KR100374038B1 - Device and method for diversity combining signals on common channel in cdma communication system - Google Patents

Abstract

In a common channel diversity combining method of a code division multiple access communication system, a process of a base station assigning a shared channel dedicated to a mobile terminal in a base station, and a base station connected to a base station is connected to a base station controller. And providing the related information, and providing the information to at least one base station connected to the base station controller and adjacent to the base station.

Description

DEVICE AND METHOD FOR DIVERSITY COMBINING SIGNALS ON COMMON CHANNEL IN CDMA COMMUNICATION SYSTEM}

The present invention relates to an apparatus and method for message communication in a communication system, and more particularly, to an apparatus and method for communicating a message through a common channel in a code division multiple access communication system.

In general, in the TIA / EIA / IS-95, a communication system uses a paging channel in a base station, which is a common channel, to exchange data between a base station and a mobile station before a voice call is established. Use Access Channel. First, when a base station transmits a message to a mobile station, the base station transmits a message through a call channel and receives a response from the mobile station through an access channel. When the mobile station transmits a message to the base station, the mobile station transmits a message through an access channel and receives a response from the base station through a call channel. Accordingly, the call channel and the access channel may exist in plural, the call channel is distinguished by Walsh code, and the access channel is distinguished by long PN code. At this time, different long codes are assigned to each channel by giving different long code masks to each access channel. Figure 1 illustrates the implementation of the long code of the access channel in IS-95 and the long code mask assigned to each channel at that time.

When a message to be transmitted is generated, the mobile station transmits the message to the base station. The mobile station selects an arbitrary channel, sets an appropriate size transmission power, transmits the message, and waits for a response from the base station. In this case, when different mobile stations select the same channel at the same time, contention may occur and the base station may not receive a message transmitted from the mobile station. Therefore, if the response message is not received even after waiting for the appropriate time, the mobile station transmits the message again using a slightly larger transmission power and waits for the response message transmitted from the base station.

When the traffic channel is transmitted on the reverse link, two or more base stations can receive the signal of the terminal more efficiently by obtaining a diversity effect by capturing and receiving a signal of the terminal. In the conventional access channel, even if two or more base stations capture a signal of one access channel, it cannot be distinguished whether the signal is received from the same user or from another user.

When a cell of an IS-95 mobile communication system is divided into several sectors, a different spreading sequence is used for each sector. This is done by assigning different PN_OFFSET for each sector. Even in this case, even if a signal of one access channel is acquired by antennas of different cells, it cannot be distinguished whether the signal is transmitted by the same user.

2 is a diagram illustrating a case where one base station is divided into three sectors α, β, and γ.

Referring to FIG. 2, when user 1 and user 2 simultaneously transmit data on the same access channel R_ACH1, even if the antennas of two sectors receive signals of the same access channel, accesses transmitted by user 1 through the antenna of α sector It is possible to capture the channel and the access channel transmitted by user 2 with the antenna of the? Sector. In this case, if the signals of the two antennas are combined in the base station receiver, normal reception is impossible due to interference between the two signals. This means that there is a difficulty in applying the multiplexing technique due to the collision phenomenon that may occur in the conventional access channel.

Accordingly, an object of the present invention is to provide an apparatus and method for combining a signal transmitted by a mobile station through a common channel in a code division multiple access communication system using a multiplexing technique.

An object of the present invention is to provide an apparatus and method for increasing the probability of successful reception of an access channel by a base station designating an access channel of a mobile station and a plurality of base stations receiving the access channel in a code division multiple access communication system.

A base station assigns a shared channel dedicated to a mobile station in a base station according to an embodiment of the present invention for achieving the above object, and the base station is connected to the base station by the base station to the allocated dedicated shared channel And providing information related to the information, and providing the information to at least one base station connected to the base station controller and adjacent to the base station.

FIG. 1A illustrates a structure of a long code generator of a reverse link in a conventional communication system, and FIG. 1B illustrates an embodiment of a long code mask.

2 is a view for explaining a problem of multiplexing combining of a common channel of a reverse link in a code division multiple access communication system;

FIG. 3A illustrates a process in which a base station designates a reverse shared channel of a mobile station according to an embodiment of the present invention, and FIG. 3B illustrates a process in which a base station designates a reverse shared channel of a mobile station by a channel designation request of the mobile station.

