Preview: Technology in Capsules
Technology in Capsules
Tutorials & Introduction to Latest Technology!!!
LatestVoIPCommunication Related ArticlesHSDPATiVoWi-MAXZigBee™Assisted GPS DTMF SignallingCDMA TechnologySIM Application ToolkitSignal Code ModulationUnlicensed Mobile AccessTDD (Time Division Duplex) Interworking 2G and 3G Networks Near Field Communication (NFC)Ultra-Wideband (UWB) TechnologyMIMO (Multiple Input Multiple Output)USTS (Uplink Synchronous Transmission Scheme)MBMS (Multimedia Broadcast / Multicast Service)Location Services - 2G/3G ImplementationEDGE (Enhanced Data rates for Global Evolution)MExE (Mobile Execution Environment)W-AMR (Wideband - Adaptive Multi Rate)RADIUS (Remote Access Dial In User Service)SCTP (Stream control transmission protocol)Engineering the GRX (GPRS Roaming eXchange)TMN (Telecommunication Management Network)Home Networking Related ArticlesHomePNAComputer Related ArticlesLinux ShellsWhat is .NETLinux FilesystemThe Story behind JavaDifference between Linux and WindowsMiscellaneous ArticlesWorld Of Transforms[...]
WiMax ou interopérabilité sans fil pour l'Access de micro-onde, est un IEEE 802.16 a basé la norme pour les réseaux sans fil de zone métropolitaine (WMANs). IEEE 802.16 est groupe de travail le numéro 16 d'IEEE 802, se spécialisant dans l'accès sans fil à bande large point-à-multipoint. WiMax est soutenu par l'industrie elle-même, y compris Intel, Dell, Motorola, Fujitsu, AT&T, British Telecom, France Telecom, confiance Infocomm, Siemens, Sify, tonneliers de Pricewatehouse et Tata Teleservices - formant une alliance appelée le forum de WiMax. Il représente la prochaine génération de la gestion de réseau sans fil. Le protocole de WiMax est une norme qui apporte la gestion de réseau capable calculant des dispositifs ensemble. Par exemple. Pour fournir l'Internet/Intranet accéder d'une manière semblable à WiFi. Tandis que la chaîne de WiFi est limitée jusqu'à 150 pieds, WiMax peut transmettre des données jusqu'à une distance de 48km. Il offre également des vitesses se reliantes mieux par rapport à d'autres protocoles. Il peut se relier à une vitesse maximum de 70Mbps. WiMax n'est pas conçu pour s'opposer avec WiFi, mais pour coexister avec lui. L'assurance de WiMax est mesurée en kilomètres carrés, alors que cela de WiFi est mesuré en mètres carrés. La norme originale de WiMax (IEEE 802.16) propose l'utilisation du spectre de fréquence de gigahertz 10-66 pour la transmission de WiMax, qui est bien au-dessus de la chaîne de WiFi (jusqu'à maximum 5GHz). Mais 802.16a a ajouté le soutien de la fréquence de gigahertz 2-11 également. Une station de base de WiMax peut être accédée par plus de 60 utilisateurs. WiMax peut également fournir des services de radiodiffusion également. Les caractéristiques de WiMax fournit également des équipements bien meilleurs que WiFi, fournissant une largeur de bande plus élevée et une sécurité de données élevée par l'utilisation des arrangements augmentés de chiffrage. WiMax peut également fournir le service dans la ligne de la vue (LOS) et la Non-Ligne des endroits de la vue (NLOS), mais la gamme changera en conséquence. WiMax permettra l'interpénétration pour la fourniture à bande large de service de VoIP, de vidéo, et d'accès d'Internet - simultanément. WiMax peut également fonctionner avec les réseaux mobiles existants. Les antennes de WiMax mettent en boîte la « part » une tour de cellules sans compromettre la fonction des rangées cellulaires déjà en place. Par conséquent la diversification des services peut être accomplie facilement. Puisque WiMax soutient plusieurs protocoles de transmission, ce réseau peut agir en tant qu'épine dorsale pour une ISP et un fournisseur de service de telecom. WiMax a été félicité comme solution pour le problème de connectivité de dernier-mille, dans des secteurs ruraux et urbains.
