A method that uses wavelength routing devices such as arrayed waveguide grating routers (AWGR) and Echelle grating routers to realize a passive interconnection network with a reduced number of wavelengths to implement all-to-all interconnection. (more...)

With the evolution of wireless and mobile devices, information centric networking (ICN) has come to the forefront as a more efficient method of data communication over a traditional host-based model, thus paving the way for ad-hoc wireless networks to finally take shape. In ad-hoc networks, routing schemes leverage on control messages to discover the network topology in order to achieve efficient end-to-end connectivity, but face challenges of data storage and bandwidth usage.  For example, epidemic forwarding algorithms implement random walks that almost certainly deliver a message to destination without need of knowing the network topology beforehand, however, such algorithms do not take into consideration the partial information that it can infer from its surroundings.  In a wireless network the medium is a precious resource thus a proper heuristic that maximizes efficiency should decide how data should be disseminated.   (more...)

An electro-optic modulator with 100 GHz bandwidth that requires less than 1V to turn on and off. (more...)

University of California researchers have developed an optimized mixture of graphene and multilayer graphene that utilizes high-yield liquid phase exfoliation techniques to significantly increase the thermal conductivity of thermal interface materials.  While current thermal interface materials have thermal conductivity values in the range of ~1 to 5 W/mK at room temperature, University of California researchers have achieved thermal conductivity values at or above 25 W/mK at room temperature with only small graphene loading fractions at 5% by volume.  The graphene and few layer graphene are utilized as filler materials with various base (or matrix) materials to form the thermal interface materials.   (more...)

(more...)

An optical signaling header technique applicable to optical networks wherein packet routing information is embedded in the same channel or wavelength as the data payload so that both the header and data payload propagate through network elements with the same path and the associated delays. (more...)

This invention achieves a highly efficient defragmentation of spectrum in an optical telecommunications network (quasi-hitless). Using this technique, spectrum may be completely defragmented between connections in less than 400 ns, regardless of how the spectrum is allocated initially and with ho need for global synchronization. (more...)

A method of fabrication for a novel photonic device with an integral guide for proper alignment of optical signal carrying apparatuses. (more...)

A novel VCSEL-based multi-wavelength transmitter and receiver module that support multi-wavelength transmission over a single optical fiber or a free-space optical link. (more...)

A novel VCSEL cluster for use in high power applications. (more...)

A fabrication technique for making a novel type of VCSEL with enhanced second harmonic generation. (more...)

A long wavelength VCSEL that is optically pumped by a shorter wavelength VCSEL and is particularly useful for fiber-optic communication systems. (more...)

A method of fabricating diode lasers whose performance is essentially unchanged over designed temperature and bias ranges. (more...)

A wavelength-division-multiplexed array of long wavelength vertical cavity lasers, pumped by a short-wavelength optical pump. (more...)

On-chip capacitively transduced vibrating polysilicon micromechanical resonators have achieved quality factor Q's over 160,000 at 61 MHz and larger than 14,000 at about 1.5 GHz -- making them suitable for on-chip frequency selecting and setting elements for filters and oscillators in wireless communication applications. However, there are applications -- such as software-defined cognitive radio, that require even higher Q's at RF to enable low-loss selection of single channels (instead of bands) to reduce power consumption down to levels conducive to battery-powered handheld devices. To address those higher Q RF applications, researchers at UC Berkeley have invented design improvements to MEMS resonators that reduce energy loss and in turn increase resonator Q. In reducing energy loss to the substrate while supporting all-polysilicon UHF MEMS disk resonators, the Berkeley design improvements enable quality factors as high as 56,061 at 329 MHz and 93,231 at 178 MHz -- that are values in the same range as previous disk resonators using multiple materials with more complex fabrication processes. Measurements confirm Q improvements of 2.6X for contour modes at 154 MHz, and 2.9X for wine glass modes around 112 MHz over values achieved by all-polysilicon resonators with identical dimensions. The results not only demonstrate an effective Q-enhancement method with minimal increase in fabrication complexity, but also provide insights into energy loss mechanisms that have been largely responsible for limiting Q's attainable by all-polysilicon capacitively transduced MEMS resonators. (more...)

