Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5501751
D. Ficara, G. Antichi, A. D. Pietro, S. Giordano, G. Procissi, F. Vitucci
Modern network devices need to perform deep packet inspection at high speed for security and application-specific services. Instead of standard strings to represent the dataset to be matched, state-of-the-art systems adopt regular expressions, due to their high expressive power. The current trend is to use Deterministic Finite Automata (DFAs) to match regular expressions. However, while the problem of the large memory consumption of DFAs has been solved in many different ways, only a few works have focused on increasing the lookup speed. This paper introduces a novel yet simple idea to accelerate DFAs for security applications: payload sampling. Our approach allows to skip a large portion of the text, thus processing less bytes. The price to pay is a slight number of false alarms which require a confirmation stage. Therefore, we propose a double-stage matching scheme providing two new different automata. Results show a significant speed-up in regular traffic processing, thus confirming the effectiveness of the approach.
{"title":"Sampling Techniques to Accelerate Pattern Matching in Network Intrusion Detection Systems","authors":"D. Ficara, G. Antichi, A. D. Pietro, S. Giordano, G. Procissi, F. Vitucci","doi":"10.1109/ICC.2010.5501751","DOIUrl":"https://doi.org/10.1109/ICC.2010.5501751","url":null,"abstract":"Modern network devices need to perform deep packet inspection at high speed for security and application-specific services. Instead of standard strings to represent the dataset to be matched, state-of-the-art systems adopt regular expressions, due to their high expressive power. The current trend is to use Deterministic Finite Automata (DFAs) to match regular expressions. However, while the problem of the large memory consumption of DFAs has been solved in many different ways, only a few works have focused on increasing the lookup speed. This paper introduces a novel yet simple idea to accelerate DFAs for security applications: payload sampling. Our approach allows to skip a large portion of the text, thus processing less bytes. The price to pay is a slight number of false alarms which require a confirmation stage. Therefore, we propose a double-stage matching scheme providing two new different automata. Results show a significant speed-up in regular traffic processing, thus confirming the effectiveness of the approach.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"45 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83004045","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502063
P. Thulasiraman, Jiming Chen, Xuemin Shen
Fairness and system throughput, influenced by wireless interference, are major objectives of resource allocation in wireless networks. Whereas traditionally max-min fairness protocols have been developed for wired networks (where interference is not a factor for network performance), in this paper we investigate the problem of flow routing and fair bandwidth allocation under the constraints of the physical interference model for multihop wireless networks. A max-min fair (MMF) routing algorithm under physical interference constraints is proposed where multiple candidate paths coexist for each user to the base station. The algorithm is formulated as a multicommodity flow problem where the lexicographically largest bandwidth allocation vector is found among all optimal allocation vectors. We compare our approach with two MMF interference routing algorithms in the literature that use the protocol interference model to garner fair bandwidth allocation. We show that our algorithm performs better in terms of blocking probability, bandwidth usage and link load.
{"title":"Max-Min Fair Multipath Routing with Physical Interference Constraints for Multihop Wireless Networks","authors":"P. Thulasiraman, Jiming Chen, Xuemin Shen","doi":"10.1109/ICC.2010.5502063","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502063","url":null,"abstract":"Fairness and system throughput, influenced by wireless interference, are major objectives of resource allocation in wireless networks. Whereas traditionally max-min fairness protocols have been developed for wired networks (where interference is not a factor for network performance), in this paper we investigate the problem of flow routing and fair bandwidth allocation under the constraints of the physical interference model for multihop wireless networks. A max-min fair (MMF) routing algorithm under physical interference constraints is proposed where multiple candidate paths coexist for each user to the base station. The algorithm is formulated as a multicommodity flow problem where the lexicographically largest bandwidth allocation vector is found among all optimal allocation vectors. We compare our approach with two MMF interference routing algorithms in the literature that use the protocol interference model to garner fair bandwidth allocation. We show that our algorithm performs better in terms of blocking probability, bandwidth usage and link load.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"1 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85548645","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502032
F. Brah, L. Vandendorpe, V. Ramon
This paper presents a novel fair scheme for resource sharing between nodes in OFDMA mesh networks. The problem is to maximize the overall system rate, under each user's maximal power and minimum rate constraints. To solve the underlying problem, we propose an approach that combines the merits of the well known Lagrange dual framework and the Lambert-W function. By using the Lambert-W function, resource allocation can not only be expressed in closed form but it can also quickly be determined without resorting to complex algorithms since a number of popular mathematical softwares, including Matlab, contain the Lambert-W function as an optimization component. Simulation results are provided to compare the performance of the proposed scheme with other allocation schemes.