VoIP – An Introduction
VoIP stands for Voice over Internet Protocol. It provides a means of transmitting voice over Internet Protocol (IP). But for that purpose, voice is to be converted into some packet format so that transmission over IP is possible. VoIP technology helps to make calls between PC and PC, PC and telephone etc. The obvious advantage is the reduction in cost.
How It Works?
First, the speech signals are sampled at or above Nyquist Rate and the samples are quantized into discrete levels. These are then converted into digital format. For the above given process, we can use any of the standard like Pulse Code Modulation (PCM), Adaptive Differential PCM (ADPCM), MP-MLQ LPC-10 etc. At the receiving end you will have to reverse the things. Decompress the encoded data, reassemble packets in order, and convert these digital values into analog using a Digital to Analog Converter (DAC). Once data is converted into digital form, we have to think about transmitting it over IP. Here comes the greatest difficulty in VoIP – the real time nature of voice is very crucial, otherwise the sound would not be so easy to understand. But normal TCP/IP implementations are not real time, just like the nature of internet. You may have to wait until each packet is routed correctly through appropriate machines. But such things should not disturb the normal voice, since we want continuous speech from the other end. Hence VoIP implementations use UDP protocol instead of TCP. VoIP data packets live in RTP (Real-Time Transport Protocol) packets which are inside UDP-IP packets.
VoIP signaling Protocols
VoIP mainly uses two signaling protocols: H.323 and SIP (Session Initiation Protocol).
H.323 is an complex suite of protocols that provides specifications for real-time, interactive videoconferencing, data sharing, and audio applications such as IP telephony. SIP is smaller, more efficient, and takes advantage of existing protocols to handle certain parts of the process. MGCP (Media Gateway Control Protocol), for example, is used by SIP to establish a gateway connecting to the PSTN.
Reduced Cost.Can handle multiple calls at a time, like we browse many sites at a time.
Unless the delay is overcome and a real time streamlining is obtained voice quality would be just unbearable.
- Insecure lines - meaning anyone can listen to your conversation because of shared servers or open platforms.
TiVo is a type of personal video recorder similar to VCR. It is a device which allows its users to capture TV programs and view them later. Hence they allow the recording of programs and allows them to be viewed later. There is an internal hard disk for capturing programs. TiVo makes sense in the fact that it allows replay of live programs.
TiVo allows to record programs based on time, programs titles, and even based on the artists and popularity. Programs may be stored on the internal hard-disk untill it is full, and when it is full the first program recorded is deleted. It can also record progrmas based on the viewing habits of the user. The playback can be done while recording another program. This is unlike the traditional tape recorders which allows either playback or recording at a time. TiVo device also allows interface with personal computer and even with home networks.Standalone TiVo systems can only record one channel at a time. Even with digital cable or satellite services that may provide multiple simultaneous signals, these units rely on an external convertor to select and decode digital signals.
TiVo was started in 1997 by veterans of Silicon Graphics and Time Warner. TiVo unit is built by TiVo Inc. They provide harware and linux based software for TiVo.TiVo systems are based on PowerPC or MIPS processors, connected to MPEG-2 encoder/decoder chips and high-capacity IDE/ATA hard drives. Early TiVo units used one or two 13GB drives; typical units have a drive of 40-140GB in size. Although not supported by TiVo or equipment manufacturers, larger drives can be added.
TiVo service is available only in United States and United Kingdom, at present. But there has been work arounds which makes it to work in Australia, New Zealand, Canada, and the Netherlands.
