Performance Analysis of Non-Ideal Sectorized SFR Cellular Systems in Rician Fading Channels With Unbalanced Diversity

Abstract

Nowadays, low reuse factors are used in cellular systems because of high traffic demand, despite it produces high co-cell interference (CCI) levels. Consequently, soft-frequency-reuse (SFR) and sectorization are used to improve the spectral efficiency and to mitigate CCI. In addition, diversity techniques are necessary for a good system performance. Motivated by this scenario, for the uplink of orthogonal-frequency-division multiple access (OFDMA) systems, the bit error rate (BER) and the cellular spectral efficiency using multilevel-quadrature-amplitude-modulation (M-QAM) and maximalratio-combining (MRC) in Rician fading channels are analyzed, where diversity branches have different Rician K-factors (unbalanced diversity). SFR is used assuming non-ideal sectorized cells due to the irregular radiation pattern of base station antennas. An exact integral-form expression and a closed-form upper-bound to evaluate the BER are obtained. In addition, an algorithm, and an expression to calculate the cellular spectral efficiency are presented considering that a target BER must be guaranteed for all users in the cell. From the analysis, it is determined that the BER can be reduced and the spectral efficiency can be improved if some system operating parameters are selected in an adequate manner. Thus, it was noticed that the number of diversity branches, the sum of the K factors of these branches, and the antenna type, are decisive to guarantee the target BER and to maximize the cellular spectral efficiency.

On the Bit Error Probability and the Spectral Efficiency of Opportunistic Wireless Transmissions in Rician Fading Channels

“…Thus, comparing 8-QAM with K = 0, and 1024-QAM with K = 4, notice that 1024-QAM requires only 6.1 dB more SNR than 8-QAM to guarantee P b = 10 −7 . Obviously, it is important to remember that the K factor depends on the position of the transmitter in relation to the receiver [34]. Moreover, from (40), the SE of the opportunistic system using 8-QAM is ξ = 2 3 log 2 (8) = 2 bits/s/Hz and the SE of the opportunistic system using 1024-QAM is ξ = 20 3 ≈ 6.67 bits/s/Hz.…”

“…Thus, if mod(log 2 M κ , 2) is equal to zero, then M κ is S-QAM, otherwise, it is NS-QAM. For each modulation, the algorithm calculates ζ k , given by (18), for S-QAM or ρ k , given by (34), for NS-QAM, as appropriate, which remain as a function of E b /N 0 (steps 5 to 9). Then, the E b /N 0 required to ensure the target ABEP is obtained recursively from (29) or (36), as appropriate (steps 11 to 18).…”

Experimental Evaluation of Transmitted Signal Distortion Caused by Power Allocation in Inter-Cell Interference Coordination Techniques for LTE/LTE-A and 5G Systems

“…For instance, they are possible using narrow-band transmit power (RNTP) indicator exchange through the X2 interface [2], [3]. In any case, from the early stages of the 4G definition to the present 5G context, a large number of works have studied ICI management based on these low-complexity schemes, resulting in the proposal of many derived variants for 4G and 5G [1]- [5], [8], [10]- [14]. First deployments of 5G networks have been made using OFDMA and proposals for new multiple access techniques are also based on OFDMA, thus, ICIC techniques derived from FFR and SFR remain an important issue to facilitate spatial reuse in both DL [10]- [13] and UL [14].…”

“…These limits are defined as the dynamic power range. However, although the required EVM must be fulfilled for all transmit configurations, it is a key aspect that is absent in almost all studies concerning RRM management, which are generally decoupled from radio frequency (RF) transmission analysis [1]- [14]. There are only a very limited number of contributions in which EVM requirements are considered [15]- [18], showing that the performance of the ideal implementations of RRM schemes are severely reduced.…”

“…1.a illustrate examples of the well-known soft frequency reuse (SFR) and fractional frequency reuse (FFR) schemes, which will be described later. In fact, ICIC derived from FFR and SFR schemes continues to be an important issue to facilitate spatial reuse in both DL [10]- [13] and UL [14] of 5G networks.…”