Abstract:
A method and structure of recovering a network time-base for radio data demodulation after an IDLE period of data communication gauges a local low frequency oscillator versus the high frequency local oscillator to compute the IDLE time as an equivalent number of low frequency oscillator clock periods. Depending upon the high frequency oscillator value, the accuracy of the gauging will directly determine the IDLE period duration versus the gauging period duration in order to keep an acceptable gauging error related to the sampling errors.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to wireless communications, and more particularly to a method of recovering a network time base for radio data demodulation after an IDLE period of communication. 
     2. Description of the Prior Art 
     A mobile terminal is required to keep itself permanently synchronized on a network time to accurately demodulate data received through a radio link. Further, the accuracy of a base-station oscillator (e.g., 0.01 ppm) is better than the accuracy of a mobile oscillator (e.g., 0.3 ppm). This difference in oscillator accuracy causes the local time associated with the mobile terminal to drift away from the network time associated with the base-station. Periodic re-synchronization is therefore required to minimize the foregoing time drift consistent with maintaining demodulator performance associated with the mobile terminal. The re-synchronization operation is based on the demodulation of received data which includes a predetermined training sequence to compute time and frequency differences between the base-station and the mobile terminal. 
     During IDLE mode, no radio transmission occurs, thus removing any possibility of re-synchronization. Since the IDLE period duration is defined by a radio standard protocol, the accuracy of the mobile terminal time-base clock must be high enough to allow a global time drift in the time range imposed by the demodulator performances. 
     Present methods of re-synchronization require constant activation of a mobile terminal high-frequency local oscillator to maintain the synchronization of the mobile time with the network time during IDLE periods. Such methods lead to high current consumption during an IDLE mode since the mobile terminal high-frequency oscillator and its associated clocking elements and counting logic will be active. A significant disadvantage of these present methods relates to shortened battery life and therefore increased operating costs associated with mobile communication terminals. 
     In view of the foregoing, it would be desirable to have a method of re-synchronizing a mobile communication terminal on the network, e.g., global system for mobile communication (GSM) network, during inactive communication periods, i.e., IDLE mode. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method of recovering a network base-station time base for radio data demodulation within a mobile terminal after an IDLE period of communication. The method gauges a low frequency local oscillator within the mobile terminal versus the network time of a radio-communication network. A local time-base within the mobile terminal stores the network time while using a local and highly stable high-frequency oscillator. The local high-frequency oscillator is shut down during the IDLE period. The local time-base is periodically updated during non-IDLE periods with a time delta correction resulting from a demodulation of received communication data. The equivalent elapsed network time during the IDLE period is computed from a mobile terminal counter using a local low-frequency counter that is clocked via the low frequency local oscillator. The local low frequency oscillator is gauged versus the local time-base with the sampling of the time-base value when starting and stopping the gauging. The gauging process does not require updating of the local time-base during the gauging period. The local time-base is then restored subsequent to an inactive period (IDLE) and having sufficient accuracy to reliably demodulate communication data. This gauging process eliminates the necessity for maintaining the high frequency local oscillator within the mobile terminal during the gauging process, thereby providing for interlacing of the gauging and IDLE periods. This gauging process further makes the accuracy of the restored local time-base independent of the duration of the inactive period (IDLE). 
     As used herein, the following words have the following meanings. The words “algorithmic software” mean an algorithmic program used to direct the processing of data by a computer or data processing device. The words “data processing device” as used herein refer to a CPU, DSP, microprocessor, micro-controller, or other like device and an interface system. The interface system provides access to the data processing device such that data could be entered and processed by the data processing device. The words “discrete” data as used herein are interchangeable with “digitized” data and “digitized” data as used herein means data which are stored in the form of singularly isolated, discontinuous data or digits. 
     One embodiment of the present method of keeping a local time-base in a mobile terminal synchronized with a network time-base during a network IDLE transmission period comprises the steps of: 
     a) starting a low frequency gauging counter C to track local low frequency (LF) oscillator cycles associated with the mobile terminal; 
     b) sampling the network time-base near the end of a network data transmission period via a local high frequency (HF) oscillator associated with the mobile terminal, upon starting the gauging counter C, to determine a network time-base value T SLEEP ; 
     c) starting an IDLE transmission period LF counter at time T SLEEP ; 
     d) stopping the local HF oscillator upon starting the IDLE transmission period LF counter; 
     e) stopping the IDLE transmission period LF counter at time T WAKE-UP , where T WAKE-UP  is dependent on the network time-base value T SLEEP , a count value LF stored by the IDLE transmission period LF counter during the IDLE transmission period, and a gauging factor R estimated  associated with a most recently previous network IDLE transmission period for the local LF oscillator in HF oscillator period units according to the relationship defined by T WAKE-UP =T SLEEP +((R estimated ) Previous *LF)+E IDLE ; 