Ethernet has been the de-facto standard for local area communication for a long time. Initially there was 10Mbit, then came 100Mbit and now its not rare to find 1GBit Ethernet. But the need for the communication medium has also been changed. Now a days the trend is to become wireless. But the often forgotten phone line can also provide a decent performance when it comes to a communication that is not very bandwidth hungry. During the mid 90’s a company provided its own technology for providing data access through telephone lines at 1Mbps and it became very popular. Then different companies like AMD formed an alliance named Home Phone-line Network Alliance (Home PNA) to provide standardization for the telephone line communication. They developed a data transfer standard based on the Tut Systems' technology for telephone lines and called it HomePNA 1.0. The first version of this standard was identical to the Tut Systems' technology - 1 Mbit/s, 25 computers in the HomePNA 1.0 network and a communication range about 150 m. Then they released network cards (PCI and USB), different communicators, Ethernet-to-HomePNA bridges etc. The HomePNA technology is a usual Ethernet with 1 Mbit/s (HomePNA 1.0) and 10 Mbit/s (HomePNA 2.0) in all aspects. The CSMA/CD, IEEE-802.3, MAC addresses are applicable not only for the Ethernet but also for both HomePNA standards. This technology differs from the Ethernet only on a physical level. And installation of HomePNA cards doesn't differ from that of HomePNA adapters. Operating systems operate with these adapters as with usual Ethernet ones.
HomePNA 1.0 is used successfully in office buildings - practically all of them have their own telephone network, which can be used for the Internet as well. It is very convenient both for clients and providers. HomePNA networks can be built in those buildings which have phone jacks. I.e. you don't need hubs and switches, but only HomePNA cards. Theoretically, the HomePNA 2.0 standard has every chance to reach 100 Mbit/s speed!
Near Field Communication (NFC)
Near Filed Communication (NFC) is a close range radio communication protocol used for very sensitive applications. It was jointly developed by Sony and Philips. The standard specifies ways to establish P2P(Peer-to-Peer) communication links for data exchange. After the P2P network has been configured, another wireless communication technology, such as Bluetooth or Wi-Fi, can be used for longer range communication or for transfering larger amounts of data. Its development was parallel to RFID (Radio Frequency Identification), but both differ in many ways. NFC offers a very short range as compared to RFID. This is an added advantage in the sense that it requires very little transmission power and cheap transmitters can be used for the purpose. Hence it is very suitable for Smartcard like applications. It can also work in both active and passive modes. NFC works on a frequency range of 13.56 MHz. It offers a baud rate of 106 kbps to 424kbps. The transmission is made from a frequency of 13.56MHz inductively, hence it uses high magnetic field. At a transaction only two participants can be involved - one transmitter (initiator) and one receiver (target). The transmission can be either in active fashion or passive fashion. Both have their own merits and demerits. The NFC transmission runs helping duplex, i.e. that one of the two devices can send only in each case or receive at a time.
Ultra-Wideband (UWB) Technology
Ultra-Wideband (UWB) Technology is a technology designed for short range, wireless personal area networks. It offers people freedom from wires, ie let them go wireless. It brings the convenience and mobility of wireless communications to high-speed interconnects in devices throughout the digital home and office. This enables wireless connection of multiple devices for transmission of video, audio and other high-bandwidth data.
UWB, short-range radio technology, complements other longer range radio technologies such as Wi-Fi*, WiMAX, and cellular wide area communications. It is used to relay data from a host device to other devices in the immediate area (up to 10 meters, or 30 feet).
ZigBee™ is the name of an alliance of companies formed around IEEE's 802.15.4 specification for low data rates in the Industrial, Scientific and Medical (ISM) radio bands. The ZigBee protocol promises to provide longer battery life and to be a lower-cost alternative to Bluetooth for wireless sensing and control applications. Companies looking for reliable and secure wireless monitoring and control solutions have a new alternative –- ZigBee™ (www.zigbee.org). ZigBee provides the network, security and application profiles layers for the IEEE 802.15.4 global standard for reliable, low-power, wireless data communications.
HSDPA(High Speed Downlink Packet Access) improves system capacity and increases user data rates in the downlink direction, that is, transmission from the Radio Access Network to the mobile terminal. This module, which is designed to supplement the UMTS Air Interface tutorial, explores the HSDPA channel architecture along with the additional functionality required in the UMTS MAC (Medium Access Control) layer. The processes of adaptive modulation and coding along with procedures by which HSDPA data is scheduled for transmission across the air interface and the re-transmission patterns that are employed to ensure the high data rates supported by this technique are maintained.
