VoIP Technology and Its Benefits

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Questions and Answers

What is the main reason G.729 codec is preferred in VoIP applications?

G.729 is preferred in VoIP applications because of its low bandwidth requirements.

How does G.723.1 function in multimedia communications?

G.723.1 functions as a dual rate speech coder, transmitting at either 5.3 or 6.3 kbit/s.

Describe the process of voice signal conversion in VoIP.

In VoIP, an analogue voice signal is converted into digital data packets using codecs before being transmitted.

What role do gateways play in VoIP telephone calls?

Gateways in VoIP act as access points that connect local calls to the Internet and bridge them to remote destinations. Signup and view all the answers

Explain how VoIP calls can reduce costs for international communication.

VoIP reduces international call costs by utilizing the Internet for long-distance portions, requiring only the local PSTN for connections. Signup and view all the answers

What is the function of a soft switch in a VoIP system?

A soft switch in a VoIP system manages the translation of phone numbers to IP addresses using a specialized database. Signup and view all the answers

How does VoIP ensure that the original voice packets are recovered at the receiving end?

VoIP recovers original voice packets by decompressing the compressed data using DSP and then converting it back to audio through a CODEC. Signup and view all the answers

What happens after digital data packets arrive at their destination in VoIP?

Once the digital data packets arrive, they are converted back into analogue voice signals for the recipient to hear. Signup and view all the answers

What key information does a soft switch maintain about an endpoint on the network?

A soft switch maintains the endpoint's location on the network, associated phone number, and current IP address. Signup and view all the answers

How does web service integration enhance customer interactions in VoIP?

Web service integration allows users to connect to a company's call center by clicking a Call button on the company's webpage. Signup and view all the answers

What advantages does VoIP provide for a company with multiple site locations?

VoIP allows for secure VPN connections over the IP network, enabling voice transmission without needing separate PSTN channels. Signup and view all the answers

What is the role of the Real-Time Transport Protocol (RTP) in VoIP?

RTP operates on top of UDP to facilitate the transport of real-time data like voice, but does not guarantee quality of service. Signup and view all the answers

What does Resource Reservation Protocol (RSVP) do in an IP network?

RSVP allows an endpoint to request a simplex flow through the network with a specified quality of service level. Signup and view all the answers

What is the significance of tunneling and ciphering IP packets in a VPN connection?

Tunneling and ciphering secure IP packets enhance privacy and security, protecting data as it travels between connected sites. Signup and view all the answers

What equipment is required in office B to utilize VoIP without a Private Automatic Branch Exchange (PABX)?

Office B only requires PCs with suitable sound cards, headsets, and VoIP software to function without PABX. Signup and view all the answers

What challenge does RSVP face in the context of telephone call establishment over an IP network?

RSVP encounters signaling issues, which relate to how telephone calls are initiated and managed across the network. Signup and view all the answers

What technology does VoIP utilize for making voice calls?

VoIP utilizes a broadband Internet connection to make voice calls instead of a regular phone line. Signup and view all the answers

Name two types of VoIP services available for users.

VoIP services can allow calling only other users of the same service or allow calls to any telephone number, including local and international. Signup and view all the answers

What is the role of an analog to digital converter (ADC) in VoIP?

The ADC amplifies and digitizes the voice signal to enable its transmission over the Internet. Signup and view all the answers

What is the sampling rate used by the ADC in VoIP technology?

The ADC samples the voice signal at a rate of 8 kHz. Signup and view all the answers

How does the bit stream for VoIP get processed to reduce data rate?

The bit stream is processed and compressed by the Digital Signal Processor (DSP). Signup and view all the answers

What compression algorithm is mentioned for VoIP and what is its bit rate?

The G.729 compression algorithm is used, which operates at a bit rate of 8 kbit/s. Signup and view all the answers

What advantage does VoIP provide to subscribers in terms of cost?

VoIP reduces the cost of international and long-distance calls for subscribers. Signup and view all the answers

What type of phone can be used with VoIP services?

Users can utilize either a special VoIP phone or a traditional phone connected to a VoIP adapter. Signup and view all the answers

What are the main two protocols used for overcoming signaling issues in VoIP?

H.323 and SIP. Signup and view all the answers

What is a key feature that H.323 offers for real-time communication?

It provides specifications for videoconferencing, data sharing, and audio applications. Signup and view all the answers

Why is H.323 considered more complex than SIP?

H.323 features a complex signaling mechanism and requires more configuration. Signup and view all the answers

How does Session Initiation Protocol (SIP) compare to H.323 in terms of flexibility?