A system that provides accurate directional guidance and leads users to a desired AP after a few measurements. This solution uses off-the-shelf smartphones and produces real-time results with a small number of measurements. (more...)

(more...)

(more...)

Baluns are extensively used for single-to-differential conversion of analog/RF/millimeter-wave/broadband signals in integrated transceivers as well as test/measurement equipment setup. Passive baluns do not consume dc power, but suffer from signal attenuation as well as being limited to narrow bands. Active baluns provide power gain and wideband operation while consuming power from dc power supply. This invention is a novel design of an active balun that improves voltage gain and linearity without sacrificing power, bandwidth or physical area. (more...)

Given here is an innovative multiple sub-carrier selection diversity receiver architecture for WLAN OFDM systems with multiple antennas. With a small increase in analog complexity, it is shown that significant gain can be achieved by the proposed technique over selection diversity for WLAN OFDM systems. The technique requires only a single A/D and DFT, which eases the baseband hardware requirements significantly. (more...)

Interference in wireless communication systems is an ongoing problem. In the past, TDMA, FDMA, CDMA or other multiple access methods have been applied to avoid interference. The problem with these approaches is that they waste valuable bandwidth resources. Researchers in UCI’s Engineering and Computer Science Department have developed and tested a cancellation and detection system that achieves full diversity (no interference) with extremely low decoding complexity. The main idea behind this novel system is based on allowing (as opposed to attempting to avoid) interference and then use uniquely designed precoders that use the channel information to remove the interference, similar to destructive interference of EM waves. (more...)

Instant Messaging or “IM” is increasingly used as a communication and awareness tool for work and entertainment. However, this instant awareness is inherently posing risks to one’s privacy. To address this conflict , researchers at UCI’s Department of Informatics have developed PRISM: a plugin that enhances support for privacy management in IM. (more...)

One of the most serious disadvantages of fully adaptive wormhole routers is its performance degradation due to the routing decision time. The key to overcome this shortcoming is the use of different clocks in a head flit and body flits because the body flits can be forwarded immediately and the FIFO operates faster than route decision logic in an adaptive router. (more...)

As the amount of processors on a VLSI chip increases, it is critical to develop a new design strategy that is scalable. The idea of Wireless Network-on-Chip (WNoC) has a great potential to address this demand for scalability of the future VLSI chip design. (more...)

The present invention is an apparatus and a method for generation of random numbers. The apparatus comprises an alpha-radiation source, such as Am 241, for which the decay product produces no secondary radiation with the energy equal or higher than that of the prime alpha radiation. The alpha particles emitted by the isotope and having reached the detector have a narrow energy spectrum and, hence, produce identical electrical pulses in a detector. An alpha-particle detection system is provided which includes a differential discriminator in combination with a logical selector. This combination of elements allows a positive identification of individual events of alpha-decay in the alpha-radiation source to be made and filters out any other signals produced by different radiation sources both inside and outside the apparatus. An electronic unit processes the stream of identical electric pulses into a stream of random numbers. (more...)

TCP is one of the core protocols of the Internet protocol suite, and TCP congestion control is one of the most important TCP related requests for comments (RFCs) in recent years. Fairness is an important criterion in congestion control such that two flows competing on the same narrow link node but with different propagation delays should achieve the fair share, but this does not happen with the TCP scheme currently deployed on the Internet. Previous TCP congestion control schemes include FAST TCP, which is round-trip-time fair and scalable, but lacks in friendliness to legacy TCP making it unusable realistically; TCP Hybla which has been successfully deployed on satellite networks but proves to be too aggressive and hence unstable when deployed on the internet; and BIC TCP which improves the fairness of some high-speed schemes, but is not as good as the fairness provided by legacy TCP. Regarding wireless networks, standard cell phones do not have a fast transport layer protocol installed, but rather rely on the old TCP Tahoe implementation at the client side, resulting in a lack of speed in 3G and beyond networks. TCP Libra as a fast transport layer protocol is a solution to improving the speed of cell phone networks. (more...)

