Monday, November 10, 2008

The making of iPhone

iPhone is a complex piece of device carrying multiple functionality, including Touch screen, video, voice, wireless phone, GPS, Internet, Etc. It is more like a hand held computer than a phone.

Special hardware has been added to the iPhone to make it an effective and powerful mobile device. This includes various sensors, such as an accelerometer and proximity sensor, multi-touch capable screen to support gestures, and of course various radios including GSM, Wi-Fi, and Bluetooth.

In this article the chipset used in iPhone are reviewed and analyzed. iPhone consists of two main boards to carry all the hardware component it needs One board is taken from iPod design and contains application processor (CPU), disk (flash memory), motion sensors and Audio amplifier. The second board contains wireless flash memory, multimedia engine, blue tooth, and WiFi.

Architecture

The iPhone runs a mobile build of Mac OS X 10.5 (Leopard), which is built upon BSD Unix and has many similarities to its desktop counterpart.

Apple has built a custom set of user interfaces around the iPhone to accommodate the proprietary hardware sensors and the use of multi-touch. While the desktop version of Leopard contains frameworks for building windows and common controls, the iPhone version of Leopard has replaced these frameworks with a version tailored for creating simple page-like user interfaces, transitions, and finger-friendly controls such as sliders and picker wheels.

Keyboard caches containing usernames, passwords, search terms, and historical fragments of typed communication. Nearly everything typed into the iPhone's keyboard is stored in a keyboard cache, which can stay in memory for sometime even after deleted.

Screenshots of the last state of an application are preserved, taken whenever the home button is pressed or an application is exited. These are used by the iPhone to create aesthetic zoom effects, and often provide several dozen snapshots of user activity.

The iPhone communicates with a computer via an interface called the Apple File Communication Protocol (AFC). This protocol is a serial port protocol that uses the USB Port and cable when it is connected to the computer and is responsible for things such as copying music and photos and installing firmware upgrades.

Wireless Board

EDGE Baseband Processor - Infineon PM8876 - S-Gold2
S-Gold2 is an advanced EDGE modem technology combined with latest multimedia functions. It is centered around ARM 926 CPU to provide horsepower for complicated, power hungry, software applications. Additionally it hosts on-chip the hardware needed for multimedia features, such as high resolution color display interface, dedicated camera interface for supporting camera applications for up to 2M Pixel, hardware support for MPEG4 encoding, Java hardware accelerator, and large number of connectivity peripherals.

S-Gold2 supports number of applications such as; still pictures and videos, 3D gaming, Java applications, and video streaming. S-Gold2 provides connectivity to Bluetooth, RF radio, WLAN, and A-GPS modules.

Some of it's key modem features include, GSM, E-GPRS, and GPRS multimedia phones, MP3 decoder, Echo cancellation, and Noise reduction.

EDGE MCP including peregrine SP4T RF switch

GSM/EDGE Power Amplifier - Skyworks Sky77340-13

WLAN - Marvel 90-nm 88W8686
This chip carries the WiFi functionality.

Bluetooth - CSR 41B14 - BlueCore4ROM
The bluetooth chip cames from CSR (Cambridge Silicon Radio).

GSM RF Transceiver - Infineon M1817A11

Wireless Flash Memory - Intel PF38F1030W0YTQ2
Wireless NOR Flash Memory (32Mbytes NOR + 16Mbytes SRAM)

iPOD Board

Application Processor (CPU) - Samsung/ARM S5L8900B01 (512Mbit SRAM dice)
The iPhone uses the ARM (advanced RISC machine) processor architecture, originally developed by ARM Ltd. In contrast, a majority of desktop machines use the Intel x86 architecture.

Early reports of the CPU clock speed put the iPhone’s ARM processor running at about 400 MHz with a bus speed at 100 MHz (Hockenberry). It is speculated that the ARM CPU can run at 600 MHz or more but is underclocked to provide for heat dissipation and battery life.

Flash Memory (Disk) - Samsung 65nm 8Gbit NAND Flash (K9MCG08U5M)
This chip is used as the main storage medium in computing and other digital applications. iPhone uses this flash memory just like a hard disk and partitions it, which is based on the Unix OS conventions as well. In order to store files on a hard disk, that raw physical device must first be prepared with partitions, or contiguous sections of a disk to store common groups of information.

There are two partitions on the iPhone. The first partition is 300 MB in size and is the system or root partition(not to be confused with the root folder which will be seen in the second partition). This partition contains the operating system and the default applications that are delivered with a factory fresh iPhone. for the life of the iPhone and contains the default applications and the untampered OS of the device. It contains most of the followings: SMS, Calendar, Photos, Camera, Youtube, Stocks, Maps, Wseather, Clock, Calculator, Notes, Setting, iTunes, Phone, Mail, Safari, and iPod.

The remaining space of the hard disk is partitioned as the user-space (or media) partition. This space is where all music, videos contacts, SMS etc are stored.

Samsung is planning to build 64Gbit multi-level cell NAND flash memory chip based on a 30nm process in 2009. For those not versed in the arts of bits-to-bytes conversion, that's a single chip capable of storing 8GByte of data. A maximum of 16 64Gbit flash devices can be combined to make a 128 Gigabyte memory card that can store 80 DVD resolution movies or 32,000 MP3 music files.

Stereo Audio Codec Processor - Wolfson WM8758BG
This chip is the I2S voice codec. A very good sound quality part, even better than used in iPod.

Motion Sensor - STMicroelectronics LIS302DT
This chip has a sensing element, capable of detecting acceralation using a dedicated process to produce internal sensors and actualtors in silicoln. It is capable of detecting free-fall, motion activated functions, and vibration monitoring.

Apple (NXP) Power Manager
This chip, from NXP (Philips before), is the power manager with the switching power supplies.

USB Battery Charger - Linear Technology 4066
This chip is maily used to charges Single Cell Li-Ion Batteries Directly from USB Port or 5v wall adapter.

Other Parts

Touch Screen: Balda
The Touch Screen is from German manufacturer Balda. There is a SPI multi-touch I/O controller from Broadcom (BCM5973A)

Camera
The camera has a Micron 2Mpixel sensor (MT9D112D00STC).

Display
The display is 320x480, can be a Samsung or AUO module.

Battery
The battery is a Li-IonPolymer 3.7V.

About me:
bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Hi-Tech site.

Tuesday, October 21, 2008

The need for Edge QAM

The "Edge QAM" came to existence with Switched Digital Video (SDV). Prior to SDV, QAM modulation was used in cable plants to carry all digital cable services. It sits in hub and is used to move video, voice and data from headends to homes. Each QAM, in a rack-mounted metal box, is capable of carrying 38.8 Mbps of downstream data which is equivalent to one analog channel, 2-3 High-Definition (HD) streams, or 10-12 Standard-Definition (SD) digital video streams.

