A new approach for improving the throughputs of multi- channel packet radio systems is proposed. Based on the charac- teristics of multi-code CDMA technology, the scheme factitiously improves the transmission bit rate...A new approach for improving the throughputs of multi- channel packet radio systems is proposed. Based on the charac- teristics of multi-code CDMA technology, the scheme factitiously improves the transmission bit rate of a terminal by compressing the packet transmission time and thereby increases the number of the orthogonal spreading codes used by the terminal. By this means, the average interference level of the system is reduced and the system capacity is improved. Simulation results show that the proposed scheme exhibits larger throughput compared with the traditional multi-code CDMA slotted Aloha systems.展开更多
This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic ac...This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.展开更多
High-throughput measurements of ciprofloxacin, clomipramine and fexofenadine hydrochlorides were performed by employing an automatic 8-channel electrical titrator. Silver nitrate （AgNO3） and sodium tetraphenylborate...High-throughput measurements of ciprofloxacin, clomipramine and fexofenadine hydrochlorides were performed by employing an automatic 8-channel electrical titrator. Silver nitrate （AgNO3） and sodium tetraphenylborate （NaTPB） were used as titrants. When AgNO3 was used for measuring the drugs in pure form, recoveries were 97.6%-102.0% with RSD values ≤1.0%; for measuring them in pharmaceutical formulations, recoveries were 96.6%-99.1% with RSD values ≤1.0%. Batch samples of eight could be measured simultaneously and maximally 30 measurements per minute could be completed. When NaTPB was used for measuring the drugs in pure form, the recoveries were 96.8%-102.6% with RSD values 〈0.8%; for measuring them in pharmaceutical formulations, the recoveries were 97.5%-102.7% with RSD values ≤0.9%. For all analyses, no auxiliary devices or chemicals were needed and there was no requirement for changing or cleaning working electrodes between measurements. The efficiency, accuracy and precision of the proposed method make it an alternative for routine quality control analyses.展开更多
Wide band or broadband access was paid much attention with the development of radio transmission technique. The wireless access control procedure play an important role in this type of system and efficiency of control...Wide band or broadband access was paid much attention with the development of radio transmission technique. The wireless access control procedure play an important role in this type of system and efficiency of control algorithm has a great impact on throughput of channel resource. Based on wide band network control model and the characteristics of radio channel, this paper proposed a channel traffic estimation method and then performed a dynamic parameter control procedure and give detail analysis on estimation error and its impact on channel throughput and delay performance. Computation and simulation of system performance show a positive solntion on system design.展开更多
In this paper pilot based channel estimation is being considered for broadband power line communication (BPLC) networks witch used orthogonal frequency division multiplexing (OFDM) in order to transmit high rate data....In this paper pilot based channel estimation is being considered for broadband power line communication (BPLC) networks witch used orthogonal frequency division multiplexing (OFDM) in order to transmit high rate data. To estimate channel in time or frequency some pilot must be used. Number of these pilots and deployment of them is very important for proper estimation in different channel with varying time and frequency. Carrier sense multiple access (CSMA) and hybrid multiple access protocol are taken into consideration in MAC sub-layer. Multilayered perceptions neural network with backpropagation (BP) learning channel estimator algorithm with different pilot deployment compare to classic algorithm in for channel estimating. Simulation results show the proposed neural network estimation decreases bit error rate and therefore network throughput increases.展开更多
Broadband power line communication (BPLC) gained a lot of interest because of low cost and high performance communication network in access area. In this paper physical (PHY) layer and medium access control (MAC) sub-...Broadband power line communication (BPLC) gained a lot of interest because of low cost and high performance communication network in access area. In this paper physical (PHY) layer and medium access control (MAC) sub-layer of BPLC are considered. Furthermore, effects of bit error rate (BER) are analyzed in MAC sub-layer. Powerful turbo convolutional code (TCC) and wideband orthogonal frequency division multiplexing (OFDM) are used in PHY layer. Carrier sense multiple access (CSMA) and virtual slot multiple access (VSMA) are taken into consideration in MAC sub-layer. Multilayered perceptrons neural network with backpropagation (BP) learning channel estimator algorithm compare to classic algorithm in for channel estimating. The simulation results show that the proposed neural network estimation decreases bit error rate then in MAC sub-layer throughput increases and access delay is decreased.展开更多
In this paper, we propose a flexible and fairness-oriented packet scheduling approach for 3GPP UTRAN long term evolution (LTE) type packet radio systems, building on the ordinary proportional fair (PF) scheduling prin...In this paper, we propose a flexible and fairness-oriented packet scheduling approach for 3GPP UTRAN long term evolution (LTE) type packet radio systems, building on the ordinary proportional fair (PF) scheduling principle and channel quality indicator (CQI) feedback. Special emphasis is also put on practical feedback reporting mechanisms, including the effects of mobile measurement and estimation errors, reporting delays, and CQI quantization and compression. The performance of the overall scheduling and feedback re-porting process is investigated in details, in terms of cell throughput, coverage and resource allocation fairness, by using extensive quasistatic cellular system simulations in practical OFDMA system environment with frequency reuse of 1. The performance simulations show that by using the proposed modified PF ap-proach, significant coverage improvements in the order of 50% can be obtained at the expense of only 10-15% throughput loss, for all reduced feedback reporting schemes. This reflects highly improved fairness in the radio resource management (RRM) compared to other existing schedulers, without essentially com-promising the cell capacity. Furthermore, we demonstrate the improved functionality increase in radio re-source management for UE’s utilizing multi-antenna diversity receivers.展开更多
