Synchronization of OFDM at low SNR over an AWGN channel

This paper is based on Extended Symbol OFDM (ES-OFDM) where symbols are extended in time. This way ES-OFDM can operate at low SNR. Each doubling of the symbol length improves the SNR performance by 3 dB in case of a coherent receiver. One of the basic questions is how to synchronize to signals far below the noise floor. An algorithm is presented which is based on the transmission of pilot symbols. At the receiver, the received signal is cross correlated with the known pilot symbol and the maximum magnitude is determined. The position of the maximum value within the cross correlation function indicates the time difference between transmitter and receiver. The performance of the algorithm in case of an Additive White Gaussian Noise (AWGN) channel, is assessed based on a theoretical approximation of the probability of correct detection of the time difference. The theoretical approximation matches with simulation results and shows that synchronization can be achieved for low (negative) SNRs

Soft output bit error rate estimation for WCDMA

This paper introduces a method that computes an estimation of the bit error rate (BER) based on the RAKE receiver soft output only. For this method no knowledge is needed about the channel characteristics nor the precise external conditions. Simulations show that the mean error of the estimation is below 2%, with only a small variance. Implementation issues for a practical use of the method are discussed

Adaptive OFDM System Design For Cognitive Radio

Recently, Cognitive Radio has been proposed as a promising technology to improve spectrum utilization. A highly flexible OFDM system is considered to be a good candidate for the Cognitive Radio baseband processing where individual carriers can be switched off for frequencies occupied by a licensed user. In order to support such an adaptive OFDM system, we propose a Multiprocessor System-on-Chip (MPSoC) architecture which can be dynamically reconfigured. However, the complexity and flexibility of the baseband processing makes the MPSoC design a difficult task. This paper presents a design technology for mapping flexible OFDM baseband for Cognitive Radio on a multiprocessor System-on-Chip (MPSoC)

Low-Complexity Hyperspectral Image Compression on a Multi-tiled Architecture

The increasing amount of data produced in satellites poses a downlink communication problem due to the limited data rate of the downlink. This bottleneck is solved by introducing more and more processing power on-board to compress data to a satisfiable rate. Currently, this processing power is often provided by custom off the shelf hardware which is needed to run the complex image compression standards. The increase in required processing power often increases the energy required to power the hardware. This in turn pushes algorithm developers to develop lower complexity algorithms which are able to compress the data for the least amount of processing per data element. On the other hand hardware developers are pushed to develop flexible hardware which can be used on multiple missions to cut development cost and can be re-used for different missions. This paper introduces an algorithm which has been developed\ud to compress hyperspectral images at low complexity and describes its mapping to a new hardware platform which has been developed to offer flexibility as well as high performance processing power called the Xentium tile processor

Interposing Flash between Disk and DRAM to Save Energy for Streaming Workloads

In computer systems, the storage hierarchy, composed of a disk drive and a DRAM, is responsible for a large portion of the total energy consumed. This work studies the energy merit of interposing flash memory as a streaming buffer between the disk drive and the DRAM. Doing so, we extend the spin-off period of the disk drive and cut down on the DRAM capacity at the cost of (extra) flash.\ud \ud We study two different streaming applications: mobile multimedia players and media servers. Our simulated results show that for light workloads, a system with a flash as a buffer between the disk and the DRAM consumes up to 40% less energy than the same system without a flash buffer. For heavy workloads savings of at least 30% are possible. We also address the wear-out of flash and present a simple solution to extend its lifetime

Communicating with Muslim parents: "the four principles" are not as culturally neutral as suggested

The “four principles approach” has been popularly accepted as a set of universal guidelines for biomedical ethics. Based on four allegedly trans-cultural principles (respect for autonomy, nonmaleficence, beneficence and justice), it is supposed to fulfil the need of a ‘culturally neutral approach to thinking about ethical issues in health care’. On the basis of a case-history, this paper challenges the appropriateness of communicating in terms of these four principles with patients with a different background. The case describes the situation in which Muslim parents bring forward that their religion keeps them from consenting to end-of-life decisions by non-religious paediatricians. In a literature analysis, the different meanings and roles of the relevant principles in non-religious and Islamic ethics are compared. In non-religious ethics, the principle of nonmaleficence may be used to justify withholding or withdrawing futile or damaging treatments, whereas Islamic ethics applies this principle to forbid all actions that may harm life. And while the non-religious version of the principle of respect for autonomy emphasises the need for informed consent, the Islamic version focuses on “respect for the patient”. We conclude that the parties involved in the described disagreement may feel committed to seemingly similar, but actually quite different principles. In such cases, communication in terms of these principles may create a conflict within an apparently common conceptual framework. The four principles approach may be very helpful in analysing ethical dilemmas, but when communicating with patients with different backgrounds, an alternative approach is needed that pays genuine attention to the different backgrounds

Extending OFDM Symbols to Reduce Power Consumption

Existing communication standards have limited capabilities to adapt to low SNR environments or to exploit low data rate requirements in a power efficient way. Existing techniques like e.g. control coding do not reduce the computational load when reducing data rates. In this paper, we introduce differential Extended Symbol OFDM (differential ES-OFDM) which is based on the transmission of symbols that are extended in time. This way it can operate at low SNR. Using differential BPSK modulation, approximately 2.1 dB SNR improvement per doubling of the symbol length (halving the bitrate) is obtained. The sensitivity to frequency offsets of differential ES-OFDM is basically independent of symbol extension. Extending symbols reduces the computational load on the radio modem within the transmitter which is essential to reduce overall power consumption. The differential ES-OFDM receiver architecture also offers opportunities to reduce power consumption