Power allocation strategies for distributed precoded multicell based systems

Abstract

Multicell cooperation is a promising solution for cellular wireless systems to mitigate intercell interference, improve system fairness, and increase capacity. In this article, we propose power allocation techniques for the downlink of distributed, precoded, multicell cellular-based systems. The precoder is designed in two phases: first the intercell interference is removed by applying a set of distributed precoding vectors; then the system is further optimized through power allocation. Three centralized power allocation algorithms with per-BS power constraint and different complexity trade-offs are proposed: one optimal in terms of minimization of the instantaneous average bit error rate (BER), and two suboptimal. In this latter approach, the powers are computed in two phases. First, the powers are derived under total power constraint (TPC) and two criterions are considered, namely, minimization of the instantaneous average BER and minimization of the sum of inverse of signal-to-noise ratio. Then, the final powers are computed to satisfy the individual per-BS power constraint. The performance of the proposed schemes is evaluated, considering typical pedestrian scenarios based on LTE specifications. The numerical results show that the proposed suboptimal schemes achieve a performance very close to the optimal but with lower computational complexity. Moreover, the performance of the proposed per-BS precoding schemes is close to the one obtained considering TPC over a supercell.

A novel distributed power allocation scheme for coordinated multicell systems

“…A centralized power allocation approach based on the minimization of average BER was proposed in [14]. Essentially, we perform the minimization min p b;k;l f g…”

“…Note that (14) does not represent any real average BER. Considering the multicell system as a superposition of B single cell systems, as shown in Figure 2, (14) can be seen as the average VBER of the bth single-cell system.…”

“…Considering the multicell system as a superposition of B single cell systems, as shown in Figure 2, (14) can be seen as the average VBER of the bth single-cell system. The motivation to use (14) is that the minimization of the average VBER reduces the dynamic range of the VSNRs between the different UTs and subcarriers, i.e., leads to an equalization of the VSNRs over all UTs and subcarriers (more power is allocated to the weaker links and less to the stronger ones as compared to equal power allocation approach), which implicitly leads to an equalization of the SINRs and therefore provides user fairness at the cell edges. The power allocation problem at each BS b, with per-BS power constraint, can be formulated as min…”

“…Also, these schemes are compared with two different power allocation strategies: equal power allocation approach, i.e., the power available at each BS is equally divided by the users and subcarrier, p b;k;l ¼ T p b =KN c ; ∀ b; k; l ð Þ, referred as EPA; DZF with joint centralized power allocation as proposed in [14], referred to here as centralized MBER power allocation (CMBER). We also present the curve for the DVSINR with joint centralized power allocation using the same strategy as for the DZF, also referred as CMBER.…”

“…In [13], a heuristic power allocation based on maximization of a metric related with the sum-rate was derived. A promising distributed precoding scheme based on zero-forcing criterion with several centralized power allocation approaches, which minimize the average bit error rate (BER) and sum of inverse of signal-to -interference noise ratio (SNIR), was proposed in [14]. These distributed schemes were evaluated and compared with some full centralized multicell schemes in [15].…”