Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Patent
1997-01-31
1999-09-14
Cuchlinski, Jr., William A.
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
370332, 370335, 370333, 370320, 371 30, 375200, 375206, 455436, 455439, 455443, 455444, H04J 1300
Patent
active
059533242
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to reception level monitoring and hand-off operation in cellular mobile communications.
BACKGROUND ART
In cellular mobile communications, a number of base stations are disposed in a large service area. The base station to be connected is successively changed over as the mobile station moves so that the mobile station can make communication with a base station of the best communication quality to continue the communication. In this case, to search for a base station to be next connected, during communication radio waves of base stations around the base station under communication are received to measure the reception levels. From the measurement results, the mobile station determines a neighboring base station the highest reception level as the new base station to be next connected, and notifies the result to the base station in communication. Using this procedure, when change-over (hand-off) of the base station becomes required, an upper level station of the base station under communication instructs the base station under communication and the new base station to begin hand-off operation. During the hand-off operation, the same transmission data is transmitted from the base station under communication and the new base station, the mobile station changes over the transmission/reception frequency from the base station under communication to the new base station, or vice versa, in alternation. This is the method of monitoring neighboring base stations and hand-off in cellular mobile communications.
In a time division multiple access (TDMA) communication system, the transmission time is divided into short times called slots, and a number of mobile stations are assigned to different slots to make transmission and reception periodically. Therefore, the time other than the transmission and reception slot of the mobile station is a blank time. Making use of the blank time, the mobile station allows monitoring neighboring base stations to select a base station easily which provides the highest reception level. Thus, hand-off is made to the selected new base station (see "digital mobile telephone system" standard specifications, RCR STD-27B, by Research & Development Center for Radio System, or "Personal digital cellular telecommunication system RCR standard, RCR STD-27", Research & Development Center for Radio System).
On the other hand, in a code division multiple access (CDMA) communication system, though it has no blank time as seen in TDMA, since all of the base stations may use the same radio frequency, it is not necessary to make neighboring base station monitoring or changing over the transmission/reception frequency at hand-off operation (see R. Padovani, "Reverse link performance of IS-95 based cellular systems," IEEE Personal Communications, vol. 1, pp.28-34, 3rd Quarter 1994). That is, in CDMA, each base station spreads the transmission data to wideband signals using different spreading code sequence with a same frequency. Therefore, at the receiving side, it is sufficient to provide another correlator for despreading the received signal with the spreading code sequence of the peripheral base stations in order to achieve neighboring base station monitoring and hand-off operation.
However, also in CDMA, there is a case where base stations cannot use the same radio frequency. This is, for example, the case of a macrocell base station with a wide communication range which is overlaid by microcell base station with a narrow communication range. Since the transmission power of the microcell base station is smaller than that of the macrocell base station, if the same radio frequency is used, the transmission signal of the macrocell base station considerably affects the reception signal of the mobile station which is under communication with the microcell base station. Further, since the transmission power of the macrocell mobile station may be higher than the transmission power of a mobile station under communication with a microcell base station, the receptio
REFERENCES:
patent: 5101501 (1992-03-01), Gilhousen et al.
patent: 5313489 (1994-05-01), Menich et al.
patent: 5347535 (1994-09-01), Karasawa et al.
patent: 5420850 (1995-05-01), Umeda et al.
patent: 5487083 (1996-01-01), Nakajima et al.
patent: 5488629 (1996-01-01), Takahashi et al.
patent: 5533014 (1996-07-01), Willars et al.
patent: 5568472 (1996-10-01), Umeda et al.
patent: 5673260 (1997-09-01), Umeda et al.
patent: 5768306 (1998-06-01), Sawahashi et al.
Beaulieu Yonel
Cuchlinski Jr. William A.
NTT Mobile Communications Network Inc.
LandOfFree
CDMA mobile communication method, system and mobile station appa does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with CDMA mobile communication method, system and mobile station appa, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CDMA mobile communication method, system and mobile station appa will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1517111