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Abstract
In the last few years, we have witnessed an explosive growth of wireless LAN deployments in both the business and consumer environments. Increasing multimedia applications and websites, the needs of many of today’s computer, PDA and smart phone users to be ubiquitously connected to the Internet or to their office networks via VPN, the use of WLAN as a complementary technology for wired networks in offices, wireless hotspots, home wireless networks, and even meshes of wireless networks covering entire cities, this has allIed to the rapid evolution of this technology to satisfy the growing needs for higher data rates.
A set of WLAN standards emerged, starting from 802.11 with data rates of 1 & 2 Mbps to the latest agreed WLAN standard, 802.1Ig, with a widely installed user base. It specifies a 2.4 GHz carrier frequency, and is based on Orthogonal Frequency Division Multiplexing (OFDM) technology for physical layer (PHY), which splits data signals across 52 separate sub-carriers to provide data rates up to 54 Mbps. Four of the sub-carriers are pilots, used as a reference to correct frequency or phase shifts of the signal during transmission, and the remaining 48 sub-carriers provide separate narrowband (0.3125 MHz) wireless pathways for sending the information in parallel to mitigate the effects of fading in the wireless channel. For backward compatibility with the 802.1 I b standard, Direct Sequence Spread Spectrum (DSSS) PHY layer is also supported.
The newest version of the 802. I 1 family of standards, currently in draft version, is labeled 802.1 In. It is based on Multiple-Input Multiple-Output (MIMO) antenna technology combined with OFDM. MIMO is concerned with spatial diversity and Space¬Time Block Coding techniques, which distribute the data signal over several transmit and receive antennas to increase the raw PHY layer data rates to nearly 600 Mbps, and/or significantly enhance performance in terms of error rates.
Hence we have set our goals in this thesis to be as follows:
• Simulate 802.11 n systems in fading channels.
• Analyze and compare the performance of different MIMO configurations.
• Study the replacement of the standard encoder.
• Compare the performance of the double bandwidth channel against the single
channel.
• Analyze the effects of motion on system performance.
• Compare the performance of different transmitted frame lengths.
• Show the effects of different delay spreads on performance.