Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2000-03-13
2004-07-06
Gelin, Jean (Department: 2681)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S447000, C455S562100
Reexamination Certificate
active
06760593
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to cellular communications, and, more particularly, is directed to arrangement of antennas in a cell.
FIG. 1
shows cell
10
of a conventional cellular communication network having a transmitting antenna
20
. In fact, the coverage area of antenna
20
has an approximately circular shape, but it is convenient to model the cellular network as formed of hexagonal (rather than circular) cells. Antenna
20
is modelled as being at the center of cell
10
, but practically, it may not be precisely centered with respect to the location of other antennas.
As shown in
FIG. 2
, antenna
20
transmits message A at a carrier frequency f
1
. When the signal to be transmitted comprises time division multiplexed signals A, B, C, the transmission from antenna
20
is as shown in FIG.
3
.
FIG. 4
shows receiving apparatus
50
, such as a cellular telephone. Antenna
51
receives messages transmitted from antenna
20
, and possibly from other antennas in other cells, supplies a received signal to receiver circuit
52
, which processes the received signal to extract the message transmitted by antenna
20
. Receiver circuit
52
supplies the extracted message to processor
53
, which converts the extracted message into a user perceivable signal, such as an audible speech signal, and applies the user perceivable signal to amplifier
54
which is adapted to convert the user perceivable signal into an acoustic signal.
Receiving apparatus
50
may be a pager, in which case the user perceivable signal is a visually displayable signal, and instead of amplifier
54
, a display is provided. Alternatively, receiving apparatus
50
may also have transmission capability (not shown).
To increase the traffic carrying capacity of a cell, various schemes are used.
FIG. 5
shows cell
11
having antennas
21
,
22
,
23
located therein, and transmitting at carrier frequencies f
1
, f
2
, f
3
, respectively. As shown in
FIG. 6
, each antenna transmits a separate message, indicated as A, B, C. Of course, the signal at each carrier frequency may use a time division multiple access (TDMA) scheme. For example, f
i
may represent messages D, E, F, D, E, F, . . . , f
2
may represent messages G, H, G, H, and f
3
may represent messages I, J, K, L, I, J, K, L . . . The antennas
21
,
22
,
23
may be a single antenna.
FIG. 7
shows cell
12
having antennas
24
,
25
,
26
located therein, and each transmitting in a wide bandwidth channel centered at carrier frequency f
1
. However, as shown in
FIG. 8
, each of the antennas
24
-
26
uses a distinct modulating code, so that a receiver demodulating its received signal with the same distinct code properly recovers the transmitted message from the intended one of antennas
24
-
26
. The scheme illustrated in
FIGS. 7 and 8
is referred to as a spread spectrum scheme, in particular, a code (or carrier) division multiple access (CDMA) scheme. Here, too, the signal transmitted by each of antennas
24
-
26
may be a time division multiplexed signal.
Edge excited cells have been proposed in which three antennas are located at respective vertices of a hexagonal cell. In known CDMA systems, each of the antennas transmits the same signal. A transmission from a mobile station is received correctly if at least one of the antennas has correctly received the transmission. This configuration of antennas in a cell is also referred to as a corner-fed hexagonal pattern.
Since traffic continues to increase, additional techniques for increasing the traffic carrying capacity of a cell are sought.
SUMMARY OF THE INVENTION
In accordance with an aspect of this invention, there are provided a method of and a system for cellular communications, and, more particularly, is directed to arrangement of antennas in a cell. In accordance with an aspect of this invention, in a cellular communication method and system having a cell with a plurality of signal transmission sites located at a sum of k−v different positions, k≧2, at least v virtual sites wherein v≧1, a plurality of antennas located at the k−v signal transmission sites each transmits one of m signals at the same carrier frequency, m≧2, so that each of the signals is transmitted from at least one of the k different positions.
REFERENCES:
patent: 6052599 (2000-04-01), Driessen
AT&T Corp.
Gelin Jean
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