SIP is more flexible and can be used with a wider range of devices and networks. Signup and view all the answers

What kind of setup process does SIP use for initiating a call?

SIP uses a simple invitation/request-response mechanism. Signup and view all the answers

In what way is SIP firewall-friendly compared to H.323?

SIP's simple request-response mechanism can be easily translated by firewalls. Signup and view all the answers

What does the acronym CODEC stand for and its purpose in VoIP?

CODEC stands for coder-decoder or compression-decompression, used for compressing and decompressing digital media. Signup and view all the answers

What role does RAS play in the context of H.323?

RAS administers user authorization, monitoring, and permission levels. Signup and view all the answers

What is the role of the H. 245 protocol in packet-based networks?

H. 245 facilitates the transmission of call management and control signals. Signup and view all the answers

How does the Real-Time Transport Protocol (RTP) differ from the Real-Time Control Protocol (RTCP)?

RTP carries media streams, while RTCP monitors transmission statistics and quality of service. Signup and view all the answers

List two advantages of VoIP for consumers.

Significantly lower costs and mobility with any internet connection. Signup and view all the answers

What is one major drawback of VoIP regarding emergency calls?

It is hard to find the geographic location of the caller during an emergency. Signup and view all the answers

Describe what an ATA (Analog Terminal Adapter) does in a home VoIP setup.

An ATA connects a standard home telephone to an existing broadband internet modem. Signup and view all the answers

What is the maximum acceptable latency for VoIP calls, and why is it important?

The maximum acceptable latency is 150 ms, as it ensures a quality communication experience. Signup and view all the answers

How does the quality of VoIP compare to traditional PSTN?

VoIP quality can be variable depending on the internet connection, while PSTN offers high quality. Signup and view all the answers

What impact do lost or delayed packets have on VoIP communications?

They can cause drop-outs in voice, affecting the clarity of the conversation. Signup and view all the answers

What is the total number of channels available for data transmission in a VoIP system with 16 total channels?

15 channels are available for data transmission. Signup and view all the answers

How is the serial data rate calculated for a VoIP system with a sampling rate of 3.5 kHz and 96 bits per frame?

The serial data rate is calculated as 336 kHz. Signup and view all the answers

Calculate the codec bit rate using the G.711 codec with an 8-bit sample and packetization interval of 0.02 ms.

The codec bit rate is 800 Kbps or 0.8 Mbps. Signup and view all the answers

What is the bandwidth required for one VoIP call using the G.711 codec at 0.8 Mbps?

The bandwidth per call is 1.6 Mbps. Signup and view all the answers

How much total bandwidth is needed for 10 concurrent VoIP calls with each call requiring 1.6 Mbps?

The total bandwidth needed is 16 Mbps. Signup and view all the answers

What is the formula for calculating packet loss rate in a VoIP system if 20 out of 200 packets are lost?

The packet loss rate is 10%. Signup and view all the answers

If the maximum jitter is 20 ms, latency is 50 ms, and there is an additional buffer of 10 ms, what is the total jitter buffer size?

The jitter buffer size is 80 ms. Signup and view all the answers

Explain the significance of calculating packet loss rate in VoIP applications.

Calculating packet loss rate is crucial for ensuring call quality. Signup and view all the answers

Study Notes

Course Information

Course title: Telecommunication Networks and Switching
Course code: EGEC4120
Chapter: 7 - VoIP (Voice over IP)
Prepared by: Analene Montesines Nagayo and Mohamed Yusuf Hasan
University: University of Technology and Applied Sciences, Al Musannah

Learning Outcome

Outcome 6: Demonstrate a broad understanding of Multimedia representation and the interaction with telecommunications protocols including IP Telephony

What is VoIP?

VoIP (Voice over Internet Protocol) is a technology that allows voice calls using a broadband Internet connection instead of a regular phone line.
It mostly bypasses the existing telephone system and relies on high-speed Internet connection.
VoIP systems include systems such as Voice over Broadband (VoB), Voice over Digital Subscriber Line (DSL), Voice over Internet (Vol), and Voice over Wireless Local Area, Network and Internet telephony, according to the ITU-U.

VoIP Functionality

Some VoIP services only allow calls among users of the same service, others can handle calls to any telephone number (including local, long-distance, mobile, and international).
Some use a special VoIP phone, some a computer and others allow using a traditional phone with a VoIP adapter.

VoIP Implementation

VoIP implementation is advantageous to subscribers because it reduces the cost of international and long-distance calls.
It's also beneficial for Internet Service Providers (ISPs) because it increases the use of their Internet services.

