32 research outputs found
Cooperative Energy-efficient Management of Federated WiFi Networks
The proliferation of overlapping, always-on IEEE 802.11 access points (APs) in urban areas, can cause inefficient bandwidth usage and energy waste. Cooperation among APs could address these problems by allowing underused devices to hand over their wireless stations to nearby APs and temporarily switch off, while avoiding to overload a BSS and thus offloading congested APs. The federated house model provides an appealing backdrop to implement cooperation among APs. In this paper, we outline a distributed framework that assumes the presence of a multipurpose gateway with AP capabilities in every household. Our framework allows cooperation through the monitoring of local wireless resources and the triggering of offloading requests toward other federated gateways. Our simulation results show that, in realistic residential settings, the proposed framework yields an energy saving between 45 and 86 percent under typical usage patterns, while avoiding congestion and meeting user expectations in terms of throughput. Furthermore, we show the feasibility and the benefits of our framework with a real test-bed deployed on commodity hardware
Cooperation Strategies for Enhanced Connectivity at Home
WHILE AT HOME , USERS MAY EXPERIENCE A POOR I NTERNET SERVICE while being connected to their 802.11 Access Points (APs). The AP is just one component
of the Internet Gateway (GW) that generally includes a backhaul connection (ADSL, fiber,etc..) and a router providing a LAN. The root cause of performance degradation may be poor/congested wireless channel between the user and the GW or congested/bandwidth limited backhaul connection.
The latter is a serious issue for DSL users that are located far from the central office because the greater the distance the lesser the achievable physical datarate. Furthermore, the GW is one of the few devices in the home that is left always on, resulting in energy waste and electromagnetic pollution increase. This thesis proposes two strategies to enhance Internet connectivity at home by (i) creating a wireless resource sharing scheme through the federation and the coordination of neighboring GWs in order to achieve energy efficiency while avoiding congestion, (ii) exploiting different king of connectivities, i.e., the wired plus the cellular (3G/4G) connections, through the aggregation of the available bandwidth across multiple access technologies.
In order to achieve the aforementioned strategies we study and develop:
โข A viable interference estimation technique for 802.11 BSSes that can be implemented on commodity hardware at the MAC layer, without requiring active measurements, changes in the 802.11 standard, cooperation from the wireless stations (WSs). We extend previous theoretical results on the saturation throughput in order to quantify the impact in term of throughput loss of any kind of interferer. We im- plement and extensively evaluate our estimation technique with a real testbed and with different kind of interferer, achieving always good accuracy.
โข Two available bandwidth estimation algorithms for 802.11 BSSes that rely only on passive measurements and that account for different kind of interferers on the ISM band. This algorithms can be implemented on commodity hardware, as they require only software modifications. The first algorithm applies to intra-GW while the second one applies to inter-GW available bandwidth estimation. Indeed, we use the first algorithm to compute the metric for assessing the Wi-Fi load of a GW and the second one to compute the metric to decide whether accept incoming WSs from neighboring GWs or not. Note that in the latter case it is assumed that one or more WSs with known traffic profile are requested to relocate from one GW to another
one. We evaluate both algorithms with simulation as well as with a real test-bed for different traffic patterns, achieving high precision.
โข A fully distributed and decentralized inter-access point protocol for federated GWs that allows to dynamically manage the associations of the wireless stations (WSs) in the federated network in order to achieve energy efficiency and offloading con- gested GWs, i.e, we keep a minimum number of GWs ON while avoiding to create congestion and real-time throughput loss. We evaluate this protocol in a federated scenario, using both simulation and a real test-bed, achieving up to 65% of energy saving in the simulated setting. We compare the energy saving achieved by our protocol against a centralized optimal scheme, obtaining close to optimal results.
