| Presentation | 2017-10-26 A Signal Space Theory of Interferences Cancellation Systems Osamu Ichiyoshi, |
|---|---|
| PDF Download Page |  PDF download Page Link |
| Abstract(in Japanese) | (See Japanese page) |
| Abstract(in English) | Interferences among signals from different sources are universal problems in communication networks. In general the directions, bandwidths, modulation schemes and even numbers of the interferences are unknown at the receiver. The main receiver is set to receive the desired signal but it may also receive an unknown number of interference signals of unknown nature. In order to cancel those interferences we set a number of auxiliary receivers aimed to collect the interference signals. The auxiliary receiver outputs are adaptively weighted in amplitude and phase and are combined with the main receiver output in order to cancel the interference signals therein. The problem is; how can we control the adaptive weights without knowledge about those interference signals? One universal method is Least-Mean-Square-Error (LMSE) method which is based on the belief that the output signal after successful cancellation of the interference signals will give the minimum power output. Although this is quite a reasonable assumption the author showed a fundamental limit exists in the method, which practically deteriorates rather than improve the quality of the output signal. The author also proposed a signal space concept that can graphically show the mechanism of the problem [1]. In this paper the author reports a further study of the signal space theory. A “tangent square summation theorem” gives the basis of the signal space theory. The square tangent of a vector in the signal space corresponds to the inverse of Signal-to-Interference power ratio (SIR), hence the theorem can be restated as “Inverse SIR summation theorem”. The theorem tells the more auxiliary paths signals bring the greater SIR deterioration of the output from the canceller based on LSME algorithm. If the number of the auxiliary paths exceeds the number of the interferences signals, we will have simply a zero output. This “trivial zero output problem” is readily explained by the signal space theory. The basis theorem is applied to generalization of the theory to include the thermal noise additive to each auxiliary path receive signal. The problem of the LMSE cancellation method can be solved by elimination of the desired signal component from the correlation measurements for control of the adaptive weights. The essence of the method lies in regeneration of the desired signal, which is the very objective of communication. The mechanism of the improvement is clearly depicted by the Signal Space theory. A few examples are given in the paper. |
| Keyword(in Japanese) | (See Japanese page) |
| Keyword(in English) | Signal Space / Correlation / Uncorrelated / Orthogonal / Vector Space / Inner Product / LMSE / Decision Feedback |
| Paper # | SAT2017-41 |
| Date of Issue | 2017-10-19 (SAT) |
| Conference Information | |
| Committee | SAT |
|---|---|
| Conference Date | 2017/10/26(2days) |
| Place (in Japanese) | (See Japanese page) |
| Place (in English) | Okinawa Cellular Telephone Company |
| Topics (in Japanese) | (See Japanese page) |
| Topics (in English) | Satellite communications, etc. |
| Chair | Toshinori Susuki(Tohoku Gakuin Univ.) |
| Vice Chair | Hiroyuki Tsuji(NICT) / Fumihiro Yamashita(NTT) |
| Secretary | Hiroyuki Tsuji(KDDI Reesarch) / Fumihiro Yamashita(NICT) |
| Assistant | |
| Paper Information | |
| Registration To | Technical Committee on Satellite Telecommunications |
|---|---|
| Language | ENG |
| Title (in Japanese) | (See Japanese page) |
| Sub Title (in Japanese) | (See Japanese page) |
| Title (in English) | A Signal Space Theory of Interferences Cancellation Systems |
| Sub Title (in English) | |
| Keyword(1) | Signal Space |
| Keyword(2) | Correlation |
| Keyword(3) | Uncorrelated |
| Keyword(4) | Orthogonal |
| Keyword(5) | Vector Space |
| Keyword(6) | Inner Product |
| Keyword(7) | LMSE |
| Keyword(8) | Decision Feedback |
| 1st Author's Name | Osamu Ichiyoshi |
| 1st Author's Affiliation | Human Network for Better 21 Century(HNB21C) |
| Date | 2017-10-26 |
| Paper # | SAT2017-41 |
| Volume (vol) | vol.117 |
| Number (no) | SAT-261 |
| Page | pp.pp.17-22(SAT), |
| #Pages | 6 |
| Date of Issue | 2017-10-19 (SAT) |