Switching Apparatus and Method for Transceiver of Cellular Base Station in Code Division Multiple Access Mobile Telecommunication System

1. Field of the Invention

The present invention relates to a Code Division Multiple Access (hereinafter, referred to as CDMA) mobile telecommunication system and, in particular, to a switching apparatus and method for switching over to a spare transceiver for maintenance and repair of a troubled transceiver when the transceiver, preferably, but not exclusively, for use in a CDMA cellular base station, gets into trouble.

2. Description of the Related Art

Generally, a CDMA mobile telecommunication system is provided with a low power radio transmitter and receiver (transceiver) and a control unit in a central area of each service area, i.e., a cell, in which a cellular base station serves as a relay to communicate by radio with a selected mobile telephone terminal equipment. A receiving frequency applied from each mobile terminal equipment is converted and amplified into a much lower radio frequency, which is often referred to as an "intermediate frequency". The cellular base station converts the receiving frequency to the intermediate frequency, which is subsequently converted to a transmit intermediate frequency on basis of a tuning frequency of each transceiver.

A cellular base station of CDMA mobile telecommunication system has a multiplicity of transceivers adapted to convert an intermediate frequency to and from the respective different radio frequencies corresponding to each mobile terminal equipment, in which system the number of those transceiver depends upon the number of radio channels. When the system needs to perform maintenance and repair of a transceiver due to any one of the transceivers operating in a CDMA cellular base station getting into trouble or malfunctioning, one of a plurality of switches, each switch corresponding to a respective transceiver, i.e., the switch coupled to the troubled transceiver, is turned off to switch over to a predetermined spare transceiver that continues the conversion of the intermediate frequency instead of the troubled transceiver.

Thus, a problem of space occurs because of such a large number of switches in use which require a lot of control cables connected with those switches, and which inevitably leads to complicated construction of the transceiver system and higher cost.

It is accordingly an object of the present invention to provide a switching apparatus and method for selecting a spare transceiver when performing maintenance and repair of a troubled transceiver in a cellular base station, preferably, but not exclusively, for use in a CDMA mobile telecommunication system, provided with a single switch module having a plurality of switches in combination.

It is another object to provide a switching apparatus and method capable of simultaneously controlling a plurality of switches with a single control signal for selecting a spare transceiver upon detection of a malfunctioning one of a plurality of transceivers in the cellular base station.

It is still another object to provide a switching apparatus and method for switching over transmission and reception frequencies of a troubled transceiver of a plurality of transceivers in a cellular base station to a spare transceiver.

These and other objects may be achieved according to the present invention can be accomplished with a transceiver switching apparatus for use in a cellular base station of a mobile telecommunication system, constructed with a plurality of transceivers each having an alarm detection and release sensing circuit, for generating an alarm signal upon occurrence of an abnormal state in the respective transceiver, and generating an alarm release signal upon removal of the abnormal state, each of the transceivers having a respective tuning frequency, the transceivers outputting a transmission intermediate frequency in response to received first and second intermediate receiving frequencies converted on basis of the respective tuning frequency; at least one spare transceiver for outputting an intermediate transmitting frequency signal converted from selected ones of the first and second intermediate receiving frequency signals upon receipt of and in response to operational data for switching the spare transceiver being adapted for performing the same function as one of the plurality of transceivers; a first receiving switching circuit having a plurality of pairs of inputs/outputs for inputting first intermediate receiving frequencies and outputting them to each transceiver corresponding thereto, for selecting the one of the first intermediate receiving frequencies for output to the spare transceiver through an alternate output in response to a detection control signal, and for switching over so as to connect the selected one of the first intermediate receiving frequencies back to the original paired output in response to a normal return control signal; a second receiving switching circuit having a plurality of pairs of inputs/outputs for inputting second intermediate receiving frequencies and outputting them to each transceiver corresponding thereto, for selecting one of the second intermediate receiving frequencies for output through an alternate output to the spare transceiver in response to the detection control signal, and for switching over so as to connect the selected one of the second intermediate receiving frequencies back to the original paired output in response to a normal return control signal; a transmitting switching circuit having a plurality of pairs of inputs/outputs corresponding to the transceivers, for receiving the intermediate transmitting frequencies from the transceivers for transmission output, an alternate input for receiving the intermediate transmitting frequency from the spare transceiver, for switching over so as to connect the alternate input to a selected output in response to the detection control signal, and for switching over so as to connect each of inputs of the input/output pairs to the corresponding output in response to the normal return control signal; a memory for storing the operational data necessary for the switching operation of the respective transceivers; and a controller for providing the operational data of an abnormally operating transceiver to the spare transceiver in response to the alarm signal, providing the detection control signal to the first and second receiving switching circuit and the transmitting switching circuit upon receipt of the alarm signal, and providing the normal return control signal to the first and second receiving switching circuit and the transmitting switching circuit upon receipt of the alarm release signal.

