Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
2002-11-27
2004-11-09
Cumming, William (Department: 2683)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
Reexamination Certificate
active
06816476
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a communication device and method for a CDMA communication system, and in particular, to a device and method for performing closed loop power control in a control hold state.
2. Description of the Related Art
A conventional Code Division Multiple Access (CDMA) mobile communication system based on the IS-95 standard primarily supports a voice service. However, a mobile communication system in accordance with the IMT-2000 standard will support not only the voice service, but also a high-speed data transfer service. For example, the IMT-2000 standard can support a high-quality voice service, a moving picture service, an Internet search service, etc.
In a mobile communication system, a data communication service is characterized by short transmissions (i.e., burst data) alternating with long non-transmission periods. Therefore, for the data communication service, a mobile communication system employs a channel assignment method in which a dedicated channel is assigned for only the short periods of (i.e., the burst duration) data transmission. That is, taking into consideration the limited radio resources, base station capacity and power consumption of a mobile station, the mobile communication system connects a traffic channel and a control channel only for an actual data transmission duration and otherwise releases the dedicated channels (i.e., the traffic channel and the control channel) when there is no data to transmit for a predetermined time. When the dedicated channels are released, communication is performed through a common channel, thus increasing the efficiency of the radio resources.
To this end, the mobile communication system includes various operating states according to the channel assignment and the existence
on-existence of state information.
FIG. 7
illustrates a state transition diagram of a mobile communication system for the various operating states describing the packet service. As shown in
FIG. 7
, the state transition diagram for the packet service illustrates a packet null state, an initialization state, an active state, a control hold state, a suspended state, a dormant state and a reconnect state. In the control hold, active and suspended states, a service option is connected and in the other states, the service option is not connected.
In a conventional CDMA mobile communication system which mainly supports the voice service, a traffic channel is released upon completion of data transmission and the traffic channel is then reconnected when it is required to transmit data. The conventional channel assignment method, however, is not suitable for a packet data service because of a time delay for reconnecting the channel. Therefore, to provide the packet data service as well as the voice service, there is required an improved channel assignment method.
In general, during the packet data service, data transmission occurs intermittently (i.e., in bursts). Therefore, a transmission duration of packet data alternates with periods of non-transmission. The mobile communication system either releases or maintains a channel in use for the periods of non-transmission. However, there are drawbacks associated with both maintaining and releasing a channel, namely, release of the channel causes an increase in service time due to a time delay for reconnection of the channel, and maintaining the channel causes a waste of the channel resources. To solve these problems, a dedicated control channel is commonly provided between a base station and a mobile station to exchange traffic channel-related control signals over the dedicated control channel for the data transmission. The traffic channel is released and only the dedicated control channel and a reverse pilot/PCB channel are maintained for the data non-transmission duration. When the dedicated control channel is not activated, only the reverse pilot/PCB channel is maintained. The reverse pilot/PCB channel is required to maintain synchronization. In this manner, the mobile communication system can prevent a waste of channel resources and rapidly reconnect the traffic channel when there is data to transmit. The operating state described above is called a control hold state (see FIG.
7
). The control hold state can be divided into a normal substate and a slotted substate, as shown in FIG.
8
. The normal substate refers to a state where there is no data to transmit over a traffic channel, and only a control signal is exchanged over a dedicated control channel or only the reverse pilot/PCB channel is maintained. The slotted substate refers to a state where connection of the dedicated control channel is maintained but no control signal and no reverse pilot/PCB channel is maintained to reduce power consumption of a mobile station. However, to make a transition from the slotted substate to the normal substate to restart control data transmission, resynchronization should be performed between a base station and a mobile station, since no control signal is exchanged between the base station and the mobile station in the slotted substate
However, when closed-loop power control of the reverse pilot/PCB channel is maintained, as in the case where there exists a dedicated control channel and the system stays in a data transmission state even though there is no message to transmit over the dedicated control channel in the normal substate, interference and power consumption may increase unnecessarily.
FIG. 1A
illustrates a conventional base station transmitter for a conventional CDMA communication system.
With regard to forward link channels, the base station includes a pilot channel for sync acquisition and channel estimation, a forward common control channel (F-CCH) for communicating a control message in common to all the mobile stations located in a cell (or service) area of the base station, a forward dedicated control channel (F-DCCH) for exclusively communicating a control message to a specific mobile station located in the cell area of the base station, and a forward dedicated traffic channel (F-DTCH) for exclusively communicating traffic data (i.e., voice and packet data) to a specific mobile station located in the cell area of the base station. The forward dedicated control channel includes a sharable forward dedicated control channel (sharable F-DCCH) for exclusively communicating a control message to a specific mobile station on a time-division basis. The forward dedicated traffic channel includes a forward fundamental channel (F-FCH) and a forward supplemental channel (F-SCH).
Referring to
FIG. 1A
, demultiplexers
120
,
122
,
124
and
126
demultiplex corresponding channel-coded interleaved channel information to I and Q channels. Here, serial-to-parallel converters can be used for the demultiplexers
120
,
122
,
124
and
126
. It is assumed herein that signals input to the demultiplexers
120
,
122
,
124
and
126
are signal-mapped signals. Mixers
110
,
130
,
131
,
132
,
133
,
134
,
135
,
136
and
137
multiply signals output from the associated demultiplexers by orthogonal codes assigned to the corresponding channels, for signal spreading and channel separation. The orthogonally spread signals output from the mixers
130
-
137
are gain controlled by associated amplifiers
140
-
147
.
Signals output from the amplifiers
140
-
147
and the mixer
110
are summed by summers
150
and
152
according to the I and Q channels. Since the signals applied to the summers
150
and
152
were channel separated by the orthogonal codes, the respective channel signals are orthogonal to one another. Outputs of the summers
150
and
152
are multiplied by PN (Pseudo Noise) sequences PN#I and PN#Q assigned to the base station for base station identification in a complex multiplier
160
. I and Q channel signals output from the complex multiplier
160
are applied to filters
170
and
171
, respectively, which bandpass filter the input signals to output bandwidth-suppressed signals. The outputs of the filte
Ahn Jae-Min
Kim Jae-Yeol
Kim Young-Ky
Park Su-Won
Cumming William
Dilworth & Barrese LLP
Samsung Electronics Co,. Ltd.
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