Enhanced Huffman Coded OFDM with Index Modulation

In this paper, we propose an enhanced Huffman coded orthogonal frequency-division multiplexing with index modulation (EHC-OFDM-IM) scheme. The proposed scheme is capable of utilizing all legitimate subcarrier activation patterns (SAPs) and adapting the bijective mapping relation between SAPs and leaves on a given Huffman tree according to channel state information (CSI). As a result, a dynamic codebook update mechanism is obtained, which can provide more reliable transmissions. We take the average block error rate (BLER) as the performance evaluation metric and approximate it in closed form when the transmit power allocated to each subcarrier is independent of channel states. Also, we propose two CSI-based power allocation schemes with different requirements for computational complexity to further improve the error performance. Subsequently, we carry out numerical simulations to corroborate the error performance analysis and the proposed dynamic power allocation schemes. By studying the numerical results, we find that the depth of the Huffman tree has a significant impact on the error performance when the SAP-to-leaf mapping relation is optimized based on CSI. Meanwhile, through numerical results, we also discuss the trade-off between error performance and data transmission rate and investigate the impacts of imperfect CSI on the error performance of EHC-OFDM-IM

Turbo-Detected Unequal Protection MPEG-4 Audio Transceiver Using Convolutional Codes, Trellis Coded Modulation and Space-Time Trellis Coding

A jointly optimised turbo transceiver capable of providing unequal error protection is proposed for employment in an MPEG-4 aided audio transceiver. The transceiver advocated consists of Space-Time Trellis Coding (STTC), Trellis Coded Modulation (TCM) and two different-rate Non-Systematic Convolutional codes (NSCs) used for unequal error protection. A benchmarker scheme combining STTC and a single-class protection NSC is used for comparison with the proposed scheme. The audio performance of the both schemes is evaluated when communicating over uncorrelated Rayleigh fading channels. It was found that the proposed unequal protection turbo-transceiver scheme requires about two dBs lower transmit power than the single-class turbo benchmarker scheme in the context of the MPEG-4 audio transceiver, when aiming for an effective throughput of 2 bits/symbol, while exhibiting a similar decoding complexity

Automatic Modulation Classification in Mobile OFDM Systems with Adaptive Modulation

Adaptive modulation is an efficient way to combat the effects of deep fades in broadband orthogonal frequency division multiplexing (OFDM) systems with time-varying multipath channels, where modulation schemes are adapted to the current channel state. Bandwidth efficient modulation schemes are applied on subcarriers with high channel quality, while robust modulation schemes or even no modulation is preferred for subcarriers in deep fades. The resulting benefit in terms of required transmit power was demonstrated for a fixed data rate in the literature, where a gain of 5 · · · 15 dB was recorded for a BER of 0.001 over the OFDM system with a fixed modulation. In literature, several algorithms for adaptive modulation have been proposed with different emphasis on bandwidth efficiency and implemental complexity. In this thesis, the algorithm proposed by Chow is used. A main drawback of adaptive modulation is that it requires the adapted modulation schemes to be provided at the receiver to enable demodulation. Traditionally, this information is provided in forms of explicit signalling, which reduces the bandwidth efficiency due to the signalling overhead. In the thesis, proposals are developed to reduce this undesirable overhead. These proposals exploit the correlation properties inherently existing in the transmission channel in both time and frequency domain, which leads to memory effects in the signalling source. State-dependent Huffman coding schemes are then applied to reduce the redundancy resulting from these memory effects. This signalling overhead can be totally eliminated by automatic modulation classification (AMC). In the past, AMC was mainly of interest in military fields like threat analysis and electronic surveillance, where no prior knowledge about the used modulation scheme is available. The received signal is the single information source for classification. Under such circumstance, maximum likelihood (ML) based AMC provides the optimum solution in the sense that the classification error probability is minimized. Nowadays, AMC is drawing more and more research interest also in civilian applications like systems with adaptive modulation, where certain co-operations are organized as in the system considered in this thesis. These co-operations provide certain prior information, which can be utilized to improve the classification reliability. Consequently, the ML based approach does not deliver the minimum error probability any more. Investigations have to be conducted to verify how much the performance can be improved by incorporating this prior information into the AMC algorithm. As one focus in this thesis, a AMC algorithm is developed, which is potentially able to minimize the classification error probability again. Another focus is to reduce the implemental complexity to enable the application of AMC in systems with high time requirements like real-time systems. In the last part of the thesis, comparisons are performed between these two approaches, namely explicit signalling and signalling-free AMC, in terms of the end-to-end packet error probability. To ensure a fair comparison, the net data rate is always maintained as a constant in both operation modes

Wireless Network Requirements and Solutions for the Future Circular Collider: A Hostile Indoor Environment

The European organization for nuclear research (CERN) is planning a high performance particle collider by 2050, which will update the currently used Large Hadron Collider (LHC). The design of the new experiment facility includes the definition of a suitable communication infrastructure to support the future needs of scientists. The huge amount of data collected by the measurement devices call for a data rate of at least 1Gb/s per node, while the need of timely control of instruments requires a low latency of the order of 0.01μs. Moreover, the main tunnel will be 100 km long, and will need appropriate coverage for voice and data traffic, in a special underground environment subject also to strong radiations. Reliable voice, data and video transmission in a tunnel of this length is necessary to ensure timely and localized intervention, reducing access time. In addition, using wireless communication for voice, control and data acquisition of accelerator technical systems could lead to a significant reduction in cabling costs, installation times and maintenance efforts. The communication infrastructure of the Future Circular Collider (FCC) tunnel must be able to circumvent the problems of radioactivity, omnipresent in the tunnel. Current technologies transceivers cannot transmit in such a severely radioactive environment. This is due to the immediate destruction of any active or passive equipment by radioactivity. The scope of this paper is to determine the feasibility of robust wireless transmission in an underground radioactive tunnel environment. The network infrastructure design to meet the demand will be introduced, and the performance of different wireless technologies will be evaluated.Peer reviewedFinal Accepted Versio

Combined Source and Channel Strategies for Optimized Video Communications

ISBN 978-953-7619-70-