Abstract:
In a fixed-site radio transceiver station, information about a tower-mounted radio frequency amplifier apparatus can be automatically transferred from the tower-mounted radio frequency amplifier apparatus to another portion of the fixed-site radio transceiver station. The information is transferred by modulating a power supply current that is drawn from the other portion by the tower-mounted radio frequency amplifier apparatus.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to fixed-site radio transceiver stations and, more particularly, to data transfer in fixed-site radio transceiver stations. 
     BACKGROUND OF THE INVENTION 
     In conventional fixed-site radio transceiver stations (also referred to as base transceiver stations or base stations) used in wireless communication networks, the radio antenna and an associated amplifier are typically mounted high atop a tower structure, and connected to the remainder of the base transceiver station via a radio frequency (RF) feeder cable. The RF feeder cable is also conventionally used to supply DC power supply current to the tower mounted amplifier (TMA). 
     FIG. 1 is a block diagram of one example of the above-described conventional base transceiver station, for example a base transceiver station used in a conventional GSM (Global System for Mobile communications) wireless communications network. The example of FIG. 1 shows the tower mounted amplifier  11  of the base station connected to the remainder  13  of the base station by RF feeder cable  15 . The remainder portion  13  includes a TMA power supply  17  for providing DC power supply current for use by the tower mounted amplifier TMA. The remainder portion  13  also includes a so-called “bias Tee” module  19  connected to the TMA power supply  17  and also connected to an RF signalling path  12  which is in turn coupled to a radio transceiver (XCVR) of the base station. 
     The bias Tee module  19  is a conventional apparatus which combines both the RF signalling from RF signalling path  12  and the DC power supply current from the TMA power supply  17  in the RF feeder cable  15 . The RF feeder cable  15  provides RF signalling and DC power supply current to the tower mounted amplifier TMA. The bias Tee module  19  of the remainder portion  13  also separates RF signalling received via RF feeder cable  15  from the power supply current in the RF feeder cable  15 . The bias Tee module described above is a conventional apparatus well known to workers in the art. 
     The tower mounted amplifier  11  also includes a bias Tee module  19  for separating the RF signalling from the DC power supply current in the RF feeder cable  15 , and for permitting RF signalling from signal path  14  to be transmitted back to the remainder portion  13  via the RF feeder cable  15  while the cable  15  also carries the DC power supply current. The bias Tee module  19  provides the DC power supply current to the local power supply  16  of the tower mounted amplifier TMA. The local power supply  16  provides the tower mounted amplifier TMA with the necessary DC power supply current. 
     In conventional base transceiver stations such as illustrated in FIG. 1, the tower mounted amplifier TMA is typically designed so that, should a fault occur in the TMA, it will typically be detectable at the remainder portion  13  by detecting changes in the power supply current drawn by the tower mounted amplifier  11  from the TMA power supply  17  of the remainder portion  13 . Such changes in current are conventionally detected by a data processor  20  which receives a digital input from an A/D converter  21  whose analog input is coupled to the DC power supply current output  24  of the TMA power supply  17 . 
     The tower mounted amplifier TMA includes an amplifier AMP that is coupled to the RF signalling path  14  and to a tower mounted antenna for appropriately amplifying RF signals that are received (Rx) by the tower mounted antenna. RF signals to be transmitted (Tx) by the antenna are typically filtered and applied to a booster before antenna transmission. Such filter and booster functions can be built into the conventional amplifier unit AMP. The tower mounted amplifier TMA of FIG. 1 has associated therewith TMA parameter data which can represent, for example, information associated with the TMA such as product information, serial numbers, filter frequency information, amplifier gain information, alarm limits, etc. When a fixed-site radio transceiver station such as illustrated in FIG. 1 (or at least the TMA thereof) is newly installed, the TMA parameter data is typically input manually to the remainder portion  13  (e.g., to the data processor  20 ). However, if a new tower mounted amplifier TMA is added, or if the existing TMA is replaced, then the parameter data associated with the added/replacement TMA must disadvantageously be manually input to the remainder portion  13  of the fixed-site transceiver. This is both costly and time-consuming. 