     f) starting the HF oscillator at time T WAKE-UP  to implement demodulation of network time-base transmission signals and thereby recover the network time-base such that the mobile terminal can be synchronized with the network time-base; 
     g) stopping the low frequency gauging counter C upon recovery of the network time-base and determining an elapsed count value associated with the gauging counter C; 
     h) generating a new gauging factor (R estimated ) New  for the LF oscillator in HF oscillator period units associated with the mobile terminal wherein the gauging factor R estimated  is dependent on the elapsed count value associated with the gauging counter C; and 
     i) repeating continuously steps a-h. 
     A structure suitable for implementing the present method comprises a mobile terminal system for keeping a local time-base synchronized with a network time-base during a network IDLE transmission period, the system comprising: 
     an IDLE period timer; 
     a data processing device; 
     an algorithmic software directing the data processor; and 
     a data storage unit, wherein discrete IDLE period data, discrete low frequency oscillator data, discrete high frequency oscillator data, discrete sampling error data, discrete algorithmic error data, discrete low frequency oscillator jitter data, discrete network time-base data, discrete rounding data, discrete low frequency oscillator aging data, and discrete low frequency oscillator drift data are stored and supplied to the data processing device such that the data processing device, directed by the algorithmic software, can automatically determine a time-base value T WAKE-UP , using algorithmically defined relationships among the discrete data and thereby cause the IDLE period timer to modulate the IDLE transmission period in response to the time-base value T WAKE-UP , such that the mobile terminal can function to be synchronized with the network time-base. 
     A feature of the present invention is associated with recovery of a network time-base necessary to accommodate communication data demodulation following an IDLE period via a local low frequency/low accuracy oscillator within a mobile terminal. 
     Another feature of-the present invention is associated with a synchronization method rendering a mobile terminal capable of maintaining synchronization during IDLE periods (no radio traffic) without using a local high frequency oscillator. 
     Still another feature of the present invention is associated with a method of operating a mobile terminal during IDLE periods such that the mobile terminal power consumption is substantially reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other aspects and features of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein: 
     FIG. 1 is a chronogram illustrating relationships among data signals associated with a base station terminal and data signals associated with a mobile terminal during periods of both active data communication and no data communication (IDLE) in accordance with one embodiment of the present invention; 
     FIGS. 2A and 2B depict a block diagram illustrating a method of recovering a network time base to accommodate radio data demodulation within a mobile terminal after an IDLE period of communication between a base-station terminal and a mobile terminal in accordance with one embodiment of the present invention; and 
     FIG. 3 is a simplified system block diagram illustrating a mobile terminal in accordance with one embodiment of the present invention. 
     While the above-identified drawing figures set forth alternative embodiments, other embodiments of the present invention are also contemplated, as noted in the discussion. In all cases, this disclosure presents illustrated embodiments of the present invention by way of representation and not limitation. Numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The substitution of a low-frequency oscillator for the high frequency oscillator within a mobile terminal, e.g., phone, to maintain a network time during the IDLE period will decrease the overall power consumption of the mobile phone in IDLE mode. This is so as the high-frequency oscillator and its clock shaper will be halted and the clock tree frozen, thereby reducing the activity of the local time-base counting logic by a ratio determined by the magnitude of the oscillator frequencies. 
     FIG. 1 is a chronogram  100  illustrating relationships among data signals associated with a base station terminal and data signals associated with a mobile terminal during periods of both active data communication and no data communication (IDLE) in accordance with one embodiment of the present invention. The principles of the present invention, as set forth herein, are accommodated via calibration of the mobile terminal low frequency (LF) clock (oscillator)  102  in association with a single LF counter  104  and two memory registers for storing a local time base  106 . The present method then replaces the conventional and well-known method of calibrating the LF clock using 2 concurrent counters respectively clocked on the LF and HF oscillators. The present calibration principle is to store the network time at the beginning and at the end of the calibration periods  112  thereby providing the equivalent elapsed network time by subtracting the start time  110  from the stop time  108 . The network time is maintained in a local time base  106 . The accuracy of the measured network time is determined by the accuracy of the network time and is not determined by the accuracy of the local high frequency oscillator  114  since the measured network occurs after the local high frequency oscillator  114  has been re-synchronized with the network time. Thus, in order to minimize the time error between the local time and the network time, the start time  110  and the stop time  108  of the calibration period  112  must be timed on the re-synchronization events of the local time-base (update following the demodulation of received communication data). 
     A more complete explanation of the foregoing signal relationships and time periods are set forth herein below with reference to the chronogram  100 . First, the gauging period is defined as: 
       T   GAUGING =( T   STOP   −T   START ) +E   GAUGING ;  (1) 
     where 
     T STOP  and T START  are the stop time  108  and start time  110  of the calibration period  112 . 
     If N is the number of elapsed periods of LF OSC    102  (counter content), and M MEASURED  is the number of elapsed periods of HF OSC    114  (delta of the 2 storage registers storing the local time base  106 ), then: 
     
