Wireless LANs have expanded greatly and rapidly in recent years. The expansio¬¬¬¬¬n has caused many benefits to the end users but at the same time it has introduced problem of overlapping BSS (Basic Service Set) where BSS (i.e. WLAN cells) is fundamental block of IEEE 802.11 WLAN architecture. OBSS occurs due to two or more unrelated BSSs are used at the same place, at the same time and with the same frequency channel. With the expansion of channel bandwidth to 80 MHz (may be, 160 MHz) in upcoming standards, the OBSS problem is likely to be very severe in the future. This paper examines how OBSS can be harmful to the networks and how it can be avoided using beam forming, distributed coordination across different APs, and power management. At the end, this text explores the effectiveness of the proposed solutions.
INTRODUCTION
Wireless Local Area Network (WLAN) is one of the most successful technologies in IEEE 802.XX standards family. WLAN provides free connectivity, mobility, and flexibility with a relatively low cost for users. The widespread use of WLAN technology in streaming videos and voice applications stimulated high bandwidth capacity for WLANs. Recently IEEE has announced latest WLAN standard 802.11ac. For 802.11ac to be effective, it requires minimum 80 MHz wide channel with optionally up to 160 MHz. The increase in bandwidth leads to problems like OBSS. OBSS problem occur when two or more BSSs operate in same channel and are close to hear each other. This is an undesirable situation where two or more BSSs compete for channel access and increase contention which ultimately degrades performance/efficiency of the WLAN system [1]. The problem was not critical with 802.11a/b/g/n where the channel bandwidth was reasonable. ...
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... on how many stations it can associate to if OBSS problem needs to be avoided. At the end, couple of novel approaches can potentially enhance performance of OBSS.
Works Cited
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[4]. Fang Y., Gu D., McDonald B. and Zhang J., “A two level carrier sensing mechanism for overlapping BSS problem in WLAN,” June 2006, Avaliable: http://www.merl.com/publications/docs/TR2005-156.pdf
My research interest of working with coding theory, information theory, multiple access methods, and adaptive equalization, all match considerably with the research focuses of EECS Berkeley’s faculty. EECS Berkeley has the finest faculty and the most developed research facilities in the World of Electrical Engineering, and more specifically, in the field of wireless & mobile communications.
Figure 6 shows the WiMAX and WiFi coverage. Once can clearly see how large is the coverage of WiMAX.
indent To alleviate the second problem, if a node has both unicast and broadcast packets to send, it negotiates the broadcast packets first. Also, smaller backoff windows are used for broadcast negotiation. The ATIM-BRD packets are control packetss used for broadcast communication. The sending node randomly selects available time slots and sends out the CUBs and CABs it plans on using for the broadcast. The nodes in the vicinity of the sending node update their CUBs based on the ATIM-BRD packet.
J. A. Gutierrez ,M. Naeve , E. Callaway , M. Bourgeois ,V. Mitter and B. Heile "IEEE 802.15.4:adeveloping standard for low-power low-cost wireless personal area networks", IEEE Network, vol. 15, no. 5, pp.12 -19 2001
[4] C. Lo, E. Masry, and L. B. Milstein, “Design and Analysis of a Fast Frequency-Hopped DBPSK Communication System, Part I,” IEEE Trans. Commun., Vol. COM-41, pp. 1552-1564, 1993
WLAN (Wireless Local Area network) and its components: The task of developing a WLAN on commercial front possesses a greater challenge. Developing initial design, purchasing and installing components, managing and providing maintenance to the systems are the main basic parts of the WLAN. When we use WLAN on a commercial front then we may face the security and privacy concerns. The total area of that particular commercial area should be accessible. This is only possible with installing huge number of access points. The various components of the WLAN are
Spectrum Decision Making calls for reconfiguration for the channel and protocol required for constantly adapting to mobile changing environments and adjustment of output power or even alteration of transmission parameters (such as modulation formats (e.g. low to high order QAM), variable symbol rates, different channel coding schemes) and characteristics by the Cognitive radio devices. CR should be able to use multiple antennas for interference knolling, capacity increase or range extension.
...n, M., & Grabianowski, E. (n.d.). HowStuffWorks "WiMAX Coverage and Speed". HowStuffWorks. Retrieved May 2, 2014, from http://computer.howstuffworks.com/wimax2.htm
The propose research will address a problem confronting many two year institutions in the present-day (i.e. how to best plan, design, and implement WLAN technologies). While WLAN technologies offer the benefits of mobility, reduced installation time, and decreased cost, many challenges must be met by institutions deploying them (Geier, 2005). These issues are related to security, speed, interoperability, and equipment selection, ease of use, reliability, signal interference, installation, and health risks.
The next modulation technique is Direct-Sequence Spread Spectrum (DSSS) which applies the (PN) code directly to the data entering the carrier modulator. The baseband signal is spread out into a much larger bandwidth greater than the minimum bandwidth required to transmit the information.
Wireless is everywhere today whether at home working from your WIFI network to work where you might be linked a wireless network or even through your phone through a 3G or 4G network to connecting to an open wireless networks. As you can see for the most part people are connecting to wireless from the moment they leave their home till they get to work and then back. While wireless comm...
Some factors responsible for interference were identified such as: spectrum due to modulation and wideband noise, spectrum due to switching, and transmitter and receiver band spurious. The need to watch out for BTS receiver sensitivity was also highlighted [21].
In today’s world there is an increasing demand for wireless connectivity. But with the present technology there is an inefficient use of the available. A large part of the spectrum is underutilised as shown in Fig 1. Due to the inefficient use of spectrum by the current spectrum allocation methods there is a need for developing new methods which aids in efficient use of available spectrum.
William A. Arbaugh, YC Justin Wan, Naren Aar Shankar, 03-30-01 Your 802.11 wireless networks has no clothes University of Maryland Department of CSIS