Femto Cell

OFDM,SC-FDMA

OFDM:-Orthogonal Frequency division multiplexing

Theory:- In OFDM, the sub-carrier frequencies are chosen so that the sub-carriers are orthogonal to each other, meaning that  between the sub-channels is eliminated and inter-carrier guard bands are not required. This greatly simplifies the design of both the transmitter and the receiver; unlike conventional FDM, a separate filter for each sub-channel is not required.

Advantages:-

• Can easily adapt to severe channel conditions without complex equalization.
• Robust against narrow-band co-channel interference.
• Robust against intersymbol interference (ISI) and fading caused by multipath propagation.
• High spectral efficiency as compared to conventional modulation schemes, spread spectrum, etc.

Disadvantages:-

• Sensitive to Doppler shift.
• Sensitive to frequency synchronization problems.
• High peak-to-average-power ratio (PAPR),

Application of OFDM:-

􀁁 DAB:- Digital Audio Broadcasting

􀁁 HDTV

􀁁Wireless LAN Networks

􀁁ADSL:- The modulation technique DMT is OFDM based

􀁁8.4 IEEE 802.16 Broadband Wireless Access System and Wimax, wireless MAN OFDM

Single carrier FDMA

In SC-FDMA, multiple access among users is made possible by assigning different users, different sets of non-overlapping fourier-coefficients (sub-carriers). This is achieved at the transmitter by inserting (prior to IFFT) silent fourier-coefficients (at positions assigned to other users), and removing them on the receiver side after the FFT.

Transmitter and Receiver Structure of LP-OFDMA/SC-FDMA

• DFT: Discrete Fourier Transform IDFT: Inverse Discrete Fourier Transform ,CP: Cyclic Prefix ,PS: Pulse Shaping ,DAC: Digital-to-Analog Conversion ,RF: Radio Frequency ,ADC: Analog-to-Digital Conversion

 

Applications of SC FDMA

Single Carrier Frequency Division Multiple Access (SC-FDMA) is a novel method of radio transmission under consideration for deployment in future cellular systems; specifically, in 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) systems. SC-FDMA has drawn great attention from the communications industry as an attractive alternative to Orthogonal Frequency Division Multiple Access (OFDMA).

NEED FOR GREEN TELECOM IN INDIA

A telecom wireless network consists of Access Network and Core network. Access mainly consists of BTS/Node B (another component is BSC/RNC) which is called telecom tower in business language whereas Core network mainly consists of MSC, SMSC, HLR, SGSN and GGSN. Concentration of network elements decreases as we go away from telecom towers.

India had 2,38,000 Telecom towers at the end of 2009 and assuming that we are adding 10m subscribers per month then this number should be somewhere 250,000-275,000. If we look at power consumption of telecom network then we find more then 70% of energy is consumed by the telecom towers itself and apart from this half of the towers are in rural areas which are running on diesel fired gensets. Many of these gensets are as old as 10 yrs and are not efficient in terms of usage of diesel and consumes more diesels then required. Each tower requires energy from 1000W to 3000W (older installation consumes more power as compare to new one because of technological advancement). Each 1000 W results in the .22 tonnes/hr of emission of CO2 if running on the state electricity, in case of the private gensets this number is many times more. Assuming average power consumption of each tower is 1200W then total CO2 emission is 44000 tonne per hour by all these towers or 550408320 tonne per year if we assume that all are running on state electricity. Each tower requires 50-60k $ for electronic hardware and half of this is required for installation and other stuff. Apart from this additional capital is required for the genset, battery back up (gensets are required in urban areas also for emergency backup) which requires close to 5000$, so total cost of ownership of a telecom tower is close to 100K $ (for 2G). These towers have an Opex of 8-10k $ per year which is mostly the cost of the energy (rural has higher energy bill because of diesel and urban areas have higher rental costs). But it is really surprising that not even 5% of these towers are running on solar power. Probably operators are already struggling with capital availability so they opted for more costly approach.

Network components are not as huge as towers but consume substantial amount of energy. As compare to tower an additional energy is required for a small or big office which is adjacent to the component for the supervision or maintenance. It is difficult to estimate the carbon footprint as well as the cost of these components as not much information is public but most of these components are as efficient as components in developed world in terms of power usage. So carbon footprint of 100000000 tonne per year would be a fair estimation as far as network is concerned.

So from above analysis is that the telecom industry can claim close to 80m carbon credits (1 carbon credit = 1 tonne of CO2) if it moves to complete green methods of power usage for its tower operations which results into 1.15B $ or 4800 $ per year per tower.Apart from this each tower will save close to 40 % energy bill i.e. 3-4K so total saving per tower would be close to 6000$ after subtracting additional maintenance cost of solar panel. Which is really a big number as far as saving is concerned but requires a huge capital and effort for rollout of green measures. However this year is really a good year for the environment lover as cost of the solar panel has gone down from 170 Rs/W to 70 Rs/w. So capital investment on each tower has gone down to as low as 15K (including the cost of installation) which can be claimed in just three years which indicates that it is not only a positive NPV investment but also a small step towards the reduction of greenhouse gases to save mother earth.

