A hybrid joint ML technique for CFO, timing offset, and channel estimations in an OFDMA uplink

Abstract

In this paper, we propose a novel hybrid joint maximum-likelihood estimator for carrier frequency offset (CFO), timing offset, and channel response of all users in the uplink of an orthogonal frequency division multiple access (OFDMA) system. The proposed estimation method significantly reduces complexity of this multiparameter, multidimensional optimization problem, using the concept of separation of the different user signals by means of newly defined projection operators. This projection technique is combined with the alternating projection method available in the literature to arrive at a new hybrid algorithm that offers significant performance advantages in terms of computational complexity and estimator performance. The joint estimation of the CFOs, timing offsets, and channel coefficients for all active users together at the base station of the OFDMA uplink is a rarely addressed task. The proposed method also offers the flexibility of application to any subcarrier assignment scheme used in OFDMA systems. Extensive simulation studies corroborate the advantages of the new hybrid method for all three estimation requirements in the multiuser OFDMA uplink. in 1998 and he is presently working as an Assistant Professor there. He has published papers in several international conferences and journals, and holds four patent applications. Sameer S. M. is a member of IEEE and a regular reviewer of many reputed international conferences and journals. He has served on the Technical Programmes and other Committees of several International Conferences. His research interests include synchronization and channel estimation techniques for multicarrier communication systems, Wi-MAX system design challenges, optimization techniques for wireless communication, cognitive radio, and physical layer issues in cooperative communication systems.

Low‐complexity joint detection of carrier frequency offset and sector cell index for LTE cellular system

“…When a UE operates in the LTE system, it is an important phase for UE to establish connection with the best serving base station as fast as possible, that is, to estimate symbol timing, frame timing, carrier frequency offset, and to identify the operating sector and cell index (CID) . Because OFDM is extremely sensitive to synchronization errors, a robust cell search technique is necessary for a UE to perform synchronization so that the cell can be recognized without the loss of orthogonality.…”

A firefly technique for estimation of carrier frequency offsets in OFDMA uplink

“…But the computational complexity is large. In [10], [11], the authors propose a hybrid algorithm that combines the alternating projection technique with a new algorithm called Minimum Residue Decomposition (MRD). In [12], an importance sampling procedure is used, which guarantees convergence to the global minimum in an ML search.…”

Cramér‐Rao bound for joint estimation problems

“…Simulation studies: In this Section we compare the performance of an algorithm called minimum residue decomposition (MRD) [5,6] for estimation of CFOs in the OFDMA uplink with the corresponding CRB derived for the problem. The system has 128 subcarriers with four active users.…”