Another aspect of the present invention can be accomplished with a method for transceiver switching in a cellular base station, operable in a transceiver switching apparatus constructed with a plurality of transceivers capable of generating an alarm signal upon occurrence of an abnormal state, and an alarm release signal upon removal of the abnormal state, each of the transceivers outputting an intermediate transmitting frequency converted from an intermediate receiving frequency signal on basis of a tuning frequency, at least one spare transceiver adapted for performing the same function as the transceivers, first and second receiving switching circuits each having pairs of inputs/outputs for delivering, respectively, first and second intermediate receiving frequencies selectively to the plurality of transceivers and/or the spare transceiver, and a transmitting switching circuit having pairs of inputs/outputs for receiving the intermediate transmitting frequencies selectively from the plurality of transceivers and/or the spare transceiver, the method including the steps of: checking whether the spare transceiver is operating when an alarm signal is detected from one of the plurality of transceivers; determining whether the troubled transceiver has a high or low priority in operation if the spare transceiver is operating, and if a low priority is detected, then returning to the preceding checking step after a lapse of a predetermined time; providing a predetermined set of data for switching operation including a tuning frequency of an abnormally operating one of the transceivers to the spare transceiver if the spare transceiver is not operating, and thereafter, applying a switching control signal to the first and second receiving switching circuits and the transmitting switching circuit to replace the abnormally operating transceiver with the spare transceiver; and applying a normal return control signal to the first and second receiving switching circuits and the transmitting switching circuit for a recovery to the original transceiver replaced by the spare transceiver when an alarm release signal is received from the previously abnormally operating transceiver.

A more complete appreciation of this invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein:

FIGS. 1A and 1B provide a block diagram illustrating the construction of a preferred embodiment of a transceiver switching apparatus for maintenance and repair of a troubled transceiver according to the principles of the present invention; and

FIG. 2 is a flow chart showing a control method for the transceiver switching apparatus of FIGS. 1A and 1B according to the principles of the present invention.

Referring now to FIG. 1, a transceiver switching apparatus for maintenance and repair of a troubled transceiver is shown, in which four different intermediate frequencies (IF) are respectively provided by means of four transceivers 111, 112, 113 and 114, and a spare transceiver 115, all of which performs the identical function and have a respective different tuning frequency by which an intermediate receiving frequency is converted to an intermediate transmitting frequency, wherein the intermediate transmitting frequency is adapted to be changed by a more or less frequency amount from the intermediate receiving frequency. Alarm detection and release sensing circuits 111A, 112A, 113A and 114A each detect an abnormal state of their respective transceivers to provide an alarm signal or an alarm release signal as an output respectively.

A memory 131 for storing tuning frequencies and operating data of transceivers 111-114, wherein memory 131 is preferably embodied with a ROM because the operating data and the tuning frequency of each transceiver need to be stored permanently. A controller 130 receiving the alarm signal provides the tuning frequency of the troubled transceiver and its operating data to the spare transceiver 115 and outputs a detection control signal. The controller receiving the alarm release signal provides a control signal for normal return.

First and second receiving switching circuits 122 and 123 each have four inputs for receiving the first to fourth intermediate receiving frequencies respectively and five outputs to the transceivers. The first and second receiving switching circuits 122 and 123 are adapted for the purpose of the so-called diversity effect and carry out the same function. The first and second receiving switching circuits 122 and 123 each serve to switch over to connect either one of outputs 1 to 4 for any troubled one of the transceivers 111 to 114 with an output 5 of the spare transceiver 115 responsive to the control signal of the controller 130. A transmitting switching circuit 121 has five inputs for receiving the intermediate transmitting frequencies from the transceivers 111 to 115, respectively, and four outputs. The transmitting switching circuit 121 serves to switch over to connect either one of the inputs 1 to 4 from any troubled one of the transceivers 111 to 114 with the input 5 from the spare transceiver 115 responsive to the control signal of the controller 130.

The controller 130 provides the detection control signal and the control signal for normal return to the transmitting switching circuits 121 and the first and second receiving switching circuits 122 and 123 through a 9-pin cable. The transmitting switching circuits 121 and the first and second receiving switching circuits 122 and 123 can be simultaneously controlled by a single control signal from the controller 130.

Referring to the above circuit construction, normally the first to fourth intermediate receiving frequencies are supplied to first and second receiving switching circuits 122 and 123 and then provided to the corresponding transceiver through their respective input and output pairs, for example, 11 to 1, 12 to 2, 13 to 3 and 14 to 4. Likewise, first to fourth intermediate transmitting frequencies are supplied to transmitting switching circuit 121 and then switched to output through their respective input and output pairs, for example, 1 to 01, 2 to 02, 3 to 03 and 4 to 04. In a normal operating state, the first to fourth intermediate receiving frequencies (Rx IF) through the first and second receiving switching circuits 122 and 123 supplied to each R1 and R2 input of the first to fourth transceivers 111 to 114 are then converted via each output Tx to the first to fourth intermediate transmitting frequencies (Tx IF). When any one of transceivers 111-114 begin to malfunction, the input and output pair of first and second receiving switching circuits 122 and 123 and transmitting switching circuit 121 coupled to the troubled transceiver is connected with spare transceiver 115 in response to the 9-bit detection control signal output by controller 130. Then, when the troubled transceiver is repaired, the control signal for normal return is provided by the controller 130, first and second receiving switching circuits 122 and 123 and transmitting switching circuit 121 are again connected to the original transceiver.