       
           T   STOP   −T   START   =M   MEASURED   *T   HF     OSC     (2) 
       
     
     
       
           T   GAUGING   =N*T   LF     OSC     (3) 
       
     
     
       
           E   GAUGING =(+/−2 *E   JITTER     —     LF     OSC   )* T   LF     OSC   ;  (4) 
       
     
     where 
     T GAUGING  is in LF oscillator  102  period units; 
     T STOP  and T START  are in HF oscillator  114  period units; and 
     E JITTER     —     LF     OSC    is the LF oscillator  102  jitter in worst case condition temperature/voltage and equals the maximum instantaneous duty-cycle variation of LF OSC    102 . 
     Further, if M theorical  is the true equivalent number of elapsed periods of HF OSC    114 , then: 
     
       
           T   STOP   −T   START =( M   theorical +/−2 *E   SAMPLING +/−2 *E   ALGO )* T   HF     OSC   ;  (5) 
       
     
     where 
     E SAMPLING  is the sampling error due to the synchronization of the LF oscillator based counter events on the HF oscillator  114  clock (sampling error when starting and stopping the counter) and is less than one period of HF OSC    114 ; and E ALGO  is the error value in HF oscillator  114  period units of the time-base value versus the real network resulting from the inaccuracy of the demodulation algorithm delivering the time-base correction value. 
     Although the theoretical result of the present gauging can be shown as 
     
       
           R   theorical   =T   LF     OSC     /T   HF     OSC     =M   theorical   /N,   (6) 
       
     
     a more accurate result of the present gauging, based upon the foregoing discussion, is seen by equation (7) below to be: 
       R   estimated   =M   measured /( N+/− 2 *E   JITTER     —     LF     OSC   )=( M   theorical +/−2 *E   SAMPLING +/−2 *E   ALGO )/( N+/− 2 *E   JITTER     —     LF     OSC   )  (7) 
     The IDLE mode  140  can be defined as a time period during which the high-frequency reference clock (Oscillator)  114  is switched off and, consequently, the reference time-base stopped, as stated herein before. When exiting the IDLE mode  140 , the equivalent network time at that current instant in time must be computed in order to recover the local time-base and, consequently, to be able to demodulate subsequent received communication data. During the IDLE mode  140  wherein the HF oscillator  114  clock is halted, the present time management system will use a counting system C  150  that is clocked on the LF oscillator  102 . This system must be activated before the stop of the HF oscillator  114  and deactivated after the restart of the HF oscillator  114 . The stop and start events of the counting system C  150  will be re-synchronized on the HF oscillator  114  in order to synchronize the LF counting system  104  with the HF local time-base  120 . 
     The time-base can therefore be recovered using equation (8) for T WAKE-UP . 
     