In WLANs, stations sharing a common wireless channel are governed by IEEE 802.11 protocol. Many conscious studies have been conducted to utilize this precious medium efficiently. However, most of these studies have be...In WLANs, stations sharing a common wireless channel are governed by IEEE 802.11 protocol. Many conscious studies have been conducted to utilize this precious medium efficiently. However, most of these studies have been done either under assumption of idealistic channel condition or with unlimited retransmitting number. This paper is devoted to investigate influence of limited retransmissions and error level in the utilizing channel on the network throughput, probability of packet dropping and time to drop a packet. The results show that for networks using basic access mechanism the throughput is suppressed with increasing amount of errors in the transmitting channel over all the range of the retry limit. It is also quite sensitive to the size of the network. On the other side, the networks using four-way handshaking mechanism has a good immunity against the error over the available range of retry limits. Also the throughput is unchangeable with size of the network over the range of retransmission limits. However, the throughput does not change with retry limits when it exceeds the maximum number of the backoff stage in both DCF’s mechanisms. In both mechanisms the probability of dropping a packet is a decreasing function with number of retransmissions and the time to drop a packet in the queue of a station is a strong function to the number of retry limit, size of the network, the utilizing medium access mechanism and amount of errors in the channel.展开更多
How to reduce interference among neighbor nodes in wireless mesh networks is still an important and key issue nowa- days. In this paper, an optimized channel assignment algorithm （OCA） is proposed to solve this prob...How to reduce interference among neighbor nodes in wireless mesh networks is still an important and key issue nowa- days. In this paper, an optimized channel assignment algorithm （OCA） is proposed to solve this problem based on link throughput and node priority. The effects of the numbers of network interface cards and channels on the network throughput are analyzed and evaluated, When there are seven of the numbers of both network interface cards and channels, the efficiency of utilizing network interface card and channel reaches highest. Compared with cen- tralized channel assignment algorithm （CCA）, the proposed algo- rithm has less packet loss rate and more network throughput sig- nificantly.展开更多
How to improve the performance of the wireless Ad Hoc network by utilizing the spectrum resources efficiently has become a hot research topic in recent years. In this paper we propose a reactive routing algorithm that...How to improve the performance of the wireless Ad Hoc network by utilizing the spectrum resources efficiently has become a hot research topic in recent years. In this paper we propose a reactive routing algorithm that supports multiple channels to improve the performance of the Ad Hoc network based on the minimizing of the channel handoff. Our approach allocates the communication channel during the route discovery, and notifies the allocated channel information to the corresponding node in the route reply packets. Each node in the route tries its best to choose the same channel with the upstream node without interference. The simulation results show that our algorithm performs better than the K-hop distinct protocols in both average delays and network throughputs展开更多
Given that satellite mobile channel is a time-varying channel,Adaptive Modulation and Coding(AMC) was proposed to provide robust and spectrally efficient transmission over satellite mobile channel.Three different kind...Given that satellite mobile channel is a time-varying channel,Adaptive Modulation and Coding(AMC) was proposed to provide robust and spectrally efficient transmission over satellite mobile channel.Three different kinds of channel environment were considered in this paper:the urban area,the rural area,and the open space.Four combinations of modulation and coding were designed to meet reliable communication on time-varying channel,and spectral efficiency and system throughput of these three kinds of channel environment were simulated.Based on the simulation results,this paper analysed the results and compared the performances of AMC with non-AMC system in these three kinds of channel environment.At last,we come to the conclusions:a system with AMC can achieve higher spectral efficiency and better system throughput;and the spectral efficiency and system throughput of AMC system will be higher on better satellite mobile channel.展开更多
Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel ...Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel state information (CSI), was investigated and a multichannel slotted ALOHA scheme was proposed accordingly. Also an analytical investigation of total system throughput and the queue state evolution of generic node in the network were present by assuming the channel has been modeled by means of a two state Markov chain. Through the theoretical model and simulation results, we confi rm that the proposed algorithm has the advantage of high throughput and low access delay.展开更多
基金supported by the National Basic Research Program of China(973 Program)(2007CB310607)the National Natural Science Foundation of China(60772061)+1 种基金the Natural Science Foundation for the Universities in Jiangsu Province(06KJB51007806KJA51001)
文摘A new approach for improving the throughputs of multi- channel packet radio systems is proposed. Based on the charac- teristics of multi-code CDMA technology, the scheme factitiously improves the transmission bit rate of a terminal by compressing the packet transmission time and thereby increases the number of the orthogonal spreading codes used by the terminal. By this means, the average interference level of the system is reduced and the system capacity is improved. Simulation results show that the proposed scheme exhibits larger throughput compared with the traditional multi-code CDMA slotted Aloha systems.