Connection of respective input and output pairs in between first and second receiving switching circuits 122, 123 and transmitting switching circuit 121 is achieved by applying a pulse of logic high value to a corresponding pin of nine pins. The following table provides an indication of which inputs are simultaneously connected to what outputs when the the control signal provides a logic high value pulse to the pins.

During normal operations of transceivers 111-114, controller 130 outputs a detection control signal of 101010100. Accordingly, controller 130 applies a pulse having a logic high value to pins 1, 3, 5, and 7 when transceivers 111-115 are operating in a normal state, generates a detection control signal of 011010100 thus providing a logic low value signal to pin 1 and a logic high value signal to pin 2 during an abnormal state of first transceiver 111, generates a detection control signal of 100110100 thus providing a logic low value signal to pin 3 and a logic high value signal to pin 4 during an abnormal state of second transceiver 112, generates a detection control signal of 101001100 thus providing a logic low value signal to pin 5 and a logic high value signal to pin 6 during an abnormal state of third transceiver 113, and generates a detection control signal of 101010010 thus providing a logic low value signal to pin 7 and a logic high value signal to pin 8 during an abnormal state of fourth transceiver 114. Controller 130 provides the normal return control signal of 101010100 to pins 1-9 in order to simultaneously return the switched condition of switching circuits 121-123 to their original state.

Referring now to FIG. 2, a troubled one of transceivers 111-114 provides an alarm signal to controller 130 when an abnormal state is detected by a respective one of alarm detection and release sensing circuits 111A-114A, the abnormal state defining any kind of physical deviation or malfunction of the transceivers operating in a condition other than a normal operating condition. When controller 130 detects the alarm signal in step 211, it checks whether spare transceiver 115 is operating in step 212, while simultaneously evaluating the switching priority of the troubled transceiver for controlling when the switching operation to the spare transceiver occurs, wherein the switching priority is predetermined for each transceiver in order to establish a controlled switching order. When controller 130 determines in step 213, that the priority of the troubled transceiver is high the process proceeds to step 215, while if the priority is low, then the process proceeds to step 214. In step 214 a check of whether spare transceiver 115 is operating in step 212 after a lapse of a given time duration is performed. When it is determined in step 212 that spare transceiver 115 is not operating, then the process proceeds to step 215. In step 215 operating data corresponding to the troubled transceiver are provided to spare transceiver 115, and, in step 216, the switching control signal is applied to first and second receiving switching circuits 122, 123 and transmitting switching circuit 121. Thereafter, controller 130 again checks for an alarm signal from alarm detection and release sensing circuits 11A-114A. If an alarm signal is detected then steps 212-216 are again performed. If no alarm signal is detected in step 211, controller 130 determines whether the troubled transceiver has been repaired by detecting an alarm release signal in step 217. When controller 130 detects the alarm release signal a determination is made, step 218, as to whether spare transceiver 115 is switched over, and in step 219, it is determined by controller 130 whether all the functions of the corresponding repaired transceiver has been recovered to a normal state.

The "switched over" determination in step 218 is a determination as to whether or not the alarm release signal is from the same transceiver that generated the alarm signal causing controller 130 to switch over to the spare transceiver. If a transceiver having a low priority had generated an alarm signal while the spare transceiver was operating for a transceiver having a high priority, and if the low priority transceiver obtained a normal operational state before the high priority transceiver, then the low priority transceiver would generate an alarm release signal. Accordingly, step 218 prevents controller 130 from generating a normal return control signal while the spare transceiver is operating for the high priority transceiver.

Once step 218 determines that the alarm release signal is from the transceiver which caused controller 130 to switch over to the spare transceiver, step 219 is performed. Therefore, when it is confirmed in the step 219 that the functions of the corresponding repaired transceiver has recovered to a normal state, controller 130 generates the normal return control signal 101010100 in step 220 thereby returning first and second receiving switching circuits 122, 123 and transmitting switching circuit 121 back to their original state for normal operations.

As may be apparent from the foregoing, the present invention enables simultaneous control of the plurality of receiving switching circuits and the transmitting switching circuit, thereby leading to simplification of the control signals for switching over of a troubled transceiver. As a result, even if any kind of trouble should occur in any one of transceivers operating in a cellular base station, then it would allow a spare transceiver to be used for the troubled one by means of a switching apparatus according to the present invention, so that the cellular base station could continue to perform its normal operation as well as the maintenance and repair without any interruption to its telecommunication service.

While there has been illustrated and described what is considered to be a preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents made be substituted for elements thereof without departing from the true scope of the present invention. In addition, many modifications may be made to adapt a particular situation to the teaching of the present invention without departing from the central scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims.