Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2001-04-26
2004-04-27
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C370S318000
Reexamination Certificate
active
06728551
ABSTRACT:
PRIORITY
This application claims priority to an application entitled “Method of Supporting Power Control on DCCH in BS” filed in the Korean Industrial Property Office on Apr. 26, 2000 and assigned Ser. No. 2000-22183; the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a CDMA (Code Division Multiple Access) mobile communication system, and in particular, to an apparatus and method for supporting forward and reverse power control on a DCCH (Dedicated Control Channel) in a BTS (Base station Transceiver System) and a BSC (Base Station Controller).
2. Description of the Related Art
A discontinuous transmission (DTX) mode refers to a mode in which data is transmitted in frames only when transmission data is generated in a wired system or a mobile communication system. Data transmission in the DTX mode minimizes transmission power and increases the whole system capacity due to the decrease of interference with the system.
The DTX, however, exhibits a problem when a receiver does not know whether frames have been transmitted or not because a transmitter transmits frames irregularly. That makes it impossible for a BTS to perform a forward power control. More specifically, when a receiver in a mobile station (MS) cannot make a right judgment about data transmission, it does not rely on decoder decision parameters including CRC (Cyclic Redundancy Code) and decoding results. Hence, the transmission power of the MS cannot be controlled accurately by known methods suitable for a continuous transmission mode.
Both a DCCH and an SCH (Supplemental Channel) support the DTX mode. The DCCH is characterized by data transmission only when transmission data is generated in a higher layer, which makes the DCCH suitable as a control channel for efficient packet services. The DCCH is supposed to transmit null frames for power control during the DTX period. The SCH supports a DTX mode in which no data is transmitted in the absence of transmission data. The SCH transmits no frames during the DTX period.
FIG. 1
is a block diagram of a prior art mobile communication system. The mobile communication system is a reference model of 3G IOS (Interoperability Specifications) with an MSC (Mobile Switching Center), BSs (Base Stations), and a digital air interface between the BSs, which are well known.
Referring to
FIG. 1
, an interface A
1
is defined for signaling and interfaces A
2
and A
5
(exclusively for circuit data) are defined for user traffic between an MSC
20
and a BSC
32
. An interface A
3
is defined to connect a target BS
40
to an SDU (Frame Selection/Distribution Unit Function)
34
of a source BS
30
to implement a soft/softer handoff. Signaling messages and user data are transmitted between the target BS
40
and the SDU
34
of the source system
30
by the interface A
3
. An interface A
7
is defined for signal transmission/reception between the target BS
40
and the source BS
30
for inter-BS soft/softer handoff.
The wired communication lines of this CDMA mobile communication system include a forward link directed from the MSC
20
to the BS
30
, a reverse link directed from the BS
30
to the MSC
20
, and a line between the BSs
30
and
40
. The MSC
20
includes a call control and mobility management block
22
and a switching block
24
. The MSC
20
is connected to a data network (not shown) such as the Internet through an IWF (InterWorking Function)
50
. Interfaces A
8
and A
9
are defined for user traffic and signaling, respectively between a BS and a PCF (Packet Control Function)
60
and interfaces A
10
and A
11
are defined for user traffic and signaling, respectively, between the PCF
60
and a PDSN (Packet Data Serving Node)
70
.
FIG. 2
is a diagram showing a DCCH signal flow between a BTS and a BSC (BSC-SDU) in conventional CDMA technology. This operation may occur between the BSC
32
(BSC-SDU
34
) and a BTS
36
in the source BS
30
, or a BSC
42
and a BTS
44
in the target BS
40
.
With continued reference to
FIG. 2
, upon detection of a DTX mode, the BTS determines the type of a data frame to transmit to the BSC and generates a reverse DCCH message in step
11
. The reverse DCCH message is supposed to be transmitted to the BSC in every predetermined period (e.g. 20 ms) in response to a reverse DCCH frame received in the predetermined period from an MS (not shown). Step
11
will be described later in more detail with reference to
FIGS. 3A and 3B
.
In step
12
, the BTS transmits the reverse DCCH message to the BSC. The reverse DCCH message may contain a data
ull/idle/erasure frame. The BSC receives and processes the reverse DCCH message and generates a forward DCCH message in step
13
. Reception of the reverse DCCH message is described below in more detail with reference to
FIG. 5
; processing the reverse DCCH message and generation of the forward DCCH message is described below with reference to
FIGS. 4A and 4B
.
In step
14
, the BSC transmits the forward DCCH message to the BTS. The forward DCCH message may contain a data
ull/idle/erasure frame. The BTS performs a forward/reverse power control for the MS based on power control information included in the forward DCCH message in step
15
. Reception of the forward DCCH message is described below in more detail with reference to FIG.
6
.
To summarize the operation shown in
FIG. 2
, after receiving a data frame in every predetermined period (20 ms) from the MS, the BTS generates a reverse DCCH message in the predetermined period and transmits it to the BSC. The BSC processes the reverse DCCH message, generates a forward DCCH message, and transmits it to the BTS. Then, the BTS performs a power control for the MS based on power control information included in the forward DCCH message.
FIGS. 3A and 3B
are flowcharts illustrating a conventional reverse DCCH message transmitting operation. In this operation, the BTS transmits a frame received in the predetermined period from the MS as a reverse DCCH message to the BSC-SDU. The following description is conducted with the appreciation that a reverse DCCH message is constructed in the same format as an FCH (Fundamental Channel) message shown in
FIGS. 7 and 10
, and thus defined as a reverse FCH/DCCH message.
Referring to
FIG. 3A
, the BTS determines whether it has secured radio resources related with the MS and acquired the MS in step
101
. If it has not, the BTS considers that it tries to synchronize with the MS and sets Frame Content in an IS-2000 reverse DCCH message shown in
FIG. 10
to an idle frame to synchronize with the BSC-SDU in step
104
. Since the BTS is being synchronized with the BSC-SDU, it sets power control information in the reverse FCH/DCCH message that will be transmitted to the BSC-SDU to values negligible to the BSC-SDU in step
106
. In step
107
, the BTS transmits the IS-2000 reverse FCH/DCCH message to the BSC-SDU.
On the other hand, if the BTS has secured the radio resources related with the MS and acquired the MS in step
101
, it checks the quality of a frame received from the MS in step
102
. If the data frame is bad, the BTS sets Frame Content of the reverse FCH/DCCH message to an erasure frame in step
104
-
1
. In step
106
-
1
, the BTS sets the power control information of the reverse FCH/DCCH message to values negligible to the BSC-SDU. The BTS transmits the IS-2000 reverse FCH/DCCH message without any data to the BSC-SDU since the received frame is bad in step
107
-
1
. Upon recognition of the erasure frame, the BSC-SDU requests the MS to increase its transmission power regarding reverse power control. That is, since the data frame received from the MS is bad, the BSC-SDU will request the MS to transmit a data frame with incremented power.
If the BTS determines that the received frame is good in step
102
, it detects a DTX mode during reception of a reverse DCCH frame from the MS by a known DTX mode detection method applied to a radio transmission period between an MS and a BTS in step
103
. If the DTX mo
Dilworth & Barrese LLP
Maung Nay
Samsung Electronics Co,. Ltd.
Trinh Tan
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