4 illustrates a configuration of a mobile station of a communication system according to an embodiment of the present invention.

5 is a diagram illustrating a configuration of a receiver of a base station of a communication system according to an embodiment of the present invention.

6 is a diagram illustrating a structure for diversity combining received signals of various base stations in a communication system according to an embodiment of the present invention.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the same parts in the figures represent the same reference signs wherever possible.

An embodiment of the present invention aims to allow multiplexing combining access channels between sectors and multiplexing access channels between different base stations in a sectorized base station by allocating a user's own access channel for some time. . As described above, a structure for avoiding collision of an access channel by allocating a designated access channel to an access channel of a mobile station for some time is disclosed in patent applications Nos. 98-03125 and 98-04099 filed by the present applicant. An embodiment of the present invention proposes a structure for multiplexing combining between sectors within a base station or between base stations using the collision avoidance technique of the common channel as described above. In the embodiment of the present invention, it will be described on the assumption that the common channel is an access channel of a reverse link.

3 illustrates methods for avoiding collision by designating a channel to be used for an access channel for some time.

In the embodiment of FIG. 3 (a), when the base station transmits message 1 to the mobile station and waits for a response, the mobile station can designate a channel to send message 2 to transmit. This consists of sending a message 1 sent by the base station, including the " channel identifier " which the mobile station will use to send the message 2. The mobile station receives message 1 transmitted by the mobile station and transmits message 2 to the access channel designated by the base station. The "channel designation flag" means a designation flag indicating whether a base station designates a channel due to a channel designation request of a mobile station, and a "channel identifier" may be used by a specific mobile station or dedicated to a few mobile stations. ID of a spreading code of an access channel. The spreading code may be a long code. Accordingly, in the embodiment of the present invention, the base station and the specific mobile station control to generate a unique dedicated spreading code of a predetermined mobile station used for the reverse shared channel. It may be a long code mask generated by using an electronic serial number, or the like, or a public long code mask, or one of specific long codes designated for dedicated use of a common channel. In the present invention, it is assumed that the channel identifier is a long code ID for which the base station and the mobile station can use an access channel exclusively. By transmitting data on the designated access channel, message 2 transmitted by the mobile station can avoid collision.

In the embodiment of Fig. 3 (b), the mobile station requests channel designation. When the terminal transmits a message through the common access channel first, and subsequently there is a message to be transmitted continuously, the terminal transmits a message I including a "message flag" and a "channel designation request flag". "Message Flag" means a more message flag indicating the presence or absence of a message following a current message, and "Channel Designation Request Flag" means a specific channel code of an access channel when a mobile station transmits a message through an access channel to a base station. It means a design request flag.

The base station receives the channel designation request flag of the message I sent from the mobile station, determines whether to designate the channel, and transmits the response message II including "channel designation flag", "channel identifier", and the like. The "channel designation flag" means a designation flag indicating whether a base station designates a channel due to a channel designation request of a mobile station, and a "channel identifier" may be used by a specific mobile station or dedicated to a few mobile stations. ID of the subscriber identification code of the access channel. The channel identifier may be an electronic serial number (ESN), a public long code, or an ID of a specific long code previously promised between the base station and the mobile station. In the present invention, it is assumed that the channel identifier is a long code ID for which the base station and the mobile station can use an access channel exclusively.

The mobile station then receives the channel designation flag and channel identifier contained in message II and transmits subsequent message III on the access channel designated by the base station as described above. By transmitting data on the designated access channel, message III transmitted by the mobile station can avoid collision.

4 illustrates a structure in which a mobile station transmits a message through an access channel according to an embodiment of the present invention. 4 is a diagram illustrating a structure in which a base station generates a control message for specifying a channel after receiving and analyzing a message output from a mobile station according to an embodiment of the present invention.

Referring to FIG. 4, the receiver 411 receives an RF signal of a forward link received through an antenna and converts the RF signal to a baseband signal. Demodulator (demodulator) 413 demodulates the received signal output from the receiver 411 to the original signal and outputs. The controller 421 generates a message for transmitting over the access channel, and also generates a long code ID of the designated access channel by analyzing field information of the control message output from the demodulator 413.

