Internet Bandwidth consumed in making VoIP calls

This one is bit technical. As many of us have started making voice calls on the IP in our smartphones, I thought many of you would be interested to know how much internet bandwidth is consumed if you make a one minute of Voive call on IP i.e. VoIP call. Caveat - Some of highly technical stuff required cross-authentication from Geeks  (Learnt this from Wiki)

Here you go.....

Number of Bytes Consumed in VOIP

To know exactly how many bytes a voice conversation consumes, one needs to know which codec her VoIP service is using. 

CODECS 

A codec is a compression engine that transforms your (analog) voice into digital data, removing the silent moments (which make up to half of all conversations), and do other things to render the data load as light as possible. A codec is an algorithm (sort of a computer program), most of the time installed as a software on a server or embedded within a piece of hardware (IP Phones), that is used to convert voice (in the case of VoIP) signals into digital data to be transmitted over the Internet or any network during a VoIP call.

The word codec comes from the composed words coder-decoder or compressor-decompressor. Codecs normally achieve the following three tasks :

• Encoding – decoding
• Compression – decompression
• Encryption - Decryption

Encoding - decoding

Codec digitizes your analog voice to digital. When you talk over normal landline phone, your voice is transported in an analog way. But with VoIP, your voice is converted into digital signals. This conversion is technically called encoding, and is achieved by a codec. At destination, digitized voice is to be decoded back to its original analog state so that the other person can hear and understand it.

Compression – decompression

Bandwidth is a scarce commodity. To make the digitized voice less bulky, it is compressed. By compression, the same data is stored but using lesser space (digital bits). Once it reaches its destination, it is decompressed back to it original state before being decoded. 

Encryption – decryption

Encryption is one of the best tools for achieving security. It is the process of changing data into such a state that it no one can understand. This way, even if the encrypted data is intercepted by unauthorized people, the data still remains confidential. Once the encrypted data reaches destination, it is decrypted back to its original form. Often, when data is compressed, it already is encrypted to a certain extent, since it is altered from its original state.

Common VoIP Codecs

Codec	Bandwidth/kbps	Comments
G.711	64	Delivers precise speech transmission. low processor requirements. Needs at least 128 kbps for two-way.
G.722	48/56/64	Adapts to varying compressions
G.723.1	5.3/6.3	High compression with high quality audio.  Lot of processor power.
G.726	16/24/32/40	An improved version of G.721 and G.723 (different from G.723.1)
G.729	8	Excellent bandwidth utilization. Error tolerant. License required.
GSM	13	High compression ratio. Free and available in many hardware and software platforms.
iLBC	15	Robust to packet loss. Free
Speex	2.15 / 44	Minimizes bandwidth usage by using variable bit rate.

The approximate values for data consumption of the most common codecs used for VoIP are as follows:

Codec      BR                     NEB

G.711      64 Kbps      87.2 Kbps

G.729      8 Kbps        31.2 Kbps

G.723.1   6.4 Kbps      21.9 Kbps

G.723.1   5.3 Kbps      20.8 Kbps

G.726      32 Kbps      55.2 Kbps

G.726      24 Kbps      47.2 Kbps

G.728      16 Kbps      31.5 Kbps

iLBC         15 Kbps      27.7 Kbps

BR = Bit rate
NEB = Nominal Ethernet Bandwidth (one direction)

Note  - The G.729 codec is one of the best performing voice codecs and most good VoIP services use it.

Calculation of Bandwidth required

Example - for one minute of talk with the G.729 codec.

Now G.729 uses 8kpbs of sampling. Normally one packet of 20 Bytes is sent. With a sampling rate of 8kpbs this means that in one sec, 50 packets are to be sent.

If we are using frame relay protocol over ethernet, the overheads to be used are as follows - 

Frame relay - 6 Bytes(incl header and trailer)

RTP - 40 bytes (breakup 20 bytes of IP, RTP-12 & UDP - 8) [Note if cRTP is used these 40 Bytes can be converted into 4 Bytes]

Ethernet - 18 bytes

Therefore, for each packet of 20 bytes in this case 64 Bytes of protocol and other header bytes are added. Therefore total 84 Bytes will be send. Overall 50 such packets are semt per sec, therefore bit rate is 50*84*8= 33.6 kbps (Mentioned as ~32 kpbs)

This translates into 1920 kilobits (60 x 32) in one minute, which in turn is 240 kilobytes (KB) per minute (1 byte is 8 bits). Now that’s only for the data going out. Inbound data (which also counts) takes the same load, so one can double the figure to 480 KB. This gives a round value to 0.5 MB per minute of conversation.

