Abstract:
Since a pair of units associated with an antenna unit and a base processing unit is separately placed at a various distance with each other, communication signals also attenuate at a various rate. The amplification gain is adjusted at one unit based upon a receiving signal and a predetermined reception sensitivity level until a desirable amplification is achieved. The desirable amplification value is then transmitted to the other unit to be utilized for reciprocal communication at a desired level between the two units.

Description:
FIELD OF THE INVENTION  
         [0001]    The current invention is generally related to a wireless communication system and and is particularly related to a variable amplifier for controlling a gain based upon the length of cable that connects units in the wireless communication system.  
         DESCRIPTION OF RELATED PRIOR ART  
         [0002]    In a wireless communication system, antennas are placed at locations where the wireless communication signal is not affected for transmission. A unit that processes wireless communication signals via the antenna is isolated from other parts or units and is connected to the rest of the system via communication cable. Due to the above separation, the antenna unit has become compact and light weight. The compact antenna unit is thus easily placed at high locations such as the top of buildings or towers. For example, wireless communication such as fixed wireless access (FWA) includes the above described separated unit in base stations and subscriber stations.  
           [0003]    Referring to FIG. 7, an exemplary wireless access systems include a base station  1  and subscriber stations  2 . The base station  1  is connected to a public network  4  via cable  3 . Although it is not illustrated, each of the subscriber stations  2  is connected to a subscriber network such as LAN. Based upon the wireless communication between the base station  1  and the subscriber stations  2 , the communication is implemented between the subscriber networks and or between the subscriber network and the public network. The base station  1  and the subscriber stations  2  include an outdoor unit (ODU)  7  for processing wireless communication signals for antennas  6 , an indoor unit (IDU)  8  for processing communication signals with communication networks such as public networks and subscriber networks in the backbone as well as a cable  9  that connects the ODU  7  to the IDU  8 . The ODU  7  is placed at high locations such as the roof top of a building  10  where there is no interfering object and optimizes the wireless communication via the antenna  6 . On the other hand, the IDU  8  is placed inside the building  10  easy maintenance without the influence by the external factors such as temperature change.  
           [0004]    Now referring to FIG. 8, a diagram illustrates an exemplary separation unit for the base station  1  and the subscriber station  2 . The ODU  7  includes a wireless communication unit or RF unit  10  for processing wireless communication signals to and from the antenna  6  while the IDU  8  includes a communication unit  11  for communicating with networks in the backbone and a control unit  12  for controlling the entire wireless communication system. That is, the ODU  7  located outdoors is made compact and light weight by removing non-wireless functions. The ODU  7  is easily handled at high locations. The wireless communication units  8  and  9  are connected via the communication cable  9 , and the amplification gain is adjusted depending upon the length of the communication cable  9 . For example, as the ODU  7  is placed at a high location or a distant location, the length of the cable  9  varies and ranges from 1 meter to 300 meters. Because of the variable cable length, the transmission loss also varies and a desirable initial reception sensitivity is not obtained between the units. As described above, the amplification gain of a transmission amplifier must be adjusted based upon the cable length. Furthermore, since the original reception sensitivity is not uniform among the IDU&#39;S  7  due to manufacturing error, the transmission amplifier gain must be also adjusted in addition to the cable length.  
           [0005]    In response to these variations, during the past wireless communication system installation, a worker measured the sensitivity between the units and adjusted the transmission amplification gain. The above described manual operation had been quite difficult. Since the ODU  7  is located outdoors and the IDU  8  is located indoors, the IDU  7  is managed under temperature control while the ODU  7  is affected by the temperature during seasons. The reception sensitivity for communication via communication cable  9  also varies depending upon temperature. In order to maintain the original reception sensitivity, the above described complex gain adjustments must be manually repeated after installation. For the above reasons, it is desired that the amplification gain is automatically adjusted to eliminate the cumbersome manual adjustments as well as to provide good communication between the units via the communication cable.  