The memory 423 stores long code information for designating an access channel. In this case, the long code ID stored in the memory 423 may be long code information for designating a common access channel. Therefore, if the control message 421 includes a long code ID for designating the access channel exclusively, the controller 421 decides to use the corresponding long code ID. However, if the long code ID is not included in the received control channel message, the controller 421 selects the long code ID of the common access channel stored in the memory 423 and outputs the long code ID to the long code generator 425.

The controller 421 outputs a long code ID stored in the memory 423 to use a common access channel when transmitting a message of an access channel for the first time (a state in which a long code to be used for an access channel is not specified), and also receives the received control message. Even when the long code ID is not specified, the long code ID stored in the memory 423 may be used. However, when the long code ID is specified in the received control message, the controller 421 controls to generate the long code of the access channel designated by the base station. The long code generator 425 generates a long code corresponding to the control of the long code controller 421.

Accordingly, the long code ID stored in the memory 423 may be long codes of a common access channel that can be shared by various mobile stations, and the long code ID output from the controller 421 is for a specific mobile station to use an access channel exclusively. It may be a long code ID or long codes of a semi-dedicated access channel that can be used by a few mobile stations.

A channel coder and an orthogonal spreader 431 encodes the reverse packet access channel message as shown in FIG. 3A generated by the controller 421 to channel coding, repetition, and interleaving. (interleaving) and orthogonal spreading (output). Multipliers 427 and 429 respectively input corresponding PN sequences PNI and PNQ, common input of long codes output from the long code generator 425, and multiplying two input signals and spreading them by the orthogonal codes. Generates a spreading code for spreading a signal of a channel. The PN spreader 433 multiplies the spread sequence of the I and Q channels output from the multipliers 427 and 429 by the orthogonal spreading or orthogonal modulating access channel signal. The transmitter 435 raises the spread signal of the access channel output from the PN spreader 433 to an RF signal and outputs the RF signal. The channel code and the quadrature spreader 431 are configurations of an access channel transmitter, and the configurations of the channel transmitters of the remaining reverse link are not shown.

5 shows a structure of a base station receiver proposed by the present invention. A base station controller (BSC) informs various base stations of the mobile station by designating a channel to use for an access channel. In addition, the base station may designate an access channel of the mobile station and notify the base station controller of the mobile station so that the base station controller may notify other base stations of the base station to demodulate the access channel. The base stations must demodulate the signal that the mobile station transmits on the designated access channel. Several base stations demodulate the designated access channel of the mobile station according to the information of the mobile station informed by the base station controller. In this case, the base station decoding the access channel of the terminal may be a partial set of the base station transmitting a message to the terminal on the forward link, or may be a whole.

The access channel signal of the mobile station demodulated by several base stations is combined according to the diversity scheme. This is similar to the behavior during softer handoff or soft handoff in IS-95. In the existing system, diversity combining is performed only on a traffic channel during softer or soft handoff. However, in the present invention, diversity combining may be extended to an access channel transmitted through a designated channel. Signals demodulated by each of several base stations may be diversity combined by various methods.

5 shows a receiver of one base station. This assumes that a cell is divided into several sectors, and that the base station transmits and receives a corresponding directional antenna for each sector. For simplicity, it is assumed that only a base station of one cell demodulates a designated access channel of the terminal. This is similar to the method of demodulating the signal of the reverse traffic channel at the soft handoff of the traffic channel of the IS-95 system. 5 illustrates a receiver structure of a base station for demodulating a signal received from two sector antennas.

It consists of several fingers that demodulate a signal received from several sector antennas. In addition, a searcher operates to detect a multipath of the received signal. The searchers 510 and 520 search for the positions of the multipath components of the signals received from the antennas 501 and 506, respectively, and allocate the same to the corresponding fingers 511-51N and 521-52N. N fingers 511-51N and 521-52N, respectively, for receiving signals output from the antennas 501 and 506 demodulate the multipath component, and a combiner 530 diversity the outputs of the fingers 511-51N and 521-52N. Apply techniques to combine.

