Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1999-04-09
2004-01-27
Appiah, Charles (Department: 2682)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S203000, C370S210000
Reexamination Certificate
active
06683864
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a transmission method for transmitting an orthogonal frequency division multiplexing (hereinafter simply referred to as an OFDM)-modulated signal and a transmission apparatus to which this transmission method is applied.
Heretofore, when a local area network (LAN) is realized among a plurality of equipment such as a variety of video-equipment, a personal computer apparatus and its peripheral devices within a relatively narrow range such as home and office in order to transmit data handled by these equipment, instead of directly connecting respective equipment via some signal lines, radio signal transmission and reception apparatus (radio transmission apparatus) are connected to the respective equipment so as to transmit data via radio waves.
The local area network is configured by the transmission of radio waves, whereby respective equipment need not be directly connected by signal lines. Thus, the system arrangement can be simplified.
When the local area network is comprised of a plurality of radio transmission apparatus, if signals are simultaneously transmitted from a plurality of transmission apparatus, there is then the possibility that a transmission error will occur. For this reason, a communication among respective transmission apparatus within the network should be access-controlled by some method.
As the access control method, there has heretofore been known a method in which a communication among transmission apparatus (nodes) within the network is unitarily managed by a transmission apparatus (route node) at the central portion of the star-connection in a small-scale radio network. As a general method of avoiding communications from colliding with each other in this case, there is used a band reservation method in which a band is reserved in advance at every transmission line regardless of the existence of transmission data and data is transmitted in the reserved band. However, according to this method, even when there is no data to be transmitted, the band of the transmission line should be maintained and the network resources are used uselessly. There is then the problem that a transmission efficiency is very poor.
As an access method in which the above-mentioned problem could be solved, there is a method in which a communication within the network is effected by controlling polling. According to this method, one arbitrary transmission apparatus within the network is used as a control station (route node) and the route node transmits a control signal for sequential polling to other nodes within the network so that each node transmits data sequentially in response to the polling. When each node receives a polling signal to its own station, if there is data which is to be transmitted from its station, each node transmits a acknowledge signal indicating the acknowledge to its polling, and then transmits data prepared in that station. Thus, it is possible to improve a transmission efficiency by effecting a transmission processing based on this polling.
An arrangement of a radio transmission apparatus for effecting a communication under the above-mentioned polling control and its processing will be described. When an apparatus is of the arrangement such that a transmission and a reception are executed in a time-division manner, a radio transmission apparatus is arranged as shown in FIG.
1
. That is, as shown in
FIG. 1
, an antenna
1
is connected to a movable contact
2
m
of an antenna change-over switch
2
, and one fixed contact
2
a
of this switch
2
is connected to a reception unit
3
, thereby receiving the signal received at the antenna
1
. The signal received by the reception unit
3
is supplied to a link layer processing unit
4
, in which the received signal is supplied to a processing apparatus side (not shown) and also the link processing based on the received signal is executed. Moreover, a signal transmitted from the link layer processing unit
4
is supplied to a transmission unit
5
, and the signal thus processed by this transmission unit
5
is supplied to the other fixed contact
2
b
of the antenna change-over switch
2
. At the timing in which this transmission signal is outputted from the transmission unit
5
, the movable contact
2
m
of the switch
2
is connected to the fixed contact
2
b
and the transmission signal is transmitted via radio waves.
The transmission processing done by this radio transmission apparatus is executed on the basis of a flowchart shown in
FIG. 2
, for example. That is, as shown in
FIG. 2
, following the start of operation, it is determined by the link layer processing unit
4
at the next decision step
201
whether a polling signal to its own station is received. If the polling signal is received by a YES at the decision step
201
, then control goes to a step
202
, whereat an acknowledge (ACK signal) which acknowledges the polling signal is made. Then, control goes to as step
203
, whereat the antenna change-over switch
2
is switched to the transmission side. Then, in a step
204
, the acknowledge signal thus made is transmitted (step
204
), and the transmission data also is transmitted. At the completion of the transmission processing, the antenna change-over switch
2
is again connected to the reception side at a step
205
, and control goes back to the decision step
201
.
The transmission processing based on this polling control is executed in the state shown in FIG.
3
. As shown in
FIG. 3
, when a reception packet Ta is received during a predetermined period, the packet received during that period is analyzed (Tb). If it is determined by the analysis of the packet that the polling is intended for its own station, then there exists a period Tc in which transmission data of acknowledge signal is created. After the transmission data is created, there exists a transmission period Td in which the transmission data is used as the transmission signal thus transmitted. That transmission signal is transmitted via radio waves during the period of a transmission packet Te. Accordingly, there occurs a processing delay Tz until the transmission packet Te for acknowledging the reception packet is transmitted.
When the radio transmission is executed, as a system for efficiently transmitting data of a relatively large capacity, there has been developed an orthogonal frequency division multiplex (hereinafter simply referred to as an OFDM)-modulation system. This system is a so-called multicarrier system in which data is dispersed into a plurality of subcarriers and then transmitted.
FIG. 4
is a block diagram showing a transmission processing circuit based on this OFDM-modulation. As shown in
FIG. 4
, transmission data (this transmission data is supplied from a link layer processing unit
4
) supplied to an input terminal
4
a
are simultaneously set in an input register
5
a
comprised of a plurality of registers. The data thus set are collectively supplied to an inverse fast Fourier transform circuit (hereinafter simply referred to as an IFFT circuit)
5
b
, in which an orthogonal transform processing is executed to transform a time axis into a frequency axis by a computation processing based on the inverse fast Fourier transform. The orthogonal transform processing of every one unit based on the inverse fast Fourier transform is executed by an inverse Fourier transform starting signal supplied from the link layer processing unit
4
through a terminal
4
b.
Then, the parallel data thus orthogonal-transformed is supplied to an output register
5
c
connected to the IFFT circuit
5
. At the stage in which the setting of the parallel data in the output register
5
c
is ended, the data thus set is supplied to a parallel-to-serial (hereinafter referred to as a P/S) converter
5
d
and thereby converted into serial data. The conversion processing of every one unit in the P/S converter
5
d
is started by an output start signal supplied from the IFFT circuit
5
. Then, the serial data thus converted by the P/S converter
5
d
is supplied to a digita
Appiah Charles
Maioli Jay H.
LandOfFree
Transmission method and transmission apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmission method and transmission apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmission method and transmission apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3214774