Unlicensed Mobile Access
Unlicensed Mobile Access (UMA) technology grants access to GSM and GPRS mobile services over unlicensed spectrum technologies, including Bluetooth and WiFi. Service providers, by enabling UMA technology, can enable subscriber roam and smoothly handover between cellular networks and between private and public unlicensed wireless networks using dual-mode mobile handsets. In the usual handover process between networks the user experience is not so good, but the UMA technology makes this process simple and provides the user with a nice experience during handover in both voice and data transfers. the convergence of mobile, fixed and Internet telephony (fixed-mobile convergence).
The core components of the system are:
- UMA enabled dual mode handset.
- UMA Network Controller (UNC) with broadband access
- Unlicensed Mobile Access Network (UMAN)
The roaming process is completely transparent to the user. The handover process is also transparent.
In order to promote the use of UMA, a number of leading companies like Kineto, Motorola, Alcatel etc. have developed an open standard. These standards are available to vendors and carriers of the mobile communications systems to develop and deploy their own solutions. addition to developing and maintaining the initial specifications, the participating companies are actively working with the 3GPP standards organization to use the specifications as the basis for the development of a formal standard.
WiMax or Wireless Interoperability for Microwave Access, is an IEEE 802.16 based standard for Wireless Metropolitan Area Networks (WMANs). IEEE 802.16 is working group number 16 of IEEE 802, specializing in point-to-multipoint broadband wireless access. WiMax is supported by the industry itself, including Intel, Dell, Motorola, Fujitsu, AT&T, British Telecom, France Telecom, Reliance Infocomm, Siemens, Sify, Pricewatehouse Coopers and Tata Teleservices – forming an alliance called WiMax Forum. It represents the next generation of wireless networking.
The WiMax protocol is a standard that brings networking capable computing devices together. Eg. To provide internet/intranet access in a way similar to WiFi. While the range of WiFi is limited up to 150 feet, WiMax can transmit data up to a distance of 48km. It also offers better connecting speeds as compared to other protocols. It can connect at a maximum speed of 70Mbps. WiMax is not designed to clash with WiFi, but to coexist with it. WiMax coverage is measured in square kilometers, while that of WiFi is measured in square meters. The original WiMax standard (IEEE 802.16) proposes the usage of 10-66 GHz frequency spectrum for the WiMax transmission, which is well above the WiFi range (up to 5GHz maximum). But 802.16a added support for 2-11 GHz frequency also. One WiMax base station can be accessed by more than 60 users. WiMax can also provide broadcasting services also.
WiMax specifications also provides much better facilities than WiFi, providing higher bandwidth and high data security by the use of enhanced encryption schemes. WiMax can also provide service in both Line Of Sight (LOS) and Non-Line Of Sight (NLOS) locations, but the range will vary accordingly. WiMax will allow the interpenetration for broadband service provision of VoIP, video, and internet access – simultaneously. WiMax can also work with existing mobile networks. WiMax antennas can "share" a cell tower without compromising the function of cellular arrays already in place. Hence diversification of services can be accomplished easily. Since WiMax supports several communication protocols, this network can act as the backbone both for an ISP and telecom service provider. WiMax has been praised as the solution for the last-mile connectivity problem, in both rural and urban areas.
MIMO (Multiple Input Multiple Output)
The dream of every communication designer is to provide good quality service to each of his customer within the limited available bandwidth. But in the recent years, the amount of data flowing through the channel has increased. But there has been no such high increase in the available bandwidth. So it is a challenge to effectively utilize the channel spectrum along with providing good quality of service across wireless links. One of the possible ways is to use multiple antennas at both the ends of the transmission link. MIMP exploits natural phenomena like multi-path propagation to increase throughput, reduce error rates etc. rather than trying to eliminate them.
