Lucent Technologies Inc.

Industrial Technology Research Institute

Tsinghua University

Chih-Peng Li

Chin-Liang Wang

Wei-Chieh Huang

Peretz Moshes Feder

Yun-Yen Chen

Wei-Wen Hu

Ming-Li Wang

Kuei-Cheng Chan

Yu-Sing Lin

Jyh-Horng Wen

The present invention discloses a communication system with a data-dependent superimposed training mechanism and a communication method thereof. The system uses a precoding module installed in front of the data-dependent superimposed training mechanism to precode data by a precoding matrix. The precoding matrix is a N&#xd7;N unitary matrix, which is constructed by Q&#xd7;Q precoding sub-matrix. Q is the block size N divided by the channel length. The precoding matrix can achieve full frequency diversity. Any two sets of data precoded by the precoding matrix must be different from each other, such that the receiver can effectively identify the data transmitted from the transmitter and the computational complexity of the receiver is reduced.

Communication system having data-dependent superimposed training mechanism and communication method thereof

The present invention discloses a channel estimation method for an orthogonal frequency-division multiplexing system with cyclic-delay diversity. The method makes pilots have the same amplitude and equally partitions the pilots into a number of pilot groups. In addition, the method equally spaces the pilots of each group in a frequency domain and determines the pilot locations and cyclic-delay coefficient of each pilot group in order to optimize the channel estimation of a receiver. The method can perform the channel estimation by using just one OFDM symbol.

Orthogonal frequency-division multiplexing system capable of optimizing channel estimation and method for optimizing channel estimation for orthogonal frequency-division multiplexing system

The invention relates to an orthogonal frequency division multiplexing system with PN-sequence. In the synchronization of the invention, both timing offset and frequency offset are estimated and compensated by utilizing a time and frequency synchronization device. In addition, the PN-sequence with the cyclic prefix is added to the OFDM symbol before transmitting. The time and frequency synchronization device of the invention comprises two synchronization circuits from the cyclic prefix and PN-sequence when calculating the timing offset and frequency offset of receiving signal. As a result, the OFDM system of the invention not only has better performance in fading channel, but also has the better bandwidth utilization without extra bandwidth for transmitting the PN-sequence.

Orthogonal frequency division multiplexing with PN-sequence

The invention relates to a symbol timing synchronization system for orthogonal frequency division multiplexing system. According to the invention, the symbol timing synchronization system utilizes a shift register and a comparing device to determine whether the symbol of the orthogonal frequency division multiplexing system has the inter-symbol interference. When the symbol has the inter-symbol interference, a compensator is utilized to compensate the interfered symbol. Therefore, depending on the symbol timing synchronization system of the invention, the symbol timing error and the inter-symbol interference can be essentially removed so as to improve the system performance.

Symbol timing synchronization system for orthogonal frequency division multiplexing systems

A Near Optimal Fairness (NOF) algorithm is disclosed for resolving data collisions in a network shared by a plurality of users. The NOF algorithm calculates an optimal back-off or contention window which is broadcast to users competing for system bandwidth. The NOF algorithm handles data contention in cycles and guarantees that each user competing for system bandwidth within a cycle will make a successful reservation before the cycle ends and a new cycle begins. The size of the back-off window is preferably equal to the number of successful reservations in the previous cycle, and functions as an estimate of the number of competing users in the current cycle.

Back off methods and systems

Disclosed is a method to reduce contention in a networked system and to provide superior bandwidth allocation to network devices contesting for network use. The method achieves reduced contention by reducing the amount of delay a network device is required to wait before attempting to transmit data after a data collision occurred. Superior bandwidth allocation is achieved by placing devices in back-off delay immediately after they transmit successfully.

Growing community of inventors

Kaohsiung, Taiwan

Chih-Peng Li