โข An application level solution that accelerates slow ADSL connections with the parallel use of cellular (3G/4G) connections. We study the feasibility and the potential performance of this scheme at scale using both extensive throughput measurement of the cellular network and trace driven analysis. We validate our solution by implementing a real test bed and evaluating it โin the wild, at several residential locations of a major European city. We test two applications: Video-on-Demand (VoD) and picture upload, obtaining remarkable throughput increase for both applications at all locations. Our implementation features a multipath scheduler which we compare to other scheduling policies as well as to transport level solution like MTCP, obtaining always better results
IEEE 802.11 ๊ธฐ๋ฐ Enterprise ๋ฌด์ LAN์ ์ํ ์์ ๊ด๋ฆฌ ๊ธฐ๋ฒ
ํ์๋
ผ๋ฌธ (๋ฐ์ฌ)-- ์์ธ๋ํ๊ต ๋ํ์ : ๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ปดํจํฐ๊ณตํ๋ถ, 2019. 2. ์ ํ์.IEEE 802.11์ด ๋ฌด์ LAN (wireless local area network, WLAN)์ ์ค์ง์ ์ธ ํ์ค์ด ๋จ์ ๋ฐ๋ผ ์ ๋ง์ ์์ธ์ค ํฌ์ธํธ(access points, APs)๊ฐ ๋ฐฐ์น๋์๊ณ , ๊ทธ ๊ฒฐ๊ณผ WLAN ๋ฐ์ง ํ๊ฒฝ์ด ์กฐ์ฑ๋์๋ค. ์ด๋ฌํ ํ๊ฒฝ์์๋, ์ด์ํ AP๋ค์ ๋์ผํ ์ฑ๋์ ํ ๋นํ๋ ๋ฌธ์ ๋ฅผ ํผํ ์ ์์ผ๋ฉฐ, ์ด๋ ํด๋น AP๋ค์ด ๊ฐ์ ์ฑ๋์ ๊ณต์ ํ๊ฒ ํ๊ณ ๊ทธ๋ก ์ธํ ๊ฐ์ญ์ ์ผ๊ธฐํ๋ค. ๊ฐ์ญ์ผ๋ก ์ธํ ์ฑ๋ฅ ์ ํ๋ฅผ ์ค์ด๊ธฐ ์ํด ์ฑ๋ ํ ๋น(channelization) ๊ธฐ๋ฒ์ด ์ค์ํ๋ค. ๋ํ, ํ ์กฐ์ง์ด ํน์ ์ง์ญ์ ๋ฐ์ง ๋ฐฐ์น๋ AP๋ค์ ๊ด๋ฆฌํ๋ค๋ฉด ํน์ ์ฌ์ฉ์๋ฅผ ์๋น์คํ ์ ์๋ AP๊ฐ ์ฌ๋ฟ์ผ ์ ์๋ค. ์ด ๊ฒฝ์ฐ, ์ฌ์ฉ์ ์ ์(user association, UA) ๊ธฐ๋ฒ์ด ์ค์ ์ (quasi-static) ํ๊ฒฝ๊ณผ ์ฐจ๋ ํ๊ฒฝ ๋ชจ๋์์ ๋คํธ์ํฌ ์ฑ๋ฅ์ ํฐ ์ํฅ์ ๋ฏธ์น๋ค. ๋ณธ ๋
ผ๋ฌธ์์๋ ๋ฐ์ง ๋ฐฐ์น๋ WLAN ํ๊ฒฝ์์ ์์ดํ์ด(WiFi) ์ฑ๋ฅ ํฅ์์ ์ํด ์ฑ๋ ํ ๋น ๊ธฐ๋ฒ์ ์ ์ํ๋ค. ๋จผ์ , ์ ์ํ ๊ธฐ๋ฒ์์๋ ๊ฐ๊ฐ์ AP์ ์ฑ๋์ ํ ๋นํ๊ธฐ ์ํด ๊ฐ์ญ ๊ทธ๋ํ(interference graph)๋ฅผ ์ด์ฉํ๋ฉฐ ์ฑ๋ ๊ฒฐํฉ(channel bonding)์ ๊ณ ๋ คํ๋ค. ๋ค์์ผ๋ก, ์ฃผ์ด์ง ์ฑ๋ ๊ฒฐํฉ ๊ฒฐ๊ณผ๋ฅผ ๊ธฐ๋ฐ์ผ๋ก ํด๋น AP๊ฐ ๋์ ์ฑ๋ ๊ฒฐํฉ์ ์ง์ํ๋์ง ์ฌ๋ถ์ ๋ฐ๋ผ ์ฃผ ์ฑ๋(primary channel)์ ๊ฒฐ์ ํ๋ค.