{"title":"A Tractable Method for Constrained Resource Sharing in OFDMA Wireless Mesh Networks","authors":"F. Brah, L. Vandendorpe, V. Ramon","doi":"10.1109/ICC.2010.5502032","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502032","url":null,"abstract":"This paper presents a novel fair scheme for resource sharing between nodes in OFDMA mesh networks. The problem is to maximize the overall system rate, under each user's maximal power and minimum rate constraints. To solve the underlying problem, we propose an approach that combines the merits of the well known Lagrange dual framework and the Lambert-W function. By using the Lambert-W function, resource allocation can not only be expressed in closed form but it can also quickly be determined without resorting to complex algorithms since a number of popular mathematical softwares, including Matlab, contain the Lambert-W function as an optimization component. Simulation results are provided to compare the performance of the proposed scheme with other allocation schemes.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"1 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85559048","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502577
Junbin Liang, Jian-xin Wang, Jianer Chen
How to improve the data persistence, i.e., the availability of all source data, is an important issue in wireless sensor networks. The issue requires that each source node can disseminate its data (packet) to a subset of nodes in the network for effective storage. In this paper, a distributed scheme based on LT(Luby Transform)-codes, named LTSIDP, is proposed. LT codes are the first rateless erasure codes that are very efficient as the amount of data grows. In LTSIDP, each node uses overhearing to get information whether a packet has been transmitted by one of its neighbors. When a node needs to transmit a packet, it randomly chooses one of its neighbors that does not transmit the packet as receiver. On the other hand, each node can compute a key parameter of LT codes by using some properties of the packet transmission mechanism, and then store the data accordingly. After the process of storage is finished, a collector (e.g., a motor vehicle) can recover all data by visiting a small subset of nodes. To the best of our knowledge, LTSIDP is the first scheme that uses overhearing to improve the data persistence. Theoretical analyses and simulations show that LTSIDP can achieve higher data persistence and energy efficiency than existing schemes.
{"title":"An Overhearing-Based Scheme for Improving Data Persistence in Wireless Sensor Networks","authors":"Junbin Liang, Jian-xin Wang, Jianer Chen","doi":"10.1109/ICC.2010.5502577","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502577","url":null,"abstract":"How to improve the data persistence, i.e., the availability of all source data, is an important issue in wireless sensor networks. The issue requires that each source node can disseminate its data (packet) to a subset of nodes in the network for effective storage. In this paper, a distributed scheme based on LT(Luby Transform)-codes, named LTSIDP, is proposed. LT codes are the first rateless erasure codes that are very efficient as the amount of data grows. In LTSIDP, each node uses overhearing to get information whether a packet has been transmitted by one of its neighbors. When a node needs to transmit a packet, it randomly chooses one of its neighbors that does not transmit the packet as receiver. On the other hand, each node can compute a key parameter of LT codes by using some properties of the packet transmission mechanism, and then store the data accordingly. After the process of storage is finished, a collector (e.g., a motor vehicle) can recover all data by visiting a small subset of nodes. To the best of our knowledge, LTSIDP is the first scheme that uses overhearing to improve the data persistence. Theoretical analyses and simulations show that LTSIDP can achieve higher data persistence and energy efficiency than existing schemes.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"117 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85791579","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5501887
M. Bhatnagar, A. Hjørungnes
In this paper, we propose a maximum likelihood~(ML) decoder for differentially encoded orthogonal space-time block codes (OSTBCs) based on multiple received data blocks. The proposed ML decoder differs from the existing ML decoders of differential OSTBC as follows: 1) Most existing ML decoders are derived on the basis of emph{two} consecutively received data matrices, whereas the proposed decoder takes emph{multiple} consecutively received data matrices into account. 2) One existing ML decoder considers multiple consecutively received specific differential OSTBC using emph{two} transmit antennas and is applicable to $M$-PSK constellation only, whereas the proposed ML decoder works with arbitrary differential OSTBCs using arbitrary number of transmit and receive antennas and arbitrary constellations which do not include zero. We have also derived an upper bound of the pairwise error probability (PEP) of the proposed ML decoder for differentially encoded orthogonal STBC (OSTBC) with $M$-QAM constellation over Rayleigh fading channels.