The Internet has become a ubiquitous tool in many aspects of society, yet remains surprisingly susceptible to attacks. Even a single malicious node along the pathway from sender to receiver can corrupt communication in a meaningful way. Secure routing protocols attempt to verify that packets of data are correctly delivered to their destination. However, the internet is large, heterogeneous, complex in topology, and dynamically changing. Failure localization and path-quality monitoring in the public key setting have therefore become two of the biggest challenges in communication. Current routing protocols such as link-state and distance-vector are susceptible to loops, slow convergence, oscillations, and suffer from high communication overhead. The number of network applications continues to increase, and the need for secure, dynamic routing that is resilient to malicious adversaries is evident. (more...)

University researchers have invented a way to leverage a set of largely commodity Ethernet switches to support the full bisection bandwidth of clusters of scalable size, even with tens of thousands of compute nodes. The invention uses an approach that requires no modifications to the end host network interface, operating system, or applications, and so it is fully backward compatible with Ethernet, IP, and TCP. This invention presents a reasonable alternative to increasing bandwidth using specialized hardware and communication protocols (such as Infiniband or Myrinet). The invention meets the following design goals: Scalable interconnection bandwidth: an arbitrary host in the data center can communicate with any other host in the network at the full bandwidth of its local network interface. Economically scaleable: just as personal computers became the basis for large-scale computing environments, this invention can leverage cheap off-the-shelf Ethernet switches the basis for high-performance large-scale data center networks. Backward Compatibility: existing data centers, which almost universally leverage commodity Ethernet and run IP, can take advantage of this new interconnect architecture with no modifications. Packaging and cabling efficiency: the topology must not introduce complexities to the hardware configuration and management. (more...)

University researchers have invented a method for providing different levels of quality of service (QoS) at the level of the web server. This allows for the follow benefits: 1) Allows for higher quality of service to paying customers 2) Can provide different QoS based on user priority or content priority 3) Provides for a complementary revenue model where paying customers receive more responsive service. (more...)

The latest video compression standard (MPEG-4) has moved the wireless industry one step closer to the world of high quality multimedia services. Commercial wireless MPEG-4 video codec systems can already support up to Level 3 of the MPEG Simple Visual Profile. However, the issue of how to effectively transport such high quality multimedia streams across fluctuating radio channels remains a challenge because highly compressed data is very susceptible to low quality fluctuating channel conditions. Advancement in adaptive antenna array technologies such as BLAST, makes it possible to support sustainable bit rate (SBR) conduits in a practical manner. However the use of multiple antennas introduces another dimension of variation - the diversity or different fading levels among sub-channels. (more...)

Some video coding applications place severe restrictions on bit rates. Video telephone systems, for example, generally require the combined audio and video rates to be less than 20 Kb/s. Mobile communications systems can be just as restrictive, since the channel bandwidth is often small. Traditional motion-compensated discrete cosine transform (DCT) coders are ill-suited to such applications, since they are forced to code the residual signal using very few DCT coefficients, each with a coarse quantization. This results in visible block edges and other distortions in the recovered sequence. Much recent research has focused on improving the prediction model, using either 2D object-based coding or full 3D facial models. Such systems are still faced with the task of coding residual signals in scene areas where the model fails. Researchers at the University of California, Berkeley have developed an algorithm appropriate for coding residual signals at very low bit rates. Instead of decomposing the residual signal on a complete basis such as the DCT, we expand the signal on an overcomplete dictionary of Gabor functions. Since this dictionary is larger and more flexible than the DCT set, it can better represent the residual signal using fewer coefficients. Also, since the Gabor dictionary functions decay smoothly at the edges, blocking artifacts are avoided. The signal is decomposed on the Gabor set using a signal analysis technique called Matching Pursuits. We extend this algorithm into the 2D discrete domain and develop an efficient search procedure to match dictionary elements to the residual signal. We also present techniques for coding the resulting parameters efficiently. To test the matching pursuit residual coder described above, we used it to replace the DCT residual coder in a standard low bit rate hybrid coding system (SIM3). At 10 Kb/s using QCIF versions of the Claire and Miss America test sequences, a 1.1 dB average gain in SIM3 during high-motion periods are much less noticeable in the matching pursuit results. Results are further improved when the matching pursuit residual coder is paired with a smooth motion model based on overlapping motion blocks. Such a system does not introduce any artificial block edges. (more...)