ํํธ, ์ค์ ์ ํ๊ฒฝ๊ณผ ์ฐจ๋ ํ๊ฒฝ์์์ UA ๋ฌธ์ ๋ ๋ค์ ์ฐจ์ด๊ฐ ์๋ค. ๋ฐ๋ผ์ ๋ณธ ๋
ผ๋ฌธ์์๋ ๊ฐ๊ฐ์ ํ๊ฒฝ์ ๋ฐ๋ผ ์๋ก ๋ค๋ฅธ UA ๊ธฐ๋ฒ์ ์ค๊ณํ์๋ค. ์ค์ ์ ํ๊ฒฝ์์์ UA ๊ธฐ๋ฒ์ ๋ฉํฐ์บ์คํธ ์ ์ก, ๋ค์ค ์ฌ์ฉ์ MIMO (multi-user multiple input multiple output), ๊ทธ๋ฆฌ๊ณ AP ์๋ฉด๊ณผ ๊ฐ์ ๋ค์ํ ๊ธฐ์ ๊ณผ ํจ๊ป AP๊ฐ์ ๋ถํ ๋ถ์ฐ(load balancing)๊ณผ ์๋์ง ์ ์ฝ์ ๊ณ ๋ คํ๋ค. ์ ์ํ๋ ๊ธฐ๋ฒ์์ UA ๋ฌธ์ ๋ ๋ค๋ชฉ์ ํจ์ ์ต์ ํ ๋ฌธ์ ๋ก ์ ์ํํ์๊ณ ๊ทธ ํด๋ฅผ ๊ตฌํ์๋ค. ์ฐจ๋ ํ๊ฒฝ์์์ UA ๊ธฐ๋ฒ์ ํธ๋์ค๋ฒ(handover, HO) ์ค์ผ์ค ๋ฌธ์ ๋ก ๊ท๊ฒฐ๋๋ค. ๋ณธ ๋
ผ๋ฌธ์์๋ ๋๋ก์ ์งํ์ ๊ณ ๋ คํ์ฌ ์ฌ์ฉ์๊ฐ ์ ์ํ AP๋ฅผ ๊ฒฐ์ ํ๋ HO ์ค์ผ์ค ๊ธฐ๋ฒ์ ์ ์ํ๋ค. ์ฌ์ฉ์๋ ๋จ์ง ๋ค์ AP๋ก ์ฐ๊ฒฐ์ ๋งบ์ ์๊ธฐ๋ง ๊ฒฐ์ ํ๋ฉด ๋๊ธฐ ๋๋ฌธ์, ์ฐจ๋ ํ๊ฒฝ์์์ ๋งค์ฐ ๋น ๋ฅด๊ณ ํจ์จ์ ์ธ HO ๊ธฐ๋ฒ์ ๊ตฌํํ ์ ์๋ค. ์ด๋ฅผ ์ํด, ๊ทธ๋ํ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ(graph modeling technique)์ ํ์ฉํ์ฌ ๋๋ก๋ฅผ ๋ฐ๋ผ ๋ฐฐ์น๋ AP์ฌ์ด์ ๊ด๊ณ๋ฅผ ํํํ๋ค. ํ์ค์ ์ธ ์๋๋ฆฌ์ค๋ฅผ ์ํด ์ง์ ๊ตฌ๊ฐ, ์ฐํ ๊ตฌ๊ฐ, ๊ต์ฐจ๋ก, ๊ทธ๋ฆฌ๊ณ ์ ํด ๊ตฌ๊ฐ ๋ฑ์ ํฌํจํ๋ ๋ณต์กํ ๋๋ก ๊ตฌ์กฐ๋ฅผ ๊ณ ๋ คํ๋ค. ๋๋ก ๊ตฌ์กฐ๋ฅผ ๊ณ ๋ คํ์ฌ ๊ฐ ์ฌ์ฉ์์ ์ด๋ ๊ฒฝ๋ก๋ฅผ ์์ธกํ๊ณ , ๊ทธ์ ๊ธฐ๋ฐํ์ฌ ๊ฐ ์ฌ์ฉ์ ๋ณ HO์ ๋ชฉ์ AP ์งํฉ์ ์ ํํ๋ค. ์ ์ํ๋ HO ์ค์ผ์ค ๊ธฐ๋ฒ์ ์ค๊ณ ๋ชฉ์ ์ HO ์ง์ฐ ์๊ฐ์ ํฉ์ ์ต์ํํ๊ณ ๊ฐ AP์์ ํด๋น ์ฑ๋์ ์ฌ์ฉํ๋ ค๋ ์ฌ์ฉ์ ์๋ฅผ ์ค์ด๋ฉด์ WiFi ์ฐ๊ฒฐ ์๊ฐ์ ์ต๋ํํ๋ ๊ฒ์ด๋ค. ๋ง์ง๋ง์ผ๋ก, ๋ณธ ๋
ผ๋ฌธ์์๋ ์ค์ ์ ํ๊ฒฝ์์ ์ ์ํ ์ฑ๋ ํ ๋น ๊ธฐ๋ฒ๊ณผ UA ๊ธฐ๋ฒ์ ํ์ค์ฑ์ ์ฆ๋ช
ํ๊ธฐ ์ํ ์ํ๋(testbed)๋ฅผ ๊ตฌ์ฑํ์๋ค. ๋ํ, ๊ด๋ฒ์ํ ์๋ฎฌ๋ ์ด์
์ ํตํด ์ค์ ์ ํ๊ฒฝ๊ณผ ์ฐจ๋ ํ๊ฒฝ์์ ์ ์ํ ๊ธฐ๋ฒ๋ค๊ณผ ๊ธฐ์กด์ ๊ธฐ๋ฒ๋ค์ ์ฑ๋ฅ์ ๋น๊ตํ์๋ค.As the IEEE 802.11 (WiFi) becomes the defacto global standard for wireless local area network (WLAN), a huge number of WiFi access points (APs) are deployed. This condition leads to a densely deployed WLANs.
In such environment, the conflicting channel allocation between the neighboring access points (APs) is unavoidable, which causes the channel sharing and interference between APs. Thus, the channel allocation (channelization) scheme has a critical role to tackle this issue. In addition, when densely-deployed APs covering a certain area are managed by a single organization, there can exist multiple candidate APs for serving a user. In this case, the user association (UA), i.e., the selection of serving AP, holds a key role in the network performance both in quasi-static and vehicular environments. To improve the performance of WiFi in a densely deployed WLANs environment, we propose a channelization scheme. The proposed channelization scheme utilizes the interference graph to assign the channel for each AP and considers channel bonding.
Then, given the channel bonding assignment, the primary channel location for each AP is determined by observing whether the AP supports the static or dynamic channel bonding.
Meanwhile, the UA problem in the quasi-static and vehicular environments are slightly different. Thus, we devise UA schemes both for quasi-static and vehicular environments. The UA schemes for quasi-static environment takes account the load balancing among APs and energy saving, considering various techniques for performance improvement, such as multicast transmission, multi-user MIMO, and AP sleeping, together.
Then, we formulate the problem into a multi-objective optimization and get the solution as the UA scheme.
On the other hand, the UA scheme in the vehicular environment is realized through handover (HO) scheduling mechanism. Specifically, we propose a HO scheduling scheme running on a server, which determines the AP to which a user will be handed over, considering the road topology. Since a user only needs to decide when to initiate the connection to the next AP, a very fast and efficient HO in the vehicular environment can be realized. For this purpose, we utilize the graph modeling technique to map the relation between APs within the road. We consider a practical scenario where the structure of the road is complex, which includes straight, curve, intersection, and u-turn area. Then, the set of target APs for HO are selected for each user moving on a particular road based-on its moving path which is predicted considering the road topology. The design objective of the proposed HO scheduling is to maximize the connection time on WiFi while minimizing the total HO latency and reducing the number of users which contend for the channel within an AP.