{"title":"Decoding of Differential OSTBC with Non-Unitary Constellations Using Multiple Received Data Blocks","authors":"M. Bhatnagar, A. Hjørungnes","doi":"10.1109/ICC.2010.5501887","DOIUrl":"https://doi.org/10.1109/ICC.2010.5501887","url":null,"abstract":"In this paper, we propose a maximum likelihood~(ML) decoder for differentially encoded orthogonal space-time block codes (OSTBCs) based on multiple received data blocks. The proposed ML decoder differs from the existing ML decoders of differential OSTBC as follows: 1) Most existing ML decoders are derived on the basis of emph{two} consecutively received data matrices, whereas the proposed decoder takes emph{multiple} consecutively received data matrices into account. 2) One existing ML decoder considers multiple consecutively received specific differential OSTBC using emph{two} transmit antennas and is applicable to $M$-PSK constellation only, whereas the proposed ML decoder works with arbitrary differential OSTBCs using arbitrary number of transmit and receive antennas and arbitrary constellations which do not include zero. We have also derived an upper bound of the pairwise error probability (PEP) of the proposed ML decoder for differentially encoded orthogonal STBC (OSTBC) with $M$-QAM constellation over Rayleigh fading channels.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"4 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86057854","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502625
Y. Tawk, C. Botteron, A. Jovanovic, P. Farine
In this paper, different correlation techniques (narrow correlator, double delta correlator and subcarrier processing) that can be applied to the new Galileo alternate binary offset carrier AltBOC(15,10) modulation are discussed with respect to their functionality, implementation, and multipath mitigation performance. Moreover, effects of the receiver parameters (precorrelation bandwidth, spacing between correlators) on the ranging errors are also presented. The performance of the multipath mitigation concepts is illustrated in 2D and 3D multipath error envelopes assuming multipath scenarios with one and two multipath components and constant signal attenuation factors. The main purpose of this paper is to provide a better understanding of the performance of the AltBOC modulation and the effect of multipath on code and carrier measurements for different multipath environments, and thus help the receiver designers to select the best correlation technique for their particular applications.
{"title":"Performance Comparison of Different Correlation Techniques for the AltBOC Modulation in Multipath Environments","authors":"Y. Tawk, C. Botteron, A. Jovanovic, P. Farine","doi":"10.1109/ICC.2010.5502625","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502625","url":null,"abstract":"In this paper, different correlation techniques (narrow correlator, double delta correlator and subcarrier processing) that can be applied to the new Galileo alternate binary offset carrier AltBOC(15,10) modulation are discussed with respect to their functionality, implementation, and multipath mitigation performance. Moreover, effects of the receiver parameters (precorrelation bandwidth, spacing between correlators) on the ranging errors are also presented. The performance of the multipath mitigation concepts is illustrated in 2D and 3D multipath error envelopes assuming multipath scenarios with one and two multipath components and constant signal attenuation factors. The main purpose of this paper is to provide a better understanding of the performance of the AltBOC modulation and the effect of multipath on code and carrier measurements for different multipath environments, and thus help the receiver designers to select the best correlation technique for their particular applications.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"1 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84179213","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502357
Taesoo Jun, Nirmalya Roy, Christine Julien
Mobile ad hoc networks (MANETs) can have widely varying characteristics under different deployments, and previous studies show that the characteristics impact the behavior of routing protocols for MANETs. To deploy applications successfully in MANETs, application developers need to comprehend the potential behavior of any underlying protocol used. In mobile networks, a major component of many of these routing protocols is some form of flooding, which facilitates message delivery over an entire network in a relatively reliable way. Several MANET protocols use flooding to support the distribution of route request messages as well as delivering broadcast packets. Therefore, to developers of applications for MANETs, a major task in understanding MANET protocols is estimating the performance of flooding in a given operating environment. In this work, we develop an analytical model for the delay experienced in flooding a message. We model the one hop delay of a flooding message in MANETs in terms of parameters that can be acquired either from a system configuration or from application designers.
