Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
1998-07-09
2001-03-13
Chin, Wellington (Department: 2664)
Multiplex communications
Communication over free space
Repeater
C370S468000, C370S522000, C455S003010, C348S014160
Reexamination Certificate
active
06201798
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to satellite broadcast systems, and a signaling waveform for facilitating the formatting of broadcast data, and the processing thereof by a satellite payload and remote radio receivers.
BACKGROUND OF THE INVENTION
There presently exists a population of over 4 billion people that are generally dissatisfied and underserved by the poor sound quality of short-wave radio broadcasts, or the coverage limitations of amplitude modulation (AM) band and frequency modulation (FM) band terrestrial radio broadcast systems. This population is primarily located in Africa, Central and South America, and Asia. A need therefore exists for a satellite-based direct radio broadcast system to transmit signals such as audio, data and images to low-cost consumer receivers.
A number of satellite communications networks have been developed for commercial and military applications. These satellite communications systems, however, have not addressed the need to provide multiple, independent broadcast service providers with flexible and economical access to a space segment, nor consumers' need to receive high quality radio signals using low-cost consumer radio receiver units. A need therefore exists for providing service providers with direct access to a satellite and choices as to the amount of space segment that's purchased and used. In addition, a need exists for a low-cost radio receiver unit capable of receiving time division multiplexed downlink bit streams.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a method of formatting a signal for broadcast transmission to remote receivers is provided whereby a broadcast service having at least one service component (e.g., an audio program, video, data, static images, paging signals, test, messages, panographic symbols, and so on) is combined with a service control header (SCH) in a broadcast channel bit stream frame. The SCH dynamically controls the reception of the service at the remote receivers.
In accordance with another aspect of the present invention, the service has an overall bit rate of K bits per second or n multiples of a minimum bit rate of L bits per second. The frame period is M seconds. The number of bits of service in a frame is n×L×M=n×P bits per frame. The SCH is n×Q bits, and the number of bits in a frame is n×(P+Q). For example, the service has an overall bit rate of 16 to 128 kilobits per second or n multiples of a minimum bit rate of 16 kilobits per second where 1≦n ≦8. The frame period is 432 milliseconds. The number of bits of service in a frame is n×16 kilobits per second×432 milliseconds or n×6912 bits. The SCH is n×224 bits, and the number of bits in a frame is n×7136.
In accordance with yet another aspect of the present invention, the service comprises more than one service component. Bits of each service component are interleaved in each broadcast channel bit stream frame.
In accordance with still yet another aspect of the present invention, the service components are integer ratios of the minimum bit rate of the service. Padding bits are added to the broadcast channel bit stream frame when one of the service components does not have a bit rate sufficient to fill each interleaved portion of the frame.
In accordance with another aspect of the present invention, the service and a SCH corresponding to each of first and second broadcast channels are synchronized using independent bit rate references. A single bit rate reference for all broadcast channels is not required. A satellite is configured to determined and compensate for time differences between the various independent bit rate references of the broadcast stations and a clock on-board the satellite.
In accordance with another aspect of the present invention, a service component comprising an analog signal such as audio is compressed using a coding scheme such as a Motion Pictures Expert Group or MPEG coding scheme (i.e., MPEG 1, MPEG 2 or MPEG 2.5) and a selected sampling frequency (e.g., 8 kilohertz, 12 kilohertz, 16 kilohertz, 24 kilohertz, 32 kilohertz and 48 kilohertz). Compression of a service component can be performed using the MPEG 2.5, layer 3 coding scheme.
In accordance with still yet another aspect of the present invention, the SCH comprises a number of fields selected from the group consisting of a preamble indicating the beginning of said frame, a bit rate index indicating the bit rate of said service, encryption control data, an auxiliary data field, an auxiliary field content indicator relating to the content of said auxiliary data field, data relating to multiframe segments transmitted using said auxiliary data field, and data indicating the number of service components which constitute said frame.
In accordance with another aspect of the present invention, a broadcast channel can be designated a primary broadcast channel and other broadcast channels can carry secondary services that are associated with the primary broadcast channel. The bandwidth of the broadcast program on the primary broadcast channel is therefore effectively increased. Information is provided in the SCH of each frame in each of the broadcast channels to assist the remote receivers in receiving broadcast services from primary and secondary broadcast channels. In accordance with a preferred embodiment of the present invention, the auxiliary field content indicator is provided with a flag to indicate whether the auxiliary data field comprises a primary or second service, and an associated service pointer comprising a unique identification code which corresponds to the next associated broadcast channel. The auxiliary data field can be changed from frame to frame, and the associated service broadcast channels need not be in contiguous frames.
In accordance with still yet another aspect of the present invention, the SCH can be used to control specific radio receiver functions requiring long bit strings. The long bit strings are transmitted via multiframe segments. The SCH comprises a start flag to indicated whether an auxiliary data field comprises the first segment or an intermediate segment of a multiframe transmission. The service control header is also provided with a segment offset and length field (SOLF) to indicate to which of a total number of multiframe segments the current segment corresponds and therefore to serve as a counter. In other words, the SOLF for each intermediate multiframe segment increases by one until the total number of segments less one is reached. Multiframe segments need not be located in contiguous broadcast channel frames. In addition, the auxiliary field content indicator comprises bits corresponding to a service label for the contents of the auxiliary data field.
In accordance with yet another aspect of the present invention, the service control header comprises a service component control field (SCCF) for each service component provided in a broadcast channel frame which facilitates demultiplexing and decoding of service components at radio receivers. The SCCF indicates the length of the service component, the type of service component (e.g., data, MPEG encoded audio, video and so on), whether or not the service component is encrypted, method of encryption, the type of program (e.g., music, speech as so on) to which the service component belongs, as well as the language used in the program.
In accordance with still yet another aspect of the present invention, the SCH comprises a dynamic auxiliary data field for transmitting a dynamic label byte stream to receivers such as text or a screen for display at the receiver. The dynamic label byte stream that is not related to a particular service. Thus, the radio receiver need not be tuned to receive a particular service in order to receive the dynamic label byte stream.
REFERENCES:
patent: 3789142 (1974-01-01), Shimasaki et al.
patent: 4425639 (1984-01-01), Acampora et al.
patent: 4480328 (1984-10-01), Alaria et al.
patent: 4660196 (1987-04-01), Gray
Campanella S. Joseph
Courseille Olivier
Dunas Etienne
Eberlein Ernst
Meltzer Stefan
Chin Wellington
Nguyen Steven
Roylance Abrams Berdo & Goodman
WorldSpace Management Corporation
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