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Friday, September 27, 2013

What are the parameters of QoS - Quality of Service?

With the arrival of the new technologies, applications and services in the field of networking, the competition is rising rapidly. Each of these technologies, services and applications are developed with an aim of delivering QoS (quality of service) that is either better with the legacy equipment or better than that. The network operators and the service providers follow from trusted brands. Maintenance of these brands is of critical importance to the business of these providers and operators. The biggest challenge here is to put the technology to work in such a way that all the expectations of the customers for the availability, reliability and quality are met and at the same time the flexibility for quick adaptation of the new techniques is offered to the network operators. 

What is Quality of Service?

- The quality of service is defined by its certain parameters which play a key role in the acceptance of the new technologies. 
- The organization working on several specifications of QoS is ETSI.
- The organization has been actively participating in the organization of the inter-operability events regarding the speech quality.
- The importance of the QoS parameters has been increasing ever since the increasing inter-connectivity of the networks and interaction between many service providers and network operators for delivering communication services.
- It is the quality of service that grants you the ability for the making parameters specifications based up on multiple queues in order to shoot up the performance as well as the throughput of wireless traffic as in VoIP (voice over internet), streaming media including audio and video of different types. 
- This is also done for usual IP over the access points.
- Configuration of the quality of service on these access points involves setting many parameters on the queues that are already there for various types of wireless traffic. 
- The minimum as well as the maximum wait times are also specified for the transmission. 
- This is done through the contention windows. 
- The flow of the traffic between the access point and the client station is affected by the EDCA (AP enhanced distributed channel access) parameters. 
The traffic flow from client to the access point is controlled by the station enhanced distribution channel access parameters. 

Below we mention some parameters:
Ø  QoS preset: The options listed by the QoS are WFA defaults, optimized for voice, custom and WFA defaults.
Ø  Queue: For different types of data transmissions between AP – to – client station, different queues are defined:
- Voice (data 0): Queue with minimum delay and high priority. Data which is time sensitive such as the streaming media and the VoIP are automatically put in this queue.
- Video (data 1): Queue with minimum delay and high priority. Video data which is time sensitive is put in to this queue automatically.
- Best effort (data 2): Queue with medium delay and throughput and medium priority. This queue holds all the traditional IP data. 
- Background (data 3): Queue with high throughput and lowest priority. Data which is bulky, requires high throughput and is not time sensitive such as the FTP data is queued up here.

Ø AIFS (inter-frame space): This puts a limit on the waiting time of the data frames. The measurement of this time is taken in terms of the slots. The valid values lie in the range of 1 to 255.
Ø Minimum contention window (cwMin): This QoS parameter is supplied as input to the algorithm for determining the random back off wait time for re-transmission.
Ø cwMax
Ø maximum burst
Ø wi – fi multimedia
Ø TXOP limit
Ø Bandwidth
Ø Variation in delay
Ø Synchronization
Ø Cell error ratio
Ø Cell loss ratio

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