Wireless communication systems are widely deployed to provide various types of communication such as voice and data. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other modulation techniques. A CDMA system provides certain advantages over other types of systems, including increased system capacity.
A CDMA system may be designed to support one or more CDMA standards such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “C.S0002-A Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “C.S0024 cdma2000 High Rate Packet Data Air Interface Specification” (the cdma2000 standard), and (4) some other standards. Non-CDMA systems include the AMPS and GSM systems.
A typical wireless system provides point-to-point communication such as voice or data calls between one or more base stations and a mobile station. It is sometimes desirable to offer point-to-multipoint communications, such as broadcast information transmitted to one or more subscribing mobile stations. Broadcast services may include news, sports, weather updates, various audio and/or video presentations, various forms of text, data, and the like.
A broadcast information signal is, by design, not adapted for individual mobile station connections, but rather adapted for transmission to various mobile stations within a cell coverage area. Thus, techniques for optimizing point-to-point links, such as power control, are not as effective when identically applied to the broadcast signal. The signal quality received at various geographical locations in the cell coverage area will vary. Block coding techniques may be employed to provide a minimum quality of service to all the area served by a cell.
Due to the varying signal conditions experienced throughout a cell, it is possible to offer additional content to mobile stations that are in a relatively better reception area. The additional content may be additional text or data to go along with the base information signal embodied in the broadcast signal. Alternatively, additional information may be provided to enhance the quality of, for example, video or audio broadcasts. This additional, or secondary, information stream may be offered on one or more separate, parallel, code-division multiplex broadcast channels that have the same duration as the main broadcast channel that supports mobile stations in all areas of the cell. However, additional complexity, increased cost, increased power consumption, and/or decreased battery life may result if parallel receiving circuitry is deployed within mobile stations to take advantage of the secondary signal.
Furthermore, if multiple broadcast streams are offered for subscription within a cell, an efficient format for transmitting the multiple broadcast streams is desired. There is therefore a need in the art for transmitting and receiving multiple channels with block coding in a communication system.