A first uplink signal is transmitted by a mobile station to a base station on a first set of subcarriers in a first OFDM symbol. The first set of subcarriers is modulated with a first signal sequence known to both the mobile station and the base station. A second uplink signal is transmitted by the mobile station to the base station on a second set of subcarriers in a second OFDM symbol. The second set of subcarriers is modulated with the first signal sequence or a transform of the first signal sequence. The second set of subcarriers is modulated with a second signal sequence containing attribute information on a third set of subcarriers of a downlink signal received by the mobile station over a downlink channel. The correspondence between the subcarriers in the third and second set is known to the mobile station and the base station.

Provided are an e-mail anti-phishing system and method, the system comprising: an email address registration and authentication subsystem, an email signature recording subsystem, and an email signature query subsystem. An email sender registers an email address in use in the email address registration and authentication subsystem. The email sender uses a signature generator to generate a signature in an email message to be sent, records the generated signature in the email signature recording subsystem in a secure way, sends the email to an email receiver after a successful recording, and adds a field to an email header of the email indicating whether the recording has been performed. The email receiver, after receiving the email, uses the signature generator to generate the signature, and queries, via the email signature query subsystem, whether the email has been recorded, thereby determining whether the email is an illegal phishing email. The system can identify a phishing email, thereby ensuring that email content has not been changed.

By applying rotated complex empirical orthogonal function (RCEOF) analysis on 1880-1999 summer rainfall at 28 selected stations over the east part of China, the spatio-temporal variations of China summer rainfall are investigated. Six divisions are identified, showing strong temporal variability, the middle and lower reaches of the Yangtze River, the Huaihe River, Southeast China, North China, Southwest China, and Northeast China. The locations of all divisions except Southwest China are in a good agreement with those of the rainband which moves northward from Southeast China to Northeast China from June-August. The phase relationship revealed by the RCEOF analysis suggests that rainfall anomalies in the middle and lower reaches of the Yangtze River, Southeast China, and Northeast China are all characterized by a stationary wave, while a traveling wave is more pronounced in the Huaihe River division, North China, and Southwest China. The fourth RCEOF mode indicates that rainfall anomalies can propagate from south of Northeast China across lower reaches of the Huanghe River and the Huaihe River to the lower reaches of the Yangtze River. A 20-25-year oscillation is found at the middle and lower reaches of the Yangtze River, the Huaihe River valley, North China, and Northeast China. The middle and lower reaches of the Yangtze River and Northeast China also show an approximately-60-year oscillation. Northeast China and the Huaihe River division are dominated by a 36-year and a 70-80-year oscillation, respectively. An 11-year oscillation is also evident in North China, with a periodicity similar to sunspot activity. The interdecadal variability in the middle and lower reaches of the Yangtze River, the Huaihe River valley, and North China shows a significant positive correlation with the solar activity.

Methods and systems for contingency communication are disclosed. In one embodiment, a method for providing emergency services may be performed by a portable device operating in a communication system. In an embodiment, the method for providing emergency services includes operating in at least one of a plurality of modes. A stress mode may be entered from a normal mode in response to receiving a beacon signal indicating an emergency status. An indication may be provided on the portable device regarding the emergency status via an audio, visual, or mechanical user interface during the stress mode. An acknowledgement signal may be transmitted in response to the beacon signal.