US3811014A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive pulse code modulation system
Assignee: Northrop Grumman Information Technology Inc
•
Filing: 1973-03-12
•
Granted: 1974-05-14
•
Expires: 1993-03-12
Abstract
Abstract An adaptive pulse code modulation system useful for increasing the channel capacity of a fixed bandwidth communication link by reducing the redundancy characteristic of nonadaptive systems. In the subject system, the transmitter allocates space in a fixed bit length sample field amongst multiple channels on a frame by frame basis. Each channel is assigned space in the sample field only when that channel is active. The activity status of each channel is determined by averaging the sample amplitudes from that channel over a specified number of frames and if that average exceeds a specified threshold, then that channel is defined to be active. The activity status of each channel is monitored at a very high rate so that when a user begins speaking, his voice will be detected and assigned space soon enough to prevent his speech from being noticeably clipped. Each frame includes at least three fields; (1) an active channel sample field, (2) an activity status field and (3) an activity sync field. The activity status field is used to represent the activity status of a different channel each frame. Thus, in a typical 30 channel system, the activity status of each channel will be reported once every 30 frames. The activity sync field is comprised of one bit which enables the receiver to assign each received activity status field to the proper channel. In constructing a frame, the transmitter samples each voice channel and allocates a portion of the adaptive sample field to each active channel leaving vacant space if the complete sample field is not required and ''''rounding off'''' the samples to ''''fit'''' them in the sample field if an unusually large number of channels are active. To process each incoming frame, the receiver counts the total number of active channels, determines the number of bits per sample, and then rescales the received samples back to full magnitude if they were rounded off.
Inventors
- 👤 N Seitz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 00:11
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/17
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
145 words
A system for communicating representations of amplitude varying signals on each of n channels at a transmitting station to a receiving station, said system comprising: sampling means for developing a digital representation of the signal amplitude on each of said n channels; activity update means for determining whether each of said n channels is active or inactive; register means for successively forming multibit output frames each comprised of a sample field and an activity status field; segmentation means for assigning a different portion of said sample field to each of said active channels and for storing a digital representation of the signal amplitude on each active channel in the sample field portion assigned thereto; and activity status means responsive to said activity update means for storing digital representations of the activity status of different ones of said n channels in said successively formed output frames.
Claim 2
Independent Claim
145 words
A system for communicating representations of amplitude varying signals on each of n channels at a transmitting station to a receiving station, said system comprising: sampling means for developing a digital representation of the signal amplitude on each of said n channels; activity update means for determining whether each of said n channels is active or inactive; register means for successively forming multibit output frames each comprised of a sample field and an activity status field; segmentation means for assigning a different portion of said sample field to each of said active channels and for storing a digital representation of the signal amplitude on each active channel in the sample field portion assigned thereto; and activity status means responsive to said activity update means for storing digital representations of the activity status of different ones of said n channels in said successively formed output frames.
Claim 3
Dependent Claim
35 words
The system of claim 1 including frame counter means for cyclically defining n successive frame counts; and wherein said register means forms one of said multibit output frames during each of said n frame counts.
Claim 4
Dependent Claim
29 words
The system of claim 2 wherein said activity status means stores the activity status of a different one of said n channels in each of n successively formed frames.
Claim 5
Dependent Claim
92 words
The system of claim 2 wherein said activity update means includes: active channel register means for storing the activity status of each of said n channels; and means for comparing the average signal amplitude on each of said channels over a predetermined number of frame counts with a threshold level and for storing an active indicator in said active channel register when said average signal amplitude is greater than said threshold level and an inactive indicator in said active channel register when said average signal amplitude is less than said threshold level.
Claim 6
Dependent Claim
70 words
The system of claim 4 wherein said sampling means includes means for sampling the signal amPlitude on each of said n channels a multiple number of times during each n frame count cycle and for providing a digital representation of each such sample; and wherein said means for comparing includes n sum registers for storing the sum of said sample digital representations accumulated over a period of n frame counts.
Claim 7
Dependent Claim
58 words
The system of claim 2 wherein said register means forms a fixed multibit length sample field; and wherein said segmentation means includes: means for determining during each frame count the total number of active channels; and means for determining the number of bits of said fixed multibit length which can be assigned to each of said active channels.
