Showing papers on "SC-FDE published in 2004"

Pilot aided timing synchronization for SC-FDE and OFDM: a comparison

Abstract: This paper deals with the pilot aided synchronization techniques for single carrier systems with frequency domain equalization (SC/FDE). This techniques are also useable for OFDM. Normally the following parameters have to be synchronized for a mobile communication system: carrier frequency and phase, clock frequency and phase and the position within a transmitted frame. In mobile communication systems, where multipath propagation occurs, a channel estimation and equalization is additionally necessary. In SC/FDE systems a very efficient, low complexity equalizer is implemented, that furthermore synchronizes the clock and carrier phase automatically. That is an important advantage of SC/FDE versus OFDM. The most critical point in burst communication systems is the frame detection and timing synchronization. This paper compares different techniques for timing synchronization and carrier frequency offset estimation.

Performance versus effort for decision feedback equalization - an analysis based on SC/FDE adapted to IEEE 802.11a

Abstract: In this work we investigate the meaning of decision feedback equalization for a single carrier system with frequency domain equalization (SC/FDE) in an overall system approach, based on the parameters of the IEEE 802.11a standard. The concept of SC/FDE allows an advantageous combination of feed forward frequency domain equalization and feed back equalization in the time domain, that combines low signal processing complexity and powerful equalization. Although the concept of decision feedback equalization (DFE) is a well known and developed theory, this nonlinear equalization is rarely investigated in an overall system approach. Based on that the possible performance gain will be characterized under the constraints of channel characteristics, error propagation, higher order modulation schemes and channel coding. It will be demonstrated that these elements have significant influence on the possible performance of DFE and may reduce the propagated high performance gain.

Single-Carrier Frequency-Domain Equalization (SC-FDE) subscriber equipment with automatic physical layer request retransmission mechanism

Abstract: The utility model discloses a single carrier frequency-domain equalization(SC-FDE) user facility that is provided with a physical layer resending request mechanism. The user facility is provided with a receiver which is provided with a physical receiver that is used for modulating packs. Each pack is specifically encoded/digitally modulated. The specific coding/digital modulating employs HSPA modulation solution and forward error correction(FEC) coding. A mixed ARQ combiner/decoder is coupled with the physical receiver so as to buffer, decode and detect the error of the package. If the error rate is acceptable, a confirmation emitter that is coupled with the mixed ARQ combiner/decoder confirms the pack.

Antenna Diversity Techniques for SC/FDE — a System Analysis

Abstract: In this work we investigate the possibilities of combining diversity techniques with a Single Carrier System with Frequency Domain Equalization (SC/FDE), as future transmission concepts will also be judged by their possibilities to be combined with multiple antennas. Concepts of multiple antennas allow either a significant performance gain through diversity (and) or significant higher capacity based on spatial multiplexing. While it is topic of many contributions to improve the concepts of antenna diversity itself, it is topic of this paper to point out the advantages when combining SC/FDE with diversity techniques. It will be demonstrated that SC/FDE shows excellent possibilities to be combined with diversity techniques, as the process of equalization itself can be combined with receive diversity as well as with space time block (STBC) decoding, that can be carried out advantageously in the frequency domain. Besides that an overall system approach will be discussed that includes aspects of implementation, equalization, modulation and coding.

Timing of the FFT-Window in SC/FDE Systems

Abstract: In this work the positioning of the FFT-window in a single carrier system with frequency domain equalization (SC/FDE) is analyzed. Similar to OFDM (orthogonal frequency division multiplexing), SC/FDE systems are based on blockwise transmission and FFT processing, which enables channel equalization in the frequency domain with low complexity. Comparable to OFDM, the interblock interference (IBI) caused by multipath propagation and by time domain pulse shaping puts some constraints on the FFT-window positioning for SC/FDE. We describe the distortions which are induced by the time domain pulse shaping in combination with blockwise processing. Since in SC/FDE systems information is carried by short pulses in time domain, the effects differ from the corresponding impacts in OFDM, where information is carried by subcarriers in frequency domain. We present error vector magnitude (EVM) measurements and error rate curves obtained from computer simulations. Our results indicate that the performance loss caused by IBI, which becomes worse for higher order modulation schemes, can be minimized by an optimization of the FFT-window position.

Decision feedback equalization in the context of enhanced high rate mobile communications systems - based on the concept of SC/FDE

Abstract: Although nonlinear equalizer structures seem to be a well developed theory, these equalizer structures are rarely investigated in an overall system approach. It is the topic of this paper to point out that it is inevitable to characterize decision feedback equalizer structures (DFE) in the context of channel characteristics, error propagation and implementation effort before talking of performance gain compared to linear equalizer structures. In particular DFE is characterized in the context of antenna diversity and channel coding as these techniques are indispensable for future high rate wireless communications systems. Only this overall system approach allows a reliable statement concerning the expected performance gain due to different equalizer strategies. The simulation results in this work are based on a single carrier system with frequency domain equalization (SC/FDE), as this concept allows an advantageous combination of feedforward frequency domain equalization and feedback equalization in the time domain, combining low signal processing complexity and powerful equalization. The simulation parameters are adapted to the parameters of the IEEE 802.11a standard.