Traditional techniques such as filtering and edge enhancement have been applied to restoring images that have been distorted due to lossy image compression. However, these techniques have ignored a unique feature that can be exploited when working with digital compression. Before the image is stored or transmitted, the sender has access to both the original and the distorted images, enabling the encoder to transmit information specifying the regions where the enhancement was successful. To utilize this feature, before storage or transmission the sender produces a codec file, and assesses the efficacy of one or more enhancement schemes. To determine which image regions have been improved by the enhancement, the enhanced codec is compared to the original. A map of where the enhancement scheme was successful is encoded into the image by making tiny adjustments to the image itself. This method can comply with many compression standards, adds nothing to the compressed images' bandwidth, and distorts the image by only a very tiny amount. (more...)

The ability to generate long optical delays with low intrinsic loss is useful for a wide range of applications including optical signal processors, RF filtering, optical buffers, and optical sensing. Optical fibers have been used for these applications with advantages such as ultra-low loss, dispersion and nonlinearity and an exceedingly large bandwidth. However, they are bulky, heavy, and lack of manufacturing scalability. Lithographically defined, chip-scale waveguides have been reported in SiO2/Si and III-V material systems. They are desirable because they are compact, light-weight, and can be integrated with other optoelectronic devices. The lowest reported loss achieved to-date in chip-based waveguides is on the order of 1 dB/m, three to four orders of magnitude higher than that of optical fibers. This loss is unacceptably high for most applications requiring 0.01 dB/m. The fundamental reasons for the high losses are direct band-edge absorption, free carrier absorption, and absorption due to interaction with optical phonons. In addition, these devices are expected to have high nonlinearity and dispersion. To address these limitations, Researchers at UC Berkeley have invented a novel ultra-low loss hollow-core waveguide structure. The new structure provides unprecedented mirror reflectivity and fabrication tolerance. The design can achieve exceedingly low propagation loss that cannot be achieved by conventional waveguide concepts. In addition, the researchers show a potential 2D design with loss estimated to be less than 0.01 dB/m. (more...)

Currently, the most common way to reconstruct the state of traffic uses inductive loop detectors embedded in the pavement to collect the speed of vehicles as they pass over the detectors. Since loop detector stations are not deployed all over the transportation network, it is usually assumed that the measurements collected by each detector stations are representative of a section of freeway around the detector (the length of the section depends on the proximity of nearby detector stations). Another current method of reconstructing the state of traffic is to use RFID devices already present in vehicles. In an urban setting, a substantial number of vehicles on the road will have these devices due to their use in collecting tolls for bridges or highways. A government agency can place readers at various points along a highway in order to collect travel time data between readers, which can then be used to reconstruct velocities between readers. These readers are generally expensive to deploy and the system relies on having many drivers with the appropriate devices in their vehicles. Researchers at the University of California have developed a system that collects positions and speeds of GPS equipped mobile devices traveling onboard vehicles. It uses a sampling strategy to assemble a data stream sufficient to reconstruct the state of traffic on the road segment of interest. It uses these measurements as input to construct the state of traffic everywhere (even where no measurements are available) (more...)

