Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-06-21
2003-09-30
Maung, Nay (Department: 2732)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S347000, C370S350000, C370S503000
Reexamination Certificate
active
06628676
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to communications systems and methods, and more particularly to systems and methods for communicating messages among devices that are serially connected.
BACKGROUND OF THE INVENTION
Wireless and wired communications systems and methods are widely used for communicating among devices. The devices may include computers or communication devices, such as cellular radiotelephone base stations. Communication between a central unit and a plurality of devices may be arranged in a “hub and spoke” or “star” arrangement, in which a central unit is individually connected to a plurality of devices.
FIG. 1
illustrates such a hub and spoke arrangement for a cellular radiotelephone communications system.
FIG. 1
illustrates a conventional terrestrial cellular radiotelephone communication system
20
. The cellular radiotelephone system may include one or more radiotelephones
21
, communicating with a plurality of cells
36
served by base stations
23
and a Mobile Telephone Switching Office (MTSO)
25
. Although only three cells
36
are shown in
FIG. 1
, a typical cellular network may comprise hundreds of cells, may include more than one MTSO, and may serve thousands of radiotelephones.
The cells
36
generally serve as nodes in the communication system
20
, from which links are established between radiotelephones
21
and the MTSO
25
, by way of the base stations
23
serving the cells
36
. Each cell will have allocated to it one or more dedicated control channels and one or more traffic channels. The control channel is a dedicated channel used for transmitting cell identification and paging information. The traffic channels carry the voice and data information. Through the communication system
20
, a duplex radio communication link
32
may be effected between two mobile stations
21
or between a radiotelephone
21
and a landline telephone user
33
. The function of the base station
23
is commonly to handle the radio communication between the cell and the mobile station
21
. In this capacity, the base station
23
functions chiefly as a relay station for data and voice signals. As shown, a plurality of base stations
23
are directly connected to the MTSO
25
in a hub and spoke arrangement.
Traditional analog radiotelephone systems generally employ a system referred to as Frequency Division Multiple Access (FDMA) to create communications channels. As a practical matter well-known to those skilled in the art, radiotelephone communications signals, being modulated waveforms, typically are communicated over predetermined frequency bands in a spectrum of carrier frequencies. These discrete frequency bands serve as channels over which cellular radiotelephones communicate with a cell, through the base station or satellite serving the cell. In the United States, for example, Federal authorities have allocated to cellular communications a block of the UHF frequency spectrum further subdivided into pairs of narrow frequency bands, a system designated EIA-553 or IS-19B. Channel pairing results from the frequency duplex arrangement wherein the transmit and receive frequencies in each pair are offset by 45 Mhz. At present there are 832, 30-Khz wide, radio channels allocated to cellular mobile communications in the United States.
Conventional cellular systems also may employ frequency reuse to increase potential channel capacity in each cell and increase spectral efficiency. Frequency reuse involves allocating frequency bands to each cell, with cells employing the same frequencies geographically separated to allow radiotelephones in different cells to simultaneously use the same frequency without interfering with each other. By so doing, many thousands of subscribers may be served by a system of only several hundred frequency bands.
Another technique which may further increase channel capacity and spectral efficiency is Time Division Multiple Access (TDMA). A TDMA system may be implemented by subdividing the frequency bands employed in conventional FDMA systems into sequential time slots, as illustrated in FIG.
2
. Although communication on frequency bands f
1
-f
m
typically occur on a common TDMA frame
210
that includes a plurality of time slots t
1
-t
n
, as shown, communications on each frequency band may occur according to a unique TDMA frame, with time slots unique to that band. Examples of systems employing TDMA are the dual analog/digital IS-54B standard employed in the United States, in which each of the original frequency bands of EIA-553 is subdivided into 3 time slots, the digital IS-136 standard employed in the United States and the European GSM standard, which divides each of its frequency bands into 8 time slots. In these TDMA systems, each user communicates with the base station using bursts of digital data transmitted during the user's assigned time slots. A channel in a TDMA system typically includes one or more time slots on one or more frequency bands. See, for example, U.S. Pat. No. 5,850,292 to Wang et al., that is assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference.
Another hub and spoke arrangement of communication devices is shown for an indoor cellular communication system in U.S. Pat. No. 5,887,267 to coinventor Fugaro, that is assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference.
FIG. 3
herein corresponds to
FIG. 1
of the '267 patent. As described therein, capacity limitations of cellular radiotelephone systems have been addressed by using microcells or picocells, that is, low power cellular transmissions that provide coverage over a smaller area. The smaller microcells can allow more cells to exist within a predefined geographic area, thereby allowing an increase in the number of users that can be serviced within that geographic area. A particular application of microcell technology is indoor cellular radiotelephone services.
As illustrated in
FIG. 3
, a conventional indoor cellular network
320
includes one or more mobile stations or units
322
, one or more base stations
324
also referred to as Radio Heads (RH), a Radio Control Interface (RCI)
326
also referred to as a Control and Radio Interface (CRI), and a mobile switching center (MSC)
328
. Although only one cell
330
is shown in
FIG. 3
, a typical indoor cellular network may have several cells
330
, each cell usually being serviced by one or more base stations
324
. The number of base stations
324
may depend on the channel capacity of the cell
330
. Each base station typically supports anywhere from 4-12 channels, depending upon its site. The cell
330
typically has one or more control channels and one or more voice/data (hereafter referred to as “traffic”) channels allocated to it. The control channel typically is a dedicated channel used for transmitting cell identification and paging information.
Each base station
324
is connected to the radio control interface
326
by a radio interface link
332
in a hub and spoke configuration. The radio control interface
326
exchanges signals between the base stations
324
and the mobile switching center
328
. Specifically, the radio control interface
326
converts the traffic and control information from the format received over the radio interface links
332
into a format suitable for transmission over a dedicated transmission link
334
interconnecting the radio control interface (RCI)
326
to the MSC
328
. In the reverse direction, the RCI
326
converts the traffic and control information received over transmission link
334
into a format suitable for transmission over radio interface links
332
to the respective base stations
324
.
The MSC
328
is the central coordinating element of the overall cellular network
320
. It typically includes a cellular processor
336
and a cellular switch
338
, and provides an interface to the public switched telephone network (PSTN)
340
. Through the cellular network
320
, a duplex radio communicatio
Fugaro Anthony S.
Grohn Ossi I.
Ericsson Inc.
Lee John J
Maung Nay
Myers Bigel & Sibley & Sajovec
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