Subject: Proposal for Quantifying Tradeoffs in Adaptive Modulation Methods for Ieee 802.16a Wireless Communication Systems

OVERVIEW The need for wireless services is growing extremely fast, but the radio spectrum has bounds imposed by practical limitations on the circuit designs and use regulations from federal governments. Spectral efficiency is therefore of primary concern in the design of future wireless data communications systems. Efficiency of a wireless cellular system may be achieved at several levels of the system design [1]: • at the radio coverage planning level by minimizing cell area and the cochannel reuse distance. • at the communication link level through bandwidth efficient coding and modulation techniques. • at the network/system level by using sophisticated channel allocation schemes that maximize the overall carried traffic. This project will be dealing with the physical and link sub-layers of the communications link layer. IEEE 802.16a uses orthogonal frequency division multiplexing (OFDM) with 256 sub-carriers. In OFDM, the data stream is divided into many parallel bit streams, which are modulated on different sub-carriers. These carriers are narrow-band, and have the property of being mathematically orthogonal to each other. Orthogonality ensures that the carriers can be separated out at the receiver without interfering with each other. Each sub-carrier experiences attenuations due to the channel independent of the others. Adaptive modulation can then be performed on a subcarrier basis rather than on the entire channel. Adaptive modulation tries to combat fading effects of the channel by employing a higher order modulation mode when the channel quality is good (high signal to noise ratio SNR), and a lower order one when the channel quality is bad (low SNR). By doing so, it tries to maximize the throughput, while keeping the bit error rate (BER) lower than the predefined threshold of 10-6 for IEEE802.16a wireless communication systems [2]. When quantifying tradeoffs in modulation techniques, we will look at the spectral efficiency, BER, and implementation complexity. PROJECT DESCRIPTION In this project, I propose to improve the existing IEEE 802.16a LabVIEW simulation, developed mainly by Mr. Ian Wong, one of Prof. Evans' PhD students. The project will consist of three parts as follows: 1) The first part will be to use the NI Modulation Toolkit [3] in order to design a more realistic wireless channel model. 2) The second part will be to implement forward error correction (FEC) in order to reduce errors in the transmission. 3) In the third part, I will look at the optimization of throughput, by implementing adaptive modulation. DESIGN CONTENT …