Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Patent
1994-12-15
1997-04-22
Olms, Douglas W.
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
455 561, H04J 1304
Patent
active
056234848
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to cellular telecommunications systems. More specifically, the present invention relates to a system and a method for controlling the radio signal quality between a plurality of mobile stations (MS) communicating via a plurality of base stations (BS) connected to a mobile switching center (MSC) of a code division multiple access (CDMA) cellular telecommunications system.
DESCRIPTION OF PRIOR ART
The use of code division multiple access (CDMA) modulation is but one of several techniques enabling digital communications among a number of mobile users utilizing a common part of the radio spectrum, as is the case for cellular telecommunications systems. If appropriately embodied, a CDMA cellular telecommunications system possesses several advantages such as increased traffic handling capacity compared to designs based on frequency division multiple access (FDMA) or time division multiple access (TDMA) radio access technologies. An exemplary application of CDMA to cellular telecommunications systems has been substantially described in "On the System Design Aspects of Code Division Multiple Access (CDMA) Applied to Digital Cellular and Personal Communications Networks", Allen Salmasi and Klein S. Gilhousen, presented at the 41st IEEE Vehicular Technology Conference on May 19-22, 1991 in St. Louis, Mo.
In the publication mentioned above, a direct-sequence CDMA (DS-CDMA, or shortly, CDMA in the following) technique is described, in which a number of user mobile stations (MS) communicate via CDMA radio spread spectrum signals with base stations (BS, also referred to as cell sites) in the uplink (mobile station to base station) and downlink (base station to mobile station) directions. The base stations convert these CDMA radio signals originating from, respectively terminating at, the mobile station of the user, into a form appropriate for use in conjunction with terrestrial telecommunications transmission equipment such as the commonly deployed Pulse Code Modulation (PCM) circuit facilities. The base stations further relay these user signals in the uplink and downlink directions to the mobile switching center (MSC, also referred to as mobile telephone switching office (MTSO)) for further processing.
The user communication signals mentioned above comprise digitized voice signals and control information (also referred to as signaling). The MSC performs multiplexing and conversion operations on the mentioned tributaries and relays the voice signal to another user, e.g. within a Public Switched Telephone Network (PSTN). The MSC also interprets, reacts upon and generates signalling information, thus controlling the overall communication link between the users. These communications link control functions comprise the management of general call-related events such as call setup or tear down as well as CDMA radio link-related events such as the deterioration of the CDMA radio link quality and subsequent handoff initiation.
If CDMA is deployed within the typical medium-to-large-sized cells of land mobile telecommunications systems, then the average time delay spread of the multipath radio propagation environment is usually larger than the chip duration of the DS-CDMA signal. This forces CDMA to operate in an asynchronous mode with the consequence that the orthogonality of the spread spectrum multiple access user signals cannot be achieved by means of orthogonal spreading codes alone. Therefore, communications suffer from system self-induced interference, not only among signals originating from different cells, but in addition to that also considerably within a single cell (referred to as CDMA intra-cell interference). For such CDMA cellular systems, it is therefore an important overall system design objective to minimize any excessive CDMA interference among the communicating users and complementary, to capture and utilize as much energy from a desired CDMA user signal as possible. This system design requirement, although a generic requirement applicable to any multipl
REFERENCES:
patent: 5265119 (1993-11-01), Gilhousen et al.
patent: 5267261 (1993-11-01), Blakeney, II et al.
patent: 5301356 (1994-04-01), Bodin et al.
Allen Salmasi and Klein S. Gilhousen "On the System Design Aspects of Code Division Multiple Access (CDMA) Applied to Digital Cellular and Personal Communications Networks", reprinted from Proceedings of the 41st IEEE Vehicular Technology Conference, St. Louis, Mo., May 19-22, 1991.
Nokia Telecommunications Oy
Olms Douglas W.
Ton Dang
LandOfFree
Method and apparatus for controlling signal quality in a CDMA ce 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 and apparatus for controlling signal quality in a CDMA ce, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for controlling signal quality in a CDMA ce will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-346690