|Title:||Interference management in wireless networks : a cross layer approach|
|Advisors:||Lou, Wei (COMP)|
Chang, Kow Chuen Rocky (COMP)
|Subject:||Wireless communication systems -- Management.|
Mobile communication systems -- Management.
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Computing|
|Pages:||xx, 167 pages : illustrations|
|Abstract:||Wireless local area networks (WLANs) have become an important communication infrastructure for internet access in the past decade because of the popularity of laptops, smartphones, and so on. They are propelled to improve the network throughput effectively to face the challenge of sustaining the rapid growth of data traffic and the high density of wireless nodes. Interference is well known to degrade the wireless network performance, and it is inevitable due to the broadcasting characteristics of wireless signals and the coexistence of various wireless nodes working at the shared channel, which makes interference management be an everlasting research topic over the years. Current 802.11 standard utilizes the carrier sense multiple access (CSMA) mechanism to make nodes access the channel to avoid interferences. However, this mechanism is inefficient because of prohibiting effective concurrent transmissions, inducing interference and existing the coordination overhead, all of the aspects will degrade the network performance. Therefore, a more efficient mechanism needs to be proposed to improve the network performance. In wireless networks, interference management always needs nodes to exchange the coordination information with adjacent nodes, so that they can obtain the requisite information to permit effective concurrent transmissions and avoid interference. However, the exchange of control frames always induce a large amount of transmission overhead; meanwhile, they may in turn make the wireless nodes waste some concurrent transmission opportunities because of avoiding the collisions induced by control frames. In this dissertation, I propose to improve the wireless network performance through designing a cross layer approach, which contains interference resistance mechanism in the physical layer to make control frames conveyed in a more efficient way, and also contains the MAC layer mechanisms that utilize the information obtained from the physical layer for effective interference management.|
Firstly, this dissertation proposes Interference Resistant Multiple Access (IRMA) to combat the exposed terminal problem and exploit transmission opportunities in wireless networks. Observations on the 802.11 standard reveal that nodes degrade the network through put from two aspects, including the so-called CA-CF problem and varied-IR problem, and the problems will make nodes around both the transmitter and receiver of the ongoing link waste concurrencies. IRMA proposes to exploit transmission opportunities from solving the two problems through utilizing a physical layer mechanism that can combat the control frames' collisions. Secondly, this dissertation proposes Interference Cancellation Multiple Reception (ICMR) to further exploit reception opportunities also from solving both the problems, through utilizing another physical layer mechanism that can successfully detect data frames when collided by control frames. Thirdly, this dissertation proposes concurrency-based coordination mechanism (CCM) that can coordinate among nodes effectively in a centralized way to maximize concurrency and avoid data packet interference in WLANs. This protocol is also based on an interference resistance mechanism in the physical layer to make the control message and data packets transmitted concurrently to avoid the coordination overhead. Experimental results based on USRP2 demonstrate the feasibility of the physical layer mechanisms, and simulations based on ns-2 show that the three protocols can outperform the other current protocols significantly. As a conclusion, this dissertation proposes a cross layer approach that benefits from both the physical layer and the upper layer design to maximize concurrent transmissions, avoid interference and decrease the coordination overhead in current wireless networks, so as to improve the network performance.
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