The layout of electrodes in the design of modern MEMS resonators has been one of the crucial aspects in ensuring a small feed-through capacitance. Consequently, complicated design are neccessary that usually require vacuum packaging to make sure that the parasitic feed-through capacitance does not render the resonator unusable. This vacuum must be maintained for the lifetime of the resonator. Approaches used to ensure correct resonator operation include: reduction of the minimum gap in the MEMS mechanical structure; the addition of CMOS transistors on the same substrate as the MEMS mechanical structure also known as integration with electronics; and vacuum encapsulation of the MEMS during the resonator fabrication instead of package level vacuum packaging. To address this complexity, researchers at the University of California, Berkeley have developed a simpler oscillator circuit that eliminates the effects of parasitic feed-through capacitance on resonators. This new circuit allows the operation of resonators with values of feed-through capacitance much larger than previously possible. As a result the new design enables simplification of the overall oscillator and resonator design and allows more freedom in the resonator architecture. The packaging of the MEMS resonator is simplified thereby reducing cost and increasing reliability. Vacuum packaging is no longer needed and minimization of feed-through capacitance can be less stringent with the new oscillator design. The new oscillator circuit supports MEMS fabrication processes with large gaps, and no integrated electronics or vacuum packaging (chip or package level). (more...)

Wireless sensor networks are an emerging research area with potential applications in a wide variety of fields. A primary impediment to the commercial adoption of these networks is that the radio in each wireless sensor node requires lots of power -- especially in comparison to comparable wired sensor nodes. This high power requirement consequently limits the range and/or economics of deploying and maintaining these wireless networks. To solve this problem, researchers at the University of California, Berkeley have developed an innovative media access protocol for wireless sensor networks. This protocol has been developed for sensor networks in which the sensor nodes periodically generate data and have limited power, but the network's main access point is not power constrained. In comparison to protocols designed for more general contention-based (random access) networks, this new protocol lowers power consumption by minimizing the power wasted due to radio operation inefficiencies at each node, and thereby increases battery lifetime. Moreover, this novel protocol offers superior real-time delay guarantees, congestion control and data transmission fairness. In modeling this protocol on a wireless sensor network for traffic management, the results showed that power consumption was 1,000 times lower than the power consumed by a similarly configured contention network protocol -- making the sensor network technology economically viable. (more...)

The Regents of the University of California has available for licensing a significant portfolio of patents related to optical coupling technology. Patent No. 5,163,107 Fiber optic coupler/connector with GRIN lens: A robust, removable, optic fiber coupler which allows for a simple, passive optic fiber alignment without concern for large mechanical discrepancies of slight contamination between the couplers as found in severe environments within the manufacturing industries. Patent No. 5,666,448 Variable splitting optical coupler: An optical coupler with a movable deflecting element to vary the relative splitting of an optical signal. Patent No. 5,757,994 Three-part optical coupler: An optical coupler with deflecting element to passively couple fiber optic signals. Patent No. 5,761,357 Fiber optic "T"coupler in-line splitter: A fiber optic "T" coupler using cutoff portions of GRIN lenses. Patent No. 5,809,187 Multi-port network using passive optical couplers: A fiber optic network with passive optic fiber connections. Patent No. 5,883,993 Fiber Optic "T" Coupler Modulator: Two quarter wave length GRIN lenses with their collimated ends facing each other with a modulation device between them. The modulation device acts on the collimated light transmitted between the GRIN lenses. The modulator can be a filter, a polarizer, an optical switch, an amplifier or any other device for modulating light. Patent No. 5,892,868 Fiber optic coupler combiner: A fiber optic coupler having multiple small lens elements coupled to a larger lens element fo rtransferring collimated light at the interface for bilaterally combining or dividing light. Patent No, 5,894,534 Fiber optic "T" coupler single-path transceiver: Fober ptic couplers for two-way communications on the same fiber optic cable. Patent No. 6,219,477 Multiport single path optical system: An optic system for multiplexing on a single optic fiber. Patent No. 6,272,226 Multipath optical coupler: Methods and apparatus for transmitting an inserted optical signal into an optical coupler and transmitting an extracted optical signal from the optical coupler so that the extracted optical signal does not contain any aspect of the inserted optical signal. (more...)

