Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1997-11-25
2001-02-13
Pascal, Leslie (Department: 2630)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06188496
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to signal regeneration, and more specifically to a physical layer link between wireless devices. In particular, a method and apparatus is disclosed for regenerating an infrared wireless signal for communication between isolated infrared wireless stations.
BACKGROUND OF THE INVENTION
Wireless communication systems are often used where it is preferable not to create a wired link to each communicating station. Wireless communication systems may be used, for example, to communicate between rooms in building.
When a wireless communication system uses infrared (IR) signals as a means for communicating, the distance between two communicating stations is limited. Limiting factors include communication speed and whether the system is diffused or directional. In addition, when IR (infrared) communicating stations are located in different rooms, they may not be able to directly communicate with each other, because IR signals can not propagate through walls. Connectivity between areas that are separated, by walls, for example, may be achieved by using signal regeneration.
Bridges or routers may also be used for transferring IR signals between areas. A bridge or router is a network layer solution. A bridge or router first desirably validates a received frame using information in the frame. The bridge or router then decides whether to retransmit and forward the frame based on the receipt and content of this information. Different criteria and different routing algorithms for forwarding a frame are known to those skilled in the art. This decision making process results in bridges or routers delaying a frame before retransmitting the frame. Another possible source of delay in a bridge or router in retransmitting a signal from one room to another is the time to convert a signal from an IR MAC protocol to a wired MAC protocol and then back to an IR MAC protocol.
Analog or digital repeaters may also be used for IR signal regeneration. A repeater is a physical layer solution that does not implement a routing protocol nor include its associated delays. However, commonly repeaters simply retransmit a received signal without validating the signal before retransmission. This may result in the regeneration of invalid signals.
A wireless communication system
100
having a common wiring infrastructure
105
topology is shown in FIG.
1
. Repeaters
112
,
122
,
132
,
142
(generally designated “R”) are connected to the common wiring infrastructure
105
. A first room
110
, a second room
120
, a third room
130
, and a fourth room
140
are separated by walls
107
. A source wire less station
118
may communicate with a destination wireless station
148
by transmitting a wireless signal
116
to the repeater
112
in the first room
110
. This transmission may be, for example, an IR signal. The repeater
112
then transmits the received wireless signal
116
onto the common wiring infrastructure
105
. From common wiring infrastructure
105
, signal
116
may be distributed to repeater
122
in Room
2
, repeater
132
in Room
3
and repeater
142
in Room
4
. When repeater
142
in Room
4
receives the retransmitted signal from the common wiring infrastructure
105
, wireless signal
146
may be transmitted to destination
148
.
Noise and unwanted signals are often present in wireless communication systems. For example, in an IR wireless communication system, thermal noise, sunlight, IR remote control devices, and light from lamps may be sources of IR noise. When the lamp
114
in
FIG. 1
is turned on, the IR radiation generated by the lamp
114
may be a source of noise received by the repeater
112
.
When a noise source, such as light from the lamp
114
, for example, is turned on, the repeater
112
may receive the wireless signal
116
from the source wireless station
118
plus noise from the lamp
114
. The noise may cause the repeater
112
to receive a false signal. A conventional physical layer repeater may retransmit the false signal, without checking for undesired signal components, onto the common wiring infrastructure
105
. This may result in repeater
122
retransmitting a false signal
126
into the second room
120
, repeater
132
retransmitting a false signal
136
into the third room
130
, and repeater
142
retransmitting a false signal
146
into the fourth room
140
and to the destination wireless station
148
.
Retransmission of a false signal by repeater
112
may inhibit communication of true signals across the common wiring infrastructure
105
between wireless stations
128
,
138
,
148
in rooms without noise sources. A possible disadvantage of a common wiring infrastructure
105
topology is the cost of the wiring infrastructure. A possible advantage of having a common wiring infrastructure
105
topology is having connectivity between N rooms with only N repeaters.
A wireless communication system
200
, having a point-to-point topology is shown in
FIG. 2. A
repeater
212
in a first room
210
is connected to a repeater
232
in a third room
230
by a wiring
234
through a wall
207
. Repeaters
233
,
242
are similarly connected between the third room
230
and the fourth room
240
. Repeaters
243
,
222
are similarly connected between the fourth room
240
and the second room
220
.
A source wireless station
218
may communicate with a destination wireless station
248
by transmitting a wireless signal
216
to the repeater
212
in the first room
210
. The repeater
212
transmits (i.e., retransmits) the received signal to the repeater
232
in the third room
230
through the wiring
234
. The repeater
232
transmits (i.e., retransmits) the received signal by a wireless transmission
236
to the repeater
233
. Repeater
233
transmits (i.e., retransmits) the received signal to the repeater
242
which transmits (i.e., retransmits) the signal using a wireless signal
246
to the destination wireless station
248
.
A light source such as a lamp
214
may generate noise as described above with reference to lamp
114
in FIG.
1
. When a noise source, such as light from the lamp
214
, for example, is turned on, an false signal may propagate from repeater
212
to repeater
232
. From repeater
232
it may propagate to wireless station
238
and repeater
233
, and so on to repeaters
242
,
243
,
222
and wireless stations
228
,
248
in the second room
220
and fourth room
240
.
Retransmission of a false signal by repeater
112
may inhibit communication of valid signals between wireless stations
228
,
238
,
248
in rooms without noise sources. A possible advantage of a point-to-point topology is that a common wiring infrastructure may not be required. A possible disadvantage of a point-to-point topology is that 2*(N−1) repeaters may be required for connectivity between N rooms.
A possible problem when using conventional physical layer repeaters that transmit and receive wireless signals on a single channel is self-distortion. The problem of self-distortion will be described with reference to FIG.
3
. Self-distortion may occur due to multiple path reception in a wireless communication system
300
.
A source wireless station
318
in a first room
310
may communicate with a destination wireless station
328
in a second room
320
using a repeater
312
. The wireless station
318
transmits a wireless signal. The wireless signal following a first signal path
316
is received by the repeater
312
. The repeater
312
retransmits the received signal to the repeater
313
which retransmits the signal into room
320
. The retransmitted signal following a second signal path
326
is received by the destination wireless station
328
. The wireless signal transmitted by the wireless station
318
may additionally follow a third signal path
317
. The signal along signal path
317
may reach the destination wireless station
328
through an opening
322
in the wall
307
as shown in FIG.
3
. The signal following path
317
may collide with the signal following path
326
from the
Krishna Arvind
Naghshineh Mahmoud
Olsen Claus Michael
International Business Machines - Corporation
Pascal Leslie
Ratner & Prestia
Singh Dalzid
LandOfFree
Wireless communication system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wireless communication system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wireless communication system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2611000