The main motive behind the MIMO was to increase the user data rates within the constrained spectrum. The initial application of MIMO was proposed for indoor wireless LAN, fixed wireless access networks etc. But now the aim to widen its applications to cover other areas also. The core idea behind the system is to exploit the de-correlation of multiple received signals in the presence of multi-path propagation, there by separating the data streams occupying same bandwidth. Hence Rayleigh fading and constrained total power comes into the figure.
Data is transmitted in busts and the receiver knows the channel pattern through the usage of training algorithms; but not necessarily the transmitter. The training sequence enables the receiver to predict the channel coefficients and extract the data coming in multiple streams. To maximize the effect of transmitting rate half of the time interval is used for data transmission and half for training. The adaptive transmission is possible only if the transmitter knows the channel coefficients in advance, so that the more data can be sent through good channels. In case of time division duplex channels, this requires the channel to be stationary and hence channel details need to be fed back at the same rate as the channel characteristics are changing. In case of the frequency division duplex channels, the coefficients should be transmitted at a different frequency. To overcome the fast feedback requirement, the spatial mean of channel coefficients has been proposed; instead of the instantaneous values. This greatly enhances the channel capacity, in case of correlated channels.
There is an ongoing effort to standardize the MIMO standard under the name IEEE 802.11n. It will offer up to eight times coverage and about six times data rates, of current 802.11g networks.
USTS (Uplink Synchronous Transmission Scheme)
To maximize the usage of 3G uplink capacity the 3GPP (Third Generation Partnership Project) is exploring techniques in which channel redundancy can be exploited. One approach is to implement USTS in which signals from mobiles within the cell are orthogonalized. That is, a number of mobiles are allocated the same scrambling code, but different channelization codes. This paper explores aspects of USTS including OVSF (Orthogonal Variable Spreading Factor) code allocation and timing both for initial synchronization and closed loop timing in order to maintain the channel timing reference within tolerable limits.
MBMS (Multimedia Broadcast / Multicast Service)
The MBMS is a unidirectional point to multipoint bearer service in which data is transmitted from a single source entity to multiple recipients. These services will typically be in the form of streaming video and audio and should not be confused with the CBS (Cell Broadcast Service) that is currently supported. This paper describes the architecture of the MBMS along with its functional notes and integration into 3G and GERAN (GSM & EDGE Radio Access Network) with Core Network, UTRAN (UMTS Terrestrial Radio Access Network) and radio aspects being explained.
Interworking 2G and 3G Networks
Ensuring seamless handover between 2G networks such as GSM and 3G networks such as UMTS will be vital if next generation cellular networks are to be rolled out successfully. This module explores many of the mobility management procedures that will need to be implemented to support effective 2G/3G interworking both in the Circuit Switched and Packet Switched domains. The paper focuses on the signalling required in order to facilitate interworking as well as issues regarding networks operating at different releases of the 3GPP specification, and how these shortfalls may be overcome.
TDD (Time Division Duplex)
The use of TDD (Time Division Duplex) across the UMTS air interface to offer low range asymmetric data flows appear an attractive option to operators who are planning to offer 3G data hotspots to subscribers. This module explores UMTS TDD operation in detail and discusses the frame formats and procedures that may be used across the air interface. The module also describes the issues surrounding TDD operation such as cell blocking and power control as well as the advantages that can be leveraged from such a system.
EDGE (Enhanced Data rates for Global Evolution)
This paper examines the rational behind EDGE and the modifications required within the network to support it. Concentrating on GSM (Global System for Mobile Communications), the principles of 8PSK (Eight Phase Shift Keying) are discussed with regards power control and planning etc. The module also examines the modifications required by GPRS (General Packet Radio Service) to support EDGE and in particular the protocols of RLC (Radio Link Control) and MAC (Medium Access Control).
The principles of convolutional coding are also examined with regards the nine modulation and coding schemes in addition to describing the significance of the EDGE families and the use of puncturing schemes.
Location Services - 2G/3G Implementation
Location based architecture may be implemented into mobile networks in a number of ways including TA (Time Advance), TOA (Time of Arrival) EOTD (Enhanced Observed Time Difference) and GPS. This module describes the concepts of these positioning methods. It also explores the location based network functions and their interaction with the cellular network nodes such as the HLR, the packet and circuit switching functions as, well as the RAN (Radio Access Networks).
