A study of orthogonal frequency division multiplexing and single-carrier frequency domain equalization

Inter-symbol interference (ISI) is a critical problem in achieving high-speed data transmission. Orthogonal Frequency Division Multiplexing (OFDM) and Single-Carrier Frequency Domain Equalization (SC-FDE) are two competing techniques to reduce its adverse effect on the receiver. They have similar structure and performance but are also different in a number of ways. This thesis investigates a variety of issues involving OFDM and SC-FDE and obtains valuable results.; First, the structure of the two systems and their utilization of cyclic prefix are described. Then a comparative capacity analysis is carried out for both systems. While OFDM converts the available frequency band into a number of subchannels with independent noise, SC-FDE leads to subchannels with correlated noise. It is demonstrated that SC-FDE has the same capacity as OFDM.; Second, the issues of adaptive modulation and inter-channel interference (ICI) are examined for OFDM. The adaptive modulation can considerably improve the performance of OFDM when perfect channel information is assumed. But imperfect channel information can cause severe performance degradation. A detailed analysis of the problem is carried out and two schemes are proposed to deal with it. For inter-channel interference in OFDM, the problem is formulated into a unified equalization framework. A previous decision-feedback algorithm is found to perform poorly when severe residual ISI or channel variation is present. A Block Decision Feedback Equalizer (B-DFE) utilizing matrix filters is introduced and shown to produce superior performance. The well-known Vertical Bell Labs Layered Space-Time (V BLAST) structure is essentially a B-DFE with the optimal order of detection.; Finally, a hybrid implementation of decision-feedback equalizers for SC-FDE is studied. Its structure is shown to be equivalent to the time-domain counterpart. A Training Cyclic Prefix (TCP) is used to address the problem of circular interference. Based on the TCP, two channel estimation methods are proposed. One uses simple averaging and the other is an approximate least square method. The optimal design and placement of the TCP is also investigated.