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This paper presents the design of an efficient low complexity orthogonal frequency division multiplexing receiver targeting wireless local area networks. The focus is on mitigation of the residual frequency synchronization error and sampling frequency offset. We propose a novel algorithm that uses an approximation instead of implementing the comple...
Contexts in source publication
Context 1
... and sampling frequency acquisition and maintenance with high accuracy is vital for successful trans- mission of long packets. Residual carrier frequency offset and sampling frequency offset tracking(phase tracking Figure 1) is thus very critical part of OFDM receivers. But, the tracking module is highly complex [2] [8], and thus has significant potential for cost optimization of OFDM receivers. ...
Context 2
... synchronization impairments that an OFDM receiver has to mitigate are Frame Timing Offset (FTO) or Symbol Timing Offset (STO), taken care of in the Time Synch (Fig- ure 1), Carrier Frequency Offset (CFO) is compensated by the frequency synch of Figure 1. ...
Context 3
... synchronization impairments that an OFDM receiver has to mitigate are Frame Timing Offset (FTO) or Symbol Timing Offset (STO), taken care of in the Time Synch (Fig- ure 1), Carrier Frequency Offset (CFO) is compensated by the frequency synch of Figure 1. ...
Context 4
... this article, we deal with the residual CFO and SFO errors, jointly termed as Residual Phase Errors (phase tracking block in Figure 1. Residual Phase Error is the combined error due to non-exact carrier frequency offset correction and existing sampling frequency offset. ...
Context 5
... carrier frequency offset in the signal even after CFO correction together with the sampling frequency offset causes phase rotation in each subcarrier to increase with OFDM symbol index as can be seen from Equation 4. Cumulative phase increment severely limits the number of OFDM symbols that can be transmitted in one packet. The receiver thus has to continuously track and compensate for the effect (phase tracking block in Figure 1). ...
Context 6
... the proposed algorithm gives double fold benefit. One it relaxes otherwise stringent performance requirement of the freq synch block of Figure 1. For higher accuracy of freq synch block (as required by the other scheme) the complexity and the cost of implementation of the receiver increases [8]. ...
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Citations
... Even the small RCFO results into phase shift across the received OFDM blocks, which accumulates linearly with time and will cause a significant performance loss for those systems with long frame durations or high-order modulations. Single CFO tracking using pilots has been well studied for single-antenna systems [11,12] and multiple-input multiple-output OFDM systems [13,14]. In fact, pilot tones are part of most OFDM standards in use today. ...
... In the second phase (i.e. the relaying phase), space-frequency (SF)-coded signals are transmitted from the relay nodes. Since only one RCFO related to each relay node presents in the broadcasting phase, conventional OFDM CFO tracking algorithms can be applied directly [11,12]. However, in the relaying phase, multiple RCFOs not only cause multiple phase shifts, but also introduce ICI across the whole received OFDM block. ...
... Letting v i =v i + Dv i , where Δω i denotes the RCFO associated with the ith relay node, the RCFO Δω i will appear in both the phase shift and ICI terms. In conventional OFDM systems, a single RCFO remains in the received signal after frequency compensation in time domain [11,14], where the RCFO-induced ICI can be equivalent to an additional noise-like term. Thus, based on the inserted pilot tones, the accumulated phase shift is estimated to obtain the RCFO [13]. ...
This study addresses the problem of carrier frequency offset (CFO) tracking in co-operative space-frequency block-coded orthogonal frequency division multiplexing (OFDM) systems with multiple CFOs. Considering that the inserted pilot tones are decayed by data subcarriers in the presence of multiple CFOs, a novel recursive residual CFO tracking (R-RCFOTr) algorithm is proposed. This method first removes CFO-induced inter-carrier interference from data subcarriers, and then updates the residual CFO (RCFO) estimation of each OFDM block recursively. When used in conjunction with a multiple CFOs estimator, the proposed R-RCFOTr can effectively mitigate the impacts from the multiple RCFOs with affordable complexity. Finally, simulation results are provided to validate the effectiveness of our proposed R-RCFOTr algorithm, which has performance close to that of perfect CFO estimation at moderate and high signal-to-noise ratio, and significantly outperforms conventional CFO tracking algorithm for large CFOs.
This paper analyses the estimation of residual frequency offset in MIMO OFDM systems using pilot subcarriers. A closed-form expression for the MSE is derived and this is used to study the pilot design problem. An orthogonal design is proposed and simulation results show that this is superior to using the same pilots on all pilot subcarriers
This paper analyses the estimation of residual frequency offset in MIMO OFDM systems using pilot subcarriers embedded in the data payload. A closed-form expression for the MSE is derived and it shows how the frequency and spatial correlation influence performance. It is also shown that an orthogonal design ensures robust performance, which is independent of the frequency correlation of the channel.
This paper presents an analysis of frequency-offset estimation in multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. Tracking of the frequency offset between a transmitter and a receiver is often aided by transmitting pilots embedded in the data payload of a packet. The extension to multiple-antenna OFDM systems means that spatial beamforming will occur when transmitting pilots from all antennas simultaneously, which can reduce the robustness of frequency-offset estimation. This paper presents a thorough analysis of the spatial beamforming problem, and shows how the spatial correlation of the MIMO channel impacts performance. Simulation results are presented for both synthetic and measured channels, which agree well with the theoretical results
