EXPERT'S EDGE


"The greatest barrier to success is the fear of failure"

by:Sven Goran Eriksson

Monday, January 25, 2010

Mesh Radio

Governments are keen to encourage the roll-out of broadband interactive multimedia services to business and residential customers because they recognise the economic benefits of e-commerce, information and entertainment. Digital cable networks can provide a compelling combination of simultaneous services including broadcast TV, VOD, fast Internet and telephony. Residential customers are likely to be increasingly attracted to these bundles as the cost can be lower than for separate provision. Cable networks have therefore been implemented or upgraded to digital in many urban areas in the developed countries.

ADSL has been developed by telcos to allow on-demand delivery via copper pairs. A bundle comparable to cable can be provided if ADSL is combined with PSTN telephony and satellite or terrestrial broadcast TV services but incumbant telcos have been slow to roll it out and 'unbundling' has not proved successful so far. Some telcos have been accused of restricting ADSL performance and keeping prices high to protect their existing business revenues. Prices have recently fallen but even now the ADSL (and SDSL) offerings are primarily targeted at provision of fast (but contended) Internet services for SME and SOHO customers. This slow progress (which is partly due to the unfavourable economic climate) has also allowed cable companies to move slowly.


A significant proportion of customers in suburban and semi-rural areas will only be able to have ADSL at lower rates because of the attenuation caused by the longer copper drops. One solution is to take fibre out to street cabinets equipped for VDSL but this is expensive, even where ducts are already available.

Network operators and service providers are increasingly beset by a wave of technologies that could potentially close the gap between their fibre trunk networks and a client base that is all too anxious for the industry to accelerate the rollout of broadband. While the established vendors of copper-based DSL and fibre-based cable are finding new business, many start-up operators, discouraged by the high cost of entry into wired markets, have been looking to evolving wireless radio and laser options.

One relatively late entrant into this competitive mire is mesh radio, a technology that has quietly emerged to become a potential holder of the title 'next big thing'. Mesh Radio is a new approach to Broadband Fixed Wireless Access (BFWA) that avoids the limitations of point to multi-point delivery. It could provide a cheaper '3rd Way' to implement residential broadband that is also independent of any existing network operator or service provider. Instead of connecting each subscriber individually to a central provider, each is linked to several other subscribers nearby by low-power radio transmitters; these in turn are connected to others, forming a network, or mesh, of radio interconnections that at some point links back to the central transmitter.


Opaque Networks Utilizing TOS

There is a potential cost, footprint and power savings by eliminating unnecessary opto-electronic conversions on a signal path in a core optical mesh network. Current networks have seen the deployment of wavelength division multiplexing (WDM) technology, followed more recently by the deployment of an optical transport layer where optical crossconnects (OXCs) are connected using WDM links .both currently deployed WDM systems and OXCs use electronics in the signal path, thereby creating an opaque network .it is very compelling to imagine an optical transport layer where signals remain in the optical domain from the time the time the enter the network until they leave the network, thereby creating a transparent network.

To carry out the assessment of opaque and transparent networks, we make the following basic assumptions on the requirements for core mesh networks:
" Network operators require a lowest cost network, not just lowest cost network elements. For example, even though optical may be cheaper than electrical network elements, a network without wavelength conversions and tunable wavelength access in the optical domain could lead to higher network cost due to inefficient capacity usage than a network with wavelength conversions in the electrical domain.
" A network operator must not be constrained to buy the entire network from a single vendor.
" In order to build a dynamic, scalable and manageable backbone network it is essential that manual configuration be eliminated as much as possible.
" An optical switching system must be easily scalable with low cost and and a small footprint as the network grows to many hundreds of wavelength channels per fiber and to a speed 40 Gb/s

NETWORK ARCHITECTURES

Increased traffic volume due to the introduction of new broadband services is driving carriers to deployment of an optical transport layer based on WDM. The network infrastructure of existing core networks is currently undergoing a transformation from rings using synchronous optical networks (SONET) add/drop multiplexers (ADMs) to mesh topologies using OXCs. Even though the applications driving large scale deployment of transparent optical switches are not currently in place, and the traffic demand does not currently justify the the use of transparent switches that are cost effective at very high bit rates, it is possible that at some point in the future transparent switches may be deployed in the network.,

Transparent network architecture

The transparent network is as shown. Since a signal from a client network element(NE),such as a router, connected via a specific wavelength must remain on the same wavelength when there is no wavelength conversion , only a small size switch fabric is needed to interconnect the WDMs and NEs in a node. This architecture also implies end-to-end bit rate and data format transparency. Another architecture of a transparent switch in a transparent network may include a single large fabric instead of multiple switch matrices of small port counts. If one is to provide flexibility, such an architecture design would require the use of tunable lasers at the clients and wavelength conversions.

DV Libraries and the Internet

The recent academic and commercial efforts in digital libraries have demonstrated the potential for white scale online search and retrieval of cataloged electronic content. By improving access to scientific, educational and historical documents and information, digital libraries create powerful opportunities for revamping education, accelerating, scientific discovery and technical advancement, and improving knowledge. Further more, digital libraries go well beyond traditional libraries in storing and indexing diverse and complex types of material such as images, video, graphics, audio, and multimedia. Concurrent with the advancements in digital libraries, the Internet has become a pervasive medium for information access and communication. With the broad penetration of the internet, network-based digital libraries can interoperate with other diverse networked information systems and provide around the clock real time access to widely distributed information catalogs.

Ideally the integration of the digital libraries and the Internet complete a powerful picture for accessing electronic content. However, in reality, the current technologies under lying digital libraries and Internet need considerable advancement before digital libraries supplant traditional libraries. While many of the benefits of the digital libraries result from their support for complex content, such as video, many challenges remain for enabling efficient search and transport. Many of the fundamental problems with digital video libraries will gain new focus in the Next Generation Internet (NGI) initiative.


DIGITAL VIDEO LIBRARIES

Digital video libraries deal with cataloging, searching, and retrieving digital video. Since libraries are designed to search large numbers of users, digital video libraries have greatest utility when deployed online. In order to effectively service users, digital video libraries need to efficiently handle both the search and transport of video.

The model for user interaction with the digital video libraries is illustrated in the figure. Video is initially added to the digital video libraries in an accessioning process that catalogs, indexes and store the video data. The user then searches the digital video library by querying the catalog and index data. The results are return to and browsed by the user. The user then has options for refining the search, such as by relevance feedback, and selecting items for delivery.

The two prevalent modes for delivering video to the user are video retrieval and streaming. In video streaming the video is played back over the network to the user. In many fast forward, reversed, pause, and so forth. In video retrieval, the video is down loaded over the network to the users local terminal. In this case, the video may be later viewed or used for other applications. Other forms of video information systems, such as video on demand (VOD), video conferencing, and video data base (VDB) systems, share characteristics with digital video libraries. The system generally differs in their support for video storage, searching, cataloging, browsing, and retrieval. Video conferencing systems typically deal with the live, real time communication of video over networks. VOD systems deliver high bandwidth video to groups of users. VDBs deal with storing and searching the structured meta-data relative to video, but are not oriented to words video streaming or concurrent play back to large numbers of users.