A multiple-access MIMO WLAN system that employs MIMO, OFDM, and TDD. The system (1) uses a channel structure with a number of configurable transport channels, (2) supports multiple rates and transmission modes, which are configurable based on channel conditions and user terminal capabilities, (3) employs a pilot structure with several types of pilot (e.g., beacon, MIMO, steered reference, and carrier pilots) for different functions, (4) implements rate, timing, and power control loops for proper system operation, and (5) employs random access for system access by the user terminals, fast acknowledgment, and quick resource assignments. Calibration may be performed to account for differences in the frequency responses of transmit/receive chains at the access point and user terminals. The spatial processing may then be simplified by taking advantage of the reciprocal nature of the downlink and uplink and the calibration.

MIMO WLAN system

It was previously proposed to adapt several transmission methods, including modulation, power control, channel coding, and antenna diversity to rapidly time variant fading channel conditions. Prediction of the channel coefficients several tens-to-hundreds of symbols ahead is essential to realize these methods in practice. We describe a novel adaptive long-range fading channel prediction algorithm (LRP) and its utilization with adaptive transmission methods. The LRP is validated for standard stationary fading models and tested with measured data and with data produced by our novel realistic physical channel model. Both numerical and simulation results show that long-range prediction makes adaptive transmission techniques feasible for mobile radio channels.

Long-range prediction of fading signals

A method and apparatus for allocating subcarriers in an orthogonal frequency division multiple access (OFDMA) system is described. In one embodiment, the method comprises allocating at least one diversity cluster of subcarriers to a first subscriber and allocating at least one coherence cluster to a second subscriber.

Ofdma with adaptive subcarrier-cluster configuration and selective loading

Methods and apparatus for addressing wireless transmit/receive unit (WTRU) behavior in response to configuration, configuration parameters and access issues related to the activation/deactivation process when the WTRU may be configured with multiple serving cells or carrier aggregation

Component carrier activation/deactivation in multi-carrier systems

A method and apparatus for pilot signal transmission is disclosed herein. In particular, a pilot transmission scheme is utilized where pilot sub-carrier bandwidth differs from data sub-carrier bandwidth. Because some user's data sub-carriers will no longer have the user's pilot sub-carriers adjacent to them, the set, or pattern of sub-carriers used by the pilot blocks changes at least once in a burst. Changing the pilot block pattern (the set of occupied pilot block sub-carriers) at least once in the burst serves to increase the frequency proximity of occupied data sub-carriers to occupied pilot sub-carriers in the burst.

Method and apparatus for pilot signal transmission

This paper proposes Variable Spreading Factor — Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) as the most promising forward link wireless access method in broadband packet wireless transmission using an approximate 50 – 100 MHz bandwidth. OFCDM is originally based on multicarrier CDMA where the spreading sequence is multiplied in the frequency domain, and OFCDM employing VSF can flexibly realize near optimum wireless access with higher link capacity by adaptively changing the appropriate spreading factor, SF, in the frequency domain based on the cell structure and radio link conditions such as the delay spread. Furthermore, by establishing the spreading factor of SF = 1, i.e., no spreading mode, VSF-OFCDM can be used as orthogonal frequency division multiplexing (OFDM). Simulation results demonstrate that, while SF = 1 (OFDM) achieves higher link capacity than SF > 1 in an isolated-cell environment, OFCDM with the optimized SF value over 1 achieves approximately 1.4 times higher capacity compared with OFDM in a multi-cell environment associated with the advantageous one-cell frequency reuse. Consequently, VSF-OFCDM can provide seamless deployment of broadband packet wireless access with high link capacity, that is, OFDM in an isolated-cell environment such as hot spot areas or indoor offices, and OFCDM with the adaptively optimized SF value over 1 in a multi-cell environment such as cellular systems according to the radio link conditions such as measured delay spread, by only changing the spreading factor.

Variable Spreading Factor-Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) for Broadband Packet Wireless Access

A base station includes an acquisition unit for acquiring a packet transmitted from a terminal device to a mobile station, a priority calculation unit for calculating priority of transmission of the packet acquired by the acquisition unit to the mobile station, a weight processing unit for conducting weighting on the priority of the packet calculated by the priority calculation unit, a channel control unit for assigning a channel for transmission of the packet to the mobile station, to the packet based on the priority of the packet weighted by the weight processing unit, and a transmission unit for transmitting the packet to the mobile station on the channel assigned by the channel control unit.

Base station, control device, communication system and communication method

A communication method includes the steps of: a) transmitting an ACK signal indicating a received packet includes no error or a NACK signal indicating the received packet includes error from a reception end to a transmission end, and performing automatic repeat request; b) obtaining reliability of the received packet when demodulating it at the reception end; and c) reporting from the reception end to the transmission end the reliability of the received packet utilizing the ACK/NACK signal by using not less than three levels.

Communication system employing automatic repeat request

Performance of Coherent Multi-Carrier/DS-CDMA and MC-CDMA for Broadband Packet Wireless Access

An object is to select destination mobile stations so as to prevent directional beams directed to the respective mobile stations from interfering with each other in application of a directional antenna, and to allocate the radio resources to the mobile stations thus selected. A base station 10, which is capable of forming a plurality of directional beams directed to a plurality of mobile stations by applying a directional antenna 11 capable of adaptively varying directivity, to a transmission-reception antenna, is provided with a location estimator 19 for estimating a location of each mobile station on the basis of orientation information of the directional antenna; a reception quality estimator 22 for estimating a reception quality of each mobile station; a transmission priority calculator 21 for calculating a transmission priority of a packet to be transmitted; a determiner 16 for determining the number and directions of directional beams to be formed, based on the reception quality of each mobile station, location of each mobile station, and transmission priorities of packets; and an allocation controller 13 for allocating the plurality of directional beams thus determined, to a plurality of mobile stations.

Sadayuki Abeta

Papers

Variable Spreading Factor-Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) for Broadband Packet Wireless Access

Base station, control device, communication system and communication method

Communication system employing automatic repeat request

Performance of Coherent Multi-Carrier/DS-CDMA and MC-CDMA for Broadband Packet Wireless Access

Radio resources allocating method, radio resources allocating apparatus, and mobile communication system