Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1999-03-02
2002-11-12
Pham, Chi (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S316000
Reexamination Certificate
active
06480523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spectrum spreading communication system, and more particularly to a spectrum spreading communication system suitable for a random burst signal transmitted from a plurality of mobile stations to a radio base station on a same frequency band at a same time using a same spreading code.
2. Description of the Related Art
As a conventional mobile communication system using a spectrum spreading communication system of this type is known the technique disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-227124), for example.
FIG. 1
is a block diagram illustrating an example of a reception system used in a CDMA communication system as the conventional technique.
The CDMA communication system is composed of a single radio base station
300
and a plurality of mobile stations
200
. A spreading code is allocated for the communication between the radio base station
300
and each mobile station
200
such that the bidirectional communication can be performed. The radio base station
300
synthesizes a pilot signal spread based on a short period code P, one period of which is set as one bit, and data transfer signals spread based on long period codes A, C and E corresponding to the respective mobile stations
200
. The synthesized signal is transmitted to the mobile stations
200
. The respective mobile stations
200
performs inverse spreading to the reception data transfer signal using the long period codes A, C and E allocated to the mobile stations, respectively. Also, the respective mobile stations
200
spreads data transfer signals using the transmission long period codes B, D and F, respectively. The radio base station
300
performs inverse spreading to a reception data transfer signal using reception long period codes B, D and F corresponding to the respective mobile stations
200
.
In such a structure, synchronization is established between a generation timing of the short period code P and each of the long period codes A to F. Also, a time mark is contained in a pilot signal to indicate a bit position of the long period code corresponding to the pilot signal so that it is possible to separate the long period codes into groups and to allocate them to a lot of mobile stations. Therefore, the synchronization can be quickly established using the pilot signal of the short period code. Also, the synchronization of a corresponding group part of the long periods code can be established based on the time mark contained in the pilot signal so that the synchronization of the long period code can be easily and quickly established. Therefore, it is possible to provide the CDMA communication system in which it is made possible to allocate unique codes to a lot of mobile stations while keeping an access random function.
However, in such a technique disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-227124), special controls are required. That is, there are synchronization establishment between the pilot signal and the data communication signal, insertion and excerption of the time mark, and the generation of a partial mark which matches to the time mark. Therefore, there is a problem in that the circuit scale becomes large so that the circuit becomes complicated.
Also, in another conventional technique, a plurality of mobile terminals transmits an same spreading code. In case of the reception of burst signals in which the plurality of mobile terminals perform access requests to a radio base station at the same time using the common spreading code, the respective signals interfere with each other.
Also, in such burst communication, it is difficult to strictly perform the transmission power control which is indispensable technique in the spectrum spreading communication system.
For these reasons, the dispersion of the levels of the signals received by the radio base station becomes large so that a delay profile used to detect paths is disordered. As a result, there is a problem in degradation of a path detecting capability.
Further, even if an initial synchronization correlating unit (a searcher) captures burst signals from the mobile stations, the mobile station in each path can not be easily identified. Therefore, there is a problem in that it is impossible to optimally realize the rake synthesis which is the technique to remarkably improve the communication quality peculiar to the spectrum spreading communication system.
In addition to the above reference, a spectrum spreading communication system is disclosed in Japanese laid Open Patent application (JP-A-Showa 56-102143). In this reference, a base band signal is formed by adding a data to be transmitted and a pilot signal. On a side of reception, the pilot signal is detected such that synchronization is established.
Also, a transmission signal system is disclosed in Japanese laid Open Patent application (JP-A-Showa 59-50603). In the this reference, a sync signal is transmitted with a transmission signal via a digital phase modulation communication line. Upon reception, the control of an antenna is performed using the sync signal as an its identification reference signal.
Also, an automobile telephone system is disclosed in Japanese laid Open Patent application (JP-A-Showa 63-202144). In the this reference, a plurality of communication channels are divided in frequency. A spectrum spreading communication is used for a line control channel to perform line control of the communication channels. A spectrum spreading code sequence on the line control channel corresponds to a mobile station telephone number.
Also, a receiving apparatus in a spectrum spreading communication system is disclosed in Japanese Examined Patent application (JP-B-Heisei 2-39139). In the this reference, the receiving apparatus is composed of a first quasi-noise code generating section, a correlation detector, a clock generating section, a second quasi-noise code generating section, a control section, and a demodulating section. The first quasi-noise code generating section generates a first quasi-noise code which always changes the phase for an inputted spectrum spread reception signal. The correlation detector always detects the correlation state between the spectrum spread reception signal and the first quasi-noise code to detect the state of the spectrum spread reception signal. The clock generating section generates a clock to control the first quasi-noise code generating section based on the detecting result by the correlation detector such that the phase of the first quasi-noise code always changes for the spectrum spread reception signal. The second quasi-noise code generating section generates a second quasi-noise code. The control section controls the second quasi-noise code from the second quasi-noise code generating section in accordance with the detecting information by the correlation detector such that the spectrum spread reception signal is coincident with the second quasi-noise code. The demodulating section performs the demodulation of the spectrum spread reception signal based on the second quasi-noise code controlled by the control section.
Also, a receiving apparatus in a spectrum spreading communication system is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 6-152564). In the this reference, [step
111
] existence or non-existence of a carrier of a Busy Tone is detected prior to a packet transmission. When an “L” level is detected over a predetermined time, a step
112
is executed. Also, a signal outputted from its station and a signal outputted from another station are compared to know a channel acquirement result of its station. When the signal is changed to the “H” level during a channel acquirement period, the channel acquirement is discarded and then a receiving process is performed. [Step
112
] A shift register outputs its identification code as the Busy Tone for one data. [Steps
113
and
114
] It is determined whether all the Busy Tone data are transmitted, a PN code is conti
Foley & Lardner
NEC Corporation
Pham Chi
Tran Khai
LandOfFree
Spectrum spreading communication system using single... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Spectrum spreading communication system using single..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spectrum spreading communication system using single... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2937818