Hotspot services will be offered in small, highly-populated public places like airports, hospitals, etc. They will play their assistive roles in the people's life only if they are secure, trusted, and nonobtrusive. Some of the challenges faced are the seamless operation between WLAN-based hotspots and other emerging wireless data networks technologies, for example body sensor networks; the exploitation of context- and location-aware information provided from the hotspot service; matching the user needs with differentiated services; preserving the privacy of the user's sensitive data and anonymity. To answer these challenges, a new solution for context-aware privacy protection for any type of fine-grained user sensitive data with profiles of the user, context, scenario and service is proposed. Based on assessment of current context and situation, the user delegates actions for protecting his privacy to the proposed mechanism that acts on his behalf. The discussed solution is presented with a medical scenario. Components model, interaction sequence, algorithm for privacy safeguarding and system implementation are described.
{"title":"Context-aware privacy protection with profile management","authors":"A. Mitseva, M. Imine, N. Prasad","doi":"10.1145/1161023.1161032","DOIUrl":"https://doi.org/10.1145/1161023.1161032","url":null,"abstract":"Hotspot services will be offered in small, highly-populated public places like airports, hospitals, etc. They will play their assistive roles in the people's life only if they are secure, trusted, and nonobtrusive. Some of the challenges faced are the seamless operation between WLAN-based hotspots and other emerging wireless data networks technologies, for example body sensor networks; the exploitation of context- and location-aware information provided from the hotspot service; matching the user needs with differentiated services; preserving the privacy of the user's sensitive data and anonymity. To answer these challenges, a new solution for context-aware privacy protection for any type of fine-grained user sensitive data with profiles of the user, context, scenario and service is proposed. Based on assessment of current context and situation, the user delegates actions for protecting his privacy to the proposed mechanism that acts on his behalf. The discussed solution is presented with a medical scenario. Components model, interaction sequence, algorithm for privacy safeguarding and system implementation are described.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130080693","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}
E. G. Villegas, Lluís Faixó, R. V. Ferré, J. Aspas
Due to the increasing number of IEEE 802.11 networks, the presence of interference is becoming an important problem to solve. In a single multicell network, the harmful effect of interference is minimized thanks to network planning; but if there are different wireless networks coexisting, which besides, belong to different owners, the presence of a distributed resource management mechanism becomes the best choice. A distributed management system involves communication among all participant devices. In the present paper two mechanisms are proposed: channel allocation algorithm and load balancing through cell breathing. The questions raised by these new communication needs are analyzed and also, different solutions are proposed based on a common idea: use of Access Points (APs) with two radio interfaces adopting ad-hoc networking mechanisms for inter-AP signaling purposes.
{"title":"Inter-Access point communications for distributed resource management in 802.11 networks","authors":"E. G. Villegas, Lluís Faixó, R. V. Ferré, J. Aspas","doi":"10.1145/1161023.1161026","DOIUrl":"https://doi.org/10.1145/1161023.1161026","url":null,"abstract":"Due to the increasing number of IEEE 802.11 networks, the presence of interference is becoming an important problem to solve. In a single multicell network, the harmful effect of interference is minimized thanks to network planning; but if there are different wireless networks coexisting, which besides, belong to different owners, the presence of a distributed resource management mechanism becomes the best choice. A distributed management system involves communication among all participant devices. In the present paper two mechanisms are proposed: channel allocation algorithm and load balancing through cell breathing. The questions raised by these new communication needs are analyzed and also, different solutions are proposed based on a common idea: use of Access Points (APs) with two radio interfaces adopting ad-hoc networking mechanisms for inter-AP signaling purposes.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134542797","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}
C. Ho, K. Ramachandran, K. Almeroth, E. Belding-Royer
The advent of small form-factor devices, falling hardware prices, and the promise of untethered communication is driving the prolific deployment of wireless networks. The monitoring of such networks is crucial for their robust operation. To this end, this paper presents VISUM, a scalable framework for wireless network monitoring. VISUM relies on a distributed set of agents within the network to monitor network devices and store the collected information at data repositories. VISUM's key features are its extensibility for new functionality, and its seamless support for new devices and agents in the monitoring framework. These features enable network operators to deploy, maintain, and upgrade VISUM with little effort. VISUM can also visualize collected data in the form of interactive network topology maps as well as real-time statistical graphs and reports. These visualizations provide an intuitive, up-to-date, and useful overview of a wireless network. We have implemented VISUM and used it to monitor a wireless network deployment at UC-Santa Barbara. In this paper, we describe the architecture of VISUM and report on the performance of the monitored network using information collected by VISUM.