6 shows an embodiment of a structure in which a base station located in another cell receives a signal transmitted by a mobile station on a designated access channel and combines the same. In FIG. 6, it is assumed that a base station located in two different cells demodulates a signal of a designated access channel of a mobile station. The receiver of each base station has the same structure as the receiver of FIG. Each base station demodulates the signal transmitted by the mobile station on the designated access channel and sends the demodulated signal to the base station controller over the wire. The base station controller includes a diversity combiner. The diversity combiner of the base station controller can obtain the diversity gain by combining the signals transmitted by each base station by wire.

In the structure as shown in FIG. 6, there are various methods of combining the signals transmitted from each base station by the diversity combiner of the base station controller and the signal transmitted by the base station controller. Some embodiments thereof will be described.

In the first embodiment, the receiver of each base station combines and decodes the multipath signals of the sector antennas in the received signal. The base station receiver then calculates the reliability of the decoded signal. This can be the decoding metric of the decoder, the signal level of the received signal, or a combination of these. Each base station transmits the reliability of the decoded signal and the received signal to the base station controller. The base station controller receives the decoded signals from several base stations and determines the decoded signal of the base station with the highest reliability as the final received message.

In the second embodiment, the receiver of each base station demodulates the multipath signal of each sector antenna from the received signal and performs diversity combining. However, channel decoding is not performed. Each base station transmits the reliability of the symbol of the received signal (e.g., output of each symbol of the combiner) to the base station controller. The diversity combiner of the base station controller combines the reliability of the symbols transmitted by each base station using a diversity scheme and channel decodes the result. In this case, the reliability of each symbol may be summed using the diversity combining technique of the base station controller. The channel decoded signal is output as the finally received message.

If the access channel is successfully received, the ACK is informed to the mobile station through the channel of the forward link.

As described above, in the embodiment of the present invention, the base stations can obtain a diversity gain by demodulating and combining the message of the terminal transmitted on the designated access channel for some time.

Claims (13)

Allocating a shared channel dedicated to a mobile station within a base station by the base station, Providing, by the base station, information related to the assigned dedicated shared channel to a base station controller connected to the base station; And combining the base station controller with the base station controller and providing the information to at least one base station adjacent to the base station. 2. The common channel of a code division multiple access communication system according to claim 1, further comprising the step of diversity combining and demodulating the common channel signal of the reverse link transmitted from the mobile station by the base stations provided with the dedicated common channel information. Diversity combining method. 3. The method of claim 2, wherein the dedicated common channel is an access channel. 3. The method of claim 2, wherein the channel identifier is an ESN of the mobile station. A first base station transmitting a channel identifier for designating a shared channel dedicated to a specific mobile station and transmitting the same to a base station controller; The base station controller receiving information of a shared channel dedicated from the first base station and notifying the received information to at least one second base station adjacent to the first base station; And a second base station for designating a corresponding common channel by a channel identifier output from the base station controller, And a base station controller for diversity combining the transmission signals of the specific mobile station through the first base station and the second base station. 6. The apparatus of claim 5, wherein the dedicated common channel is an access channel. 7. The apparatus of claim 6, wherein the channel identifier is an ESN of the mobile station. Transmitting a channel identifier for allocating a dedicated common channel to a mobile terminal in one base station, and designating a shared channel of at least two adjacent sectors as a dedicated shared channel by the channel identifier; And combining the signals of the mobile terminal received through the dedicated shared channels of at least two adjacent sectors. 10. The method of claim 8, wherein the dedicated common channel is an access channel. 10. The method of claim 9, wherein the channel identifier is an ESN of the mobile station. A base station transmitter for transmitting a channel identifier for designating a shared channel dedicated to a specific mobile station; A channel receiver of a first sector receiving a signal of a designated channel received through the antenna of the first sector, the corresponding dedicated channel being designated by the channel identifier; A channel receiver of a second sector receiving a signal of a designated channel received through the antenna of a second sector by designating a corresponding dedicated channel by the channel identifier; And a common channel diversity combining apparatus of a code division multiple access communication system comprising a combiner for diversity combining the transmission signals of the specific mobile stations output from the first and second sector receivers. 12. The apparatus of claim 11, wherein the dedicated common channel is an access channel. 13. The apparatus of claim 12, wherein the channel identifier is an ESN of the mobile station.