Even though all QAM use the same architecture, each QAM is dedicated to a specific service. For example, one QAM is used to move Web pages to your cable modem, while another one is assigned to move the digital video channels to your HDTV. Likewise, a QAM dedicated to video on demand (VOD) could not be used for Switched Digital Video (SDV). Hence, the cable operators had to purchase QAM based on services they wanted to provide.

This fundamental issue, created the need for building "Edge QAM", which by definition is capable of carrying both VOD and SDV streams. The next generation Edge QAM will be able to carry IP related services, such as data (Internet service) and voice (VoIP service) in addition to VOD and SDV.

The Players

Some of major vendors of Edge QAM are, Scientific Atlanta/Cisco, RGB Spectrum, Arris, BigBand Networks, Harmonic, Motorola.

The cable operator evaluate the Edge QAM based on three objectives, Price, Density and Openness. With respect to price, currently the QAM are in range on $250. The goal is to reduce to price to $25 range. With respect to density, currently one rack-mounted unit can take between 8-24 QAMs. The cable operators expecting new innovation will increase the density which will ultimately bring the price down. With respect to openness, the cable operator are looking for vendors that eventually can adopt standards protocols.

Functionality

In order Edge QAM move VOD and SDV streams to homes, it needs to communicate with two other device in the network. The "Session Manager", which sets up the linkage between VOD/SDV server and Set-Top-Box and acts upon selecting a channel by viewer. The "Resource Manager", which determines which QAMs are supposed to be moving what stuff and to where. Also see SDV Architecture and IPTV - The software behind SDV for more information.

Currently, the devices are tightly coupled, meaning that they work on propriety protocols. Each manufacturer has developed it's own protocol which makes cable operators bound to purchase set of devices from same vendor. New standard is underway to make the communication protocols between devices consistent. This will create competition among vendors to cut the prices, since cable operators will be able to purchase their devices from multiple vendors. A switch from vendor, a resource manager from another and a session manager from yet a different vendor.

About me:
bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Hi-Tech site.

Thursday, October 9, 2008

Launching and maintaining successful IPTV services

IPTV operation is booming worldwide at a rapid pace. In Europe alone the IPTV subscribers is more than 1.535 millions. Ever since YouTube began demonstrating the potential of the Internet medium, everyone is racing to launch IPTV, which will eventually replace traditional television broadcasting.

Following some fundamental guideline can help launching and maintaining successful IPTV services. The following outlines some of these guidelines:

Simplicity. Make the services very simple and easy to use. Providing innovative services, but as simple as possible will appeal to a wider audiences covering youngest, Internet savvy generation through oldest grandpa and grandma generations.

Packaged Services. Triple-Play package provides TV, Internet and voice all in one deal. The triple-play can also bolsters operational continuity.

Content delivery Services.

Content delivery to TV, PC and Mobile devices
Exclusive content and features for certain viewers with common interest, such as major/minor league football games
Interactive options to access real-line match stats, such as goal count, attempts, and cards
On-demand titles
International television programs
Ability to transfer downloaded content to mobile device
Hybrid IPTV/Satellite service

Quality of Services. Quality of Service is one of the most important reason for successful IPTV operation. People will not tolerate poor quality of service or any quality inferior to other pay-TV services such as satellite.

Super fast broadband network. FTTH (Fiber-To-The-Home) provides much more bandwidth and enabling ability to offer high-definition, added-value services and whole home distribution. ATT recently introduced Total Home DVR, which allows delivery of five simultaneous high-definition MPEG-4 video streams around the home - two live and three recorded from DVR, for it's IPTV service via copper VDSL network.

Thursday, October 2, 2008

Attacking IPTV QoE issue

One of the most critical challenges of IPTV cable operators is to provide quality of service to their viewers. Since IPTV uses IP networking mechanism to reach the subscribers, many artifacts of Internet can cause poor Quality of Experience (QoE) to viewers, which leads decreased customer satisfaction and increased customer complains through call centers. It is very essential for IPTV operators to resolve QoE issues, in order to increase customer satisfaction and be able to maintain customers for long run.

A recent study shows that QoE accounts for more than 25% of IPTV adaptation obstacles. The other obstacles include, high subscriber fee - equipment (19%), lack of completing programs (15%), satisfied with existing programs (12%), compelling offers from competitions (11%), high subscriber fee - content (11%), poor customer service and support (6%), others (2%).

One of the most common culprit of poor QoE is packet loss, a normal occurrence in any IP network. packet loss happens for many reasons in variety of different locations. There is no way for an IPTV operator to protect the network against all possible causes and different location of packet losses. many packet losses occur in last mile which makes it even more difficult for IPTV operator to detect and address the problem. The following outlines some of common reasons for packet loss:

Environmental effect, such as home appliances and electrical public transportation systems
Congestion which normally happens on prime time viewing time
Bad wiring at customers premises
Heterogeneous network equipment
Out of sequence packets
Duplicate packets
Core network issues, such as lost network links and route convergence

Some other reasons which can impact QoE follows:

Mismatch TSID to service group configuration
RF interference on specific frequency/QAM channels
Reed-Solomon error correction efficiency
Over-subscription/blocking of SDV QAM channels
Mini-carousel distribution and configuration
Grooming/muxing issues at the edge QAM device

Solving packet loss issue

One of the simplest, most effective, and least expensive way of correcting packet loss issue is to deploy a layer of software that detects and corrects the packet losses on the fly from the video stream that is being received by customer. The software recovers the packet losses using an algorithm that generates the missing packets and sends them along with the original video content to customer set-top-box which in turn repairs the video before showing it on the customer's monitor.

The followings outlines some of the benefits this software solution that can bring to IPTV operators:

Scalability - once installed on the headend, it supports an unlimited number of set-top-boxes
Fixes all loss types, regardless of single or multiple events or where it comes from
Configurable network overhead, with granularity of one packet
Configurable latency

Tuesday, September 30, 2008

IPTV, the next generation TV

IPTV is becoming more and more popular among cable and telco operators as demand for it is growing very rapidly. IPTV not only provides better advertising solution for the cable operators, it makes it easier for cable operators to be more innovative on pay-TV services. IPTV leverages the IP network to deliver video content to TV viewers using set-top-box, and providing picture quality services.

According to a new research by Gartner, reported on September 25, 2008, the worldwide subscription to IPTV is growing rapidly. Gartner projects the IPTV subscripers will reach 19.6 millions by end of 2008, an increas of 64.1% from 12 millions in 2007.

