Vector Sum Excited Linear Prediction (VSELP) speech coding at 4.8 kbps

Code Excited Linear Prediction (CELP) speech coders exhibit good performance at data rates as low as 4800 bps. The major drawback to CELP type coders is their larger computational requirements. The Vector Sum Excited Linear Prediction (VSELP) speech coder utilizes a codebook with a structure which allows for a very efficient search procedure. Other advantages of the VSELP codebook structure is discussed and a detailed description of a 4.8 kbps VSELP coder is given. This coder is an improved version of the VSELP algorithm, which finished first in the NSA's evaluation of the 4.8 kbps speech coders. The coder uses a subsample resolution single tap long term predictor, a single VSELP excitation codebook, a novel gain quantizer which is robust to channel errors, and a new adaptive pre/postfilter arrangement

Uphold the nuclear weapons test moratorium

The Trump administration is considering renewing nuclear weapons testing (1), a move that could increase the risk of another nuclear arms race as well as an inadvertent or intentional nuclear war. Following in the long tradition of scientists opposing nuclear weapons due to their harmful effects on both humanity and the planet (2), we ask the U.S. government to desist from plans to conduct nuclear tests. During the Cold War, the United States conducted 1030 nuclear weapons tests, more than all other nuclear-armed nations combined (3). In 1996, the United States signed the Comprehensive Nuclear Test Ban Treaty (CTBT), agreeing not to conduct a nuclear weapons test of any yield (4). The United States has not yet ratified the CTBT but did spearhead the 2016 adoption of UN Security Council Resolution 2310, which calls upon all countries to uphold the object and purpose of the CTBT by not conducting nuclear tests (5). Eight of the nine nuclear-armed states, including the five permanent members of the UN Security Council, have observed a moratorium on nuclear testing since 1998 (3, 4). The ninth, North Korea, responding to international pressure, stopped testing warhead detonations (as opposed to missile flights) in 2017 (6). If the United States ratified the CTBT, joining the 168 countries who have already done so (4), there is a good chance that the other holdout countries would ratify the treaty as well (7)

Uphold the nuclear weapons test moratorium

The Trump administration is considering renewing nuclear weapons testing (1), a move that could increase the risk of another nuclear arms race as well as an inadvertent or intentional nuclear war. Following in the long tradition of scientists opposing nuclear weapons due to their harmful effects on both humanity and the planet (2), we ask the U.S. government to desist from plans to conduct nuclear tests. During the Cold War, the United States conducted 1030 nuclear weapons tests, more than all other nuclear-armed nations combined (3). In 1996, the United States signed the Comprehensive Nuclear Test Ban Treaty (CTBT), agreeing not to conduct a nuclear weapons test of any yield (4). The United States has not yet ratified the CTBT but did spearhead the 2016 adoption of UN Security Council Resolution 2310, which calls upon all countries to uphold the object and purpose of the CTBT by not conducting nuclear tests (5). Eight of the nine nuclear-armed states, including the five permanent members of the UN Security Council, have observed a moratorium on nuclear testing since 1998 (3, 4). The ninth, North Korea, responding to international pressure, stopped testing warhead detonations (as opposed to missile flights) in 2017 (6). If the United States ratified the CTBT, joining the 168 countries who have already done so (4), there is a good chance that the other holdout countries would ratify the treaty as well (7)