Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1996-03-21
2001-11-27
Bost, Dwayne D. (Department: 2744)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S406000, C455S432300
Reexamination Certificate
active
06324404
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is concerned with wireless over-the-air communication using a plurality of transmit/receive cell sites or relay points. It should be understood that the transmit/receive relay points can be either land based or non-land based, such as satellite based, and that as used herein, the term “cell site” or its equivalent refers to one of the relay points of the system. CMR (Cellular Mobile Radio) is an example of one type of wireless over-the-air communication system that can be included in the present disclosure. It is understood that the term CMR is not intended to be limiting, but is merely used as an example for the purposes of discussion. It is also to be understood that the term “cellular telephone system” or its equivalents is intended to be shorthand notation for the term “wireless over-the-air communications system” and no limitation is intended by the use of the term “cellular.” Also, as used herein, the terms “CD (Communication Device)” and “MU (Mobile Unit)” are intended to include any device used to communicate in the wireless over-the-air communication system. Also, the term “cellular telephone system” is used for purposes of discussion but can include any form of wireless over-the-air communication system. It is also noted that many forms of communication are and will be conducted over the wireless over-the-air networks. Therefore, the present disclosure will refer to a “communication process” which is intended to cover calls as well as other forms of communication that can be conducted in this manner.
CMR is a rapidly growing telecommunications system. The typical CMR system includes a multiplicity of cells. A particular geographic area can be subdivided into a multiplicity of subareas, with each of the subareas being serviced by a stationary transmitter/receiver setup. The cells are set up to carry signals to and from mobile units in the range of the cell. If one cell site becomes too crowded, it can be divided into smaller cells, by a process known as cell site splitting. Any particular geographic area can become quite complicated with cells overlapping each other, and overlapping cells of other neighboring cellular systems. Further, null zones with inadequate coverage, or even no coverage, can result. It is noted that the term “cellular” is intended to be a term of convenience, and is not intended to be limiting. The present disclosure is intended to encompass any communication system in which an overall area can be divided into one or more subareas, and also to any communication system having at least some portion of the communications occurring over the air.
A typical CMR set up is indicated in
FIGS. 1 and 2
, and will be described so an understanding of the problem to which this invention is directed can be obtained.
Shown is a typical cellular telephone unit having a unique mobile identification number stored in a suitable location such as an electrically erasable programmable read-only memory (not shown). Telephone units of this kind are known to those skilled in this art, and thus will not be described in detail.
The telephone unit includes a handset
4
having a keypad
5
as well as a speaker
6
and a microphone
7
. A transceiver
8
, ordinarily built into the telephone unit, exchanges signals via an antenna
10
with a mobile telecommunications switching office or MTSO
12
via a cell site
14
. A duplexer
15
connects the antenna to the transceiver. The cell site
14
includes an antenna
16
connected to a control terminal
17
via a transceiver
18
. The cell site
14
is connected to the MTSO via a transmission link
20
. The Mobile Telephone Switching Office has historically been known as the center of the wireless over-the-air communications system. It is where the communication process management decisions are made, billing records are produced and where maintenance activities are initiated for wireless over-the-air communications systems. The MTSO is not a specific piece of equipment, but is comprised of many individual pieces. The MTSO will contain a telephone switch, peripheral processors, adjunct processors, and various other information gathering equipment used in the operation and management of a wireless over-the-air communications system. Each of the different pieces of equipment may directly or indirectly be involved providing the highest quality connection possible. The makeup of the MTSO therefore comprises many different pieces of equipment and many components, which can be supplied by different vendors. Therefore, communication process management decisions made at the MTSO can actually be made outside of a switch and can be made in a cluster of nodes housed along the network or even in separate cell sites. Therefore, as used herein the term MTSO really refers to all of the systems, nodes, modules, equipment and components that combine to define a wireless over-the-air communication process management network, regardless of the physical or system location of these elements. The term MTSO therefore is not intended to be limiting to the “switching off ice” as it may have been viewed in the prior art. The term is intended to be much broader than that and to include any combinations of equipment, etc that may be connected within the communication processing network of the service provider. The term MTSO is one of convenience and is intended to include all the information processing hardware and software associated with the wireless over-the-air communication process management process within a wireless over-the-air system, no matter where the hardware or software is located in the system. It is also noted that the term “intrasystem” refers to actions and components within a particular system; whereas, the term “intersystem” refers to actions and components located outside a particular system.
Referring to
FIGS. 1 and 2
, the operation of the CMR can be understood. The mobile unit M moves about the geographic areas covered by the various cells. As that mobile unit moves about, it decodes the overhead message control signals generated by various cell site control channels. The mobile unit locks onto the cell site that is emitting the strongest signal. The mobile unit rescans channels periodically to update its status. If, for example, a fixed-position land-based telephone T is used to call the mobile unit, a signal is sent via landlines L, to the central office CO of a public/switched telephone system (PTSN)
12
A. This system then utilizes the switching network SN associated therewith to call the MTSO
12
via a transmission link L
1
. The MTSO then utilizes its own switching network and generates a page request signal to cell sites via transmission links, such as the transmission link
20
. The cell site which has been notified of the presence of the mobile unit M sends a signal back to the MTSO via the landlines or wireless links alerting the MTSO of the presence of the mobile unit. The MTSO then orders the mobile unit, via the notifying cell site, to tune to an assigned channel and receive the communication process.
On the other hand, during communication process origination, the mobile unit rescans the control channels to determine which is the best server based on signal strength. Upon selecting the best server, the mobile unit transmits cell site information on the control channel receive frequency and then receives a voice channel to tune to if the mobile unit is authorized to place a communication process.
As the mobile unit moves, the signal strength between that mobile unit and the originating cell site changes, and perhaps diminishes. Since signal strength is an inverse function of the square of the distance between the mobile unit and the cell site, signal strength can change rapidly and drastically as the mobile unit moves with respect to the cell site and therefore must be monitored closely. The MTSO has a signal strength table, and signal strength from the mobile unit is constantly compared to acceptable signal strength levels in the table. Such a table can be located in e
Dennison Everett
Duffy Timothy J.
Jones Scott L.
Pauley Gregory T
Pharis, Jr. Albert H.
Bost Dwayne D.
Gernstein Terry M
Maung Nay
Sycord Limited Partnership
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