{"title":"A scalable framework for wireless network monitoring","authors":"C. Ho, K. Ramachandran, K. Almeroth, E. Belding-Royer","doi":"10.1145/1024733.1024745","DOIUrl":"https://doi.org/10.1145/1024733.1024745","url":null,"abstract":"The advent of small form-factor devices, falling hardware prices, and the promise of untethered communication is driving the prolific deployment of wireless networks. The monitoring of such networks is crucial for their robust operation. To this end, this paper presents VISUM, a scalable framework for wireless network monitoring. VISUM relies on a distributed set of agents within the network to monitor network devices and store the collected information at data repositories. VISUM's key features are its extensibility for new functionality, and its seamless support for new devices and agents in the monitoring framework. These features enable network operators to deploy, maintain, and upgrade VISUM with little effort. VISUM can also visualize collected data in the form of interactive network topology maps as well as real-time statistical graphs and reports. These visualizations provide an intuitive, up-to-date, and useful overview of a wireless network. We have implemented VISUM and used it to monitor a wireless network deployment at UC-Santa Barbara. In this paper, we describe the architecture of VISUM and report on the performance of the monitored network using information collected by VISUM.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"126 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123275627","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 a public WLAN hotspot, a roaming mobile terminal (MT) may be within radio range of more than one access point (AP), each of which may or may not have roaming agreements with the service provider of the user of the MT. In this case, the MT may need to discover some service information before it can make an intelligent network-selection decision. The most critical is roaming information; while other information such as security policies, price, AP workload may also be useful. Currently, roaming information is typically provisioned on the MTs as static roaming tables or roaming lists. However, this approach may not scale well when there are millions of hotspots globally. Addressing this shortcoming, recently several solutions have been proposed by different groups. In this paper, we contrast these solutions, and propose our own solution called Roaming Information Code (RIC), which can be transported as SSID or a new Information Element of the 802.11 standard. RIC is scalable and can be fully backward compatible with existing APs (if transported as SSID). Furthermore, it does not hinder fast handoffs. In the second half of the paper, we will also discuss two other schemes addressing the other service information: a scheme called RIC-VAP for provider-specific security information; and a scheme that allows an AP to announce price and workload information.
{"title":"Network selection and discovery of service information in public WLAN hotspots","authors":"Yui-Wah Lee","doi":"10.1145/1024733.1024744","DOIUrl":"https://doi.org/10.1145/1024733.1024744","url":null,"abstract":"In a public WLAN hotspot, a roaming mobile terminal (MT) may be within radio range of more than one access point (AP), each of which may or may not have roaming agreements with the service provider of the user of the MT. In this case, the MT may need to discover some <i>service information</i> before it can make an intelligent <i>network-selection</i> decision. The most critical is <i>roaming information</i>; while other information such as <i>security policies</i>, <i>price</i>, <i>AP workload</i> may also be useful. Currently, roaming information is typically provisioned on the MTs as static <i>roaming tables</i> or <i>roaming lists</i>. However, this approach may not scale well when there are millions of hotspots globally. Addressing this shortcoming, recently several solutions have been proposed by different groups. In this paper, we contrast these solutions, and propose our own solution called <i>Roaming Information Code (RIC)</i>, which can be transported as SSID or a new Information Element of the 802.11 standard. RIC is scalable and can be fully backward compatible with existing APs (if transported as SSID). Furthermore, it does not hinder fast handoffs. In the second half of the paper, we will also discuss two other schemes addressing the other service information: a scheme called <i>RIC-VAP</i> for provider-specific security information; and a scheme that allows an AP to announce price and workload information.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114867975","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}
Short Message Service (SMS) has become extremely popular in many countries, and represents a ~multi-billion dollars market. Yet many consumers consider that the price charged by the cellular network operators is too high. In this paper, we explain that there exist alternatives to cellular networks for the provision of SMS. In particular, we present the Self-Organizing Wireless messaging nEtwoRk (SOWER), an all-wireless network operable in cities. In SOWER, each user installs a wireless, power-plugged device at home and communicates by means of a mobile device. Based on our experimental measurements of IEEE 802.11 equipped devices, we show the feasibility of the concept in various urban scenarios. We also show that city-wide connectivity can be achieved even with a limited market penetration. We explain that the capacity of such networks is sufficient to support messaging communication.
