Abstract— In this article we show that a Code Division Multiple Access (CDMA) system employing long codes can be interpreted as a Multiple Input Multiple Output system where the transmit filters are time-varying. We derive conditions for existence of zero-forcing equalizers and verify through simulations that these conditions are useful guidelines for the design of appropriate solution in the p...

あらまし 厳しい周波数選択性環境下では大きな符号間干渉(ISI)が発生するため,シングルキャリア(SC)伝送の 平均ビット誤り率(BER)特性は著しく劣化してしまう.最近,周波数選択性フェージングを克服する技術として, 最小平均二乗誤差規範に基づく周波数領域等化(MMSE-FDE)が注目を浴びている.MMSE-FDE では,ISI を抑圧し つつ周波数ダイバーシチ利得を獲得できるため,SC 伝送の BER 特性を大幅に改善できる.しかし ISI が残留する ため,BER の理論的な下界を達成することはできない.筆者らはこれまで,送信機で Tomlinson-Harashima precoding (THP)を用いることで受信機での FDE 後の残留 ISI を抑圧し,特に 16QAM や 64QAM などの高レベル多値変調を用 いたときの BER 特性を改善できることを示してきた.本...

The effects of cooperating base stations in the downlink of an OFDM-based cellular network with frequency reuse factor one are studied. In this so-called network MIMO scenario the signals of several users are jointly processed before transmission in order to handle the unavoidable multi-user interference. We apply and study pre-processing techniques well-known from conventional MIMO scenarios i...

The performance of linear interference suppression in a DS-CDMA (Direct-Sequence Code Division Multiple Access) system using random codes varies over the user population due to the random set of interfering sequences. As a result , the capacity of such systems depends on the distribution of the interfering signature sequences and consequently the distribution of the signal-to-interference ratio...

Multi objective quadratic fractional programming (MOQFP) problem involves optimization of several objective functions in the form of a ratio of numerator and denominator functions which involve both contains linear and quadratic forms with the assumption that the set of feasible solutions is a convex polyhedral with a nite number of extreme points and the denominator part of each of the objecti...

in this paper we introduce the notions of fuzzy transposition hypergroupsand fuzzy regular relations and investigate their basic properties.we also study fuzzy quotient hypergroups of a fuzzy transposition hypergroup.

We prove a variety of theorems about stationary set reflection and concepts related to internal approachability. that an implication Fuchino-Usuba relating version Strong Chang's Conjecture cannot be reversed; strengthen simplify some results Krueger forcing axioms approachability; other are sharp. also adapt ideas Woodin unify many arguments in the literature involving preservation axioms.

In this letter, we discuss the problem of receive antenna selection in the downlink of multiuser multiple-input multiple-output (MIMO) systems with Tomlinson-Harashima precoding (THP), where the number of receivers is assumed equal to that of transmit antennas. Based on the criterion of maximum system sum-capacity, a per-layer receive antenna selection scheme is proposed. This scheme, which sel...

A new version of Tomlinson-Harashima Precoding (THP) for multiple-input/multiple-output (MIMO) channels with decentralised receivers employing lattice reduction is introduced. The proposed method clearly outperforms linear equalisation and conventional THP and in particular shows full diversity order.

Spatial multiplexing techniques send independent data streams on different transmit antennas to maximally exploit the capacity of multiple-input multiple-output (MIMO) fading channels. Most existing multiplexing techniques are based on an idealized MIMO channel model representing a rich scattering environment. Realistic channels corresponding to scattering clusters exhibit correlated fading and...