Pulse or digital communications – Receivers
Reexamination Certificate
1998-06-11
2002-02-19
Bocure, Tesfaldet (Department: 2631)
Pulse or digital communications
Receivers
Reexamination Certificate
active
06349119
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of prior PCT International Application No., PCT/JP96/03443, which has an International filing date of Nov. 22, 1996, which designated the United States of America, the entire contents of which are hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to a channel estimation circuit for estimating the conditions of a channel through the use of a modeled channel prior to communication and to a modem having such a channel estimation circuit for use in a mobile communication system or mobile satellite communication system.
BACKGROUND ART
As a system for estimating the conditions of channels, there has been proposed a system that uses a six-beam antenna for each of transmission and reception and chooses the best route from a total of thirty-six channels.
An example of such conventional channel estimation systems there is illustrated in
FIGS. 1 and 2
, which are simplified versions of the figures presented in an article entitled “A Technical Trend of High-speed Wireless Lans” (Tsutsumi et al.), 6th Karuizawa Workshop on Circuit and System (1993). In
FIG. 1
, reference numeral
1
denotes a radio terminal called a user module (hereinafter referred to as UM) mounted on a table or the like,
2
a radio terminal which is called a control module (hereinafter referred to as CM) mounted on a ceiling of a room, for example, and connected with plural user modules UM
1
by radio, and
3
schematically depicted walls of a room. Solid lines in
FIG. 1
represent possible channels between CM
2
and UM
1
. Terms “Good”, “Better”, and “Bad” in cells shown in
FIG. 2
imply that the channels associated with the cells have “Good”, “Ordinary”, and “Bad” communication conditions, respectively. Void cells imply that the corresponding channels are not available for the current communication.
As shown in
FIG. 1
, CM
2
and UM
1
each have a six beam antenna, so that a total of thirty-six channels are available between CM
2
and UM
1
. CM
2
and UM
1
are always aware of individual transmission qualities of the thirty-six channels in such a tabular form as depicted in
FIG. 2
, and may select the best one for use when the communication is actually performed.
The operation will now be described below.
It is supposed that CM
2
and UM
1
are arranged in a room surrounded by the walls
3
and that the channels between UM
1
and CM
2
at a given moment have such transmission qualities as shown in FIG.
1
. At this time, only four channels are presented as indicated by the solid lines in FIG.
1
. If the best channel is searched in the four channels, there is one way from the fifth antenna of CM
2
to the sixth antenna of UM
1
. Thus, the channel from the fifth antenna of CM
2
to the sixth antenna of UM
1
will be selected when the communication is actually started.
Because the conventional channel estimation systems have such a configuration as described above, they use received signals to estimate the qualities of the channel and determine the channel for the current burst through utilization of a signal of the immediately preceding burst, whereby this gives rise to a problem that the system cannot follow quick changes on transmission quality.
In addition, such a conventional system needs continual monitoring of transmission qualities of the channel, and the transmission and reception it is performed between CM
2
and UM
1
, also there is a problem that the efficiency in lines is lowered.
Further, the conventional channel estimation systems normally presume communication between fixed stations, and no consideration is given to a system which involves frequent channel switching by a radio terminal like UM
1
during communication, with the radio terminal being moved.
The present invention is intended to overcome the above-mentioned problems, and has for its object to provide a channel estimation circuit capable of estimating the conditions of channels between a transmitter and a receiver with higher accuracy by obtaining models of the channel in geometrical form, then recognizing the position of the transmitting antenna through utilization of geometrical information based on the models, and estimating the path between the transmitter and the receiver.
It is another object to provide a channel estimation circuit that improves the transmission efficiency by geometrically estimating the path between the transmitter and the receiver.
It is a further object to provide a modem that permits high quality communication by following the path between the transmitter and the receiver through the use of geometrically modeled channels.
It is still a further object to provide a modem that permits fast channel switching by a terminal while moving during communication.
DISCLOSURE OF THE INVENTION
A channel estimation circuit according to the invention defined in claim
1
is one that first takes in geometrically ambient conditions by a geometrical data input device, then searches the input geometrical information for position information on the antenna of a distant station by a geometrical information recognition device, and geometrically formulates models of channels between radio terminals of the local station and the distant station by a modeling device through utilization of the searched-out position information on the antenna and the input geometrical information.
Therefore, it is possible to search for the antenna of the distant station with higher accuracy from its geometrically estimated position and estimate channel conditions with higher accuracy by using the channel models formulated from the input geometrical information, thereby eliminating the need for monitoring the transmission performance of every channel at all time and hence providing for increased line efficiency.
A channel estimation circuit according to the invention defined in claim
2
is one that is adapted to limit the range over which to search for the position of the antenna of the distant station through the use of information from an auxiliary geometrical information recognition device when the antenna position and surrounding buildings affecting the channels between the radio terminals of the local and distant stations are known at the time of geometrically formulating models of the channels.
Thus, it is possible to produce an effect of speeding up the search for the antenna of the distant station through the use of the information provided by the auxiliary geometrical information recognition device, in addition to the merit of the invention defined in claim
1
.
A modem according to the invention defined in claim
3
is one that geometrically estimates the position of the antenna of the distant station by the use of the channel estimation circuit of claim
1
, and enables the antenna of the local station to shift its directivity toward the antenna of the distant station.
Accordingly, the position of the antenna of the distant station can be estimated geometrically with accuracy and hence direct waves can be received with higher accuracy, therefore, it is possible to remove a multi-path component, thus producing an effect of achieving higher quality communication.
A modem according to the invention defined in claim
4
is one that formulates models of channels through the use of the channel estimation circuit of claim
1
, estimates paths between radio terminals of the local and distant stations by a path estimating device based on the channel models, selects an optimal one of the estimated paths, and controls the antenna of the local station to shift its directivity toward the selected path.
Therefore, it is possible to produce the same effects as those obtainable with the invention of claim
3
, and further, since the modem uses an optimal path based on the channel models for communication, high quality communication can be maintained even if the direct wave is blocked by an obstacle or even if sudden channel switching occurs.
A modem according to the invention defined in claim
5
is one that formulates models of channels through the use of the channel e
Akiyoshi Masanori
Sogabe Yasushi
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