Resource Allocation in Multi-Tier Femtocell and Visible-Light Heterogeneous Wireless Networks

Resource Allocation in Multi-Tier Femtocell and Visible-Light Heterogeneous Wireless Networks

Eirini Eleni Tsiropoulou (University of Texas at Dallas, USA), Panagiotis Vamvakas (National Technical University of Athens, Greece) and Symeon Papavassiliou (National Technical University of Athens, Greece)
DOI: 10.4018/978-1-5225-2023-8.ch010
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The increasing demand in mobile data traffic, data hungry services and high QoS prerequisites have led to the design of advanced multi-tier heterogeneous cellular networks. In this chapter, a multi-tier heterogeneous wireless network is examined consisting of the macrocell, multiple femtocells and multiple Visible Light Communication (VLC) cells. Distributed resource allocation approaches in two-tier femtocells are presented focusing on (a) power allocation and interference management, (b) joint power and rate allocation, and (c) resource allocation and pricing policies. Similarly, the most prominent resource allocation approaches in two-tier VLC cells are examined, including (a) user association and adaptive bandwidth allocation, (b) joint bandwidth and power allocation, and (c) interference bounded resource blocks allocation and power control. The resource allocation problem in the two-tier heterogeneous environment where both femtocells and VLC-LANs are simultaneously present is also discussed. Finally, detailed future directions and comprehensive conclusions are provided.
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The demand for higher data rates, energy-efficiency and interference improved solutions in wireless networks is unrelenting. The even-increasing support of wireless services, e.g. data transfer, voice, video streaming, e-Health, glasses / touch Internet, e-gaming, etc. via wireless networks has dictated the necessity for deploying more data supportive cellular architectures. The Ericsson Mobility Report (Cerwall et. al, 2015) presented in June 2015 predicts 9.2 billion total mobile subscriptions (i.e. mobile broadband, smartphones, mobile PCs, tablets and routers) by 2020, which is an increase of 30% compared to 2014. Furthermore, it is estimated that 90% of the world’s population over 6 years old will have a mobile phone by 2020 (ITU, 2009; CISCO, 2012).

The next generation cellular wireless networks should be appropriately designed and amended to accommodate the ongoing growth of mobile data traffic, while in parallel improve their spectral and energy-efficiency. To cope with this trend, the current technologies and standards adopted in cellular wireless networks, i.e. Long Term Evolution (LTE), LTE-Advanced (LTE-A), High Speed Packet Access (HSPA), Worldwide Interoperability for Microwave Access (WiMAX), etc. should evolve towards supporting a multi-tier cellular architecture, where system’s bandwidth reusability will be supported.

Aiming at achieving system’s bandwidth reusability in the same physical area, the idea of cell splitting has been proposed and it is based on the hierarchical cell deployment model, where small cells with possibly different transmission technologies lie in the coverage area of a macrocell. This hierarchical infrastructure of a wireless network constitutes a heterogeneous network, i.e. HetNet (Damnjanovic et. al, 2011). However, though system capacity may increase via such an approach, several drawbacks exist in their deployment. These may include:

  • The installation and maintenance of the cell towers is prohibitively expensive,

  • They do not completely solve the indoor coverage problem,

  • The radio frequency interference in the same bandwidth diminishes system’s capacity,

  • The backhaul deployment costs cannot be avoided.

Based on the above observations, more cost-effective solutions have emerged, such as femtocells and visible light communication cells.

A femtocell consists of a short-range (10-30m) low-cost and low-power (10-100mW) Femtocell Access Point (FAP) being installed by the consumers towards achieving better indoor coverage and capacity. FAPs transmit over a licensed Radio Frequency (RF) spectrum and are connected to the macrocell network via a broadband connection, e.g. Digital Subscriber Line (DSL), cable modem or via a dedicated RF backhaul channel. The main advantages of femtocells are:

  • 1.

    Lower transmission power,

  • 2.

    Prolongation of mobile users’ battery life,

  • 3.

    Higher signal-to-interference-plus-noise ratio (SINR),

  • 4.

    Increased system capacity,

  • 5.

    Reduced interference,

  • 6.

    Low cost installation,

  • 7.

    Increased number of served users in the same physical area (Chandrasekhar et. al, 2008).

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