Multiplex communications – Communication over free space
Reexamination Certificate
1998-04-28
2001-06-12
Ton, Dang (Department: 2732)
Multiplex communications
Communication over free space
C704S260000
Reexamination Certificate
active
06246672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to wireless communications systems and methods thereof and, more specifically, the present invention relates to individualized and interactive radio and communications services, including interactively controlled creation, repository, and delivery of content by human quality voice via a digital wireless communication infrastructure, to a wireless network computer, either hand-held or mountable in vehicles.
2. Background of the Prior Art
There have been a number of various technology advances in the radio broadcast industry which expand the available bandwidth to mobile customers, add some interactive control functions, improve reception, and allow radio programming to incorporate alphanumeric data. Mobile radios started integrating additional subsystems, e.g., U.S. Global Positioning System (GPS) receivers to locate vehicle coordinates, LCD screens for displaying alphanumeric data, e.g., song lyrics, paging, or for displaying graphic information, such as a local map retrieved from a co-located CD-ROM.
However, the fundamental radio technology has changed very little ever since its conception. It is still based on the original idea of channeled broadcast, which offers very little customization to listeners. That is, listeners can merely choose among a few channels, limited by the scarcely available bandwidth.
There have been revolutionary changes in the information technology in the recent years, e.g.: (1) a large amount of information has become available due to the advent of the Internet and other similar repositories; and (2) a sufficient overall communications bandwidth has become available to mobile consumers due to the advent of wireless technologies, e.g., cellular telephony, satellite communications.
Currently, this vast amount of information is primarily tuned for visual presentations on computer screens. Similar to computer users, radio listeners have a constantly increasing need for the capability to choose what they want to listen to, and when they want to listen to it.
There have been conventional computer-based attempts to deliver audio presentation of information to computer users on demand. The traditional method to achieve the above employs audio compression techniques and is quite straightforward. The textual information is first read by a human, the human voice is captured in an audio file, the audio file is then compressed and stored in a network-based information repository for consumption. The playback device, hard-wired to the same wired line network as the repository, retrieves the compressed audio files from the repository, decompresses them, and then plays them back.
Using such a scheme, Real Audio technology delivers AM quality audio (speech or music), if the client communicates with the Real Audio server at about 14 Kbps (kilobits per second), and provides FM quality audio when the available transmission rate is about or better than 28 Kbps. AM quality voice compression may be achieved at lower rates. Clearly, there is a trade-off between the compression ratio and the quality of the restored audio. Today, the maximum voice compression accepted by the wireless telephony industry is approximately 7-8 Kbps. For example, a compression scheme is used by digital cellular telephony standard IS-54 and is based on a vector-sum excited linear prediction (VSELP) coding technique which achieves 7.95 Kbps data rate.
However, this traditional radio on demand scheme assumes transmitting large volumes of digital audio data over long periods of time, i.e., on the order of hours. Using wired lines with its relatively cheap communications cost is economically acceptable for digital audio transmission. The customer is usually connected to the Internet or similar services by using a 14.4 Kbps or 28.8 Kbps modem over a single local telephone line. Therefore, even FM quality audio can be delivered to the customer very cheaply. The charge usually includes the cost of the local call (usually no additional charge is incurred to the basic phone connection cost) and a proportion of the charge paid to the Internet Service Provider (ISP). The latter also may be considered zero (no additional charge), if the ISP service charge is a flat rate.
Alternatively, even a contemporary system based on the widely used AMPS (Advanced Mobile Phone Service which is a wireless network used by analog cellular phones) modem still only reliably delivers about 4 Kbps to 8 Kbps depending on the speed of the vehicle, local geographic landscape and number of users simultaneously sharing the available local bandwidth.
Overall, the cost of wireless data transmission is usually about one or two orders of magnitude more expensive than in the case of wired data transmission. Clearly, such a method of transmitting compressed voice defeats the purpose of using wireless communication in the first place, because compressed speech takes at least as much data bandwidth as can be transmitted over a wireless telephony channel. In other words, the cost of digital voice transmission over AMPS is then approximately the same as transmission of an analog source without compression.
To allow users to share the cost of wireless data transmission, several companies have introduced the so-called Cellular Digital Packet Data (CDPD) technique. It allows multiple users to be connected to an IP (Internet Protocol) network permanently by sharing an idle AMPS channel and hopping between idle AMPS channels. An average data rate per CDPD user depends on the number of users sharing the channel. For example, if 20 users simultaneously send or receive data via one channel, individual average data rate will be just about 400 bps, which is sufficient for e-mail and other relatively short messages. The cost of transmission per byte is somewhat higher than using AMPS, but the packet approach to data transmission allows providers to charge users for the amount of data transmitted, not for the connection time. However, the above-described traditional scheme of compressed audio transmission requires much more bandwidth than is available to users connected to the audio source via CDPD network.
It is anticipated that in a few years, Personal Communication Systems (PCS) will have a somewhat better digital data transmission rate then AMPS and CDPD, but still will not be economical for long hours of wireless digital audio transmission.
It is clear from the above discussion that using traditional methods of transmitting large volumes of digital audio data to radio devices is prohibitively expensive, because the cost of the wireless communications media is optimized for relatively short transmissions, e.g., an average voice phone call or electronic mail. In the foreseeable future, known techniques will not yield the compression ratios necessary for economical transmission of audio data over wireless lines while providing an acceptable broadcast audio quality.
Today, the only known method to deliver large amounts of data wirelessly is using a speech synthesis method. Low bit rate may be obtained using Text-To-Speech (TTS) conversion technology. Regular text is represented by about 8 to 20 characters per second, or requires a maximum 160 bps transmission data rate; however, resulting speech does not deliver an acceptable human intonation.
Although arbitrary speech conversion is based on prosody rules as well as syntactic and morphological analysis, achieving human speaker's voice quality has not been feasible so far. One of the requirements of radio transmission is to deliver a speaker's intonation accurately, because the speaker prosody reflects certain aspects of his/her personality and the state of mind of the speaker. While speech compression delivers speaker's intonation precisely, arbitrary speech synthesis frequently does not.
Experiments show that such a “synthetic” intonation is not acceptable for the majority of radio listeners. As a result, the majority of radio listeners usually feel aggravated in a few minutes or loose their attention. Th
F. Chau & Associates LLP
International Business Machines Corp.
Ton Dang
Vanderpuye Ken
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