An Adaptive Common Control Channel MAC with Transmission Opportunity in IEEE 802.11ac

Spectral utilization is a major challenge in wireless ad hoc networks due in part to using limited network resources. For ad hoc networks, the bandwidth is shared among stations that can transmit data at any point in time. It  is important to maximize the throughput to enhance the network service. In this paper, we propose an adaptive multi-channel access with transmission opportunity protocol for multi-channel ad hoc networks, called AMCA-TXOP. For the purpose of coordination, the proposed protocol uses an adaptive common control channel over which the stations negotiate their channel selection based on the entire available bandwidth and then switch to the negotiated channel. AMCA-TXOP requires a single radio interface so that each station can listen to the control channel, which can overhear all agreements made by the other stations. This allows parallel transmission to multiple stations over various channels, prioritizing data traffic to achieve the quality-of-service requirements. The proposed approach can work with the 802.11ac protocol, which has expanded the bandwidth to 160 MHz by channel bonding. Simulations were conducted to demonstrate the throughput gains that can be achieved using the AMCA-TXOP protocol. Moreover, we compared our protocol with  the IEEE 802.11ac standard protocols

Tiheiden Wi-Fi verkkojen optimointi Markov-ketjumallien ja simuloidun jäähdytyksen avulla

Currently, the demand for wireless communication capacity is rising rapidly due to challenging applications such as video streaming and the emerging Internet of things. In meeting these ambitious requirements, the most important factor is predicted to be network densification, which refers to increasing the geographical density of simultaneously communicating devices. A natural choice for implementing dense networks is the wireless local area network technology Wi-Fi, characterized by being cheap and easy to deploy. Network density aggravates the harmful effects of interference and causes scarcity of free transmission bandwidth. To counter this, dense networks need radio resource management algorithms. This thesis presents a Wi-Fi radio resource management algorithm, which jointly optimizes access point channels, user association and transmission power. It estimates future throughput using a continuous time Markov chain based model, and finds solutions maximizing this estimate via a discrete search metaheuristic called simulated annealing. The algorithm is validated through a wide range of simulations where for instance network density is varied. The algorithm is found to be highly versatile, yielding good performance in all scenarios. Moreover, the general design approach places few restrictions on further algorithm improvement and extension. Markov chain modeling, although accurate in an idealized setting, turns out to be inaccurate with real-world Wi-Fi, with a simpler model offering similar accuracy but lighter computational load.Nykyisin vaatimukset langattoman tiedonsiirron kapasiteetille ovat voimakkaassa kasvussa johtuen haastavista sovelluksista kuten videon suoratoistosta ja tulossa olevasta esineiden Internetistä. Näiden vaatimusten täyttämiseksi tärkein keino on langattomien tiedonsiirtoverkkojen tihentäminen, mikä tarkoittaa yht’aikaa samalla maantieteellisellä alueella kommunikoivien laitteiden määrän kasvattamista. Luonnollinen valinta tiheiden verkkojen toteuttamiseen on langattomien lähiverkkojen teknologia Wi-Fi, jonka etuja ovat edullisuus ja asennuksen helppous. Langattoman verkon tiheys lisää haitallista interferenssiä ja aikaansaa pulaa vapaista lähetystaajuuksista. Näiden ongelmien ratkaisemiseksi tarvitaan radioresurssien hallinta-algoritmeja. Tässä työssä suunnitellaan Wi-Fiä varten radioresurssien hallinta-algoritmi, joka optimoi samanaikaisesti tukiasemien kanavia, käyttäjien allokaatiota tukiasemille sekä lähetystehoja. Se estimoi tulevia tiedonsiirtonopeuksia jatkuvan ajan Markov-ketjuihin pohjautuvan mallin avulla ja löytää tämän estimaatin maksimoivia ratkaisuja hyödyntämällä diskreettiä hakumenetelmää nimeltä simuloitu jäähdytys. Algoritmi validoidaan käyttäen monipuolista joukkoa simulaatioita, jossa vaihtelee esimerkiksi verkon tiheys. Algoritmi osoittautuu erittäin monipuoliseksi, sillä sen suorituskyky on hyvä kaikissa simulaatioskenaarioissa. Käytetyn lähestymistavan etuna on myös se, että se asettaa varsin vähän rajoituksia algoritmin jatkokehitykselle. Markov-ketjumallit osoittautuvat todellisen Wi-Fin tapauksessa epätarkoiksi, vaikka ne idealisoidussa ympäristössä ovatkin tarkkoja. Käy ilmi, että yksinkertaisemmalla mallilla saadaan vastaava tarkkuus, mutta laskentatehoa tarvitaan vähemmän

A novel multipath-transmission supported software defined wireless network architecture

The inflexible management and operation of today\u27s wireless access networks cannot meet the increasingly growing specific requirements, such as high mobility and throughput, service differentiation, and high-level programmability. In this paper, we put forward a novel multipath-transmission supported software-defined wireless network architecture (MP-SDWN), with the aim of achieving seamless handover, throughput enhancement, and flow-level wireless transmission control as well as programmable interfaces. In particular, this research addresses the following issues: 1) for high mobility and throughput, multi-connection virtual access point is proposed to enable multiple transmission paths simultaneously over a set of access points for users and 2) wireless flow transmission rules and programmable interfaces are implemented into mac80211 subsystem to enable service differentiation and flow-level wireless transmission control. Moreover, the efficiency and flexibility of MP-SDWN are demonstrated in the performance evaluations conducted on a 802.11 based-testbed, and the experimental results show that compared to regular WiFi, our proposed MP-SDWN architecture achieves seamless handover and multifold throughput improvement, and supports flow-level wireless transmission control for different applications