Femtocell Tutorial : Comprehensive Guide to Femtocell Basics, Types, Architecture and Advanced Concepts
Femtocells are compact, low-power cellular base stations that enhance indoor coverage and connectivity by providing localized signal support. With their ability to extend cellular network services into homes, offices, and remote areas, femtocells play a crucial role in modern telecommunications. This tutorial delves into the fundamentals of femtocell technology, including its network architecture, handover mechanisms, security considerations, and interference management. Additionally, it covers femtocell testing techniques and introduces some of the leading manufacturers in this domain.
As we know wireless signal become weak when it travels from its initiation till reception. This happens due to signal path loss as well as due to interference. Hence it is required to be boosted or amplified to obtain better coverage. The other option is to have smaller internal base stations within the home or office premises which will take care of providing boosted cellular signal to extend the coverage. This small base station is known as femtocell. The femtocell will interact with femtocell gateway which interfaces with the cellular mobile operator infrastructure. This backbone infrastructure will be connected with internet.
For different technologies different femtocells have been developed to provide the respective boosted signal to the users or subscribers or CPEs. Hence wimax femtocell, 3G femtocell and LTE femtocell are available as per wimax, UMTS and LTE standards respectively.
Femtocell provides benefits to both the users and operators. It provides improved performance to the users and extra money to the operators due to addition of extra services.
Femtocell standards
3GPP release 8 specifies 3G femtocell(UMTS femtocell) and 3GPP release 9 specifies LTE femtocell specifications. Please note that UMTS femtocell is known as HNB and LTE femtocel is known as HeNB. HNB refers to Home NodeB and HeNB refers to Home eNodeB or Home eNB.
ITU-R IMT family have defined femtocell standards. They are as follows.
• 3GPP standard for HNB for WCDMA and TD-SCDMA.
Both TDD and FDD topologies aee defined in the specifications.
• 3GPP standard for Home eNode-B(HeNB) for LTE, both TDD and FDD are specified.
• 3GPP program for femtocells as per CDMA2000 1X, 1X EV-DO, CDMA2000
• WiMAX Forum program for femtocell compliant to IEEE wimax standard.
Femtocell network architecture
Figure-1 depicts high level femtocell architecture irrespective of any standard based technology.
As shown femtocell system consists of following elements.
• Femtocell device• Router(DSL or Cable)• ISP link• mobile operator network• cellular tower
Based on the technologies different femtocell network architectures exist viz. wimax, UMTS(3G), CDMA2000, LTE etc. The architecture consists of various femtocell interfaces with the other network system elements. Basically there will be two main elements femtocell and gateway. Femtocell provides connectivity with various subscribers/users. Gateway is the interface between femtocell and the network.
For example, UMTS network consists of Home NodeB (HNB) i.e. femtocell and Home NodeB Gateway. The femtocell architectures of 3GPP and 3GPP2 are different. 3GPP is the standardization body behind UMTS which is 3G upgradation to GSM. 3GPP2 is the body behind CDMA2000 which is 3G upgradation to cdmaOne network. This is the difference between 3GPP and 3GPP2. Refer Femtocell Architecture➤
Femtocell handover
As shown in the figure-2, the femtocell network consists of femtocell in the office or home or apartment premises and macro cells in the outside.
Based on this, there are various types of femtocell handovers. Macrocell refers to the region usually covered by standard cellular network.
• From macrocell to the femtocell
• From femtocell to the macrocell
• between femtocell to the other femtocell in the region
Femtocell provides hard handover which is automatic as well as seamless between home network(such as wifi) and cellular network(such as UMTS or LTE) in use. Refer Femtocell handover➤.
Femtocell interference
As we know interference is usually caused due to high power of nearby channel interfering into proper functioning of the desired channel as expected. To overcome this, there are many solutions. One such solution is limiting the transmitter power enough to keep the transmission within the coverage as designed. Refer Femtocell interference➤ and Femtocell timing and synchronization➤
Femtocell security
Though wireless system provides better security compare to the wired networks. The security of femtocell is threatened due to various probable security aspects such as intrusion, hacking and so on. In femtocell, the security lies with the protection provided to the IP packets travelling between network elements. IPsec protocol provides security in femtocell based network.
Femtocell testing
Based on the various stages of femtocell development, there are various tests which are essential to be performed. The tests are related to verification, conformance, regulatory, manufacturing and interoperability of femtocell devices. In all the tests, transmitter and receiver modules are required to be tested. All the protocol stack layers are required to be tested based on the test type. The protocol stack layers are different based on technologies. Femtocell testing helps avoid any functional and performance related issues. Refer Femtocell testing➤.
Femtocell manufacturers
Following are the femtocell developers or femtocell manufacturers.
• Gemtek, taiwan
• SagemComm
• Tecom, Taiwan. It is one of the ODM of Ubiquisys.
• Zyxel, Taiwan
• Foxconn
• C & S microwave
• Askey
• Comba
➨Also refer LTE femtocell vendors page.
Conclusion
Femtocell technology addresses the challenges of indoor coverage and network capacity, making it a valuable addition to cellular networks. As femtocell technology continues to evolve, it will remain instrumental in shaping the future of wireless communication by providing innovative solutions for enhanced indoor coverage and network efficiency.