Cisco 7970 IP Phone

The Cisco 7970 IP phone has an LCD display with XML applications, softkeys, a keypad, rocker key and services button. Phone lines are also displayed.

How VoIP Works

The voice signal is first amplified and digitized by an analog to digital converter (ADC) which is part of a coder-decoder (codec) circuit that includes a DAC.
The ADC samples the voice signal at 8kHz and produces an 8-bit word for each sample in a serial manner.
A higher bandwidth is needed to transmit the bit stream (64kHz or more).
A codec compresses the digital data from the ADC and sends it over the Internet.
The destination phone decompresses the data, converts it back into an analog signal, and plays it through speakers.

VoIP Compression Methods

G.729 is a narrow-band vocoder-based audio data compression algorithm using a frame length of 10 milliseconds.
G.729 is a coding of speech at 8 kbit/s; it uses code-excited linear prediction speech coding (CS-ACELP).
G.723.1 is a dual-rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s.

VoIP at the Transmission/Reception Point

At the transmitting phone, the voice signal is converted into digital data packets and sent.
At the receiving phone, the digital data packets are converted back into an analog signal, enabling communication.
VoIP recovers the original packets, decompresses them, converts them back to the original digital sound.

VoIP Applications (Cases)

Case I: IP telephone service provider's local office uses PSTN to connect to the gateway on the Internet and then the gateway connects to the remote office to make the call.
Case II: A customer surfing the internet clicks on a call button located on a company's webpage to contact customer support, ordering department or help desk using a web browser and a personal computer with a compatible speech encoder.
Case III: Two company locations (A & B) use IP Network to connect using a VPN. The IP Network is used for both data and voice communication. No need for separate channels.

IP Address to Phone Number Translation

VoIP translates phone numbers to IP addresses using a central call processor/soft switch.
The soft switch knows the endpoint's location on the network, the associated phone number, and current IP address.

VoIP Protocols

Real-Time Transport Protocol (RTP): Runs on top of UDP, used for audio/video streaming, does not guarantee quality of service (QoS).
Resource Reservation Protocol (RSVP): Designed for controlling lower-layer protocols to maintain/monitor bandwidth/delay, throughput, etc..
H.323: Widely used protocol for real-time, interactive videoconferencing, data sharing, and audio applications. Initially designed for video conferencing and is adapted for VoIP.
Session Initiation Protocol (SIP): A more streamlined protocol designed specifically for VoIP with wider range of devices (mobile, wireless). Simpler call setup and more firewall-friendly.
Signaling protocols: Define messages for call establishment, maintenance, and clearing functions.

VoIP Advantages

For businesses: security at a lower cost.
For consumers: significantly lower costs.
For service providers: lower investment, capital and operating costs.
Less bandwidth requirements.
Low/no cost software and hardware, free VoIP to VoIP and low cost VoIP to Public Switch Telephone Network(PSTN).
Mobility: Any internet connection and growing number of wireless broadband locations.

VoIP Disadvantages

Quality: High Quality PSTN, variable VoIP quality depending on connection quality, dependent on wall power.
Packet Loss: Lost or delayed packets may cause voice drop-out.
Emergency Calls: Difficulty locating geographic location.
Security: Most VoIP services do not support encryption.
Latency: Relatively long time for voice transmission, reassembling time of packets at the destination, latency from passing through numerous routers and servers, Maximum acceptable latency of 150ms.

Internet Phone Systems

Two basic types of IP phones: Home VoIP (high-speed internet service and ATA/Analog Terminal Adapter which connects standard home phones to broadband Internet modem) and Enterprises IP Phones.

Drill Problems (and Answers)

Drill Problem 1: Calculations related to a PCM system using 16 channels of data, including synchronization.
Drill Problem 2: Calculations related to a VoIP system using the G.711 codec. Number of concurrant calls= 10
Drill Problem 3: Packet loss rate calculation. Example: 200 sent and 20 lost = 10%.
Drill Problem 4: Calculation for determining the jitter buffer size, given maximum jitter, latency and additonal buffer size (example: 80ms).

References

Frenzel, Louis E. Jr. Principle of Electronics communication systems (3rd Edition).
Tarmo Anttalainen. Introduction to Telecommunications Network Engineering (2nd Edition). (Reference URL provided in document)

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Description

Explore the fundamental concepts of Voice over Internet Protocol (VoIP) through this quiz. Learn about codecs like G.729 and G.723.1, the role of soft switches, gateways, and how VoIP reduces costs for international communication. This quiz covers the key processes and protocols that enhance multimedia communications.