           [0006]    Japanese Patent Publication Hei 6-291685 discloses a wireless communication system for automatically adjusting amplification between two units. The units must transmit the original output level information in the data signal to a receiving unit in the above described system. Because of the above and other requirements, it is desired to simplify the system  
         SUMMARY OF THE INVENTION  
         [0007]    In order to solve the above and other problems, according to a first aspect of the current invention, a method of adjusting amplification gain for a communication signal, includes the steps of: storing a predetermined standard reception sensitivity value; amplifying the communication signal at an amplification level at a first unit; transmitting the amplified communication signal from the first unit to a second unit; receiving the communication signal at the second unit; comparing the received communication signal to the predetermined standard reception sensitivity value to generate a comparison signal; adjusting the amplification level at the first unit based upon the comparison signal until a desirable amplification is reached; transmitting the amplification level from the first unit to the second unit upon achieving the desirable amplification; and storing the amplification level at the second unit for amplification gain at the second unit.  
           [0008]    According to a second aspect of the current invention, a system for adjusting amplification gain for a communication signal, includes: a first unit including a first amplifier for amplifying the communication signal at an amplification level, a first transmitter connected to the amplifier for transmitting the amplified communication signal and a first memory for storing an amplification level; and a second unit connected to said first unit including a receiver for receiving the communication signal, a second memory for storing a predetermined standard reception sensitivity value and a comparator for comparing the received communication signal to the predetermined standard reception sensitivity value to generate a comparison signal, wherein said first unit adjusts the amplification level of the first amplifier to a desirable amplification level based upon the comparison signal until a desirable amplification is reached at said second unit, said first unit storing the amplification level in the first memory, said first unit transmitting the desirable amplification level to said second unit upon achieving the desirable amplification, the second unit storing the desirable amplification level.  
           [0009]    According to a third aspect of the current invention, a system for adjusting amplification gain for a communication signal, includes: a first unit including a first amplifier for amplifying the communication signal at an amplification level, a first transmitter connected to the amplifier for transmitting the amplified communication signal, a first memory for storing a predetermined standard reception sensitivity value and a comparator for comparing two signals; and a second unit connected to said first unit including a receiver for receiving the communication signal, said second unit transmitting the received communication signal back to said first unit, wherein the comparator compares the received communication signal from said second unit to the predetermined standard reception sensitivity value to generate a comparison signal, said first unit adjusting the amplification level of the first amplifier to a desirable amplification level based upon the comparison signal until a desirable amplification is reached at said second unit, said first unit transmitting the desirable amplification level to said second unit upon achieving the desirable amplification, said second unit storing the desirable amplification level.  
           [0010]    According to a fourth aspect of the current invention, a system for adjusting amplification gain for a communication signal, includes: a first unit including a first amplifier for amplifying the communication signal at an amplification level, a first transmitter connected to the amplifier for transmitting the amplified communication signal, a first memory for storing an amplification value and a comparator for comparing two signals; and a second unit connected to said first unit including a receiver for receiving the communication signal and a second memory for storing a predetermined standard reception sensitivity value, said second unit sending the predetermined standard reception sensitivity value to the first memory in said first unit, said second unit transmitting the received communication signal back to said first unit, wherein the comparator compares the received communication signal from said second unit to the predetermined standard reception sensitivity value to generate a comparison signal, said first unit adjusting the amplification level of the first amplifier to a desirable amplification level based upon the comparison signal until a desirable amplification is reached at said second unit, said first unit transmitting the desirable amplification level to said second unit upon achieving the desirable amplification, said second unit storing the desirable amplification level.  
           [0011]    These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a diagram illustrating a first preferred embodiment of the base station in the wireless communication system according to the current invention.  
         [0013]    [0013]FIG. 2 is a timing chart illustrating a process of setting a transmission amplifier gain value as used by the first preferred embodiment of the base station according to the current invention.  
         [0014]    [0014]FIG. 3 is a diagram illustrating a second preferred embodiment of the base station in the wireless communication system according to the current invention.  
         [0015]    [0015]FIG. 4 is a timing chart illustrating a process of setting a transmission amplifier gain value as used by the second preferred embodiment of the base station according to the current invention.  
         [0016]    [0016]FIG. 5 is a diagram illustrating a third preferred embodiment of the base station in the wireless communication system according to the current invention.  
         [0017]    [0017]FIG. 6 is a timing chart illustrating a process of setting a transmission amplifier gain value as used by the third preferred embodiment of the base station according to the current invention.  
         [0018]    [0018]FIG. 7 is a diagram illustrating an exemplary wireless access systems with a base station and subscriber stations.  
