In packet-based OFDM WLAN systems (IEEE 802.11a/g/n), each packet has a fixed-length preamble for synchronization and channel estimation purposes. The preamble carries no data information and hence causes considerable overhead during transmission when the payload is short and the data rate is high. In this work, we propose a new scheme, called superimposed preamble, to improve the efficiency of 802.11a alike systems. We design a new signal structure using variable data rate and propose an efficient receiver processing scheme to perform joint training (time and frequency synchronization and channel estimation) and data detection. It is shown that the proposed superimposed preamble system achieves training performance similar to the conventional 802.11a systems while gaining in robustness because of the reduced overhead.
{"title":"A Novel Preamble Scheme for Packet-Based OFDM WLAN","authors":"Y. Wang, J. Oostveen, A. Filippi, Stefan Wesemann","doi":"10.1109/WCNC.2007.279","DOIUrl":"https://doi.org/10.1109/WCNC.2007.279","url":null,"abstract":"In packet-based OFDM WLAN systems (IEEE 802.11a/g/n), each packet has a fixed-length preamble for synchronization and channel estimation purposes. The preamble carries no data information and hence causes considerable overhead during transmission when the payload is short and the data rate is high. In this work, we propose a new scheme, called superimposed preamble, to improve the efficiency of 802.11a alike systems. We design a new signal structure using variable data rate and propose an efficient receiver processing scheme to perform joint training (time and frequency synchronization and channel estimation) and data detection. It is shown that the proposed superimposed preamble system achieves training performance similar to the conventional 802.11a systems while gaining in robustness because of the reduced overhead.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114817396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose a link adaptation technique for IEEE 802.11n MIMO-OFDM systems with convolutional coding. The technique dynamically selects the best modulation and coding scheme (MCS) based on channel conditions and on the medium access control (MAC) layer performance (coded BER or PER) requested by applications. We show that the coded performance at decoder output can be modeled as a function of decoder-input uncoded BER and the code rate. For MIMO-OFDM systems with different modulation types for different spatial streams at each subcarrier, we propose a simple and accurate method for computing the BER for each spatial stream mixed from different subcarriers. We also discuss approaches for searching and selecting the MCS.
{"title":"Adaptive Modulation and Coding for IEEE 802.11n","authors":"Fei Peng, Jinyun Zhang, W. Ryan","doi":"10.1109/WCNC.2007.126","DOIUrl":"https://doi.org/10.1109/WCNC.2007.126","url":null,"abstract":"We propose a link adaptation technique for IEEE 802.11n MIMO-OFDM systems with convolutional coding. The technique dynamically selects the best modulation and coding scheme (MCS) based on channel conditions and on the medium access control (MAC) layer performance (coded BER or PER) requested by applications. We show that the coded performance at decoder output can be modeled as a function of decoder-input uncoded BER and the code rate. For MIMO-OFDM systems with different modulation types for different spatial streams at each subcarrier, we propose a simple and accurate method for computing the BER for each spatial stream mixed from different subcarriers. We also discuss approaches for searching and selecting the MCS.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"169 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114376594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An analytical formulation of the saturated throughput of prioritized contention access (PCA) in the presence of hard distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC (formerly multi-band OFDM alliance (MBOA) MAC) is presented. The analytical framework is formulated for one hard DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. Numerical results of the saturated throughput corresponding to typical parameter values are presented.
{"title":"Performance Analysis of Saturated Throughput of PCA in the Presence of Hard DRPs in WiMedia MAC","authors":"D. Wong, F. Chin, M. R. Shajan, Y. Chew","doi":"10.1109/WCNC.2007.83","DOIUrl":"https://doi.org/10.1109/WCNC.2007.83","url":null,"abstract":"An analytical formulation of the saturated throughput of prioritized contention access (PCA) in the presence of hard distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC (formerly multi-band OFDM alliance (MBOA) MAC) is presented. The analytical framework is formulated for one hard DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. Numerical results of the saturated throughput corresponding to typical parameter values are presented.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114505605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Constrained codes are widely used in digital transmission systems and digital recording systems to generate constrained sequences with properties that comply with the given physical characteristics of the transmission or recording channels. The power spectral density (PSD) of encoded signals often plays an important role in the design of constrained codes. In this article the authors introduce a new approach for constructing finite-state sequential machine (FSSM) modeled encoders to satisfy desired spectral constraints. This approach involves constructing either a Mealy or a Moore FSSM to represent the encoder, and evaluating the state transition probabilities and codeword values in order that the PSD of the encoded signal meets a predefined shape.