     It is desirable in view of the foregoing to avoid the delay and expense of manually inputting TMA parameter data to the remainder portion  13  of the base transceiver station whenever a new or replacement tower mounted amplifier TMA is installed. 
     According to the present invention, a tower mounted amplifier can automatically signal the parameter data of the tower mounted amplifier to the remainder portion of the base transceiver station using a power supply current path coupled between the tower mounted amplifier and the remainder portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates pertinent portions of a conventional base transceiver station for use in a wireless communication system. 
     FIG. 2 illustrates pertinent portions of an example base transceiver station according to the present invention. 
     FIG. 3 illustrates a plurality of nominal power supply current levels used to transmit on the RF feeder cable of FIG. 2 parameter data associated with the tower mounted amplifier of FIG.  2 . 
     FIG. 4 illustrates how the current levels of FIG. 3 can be used to transmit multiple level coded data on the RF feeder of FIG.  2 . 
     FIG. 5 is similar to FIG. 2, including a detailed example of the power supply current modulator of FIG.  2 . 
     FIG. 6 illustrates in flow diagram format exemplary operations which can be performed by the power supply current modulators of FIGS. 2 and 5. 
    
    
     DETAILED DESCRIPTION 
     FIG. 2 illustrates diagrammatically pertinent portions of an example base transceiver station according to the invention. The base transceiver station of FIG. 2, which could be used in, for example, a GSM network, includes a tower mounted amplifier (TMA)  23  and a remainder portion  25 . The tower mounted amplifier portion  23  of FIG. 2 includes a power supply current modulator  22  coupled between the bias Tee module  19  and the local power supply  16 . The modulator  22  uses the TMA parameter data to modulate the power supply current drawn from the TMA power supply  17  (through RF feeder  15 ) by the tower mounted amplifier portion  23 . 
     The power supply current drawn from the TMA power supply  17  is monitored by an A/D converter  21  coupled to the TMA power supply output  24 , and the digital output of the A/D converter is input to a data processor  27  coupled to the A/D converter. The data processor  27  interprets the digital data received from the A/D converter to thereby recover the TMA parameter data as modulated by modulator  22  onto the TMA power supply current drawn from the TMA power supply  17 . The A/D converter  21  and data processor  27  thus detect and decode the TMA parameter data as modulated onto the TMA power supply current. 
     The power supply current modulator  22  of FIG. 2 causes the power supply current drawn from the TMA power supply  17  to vary among a plurality of distinct current levels in response to the TMA parameter data input to the modulator  22 . The various current levels are used to represent the TMA parameter data. In order to ensure that the A/D converter  21  can properly resolve the differences between the various current levels used to represent the TMA parameter data, adjacent ones of current levels seen by the A/D converter  21  should preferably be separated from one another by a known minimum amount. The smallest possible separation between two current levels is dependent on the accuracy specifications of (1) the A/D converter  21  and (2) conventional signal conditioning circuits (not shown) included in the current path  28  coupling the TMA power supply  17  to the A/D converter  21 . 
     Assume, for example, that the current level seen by the A/D converter can be expected to be within a ±7 mA uncertainty range of the actual current level output by the TMA power supply  17 . Assume also for this example that 8 distinct current levels are to be used to transfer the TMA parameter data. A suitable separation between adjacent current levels can then be calculated by subtracting the lowest of the current levels from the highest of the current levels, and dividing the result by 8. The aforementioned ±7 mA uncertainty range introduces an error of ±14/8 mA (=±1.75 mA) into the aforementioned calculation of the separation between adjacent current levels. Thus, a total uncertainty of ±8.75 mA (±7 mA±1.75 mA) must be accounted for when calculating the current level separation. 