Worldwide IPTV revenues are projected to total US$ 4.5bn in 2008, an increase of 93.5% from an estimated US$ 2.3bn last year, and go on to reach US$ 19bn in 2012. Approximately 1.1% of households worldwide are expected to subscribe to IPTV services in 2008, and Gartner predicts that global penetration will reach 2.8% by the end of 2012.

One of the reasons for this rapid demand is that the consumer video consumption is increasingly big time.

Portal-based Internet video providers such as YouTube and Joost and over-the-top video providers like Amazon's Video on Demand are also presenting competition for IPTV operators, with some developing their own combined set-top box and video download service, like Netflix and Blockbuster.

Western Europe is found to be the region with the largest number of IPTV subscribers. North America, on the other hand, is identified as the largest market for IPTV revenue.

IPTV News

Sunday, September 21, 2008

Elements of a Web-based Services

Designing web sites that are responsive to customer needs is a critical prerequisite for the success of online services. In this article three primary development aspects of Web-based services are discussed. The common style and architecture used to design Web-based services, Software development methodology, Software management methodology and Internet Routing Protocol.

Building Web Services

One of most common methods of building a Web-based services is REST. Many common Web-based services, such as book-ordering services, search services, online dictionary services, etc - are REST-based Web services. REST is an architecture style (not standard) of networked systems and stands for Representational State Transfer. It was first introduced by Roy Fileding in his PhD dissertation.

The Web is comprised of resources. REST style refers to transferring Web activities from one resource to another till what user (client) is looking for is accessed and provided to user. For example, when a client is looking for a piece of information from a website, by definition of REST, the Web activities present series of hyperlinks that user traverse through till the last piece of information user is interested is displayed. Each of these hyperlinks is a representation of a resource which basically places the client application in a state. Thus, the client application changes (transfers) state with each resource representation.

Although the REST is not a standard it uses the following Web standards

HTTP
URL
XML/HTML/GIF/JPEG/etc (Resource Representations)
text/xml, text/html, image/gif, image/jpeg, etc (MIME Types)

REST hides the implementation details (e.g., using Java servlets or CGI to implement a Web service) from the client and provides only the "big picture" of the Web to client. The following outlines the characteristics of REST:

Client-Server: a pull-based interaction style: consuming components pull representations.
Stateless: each request from client to server must contain all the information necessary to understand the request, and cannot take advantage of any stored context on the server.
Cache: to improve network efficiency responses must be capable of being labeled as cacheable or non-cacheable.
Uniform interface: all resources are accessed with a generic interface (e.g., HTTP GET, POST, PUT, DELETE).
Named resources - the system is comprised of resources which are named using a URL.
Interconnected resource representations - the representations of the resources are interconnected using URLs, thereby enabling a client to progress from one state to another.
Layered components - intermediaries, such as proxy servers, cache servers, gateways, etc, can be inserted between clients and resources to support performance, security, etc.

Web Service Design using REST method

Identify all of the conceptual entities that you wish to expose as services.
Create a URL to each resource.
The resources should be nouns, not verbs.
Categorize your resources according to whether clients can just receive a representation of the resource.
All resources accessible via HTTP GET should be side-effect free, that is, invoking the resource should not result in modifying the resource.
Put hyperlinks within resource representations to enable clients to drill down for more information, and/or to obtain related information.
Design to reveal data gradually. Don't reveal everything in a single response document.
Specify the format of response data using a schema (DTD, W3C Schema, RelaxNG, or Schematron).

Software Development Methodology

Since the Web-based services are normally based on customer requirement and is subject to change frequently, Agile method is commonly used to develop software. Agile means being able to quickly change direction. Agile method is a method opposed to waterfall model, in which software development is seen as flowing steadily downwards through the phases of requirement analysis, design, coding, testing, integration and maintenance.
Agile methods focuses on working software as the primary measure of progress. It promotes the iterations in software development life cycle and chooses to do things in small increments, with minimal planning, rather than plan at length. This allows responding to the customer needs much faster by adapting changes quickly into the development cycle and minimizing the overall risk. Also the project stakeholders get more involved in the process and at the end of each iteration are updated to provide feedback.

In agile development method, a deliverable and shippable software is developed in a short time frame, also known as "timeboxes". The software developed during each timebox is referred to as an iteration, which normally takes 2-4 weeks. Each iteration goes through full software development cycle, including planning, requirement analysis, design, code, unit test, integration test, QA, demo to product stakeholders and documentations to prepare software delivery to customers. The goal of agile development is to have an available release with minimum bugs at the end of each iteration. It may not add a new functionality to the software. At the end of each iteration, the stakeholders re-evaluate the project priorities with respect to revenue and return on investment. Every agile team has a committed customer representative who makes himself available for developers to answer mid-iteration problem-domain questions.

Managing Agile Software Development Projects

Scrum is one of the methods commonly used to manage agile software development method.

Scrum is a process that includes a set of practices and predefined roles. The main roles in Scrum are the ScrumMaster (project manager), the Product Owner (stakeholders representative), and the Team which includes the developers.

During each development period (sprint), which usually takes two to four weeks, the team creates an increment of a shippable software. The feature set for each sprint is prioritized by Product Owner who informs the team of the items that he wants completed. The team then determines how much of this they can commit to complete during the next sprint.

One of Scrum's biggest advantages is that it is very easy to learn and requires little effort to start using. Following are some general practices of Scrum:

Customers become a part of the development team.
Like all other forms of agile software processes, Scrum has frequent intermediate deliveries with working functionality. This enables the customer to get working software earlier and enables the project to change its requirements according to changing needs.
Frequent risk and mitigation plans developed by the development team itself.
Frequent stakeholder meetings to monitor progress – Balanced (Delivery, Customer, Employee, Process) Dashboard updates – Stakeholders' update – You have to have Advance Warning Mechanism, i.e. visibility to potential slippage / deviation ahead of time.
No problems are swept under the carpet. No one is penalized for recognizing or describing any unforeseen problem.

Internet Routing Protocol

To connect a client to a Web server, series of routing protocols are used to locate and reach the Web server that can provide the service to client. Some of the most common used protocols are BGP and OSPF.

BGP
Border Gateway Protocol (BGP) is the routing protocol used to exchange routing information across the Internet. BGP is an exterior routing protocol and as such is concerned with routing between networks rather than within them (this is the domain of the interior routing protocols such as RIP, OSPF).

BGP is designed to efficiently manage a large, multi-organisation routing table, such as the global Internet routing table. BGP uses TCP as a reliable transport medium and so it needs only to send out updates when necessary rather than continuously. BGP also has many features to manage routing announcements which are not needed in an interior routing protocol.