       
           T   WAKE-UP   =T   SLEEP   +T   IDLE   +E   IDLE   =T   SLEEP +( R   estimated   *C )+ E   IDLE ;  (8) 
       
     
     wherein 
     
       
           E   IDLE =2 *E   SAMPLING   +E   ALGO   +E   ROUNDING   +R   estimated *( E   AGING     —     LF     OSC     +/−E   DRIFT     —     LF     OSC   +/−2 *E   JITTER     —     LF     OSC   );  (9) 
       
     
     wherein 
     C is the value at the end of the IDLE period of the C counter  150  in LF oscillator  102  period units; 
     T WAKE-UP  is the recovered value: of the time-base in HF oscillator  114  period units; 
     T SLEEP  is the sampled value of the time-base in HF oscillator  114  period units when starting the LF counter  104 ; 
     E ROUNDING  is the rounding error when computing (R*C) and is less than one-half the period of the time-base; 
     E SAMPLING  is the sampling error due to the synchronization of the LF oscillator  102  based C counter  150  events on the HF oscillator  114  clock (sampling error when starting and stopping the C counter  150 ) and is less than one period of the HF oscillator  114 ; 
     E AGING  is the aging error of the LF oscillator  102  and can be estimated to be zero or non-existent for mobile applications wherein the IDLE period is on the order of only a few seconds; 
     E JITTER     —     LF     OSC    is the LF oscillator  102  jitter in worst case condition temperature/voltage and is equal to the maximum instantaneous duty-cycle variation of the LF oscillator  102 ; 
     E ALGO  is the time error in HF oscillator  114  period units of the time-base value versus the real network resulting from the inaccuracy of the demodulation algorithm delivering the time-base correction value; and 
     E DRIFT     —     LF     OSC    is the LF oscillator  102  time drift during the IDLE period and is due to the voltage variation (regulator output ripple voltage) and to the temperature variation; 
     E DRIFT     —     LF   OSC  is therefore the sum of E VDRIFT     —     LF   OSC  and E TDRIFT     —     LF   OSC . 
     An application of the technique set forth above is now presented in detail below to exemplify the principles of the present invention. The instant application is directed to GSM900 communications using a 32 kHz LF oscillator in association with operational parameters from a commercially available ultra low power down controller specification as shown in Table 1 below. 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 (Parameters &amp; Numerical Values) 
               
             
          
           
               
                   
                 Parameter 
                 Value 
                 Comment 
               
               
                   
                   
               
               
                   
                 T HFosc   
                 77 ns 
                 F HFosc  = 13 MHz 
               
               
                   
                 T LFosc   
                 30,517 μs 
                 F LFosc  = 32 KHz 
               
               
                   
                 T TimeBase   
                 308 ns 
                 F TimeBase  = 13/4 MHz (˜1/16 
               
               
                   
                   
                   
                 GSM bit) 
               
               
                   
                 E JITTER     —     LFosc   
                 5 * 10 −3   
                 +/− 0.5% duty cycle worse 
               
               
                   
                   
                   
                 case in TSC6K for OSC32K 
               
               
                   
                 E ALGO   
                 24 * T HFosc   
                 GSM chipset demodulator 
               
               
                   
                   
                   
                 accuracy ˜1/2 GSM bit 
               
               
                   
                 E ROUNDING   
                 ½ * T TimeBase   
                 SW or HW solution of 
               
               
                   
                   
                   
                 implementation 
               
               
                   
                 E SAMPLING   
                 1 * T HFosc   
                 Start &amp; stop re- 
               
               
                   
                   
                   
                 synchronization on 13 MHz 
               
               
                   
                 E AGING     —     LFosc   
                 2 ppm/year 
                 Aging not meaningful on 
               
               
                   
                   
                   
                 short time period (few ns) 
               
               
                   
                 E VDRIFT     —     LFosc   
                 45 ppm 
                 32 KHz oscillator frequency 
               
               
                   
                   
                   
                 drift versus voltage 
               
               
                   
                   
                   
                 (1V5/3V6) 
               
               
                   
                 E TDRIFT     —     LFosc   
                 5 ppm 
                 32 KHz oscillator frequency 
               
               
                   
                   
                   
                 drift versus T° C. (−40/+80) 
               
               
                   
                   
               
             
          
         
       
     
     The GSM900 protocol defines the IDLE period as: 
     
