Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2000-02-14
2003-11-25
Nguyen, Lee (Department: 2685)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C455S070000, C370S335000, C370S342000, C370S347000
Reexamination Certificate
active
06654613
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a device and method of continuous outer-loop power control in a discontinuous transmission (DTX) mode for a CDMA (Code Division Multiple Access) mobile communication system, and in particular, to a device and method for implementing an outer-loop power control in a non-frame data transmission period as well as a frame data transmission period.
2. Description of the Related Art
For packet transmission in the American IMT-2000 standard, IS-95C, P
1
, P
2
, and P
3
options are used. The P
1
, P
2
, and P
3
options utilize a fundamental traffic channel & a supplemental channel, a fundamental traffic channel & a dedicated control channel (DCCH), and a fundamental traffic channel, a DCCH, & a supplemental channel, respectively. Control information about a packet and a signaling message are transmitted on the fundamental traffic channel and the DCCH and packet data is transmitted on the supplemental channel. The control information and the signaling message do not occur all the time. When no control information and signaling message exist, the fundamental traffic channel transmits null traffic, whereas the DCCH transmits power control bits (PCBs) on a forward link and pilot symbols & PCBs on a reverse link. The mode of the DCCH is termed a DTX mode during which only null frames are transmitted when there is no transmission frame data. The fundamental traffic channel and dedicated control channel (DCCH) are dedicated channels. In other words, it is also a dedicated channel that the channel is assigned to a specific user in traffic period.
For power control, an outer-loop power control and a closed-loop power control are concurrently performed in the DTX mode. The closed-loop power control refers to controlling power for each power control group (PCG), using a threshold determined for each frame. On the other hand, the outer-loop power control scheme changes the threshold set for the closed-loop power control depending on the presence or absence of frame errors. Specifically, the threshold is increased or decreased by a predetermined level according to whether a frame has errors or not. Then, a closed-loop power controller implements a closed-loop power control using the changed threshold. In the case that the outer-loop power control and the closed-loop power control are employed together, the closed-loop power control is implemented using a threshold determined by the outer-loop power control upon presence of a frame and an existing threshold upon absence of a frame, in a DTX mode.
A description of power control in a DTX mode for a communication system employing both the outer-loop power control scheme and closed-loop power control scheme is provided below.
FIG. 1A
is a block diagram of a forward link transmitter in a general CDMA mobile communication system. Referring to
FIG. 1
, insertion of PCBs in a DTX mode will be described.
In
FIG. 1
, a control message buffer
111
is a memory for temporarily storing a control message to be transmitted on a DCCH. The capacity of the control message buffer
111
can be set to one or more frames. The control message buffer
111
interfaces a control message between a higher-layer processor and a MODEM controller
113
. The higher-layer processor stores a control message with header information for identifying a frame according to a message type in the control message buffer
111
and sets a flag to indicate the storage. The MODEM controller
113
reads the control message from the control message buffer
111
and then clears a flag to indicate the reading. By the operations, the higher-layer processor and the MODEM controller
113
prevent over-writing and over-reading.
After reading the control message from the control message buffer
111
, the MODEM controller
113
determines a message type by analyzing the header of the control message, and outputs a payload to be transmitted on a DCCH according to the message type and a corresponding control signal. The output control message is variable in duration, that is, 5 or 20 ms according to the analysis result. In the following description, no distinction is made between a 5 ms-control message and a 20 ms-control message. The MODEM controller
113
determines whether there is a control message to transmit and controls transmission of the DCCH. That is, the MODEM controller
113
generates a first gain control signal upon presence of a control message to be transmitted and a second gain control signal for blocking signal transmission on the DCCH upon absence of a control message. The gain control signals are signals for controlling the transmission power of the DCCH. While the multiplier
125
is located at the frontal end of a spreader, the same effect can be produced even if it is at the rear end of the spreader.
A CRC (Cyclic Redundancy Check) generator
115
adds a CRC to the control message received from the MODEM controller
113
to allow a receiver to determine the quality of a frame, that is, the presence or absence of a frame. The CRC generator
115
outputs a control message with the CRC under the control of the MODEM controller
113
. A 40-bit control message with a 16-bit CRC is generated for a 5 ms-frame, and a 184-bit control message with a 12-bit CRC for. a 20 ms-frame.
A tail bit encoder
117
analyzes the output of the CRC generator
115
and adds corresponding tail bits to the output of the CRC generator
115
, for terminating an error correction code. Here, the tail bit encoder
117
generates 8 tail bits.
An encoder
119
encodes the output of the tail bit encoder
117
at a code rate of ⅓. The encoder
119
can be a convolutional encoder or a turbo encoder. An interleaver
121
permutes the bit sequence of encoded symbols received from the encoder
119
in frame units to protect the data from burst errors.
The CRC generator
115
, the tail bit encoder
117
, the encoder
119
, and the interleaver
121
form a control message generator
150
for generating a control message and transmitting it on a physical channel. While the control message generator
150
processes a control message for a frame in
FIG. 1A
, it can be contemplated that the MODEM controller
113
selects a control message generator corresponding to the length of a frame to transmit among as many control message generators as the frame lengths of control messages transmitted on the DCCH. In this case, each control message generator should be provided with a CRC generator, a tail bit encoder, an encoder, and an interleaver according to the frame length of a control message processed in the control message generator.
A signal mapper
123
maps 1s and 0s of the interleaved symbols to −1s and 1s, respectively. A gain multiplier
125
performs a DTX mode function by establishing a path for transmitting the DCCH control message or blocking the path depending on which gain control message is received from the MODEM controller
113
.
A PCB puncturer
129
inserts a PCB into a signal received from the multiplier
125
. A serial-to-parallel converter (SPC)
127
multiplexes control message symbols received from the PCB puncturer
129
and distributes the multiplexed symbols to carrier spreaders. Here, three carriers are used by way of example. For the three carriers, six channels are produced from three carrier frequencies and two phases (I and Q channels) of each carrier. The PCB can be used for controlling reverse link power of a mobile station.
FIG. 1B
is a block diagram of a spreader for spreading symbols received from the PCB puncturer
129
. A forward link transmitter includes as many spreaders as carriers. For example, three spreaders exist in the forward link transmitter shown in FIG.
1
A.
Referring to
FIG. 1B
, an orthogonal code generator
135
generates a DCCH orthogonal code which can be a Walsh code or a quasi-orthogonal code. Multipliers
131
and
133
multiply I- and Q-channel signals of the forward DCCH control message by the orthogonal code, for orthogonal spreading.
A modulator
137
PN
Ahn Jae-Min
Kim Young Ky
Maeng Seung-Joo
Yeom Jae-Heung
Dilworth & Barrese LLP
Iqbal Khawar
Nguyen Lee
Samsung Electronics Co,. Ltd.
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