Runfeng Yang

Enhancing MB-OFDM throughput with dual circular 32-QAM

Quadrature phase shift keying (QPSK) and dual carrier modulation (DCM) are currently used as the modulation schemes for multiband orthogonal frequency division multiplexing (MB-OFDM) in the ECMA-368 defined ultra-wideband (UWB) radio platform. ECMA-368 has been chosen as the physical radio platform for many systems including wireless USB (W-USB), Bluetooth 3.0 and wireless HDMI; hence ECMA-368 is an important issue to consumer electronics and the users experience of these products. To enable the transport of high-rate USB, ECMA-368 offers up to 480 Mb/s instantaneous bit rate to the medium access control (MAC) layer, but depending on radio channel conditions dropped packets unfortunately result in a lower throughput. This paper presents an alternative high data rate modulation scheme that fits within the configuration of the current standard increasing system throughput by achieving 600 Mb/s (reliable to 3.1 meters) thus maintaining the high rate USB throughput even with a moderate level of dropped packets. The modulation system is termed dual circular 32-QAM (DC 32-QAM). The system performance for DC 32-QAM modulation is presented and compared with 16-QAM and DCM.

A dual QPSK soft-demapper for multiband OFDM exploiting time-domain spreading and guard interval diversity

When considering the relative fast processing speeds and low power requirements for wireless personal area networks (WPAN) including wireless universal serial bus (WUSB) consumer based products, then the efficiency and cost effectiveness of these products become paramount. This paper presents an improved soft-output QPSK demapper suitable for the products above that not only exploits time diversity and guard carrier diversity, but also merges the demapping and symbol combining functions together to minimize CPU cycles, or memory access dependant upon the chosen implementation architecture. The proposed demapper is presented in the context of multiband OFDM version of ultra wideband (UWB) (ECMA-368) as the chosen physical implementation for high-rate wireless USB.

Fixed point Dual Carrier Modulation performance for wireless USB

Dual Carrier Modulation (DCM) is currently used as the higher data rate modulation scheme for Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the ECMA-368 defined Ultra-Wideband (UWB) radio platform. ECMA-368 has been chosen as the physical radio platform for many systems including Wireless USB (W-USB), Bluetooth 3.0 and Wireless HDMI; hence ECMA-368 is an important issue to consumer electronics and the users experience of these products. In this paper, Log Likelihood Ratio (LLR) demapping method is used for the DCM demaper implemented in fixed point model. Channel State Information (CSI) aided scheme coupled with the band hopping information is used as the further technique to improve the DCM demapping performance. The receiver performance for the fixed point DCM is simulated in realistic multi-path environments1.

A Practical Low Cost Architecture for a MB-OFDM Equalizer (ECMA-368)

The relative fast processing speed requirements in wireless personal area network (WPAN) consumer based products are often in conflict with their low power and cost requirements. In order to solve this conflict the efficiency and cost effectiveness of these products and the underlying functional modules become paramount. This paper presents a low-cost, simple, yet high performance solution for the receiver channel estimator and equalizer for the mutiband OFDM (MB-OFDM) system, particularly directed to the WiMedia Consortium Physical Later (ECMA-368) consumer implementation for wireless-USB and fast Bluetooth. In this paper, the receiver fixed point performance is measured and the results indicate excellent performance compared to the current literature.

Multiband OFDM Modulation and Demodulation for Ultra Wideband Communications

This chapter considers the Multiband Orthogonal Frequency Division Multiplexing (MB- OFDM) modulation and demodulation with the intention to optimize the Ultra-Wideband (UWB) system performance. OFDM is a type of multicarrier modulation and becomes the most important aspect for the MB-OFDM system performance. It is also a low cost digital signal component efficiently using Fast Fourier Transform (FFT) algorithm to implement the multicarrier orthogonality. Within the MB-OFDM approach, the OFDM modulation is employed in each 528 MHz wide band to transmit the data across the different bands while also using the frequency hopping technique across different bands. Each parallel bit stream can be mapped onto one of the OFDM subcarriers. Quadrature Phase Shift Keying (QPSK) and Dual Carrier Modulation (DCM) are currently used as the modulation schemes for MB-OFDM in the ECMA-368 defined UWB radio platform. A dual QPSK soft-demapper is suitable for ECMA-368 that exploits the inherent Time-Domain Spreading (TDS) and guard symbol subcarrier diversity to improve the receiver performance, yet merges decoding operations together to minimize hardware and power requirements. There are several methods to demap the DCM, which are soft bit demapping, Maximum Likelihood (ML) soft bit demapping, and Log Likelihood Ratio (LLR) demapping. The Channel State Information (CSI) aided scheme coupled with the band hopping information is used as a further technique to improve the DCM demapping performance. ECMA-368 offers up to 480 Mb/s instantaneous bit rate to the Medium Access Control (MAC) layer, but depending on radio channel conditions dropped packets unfortunately result in a lower throughput. An alternative high data rate modulation scheme termed Dual Circular 32-QAM that fits within the configuration of the current standard increasing system throughput thus maintaining the high rate throughput even with a moderate level of dropped packets.

A Dual QPSK Soft-demapper for ECMA-368 Exploiting Time-Domain Spreading and Guard Interval Diversity

When considering the relative fast processing speed and low power requirements for wireless personal area networks (WPAN) and wireless universal serial bus (USB) consumer based products, then the efficiency and cost effectiveness of these products become paramount. This paper presents an improved soft-output QPSK demapper suitable for the products above that not only exploits time diversity and guard carrier diversity, but also merges the demapping and symbol combining functions together to minimize CPU cycles, or memory access dependant upon the chosen implementation architecture. The proposed demapper is presented in the context of multiband OFDM version of UWB (ECMA-368) as the chosen physical implementation for high-rate wireless USB.