As we are approaching the 5G standard for wireless communication, the traditional network infrastructure has a lot of limitations. 5G technology has to address many challenges in terms of data speed, reliability, and latency specifications. To provide a higher bandwidth signal and extend coverage for more users, 5G technology will have to use the small cell concept.
What are small cells in 5G technology?
Small cells are low-power, short-range wireless transmission systems (base stations) to cover a small geographical area or indoor/outdoor applications. However, small cells have all the basic characteristics of conventional base stations and it is capable of handling high data rate for individual users. In LTE advanced and 5G deployments, small cells will play a significant role in efficiently delivering high-speed mobile broadband and other low latency applications.
Small cells are further divided into three major categories based on the coverage area and number of users they can support.
Femtocells
Femtocells are small mobile base stations designed to provide extended coverage for residential and enterprise applications. The poor signal strength from mobile operators’ base stations can be solved using Femtocell implementation. Femtocells are primarily introduced to offload network congestion, extend coverage and increase data capacity for indoor users.
Key features / Specifications
| Â Coverage area | 10 meters to 50 meters (indoors) |
| Â Power | Typically 100 milliwatts |
| Â Number of users | 8 to 16 users |
| Â Backhaul | Wired, fiber connection |
| Â Application | Indoor (primarily for indoor application, can be used for outdoor applications) |
| Â Cost | Low cost |
Picocells
Pico cells are another category of small cells suitable for small enterprise applications for extended network coverage and data throughput.
Key features / Specifications
| Â Coverage area | 100 meters to 250 meters (indoors) |
| Â Power | Typically 250 milliwatts |
| Â Number of users | 32 to 64 users |
| Â Backhaul | Wired, fiber connection |
| Â Application | Indoor applications (offices, hospitals, shopping centers, and schools) |
| Â Cost | Low cost |
Microcells
Micro cells are designed to support a lightly large number of users compared to femtocells and pico cells. Due to high transmission power, it is capable to cover larger cells size and is suitable for applications like smart cities, smart metro etc…
Key features / Specifications
| Â Coverage area | 500 meters to 2.5 kilometers |
| Â Power | 2 to 5 watts |
| Â Number of users | up to 200 simultaneous users |
| Â Backhaul | Wired, fiber connection and microwave links |
| Â Application | Outdoor applications |
| Â Cost | Medium cost |
Why 5G requires small cells?
5G technology has been designed to focus on three major areas like:
Enhanced mobile broadband high-speed mobile broadband connection up a to few gigabytes per second rate.
Ultra reliable and low latency network: a smart network with less th1-millisecondond latency ultra-reliability for mission-critical applications.
Massive IoT: The Internet of Things will connect huge number (millions or billions) of devices and smart sensors for massive machine communication and several applications in smart home, healthcare etc…
Conventional mobile network has limitations for further enhancements due to technology, frequency spectrum (bandwidth) and infrastructure. Each cell has limited number of users and data capacity. Advanced technologies like massive MIMO and beamforming are used in 5G technology to increase data rate and spectrum efficiency.
How does a small cell work?
Small cells works exactly similar to the conventional cell concept with advanced techniques like MIMO, beamforming and millimeter waves for transmission. Low power transmitting stations can be easily deployed using small cell concept. Moreover, small cell hardware units are designed to reduce complexity and thus implementation is faster and easier.
Small base stations (transceivers) can be fixed on a wall for indoor applications and small towers or lamp posts can be used for outdoor applications. Backhaul connections can be made using fiber connections, wired connection and via microwave links. Configuration is less complex, it just need to be connected to backhaul and power source.
Factors affecting the cell coverage and data capacity
Frequency: higher frequency has lower penetration rate and subjected to higher distortion. Bandwidth of the signal is depends on frequency, higher frequency has higher bandwidth to utilize.
Power: transmission power is another factor limit the cell coverage area. High power transmitters can cover larger surrounding area.
Antenna techniques: the height, angle and the number of antenna array (MIMO) contribute significantly in cell coverage and data rate.
Virtualization in wireless networks
Early generation of cellular base stations were complex and it required lot of hardware complexity (for example radio access networks – RANs). In LTE and later versions of wireless technology centralized radio access networks C-RANs replaced distributed RANs. The complex processing task has been performed at a central processing cloud station situated away from the cell location.
Modern small cell solutions are much advanced and easily configurable with existing network standards.
Future applications of small cells
- Major applications are LTE advanced and 5G network deployment solution for enhanced mobile broadband at highly populated areas to avoid data traffic congestions and provide better user experience.
- To support mission critical services that requires low latency and highly reliable network.
- Various Internet of Things applications like industrial IoT, smart healthcare, smart city and smart home
- Support huge number of users during special events like sports and games with multiple cell deployments
- Disaster management application (like cell on wheel COW) and drones
Advantages of small cells
- Small cells can deliver higher data rate up to few gigabit per second
- Less complex solutions, can be easily implemented
- Cost effective
- Faster deployments
- Location requirements are minimum (convenient to deploy indoors and outdoors)
Disadvantages of small cells
- One of the major disadvantages is coverage limitation due to low power
- Number of users under one cell is limited due to resources
- Need huge budget for large number of deployments
Conclusion
Since 5G technology is a future framework to support various applications, it has to meet all necessary specifications. Small cell concept is a perfect solution to deliver enhanced mobile broadband, low latency and reliable service to users. Higher order modulation techniques, MIMO technology and millimeter wave spectrum will ensure proper functioning of future small cell deployments.
Source: https://www.rfpage.com/