Superposition Coding Scheme for Subcarrier & Bit Allocation in OFDM System
Ashish Tiwari1, Mukesh Kumar2, A.K.Jaiswal3, Rohini Saxena4

1AshishTiwari is pursuing M.Tech in Communication System Engineering from SHIATS, Allahabad (U.P.), India.
2Mukesh Kumar is working as a Asst.Prof. in the Department of Electronics &Communication Engineering in SHIATS, Allahabad (U.P.), India.
3Arvind Kumar Jaiswal is workingas Prof. and Head of Department in the Departmentof Electronics & CommunicationEngineering in SHIATS, Allahabad (U.P.), India.
4Rohini Saxena is working as a Asst. Prof. in the Department of Electronics & Communication Engineering in SHIATS, Allahabad (U.P.), India.

Manuscript received on July 01, 2012. | Revised Manuscript received on July 04, 2012. | Manuscript published on July 05, 2012. | PP: 487-491 | Volume-2, Issue-3, July 2012. | Retrieval Number: C0824062312/2012©BEIESP
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Abstract: Orthogonal Frequency Division Multiple Access (OFDMA) refers to aradio transmission technique based on dividing the frequency channelinto narrowband sub-channels. In this dissertation studied that margin adaptive – superposition coding (MA-SC) algorithm and rate adaptive – superposition coding (RA-SC) algorithm, where at most two users can share each subcarrier as compared to MA and RA algorithm, where each subcarrier is shared by only single user without SC scheme. Then apply SC scheme over MA and RA to achieve maximum system throughput with separate power constraint for real and non-real time users, ensuring that QoS requirement for real time and proportional fairness among non-real time users is satisfied. The overall computational complexity of RA-SC algorithm is same as RA algorithm. In MA-SC, complexity increases in some of the steps due to addition of SC scheme over MA algorithm, but overall complexity remains the same. Matlab simulations are being carried out to show that the performance of algorithm in terms of power required and throughput.

Keywords: MA-SC, RA-SC, OFDM Superposition coding