     Assuming also for this example that the A/D converter has a maximum step size of 3.5 mA/step, the aforementioned ±8.75 mA range requires ±3 steps of the A/D converter. Thus, each current level used in the TMA data transfer should be preferably centered in a current level decision interval which extends at least 3 steps of the A/D converter above and at least 3 steps of the A/D converter below that current level. In this example, one additional step is added between adjacent intervals to ensure separation of the adjacent intervals. 
     FIG. 3 illustrates the above-described example of current levels for use in transferring the TMA parameter data. As shown in FIG. 3, each current level  31  is centered in an interval which extends three steps above and three steps below the current level, and each interval is separated from each adjacent interval by a one step gap. Accordingly, each current level is separated from the next adjacent current level by seven steps, which corresponds in this example to 24.5 mA (7 steps×3.5 mA/step). 
     FIG. 4 illustrates an example current waveform representing the power supply current i TMA  drawn from (output by) the TMA power supply  17  in response to operation of the power supply current modulator  22  of FIG.  2 . The diagram of FIG. 4 illustrates eight current levels, thus providing eight possible signalling symbols. In the example of FIG. 4, i n  represents the nominal TMA power supply current drawn by the tower mounted amplifier portion  23  under normal conventional operating conditions, and the remaining current levels are defined by the aforementioned 24.5 mA separations. In FIG. 4, the highest current level, i n +171.5 mA, represents a start symbol, and the nominal current level i n  represents a stop (or idle) symbol. In this example, eight symbol times (designated  0 - 7 ) exist between the start and stop symbols, so a symbol octet including eight separate symbols can be transferred during the time between the start and stop symbols. The minimum possible length of the symbol times is determined by the speed of A/D converter  21  and the limits imposed by the RF feeder cable  15  and path  28 . 
     Also according to the invention, multiple level coding can be utilized in conjunction with the modulation of TMA parameter data. For example, using the eight current levels of FIG. 4, each current level can represent a three bit symbol as shown in FIG.  4 . Thus, in FIG. 4, the symbol transmitted during symbol time  0  corresponds to 110, the symbol transmitted during symbol time  1  corresponds to 101, the symbol transmitted during symbol time  2  corresponds to 110, the symbol transmitted during symbol time  3  corresponds to 011, the symbol transmitted during symbol time  4  corresponds to 111, the symbol transmitted during symbol time  5  corresponds to 000, the symbol transmitted during symbol  6  corresponds to 001 and the symbol transmitted during symbol time  7  corresponds to 011. Thus, the received pattern of bits in this example will be 1101 0111 0011 1110 0000 1011. Such multiple level coding greatly increases data throughput, and can be easily interpreted by data processor  27  which can be, for example, a digital signal processor, a microprocessor, or another suitable data processing apparatus. 
     FIG. 5 illustrates diagrammatically an exemplary radio base transceiver station according to the invention. FIG. 5 is similar to FIG. 2, and includes a detailed example of the power supply current modulator  22  of FIG.  2 . The exemplary power supply current modulator of FIG. 5 includes a clock  51  having a frequency that corresponds to the symbol rate of the data transfer illustrated in FIG.  4 . The clock  51  is connected to a clock input of a counter  53 . The counter  53  includes parallel outputs which are connected to address inputs A 0 -A 7  of a memory  55 . The memory  55  can be, for example, a non-volatile memory circuit. The memory  55  has data outputs D 0 -D 2  which are connected to respective data inputs of a D/A converter  58 . The three data outputs D 0 -D 2  correspond to the eight current levels of the FIG. 4 example. The analog output Aout of the D/A converter is connected to a control input  52  of a transistor circuit  59  that can sink desired amounts of current and thereby vary the current drawn from the TMA power supply  17 . 