There has been tremendous progress in research and commercialization of dense wavelength division multiplexing (DWDM) optical fiber communications. Transmission capacity as high as 10 terabits/second through a single fiber has been demonstrated in the laboratory. This huge capacity can create enormous data traffic congestion at major interconnections. An all-optical packet switched network can potentially eliminate this major bottleneck by allowing the data packets to route through the network without optoelectronic conversion. One of the most important components in a router is a buffer. A buffer must be able to store data packets for a substantial period of time and must be able to release the data within an acceptable delay when the switch is clear for routing. Researchers at the University of California, Berkeley have developed a novel concept for an all-optical buffer with variable memory, based on slowing the group velocity of the optical data packet in the buffer wtih a controlled reduction, such that it is effectively an optical memory. By varying the group velocity reduction factor, the memory length and the delay time can be adjusted. (more...)

Rapidly tunable, ultra-compact, room temperature infrared source (more...)

Edge Router for Optical Label Switched Network (more...)

Ultra-low Latency Multi-Protocol Optical Routers (more...)

Reconfigurable Multi-Channel All-Optical Regenerators (more...)

The AlGaAsSb semiconductor system has demonstrated great promise for heterojunction transistors and optoelectronics systems in the 1.3-1.55 micrometer wavelength range used in long-distance optical communications. Although AlGaAsSb/AlAsSb system have been successfully grown on both GaAs and InP substrates, the accuracy and reproducibility of the (As, Sb) composition is difficult to achieve due to wide miscibility gap effects. The same amount of both As and Sb on the surface can lead to interactions that modify the incorporation process of each species. This presents difficulties in controlling the group-V composition due to a tendency to be either As-rich or Sb-rich, depending upon which species has the best sticking coefficient. (more...)

The low active volume of vertical-cavity surface-emitting lasers (VCSELs) presents many advantages, providing that the Bragg mirrors (DBRs) simultaneously exhibit high reflectivity, good electrical conduction, and low thermal resistance. Current approaches, such as the GaAs/AlAs DBRs, have performed well, but several problems still remain with regards to long-wavelength VCSELs, such as thermal conductivities, costly fabrication processes, and optical difficulties. (more...)

The characteristics of long-wavelength VCSELs are very sensitive to temperature. However, the materials used in these lasers do not manage heat effectively. For example, these types of lasers that are made on InP substrates typically suffer from excessive heating due to the poor thermal conductivity of the ternary and quaternary materials used in the distributed Bragg reflectors (DBRs). (more...)

Intracavity-contacted VCSELs, in which only a cladding layer serves as a contact layer, often demonstrate lower optical loss than VCSEL structures with conducting mirrors. However, much of this optical loss usually returns in the thick p-type contact layers, which results in the need for a higher doping level and increased thickness in these layers to minimize the electrical resistance. Therefore, optical loss in the p-type contact layer presents a limiting factor in double intracavity VCSELs. (more...)

Internet traffic has increased at an exponential rate, which has created the need to scale networks far beyond their present capabilities with respect to speed, capacity, and performance. Optical fibers can transmit large amounts of data at high speeds while greatly reducing the need to retransmit signals periodically over long distances. Simultaneous transmission of optical signals over the same fiber from many different light sources that have properly spaced peak emission wavelengths can dramatically increase the information capacity of an optical fiber. Operating each source at a different peak wavelength maintains the integrity of the independent messages from each source for subsequent conversion to electrical signals at the receiving end. This method is the foundation of wavelength division multiplexing (WDM), which can potentially offer solutions to the performance and scaling bottlenecks currently seen in Internet Protocol (IP) networks. Although optical fibers allow for extremely fast transmission of data, the electronic switches used in most networks greatly slows these speeds. (more...)