Global Sources
EE Times-Asia
Stay in touch with EE Times Asia
EE Times-Asia > Embedded

Voice over IP in the computer telephony (CT) server

Posted: 29 Jun 1999 ?? ?Print Version ?Bookmark and Share

Keywords:ct server? in? intelligent network? somo? small office medium office?


82 IIC-Taipei ? Conference Proceedings System Level Integration for Mobile PCs Introduction Today's PC industry is supported by various system configura- tions for mobile PC's: (a) Standalone CPU, Northbridge, South bridge, and peripheral components, (b) Integrated CPU's with companion I/O and peripheral components, (c) Fu- ture generation mobile PC based on a single chip PC concepts will be explained. Mobile PC performance issues: Power, Battery life, system speed, and bus latency issues will be discussed. The demand for Mobile applications: StreamingAudio,Video, 1394, Modem, LAN, DSL, DVD, etc. will be addressed to highlight the advantages of single chip mobile PC. Mobile PC card bus interface, Remote wake-on- LAN, Wake-on-ring, boot integrity services, and problem resolution implementation details will be presented. Today's personal computers continue to demand greater bandwidth and shorter response time from the Input/Output (I/O) and Graphics/Video (G/ V) buses. The PC internal system bus demands are increasing due to StreamingAudio,Video, 1394,Mo- dem, LAN, DSL, DVD, and Graphics etc. A high performance PC must have balanced system archi- tecture with equally good performance in the pro- cessor, graphics, and input and output (I/O) buses. The present PC I/O buses are limited to asynchro- nous traffic. Standalone CPU based mobile PC ver- sus Single Chip mobile PC technical merits will be presented. Detailed mobile PC requirements and how the single chip integration supports for mobile PC/ IA performance issues will be addressed with vari- ous practical mobile IA applications. Mobile/IA System Configurations Mobile system configurations: normal (a) Standalone CPU, Northbridge, South bridge, and peripheral components, (b) Integrated CPU's with companion I/O and peripheral components, (c) Fu- ture generation mobile PC based on a single chip PC concepts will be explained. This is a single chip mobile PC/IA configuration, where the processor, memory controller, graphics con- troller, and peripheral components are integrated. Mobile System Applications Streaming Data Transfers: A technique for transferring data such that it can be processed as a steady and continuous stream. Dr. Venkat Rayapati Chief Systems Architect National Semiconductor Corporation 83IIC-Taipei ? Conference Proceedings Streaming technologies are becoming increasingly impor- tant with the growth of the Internet because most users do not have fast enough access to download large mul- timedia files quickly. With streaming, the client browser or plug-in can starts displaying the data before the entire file has been transmitted. For streaming to work, the client side receiving the data must be able to collect the data and send it as a steady stream to the application that is pro- cessing the data and converting it to sound or pic- tures. This means that if the streaming client re- ceivesthedatamorequicklythanrequired,itneeds tosavetheexcessdatainabuffer.Ifthedatadoesn't come quickly enough, however, the presentation of the data will not be smooth. There is a number ofcompetingstreamingtechnologiesemerging.For audio data on the Internet, the de facto standard is Progressive Network's RealAudio. Data transfer rate is the amount of data trans- ferred from one place to another or processed in a specified amount of time. Data transfer rates for disk drives and networks are measured in terms of throughput. Typically, throughputs are measured in Kbps, Mbps and Gbps. Mobile infor- mation appliances have wide range of applications, for example:WebPAD, handheld devices, PalmAs- sistant Devices etc. Mobile System Design/Performance Issues Ease of Use: For consumer mobile devices must be easy-to-use and deliver similar graphic resolu- tion and text imaging to that of the magazines. A well-designed GUI is of critical importance for mobile PC/IA devices. However, given the given the broad range of mobile device forms and func- tions, the user interface must take into account several applications and usage models. For ex- ample: WebPAD should be able to use for several applications: Email, web browsing, home shop- ping, and magazine reading etc. User interface of the current mobile PC has several limitations. In order for an operating system to have differ- ent user interfaces for different applications, but maintains consistency of adapting the sameAPI for manymobileapplications.OSflexibilityisalsovery important, for example: QNX, VXworks, Win CE and Linux etc. Power: Mobile/IA processors core operating volt- ages range from 1.8V to 2.7 V, depending upon the process technology and design considerations. Some of the IA applications demand for very low operating core voltage less than 12 hours active usage plus standby upto 72 hours. For Information Appliance (IA) devices follow the same path from 2 hours to 6 hours, in future the requirement is >12 hours minimum. For example one of the major practical limitation for portability PC/IA devices. Mobile PC/IA device size and form factor are critical user requirements. Mobile I/A System Power Dissipation 84 IIC-Taipei ? Conference Proceedings Hardware form factor reduction is practically viable if move towards system level integration. A single chip mobile PC/IA device solution will meet the end user requirements. The Bat- tery life depends on the