Company	Approximate number of towers
Indus (joint venture of Vodafone, Bharti Airtel and IDEA)	100000
Reliance Infratel	48000
Bharti Infratel	30000
Quippo Telecom Infrastructure (QTIL)	25000
GTL	10000
Aircel Tower	12000
IDEA Tower	11000
American Tower	2500

Number of towers	238000
Average Power Req per hr per tower (W)	1200
Carbon Emission per hr (1.2 * .22)	0.264
Carbon Emission Tonnes Per Year (C3*24*365)	2312.64
Total CO2 Emission in tonnes (C4*C1)	550408320

Carbon Credit Details

Total CO2 Emission (from towers)	550408320
Average Power Req per hr per tower (W)	1200
Base Watt for the Tower	450
Load Factor	40%
Carbon Credits (which can be monetized)	82561248
Current cost of the carbon credit ($)	14
Total Claim($)	1155857472
Claim per tower ($)	4846.36257

LINKS TO IMPORTANT TELECOM SITES

http://www.telecomtiger.com/

http://www.telecomtalk.info/

http://www.3g4g.blogspot.com/

http://www.heavyreading.com/

http://www.lightreading.com/

http://www.telecomyatra.com/

http://www.thetelecomnews.com/

http://www.telecomindiaonline.com/

http://www.indiatelecomnews.com/

http://www.trai.gov.in/

http://www.auspi.in/

http://www.coai.com/

2G SCAM IN INDIA

Telecom minister A Raja is facing the wrath of CAG, PIL filing institutions and court for awarding the 2G licence to new entrants in 2008 at price much below the market price causing a huge loss to the exchequer. The new entrants were awarded 2G pan India licence at cost of Rs 1,651 crore, a price fixed in 2001 when the subscriber base was only 45 million and the evaluation of telecom industry was low. Nine companies were issued licences in the process that was controversial from the very beginning. According to A Raja, the reason for such a step was to promote competition in Indian telecom sector, thereby benefiting the customer through low tariffs and better quality of services. A Raja insists there was no wrong doing.

After the allocation of spectrum, some months later, Swan Telecom and Unitech, two of the winners, sold large stakes in their operations to overseas companies at stupendous valuations. This triggered a huge furore. Opposition parties said Raja, by favouring a few, was involved in a scam worth Rs 50,000 crore, the loss to the government exchequer for selling the licences cheap. Petitions were also filed regarding the wrong doings in the allocation of spectrum. Currently, Supreme Court is hearing two petitions in this matter. One of them being filed by a NGO, Centre for Public Interest Litigation (CPIL). Even CBI has filed a case against unknown officials of the DoT and some private persons to investigate the irregularities in the 2G licences allocation.

Comptroller and Auditor General of India (CAG), the auditor of India’s state run institutions, in its queries to Department of Telecom (DoT) has alleged that Mr Raja’s failure to auction telecom licences in 2008 had led to losses of Rs 26,000 crore to the exchequer. DoT responded to the CAG by declining to reply to the queries of CAG claiming that it was a policy decision. DoT had also sought advice from Law ministry which said the Auditor had no right to challenge the policy decisions.

CAG has also alleged that new entrants were granted licence without proper verification of their credentials. CAG also asked the communications ministry to amend licence conditions of telecom operators and add a new clause enabling it to audit the accounts of private operators that recently bagged 3G and broadband wireless access spectrum. But DoT has refused to give into this demand and has decided to seek the law ministry’s opinion. In the latest development, CAG has issued drafts reports saying that 2G spectrum allocation has caused the exchequer a loss between Rs 26,000 crore to Rs 140,000 crore, depending on the formula used for the calculation of loss.
                                             
                                                                                                                                  By -  Sudhir Tripathi

BUSINESS IMPLICATION OF NGN

It is certainly true that we are moving from Time Division Multiplex (TDM)-based, circuit switched networks to packet-, cell-, and frame-based networks. The major benefits of NGN can be listed as follows:-

1.       Heterogeneity of the Telecommunications Infrastructure. 

The growing number of services with different has increased the complexity of the overall infrastructure. The problems of interoperability between the various systems are becoming more serious. Maintaining these platforms involves high  OPEX for the network operators. NGN provides an obvious solution to this problem.

2.       Falling Call Sales.

Increasing losses on the domestic fixed-network market are therefore forcing the operators to develop new strategies to secure their future and to boost their profitability. No further growth can be expected through the revenue obtained from call sales alone.

3.       Cost reduction:With NGN, the established network operators plan to develop a sustainable infrastructure that will remain competitive in a convergent environment. The primary focus will be on the potential for cost savings

4.       New Sources of Income:Established network operators see the possibility of new income as another motivation for promoting NGN. More and more innovations with new sales opportunities are expected in the field of value-added services with enhanced QoS.

5.       Ease of Maintainence: IP-based networks are likely to be simpler and easier to operate and maintain as compared to the existing legacy networks and provide  operators with sufficient flexibility  to reduce both OPEX and CAPEX.

6. Converged IP Core transport: Integration of their disparate networks towards IP/MPLS based transport core for superior control and OPEX reduction. Migration from TDM to IP and Fixed Mobile Convergence are also motivating factors for the carriers to reduce OPEX.

Future applications

Most traditional services relate to basic access/transport/routing/switching services, basic connectivity/resource and session control services, and various value-added services

• Voice Telephony – NGNs will likely need to support various existing voice telephony services (e.g., Call Waiting, Call Forwarding, 3-Way Calling, various AIN features and various Centrex features).

•  Data (Connectivity) Services – Allows for the real-time establishment of connectivity between endpoints, along with various value-added features (e.g., bandwidth-on-demand, resilient Switched Virtual Connections [SVCs], and call admission control).

•  Multimedia Services – Allows multiple parties to interact using voice, video, and/or data. This allows customers to converse with each other while displaying visual information.  It also allows for collaborative computing and groupware.

Public Network Computing (PNC) – Provides public network-based computing servicesfor businesses and consumers (e.g., to host a web page, store/maintain/backup data files, or run a computing application). 

• Unified Messaging – Supports the delivery of voice mail, email, fax mail, and pages through common interfaces ,independent of the means of access .

•  virtual  call centres – A subscriber could place a call to a call centre agent by clicking on a Web page.  The call could be routed to an appropriate agent, who could be located anywhere, even at home .