Timing and Frequency Synchronization for OFDM Downlink Transmissions Using Zadoff-Chu Sequences

Abstract

Orthogonal frequency division multiplexing (OFDM) technique has been widely adopted in wireless systems, but it is known for being sensitive to synchronization errors. In this paper, we present timing and frequency synchronization algorithms for OFDM downlink transmissions using Zadoff-Chu sequences. We show that the current timing synchronization method employing Zadoff-Chu sequences is sensitive to carrier frequency offsets. To reduce this sensitivity, we develop conditions for the selection of appropriate Zadoff-Chu sequences. We then design a training sequence and propose joint signal detection, timing, and carrier frequency offset estimation algorithms for OFDM downlink transmissions. We show that the proposed schemes simplify the overall synchronization architecture and improve the performance compared to the existing schemes in the literature.

Evaluation of OFDM Channel Sounding Techniques with Three Modulation Sequences

“…The ZC sequence presented sligthly smaller sounding errors and fluctuations, and a smaller peak to average power ration. These results are in accordance with [14], that first proposed the use of this ZC sequence for broadband channel sounding. The differences, however, are not enough to indicate definite advantages of the use a particular sequence.…”

“…The third sequence considered is the ZC sequence that, due to its better autocorrelation properties [14]- [16], is often used as a synchronization sequence in modern wireless systems replacing the conventional PN sequence. The ZC sequence is included in a class of polyphase sequences defined by (5) in which is the root of the sequence and N is the number of samples, odd and prime.…”

Packet Detection by a Single OFDM Symbol in URLLC for Critical Industrial Control: A Realistic Study

“…In this case, the AGC should slowly tune the receiving gain along the time and the transmission prediction could be combined to the AGC, as it can help avoid sudden receiver gain fluctuations caused by counting the signal power from the false alarms. For the preamble design, the Zadoff-Chu sequence is known to have better auto-correlation properties than PN sequence [32], and we consider to investigate the performance of such sequence as future work. Moreover, whereas this work focuses on physical layer design, higher layer design to achieve low latency and deterministic communications will be the subject of following research.…”

Distributed signal processing for dense 5G IoT platforms: Networking, synchronization, interference detection and radio sensing

“…where the ambiguity function X ZC (τ, ω) is characterized by a periodic sinc (•) which contains the same (but opposite in sign) time shift that solve for TO/CFO the ambiguity similar to [49] (6) with an increased interference proportional to |N k |. This mutual interference can be mitigated by increasing N , taking advance of the orthogonality properties of ZC sequences [47], even if in OFDM system the length N is constrained by the number of sub-carriers.…”