How to Improve VoIP Gateways

Increased demand for video-based applications in the mobile network drive the deployment of 3G networks. Inherent complexities in traditional video gateways cause performance bottlenecks and inflate costs. If the industry expects to absorb the impending explosion in demand, these proposed cost-saving and complexity-reducing changes are needed.

Unrelenting market demand for video-based applications over mobile networks is driving the increased deployment of 3G networks. The 3G-324M protocol is used by 3GPP and 3GPP2 standards organizations to combine voice, video, data and control into a single 64kbps stream of circuit-switched data. This is a departure from the standard Real-Time Transport Protocol/Real-Time Transport Control Protocol (RTP/RTCP) used to transport real-time video and voice over IP networks. The industry’s use of traditional video gateways to bridge video in the mobile network (3G-324M) and in the IP network (video/voice over RTP) has multiple deficiencies impeding migration to 3G networks including:

Excessive system complexity Excessive costs per port Separate voice and video gateways systems adds to costs and complexity Degraded customer experience State of Traditional 3G-324M to IP Video Gateways Current Mobile-to-IP video gateways convert video and audio signals from their state in the mobile network into the state required for transmission over the IP network.

Once in the IP network, video content is carried by three separate UDP/IP streams: 1. A compressed video stream encapsulated in an RTP stream and inserted into a UDP/IP packet. 2. A compressed audio stream encapsulated in an RTP stream and inserted into a UDP/IP packet. 3. Signaling and control information transported using SIP or H.323. In the mobile network, 3G-324M based video content is transported using a single H.223 64kbps stream that multiplexes audio, video, data, and control information. The video portion of the H.223 protocol is usually MPEG-4 and the audio portion uses NB-AMR compression. The channel parameter exchange and session control portion uses the H.245 protocol. The complexities involved in delivering these services result in significant performance derogation and increased operational costs.

For the industry to absorb the impending explosion in demand for video-based applications over mobile networks, radical cost-saving and complexity-reducing changes are needed. Those changes require a gateway capable of handling the circuit-switch to backet-switch layer while offloading other tasks to a separate media server or to the IP videophone itself. The Solution The key to improving VoIP gateway performance and lowering costs is a high-performance video gateway with the following properties:

1. It is not used for IP video protocol termination (3G-324M). 2. It is not used for IP video protocol termination (video/audio over RTP, with SIP/H.323 for control). 3. It hands voice and video transcoding over to a media server. Items 1 and 2 will result in a reduction in operational complexity while item 3 will significantly reduce per-port costs and increase video quality and service flexibility. The following methods (3G-324M over IP) provide the ability to implement a streamlined and cost-saving solution. Method 1 - IP conversion done by IP videophone 1. Mobile and IP end points implement video sessions using the 3G-324M protocol which is terminated end-to-end. On the mobile side, video is transmitted as a standard 64kbps stream.

On the IP side, the 64kbps stream is encapsulated in UDP/IP packets. The end point on the IP side is implemented in the IP videophone. 2. Encapsulation of 3G-324M into IP packets is similar to encapsulation of voiceband data into IP packets. It could involve breaking up the 3G-324M stream into frames of a given size and then adding RTP heads with optional redundancy and forward error correction mechanisms to increase transport reliability. 3. RTP encryption should be used. 4.

In messaging and video surveillance applications where end-to-end delay is not a concern, transportation via reliable UDP packets such as the SPRT protocol used in ITU-V.150 may be substituted.

Method 2 - IP conversion is done by the media server 1. The mobile end point implements video sessions using the 3G-324M protocol, and the IP video end point implements video sessions using video/voice over RTP. SIP/H.323 is used for signaling and control. The media server in the IP network converts IP video into a H.223 64kbps stream that is encapsulated over RTP/UDP. Steps 2, 3 and 4 are the same as method 1.

Implementation This powerful solution is simply a regular VoIP gateway operating in VBD (Voice Band Data) mode with these requirements and features: a. Media type set to transparent pass-through of 64kbps data from the IP/UDP/RTP side to the E1/T1 side and vice versa. The VoIP gateways enter this mode of operation under any of these scenarios:

The gateway was configured to automatically operate in this mode. The gateway receives PSTN signaling information in the user-to-user information field of the ISDN-PRI signaling. The gateway receives IP signaling such as MGCP within the media gateway controller. The gateway receives modem or fax tones. The 3G-324M stack of the mobile phone must transmit a modem tone in order to force the gateway into pass-through mode as if it were handling a modem call. b. The gateway’s jigger buffer must adapt slowly or be configured to a fixed depth of 80 ms in order to avoid unwanted frame loss.

c. The RTP payload type carrying the 3G-324M stream can be the same as regular G.711 voice.

d. The same redundancy and FEC mechanisms can be used for modem transmissions over G.711 (VBD mode). e. The IP payload frame size should be set to the smallest possible value permitted by all components on the IP side of the system. 10ms is recommended. f. The E1/T1 interface must be a link without attenuation pads and robbed-bit signaling to ensure that a transparent 64kbs stream flows from the mobile phone to the IP network.

Summary Benefits for This Approach

1. Low gateway costs.

2. Easy upgrade path for voice gateway manufacturers supporting video when bridging between IP and mobile networks.

3. Media server manufacturers can support the 3G-324M protocol without physically supporting T1/E1 circuit-switched interfaces.

4. Decoupling the IP-to-TDM conversion process from the video processing makes IP-to-TDM conversion as simple as implementing a G.711 VOIP gateway and offloading the heavy video processing to TDM-based networks.

