Patent EA-000310-B1 (EA)
Title: Method and apparatus for determining signal strength in a spread spectrum communication system having a variable data rate
Inventor: ZIV NOAM ABRAHAM
IPC: H04J13/00
Filed: 1996-06-17
Abstract: 1. A method of determining a signal strength of an incoming signal in a system receiving variable rate data wherein said incoming signal is comprised of a series of frames, each frame having a corresponding unknown data rate, each frame comprised of a plurality of data segments wherein the number of said data segments containing data in each frame depends upon said corresponding unknown data rate said corresponding unknown data rate may correspond to at least a highest rate and a lowest rate, said method comprising the steps of: receiving a first energy value corresponding to a first one of said data segments; and summing said first energy value with a previously accumulated total if said first one of said data segments corresponds to a data segment containing data at said lowest data rate to produce an estimate of said signal strength. 2. The method of Claim 1 wherein each of said plurality of data segments is comprised of a set of chips, further comprising the steps of: receiving a set of energy values corresponding to a plurality of chips within said first one of said data segments; and adding said set of energy values corresponding to said plurality of chips to produce said first energy value. 3. The method of Claim 1 wherein said step of summing further comprises the steps of: storing said first energy value in a first storage register wherein said first storage register is one of a plurality of storage registers each storing a value corresponding to a previously stored energy value; removing an oldest stored value stored in said plurality of storage registers; and adding together each said previously stored energy values and said first energy value to produce said estimate of said signal strength. 4. The method of Claim 1 wherein said step of summing further comprises the steps of: storing said first energy value in a first storage register wherein said first storage register is one of a plurality of storage registers each storing a value corresponding to a previously stored energy value; scaling each previously stored energy value according to a scaling constant associated with each of said plurality of storage registers; and adding together each said scaled previously stored energy values and said first energy value to produce said estimate of said signal strength. 5. The method of Claim 1 wherein said first energy value is received from a demodulation element assigned to a single propagation of said incoming signal and wherein said estimate of said signal strength is compared to a threshold to determine if said demodulation element is locked onto said single propagation. 6. The method of Claim 1 wherein said first energy value is received from one of a plurality of demodulation elements each assigned to a single propagation of said incoming signal, further comprising the steps of: comparing said estimate of said signal strength to a combine threshold signal; and enabling combination, based on a result of said step of comparing, of an output data signal from said one of said plurality of demodulation elements with an output data signal corresponding to a second one of said plurality of demodulation elements, said combination producing a resultant aggregate signal. 7. The method of Claim 1 wherein said data segments containing data are pseudorandomly positioned within each of said frames further comprising the step' of determining an active set of data segments corresponding to a first frame based on an identity of a unit transmitting said incoming signal wherein said active set of data segments corresponds to data segments containing data if said incoming is at said lowest rate. 8. The method of Claim 1 wherein said data segments containing data are pseudorandomly positioned within each of said frames further comprising the step of determining an active set of data of data segments corresponding to a first frame based on a time of day wherein said active set of data segments corresponds to data segments containing data if said incoming is at said lowest rate. 9. The method of Claim 1 wherein said unknown data rate may correspond to an intermediate data rate, wherein said data segments containing data are pseudorandomly positioned within each of said frames, and wherein within a given frame said data segments containing data at said lowest rate are positioned as a subset of data segments containing data at said intermediate rate and said data segments containing data at said intermediate rate are positioned as a subset of data segments containing data at said highest rate. 10. The method of Claim 1 wherein said step of summing comprises the steps of: storing said first energy value in a first energy storage register wherein said first energy register is one of a series of first-in-last-out (FIFO) storage registers such that each previously stored value is transitioned by one storage register and an oldest stored value is deleted from a final storage register; and adding together a value stored in each one of said series of FIFO storage registers. 11. The method of Claim 10 wherein said first energy value is received from a demodulation element assigned to a single propagation of said incoming signal and wherein said estimate of said signal strength is compared to a threshold to determine if said demodulation element is locked onto said single propagation of said incoming signal further comprising the step of initializing said series of FIFO storage registers when said demodulation element is assigned to a new propagation of said incoming signal. 12. The method of Claim 11 wherein said step of initializing said series of FIFO storage registers comprises the step of storing in said series of FIFO storage registers a set of values which correspond to a locked condition. 13. The method of Claim 11 wherein said step of initializing said series of FIFO storage registers comprises the step of storing in said series of FIFO storage registers a set of values which correspond to an unlocked condition. 14. The method of Claim 1 further comprising the steps of: comparing said estimate of said signal strength to a first threshold level; indicating a sufficiency condition if said estimate of said signal strength exceeds said first threshold level; comparing said estimate of said signal strength to a second lower threshold level after indication of said sufficiency condition; and removing said sufficiency condition if said estimate of said signal strength falls below said second lower threshold level. 15. The method of Claim 14 wherein said first energy value is received from a demodulation element assigned to a single propagation of said incoming signal and wherein said demodulation element comprises time tracking function further comprising the step or disabling said time tracking function upon removal of said sufficiency condition. 16. The method of Claim 14 wherein said first energy value is received from a demodulation element assigned to a single propagation of said incoming signal and wherein removal of said sufficiency condition indicates that said demodulation element is available for assignment to a different propagation of said incoming signal. 17. An apparatus providing a signal strength estimate comprising: a demodulation element having an output producing a series of symbol energies corresponding to a data signal of an unknown data rate; a summation register having an input coupled to said demodulation element output, having an enable input, and having an output producing a sum of a plurality of said series of symbol energies conditioned upon a signal received by said enable input; an active group clock having an output coupled to said enable input of said summation register, said output producing an indication of a group of said series of symbol energies corresponding to symbols containing data independent of said unknown data rate of said data signal; a first-in-first-out storage register having an input coupled to said summation register output and having a plurality of outputs each producing an indication of a previous value of said sum at said output of said summation register; and an adder having a plurality of inputs coupled to each of said plurality of outputs of said first-in-first-out storage register and having an output producing said signal strength indication. 18. A means for determining a signal strength of an incoming signal in a system receiving variable rate data wherein said incoming signal is comprised of a series of frames, each frame having a corresponding unknown data rate, each frame comprised of a plurality of data segments wherein the number of said data segments containing data in each frame depends upon said corresponding unknown data rate, said corresponding unknown data rate may correspond to at least a highest rate and a lowest rate, said method comprising the steps of: means receiving a first energy value corresponding to a first one of said data segments; and means summing said first energy value with a previously accumulated total if said first one of said data segments corresponds to a data segment containing data at said lowest data rate to produce an estimate of said signal strength. 19. The means for determining a signal strength of Claim 18 wherein each of said pluraliyt of data segments is comprised of a set of chips, further comprising the steps of: means for receiving a set of energy values corresponding to a plurality of chips within said first one of said data segments; and means for adding said set of energy values corresponding to said plurality of chips to produce said first energy value. 20. The method determining a signal strength of Claim 18 wherein said step of summing further comprises the steps of: means for storing said first energy value in a first storage register wherein said first storage register is one of a plurality of storage registers each storing a value corresponding to a previously stored energy value; means for removing an oldest stored