1. Green Cellular Networks: A Survey, Some Research Issues and Challenges
Nourah Alhassoun
February 29, 2012

2. Part I Objective: Results:
A brief survey of methods to improve the power efficiency of cellular networks and explore some research issues and challenges
Suggest some techniques to enable an energy efficient or green cellular network
Results:
A survey on methods to obtain energy savings in base stations such as architectural changes in base stations and heterogeneous network deployment
Propose a research vision by using some techniques(cognitive radio and cooperative relaying technologies) to make energy more efficient

3. Part II
Important Aspects of a Green Networking: I. Defining Green Metrics II. Architecture Changes in Base Stations III. Network Planning IV. Addressing Energy Efficiency in Future Generation Wireless Systems V. Some Broader Perspectives

4. I. Measuring Greenness Energy Efficiency Metrics:
Facility-level: High-level systems where equipment is deployed
Equipment-level: Evaluate performance of an individual equipment
Network-level: Assess the performance of equipment with the consideration of features and properties

5. II. Architecture: Energy Saving in Base Stations
Minimizing BS Energy Consumption
Improvements in Power Amplifier: Switch mode PA
Power Saving Protocols: Sleep Mode
Energy Aware Cooperative BS Power Management
Cell Zooming: BS can adjust its size according to network or traffic situation
Renewable Energy Resources
Solar and Wind Energy instead of off-grid sites

6. III. Network Planning Heterogeneous Network Deployment:
Based on smaller cells such as micro, pico and femtocells
Advantages:
Energy consumption of the network can be reduced up to 60% compared to a network with macro-cells only
Smaller cells use higher frequency bands to provide high data rates
Draw Backs:
The efficiency of macro-cell Base Station might be reduced

7. Part III IV. Addressing Energy Efficiency in Future Generation Wireless Systems
Enabling Technologies:
Green Communication via Cognitive Radio:
Purpose: Collect information on the spectrum usage and access the unused frequency bands
Manage the spectrum optimally and dynamically
Green Communication delivered by Cooperative Relays:
Purpose: Improvement in throughput and coverage
Provide service to more users using less power

8. IV. Addressing Energy Efficiency in Future Generation Wireless Systems
Low Energy Spectrum Sensing
Cognitive Radio: design low complex cyclostationary detectors instead of energy detectors
Energy Efficient Resource Management with Applications in Heterogeneous Networks
Relay placement, optimal relay selection criterion
Addressing Uncertainty Issues
Cognitive Radio: did not take into account the effect of imperfect sensing
Cooperative Relays: optimal relays with perfect CSI

9. VI. Some Broader Perspective
Ideas to achieve energy efficient cellular network:
Statistical Power Profiles:
Dynamic algorithms can be designed to switch BS to different power profile appropriate for that time of the day
Smart Grid Technology:
Adding measurement sensors which can update the status of BSs then transmit them to other BSs and smart grid control system
Embodied Energy:
Reducing the number of BS since embodied energy accounts for a significant proportion of energy consumed by the BS

10. Energy Saving Obtained by Some of the Discussed Techniques

11. Reference
Hasan, Z. Boostanimehr, H “Green Cellular Networks: A survey, some research issues and challenges”. IEEE Communications Survey & Tutorials. V13,2,4.