Frederick L. Martin

A new chip-level differential detection system for DS-CDMA

In this paper we mathematically prove that if the original spreading Pseudo-Noise (PN) code is an m-sequence or a Gold-sequence, then the chip-by-chip differential decoding (CBCDD) sequence of the original PN code is a cyclic shift version of the original PN sequence. By utilizing this property, we design a new chip-level differential detection system for DS-CDMA, which does not require any chip-level differential encoding in the transmitter. We demonstrate simplicity of implementation and robust operation in the presence of carrier frequency shift.

Performance of chip-level differential detection with phase noise

Chip-level differential encoding/detection of direct-sequence spread-spectrum signals has been shown to improve receiver robustness in the presence of oscillator frequency offsets and fast fading channels. These gains are achieved at the expense of SNR performance in an AWGN channel, with spreading factor governing the tradeoff. This paper explores the performance of chip-level differential detection in the presence of oscillator phase noise. It is shown that phase noise mitigation is an additional benefit of chip-level differential detection, with higher spreading factors permitting the use of lower-cost, noisier oscillators. Simulations of a DS/SS BPSK system illustrate the relationship between phase noise tolerance and spreading factor, and a simple analytical model is derived for efficient evaluation of systems with high spreading factor.

Early Opportunities for Commercialization of TV Whitespace in the U.S

We propose the use of IP-based broadband wireless protocols to address many of the applications needs in the Television White Space (TVWS) frequencies that will be available for secondary usage in the U.S. beginning in 2009. The work includes a discussion of TVWS physical and regulatory characteristic and a view of the TVWS usage models that may be applied in various market spaces, including the home, the enterprise, public safety and wireless mobile service providers. We show that a protocol based on IEEE 802.16e or a similar broadband wireless protocol could be adapted to meet many of the needs in this space.

Guest editorial: special issue on cognitive radio oriented wireless networks and communications

In recent years, there has been an exponential rise in the number of wireless standards such as 802.11 a,b,g,n (and more), 802.15 (Bluetooth, Zigbee, UWB), WCDMA (and several modes), CDMA 2000 (1xEV-DV, 1xEVDO), Wireless USB, and 802.16 (various modes) to name just the most prominent standards. The abundance of standards today is the result of a desire in the industry to support new applications, with each standard custom-tailored to a specific operating environment and spectrum. It is not hard to envision that wireless coverage will be pervasive in the future and will support a variety of applications that are undreamed of today. On the other hand, wireless spectrum access has been regulated with static spectrum allocation since the early 1920s, which assigns a fixed block of spectrum to each new wireless service for its exclusive use. Over the years, the remaining useful spectrum available for new wireless services is being exhausted. This is a serious problem since new wireless services and devices are now rolling out at an unprecedented pace. This trend will continue as wireless becomes pervasive in the future. Recent studies sponsored by the FCC have shown that traditional fixed allocation policy is becoming inadequate in addressing today’s rapidly evolving wireless communications. Studies show that many allocated spectrum blocks are used only in certain geographical areas and are idle most of the time. These frequency bands are called the spectrum “white space” (or “hole”). Measurements conducted by the Shared Spectrum Company [1] find that even in the most crowded area near downtown Washington, DC, where both government and commercial spectrum use is considered intensive, 62% of the spectrum remain white space. Another measurement (funded by NSF), also conducted by the Shared Spectrum Company [2], shows Mobile Netw Appl (2008) 13:411–415 DOI 10.1007/s11036-008-0077-x

A BiCMOS 50-MHz voltage-controlled oscillator with quadrature outputs

Design, analysis, and measured results are presented for a completely integrated voltage-controlled oscillator characterized over the range 25.6 to 76 MHz. The oscillator is based on a fully differential four-stage ring architecture with identical stages tuned via p-channel FETs operating in the linear region. Fabricated for 3.0 to 5.0 V operation in a 1.0-/spl mu/m BiCMOS process, the circuit operates with power dissipation on the order of 3 mW and FM sideband noise below -80 dBc Hz at 25 kHz offset from the carrier. The intended application is in communications products, where tunability, well-characterized spectral characteristics, and quadrature signals are important.

Toward wireless receivers without crystals

In new low cost, low bit rate wireless protocols such as Zigbee/spl trade/ and Bluetooth/spl trade/, there is significant economic motivation to implement transceivers with a completely integrated alternative to quartz crystals. In this paper, we explore a differential detection based method of recovering a direct sequence spread spectrum signal with a receiver that does not have a crystal reference. Despite the additional frequency offset and phase introduced by using an integrated crystalless reference oscillator, we find that such a receiver is feasible and can perform sufficiently for many applications.

A wideband 1.3 GHz PLL for transmit remodulation suppression

A 1.3 GHz 0.5 /spl mu/m BiCMOS offset PLL realizes -132 dBc/Hz in-band phase noise while reducing re-radiated transmission by 53 dB. The circuit operates without an offset signal. Elements include digital phase detector with steering operating to 1.3 GHz and digital frequency divider with programmable modulus from 1 to 1.5 in steps of 0.03125. Current is 10 mA from 2.7 V. Die is 1.2 mm/sup 2/.