Showing posts with label QoS. Show all posts
Showing posts with label QoS. Show all posts

February 12, 2009

VoIP Next-Generation Network Overview

As far as I’m concerned, many modern telco engineers agree that VoIP can be deployed in many different network segments. To date, it has been progressively deployed in the backbone and enterprise networks. Deploying VoIP as an end-to-end Next-Generation Network solution introduces additional constraints and issues discussed by many VoIP researcher.

 

voip-arch
example of VoIP Next Generation Network architecture

 

Whatever the justifications brainstormed by many researcher, it come to conclusion that most service providers recognize the VoIP is the direction of the future. However when looking at a future PSTN scale solution service providers must ensure that the following key requirements are met to provide equivalence with the PSTN:

· Security
· Quality of Service
· Reliability
· Migration path
· OSS support
· Billing
· Network Interconnection

These issues are by no means simple and in many cases have delayed roll out of VoIP services. Future research in this field will look into more detail issues to consider at a high level how this next-generation network might be addressed. Perhaps, it can tackled as many issues as concerned by the researchers.


April 7, 2008

WiMax vs WiFi

WiMax (802.16e) is a newer standard of wireless networking designed to provide the last mile of high speed internet access to the end user. Some people would call Wimax WiFi on steroids but this would be to broad of an assessment. Wifi was and still will be used in LAN environments for the foreseeable future. WiMax was designed to provide (MAN) Metropolitan Area Access, to homes and businesses.
WiMax base stations will have the ability to provide approximately 60 businesses with T1 access and hundreds of homes with DSL/Cable speed access…in theory. Engineers are stating that WiMax has the capability of reaching 30 Miles but real world testing has shown 4-8 mile working radius.

WiMax (MAN) deployments are similar to a WiFi network. First the ISP would have their T3 or higher access. The ISP would then use line of sight antennas (Bridges) to connect to towers that would distribute the non line of sight signal to (MAN) residential/business clients.

WiMax line of sight antennas operate at a higher Frequency up to 66mhz. Distribution antennas do not have to be in the line of sight with their clients. Non – line of sight towers operate on a range similar to WiFi . WiMax can operate right next to cell phone towers with no interference.
WiMax networks are similar to Wifi in deployment. The Wimax Base station/Tower will beam a signal to a WiMax Receiver. Similar to a WiFi access point sending a signal to a laptop. As far as I can tell laptops will be shipping with Wimax receivers in 2006.

Wimax Diagram

QOS (Quality of Service) is an major issue with WiMax because of the number of people accessing a tower at once. Some would think that a tower could be easily overloaded with a lot of people accessing it at once. Built into the WiMax standard is an algorithm that when the tower/base station is nearing capacity then it automatically will transfer the user to another WiMax tower or cell. Unlike a Wifi clients who have to kind of fight to stay associated with a given access point; WiMax will only have to perform this hand shake at the MAC level the first time they access the network.

WiMax is designed for building a network infrastructure when the environment or distance is not favorable to a wired network. Also, WiMax is a cheaper and quicker alternative than having to lay wire. Third world countries will greatly benefit from deploying WiMax networks. WiMax can handle virtually all the same protocols Wifi can including VOIP. African countries are now going to start deploying WiMax networks instead of cell phone networks. Disaster zones can also utilize WiMax giving them the ability to distribute crisis information quickly and cheaply.

Militaries are already using wireless technology to connect remote sites. Logistics will be simplified with the ease of tracking with RF technologies. WiMax can also handle Webcams and streaming video which would give commanders eyes on target capability. Just imagine if planes were able to drop preconfigured self deploying WiMax antennas in strategic areas giving troops real time battlefield intel. Armed with wireless cameras, drones and a GPS one soldier would truly be an Army of One.

As WiMax is deployed in more areas theory and real life capabilities of WiMax will come to light. The differences between WiMax and Wifi are simple. Think of a WiMax network as an ISP with out wires, with the signal providing your internet access to your business/ home. Wifi will be used within in your LAN for the near future.

Eric Meyer writes about networking wireless technology. Visit his blog here.

November 2, 2007

CROSS-LAYER WIRELESS MULTIMEDIA TRANSMISSION:

BRIEF REVIEW OF ADAPTATION AND PROTECTION STRATEGIES AT DIFFERENT LAYERS

Numerous solutions have been proposed for efficient multimedia streaming over wireless networks. Potential solutions for robust wireless multimedia transmission over error-prone networks include application-layer packetization, (rate-distortion optimized) scheduling, joint source-channel coding, error resilience, and error concealment mechanisms. An excellent review of channel-adaptive multimedia streaming research is provided in.

Transport issues for wireless (multimedia) transmission have been examined in. At the PHY and MAC layers, significant gains have been reported by adopting cross-layer optimization, such as link adaptation, channelaware scheduling, and optimal power control. However, these contributions are aimed at improving throughput or reducing power consumption without taking into consideration multimedia content and traffic characteristics. Explicit consideration of multimedia characteristics and requirements can further enhance the important advances achieved in cross-layer design at the lower layers. Possible solutions and architectures for cross-layer optimized multimedia transmission have been proposed in.

To provide QoS for multimedia applications, the IEEE 802.11 Working Group has currently defined a new supplement to the existing legacy 802.11 MAC sublayer, called IEEE 802.11e. Note that even though emerging MAC standards provide QoS support, there are no QoS guarantees for multimedia applications, and systemwide resource management is not always fair or efficient. This is due to the time-varying nature of the wireless channel and multimedia characteristics, and also the lack of cross-layer awareness of the application and MAC layers about each other.
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