On a Cisco router you can configure BGP using the following commands:

router bgp ASN
neighbor neighbor remote-as remote-AS
neighbor neighbor filter-list 1 out
!
ip as-path access-list 1 permit ^$

The main thing to remember is to announce only the networks that you originate or are providing transit to. In general this means applying an AS path filter so that only the NULL path is announced. This avoids announcing all of AAPT's routes to your other provider(s) and then having them use you for transit, which could be expensive! AAPT uses BGP communities (public and private) to control routing announcements, i.e. the routes we send to customers as well as the routes we send to our peers and providers.

OSPF
Open Shortest Path First (OSPF) is an interior routing protocol used within larger autonomous system network in preference to the RIP (Routing Information Protocol), an older routing protocol that is installed in many of today's corporate networks.

Using OSPF, a host that obtains a change to a routing table or detects a change in the network immediately multicasts the information to all other hosts in the network so that all will have the same routing table information. Unlike the RIP in which the entire routing table is sent, the host using OSPF sends only the part that has changed. With RIP, the routing table is sent to a neighbor host every 30 seconds. OSPF multicasts the updated information only when a change has taken place.

Rather than simply counting the number of hops, OSPF bases its path descriptions on "link states" that take into account additional network information. OSPF also lets the user assign cost metrics to a given host router so that some paths are given preference. OSPF supports a variable network subnet mask so that a network can be subdivided. RIP is supported within OSPF for router-to-end station communication. Since many networks using RIP are already in use, router manufacturers tend to include RIP support within a router designed primarily for OSPF.

About me:
bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Hi-Tech site.

References
REST-Web-Services
info-connect

Tuesday, September 9, 2008

iPod Nano, the Genius

Apple just announced the new version of iPod Touch, iPod Nano and iTunes 8. These new products, as announced on 9/9/08, all include a new features called "Genius", which is a new technology from Apple to create playlists based on the song you're listening to and the music in your library in an easy way.

The fourth-generation iPod Nano is only 0.2 inches thick, the thinnest player Apple has ever made. The screen size, however, is kept as previous model. In addition a new accelerometer is built into Nano to enable resizing photos and menus based on the orientation of the player which was available on iPhone and iPod Touch previous models.

The new cool feature "Shake to shuffle", which senses when you shake the player and automatically enters into the shuffle mode. The "Shake to shuffle" feature also uses accelerometer technology.

The user interface of new iPod Nano has much improvements that attempts to solve some of the limitations the Clickwheel has in the iPod Touch and iPhone UIs.

The iPod Nano can play 24-hours of music or four hours of video in a single charge. The prices are set for $149 for an 8G and $199 for 16G.

The new model of iPod Touch has a new look with a curved back, similar to iPhone 3G, kept it's stainless steel as previous iPod Touch model. It's being advertised by Apple as very capable when it comes to play games. The new iPod Touch also has volume control on the side of unit and comes with it;s own build-in speakers. Another fun feature of iPod Touch is a build-in sensor for the popular Nike + iPod system. Unlike the previous model, you can get the shoe attachment and activate the included software.

iPod Touch can play 36 hours of music and six hours of video on a single charge. The prices are set as $229 for 16G and $399 for 32G. The previous owners of iPod Touch may get all new feature by software upgrade and no need to purchase a new unit. The update is free for users who already have the 2.0 version, and $9.95 for users with version 1.

More than 160 million iPods have been sold worldwide since 2004, and sales of the device account for almost 75 per cent of the MP3 player market.

Architecture

The iPod Nano uses general-purpose integrated circuits (IC) instead of smaller, low-cost custom-developed chips, possibly to reduce time-to-market. This design, however, increases the number of electronic components and increases the cost. It uses PortalPlayer PP5021C "system on a chip" with dual embedded 80 MHz ARM 7TDMI processors. It also uses "surface mount technology" which was employed in mobile phones in 2005.

Surface-mounted technology is a method for constructing electronic circuits in which the components are mounted directly onto the surface of PCB (Printed Circuit Board).

PortalPlayer is a fabless semiconductor company that supplies system-on-a-chip semiconductor, firmware and software for personal medial players. PortalPlayer was acquired by NVIDIA on January 2005.

Past Incidents

In Australia, an iPod Nano flamed up while being charged on a PC.
iPod Nano set a man's pants on fire while he was working in the Hartsfield-Jackson Atlanta International Airport.
In Japan, an iPod Nano sparked while it was still recharging. Apple still is investigating this incident.
Last report came out from Japan in August 2008 indicates that 17 incidents of abnormal overheating with 1st-generation iPod Nano units while recharging, causing the cases to catch fire and burn.

Switched Digital Video (SDV) jargons

IPTV and especially SDV is becoming very hot among all telco and cable operators for numurous benefits they bring to them, including bandwidth allocation, local advertisement, better QoS and QoE. Along with them, these new emerging technologies bring many terminologies and jorgons. In this article, I have collected the most commonly used terminologies in this catorgory from various sources to make it easier to look and understand these terms.

Bulk ncryptor
scrambles the signal in such a way that only the appropriate set-top box (STB) can unscramble it.

DB - Digital Broadcast
Encoded/compressed programs are sent to a subscriber's set-top box (STB), Where they are decoded/uncompressed for playback on a TV. All programs are sent to all subscribers regardless of which programs are actually being watched.

DTH - Direct To Home

DTH Typically refers to satellite TV broadcasting directly to a dish antenna on the roof of a house.

CBR - Constant Bit Rate
Constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant. CBR is useful for streaming multimedia content on limited capacity channels since it is the maximum bit rate that matters, not the average, so CBR would be used to take advantage of all of the capacity.

ERM/SRM - edge resource manager/session resource manager

ERM/SRM server Controls and arbitrates capacity allocation among various application (such as VOD, SDV channels, etc.) and the edge QAM devices. The ERM/SRM keeps a stateful view of the spectrum allocation.

Groomer

Groomer transrates content into a maximum bandwidth, limiting the rate of video bursts.

HE - Headend
HE (equivalent to a telco video headend office, or VHO) is where content acquisition occurs for both the broadcast and on-demand services. The HE is also where most of the backoffice systems reside. (Backoffice systems include billing systems, asset management systems, authorization systems, and so on.)

The headend section of SDV architecture is where the video and Internet feed sources enter the system. It includes the equipment directly connected to the cable company.

Some elements of the headend only flow one way into the system, such as the cable company's video feed. Others, like the applications servers, communicate back and forth with the network to ensure that everything is running smoothly.

HFC

HFC netwrok is the fiber-coax access network for distribution to the subscriber.

IP Network
The IP network transports IP services from the HE to a number of hubs, aggregating a
number of services [for example, video, high-speed data (HSD), and voice over IP] while providing appropriate quality of service (QoS), or priority, for each service class.

