Tag Archives: VoIP

Technology of VoIP and its working

VoIP term refers to transference of Voice over Internet Protocol (IP) of TCP/IP suite of protocol. By using technology of “VoIP” we make traditional calls of telephones from phone or computer to other phone or computer either. We use Internet (that is packet switched network) and public switched telephone network (PSTN) both. All that is required is connection of Internet for VoIP. Technology like this changes all things really because it permits people for receiving phone calls from any place where there is existence of connection of internet. This is just in similar ways as for you could receive emails of yours in any place where you have internet connection.

“Technology of VoIP” term covers wide ranges of technology which includes fax-over-IP services too. This is carried over private IP based network and internet networks both. VoIP are parts of packet voices. This includes frame relay networks and voice-over-asynchronous-transmission-mode (ATM). These run faster than IP but are less prevalent. VoIP has connection across combination of PC, web based telephones and phones. These are connected by means of public lines of telephones for remote gateways of voices. Since, information passes through in discrete packets, therefore there is no need of relying on continuous switched circuit available. By taking use of VoIP we could enhance data and voice services in single network. End user devices (called also client devices) are referred normally as VoIP phones being used in VoIPs. “VoIP Phone” development requires “system on a chip” development. This combines associated logic of glues, (DSP) digital signal processing functions, telephone user interface, and analog interface and (MCU) micro-controller functions.

VoIP working: Steps basically involved in origination of VoIP calls are: Conversion of voice analog signal to formats digitally. Translation and compression of signals to packets of Internet protocol (IP) for internet transmission. Reversal of process at receiving ends. Switching formats digitally back to analog such that telephone calls go across as normal. Calls of VoIP originate on whatever lines of broadband like wireless, coaxial cable, satellite even or Digital Subscriber Line (DSL). Routing calls to VoIP Company. In this place computer converts sounds to packets of data. It is same as packets utilized for transferring internet data like emails. Data is send by packets. This is more efficient far because it enables similar lines. It handles simultaneously more information. Packets of data are sent by means of any multiple network of internet to call’s recipient. Caller receives call. This is done through local carrier of phone, provider wireless or provider broadband. For understanding VoIP it is important for having complete knowledge of differences in between packet switching and circuit switching. Normal telephones use circuit switching for calls over phones. It involves call routing by means of switches at local carriers to person being called. 2 point connection in both directions is called circuit. Differently, packet switching is very efficient in transmission of data. Small data amounts known as packets are sent from 1 system to other. In systems of VoIP, once party in question answers, voice is transmitted by conversion of voice to digitized form. Then segment voice signals to packet stream. 1st step in the process is conversion of voiced analog signals to digital by using analog-digital converter. As because voice digitized needs large bits numbers, compression algorithms are used for reducing volumes of transmitted data. Next, samples of voice have to be inserted to packets of data for carrying on internet. Voice packets protocols are Real time Transport Protocol (RTP) typically. Packets of RTP have header fields specially holding data required for correct re-assemblence of packets to voice signals on other ends. Security and scalability are key issues.

Packet Cable – Its technical Overview and Deployments

Packet Cable is consortium and association of industry being founded by CableLabs with goals of standard definition for modem cable television industry accessibilities. CableLabs in turn leads these initiatives for interface interoperability specifications for delivering multimedia real time services over 2 way cable networks. It is built on top of industry’s cable modem Data over Cable Service Interface Specifications (DOCSIS) infrastructure. Packet Cable network uses (IP) Internet Protocol for enabling wide ranges of services of multimedia like interactive gaming, (IP telephony) Voice over IP, multimedia general applications and multimedia conferencing. DOCSIS networks with Packet Cable Network extensions enable cable operators delivering voice and data traffic using efficiently single high speeded (QoS) quality-of-service cable broadband enabled architecture. Packet Cable Network efforts date back to 1997 year when cabling operators identify needs for multimedia real time architectures. This supports modern multimedia services delivery over architecture of DOCSIS. Packet Cable Network has original specifications on basis of network physical characteristics of operators in US for European market, EuroPacketCable on basis of European implementations of network and Cable Europe Labs for maintaining separate by equivalent efforts.

Overview technically: Packet Cable Network interconnects 3 networks namely Public Switched Telephone Network (PSTN), TCP/IP Managed IP Networks and Hybrid Fibre Coaxial (HFC) Access Network. Packet Cable Network protocols: There should be (RTCP) Real Time Control Protocol and (RTP) Real time Transport Protocol needed for media transfers. There should be PSTN Gateway Call Signalling Protocol Specification (TGCP) that is MGCP extensions for Media Gateways. There should be Network based Call Signalling Protocol Specification (NCS) that is MGCP extensions for residential analog Media Gateways. NCS specification is derived from IETF MGCP RFC 2705 with details of VoIP signalling. IETF versions are basically NCS version’s subset. Packet Cable groups have defined more features and messages than IETF. There should be Common Open Policy Service (COPS) for Quality of Service. There should be DOCSIS standards for data over cables and details on RF bands mostly. Packet Cable Voice Codecs per Packet Cable Codec Specifications: Required things are ITU G.711 for V 1.0 and V1.5 (a-law and micro-law both), iLBC for V1.5 and BV16 for V1.5. Recommended things are ITU G.729 Annex E and ITU G.728. There can be any optional things.

PacketCable 1.0: This PacketCable 1.0 comprises of 6 technical reports and 11 specifications. It defines Quality of Service (QoS), call signalling, interconnection of Public Switched Telephone Network (PSTN), Codec, interfaces of security, billing message collections of events and client provisioning needed for implementing single zone’s PacketCable solutions for (IP) Internet Protocol residential voice services. PacketCable 1.5: This PacketCable 1.5 has capabilities additionally not existing in PacketCable 1.0. It supersedes versions previously namely V1.1, V1.3 and V1.2. PacketCable 1.5 consists of 1 technical report and 21 specifications. It defines together Quality of Service (QoS), call signalling, interconnection of Public Switched Telephone Network (PSTN), Codec, interfaces of security, billing message collections of events and client provisioning needed for implementing multi zone’s or single zone’s PacketCable solutions for (IP) Internet Protocol residential voice services. PacketCable 2.0: This PacketCable 2.0 introduces IMS Release 7 IP Multimedia Subsystem to architectural cores. Packet Cable thereby uses IMS simplified in few areas in turn enhancing it in few cable specific places. Packet Cable defines Delta Specs being related with very important IMS Specs from 3GPP.

Deployment: VoIP services are based on architecture of PacketCable widely being deployed by operators like Cogeco: Cogeco Home Phone (Canada), Time Warner Cable: Digital Phone (System wide), Cox: Cox Digital Telephone (System Wide), Bright House Networks (Florida), GCI (Alaska), Optus- SingTel Optus Pty Ltd (Australia), Liberty Cablevision (Puerto Rico) and Comcast: Comcast Digital Voice System wide).


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