In the past few years, an exciting progress has been made on CSMA (Carrier Sense Multiple Access) algorithms that achieve throughput and utility optimality for wireless networks. However, most of these algorithms are known to exhibit poor delay performance making them impractical for implementation. Recently, several papers have addressed the delay issue of CSMA and yet, most of them are limited, in the sense that they focus merely on specific network scenarios with certain conditions rather than general network topology, achieve low delay at the cost of throughput reduction, or lack rigorous provable guarantees. In this paper, we focus on the recent idea of exploiting multiple channels (actually or virtually) for delay reduction in CSMA, and prove that it is per-link delay order-optimal, i.e., O(1)-asymptotic-delay per link, if the number of virtual channels is logarithmic with respect to mixing time of the underlying CSMA Markov chain. The logarithmic number is typically small, i.e., at most linear with respect to the network size. In other words, our contribution provides not only a provable framework for the multiple-channel based CSMA, but also the required explicit number of virtual-multi-channels, which is of great importance for actual implementation. The key step of our analytic framework lies in using quadratic Lyapunov functions in conjunction with (recursively applying) Lindley equation and Azuma's inequality for obtaining an exponential decaying property in certain queueing dynamics. We believe that our technique is of broader interest in analyzing the delay performance of queueing systems with multiple periodic schedulers.

The CDN (Content Delivery Network) market consists of content providers (CPs), Internet service providers (ISPs), and CDN providers and evolves based on their complex cooperation and competition. Recently, the rapid growth of content-oriented traffic has brought forth a new entity called Telco CDNs in the content delivery supply chain, where Telco CDNs are the ISP-operated CDN providers, vertically integrating content delivery service with traffic engineering, so as to provide better reliability and QoS to users and reduce infrastructure investments. Telco CDNs and traditional CDNs would compete for their market shares with their unique advantages: Telco CDNs are capable of jointly optimizing network costs and user-perceived QoS, but possibly with their geographical limitation in service areas, whereas traditional CDNs operate a network of servers worldwide, with the advantages of performing global, sophisticated analytics or providing better security solutions. Telco CDNs may form an alliance (e.g., cache server sharing) to compete with traditional CDNs, but with some alliance cost. With this CDN market evolution, this paper conducts a game-theoretic study of when and how traditional CDNs survive in the competition with Telco CDNs. In particular, our study answers the questions about the impact of Telco CDNs' unique characteristics on the long-term competition against traditional CDNs, and the impact of Telco CDNs' alliance. Our analysis provides useful implications on the economics of the future CDN market, e.g., what factors can be Achilles' heel and thus what features should be more focused for Telco and traditional CDNs.

In the past few years, an exciting progress has been made on CSMA (Carrier Sense Multiple Access) algorithms that achieve throughput and utility optimality for wireless networks. However, most of these algorithms are known to exhibit poor delay performance making them impractical for implementation. Recently, several papers have addressed the delay issue of CSMA and yet, most of them are limited, in the sense that they focus merely on specific network scenarios with certain conditions rather than general network topology, achieve low delay at the cost of throughput reduction, or lack rigorous provable guarantees. In this paper, we focus on the recent idea of exploiting multiple channels (actually or virtually) for delay reduction in CSMA, and prove that it isper-link delay orderoptimal, i.e.,O(1)-asymptotic-delay per link, if the number of virtual channels is logarithmic with respect to mixing time of the underlying CSMA Markov chain. The logarithmic number is typically small, i.e., at most linear with respect to the network size. In other words, our contribution provides not only a provable framework for the multiple-channel based CSMA, but also the required explicit number of virtual-multi-channels, which is of great importance for actual implementation. The key step of our analytic framework lies in using quadratic Lyapunov functions in conjunction with (recursively applying) Lindley equation and Azuma's inequality for obtaining an exponential decaying property in certain queueing dynamics. We believe that our technique is of broad interest in analyzing the delay performances of other general queueing systems.

In this paper, we consider revenues of the NSP (network service provider) when there exists a "congestion externality." In particular, we compare revenues obtained using a flat price and two-part tariff and analyze the effect of congestion on the revenue loss when using a simple entry fee in lieu of the two-part tariff. Previous study has shown that when there is no delay disutility the revenue loss is small, which leads to a low "Price of Simplicity." However, in this study, we show that in an extreme case where all users are identical, the price of simplicity is substantial. Then we consider a more practical scenario where users have different preferences, and show that even in this case, under congestion externality, the price can be extremely high.

This paper presents a low-power, gigabit limiting amplifier (LA) for application to optical receivers that employ the negative impedance compensation technique not only to enhance the gain and bandwidth characteristics simultaneously, but also to allow low-voltage, low-power operations. Test chips of the LA were implemented in a standard 0.18-μ m CMOS process, demonstrating 2.5-Gb/s operation with 40-dB gain, 0.053-UI rms jitter for 231-1 pseudorandom bit sequence inputs, 9.5-mVppinput sensitivity for 10-12bit error rate (BER), and 5.2-mW power dissipation from a single 1.2-V supply. The chip core occupies the area of only 0.25 × 0.1 mm2. The proposed LA was adopted to realize a low-power, gigabit optical receiver. Fabricated using the same 0.18-μm CMOS technology, the measured results of the optical receiver chip reveal 132.6-dB Ω transimpedance gain, 2.7-GHz bandwidth even with a large 1.5-pF input parasitic capacitance, -16-dBm optical sensitivity for 10-12BER, and 51-mW power dissipation from a single 1.8-V supply. The area of the whole chip is 1.75 × 0.45 mm2.

A human eye has the logarithmic response over wide range of light intensity. Although the gain can be set high to identify details in darker area on the image, this results in saturation in brighter area. The gamma correction is essential to fit the human eye. However, the digital gamma correction degrades image quality especially for darker area on the image due to the limited ADC resolution and the dynamic range. This paper proposes a CMOS image sensor (CIS) with nonlinear analog-to-digital converter (ADC) which performs analog gamma correction. The CIS with the proposed nonlinear ADC conversion scheme was fabricated with a 0.35-/spl mu/m CMOS process. The test results show the improved image quality than digital gamma correction.