INDIAN INSTITUTE OF TECHNOLOGY ROORKEE

Seminar Presentation On

Energy-Efficient Wireless Access Networks:LTE and LTE-Advanced

Under the Guidance of

Dr. Meenakshi Rawat

Presented by :Rajnish Kumar Singh(15531014)

M.Tech , Communication Systems

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Outline

• Brief overview of cellular generations• Energy Efficiency in Wireless Access Networks• Base Stations’s power consumption model• LTE Advanced Functionalities• Carrier Aggregation• Heterogeneous Deployments(macrocell and femtocell)• MIMO (Multiple Input Multiple Output)• Conclusion• Research Gaps• Future work• References

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Brief overview of cellular generations

First Generations Cellular Networks(1G)• Introduced in 1980’s, Speed was upto 2.4kbps• Used Analog radio Signal for voice services• Used Circuit Switched technology• Used FDMA for transmission• Cellular Standard: AMPS:  Developed by Bell Labs , First launched in USA • Drawbacks: Poor Voice Quality

No Security

Limited Capacity

Poor Handoff Reliability

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Brief overview of cellular generations(cont.)

Second Generations Cellular Networks(2G)• Uses Digital signals for voice transmission• It’s data speed was upto 64kbps and Bandwidth range of 30-200Khz• Introduced facility of SMS(Short Message Service)• Main cellular standards: 1) GSM -TDMA based Today accounts for over 80% of all subscribers in the world 2) IS-95 –CDMA based• Drawback: Limited speed

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Brief overview of cellular generations(cont.)

Third Generations Cellular Networks(3G)

• Data Transmission speed increased to 2Mbps• Increased its bandwidth (15-20 Mhz) and data transfer rates

for High speed internet services like video calling,MMS• Uses Packet switching for data transmission and circuit switching for voice call transmission • Based on  spread spectrum radio transmission technology • Drawbacks: 1) Costly compared to 2G 2) High Bandwidth requirement leading to high power consumption resulting in reduced battery life

•

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Brief overview of cellular generations(cont.)

Fourth Generations Cellular Networks(4G)• Basically an extension in 3G technology• All Internet Protocol (IP) packet based communication • High speed (100Mbps-1Gbps )and high capacity• OFDMA multi -carrier transmission•  Multiple-input multiple-output (MIMO) communications• Standards: 1) LTE- Long Term Evolution(release 8) 2) LTE Advanced-  standardized by the 3GPP (release 10)

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Energy Efficient Wireless Access Networks

Introduction• Recent years have seen a tremendous increase in the number of

mobile users.• This growth has affected wireless access networks (WANs), which

are already large energy consumers within the information communication technology (ICT) domain.

• Base stations account for up to 90 percent of a WAN’s power consumption.

• A thorough study of a base station’s power consumption can help us to develop guidelines for reducing these networks’ power consumption.

• Hence there is a need of energy efficient wireless access networks.• Hence Comparison between LTE(release 8/9) networks and LTE

Advanced (release 10) is done

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Energy Efficiency in Wireless Access Networks

• Which base station type is most energy efficient (EE) ?• Different performance parameters: (bandwidth, coverage, served

users, and so on). • Here it defines energy efficiency EE ( [0, ∞[) (in (∈ km2 .Mbps)/W

as Where : the base station’s power consumption(in watts) R : is the range (in km) B: is the physical bit rate by the base station (in Mbps) U :is the number of served users• The higher the EE, the more energy efficient the base station is.

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Base Stations’s power consumption model

Base Stations Types: • Macrocell : Bigger than the

base station of Femtocell , serves more users and has higher Range

• Femtocell :is much smaller than a macrocell base station and is comparable to the base station of a Wi-Fi access point

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LTE-Advanced functionalities

• LTE-Advanced introduces three new functionalities: 1) Carrier aggregation 2)Heterogeneous networks 3)Extended (MIMO) support -multiple-input, multiple output• Note:The first two releases (release 8/9) are known as LTE.

Release 10, is also known as LTE-Advanced.• It supports bandwidths roughly upto 20 MHZ(in both versions)• Note:

This bandwidth can be further extended in LTE-Advanced by carrier aggregation, which lets the base station transmit multiple LTE carriers, each with a bandwidth of up to 20 MHz.

• LTE-Advanced enhances support for MIMO up to eight transmit antennas.

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Carrier Aggregation

• Carrier aggregation is used in LTE-Advanced in order to increase the bandwidth, and thereby increase the bit rate.