文摘This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.
基金supported by Special Scientific Research Funds for Central Non-profit Institutes,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences(YSFRI-CAFS)(No.20603022016003)Import of International Advanced Agricultural Science and Technology Plan(948 Project)of Chinese Ministry of Agriculture(No.2016-X28)+2 种基金Central Public Interest Scientific Institution Basal Research Fund,CAFS(No.2016RC-BR02)Qingdao National Laboratory for Marine Science and Technology(No.2015ASKJ02-05)Key R&D Program of Shandong Province(No.2016GSF120008)
文摘High-throughput measurements of ciprofloxacin, clomipramine and fexofenadine hydrochlorides were performed by employing an automatic 8-channel electrical titrator. Silver nitrate （AgNO3） and sodium tetraphenylborate （NaTPB） were used as titrants. When AgNO3 was used for measuring the drugs in pure form, recoveries were 97.6%-102.0% with RSD values ≤1.0%; for measuring them in pharmaceutical formulations, recoveries were 96.6%-99.1% with RSD values ≤1.0%. Batch samples of eight could be measured simultaneously and maximally 30 measurements per minute could be completed. When NaTPB was used for measuring the drugs in pure form, the recoveries were 96.8%-102.6% with RSD values 〈0.8%; for measuring them in pharmaceutical formulations, the recoveries were 97.5%-102.7% with RSD values ≤0.9%. For all analyses, no auxiliary devices or chemicals were needed and there was no requirement for changing or cleaning working electrodes between measurements. The efficiency, accuracy and precision of the proposed method make it an alternative for routine quality control analyses.
基金Sponsored by the Scientific Research Foundation of Harbin Institute of Technology(Grant No. 2001.01)
文摘Wide band or broadband access was paid much attention with the development of radio transmission technique. The wireless access control procedure play an important role in this type of system and efficiency of control algorithm has a great impact on throughput of channel resource. Based on wide band network control model and the characteristics of radio channel, this paper proposed a channel traffic estimation method and then performed a dynamic parameter control procedure and give detail analysis on estimation error and its impact on channel throughput and delay performance. Computation and simulation of system performance show a positive solntion on system design.
文摘In this paper pilot based channel estimation is being considered for broadband power line communication (BPLC) networks witch used orthogonal frequency division multiplexing (OFDM) in order to transmit high rate data. To estimate channel in time or frequency some pilot must be used. Number of these pilots and deployment of them is very important for proper estimation in different channel with varying time and frequency. Carrier sense multiple access (CSMA) and hybrid multiple access protocol are taken into consideration in MAC sub-layer. Multilayered perceptions neural network with backpropagation (BP) learning channel estimator algorithm with different pilot deployment compare to classic algorithm in for channel estimating. Simulation results show the proposed neural network estimation decreases bit error rate and therefore network throughput increases.
文摘Broadband power line communication (BPLC) gained a lot of interest because of low cost and high performance communication network in access area. In this paper physical (PHY) layer and medium access control (MAC) sub-layer of BPLC are considered. Furthermore, effects of bit error rate (BER) are analyzed in MAC sub-layer. Powerful turbo convolutional code (TCC) and wideband orthogonal frequency division multiplexing (OFDM) are used in PHY layer. Carrier sense multiple access (CSMA) and virtual slot multiple access (VSMA) are taken into consideration in MAC sub-layer. Multilayered perceptrons neural network with backpropagation (BP) learning channel estimator algorithm compare to classic algorithm in for channel estimating. The simulation results show that the proposed neural network estimation decreases bit error rate then in MAC sub-layer throughput increases and access delay is decreased.
