Peak Electronic Design Ltd

<p>The purpose of MPLS is to improve the speed, provisioning and scalability of the network, thus offering network providers a valuable tool for traffic engineering and for virtual private networks. A VPN is a private network that uses a public-access IP infrastructure as its transport mechanism. The most obvious application is access by remote and mobile business users and telecommuters. VPNs are all about security, bandwidth and availability/reliability.</p>

In May, this specification was accepted by the T10 committee, the official SCSI standards group of the International Committee for Information Technology Standards, as a working draft of the Serial Attached SCSI standard. Since then, work has continued with the goal of completing the specification for letter ballot by the end of the year.

In addition, the SCSI Trade Association (STA), a member-run industry group that has taken responsibility for Serial Attached SCSI, is working to define marketing requirements for the Serial Attached SCSI specification and to promote the technology to the industry. The STA estimates that Serial Attached SCSI products will enter the market in early 2004.


Serial Attached SCSI will support internal and near-attached storage devices. At the same time, it addresses the storage market's future needs by giving system engineers the chance to develop a common infrastructure that supports enterprise-class Serial Attached SCSI and desktop-class SATA drives.

Both SATA and Serial Attached SCSI drives can be physically inserted on the same backplane connector. At the protocol level, the subsystem will use SATA Tunneling Protocol for SATA devices and Serial SCSI Protocol for Serial Attached SCSI devices as required.


Serial Attached SCSI defines a switching architecture for connecting multiple drives to multiple ports. Low-cost expanders allow designers to maintain a point-to-point architecture while connecting multiple drives. Devices can be easily swapped and redeployed as needed, with minimal disruption for users.

Serial Attached SCSI offers backward compatibility with SCSI software and middleware, and leverages existing technology and standards to reduce risk and time-to-market. Its point-to-point switched architecture provides wide links for performance as well as expansion and connectivity. This scalability and expandability is a substantial benefit over the shared-media approach of existing interconnects.


From a reliability perspective, both Serial Attached SCSI and SATA will provide solutions consistent with their parallel counterparts. When cost is the primary design consideration, a SATA configuration is indicated, providing a bounded solution and modest performance at a modest price. For mission-critical applications that require increased availability, scalability and performance, Serial Attached SCSI is the answer. Its single infrastructure provides access to both multiple hosts and multiple paths, serving a broad range of applications and uses. Mixed pools of storage can meet cost objectives with high-capacity SATA drives for near-line devices, archival storage and backup, as well as high-performance Serial Attached SCSI drives for transaction-based applications.

Fibre Channel will continue to evolve for use in very high-end large-enterprise storage configurations, offering 16 million addresses (public loop) and longer cabling distances appropriate for complex SAN applications. Bridging between a Fibre Channel SAN and Serial Attached SCSI configuration is a straightforward design process, since they share the same SCSI packet formats. In configurations where long distance and public loop are not needed, consider using Serial Attached SCSI as a device-level interconnect.

Figure 7:  Angular amplification for a grating of 1200 grooves/mm at l = 632.8 nm

As the mirrors are continuously oscillating, it is not possible to permanently address one data page of memory. We need to synchronize the AOD and the mirrors. With synchronization, the angular-encoding problem becomes a time-encoding problem. By knowing mirror parameters such as amplitude of deflection and oscillating period, it is possible to control the switching time of the AOD. This allows us to access one defined mirror, which lets us address a desired position on the memory. With the AOD we can redirect the laser beam on a chosen mirror at a given time.

The limiting factor of the system is not the commutation time of the digital direct synthesizer (DDS), which controls the acoustic frequency. System limitations depend on the fill factor t , which depends on the velocity of the acoustic wave (650 m/s for a shear wave with an incident angle of 48º in TeO2 ), and on the size of the optical aperture of the acousto-optic cell. In our case the fill time factor is about 15 µs, so we can consider the mirror to be fixed relatively to the AOD.

The multi-resolution decomposition of a function is similar to passing the signal through a bank of orthogonal filters. In signal-detection applications, a signal in the presence of noise is decomposed with the wavelet transform. A wavelet matched to the signal would produce a sharper peak in the time-scale space as compared to standard non-matched wavelets. The sharper peak is the result of the similarity between the shape of the wavelet and the signal to be detected. However, this requires the design of a suitable wavelet for a given application. The design techniques developed to date do not specifically address this need for maximizing correlation of the designed wavelet with a specific signal.

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