         [0019]    [0019]FIG. 8 is a diagram illustrating an exemplary separation unit for the base station and the subscriber station. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]    One preferred embodiment of the wireless communication system according to the current invention generally includes a first unit or the ODU having the wireless function primarily via antenna and a second unit or the IDU having the wireless function with the backbone communication network as shown in FIGS. 7 and 8. The preferred embodiment is applicable to both the base station  1  as well as to the subscriber station  2 , and the difference is that the subscriber station  2  is connected to the back bone communication networks.  
         [0021]    Referring to FIG. 1, a first preferred embodiment of the base station in the wireless communication system according to the current invention includes the ODU  7 , the IDU  8  and the cable  9  connecting the ODU  7  to the IDU  8 . The ODU  7  and the IDU  8  communicate transmission data such as voice information, image information and text information as well as control data such as notices and commands between the ODU  7  and the IDU  8 . The ODU  7  further includes a reception unit  15  for receiving and processing a signal transmitted from the IDU  8  via the cable  9 , a sensitivity detection unit  16  for detecting the reception sensitivity level at the reception unit  15 , a PDET memory unit  17  for storing a predetermined standard reception sensitivity value for the ODU  7 , a determination unit  18  for comparing and determining whether or not the reception sensitivity value that is detected by the sensitivity detection unit  16  matches the standard reception sensitivity value stored in the PDET memory unit  17 , a transmission unit  19  for transmitting signals from the RF unit  10  to the IDU  8  via the communication cable  9 , a transmission amplifier  20  for amplifying signals to be transmitted by the transmission unit  19 , a gain setting unit  21  for setting a gain value of the transmission amplifier  20 , and a control unit or MPU  22  for controlling the units of the IDU  8  and communicating with another control unit or MPU  30  on control information such as notices via the communication cable  9 . The RU unit  10  wirelessly transmits via the antenna  6  signals that are received at the receiving unit  15  and whose test signal has been removed.  
         [0022]    Still referring to FIG. 1, other than a communication unit  11  that processes the communication with the public communication network via a cable  3 , the IDU  8  includes a receiving unit  25  for processing the transmitted signal from the ODU  7  via the communication cable  9 , a transmission or transmitting unit  26  for transmitting a signal to the ODU  7  from the public communication network via the communication cable  9 , a transmission amplifier  27 , a test signal generating unit  29  for generating a test signal to be transmitted from the transmitting unit  26  upon the gain setting, and a control unit or MPU  30  for controlling the units of the IDU  8  as well as communicating with another control unit or MPU  22  on the ODU  7  side via the communication cable  9  on control information and notices. The communication unit  11  transmits the signal received and processed by the receiving unit  25  after the test signal has been removed.  
         [0023]    Now referring to FIG. 2, a timing chart illustrates a process of setting a transmission amplifier gain value as used by the preferred embodiment of the base station  1  according to the current invention. Although the illustrated process initiates the gain setting process upon installing the base station unit  1 , the gain setting process is performed under the control by the control unit  22  or  30  on a periodic or non-periodic basis. Initially, the gain setting unit  28  of the IDU  8  stores an initialized value such as 10 dBm for gain (GTA) in the transmission amplifier  27  upon delivering from a factory. The amplifier  27  amplifies the test signal that has been generated by the signal generation unit  29  according to the above initialized gain value. The transmitting unit  26  transmits the amplified signal to the ODU  7  via the communication cable  9 . In the ODU  7 , the receiving unit  15  receives the test signal. The detection unit  16  detects the reception sensitivity level (PDET). The determination unit  18  compares the detected PDET to the standard reception sensitivity level that is stored in the PDET storing unit  17  and determines whether or not the reception sensitivity level of the test signal satisfies the standard reception sensitivity level. Based upon the above comparison or determination result, the control unit  22  via the communication cable  9  transmits a comparison signal such as a positive signal or ACK to the control unit  30  on the IDU side when the comparison result indicates the satisfaction of the standard reception sensitivity level.  
