Telecommunications – Transmitter and receiver at separate stations – With control signal
Reexamination Certificate
1999-08-20
2004-07-20
Kincaid, Lester G. (Department: 2685)
Telecommunications
Transmitter and receiver at separate stations
With control signal
C455S101000, C455S562100
Reexamination Certificate
active
06766146
ABSTRACT:
PRIORITY
This application claims priority to an application entitled “Channel Communication Device and Method for Mobile Communication System Using Transmission Antenna Diversity” filed in the Korean Industrial Property Office on Aug. 20, 1998 and assigned Serial No. 98-34187, 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 mobile communication system, and in particular, to a channel communication device and method using transmission antenna diversity.
2. Description of the Related Art
CDMA (Code Division Multiple Access) mobile communication systems have developed a voice-based mobile communication standard called IMT-2000 which is capable of transmitting data at a high rate as well as voice. The IMT-2000 standard provides services such as high-quality voice, moving pictures and Internet search. In a CDMA mobile communication system, a communication path between a mobile station and a base station is classified into a forward link, where data is transmitted from the base station to the mobile station, and a reverse link, where data is transmitted from the mobile station to the base station.
The capacity of the forward link requires much higher gain as the traffic increases. If the mobile station moves slowly, transmission antenna diversity on the forward link has a gain of about 1-7 dB as compared with non-transmission antenna diversity. This means that the capacity of the system can be increased two or three times. The performance of the system is greatly improved when the receiver of the mobile station cannot obtain sufficient path diversity and when the moving velocity of the mobile station is low.
Transmission antenna diversity indicates that a path over which a signal transmitted from the base station reaches the mobile station is multiplexed to raise the reliability of a received signal with respect to the same transmission signal power of the base station. In this context, the path means not only a spatial path, but a physical path which can transmit a signal from a transmitting side to a receiving side. For instance, the path can be the direction of a transmission antenna, polarization of a transmission signal, position of a transmission antenna, different carrier wave frequencies on a frequency axis, and different transmission time points on a time axis. As an example of transmission diversity, there is TSTD (Time-Switched Transmission Diversity) in which the base station has a plurality of antennas and the signal to be output through a transmitter is selected by a switch, thereby multiplexing a path reaching the mobile station from the base station.
Referring to
FIG. 1
, which illustrates a conventional TSTD transmitter, a signal mapping circuit
111
receives a combined signal of encoded user data and long codes, and maps the level of the received signal. That is, the signal mapping circuit
111
converts an input signal “0” into “+1” and “1” into “−1”. A serial-to-parallel converter
113
converts a serial signal output from the signal mapping circuit
111
into a parallel signal and separately outputs odd signals and even signals. Multipliers
115
and
117
respectively multiply the even signals and odd signals output from the serial-to-parallel converter
113
by an orthogonal code W
m
. The multipliers
115
and
117
are to modulate (or spread) a desired user signal to the orthogonal code. A Walsh code may be used for the orthogonal code. A complex PN (Pseudo Noise) spreader
119
spreads the orthogonally modulated signals output from the multipliers
115
and
117
by using PN sequences PN
I
and PN
Q
. A controller
120
generates a switching control signal for distributing a transmission signal to a plurality of antennas by using TSTD.
A switch
121
switched by the switching control signal provided from the controller
120
has a common terminal connected to I-channel and Q-channel spread signal output terminals of the complex PN spreader
119
, a first output terminal connected to LPFs (Low-Pass Filters)
123
and
125
, and a second output terminal connected to LPFs
127
and
129
. The switch
121
switches the spread signal output from the complex PN spreader
119
to either one of two pairs of the LPFs
123
and
125
and the LPFs
127
and
129
by the switching control signal.
The LPFs
123
and
125
low-pass filter the I-channel and Q-channel PN spread signals output through the switch
121
. Multipliers
131
and
133
respectively multiply the outputs of the LPFs
123
and
125
by carrier wave frequency signals to output up-converted frequency signals. An adder
141
adds signals output from the multipliers
131
and
133
to each other. The added signal is transmitted via transmission antenna A.
The LPFs
127
and
129
low-pass filter the I-channel and Q-channel PN spread signals output through the switch
121
. Multipliers
135
and
137
respectively multiply the outputs of the LPFs
127
and
129
by carrier wave frequency signals to output up-converted frequency signals. An adder
143
adds signals output from the multipliers
135
and
137
to each other. The added signal is transmitted via transmission antenna B.
In addition to TSTD, there is STD (Selective Transmission Diversity) in which the mobile station measures the power strength of pilots received from two transmission antennas, compares its relative rate with a threshold, and then periodically transmits an antenna selection signal to the base station. The base station then transmits data via the one antenna with better reception, as selected by the mobile station.
Referring to
FIG. 2
, which illustrates a conventional STD transmitter, a channel encoder
211
encodes data to be transmitted. A convolution encoder or a turbo encoder may be used for the channel encoder
211
. An interleaver
212
interleaves symbols output from the channel encoder
211
to prevent a burst error. A multiplexer (MUX)
213
multiplexes a pilot symbol, a transmission power control bit (TPC), rate information (RI), and data interleaved by the interleaver
102
. A serial-to-parallel converter
214
maps an input channel signal and converts the mapped signal into a parallel signal. For instance, the serial-to-parallel converter
214
converts an input signal “0” into “+1” and “1” into “−1” and separately outputs in parallel odd signals and even signals. Multipliers
215
,
225
and
235
respectively multiply the parallel channel signals output from the serial-to-parallel converter
214
by corresponding orthogonal codes. An adder
216
adds the orthogonally modulated signals output from the multipliers
215
,
225
and
235
to each other. A complex spreader
217
spreads the output of the adder
216
by using PN sequences PN
I
and PN
Q
. A switch
218
switches the output of the complex spreader
217
by an antenna selection signal (AS) provided by a controller. The antenna selection signal is determined by an antenna switching command from the mobile station. Baseband filters
219
and
220
low-pass filter the I-channel and Q-channel PN spread signals switched by the switch
218
.
FIG. 3
is a diagram illustrating the structure of signals exchanged between the base station and a mobile station in a conventional asynchronous mobile communication system that does not use transmission antenna diversity. Reference numeral
301
denotes a forward perch channel received by the mobile station (MS). The perch channel includes a search code for time synchronization. The search code is used to determine to which cell group a mobile station belongs in order to acquire slot sync and frame sync. That is, the mobile station acquires frame sync and slot sync using the search code of the perch channel, and obtains the dedicated physical channel information using a time offset provided from the base station. The mobile station measures the phase and power of the pilot symbols to estimate a channel condition. Reference numeral
302
indicates a forward dedicated physical channel (DPCH
Ahn Jae-Min
Lee Hyeon-Woo
Park Jin-Soo
Yeom Jae-Heung
Dilworth & Barrese LLP
Kincaid Lester G.
Samsung Electronics Co,. Ltd.
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