{"title":"A New Approach for Constructing FSSM Modeled Encoders to Satisfy Spectral Constraints","authors":"Yongguang Zhu, I. Fair","doi":"10.1109/WCNC.2007.100","DOIUrl":"https://doi.org/10.1109/WCNC.2007.100","url":null,"abstract":"Constrained codes are widely used in digital transmission systems and digital recording systems to generate constrained sequences with properties that comply with the given physical characteristics of the transmission or recording channels. The power spectral density (PSD) of encoded signals often plays an important role in the design of constrained codes. In this article the authors introduce a new approach for constructing finite-state sequential machine (FSSM) modeled encoders to satisfy desired spectral constraints. This approach involves constructing either a Mealy or a Moore FSSM to represent the encoder, and evaluating the state transition probabilities and codeword values in order that the PSD of the encoded signal meets a predefined shape.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114897165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper we investigate MIMO systems where faster-than-Nyquist (FTN) signaling is used as modulation. On the AWGN channel, the main characteristic of FTN is the so called Mazo limit; it is possible to signal considerably faster than conventional without loss in minimum Euclidean distance. We show that MIMO-FTN systems inherit this property from the AWGN-FTN systems. Moreover, not only does it exist a Mazo limit in MIMO, but it occurs at exactly the same signaling rate as for the AWGN channel. We also discuss information rates of MIMO-FTN systems.
{"title":"A First Encounter with Faster-than-Nyquist Signaling on the MIMO Channel","authors":"F. Rusek","doi":"10.1109/WCNC.2007.207","DOIUrl":"https://doi.org/10.1109/WCNC.2007.207","url":null,"abstract":"In this paper we investigate MIMO systems where faster-than-Nyquist (FTN) signaling is used as modulation. On the AWGN channel, the main characteristic of FTN is the so called Mazo limit; it is possible to signal considerably faster than conventional without loss in minimum Euclidean distance. We show that MIMO-FTN systems inherit this property from the AWGN-FTN systems. Moreover, not only does it exist a Mazo limit in MIMO, but it occurs at exactly the same signaling rate as for the AWGN channel. We also discuss information rates of MIMO-FTN systems.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123584160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Although radio frequency identification (RFID) technology is promising, it is vulnerable and subject to a wide range of attacks due to possible tags compromise, difficulty in physical protection, absence of infrastructure and so on. Generally speaking, the threat to RFID systems mainly comes from the illegal reader's attempt to compromise tag identity. In order to protect the tag carries' privacy (intuitively, privacy for RFID tags means that the communication of a tag does not allow an adversary to determine the identity of the tag (non-traceability), however the reader should be able to determine whether the tag it reads is valid (completeness) and only such tags (soundness)), a security model that supports the analytical argument of properties, addressing both security and performance issues for RFID tags is introduced and formalized in this paper. The significant feature of our model is that a back-end database for a reader is explicitly introduced which allows the reader to search key-index set used by individual tags more efficiently, and describe the protocols in a unique way, where properties can be isolated and analyzed. We then propose an authentication protocol for securing RFID tags, and show that our implementation is completeness, soundness and non-traceability in the independent random oracle model.