         [0024]    On the other hand, as indicated in FIG. 2, the control level  22  via the communication cable  9  transmits a negative signal or NAK to the control unit  30  on the IDU side when the comparison result fails to indicate the standard reception sensitivity level. Upon receiving the NAK or the determination result in the IDU  8 , the gain setting unit  28  increments the GTA by 1 dBm, and the transmitting amplifier  27  amplifies the test signal from the signal generation unit  29  based upon the increased gain. The transmitting unit  26  transmits the amplified test signal at 11 dBm to the ODU  7  via the communication cable  9 . The ODU  7  subsequently performs the above described similar process upon receiving the test signal. Until the determination unit  18  obtains the positive result or ACK, the IDU  8  repeatedly and gradually increases the gain for the transmission amplifier  28  and transmits the test signal at 20 dBm. When the IDU  8  receives the positive ACK, the gain setting unit  28  has set 20 dBm for the corresponding transmission amplifier  27 , and the control unit  30  transmits a GTA setting report signal that includes the above gain value to the control unit  22  of the ODU  7 . In response to the report signal, the control unit  22  of the ODU  7  sets the new gain the value of the 20 dBm at the corresponding transmission amplifier  20 . That is, the gain value of the transmission amplifier  27  on the IDU side for amplifying the signal from the IDU  8  to the ODU  7  is automatically reset so that the initial reception sensitivity level is obtained at the reception device. Similarly, the gain value of the transmission amplifier  20  on the ODU side for amplifying the signed from the ODU  7  to the IDU  8  is also automatically reset so that the initial reception sensitivity level is obtained at the reception device.  
         [0025]    Now referring to FIG. 3, a diagram illustrates a second preferred embodiment of the base station  1  in the wireless communication system according to the current invention. In the second preferred embodiment, the ODU  7 A and the IDU  8 A are connected via the coaxial cable  9  as in the first preferred embodiment. The components of the second preferred embodiment that are substantially identical to those of the first preferred embodiment will not be described and are referenced by the same reference numerals. In comparison to the first preferred embodiment, the second preferred embodiment of the base station  1  has simplified functions for setting a gain value in the ODU side. The ODU  7 A is compact and light weight in the second preferred embodiment by transferring the storing function and the determination function of the standard reception sensitivity level to the IDU  8 A. That is, the detection unit  16  detects the reception sensitivity level of the test signal that is received by the reception unit  15  in the ODU  7 A. The control unit  22 A transmits the detected signal level to the control unit  30 A of the IDU  8 A without making any determination. On the other hand, the IDU  8 A includes a PDET storing unit  33  for storing a predetermined standard reception sensitivity level value and a comparison unit  34  for determining whether or not the detected reception sensitivity value from the ODU  7 A matches the standard reception sensitivity level as stored in the PDET storing unit  33  identically or within a predetermined range.  
         [0026]    Now referring to FIG. 4, a timing chart illustrates a process of setting a transmission amplifier gain value as used by the second preferred embodiment of the base station  1  according to the current invention. Although the gain setting process is performed as an initial setting procedure upon installing the base station  1 , the gain setting process is alternatively performed on a predetermined periodic basis or an irregular basis by the control unit  22 A or  30 A. Initially, the transmission amplifier  27  amplifies the test signal from the signal generation unit  29  according to a predetermined initial gain value of 10 dBm that is stored in the gain setting unit  27  of the IDU  8 A. The transmission unit  26  transmits the amplified signal to the ODU  7 A via the communication cable  9 . The reception unit  15  in the ODU  7 A receives the test signal, and the detection unit  16  detects the reception sensitivity or PDET. The control unit  22 A sends the detected reception sensitivity level to the control unit  30 A of the IDU  8 A via the communication cable  9 . Upon receiving the detected reception sensitivity value at the IDU  8 A, the determination unit  34  compares the standard reception sensitivity level stored in the PDET storing unit  33  with the detected test signal sensitivity level on the ODU side and determines whether or not the test signal reception sensitivity level satisfies the standard reception sensitivity level. When a negative result is obtained, the gain setting unit  28  slightly increases the gain by 1 dBm, the transmission amplifier  27  amplifies the test signal from the signal generation unit  29  according to the increased gain value at 11 dBm. The transmission unit  26  sends the amplified signal to the ODU  7 A via the communication cable  9 . The ODU  7 A performs the detection and reporting process based upon the above similar test signal. Until the determination unit  34  obtains a positive result, the IDU  8  gradually increases the gain to 20 dBm for the transmission amplifier  28  and transmits the test signal.  