Finally, we develop a WLAN testbed to demonstrate the practicality and feasibility of the proposed channelization and UA scheme in a quasi-static environment. Furthermore, through extensive simulations, we compare the performance of the proposed schemes with the existing schemes both in quasi-static and vehicular environments.1 Introduction
1.1 Background and Motivation
1.2 Related Works
1.3 Research Scope and Proposed Schemes
1.3.1 Centralized Channelization Scheme for Wireless LANs Exploiting Channel Bonding
1.3.2 User Association for Load Balancing and Energy Saving in Enterprise WLAN
1.3.3 A Graph-Based Handover Scheduling for Heterogenous Vehicular Networks
1.4 Organization
2 Centralized Channelization Scheme for Wireless LANs Exploiting Channel Bonding
2.1 System Model
2.2 Channel Sharing and Bonding
2.2.1 Interference between APs
2.2.2 Channel Sharing
2.2.3 Channel Bonding
2.3 Channelization Scheme
2.3.1 Building Interference Graph
2.3.2 Channel Allocation
2.3.3 Primary Channel Selection
2.4 Implementation
3 User Association for Load Balancing and Energy Saving in Enterprise Wireless LANs
3.1 System Model
3.1.1 IEEE 802.11 ESS-based Enterprise WLAN
3.1.2 Downlink Achievable Rate for MU-MIMO Groups
3.1.3 Candidate MU-MIMO Groups
3.2 User Association Problem
3.2.1 Factors of UA Objective
3.2.2 Problem Formulation
3.3 User Association Scheme
3.3.1 Equivalent Linear Problem
3.3.2 Solution Algorithm
3.3.3 Computational Complexity (Execution Time)
3.4 Implementation
4 A Graph-Based Handover Scheduling for Heterogenous Vehicular Networks
4.1 System Model
4.2 Graph-Based Modeling
4.2.1 Division of Road Portion into Road Segments
4.2.2 Relation between PoAs on a Road Segment
4.2.3 Directed Graph Representation
4.3 Handover Scheduling Problem
4.3.1 Problem Formulation
4.3.2 Weight of Edge
4.3.3 HO Scheduling Algorithm
4.4 Handover Scheduling Operation
4.4.1 HO Schedule Delivery
4.4.2 HO Triggering and Execution
4.4.3 Communication Overhead
5 Performance Evaluation
5.1 CentralizedChannelizationSchemeforWirelessLANsExploitingChannel Bonding
5.1.1 Experiment Settings
5.1.2 Comparison Schemes
5.1.3 Preliminary Experiment for Building Interference Graph
5.1.4 Experiment Results
5.2 User Association for Load Balancing and Energy Saving in Enterprise Wireless LANs
5.2.1 Performance Metrics
5.2.2 Experiment Settings
5.2.3 Experiment Results
5.2.4 Simulation Settings
5.2.5 Comparison Schemes
5.2.6 Simulation Results
5.2.7 Simulation for MU-MIMO System
5.3 A Graph-BasedHandover Scheduling for Heterogenous Vehicular Networks
5.3.1 Performance Metrics
5.3.2 Simulation Settings
5.3.3 Simulation Results
6 Conculsion
Bibliography
AcknowledgementsDocto
Reliable Multicast transport of the video over the WiFi network
Le transport multicast est une solution efficace pour envoyer le mรชme contenu ร plusieurs rรฉcepteurs en mรชme temps. Ce mode est principalement utilisรฉ pour fournir des flux multimรฉdia en temps rรฉel. Cependant, le multicast classique de l IEEE 802.11 n'utilise aucun mรฉcanisme d acquittement. Ainsi, l รฉchec de rรฉception implique la perte dรฉfinitive du paquet. Cela limite la fiabilitรฉ du transport multicast et impact la qualitรฉ des applications vidรฉo. Pour rรฉsoudre ce problรจme, 802.11v et 802.11aa sont dรฉfinis rรฉcemment. Le premier amendement propose Direct Multicast Service (DMS). D'autre part, le 802.11aa introduit GroupCast with Retries (GCR). GCR dรฉfinit deux nouvelles politiques de retransmission : Block Ack (BACK) et Unsolicited Retry (UR).Dans cette thรจse, nous รฉvaluons et comparons les performances de 802.11v/aa. Nos rรฉsultats montrent que tous les nouveaux protocoles multicast gรฉnรจrent un overhead de transmission important. En outre, DMS a une scalabilitรฉ trรจs limitรฉe, et GCR-BACK n'est pas appropriรฉ pour des grands groupes multicast. D autre part, nous montrons que DMS et GCR-BACK gรฉnรจrent des latences de transmission importantes lorsque le nombre de rรฉcepteurs augmente. Par ailleurs, nous รฉtudions les facteurs de pertes dans les rรฉseaux sans fil. Nous montrons que l'indisponibilitรฉ du rรฉcepteur peut รชtre la cause principale des pertes importantes et de leur nature en rafales. En particulier, nos rรฉsultats montrent que la surcharge du processeur peut provoquer un taux de perte de 100%, et que le pourcentage de livraison peut รชtre limitรฉ ร 35% lorsque la carte 802.11 est en mode d รฉconomie d'รฉnergie.Pour รฉviter les collisions et amรฉliorer la fiabilitรฉ du transport multicast, nous dรฉfinissons le mรฉcanisme Busy Symbol (BS). Nos rรฉsultats montrent que BS รฉvite les collisions et assure un taux de succรจs de transmission trรจs important. Afin d'amรฉliorer davantage la fiabilitรฉ du trafic multicast, nous dรฉfinissons un nouveau protocole multicast, appelรฉ Block Negative Acknowledgement (BNAK). Ce protocole opรจre comme suit. L AP envoi un bloc de paquets suivi par un Block NAK Request (BNR). Le BNR permet aux membres de dรฉtecter les donnรฉes manquantes et d envoyer une demande de retransmission, c.