{"title":"Securing RFID Tags: Authentication Protocols with Completeness, Soundness, and Non-Traceability","authors":"Huafei Zhu, F. Bao","doi":"10.1109/WCNC.2007.501","DOIUrl":"https://doi.org/10.1109/WCNC.2007.501","url":null,"abstract":"Although radio frequency identification (RFID) technology is promising, it is vulnerable and subject to a wide range of attacks due to possible tags compromise, difficulty in physical protection, absence of infrastructure and so on. Generally speaking, the threat to RFID systems mainly comes from the illegal reader's attempt to compromise tag identity. In order to protect the tag carries' privacy (intuitively, privacy for RFID tags means that the communication of a tag does not allow an adversary to determine the identity of the tag (non-traceability), however the reader should be able to determine whether the tag it reads is valid (completeness) and only such tags (soundness)), a security model that supports the analytical argument of properties, addressing both security and performance issues for RFID tags is introduced and formalized in this paper. The significant feature of our model is that a back-end database for a reader is explicitly introduced which allows the reader to search key-index set used by individual tags more efficiently, and describe the protocols in a unique way, where properties can be isolated and analyzed. We then propose an authentication protocol for securing RFID tags, and show that our implementation is completeness, soundness and non-traceability in the independent random oracle model.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121979064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Previous work on antenna selection in MIMO systems, which deal with error performance, has mainly focused on frequency-flat channels. As a result, the objective was to minimize the symbol error rate (SER) or pairwise error probability (PEP). However, in present and future communication systems, where high throughput is one of the major features, wideband systems with frequency selectivity are now becoming common. Therefore, SER in flat-fading channels may not be a good measure for evaluating antenna selection in practical systems. In this paper, instead, we formulate the antenna selection problem based on a frequency-selective WLAN system. Hence the objective is to reduce the packet error rate (PER). We propose different antenna selection algorithms depending on the extent of channel state information we have. Simulation results are provided to demonstrate the effectiveness of the algorithms proposed.
{"title":"Effective Antenna Selection in a Frequency-Selective Wireless LAN System","authors":"H.-T. Meng, R. Murch, R. Cheng","doi":"10.1109/WCNC.2007.389","DOIUrl":"https://doi.org/10.1109/WCNC.2007.389","url":null,"abstract":"Previous work on antenna selection in MIMO systems, which deal with error performance, has mainly focused on frequency-flat channels. As a result, the objective was to minimize the symbol error rate (SER) or pairwise error probability (PEP). However, in present and future communication systems, where high throughput is one of the major features, wideband systems with frequency selectivity are now becoming common. Therefore, SER in flat-fading channels may not be a good measure for evaluating antenna selection in practical systems. In this paper, instead, we formulate the antenna selection problem based on a frequency-selective WLAN system. Hence the objective is to reduce the packet error rate (PER). We propose different antenna selection algorithms depending on the extent of channel state information we have. Simulation results are provided to demonstrate the effectiveness of the algorithms proposed.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125889782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Co-channel interference (CCI) on pilot subcarriers can severely degrade the channel estimation accuracy in reuse-1 cellular OFDM systems. Currently most OFDM channel estimation schemes use a Kalman filter, which implicitly assumes that the CCI is Gaussian. However, when only one or two strong CCI signals are present, the Gaussianity assumption of the disturbance sequence is usually not valid. We propose Hinfin based channel estimation for such CCI limited OFDM systems. Simulated performance results of normalized mean squared error as well as singular value plots indicate that the Hinfin based algorithm yields a significantly superior performance when compared to the Kalman filter.
{"title":"Hinfin Channel Estimation for Cellular OFDM","authors":"R. Lakshminarayanan, K. Giridhar","doi":"10.1109/WCNC.2007.267","DOIUrl":"https://doi.org/10.1109/WCNC.2007.267","url":null,"abstract":"Co-channel interference (CCI) on pilot subcarriers can severely degrade the channel estimation accuracy in reuse-1 cellular OFDM systems. Currently most OFDM channel estimation schemes use a Kalman filter, which implicitly assumes that the CCI is Gaussian. However, when only one or two strong CCI signals are present, the Gaussianity assumption of the disturbance sequence is usually not valid. We propose Hinfin based channel estimation for such CCI limited OFDM systems. Simulated performance results of normalized mean squared error as well as singular value plots indicate that the Hinfin based algorithm yields a significantly superior performance when compared to the Kalman filter.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126126787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The IEEE 802.16e standard is a rapidly developing technology for broadband wireless access system. Its PHY OFDMA mode defines two subchannel building methods: diversity permutation and contiguous permutation (AMC subchannel). In this paper we propose a joint packet scheduling and subchannel allocation scheme applicable for the IEEE 802.16e OFDMA AMC subchannel. Since it is a multiuser, multi-service and multichannel packet-switched system, we define a distinct scheduling priority for each packet on each subchannel that integrates MAC QoS requirements, service type and PHY channel state information (CSI). Based on these scheduling priorities and specific scheduling mechanism, efficient QoS guaranteed resource allocation is achieved in our scheme. Intensive simulations show that our scheme outperforms throughput-oriented maximum C/I (MCI) and QoS-oriented priority schemes under various conditions.