MPEG encoders
MPEG encoders convert the raw digital or analog signal into an MPEG format

MPTS - multi-program transport streams

OOB - Out-Of-Band
An out-of-band (OOB) channel provides the STB with basic tuning information, such as a channel map, decryption keys, IP address of the Session Manager, and software upgrades.

QAM - quadrature amplitude modulation
Edge QAM devices: special session-based QAM modulators that receive ingress video traffic through IP (using IGMPv2/v3, etc.) and then route and switch it across the RF/QAM network by interfacing with the SRM/ERM.

QoE - quality of experience
QoE is a subjective measurement of the perceived value of the overall service and customer experience. It is closely tied to QoS but is different in that QoE measures from the point of view of the subscriber. QoE measurements are often done in the form of mean opinion score (MOS).

QoS - quality of service
QoS role is to objectively measure the service delivery by the provider itself.

SDV - swithced digital video

SDV is like DB in that all programs are encoded/compressed. SDV is the first implementation of a broadcast video service in which only requested programs are sent to the group of subscribers (the subscriber group). SDV is the first broadcast video service that requires two-way communication with the subscriber for content selection. Like DB, SDV is sent to a subscriber’s STB; where it is decoded/uncompressed for playback on a TV.

SDV server tracks all of the channel-change requests and viewing patterns, helps broker bandwidth assignments to requested channels, and generates the SDV mini data-carousel.

SDV client: This is special software residing on the set-top box that interfaces with the SDV server and the SDV network.

Splicer
Splicer inserts ads into programming breaks, as needed for a geographical market.

SPTS - single program transport streams

Statmux
Statmux Performs statistical time-division multiplexing.

VOD - video on demand

Content (e.g. a movie) is stored on a server. A subscriber views a list of titles and requests to view a specific title. The VoD system authorizes and streams the requested content to that specific user.

VBR - variable bit rate

VBR allows a higher bitrate (and therefore more storage space) to be allocated to the more complex segments of media files while less space is allocated to less complex segments

The advantages of VBR are that it produces a better quality-to-space ratio compared to a CBR file of the same size. The bits available are used more flexibly to encode the sound or video data more accurately, with fewer bits used in less demanding passages and more bits used in difficult-to-encode passages. The disadvantages are that it may take more time to encode, as the process is more complex, and that some hardware might not be compatible with VBR files.

References:

Gaining Visibility into the Complexities of SDV, By: Gino Dion
IPTV Architectures for Cable Systems – An Evolutionary Approach, By: S.V. Vasudevan, Xiaomei Liu, and Kurt Kollmansberger
Wikipedia

Monday, September 8, 2008

SDV sequence of operations

In this article Switched Digital Video (SDV) sequence of operation is described in details. This sequence can be used as a guideline to program SDV client-server operations. The SDV sequence of operation is classified into two main area: Set-Top-Box (STB) Auto-Discovery Process and Subscriber surfs to a switched channel. All these activities should not take more than 150ms.

For overview of the SDV architecture, see my article SDV Architecture.

STB Auto-Discovery Process
Prior to STB Auto-Discovery, STB is signed onto the SDV network

SDV server (a server that manages STB interactions) streams configuration information out-of-band using data PID
STB is powered on.
STB looks for data PID and gets configuration information including list of SDV frequencies.
STB scans SDV frequencies and finds TSIDs that it happens to see.
STB responds to SDV server with TSID list.
SDV Server identifies STB’s Service Group
SDV server reports Service Group back to STB [ACK].

Subscriber Surfs to a Switched Channel

Source content streams (and is encrypted) through the GigE switches as multicast SPTSs (Single Program Transport Steam)
Subscriber selects a switched channel
Client sends channel change message indicating desired channel and its TSID group. Note: If the channel is already in the mini carousel the SDV client [STB] can tune to it prior to receiving a message back from the SDV server
SDV server determines source details for the requested channel
SDV server requests QAM resources for the selected channel from ERM (Edge Resource Manager that manages edge QAM device) based on TSID group
ERM directs Edge Device to join a multicast stream and bind it to a frequency [QAM], assigning a program number determined by the ERM
Edge Device joins the multicast stream and sends it out the specified QAM using the selected program number
SDV server returns frequency and program number to the STB IP
STB tunes to frequency and program. Subscriber is now watching the selected program.
SDV server updates channel list on out-of-band mini carousel and ‘locks’ the selected channel after a MSO defined time interval
Every five minutes the SDV monitoring server gets raw customer behavior data from the SDV server and QAM usage from the ERM for processing into user friendly reports

About me
bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Hi-Tech site.

Thursday, August 28, 2008

Which Phone to choose - CDMA or GSM

In this article the advantages and features of both CDMA and GSM technology is described, followed by comparison between the two.

CDMA (Code Division Multiple Access) is a channel access method which allows several transmitters to send information simultaneously over a single communication channel and hence multiplexing many users over the same physical channel. This technology is used by cell phone companies to allow many users to share the bandwidth of frequencies.

CDMA is a digital cellular technology that uses “spread spectrum” techniques. Unlike GSM technology that uses TDMA (Time Division Multiple Access), CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence.

CDMA consistently provides better capacity for voice and data communications than GSM, allowing more subscribers to connect at any given time. CDMA technology separates signals from both data and voice and then transmits using wide frequency range. Because of this more space is available for transferring data. This is one of the primary reasons to select CDMA for 3G (3rd generation) as preferred technology.

CDMA is widely used in Asia and in particular South Korea. It has 17% of world cell phone market share.

GSM (Global System for Mobil communication) is the most popular standard for cell phones in the world. According to GSM association, it’s estimated 82% of the global cell phone market uses GSM standard. More than 3 billion people from 212 countries use GSM phones.

GSM is a cellular network. The cell phone users connect to it by searching for cells in the immediate vicinity.

GSM networks commonly operate in four different frequency ranges, 850MHz, 900MHz, 1800MHZ and 1900MHz. In US and Canada 850MHz and 1900MHz are used.
GSM-900 uses 890–915 MHz to send information from the cell phone to base station (uplink) and 935–960 MHz for sending information from base station to cell phone (downlink), providing 124 RF channels (channel numbers 1 to 124) spaced at 200 kHz.

GSM is considered as 2G (2nd generation) cell phone technology for providing digital signaling and speech.

Some of main features of GSM phones are as follows:
• Provides international roaming very common between cell phone users.
• Provides capability to prevent fraud when cell phone is stolen or lost.
• Provides low-cost SMS (short message service), also known as “text messaging” service, as an alternative to voice calls.
• Provides one international Emergency phone number, “112”, which can be used by international travelers to connect to emergency services without knowing the local emergency number.