following factors: ? System CPU clock speed ? System CPU Duty cycle factor ? System OS controlling and configuration features ? System Bus operational modes ? System Power management ? System operational Requirements All these factors can be controlled, and their impact can be minimized through a well-controlled hardware and software design process. Mobile/IA System Speed ? Mobile note book processor speed range from 233 Mhz to 500 Mhz ? MobileWeb/Internet PAD devices processor speed range from 100Mhz to 266 Mhz ? Mobile handheld devices processor speed range from 100 Mhz to 166 Mhz ? Mobile IP phones processor speed range from 90 Mhz to 133 Mhz ? Mobile student PAD/traveler PAD processor speed range from 100 Mhz to 166 Mhz The processor core speed depends on the application imple- mentation, and scalability. Form Factor: Mobile PC/IA device design, and system soft- wareisinfluencedbythedevicefunctions.Forexample:WebPAD deviceneedstomeetdifferentconnectivityrequirementsforcable, DSL, and modem etc. The Web PAD user interface is very criti- cal to enable email, FTP, web browsing, and home shopping ap- plications. The mobile PC/IA device form factors depends on the following considerations: Web PAD size, display resolution, stylus, PCMCIA slots, batteries, connectors, and so on. Every- thing that contributes to the form factor trade-off's. As the mo- bile device market grows, customer diversity increases, the vari- ety of functions, and the variety of devices will increase. Inalllikelihood,consumersusemoremobilePC/IAsolutionsin the information transfer between the home office and small office applications. The implication for software system is that it must be abletomigrateacrossthesedevices,andenableinteroperability.Some examples related to system software must adapt: ? TFT vs. DSTN screen resolution ? Input modes of operation: Stylus, keyboard, hard icons etc ? Port configurations: Serial, PCMCIA, USB, ? Connectivity: Blue-tooth, DSL, HPNA, Cable, 56K modem etc The mobile PC/IA device should be flexible enough to adapt to these configurations and provide option for future expansion. System Internal Bus and Latency: A collection of wires through which data is transmitted from one part of a computer to another.You can think of a bus as a highway on which data trav- els within a computer. When used in reference to personal computers, the term bus usually refers to internal bus. This is a bus that connects alltheinternalcomputercomponentstotheCPUandmainmemory. There's also an expansion bus that enables expansion boards to access the CPU and memory. All buses consist of two parts -- an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about where the data should go. The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits of data. Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred faster, which makes applications run faster. On PCs, the old ISA bus is being replaced by faster buses such as PCI and USB etc. Nearly all PCs made today include a local bus for data that requires especially fast transfer speeds, such as Video data. The local bus is a high-speed pathway that connects directly to the processor. Several different types of buses are used on person- nel computers. System Bandwidth: The amount of data that can be transmit- ted in a fixed amount of time. For digital devices, the band- width is usually expressed in bits per second(bps) or bytes per second( B/S. For analog devices, the bandwidth is expressed in cycles per second, or Hertz (Hz). Bus bandwidth is calculated using the formula provided below: Mobile I/A System Bus Mobile/IA System Battery Performance 85IIC-Taipei ? Conference Proceedings Bus bandwidth = Bus Frequency* Bus width/cycles per transfer The bandwidth is particularly important for I/O devices. For example, a fast disk drive can be hampered by a bus with a low bandwidth. This is the main reason that new buses, such asAGP, have been developed for the PC. Latency In general, latency is the period of time that one component sits idle while waiting for an other to deliver. Latency, therefore, is wasted time. For example, in accessing data on a disk, latency is defined as the time it takes to position the proper sector un- der the read/write head. Latency depends on several factors ? Arbitration mechanism ? Bus operational modes ? Point-to-point vs point-to- multi-point ? Isochronous data support Quality of Service (QOS) The PC system I/O and G/V bus need to ensure the Quality of Service (QOS), system bus QOS term that specifies a guaran- teed throughput level. One of the biggest advantages of isoch- ronous bus over competing technologies such as PCI, AGP is that it supports QOS levels. This allows isochronous system bus providers a guarantee to their customers that end-to-end latency will not exceed a specified level. System Memory Bandwidth The mobile/IA devices memory bandwidth and processor per- formance relationship is expressed through this formula: Mobile /IA CPU performance = K1 (memory system bandwidth) = K1 (memory data rate) And Mobile /IA CPU performance = K2 (memory system capacity) = K2 (memory density) The memory controller using the LVDS interface supports very high data rates from 400 Mbits/sec to 1.0 Gbit/sec. LVDS interface does not require any significant changes to the DRAM cell architecture versus other memory controller configurations. System Power Management: Mobile/IA system power man- agement allows a system to consume less power, but still be fully operational in a short period of time. To reduce power consumption, more and more mobile/IA systems are being man- aged into