Power and Bandwidth Efficient Coded Modulation for Linear Gaussian Channels

A scheme for power- and bandwidth-efficient communication on the linear Gaussian channel is proposed. A scenario is assumed in which the channel is stationary in time and the channel characteristics are known at the transmitter. Using interleaving, the linear Gaussian channel with its intersymbol interference is decomposed into a set of memoryless subchannels. Each subchannel is further decomposed into parallel binary memoryless channels, to enable the use of binary codes. Code bits from these parallel binary channels are mapped to higher-order near-Gaussian distributed constellation symbols. At the receiver, the code bits are detected and decoded in a multistage fashion. The scheme is demonstrated on a simple instance of the linear Gaussian channel. Simulations show that the scheme achieves reliable communication at 1.2 dB away from the Shannon capacity using a moderate number of subchannels

Superposition coding for power- and bandwidth efficient communication over the Gaussian channel

A method for power- and bandwidth efficient communication over the Gaussian channel is presented. The method is based on the superposition of binary random variables. As an example we design a signal constellation for a spectral efficiency of 10 bit/s/Hz. The constellation has a constrained capacity limit only 0.18 dB from the Gaussian capacity limit. Moreover, we show that combined with multi-level coding and low-density parity-check codes, a low bit-error rate is achieved at 0.6 dB from the Gaussian capacity limit for a large codeword length.Electrical Engineering, Mathematics and Computer Scienc

Modulation and coding for quantized channels

We investigate reliable communication over quantized channels from an information theoretical point of view. People seldom consider the effect of quantization in conventional coded modulation systems since Analog-to-Digital (AD) converters used in these systems always have high resolution, e.g. 2/3 source bits are often quantized into 10/12 bits. However, AD converters with a high resolution are power consuming. In this paper, we present a scheme to design an optimum quantizer with low resolution which can be used to communicate over the quantized channel. Moreover, we show that reliable transmission over the Additive White Gaussian Noise (AWGN) channel at a rate of R bit/use is possible with R + 1 or R + 2 quantized bits

Fountain codes for frequency occupancy information dissemination

Cognitive radio (CR) is defined as an intelligent wireless communication system based on secondary utilization of an already licensed frequency band. In order to communicate without interfering the legal users (primary users), cognitive radio nodes should have the same overview of the spectrum occupancy information. In other words, each cognitive radio node should disseminate frequency occupancy information (FOI) to other CR nodes reliably after sensing the environment. Normally, people employ retransmission protocols to communicate reliably. This leads to redundancy in reliable dissemination, especially in a multicasting or broadcasting situation. However, the application of fountain codes could make reliable dissemination possible without too much redundancy. A fountain-code based approach is more efficient than using retransmission protocols for disseminating large-sized file. In the paper we show this is also the case when applying fountain codes in disseminating a small FOI file (e.g. a binary vector originating from a 512 points FFT). Fountain codes only work optimally in an erasure channel. In the paper we show the utilization of error-correcting codes to convert a noisy channel into an erasure channel

RF performance of T-DAB receivers

In every wireless system, the weakest link determines the performance of the network. In this paper the Radio Frequency (RF) performance of both band III and L-band Terrestrial Digital Audio Broadcasting (T-DAB) consumer receivers are discussed. The receivers have been tested based on the EN 50248 standard. The test results show that the average consumer receiver for band III meets the requirements set by EN 50248, except for the non-adjacent interferer experiments. In this experiment, the average consumer receiver performs up to 10 dB worse than required. In addition, the experiments reveal that there is a large difference in performance between consumer receivers. Besides band III, also L-band consumer receivers have been evaluated. The results of the L-band experiments show that the consumer receivers are not capable of decoding a DAB signal with a COST207 rural area channel model in case of T-DAB mode IV. Network operators should for this reason use mode II for the L-band and should expect a larger influence of non-adjacent interference on receiver performance in band III than anticipated based on EN 50248

Feasibility of energy detection for dynamic spectrum access

In the Adaptive Ad-hoc Free band Wireless communications (AAF) project, a radio system is investigated that senses its environment to detect un-utilised radio spectrum and use it for ad-hoc networking. In this paper the performance in terms of Quality of Detection (QoD) of a simple energy detection system is studied. It is shown that noise-level uncertainty poses a hard limit on the detectability of signals. In the case that sub-noise signal detection is required, a noise-level measurement function may have to be included in the system architecture