{"title":"Modeling Delivery Delay for Flooding in Mobile Ad Hoc Networks","authors":"Taesoo Jun, Nirmalya Roy, Christine Julien","doi":"10.1109/ICC.2010.5502357","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502357","url":null,"abstract":"Mobile ad hoc networks (MANETs) can have widely varying characteristics under different deployments, and previous studies show that the characteristics impact the behavior of routing protocols for MANETs. To deploy applications successfully in MANETs, application developers need to comprehend the potential behavior of any underlying protocol used. In mobile networks, a major component of many of these routing protocols is some form of flooding, which facilitates message delivery over an entire network in a relatively reliable way. Several MANET protocols use flooding to support the distribution of route request messages as well as delivering broadcast packets. Therefore, to developers of applications for MANETs, a major task in understanding MANET protocols is estimating the performance of flooding in a given operating environment. In this work, we develop an analytical model for the delay experienced in flooding a message. We model the one hop delay of a flooding message in MANETs in terms of parameters that can be acquired either from a system configuration or from application designers.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"102 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84194086","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502420
D. Adami, C. Callegari, S. Giordano, M. Pagano
DiffServ-aware MPLS-TE (DS-TE) significantly enhances the MPLS-TE architecture by enabling bandwidth reservation on a per-class basis. More specifically, to this aim, the so-called Bandwidth Constraint Models (BCMs) are introduced as a key architectural element. This paper describes a new NS2 module that offers a complete support for the DS-TE architecture including the standard BCMs (MAM and RDM) and a new BCM (G-RDM), recently proposed by the authors. Moreover, the paper shows the results of simulations carried out to evaluate the behaviour of the above mentioned BCMs in a real network scenario.
{"title":"NS2 Extensions for the Simulation of RDM and G-RDM in DS-TE Networks","authors":"D. Adami, C. Callegari, S. Giordano, M. Pagano","doi":"10.1109/ICC.2010.5502420","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502420","url":null,"abstract":"DiffServ-aware MPLS-TE (DS-TE) significantly enhances the MPLS-TE architecture by enabling bandwidth reservation on a per-class basis. More specifically, to this aim, the so-called Bandwidth Constraint Models (BCMs) are introduced as a key architectural element. This paper describes a new NS2 module that offers a complete support for the DS-TE architecture including the standard BCMs (MAM and RDM) and a new BCM (G-RDM), recently proposed by the authors. Moreover, the paper shows the results of simulations carried out to evaluate the behaviour of the above mentioned BCMs in a real network scenario.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"23 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77979634","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502293
J. A. Briffa, H. G. Schaathun, S. Wesemeyer
The Deletion-Insertion Correcting Code construction proposed by Davey and MacKay consists of an inner code that recovers synchronization and an outer code that provides substitution error protection. The inner code uses low-weight codewords which are added (modulo two) to a pilot sequence. The receiver is able to synchronise on the pilot sequence in spite of the changes introduced by the added codeword. The original bit-level formulation of the inner decoder assumes that all bits in the sparse codebook are identically and independently distributed. Not only is this assumption inaccurate, but it also prevents the use of soft a- priori input to the decoder. We propose an alternative symbol-level inner decoding algorithm that takes the actual codebook into account. Simulation results show that the proposed algorithm has an improved performance with only a small penalty in complexity, and it allows other improvements using inner codes with larger minimum distance.
