Adaptive modem for varying communication channel
US5127051A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 13, 1988 |
| Grant date | Jun 30, 1992 |
| Priority date | — |
| Expiry date | Jun 13, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B7/005
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An improved modem system for HF data transmission over a varying communication channel transmits data in packets formatted into successive frames, each having two identical training sequences following a sequence of data. Each training sequence has a time length longer than the expected time length of the multipath dispersion in the communication channel, in order to isolate one training sequence in each frame from multipath interference from the preceding data sequence. The "clean" training sequence allows the receiving modem system to derive very accurate channel estimates for each frame by autocorrelation to the known symbol sequence stored at the receiver. By interpolating across the channel estimates for the current and previous frames, the modem system can track the communication channel by interpolated estimates for any part or any point in time of the data sequence. An improved data recovery algorithm divides the received data sequence in each frame into a series of data blocks, each of which is processed through a respective decision loop using the interpolated channel estimates corresponding to the time position of the data block in the data sequence. The interpolated cha…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.