Acquisition and tracking in communication system with multicarrier telephony transport

Abstract

A method for initializing a service unit in a communication system is provided. The method comprises receiving a synchronization signal from a head end at the remote unit, receiving an identifier specifying the remote unit and receiving an upstream frequency band and control channel designation at the remote unit. The frequency band includes a number of subbands with at least one control channel in each subband. The method further comprises tuning to the designated frequency band, transmitting a reference signal on a selected channel to the head end, receiving adjustment signals based on the reference signal transmitted to the head end to allow signals transmitted from the remote unit to be orthogonal at the head end to signals from at least one other remote unit and adjusting parameters at the remote unit based on the adjustment signals.

1 . In a bidirectional multipoint-to-point multichannel communications system having a single central head end and a plurality of remote units located remotely from the head end and from each other, said system communicating by means of multiple coherent carriers wherein at least one of said remote units receives and transmits less than all of said carriers, a method performed by both said one remote unit and said central head end for tracking one of said remote units into said system, said carriers including at least one sync tone, a plurality of sets of payload carriers and a plurality of command carriers, at least one of said command channels being within each of said sets, said method comprising: 
 tuning said remote unit to said at least one sync tone;    acquiring one of said remote units into said system in frequency, phase, and amplitude in response to said sync tone;    returning said remote unit to a predetermined one of said sets of carriers including a predetermined one of said command carriers;    at said remote unit, thereafter, adjusting at least the timing and amplitudes of transmissions from said remote unit to said head end over said set of carriers in response to the timing and amplitude of said one command carrier.    
     
     
         2 . The method of  claim 1 , further comprising: 
 at said remote unit, detecting that the timing or amplitude of said one command carrier differs by at least a predetermined threshold from an optimum value;    in response thereto, reexecuting said acquiring step.    
     
     
         3 . The method of  claim 2 , further comprising detecting that the timing or amplitude of said one command carrier differs by less than said predetermined threshold from an optimum value, and in response thereto, reexecuting said adjusting step.  
     
     
         4 . A method for initializing a service unit in a communication system, the method comprising: 
 receiving a synchronization signal from a head end at the remote unit;    receiving an identifier specifying the remote unit;    receiving an upstream frequency band and control channel designation at the remote unit, wherein the frequency band includes a number of subbands with at least one control channel in each subband;    tuning to the designated frequency band;    transmitting a reference signal on a selected channel to the head end;    receiving adjustment signals based on the reference signal transmitted to the head end to allow signals transmitted from the remote unit to be orthogonal at the head end to signals from at least one other remote unit; and    adjusting parameters at the remote unit based on the adjustment signals.    
     
     
         5 . The method of  claim 4 , wherein receiving an identifier comprises receiving an identifier based on a serial number of the remote unit.  
     
     
         6 . The method of  claim 4 , wherein receiving an identifier further comprises receiving a personal identification number (PIN) code.  
     
     
         7 . The method of  claim 4 , wherein receiving the remote identifier comprises: 
 selecting a subband within a frequency band;    tuning to a control channel within the subband;    listening for no more than a selected period of time for an identifier specifying the remote unit; and    repeating the selecting, tuning and listening until an identifier specifying the remote unit is received.    
     
     
         8 . The method of  claim 7 , and further comprising latching a personal identification number (PIN) code when the identifier specifying the remote unit is received.  
     
     
         9 . The method of  claim 4 , wherein adjusting parameters comprises adjusting parameters affecting one or more of amplitude, carrier frequency, symbol alignment, and path delay.  
     
     
         10 . A method for acquiring a service unit in a communication system, the method comprising: 
 initializing the service unit to communicate with a head end;    broadcasting a synchronization signal from the head end;    sending from said head end an identifier specifying the service unit;    recognizing the identifier at the service unit;    sending an upstream frequency-band designation from the head end to the service unit;    tuning the service unit to the designated frequency band;    transmitting a ranging signal at a selected power level from the service unit to the head end;    comparing aspects of the ranging signal with selected values;    generating adjustment commands;    adjusting parameters of the service unit based on the adjustments commands from the head end; and    sending a locked-in message to the head end.    
     
     
         11 . The method of  claim 10 , wherein comparing aspects of the ranging signal with selected values and generating adjustment commands comprises: 
 comparing a power level of said ranging signal at the head end to a selected power level;    sending a power-adjust message to the service unit;    adjusting a transmission power level in response to the power-adjust message at the service unit;    comparing the phase of the ranging signal to the phase of the synchronization signal;    sending a phase-adjust message to the service unit; and    adjusting the phase of the ranging signal toward a desired phase in response to said phase-adjust message at the service unit.    
     
     
         12 . The method of  claim 10 , wherein initializing the service unit includes associating a serial number for the service unit with a shorter personal identification number (PIN) and sending the PIN to the service unit along with the serial number.  
     
     
         13 . The method of  claim 10 , wherein the service unit contains a table of capabilities for the service unit, the method further comprising: 
 requesting a set of capabilities from the service unit;    sending the requested capabilities to the head end;    storing the requested capabilities at the head end; and    adjusting commands to the service unit in response to the capabilities stored at the head end.    
     
     
         14 . The method of  claim 10 , wherein: 
 broadcasting the synchronization signal comprises broadcasting a pattern of signals repeated over a predetermined number of data frames; and    transmitting a ranging signal comprises adjusting the phase of the ranging signal so as to achieve a predetermined relationship with respect to the pattern of the synchronization signal.    
     
     
         15 . The method of  claim 10 , and further comprising returning the service unit to receive the synchronization signal prior to transmitting the ranging signal from the service unit.  
     
     
         16 . A method for tracking parameters of a service unit in a bidirectional multipoint-to-point multichannel communications system having a head end and a plurality of service units, for each service unit the method comprising: 
 tuning the service unit to at least one synchronization tone in a frequency bandwidth, the frequency bandwidth further including a plurality of subbands with at least one control channel in each subband;    acquiring the service unit into the system in frequency, phase, and amplitude in response to said synchronization tone;    returning the service unit to a selected control channel in the frequency bandwidth;    selectively adjusting at least the timing and amplitudes of transmissions from the service unit to the head end over said set of carriers in response to the timing and amplitude of said one command carrier.    
     
     
         17 . The method of  claim 16 , further comprising: 
 detecting that the timing or amplitude of the control channel differs by at least a predetermined threshold from a selected value at the service; and    re-acquiring the service unit into the system in frequency, phase, and amplitude when the timing or amplitude differs by at least the predetermined amount.    
     
     
         18 . The method of  claim 17 , further comprising: 
 detecting that the timing or amplitude of the control channel differs by less than the predetermined threshold from a selected value; and    re-adjusting at least the timing and amplitudes of transmissions from the service unit to the head end.