Yu-Tao Hsieh

Cross-layer design of ranging code expansion in OFDMA BWA network

Zadoff-Chu (ZC) sequence has been proposed as the contention based ranging preamble code (RPC) in 3GPP LTE and IEEE 802.16m specifications. The performance of the initial ranging process is affected by the number of available RPCs. In scenarios with high mobility and large round-trip delay (RTD), however, the number of available RPCs is limited; this would result in a higher collision probability. In this paper, we propose two efficient schemes to reduce the collision probability, namely ranging preamble codes division (RPCD) and ranging preamble codes partition (RPCP). Both schemes can effectively increase the number of available RPCs in the initial ranging process. The superiorities of the proposed schemes are demonstrated via computer simulations.

Statistical Distributions for Link Gain and Capacity of MIMO-GMD Transceivers in Rayleigh Fading Channels

Geometric mean decomposition (GMD) has been proposed as an elegant tool for MIMO transceiver architecture design. Under the ideal assumptions, MIMO-GMD schemes can realize multiple spatial sub-channels with identical gains. The main goal of this paper is to provide analytical distribution functions for sub-channels gains and capacities of MIMO-GMD schemes. In particular, we have derived closed-form results for MIMO-GMD transceivers with two spatial streams. Furthermore, we show that the sub-channel gains for cases with arbitrary number of spatial streams can be approximated by Gamma random variables with excellent accuracy. Additionally, some practical applications of these results are also presented in this paper.

A Novel Relay Recruitment Algorithm for Cooperative Spatial Multiplexing in Clustered Systems

Cooperative spatial multiplexing (CSM) can in- crease the system spectral efficiency via collaboration among multiple distributed nodes. How the relays for cooperation are chosen is an important issue as it may affect the system performance. In this paper, we propose a new relay selection method for CSM in a clustered environment where the source and relays are close in proximity. Instead of directly optimizing the channel capacity, our algorithm considers the suitability of spatial multiplexing based on the condition number of the effective channel. The simulation results have shown that our method can achieve better error performance than some other relay selection schemes. I. INTRODUCTION During the last decade, multiple-input multiple-output (MIMO) systems, where both the transmitter and receiver are equipped with multiple antennas, have been verified to be a very promising technique for the next-generation wireless communications. The potential benefits of MIMO systems are

Investigation of MIMO channel metric-dependent scheduling methods for collaborative spatial multiplexing

The standards for next-generation wireless communications have adopted collaborative spatial multiplexing (CSM) as an advanced feature to increase the spectral efficiency. In this paper, we aim to compare a few user pairing modes and MIMO channel-dependent selection metrics of uplink scheduling for CSM, with the inclusion of proposing a novel selection metric that is related to channel condition number. The performances of these pairing modes and selection metrics are compared through simulations, and the results show that the proposed metric can provide lower error rates and better fairness than the traditional schedulers based on maximum capacity.