Non-Gaussian noise/interference severely limits communication performance of narrowband powerline communication (PLC) systems. Such noise/interference is dominated by periodic impulsive noise whose statistics varies with the AC cycle. The periodic impulsive noise statistics deviate significantly from that of additive white Gaussian noise, thereby causing dramatic performance degradation in conventional narrowband PLC systems. In this paper, we propose a robust transmission scheme and corresponding receiver methods to combat periodic impulsive noise in OFDM-based narrowband PLC. Towards that end, we propose (1) a time-frequency modulation diversity scheme at the transmitter and a diversity demodulator at the receiver to improve communication reliability without decreasing data rates; and (2) a semi-online algorithm that exploits the sparsity of the noise in the frequency domain to estimate the noise power spectrum for reliable decoding at the diversity demodulator. In the simulations, compared with a narrowband PLC system using Reed-Solomon and convolutional coding, whole-packet interleaving and DBPSK/BPSK modulation, our proposed transceiver methods achieve up to 8 dB gains in Eb/N0with convolutional coding and a smaller-sized interleaver/deinterleaver.

Non-Gaussian noise/interference severely limits communication performance of narrowband powerline communication (PLC) systems. Such noise/interference is dominated by periodic impulsive noise whose statistics varies with the AC cycle. The periodic impulsive noise statistics deviates significantly from that of additive white Gaussian noise, thereby causing dramatic performance degradation in conventional narrowband PLC systems. In this paper, we propose a robust transmission scheme and corresponding receiver methods to combat periodic impulsive noise in OFDM-based narrowband PLC. Towards that end, we propose (1) a time-frequency modulation diversity scheme at the transmitter and a diversity demodulator at the receiver to improve communication reliability without decreasing data rates; and (2) a semi-online algorithm that exploits the sparsity of the noise in the frequency domain to estimate the noise power spectrum for reliable decoding at the diversity demodulator. In the simulations, compared with a narrowband PLC system using Reed-Solomon and convolutional coding, whole-packet interleaving and DBPSK/BPSK modulation, our proposed transceiver methods achieve up to 8 dB gains in Eb/N0with convolutional coding and a smaller-sized interleaver/deinterleaver.

Medical Body Area Network (MBAN) technology is a promising solution to improve patient care outcomes and lower healthcare costs. To foster MBAN innovations, the FCC recently allocated dedicated spectrum for MBAN services. In this paper, we present a brief summary of the FCC MBAN rules. Then, we discuss the technical rationale for the selection of key parameters, such as frequency band selection, emission bandwidth limit, and transmission power limit. Finally, we provide link budget analysis and MBAN coexistence simulations to demonstrate that the FCC rules can meet the requirements of MBAN applications.

In this paper, we investigate the issue of 20/40 MHz coexistence in next generation wireless local area networks (WLAN). To that end, we present simulation results of overlapping basic service sets (BSSs) an 802.11n BSS operating in 20/40 MHz mode and a legacy BSS operating in 20 MHz channel. Our results show that if clear channel assessment (CCA) is not used in the overlapping channel; i.e., the 20 MHz channel used by both BSSs, the throughput in legacy BSS falls to zero, while the throughput of 802.11n BSS decreases dramatically. If CCA is used in the overlapping channel, the throughput of both, legacy and 802.11n BSS increases compared to the earlier case. When devices operating in 20/40 MHz BSS are able to dynamically switch between 20 and 40 MHz transmissions and in addition, CCA is used in the overlapping channel, the throughput of both BSSs further increases. Reducing transmission opportunity (TXOP) interval for 40 MHz transmissions also improves fairness and throughput for legacy BSSs.

In this paper, enhancements to the multi-band OFDM (MB-OFDM) system for ultra-wideband (UWB) communication are described. A dual-carrier modulation scheme that increases the range of the MBOFDM system at higher data rates is presented. Techniques to enhance the robustness of the PLCP header and improve the multi-piconet capability are discussed. In addition, performance results in realistic multi-path environments are provided.

Ultra-wideband (UWB) communication systems are able to achieve high data rates by utilizing a large amount of spectrum. This signal typically overlaps with many existing and potentially future services. Therefore, for an UWB device to be successful, it will need to be able to identify and protect these victim receivers via cognitive radio techniques. Multi-band orthogonal frequency division modulation (MB-OFDM) has an inherent ability to perform the functions of a cognitive radio. With minimal changes to the technology, it is possible to identify victim services and provide the necessary protection mechanisms via spectral notches based on distance, bandwidth and other such measures. In this paper, the techniques for detecting interfering signals, estimating the distance between victim and interfering devices, and shaping the spectrum to mitigate interference into the victim receiver are described

The cellular wireless market has begun the transition to data centric services including high speed internet access, video, high quality audio, and gaming. Communications technology can meet the need for very high data link speeds, and can also improve network throughput, but dramatically more spectrum will be needed to provide ubiquitous wireless data service. Cognitive radio is a new technology that allows spectrum to be dynamically shared between users. It offers the potential to dramatically change the way spectrum is used in systems and to substantially increase the amount of spectrum available for wireless communications. This paper introduces cognitive radio and explains the promise, possible operating modes, and benefits it may offer.

Multiple-antenna wireless systems are of interest because they provide increased capacity over single-antenna systems. Several space-time signaling schemes have been proposed to make use of this increased capacity. Space-time techniques, such as space-time block coding and spatial multiplexing, can all be viewed as signaling with a multidimensional constellation. Because of the large capacity of multiple-input multiple-output (MIMO) channels, these multidimensional constellations often have large cardinalities. For this reason, it is impractical to perform optimal maximum-likelihood (ML) decoding for space-time systems, even for a moderate number of transmit antennas. In this paper, we propose a modified version of the classic Chase decoder for multiple-antenna systems. The decoder applies successive detection to yield an initial estimate of the transmitted bit sequence, constructs a list of candidate symbol vectors using this initial estimate, and then computes bit likelihood information over this list. Three algorithms are presented for constructing the candidate vector list. This decoder can be adjusted to have a fixed or variable complexity, while maintaining performance close to that of an ML decoder.