       
           T   IDLE   =bfbamfrms*M   51  with 2 &lt;bfbamfrms&lt; 9 and  M   51 =51*1250*48 T   HF     OSC     (10) 
       
     
     Table 2 illustrates the results of using the present method of time-base recovery to recover the value of the time-base in HF oscillator  114  period units for a T IDLE  range between 2*M 51  and 9*M 51 . 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 (Time Recovery Error Versus Gauging Duration) 
               
             
          
           
               
                 T IDLE   
                 T GAUGING   
                 T HFosc  units 
                 T LFosc  units 
                 R estimated   
                 T GSM     —     Error   
               
               
                   
               
             
          
           
               
                 9 * M 51   
                 1 * T IDLE   
                 27,540 * 10 +3   
                 68,850 
                 400.00078 
                 86.0 T 13M   
                 1.79 GSM bits   
               
               
                 4 * M 51   
                 1 * T IDLE   
                 12,240 * 10 +3   
                 30,600 
                 400.00176 
                 86.0 T 13M   
                 1.79 GSM bits   
               
               
                 2 * M 51   
                 1 * T IDLE   
                  6,120 * 10 +3   
                 15,300 
                 400.00353 
                 86.0 T 13M   
                 1.79 GSM bits   
               
               
                   
               
             
          
         
       
     
     The above results are obtained with T GAUGING  is equal to T IDLE  due to interlacing the calibration period  112  and the IDLE period  140  as described above. When bfbamfrms=9, for example, T IDLE  is determined as follows:                T   IDLE     =       68   ,   850   *     T   LFosc       =                27   ,   540   ,   000   *     T   HFosc                     =                68   ,   850   *     R   theorical     *     T   HFosc                                    
     with R theorical =T LF     OSC   /T HF     OSC    as shown by equation (6) above. In fact, R estimated  can be determined by equation (7):                R   estimated     =                  (       27   ,   540   *     10     +   3         +     2   *     E   SAMP       +     2   *     E   ALGO         )     /                (       68   ,   850     -     2   *     E   JIT_LFosc         )                   =                  (       27   ,   540   *     10     +   3         +   2   +     2   *   24       )     /     (       68   ,          850   -     2   *   5   *     10     -   3             )                   =                400.00078                 as                 shown                 in                 Table                 2                   above   .                                    
     The time-base value (T WAKE-UP ) at the end of the IDLE period using equations (8) and (9) with C being the 32 KHz counter value, then will be:                T     WAKE        -        UP       =                  T   SLEEP     +     T   IDLE     +     E   IDLE                   =                  T   SLEEP     +     (       R   estimated     *   C     )     +     E   IDLE                   =                  T   SLEEP     +     (       R   estimated     *   C     )     +     2   *     E   SAMP       +     E   ALGO     +                                E   ROUNDING     +       R   estimated     *                                (       E   AGING_LFosc     +     2   *     E   JITTER_LFosc       +     E   DRIFT_LFosc       )                 =                  T   SLEEP     +     (     400.00078   *   C     )     +   2   +   24   +   2   +                              400.0078   *     (     0   +     2   *   5   *     10     -   3         +     45   *     10     -   6         +     5   *     10     -   6           )                   =                  T   SLEEP     +     (     400.00078   *   C     )     +   32.00                 =                  T   SLEEP     +     (     400   *   C     )     +   86.00                                  
     Then, with C=68,850 for an IDLE period of T IDLE =9*M 51 , as described above with reference to Table 2, the time uncertainty on the recovered GSM time is: 
     
