Pub Date : 2011-11-01DOI: 10.1109/IWCLD.2011.6123078
Sami Ben Cheikh, Tim Esemann, H. Hellbruck
Wireless systems based on WLAN (802.11), ZigBee (802.15.4) and Bluetooth (802.15.1) are continuously deployed in new applications covering consumer, industry or medical fields. Especially, Bluetooth is recommended by the Health-Care-Organization for medical applications as frequency hopping is considered as a robust scheme. However dealing with frequency-dynamic sources of interference in the 2.4GHz ISM band is important due to the increase of wireless devices. Adaptive frequency hopping (AFH) suggested by the Bluetooth standard and implemented in many of todays products identifies and avoids using bad channels. It is a good and established coexistence mechanism in the presence of frequency-static sources of interference such as WLANs when the 2.4GHz band is not crowded. However, AFH is facing problems in a crowded 2.4GHz band, especially when the interference is dynamic. We developed a cross-layer algorithm SAFH (Smooth Adaptive Frequency Hopping) that is inspired by entropy maximization and the conventional Bluetooth AFH. SAFH assigns usage probabilities to all channels based on an exponential smoothing filter for frame error rates to estimate and predict the channel conditions. The application layer can adapt SAFH by parameter settings in a cross-layer approach. SAFH achieves low average frame error rate and responds fast to changing channel conditions if required from the application. Simulative Evaluation in the presence of different types of interference (802.11b, 802.15.4 and 802.15.1) shows that our algorithm outperforms conventional frequency hopping and AFH. Additionally, SAFH works smoothly and stable exploiting frequency diversity compared to previous approaches like entropy-maximization based adaptive frequency hopping and Utility Based Adaptive Frequency Hopping (UBAFH).
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Pub Date : 2011-11-01DOI: 10.1109/IWCLD.2011.6123080
Amir Minayi Jalil, V. Meghdadi, J. Cances
This paper deals with the problem of relay assignment in cooperative networks. We consider a network which consists of N nodes and a single destination. Each node is a potential relay to help other nodes to communicate with the destination. The problem is how to assign some nodes (as relays) to some nodes (as sources) in order to optimize a convenient objective function in the network. To find the optimized topology, we need to feedback the SNR information to a centralized resource allocator. Throughout this paper, we introduce a Vehicle Routing Problem (VRP) formulation for the problem at hand which can be efficiently solved with Binary Integer Programming (BIP). The proposed formulation can solve many clustering and relay assignment problems in a unified framework. Two different scenarios are described to show this flexibility. In the first scenario, only one of the nodes in each cooperating set benefits from the cooperation whereas in the other scenario both nodes benefit. The proposed approach combines a simultaneous optimization of physical and network layers with the cooperative diversity concept. Some scenarios and network configurations are described throughout the paper to show the flexibility of the proposed method.
{"title":"A cross-layer approach to clustering and relay assignment based on Vehicle Routing Problem","authors":"Amir Minayi Jalil, V. Meghdadi, J. Cances","doi":"10.1109/IWCLD.2011.6123080","DOIUrl":"https://doi.org/10.1109/IWCLD.2011.6123080","url":null,"abstract":"This paper deals with the problem of relay assignment in cooperative networks. We consider a network which consists of N nodes and a single destination. Each node is a potential relay to help other nodes to communicate with the destination. The problem is how to assign some nodes (as relays) to some nodes (as sources) in order to optimize a convenient objective function in the network. To find the optimized topology, we need to feedback the SNR information to a centralized resource allocator. Throughout this paper, we introduce a Vehicle Routing Problem (VRP) formulation for the problem at hand which can be efficiently solved with Binary Integer Programming (BIP). The proposed formulation can solve many clustering and relay assignment problems in a unified framework. Two different scenarios are described to show this flexibility. In the first scenario, only one of the nodes in each cooperating set benefits from the cooperation whereas in the other scenario both nodes benefit. The proposed approach combines a simultaneous optimization of physical and network layers with the cooperative diversity concept. Some scenarios and network configurations are described throughout the paper to show the flexibility of the proposed method.","PeriodicalId":149596,"journal":{"name":"2011 Third International Workshop on Cross Layer Design","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125966703","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}
Much attention has been paid to schedulers exploiting multiuser diversity in wireless networks, because such schedulers can increase the information theoretic capacity. It is, however, known that there exists a tradeoff between capacity and fairness achieved by schedulers exploiting multiuser diversity. Due to its good balance between capacity and fairness, the one-bit feedback fair scheduler is considered as an attractive choice. In this paper, we consider the one-bit feedback fair scheduler and investigate its short term fairness. In particular, we consider the statistical time-access fairness index (STAFI) as a short term fairness index, and we study the impact of the initial states of mobile stations (MSs) on the STAFI. Numerical results show that the effect of the initial states of MSs on the STAFI remains for a relatively long time.
{"title":"Effect of initial states on statistical time-access fairness index of one-bit feedback fair scheduler","authors":"F. Ishizaki","doi":"10.1145/2021216.2021225","DOIUrl":"https://doi.org/10.1145/2021216.2021225","url":null,"abstract":"Much attention has been paid to schedulers exploiting multiuser diversity in wireless networks, because such schedulers can increase the information theoretic capacity. It is, however, known that there exists a tradeoff between capacity and fairness achieved by schedulers exploiting multiuser diversity. Due to its good balance between capacity and fairness, the one-bit feedback fair scheduler is considered as an attractive choice. In this paper, we consider the one-bit feedback fair scheduler and investigate its short term fairness. In particular, we consider the statistical time-access fairness index (STAFI) as a short term fairness index, and we study the impact of the initial states of mobile stations (MSs) on the STAFI. Numerical results show that the effect of the initial states of MSs on the STAFI remains for a relatively long time.","PeriodicalId":149596,"journal":{"name":"2011 Third International Workshop on Cross Layer Design","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114318387","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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