Minoru Namekata

Antenna-selective transmit diversity technique for OFDM-based WLANs with dual-band printed antennas

An antenna-selective transmit diversity (ASTD) technique, applied to a PC card for an orthogonal frequency division multiplexing (OFDM)-based wireless local area network (WLAN) system, is presented. The PC card, which is based on IEEE 802.11 a/g, is equipped with dual-band printed antennas. The ASTD processing is implemented in the developed WLAN system, which has two antennas for transmit and receive modes. The effects of the ASTD technique on the TCP (transmission control protocol) throughput performance are experimentally evaluated. Measurement results with the PC card in an imitated office show that the TCP throughput is improved on both the 2.4 and 5.2 GHz bands under the conditions of an indoor radio propagation channel due to the ASTD technique. In particular, application of the ASTD technique to an access point (AP) achieves four times the average TCP throughput on the 5.2 GHz band.

Development of a PC card using planar antennas for wireless LAN on 2.4/5 GHz bands

We have developed a wireless LAN PC card for 2.4 GHz and 5 GHz dual-band operation using printed planar antennas, and evaluated its throughput performance. The planar antennas, which combine an inverted-F antenna with an inverted-L antenna, can realize a dual-band at low cost in a limited integrated area on the PC card. The radio propagation performance was evaluated in a shielded room which is modeled after an office. In the 2.4 GHz band, operation is stable and independent of the deployed position and the direction of a laptop PC with the PC card. On the other hand, in the 5 GHz band, although the performance is affected by surrounding objects and antenna directivity, the PC card with the printed antennas can realize as high a throughput as one with external omnidirectional antennas.

Feasible criteria of link adaptation for wireless LANs using soft output Viterbi decoder

This work presents a simple data rate choosing method for multi data rate communication systems. This method is based on Viterbi decoding and aims to utilize relative likelihood between selected and unselected paths in the decoding. We confirmed the validity of our proposed method with computer simulations. The physical layer specifications follow the IEEE standard 802.11a, and then an AWGN channel and an ETSI-profile multipath channel are assumed in the simulations. The simulation results show that the proposed method can provide an effective link adaptation for communication systems that equip a Viterbi decoder and support plural data rate.