Assisted GPS works by providing a GPS reference network in which a series of receivers have a clear view of the sky and can operate continuously. This reference information is then made available to cellular networks such as GSM and UMTS to refine location accuracy within the sphere of location based services. This module discusses the interaction between the reference network and the Location functions within a cellular network and how these combine to offer accurate location information.
MExE (Mobile Execution Environment)
MExE provides a standardized execution environment within the UE, and enables the negotiation of capabilities with the MExE service provider. This paper describes the types of service that can typically be delivered using MExE and the architecture of the MExE environment. It then goes on to discuss how MExE services may be accessed such as remote service access or application download. Finally the concepts of MExE and UE classmarks are discussed along with an overview of MExE Classmarks 1, 2 and 3.
W-AMR (Wideband - Adaptive Multi Rate)
Wideband variable rate speech codecs such as the W-AMR codec used in UMTS systems offers superior wideband speech quality at data rates comparable to current narrowband speech codecs. This paper does not focus on the actual operation of the W-AMR speech codec itself, but its impact on the UTRAN (UMTS Terrestrial Radio Access Network) and air interface channels that must support its operation.
SIM Application Toolkit
The SAT (SIM Application Toolkit) provides a flexible interface through which developers can build services and MMI (Man Machine Interface) in order to enhance the functionality of the mobile. This module is not designed for service developers, but network engineers who require a grounding in the concepts of the SAT and how it may impact on network architecture and performance. It explores the basic SAT interface along with the architecture required in order to deliver effective SAT based services to the handset.
RADIUS (Remote Access Dial In User Service)
<>Radius is an acronym that stands for Remote Authentication Dial In User Service is a protocol used for applications such as IP mobility and network access –both for local access and roaming access. It is a protocol for Authorization, Authentication and Accounting. RADIUS was originally developed by Livingston Enterprises. But now there exist many commercial and open source RADIUS servers. RADIUS server is responsible for the verification of the login information (Username & Password) that is passed over the RADIUS protocol. It uses any of the authentication protocols like PAP, CHAP or EAP to authenticate this information and then provided the desired level of access if things were right. The login information is passed on to a Network Access Server (NAS) over Point-to-Point Protocol (PPP). RADIUS also provides billing information and the servers are notified when a session starts and stops so that the user is billed accordingly. The billing information is also kept as a log in the servers so that they can be used accordingly in case of any analysis is required.
RADIUS servers can also read and write information from various data sources like text files and database etc. Simple Network Management Protocol (SNMP) is used for the remote monitoring of RADIUS servers. RADIUS is extensible, and many of the commercial products have their own hardware and software implementations for their own dialects.
<>RADIUS has a limitation when coming to the mobile communications involving 3G devices. They require highly sophisticated billing functions as they provide more services. Hence, a replacement for RADUIS, DIAMETER is also under consideration. The DIAMETER protocol provides full backward compatibility with RADIUS protocol and is expected to solve the current issues related to RADIUS.
Engineering the GRX (GPRS Roaming eXchange)
This paper describes the rational behind the GRX in terms of worldwide access, security, reliability and scalability. It explores the structure of commercial, wide area, IP networks and the typical security and routing protocols employed within this environment. It is designed enable engineers who are working in this area to gain a firm understanding of the modern mobile packet switching architecture as well as a detailed insight into the requirement for, and operation of, the GRX.
SCTP (Stream control transmission protocol)
SCTP (Stream control transmission protocol) is a transport level protocol providing end-to-end communication between two or more applications running in separate hosts. SCTP operates on top of the connectionless packet network supported by IP (Internet Protocol) offering a connection oriented, reliable transport mechanism for independently sequenced message streams. It was originally designed to provide a general purpose transport for message-oriented applications transporting signalling data. This paper describes the architecture and operation of SCTP including its features, the setting up of SCTP associations, data delivery and shutdown. Its position within the Sigtran architecture as a whole is also included.