ABSTRACT
Contents 10.1 Introduction to Femtocell Technology ............................................. 362 10.2 Deployment Considerations ............................................................ 365
10.2.1 Frequency Planning ............................................................ 365 10.2.2 UE Selection of the Femtocell .............................................. 366 10.2.3 Access Control ................................................................... 367
10.3 RF Provisioning and Downlink Interference Mitigation ..................... 368 10.3.1 RF Provisioning Problem Formulation .................................. 370 10.3.2 Downlink Interference Scenarios .......................................... 376
10.3.2.1 Interference to Macrocell Mobiles from Femtocells ... 376 10.3.2.2 Interference to Femtocell Mobiles from
Macrocells and Other Femtocells ............................ 379 10.4 Uplink Interference Scenarios and Mitigation Techniques .................. 380
10.4.1 Interference to Femtocell Reverse Link from Macrocell UEs .... 381 10.4.1.1 Mitigating Uplink Interference
to Femtocell Receivers ........................................... 384 10.4.2 Interference to the Macrocell Reverse Link Due
to Femtocell UEs ............................................................... 387 10.4.2.1 Measurements of Uplink Interference
to Macrocell Base Stations ..................................... 389
10.4.3 Mitigating Uplink Interference from Femtocell UEs to Macrocell Base Stations ................................................... 389
10.4.4 Limiting Interference to Other Femtocells ............................. 392 10.5 Summary, Challenges, and Opportunities ......................................... 392
10.5.1 Summary of Interference Mitigation Techniques .................... 393 10.5.2 Inter-Femtocell Communications ......................................... 394 10.5.3 Standardization in the Deployment of Femtocell Networks ..... 394
References .............................................................................................. 395
10.1 Introduction to Femtocell Technology This chapter discusses the issues and challenges associated with the deployment and optimization of UMTS femtocell networks. UMTS femtocell access points (FAPs), also known as home NodeBs (HNBs), or just femtocells, are small, inexpensive, lowpower NodeB base stations designed primarily for home use to provide high-quality indoor coverage. Additionally, they allow home-user traffic to be offloaded from the macrocell network. They generally have peak transmitter powers on the order of less than 13 to 17 dBm (which is less than the maximum power of a typical handset device), and generally can support between 4 and 10 radio access bearers (RABs). While physically small, femtocells must support the standard UMTS RABs: voice (e.g., AMR), data (HSDPA/HSUPA), and supplemental services such as SMS, caller ID, call forwarding, voice mail notification, etc. UMTS femtocells generally implement a flat architecture incorporating both the NodeB and RNC functionality. For their backhaul connection to the operator’s packet-switched and circuit-switched core networks, they use home Internet connections such as DSL, cable, or fiber to the home. They generally connect to the operator’s core through a concentrator via secure tunnels using either a variant of Iu or other protocols. Key to understanding the deployment of femtocells is having an understanding of the differences between an HNB (femtocell) and an access point technology such as Wi-Fi, as well as the differences compared to a fixed infrastructure such as macro, micro, and picocellular NodeB.
