Improved time and frequency synchronization in presence of imperfect channel state information

Abstract

This paper addresses altogether time and frequency synchronization in IEEE 802.11a orthogonal frequency division multiplexing (OFDM) wireless communication systems. The proposed algorithms have two main features: (i) they make use of an additional source of information available at IEEE 802.11a physical layer, on top of the usual ones typically adopted for synchronization such as training sequences. This additional source of information is provided by the higher layers of the communication protocol. In fact, when the carrier sense multiple access with collision avoidance (CSMA/CA) protocol is activated, the receiver is able to predict some parts of the SIGNAL field that are classically assumed unknown. Moreover, during the negotiation of the transmission medium reservation, the exchanged frames not only help the receiver to predict the SIGNAL field but also to obtain information about the channel state. (ii) Based on this property, we propose a joint MAP time and frequency synchronization algorithm using all available information. Finally, the time synchronization is fine tuned by means of a specific metric in the frequency domain that allows us to minimize the expectation of the transmission error function over all channel estimate errors. Simulation results compliant with the IEEE 802.11a standard in both indoor and outdoor environments show that the proposed algorithm drastically improves the performance in terms of synchronization failure probability and bit error ratio, compared to state-of-the-art algorithms.

A New Approach to Improve Transmitting and Receiving Timing in Orthogonal Frequency Division Multiplexing (OFDM) Systems

“…Simulation results compatible with the IEEE 802.11a standard in both indoor and outdoor situations showed that the recommended method significantly improved the performance in terms of synchronization. Bit error rate and failure probability are measured in comparison to the most recent techniques [15].…”

A Reference Model for Monitoring IoT WSN-Based Applications

“…A synchronization algorithm, such as [41] or [42], should be considered at the Information Layer Protocol, to keep the same timeline in all the MDP data from every monitoring mote. Usually, the accuracy of the analysis will depend on the precision offered by the synchronization algorithms.…”

“…These allow, not only the correct timeline characterization, but also may be fundamental in order to analyze the time constrictions of the system, which is a key characteristic of time critical applications. In this way, last advances in this area [41,42,43] can be applied at this layer to obtain the best results. The used synchronization algorithm must be part of the Information Layer Protocol, which must offer the user the possibility to select the most appropriated synchronization protocol for the characteristics of the monitoring application.…”