     The parameter data for the tower mounted amplifier TMA is stored in the memory  55 , and this stored parameter data is addressed by the counter circuit  53 . In response to the clock circuit  51 , the counter  53  steps through the addresses where the TMA parameter data is stored in the memory  55 . Continuing with reference to the example data transfer of FIG. 4, the three-bit output of memory  55  can be converted by the D/A converter  58  into eight distinct control signals (e.g., control voltages) which cause the transistor circuit  59  to sink eight distinct amounts of current, thus resulting in eight distinct power supply current levels (see FIG. 4) drawn from the TMA power supply  17  and seen by the A/D converter  21 . Although a transistor circuit is shown at  59  as a controllable current sink, other suitable controllable current sinks can be used as well. 
     The clock circuit  51  causes the counter circuit  53  to count up to the number of addresses needed for the complete message. For each memory location addressed by the parallel outputs of the counter circuit  53 , the associated data bits are output to the D/A converter  58 , which converts the bit pattern to a control signal for controlling the transistor circuit  59 . Note that the stop (or idle) symbol 000 of FIG. 4 will, in this example, cause the transistor circuit  59  to assume a high impedance state so that the normal conventional operating current i n  is drawn from TMA power supply  17 . The counter  53  is reset at power on, and is also advantageously reset after the stop symbol is output. The counter is easily programmable to count through a sequence of addresses corresponding to the symbol sequence of FIG. 4, namely from stop symbol to stop symbol. Of course, the counter can be programmed to count through any desired sequence of addresses to transmit any desired number of symbol octets (and associated start and stop symbols) like the one shown in FIG.  4 . The reset count preferably selects the stop symbol so no current is sunk at  59  while the counter is reset. The clock  51  can be started at power on (or at system restart) and halted after the stop symbol is output. 
     The data processor  27  can process the digital output of the A/D converter  21  in the following exemplary manner. Referring also to FIG. 4, before the start symbol ( 111 ) is detected, the data processor  27  can perform, for example, a five times oversampling of the digital output of the A/D converter  21 . Once a change from the idle symbol to the start symbol is detected, the data processor sets sampling points for the remaining symbols in the data transfer at the middle of each of the successive symbol periods  0 - 7  illustrated in FIG.  4 . The digital output from the A/D converter  21  (in this example a three-bit output) is read by the data processor  27  at each sampling point. When the data processor  27  detects the stop symbol (after symbol period  7  in this example), the five times oversampling can start again. After the data processor  27  has received the stop symbol, the data processor  27  can then assemble the message, for example, in the manner described above with respect to FIG.  4 . 
     The above-described transfer of TMA parameter data from the tower mounted portion to the remainder portion can be executed, for example, whenever the tower mounted amplifier TMA is powered up or restarted. 
     It should be noted that the above-described current modulation techniques are also applicable to current in a dedicated power supply line rather than the combined power supply/RF feeder line  15 . 
     FIG. 6 illustrates exemplary operations performed by the power supply current modulator example of FIG.  5 . After power on or restart, at  61  the counter  53  applies the initial address (e.g., the address of the start symbol for the first symbol octet) to the memory  55 . Thereafter at  63 , the memory  55  outputs the addressed data to the D/A converter  58 . At  65 , the D/A converter converts the digital data to an analog control signal for controlling the transistor circuit  59 . At  67 , the transistor circuit  59  sinks an amount of current corresponding to the control signal received from the D/A converter (and thus also corresponding to the digital data output from memory  55 ). If it is determined at  69  that there is more data to be transmitted, then the output of counter  53  is incremented to the next address at  68 , and the procedure is repeated until it is determined at  69  that all data (including the final idle symbol) has been transmitted. 
     It will be apparent to workers in the art that the controllable current sink can also be readily controlled in the manner described above using a suitably programmed data processing apparatus to input digital data to the D/A converter  58 . 
     It can be seen from the foregoing that the invention advantageously permits automatic transfer of TMA parameter data using power supply current modulation, and also enhances the data throughput by using multiple level coding. 
     Although exemplary embodiments of the present invention have been described above in detail, this does not limit the scope of the invention, which can be practiced in a variety of embodiments.