{"title":"SOWER: self-organizing wireless network for messaging","authors":"M. Félegyházi, Srdjan Capkun, J. Hubaux","doi":"10.1145/1024733.1024735","DOIUrl":"https://doi.org/10.1145/1024733.1024735","url":null,"abstract":"Short Message Service (SMS) has become extremely popular in many countries, and represents a ~multi-billion dollars market. Yet many consumers consider that the price charged by the cellular network operators is too high. In this paper, we explain that there exist alternatives to cellular networks for the provision of SMS. In particular, we present the Self-Organizing Wireless messaging nEtwoRk (SOWER), an all-wireless network operable in cities. In SOWER, each user installs a wireless, power-plugged device at home and communicates by means of a mobile device. Based on our experimental measurements of IEEE 802.11 equipped devices, we show the feasibility of the concept in various urban scenarios. We also show that city-wide connectivity can be achieved even with a limited market penetration. We explain that the capacity of such networks is sufficient to support messaging communication.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117050688","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 recent years, many protocols have been developed to support mobility of wireless network nodes, e.g. Mobile IP suite of protocols designed to support IP routing to mobile nodes. However, support for truly seamless mobility requires more than just routing; every service associated with the mobile user needs to be transferred smoothly to the new access network. In this paper, we consider the problem of transferring service state (context) at both the link and IP layers. Based on the rate of SNR change in the wireless access channel, we propose a scheme that proactively transfers context information associated with the mobile user. The proposed scheme estimates the best moment in time for transferring context information, to assure the shortest waiting time of the transferred context at the new access network. We also propose and describe a new concept, forced handover, helpful in proactive transfer of context information when the mobile node moves from one access sub network to another. We present preliminary simulation results and a discussion on the performance of the proposed scheme. The scheme is shown to be helpful in ensuring seamless mobility, while the number of unnecessary handovers resulting from the proactive nature of the scheme can be kept at a controllable level.
{"title":"Proactive context transfer in WLAN-based access networks","authors":"H. Duong, A. Dadej, S. Gordon","doi":"10.1145/1024733.1024742","DOIUrl":"https://doi.org/10.1145/1024733.1024742","url":null,"abstract":"In recent years, many protocols have been developed to support mobility of wireless network nodes, e.g. Mobile IP suite of protocols designed to support IP routing to mobile nodes. However, support for truly seamless mobility requires more than just routing; every service associated with the mobile user needs to be transferred smoothly to the new access network. In this paper, we consider the problem of transferring service state (context) at both the link and IP layers. Based on the rate of SNR change in the wireless access channel, we propose a scheme that proactively transfers context information associated with the mobile user. The proposed scheme estimates the best moment in time for transferring context information, to assure the shortest waiting time of the transferred context at the new access network. We also propose and describe a new concept, forced handover, helpful in proactive transfer of context information when the mobile node moves from one access sub network to another. We present preliminary simulation results and a discussion on the performance of the proposed scheme. The scheme is shown to be helpful in ensuring seamless mobility, while the number of unnecessary handovers resulting from the proactive nature of the scheme can be kept at a controllable level.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123344789","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 recent years, wireless Internet service providers (WISPs) have established thousands of WiFi hot spots in cafes, hotels and airports in order to offer to travelling Internet users access to email, web or other Internet service. However, two major problems still slow down the deployment of this kind of networks: the lack of a seamless roaming scheme and the variable quality of service experienced by the users. This paper provides a response to these two problems: We present a solution that, on the one hand, allows a mobile node to connect to a foreign WISP in a secure way while preserving its anonymity and, on the other hand, encourages the WISPs to provide the users with good QoS. We analyse the robustness of our solution against various attacks and we prove by means of simulations that our reputation model indeed encourages the WISPs to behave correctly.
