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Methods and apparatus for providing robust synchronization of radio transceivers
| Details |
Inventors: Mattisson, Sven; Persson, Joakim; Haartsen, Jacobus Cornelius;
Assignee: Telefonaktiebolaget L M Ericsson (Stockholm, SE)
Primary Examiner: Chin; Stephen
Assistant Examiner: Williams; Lawrence
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis, L.L.P.
Methods and apparatus for performing synchronization and DC-offset compensation in FM transmission systems significantly reduce the overhead associated with transmitting a conventional digital preamble at the start of each of a succession of transmitted digital data packets. According to exemplary embodiments, a multi-part digital preamble includes a short, substantially DC-free leading part followed by a code-protected synchronization part which is not necessarily substantially DC-free. The leading part provides for coarse DC offset estimation and synchronization, while the coded synchronization part carries timing and/or other useful information which can be unique for each packet. One or more substantially DC-free trailing parts follow the synchronization part, or are included in the synchronization part itself, and provide for fine tuning of the DC-offset estimate. Since the substantially DC-free leading and trailing parts are extremely short, and since the synchronization part carries useful information, the overhead associated with a preamble according to the invention is significantly reduced as compared to a conventional, entirely DC-free, preamble. |
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DETAILED DESCRIPTION The present invention fulfills the above-described and other needs by providing a multi-part digital preamble for use in transmitting digital data packets.
Advantageously, a preamble according to the invention substantially reduces the overall length of DC-free sequences that are transmitted with each data packet in a digital FM system.
According to exemplary embodiments, a multi-part preamble includes a short, substantially DC-free leading part which enables coarse estimation of a prevailing DC level at an FM receiver.
The exemplary preamble also includes a synchronization part which is not necessarily substantially DC-free and which carries timing and/or other useful information (e.
g.
, channel identification, destination address, etc.
) that can vary from data packet to data packet (e.
g.
, depending on sender, recipient, time of day, etc.
).
According to the invention, the synchronization word is protected by code to reduce false detection probability and can therefore be successfully detected using only the coarse DC-offset correction provided by the short leading portion of the preamble.
Following the synchronization part, or within the synchronization part itself, the exemplary multi-part preamble includes one or more substantially DC-free trailing parts that can be used to perform final DC-offset estimation and compensation.
Since signal timing is well known after the synchronization part is detected, the substantially DC-free trailing part(s) can be made extremely short.
Moreover, since the substantially DC-free leading and trailing parts are short, and since the synchronization part carries useful information which can be different for each data packet, the overhead associated with a digital data packet preamble according to the invention is significantly reduced as compared to conventional digital data packet preambles.
An exemplary radio transmitter according to the invention includes a modulator transmitting a succession of digital data packets by modulation of a carrier signal
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