       
           T   GSM     —     Error =1.79*GSM bits, with GSM bit=48 *T   
       
     
     Since, the maximum allowable GSM900 time error for data demodulation as defined in GSM recommendations is 3*GSM bits, the present method of time-base recovery is seen to provide a significant advancement in the art of demodulation that is useful in GSM applications among other protocols. 
     FIGS. 2A and 2B depict a block diagram  200  illustrating a method of recovering a network time base to accommodate radio data demodulation within a mobile terminal after an IDLE period of communication between a base-station terminal and a mobile terminal in accordance with a preferred embodiment of the present invention. The present method begins by first determining the periods T HF     OSC   , T LF     OSC    and T TimeBase  associated with the high frequency oscillator  114 , low frequency oscillator  102  and network time-base respectively as shown in block  202 . Simultaneously, error parameters associated with the demodulator hardware associated with the local time-base  106  are determined along with error parameters associated with sampling, approximation and algorithmic techniques necessary to implement the present method as shown in block  204 . Upon determination and entry of the foregoing parameters, the method continues by next determining the IDLE period T IDLE  in HF oscillator  114  units (T HF     OSC    units) as shown in block  206 . The present method can accommodate a wide variety of data communication protocols. Since each data communication protocol will have a set of communication characteristics such as a frequency of transmission and idle period defined by a particular industry standard, the present method  200  is described in terms of a GSM900 data communication protocol that is unique to GSM data communications in order to simplify explanation of the present method  200 . As stated above, the present invention is not so limited however, and can accommodate a wide variety of data communication protocols. Thus, T IDLE  is determined via equation (10) as set forth and defined for the GSM900 data communication protocol. Subsequent to determination of the foregoing time periods and error parameters, a low frequency (LF) gauging counter LF counter    104  is started and the network time-base is sampled using the local HF oscillator  114  to determine the network time T SLEEP  at the beginning of the IDLE period  140  as shown in blocks  207  and  208 . The local HF oscillator  114  is shut down immediately following the turn-on of the IDLE period C counter  150  in order to preserve mobile terminal power consumption during the IDLE period  140 . When the IDLE period  140  ends, the HF oscillator  114  is then turned back on and the C counter  150  subsequently turned off as shown in block  212 . When exiting the IDLE mode  140 , the equivalent network time at that current instant in time is computed in order to recover the local time-base and, consequently, to be able to demodulate subsequent received communication data. Since the C counter  150  will then be characterized by a number C of counts taken during the IDLE mode  140 , the local time-base T WAKE-UP  can be determined using the foregoing values for T SLEEP  and C in combination with a gauging factor that was determined in association with the most immediately preceding IDLE mode  140 , also shown in block  212 . Using the computed equivalent network time at T WAKE-UP , the data signals received from the network terminal can then be demodulated and the local time-base updated using results of the demodulated data signals as depicted in block  214 . Once the local time-base has been updated, the LF gauging counter  104  is stopped as shown in block  216 . Since the number LF of low frequency oscillator  102  periods has been determined, a gauging factor R estimated  can then be determined in HF oscillator  114  units as shown in block  218  by using equation (7) described above according to the present method  200 . This gauging factor R estimated  can then be used to program the IDLE period C counter  150  to schedule the duration of the immediately following IDLE period such that the foregoing process depicted in blocks  207 - 218  can be continuously repeated. In this manner, the mobile terminal can remain synchronized with the network terminal while achieving the herein before described benefits. 
     FIG. 3 is a simplified block diagram showing a mobile terminal  300  suitable for implementing the present method  200  according to one embodiment of the present invention. The mobile terminal  300  has a data processing device  302 . The present algorithmic software  304  is preferably stored in a non-destructive memory location such as in a ROM  306  or other like device. Any discrete data associated with hardware and software parameters relating to the communication network and devices described herein are preferably stored in a random access memory (RAM)  308  or other like device accessible by the data processing device  302 , e.g. DSP, to implement the algorithmic software  304  such that the mobile terminal  300  time-base can be synchronized with the network time-base following an IDLE period of data transmission. 
     The present method then, represents a significant advancement in the art of wireless data communications. In summary, a method and structure ensures permanent synchronization between a mobile terminal and a network terminal, even during IDLE periods, without use of a high frequency oscillator. Mobile terminal power consumption is thereby reduced during IDLE communication periods, thereby preserving power consumption and increasing battery longevity. 
     This invention has been described in considerable detail in order to provide those skilled in the equalizer art with the information needed to apply the novel principles and to construct and use such specialized components as are required. In view of the foregoing descriptions, it should be apparent that the present invention represents a significant departure from the prior art in construction and operation. However, while particular embodiments of the present invention have been described herein in detail, it is to be understood that various alterations, modifications and substitutions can be made therein without departing in any way from the spirit and scope of the present invention, as defined in the claims which follow. For example, although various embodiments have been presented herein with reference to particular communication protocols, the present inventive methods are not limited to a particular communication protocol as used herein.