One of the key features of GSM is the SIM (Subscriber Identity Module), commonly known as a SIM card. The SIM card contains the user's subscription information and phone book. The cell phone user can retain his or her information after switching the phone by removing the SIM card from the old phone and putting it in the new one. Alternatively, the user can also change service provider while keeping the same phone by changing the SIM card. Some service providers block this action by allowing the phone to accept only a single SIM issued by them.

Which cell phone technology to choose, CDMA or GSM

There are many opinions on the advantages and features of CDMA and GSM technologies and which one is a better choice.

The GSM phone vendors claim that GSM is a feature rich system. It has more services and allows more data transfer. On the other hand the CDMA phone vendors claim that CDMA technology is maturing and is capable of providing the same features found on GSM. Some analyst, such as Dell’Oro Group even go further and has declared CDMA already "dead.” They believe because the large service providers like Sprint Nextel and Verizon Wireless, are not spending that much on CDMA and putting all their effort on GSM growth, means that CDMA market is dead.

Nowadays, it is not possible to say that GSM services are better than CDMA. Most of the features, such as, Multimedia messages, video, high-speed Internet access, digital camera and even PDA function can be found on both technologies. The new CDMA 1XRTT technology is more advanced than EDGE (Enhanced Data Rates for Global Evolution) technology from the beginning of 3G generation, allowing higher transfer rates.

The GSM SIM advantage is being challenged by CDMA service providers by allowing users to store their phone book on operator’s database and recovering it when cell phone is lost or stolen. This brings advantage over GSM, in which when cell phone is lost or stolen, phone book recovery is not possible because the SIM card along with the phone gets lost too.

Recently GSM operators are offering SIM backup to counter CDMA database feature.

How cell phone communication works

Communication between base stations and cell phone is established by a negotiation upon call origination. Once communication is established between base and mobile, movement of the cell phone is detected and the service is handed over from one base station to another. One cell at a time services each mobile in the narrowband services.

Cell Phone Network

The cell phone network is large and complicated. This network enables the service providers to provide services such as voice and text messaging. In summary the cell phone network consists of the three main sections:
1. The base Station Subsystem, including the base stations and their controller
2. Network and Switching Subsystems or core network
3. GPRS (General Packet Radio Services) Core network, which allows packet based Internet connections

History

CDMA is a military technology first used during World War II by English allies to block German attempts at jamming transmissions. The allies decided to transmit over several frequencies, instead of one, making it difficult for the Germans to pick up the complete signal. Qualcomm created the first communications chips for CDMA technology and first to commercialize it..

Future Alternatives

Mobile VoIP (Voice over IP) will become an important service in the coming years as device manufacturers exploit more powerful processors and less costly memory to meet user never ending needs.

Glossary

• TDMA (Time Division Multiple Access): works by dividing the spectrum into frequency channels and each user uses each channel for a specific time, to avoid interference.
• CDMA 1XRTT: 2.5G technology which allows data transfers up to 144 Kbps.
• EDGE (Enhanced Data Rates for Global Evolution): Technology promoted by GSM operators. Before migrating to WCDMA, EDGE will allow third generation data and voice access with 384 kbps transfer rate.
• EV-DO: Third generation from CDMA 1xEV-DO technology. "EV" comes from Evolution and "DO" from data-only. It uses a second channel, of 1.25 MHz, exclusively for data transmission. Some countries are already running this standard. In the USA, Verizon and Sprint started this technology in 2004. This technology allows hi-speed Internet access (2.4 Mbps) using the cell phone or using a wireless connection from a laptop or PDA.
• EV-DV: Evolution of EV-DO, but still under development. "DV" comes from data-and-voice. It uses the same channel for transmitting data and voice. The transfer rate can reach 5.2 Mbps.
• WCDMA: Wideband CDMA. Third generation technology that will be adopted by GSM operators. Its European version is known as UMTS (Universal Mobile telecommunication System). It can reach transfer rates up to 2 Mbps.
• 2G technologies can be divided into TDMA-based and CDMA-based standards depending on the type of multiplexing used. The main 2G standards are: GSM (TDMA-based) – used in all countries; IS-95 (CDMA-based), also know as CDMA – used in America and part of Aisa; PDC (TDMA-based) – used in Japan only; iDEN (TDMA-based), proprietary network used by Nextel in US and Telus Mobility in Canada; IS-136 (TDMA-based), also know as TDMA in US.
• 2.5G services enable high-speed data transfer over upgraded existing 2G networks.
• 3G technologies enable network operators to offer users a wider range of more advanced services including wide-area wireless voice telephony, video calls, and broadband wireless data, all in a mobile environment. Additional features also include HSPA data transmission capabilities able to deliver speeds up to 14.4Mbit/s on the downlink and 5.8Mbit/s on the uplink.
• 4G system will be able to provide a comprehensive IP solution where voice, data and streamed multimedia can be given to users on an "Anytime, Anywhere" basis, and at higher data rates than previous generations. Currently there is no commercial 4G but that is being standardized globally, with expected commercial 4G launches starting around 2012-2015.

About me:

bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Hi-Tech site.

Tuesday, July 22, 2008

Switched Digital Video (SDV) - The Benefits

Telco and cable operators are recognizing numerous benefits of SDV and getting more attractive to deploying it. Prior to SDV, the digital video broadcasting started with satellite DTH (Direct To Home) which gave to the cable industry the ability to provide a mixed of analog and MPEG-2 digital services as follows:

70 to 90 analog 6 MHz channels

8 to 10 MPEG-2 simulcast standard definition (SD) 6 MHz QAM channels

8 to 10 high definition (HD) 6 MHz QAM channels

4 to 6 video-on-demand (VOD) 6 MHz QAM channels

1 to 2 high-speed data (HSD) and voice-over-IP (VoIP) channels

With DTH the badwidth is wasted and, with the exception of the premium channels, the MPEG-2 standard definition (SD) programs are predominantly simulcast analog channels. The MPEG-2 High Defination (HD) content consists of between 15 to 30 HD programs and is also, in large part, duplicating the SD content. Worse, MPEG-2 HD content is a bandwidth hog, where only two to three programs can be put in one 6 MHz QAM channel, so there is limited space to add more HD content.

SDV optimizes the bandwithd and uses 50 to 75 percent less bandwidth as compared to traditional broadcast model. For broadcast services, all services go to all homes all the time, regardless of whether anyone is watching those services. The SDV provides dynamic switching of digital services hence the cable operators are able to broadcast only the programs that are requested by the subscribers. Niche programs switched at service group level instead of broadcast to all subscribers. Unwatched digital tier programs will no longer waste valuable bandwidth.

