06515063.pdf - SPAGNOLINI LAYOUT_Layout 1 1:11 PM Page 178 ACCEPTED FROM OPEN CALL Wireless over Cable for Femtocell Systems Jonathan Gambini and

06515063.pdf - SPAGNOLINI LAYOUT_Layout 1 1:11 PM Page 178...

This preview shows page 1 - 2 out of 8 pages.

IEEE Communications Magazine • May 2013 178 0163-6804/13/$25.00 © 2013 IEEE I NTRODUCTION Spectrum scarcity below 1–2GHz and the increased users’ density/traffic are two leading aspects that motivate the efforts in cell-size reduction experienced in recent years. Cell reduction down to the range 10–50m, possibly indoor, is the paradigm of femtocells, based on low-power base stations (BSs) as home equip- ment, also referred to as Home eNodeBs (HeNBs) in LTE. Conventional HeNBs are con- nected to the operator’s core network through a broadband connection such as xDSL (Fig. 1a) for the purpose of providing wireless voice and broadband services to customers in home/office environments. The key benefits of femtocells are the reduced deployment cost for the service pro- viders, and the increased indoor coverage for spectrum allocations beyond 2GHz [1]. The pico/femtocell paradigm unavoidably leads to several (still) open issues such as synchronization (namely when using OFDM/A as air protocol), security, interference, and mobility management. All these could be more efficiently handled by a centralized approach rather than by independent and/or loosely-cooperative HeNBs. Even if an access control mechanism plays a relevant role in interference reduction, many issues remain open [2]. Focusing on the physical layer, operators experience the dichotomy between mitigating RF interference and allocating spectrum to fem- tocell and macrocell users. The scarcity of radio resources, together with flexibility in the deploy- ment, would preferably lead to reuse the same spectrum with the unpleasant effect of raising the RF interference, both co-tier (among neigh- boring femtocells) and cross-tier (femtocell-to- macrocell and macrocell-to-femtocell). Even if centralized frequency/power planning strategies would be highly beneficial for interference con- trol, the heavy signalling and the unpredictable activation/deactivation of HeNBs make this approach practically unfeasible. In counter-trend with the conventional approach of deploying non-cooperative HeNBs, here it is proposed that all home-devices are replaced with antenna elements that are con- nected via cable links to the same remotely deployed baseband processing unit that acts as the centralized multicell BS (McBS). This dis- tributed antennas system (DAS) architecture, referred to as FemtoWoC architecture (Fig. 1b), resorts to the wireless over cable (WoC) paradigm. The radio frequency wireless signals are relayed over the cable infrastructure (tele- phone wire, coax, power lines or even optical fiber) through a bidirectional AF device (name- ly, the A/A converter) that translates the band- width of wireless signals to comply with the specifications of the wired links (and vice-versa). Notice that each A/A device can translate differ- ent portions of the wireless spectrum to the lower frequency (f low ) that matches the cable bandwidth, and therefore the A/A converter can be remotely configured to accommodate differ- ent radio protocols from radio access (LTE
Image of page 1

Subscribe to view the full document.

Image of page 2
  • Summer '18
  • Fahad Bin Zamal

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask You can ask ( soon) You can ask (will expire )
Answers in as fast as 15 minutes