         [0027]    When the determination result at the IDU  8 A becomes positive, the gain setting unit  28  has set the corresponding amplifier  27  at 20 dBm. The control unit  30 A sends a setting report including the current gain value to the control unit  22 A of the ODU  7 A. In response to the above report, the control unit  22 A sets the reported gain value for 20 dBm at the corresponding transmission amplifier  20 . In other words, the gain value of the amplifiers  27  and  20  for the signal going to and from the ODU  7 A is automatically set so that the initial reception sensitivity level is obtained at the reception device.  
         [0028]    Now referring to FIG. 5, a diagram illustrates a third preferred embodiment of the base station  1  in the wireless communication system according to the current invention. In the third preferred embodiment, the ODU  7 B and the IDU  8 B are connected by the coaxial cable  9  as in the first and second preferred embodiments, the components that are substantially identical to those in the first or second preferred embodiment will not be described and are referred by the same reference numerals. The third preferred embodiment of the base station  1  is simplified by transferring the determination function of the reception sensitivity to the IDU  8 B as in the second preferred embodiment. However, the storing function for the standard reception sensitivity level is in the ODU  7 B. The standard reception sensitivity level as uniquely set for the ODU  7 B is used for the sensitivity determination. In other words, the PDET storing unit  17  of the ODU  7 B stores a predetermined standard reception sensitivity level. Prior to setting the gain, the control unit  22 B sends the standard reception sensitivity level value to the control unit  30 B in the IDU  8 B via the communication cable  9 . During the gain setting process, the detection unit  16  detects the reception sensitivity level of the test signal that is received by the reception unit  15 . The control unit  22 B sends the reception sensitivity level to the control unit  30 B without evaluating it. On the other hand, the IDU  8 B includes a PDET storing unit  35  the standard reception sensitivity level value for the ODU  7 B at least until the gain setting is finished. The determination unit  34  compares and determines whether or not the detected reception sensitivity level from the ODU  7 B matches or is within a predetermined range of the standard reception sensitivity value that is stored in the PDET memory unit  35 .  
         [0029]    Now referring to FIG. 6, a timing chart illustrates a process of setting a transmission amplification gain value as used by the third preferred embodiment of the base station  1  according to the current invention. Although the gain setting process is performed as an initial setting procedure upon installing the base station  1 , the gain setting process is alternatively performed on a predetermined periodic basis or an irregular basis by the control unit  22 B or  30 B. Prior to setting the gain after turning on the IDU  8 B, the ODU  7 B reports the standard reception sensitivity level value as stored unit  35  in the IDU  8 B stores the above standard reception sensitivity level value. The subsequent gain setting process is similarly performed as the second preferred process. The IDU  8 B transmits the test signal that has bee amplified by the transmission amplifier  27  based upon the initial gain value to the ODU  7 B via the communication cable  9 . The detection unit  16  in the ODU  7 B detects the reception sensitivity level of the test signal the control unit  22 B sends to the control unit  30 B in the IDU  8 B. The above detected reception sensitivity level value via the communication cable  9 . In the IDU  8 B, the determination unit  34  compares the above detected reception sensitivity level value as store in the PDET storing unit  35  to determine whether or not the reception sensitivity level of the test signal satisfies the standard reception sensitivity level. If the above comparison is negative, the IDU  8 B increases the gain for the transmission amplifier  28  in a repeated manner until the above comparison result becomes positive. When the comparison result becomes positive, the gain setting unit  28  sets the corresponding gain value at the transmission amplifier  27 . The control unit  30 B sends to the control unit  22 B in the ODU  7 B a report including the above gain value. The gain setting unit  21  of the ODU  7 B sets the reported gain value at the corresponding transmission amplifier  20 .  
         [0030]    In the above preferred embodiment, the detected reception sensitivity level is lower than the standard reception sensitivity level. However, when the detected reception sensitivity level is higher than the standard reception sensitivity level, the gain of the transmission amplifier  28  is gradually decreased until the standard reception sensitivity level is satisfied. The corresponding gain value is used to set the transmission amplifier  20  or  27 .  
         [0031]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and that although changes may be made in detail, especially in matters of shape, size and arrangement of parts, as well as implementation in software, hardware, or a combination of both, the changes are within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.