文摘In this paper, we propose a flexible and fairness-oriented packet scheduling approach for 3GPP UTRAN long term evolution (LTE) type packet radio systems, building on the ordinary proportional fair (PF) scheduling principle and channel quality indicator (CQI) feedback. Special emphasis is also put on practical feedback reporting mechanisms, including the effects of mobile measurement and estimation errors, reporting delays, and CQI quantization and compression. The performance of the overall scheduling and feedback re-porting process is investigated in details, in terms of cell throughput, coverage and resource allocation fairness, by using extensive quasistatic cellular system simulations in practical OFDMA system environment with frequency reuse of 1. The performance simulations show that by using the proposed modified PF ap-proach, significant coverage improvements in the order of 50% can be obtained at the expense of only 10-15% throughput loss, for all reduced feedback reporting schemes. This reflects highly improved fairness in the radio resource management (RRM) compared to other existing schedulers, without essentially com-promising the cell capacity. Furthermore, we demonstrate the improved functionality increase in radio re-source management for UE’s utilizing multi-antenna diversity receivers.
文摘In WLANs, stations sharing a common wireless channel are governed by IEEE 802.11 protocol. Many conscious studies have been conducted to utilize this precious medium efficiently. However, most of these studies have been done either under assumption of idealistic channel condition or with unlimited retransmitting number. This paper is devoted to investigate influence of limited retransmissions and error level in the utilizing channel on the network throughput, probability of packet dropping and time to drop a packet. The results show that for networks using basic access mechanism the throughput is suppressed with increasing amount of errors in the transmitting channel over all the range of the retry limit. It is also quite sensitive to the size of the network. On the other side, the networks using four-way handshaking mechanism has a good immunity against the error over the available range of retry limits. Also the throughput is unchangeable with size of the network over the range of retransmission limits. However, the throughput does not change with retry limits when it exceeds the maximum number of the backoff stage in both DCF’s mechanisms. In both mechanisms the probability of dropping a packet is a decreasing function with number of retransmissions and the time to drop a packet in the queue of a station is a strong function to the number of retry limit, size of the network, the utilizing medium access mechanism and amount of errors in the channel.
基金Supported by the Scientific Research Fund of Liaoning Province(L2013433)
文摘How to reduce interference among neighbor nodes in wireless mesh networks is still an important and key issue nowa- days. In this paper, an optimized channel assignment algorithm （OCA） is proposed to solve this problem based on link throughput and node priority. The effects of the numbers of network interface cards and channels on the network throughput are analyzed and evaluated, When there are seven of the numbers of both network interface cards and channels, the efficiency of utilizing network interface card and channel reaches highest. Compared with cen- tralized channel assignment algorithm （CCA）, the proposed algo- rithm has less packet loss rate and more network throughput sig- nificantly.
基金Supported by the National Natural Science Foundation of China (No. 60772062)973 Program (2007CB310607)+1 种基金National Science & Technology Key Project (2009ZX 03003-002, 2011ZX03001-006-02, 2011ZX03005-004-03)863 Program (2009AA01Z241)
文摘How to improve the performance of the wireless Ad Hoc network by utilizing the spectrum resources efficiently has become a hot research topic in recent years. In this paper we propose a reactive routing algorithm that supports multiple channels to improve the performance of the Ad Hoc network based on the minimizing of the channel handoff. Our approach allocates the communication channel during the route discovery, and notifies the allocated channel information to the corresponding node in the route reply packets. Each node in the route tries its best to choose the same channel with the upstream node without interference. The simulation results show that our algorithm performs better than the K-hop distinct protocols in both average delays and network throughputs
文摘Given that satellite mobile channel is a time-varying channel,Adaptive Modulation and Coding(AMC) was proposed to provide robust and spectrally efficient transmission over satellite mobile channel.Three different kinds of channel environment were considered in this paper:the urban area,the rural area,and the open space.Four combinations of modulation and coding were designed to meet reliable communication on time-varying channel,and spectral efficiency and system throughput of these three kinds of channel environment were simulated.Based on the simulation results,this paper analysed the results and compared the performances of AMC with non-AMC system in these three kinds of channel environment.At last,we come to the conclusions:a system with AMC can achieve higher spectral efficiency and better system throughput;and the spectral efficiency and system throughput of AMC system will be higher on better satellite mobile channel.
文摘Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel state information (CSI), was investigated and a multichannel slotted ALOHA scheme was proposed accordingly. Also an analytical investigation of total system throughput and the queue state evolution of generic node in the network were present by assuming the channel has been modeled by means of a two state Markov chain. Through the theoretical model and simulation results, we confi rm that the proposed algorithm has the advantage of high throughput and low access delay.
