Dynamic subcarrier allocation with transmit diversity for OFDMA based wireless multicast systems | |
| Author | Shrestha, Natasha |
| Call Number | AIT Thesis no.TC-09-03 |
| Subject(s) | Orthogonal frequency division multiplexing Wireless communication systems |
| Note | A thesis submitted in partial fulfillment of the re quirements for the degree of Master of Engineering in Telecommunications, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. TC-09-03 |
| Abstract | This thesis work considers the subcarrier allocation problem for multicast transmissions in the downlink for an OFDMA based wireless cellular network. When a number of users in a cell require the same information, multicasting is more efficient than unicasting to each of the users. However, variations in channel conditions of the users in the same multicast group impose a difficulty in fixing a single rate of transmission to the multicast group. To support all the users, conventional multicast systems use the data rate of the worst case user whose channel condition is the poorest. We have developed a new technique called subcarrier pair allocation (SPA) to allocate OFDM subcarriers to multicast groups dynamically to account for the channel variation by making use of the multiuser diversity and frequency diversity offered by OFDMA systems. In the proposed technique, subcarriers are grouped into pairs of two and identical copies of data are transmitted on each pair of subcarriers. For each user, the intermediate data rate is calculated as the maximum of the rates in the two subcarriers. The data rate of a multicast group is then set to the minimum of these maximum rates of the users. We derive expressions for the average multicast capacity of a multicast group in terms of the group size and the number of groups for both the conventional multicast scheme and for SPA. Numerical and simulation results show that there is a significant capacity increase provided by the SPA scheme over the conventional scheme especially in low SNR regions and for systems with large multicast group sizes. |
| Year | 2009 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TC-09-03 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Poompat Saengudomlert |
| Examination Committee(s) | Rajatheva, R. M. A. P.;Ahmed, Kazi M.;Ji, Yusheng |
| Scholarship Donor(s) | Findland Government;AIT Fellowship |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2009 |