ร .d. un Block NAK Response (BNAK). Un BNAK est transmis en utilisant la procรฉdure classique d accรจs au canal afin d'รฉviter toute collision avec d'autres paquets. En plus, cette demande est acquittรฉe. Sous l'hypothรจse que 1) le rรฉcepteur est situรฉ dans la zone de couverture du dรฉbit de transmission utilisรฉ, 2) les collisions sont รฉvitรฉes et 3) le terminal a la bonne configuration, trรจs peu de demandes de retransmission sont envoyรฉes, et la bande passante est prรฉservรฉe. Nos rรฉsultats montrent que BNAK a une trรจs grande scalabilitรฉ et gรฉnรจre des dรฉlais trรจs limitรฉs. En outre, nous dรฉfinissons un algorithme d'adaptation de dรฉbit pour BNAK. Nous montrons que le bon dรฉbit de transmission est sรฉlectionnรฉ moyennant un overhead trรจs rรฉduit de moins de 1%. En plus, la conception de notre protocole supporte la diffusion scalable de lavvidรฉo. Cette caractรฉristique vise ร rรฉsoudre la problรฉmatique de la fluctuation de la bande passante, et ร prendre en considรฉration l'hรฉtรฉrogรฉnรฉitรฉ des rรฉcepteurs dans un rรฉseau sans fil.The multicast transport is an efficient solution to deliver the same content to many receivers at the same time. This mode is mainly used to deliver real-time video streams. However, the conventional multicast transmissions of IEEE 802.11 do not use any feedback policy. Therefore missing packets are definitely lost. This limits the reliability of the multicast transport and impacts the quality of the video applications. To resolve this issue, the IEEE 802.11v/aa amendments have been defined recently. The former proposes the Direct Multicast Service (DMS). On the other hand, 802.11aa introduces Groupcast with Retries (GCR) service. GCR defines two retry policies: Block Ack (BACK) and Unsolicited Retry (UR).In this thesis we evaluate and compare the performance of 802.11v/aa. Our simulation results show that all the defined policies incur an important overhead. Besides, DMS has a very limited scalability, and GCR-BACK is not appropriate for large multicast groups. We show that both DMS and GCR-BACK incur important transmission latencies when the number of the multicast receivers increases. Furthermore, we investigate the loss factors in wireless networks. We show that the device unavailability may be the principal cause of the important packet losses and their bursty nature. Particularly, our results show that the CPU overload may incur a loss rate of 100%, and that the delivery ratio may be limited to 35% when the device is in the power save mode.To avoid the collisions and to enhance the reliability of the multicast transmissions, we define the Busy Symbol (BS) mechanism. Our results show that BS prevents all the collisions and ensures a very high delivery ratio for the multicast packets. To further enhance the reliability of this traffic, we define the Block Negative Acknowledgement (BNAK) retry policy. Using our protocol, the AP transmits a block of multicast packets followed by a Block NAK Request (BNR). Upon reception of a BNR, a multicast member generates a Block NAK Response (BNAK) only if it missed some packets. A BNAK is transmitted after channel contention in order to avoid any eventual collision with other feedbacks, and is acknowledged. Under the assumption that 1) the receiver is located within the coverage area of the used data rate, 2) the collisions are avoided and 3) the terminal has the required configuration, few feedbacks are generated and the bandwidth is saved. Our results show that BNAK has a very high scalability and incurs very low delays. Furthermore, we define a rate adaptation scheme for BNAK. We show that the appropriate rate is selected on the expense of a very limited overhead of less than 1%. Besides, the conception of our protocol is defined to support the scalable video streaming. This capability intends to resolve the bandwidth fluctuation issue and to consider the device heterogeneity of the group members.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF
Cooperation Strategies for Enhanced Connectivity at Home