{"title":"Reputation-based Wi-Fi deployment protocols and security analysis","authors":"N. Salem, J. Hubaux, M. Jakobsson","doi":"10.1145/1024733.1024738","DOIUrl":"https://doi.org/10.1145/1024733.1024738","url":null,"abstract":"In recent years, wireless Internet service providers (WISPs) have established thousands of WiFi hot spots in cafes, hotels and airports in order to offer to travelling Internet users access to email, web or other Internet service. However, two major problems still slow down the deployment of this kind of networks: the lack of a seamless roaming scheme and the variable quality of service experienced by the users. This paper provides a response to these two problems: We present a solution that, on the one hand, allows a mobile node to connect to a foreign WISP in a secure way while preserving its anonymity and, on the other hand, encourages the WISPs to provide the users with good QoS. We analyse the robustness of our solution against various attacks and we prove by means of simulations that our reputation model indeed encourages the WISPs to behave correctly.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130550754","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}
G. Manjunath, T. Simunic, V. Krishnan, J. Tourrilhes, D. Das, V. Srinivasmurthy, A. McReynolds
Wireless access at cafes, airports, homes and businesses have proliferated all over the globe with several different Wireless Internet Service Providers. Similarly, digital media has created a paradigm shift in media processing resulting in a complete change in media usage models, revamped existing businesses and has introduced new industry players. We believe there is a tremendous opportunity for application and system services at the intersection of the above two domains for exploiting the wireless connectivity to provide ease of use in handling media. In this paper, we propose a feature-rich, secure wireless service delivery framework over enhanced public access points (called Smart Edge Servers), which provides the right platform for deployment of specialized services to the mobile users. The Smart Edge Server provides secure wireless access to the clients, has sophisticated media handling and storage capabilities and uses advanced techniques to manage resources available to it, such as bandwidth, power and the type of connectivity. A prototype implementation of our Smart Edge Server has been built that implements all the features discussed above.
{"title":"Smart edge server: beyond a wireless access point","authors":"G. Manjunath, T. Simunic, V. Krishnan, J. Tourrilhes, D. Das, V. Srinivasmurthy, A. McReynolds","doi":"10.1145/1024733.1024739","DOIUrl":"https://doi.org/10.1145/1024733.1024739","url":null,"abstract":"Wireless access at cafes, airports, homes and businesses have proliferated all over the globe with several different Wireless Internet Service Providers. Similarly, digital media has created a paradigm shift in media processing resulting in a complete change in media usage models, revamped existing businesses and has introduced new industry players. We believe there is a tremendous opportunity for application and system services at the intersection of the above two domains for exploiting the wireless connectivity to provide ease of use in handling media. In this paper, we propose a feature-rich, secure wireless service delivery framework over enhanced public access points (called Smart Edge Servers), which provides the right platform for deployment of specialized services to the mobile users. The Smart Edge Server provides secure wireless access to the clients, has sophisticated media handling and storage capabilities and uses advanced techniques to manage resources available to it, such as bandwidth, power and the type of connectivity. A prototype implementation of our Smart Edge Server has been built that implements all the features discussed above.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129283921","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 Publish-Subscribe paradigm has become an important architectural style for designing distributed systems. In the recent years, we have been witnessing an increasing demand for supporting publish-subscribe for mobile systems in wireless environments. In this paper we present SUBLIM, a stateful model for publish-subscribe systems, which is suitable for mobile systems. In our system, the server maintains a state for each client, which contains variables that describe the properties of particular clients, such as the quality of the connection or the battery utilization. The interest of each subscriber can be expressed in terms of these variables. Based on the subscriber interests, an associated agent is created on the server. The agent filters the data that reach the subscriber based on the content of the message and the current subscriber state. Experimental results show good performance and scalability of our approach.
