OFDM/FM frame synchronization for mobile radio data communication

Abstract

A synchronization scheme enabling the use of orthogonal frequency division multiplexing OFDM/FM over a mobile radio channel in a pure ALOHA environment is proposed. The scheme encodes synchronization information in parallel with data in the same manner in which data is encoded in the OFDM/FM frame. The synchronization information is in the form of tones, centered in certain reserved frequency sub-channels of the OFDM signal. The receiver uses a correlation detector, implemented in the frequency domain, to acquire synchronization accurately on a packet-by-packet basis. Experimental results indicate that the bit-error-rate performance achievable with the proposed scheme is within 1.5 dB of the performance obtained with ideal synchronization. In general, the number of bits assigned to each sub-carrier can vary from one sub-carrier to the next [ll].

Synchronization for OFDM-Based Systems

“…Thus, it can be used to find coarse timing and frequency offset in the initial communication link. Several data-aided techniques have been proposed (Classen & Meyr, 1994, Daffara & Chouly, 1993, Kapoor et al, 1998, Luise & Reggiannini, 1996, Moose, 1994, Warner & Leung, 1993. Moreover, the SNR at the front end in the receiver is often too low to ineffectively detect pilot symbols; thus, a blind approach is usually much more desirable.…”

Measurement results of frequency offset in DVB-C2 receiver

“…Figure 4 shows FFO estimator [4], [5] , [6], [7], [8], [9], [10]. The estimation of in Figure 4 can be expressed as equation (2) and estimated in time domain using CP of OFDM symbol.…”

Joint synchronization in Eureka 147 DAB system based on abrupt phase change detection

“…When the received signal reaches the last period of a symbol, we have samples of at the output of the "Correlation" block in Fig. 3, where (14) In (14), is the received symbol when frequency offset is zero, and is defined as (15) The approximation holds because we assume the OFDM symbol rate is much higher than the channel fading rate. We can estimate , the normalized fractional frequency offset from (16) In the last period of a symbol, is almost a constant and is proportional to .…”

“…Many synchronization methods have been proposed for OFDM systems. However, they usually either require a special pilot tone structure or solve only part of the synchronization problems [9]- [14]. A complete synchronization system using a DSP approach has been proposed by some authors [15], [16].…”