However, there are many parameters, that are rather technical in nature, affecting the values above. Among them are the compression technology, the size (payload) of the voice packets, the intervals at which they are sent, packet overhead, network protocol used and whether silence suppression is used. (Pl refer table below). If silence suppression/voice activity detection is used, the bandwidth consumption may drop 50%

Packet voice transmission requirements (Bits per second per voice channel)
Codec	Voice bit rate	Sample time	Voice payload	Packets per second	Ethernet	PPP or Frame Relay RTP cRTP
G.711	64 Kbps	20 msec	160 bytes	50	87.2 Kbps	82.4 Kbps	68.0 Kbps
G.711	64 Kbps	30 msec	240 bytes	33.3	79.4 Kbps	76.2 Kbps	66.6 Kbps
G.711	64 Kbps	40 msec	320 bytes	25	75.6 Kbps	73.2 Kbps	66.0 Kbps
G.729A	8 Kbps	20 msec	20 bytes	50	31.2 Kbps	26.4 Kbps	12.0 Kbps
G.729A	8 Kbps	30 msec	30 bytes	33.3	23.4 Kbps	20.2 Kbps	10.7 Kbps
G.729A	8 Kbps	40 msec	40 bytes	25	19.6 Kbps	17.2 Kbps	10.0 Kbps
Note: RTP assumes 40-octets RTP/UDP/IP overhead per packet Compressed RTP (cRTP) assumes 4-octets RTP/UDP/IP overhead per packet Ethernet overhead adds 18-octets per packet PPP/Frame Relay overhead adds 6-octets per packet

If we take the value of 50 kbps for any codec, it will give (after calculations and approximations) 0.75 MB per minute of conversation.

China has 338 Million internet users !!

The state-run China Internet Network Information Center (CNNIC) said that its Internet statistics show that Internet users in China are up by an estimated 40 million from the end of last year. The internet user base has reached reaching 338 million users by June 2009 and the country has achieved a density of 25.5 percent, which is above the global average of 23.8 percent. By the end of June, there were 3,061 million websites registered in China, 16.25 million domain names and 205 million IP addresses.

In China, internet service providers include companies like Baidu, Alibaba group and Tencent.
Many of these Internet service companies have carved out niches using their market knowledge to satisfy consumer demand for music, news, instant messaging and search functions with the other four popular services being in way of online gaming, videos, email and blogging. As reported in Telecommunications online, Tencent Holdings achieved a total revenue of CNY 5.38 billion (US$787.9 million), an increase of 77.5 percent increase over the same period last year. It had a cash position of CNY 7.7 billion (US$1.1 billion) at the end of first half 2009. Noted for its instant messaging service, it reportedly has 990 million user accounts of which 448 million are active.

Also reporting positive results is China’s leading Internet search provider, Baidu, which attained a turnover of CNY 1.1 billion (US$161 million) for its second quarter in 2009, representing a 36.7 percent increase year-on-year. As for the online auction provider Taobao, the country’s equivalent of eBay, it had a favourable first half year of 2009 recording revenue of CNY 80.9 billion (US$11.8 billion) and it reportedly has set a target of CNY 200 billion (US$29 billion) for the whole year. Taobao is part of the Alibab group which also has interests in online payment and business-to-business platforms in 240 countries.

According to the CNNIC, the number of Chinese shopping online grew in the first six months with 14 million more shoppers to reach a total of 87.8 million. Online shoppers, however, only account for a quarter of Chinese Internet users, compared to two out of three in South Korea, the United States and Europe. Security risks of shopping on the Net may be one withholding factor.

I presume the things will not be much different in India

Indian regulator targets non-performing ISPs

Concerned over poor track record of Internet Service Providers, Indian telecom regulator TRAI has recommended lowering of foreign direct investment on par with telecom sector at 74 per cent from the existing 100 per cent. ISPs having 100 per cent FDI equity should be given two years for reducing foreign holding to 74 per cent, it said.

In its recommendations to Department of Telecom, TRAI has also suggested major changes in financial and regulatory levies. Instead of free entry, it recommended levying an entry fee of up to Rs 20 lakh along with a uniform licence fee of six per cent of gross revenue. ISPs seeking licence at national level will have to pay Rs 20 lakh as entry fee while it will be Rs 10 lakh for state level ISPs. The minimum annual licence fee has been pegged at Rs 5,000 for district level ISP, Rs 10,000 for state level and Rs 50,000 for national level ISP.

The regulator has taken a tough stand as the objective of competition and growth of Internet have not been met. "Out of 700 licences issued within three years of opening of ISP sector to private service providers, only 389 licensees exist on Thursday. As per the performance monitoring report with TRAI, only 135 Internet service licensees are functionally active," TRAI said.