{"title":"An Improved Decoding Algorithm for the Davey-MacKay Construction","authors":"J. A. Briffa, H. G. Schaathun, S. Wesemeyer","doi":"10.1109/ICC.2010.5502293","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502293","url":null,"abstract":"The Deletion-Insertion Correcting Code construction proposed by Davey and MacKay consists of an inner code that recovers synchronization and an outer code that provides substitution error protection. The inner code uses low-weight codewords which are added (modulo two) to a pilot sequence. The receiver is able to synchronise on the pilot sequence in spite of the changes introduced by the added codeword. The original bit-level formulation of the inner decoder assumes that all bits in the sparse codebook are identically and independently distributed. Not only is this assumption inaccurate, but it also prevents the use of soft a- priori input to the decoder. We propose an alternative symbol-level inner decoding algorithm that takes the actual codebook into account. Simulation results show that the proposed algorithm has an improved performance with only a small penalty in complexity, and it allows other improvements using inner codes with larger minimum distance.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"322 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77993205","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}
Pub Date : 2010-05-23DOI: 10.1109/ICC.2010.5502096
S. Sugiura, Sheng Chen, L. Hanzo
In this paper, we propose a differential Space-Time Coding (STC) scheme designed for asynchronous cooperative networks, where neither channel estimation nor symbol-level synchronization is required at the cooperating nodes. More specifically, our system employs differential encoding during the broadcast phase and a Space-Time Spreading (STS)-based amplify-and-forward scheme during the cooperative phase in conjunction with interference rejection Direct Sequence (DS) spreading codes, namely Loosely Synchronized (LS) codes. The LS codes exhibit a so-called Interference Free Window (IFW), where both the autocorrelation and cross-correlation values of the codes become zero. The IFW allows us to eliminate both the Multi-User Interference (MUI) as well as the potential dispersion-induced orthogonality degradation of the cooperative space-time codeword and the interference imposed by the asynchronous transmissions of the relay nodes. Furthermore, the destination node can beneficially combine both the directly transmitted and the relayed symbols using low-complexity correlation operations combined with a hard-decision detector. Our simulation results demonstrate that the proposed Cooperative Differential STS (CDSTS) scheme is capable of combating the effects of asynchronous uplink transmissions without any Channel State Information (CSI), provided that the maximum synchronization delay of the relay nodes is within the width of IFW. It will be demonstrated that in the frequency-selective environment considered our CDSTS arrangement is capable of exploiting both space-time diversity and multi-path diversity with the aid of a RAKE combiner.
{"title":"Distributed Differential Space-Time Spreading for the Asynchronous Relay Aided Interference-Free Cooperative CDMA Uplink","authors":"S. Sugiura, Sheng Chen, L. Hanzo","doi":"10.1109/ICC.2010.5502096","DOIUrl":"https://doi.org/10.1109/ICC.2010.5502096","url":null,"abstract":"In this paper, we propose a differential Space-Time Coding (STC) scheme designed for asynchronous cooperative networks, where neither channel estimation nor symbol-level synchronization is required at the cooperating nodes. More specifically, our system employs differential encoding during the broadcast phase and a Space-Time Spreading (STS)-based amplify-and-forward scheme during the cooperative phase in conjunction with interference rejection Direct Sequence (DS) spreading codes, namely Loosely Synchronized (LS) codes. The LS codes exhibit a so-called Interference Free Window (IFW), where both the autocorrelation and cross-correlation values of the codes become zero. The IFW allows us to eliminate both the Multi-User Interference (MUI) as well as the potential dispersion-induced orthogonality degradation of the cooperative space-time codeword and the interference imposed by the asynchronous transmissions of the relay nodes. Furthermore, the destination node can beneficially combine both the directly transmitted and the relayed symbols using low-complexity correlation operations combined with a hard-decision detector. Our simulation results demonstrate that the proposed Cooperative Differential STS (CDSTS) scheme is capable of combating the effects of asynchronous uplink transmissions without any Channel State Information (CSI), provided that the maximum synchronization delay of the relay nodes is within the width of IFW. It will be demonstrated that in the frequency-selective environment considered our CDSTS arrangement is capable of exploiting both space-time diversity and multi-path diversity with the aid of a RAKE combiner.","PeriodicalId":6405,"journal":{"name":"2010 IEEE International Conference on Communications","volume":"17 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2010-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82479684","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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