WHILE AT HOME , USERS MAY EXPERIENCE A POOR I NTERNET SERVICE while being connected to their 802.11 Access Points (APs). The AP is just one component of the Internet Gateway (GW) that generally includes a backhaul connection (ADSL, fiber,etc..) and a router providing a LAN. The root cause of performance degradation may be poor/congested wireless channel between the user and the GW or congested/bandwidth limited backhaul connection. The latter is a serious issue for DSL users that are located far from the central office because the greater the distance the lesser the achievable physical datarate. Furthermore, the GW is one of the few devices in the home that is left always on, resulting in energy waste and electromagnetic pollution increase. This thesis proposes two strategies to enhance Internet connectivity at home by (i) creating a wireless resource sharing scheme through the federation and the coordination of neighboring GWs in order to achieve energy efficiency while avoiding congestion, (ii) exploiting different king of connectivities, i.e., the wired plus the cellular (3G/4G) connections, through the aggregation of the available bandwidth across multiple access technologies. In order to achieve the aforementioned strategies we study and develop: โข A viable interference estimation technique for 802.11 BSSes that can be implemented on commodity hardware at the MAC layer, without requiring active measurements, changes in the 802.11 standard, cooperation from the wireless stations (WSs). We extend previous theoretical results on the saturation throughput in order to quantify the impact in term of throughput loss of any kind of interferer. We im- plement and extensively evaluate our estimation technique with a real testbed and with different kind of interferer, achieving always good accuracy. โข Two available bandwidth estimation algorithms for 802.11 BSSes that rely only on passive measurements and that account for different kind of interferers on the ISM band. This algorithms can be implemented on commodity hardware, as they require only software modifications. The first algorithm applies to intra-GW while the second one applies to inter-GW available bandwidth estimation. Indeed, we use the first algorithm to compute the metric for assessing the Wi-Fi load of a GW and the second one to compute the metric to decide whether accept incoming WSs from neighboring GWs or not. Note that in the latter case it is assumed that one or more WSs with known traffic profile are requested to relocate from one GW to another one. We evaluate both algorithms with simulation as well as with a real test-bed for different traffic patterns, achieving high precision. โข A fully distributed and decentralized inter-access point protocol for federated GWs that allows to dynamically manage the associations of the wireless stations (WSs) in the federated network in order to achieve energy efficiency and offloading con- gested GWs, i.e, we keep a minimum number of GWs ON while avoiding to create congestion and real-time throughput loss. We evaluate this protocol in a federated scenario, using both simulation and a real test-bed, achieving up to 65% of energy saving in the simulated setting. We compare the energy saving achieved by our protocol against a centralized optimal scheme, obtaining close to optimal results. โข An application level solution that accelerates slow ADSL connections with the parallel use of cellular (3G/4G) connections. We study the feasibility and the potential performance of this scheme at scale using both extensive throughput measurement of the cellular network and trace driven analysis. We validate our solution by implementing a real test bed and evaluating it "in the wild, at several residential locations of a major European city. We test two applications: Video-on-Demand (VoD) and picture upload, obtaining remarkable throughput increase for both applications at all locations. Our implementation features a multipath scheduler which we compare to other scheduling policies as well as to transport level solution like MTCP, obtaining always better result
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Interoperability of wireless communication technologies in hybrid networks: Evaluation of end-to-end interoperability issues and quality of service requirements
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Hybrid Networks employing wireless communication technologies have nowadays brought closer the vision of communication โanywhere, any time with anyoneโ. Such communication technologies consist of various standards, protocols, architectures, characteristics, models, devices, modulation and coding techniques. All these different technologies naturally may share some common characteristics, but there are also many important differences. New advances in these technologies are emerging very rapidly, with the advent of new models, characteristics, protocols and architectures. This rapid evolution imposes many challenges and issues to be addressed, and of particular importance are the interoperability issues of the following wireless technologies: Wireless Fidelity (Wi-Fi) IEEE802.11, Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16, Single Channel per Carrier (SCPC), Digital Video Broadcasting of Satellite (DVB-S/DVB-S2), and Digital Video Broadcasting Return Channel through Satellite (DVB-RCS). Due to the differences amongst wireless technologies, these technologies do not generally interoperate easily with each other because of various interoperability and Quality of Service (QoS) issues.