low power states. Therefore, consideration must be given to which functions are reasonably available in low power states, how functions react as the system transitions between power states, and how the system returns to a higher power state which provides the full set of management capabilities. This enables low power consumption and improved end-user experience when starting up (really `Waking up') a system. Mobile/IA systems also capable of being awakened by a com- munications event if they are connected to a communications link. Mobile/IA system can support wake-on ring, packet fil- tering, bus power management etc. System Reliability: Mobile users expect their devices to respond instant response, no matter what happens in the system con- figuration. For example, when the user is updating his appoint- ment schedule, the device must be able to receive an incoming fax or call from the pager in the background. This simultaneous operation must be transparent to the user, and the system must operate reliably. Meeting the end user expectations poses a particular challenge in the system hardware/ software design. The OS must be so- phisticated enough to handle multiple complex tasks and yet still work with minimum system memory requirements. Mo- bile systems require multi-tasking and multi-thread applications support. The system design must adhere to more stringent en- vironmental requirements for the mobile devices. Overall the mobile PC/IA devices have to support more robust design require- ments to ensure the instant system avail- ability, reliable operation at all times, and low cost maintainability functions. Mobile/IA System level Integration Single Chip Mobile PC/IA Requirements The single chip PC/IA product solution re- quirescomplexsilicontechnologyintegration: ? CPU, core logic, and memory controller ? Analog and mixed signal device inter faces ? Advanced Packaging technology to enable low ESD/Latch-up ? Low EMIC/EMC ? Low power ? Enables multiple applications Mobile I/A System Power Management LVDS Memory Controller Interface for Mobile System 86 IIC-Taipei ? Conference Proceedings Single Chip Implementation Overview Mobile/IA core processor operates from 200 Mhz to 300 Mhz or above, which integrates with memory controller, graphics/video bus and I/O bus, and super I/O interface compo- nents into a single chip. Mobile/IA System re- quired to support low voltage, very complex form factor, and operate at moderate system speeds upto 300 Mhz or above, depending on the application. In order to accomplish the above mentioned design factors, we need to very robust signaling scheme to support graphic/video bus, I/O bus, and memory con- troller interface. Our proposal describes the LVDS implementation. Proposed LVDS Implementation The LVDS signaling is proposed be- cause it has all the characteristics nec- essary as explained previously. Pro- posed LVDS signaling scheme for the isochronous bus are explained as fol- lows: What is LVDS? ? LVDS [Low voltage diffrential sig- naling] an electrical standard for com- municating high speed digital data (usually 87IIC-Taipei ? Conference Proceedings Acknowledgements The author would like to thank the following team members: Baljeet Grewal, Jason Kim, John Mallard and John Goldie for their support and feedback. References 1. IEEE Micro Nov/Dec 1997 2. 394 HCI Open Host Controller Interface Specification, 1997 3. P1394a Draft Standard for High Performance Serial Bus ( Supplement) , 1998 4. IEEE 1394 b Draft Standard for High Performance Serial Bus, 1998 5. Preliminary Draft of Accelerated Graphics Port Interface Specification, 1997 6. PCI Local Bus Specification, 1995 & 1998 7. IEEE Standard for a High Perfor mance Synchronous 32-bit Bus:MULTIBUS II, ANSI/IEEE Std 1296 8. IEEE Standard for Low-Voltage Dif ferential Signals (LVDS) for Scalable Coherent Interface (SCI) - IEEE Std 1596-1996 Acronyms PCI Peripheral Component Interface USB Universal Serial Bus ISA Industry Standard Architecture expansion bus built into the IBM PC AT computer AGP Advanced Graphics Port LAN Local Area Network DSL Digital Subscriber Loop DVD Digital Video Decoder I/O Input/Output G/V Graphics/Video CPU Central Processing Unit SM System Memory GB Graphics Bus NB North Bridge ATM Asynchronous Transmission Mode COM Communication Module PC Personnel Computer QOS Quality of Service ROM Read only Memory NTSC National Television System Committee PAL Phase Alteration Line Format LVDS Low Voltage Differential Signaling BLVDS Bus Low Voltage Differen tial Signaling IDE Integrated Device Electronics Tx Transmit Rx Receive PHY Physical Layer ACPI Advanced Configuration and Power Interface BIOS Basic Input/Output System PM Power Management CMOS Complementary Metal Oxide Semiconductor EMI Electromagnetic Interference PCB Printed Circuit Board HCI Host Controller Interface 88 IIC-Taipei ? Conference Proceedings System on a Chip PC/IA Applications Bus Performance issues Common Mode Rejection LVDS PCB Layout Guidelines Examples of mobile/ information appliance device applications: Consumer - WebPAD Internet access device - Internet Digital Set Top Boxes - DVD Players - PC games convergence - Business and Education - Streaming Video Client - Microsoft Hydra WBT/NC clients - The demand for Mobile applications: StreamingAudio,Video, 1394, Modem, LAN, DSL, DVD, etc - Point of Sale (POS) / ATM terminals - Thin Clients

Article Comments - Voice over IP in the computer teleph...
*? You can enter [0] more charecters.
*Verify code:


Visit Asia Webinars to learn about the latest in technology and get practical design tips.

Back to Top