=>hence increasing EE(Energy Efficiency)• We investigate how adding carrier aggregation influences energy efficiency.• To obtain the results in the following figure , we determine the power consumption, range, and bit rate as discussed earlier.• The number of served users is fixed.• Channel bandwidth 5 MHz • We then calculate EE for both macrocell and femtocell

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Results (LTE & LTE Adv.) –carrier aggregation

Figure 2. Energy efficiency of LTE and LTE-Advanced in a 5-MHz channel. The figure compares the energy efficiency when aggregating no carriers (LTE) and when aggregating two or five carriers (LTE-Advanced) for different modulation schemes and coding rates and for both a macrocell and a femtocell base station. (CA = carrier aggregation; QAM = quadrature amplitude modulation; QPSK = quadrature phase shift keying) [3]

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Curve Notes for carrier aggregation

• Carrier Aggregation increases the EE(Energy Efficiency)

• Higher modulation scheme or coding rate results in lower EE because a higher modulation scheme and coding rate lead to a shorter range for a higher bit rate.(EE )

• Introducing carrer aggregation has little impact on base station’s power consumption( i.e extra power consumed is negligible)

• With carrer aggregation, we can obtain high bit rates with a lower modulation scheme

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Heterogeneous Deployments

• We might think that a femtocell base station is less energy efficient than a macrocell basestation. However, this isn’t always the case.

• Following figure compares the energy efficiency of LTE-Advanced macrocell and femtocell base stations as a function of attainable bit rates.

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Results of Heterogeneous Deployments

Figure 3. Comparison of the energy efficiency of an LTE-Advanced macrocell and femtocell base station for different bit rates [3]

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Curve Notes Heterogeneous Deployments

• Which base station type is most energy efficient?

• For bit rate >20 Mbps, the macrocell base station is the most energy efficientdue to its longer range and higher number of served users (despite its higher power consumption)

• For bit rate 5 to 20 Mbps- Ambiguous

• For bit rate < 5 Mbps, femtocell is more Energy Efficient

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MIMO

• MIMO  is used to increase the overall bit rate through transmission of two (or more) different data streams on two (or more) different antennas

=>hence increasing EE(Energy Efficiency)• A major change in LTE-Advanced is the introduction of 8x8 MIMO

in the DL and 4x4 in the UL• Now we consider the influence of spatial diversity on energy

efficiency for different MIMO modes in both macrocell and femtocell base stations assuming a bit rate of 2.8 Mbps in a 5-MHz channel

• We use single-input, single-output (SISO)— that is, only one transmitting and one receiving antenna— as a reference scenario

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Results for MIMO

Figure 4. Influence of spatial diversity on energy efficiency for different MIMO modes using 1/3 QPSK in a 5-MHz channel. (Percentages on the right side of each bar show the improvement compared to single-input, single-output [SISO]; the numbers at the top of each bar indicate the EE-values.) [3]

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Curve Results for MIMO

• Shows that more the transmitting and receiving antennas, the higher the EE.

• For the macrocell base station - EE increases upto 433 % when using 8×8 MIMO• For the macrocell base station- EE increases upto 454.6 % when using 8×8 MIMO

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Conclusion

• Hence power consumption model for both LTE and LTE-Advanced macrocell and femtocell base stations, as well as a suitable energy-efficiency measures were discussed

• We saw that LTE-Advanced’s carrier aggregation and MIMO improve networks’ energy efficiency up to 400 and 450 percent, respectively.

=> which proved that LTE-Advanced (release 10)  is more energy-efficient than LTE (release 8/9)

• Future networks should implement LTE-Advanced, which will improve energy efficiency better than LTE

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Research gap

• We will need a good estimation of the needed bit rate, coverage, and number of served users to determine which base station type is most suitable in each network location to reduce the network's power consumption.

• We saw that, in some cases the macrocell base station is most energy efficient , while in other cases the femtocell base station is most energy efficient.

• It didn’t discussed the combination of both type of cells (Since user demand varies over time, both base station types are

needed to be deployed in the network).

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Future Work• Since user demand varies over time, both base station types must be

deployed in the network, with the optimal combination resulting in a more energy-efficient network.

• We can find this optimal combination by - 1) placing macrocell base stations to cover the area first,then 2) femtocell base stations to provide coverage in the coverage holes. 3) hence we can extend the macrocell base station’s capacity as needed using femtocell base stations

• LTE-Advanced also adds enhanced support for relaying, which can probably also improve energy efficiency

• Study how the features investigated here will perform in terms of energy efficiency when applied on an actual network.

• Future networks can benefit from MIMO, which currently has only limited deployment.

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Main References

[1] S. CHEN and M. Deruyck ,“The Development of TD-SCDMA 3G to TD-LTE-Advanced 4G From 1998 To 2013”, Wireless Communications, IEEE vol. 21, no. 6, 2014, pp.167-176[2] V. K. Garg, “Wireless Network Evolution: 2G to 3G”, Prentice Hall[3] Margot Deruyck, E. Dahlman  Wout Joseph, Bart Lannoo, Didier Colle and  LucMartens, Designing Energy-Efficient Wireless Access Networks: LTE and LTE Advanced, IEEE Internet Computing, IEEE, vol. 23, no. 4, 2013, pp. 39-45[4] E. Dahlman, S. Parkvall and J. Sko, 4G LTE/LTE-Advanced for Mobile Broadband,Academic Press.[5] J. Baliga et al. and Idquo,Energy Consumption in Wired and Wireless Access Networks, IEEE Comm., vol. 49, no. 6, 2011, pp. 70-77.

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End of seminar

THANK YOU