Optimizacija protokola i metrika rutiranja za višekanalne višeinterfejsne bežične mesh mreže

Abstract

Bežične mesh mreže – WMN (Wireless Mesh Network) predstavljaju noviji trend u bežičnim komunikacijama kojim se obezbeđuje veća fleksibilnost, pouzdanost i bolje performanse nego standardnim bežičnim lokalnim mrežama. Imajući u vidu sve veće potrebe korisnika za brzim i efikasnim prenosom podataka, kao i prenosom multimedijalnih (govornih i video) sadržaja, povećanje protoka, ostvareno uvođenjem višekanalnih višeinterfejsnih – MCMI (Multi Channel Multi Interface) WMN, i vođenje računa o kvalitetu servisa, QoS (Quality of Service), predstavljaju glavne izazove u projektovanju WMN. Kako bi se ostvarile što bolje mrežne performanse neophodno je definisati protokole i metrike rutiranja kojima se određuje optimalna putanja između izvorišnog i odredišnog čvora. S obzirom da WMN karakteriše velika dinamika signala, posebno u kompleksnim okruženjima (sa stanovišta radio pokrivanja), kakva su zatvoreni objekti, u okviru doktorske disertacije definisane su metrike rutiranja koje mogu da isprate brze promene uslova propagacije koje se dešavaju na svakom pojedinačnom linku u mreži. Predložene su tri nove metrike: powerETX (Expected Transmission Count), powerWCETT (Weighted Cumulative Expected Transmission Time) i powerMIC (Metric of Interference and Channel-switching), koje u cenu linka, osim parametara definisanih u okviru postojećih metrika ETX, WCETT i MIC, respektivno, uključuju i parametar koji zavisi od nivoa snage signala na prijemu. Nove metrike obezbeđuju veće protoke korisničkih podataka i manje kašnjenje s kraja na kraj u poređenju sa postojećim, a njihova praktična realizacija moguća je bez dodatnih hardverskih ulaganja, i uz minimalne softverske izmene. Imajući u vidu da postojeći algoritmi dodele kanala ne uključuju QoS podršku u MCMI-WMN, i da se prenos multimedijalnih sadržaja obavlja uz neprihvatljiva kašnjenja, predložen je novi protokol za sloj linka, QoS-HMCP (QoS-Hybrid Multi Channel Protocol), koji uvodi podršku QoS kroz EDCA (Enhanced Distributed Channel Access) mehanizam pristupa, i koristi dobre karakteristike hibridnog algoritma dodele kanala definisane HMCP protokolom za sloj linka. Predložene su četiri varijante QoS-HMCP protokola koji u obzir uzimaju različite kriterijume za promenu kanala i...

Wireless mesh networks (WMNs) are a new trend in wireless communications which provide greater flexibility, reliability and better network performances than standard wireless local area networks. Having in mind the growing demand for the fast and efficient data transfer as well as multimedia transmission (voice and video), the major challenges in designing WMN are increasing throughput (by introducing multichannel multi-interfaces (MCMI) approach into the WMN), and taking into account the quality of service (QoS). To achieve the best network performances, it is necessary to define protocols and routing metrics that determine the optimal path between the source and the destination node. Since the WMN is characterized by high dynamics of the signal, especially in complex environments (from the radio coverage point of view), such as those found indoors, routing metrics that can track fast changes in propagation conditions at each link in the network, are proposed in this dissertation. The link costs of the three new metrics, powerETX (Expected Transmission Count), powerWCETT (Weighted Cumulative Expected Transmission Time) and powerMIC (Metric of Interference and Channel-switching), besides the parameters defined in the existing ETX, WCETT and MIC metrics, respectively, include the parameter that depends on the received signal level. In comparison with existing metrics, these new metrics not only provide a greater data throughput and less average end-to-end delay, but also can be realized without any additional hardware and with minimal software changes. Keeping in mind that existing channel assignment (CA) algorithms do not include QoS support in MCMI-WMNs and that the multimedia transmission can suffer from unacceptable delays, a new protocol for link layer QoS-HMCP (QoS Hybrid Multi-Channel Protocol) which introduces QoS support through EDCA (Enhanced Distributed Channel Access) mechanism, and uses the good characteristics of the hybrid CA algorithm defined by HMCP protocol for link layer, is proposed in this dissertation. Four versions of the QoS-HMCP protocols, which take into account different criteria for channel switching and procedure for medium competition, are proposed. These versions are compared with basic HMCP protocol with regards to the throughput of user data and...