Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
1997-11-20
2001-09-04
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication over free space
Repeater
C370S350000, C370S324000
Reexamination Certificate
active
06285666
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spread-spectrum communication method and apparatus.
2. Description of the Related Art
In a time-sharing communication method for converting data to bursts, in order to receive and demodulate data bursts it is necessary to establish synchronization with the data bursts to be received. It is also necessary that only desired information addressed to the receiving end be detected and extracted from the received signals. In addition, conflict between one station and another station must be avoided. Accordingly, in general, in such a communication method data is transmitted in accordance with a regular format.
FIG. 1
shows an example of a format for a data burst in the above communication method. For example, data bursts each include a preamble consisting of a synchronization code (SY), a unique word (UW) and a station-identification code (ID), and data (DA). Between the data bursts there is a guard time (GT).
A receiving end which receives the data bursts uses the synchronization code in the preamble period to perform reproduction of a carrier, input of automatic gain control (AGC), establishment of clock synchronization, and so forth. The receiving end further detects the unique word (UW) and the station-identification code (ID), and when it perceives that the successive data (DA) is desired data addressed to itself, it holds a reproduced carrier, AGC, clock synchronization and so forth until the data terminates, and it demodulates the data.
However, this communication method causes an error in the reference clock frequency between the transmitting and receiving ends. Thus, with the lapse of time, the receiving end's clock which has held the established synchronization in the preamble, also has increased synchronization errors with respect to the transmitting end's clock. In addition, for example, if the transmission line is wireless, communication quality may vary with time, which results in the possibility of the input AGC held in the preamble losing its optimum condition with the lapse of time. According to this communication method, the maximum time during which data can be transmitted with one data burst is limited by the time during which synchronization precision, AGC precision and so forth can be maintained.
According to the above communication method, when a large amount of digital data (e.g., image data or the like) adapted for recent multimedia applications is transmitted, as shown in
FIG. 2
, data is divided into a plurality of portions, and the complete data must be transmitted as a plurality of data bursts. As a result, the preamble time and the guard time with respect to the time used for transmission of the actual data increases, and there is the possibility of an interrupting burst from another station occurring between the divided data bursts. Consequently, the data throughput deteriorates.
In order to extend the maximum time during which the data can be transmitted with one data burst, a precise frequency oscillator, and a complicated synchronization circuit or AGC must be used, which disadvantageously requires an expensive, large-sized apparatus.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a spread-spectrum communication method and apparatus having a high throughput.
It is another object of the present invention to provide a spread-spectrum communication method and apparatus adapted for performing large-amount data communication.
It is a further object of the present invention to provide a spread-spectrum communication method and apparatus in which an adjustment period for receiving spread spectrum data is provided in a period for transmitting spread spectrum data.
It is a still further object of the present invention to provide a spread-spectrum communication method and apparatus which communicate an adjustment signal for adjusting reception of spread spectrum data in a plurality of divided data-communication periods.
Other objects of the present invention will be apparent from the embodiments described below, based on the attached drawings.
To this end, according to a first aspect of the present invention, the foregoing objects have been achieved through provision of a spread spectrum communication method comprising the steps of: dividing a communication period for spread spectrum data into a plurality of communication periods; and providing an adjustment period for receiving the spread spectrum data between one data-communication period and another data-communication period.
The spread spectrum communication method may further comprise the step of synchronizing a spread code in the adjustment period.
The spread spectrum communication method may further comprise the step of providing the adjustment period prior to the plurality of data-communication periods.
The spread spectrum communication method may further comprise the step of holding the adjusted setting of the receiving end in the data-communication period.
The spread spectrum communication method may further comprise the step of holding gain in the data-communication period.
The spread spectrum communication method may further comprise the step of communicating code-division-multiplexed data in the data-communication period.
The spectrum communication method further comprising the step of providing the adjustment period prior to the plurality of data-communication periods, may still further comprise the steps of establishing the setting of a receiving end in the adjustment period prior to the plurality of data communication periods; and correcting the established setting in the adjustment period between one data-communication period and the next data-communication period.
Preferably, in the spread spectrum communication method further comprising the step of providing the adjustment period prior to the plurality of data-communication periods, the gain for the adjustment in the adjustment period prior to the plurality of data-communication periods is larger than the gain for the adjustment in the adjustment period between the one data-communication period and the next data-communication period.
Preferably, in the spread spectrum communication method further comprising the step of providing the adjustment period prior to the plurality of data-communication periods, an adjusting signal communicated in the adjustment period prior to the plurality of data-communication periods is longer than an adjusting signal communicated in the adjustment period between the one data-communication period and the next data-communication period.
The spread spectrum communication method further comprising the step of communicating code-division-multiplexed data in the data-communication period may further comprise the step of communicating a signal not multiplexed by code division multiplexing, in the adjustment period.
According to a second aspect of the present invention, the foregoing objects have been achieved through provision of a spread spectrum communication apparatus comprising: data communication means for communicating spread spectrum data in a plurality of divided data-communication periods; and adjustment-signal communication means for communicating an adjustment signal for adjusting reception of spread spectrum data between one data-communication period and another communication period.
The spread spectrum communication apparatus may further comprise adjustment means for establishing the setting of a receiving end in accordance with the adjustment signal prior to the plurality of data-communication periods and correcting the established setting in accordance with the adjustment means between the one data-communication period and the next data-communication period.
The spread spectrum communication apparatus may further comprise holding means for holding the setting of the receiving end in the data-communication period.
REFERENCES:
patent: 4859964 (1989-08-01), Jorgensen
patent: 4958359 (1990-09-01), Kato
patent: 5260969 (1993-11-01), Kato et al.
patent: 5537396 (19
Boakye Alexander O.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Chau
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