Proposed systems for digital audio broadcasting (DAB) in the AM and FM radio bands are expected to provide improved-quality audio, data services, and more robust coverage than existing analog transmissions. These all-digital systems are often referred to as in-band on-channel (IBOC) DAB systems. However, until such time as a transition to all-digital DAB can be achieved, broadcasters require an intermediate solution in which the analog and digital signals can be transmitted simultaneously within the same licensed band. Such systems are typically referred to as hybrid in-band on-channel (HIBOC) DAB systems, and are currently being developed for both the AM and FM radio bands.
The above-noted DAB systems may be designed such that partial-band interference exists in certain areas of the system or under certain operating conditions. For example, it may be desirable in these systems to allow digital sidebands of adjacent carriers to overlap to a limited extent in specified areas or operating conditions, such that higher bit rates can be supported.
Techniques for alleviating the effects of partial-band interference and otherwise improving the performance of IBOC and HIBOC DAB systems are described in U.S. patent application Ser. No. 09/290,819 filed Apr. 13, 1999 in the name of inventors D. Mansour, D. Sinha and C.-E. W. Sundberg and entitled “Multistream In-band On-channel Systems,” U.S. patent application Ser. No. 09/322,848 filed May 28, 1999 in the name of inventors J. N. Laneman and C.-E. W. Sundberg and entitled “Soft Selection Combining Based on Successive Erasures of Frequency Band Components in a Communication System,” U.S. patent application Ser. No. 09/464,042 filed Dec. 15, 1999 in the name of inventors J. N. Laneman, D. Sinha, C.-E. W. Sundberg and J. W. Tracey and entitled “Error Screening Based on Code and Control Information Consistency in a Communication System,” and U.S. patent application Ser. No. 09/464,043 filed Dec. 15, 1999 in the name of inventors J. N. Laneman, D. Sinha and C.-E. W. Sundberg and entitled “Channel Code Configurations for Digital Audio Broadcasting Systems And Other Types of Communication Systems,” all of which are assigned to the assignee of the present invention and incorporated by reference herein.
Despite the considerable advances provided by the techniques described in the above-cited U.S. Patent Applications, a need nonetheless remains for further improvements in DAB system performance.