The aim of this study is to assess and investigate end-to-end interoperability issues and QoS requirements, such as bandwidth, delays, jitter, latency, packet loss, throughput, TCP performance, UDP performance, unicast and multicast services and availability, on hybrid wireless communication networks (employing both satellite broadband and terrestrial wireless technologies).
The thesis provides an introduction to wireless communication technologies followed by a review of previous research studies on Hybrid Networks (both satellite and terrestrial wireless technologies, particularly Wi-Fi, WiMAX, DVB-RCS, and SCPC). Previous studies have discussed Wi-Fi, WiMAX, DVB-RCS, SCPC and 3G technologies and their standards as well as their properties and characteristics, such as operating frequency, bandwidth, data rate, basic configuration, coverage, power, interference, social issues, security problems, physical and MAC layer design and development issues. Although some previous studies provide valuable contributions to this area of research, they are limited to link layer characteristics, TCP performance, delay, bandwidth, capacity, data rate, and throughput. None of the studies cover all aspects of end-to-end interoperability issues and QoS requirements; such as bandwidth, delay, jitter, latency, packet loss, link performance, TCP and UDP performance, unicast and multicast performance, at end-to-end level, on Hybrid wireless networks.
Interoperability issues are discussed in detail and a comparison of the different technologies and protocols was done using appropriate testing tools, assessing various performance measures including: bandwidth, delay, jitter, latency, packet loss, throughput and availability testing. The standards, protocol suite/ models and architectures for Wi-Fi, WiMAX, DVB-RCS, SCPC, alongside with different platforms and applications, are discussed and compared. Using a robust approach, which includes a new testing methodology and a generic test plan, the testing was conducted using various realistic test scenarios on real networks, comprising variable numbers and types of nodes. The data, traces, packets, and files were captured from various live scenarios and sites. The test results were analysed in order to measure and compare the characteristics of wireless technologies, devices, protocols and applications.
The motivation of this research is to study all the end-to-end interoperability issues and Quality of Service requirements for rapidly growing Hybrid Networks in a comprehensive and systematic way.
The significance of this research is that it is based on a comprehensive and systematic investigation of issues and facts, instead of hypothetical ideas/scenarios or simulations, which informed the design of a test methodology for empirical data gathering by real network testing, suitable for the measurement of hybrid network single-link or end-to-end issues using proven test tools.
This systematic investigation of the issues encompasses an extensive series of tests measuring delay, jitter, packet loss, bandwidth, throughput, availability, performance of audio and video session, multicast and unicast performance, and stress testing. This testing covers most common test scenarios in hybrid networks and gives recommendations in achieving good end-to-end interoperability and QoS in hybrid networks.
Contributions of study include the identification of gaps in the research, a description of interoperability issues, a comparison of most common test tools, the development of a generic test plan, a new testing process and methodology, analysis and network design recommendations for end-to-end interoperability issues and QoS requirements. This covers the complete cycle of this research.
It is found that UDP is more suitable for hybrid wireless network as compared to TCP, particularly for the demanding applications considered, since TCP presents significant problems for multimedia and live traffic which requires strict QoS requirements on delay, jitter, packet loss and bandwidth. The main bottleneck for satellite communication is the delay of approximately 600 to 680 ms due to the long distance factor (and the finite speed of light) when communicating over geostationary satellites.
The delay and packet loss can be controlled using various methods, such as traffic classification, traffic prioritization, congestion control, buffer management, using delay compensator, protocol compensator, developing automatic request technique, flow scheduling, and bandwidth allocation
Improving the Performance of Wireless LANs
This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids
Performance and energy efficiency in wireless self-organized networks
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