They can monitor the channel programming and determine if a requested program is already being watched. If so, the requested program is placed into the group of the realted viewers. If there is no one watching a show, then the operator removes that show from the list of broadcast which creates more bandwidth for other programs.

The SDV can be desinged to be intgelligent to determine which video format the subscriber's reciever is capable of and based on this data broadcasts the best format to subscriber. For example, the oprerator can determine whether to send MPEG2 or MPEG4 based on the subscriber's set-top-box capability.

MPEG4 format is twice as faster as MPEG2 and provides High Defination (HD). Of course the subscribers want to see all program in HD. This will force the cable operators to provide MPEG4 capable set-top-boxes to the subscribers. Mirgrating from MPEG2 to MPEG4 can cost billions of dollars and has to be done in phases. The SDV can provide efficient mechanism to cable operators to migrate from MPEG2 to MPEG4 in phases. Also see SDV Architecture for more info.

The following lists benefits SDV can offer cable operators.

SDV Benefits:

Bandwidth optimizmation. More HD Services. More Digital Simulcast.

Provides ability to monitor channel programming effectively.

Provides ability to transmit the best format to the subscribes.

Delivers the requested content to subscribers in real-time.

Provides efficeint mechanism for migrating from MPEG2 to MPEG4.

Facilitates the creation of new services.

More International & Special Interest Content

Boosts total number of channels available.

Enables market-specfic niche, including high definition programming.

Increases the level of concurrent video on demand (VOD) sessions being served to various nodes.

Provides methods for advanced targeted ad-insertion solutions.

Frees up bandwidth for data delivery. Increased high speed data [internet / VoIP] via DOCSIS 3.0 channel bonding

About me:

bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Telecomm site.

Thursday, July 17, 2008

Switched Digital Video (SDV) Architecture

Switched Digital Video (SDV)

With sufficient switching capacity placed at the central office, the amount of content that can be delivered to a single household is infinite. The ability to offer such an amount of video programming in a telco network could be exploited as a competitive advantage. Switched digital video (SDV) is a cable technology that attempts to answer this challenge. It was designed as a cost-effective method to expand program availability, in a way different from the previously used methods of plant upgrades or video compression enhancements.

SDV is the first implementation of a broadcast video service in which only requested programs are sent to the group of subscribers (the subscriber group). SDV is the first broadcast video service that requires two-way communication with the subscriber for content selection. SDV is sent to a subscriber’s Set-Top-Box (STB) where it is decoded/uncompressed for playback on a TV.

With traditional digital broadcast a video program is carried to customer, whether it is being watched or not. With SDV, as with IPTV, programming terminates at the headend and hub does not explicitly send the video program unless requested. Instead, a receiver signals upstream to request programming, and a hub-based controller receives the request and enables the stream into the HFC network by means of a pool of allocated frequencies. See SDV Benefits for more.

In an SDV system, metadata that describes all broadcast programming is amended to indicate which programs are SDV programs. When an SDV program is selected, tuning software in the receiver sends an upstream signal. An SDV session manager receives the request and maps the program to a frequency within the allocated pool. This dynamic tuning information is returned to the receiver. If the program is already being viewed within the same subscriber group, then the task is as simple as reusing the session frequency information.

The following diagram depicts the SDV overall architecture.

Headend (HE)
The HE of SDV architecture is where the video and Internet feed sources enter the system. The HE is also where most of the backoffice systems, including billing systems, asset management systems, authorization systems, and so on, reside. HE includes the following equipment that are directly connected to the cable company:

MPEG encoders, which convert the raw digital or analog signal into an MPEG format
A bulk encryptor, which scrambles the signal in such a way that only the appropriate set-top box (STB) can unscramble it.
Internet servers, which allow customers to access the Internet using cable modems.
Applications servers, including a Session and Resource Manager (SRM), which determine how much system bandwidth each application can access, and another server that monitors and manages other system component (SDV systems can be very complex and require powerful machines dedicated to keep them properly configured.)
A Groomer which translates content into a maximum bandwidth, limiting the rate of video bursts.

The IP network
Once the headend converts the video feed into MPEG format and encrypts it, it sends the signal on to the transport system of the SDV architecture. This section consists of nodes and routers where cable connections intersect and branch off. Nodes and routers redistribute the signal to other nodes and routers so that the original feed covers the cable company's entire customer base. The transport system's path connects the headend to the hub (access system).

Hub
Hub is where the control of bandwidth-intensive applications, such as on Demand streaming, and HFC-connected components reside. The hub (access system) is where the actual digital switching takes place. The core of the access system is the SDV server. It's the SDV server's job to keep track of customers' channel change requests. The server sends commands to an Edge Resource Manager (ERM) and several Edge QAM devices to meet demands. An edge QAM modulates the multiple program transport stream (MPTS) and places the active channels on the HFC plant.

HFC network
HFC network is the fiber-coax access network for distribution to the subscriber. The HFC network is a shared medium, where groups of homes are connected on a common branch of coax cable. Groups of subscribers share access to the same downstream frequencies, and arbitrate for access to shared upstream frequencies.

Subscriber Site
Subscriber Site is a business or residential location where coax receivers, such as the Set-Top-Box (STB) and cable modems are placed. A set-top box receives and decrypts signals from the access system and a cable modem if the customer subscribes to cable Internet service. Each company uses a different interface between the customer network and the access system. A STB also contains a SDV client that communicates with SDV server.

SDV sequence of operations:

A software client in the set-top box sends channel change requests to the SDV server.
The SDV server and Session/Resource Manager support the channel switching, by allocating the requested channel to an edge QAM, and telling the set-top client where it can be found, by providing the program's frequency and MPEG program number.
The client then tunes the set-top to the channel. In addition, the client periodically sends a "heartbeat" message to indicate that it is still tuned to that service.
While the channel is active, the SDV server in conjunction with Session/Resource Manager periodically generates a "fast channel map" of active channels and carousels it out to the clients.
When the SDV server determines that no subscribers are tuned to a channel, it communicates with edge QAM and tears the channel down, freeing the bandwidth for use by other channels.

For more detail of SDV sequence of operation, see my article "SDV Sequence of operations".

About me:

bruce atlasi is a professional computer engineer, skilled in telecomm and datacomm technologies and architecture. He has diverse working experience with many telecomm start-ups and fortune 100 companies, including Cisco Systems, IBM, and Siemens. He regularly blogs on About Hi-Tech site.

Monday, July 14, 2008

Switched Digital Video (SDV) - issues and challenges

The SDV is becoming more and more attractive among telco and cable operators for number of benefits it brings to telcos. In this article some of the common and major issues of SDV with possible solutions is described.

