Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1999-01-27
2003-04-22
Hsu, Alpus H. (Department: 2733)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S466000, C370S467000, C370S395100
Reexamination Certificate
active
06553038
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a communication system suitably applied to a case wherein a signal transmitted by, e.g., a predetermined communication network is wireless-transmitted to a mobile station and, more particularly, to a case wherein digital data is transmitted in an asynchronous transfer mode.
As a digital data transmission process, an asynchronous transfer mode (to be referred to as an ATM hereinafter) is known. This ATM asynchronously transmits various digital data. Here, an ATM communication network developed to perform conventional ATM transmission is to perform transmission with a wire transmission path. In addition, the ATM communication network is designed on the assumption that data is transmitted with a high-quality signal line such as an optical fiber cable having small transmission degradation.
In contrast to this, there is a demand that ATM communication should be performed even in mobile communication. For this reason, it is considered that the ATM communication network should be connected to a wireless communication network.
FIG. 13
is a view showing an example of a conventional arrangement obtained when end-end communication is performed between a terminal device
1
connected to the ATM communication network and a terminal device
4
connected to a mobile station. The terminal device
1
is connected to an ATM network b with a user-network interface a, and a radio base station
2
for performing wireless communication is connected to the ATM network b with a user-network interface c. A mobile station
3
for performing wireless communication with an air interface d is prepared, and the mobile station
3
is connected to the terminal device
4
with a user-network interface e. The radio base station
2
and the mobile station
3
comprise transmission/reception antennas
2
a
and
3
a
, respectively.
The radio base station
2
performs a conversion process between an ATM cell used in the ATM network and a wireless communication format. The mobile station
3
performs a conversion process between the air interface d and the user-network interface e.
Here, an example of an arrangement of an ATM cell serving as a format of a signal transmitted through an ATM network is shown in
FIGS. 2 and 3
. In transmission in an asynchronous transfer mode, one unit of signal is defined as a signal of a unit called a cell. One unit of ATM cell
100
is constituted by a header information portion
110
and a user information portion
120
as shown in FIG.
2
. In this example, one unit of ATM cell
100
consists of 53 bytes. The start header information portion
110
has 5 bytes, and the subsequent user information portion
120
has 48 bytes.
The detail example of the format of one unit of ATM cell
100
is shown in FIG.
3
. Four bits of the first octet are bits of generic flow control (GFC)
111
, eight bits including four bits of the first octet and four bits of the second octet are bits of virtual path identifiers (VPIs)
112
and
113
. Sixteen bits including the second four bits of the second octet to the first four bits of the fourth octet are bits of a virtual channel identifier (VCI)
114
, and three bits of the fourth octet are bits of a payload type (PT)
115
. One bit of the fourth octet is a bit of a cell loss priority (CLE)
116
, and eight bits of the fifth octet are bits of a header error control information (HEC)
117
. The arrangement described above is the arrangement of the header information portion
110
. Forty-eight bits of the sixth octet to the 53rd octet denote a user information region
120
. In this specification, user information transmitted in the user information region is called a payload.
Of the data in the header information portion
110
, data for determining a routing of an ATM cell are the virtual path identifiers (VPIs)
112
and
113
and the virtual channel identifier (VCI)
114
. An 8-bit (1 byte) header error control information (HEC)
117
is constituted by a cyclic redundancy check (to be referred to as a CRC hereinafter) serving as an error detection signal. The CRC is a code given to be generated from 4-byte header information of the first octet to the fourth octet, and functions to protect the header information in this partition. The header error control information (HEC)
117
also has a cell-synchronization function of specifying the position of a cell in an arbitrary byte string.
In 1-byte information constituting the header error control information (HEC)
117
, 4-byte header information of the first octet to the fourth octet is regarded as a 31-order polynomial on the transmission side. The 31-order polynomial is multiplied by X
8
, the product is divided by a polynomial X
8
+X
2
+X+1 to obtain remainder. A value obtained by adding “01010101” to the remainder is defined as header error control (HEC). On the reception side, “01010101” is added to a value of the header error control (HEC), and the resultant value is divided by the same polynomial as that on the transmission side to obtain a remainder. If the remainder is not 0, it is determined that an error is detected.
As described above, data is transmitted as formatted data through an ATM network. However, in the air interface d shown in
FIG. 13
, the data must be transmitted in a format for wireless transmission. More specifically, as described above, the ATM network is basically a network used in a state wherein line quality is good, and the header error control (HEC) added to the header information has a very simple arrangement having a small number of bits as an error correction code. The payload transmitted in the user information region is transmitted without adding an error detection code to the payload. In contrast to this, when data is transmitted by a radio circuit, a transmission error is probably generated for various factors. The data must be transmitted while an error detection code having check capability which is high to some extent is added to the data. In the radio base station
2
, format conversion is made to add the error detection code to the data.
An example of a signal wireless-transmitted between the radio base station
2
and the mobile station
3
is shown in FIG.
14
. Referring to
FIG. 14
, a case wherein data transmission is performed by using a slot having a predetermined fixed length in a time division multiplex access (TDMA) scheme. In this example, data of one ATM cell is allocated to one slot
200
. In the slot
200
, one slot consists of 67 bytes, and a 4-byte preamble (PR)
201
for slot synchronization, a 4-byte unique word (UW)
202
representing the start of data, and a 2-byte control signal (CAC)
203
are sequentially arranged. The subsequent 53-byte partition is defined as a user information partition. In this example, a 5-byte header information portion
204
of the ATM cell and a 48-byte ATM payload
205
are arranged. As the 5-byte header information portion
110
and the 48-byte ATM payload
205
, the 5-byte header information portion
204
and the 48-byte payload
120
shown in
FIG. 3
are directly arranged. An error detection code
206
(CRC) is added to the last four bytes of the slot
200
. The error detection code
206
is a code generated for data of a partition ranging from the control signal (CAC) to the ATM payload. As the code, a code having relatively high check capability is used.
The example in
FIG. 14
is obtained when data of one ATM cell can be arranged in a user information partition of one slot. However, the length of one slot may be shortened, and the data of one ATM cell may be wireless-transmitted.
FIG. 15
is a view showing an example of this case. In this example, two slots
210
and
220
each having a slot length of 50 bytes are used. In the slots
210
and
220
, from the start, 4-byte preambles (PRs)
211
and
221
, 4-byte unique words (UWs)
212
and
222
, and 4-byte control signals (CACs)
213
and
223
are sequentially arranged. In a 36-byte user information partition, a 5-byte ATM header
214
of the first cell is arranged. An ATM pa
Hsu Alpus H.
Maioli Jay H.
Sony Corporation
Tran Thien D
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