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The chemical modification of oil palm empty fruit bunches (EFB) using non‐catalysed reaction with acetic, propionic and succinic anhydrides were investigated. Proof of modification was indicated by the increase of weight and was confirmed by Fourier‐transform infrared analysis (FT‐IR). The mechanical and water‐absorption properties of all anhydride‐modified EFB composites were evaluated at different volume fractions (Vf). The properties were improved for these modified fibres, whereas unmodified EFB fibres exhibited poor mechanical properties and higher water absorption. Acetic anhydride modification showed the greatest benefit on composite properties, followed by propionic and succinic anhydride modification. © 2001 Society of Chemical Industry

Some communication applications, like multimedia, deliver data of different importance classes allowing unequal error protection (UEP) levels. In this paper, a multiple-input multiple-output (MIMO) system using orthogonal frequency division multiplexing (OFDM) is considered with a new UEP bit-loading algorithm based on the non-UEP algorithm by Chow, Cioffi, and Bingham. In the proposed bit-loading algorithm, bits are distributed across the unitarily transformed eigenbeams in case of partial channel information (CSI) knowledge. However, ideal performance can not withstand the rapid wireless channel variation unless a restricted beamforming is used. For the case of partial CSI, we proposed a switched beamforming technique that can maintain the required performance protection levels.

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We investigate the realization of unequal error protection (UEP) using multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM). In our work, we consider different adaptation schemes, a robust and an intuitive bit-loading. We also study the optimum antenna beamforming that utilizes the partially known channel state information (CSI) at the transmitter, such as channel correlation feedback. However, this introduces a wide range of interferences which could be resolved by an equalizer. Our results show that a certain robustness to this interference and a stable performance for high-priority data can be achieved.

In this work we focus on ultra-dense heterogeneous networks which are one of the key-concepts to increase the spectral efficiency for future mobile networks. Therefore, macro and small cells are operating on the same frequencies to increase the reuse of the spectrum. With this, interference caused by the macro toward users attached to the small cells becomes the limiting performance factor. Aiming for ultra-dense networks with many small cells, also interference from the small-cells to macro-attached, and other small-cell users has an impact which cannot be neglected. To cope with this challenge we use a novel two-stage hierarchical precoding/beamforming approach to protect small-cell users from macro-interference, while still serving macro-users at the same time. In doing so, Channel State Information (CSI) at the transmitter (CSIT) between the macro and small-cell users is required at the macro cell. We adapted an iterative Interference Alignment (IA) algorithm operating in the common null space of the macro-users to ensure interference decoupling of macro and small cell users. All the processing is done at the macro Base Station (BS) allowing independent transmission of the small-cells. This means no further feedback, information (e.g. precoder) or user data exchange between transmit nodes is required

First unequal error protection (UEP) proposals date back to the 1960's (Masnick and Wolf; 1967), but now with the introduction of scalable video, UEP develops to a key concept for the transport of multimedia data. The paper presents an overview of some new approaches realizing UEP properties in physical transport, especially multicarrier modulation, or with LDPC and Turbo codes. For multicarrier modulation, UEP bit-loading together with hierarchical modulation is described allowing for an arbitrary number of classes, arbitrary SNR margins between the classes, and arbitrary number of bits per class. In Turbo coding, pruning, as a counterpart of puncturing is presented for flexible bit-rate adaptations, including tables with optimized pruning patterns. Bit- and/or check-irregular LDPC codes may be designed to provide UEP to its code bits. However, irregular degree distributions alone do not ensure UEP, and other necessary properties of the parity-check matrix for providing UEP are also pointed out. Pruning is also the means for constructing variable-rate LDPC codes for UEP, especially controlling the check-node profile.