5. Reduced end-to-end delay provides better conversational video experience for IP videophones supporting 3G-324M-over-IP.

6. Shorter call setup time.

Avi Fisher is CTO of Surf Communications. He is an expert on Triple Play DSPs and was the first contributor to the ITU V.150 standard. A longer version of this article on VoIP Gateways with illustrations as well additional resources is available at http://www.surf-com.com

Jun

22

How an AMC DSP Farm Can Simplify and Accelerate Your Telecom Development Efforts

Filed Under Mobile - Cell Phones | Leave a Comment

AMC Solutions Speed up Telecom Development The availability of ATCA (Advanced Telecom Computing Architecture) and MicroTCA (Micro Telecom Computing Architecture) platforms, and with them, AMC (Advanced Mezzanine Card) solutions, represents a new era in which developers of telecom, military, medical and other processing-intensive applications are able to reduce internal R&D efforts, as well as manufacturing and operational expenses, by using commercial off-the-shelf (COTS) building blocks from 3rd party suppliers. This trend is driving a wave of new systems and architectures for a wide variety of applications: audio and video gateways for 3G, IMS and other networks, media servers, packet-to-packet applications, session border controllers, cryptography, lawful interception, and medical image processing, to name a few. Many equipment manufacturers are entering the prototype stages today in order to define the systems of tomorrow.

The Design Conflict The prototype stage is typically characterized by an internal design conflict: how to deal with high-level system issues without neglecting the detail-level issues necessary to ensure that the system will meet marketing requirements. This is the stage where a flexible solution can come in handy.

DSP Based AMC Board The good news for those seeking such a solution is that it already exists, in the form of a DSP-based AMC board for ATCA, TCA or proprietary systems. This modular AMC form factor DSP resource board has advanced triple play (voip, video, modem, fax) processing; a modular plug-in that carries up to four pairs of same/mixed types of DSPs; is RoHS-
compliant; and supports a variety of configurations. This paradigm allows
varying types of DSPs to be assembled simultaneously on a single AMC carrier.

The Luxury and Benefits of Deferred Decision-Making The great advantage of selecting such a flexible AMC-based solution is that the same resource board can be used for all stages in the development cycle, from prototype through final production, since you can start designing your system without committing to: * the specific serial interfaces (such as AMC.1,2,3,4) to be used in the final AMC solution * the specific type of DSPs to be used in the final system * the number of DSPs per board needed to achieve the required channel density * the types of DSPs to be integrated on the same board simultaneously

The Result: Shortened Time-to-Market This flexibility enables equipment manufacturers, during the critical initial phase of product design, to focus on the system level issues, such as chassis specifications, blade types, throughputs and other required capabilities. This type of approach saves valuable research and development resources, since the detailed design decisions relating to the AMC board can be modified at any time during the development cycle. As a result, the first prototype can be achieved quickly, and overall time-to-market will be shortened considerably.

For more information, visit www.surf-com.com.

Danny Frydman is VP Research & Development. He is responsible for Surf’s development activities, including hardware and software R&D, production-readiness, and support for field deployment. A longer version of this article on VoIP Gateways with illustrations as well additional resources is available at http://www.surf-com.com

Jun

22

How to Customise your Cellular/Mobile Phone?

Filed Under Mobile - Cell Phones | Leave a Comment

Our current choices of Cellular/Mobile handsets are really quite amazing, it seems that there is a phone to suit everyone, what ever your requirements and necessities. The features of our phones are ever increasing and we feel somewhat comforted by the multiple uses of our handsets. Almost everyone is sure to find a phone that will fit their needs, not just in the variety of the phones uses but also a handset that is aesthetically pleasing.

It might be the colour or the shape or even the feel of the phone or a combination of all three. To many individuals it is as important to them to be seen with a smart phone as it is to be seen with the latest hair cut or that great pair of jeans that are a must have item of the time. People are conscious of fashions and trends, of what they possess at the time and also of what others possess around them.

But what really makes people stand out is having something customised exactly to their tastes. We are able to dress up our phones with accessories that will change the colours of the handset or we can add flashing accessories and a whole host of modifications to make our phone unique. It gives us a feeling of being individual and aswell as being able to customise the hardware of the phone we find that we can also very easily customise the phone with content.

Ringtones are sounding better than they ever have, this is down to the handsets being able to handle more voices and Polyphonic Ringtones and Truetones sounding so much more pleasant compared to the ear piercing and harsh tones that used to emit from our bulky handsets years ago. The choice of Cellular/Mobile content is enormous, with sites like Ringtonesbase.com providing a constantly growing library of everything from Ringtones and Truetones to Video, Games and Screensavers to brighten up your handset. Customising your phone can be done very quickly and with a number of options to obtain the required content means that it will take up very little time of anyone’s day.

The fun part is that you get to show off to the world, well at least your friends and family, the unique looks and sounds of your Cellular/Mobile phone, and if you get bored of the Ringtone on your phone it is just a case of taking a look at the huge amount of content available and in no time your handset will be feeling like brand new again with the great sounding Tones available or Games to keep you occupied or what ever you choose. The future looks even brighter for the Cellular/Mobile world with new technologies always in the pipeline ensuring that we will all have new features and new ways of upgrading and customising our handsets.

Changing our phones appearance both inside and out is just a matter of choosing what we like best and what we feel says something about us personally. We are all unique and we like to show that in our lives when ever possible, the good thing is that the choice for us is huge, all we have to do is choose

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