{"title":"Stateful publish-subscribe for mobile environments","authors":"M. Ionescu, I. Marsic","doi":"10.1145/1024733.1024737","DOIUrl":"https://doi.org/10.1145/1024733.1024737","url":null,"abstract":"The Publish-Subscribe paradigm has become an important architectural style for designing distributed systems. In the recent years, we have been witnessing an increasing demand for supporting publish-subscribe for mobile systems in wireless environments. In this paper we present SUBLIM, a stateful model for publish-subscribe systems, which is suitable for mobile systems. In our system, the server maintains a state for each client, which contains variables that describe the properties of particular clients, such as the quality of the connection or the battery utilization. The interest of each subscriber can be expressed in terms of these variables. Based on the subscriber interests, an associated agent is created on the server. The agent filters the data that reach the subscriber based on the content of the message and the current subscriber state. Experimental results show good performance and scalability of our approach.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129460313","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}
Chi-hsien Lin, Hui Dong, Upamanyu Madhow, A. Gersho
We consider the problem of supporting real-time traffic over packetized wireless ad hoc networks. Our specific emphasis is on speech, since this is a critical application in many scenarios such as emergency deployment of ad hoc networks. Standard retransmission-based Medium Access Control (MAC) strategies are poorly matched to speech applications, because the payload size for speech as well as for MAC-layer acknowledgements (ACKs) is small compared to the packet header, which contains a large synchronization preamble. In this paper, we show that inter-packet redundancy is significantly more efficient than traditional MAC layer retransmissions, in terms of both network capacity and end-to-end delay. The key observations regarding our design and results are as follows. Because of the small payloads, introducing redundancy across packets only increases the packet transmission time slightly, and hence has negligible impact on the packet collision rate. Thus, we obtain large gains from redundant transmission essentially "for free." Because of the large packet header, elimination of ACKs leads to substantial bandwidth savings. Overall, a combination of inter-packet redundancy (at the MAC layer), path diversity (at the network layer), and multiple description source coding (at the application layer), is shown to provide significant improvements in bandwidth efficiency and delay.
{"title":"Supporting real-time speech on wireless ad hoc networks: inter-packet redundancy, path diversity, and multiple description coding","authors":"Chi-hsien Lin, Hui Dong, Upamanyu Madhow, A. Gersho","doi":"10.1145/1024733.1024736","DOIUrl":"https://doi.org/10.1145/1024733.1024736","url":null,"abstract":"We consider the problem of supporting real-time traffic over packetized wireless ad hoc networks. Our specific emphasis is on speech, since this is a critical application in many scenarios such as emergency deployment of ad hoc networks. Standard retransmission-based Medium Access Control (MAC) strategies are poorly matched to speech applications, because the payload size for speech as well as for MAC-layer acknowledgements (ACKs) is small compared to the packet header, which contains a large synchronization preamble. In this paper, we show that inter-packet redundancy is significantly more efficient than traditional MAC layer retransmissions, in terms of both network capacity and end-to-end delay. The key observations regarding our design and results are as follows. Because of the small payloads, introducing redundancy across packets only increases the packet transmission time slightly, and hence has negligible impact on the packet collision rate. Thus, we obtain large gains from redundant transmission essentially \"for free.\" Because of the large packet header, elimination of ACKs leads to substantial bandwidth savings. Overall, a combination of inter-packet redundancy (at the MAC layer), path diversity (at the network layer), and multiple description source coding (at the application layer), is shown to provide significant improvements in bandwidth efficiency and delay.","PeriodicalId":441921,"journal":{"name":"Wireless Mobile Applications and Services on WLAN Hotspots","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130785537","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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