Prior to SDV system

When satellite DTH started to offer digital video, the cable industry response was a mixed analog and MPEG-2 digital plant with provisions for:

70 to 90 analog 6 MHz channels
8 to 10 MPEG-2 simulcast standard definition (SD) 6 MHz QAM channels
8 to 10 high definition (HD) 6 MHz QAM channels
4 to 6 video-on-demand (VOD) 6 MHz QAM channels
1 to 2 high-speed data (HSD) and voice-over-IP (VoIP) channels

SDV Benefits:

Optimizes bandwidth; SDV uses 50 to 75 percent less bandwidth as compared to traditional broadcast model. Without SDV, with the exception of the premium channels, the MPEG-2 standard definition (SD) programs are predominantly simulcast analog channels. The MPEG-2 High Defination (HD) content consists of between 15 to 30 HD programs and is also, in large part, duplicating the SD content. Worse, MPEG-2 HD content is a bandwidth hog, where only two to three programs can be put in one 6 MHz QAM channel, so there is limited space to add more HD content.
Provides ability to monitor channel programming effectively
Provides ability to transmit the best format to the subscribes
Delivers the requested content to subscribers in real-time
Provides efficeint mechanism for migrating from MPEG2 to MPEG4
Facilitates the creation of new services
Boosts total number of channels available
Enables market-specfic niche, including high definition programming
Increases the level of concurrent video on demand (VOD) sessions being served to various nodes
Provides methods for advanced targeted ad-insertion solutions
Frees up bandwidth for data delivery

SDV Issues and challenges:

Some of the common issues cable and telco operators face when deploying SDV are as outlined below:

RF access network
Long-haul transport issues
Signaling between many hetrogence components that must operate in unison
Scalability of SDV implementation is one of the major challenges of telco operators which will require industrial-strength software control systems with a provision for hardware redundancy and hitless upgrades to support millions of subscribers
Adopting MPEG4 technology is another major challenge for the cable operators, which has twice badwidth effieciency as MPEG2. Replacing millions of existing MPEG2 set-top-boxes with MPEG4 is a multi-billions dollars proposition.

SDV common implementation requirements

Among the most common SDV implementation requirements are the following:

Converting video streams from multi-program transport streams (MPTSs) to single program transport streams (SPTSs)
Converting from variable bit rate (VBR) to constant bit rate (CBR)
Increasing exponentially the number of multicast flows
Increasing the required network computing resources of routers, switches, edge quadrature amplitude modulation (QAM) modulators and other components
Reducing the relative throughput of those devices while increasing the chances of queuing overflows or underflows
Increasing network communication overhead for both the video delivery (data plane) and control plane networks (control and signaling)
Associating and switching video flows to the home to enable seamless channel changes

Current SDV technology

Current SDV systems consist of the following functional elements:

A staging processor, which breaks a multiple program transport stream (MPTS) into single program transport streams (SPTS), and "clamps" the video bit rate of the streams (that is, converts any variable bit rate streams into constant bit rate streams). It also assigns Multicast IP/UDP port addresses to each SPTS.
The SDV server and Session/Resource manager, which processes set-top box channel change requests, sets up and tears down active channels on the QAMs, and generates a list of the current service group (collection of users) active channels for inclusion in the mini-carousel that is continuously sent to the STB.
A bulk encryptor, which provides payload scrambling to support conditional access.
A content routing network that transports the multicast streams to the QAMs.
An edge QAM that modulates the MPTS and places the active channels on the HFC plant.
An SDV software client in the set-top box.

Also see "SDV Architecture" for more information on current SDV architecture.

Issue with current SDV technology

Because the SDV system is not aware that there are multiple types of set-top boxes, and only HD set-tops can decode HD channels, the cable operator must rely on an often-times confused subscriber to make the right channel choice. That's because the SDV system transmits to the subscriber the same program in two different format, one in HD and another one in SD, available in two different channels. There is no correlation in the numbering scheme to relate the two as the same programming, just different video resolutions. This creates confusion for the viewer. The owner of HD set-top-box must know which channel is showing HD version of the program, otherwise, he might be watching SD digital version of the program which of course has lower quality of HD but paying for more expensive HD set-top-box.

A possible solution for this confusion problem is to add a set-top awareness capability to SDV system. By adding this capability, the SDV selects the format that's desirable for the subscribers set-top-box and displays on one channel. Implementing set-top awareness capability requires a number of new functions as described below:

A device manager that maintains information on the capabilities of set-tops, edge QAMs, service groups, transcoders, and stream processors, as well as the source of different formats of the content for delivery to each service group.
A subscriber manager that connects a subscriber to the devices that are used to deliver services to that subscriber. It also maintains a heuristic analysis of subscriber viewing patterns.
An SDV manager provides centralized management and control of the SDV system. It registers all of the SDV servers/RM, edge QAMs, and service groups, maintains a central database for the events associated with the channel change requests for each subscriber, and tracks set-up and tear-down of active channels in each service group. Additionally, it provides the interface with the global session resource manager (GSRM) for request and allocation of shared QAM resources. Finally, it provides control, configuration management, and reporting functions of the entire SDV system.
A bank of shared transcoders for dynamically creating different formats for replicated versions of the same program.
A monitoring/reporting function is critically important for optimizing and troubleshooting the network, and ensures that the operator knows when a service is switched to a service group and that the content was actually transmitted over the HFC.

A hybrid model to managed transition to MPEG-4 set-tops

A hybrid model provides ability to cable operators to gradually swap out the STBs to customers based on their programming preferences and location in the system. With hybrid model, the SDV system automatically makes the most bandwidth efficient format decision for each program being transmitted within each service group based on which subscribers are watching the program and their STB capabilities.

An intelligent management layer

An intelligent management layer can help cable operators to configure the SDV system easier as cable system become more complex through regional clustering. The following outlines the elements of an intelligent management layer:

A workflow engine manages and tracks the processes needed to implement new services, devices and even software applications. Additionally, it manages and tracks the creation of the different video resolutions and compression formats for all content to support installed STBs.
An element manager monitors and assists in the configuration management of hardware and software within the network, and provides reports to the operator on impairments, loading and outages.
A device (and subscriber) manager maintains a database of each device in the network and in use by subscribers, including hardware and software versions, compatibilities and incompatibilities of the same, and the video resolutions and compression formats supported by each device.
A global session resource manager (GSRM) arbitrates bandwidth usage between services based on loading balancing, value of the services, and subscriber experience.
A service manager maintains a database for how each subscriber device receives and supports service information.
A code download manager manages the distribution of code objects, easing the operator involvement in upgrading code to the set-tops and other network devices.