IEEE 802.16e标准是一项发展迅速的宽带无线接入技术。其PHY OFDMA模式定义了两种子信道构建方法:分集置换和连续置换(AMC子信道)。本文提出了一种适用于ieee802.16 e OFDMA AMC子信道的联合分组调度和子信道分配方案。由于它是一个多用户、多服务和多通道分组交换系统，我们为每个子通道上的每个数据包定义了一个独特的调度优先级，该优先级集成了MAC QoS要求、服务类型和PHY通道状态信息(CSI)。基于这些调度优先级和特定的调度机制，我们的方案实现了高效的QoS保证资源分配。仿真结果表明，该方案在各种条件下都优于面向吞吐量的最大C/I (MCI)和面向qos的优先级方案。
{"title":"A Cross-layer Packet Scheduling and Subchannel Allocation Scheme in 802.16e OFDMA System","authors":"Lihua Wan, Wenchao Ma, Zihua Guo","doi":"10.1109/WCNC.2007.350","DOIUrl":"https://doi.org/10.1109/WCNC.2007.350","url":null,"abstract":"The IEEE 802.16e standard is a rapidly developing technology for broadband wireless access system. Its PHY OFDMA mode defines two subchannel building methods: diversity permutation and contiguous permutation (AMC subchannel). In this paper we propose a joint packet scheduling and subchannel allocation scheme applicable for the IEEE 802.16e OFDMA AMC subchannel. Since it is a multiuser, multi-service and multichannel packet-switched system, we define a distinct scheduling priority for each packet on each subchannel that integrates MAC QoS requirements, service type and PHY channel state information (CSI). Based on these scheduling priorities and specific scheduling mechanism, efficient QoS guaranteed resource allocation is achieved in our scheme. Intensive simulations show that our scheme outperforms throughput-oriented maximum C/I (MCI) and QoS-oriented priority schemes under various conditions.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124694786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In wireless local area networks (WLANs), the power saving mechanism for distributed coordination function (DCF) allows stations (STAs) to periodically wake up and check the existence of buffered packets in the access point (AP). If notified by the beacon of buffered packet's presence, an STA contends for sending the PS-Poll to the AP which will respond with the corresponding buffered packet either 1) immediately (immediate-send), or 2) at a later time (later-send). IEEE 802.11 standard does not specify the detailed scheme of later-send and most current mechanisms adopt immediate-send. Though immediate-send performs well under light load condition, it is inefficient under heavy load condition because of the existence of some STAs contending throughout the whole beacon interval at the price of corresponding power consumption but getting no access opportunity, which degrades the power saving performance of both total power consumption and energy efficiency, i.e. the average power consumed for one unit of payload. The authors propose and analyze a load aware power saving mechanism (LAPS) that uses immediate-send under light load condition and uses a proposed detailed mechanism of later-send under heavy load condition. The threshold to divide light and heavy load is also calculated-numerical results show the effectiveness of our mechanism.
{"title":"Load-Aware Power Saving Mechanism in WLAN","authors":"Fan Zhu, Z. Niu","doi":"10.1109/WCNC.2007.391","DOIUrl":"https://doi.org/10.1109/WCNC.2007.391","url":null,"abstract":"In wireless local area networks (WLANs), the power saving mechanism for distributed coordination function (DCF) allows stations (STAs) to periodically wake up and check the existence of buffered packets in the access point (AP). If notified by the beacon of buffered packet's presence, an STA contends for sending the PS-Poll to the AP which will respond with the corresponding buffered packet either 1) immediately (immediate-send), or 2) at a later time (later-send). IEEE 802.11 standard does not specify the detailed scheme of later-send and most current mechanisms adopt immediate-send. Though immediate-send performs well under light load condition, it is inefficient under heavy load condition because of the existence of some STAs contending throughout the whole beacon interval at the price of corresponding power consumption but getting no access opportunity, which degrades the power saving performance of both total power consumption and energy efficiency, i.e. the average power consumed for one unit of payload. The authors propose and analyze a load aware power saving mechanism (LAPS) that uses immediate-send under light load condition and uses a proposed detailed mechanism of later-send under heavy load condition. The threshold to divide light and heavy load is also calculated-numerical results show the effectiveness of our mechanism.","PeriodicalId":292621,"journal":{"name":"2007 IEEE Wireless Communications and Networking Conference","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124823069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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