Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1997-09-29
2002-10-08
Eisenzopf, Reinhard J. (Department: 2745)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S434000
Reexamination Certificate
active
06463298
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to wireless communication systems and devices. More particularly, the present invention relates to a novel and improved method for rapidly and automatically switching between wireless communication systems in a multiple-mode wireless communication device upon the failure of reverse link communications with a current base station.
II. Description of the Related Art
The use of code division multiple access (CDMA) modulation techniques is one of several techniques for facilitating communications in a wireless communication system in which a large number of system users are present. Other multiple access communication system techniques, such as time division multiple access (TDMA) and frequency division multiple access (FDMA) are known in the art. An example of a TDMA communication system is the pan-European Global System for Mobile Communications (GSM). An example of an analog FDMA system is the Advanced Mobile Phone System (AMPS) presently used in the U.S. for cellular communications.
However, the spread spectrum modulation technique of CDMA has significant advantages over these other techniques for multiple access communication systems. The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, issued Feb. 13, 1990, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein.
CDMA by its inherent nature of being a wideband signal offers a form of frequency diversity by spreading the signal energy over a wide bandwidth. Therefore, frequency selective fading affects only a small part of the CDMA signal bandwidth. Space or path diversity is obtained by providing multiple signal paths through simultaneous links from a mobile user through two or more cell-sites. Furthermore, path diversity may be obtained by exploiting the multipath environment through spread spectrum processing by allowing a signal arriving with different propagation delays to be received and processed separately. Examples of path diversity are illustrated in U.S. Pat. No. 5,101,501, issued Mar. 31, 1992, entitled “SOFT HANDOFF IN A CDMA CELLULAR TELEPHONE SYSTEM”, and U.S. Pat. No. 5,109,390, issued Apr. 28, 1992, entitled “DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM”, both assigned to the assignee of the present invention and incorporated by reference herein.
The deleterious effects of fading can be further controlled to a certain extent in a CDMA system by controlling transmitter power. A system for cell-site and mobile unit power control is disclosed in U.S. Pat. No. 5,056,109, issued Oct. 8, 1991, entitled “METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILE TELEPHONE SYSTEM”, Ser. No. 07/433,031, filed Nov. 7, 1989, also assigned to the assignee of the present invention. The use of CDMA techniques in a multiple access communication system is further disclosed in U.S. Pat. No. 5,103,459, issued Apr. 7, 1992, entitled “SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM”, assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein.
In the field of wireless communications, such as cellular, wireless local loop, and Personal Communication Services (PCS), base stations communicate with remote subscriber units such as portable radiotelephones. For simplicity, the term “mobile station” will be used herein to refer to such remote subscriber units, although it is understood that some remote subscriber units, such as wireless local loop phones, do not often move throughout the wireless environment, but rather are generally stationary.
Typically, in any geographic service area, there will be more than one wireless communication service provider. For example, in cellular systems in the United States, there are usually two service providers, one whose system is designated System “A”, and another whose system is designated System “B”. For the currently planned PCS services in the United States, there are many more service providers, denoted by blocks “A”-“F”, covering the same geographical service area. The available frequency spectrum for each geographical service area is divided up among these wireless telecommunication service providers. Each service provider typically operates its own base stations and other network equipment.
In accordance with the various wireless communication standards, including Telecommunications Industry Association (TIA)/Electronic Industries Association (EIA) Interim Standard IS-95, entitled “Mobile Station—Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System”, there exist dual-mode CDMA/AMPS portable radiotelephones which may communicate with either a CDMA base station or an AMPS base station. Furthermore, there are other industry standards existing or in development which provide for dual-mode operation among other modulation and multiplexing schemes such as dual-mode CDMA PCS band and AMPS, dual-mode CDMA PCS band and CDMA cellular band, dual-mode GSM and AMPS, and various other combinations of the known modulation and multiplexing schemes. Other dual-mode mobile stations operate according to one standard when in a first mode, and according to another standard when in a second mode. For example, a dual-mode mobile station may operate according to ANSI J-STD-008, entitled “Personal Station-Base Station Compatibility Requirements for 1.8 to 2.0 GHz Code Division Multiple Access (CDMA) Personal Communication Systems” when in a PCS mode of operation, and according to the AMPS standard when in an AMPS mode of operation.
As can easily be appreciated from the number of co-located service providers and the number of communication protocols that may be used, there are a large number of possible communication systems that may be operating in a single geographic area, each with varying degrees of coverage. For example, since AMPS was the first analog FM-based cellular system to gain wide market acceptance in the United States, AMPS communications systems presently provide nearly 100% coverage for the entire populated regions of the U.S. However, as other competing communication systems such as CDMA cellular and CDMA PCS systems are being deployed, their total coverage area is rapidly expanding. Thus, it is anticipated that there will be many co-located communication systems with varying and overlapping degrees of coverage.
Due to the advantages of CDMA as outlined above, many users of dual-mode CDMA/AMPS mobile stations prefer to use CDMA service whenever it is available and use AMPS service only when CDMA service is not available. Furthermore, a particular user of a dual-mode CDMA cellular and CDMA PCS portable radiotelephone may prefer to use the PCS services over the cellular services for various reasons. For these reasons, dual-mode mobile stations designed in accordance with IS-95 generally allow the user to select a preferred mode of operation (i.e. CDMA or AMPS), and the mobile station will operate accordingly. Other standards may allow the same user-preferences, or may “hard-code” a particular system priority.
This “hard-coded” preferences list is often referred to in the art as a “preferred roaming” list. Put simply, a preferred roaming list is a list of systems that are preferred over other system choices when the mobile station is seeking to establish service. The service providers on these preferred roaming lists may have inter-system roaming agreements to facilitate billing and other administrative or operational activities.
In any event, whenever the user of a dual-mode mobile station is in a geographical area where good coverage exists for one of the non-preferred communication systems, for example AMPS, but imperfect coverage for the preferred system, for example CDMA, the user will generally wish to make a “seamless” tra
Ault Jan C.
Hutchison, IV James A.
Sorenson John R.
Banks-Harold Marsha D.
Brown Charles D.
Eisenzopf Reinhard J.
Martin Roger W.
Miller Russell B.
LandOfFree
Method of acquiring an alternate communication system upon... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of acquiring an alternate communication system upon..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of acquiring an alternate communication system upon... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2961433