Friday, 21 August 2009

Reliability and QoS in CATV Industry

With the digital technology becoming cheaper and fast developments in the telecom and broadcast field, the cable television industry in India is undergoing a vital change, from a disorganised mom and pop service to a much organised affair on a large scale. Surprisingly it is not the new comers who are initiating the changes, instead it is the same unorganised units who started this industry, who are fast upgrading their networks keeping in mind the future requirements. 
CAS or conditional access regulation has been the biggest prime mover for this second revolution in the cable TV industry. All the big MSOs are transforming their analog networks to digital with the result that their franchisees have to maintain the same standards to provide better services to their subscribers. Even the independent cable operators are installing digital headends and consolidating the neighbourhood networks with HFC networking. Fiber is also being used extensively by the rural area operators to cover long distance. 

Although quality of service plays an important role in any service oriented industry, yet cable operators, by the very inherent style of their working did not realise this so far. 
Government's attitude towards telecom industry, that is making it private and liberal is bringing in large corporate houses into the field of converging technologies of computers, broadcasting and telecommunications.This has necessitated all players in the cable television field to change their attitude too, to join the bandwagon of large scale service providers and make the quality and reliability of their services the main focus of their business. Some other factors necessitating these changes are : 
• Digital Technology is becoming affordable. 
• Rates of fiber optic cables and equipment have crashed. 
• Establishment of HFC networks by the MSOs and large independent cable operators. 
• Customers expectation of service quality in CAS implemented areas has gone up. 
• DTH customers are exposed to the latest in technology including interactive television and HDTV. 
• Telcos are promoting IPTV with hyped announcements. 
• In this competitive digital world last mile operators will require to provide all channels with good quality otherwise payments will be held up. 
Considering the above, reliability and quality of cable TV services will gain a lot of importance. Most important of all, due care will be given to design of the network, HFC or plain co-ax. 

Network Requirements 
1. Transmission quality: Bureau of Indian Standards (BIS) has already laid down the minimum standards of service that the operators must ensure at the customer end. These are : 
C/N>44 dB - depends on input levels to amplifiers. 
Minimum Carrier level 60 dbμV 
Maximum Carrier level 80 dbμV 
Slope<12 dB- depends upon quality of Coax cable and passives used. 
X-Mod better than 57 dB-depends upon output level of amplifier (higher the level lesser the cascading limit and hence the radius of operation). 
CSO better than 57 dB-depends upon output level of amplifier. 
2. Effective Bandwidth: Effective bandwidth of the network must cater for all the channels provided by the network as well as a minimum of 10% additional channels for future enhance-ment. In the metros, 860 MHz has become the industry standard for networks introducing VoD. All components in the network including taps and splitters must have this bandwidth capability to ensure better service. 
3. Service Reliability: This is the probability that a system will survive without interruption for a defined period. Network reliability should also take "degraded services" into account and not focus on complete failure of a service. 
4. Outage Rate: This is the average rate at which service interruptions occur. 
5. Availability: This is the percentage of time the service is available. 
 * Availability Objectives
International availability objectives for different industries are given below 
(A) Telephony Industry-99.99% (53 minutes per year) 
(B) Cable Industry/Broadcast video- 99.7% (26.3 hr per year) 34 
• Traditional HFC Plants - 99+% (3.7 days/year) 
• Broadcast Video - 99.7% (26 hrs/year) 
• Cable Modems - 99.8% (13 hrs/year) 
• Primary Line Telephony -99.99% (53 mns/year) 
• Secondary Line Telephony -99.7% (26 hrs/year) 

In home local wiring is largest single cause of service outage for CATV industry. This brings us to the importance of better drop cable wiring in the customer home. This includes use of better cable, tap and splitters and RF connection to the television/ modem. Subscribers and Builders need to be educated to get proper internal wiring done for CATV by professionals and not ordinary electricians while building homes. Main causes of service interruption in a network can be listed as below: 
• Signal Quality 
• Commercial Power Problems 
• Equipment failure 
• Interfering signals 
• Network capacity 
• Customer misuse 
Signal Quality: The following types of interruptions can be experienced: 
(a) Digital Video 
Blocking the freeze frames, and loss of detail with heavy compression. Advances like HDTV will also increase expectations of Standard Digital Video. 
(b) Cable Modem 
Availability of cable modem service is already important to many customers. Home users will demand higher availability as "reliable" service providers offer alternative techno-logies at similar prices (xDSL, Satellite/ISPs). 
 (c) Telephony 
Hard for many people to leave existing reliable phone service. However, proliferation of cell phones and Internet telephony (including VoIP) have gotten people used to lesser quality phone service. 
Signal Quality can be made better by pro-active plant maintenance, RF monitoring test equipment and making use of intelligent agents in the network like Set-Top-Boxes and Cable Modems. 

Stand by power systems in the form of battery, generators and mobile generators must be installed to cater for this interruption. Also operators have to ground their equipments to protect them from lightening strikes and failure. 
• To avoid equipment failure the following steps must be taken: 
• Install high quality reliable equipment 
• Employ a good network architecture to affect minimum number of subscribers by single point of failure. 
• Deploy monitoring equipment to isolate failure, decreasing repair time 
• Deploy redundant hardware. 
• Use self healing rings in HFC network 
• Cater for sufficient number of spares 

• Major problems encountered from interfering signals are: 
• Ingress from - 
• CB Radios 
• Automobile Ignition 
• Consumer Electronics 
• Internally generated signals- 
• CSO-composite second order interference 
• CTB - composite triple beat 
• XMOD - cross modulation 
• C/N - carrier to noise ratio 
• Common Path Distortion 
• Improperly balanced plant 
• Equipment failures (active and passive) 
Interfering signals can be avoided by using- 
• Cut-off switches (Located in taps, nodes or amplifiers) 
• Ingress test equipment 
• Use intelligent agents (STB's, CM's) distributed in network 
• Frequency Agility 
• Highly trained technicians 
• Develop ingress mitigation techniques 
• Pre-test of equipment and signal loading to verify margins in 
• system engineering calculations and manufacturers specifications. 

Network Capacity 
This is more relevant when providing internet, telephony and other broadband services on cable TV networks. It generally refers to slow POP to internet, no dial tone and back haul congestion. This can be dealt with by proper traffic engineering and monitoring. 

• The following problems are experienced at customer end: 
• Power off to Modem or STB 
• PC's not configured properly 
• Not connected properly 
• Customer extending telephone/ cable connection to other instruments or TV sets in the house. 
• Tapping in distribution cables to get an illegal connection. 
Customer misuse can be avoided by properly training, educating, making call centre based technical support system, providing equipment literature and giving online assistance to customers. 

With the advancement in technology consumer expectations have also grown over the years. Ten years ago television sets were not capable of displaying full resolution of cable TV signals. With better and flat screen television sets and also availability of large screen television, video impairments become more evident and customers less tolerant. With the introduction of DTH, IPTV, VCDs and DVDs customer expects a similar experience from cable TV signals too. This expectation will further grow with the introduction of High Definition (HD) TV. Providing good service and making the networks more reliable is an ongoing effort where no laxity can be tolerated. By following the above mentioned solutions operator can have a peaceful and profitable business environment.


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