Capacity investigation of on-off keying in noncoherent channel settings at low SNR

On–off keying (OOK) has repossessed much new research interest to realize green communication for establishing autonomous sensor networks. To realize ultra-low power wireless design, we investigate the minimum energy per bit required for reliable communication of using OOK in a noncoherent channel setting where envelope detection is applied at the receiver. By defining different OOK channels with average transit power constraints, the achievability of the Shannon limit for both cases of using soft and hard decisions at the channel output is evaluated based on the analysis of the capacity per unit-cost at low signal-to-noise ratio. We demonstrate that in phase fading using hard decisions cannot destroy the capacity only if extremely asymmetric OOK inputs are used with a properly chosen threshold. The corresponding pulse-position modulation scheme is explicitly studied and demonstrated to be a Shannon-type solution. Moreover, we also consider a slow Rayleigh fading scenario where the transmitter and receiver have no access to channel realizations.Throughput per unit-cost results are developed to explore the trade-off between power efficiency and channel quality for noncoherent OOK using soft and hard decisions

Communication for wideband fading channels : on theory and practice

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 163-167).This dissertation investigates some information theoretic aspects of communication over wideband fading channels and their applicability to design of signaling schemes approaching the wideband capacity limit. This work thus leads to enhanced understanding of wideband fading channel communication, and to the proposal of novel efficient signaling schemes, which perform very close to the optimal limit. The potential and limitations of such signaling schemes are studied. First, the structure of the optimal input signals is investigated for two commonly used channel models: the discrete-time memoryless Rician fading channel and the Rayleigh block fading channel. When the input is subject to an average power constraint. it is shown that the capacity-achieving input amplitude distribution for a Rician channel is discrete with a finite number of mass points in the low SNR regime. A similar discrete structure for the optimal amplitude is proven to hold over the entire SNR range for the average power limited Rayleigh block fading channel. Channels with a peak power constraint are also analyzed. When the input is constrained to have limited peak power, we show that if its Kuhn-Tucker condition satisfies a sufficient condition, the optimal input amplitude is discrete with a finite number of values.(cont.) In the low SNR regime, the discrete structure becomes binary. Next, we consider signaling over general fading models. Multi-tone FSK, a signaling scheme which uses low duty cycle frequency-shift keying signals (essentially orthogonal binary signals, is proposed and shown to be capacity achieving in the widceband limit. Transmission of information over wideband fading channels using Multi-tonc FSK is considered by using both theoretic analysis and numerical simulation. With a finite bandwidth and noncoherent detection, the achievable data rate of the Multi-tone FSK scheme is close to the wideband capacity limit. furthermore, a feedback scheme is proposed for Multi-tone FSK to improve the codeword error performance. It is shown that if the receiver can feedback received signal quality to the transimitter. a significant improvement in codeword error probability can be achieved. Experimental results are also obtained to dlenlonstrate features and practicality of Multi-tone FSK.by Cheng Luo.Ph.D

Some fundamental issues in receiver design and performance analysis for wireless communication

Ph.DDOCTOR OF PHILOSOPH

Turbo Codes Performance Optimization over Block Fading Channels

In this paper, the best achievable performance of a turbo coded system on a block fading channel is obtained, assuming binary antipodal modulation. A rate 1/3 turbo code is considered, obtained by concatenating, through a random interleaver, an 8-states rate 1/2 and a rate 1 convolutional codes (CC). The block fading channel model is motivated by the fact that in many wireless systems the coherence time of the channel is much longer than one symbol interval, resulting in adjacent symbols being affected by the same fading value. The fading blocks will experience independent fades, assuming a sufficient separation in time, in frequency, or both in time and in frequency. This channel model is suitable for analyzing, for instance, wireless communication systems employing techniques such as slow frequency-hopping, as is done in the Global System for Mobile communications (GSM). In such systems, coded information is transmitted over a small number of fading channels in order to achieve diversity. The best coded information allocations over a certain number of fading channels are evaluated, using the Eades McKay algorithm to generate distinct permutations of a multiset. Bounds on the achievable performance due to coding are derived using information-theoretic techniques. In particular, in the paper an analytical method is proposed, based on the sphere-packing bounding technique, to assess the achievable performance. Moreover, simulation results are obtained and compared with the theoretical ones