Claim 8
Dependent Claim
96 words
The system of claim 2 wherein said register means forms a fixed multibit length sample field; and wherein said segmentation means includes: means for determining during each frame count the total number A of active channels; means for determining the length Q of equal bit length sample field portions within said fixed multibit length sample field which can be assigned to each of said active channels; and means responsive to said fixed multibit length exceeding the product AQ by a remainder R for increasing the bit length of R sample field portions to Q + 1.
Claim 9
Dependent Claim
46 words
The system of claim 7 wherein said means for increasing the bit length of sample field portions includes: means responsive to the count defined by said frame counter for increasing the bit length of different groups of R sample field portions dependent on said frame count.
Claim 10
Dependent Claim
44 words
The system of claim 2 wherein said register means includes first and second identical registers; means for alternatively coupling said segmentation means to said first and second registers during successive frame counts to form said output frame alternately in said first and second registers.
Claim 11
Dependent Claim
31 words
The system of claim 9 including output means for reading information out from said first and second registers alternately and out of phase with the coupling of said segmentation means thereto.
Claim 12
Independent Claim
170 words
A system for communication representations of amplitude varying signals on up to n Input channels at a transmitting station over a common communication link to n output channels at receiving station, said system comprising: transmitter means including: sampling means for developing an M-bit representation of the signal amplitude on each of said n channels; activity update means for determining which of said n channels are active and the total number A of active channels; register means for successively forming output frames each comprised of a sample field having a fixed number of bits F; segmentation means responsive to the product A.M exceeding said fixed number F for truncating those M-bit representations corresponding to active channels and for storing Q-bit length representations in said register means where the product A.Q < or = F; output means for applying said output frames formed in said register means to said common communication link; and receiver means coupled to said common communication link and responsive to said Q-bit representations for reforming M bit representations.
Claim 13
Independent Claim
170 words
A system for communication representations of amplitude varying signals on up to n Input channels at a transmitting station over a common communication link to n output channels at receiving station, said system comprising: transmitter means including: sampling means for developing an M-bit representation of the signal amplitude on each of said n channels; activity update means for determining which of said n channels are active and the total number A of active channels; register means for successively forming output frames each comprised of a sample field having a fixed number of bits F; segmentation means responsive to the product A.M exceeding said fixed number F for truncating those M-bit representations corresponding to active channels and for storing Q-bit length representations in said register means where the product A.Q < or = F; output means for applying said output frames formed in said register means to said common communication link; and receiver means coupled to said common communication link and responsive to said Q-bit representations for reforming M bit representations.
Claim 14
Dependent Claim
80 words
The system of claim 11 wherein each of said output frames further includes an activity status field; said transmitter means further including activity status means responsive to said activity update means for storing digital representations of the activity status of different ones of said n channels in said successively formed output frames; and said receiver means further including means responsive to said activity status representations for applying said reformed M bit representations to appropriate ones of said n output channels.
Claim 15
Dependent Claim
60 words
The system of claim 12 including frame counter means for cyclically defining n successive frame counts; and wherein said Register means forms one of said output frames during each of said n frame counts; and wherein said activity status means stores the activity status of a different one of said n input channels in each of n successively formed frames.
Claim 16
Independent Claim
140 words
A method of communicating amplitude of varying signals on n input channels over a common communication link to n output channels, said method comprising: sampling each of said n input channels and generating an M-bit digital representation of the signal amplitude in each channel; determing which of said n input channels are active and the total number A of active input channels; forming successive output frames each including (1) a sample field having F bits comprised of A sample field portions each having said M bits if F > or = A.M and comprised of A sample field portions each having Q bits if A.M>F where Q<M and A.Q < or = F and (2) an activity status field, the activity status field in each output frame identifying the activity status of a different one of said n input channels.
Claim 17
Independent Claim
140 words
A method of communicating amplitude of varying signals on n input channels over a common communication link to n output channels, said method comprising: sampling each of said n input channels and generating an M-bit digital representation of the signal amplitude in each channel; determing which of said n input channels are active and the total number A of active input channels; forming successive output frames each including (1) a sample field having F bits comprised of A sample field portions each having said M bits if F > or = A.M and comprised of A sample field portions each having Q bits if A.M>F where Q<M and A.Q < or = F and (2) an activity status field, the activity status field in each output frame identifying the activity status of a different one of said n input channels.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-13 | 1977-11-12 | 1978-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-13 | 1981-11-12 | 1982-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-13 | 1985-11-12 | 1986-05-14 | $7700.00 | Window Closed / Lapsed |