Different Resource Allocation Schemes In Femtocell Network Toha Ardi Nugraha
Overview• Introduction• System Model – OFDMA-System (sub carrier) – Using Fractional Frequency Reuse (Interference Control) – Resource Allocation Scheme• Simulation Result – Throughput (cell edge and total)• Conclusion
IntroductionProblems• The growth of mobile subscribers increase the number of data traffic.• Weak network signal in the building/home (indoor areas).• In other case, subscribers in the cell edge are usually not getting good signal from serving macro cell.Solution• That condition will be improved by using the femtocell. – Problems ; Co Channel Interferences [Pic] Small Cell/Femto ForumProposesSubcarrier allocation by using difference reuse schemes.
Fractional Frequency Reuse (FFR)• OFDMA-based (Sub Carrier)• FFR (Fractional Frequency Reuse) is one effective solution of inter-cell interference control.• FFR can control the interference in cell edges to enhance the frequency reuse factor and performance in the cell edges. Cell Center Cell Center Cell Center Power Cell 1 Power Cell 1 Power Cell 1 Frequency Frequency Frequency Cell Edge Cell Edge Cell Edge Total System Total System Total System BW BW BW
System ModelThe allocation of subcarriers use two scenarios A. Macro Reuse only (M-Reuse) B. Macro-Femto Reuse (MF-Reuse).
System Model• Formula (SINR)Where m is the macro cell users and k is the sub-carrier. andare transmit power of serving and neighbor macrocell . in thesubcarrier k. is the channel gain between macro user m and neighborfemtocell F in the sub-carrier k.For No is the white noise power spectral density, and is the subcarrierspacing.PLind = where• Lwalls=7 dB, if d in(0-10m)• Lwalls=10 dB, if d in(10-20m)• Lwalls=15 dB, if d in(20-30m)
System Model• Model Propagation Outdoor (SUI)Where do = 100 m, = wavelength, d = cell radius, and s = shadowfading.And calculation of the capacity of macrocell users can be written as;Where is a constant of Bit Error Rate (BER) and can be defined = -1.5/ln (5BER).So, the setting of BER is 10-6.
System Model• ThroughputWhere represents the sub-carrier assignment for macrocell users.When = 1 means that sub-carrier k is assigned to macrocell user .Otherwise, = 0. From the characteristics of the OFDMA-system, each sub-carrieris allocated only one macro user in a macrocell in every time slot.This implies thatWhere is the number of macro users in a macrocell. Similar expression is used forfemtocell.
Simulation Result : Throughput in Cell EdgeThroughput vs. Number of femtocell, for different resourceallocation and schemes in the cell edge Based on the simulation, M-Reuse scheme had higher interference than the proposed scheme (MF- Reuse). MF-Reuse2a (50% BA for macrocell, and the other BA for each femtocell) is the effective scheme to increase performance but in the cell edge. (increases throughput gradually amount 20 percent every adding five femtocells)
Simulation Result : Total ThroughputTotal Throughput vs. Number of femtocell, for different resourceallocation and schemes in the cellFor the total throughput,Macro-Femto Reuse (2b schemes,40% BA for macrocell, and 20% BAfor each femtocell)is the best performance for thenetwork compared with theother scheme.
Conclusion• Resource allocation schemes can provide a solution to improve the network performances• The best result reuse scheme based on the simulation is about 20 percent of total bandwidth allocated for each femtocell in the cell.
References1. M. Assaad, “Optimal Fractional Frequency reuse (FFR) in Multicellular Of dma System,” in Vehicular Technology Conference, 2008. VTC 2008-Fall. I EEE 68th, Sept 2008, pp. 1–5.2. A. Dalal, H. Li, and D. Agrawal, “A Novel Multi-cell Ofdma System Structur e Using Fractional Frequency Reuse,” in Personal, Indoor and Mobile Radi o Communications, 2007. PIMRC 2007. IEEE 18th Inter-national Symposi um on, Sept 2007, pp. 1–5.3. L. Poongup, L. Taeyoung, J. Jangkeu, and S. Jitae, “Interference Managem ent In LTE Femtocell Systems Using Fractional Frequency Reuse,” in Adva nced Communication Technology (ICACT), Feb 2010, pp. 1047–1051.