open-loop SDMA scheme to address potential issues associated with dynamic and heterogeneous MIMO configurations and to adjust the long-term power allocation between the cell-edge MS (cooperatively served by L BSs) and the cell-center MS at each of the L BSs, we formulate the long-term distributive power control problem using game theoretic approach. Through numerical simulations, we show that the proposed open-loop SDMA scheme with distributed long-term power allocation can achieve significant performance advantages over the other reference baseline schemes.

Cooperative communication is an important technology in next generation wireless networks. Partial decode-and-forward provides an alternative solution for the conventional amplify-and-forward as well as decode-and-forward relay protocols. However, there are several important issues to be addressed regarding the application of partial decode-and-forward protocol. In this paper, we address the practical issues by proposing a joint MIMO precoder design for the multi-antenna cooperative system with correlated MIMO fading and partial decode-and-forward relay protocol. In addition, the MIMO precoders at both the source and the relay are matched to the MMSE-SIC receivers at the destination. We find that under similar system settings, joint MIMO precoder design with partial decode-and-forward relay protocol and MMSE-SIC receivers achieves substantial performance enhancement and has important practical significance.

The achievable transmission rate of the multicast services is in general limited by the worst case mobile users within the multicast service sectors. Yet, unlike relay-assisted unicast service, there is a unique challenge in applying relay to multicast service. To be more specific, the multicast service shall be able to provide a uniform treatment for the mobile users within and without the relay coverage, which is known as the heterogeneous coverage issue. In this paper, a novel cooperative source diversity scheme is proposed to address the above issue. Compared with direct transmission and conventional cooperative source diversity scheme, the proposed approach achieves better link-layer performance in terms of packet error rate (PER) and system-level performance in terms of average spectrum efficiency and hence has practical design importance.

Cognitive and cooperative technologies are two core components in the design of next generation wireless networks. One key issue associated with cognitive transmission is the inefficient spectrum sharing of the secondary system, especially for secondary communications separated by long distance. To boost the spectrum sharing efficiency, cognitive multi-relay system appears to be an attractive solution for the cognitive transmission systems. In this paper, we consider a cognitive multi-relay (CMR) system and propose a novel CMR buffered decode-and-forward protocol that exploit the buffers in the source and each relay node. Moreover, we derive the closed-form average end-to-end delay and the stability region by exploiting the birth-death nature of the queue dynamics and the methods of state aggregation and queue dominance. Comparing with the baseline protocols through analytical and numerical results, the proposed CMR-BDF scheme can dynamically adjust the cognitive transmission to exploit the spatial PU burstiness while simultaneously benefits from the advantage of double-sided selection diversity in both the source-relay and relay-destination interfaces.

This paper considers the resource allocation problem in the wireless OFDMA systems with a relay node. We consider half-duplex relay in which the relay node cannot transmit and receive simultaneously on the same frequency. As a result, the use of relay node may enhance or degrade the system throughput depending on the instantaneous channel states between the source and relay, the relay and the destination as well as the source and destination. Hence, it is very important to dynamically adjust the resource (subcarrier) allocated to the relay node so that the relay is used only at the right time according to the instantaneous channel states. Conventional approaches dynamically schedule the usage of the relay node in a centralized manner in which full knowledge of the channel states between any two nodes in the network is required. However, perfect knowledge of the channel states at various nodes are very difficult to obtain. In this paper, we shall propose a distributed resource allocation algorithm on the OFDMA system with half-duplex relay by employing rateless code. Based on the ACK/NAK exchanges between the source, destination and relay, the proposed algorithm iteratively allocates resource to the source and relay, and converge to the close-to-optimal allocation within finite steps. The resource allocation algorithm has low complexity and provable convergence property. Asymptotic throughput performance of the proposed algorithm is derived. We show that the system achieves significant throughput gain compared to the point-to-point baseline system without relay as well as the baseline system with random subcarrier allocation.

Channel estimation is crucial for modern WiFi system and becomes more and more challenging with the growth of user throughput in multiple input multiple output configuration. Plenty of literature spends great efforts in improving the estimation accuracy, while the interpolation schemes are overlooked. To deal with this challenge, we exploit the super-resolution image recovery scheme to model the non-linear interpolation mechanisms without pre-assumed channel characteristics in this paper. To make it more practical, we offline generate numerical channel coefficients according to the statistical channel models to train the neural networks, and directly apply them in some practical WiFi prototype systems. As shown in this paper, the proposed super-resolution based channel estimation scheme can outperform the conventional approaches in both LOS and NLOS scenarios, which we believe can significantly change the current channel estimation method in the near future., Comment: 7 pages, 7 figures, conference